Dirac equation in low dimensions: The factorization method
Energy Technology Data Exchange (ETDEWEB)
Sánchez-Monroy, J.A., E-mail: antosan@if.usp.br [Instituto de Física, Universidade de São Paulo, 05508-090, São Paulo, SP (Brazil); Quimbay, C.J., E-mail: cjquimbayh@unal.edu.co [Departamento de Física, Universidad Nacional de Colombia, Bogotá, D. C. (Colombia); CIF, Bogotá (Colombia)
2014-11-15
We present a general approach to solve the (1+1) and (2+1)-dimensional Dirac equations in the presence of static scalar, pseudoscalar and gauge potentials, for the case in which the potentials have the same functional form and thus the factorization method can be applied. We show that the presence of electric potentials in the Dirac equation leads to two Klein–Gordon equations including an energy-dependent potential. We then generalize the factorization method for the case of energy-dependent Hamiltonians. Additionally, the shape invariance is generalized for a specific class of energy-dependent Hamiltonians. We also present a condition for the absence of the Klein paradox (stability of the Dirac sea), showing how Dirac particles in low dimensions can be confined for a wide family of potentials. - Highlights: • The low-dimensional Dirac equation in the presence of static potentials is solved. • The factorization method is generalized for energy-dependent Hamiltonians. • The shape invariance is generalized for energy-dependent Hamiltonians. • The stability of the Dirac sea is related to the existence of supersymmetric partner Hamiltonians.
Spinors, tensors and the covariant form of Dirac's equation
International Nuclear Information System (INIS)
Chen, W.Q.; Cook, A.H.
1986-01-01
The relations between tensors and spinors are used to establish the form of the covariant derivative of a spinor, making use of the fact that certain bilinear combinations of spinors are vectors. The covariant forms of Dirac's equation are thus obtained and examples in specific coordinate systems are displayed. (author)
Relativistic quantum vorticity of the quadratic form of the Dirac equation
International Nuclear Information System (INIS)
Asenjo, Felipe A; Mahajan, Swadesh M
2015-01-01
We explore the fluid version of the quadratic form of the Dirac equation, sometimes called the Feynman–Gell-Mann equation. The dynamics of the quantum spinor field is represented by equations of motion for the fluid density, the velocity field, and the spin field. In analogy with classical relativistic and non-relativistic quantum theories, the fully relativistic fluid formulation of this equation allows a vortex dynamics. The vortical form is described by a total tensor field that is the weighted combination of the inertial, electromagnetic and quantum forces. The dynamics contrives the quadratic form of the Dirac equation as a total vorticity free system. (paper)
Dirac-Kahler fermion with noncommutative differential forms on a lattice
International Nuclear Information System (INIS)
Kanamori, I.; Kawamoto, N.
2004-01-01
Noncommutativity between a differential form and a function allows us to define differential operator satisfying Leibniz's rule on a lattice. We propose a new associative Clifford product defined on the lattice by introducing the noncommutative differential forms. We show that this Clifford product naturally leads to the Dirac-Kaehler fermion on the lattice
International Nuclear Information System (INIS)
Singh, S.K.
2002-01-01
The present status of electroweak nucleon form factors and the N - Δ transition form factors is reviewed. Particularly the determination of dipole mass M A in the axial vector form factor is discussed
Energy Technology Data Exchange (ETDEWEB)
Frederic D. R. Bonnet; Robert G. Edwards; George T. Fleming; Randal Lewis; David Richards
2003-07-22
We have started a program to compute the electromagnetic form factors of mesons. We discuss the techniques used to compute the pion form factor and present preliminary results computed with domain wall valence fermions on MILC asqtad lattices, as well as Wilson fermions on quenched lattices. These methods can easily be extended to rho-to-gamma-pi transition form factors.
Neutron electromagnetic form factors
International Nuclear Information System (INIS)
Finn, J.M.; Madey, R.; Eden, T.; Markowitz, P.; Rutt, P.M.; Beard, K.; Anderson, B.D.; Baldwin, A.R.; Keane, D.; Manley, D.M.; Watson, J.W.; Zhang, W.M.; Kowalski, S.; Bertozzi, W.; Dodson, G.; Farkhondeh, M.; Dow, K.; Korsch, W.; Tieger, D.; Turchinetz, W.; Weinstein, L.; Gross, F.; Mougey, J.; Ulmer, P.; Whitney, R.; Reichelt, T.; Chang, C.C.; Kelly, J.J.; Payerle, T.; Cameron, J.; Ni, B.; Spraker, M.; Barkhuff, D.; Lourie, R.; Verst, S.V.; Hyde-Wright, C.; Jiang, W.-D.; Flanders, B.; Pella, P.; Arenhoevel, H.
1992-01-01
Nucleon form factors provide fundamental input for nuclear structure and quark models. Current knowledge of neutron form factors, particularly the electric form factor of the neutron, is insufficient to meet these needs. Developments of high-duty-factor accelerators and polarization-transfer techniques permit new experiments that promise results with small sensitivities to nuclear models. We review the current status of the field, our own work at the MIT/Bates linear accelerator, and future experimental efforts
Rivasseau, Vincent; Fuchs, Jean-Nöel
2017-01-01
This fifteenth volume of the Poincare Seminar Series, Dirac Matter, describes the surprising resurgence, as a low-energy effective theory of conducting electrons in many condensed matter systems, including graphene and topological insulators, of the famous equation originally invented by P.A.M. Dirac for relativistic quantum mechanics. In five highly pedagogical articles, as befits their origin in lectures to a broad scientific audience, this book explains why Dirac matters. Highlights include the detailed "Graphene and Relativistic Quantum Physics", written by the experimental pioneer, Philip Kim, and devoted to graphene, a form of carbon crystallized in a two-dimensional hexagonal lattice, from its discovery in 2004-2005 by the future Nobel prize winners Kostya Novoselov and Andre Geim to the so-called relativistic quantum Hall effect; the review entitled "Dirac Fermions in Condensed Matter and Beyond", written by two prominent theoreticians, Mark Goerbig and Gilles Montambaux, who consider many other mater...
It! What is Soil? Chip Off the Old Block Soil Forming Factors Matters of Life and Death Underneath It All Wise Choices A World of Soils Soil Forming Factors 2 A Top to Bottom Guide 3 Making a Soil Monolith 4 Soil Orders 5 State Soil Monoliths 6 Where in the Soil World Are You? >> A Top to
Disconnected electromagnetic form factors
International Nuclear Information System (INIS)
Wilcox, Walter
2001-01-01
Preliminary results of a calculation of disconnected nucleon electromagnetic factors factors on the lattice are presented. The implementation of the numerical subtraction scheme is outlined. A comparison of results for electric and magnetic disconnected form factors on two lattice sizes with those of the Kentucky group is presented. Unlike previous results, the results found in this calculation are consistent with zero in these sectors
Spin factor and spinor structure of Dirac propagator in constant field
Energy Technology Data Exchange (ETDEWEB)
Gitman, D.M.; Cruz, W. da [Sao Paulo Univ., SP (Brazil). Inst. de Fisica; Zlatev, S.I. [Sergipe Univ., Aracaju, SE (Brazil). Dept. de Fisica
1996-06-01
We use bosonic path integral representation of Dirac propagator with a spin factor to calculate the propagator in a constant uniform electromagnetic field. Such a way of calculation allows us to get the explicit spinor structure of the propagator in the case under consideration. The representation obtained differs from the Schwinger`s one but the equivalence can be checked. (author). 21 refs.
Spin factor and spinor structure of Dirac propagator in constant field
International Nuclear Information System (INIS)
Gitman, D.M.; Cruz, W. da; Zlatev, S.I.
1996-01-01
We use bosonic path integral representation of Dirac propagator with a spin factor to calculate the propagator in a constant uniform electromagnetic field. Such a way of calculation allows us to get the explicit spinor structure of the propagator in the case under consideration. The representation obtained differs from the Schwinger's one but the equivalence can be checked. (author). 21 refs
Form factors of Ising spin and disorder fields on the Poincare disc
International Nuclear Information System (INIS)
Doyon, Benjamin
2004-01-01
Using recent results concerning form factors of certain scaling fields in the massive Dirac theory on the Poincare disc, we find expressions for the form factors of Ising spin and disorder fields in the massive Majorana theory on the Poincare disc. In particular, we verify that these recent results agree with the factorization properties of the fields in the Dirac theory representing tensor products of spin and of disorder fields in the Majorana theory
Effects of acceleration through the Dirac sea
International Nuclear Information System (INIS)
Hacyan, S.
1986-01-01
The effects of acceleration through massive scalar and spin-1/2 fields are investigated. It is shown that the density-of-states factor in a uniformly accelerated frame takes a complicated form, but the energy spectrum exhibits a Bose-Einstein or Fermi-Dirac distribution function. In particular, the Dirac sea shows thermal-like effects
Hyperon decay form factors in chiral perturbation theory
International Nuclear Information System (INIS)
Lacour, Andre; Kubis, Bastian; Meissner, Ulf-G.
2007-01-01
We present a complete calculation of the SU(3)-breaking corrections to the hyperon vector form factors up to O(p 4 ) in covariant baryon chiral perturbation theory. Partial higher-order contributions are obtained, and we discuss chiral extrapolations of the vector form factor at zero momentum transfer. In addition we derive low-energy theorems for the subleading moments in hyperon decays, the weak Dirac radii and the weak anomalous magnetic moments, up to O(p 4 )
International Nuclear Information System (INIS)
Desplanques, B.
1987-01-01
Electromagnetic form factors, in first approximation, are sensitive to spatial distribution of nucleons and to their current. In second approximation, more precise effects are concerned, whose role is increasing with momentum transfer and participating essentially of short range nuclei description. They concern of course the nucleon-nucleon interaction while approaching each other and keeping their free-state identity, but also mutually polarizing one the other. In this last effect, radial and orbital excitations of nucleon, the nucleon mesonic cloud modification and the nucleon antinucleon pair excitation are included. In this paper, these contributions are discussed while trying to find the important elements for a good description of form factors. Current questions are also discussed. Light nuclei are essentially concerned [fr
Quantum effects of a massive 3-form coupled to a Dirac field
International Nuclear Information System (INIS)
Aurilia, Antonio; Spallucci, Euro
2004-01-01
The computation of the quantum vacuum pressure must take into account the contribution of zero-point oscillations of a rank-three gauge field A μνρ . This result was established in a previous paper where we calculated both the Casimir pressure within a region of vacuum simulating a hadronic bag and the Wilson factor for the three-index potential associated with the boundary of the bag. The resulting 'volume law' satisfied by the Wilson loop is consistent with the basic confining requirement that the static interquark potential increases with the distance between two test charges. As a sequel to that paper, we consider here the coupling of A μνρ to the generic current of a matter field, later identified with the spin density current of a Dirac field. In fact, one of the objectives of this paper is to investigate the impact of the quantum fluctuations of A μνρ on the effective dynamics of the spinor field. The consistency of the field equations, even at the classical level, requires the introduction of a mass term for A μνρ . In this case, the Casimir vacuum pressure includes a contribution that is explicitly dependent on the mass of A μνρ and leads us to conclude that the mass term plays the same role as the infrared cutoff needed to regularize the finite volume partition functional previously calculated in the massless case. Remarkably, even in the presence of a mass term, A μνρ contains a mixture of massless and massive spin-0 fields so that the resulting equation is still gauge invariant. This is yet another peculiar, but physically relevant property of A μνρ since it is reflected in the effective dynamics of the spinor fields and confirms the confining property of A μνρ already expected from the earlier calculation of the Wilson loop
Dirac-like operators on the Hilbert space of differential forms on manifolds with boundaries
Pérez-Pardo, Juan Manuel
The problem of self-adjoint extensions of Dirac-type operators in manifolds with boundaries is analyzed. The boundaries might be regular or non-regular. The latter situation includes point-like interactions, also called delta-like potentials, in manifolds of dimension higher than one. Self-adjoint boundary conditions for the case of dimension 2 are obtained explicitly.
A new form of Ca{sub 3}P{sub 2} with a ring of Dirac nodes
Energy Technology Data Exchange (ETDEWEB)
Xie, Lilia S.; Schoop, Leslie M.; Seibel, Elizabeth M.; Gibson, Quinn D.; Xie, Weiwei; Cava, Robert J., E-mail: rcava@princeton.edu [Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States)
2015-08-01
We report the synthesis and crystal structure of a new high-temperature form of Ca{sub 3}P{sub 2}. The crystal structure was determined through Rietveld refinements of synchrotron powder x-ray diffraction data. This form of Ca{sub 3}P{sub 2} has a crystal structure of the hexagonal Mn{sub 5}Si{sub 3} type, with a Ca ion deficiency compared to the ideal 5:3 stoichiometry. This yields a stable, charge-balanced compound of Ca{sup 2+} and P{sup 3−}. We also report the observation of a secondary hydride phase, Ca{sub 5}P{sub 3}H, which again is a charge-balanced compound. The calculated band structure of Ca{sub 3}P{sub 2} indicates that it is a three-dimensional Dirac semimetal with a highly unusual ring of Dirac nodes at the Fermi level. The Dirac states are protected against gap opening by a mirror plane in a manner analogous to what is seen for graphene.
Pais, Abraham; Jacob, Maurice; Olive, David I.; Atiyah, Michael F.
2005-09-01
Preface Peter Goddard; Dirac memorial address Stephen Hawking; 1. Paul Dirac: aspects of his life and work Abraham Pais; 2. Antimatter Maurice Jacob; 3. The monopole David Olive; 4. The Dirac equation and geometry Michael F. Atiyah.
Energy Technology Data Exchange (ETDEWEB)
Ryong Ji, C.; Pang, A.; Szczepaniak, A. [North Carolina State Univ., Raleigh, NC (United States)
1994-04-01
It is pointed out that the correct criterion to define the legal PQCD contribution to the exclusive processes in the lightcone perturbative expansion should be based on the large off-shellness of the lightcone energy in the intermediate states. In the lightcone perturbative QCD calculation of the pion form factor, the authors find that the legal PQCD contribution defined by the lightcone energy cut saturates in the smaller Q{sup 2} region compared to that defined by the gluon four-momentum square cut. This is due to the contribution by the highly off-energy-shell gluons in the end point regions of the phase space, indicating that the gluon four-momentum-square cut may have cut too much to define the legal PQCD.
Nucleon Electromagnetic Form Factors
Energy Technology Data Exchange (ETDEWEB)
Marc Vanderhaeghen; Charles Perdrisat; Vina Punjabi
2007-10-01
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has greatly improved by performing double polarization experiments, in comparison with previous unpolarized data. Here we review the experimental data base in view of the new results for the proton, and neutron, obtained at JLab, MAMI, and MIT-Bates. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed, including the recent progress in the determination of the valence quark generalized parton distributions of the nucleon, as well as the steady rate of improvements made in the lattice QCD calculations.
Weak form of Stokes-Dirac structures and geometric discretization of port-Hamiltonian systems
Kotyczka, Paul; Maschke, Bernhard; Lefèvre, Laurent
2018-05-01
We present the mixed Galerkin discretization of distributed parameter port-Hamiltonian systems. On the prototypical example of hyperbolic systems of two conservation laws in arbitrary spatial dimension, we derive the main contributions: (i) A weak formulation of the underlying geometric (Stokes-Dirac) structure with a segmented boundary according to the causality of the boundary ports. (ii) The geometric approximation of the Stokes-Dirac structure by a finite-dimensional Dirac structure is realized using a mixed Galerkin approach and power-preserving linear maps, which define minimal discrete power variables. (iii) With a consistent approximation of the Hamiltonian, we obtain finite-dimensional port-Hamiltonian state space models. By the degrees of freedom in the power-preserving maps, the resulting family of structure-preserving schemes allows for trade-offs between centered approximations and upwinding. We illustrate the method on the example of Whitney finite elements on a 2D simplicial triangulation and compare the eigenvalue approximation in 1D with a related approach.
Electromagnetic Hadronic Form-Factors
International Nuclear Information System (INIS)
Edwards, Robert G.
2005-01-01
We present a calculation of the nucleon electromagnetic form-factors as well as the pion and rho to pion transition form-factors in a hybrid calculation with domain wall valence quarks and improved staggered (Asqtad) sea quarks
Covariance dynamics and symmetries, and hadron form factors
International Nuclear Information System (INIS)
Bhagwat, M.S.; Cloet, I.C.; Roberts, C.D.
2007-01-01
We summarize applications of Dyson-Schwinger equations to the theory and phenomenology of hadrons. Some exact results for pseudoscalar mesons are highlighted with details relating to the U A (1) problem. We describe inferences from the gap equation relating to the radius of convergence for expansions of observables in the current-quark mass. We recapitulate upon studies of nucleon electromagnetic form factors, providing a comparison of the ln-weighted ratios of Pauli and Dirac form factors for the neutron and proton.
Unexpected low thermal conductivity and large power factor in Dirac semimetal Cd3As2
Cheng, Zhang; Tong, Zhou; Sihang, Liang; Junzhi, Cao; Xiang, Yuan; Yanwen, Liu; Yao, Shen; Qisi, Wang; Jun, Zhao; Zhongqin, Yang; Faxian, Xiu
2016-01-01
Thermoelectrics has long been considered as a promising way of power generation for the next decades. So far, extensive efforts have been devoted to the search of ideal thermoelectric materials, which require both high electrical conductivity and low thermal conductivity. Recently, the emerging Dirac semimetal Cd3As2, a three-dimensional analogue of graphene, has been reported to host ultra-high mobility and good electrical conductivity as metals. Here, we report the observation of unexpected low thermal conductivity in Cd3As2, one order of magnitude lower than the conventional metals or semimetals with a similar electrical conductivity, despite the semimetal band structure and high electron mobility. The power factor also reaches a large value of 1.58 mW·m-1·K-2 at room temperature and remains non-saturated up to 400 K. Corroborating with the first-principles calculations, we find that the thermoelectric performance can be well-modulated by the carrier concentration in a wide range. This work demonstrates the Dirac semimetal Cd3As2 as a potential candidate of thermoelectric materials. Project supported by the National Young 1000 Talent Plan China, the Pujiang Talent Plan in Shanghai, China, the National Natural Science Foundation of China (Grant Nos. 61322407 and 11474058), the Fund for Fostering Talents in Basic Science of the National Natural Science Foundation of China (Grant No. J1103204), and the National Basic Research Program of China (Grant No. 2011CB921803).
Wehling, T. O.; Black-Schaffer, A. M.; Balatsky, A. V.
2014-01-01
A wide range of materials, like d-wave superconductors, graphene, and topological insulators, share a fundamental similarity: their low-energy fermionic excitations behave as massless Dirac particles rather than fermions obeying the usual Schrodinger Hamiltonian. This emergent behavior of Dirac fermions in condensed matter systems defines the unifying framework for a class of materials we call "Dirac materials''. In order to establish this class of materials, we illustrate how Dirac fermions ...
Electromagnetic form factors of hadrons
International Nuclear Information System (INIS)
Zidell, V.S.
1976-01-01
A vector meson dominance model of the electromagnetic form factors of hadrons is developed which is based on the use of unstable particle propagators. Least-square fits are made to the proton, neutron, pion and kaon form factor data in both the space and time-like regions. A good fit to the low-energy nucleon form factor data is obtained using only rho, ω, and phi dominance, and leads to a determination of the vector meson resonance parameters in good agreement with experiment. The nucleon-vector meson coupling constants obey simple sum rules indicating that there exists no hard core contribution to the form factors within theoretical uncertainties. The prediction for the electromagnetic radii of the proton is in reasonable agreement with recent experiments. The pion and kaon charge form factors as deduced from the nucleon form factors assuming vector meson universality are compared to the data. The pion form factor agrees with the data in both the space and time-like regions. The pion charge radius is in agreement with the recent Dubna result, but the isovector P-wave pion-pion phase shift calculated from the theory disagrees with experiment. A possible contribution to the form factors from a heavy rho meson is also evaluated
Nucleon electromagnetic form factors in twisted mass lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Jansen, K.; Korzec, T.; Humboldt Univ. Berlin
2011-02-01
We present results on the nucleon electromagnetic form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1 fm and L=2.8 fm. Cut-off effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm. The nucleon magnetic moment, Dirac and Pauli radii are obtained in the continuum limit and chirally extrapolated to the physical pion mass allowing for a comparison with experiment. (orig.)
Nucleon electromagnetic form factors in twisted mass lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Brinet, M.; Carbonell, J.; Harraud, P. A.; Papinutto, M.; Guichon, P.; Jansen, K.; Korzec, T.; Constantinou, M.
2011-01-01
We present results on the nucleon electromagnetic form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1 fm and L=2.8 fm. Cutoff effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm. The nucleon magnetic moment, Dirac and Pauli radii are obtained in the continuum limit and chirally extrapolated to the physical pion mass allowing for a comparison with experiment.
Nucleon form factors with NF=2 twisted mass fermions
International Nuclear Information System (INIS)
Alexandrou, C.; Korzec, T.; Brinet, M.; Carbonell, J.; Harraud, P.A.; Jansen, K.
2009-10-01
We present results on the electromagnetic and axial nucleon form factors using two degenerate flavors of twisted mass fermions on lattices of spatial size 2.1 fm and 2.7 fm and a lattice spacing of about 0.09 fm. We consider pion masses in the range of 260-470MeV.We chirally extrapolate results on the nucleon axial charge, the isovector Dirac and Pauli root mean squared radii and magnetic moment to the physical point and compare to experiment. (orig.)
Calculation of pion form factor
International Nuclear Information System (INIS)
Vahedi, N.; Amirarjomand, S.
1975-09-01
The pion form factor is calculated using the structure function Wsub(2), which incorporates kinematical constraints, threshold behaviour and scaling. The Bloom-Gilman sum rule is used and only the two leading Regge trajectories are taken into account
Energy Technology Data Exchange (ETDEWEB)
Anon.
1988-04-15
It was Paul Dirac who cast quantum mechanics into the form we now use, and many generations of theoreticians openly acknowledge his influence on their thinking. When Dirac died in 1984, St. John's College, Cambridge, his base for most of his lifetime, instituted an annual lecture in his memory at Cambridge. The first lecture, in 1986, attracted two heavyweights - Richard Feynman and Steven Weinberg. Far from using the lectures as a platform for their own work, in the Dirac tradition they presented stimulating material on deep underlying questions.
International Nuclear Information System (INIS)
Anon.
1988-01-01
It was Paul Dirac who cast quantum mechanics into the form we now use, and many generations of theoreticians openly acknowledge his influence on their thinking. When Dirac died in 1984, St. John's College, Cambridge, his base for most of his lifetime, instituted an annual lecture in his memory at Cambridge. The first lecture, in 1986, attracted two heavyweights - Richard Feynman and Steven Weinberg. Far from using the lectures as a platform for their own work, in the Dirac tradition they presented stimulating material on deep underlying questions
Nucleon electromagnetic form factors in a relativistic quark model with chiral symmetry
International Nuclear Information System (INIS)
Barik, N.
1987-01-01
The nucleon electromagnetic form factors are computed in an independent quark model based on the Dirac equation. Corrections for centre-of-mass motion and pion-cloud effects are incorporated. Results for static quantities are in reasonable agreement with the experimental data. (author)
Nucleon electromagnetic form factors in a relativistic quark model with chiral symmetry
Energy Technology Data Exchange (ETDEWEB)
Barik, N; Das, M
1987-05-01
The nucleon electromagnetic form factors are computed in an independent quark model based on the Dirac equation. Corrections for centre-of-mass motion and pion-cloud effects are incorporated. Results for static quantities are in reasonable agreement with the experimental data.
Nucleon form factors, generalized parton distributions and quark angular momentum
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kroll, Peter [Bergische Univ., Wuppertal (Germany). Fachbereich Physik; Regensburg Univ. (Germany). Institut fuer Theoretische Physik
2013-02-15
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale {mu}=2 GeV to be J{sup u}{sub v}=0.230{sup +0.009}{sub -0.024} and J{sup d}{sub v}=-0.004{sup +0.010}{sub -0.016}.
Nucleon form factors, generalized parton distributions and quark angular momentum
International Nuclear Information System (INIS)
Diehl, Markus; Kroll, Peter; Regensburg Univ.
2013-02-01
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale μ=2 GeV to be J u v =0.230 +0.009 -0.024 and J d v =-0.004 +0.010 -0.016 .
TRASYS form factor matrix normalization
Tsuyuki, Glenn T.
1992-01-01
A method has been developed for adjusting a TRASYS enclosure form factor matrix to unity. This approach is not limited to closed geometries, and in fact, it is primarily intended for use with open geometries. The purpose of this approach is to prevent optimistic form factors to space. In this method, nodal form factor sums are calculated within 0.05 of unity using TRASYS, although deviations as large as 0.10 may be acceptable, and then, a process is employed to distribute the difference amongst the nodes. A specific example has been analyzed with this method, and a comparison was performed with a standard approach for calculating radiation conductors. In this comparison, hot and cold case temperatures were determined. Exterior nodes exhibited temperature differences as large as 7 C and 3 C for the hot and cold cases, respectively when compared with the standard approach, while interior nodes demonstrated temperature differences from 0 C to 5 C. These results indicate that temperature predictions can be artificially biased if the form factor computation error is lumped into the individual form factors to space.
Strange mesonic transition form factor
International Nuclear Information System (INIS)
Goity, J.L.; Musolf, M.J.
1996-01-01
The strange-quark vector current ρ-to-π meson transition form factor is computed at one-loop order using strange meson intermediate states. A comparison is made with a φ-meson dominance model estimate. We find that one-loop contributions are comparable in magnitude to those predicted by φ-meson dominance. It is possible that the one-loop contribution can make the matrix element as large as those of the electromagnetic current mediating vector meson radiative decays. However, due to the quadratic dependence of the one-loop results on the hadronic form factor cutoff mass, a large uncertainty in the estimate of the loops is unavoidable. These results indicate that non-nucleonic strange quarks could contribute appreciable in moderate-parallel Q 2 parallel parity-violating electron-nucleus scattering measurements aimed at probing the strange-quark content of the nucleon. copyright 1996 The American Physical Society
Shot noise and Fano factor in tunneling in three-band pseudospin-1 Dirac-Weyl systems
Zhu, Rui; Hui, Pak Ming
2017-06-01
Tunneling through a potential barrier of height V0 in a two-dimensional system with a band structure consisting of three bands with a flat band intersecting the touching apices of two Dirac cones is studied. Results of the transmission coefficient at various incident angles, conductivity, shot noise, and Fano factor in this pseudospin-1 Dirac-Weyl system are presented and contrasted with those in graphene which is typical of a pseudospin-1/2 system. The pseudospin-1 system is found to show a higher transmission and suppressed shot noise in general. Significant differences in the shot noise and Fano factor due to the super Klein tunneling effect that allows perfect transmission at all incident angles under certain conditions are illustrated. For Fermi energy EF =V0 / 2, super Klein tunneling leads to a noiseless conductivity that takes on the maximum value 2e2 DkF / (πh) for 0 ≤EF ≤V0. This gives rise to a minimum Fano factor, in sharp contrast with that of a local maximum in graphene. For EF =V0, the band structure of pseudospin-1 system no longer leads to a quantized value of the conductivity as in graphene. Both the conductivity and the shot noise show a minimum with the Fano factor approaching 1/4, which is different from the value of 1/3 in graphene.
Casajús Ramo, A
2006-01-01
DIRAC is the LHCb Workload and Data Management System. Based on a service-oriented architecture, it enables generic distributed computing with lightweight Agents and Clients for job execution and data transfers. DIRAC implements a client-server architecture exposing server methods through XML Remote Procedure Call (XML-RPC) protocol. DIRAC is mostly coded in python. DIRAC security infrastructure has been designed to be a completely generic XML-RPC transport over a SSL tunnel. This new security layer is able to handle standard X509 certificates as well as grid-proxies to authenticate both sides of the connection. Serve and client authentication relies over OpenSSL and py-Open SSL, but to be able to handle grid proxies some modifications have been added to those libraries. DIRAC security infrastructure handles authorization and authorization as well as provides extended capabilities like secure connection tunneling and file transfer. Using this new security infrastructure all LHCb users can safely make use o...
Factorization and pion form factor in QCD
International Nuclear Information System (INIS)
Efremov, A.V.; Radyushkin, A.V.
1979-01-01
The behaviour of the pion electromagnetic form factor (EMFF) in the framework of quantum chromodynamics (QCD) is discussed. Pion is considered to be a quark-antiquark bound state. It is proposed to use an OPE description of the bound state structure by matrix elements of certain local gauge-invariant operators. Short-distance quark interactions is proved using a direct analysis of perturbation theory in the α-parametric representation of the Feynman diagrams. It is shown that the short-distance parton picture privides a self-consistent description of the large Q 2 momentum behaviour of the pion EMFF in QCD. Pion EMFF asymptotics is expressed in terms of fu fundamental constants of the theory
Electroweak form factors of the Skyrmion
International Nuclear Information System (INIS)
Braaten, E.; Sze-Man Tse; Willcox, C.
1986-01-01
The electroweak form factors of baryons are studied in the semiclassical approximation to the Skyrme model. General expressions for the form factors are given for arbitrary choices of the Skyrme-model Lagrangian. They are applied to the original two-parameter Skyrme model to compute the electric, magnetic, and axial-vector form factors of the nucleon and the electromagnetic nucleon-Δ transition form factors. The dependence of the form factors on the momentum transfer is compared with phenomenological dipole parametrizations
International Nuclear Information System (INIS)
Gomez, F.; Adeva, B.; Afanasev, L.; Benayoun, M.; Brekhovskikh, V.; Caragheorgheopol, G.; Cechak, T.; Chiba, M.; Constantinescu, S.; Doudarev, A.; Dreossi, D.; Drijard, D.; Ferro-Luzzi, M.; Gallas, M.V.; Gerndt, J.; Giacomich, R.; Gianotti, P.; Goldin, D.; Gorin, A.; Gortchakov, O.; Guaraldo, C.; Hansroul, M.; Hosek, R.; Iliescu, M.; Jabitski, M.; Kalinina, N.; Karpoukhine, V.; Kluson, J.; Kobayashi, M.; Kokkas, P.; Komarov, V.; Koulikov, A.; Kouptsov, A.; Krouglov, V.; Krouglova, L.; Kuroda, K.-I.; Lanaro, A.; Lapshine, V.; Lednicky, R.; Leruste, P.; Levisandri, P.; Lopez Aguera, A.; Lucherini, V.; Maki, T.; Manuilov, I.; Montanet, L.; Narjoux, J.-L.; Nemenov, L.; Nikitin, M.; Nunez Pardo, T.; Okada, K.; Olchevskii, V.; Pazos, A.; Pentia, M.; Penzo, A.; Perreau, J.-M.; Petrascu, C.; Plo, M.; Ponta, T.; Pop, D.; Riazantsev, A.; Rodriguez, J.M.; Rodriguez Fernandez, A.; Rykaline, V.; Santamarina, C.; Saborido, J.; Schacher, J.; Sidorov, A.; Smolik, J.; Takeutchi, F.; Tarasov, A.; Tauscher, L.; Tobar, M.J.; Trusov, S.; Vazquez, P.; Vlachos, S.; Yazkov, V.; Yoshimura, Y.; Zrelov, P.
2001-01-01
The main objective of DIRAC experiment is the measurement of the lifetime τ of the exotic hadronic atom consisting of π + and π - mesons. The lifetime of this atom is determined by the decay mode π + π - → π 0 π 0 due to the strong interaction. Through the precise relationship between the lifetime and the S-wave pion-pion scattering length difference |a 0 - a 2 | for isospin 0 and 2 (respectively), a measurement of τ with an accuracy of 10% will allow a determination of |a 0 - a 2 | at a 5% precision level. Pion-pion scattering lengths have been calculated in the framework of chiral perturbation theory with an accuracy below 5%. In this way DIRAC experiment will provide a crucial test of the chiral symmetry breaking scheme in QCD effective theories at low energies
Energy Technology Data Exchange (ETDEWEB)
Gomez, F.; Adeva, B.; Afanasev, L.; Benayoun, M.; Brekhovskikh, V.; Caragheorgheopol, G.; Cechak, T.; Chiba, M.; Constantinescu, S.; Doudarev, A.; Dreossi, D.; Drijard, D.; Ferro-Luzzi, M.; Gallas, M.V.; Gerndt, J.; Giacomich, R.; Gianotti, P.; Goldin, D.; Gorin, A.; Gortchakov, O.; Guaraldo, C.; Hansroul, M.; Hosek, R.; Iliescu, M.; Jabitski, M.; Kalinina, N.; Karpoukhine, V.; Kluson, J.; Kobayashi, M.; Kokkas, P.; Komarov, V.; Koulikov, A.; Kouptsov, A.; Krouglov, V.; Krouglova, L.; Kuroda, K.-I.; Lanaro, A.; Lapshine, V.; Lednicky, R.; Leruste, P.; Levisandri, P.; Lopez Aguera, A.; Lucherini, V.; Maki, T.; Manuilov, I.; Montanet, L.; Narjoux, J.-L.; Nemenov, L.; Nikitin, M.; Nunez Pardo, T.; Okada, K.; Olchevskii, V.; Pazos, A.; Pentia, M.; Penzo, A.; Perreau, J.-M.; Petrascu, C.; Plo, M.; Ponta, T.; Pop, D.; Riazantsev, A.; Rodriguez, J.M.; Rodriguez Fernandez, A.; Rykaline, V.; Santamarina, C.; Saborido, J.; Schacher, J.; Sidorov, A.; Smolik, J.; Takeutchi, F.; Tarasov, A.; Tauscher, L.; Tobar, M.J.; Trusov, S.; Vazquez, P.; Vlachos, S.; Yazkov, V.; Yoshimura, Y.; Zrelov, P
2001-04-01
The main objective of DIRAC experiment is the measurement of the lifetime {tau} of the exotic hadronic atom consisting of {pi}{sup +} and {pi}{sup -} mesons. The lifetime of this atom is determined by the decay mode {pi}{sup +} {pi}{sup -} {yields} {pi}{sup 0} {pi}{sup 0} due to the strong interaction. Through the precise relationship between the lifetime and the S-wave pion-pion scattering length difference |a{sub 0} - a{sub 2}| for isospin 0 and 2 (respectively), a measurement of {tau} with an accuracy of 10% will allow a determination of |a{sub 0} - a{sub 2}| at a 5% precision level. Pion-pion scattering lengths have been calculated in the framework of chiral perturbation theory with an accuracy below 5%. In this way DIRAC experiment will provide a crucial test of the chiral symmetry breaking scheme in QCD effective theories at low energies.
The Dirac equation for accountants
International Nuclear Information System (INIS)
Ord, G.N.
2006-01-01
In the context of relativistic quantum mechanics, derivations of the Dirac equation usually take the form of plausibility arguments based on experience with the Schroedinger equation. The primary reason for this is that we do not know what wavefunctions physically represent, so derivations have to rely on formal arguments. There is however a context in which the Dirac equation in one dimension is directly related to a classical generating function. In that context, the derivation of the Dirac equation is an exercise in counting. We provide this derivation here and discuss its relationship to quantum mechanics
Wigner function for the Dirac oscillator in spinor space
International Nuclear Information System (INIS)
Ma Kai; Wang Jianhua; Yuan Yi
2011-01-01
The Wigner function for the Dirac oscillator in spinor space is studied in this paper. Firstly, since the Dirac equation is described as a matrix equation in phase space, it is necessary to define the Wigner function as a matrix function in spinor space. Secondly, the matrix form of the Wigner function is proven to support the Dirac equation. Thirdly, by solving the Dirac equation, energy levels and the Wigner function for the Dirac oscillator in spinor space are obtained. (authors)
Alternatives to the Dirac equation
International Nuclear Information System (INIS)
Girvin, S.M.; Brownstein, K.R.
1975-01-01
Recent work by Biedenharn, Han, and van Dam (BHvD) has questioned the uniqueness of the Dirac equation. BHvD have obtained a two-component equation as an alternate to the Dirac equation. Although they later show their alternative to be unitarily equivalent to the Dirac equation, certain physical differences were claimed. BHvD attribute the existence of this alternate equation to the fact that their factorizing matrices were position-dependent. To investigate this, we factor the Klein-Gordon equation in spherical coordinates allowing the factorizing matrices to depend arbitrarily upon theta and phi. It is shown that despite this additional freedom, and without involving any relativistic covariance, the conventional four-component Dirac equation is the only possibility
On form factors of boundary changing operators
Energy Technology Data Exchange (ETDEWEB)
Bajnok, Z., E-mail: bajnok.zoltan@wigner.mta.hu [MTA Lendület Holographic QFT Group, Wigner Research Centre for Physics, P.O.B. 49, H-1525 Budapest 114 (Hungary); Hollo, L., E-mail: hollo.laszlo@wigner.mta.hu [MTA Lendület Holographic QFT Group, Wigner Research Centre for Physics, P.O.B. 49, H-1525 Budapest 114 (Hungary); Laboratoire de Physique Théorique, École Normale Supérieure, 24, rue Lhomond, 75005 Paris (France)
2016-04-15
We develop a form factor bootstrap program to determine the matrix elements of local, boundary condition changing operators. We propose axioms for these form factors and determine their solutions in the free boson and Lee–Yang models. The sudden change in the boundary condition, caused by an operator insertion, can be interpreted as a local quench and the form factors provide the overlap of any state before the quench with any outgoing state after the quench.
Charge-symmetry-breaking nucleon form factors
Energy Technology Data Exchange (ETDEWEB)
Kubis, Bastian, E-mail: kubis@hiskp.uni-bonn.de [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics (Germany)
2011-11-15
A quantitative understanding of charge-symmetry breaking is an increasingly important ingredient for the extraction of the nucleon's strange vector form factors. We review the theoretical understanding of the charge-symmetry-breaking form factors, both for single nucleons and for {sup 4}He.
Charge-symmetry-breaking nucleon form factors
International Nuclear Information System (INIS)
Kubis, Bastian
2011-01-01
A quantitative understanding of charge-symmetry breaking is an increasingly important ingredient for the extraction of the nucleon’s strange vector form factors. We review the theoretical understanding of the charge-symmetry-breaking form factors, both for single nucleons and for 4 He.
Calculation of nucleon electromagnetic form factors
International Nuclear Information System (INIS)
Renner, D.B.; Brower, R.; Dolgov, D.; Eicker, N.; Lippert, Th.; Negele, J.W.; Pochinsky, A.; Schilling, K.
2003-01-01
The formalism is developed to express nucleon matrix elements of the electromagnetic current in terms of form factors consistent with the translational, rotational, and parity symmetries of a cubic lattice. We calculate the number of these form factors and show how appropriate linear combinations approach the continuum limit
Electromagnetic form factors of a massive neutrino
International Nuclear Information System (INIS)
Dvornikov, M.S.; Studenikin, A.I.
2004-01-01
Electromagnetic form factors of a massive neutrino are studied in a minimally extended standard model in an arbitrary R ξ gauge and taking into account the dependence on the masses of all interacting particles. The contribution from all Feynman diagrams to the electric, magnetic, and anapole form factors, in which the dependence of the masses of all particles as well as on gauge parameters is accounted for exactly, are obtained for the first time in explicit form. The asymptotic behavior of the magnetic form factor for large negative squares of the momentum of an external photon is analyzed and the expression for the anapole moment of a massive neutrino is derived. The results are generalized to the case of mixing between various flavors of the neutrino. Explicit expressions are obtained for the electric, magnetic, and electric dipole and anapole transitional form factors as well as for the transitional electric dipole moment
The pion form factor from first principles
International Nuclear Information System (INIS)
Heide, J. van der
2004-01-01
We calculate the electromagnetic form factor of the pion in quenched lattice QCD. The non-perturbatively improved Sheikoleslami-Wohlert lattice action is used together with the O(a) improved current. We calculate form factor for pion masses down to mπ = 380 MeV. We compare the mean square radius for the pion extracted from our form factors to the value obtained from the 'Bethe Salpeter amplitude'. Using (quenched) chiral perturbation theory, we extrapolate our results towards the physical pion mass
Measurement of the pion form factor
International Nuclear Information System (INIS)
Dally, E.; Hauptman, J.; May, C.
1977-01-01
The pion form factor has been measured in the momentum transfer range of 0.03( 2 by scattering pions from atomic electrons in a liquid hydrogen target. The pion form factor is defined to be the elastic scattering cross section divided by that predicted for a point pion. The experiment has been performed in a 100 GeV/c negative pion beam incident on a 50 cm liquid hydrogen target at Fermi laboratory. The corrected form factor equals 0.33+-0.06 f 2 . Vector dominance predicts 0.40 f 2
Small Form Factor RFID Applicator, Phase I
National Aeronautics and Space Administration — The proposed development of a small form factor Astrobee dedicated RFID label applicator will allow current and future free flying vehicles to place RFID labels...
Heavy meson form factors from QCD
International Nuclear Information System (INIS)
Falk, A.F.; Georgi, H.; Grinstein, B.
1990-01-01
We calculate the leading QCD radiative corrections to the relations which follow from the decoupling of the heavy quark spin as the quark mass goes infinity and from the symmetry between systems with different heavy quarks. One of the effects we calculate gives the leading q 2 -dependence of the form factor of a heavy quark, which in turn dominates the q 2 -dependence of the form factors of bound states of the heavy quark with light quarks. This, combined with the normalization of the form factor provided by symmetry, gives us a first principles calculation of the heavy meson (or baryon) form factors in the limit of very large heavy quark mass. (orig.)
Make Projects Small Form Factor PCs
Wessels, Duane
2006-01-01
Shoebox sized and smaller, small-form-factor PCs can pack as much computing muscle as a full-sized desktop computer. They consumer less power, have few or no moving parts, and are very quiet. Whether you plan to use one as a standalone PC or want to embed it in your next hacking project, a small-form-factor PC can be a lot of fun to build. Make Projects: Small Form Factor PCs is the only book available that shows you how to build small-form-factor PCs -- from kits and from scratch -- that are more interesting and more personalized than what a full-sized PC can give you. Included in the book
Parallel Integer Factorization Using Quadratic Forms
National Research Council Canada - National Science Library
McMath, Stephen S
2005-01-01
.... In 1975, Daniel Shanks used class group infrastructure to modify the Morrison-Brillhart algorithm and develop Square Forms Factorization, but he never published his work on this algorithm or provided...
Hadron collisions and the fifth form factor
International Nuclear Information System (INIS)
Dokshitzer, Yu.L.; Marchesini, G.
2005-01-01
Logarithmically enhanced effects due to radiation of soft gluons at large angles in 2->2 QCD scattering processes are treated in terms of the ''fifth form factor'' that accompanies the four collinear singular Sudakov form factors attached to incoming and outgoing hard partons. Unexpected symmetry under exchange of internal and external variables of the problem is pointed out for the anomalous dimension that governs soft gluon effects in hard gluon-gluon scattering
Magnetic form factors of the trinucleons
Energy Technology Data Exchange (ETDEWEB)
Schiavilla, R; Pandharipande, V R; Riska, Dan-Olof
1989-11-01
The magnetic form factors of ^{3}H and ^{3}He are calculated with the Monte Carlo method from variational ground-state wave functions obtained for the Argonne and Urbana two- and three-nucleon interactions. The electromagnetic current operator contains one- and two-body terms that are constructed so as to satisfy the continuity equation with the two-nucleon potential in the Hamiltonian. The results obtained with the Argonne two-nucleon interaction are in overall agreement with the empirical values. It appears that the remaining theoretical uncertainty, in the calculation of these form factors from a given interaction model, is dominated by that in the electromagnetic form factors of the nucleon. It is found that the isovector magnetic form factors are rather sensitive to the details of the isospin-dependent tensor force, and they are much better reproduced with the Argonne than the Urbana potential. The isoscalar magnetic form factors appear to be sensitive to the spin-orbit interactions, and are better reproduced with the Urbana potential. The Argonne potential has a stronger τ1∙τ2 tensor force, while the Urbana one has a shorter-range spin-orbit interaction.
Asymptotics of Heavy-Meson Form Factors
Grozin, A.G.; Grozin, Andrey G.; Neubert, Matthias
1997-01-01
Using methods developed for hard exclusive QCD processes, we calculate the asymptotic behaviour of heavy-meson form factors at large recoil. It is determined by the leading- and subleading-twist meson wave functions. For $1\\ll |v\\cdot v'|\\ll m_Q/\\Lambda$, the form factors are dominated by the Isgur--Wise function, which is determined by the interference between the wave functions of leading and subleading twist. At $|v\\cdot v'|\\gg m_Q/\\Lambda$, they are dominated by two functions arising at order $1/m_Q$ in the heavy-quark expansion, which are determined by the leading-twist wave function alone. The sum of these contributions describes the form factors in the whole region $|v\\cdot v'|\\gg 1$. As a consequence, there is an exact zero in the form factor for the scattering of longitudinally polarized $B^*$ mesons at some value $v\\cdot v'\\sim m_b/\\Lambda$, and an approximate zero in the form factor of $B$ mesons in the timelike region ($v\\cdot v'\\sim -m_b/\\Lambda$). We obtain the evolution equations and sum rules ...
Color-kinematic duality for form factors
International Nuclear Information System (INIS)
Boels, Rutger H.; Kniehl, Bernd A.; Tarasov, Oleg V.; Yang, Gang
2012-12-01
Recently a powerful duality between color and kinematics has been proposed for integrands of scattering amplitudes in quite general gauge theories. In this paper the duality proposal is extended to the more general class of gauge theory observables formed by form factors. After a discussion of the general setup the existence of the duality is verified in two and three loop examples in four dimensional maximally supersymmetric Yang-Mills theory which involve the stress energy tensor multiplet. In these cases the duality reproduces known results in a particularly transparent and uniform way. As a non-trivial application we obtain a very simple form of the integrand of the four-loop two-point (Sudakov) form factor which passes a large set of unitarity cut checks.
Color-kinematic duality for form factors
Energy Technology Data Exchange (ETDEWEB)
Boels, Rutger H.; Kniehl, Bernd A.; Tarasov, Oleg V.; Yang, Gang [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik
2012-12-15
Recently a powerful duality between color and kinematics has been proposed for integrands of scattering amplitudes in quite general gauge theories. In this paper the duality proposal is extended to the more general class of gauge theory observables formed by form factors. After a discussion of the general setup the existence of the duality is verified in two and three loop examples in four dimensional maximally supersymmetric Yang-Mills theory which involve the stress energy tensor multiplet. In these cases the duality reproduces known results in a particularly transparent and uniform way. As a non-trivial application we obtain a very simple form of the integrand of the four-loop two-point (Sudakov) form factor which passes a large set of unitarity cut checks.
Hadronic form factors in kaon photoproduction
Energy Technology Data Exchange (ETDEWEB)
Syukurilla, L., E-mail: tmart@fisika.ui.ac.id; Mart, T., E-mail: tmart@fisika.ui.ac.id [Department Fisika, FMIPA, Universitas Indonesia, Depok, 164242 (Indonesia)
2014-09-25
We have revisited the effect of hadronic form factors in kaon photoproduction process by utilizing an isobaric model developed for kaon photoproduction off the proton. The model is able to reproduce the available experimental data nicely as well as to reveal the origin of the second peak in the total cross section, which was the main source of confusion for decades. Different from our previous study, in the present work we explore the possibility of using different hadronic form factors in each of the KΛN vertices. The use of different hadronic form factors, e.g. dipole, Gaussian, and generalized dipole, has been found to produce a more flexible isobar model, which can provide a significant improvement in the model.
Paramagnetic form factors from itinerant electron theory
International Nuclear Information System (INIS)
Cooke, J.F.; Liu, S.H.; Liu, A.J.
1985-01-01
Elastic neutron scattering experiments performed over the past two decades have provided accurate information about the magnetic form factors of paramagnetic transition metals. These measurements have traditionally been analyzed in terms of an atomic-like theory. There are, however, some cases where this procedure does not work, and there remains the overall conceptual problem of using an atomistic theory for systems where the unpaired-spin electrons are itinerant. We have recently developed computer codes for efficiently evaluating the induced magnetic form factors of fcc and bcc itinerant electron paramagnets. Results for the orbital and spin contributions have been obtained for Cr, Nb, V, Mo, Pd, and Rh based on local density bands. By using calculated spin enhancement parameters, we find reasonable agreement between theory and neutron form factor data. In addition, these zero parameter calculations yield predictions for the bulk susceptibility on an absolute scale which are in reasonable agreement with experiment in all treated cases except palladium
Weak form factors of beauty baryons
International Nuclear Information System (INIS)
Ivanov, M.A.; Lyubovitskij, V.E.
1992-01-01
Full analysis of semileptonic decays of beauty baryons with J p =1/2 2 and J p =3/2 2 into charmed ones within the Quark Confinement Model is reported. Weak form factors and decay rates are calculated. Also the heavy quark limit m Q →∞ (Isgur-Wise symmetry) is examined. The weak heavy-baryon form factors in the Isgur-Wise limit and 1/m Q -corrections to them are computered. The Ademollo-Gatto theorem is spin-flavour symmetry of heavy quarks is checked. 33 refs.; 1 fig.; 9 tabs
Nucleon electromagnetic form factors with Wilson fermions
International Nuclear Information System (INIS)
Goeckeler, M.; Haegler, P.; Horsley, R.
2007-10-01
The nucleon electromagnetic form factors continue to be of major interest for experimentalists and phenomenologists alike. They provide important insights into the structure of nuclear matter. For a range of interesting momenta they can be calculated on the lattice. The limiting factor continues to be the value of the pion mass. We present the latest results of the QCDSF collaboration using gauge configurations with two dynamical, non-perturbatively improved Wilson fermions at pion masses as low as 350 MeV. (orig.)
Nucleon electromagnetic form factors with Wilson fermions
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)
2007-10-15
The nucleon electromagnetic form factors continue to be of major interest for experimentalists and phenomenologists alike. They provide important insights into the structure of nuclear matter. For a range of interesting momenta they can be calculated on the lattice. The limiting factor continues to be the value of the pion mass. We present the latest results of the QCDSF collaboration using gauge configurations with two dynamical, non-perturbatively improved Wilson fermions at pion masses as low as 350 MeV. (orig.)
The impact of s- anti s asymmetry on the strange electromagnetic form factor
Energy Technology Data Exchange (ETDEWEB)
Ghasempour Nesheli, Ali [Islamic Azad University, Department of Physics, Shiraz Branch, Shiraz (Iran, Islamic Republic of)
2016-09-15
The existence of the strange quark asymmetry in the nucleon sea has been indicated by both the experimental and theoretical analyses. Although it is well known that the s- anti s asymmetry is important for some processes in high-energy hadron collisions, it has also been indicated that it can be related to the strange Dirac form factor F{sub 1}{sup s}. In this work, we have studied the impact of s- anti s asymmetry and its uncertainty from various modern parton distribution functions (PDFs) on F{sub 1} {sup s} and compared the obtained results with the available experimental information. As a result, we found that the uncertainty in F{sub 1}{sup s}(t) due to the s(x) - anti s (x) distribution is rather large so that it dominates the model uncertainty at all values of the squared momentum transfer t. However, taking into account the uncertainties, the theoretical predictions of F{sub 1}{sup s}(t) are fully compatible with the estimate extracted from experiment. We concluded that the future accurate experimental data of the strange Dirac form factor might be used to put direct constraints on the strange content of the proton and reduce its uncertainty that has always been a challenge. (orig.)
Chiral analysis of baryon form factors
Energy Technology Data Exchange (ETDEWEB)
Gail, T.A.
2007-11-08
This work presents an extensive theoretical investigation of the structure of the nucleon within the standard model of elementary particle physics. In particular, the long range contributions to a number of various form factors parametrizing the interactions of the nucleon with an electromagnetic probe are calculated. The theoretical framework for those calculations is chiral perturbation theory, the exact low energy limit of Quantum Chromo Dynamics, which describes such long range contributions in terms of a pion-cloud. In this theory, a nonrelativistic leading one loop order calculation of the form factors parametrizing the vector transition of a nucleon to its lowest lying resonance, the {delta}, a covariant calculation of the isovector and isoscalar vector form factors of the nucleon at next to leading one loop order and a covariant calculation of the isoscalar and isovector generalized vector form factors of the nucleon at leading one loop order are performed. In order to perform consistent loop calculations in the covariant formulation of chiral perturbation theory an appropriate renormalization scheme is defined in this work. All theoretical predictions are compared to phenomenology and results from lattice QCD simulations. These comparisons allow for a determination of the low energy constants of the theory. Furthermore, the possibility of chiral extrapolation, i.e. the extrapolation of lattice data from simulations at large pion masses down to the small physical pion mass is studied in detail. Statistical as well as systematic uncertainties are estimated for all results throughout this work. (orig.)
Simple parametrization of nucleon form factors
International Nuclear Information System (INIS)
Kelly, J.J.
2004-01-01
This Brief Report provides simple parametrizations of the nucleon electromagnetic form factors using functions of Q 2 that are consistent with dimensional scaling at high Q 2 . Good fits require only four parameters each for G Ep , G Mp , and G Mn and only two for G En
From form factors to generalized parton distributions
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus
2013-06-15
I present an extraction of generalized parton distributions from selected data on the electromagnetic nucleon form factors. The extracted distributions can in particular be used to quantify the contribution to the proton spin from the total angular momentum carried by valence quarks, as well as their transverse spatial distribution inside the proton.
Form factor expansion for thermal correlators
Pozsgay, B.; Takács, G.
2010-01-01
We consider finite temperature correlation functions in massive integrable quantum field theory. Using a regularization by putting the system in finite volume, we develop a novel approach (based on multi-dimensional residues) to the form factor expansion for thermal correlators. The first few terms
Electron form factors of deformable nuclei
International Nuclear Information System (INIS)
Tartakovskii, V.K.; Isupov, V.Yu.
1988-01-01
Using the smallness of the deformation parameter of the nucleus, we obtain simple explicit expressions for the form factors of electroexcitation of the low-lying rotation-vibration states of light, deformable, even-even nuclei. The expressions satisfactorily describe the experimental data on the excitation of collective nuclear states by the inelastic scattering of fast electrons
Baryon electromagnetic form factors at BESIII
Directory of Open Access Journals (Sweden)
Dbeyssi Alaa
2017-01-01
Full Text Available Electromagnetic form factors are fundamental quantities which parameterize the electric and magnetic structure of hadrons. This contribution reports on the measurements of baryon electromagnetic form factors at the BESIII experiment in Beijing. The Beijing e+e− collider BEPCII is a double-ring symmetric collider running at √s between 2.0 and 4.6 GeV. Baryon electromagnetic form factors can be measured at BESIII in direct e+e−-annihilation and in initial state radiation processes. Based on the data collected by the BESIII detector at 12 center of mass energies between 2.23 and 3.67 GeV, the e+e− → p̄p cross section and the time-like proton form factor is measured. Preliminary results from the analysis of the initial state radiation process e+e− → p̄pγ using a data set of 7.408 fb−1 collected at center-of-mass energies between 3.773 and 4.6 GeV, are also presented. The cross section for e+e−→Λ¯Λ${e^ + }{e^ - } \\to \\bar \\Lambda \\Lambda $ is measured based on 40.5 pb−1 data collected at 4 energy points from the threshold up to 3.08 GeV. Preliminary results on the total cross section and the Λ effective form factor are shown. Ongoing analysis based on the high luminosity energy scan from 2015 and from radiative return at different √s are also described.
New symmetries for the Dirac equation
International Nuclear Information System (INIS)
Linhares, C.A.; Mignaco, J.A.
1990-01-01
The Dirac equation in four dimension is studied describing fermions, both as 4 x 4 matrices and differential forms. It is discussed in both formalisms its properties under transformations of the group SU(4). (A.C.A.S.) [pt
DIRAC distributed secure framework
International Nuclear Information System (INIS)
Casajus, A; Graciani, R
2010-01-01
DIRAC, the LHCb community Grid solution, provides access to a vast amount of computing and storage resources to a large number of users. In DIRAC users are organized in groups with different needs and permissions. In order to ensure that only allowed users can access the resources and to enforce that there are no abuses, security is mandatory. All DIRAC services and clients use secure connections that are authenticated using certificates and grid proxies. Once a client has been authenticated, authorization rules are applied to the requested action based on the presented credentials. These authorization rules and the list of users and groups are centrally managed in the DIRAC Configuration Service. Users submit jobs to DIRAC using their local credentials. From then on, DIRAC has to interact with different Grid services on behalf of this user. DIRAC has a proxy management service where users upload short-lived proxies to be used when DIRAC needs to act on behalf of them. Long duration proxies are uploaded by users to a MyProxy service, and DIRAC retrieves new short delegated proxies when necessary. This contribution discusses the details of the implementation of this security infrastructure in DIRAC.
International Nuclear Information System (INIS)
Casajus Ramo, A; Graciani Diaz, R; Tsaregorodtsev, A
2012-01-01
The DIRAC framework for distributed computing has been designed as a flexible and modular solution that can be adapted to the requirements of any community. Users interact with DIRAC via command line, using the web portal or accessing resources via the DIRAC python API. The current DIRAC API requires users to use a python version valid for DIRAC. Some communities have developed their own software solutions for handling their specific workload, and would like to use DIRAC as their back-end to access distributed computing resources easily. Many of these solutions are not coded in python or depend on a specific python version. To solve this gap DIRAC provides a new language agnostic API that any software solution can use. This new API has been designed following the RESTful principles. Any language with libraries to issue standard HTTP queries may use it. GSI proxies can still be used to authenticate against the API services. However GSI proxies are not a widely adopted standard. The new DIRAC API also allows clients to use OAuth for delegating the user credentials to a third party solution. These delegated credentials allow the third party software to query to DIRAC on behalf of the users. This new API will further expand the possibilities communities have to integrate DIRAC into their distributed computing models.
Perturbative QCD and electromagnetic form factors
International Nuclear Information System (INIS)
Carlson, C.E.; Gross, F.
1987-01-01
We calculate nucleon magnetic form factors using perturbative QCD for several distribution amplitudes including a general one given in terms of Appell polynomials. We find that the magnitude and sign of both nucleon magnetic form factors can be explained within perturbative QCD. The observed normalization of G/sub Mp/ requires that the distribution amplitude be broader than its superhigh momentum transfer limit, and the G/sub Mn//G/sub Mp/ data may require the distribution amplitude to be asymmetric, in accord with distribution amplitudes derived from QCD sum rules. Some speculation as to how an asymmetric distribution amplitude can come about is offered. Finally, we show that the soft contributions corresponding to the particular distribution amplitudes we use need not be bigger than the data. 16 refs., 6 figs
Nucleon electromagnetic form factors from lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Koutsou, G.; Negele, J. W.; Tsapalis, A.
2006-01-01
We evaluate the isovector nucleon electromagnetic form factors in quenched and unquenched QCD on the lattice using Wilson fermions. In the quenched theory we use a lattice of spatial size 3 fm at β=6.0 enabling us to reach low momentum transfers and a lowest pion mass of about 400 MeV. In the unquenched theory we use two degenerate flavors of dynamical Wilson fermions on a lattice of spatial size 1.9 fm at β=5.6 and lowest pion mass of about 380 MeV enabling comparison with the results obtained in the quenched theory. that unquenching effects are small for the pion masses considered in this work. We compare our lattice results to the isovector part of the experimentally measured form factors
Nucleon form factors. Probing the chiral limit
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Physik-Dept.; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)
2006-10-15
The electromagnetic form factors provide important hints for the internal structure of the nucleon and continue to be of major interest for experimentalists. For an intermediate range of momentum transfers the form factors can be calculated on the lattice. However, reliability of the results is limited by systematic errors due to the required extrapolation to physical quark masses. Chiral effective field theories predict a rather strong quark mass dependence in a range which was yet unaccessible for lattice simulations. We give an update on recent results from the QCDSF collaboration using gauge configurations with Nf=2, non-perturbatively O(a)-improved Wilson fermions at very small quark masses down to 340 MeV pion mass, where we start to probe the relevant quark mass region. (orig.)
Form factors of heavy mesons in QCD
International Nuclear Information System (INIS)
Shifman, M.A.; Vysotsky, M.I.
1980-01-01
Logarithmic corrections to form factors of mesons built from heavy quarks are dirived in the framework of quantum chromodynamics. The reactions e + e - → etasub(c)γ and H → J/PSIγ are considered as an example. A novel feature as compared to the well studied problem of the pion form factor is the existence of the transformations between the quark-antiquark state c anti c and the gluonic one. O(αsub(s)) corrections are calculated exactly. An infinite series of the leading logarithmic terms is summed up with the help of the operator technique. Apart from already known results for quark operators some new results referring to gluon operators and their mixing with the quark ones are used. Two alternative derivations of the multiplicatively renormalizable operators are given. The first one reduces to a direct computation of the mixing matrix and its diagonalization, the second derivation is based on conformal symmetry considerations
Nucleon form factors. Probing the chiral limit
International Nuclear Information System (INIS)
Goeckeler, M.; Haegler, P.; Horsley, R.
2006-10-01
The electromagnetic form factors provide important hints for the internal structure of the nucleon and continue to be of major interest for experimentalists. For an intermediate range of momentum transfers the form factors can be calculated on the lattice. However, reliability of the results is limited by systematic errors due to the required extrapolation to physical quark masses. Chiral effective field theories predict a rather strong quark mass dependence in a range which was yet unaccessible for lattice simulations. We give an update on recent results from the QCDSF collaboration using gauge configurations with Nf=2, non-perturbatively O(a)-improved Wilson fermions at very small quark masses down to 340 MeV pion mass, where we start to probe the relevant quark mass region. (orig.)
Elastic form factors at higher CEBAF energies
Energy Technology Data Exchange (ETDEWEB)
Petratos, G.G. [Kent State Univ., OH (United States)
1994-04-01
The prospects for elastic scattering from few body systems with higher beam energies at CEBAF is presented. The deuteron and{sup 3}He elastic structure functions A(Q{sup 2}) can be measured at sufficiently high momentum transfers to study the transition between the conventional meson-nucleon and the constituent quark-gluon descriptions. Possible improvements in the proton magnetic form factor data are also presented.
Baryon form factors in chiral perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Kubis, B.; Meissner, U.G. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Kernphysik
2001-01-01
We analyze the electromagnetic form factors of the ground state baryon octet to fourth order in relativistic baryon chiral perturbation theory. Predictions for the {sigma}{sup -} charge radius and the {lambda}-{sigma}{sup 0} transition moment are found to be in excellent agreement with the available experimental information. Furthermore, the convergence behavior of the hyperon charge radii is shown to be more than satisfactory. (orig.)
Electromagnetic form factors of composite systems
International Nuclear Information System (INIS)
Nowak, E.J.
1978-01-01
Electromagnetic form factors are examined for a spin-zero, two-body composite system with emphasis on the case of small momentum transfer and/or deep (relativistic) binding. Perturbation theory calculations are first performed using spin-zero and then spin-one-half constituents. A dispersion representation of the bound-state vertex function is conjectured first for scalar and then for fermion constituents. Then a relativistic effective range approximation (RERA) is developed for each case and applied to the calculation of the electromagnetic form factor. The approach is applied to the study of the charge radii of the K 0 and K + mesons. The K/sub l3/ form factor is calculated in the fermion constituent RERA model, and restrictions are imposed on the model parameters from available experimental data. With these restrictions the limits 0.24fm less than or equal to √[abs. value ( 2 >/sub K 0 /)] less than or equal to = 0.36fm and 0.66fm less than or equal to = √( 2 >/sub K + /) less than or equal to 0.79fm are obtained for the kaon charge radii, and -.22 less than or equal to xi less than or equal to -.13 is found for the ratio of the neutral to charged kaon charge radius squared
Photoconductivity in Dirac materials
International Nuclear Information System (INIS)
Shao, J. M.; Yang, G. W.
2015-01-01
Two-dimensional (2D) Dirac materials including graphene and the surface of a three-dimensional (3D) topological insulator, and 3D Dirac materials including 3D Dirac semimetal and Weyl semimetal have attracted great attention due to their linear Dirac nodes and exotic properties. Here, we use the Fermi’s golden rule and Boltzmann equation within the relaxation time approximation to study and compare the photoconductivity of Dirac materials under different far- or mid-infrared irradiation. Theoretical results show that the photoconductivity exhibits the anisotropic property under the polarized irradiation, but the anisotropic strength is different between 2D and 3D Dirac materials. The photoconductivity depends strongly on the relaxation time for different scattering mechanism, just like the dark conductivity
Superconductivity in doped Dirac semimetals
Hashimoto, Tatsuki; Kobayashi, Shingo; Tanaka, Yukio; Sato, Masatoshi
2016-07-01
We theoretically study intrinsic superconductivity in doped Dirac semimetals. Dirac semimetals host bulk Dirac points, which are formed by doubly degenerate bands, so the Hamiltonian is described by a 4 ×4 matrix and six types of k -independent pair potentials are allowed by the Fermi-Dirac statistics. We show that the unique spin-orbit coupling leads to characteristic superconducting gap structures and d vectors on the Fermi surface and the electron-electron interaction between intra and interorbitals gives a novel phase diagram of superconductivity. It is found that when the interorbital attraction is dominant, an unconventional superconducting state with point nodes appears. To verify the experimental signature of possible superconducting states, we calculate the temperature dependence of bulk physical properties such as electronic specific heat and spin susceptibility and surface state. In the unconventional superconducting phase, either dispersive or flat Andreev bound states appear between point nodes, which leads to double peaks or a single peak in the surface density of states, respectively. As a result, possible superconducting states can be distinguished by combining bulk and surface measurements.
Electric Form Factor of the Neutron
Feuerbach, Robert
2007-10-01
Recent polarization-based precision measurements of the nucleons' elastic electric form factors have led to surprising results. The measurement of the ratio of the proton's electromagnetic form factors, μpGE^p/GM^p, was found to drop nearly linearly with Q^2 out to at least 5 GeV^2, inconsistent with the older Rosenbluth-type experiments. A recent measurement of GE^n, the neutron's electric form-factor saw GE^n does not fall off as quickly as commonly expected up to Q^2 1.5 GeV^2. Extending this study, a precision measurement of GE^n up to Q^2=3.5 GeV^2 was completed in Hall A at Jefferson Lab. The ratio GE^n/GM^n was measured through the beam-target asymmetry A of electrons quasi-elastically scattered off polarized neutrons in the reaction ^3He(e,e' n). The experiment took full advantage of the electron beam, recent target developments, as well as two detectors new to Jefferson Lab. The measurement used the accelerator's 100% duty-cycle high-polarization (typically 84%) electron beam and a new, hybrid optically-pumped polarized ^3He target which achieved in-beam polarizations in excess of 50%. A medium acceptance (80msr) open-geometry magnetic spectrometer (BigBite) detected the scattered electron, while a geometrically matched neutron detector observed the struck neutron. Preliminary results from this measurement will be discussed and compared to modern calculations of GE^n.
Dirac, Weyl, Majorana, a review
International Nuclear Information System (INIS)
Uschersohn, J.
1982-05-01
The Dirac equation and the properties of Dirac matrices are presented and discussed. A large number of representations of the Dirac matrices is identified. Special emphasis is put on aspects rarely treated or neglected in textbooks
Form factors and excitations of topological solitons
International Nuclear Information System (INIS)
Weir, David J.; Rajantie, Arttu
2011-01-01
We show how the interaction properties of topological solitons in quantum field theory can be calculated with lattice Monte Carlo simulations. Topologically nontrivial field configurations are key to understanding the nature of the QCD vacuum through, for example, the dual superconductor picture. Techniques that we have developed to understand the excitations and form factors of topological solitons, such as kinks and 't Hooft-Polyakov monopoles, should be equally applicable to chromoelectric flux tubes. We review our results for simple topological solitons and their agreement with exact results, then discuss our progress towards studying objects of interest to high energy physics.
Recent Studies of Nucleon Electromagnetic Form Factors
International Nuclear Information System (INIS)
Gilad, Shalev
2010-01-01
The electromagnetic form factors of nucleons are fundamental quantities in nucleon structure. As such, they have been studied extensively both theoretically and experimentally. Significant progress has been made with new measurements at Jlab, MAMI and MIT-Bates, with emphases on expanding the momentum-transfer range and on higher precision. In this paper, we describe the status of this field and present new results from measurements at both low and high momentum transfers. We also compare the experimental data to model predictions, and mention possible implications of the new results to other fields.
Medium modifications of nucleon electromagnetic form factors
Energy Technology Data Exchange (ETDEWEB)
Horikawa, T. [Department of Physics, School of Science, Tokai University, Hiratsuka-shi, Kanagawa 259-1292 (Japan); Bentz, W. [Department of Physics, School of Science, Tokai University, Hiratsuka-shi, Kanagawa 259-1292 (Japan)]. E-mail: bentz@keyaki.cc.u-tokai.ac.jp
2005-11-28
We use the Nambu-Jona-Lasinio model as an effective quark theory to investigate the medium modifications of the nucleon electromagnetic form factors. By using the equation of state of nuclear matter derived in this model, we discuss the results based on the naive quark-scalar diquark picture, the effects of finite diquark size, and the meson cloud around the constituent quarks. We apply this description to the longitudinal response function for quasielastic electron scattering. RPA correlations, based on the nucleon-nucleon interaction derived in the same model, are also taken into account in the calculation of the response function.
Neutron electric form factor via recoil polarimetry
International Nuclear Information System (INIS)
Richard Madey; Andrei Semenov; Simon Taylor; Aram Aghalaryan; Erick Crouse; Glen MacLachlan; Bradley Plaster; Shigeyuki Tajima; William Tireman; Chenyu Yan; Abdellah Ahmidouch; Brian Anderson; Razmik Asaturyan; O. Baker; Alan Baldwin; Herbert Breuer; Roger Carlini; Michael Christy; Steve Churchwell; Leon Cole; Samuel Danagoulian; Donal Day; Mostafa Elaasar; Rolf Ent; Manouchehr Farkhondeh; Howard Fenker; John Finn; Liping Gan; Kenneth Garrow; Paul Gueye; Calvin Howell; Bitao Hu; Mark Jones; James Kelly; Cynthia Keppel; Mahbubul Khandaker; Wooyoung Kim; Stanley Kowalski; Allison Lung; David Mack; D. Manley; Pete Markowitz; Joseph Mitchell; Hamlet Mkrtchyan; Allena Opper; Charles Perdrisat; Vina Punjabi; Brian Raue; Tilmann Reichelt; Joerg Reinhold; Julie Roche; Yoshinori Sato; Wonick Seo; Neven Simicevic; Gregory Smith; Samuel Stepanyan; Vardan Tadevosyan; Liguang Tang; Paul Ulmer; William Vulcan; John Watson; Steven Wells; Frank Wesselmann; Stephen Wood; Chen Yan; Seunghoon Yang; Lulin Yuan; Wei-Ming Zhang; Hong Guo Zhu; Xiaofeng Zhu
2003-01-01
The ratio of the electric to the magnetic form factor of the neutron, G En /G Mn , was measured via recoil polarimetry from the quasielastic d((pol-e),e(prime)(pol-n)p) reaction at three values of Q 2 [viz., 0.45, 1.15 and 1.47 (GeV/c) 2 ] in Hall C of the Thomas Jefferson National Accelerator Facility. Preliminary data indicate that G En follows the Galster parameterization up to Q 2 = 1.15 (GeV/c) 2 and appears to rise above the Galster parameterization at Q 2 = 1.47 (GeV/c) 2
Axial nucleon form factors from lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Brinet, M.; Carbonell, J.; Harraud, P. A.; Papinutto, M.; Constantinou, M.; Guichon, P.; Jansen, K.; Korzec, T.
2011-01-01
We present results on the nucleon axial form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1 fm and L=2.8 fm. Cut-off effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm. The nucleon axial charge is obtained in the continuum limit and chirally extrapolated to the physical pion mass enabling comparison with experiment.
Foster, Tobias
2011-09-01
A novel analytical and continuous density distribution function with a widely variable shape is reported and used to derive an analytical scattering form factor that allows us to universally describe the scattering from particles with the radial density profile of homogeneous spheres, shells, or core-shell particles. Composed by the sum of two Fermi-Dirac distribution functions, the shape of the density profile can be altered continuously from step-like via Gaussian-like or parabolic to asymptotically hyperbolic by varying a single "shape parameter", d. Using this density profile, the scattering form factor can be calculated numerically. An analytical form factor can be derived using an approximate expression for the original Fermi-Dirac distribution function. This approximation is accurate for sufficiently small rescaled shape parameters, d/R (R being the particle radius), up to values of d/R ≈ 0.1, and thus captures step-like, Gaussian-like, and parabolic as well as asymptotically hyperbolic profile shapes. It is expected that this form factor is particularly useful in a model-dependent analysis of small-angle scattering data since the applied continuous and analytical function for the particle density profile can be compared directly with the density profile extracted from the data by model-free approaches like the generalized inverse Fourier transform method. © 2011 American Chemical Society
New exact solutions of the Dirac equation
International Nuclear Information System (INIS)
Bagrov, V.G.; Gitman, D.M.; Zadorozhnyj, V.N.; Lavrov, P.M.; Shapovalov, V.N.
1980-01-01
Search for new exact solutions of the Dirac and Klein-Gordon equations are in progress. Considered are general properties of the Dirac equation solutions for an electron in a purely magnetic field, in combination with a longitudinal magnetic and transverse electric fields. New solutions for the equations of charge motion in an electromagnetic field of axial symmetry and in a nonstationary field of a special form have been found for potentials selected concretely
Form factors of heavy mesons in QCD
Energy Technology Data Exchange (ETDEWEB)
Shifman, M A; Vysotsky, M I [Moskovskii Inst. Theoreticheskoj i Ehksperimental' noj Fiziki (USSR)
1981-08-10
We discuss logarithmic corrections to form factors of mesons built from heavy quarks. The reactions e/sup +/e/sup -/ ..-->.. etasub(c)..gamma.. and H ..-->.. J/psi..gamma.. are considered as an example. A novel feature as compared to the well-studied problem of the pion form factor is the existence of transitions between the quark-antiquark state canti c and the gluonic one. O(..cap alpha..sub(s)) corrections are calculated exactly. An infinite series of the leading logarithmic terms (..cap alpha..sub(s)ln(Q/sup 2//m/sup 2/sub(c)))sup(n) is summed up with the help of the operator technique. Apart from results already known for quark operators, we use some new results referring to gluon operator and their mixing with those made from quarks. Two alternative derivations of the multiplicatively renormalizable operators are given. The first one reduces to a direct computation of the mixing matrix and its diagonalization, the second is based on conformal symmetry considerations.
Helium Compton Form Factor Measurements at CLAS
Energy Technology Data Exchange (ETDEWEB)
Voutier, Eric J.-M. [Laboratoire de Physique Subatomique et Cosmologie
2013-07-01
The distribution of the parton content of nuclei, as encoded via the generalized parton distributions (GPDs), can be accessed via the deeply virtual Compton scattering (DVCS) process contributing to the cross section for leptoproduction of real photons. Similarly to the scattering of light by a material, DVCS provides information about the dynamics and the spatial structure of hadrons. The sensitivity of this process to the lepton beam polarization allows to single-out the DVCS amplitude in terms of Compton form factors that contain GPDs information. The beam spin asymmetry of the $^4$He($\\vec {\\mathrm e}$,e$' \\gamma ^4$He) process was measured in the experimental Hall B of the Jefferson Laboratory to extract the real and imaginary parts of the twist-2 Compton form factor of the $^4$He nucleus. The experimental results reported here demonstrate the relevance of this method for such a goal, and suggest the dominance of the Bethe-Heitler amplitude to the unpolarized process in the kinematic range explored by the experiment.
Nucleon Form Factors Using Spin Degrees of Freedom
International Nuclear Information System (INIS)
Jones, Mark
2002-01-01
An overview of recent measurements of the neutron and proton electromagnetic form factors from double polarization experiments. Spin observables are sensitive to the product of nucleon form factor which allows access to the small nucleon electric form factors
Indian Academy of Sciences (India)
IAS Admin
Pauli exclusion principle, Fermi–. Dirac statistics, identical and in- distinguishable particles, Fermi gas. Fermi–Dirac Statistics. Derivation and Consequences. S Chaturvedi and Shyamal Biswas. (left) Subhash Chaturvedi is at University of. Hyderabad. His current research interests include phase space descriptions.
Dimock, J.
2010-01-01
We give an alternate definition of the free Dirac field featuring an explicit construction of the Dirac sea. The treatment employs a semi-infinite wedge product of Hilbert spaces. We also show that the construction is equivalent to the standard Fock space construction.
Indian Academy of Sciences (India)
IAS Admin
We present an account of the work of Niels Bohr and Paul Dirac, their interactions and personal- ities. 1. Introduction. In this essay I would like to convey to my readers some- thing about the personalities and work of Niels Bohr and Paul Dirac, juxtaposed against one another. Let me hope that the portraits I will paint of these ...
International Nuclear Information System (INIS)
Rodrigues, R. de Lima
2007-01-01
In the present work we obtain a new representation for the Dirac oscillator based on the Clifford algebra C 7. The symmetry breaking and the energy eigenvalues for our model of the Dirac oscillator are studied in the non-relativistic limit. (author)
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education. P A M Dirac. Articles written in Resonance – Journal of Science Education. Volume 8 Issue 8 August 2003 pp 102-110 Classics. XI. The Relation between Mathematics and Physics · P A M Dirac · More Details Fulltext PDF ...
Stagni, F.; McNab, A.; Luzzi, C.; Krzemien, W.; Consortium, DIRAC
2017-10-01
In the last few years, new types of computing models, such as IAAS (Infrastructure as a Service) and IAAC (Infrastructure as a Client), gained popularity. New resources may come as part of pledged resources, while others are in the form of opportunistic ones. Most but not all of these new infrastructures are based on virtualization techniques. In addition, some of them, present opportunities for multi-processor computing slots to the users. Virtual Organizations are therefore facing heterogeneity of the available resources and the use of an Interware software like DIRAC to provide the transparent, uniform interface has become essential. The transparent access to the underlying resources is realized by implementing the pilot model. DIRAC’s newest generation of generic pilots (the so-called Pilots 2.0) are the “pilots for all the skies”, and have been successfully released in production more than a year ago. They use a plugin mechanism that makes them easily adaptable. Pilots 2.0 have been used for fetching and running jobs on every type of resource, being it a Worker Node (WN) behind a CREAM/ARC/HTCondor/DIRAC Computing element, a Virtual Machine running on IaaC infrastructures like Vac or BOINC, on IaaS cloud resources managed by Vcycle, the LHCb High Level Trigger farm nodes, and any type of opportunistic computing resource. Make a machine a “Pilot Machine”, and all diversities between them will disappear. This contribution describes how pilots are made suitable for different resources, and the recent steps taken towards a fully unified framework, including monitoring. Also, the cases of multi-processor computing slots either on real or virtual machines, with the whole node or a partition of it, is discussed.
Three-dimensional periodic dielectric structures having photonic Dirac points
Bravo-Abad, Jorge; Joannopoulos, John D.; Soljacic, Marin
2015-06-02
The dielectric, three-dimensional photonic materials disclosed herein feature Dirac-like dispersion in quasi-two-dimensional systems. Embodiments include a face-centered cubic (fcc) structure formed by alternating layers of dielectric rods and dielectric slabs patterned with holes on respective triangular lattices. This fcc structure also includes a defect layer, which may comprise either dielectric rods or a dielectric slab with patterned with holes. This defect layer introduces Dirac cone dispersion into the fcc structure's photonic band structure. Examples of these fcc structures enable enhancement of the spontaneous emission coupling efficiency (the .beta.-factor) over large areas, contrary to the conventional wisdom that the .beta.-factor degrades as the system's size increases. These results enable large-area, low-threshold lasers; single-photon sources; quantum information processing devices; and energy harvesting systems.
Three-dimensional periodic dielectric structures having photonic Dirac points
Energy Technology Data Exchange (ETDEWEB)
Bravo-Abad, Jorge; Joannopoulos, John D.; Soljacic, Marin
2015-06-02
The dielectric, three-dimensional photonic materials disclosed herein feature Dirac-like dispersion in quasi-two-dimensional systems. Embodiments include a face-centered cubic (fcc) structure formed by alternating layers of dielectric rods and dielectric slabs patterned with holes on respective triangular lattices. This fcc structure also includes a defect layer, which may comprise either dielectric rods or a dielectric slab with patterned with holes. This defect layer introduces Dirac cone dispersion into the fcc structure's photonic band structure. Examples of these fcc structures enable enhancement of the spontaneous emission coupling efficiency (the .beta.-factor) over large areas, contrary to the conventional wisdom that the .beta.-factor degrades as the system's size increases. These results enable large-area, low-threshold lasers; single-photon sources; quantum information processing devices; and energy harvesting systems.
B-decay form factors from QCD sum rules
International Nuclear Information System (INIS)
Offen, Nils
2008-01-01
In the Standard Model of particle physics there is only one source of CP-violation. Namely, a single complex phase in the unitary 3 x 3 CKM-Matrix governing flavor transitions in the weak interaction. The unitarity is usually visualized by a triangle in the complex ρ - η-plane. Therefore testing this framework comes down to measuring weak decays, relating observables to sides and angles of this so called Unitarity Triangle(UT). Particular interest in this respect is payed to decays of mesons containing a heavy b-quark, giving the opportunity to alone determine all parameters of the UT. Doing this is far from easy. Besides tedious experimental measurements the theoretical calculations are plagued by hadronic quantities which cannot be determined by perturbation theory. In this work several of these quantities so called form factors are computed using the well known method of light cone sum rules(LCSR). Two different setups have been used. One, established in this work, utilizing a correlation function with an on-shell B-Meson and one following the traditional calculation by taking the light meson on-shell. Both using light cone expansion in the respective on-shell mesons distribution amplitudes. While the first approach allows to calculate a whole bunch of phenomenologically interesting quantities by just changing Dirac-structures of the relevant currents it has the drawback that it does not have access to the well developed twist expansion of the latter. To incorporate higher Fock-state contributions the first models for three-particle distribution amplitudes of the B-Meson have been derived. α s -corrections remain out of the scope of this work. Nevertheless does a comparison with more sophisticated methods show an encouraging numerical agreement. In the second setup all known corrections especially the never verified α s -corrections to Twist three terms have been recalculated and a competitive result for the CKM-matrixelement vertical stroke V ub vertical
Halogenated arsenenes as Dirac materials
International Nuclear Information System (INIS)
Tang, Wencheng; Sun, Minglei; Ren, Qingqiang; Wang, Sake; Yu, Jin
2016-01-01
Highlights: • We have revealed the presence of Dirac cone in fully-halogenated arsenene compounds. • All fully-halogenated arsenene except As_2I_2 would spontaneously form and stable in defending the thermal fluctuation in room temperature. - Abstract: Arsenene is the graphene-like arsenic nanosheet, which has been predicted very recently [S. Zhang, Z. Yan, Y. Li, Z. Chen, and H. Zeng, Angewandte Chemie, 127 (2015) 3155–3158]. Using first-principles calculations, we systematically investigate the structures and electronic properties of fully-halogenated arsenenes. Formation energy analysis reveals that all the fully-halogenated arsenenes except iodinated arsenene are energetically favorable and could be synthesized. We have revealed the presence of Dirac cone in fully-halogenated arsenene compounds. They may have great potential applications in next generation of high-performance devices.
Three Dimensional Dirac Semimetals
Zaheer, Saad
2014-03-01
Dirac points on the Fermi surface of two dimensional graphene are responsible for its unique electronic behavior. One can ask whether any three dimensional materials support similar pseudorelativistic physics in their bulk electronic spectra. This possibility has been investigated theoretically and is now supported by two successful experimental demonstrations reported during the last year. In this talk, I will summarize the various ways in which Dirac semimetals can be realized in three dimensions with primary focus on a specific theory developed on the basis of representations of crystal spacegroups. A three dimensional Dirac (Weyl) semimetal can appear in the presence (absence) of inversion symmetry by tuning parameters to the phase boundary separating a bulk insulating and a topological insulating phase. More generally, we find that specific rules governing crystal symmetry representations of electrons with spin lead to robust Dirac points at high symmetry points in the Brillouin zone. Combining these rules with microscopic considerations identifies six candidate Dirac semimetals. Another method towards engineering Dirac semimetals involves combining crystal symmetry and band inversion. Several candidate materials have been proposed utilizing this mechanism and one of the candidates has been successfully demonstrated as a Dirac semimetal in two independent experiments. Work carried out in collaboration with: Julia A. Steinberg, Steve M. Young, J.C.Y. Teo, C.L. Kane, E.J. Mele and Andrew M. Rappe.
Monti, Dalida
1996-01-01
Relativamente poco noto al gran pubblico, il premio Nobel Paul Adrien Maurice Dirac appartiene a quel gruppo di uomini di ingegno che nei primi decenni del secolo contribuirono a dare alla nostra concezione del mondo fisico la sua impronta attuale. Assolutamente cruciali, per una valutazione dell'opera di Dirac, sono gli anni compresi tra il 1925 e il 1931: un periodo in cui il fisico fornisce la prima spiegazione chiara e coerente delle proprietà di spin dell'elettrone (equazione di Dirac) e perviene, in forza della pura deduzione matematica, alla scoperta dell'esistenza dell'elettrone positivo o positrone.
Pion transition form factor in k{sub T} factorization
Energy Technology Data Exchange (ETDEWEB)
Li, Hsiang-nan [Academica Sinica, Taipei, Taiwan (China). Inst. of Physics; Tsing-Hua Univ., Hsinchu, Taiwan (China). Dept. of Phyiscs; National Cheng-Kung Univ., Tainan, Taiwan (China). Dept. of Physics; National Cheng-Chi Univ, Taipei, Taiwan (China). Inst. of Applied Physics; Mishima, Satoshi [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2009-07-15
It has been pointed out that the recent BaBar data on the {pi}{gamma}{sup *} {yields} {gamma} transition form factor F{sub {pi}}{sub {gamma}}(Q{sup 2}) at low (high) momentum transfer squared Q{sup 2} indicate an asymptotic (flat) pion distribution amplitude. These seemingly contradictory observations can be reconciled in the k{sub T} factorization theorem: the increase of the measured Q{sup 2}FF{sub {pi}}{sub {gamma}}(Q{sup 2}) for Q{sup 2} > 10 GeV{sup 2} is explained by convoluting a k{sub T} dependent hard kernel with a flat pion distribution amplitude, k{sub T} being a parton transverse momentum. The low Q{sup 2} data are accommodated by including the resummation of {alpha}{sub s} ln{sup 2}x, x being a parton momentum fraction, which provides a stronger suppression at the endpoints of x. The next-to-leading-order correction to the pion transition form factor is found to be less than 20% in the considered range of Q{sup 2}. (orig.)
DIRAC distributed computing services
International Nuclear Information System (INIS)
Tsaregorodtsev, A
2014-01-01
DIRAC Project provides a general-purpose framework for building distributed computing systems. It is used now in several HEP and astrophysics experiments as well as for user communities in other scientific domains. There is a large interest from smaller user communities to have a simple tool like DIRAC for accessing grid and other types of distributed computing resources. However, small experiments cannot afford to install and maintain dedicated services. Therefore, several grid infrastructure projects are providing DIRAC services for their respective user communities. These services are used for user tutorials as well as to help porting the applications to the grid for a practical day-to-day work. The services are giving access typically to several grid infrastructures as well as to standalone computing clusters accessible by the target user communities. In the paper we will present the experience of running DIRAC services provided by the France-Grilles NGI and other national grid infrastructure projects.
Casajus Ramo, A.; Graciani Diaz, R.
2012-12-01
DIRAC framework for distributed computing has been designed as a group of collaborating components, agents and servers, with persistent database back-end. Components communicate with each other using DISET, an in-house protocol that provides Remote Procedure Call (RPC) and file transfer capabilities. This approach has provided DIRAC with a modular and stable design by enforcing stable interfaces across releases. But it made complicated to scale further with commodity hardware. To further scale DIRAC, components needed to send more queries between them. Using RPC to do so requires a lot of processing power just to handle the secure handshake required to establish the connection. DISET now provides a way to keep stable connections and send and receive queries between components. Only one handshake is required to send and receive any number of queries. Using this new communication mechanism DIRAC now provides a new type of component called Executor. Executors process any task (such as resolving the input data of a job) sent to them by a task dispatcher. This task dispatcher takes care of persisting the state of the tasks to the storage backend and distributing them among all the Executors based on the requirements of each task. In case of a high load, several Executors can be started to process the extra load and stop them once the tasks have been processed. This new approach of handling tasks in DIRAC makes Executors easy to replace and replicate, thus enabling DIRAC to further scale beyond the current approach based on polling agents.
International Nuclear Information System (INIS)
Casajus Ramo, A; Graciani Diaz, R
2012-01-01
DIRAC framework for distributed computing has been designed as a group of collaborating components, agents and servers, with persistent database back-end. Components communicate with each other using DISET, an in-house protocol that provides Remote Procedure Call (RPC) and file transfer capabilities. This approach has provided DIRAC with a modular and stable design by enforcing stable interfaces across releases. But it made complicated to scale further with commodity hardware. To further scale DIRAC, components needed to send more queries between them. Using RPC to do so requires a lot of processing power just to handle the secure handshake required to establish the connection. DISET now provides a way to keep stable connections and send and receive queries between components. Only one handshake is required to send and receive any number of queries. Using this new communication mechanism DIRAC now provides a new type of component called Executor. Executors process any task (such as resolving the input data of a job) sent to them by a task dispatcher. This task dispatcher takes care of persisting the state of the tasks to the storage backend and distributing them among all the Executors based on the requirements of each task. In case of a high load, several Executors can be started to process the extra load and stop them once the tasks have been processed. This new approach of handling tasks in DIRAC makes Executors easy to replace and replicate, thus enabling DIRAC to further scale beyond the current approach based on polling agents.
Parallel Integer Factorization Using Quadratic Forms
National Research Council Canada - National Science Library
McMath, Stephen S
2005-01-01
Factorization is important for both practical and theoretical reasons. In secure digital communication, security of the commonly used RSA public key cryptosystem depends on the difficulty of factoring large integers...
Special function solutions of the free particle Dirac equation
International Nuclear Information System (INIS)
Strange, P
2012-01-01
The Dirac equation is one of the fundamental equations in physics. Here we present and discuss two novel solutions of the free particle Dirac equation. These solutions have an exact analytical form in terms of Airy or Mathieu functions and exhibit unexpected properties including an enhanced Doppler effect, accelerating wavefronts and solutions with a degree of localization. (paper)
A matricial approach for the Dirac-Kahler formalism
International Nuclear Information System (INIS)
Goto, M.
1987-01-01
A matricial approach for the Dirac-Kahler formalism is considered. It is shown that the matrical approach i) brings a great computational simplification compared to the common use of differential forms and that ii) by an appropriate choice of notation, it can be extended to the lattice, including a matrix Dirac-Kahler equation. (author) [pt
Effects of an electromagnetic quark form factor on meson properties
International Nuclear Information System (INIS)
Silvestre-Brac, B.
2002-01-01
A form factor is introduced in the quark electromagnetic current. Its effect is analyzed on charge mean square radii and form factors in the mesonic sector. The decay of a vector meson into lepton-antilepton pair is also affected. Two different expressions for the form factors, and two different types of quark potential are tested and some relativistic kinematical corrections are proposed. In any case the introduction of a quark form factor greatly improves the agreement with experimental data
Form factors in (HI,HI') direct reactions
International Nuclear Information System (INIS)
Chu, Y.H.
1981-01-01
Using the semiclassical theory, the inelastic transition form factors are analyzed. For the first order form factors, we find that: (i) In the strong absorption limit, the Austern-Blair theory is a good approximation to the inelastic form factor--even in highly mismatched reactions. (ii) In weak to moderate absorption, the amplitude of the inelastic form factor oscillates due to overlapping potential resonances. The internal part of the form factor can be expressed in a simple form, which may easily be used to analyze heavy-ion inelastic scattering. (iii) In the presence of an isolated resonance, the inelastic form factor is enhanced greatly at the resonance due to multiple reflections inside the potential well. The second order form factors contain two terms, i.e. the one-step direct process (OSD) term and the two-step process (TS) term. It is found that: (i) In the strong absorption limit, OSD and TS form factors are equally important and interfere destructively near the grazing angular momentum. The Austern-Blair theory gives satisfactory results for well-matched reactions. The angular distributions of the mutual and double excitations are out of phase compared with that of the single excitation. (ii) For the weak absorption case, the internal part of the TS form factor is so enhanced that the OSD form factor can simply be neglected. The internal TS form factor can be parameterized in a form proportional to the internal-wave elastic Smatrix, where the angular distribution shows characteristically refractive phenomenon
MesonNet Workshop on Meson Transition Form Factors
Eidelman, S; Hanhart, C; Kubis, B; Kupsc, A; Leupold, S; Moskal, P; Schadmand, S
2012-01-01
The mini-proceedings of the Workshop on Meson Transition Form Factors held in Cracow from May 29th to 30th, 2012 introduce the meson transition form factor project with special emphasis on the interrelations between the various form factors (on-shell, single off-shell, double off-shell). Short summaries of the talks presented at the workshop follow.
Zeros in the electromagnetic and hadronic form factors
International Nuclear Information System (INIS)
Martini, A.F.; Menon, M.J.; Montanha, J.
2004-01-01
We discuss the evidences for the existence of zeros in the electric and in the hadronic form factors of the proton. We show that the shape of both form factors are similar, but there is indication that the hadronic form factors can depend on the energy. (author)
DIRAC optimized workload management
Paterson, S K
2008-01-01
The LHCb DIRAC Workload and Data Management System employs advanced optimization techniques in order to dynamically allocate resources. The paradigms realized by DIRAC, such as late binding through the Pilot Agent approach, have proven to be highly successful. For example, this has allowed the principles of workload management to be applied not only at the time of user job submission to the Grid but also to optimize the use of computing resources once jobs have been acquired. Along with the central application of job priorities, DIRAC minimizes the system response time for high priority tasks. This paper will describe the recent developments to support Monte Carlo simulation, data processing and distributed user analysis in a consistent way across disparate compute resources including individual PCs, local batch systems, and the Worldwide LHC Computing Grid. The Grid environment is inherently unpredictable and whilst short-term studies have proven to deliver high job efficiencies, the system performance over ...
Chou-Yang model and PHI form factor
Energy Technology Data Exchange (ETDEWEB)
Fazal-e-Aleem; Saleem, M.; Rafique, M.
1988-03-01
By using the deduced differential cross-section data for PHIp elastic scattering at 175 GeV/c in the Chou-Yang model, the PHI form factor has been computed and parametrized. Then in conjunction with the proton form factor this form factor is used in the pristine Chou-Yang model to obtain differential cross-section data at Fermilab energies. The theoretical results agree with the experimental measurements, endorsing the conjecture that the hadronic form factor of neutral particle is proportional to its magnetic form factor.
Electromagnetic form factors in the light-front dynamics
International Nuclear Information System (INIS)
Karmanov, V.A.; Smirnov, A.V.
1992-01-01
It is shown that the electromagnetic vertex of a nucleus (and of any bound system), expressed through the wave function in the light-front dynamics at relativistic values of momentum transfer, contains a contribution of nonphysical form factors which increases the total number of invariant form factors (for the deuteron from 3 up to 11). This fact explains an ambiguity in the form factors calculated previously. The physical and nonphysical form factors are covariantly separated. Explicit expressions for physical form factors of systems with spin 0, 1/2 and 1 through the vertex functions are obtained. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Abel, Steven [Durham Univ. (United Kingdom). Inst. for Particle Physics Phenomenology; CERN, Geneva (Switzerland); Goodsell, Mark [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2011-02-15
A simple and natural model is presented that gives Dirac gauginos. The configuration is related to ''deconstructed gaugino mediation''. A high energy completion is provided based on existing ISS-like models of deconstructed gaugino mediation. This provides a complete picture of Dirac gauginos that includes the necessary extra adjoint fermions (generated as magnetic quarks of the ISS theory) and supersymmetry breaking (via the ISS mechanism). Moreover the screening of the scalar masses means that they can similar to or less than the gaugino masses, even though the supersymmetry breaking is driven by F-terms. (orig.)
International Nuclear Information System (INIS)
Abel, Steven; Goodsell, Mark
2011-02-01
A simple and natural model is presented that gives Dirac gauginos. The configuration is related to ''deconstructed gaugino mediation''. A high energy completion is provided based on existing ISS-like models of deconstructed gaugino mediation. This provides a complete picture of Dirac gauginos that includes the necessary extra adjoint fermions (generated as magnetic quarks of the ISS theory) and supersymmetry breaking (via the ISS mechanism). Moreover the screening of the scalar masses means that they can similar to or less than the gaugino masses, even though the supersymmetry breaking is driven by F-terms. (orig.)
Magnetic form factors of rare earth ions
International Nuclear Information System (INIS)
Deckman, H.W.
1976-01-01
The magnetic scattering of neutrons by atoms has been investigated by exploiting its similarity to the radiation problem in spectroscopy. Expressions for the magnetic scattering amplitude were developed for cases in whcih an atom in the l/sup n/ electronic configuration is described either by a relativistic or nonrelativistic Hamiltonian. For each of these cases, it has been shown that the magnetic scattering amplitude can be expressed in terms of relativistic or nonrelativistic matrix elements of magnetic and electric multipole operators. For a nonrelativistic atom, the calculation of these matrix elements has been separated into evaluating radial matrix elements and matrix elements of Racah tensors W/(sup 0,k)k/ and W/(sup 1,k')k/. For a relativistic atom the effective operator approach has been used to define effective multipole operators so that a relativistic result is obtained by taking matrix elements of these effective operators between nonrelativistic states of the atom. The calculation of matrix elements of these effective operators has been reduced to evaluating relativistic radial integrals and matrix elements of the Racah tensors taken between nonrelativistic states of the atom. It is shown tha for the case of elastic scattering by either a relativistic or nonrelativistic atom in single Russel-Saunders state, the magnetic scattering amplitude can be written in the conventional form p(vector q)vector q/sub m/.vector sigma. General expressions for p(vector q) as well as elastic magnetic form factorshave been obtained. The formalism has been illustrated throughout by applying it to the case of scattering by rare earth ions
THE FACTORS FORMING QUALITY OF GRANULATED SUGAR
Directory of Open Access Journals (Sweden)
N. G. Kulneva
2015-01-01
Full Text Available Sugar, with good taste and high caloric, is one of the most popular human food. Consumers sugar must be sure that the sugar under normal conditions of use is of high quality and is not harmful to the health of the product. One reason for the decline in the quality of sugar is bacterial contamination. This is because the sugar industry products are good targets for the development of different groups of microorganisms, e.g., Bacillus subtilis, Clostridium perfringes, Leuconostoc dextranicum, Torula alba, Pseudomonas fluorescens, Sarcina lutea and others. These organisms are affected with beets, and then with sugar beet chips and diffusion juice fall into the processing line of sugar production. Their number in the diffusion juice varies and depends on many facto rs such as the quality of raw materials, the quality of cleaning beet root colonization of transporter-washing and the supply of water to the diffusion process, the temperature of the diffusion and others. In the diffusion unit has the most favorable conditions for the development of micro-organisms. Some of them, especially resistant bacteria and thermophilic bacteria or their spores, forming a capsule which protects against external influences occur in the final product sugar. When injected into the fresh crop of product (juice, syrup, they begin to multiply rapidly, causing difficulties in the process. The higher seeding beet microorganisms, the more they decompose and emit sucrose metabolism byproducts. To reduce the negative impact of microbiological and reduce losses from decomposition of sucrose conducted research on the possibility of using chlorine-containing substances in the sugar industry. It was established experimentally that the investigated chlorinated drug has bacteriostatic action and can be recommended for use in sugar beet production.
International Nuclear Information System (INIS)
Thaller, B.
1992-01-01
This monograph treats most of the usual material to be found in texts on the Dirac equation such as the basic formalism of quantum mechanics, representations of Dirac matrices, covariant realization of the Dirac equation, interpretation of negative energies, Foldy-Wouthuysen transformation, Klein's paradox, spherically symmetric interactions and a treatment of the relativistic hydrogen atom, etc., and also provides excellent additional treatments of a variety of other relevant topics. The monograph contains an extensive treatment of the Lorentz and Poincare groups and their representations. The author discusses in depth Lie algebaic and projective representations, covering groups, and Mackey's theory and Wigner's realization of induced representations. A careful classification of external fields with respect to their behavior under Poincare transformations is supplemented by a basic account of self-adjointness and spectral properties of Dirac operators. A state-of-the-art treatment of relativistic scattering theory based on a time-dependent approach originally due to Enss is presented. An excellent introduction to quantum electrodynamics in external fields is provided. Various appendices containing further details, notes on each chapter commenting on the history involved and referring to original research papers and further developments in the literature, and a bibliography covering all relevant monographs and over 500 articles on the subject, complete this text. This book should satisfy the needs of a wide audience, ranging from graduate students in theoretical physics and mathematics to researchers interested in mathematical physics
The QCD form factor of massive quarks and applications
International Nuclear Information System (INIS)
Moch, S.
2009-11-01
We review the electromagnetic form factor of heavy quarks with emphasis on the QCD radiative corrections at two-loop order in the perturbative expansion. We discuss important properties of the heavy-quark form factor such as its exponentiation in the high-energy limit and its role in QCD factorization theorems for massive n-parton amplitudes. (orig.)
Asymptotical behaviour of pion electromagnetic form factor in QCD
International Nuclear Information System (INIS)
Efremov, A.V.; Radyushkin, A.V.
1978-01-01
In the framework of the renormalizable quantum field theory a new approach is developed to the investigation of asymptotical behaviour of two-particle bound state electromagnetic form factor. It is shown that the behaviour of the pion EM form factor in quantum chromodynamics at sufficiently large momentum transfers is controlled by the short-distance dynamics only. The formula is obtained which expresses the asymptotical behaviour of the pion form factor in terms of the fundamental constants of the theory
Weak electric and magnetic form factors for semileptonic baryon decays in an independent-quark model
International Nuclear Information System (INIS)
Barik, N.; Dash, B.K.; Das, M.
1985-01-01
Weak electric and magnetic form factors for semileptonic baryon decays are calculated in a relativistic quark model based on the Dirac equation with the independent-quark confining potential of the form (1+γ 0 )V(r). The values obtained for (g 2 /g 1 ), for various decay modes in a model with V(r) = a'r 2 , are roughly of the same order as those predicted in the MIT bag model. However in a similar model with V(r) = (a/sup nu+1/r/sup ν/+V 0 ), the (g 2 /g 1 ) values agree with the nonrelativistic results of Donoghue and Holstein. Incorporating phenomenologically the effect of nonzero g 2 in the ratio (g 1 /f 1 ), we have estimated the values for (f 2 /f 1 ) for various semileptonic transitions. It is observed that SU(3)-symmetry breaking does not generate significant departures in (f 2 /f 1 ) values from the corresponding Cabibbo values
Analytical evaluation of atomic form factors: Application to Rayleigh scattering
Energy Technology Data Exchange (ETDEWEB)
Safari, L., E-mail: laleh.safari@ist.ac.at [IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg (Austria); Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Santos, J. P. [Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação (LIBPhys-UNL), Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Amaro, P. [Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação (LIBPhys-UNL), Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg (Germany); Jänkälä, K. [Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Fratini, F. [Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Institute of Atomic and Subatomic Physics, TU Wien, Stadionallee 2, 1020 Wien (Austria); Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG (Brazil)
2015-05-15
Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wave functions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.
Axial anomaly and index theorem for Dirac-Kaehler fermions
International Nuclear Information System (INIS)
Fonseca Junior, C.A.L. da.
1985-02-01
Some aspects of topological influence on gauge field theory are analysed, considering the geometry and differential topology methods. A review of concepts of differential forms, fibered spaces, connection and curvature, showing an interpretation of gauge theory in this context, is presented. The question of fermions, analysing in details the Dirac-Kaehler which fermionic particle is considered a general differential form, is studied. It is shown how the explicit expressions in function of the Dirac spinor components vary with the Dirac matrix representation. The Dirac-Kahler equation contains 4 times (in 4 dimensions) the Dirac equation, each particle being associated an ideal at left of the algebra of general differential forms. These ideals and the SU(4) symmetry among them are also studied on the point of view of spinors and, the group of reduction to one of the ideals is identified as the Cartan subalgebra of this SU(4). Finally, the axial anomaly is calculated through the functional determinant given by the Dirac-Kaehler operator. The regularization method is the Seeley's coefficients. From that results a comparison of the index theorems for the twisted complexes of signature and spin, which proportionality is given by the number of the algebra ideals contained in the Dirac-Kaehler equation and which also manifests in the respective axial anomaly equations. (L.C.) [pt
Nucleon mass difference and off-shell form factors
International Nuclear Information System (INIS)
Kimel, I.
1981-08-01
The use of off-shell form factors in calculating the proton-neutron mass difference is advocated. These form factors appear in a Cottingham rotated Born-like expression for the mass difference and could lead to a good value for Δ = M sub(p) - M sub(n). (Author) [pt
The heavy quark form factors at two loops
Energy Technology Data Exchange (ETDEWEB)
Ablinger, J.; Schneider, C. [Johannes Kepler Univ., Linz (Austria). Research Inst. for Symbolic Computation (RISC); Behring, A. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); RWTH Aachen Univ. (Germany). Inst. fuer Theoretische Teilchenphysik und Kosmologie; Bluemlein, J.; Freitas, A. de; Marquard, P.; Rana, N. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Falcioni, G. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Nikhef, Amsterdam (Netherlands). Theory Group
2017-12-15
We compute the two-loop QCD corrections to the heavy quark form factors in case of the vector, axial-vector, scalar and pseudo-scalar currents up to second order in the dimensional parameter ε=(4-D)/2. These terms are required in the renormalization of the higher order corrections to these form factors.
Model of separated form factors for unilamellar vesicles
International Nuclear Information System (INIS)
Kiselev, M.A.; Aksenov, V.L.; Lesieur, P.; Lombardo, D.; Kiselev, A.M.
2001-01-01
A new model of separated form factors is proposed for the evaluation of small-angle neutron scattering curves from large unilamellar vesicles. The validity of the model was checked via comparison with the model of a hollow sphere. The model of separated form factors and the hollow sphere model give a reasonable agreement in the evaluation of vesicle parameters
Molecular form factors in X-ray crystallography
Groenewegen, P.P.M.; Feil, D.
1969-01-01
The calculation of molecular form factors from ab initio molecular electronic wavefunctions is discussed, and a scheme for application to X-ray diffraction structure analysis is given. The method is used to calculate the form factor of the NH+4 molecular ion from three accurate molecular
Surface sensitivity of nuclear-knock-out form factors
International Nuclear Information System (INIS)
Fratamico, G.
1984-01-01
A numerical calculation has been performed to investigate the sensitivity of nuclear-knock-out form factors to nuclear-surface behaviour of bound-state wave functions. The result of our investigation suggests that one can extract the bound-state behaviour at the surface from experimental information on nuclear-knock-out form factors
Analytic properties of form factors in strictly confining models
International Nuclear Information System (INIS)
Csikor, F.
1979-12-01
An argument is presented showing that strict confinement implies the possible existence of an (unwanted) branch point at q 2 =0 in the form factors. In case of a bag extended to infinity in the relative time, the branch point is certainly there (provided that the form factor is non zero at q 2 =0). (author)
Directory of Open Access Journals (Sweden)
Wei Khim Ng
2009-02-01
Full Text Available We construct nonlinear extensions of Dirac's relativistic electron equation that preserve its other desirable properties such as locality, separability, conservation of probability and Poincaré invariance. We determine the constraints that the nonlinear term must obey and classify the resultant non-polynomial nonlinearities in a double expansion in the degree of nonlinearity and number of derivatives. We give explicit examples of such nonlinear equations, studying their discrete symmetries and other properties. Motivated by some previously suggested applications we then consider nonlinear terms that simultaneously violate Lorentz covariance and again study various explicit examples. We contrast our equations and construction procedure with others in the literature and also show that our equations are not gauge equivalent to the linear Dirac equation. Finally we outline various physical applications for these equations.
International Nuclear Information System (INIS)
Joshipura, A.S.; Rindani, S.D.
1991-01-01
The consequences of imposing an exact L e +L τ -L μ symmetry on a 6x6 matrix describing neutrino masses are discussed. The presence of right-handed neutrinos avoids the need of introducing any SU(2) Higgs triplet. Hence the conflict with the CERN LEP data on the Z width found in earlier models with L e +L τ -L μ symmetry is avoided. The L e +L τ -L μ symmetry provides an interesting realization of a recent proposal of Glashow to accommodate the 17-keV Dirac neutrino in the SU(2)xU(1) theory. All the neutrinos in this model are Dirac particles. The solar-neutrino problem can be solved in an extension of the model which generates a large (∼10 -11 μ B ) magnetic moment for the electron neutrino
bin Pet, Mokhtar; Sihes, Ahmad Johari Hj
2015-01-01
This study aims to examine the external factors of form six teachers who can influence thinking domain form six teachers in their teaching. This study was conducted using a quantitative approach using questionnaires. A total of 300 form six teacher schools in Johor were chosen as respondents. The findings were obtained as student background…
Alarcón, J. M.; Weiss, C.
2018-05-01
We study the nucleon electromagnetic form factors (EM FFs) using a recently developed method combining chiral effective field theory (χ EFT ) and dispersion analysis. The spectral functions on the two-pion cut at t >4 Mπ2 are constructed using the elastic unitarity relation and an N /D representation. χ EFT is used to calculate the real functions J±1(t ) =f±1(t ) /Fπ(t ) (ratios of the complex π π →N N ¯ partial-wave amplitudes and the timelike pion FF), which are free of π π rescattering. Rescattering effects are included through the empirical timelike pion FF | Fπ(t) | 2 . The method allows us to compute the isovector EM spectral functions up to t ˜1 GeV2 with controlled accuracy (leading order, next-to-leading order, and partial next-to-next-to-leading order). With the spectral functions we calculate the isovector nucleon EM FFs and their derivatives at t =0 (EM radii, moments) using subtracted dispersion relations. We predict the values of higher FF derivatives, which are not affected by higher-order chiral corrections and are obtained almost parameter-free in our approach, and explain their collective behavior. We estimate the individual proton and neutron FFs by adding an empirical parametrization of the isoscalar sector. Excellent agreement with the present low-Q2 FF data is achieved up to ˜0.5 GeV2 for GE, and up to ˜0.2 GeV2 for GM. Our results can be used to guide the analysis of low-Q2 elastic scattering data and the extraction of the proton charge radius.
Sheka, Elena F.
2016-01-01
The paper presents the author view on spin-rooted properties of graphene supported by numerous experimental and calculation evidences. Dirac fermions of crystalline graphene and local spins of graphene molecules are suggested to meet a strict demand - different orbitals for different spins- which leads to a large spectrum of effects caused by spin polarization of electronic states. The consequent topological non-triviality, making graphene topological insulator, and local spins, imaging graph...
Comments on electromagnetic form factors of the nucleon
International Nuclear Information System (INIS)
Sachs, R.G.; Wali, K.C.
1989-01-01
This paper draws the concept of nucleon form factors further to consider the electromagnetic aspect based on the magnetic moment of the nucleon. These are seen as valid physical interpretations of form factors in electron-nucleon interactions. A linear combination of two functions, associated with charge radius, is derived, which agreed well with experimental results. The paper also expands the specific form to include relativistic cases and consider appropriate frames of reference. (UK)
Energy Technology Data Exchange (ETDEWEB)
Costella, J P
1995-05-22
In this short note, it is argued that [p, q] {ne} i{Dirac_h}, contrary to the oiginal claims of Born and Jordan, and Dirac. Rather, [p, q] is equal to something that is infinitesimally different from i{Dirac_h}. While this difference is usually harmless, it does provide the solution of the Born-Jordan `trace paradox` of [p, q]. More recently, subtleties of a very similar form have been found to be of fundamental importance in quantum field theory. 3 refs.
Potential scattering of Dirac particles
International Nuclear Information System (INIS)
Thaller, B.
1981-01-01
A quantum mechanical interpretation of the Dirac equation for particles in external electromagnetic potentials is discussed. It is shown that a consequent development of the Stueckelberg-Feynman theory into a probabilistic interpretation of the Dirac equation corrects some prejudices concerning negative energy states, Zitterbewegung and bound states in repulsive potentials and yields the connection between propagator theory and scattering theory. Limits of the Dirac equation, considered as a wave mechanical equation, are considered. (U.K.)
Form factors in the projected linear chiral sigma model
International Nuclear Information System (INIS)
Alberto, P.; Coimbra Univ.; Bochum Univ.; Ruiz Arriola, E.; Fiolhais, M.; Urbano, J.N.; Coimbra Univ.; Goeke, K.; Gruemmer, F.; Bochum Univ.
1990-01-01
Several nucleon form factors are computed within the framework of the linear chiral soliton model. To this end variational means and projection techniques applied to generalized hedgehog quark-boson Fock states are used. In this procedure the Goldberger-Treiman relation and a virial theorem for the pion-nucleon form factor are well fulfilled demonstrating the consistency of the treatment. Both proton and neutron charge form factors are correctly reproduced, as well as the proton magnetic one. The shapes of the neutron magnetic and of the axial form factors are good but their absolute values at the origin are too large. The slopes of all the form factors at zero momentum transfer are in good agreement with the experimental data. The pion-nucleon form factor exhibits to great extent a monopole shape with a cut-off mass of Λ=690 MeV. Electromagnetic form factors for the vertex γNΔ and the nucleon spin distribution are also evaluated and discussed. (orig.)
Absorptive form factors for high-energy electron diffraction
International Nuclear Information System (INIS)
Bird, D.M.; King, Q.A.
1990-01-01
The thermal diffuse scattering contribution to the absorptive potential in high-energy electron diffraction is calculated in the form of an absorptive contribution to the atomic form factor. To do this, the Einstein model of lattice vibrations is used, with isotropic Debye-Waller factors. The absorptive form factors are calculated as a function of scattering vector s and temperature factor M on a grid which enables polynomial interpolation of the results to be accurate to better than 2% for much of the ranges 0≤Ms 2 ≤6 and 0≤M≤2 A 2 . The computed values, together with an interpolation routine, have been incorporated into a Fortran subroutine which calculates both the real and absorptive form factors for 54 atomic species. (orig.)
Pseudoscalar form factors in tau-neutrino nucleon scattering
International Nuclear Information System (INIS)
Hagiwara, K.; Mawatari, K.; Yokoya, H.
2004-01-01
We investigate the pseudoscalar transition form factors of nucleon for quasi-elastic scattering and Δ resonance production in tau-neutrino nucleon scattering via the charged current interactions. Although the pseudoscalar form factors play an important role for the τ production in neutrino-nucleon scattering, these are not known well. In this Letter, we examine their effects in quasi-elastic scattering and Δ resonance production and find that the cross section, Q 2 distribution, and spin polarization of the produced τ ± leptons are quite sensitive to the pseudoscalar form factors
Anomaly, mixing and transition form factors of pseudoscalar mesons
International Nuclear Information System (INIS)
Klopot, Yaroslav; Oganesian, Armen; Teryaev, Oleg
2011-01-01
We derive the exact non-perturbative QCD sum rule for the transition form factors of η and η ′ using the dispersive representation of axial anomaly. This sum rule allows to express the transition form factors entirely in terms of meson decay constants. Using this sum rule several mixing schemes were analyzed and compared to recent experimental data. A good agreement with experimental data on η,η ′ transition form factors in the range from real to highly virtual photons was obtained.
Anomaly, mixing and transition form factors of pseudoscalar mesons
Energy Technology Data Exchange (ETDEWEB)
Klopot, Yaroslav, E-mail: klopot@theor.jinr.ru [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna 141980 (Russian Federation); Oganesian, Armen, E-mail: armen@itep.ru [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna 141980 (Russian Federation); Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya 25, Moscow 117218 (Russian Federation); Teryaev, Oleg, E-mail: teryaev@theor.jinr.ru [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna 141980 (Russian Federation)
2011-10-15
We derive the exact non-perturbative QCD sum rule for the transition form factors of {eta} and {eta}{sup Prime} using the dispersive representation of axial anomaly. This sum rule allows to express the transition form factors entirely in terms of meson decay constants. Using this sum rule several mixing schemes were analyzed and compared to recent experimental data. A good agreement with experimental data on {eta},{eta}{sup Prime} transition form factors in the range from real to highly virtual photons was obtained.
Form factors and QCD in spacelike and timelike region
International Nuclear Information System (INIS)
A.P. Bakulev; A.V. Radyushkin; N.G. Stefanis
2000-01-01
The authors analyze the basic hard exclusive processes: πγ * γ-transition, pion and nucleon electromagnetic form factors, and discuss the analytic continuation of QCD formulas from the spacelike q 2 2 > 0 of the relevant momentum transfers. They describe the construction of the timelike version of the coupling constant α s . They show that due to the analytic continuation of the collinear logarithms each eigenfunction of the evolution equation acquires a phase factor and investigate the resulting interference effects which are shown to be very small. They found no sources for the K-factor-type enhancements in the perturbative QCD contribution to the hadronic form factors. To study the soft part of the pion electromagnetic form factor, they use a QCD sum rule inspired model and show that there are non-canceling Sudakov double logarithms which result in a K-factor-type enhancement in the timelike region
Form factors and QCD in spacelike and timelike regions
International Nuclear Information System (INIS)
Bakulev, A. P.; Radyushkin, A. V.; Stefanis, N. G.
2000-01-01
We analyze the basic hard exclusive processes, the πγ * γ-transition and the pion and nucleon electromagnetic form factors, and discuss the analytic continuation of QCD formulas from the spacelike q 2 2 >0 of the relevant momentum transfers. We describe the construction of the timelike version of the coupling constant α s . We show that due to the analytic continuation of the collinear logarithms, each eigenfunction of the evolution equation acquires a phase factor and investigate the resulting interference effects which are shown to be very small. We find no sources for the K-factor-type enhancements in the perturbative QCD contribution to the hadronic form factors. To study the soft part of the pion electromagnetic form factor, we use a QCD sum rule inspired model and show that there are noncanceling Sudakov double logarithms which result in a K-factor-type enhancement in the timelike region
Dirac Mass Dynamics in Multidimensional Nonlocal Parabolic Equations
Lorz, Alexander
2011-01-17
Nonlocal Lotka-Volterra models have the property that solutions concentrate as Dirac masses in the limit of small diffusion. Is it possible to describe the dynamics of the limiting concentration points and of the weights of the Dirac masses? What is the long time asymptotics of these Dirac masses? Can several Dirac masses coexist? We will explain how these questions relate to the so-called "constrained Hamilton-Jacobi equation" and how a form of canonical equation can be established. This equation has been established assuming smoothness. Here we build a framework where smooth solutions exist and thus the full theory can be developed rigorously. We also show that our form of canonical equation comes with a kind of Lyapunov functional. Numerical simulations show that the trajectories can exhibit unexpected dynamics well explained by this equation. Our motivation comes from population adaptive evolution a branch of mathematical ecology which models Darwinian evolution. © Taylor & Francis Group, LLC.
Strange nucleon electromagnetic form factors from lattice QCD
Alexandrou, C.; Constantinou, M.; Hadjiyiannakou, K.; Jansen, K.; Kallidonis, C.; Koutsou, G.; Avilés-Casco, A. Vaquero
2018-05-01
We evaluate the strange nucleon electromagnetic form factors using an ensemble of gauge configurations generated with two degenerate maximally twisted mass clover-improved fermions with mass tuned to approximately reproduce the physical pion mass. In addition, we present results for the disconnected light quark contributions to the nucleon electromagnetic form factors. Improved stochastic methods are employed leading to high-precision results. The momentum dependence of the disconnected contributions is fitted using the model-independent z-expansion. We extract the magnetic moment and the electric and magnetic radii of the proton and neutron by including both connected and disconnected contributions. We find that the disconnected light quark contributions to both electric and magnetic form factors are nonzero and at the few percent level as compared to the connected. The strange form factors are also at the percent level but more noisy yielding statistical errors that are typically within one standard deviation from a zero value.
Infrared photons and gluons and the electromagnetic quark form factor
International Nuclear Information System (INIS)
Scholz, B.
1982-01-01
A method for a consistent treatment of the infrared behaviour of QED and QCD is presented. As an application of the method the calculation of the electromagnetic quark form factor is discussed. (M.F.W.)
Hadronic Form Factors in Asymptotically Free Field Theories
Gross, D. J.; Treiman, S. B.
1974-01-01
The breakdown of Bjorken scaling in asymptotically free gauge theories of the strong interactions is explored for its implications on the large q{sup 2} behavior of nucleon form factors. Duality arguments of Bloom and Gilman suggest a connection between the form factors and the threshold properties of the deep inelastic structure functions. The latter are addressed directly in an analysis of asymptotically free theories; and through the duality connection we are then led to statements about the form factors. For very large q{sup 2} the form factors are predicted to fall faster than any inverse power of q{sup 2}. For the more modest range of q{sup 2} reached in existing experiments the agreement with data is fairly good, though this may well be fortuitous. Extrapolations beyond this range are presented.
Hadron form factors in the constituent quark model
International Nuclear Information System (INIS)
Cardarelli, F.; Salme', G.; Simula, S.; Pace, E.
1998-01-01
Hadron electromagnetic form factors are evaluated in a light-front constituent quark model based on the eigenfunctions of a mass operator, including in the q-q interaction a confining term and a one-gluon-exchange term (OGE). The spin-dependent part of the interaction plays an essential role for obtaining both a proper fit of the experimental nucleon electromagnetic form factors and the faster than dipole decrease of the magnetic N-P 33 (1232) transition form factor. The effects of the D wave, produced by the tensor part of the OGE interaction, on the quadrupole and Coulomb N-P 33 (1232) transition form factors have been found to be negligible. (author)
Finite volume form factors in the presence of integrable defects
International Nuclear Information System (INIS)
Bajnok, Z.; Buccheri, F.; Hollo, L.; Konczer, J.; Takacs, G.
2014-01-01
We developed the theory of finite volume form factors in the presence of integrable defects. These finite volume form factors are expressed in terms of the infinite volume form factors and the finite volume density of states and incorporate all polynomial corrections in the inverse of the volume. We tested our results, in the defect Lee–Yang model, against numerical data obtained by truncated conformal space approach (TCSA), which we improved by renormalization group methods adopted to the defect case. To perform these checks we determined the infinite volume defect form factors in the Lee–Yang model exactly, including their vacuum expectation values. We used these data to calculate the two point functions, which we compared, at short distance, to defect CFT. We also derived explicit expressions for the exact finite volume one point functions, which we checked numerically. In all of these comparisons excellent agreement was found
Dispersive analysis of the pion transition form factor
Hoferichter, M.; Kubis, B.; Leupold, S.; Niecknig, F.; Schneider, S. P.
2014-11-01
We analyze the pion transition form factor using dispersion theory. We calculate the singly-virtual form factor in the time-like region based on data for the cross section, generalizing previous studies on decays and scattering, and verify our result by comparing to data. We perform the analytic continuation to the space-like region, predicting the poorly-constrained space-like transition form factor below , and extract the slope of the form factor at vanishing momentum transfer . We derive the dispersive formalism necessary for the extension of these results to the doubly-virtual case, as required for the pion-pole contribution to hadronic light-by-light scattering in the anomalous magnetic moment of the muon.
The connected prescription for form factors in twistor space
Energy Technology Data Exchange (ETDEWEB)
Brandhuber, A.; Hughes, E.; Panerai, R.; Spence, B.; Travaglini, G. [Centre for Research in String Theory, School of Physics and Astronomy,Queen Mary University of London,Mile End Road, London E1 4NS (United Kingdom)
2016-11-23
We propose a connected prescription formula in twistor space for all tree-level form factors of the stress tensor multiplet operator in N=4 super Yang-Mills, which is a generalisation of the expression of Roiban, Spradlin and Volovich for superamplitudes. By introducing link variables, we show that our formula is identical to the recently proposed four-dimensional scattering equations for form factors. Similarly to the case of amplitudes, the link representation of form factors is shown to be directly related to BCFW recursion relations, and is considerably more tractable than the scattering equations. We also discuss how our results are related to a recent Grassmannian formulation of form factors, and comment on a possible derivation of our formula from ambitwistor strings.
Normalization Of Thermal-Radiation Form-Factor Matrix
Tsuyuki, Glenn T.
1994-01-01
Report describes algorithm that adjusts form-factor matrix in TRASYS computer program, which calculates intraspacecraft radiative interchange among various surfaces and environmental heat loading from sources such as sun.
Classical limit of diagonal form factors and HHL correlators
Energy Technology Data Exchange (ETDEWEB)
Bajnok, Zoltan [MTA Lendület Holographic QFT Group, Wigner Research Centre,H-1525 Budapest 114, P.O.B. 49 (Hungary); Janik, Romuald A. [Institute of Physics, Jagiellonian University,ul. Łojasiewicza 11, 30-348 Kraków (Poland)
2017-01-16
We propose an expression for the classical limit of diagonal form factors in which we integrate the corresponding observable over the moduli space of classical solutions. In infinite volume the integral has to be regularized by proper subtractions and we present the one, which corresponds to the classical limit of the connected diagonal form factors. In finite volume the integral is finite and can be expressed in terms of the classical infinite volume diagonal form factors and subvolumes of the moduli space. We analyze carefully the periodicity properties of the finite volume moduli space and found a classical analogue of the Bethe-Yang equations. By applying the results to the heavy-heavy-light three point functions we can express their strong coupling limit in terms of the classical limit of the sine-Gordon diagonal form factors.
Conformal symmetry and pion form factor: Soft and hard contributions
International Nuclear Information System (INIS)
Choi, Ho-Meoyng; Ji, Chueng-Ryong
2006-01-01
We discuss a constraint of conformal symmetry in the analysis of the pion form factor. The usual power-law behavior of the form factor obtained in the perturbative QCD analysis can also be attained by taking negligible quark masses in the nonperturbative quark model analysis, confirming the recent AdS/CFT correspondence. We analyze the transition from soft to hard contributions in the pion form factor considering a momentum-dependent dynamical quark mass from an appreciable constituent quark mass at low momentum region to a negligible current quark mass at high momentum region. We find a correlation between the shape of nonperturbative quark distribution amplitude and the amount of soft and hard contributions to the pion form factor
Electromagnetic form factors at large momenta from lattice QCD
Chambers, A. J.; Dragos, J.; Horsley, R.; Nakamura, Y.; Perlt, H.; Pleiter, D.; Rakow, P. E. L.; Schierholz, G.; Schiller, A.; Somfleth, K.; Stüben, H.; Young, R. D.; Zanotti, J. M.; Qcdsf/Ukqcd/Cssm Collaborations
2017-12-01
Accessing hadronic form factors at large momentum transfers has traditionally presented a challenge for lattice QCD simulations. Here, we demonstrate how a novel implementation of the Feynman-Hellmann method can be employed to calculate hadronic form factors in lattice QCD at momenta much higher than previously accessible. Our simulations are performed on a single set of gauge configurations with three flavors of degenerate mass quarks corresponding to mπ≈470 MeV . We are able to determine the electromagnetic form factors of the pion and nucleon up to approximately 6 GeV2 , with results for the ratio of the electric and magnetic form factors of the proton at our simulated quark mass agreeing well with experimental results.
ELECTROMAGENTIC FORM FACTORS OF THE PROTON AND NEUTRON
Energy Technology Data Exchange (ETDEWEB)
Griffy, T. A.; Hofstadter, R.; Hughes, E. B.; Janssens, T.; Yearian, M. R.
1963-06-15
Proton form factors in the four-momentum-transfer range q/sup 2/ = 4.6 to 32.0 f/sup -2/ and neutron form factors in the range q/sup 2/ = 2.5 to 10.0 f/ sup -2/ are measured by means of electron elastic scattering by protons and electron inelastic scattering by deuterons. (T.F.H.)
Low-energy analysis of the nucleon electromagnetic form factors
International Nuclear Information System (INIS)
Kubis, Bastian.; Meissner, Ulf-G.
2001-01-01
We analyze the electromagnetic form factors of the nucleon to fourth order in relativistic baryon chiral perturbation theory. We employ the recently proposed infrared regularization scheme and show that the convergence of the chiral expansion is improved as compared to the heavy-fermion approach. We also discuss the inclusion of vector mesons and obtain an accurate description of all four-nucleon form factors for momentum transfer squared up to Q 2 ≅0.4 GeV 2
Form factors and other measures of strangeness in the nucleon
Energy Technology Data Exchange (ETDEWEB)
Diehl, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Feldmann, T. [Siegen Univ. (Germany). Theoretische Physik I; Kroll, P. [Bergische Univ., Wuppertal (Germany). Fachbereich Physik
2007-11-15
We discuss the phenomenology of strange-quark dynamics in the nucleon, based on experimental and theoretical results for electroweak form factors and for parton densities. In particular, we construct a model for the generalized parton distribution that relates the asymmetry s(x)- anti s(x) between the longitudinal momentum distributions of strange quarks and antiquarks with the form factor F{sup s}{sub 1}(t), which describes the distribution of strangeness in transverse position space. (orig.)
Form factors and other measures of strangeness in the nucleon
International Nuclear Information System (INIS)
Diehl, M.; Feldmann, T.; Kroll, P.
2007-11-01
We discuss the phenomenology of strange-quark dynamics in the nucleon, based on experimental and theoretical results for electroweak form factors and for parton densities. In particular, we construct a model for the generalized parton distribution that relates the asymmetry s(x)- anti s(x) between the longitudinal momentum distributions of strange quarks and antiquarks with the form factor F s 1 (t), which describes the distribution of strangeness in transverse position space. (orig.)
From quarks and gluons to baryon form factors.
Eichmann, Gernot
2012-04-01
I briefly summarize recent results for nucleon and [Formula: see text] electromagnetic, axial and transition form factors in the Dyson-Schwinger approach. The calculation of the current diagrams from the quark-gluon level enables a transparent discussion of common features such as: the implications of dynamical chiral symmetry breaking and quark orbital angular momentum, the timelike structure of the form factors, and their interpretation in terms of missing pion-cloud effects.
Einstein-Cartan-Dirac theory in (1+2)-dimensions
Energy Technology Data Exchange (ETDEWEB)
Dereli, Tekin [Koc University, Department of Physics, Istanbul (Turkey); Oezdemir, Nese [Istanbul Technical University, Department of Physics Engineering, Istanbul (Turkey); Sert, Oezcan [Pamukkale University, Department of Physics, Denizli (Turkey)
2013-01-15
Einstein-Cartan theory is formulated in (1+2) dimensions using the algebra of exterior differential forms. A Dirac spinor is coupled to gravity and the field equations are obtained by a variational principle. The space-time torsion is found to be given algebraically in terms of a quadratic spinor condensate field. Circularly symmetric, exact solutions that collapse to AdS{sub 3} geometry in the absence of the Dirac condensate are found. (orig.)
Lie algebras for the Dirac-Clifford ring
International Nuclear Information System (INIS)
Mignaco, J.A.; Linhares, C.A.
1992-01-01
It is shown in a general way that the Dirac-Clifford ring formed by the Dirac matrices and all their products, for all even and odd spacetime dimensions D, span the cumulation algebras SU(2 D/2 ) for even D and SU(2 (D- 1 )/2 ) + SU(2 (D-1)/2 ) for odd D. Some physical consequences of these results are discussed. (author)
The Dirac equation in the Lobachevsky space-time
International Nuclear Information System (INIS)
Paramonov, D.V.; Paramonova, N.N.; Shavokhina, N.S.
2000-01-01
The product of the Lobachevsky space and the time axis is termed the Lobachevsky space-time. The Lobachevsky space is considered as a hyperboloid's sheet in the four-dimensional pseudo-Euclidean space. The Dirac-Fock-Ivanenko equation is reduced to the Dirac equation in two special forms by passing from Lame basis in the Lobachevsky space to the Cartesian basis in the enveloping pseudo-Euclidean space
International Nuclear Information System (INIS)
Leo, Stefano de; Rotelli, Pietro
2009-01-01
We present the results of the planar diffusion of a Dirac particle by step and barrier potentials, when the incoming wave impinges at an arbitrary angle with the potential. Except for right-angle incidence this process is characterized by the appearance of spin flip terms. For the step potential, spin flip occurs for both transmitted and reflected waves. However, we find no spin flip in the transmitted barrier result. This is surprising because the barrier result may be derived directly from a two-step calculation. We demonstrate that the spin flip cancellation indeed occurs for each ''particle'' (wave packet) contribution. (orig.)
Form factors of the finite quantum XY-chain
International Nuclear Information System (INIS)
Iorgov, Nikolai
2011-01-01
Explicit factorized formulas for the matrix elements (form factors) of the spin operators σ x and σ y between the eigenvectors of the Hamiltonian of the finite quantum periodic XY-chain in a transverse field were derived. The derivation is based on the relations between three models: the model of quantum XY-chain, Ising model on 2D lattice and N = 2 Baxter-Bazhanov-Stroganov τ (2) -model. Due to these relations we transfer the formulas for the form factors of the latter model recently obtained by the use of separation of variables method to the model of quantum XY-chain. Hopefully, the formulas for the form factors will help in analysis of multipoint dynamic correlation functions at a finite temperature. As an example, we re-derive the asymptotics of the two-point correlation function in the disordered phase without the use of the Toeplitz determinants and the Wiener-Hopf factorization method.
International Nuclear Information System (INIS)
Ferreira, P.L.; Palladino, B.E.
1985-01-01
The problem of a Dirac particle in stationary motion on S 2 - a two dimensional sphere embedded in Euclidean space E 3 - is discussed. It provides a particularly simple case of an exactly solvable constrained Dirac particle whose properties are here studied, with emphasis on its magnetic moment. (Author) [pt
LHCb: DIRAC Secure Distributed Platform
Casajus, A
2009-01-01
DIRAC, the LHCb community grid solution, provides access to a vast amount of computing and storage resources to a large number of users. In DIRAC users are organized in groups with different needs and permissions. In order to ensure that only allowed users can access the resources and to enforce that there are no abuses, security is mandatory. All DIRAC services and clients use secure connections that are authenticated using certificates and grid proxies. Once a client has been authenticated, authorization rules are applied to the requested action based on the presented credentials. These authorization rules and the list of users and groups are centrally managed in the DIRAC Configuration Service. Users submit jobs to DIRAC using their local credentials. From then on, DIRAC has to interact with different Grid services on behalf of this user. DIRAC has a proxy management service where users upload short-lived proxies to be used when DIRAC needs to act on behalf of them. Long duration proxies are uploaded by us...
Current algebra constraints on K13 form factors
International Nuclear Information System (INIS)
Simmons, L.D.
1975-01-01
New theoretical constraints on the divergence form factor in K 13 decays are derived. The assumptions underlying the derivation are presented. The constraints on the divergence form factor are derived and summarized in the form of a theorem. It is shown that the finiteness of the leakage charge is a natural consequence of the parallelΔI vectorparallel = 1 / 2 rule. The Lorentz invariance of current algebra sum rules is discussed. The theorem is rederived within the context of the conserved vector current hypothesis. Finally, the implications of the present work are noted with attention being paid to both the theoretical and experimental consequences
Describing the nucleon electromagnetic form factors at high momentum transfers
International Nuclear Information System (INIS)
Theussl, L.; Desplanques, B.; Silvestre-Brac, B.; Varga, K.
1999-01-01
Electromagnetic form factors of the nucleon are calculated within the framework of a non-relativistic constituent-quark model. The emphasis is put on the reliability and accuracy of present day numerical methods used to solve the three-body problem. The high-q 2 behaviour of the form factors is determined by the form of the wave function at short distances and, due to the small absolute values that one deals with, an accurate solution is essential. Refs. 5, figs. 2 (author)
Dispersionless wave packets in Dirac materials
International Nuclear Information System (INIS)
Jakubský, Vít; Tušek, Matěj
2017-01-01
We show that a wide class of quantum systems with translational invariance can host dispersionless, soliton-like, wave packets. We focus on the setting where the effective, two-dimensional Hamiltonian acquires the form of the Dirac operator. The proposed framework for construction of the dispersionless wave packets is illustrated on silicene-like systems with topologically nontrivial effective mass. Our analytical predictions are accompanied by a numerical analysis and possible experimental realizations are discussed.
DIRAC: data production management
International Nuclear Information System (INIS)
Smith, A C; Tsaregorodtsev, A
2008-01-01
The LHCb Computing Model describes the dataflow for all stages in the processing of real and simulated events, and defines the role of LHCb associated Tier-1 and Tier-2 computing centers. The WLCG 'Dress Rehearsal' exercise aims to allow LHC experiments to deploy the full chain of their Computing Models, making use of all underlying WLCG services and resources, in preparation for real data taking. During this exercise simulated RAW physics data, matching the properties of eventual real data, will be uploaded from the LHCb Online storage system to Grid enabled storage. This data will then be replicated to LHCb Tier-1 centers and subsequently processed (reconstructed and stripped). The product of this processing is user analysis data that are distributed to all LHCb Tier-1 centers. DIRAC, LHCbs Workload and Data Management System, supports the implementation of the Computing Model in a data driven, real time and coordinated fashion. In this paper the LHCb Computing Model will be reviewed and the DIRAC components providing the needed functionality to support the Computing Model will be detailed. An evaluation of the preparedness for real data taking will also be given
DIRAC: data production management
Energy Technology Data Exchange (ETDEWEB)
Smith, A C [CERN, CH-1211, Geneva (Switzerland); Tsaregorodtsev, A [CPPM, Marseille (France)], E-mail: a.smith@cern.ch, E-mail: atsareg@in2p3.fr
2008-07-15
The LHCb Computing Model describes the dataflow for all stages in the processing of real and simulated events, and defines the role of LHCb associated Tier-1 and Tier-2 computing centers. The WLCG 'Dress Rehearsal' exercise aims to allow LHC experiments to deploy the full chain of their Computing Models, making use of all underlying WLCG services and resources, in preparation for real data taking. During this exercise simulated RAW physics data, matching the properties of eventual real data, will be uploaded from the LHCb Online storage system to Grid enabled storage. This data will then be replicated to LHCb Tier-1 centers and subsequently processed (reconstructed and stripped). The product of this processing is user analysis data that are distributed to all LHCb Tier-1 centers. DIRAC, LHCbs Workload and Data Management System, supports the implementation of the Computing Model in a data driven, real time and coordinated fashion. In this paper the LHCb Computing Model will be reviewed and the DIRAC components providing the needed functionality to support the Computing Model will be detailed. An evaluation of the preparedness for real data taking will also be given.
Overview of factors affecting the leachability of nuclear waste forms
International Nuclear Information System (INIS)
Stone, J.A.
1980-01-01
An overview of various factors that affect the leachability of nuclear waste forms is presented. The factors affect primarily the leaching system (temperature, for example), the leachant (pH, for example), or the solid being leached (surface condition, for example). A qualitative understanding exists of the major factors affecting leaching, but further studies are needed to establish leaching mechanisms and develop predictive models. 67 refs
Neural network real time event selection for the DIRAC experiment
Kokkas, P; Tauscher, Ludwig; Vlachos, S
2001-01-01
The neural network first level trigger for the DIRAC experiment at CERN is presented. Both the neural network algorithm used and its actual hardware implementation are described. The system uses the fast plastic scintillator information of the DIRAC spectrometer. In 210 ns it selects events with two particles having low relative momentum. Such events are selected with an efficiency of more than 0.94. The corresponding rate reduction for background events is a factor of 2.5. (10 refs).
International Nuclear Information System (INIS)
Casajus, A; Ciba, K; Fernandez, V; Graciani, R; Hamar, V; Mendez, V; Poss, S; Sapunov, M; Stagni, F; Tsaregorodtsev, A; Ubeda, M
2012-01-01
The DIRAC Project was initiated to provide a data processing system for the LHCb Experiment at CERN. It provides all the necessary functionality and performance to satisfy the current and projected future requirements of the LHCb Computing Model. A considerable restructuring of the DIRAC software was undertaken in order to turn it into a general purpose framework for building distributed computing systems that can be used by various user communities in High Energy Physics and other scientific application domains. The CLIC and ILC-SID detector projects started to use DIRAC for their data production system. The Belle Collaboration at KEK, Japan, has adopted the Computing Model based on the DIRAC system for its second phase starting in 2015. The CTA Collaboration uses DIRAC for the data analysis tasks. A large number of other experiments are starting to use DIRAC or are evaluating this solution for their data processing tasks. DIRAC services are included as part of the production infrastructure of the GISELA Latin America grid. Similar services are provided for the users of the France-Grilles and IBERGrid National Grid Initiatives in France and Spain respectively. The new communities using DIRAC started to provide important contributions to its functionality. Among recent additions can be mentioned the support of the Amazon EC2 computing resources as well as other Cloud management systems; a versatile File Replica Catalog with File Metadata capabilities; support for running MPI jobs in the pilot based Workload Management System. Integration with existing application Web Portals, like WS-PGRADE, is demonstrated. In this paper we will describe the current status of the DIRAC Project, recent developments of its framework and functionality as well as the status of the rapidly evolving community of the DIRAC users.
Dirac equation in Kerr space-time
Energy Technology Data Exchange (ETDEWEB)
Iyer, B R; Kumar, Arvind [Bombay Univ. (India). Dept. of Physics
1976-06-01
The weak-field low-velocity approximation of Dirac equation in Kerr space-time is investigated. The interaction terms admit of an interpretation in terms of a 'dipole-dipole' interaction in addition to coupling of spin with the angular momentum of the rotating source. The gravitational gyro-factor for spin is identified. The charged case (Kerr-Newman) is studied using minimal prescription for electromagnetic coupling in the locally intertial frame and to the leading order the standard electromagnetic gyro-factor is retrieved. A first order perturbation calculation of the shift of the Schwarzchild energy level yields the main interesting result of this work: the anomalous Zeeman splitting of the energy level of a Dirac particle in Kerr metric.
Magnetotransport in Layered Dirac Fermion System Coupled with Magnetic Moments
Iwasaki, Yoshiki; Morinari, Takao
2018-03-01
We theoretically investigate the magnetotransport of Dirac fermions coupled with localized moments to understand the physical properties of the Dirac material EuMnBi2. Using an interlayer hopping form, which simplifies the complicated interaction between the layers of Dirac fermions and the layers of magnetic moments in EuMnBi2, the theory reproduces most of the features observed in this system. The hysteresis observed in EuMnBi2 can be caused by the valley splitting that is induced by the spin-orbit coupling and the external magnetic field with the molecular field created by localized moments. Our theory suggests that the magnetotransport in EuMnBi2 is due to the interplay among Dirac fermions, localized moments, and spin-orbit coupling.
Dispersion-theoretical analysis of the nucleon electromagnetic form factors
Energy Technology Data Exchange (ETDEWEB)
Belushkin, M.
2007-09-29
The structure of the proton and the neutron is of fundamental importance for the study of the strong interaction dynamics over a wide range of momentum transfers. The nucleon form factors encode information on the internal structure of the nucleon as probed by the electromagnetic interaction, and, to a certain extent, reflect the charge and magnetisation distributions within the proton and the neutron. In this thesis we report on our investigation of the electromagnetic form factors of the proton and the neutron with dispersion relation techniques, including known experimental input on the {pi}{pi}, K anti K and the {rho}{pi} continua and perturbative QCD constraints. We include new experimental data on the pion form factor and the nucleon form factors in our simultaneous analysis of all four form factors in both the space- and the timelike regions for all momentum transfers, and perform Monte- Carlo sampling in order to obtain theoretical uncertainty bands. Finally, we discuss the implications of our results on the pion cloud of the nucleon, the nucleon radii and the Okubo-Zweig-Iizuka rule, and present our results of a model-independent approach to estimating two-photon effects in elastic electron-proton scattering. (orig.)
Dispersion-theoretical analysis of the nucleon electromagnetic form factors
International Nuclear Information System (INIS)
Belushkin, M.
2007-01-01
The structure of the proton and the neutron is of fundamental importance for the study of the strong interaction dynamics over a wide range of momentum transfers. The nucleon form factors encode information on the internal structure of the nucleon as probed by the electromagnetic interaction, and, to a certain extent, reflect the charge and magnetisation distributions within the proton and the neutron. In this thesis we report on our investigation of the electromagnetic form factors of the proton and the neutron with dispersion relation techniques, including known experimental input on the ππ, K anti K and the ρπ continua and perturbative QCD constraints. We include new experimental data on the pion form factor and the nucleon form factors in our simultaneous analysis of all four form factors in both the space- and the timelike regions for all momentum transfers, and perform Monte- Carlo sampling in order to obtain theoretical uncertainty bands. Finally, we discuss the implications of our results on the pion cloud of the nucleon, the nucleon radii and the Okubo-Zweig-Iizuka rule, and present our results of a model-independent approach to estimating two-photon effects in elastic electron-proton scattering. (orig.)
Electromagnetic form factors at large momenta from lattice QCD
International Nuclear Information System (INIS)
Chambers, Alexander J.; Dragos, J.; Michigan State Univ., East Lansing, MI; Horsley, R.
2017-01-01
Accessing hadronic form factors at large momentum transfers has traditionally presented a challenge for lattice QCD simulations. Here we demonstrate how a novel implementation of the Feynman-Hellmann method can be employed to calculate hadronic form factors in lattice QCD at momenta much higher than previously accessible. Our simulations are performed on a single set of gauge configurations with three flavours of degenerate mass quarks corresponding to m_π∼470 MeV. We are able to determine the electromagnetic form factors of the pion and nucleon up to approximately 6 GeV"2, with results for G_E/G_M in the proton agreeing well with experimental results.
Two-loop SL(2) form factors and maximal transcendentality
International Nuclear Information System (INIS)
Loebbert, Florian; Sieg, Christoph; Wilhelm, Matthias; Yang, Gang
2016-01-01
Form factors of composite operators in the SL(2) sector of N=4 SYM theory are studied up to two loops via the on-shell unitarity method. The non-compactness of this subsector implies the novel feature and technical challenge of an unlimited number of loop momenta in the integrand’s numerator. At one loop, we derive the full minimal form factor to all orders in the dimensional regularisation parameter. At two loops, we construct the complete integrand for composite operators with an arbitrary number of covariant derivatives, and we obtain the remainder functions as well as the dilatation operator for composite operators with up to three covariant derivatives. The remainder functions reveal curious patterns suggesting a hidden maximal uniform transcendentality for the full form factor. Finally, we speculate about an extension of these patterns to QCD.
Two-body form factors at high Q2
International Nuclear Information System (INIS)
Gross, F.; Keister, B.D.
1983-02-01
The charge form factor of a scalar deuteron at high momentum transfer is examined in a model employing scalar nucleons and mesons. With an eye toward establishing consistency criteria for more realistic calculations, several aspects of the model are examined in detail: the role of nucleon and meson singularities in the one-loop impulse diagram, the role of positive-and negative-energy nucleons, and the relationship to time-ordered perturbation theory. It is found that at large Q 2 (1) the form factor is dominated by a term in which the spectator nucleon is on the mass shell, and (2) the meson singularity structure of the d-n-p vertex function is unimportant in determining the overall high-Q 2 behaviour of the form factor
Computation of 3D form factors in complex environments
International Nuclear Information System (INIS)
Coulon, N.
1989-01-01
The calculation of radiant interchange among opaque surfaces in a complex environment poses the general problem of determining the visible and hidden parts of the environment. In many thermal engineering applications, surfaces are separated by radiatively non-participating media and may be idealized as diffuse emitters and reflectors. Consenquently the net radiant energy fluxes are intimately related to purely geometrical quantities called form factors, that take into account hidden parts: the problem is reduced to the form factor evaluation. This paper presents the method developed for the computation of 3D form factors in the finite-element module of the system TRIO, which is a general computer code for thermal and fluid flow analysis. The method is derived from an algorithm devised for synthetic image generation. A comparison is performed with the standard contour integration method also implemented and suited to convex geometries. Several illustrative examples of finite-element thermal calculations in radiating enclosures are given
Two-loop SL(2) form factors and maximal transcendentality
Energy Technology Data Exchange (ETDEWEB)
Loebbert, Florian [Institut für Physik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Sieg, Christoph [Institut für Physik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Institut für Mathematik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Wilhelm, Matthias [Institut für Physik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Institut für Mathematik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Niels Bohr Institute, Copenhagen University,Blegdamsvej 17, 2100 Copenhagen Ø (Denmark); Yang, Gang [CAS Key Laboratory of Theoretical Physics,Institute of Theoretical Physics, Chinese Academy of Sciences,Beijing 100190 (China); Institut für Physik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany)
2016-12-19
Form factors of composite operators in the SL(2) sector of N=4 SYM theory are studied up to two loops via the on-shell unitarity method. The non-compactness of this subsector implies the novel feature and technical challenge of an unlimited number of loop momenta in the integrand’s numerator. At one loop, we derive the full minimal form factor to all orders in the dimensional regularisation parameter. At two loops, we construct the complete integrand for composite operators with an arbitrary number of covariant derivatives, and we obtain the remainder functions as well as the dilatation operator for composite operators with up to three covariant derivatives. The remainder functions reveal curious patterns suggesting a hidden maximal uniform transcendentality for the full form factor. Finally, we speculate about an extension of these patterns to QCD.
Electromagnetic form factors of the Ω- in lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Korzec, T.; Koutsou, G.; Negele, J. W.; Proestos, Y.
2010-01-01
We present results on the omega baryon (Ω - ) electromagnetic form factors using N f =2+1 domain-wall fermion configurations for three pion masses in the range of about 350 to 300 MeV. We compare results obtained using domain-wall fermions with those of a mixed-action (hybrid) approach, which combines domain-wall valence quarks on staggered sea quarks, for a pion mass of about 350 MeV. We pay particular attention in the evaluation of the subdominant electric quadrupole form factor to sufficient accuracy to exclude a zero value, by constructing a sequential source that isolates it from the dominant form factors. The Ω - magnetic moment, μ Ω - , and the electric charge and magnetic radius, E0/M1 2 >, are extracted for these pion masses. The electric quadrupole moment is determined for the first time using dynamical quarks.
Evaluation of E2 form factor = 24Mg
International Nuclear Information System (INIS)
Marinelli, J.R.; Moreira, J.R.
1988-11-01
Longitudinal and transverse electron scattering form factors for the 2 + state at 1.37 Mev of the 24 Mg nucleus was evaluated with rotational model wavefunctions. Four different approaches were used for the transverse E2 form factor: PHF, cranking model, ridig rotor and irrotational flow. For the nuclear intrinsic wavefunction, the Nilsson model was assumed in all approaches yielding the calculation of the form factor in PWBA and DWBA. The results are discussed and compared with a recent measurement performed with 180 0 electron scattered from this state. The DWBA calculation, taking into account first order corrections shows that PHF and irrotational flow models give the best agreements with the available data and compete in quality with more complex calculation performed under the 'shell model' approach. (author) [pt
Crucial test of the Dirac cosmologies
International Nuclear Information System (INIS)
Steigman, G.
1978-01-01
In a cosmology consistent with the Cosmological Principle (large scale, statistical isotropy and homogeneity of the universe), a Planck spectrum is not preserved as the universe evolves unless the number of photons in a comoving volume is conserved. It is shown that a large class of cosmological models based on Dirac's Large Numbers Hypothesis (LNH) violate this constraint. The observed isotropy and spectral distribution of the microwave background radiation thus provide a crucial test of such cosmologies. After reviewing the LNH, the general evolution of radiation spectra in cosmologies consistent with the cosmological principle is outlined. It is shown that the predicted deviations from a Planck spectrum for Dirac cosmologies (as well as for ''tired-light'' cosmologies) are enormous. The Planckian (or near-Planckian) spectral form for the microwave radiation provides a crucial test, failed by such cosmologies
Master integrals for the four-loop Sudakov form factor
International Nuclear Information System (INIS)
Boels, Rutger; Kniehl, Bernd A.; Yang, Gang; Chinese Academy of Sciences, Beijing
2015-08-01
The light-like cusp anomalous dimension is a universal function in the analysis of infrared divergences. In maximally (N=4) supersymmetric Yang-Mills theory (SYM) in the planar limit, it is known, in principle, to all loop orders. The non-planar corrections are not known in any theory, with the first appearing at the four-loop order. Probably the simplest quantity which contains this correction is the four-loop two-point form factor of the stress tensor multiplet. This form factor was obtained in integrand form in a previous work for N=4 SYM, up to a single parameter. In this work, a reduction of the appearing integrals obtained by solving integration-by-parts (IBP) identities using (a tweaked version of) Reduze is reported. The form factor is shown to be independent of the remaining parameter at integrand level due to an intricate pattern of cancellations after IBP reduction. The appearing master integrals are cross-checked using algebraic techniques explored in the Mint package. The latter results provide the basis of master integrals applicable to generic form factors, including those in Quantum Chromodynamics. Remaining bottlenecks to completing the computation of the four-loop non-planar cusp anomalous dimension in N=4 SYM and beyond are identified.
Master integrals for the four-loop Sudakov form factor
Directory of Open Access Journals (Sweden)
Rutger H. Boels
2016-01-01
Full Text Available The light-like cusp anomalous dimension is a universal function in the analysis of infrared divergences. In maximally (N=4 supersymmetric Yang–Mills theory (SYM in the planar limit, it is known, in principle, to all loop orders. The non-planar corrections are not known in any theory, with the first appearing at the four-loop order. The simplest quantity which contains this correction is the four-loop two-point form factor of the stress tensor multiplet. This form factor was largely obtained in integrand form in a previous work for N=4 SYM, up to a free parameter. In this work, a reduction of the appearing integrals obtained by solving integration-by-parts (IBP identities using a modified version of Reduze is reported. The form factor is shown to be independent of the remaining parameter at integrand level due to an intricate pattern of cancellations after IBP reduction. Moreover, two of the integral topologies vanish after reduction. The appearing master integrals are cross-checked using independent algebraic-geometry techniques explored in the Mint package. The latter results provide the basis of master integrals applicable to generic form factors, including those in Quantum Chromodynamics. Discrepancies between explicitly solving the IBP relations and the MINT approach are highlighted. Remaining bottlenecks to completing the computation of the four-loop non-planar cusp anomalous dimension in N=4 SYM and beyond are identified.
Nucleon quark structure and strong meson-nucleon form factors
International Nuclear Information System (INIS)
Efimov, G.V.; Ivanov, M.A.
1987-01-01
The nucleon is considered as a three-quark system in virton-quark model. The main statistic properties of proton and neutron are calculated: magnetic moments, electromagnetic radii, G A /G V ratio in weak neutron decay. Strong meson-nucleon form factors which determine nucleon-nucleon potential are obtained as a function of squared transfer momentum of mesons. The results are compared with phenomenological form factors used for description of phases of NN-scattering in the one-boson-, exchange model
Towards a dispersive determination of the pion transition form factor
Leupold, Stefan; Hoferichter, Martin; Kubis, Bastian; Niecknig, Franz; Schneider, Sebastian P.
2018-01-01
We start with a brief motivation why the pion transition form factor is interesting and, in particular, how it is related to the high-precision standard-model calculation of the gyromagnetic ratio of the muon. Then we report on the current status of our ongoing project to calculate the pion transition form factor using dispersion theory. Finally we present and discuss a wish list of experimental data that would help to improve the input for our calculations and/or to cross-check our results.
Towards a dispersive determination of the pion transition form factor
Directory of Open Access Journals (Sweden)
Leupold Stefan
2018-01-01
Full Text Available We start with a brief motivation why the pion transition form factor is interesting and, in particular, how it is related to the high-precision standard-model calculation of the gyromagnetic ratio of the muon. Then we report on the current status of our ongoing project to calculate the pion transition form factor using dispersion theory. Finally we present and discuss a wish list of experimental data that would help to improve the input for our calculations and/or to cross-check our results.
Measurement of the Charged Pion Electromagnetic Form Factor
International Nuclear Information System (INIS)
J. Volmer; David Abbott; H. Anklin; Chris Armstrong; John Arrington; K. Assamagan; Steven Avery; Oliver K. Baker; Henk Blok; C. Bochna; Ed Brash; Herbert Breuer; Nicholas Chant; Jim Dunne; Tom Eden; Rolf Ent; David Gaskell; Ron Gilman; Kenneth Gustafsson; Wendy Hinton; Garth Huber; Hal Jackson; Mark K. Jones; Cynthia Keppel; P.H. Kim; Wooyoung Kim; Andi Klein; Doug Koltenuk; Meme Liang; George Lolos; Allison Lung; David Mack; D. McKee; David Meekins; Joseph Mitchell; H. Mkrtchian; B. Mueller; Gabriel Niculescu; Ioana Niculescu; D. Pitz; D. Potterveld; Liming Qin; Juerg Reinhold; I.K. Shin; Stepan Stepanyan; V. Tadevosian; L.G. Tang; R.L.J. van der Meer; K. Vansyoc; D. Van Westrum; Bill Vulcan; Stephen Wood; Chen Yan; W.X. Zhao; Beni Zihlmann
2001-01-01
Separated longitudinal and transverse structure functions for the reaction 1H(e,eprime pi+)n were measured in the momentum transfer region Q2=0.6-1.6 (GeV/c)**2 at a value of the invariant mass W=1.95 GeV. New values for the pion charge form factor were extracted from the longitudinal cross section by using a recently developed Regge model. The results indicate that the pion form factor in this region is larger than previously assumed and is consistent with a monopole parameterization fitted to very low Q2 elastic data
Form factors and structure functions of hadrons in parton model
International Nuclear Information System (INIS)
Volkonskij, N.Yu.
1979-01-01
The hadron charge form factors and their relation to the deep-inelastic lepton-production structure functions in the regions of asymptotically high and small momentum transfer Q 2 are studied. The nucleon and pion charge radii are calculated. The results of calculations are in good agreement with the experimental data. The K- and D-meson charge radii are estimated. In the region of asymptotically high Q 2 the possibility of Drell-Yan-West relation violation is analyzed. It is shown, that for pseudoscalar mesons this relation is violated. The relation between the proton and neutron form factor asymptotics is obtained
Deuteron form factor measurements at low momentum transfers
Directory of Open Access Journals (Sweden)
Schlimme B. S.
2016-01-01
Full Text Available A precise measurement of the elastic electron-deuteron scattering cross section at four-momentum transfers of 0.24 fm−1 ≤ Q ≤ 2.7 fm−1 has been performed at the Mainz Microtron. In this paper we describe the utilized experimental setup and the necessary analysis procedure to precisely determine the deuteron charge form factor from these data. Finally, the deuteron charge radius rd can be extracted from an extrapolation of that form factor to Q2 = 0.
DIRAC data production management
Smith, A C
2008-01-01
The LHCb Computing Model describes the dataflow for all stages in the processing of real and simulated events, and defines the role of LHCb associated Tier-1 and Tier-2 computing centers. The WLCG 'Dress Rehearsal' exercise aims to allow LHC experiments to deploy the full chain of their Computing Models, making use of all underlying WLCG services and resources, in preparation for real data taking. During this exercise simulated RAW physics data, matching the properties of eventual real data, will be uploaded from the LHCb Online storage system to Grid enabled storage. This data will then be replicated to LHCb Tier-1 centers and subsequently processed (reconstructed and stripped). The product of this processing is user analysis data that are distributed to all LHCb Tier-1 centers. DIRAC, LHCbs Workload and Data Management System, supports the implementation of the Computing Model in a data driven, real time and coordinated fashion.
Smith, A C
2007-01-01
The LHCb experiment being built to utilize CERN’s flagship Large Hadron Collider will generate data to be analysed by a community of over 600 physicists worldwide. DIRAC, LHCb’s Workload and Data Management System, facilitates the use of underlying EGEE Grid resources to generate, process and analyse this data in the distributed environment. The Data Management System, presented here, provides real-time, data-driven distribution in accordance with LHCb’s Computing Model. The data volumes produced by the LHC experiments are unprecedented, rendering individual institutes and even countries, unable to provide the computing and storage resources required to make full use of the produced data. EGEE Grid resources allow the processing of LHCb data possible in a distributed fashion and LHCb’s Computing Model is based on this approach. Data Management in this environment requires reliable and high-throughput transfer of data, homogeneous access to storage resources and the cataloguing of data replicas, all of...
The Nucleon Axial Form Factor and Staggered Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Meyer, Aaron Scott [Chicago U.
2017-01-01
The study of neutrino oscillation physics is a major research goal of the worldwide particle physics program over the upcoming decade. Many new experiments are being built to study the properties of neutrinos and to answer questions about the phenomenon of neutrino oscillation. These experiments need precise theoretical cross sections in order to access fundamental neutrino properties. Neutrino oscillation experiments often use large atomic nuclei as scattering targets, which are challenging for theorists to model. Nuclear models rely on free-nucleon amplitudes as inputs. These amplitudes are constrained by scattering experiments with large nuclear targets that rely on the very same nuclear models. The work in this dissertation is the rst step of a new initiative to isolate and compute elementary amplitudes with theoretical calculations to support the neutrino oscillation experimental program. Here, the eort focuses on computing the axial form factor, which is the largest contributor of systematic error in the primary signal measurement process for neutrino oscillation studies, quasielastic scattering. Two approaches are taken. First, neutrino scattering data on a deuterium target are reanalyzed with a model-independent parametrization of the axial form factor to quantify the present uncertainty in the free-nucleon amplitudes. The uncertainties on the free-nucleon cross section are found to be underestimated by about an order of magnitude compared to the ubiquitous dipole model parametrization. The second approach uses lattice QCD to perform a rst-principles computation of the nucleon axial form factor. The Highly Improved Staggered Quark (HISQ) action is employed for both valence and sea quarks. The results presented in this dissertation are computed at physical pion mass for one lattice spacing. This work presents a computation of the axial form factor at zero momentum transfer, and forms the basis for a computation of the axial form factor momentum dependence
Perturbative corrections to B → D form factors in QCD
Wang, Yu-Ming; Wei, Yan-Bing; Shen, Yue-Long; Lü, Cai-Dian
2017-06-01
We compute perturbative QCD corrections to B → D form factors at leading power in Λ/ m b , at large hadronic recoil, from the light-cone sum rules (LCSR) with B-meson distribution amplitudes in HQET. QCD factorization for the vacuum-to- B-meson correlation function with an interpolating current for the D-meson is demonstrated explicitly at one loop with the power counting scheme {m}_c˜ O(√{Λ {m}_b}) . The jet functions encoding information of the hard-collinear dynamics in the above-mentioned correlation function are complicated by the appearance of an additional hard-collinear scale m c , compared to the counterparts entering the factorization formula of the vacuum-to- B-meson correction function for the construction of B → π from factors. Inspecting the next-to-leading-logarithmic sum rules for the form factors of B → Dℓν indicates that perturbative corrections to the hard-collinear functions are more profound than that for the hard functions, with the default theory inputs, in the physical kinematic region. We further compute the subleading power correction induced by the three-particle quark-gluon distribution amplitudes of the B-meson at tree level employing the background gluon field approach. The LCSR predictions for the semileptonic B → Dℓν form factors are then extrapolated to the entire kinematic region with the z-series parametrization. Phenomenological implications of our determinations for the form factors f BD +,0 ( q 2) are explored by investigating the (differential) branching fractions and the R( D) ratio of B → Dℓν and by determining the CKM matrix element |V cb | from the total decay rate of B → Dμν μ .
On form factors and correlation functions in twistor space
International Nuclear Information System (INIS)
Koster, Laura; Mitev, Vladimir; Staudacher, Matthias; Wilhelm, Matthias
2017-01-01
In this paper, we continue our study of form factors and correlation functions of gauge-invariant local composite operators in the twistor-space formulation of N=4 super Yang-Mills theory. Using the vertices for these operators obtained in our recent papers (DOI: 10.1103/PhysRevLett.117.011601; 10.1007/JHEP06(2016)162 ), we show how to calculate the twistor-space diagrams for general N k MHV form factors via the inverse soft limit, in analogy to the amplitude case. For general operators without α-dot indices, we then reexpress the NMHV form factors from the position-twistor calculation in terms of momentum twistors, deriving and expanding on a relation between the two twistor formalisms previously observed in the case of amplitudes. Furthermore, we discuss the calculation of generalized form factors and correlation functions as well as the extension to loop level, in particular providing an argument promised in https://www.doi.org/10.1002/prop.201400085.
Heavy quark form factors at two loops in perturbative QCD
International Nuclear Information System (INIS)
Ablinger, J.; Schneider, C.; Behring, A.; Falcioni, G.
2017-11-01
We present the results for heavy quark form factors at two-loop order in perturbative QCD for different currents, namely vector, axial-vector, scalar and pseudo-scalar currents, up to second order in the dimensional regularization parameter. We outline the necessary computational details, ultraviolet renormalization and corresponding universal infrared structure.
Generation of truncated recombinant form of tumor necrosis factor ...
African Journals Online (AJOL)
7. Original Research Article. Generation of truncated recombinant form of tumor necrosis factor ... as 6×His tagged using E.coli BL21 (DE3) expression system. The protein was ... proapoptotic signaling cascade through TNFR1. [5] which is ...
Pion form factor within QCD instanton vacuum model
International Nuclear Information System (INIS)
Dorokhov, A.E.
1997-01-01
Instanton induced pion wave function is constructed. It provides an intrinsic k 1 dependence which suppress soft virtual one-gluon exchanges and thus legitimate the perturbative QCD (pQCD) calculations of the pion electromagnetic form factor in the region of momentum transfers above the scale. (author)
Form factors and charge radii in a quantum chromodynamics ...
Indian Academy of Sciences (India)
tic form factors and charge radii of D, Ds,B,Bs and Bc mesons in a quantum chromodynamics. (QCD)-inspired ... as pointed out in [12,13], one can expect a similar success here too. .... 0 were large and the formalism failed to account for large ...
Numerical study of the lattice meson form factor
International Nuclear Information System (INIS)
Woloshyn, R.M.; Kobos, A.M.
1986-01-01
The electric form factor of the pseudo-Goldstone meson (the generic pion) is calculated in quenched lattice quantum chromodynamics with SU(2) color. Charge radii are calculated for different values of the bare-quark mass. The results are in agreement with the physically reasonable expectation that heavier quarks have distributions of smaller radius
Dispersive analysis of the pion transition form factor
Energy Technology Data Exchange (ETDEWEB)
Hoferichter, M. [Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, ExtreMe Matter Institute EMMI, Darmstadt (Germany); University of Bern, Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, Bern (Switzerland); Kubis, B.; Niecknig, F.; Schneider, S.P. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Bonn (Germany); Leupold, S. [Uppsala Universitet, Institutionen foer fysik och astronomi, Box 516, Uppsala (Sweden)
2014-11-15
We analyze the pion transition form factor using dispersion theory. We calculate the singly-virtual form factor in the time-like region based on data for the e{sup +}e{sup -} → 3π cross section, generalizing previous studies on ω, φ → 3π decays and γπ → ππ scattering, and verify our result by comparing to e{sup +}e{sup -} → π{sup 0}γ data. We perform the analytic continuation to the space-like region, predicting the poorlyconstrained space-like transition form factor below 1 GeV, and extract the slope of the form factor at vanishing momentum transfer a{sub π} = (30.7 ± 0.6) x 10{sup -3}. We derive the dispersive formalism necessary for the extension of these results to the doubly-virtual case, as required for the pion-pole contribution to hadronic light-by-light scattering in the anomalous magnetic moment of the muon. (orig.)
Measurement of the pion form factor at higher energies
Energy Technology Data Exchange (ETDEWEB)
Mack, D.J. [CEBAF, Newport News, VA (United States)
1994-04-01
One of the strongest arguments for increasing the nominal CEBAF beam energy to equal or exceed 6 GeV is that one would be able to make quality high Q{sup 2} measurements of the charged pion form factor.
Δ(1232) Axial Charge and Form Factors from Lattice QCD
International Nuclear Information System (INIS)
Alexandrou, Constantia; Gregory, Eric B.; Korzec, Tomasz; Koutsou, Giannis; Negele, John W.; Sato, Toru; Tsapalis, Antonios
2011-01-01
We present the first calculation on the Δ axial vector and pseudoscalar form factors using lattice QCD. Two Goldberger-Treiman relations are derived and examined. A combined chiral fit is performed to the nucleon axial charge, N to Δ axial transition coupling constant and Δ axial charge.
On form factors and correlation functions in twistor space
Energy Technology Data Exchange (ETDEWEB)
Koster, Laura [Institut für Mathematik, Institut für Physik und IRIS Adlershof,Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Mitev, Vladimir [PRISMA Cluster of Excellence, Institut für Physik, WA THEP,Johannes Gutenberg-Universität Mainz,Staudingerweg 7, 55128 Mainz (Germany); Staudacher, Matthias [Institut für Mathematik, Institut für Physik und IRIS Adlershof,Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Wilhelm, Matthias [Niels Bohr Institute, Copenhagen University,Blegdamsvej 17, 2100 Copenhagen Ø (Denmark)
2017-03-24
In this paper, we continue our study of form factors and correlation functions of gauge-invariant local composite operators in the twistor-space formulation of N=4 super Yang-Mills theory. Using the vertices for these operators obtained in our recent papers (DOI: 10.1103/PhysRevLett.117.011601; 10.1007/JHEP06(2016)162 ), we show how to calculate the twistor-space diagrams for general N{sup k}MHV form factors via the inverse soft limit, in analogy to the amplitude case. For general operators without α-dot indices, we then reexpress the NMHV form factors from the position-twistor calculation in terms of momentum twistors, deriving and expanding on a relation between the two twistor formalisms previously observed in the case of amplitudes. Furthermore, we discuss the calculation of generalized form factors and correlation functions as well as the extension to loop level, in particular providing an argument promised in https://www.doi.org/10.1002/prop.201400085.
Heavy quark form factors at two loops in perturbative QCD
Energy Technology Data Exchange (ETDEWEB)
Ablinger, J.; Schneider, C. [Johannes Kepler Univ., Linz (Austria). Research Inst. for Symbolic Computation (RISC); Behring, A. [RWTH Aachen Univ. (Germany). Inst. fuer Theoretische Teilchenphysik und Kosmologie; Bluemlein, J.; Freitas, A. de; Marquard, P.; Rana, N. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Falcioni, G. [Nikhef, Amsterdam (Netherlands). Theory Group
2017-11-15
We present the results for heavy quark form factors at two-loop order in perturbative QCD for different currents, namely vector, axial-vector, scalar and pseudo-scalar currents, up to second order in the dimensional regularization parameter. We outline the necessary computational details, ultraviolet renormalization and corresponding universal infrared structure.
Finite nucleus Dirac mean field theory and random phase approximation using finite B splines
International Nuclear Information System (INIS)
McNeil, J.A.; Furnstahl, R.J.; Rost, E.; Shepard, J.R.; Department of Physics, University of Maryland, College Park, Maryland 20742; Department of Physics, University of Colorado, Boulder, Colorado 80309)
1989-01-01
We calculate the finite nucleus Dirac mean field spectrum in a Galerkin approach using finite basis splines. We review the method and present results for the relativistic σ-ω model for the closed-shell nuclei 16 O and 40 Ca. We study the convergence of the method as a function of the size of the basis and the closure properties of the spectrum using an energy-weighted dipole sum rule. We apply the method to the Dirac random-phase-approximation response and present results for the isoscalar 1/sup -/ and 3/sup -/ longitudinal form factors of 16 O and 40 Ca. We also use a B-spline spectral representation of the positive-energy projector to evaluate partial energy-weighted sum rules and compare with nonrelativistic sum rule results
Form factors and radiation widths of the giant multipole resonances
International Nuclear Information System (INIS)
Denisov, V.Yu.
1990-01-01
Simple analytic relations for the form factors of inelastic electron scattering in the Born approximation and radiation widths of the isovector and isoscalar giant multipole resonances are derived. The dynamic relationship between the volume and surface density vibrations were taken into account in this calculation. The form factors in the Born approximation were found to be in satisfactory agreement with experimental data in the region of small transferred momenta. The radiation widths of isoscalar multipole resonances increase when the number of nucleons increase as A 1/3 , and for isovector resonances this dependence has the form f(A)A 1/3 , where f(A) is a slowly increasing function of A. Radiation widths well fit the experimental data
A compact expression for bilinear combination of Dirac spinors via world tensors
International Nuclear Information System (INIS)
Rogalev, R.N.
1994-01-01
A compact expression for a product of two Dirac spinors is obtained as a linear combination of 16 Dirac γ-matrices. The result is presented in a convenient from, which can give rise to using it for analytical calculations of multiparticle amplitudes. It has been shown that a bilinear combination of Dirac spinors can be expressed by momentum and spin vectors of the corresponding particles up to a phase factor. 8 refs
International Nuclear Information System (INIS)
Skyrme, T.H.R.
1994-01-01
In a model quantum theory of interacting mesons, the motion of certain conserved particle-like structures is discussed. It is shown how collective coordinates may be introduced to describe them, leading, in lowest approximation, to a Dirac equation. (author)
Self-Assembled Si(111) Surface States: 2D Dirac Material for THz Plasmonics
Wang, Z. F.; Liu, Feng
2015-07-01
Graphene, the first discovered 2D Dirac material, has had a profound impact on science and technology. In the last decade, we have witnessed huge advances in graphene related fundamental and applied research. Here, based on first-principles calculations, we propose a new 2D Dirac band on the Si(111) surface with 1 /3 monolayer halogen coverage. The s p3 dangling bonds form a honeycomb superstructure on the Si(111) surface that results in an anisotropic Dirac band with a group velocity (˜106 m /s ) comparable to that in graphene. Most remarkably, the Si-based surface Dirac band can be used to excite a tunable THz plasmon through electron-hole doping. Our results demonstrate a new way to design Dirac states on a traditional semiconductor surface, so as to make them directly compatible with Si technology. We envision this new type of Dirac material to be generalized to other semiconductor surfaces with broad applications.
Analysis of the strong coupling form factors of ΣbNB and ΣcND in QCD sum rules
Yu, Guo-Liang; Wang, Zhi-Gang; Li, Zhen-Yu
2017-08-01
In this article, we study the strong interaction of the vertices Σ b NB and Σ c ND using the three-point QCD sum rules under two different Dirac structures. Considering the contributions of the vacuum condensates up to dimension 5 in the operation product expansion, the form factors of these vertices are calculated. Then, we fit the form factors into analytical functions and extrapolate them into time-like regions, which gives the coupling constants. Our analysis indicates that the coupling constants for these two vertices are G ΣbNB = 0.43±0.01 GeV-1 and G ΣcND = 3.76±0.05 GeV-1. Supported by Fundamental Research Funds for the Central Universities (2016MS133)
Analytical solutions for Dirac and Klein-Gordon equations using Backlund transformations
Energy Technology Data Exchange (ETDEWEB)
Zabadal, Jorge R.; Borges, Volnei, E-mail: jorge.zabadal@ufrgs.br, E-mail: borges@ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Dept. de Engenharia Mecanica; Ribeiro, Vinicius G., E-mail: vinicius_ribeiro@uniritter.edu.br [Centro Universitario Ritter dos Reis (UNIRITTER), Porto Alegre, RS (Brazil); Santos, Marcio, E-mail: marciophd@gmail.com [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Centro de Estudos Interdisciplinares
2015-07-01
This work presents a new analytical method for solving Klein-Gordon type equations via Backlund transformations. The method consists in mapping the Klein-Gordon model into a first order system of partial differential equations, which contains a generalized velocity field instead of the Dirac matrices. This system is a tensor model for quantum field theory whose space solution is wider than the Dirac model in the original form. Thus, after finding analytical expressions for the wave functions, the Maxwell field can be readily obtained from the Dirac equations, furnishing a self-consistent field solution for the Maxwell-Dirac system. Analytical and numerical results are reported. (author)
CERN Bulletin
2010-01-01
When a group of physicists entered the Main Auditorium, during the evening of 29 June, they felt they had opened a time portal. Paul Dirac in front of a blackboard showing his formula. ©Sandra Hoogeboom An attentive audience, dressed in early 1900 costumes, were watching a lecture by the elusive Paul Dirac, presenting for the first time his famous formula on the blackboard. Paul Adrien Maurice Dirac (1902-1984) was a British mathematical physicist at Cambridge, and one of the "fathers" of quantum mechanics. When he first wrote it, in 1928, Dirac was not sure what his formula really meant. As demonstrated by Andersson four year later, what Dirac had written on the blackboard was the first definition of a positron, hence he is credited with having anticipated the existence of antimatter. The actor John Kohl performs as Paul Dirac. ©Sandra Hoogeboom What the group of puzzled physicists were really observing when they entered the CERN Auditorium was the shoo...
The Factors of Forming the National HR-Management Model
Directory of Open Access Journals (Sweden)
Elena P. Kostenko
2017-12-01
Full Text Available There are some factors considered in this article, which influence the forming of national HR-management model. The group-forming criterion is the nature of factors, that determine the system of HR-management as a system of corporate culture values, norms and rules of organizational behavior, ways of realization some important managing functions and dominating approaches to make decisions. This article shows that the plurality of combinations in different factors leads to forming the unique HR-management model. The geoclimatic factor influences the principles of the labor organization (orientation primarily on individual or collective forms of labor, attitude to the management experience of other countries, attitude to resources, etc., the distribution of labor resources, the level of labor mobility, and the psychosocial type of employee. Models of man's labor behavior are constituted In the process of historical development. Attention is focused on the formation of a national HR-model, such as the conducted socio-economic policy, the characteristics of the institutional environment, economic goals and priorities of the country's development, the level of development and the nature of the national productive forces and economic structures. Much attention was paid to the analysis of the historically formed value system and labor traditions, which influence the approaches to HR-management. As far as religion influences the model of person’s inclusion in labor, motives of labor behavior, management culture of a certain employee, preferred payment etc., we examined how the main traditional religions (Christianity, Islam, Judaism, Buddhism, Confucianism, Hinduism influence the HR-management system in different countries.
Form factor of some types of toroidal solenoids
International Nuclear Information System (INIS)
Koryavko, V.I.; Litvinenko, Yu.A.
1979-01-01
Obtained were the type of dependence between consumed power and formed field for toroidal helical-wound solenoids and the expression for the form factor analogous to the Fabry coefficient for cylindrical solenoids. Determined were optimum dimensions of the helical winding of ''forceless'' toroidal solenoids satisfying the condition of the formation of maximum field at minimum consumed power. Investigations also covered some types of conventional toroidal solenoids. Presented in the paper diagrams permitted to chose dimensions of the considered toroidal solenoids according to their consumed power and winding material volume
Quantum transport through 3D Dirac materials
Energy Technology Data Exchange (ETDEWEB)
Salehi, M. [Department of Physics, Sharif University of Technology, Tehran 11155-9161 (Iran, Islamic Republic of); Jafari, S.A., E-mail: jafari@physics.sharif.edu [Department of Physics, Sharif University of Technology, Tehran 11155-9161 (Iran, Islamic Republic of); Center of Excellence for Complex Systems and Condensed Matter (CSCM), Sharif University of Technology, Tehran 1458889694 (Iran, Islamic Republic of)
2015-08-15
Bismuth and its alloys provide a paradigm to realize three dimensional materials whose low-energy effective theory is given by Dirac equation in 3+1 dimensions. We study the quantum transport properties of three dimensional Dirac materials within the framework of Landauer–Büttiker formalism. Charge carriers in normal metal satisfying the Schrödinger equation, can be split into four-component with appropriate matching conditions at the boundary with the three dimensional Dirac material (3DDM). We calculate the conductance and the Fano factor of an interface separating 3DDM from a normal metal, as well as the conductance through a slab of 3DDM. Under certain circumstances the 3DDM appears transparent to electrons hitting the 3DDM. We find that electrons hitting the metal-3DDM interface from metallic side can enter 3DDM in a reversed spin state as soon as their angle of incidence deviates from the direction perpendicular to interface. However the presence of a second interface completely cancels this effect.
Quantum transport through 3D Dirac materials
International Nuclear Information System (INIS)
Salehi, M.; Jafari, S.A.
2015-01-01
Bismuth and its alloys provide a paradigm to realize three dimensional materials whose low-energy effective theory is given by Dirac equation in 3+1 dimensions. We study the quantum transport properties of three dimensional Dirac materials within the framework of Landauer–Büttiker formalism. Charge carriers in normal metal satisfying the Schrödinger equation, can be split into four-component with appropriate matching conditions at the boundary with the three dimensional Dirac material (3DDM). We calculate the conductance and the Fano factor of an interface separating 3DDM from a normal metal, as well as the conductance through a slab of 3DDM. Under certain circumstances the 3DDM appears transparent to electrons hitting the 3DDM. We find that electrons hitting the metal-3DDM interface from metallic side can enter 3DDM in a reversed spin state as soon as their angle of incidence deviates from the direction perpendicular to interface. However the presence of a second interface completely cancels this effect
Measurement of weak meson form factors in spacelike regions
Brene, N
1973-01-01
With the construction of high energy, high intensity accelerators (NAL & CERN, SPS) investigation of neutrino scattering on virtual pions, a la Chew-Low, becomes experimentally possible. The process nu +N to mu /sup -/+K+ Delta is analysed to extract the usual K/sub l3/ form factor(s) for spacelike momentum transfer. A model calculation suggests that f/sub +/(T) can be determined reasonably well from a triple differential cross section, whereas only rough information on f /sub -/(T) may be obtained from the transverse polarization of the muon. The experiment proposed requires scanning of several millions of bubble chamber pictures. (14 refs).
Electromagnetic form factors and vertex constants for 6Li
International Nuclear Information System (INIS)
Blokhintsev, L.D.; Shvarts, I.A.
1977-01-01
It has been assumed that the main contribution to the rapidly changing part of the charge form factor of 6 Li provides the amplitude of the triangle diagram containing virtual lines of deuteron and α particle. The vertex constant G 2 for the 6 Li→α+d decay is expressed through the nuclear charge radii for 6 Li, d, and α. Taking into account coulomb interaction in the vertex of the 6 Li→α+d reaction increases G 2 by about a factor of two. The account of virtuality of a deuteron cluster also leads to an increase in G 2
Revisiting the pion's scalar form factor in chiral perturbation theory
Juttner, Andreas
2012-01-01
The quark-connected and the quark-disconnected Wick contractions contributing to the pion's scalar form factor are computed in the two and in the three flavour chiral effective theory at next-to-leading order. While the quark-disconnected contribution to the form factor itself turns out to be power-counting suppressed its contribution to the scalar radius is of the same order of magnitude as the one of the quark-connected contribution. This result underlines that neglecting quark-disconnected contributions in simulations of lattice QCD can cause significant systematic effects. The technique used to derive these predictions can be applied to a large class of observables relevant for QCD-phenomenology.
SU(3) breaking in hyperon transition vector form factors
International Nuclear Information System (INIS)
Shanahan, P.E.; Thomas, A.W.; Young, R.D.; Zanotti, J.M.; Rakow, P.E.L.
2015-08-01
We present a calculation of the SU(3)-breaking corrections to the hyperon transition vector form factors to O(p 4 ) in heavy baryon chiral perturbation theory with finite-range regularisation. Both octet and decuplet degrees of freedom are included. We formulate a chiral expansion at the kinematic point Q 2 =-(M B 1 -M B 2 ) 2 , which can be conveniently accessed in lattice QCD. The two unknown low-energy constants at this point are constrained by lattice QCD simulation results for the Σ - →n and Ξ 0 →Σ + transition form factors. Hence we determine lattice-informed values of f 1 at the physical point. This work constitutes progress towards the precise determination of vertical stroke V us vertical stroke from hyperon semileptonic decays.
Sine-Gordon breather form factors and quantum field equations
International Nuclear Information System (INIS)
Babujian, H; Karowski, M
2002-01-01
Using the results of previous investigations on sine-Gordon form factors, exact expressions of all breather matrix elements are obtained for several operators: all powers of the fundamental Bose field, general exponentials of it, the energy-momentum tensor and all higher currents. Formulae for the asymptotic behaviour of bosonic form factors are presented which are motivated by Weinberg's power counting theorem in perturbation theory. It is found that the quantum sine-Gordon field equation holds, and an exact relation between the 'bare' mass and the renormalized mass is obtained. Also a quantum version of a classical relation for the trace of the energy-momentum is proved. The eigenvalue problem for all higher conserved charges is solved. All results are compared with perturbative Feynman graph expansions and full agreement is found
Nucleon form factors on the lattice with light dynamical fermions
International Nuclear Information System (INIS)
Goeckeler, M.; Haegler, P.; Horsley, R.
2007-09-01
The electromagnetic form factors provide important insight into the internal structure of the nucleon and continue to be of major interest for experiment and phenomenology. For an intermediate range of momenta the form factors can be calculated on the lattice. However, the reliability of the results is limited by systematic errors mostly due to the required extrapolation to physical quark masses. Chiral effective field theories predict a rather strong quark mass dependence in a range which was yet inaccessible for lattice simulations. We give an update on recent results from the QCDSF collaboration using gauge configurations with dynamical N f =2, non-perturbatively O(a)-improved Wilson fermions at pion masses as low as 350 MeV. (orig.)
Nucleon form factors on the lattice with light dynamical fermions
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Theoretische Physik T39; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)
2007-09-15
The electromagnetic form factors provide important insight into the internal structure of the nucleon and continue to be of major interest for experiment and phenomenology. For an intermediate range of momenta the form factors can be calculated on the lattice. However, the reliability of the results is limited by systematic errors mostly due to the required extrapolation to physical quark masses. Chiral effective field theories predict a rather strong quark mass dependence in a range which was yet inaccessible for lattice simulations. We give an update on recent results from the QCDSF collaboration using gauge configurations with dynamical N{sub f}=2, non-perturbatively O(a)-improved Wilson fermions at pion masses as low as 350 MeV. (orig.)
Quark-flavor mixing and the nucleon strangeness form factors
International Nuclear Information System (INIS)
Ito, H.
1995-01-01
We have calculated the strangeness form factors of the nucleon G E s (Q), G M s (Q) and G A s (Q) and the electromagnetic form factors G E N (Q) as well, by using a relativistic constituent quark model of the nucleon wave function on the light-cone. Octet of Goldstone bosons (π, K, η) are assumed to induce the SU flavor mixing among the light constituent quarks; d-→K+s →d for example, and this mechanism induces the strangeness content in the nucleon. To calculate the meson-loop corrections to the electroweak couplings of constituent quarks, we have employed two models of the quark-meson vertex; (1) composite model of the Goldstone bosons (2) and (3) chiral quark Lagrangian. The loop momenta are regulated in a gauge-invariant way for both models
Dirac fields in loop quantum gravity and big bang nucleosynthesis
International Nuclear Information System (INIS)
Bojowald, Martin; Das, Rupam; Scherrer, Robert J.
2008-01-01
Big bang nucleosynthesis requires a fine balance between equations of state for photons and relativistic fermions. Several corrections to equation of state parameters arise from classical and quantum physics, which are derived here from a canonical perspective. In particular, loop quantum gravity allows one to compute quantum gravity corrections for Maxwell and Dirac fields. Although the classical actions are very different, quantum corrections to the equation of state are remarkably similar. To lowest order, these corrections take the form of an overall expansion-dependent multiplicative factor in the total density. We use these results, along with the predictions of big bang nucleosynthesis, to place bounds on these corrections and especially the patch size of discrete quantum gravity states.
Dirac operator, chirality and random matrix theory
International Nuclear Information System (INIS)
Pullirsch, R.
2001-05-01
related to QCD, compact QED differs considerably from the point of view of the global symmetry and the topological structure. It was a challenge to compare its eigenvalue spectra to analytical results from chRMT and verify possible universalities concerning the chiral structure and the appearance of quantum chaos. We find that the spectrum of the Dirac operator exhibits typical features associated with quantum chaos both in the confinement and the Coulomb phase. Furthermore, we show that in the confinement phase of compact U(1) gauge theory on the lattice, the distribution of the small Dirac eigenvalues is described by chRMT up to the Thouless energy. Searching for the origin of the small eigenvalues in quenched QED on the lattice we factorize the gauge fields into monopole parts and photon parts and observe that the physical relevance lies in the monopole contribution to the observables. Finally, we investigate the small eigenvalues of the chiral overlap-Dirac operator and we find exact chiral zero-modes in the confinement region. (author)
Generation of truncated recombinant form of tumor necrosis factor ...
African Journals Online (AJOL)
Purpose: To produce truncated recombinant form of tumor necrosis factor receptor 1 (TNFR1), cysteine-rich domain 2 (CRD2) and CRD3 regions of the receptor were generated using pET28a and E. coli/BL21. Methods: DNA coding sequence of CRD2 and CRD3 was cloned into pET28a vector and the corresponding ...
Coverlayer fabrication for small form factor optical disks
Kim, Jong-Hwan; Lee, Seung-Won; Kim, Jin-Hong
2004-09-01
Two different coverlayers made of UV resin and coversheet were prepared for small form factor optical disks. Thin coverlayer of 10 mm and thick coverlayer of 80 mm were fabricated for flying optical head and non-flying optical head, respectively. Thickness uniformity was analyzed for both coverlayers, and new designs to diminish a ski-jump phenomenon were suggested. Mechanical properties of protective film made of UV resin were investigated.
Nucleon structure functions, resonance form factors, and duality
International Nuclear Information System (INIS)
Davidovsky, V.V.; Struminsky, B.V.
2003-01-01
The behavior of nucleon structure functions in the resonance region is explored. For form factors that describe resonance production, expressions are obtained that are dependent on the photon virtuality Q 2 , which have a correct threshold behavior, and which take into account available experimental data on resonance decay. Resonance contributions to nucleon structure functions are calculated. The resulting expressions are used to investigate quark-hadron duality in electron-nucleon scattering by taking the example of the structure function F 2
Stackable Form-Factor Peripheral Component Interconnect Device and Assembly
Somervill, Kevin M. (Inventor); Ng, Tak-kwong (Inventor); Torres-Pomales, Wilfredo (Inventor); Malekpour, Mahyar R. (Inventor)
2013-01-01
A stackable form-factor Peripheral Component Interconnect (PCI) device can be configured as a host controller or a master/target for use on a PCI assembly. PCI device may comprise a multiple-input switch coupled to a PCI bus, a multiplexor coupled to the switch, and a reconfigurable device coupled to one of the switch and multiplexor. The PCI device is configured to support functionality from power-up, and either control function or add-in card function.
QCD constraints for the electromagnetic form factor of the pion
International Nuclear Information System (INIS)
Machet, B.
1980-07-01
Using the modulus representation, we derive constraints for the behaviour of the electromagnetic form factor of the pion in the time like region [1 GeV 2 , + infinity[, from information given by perturbative QCD in the space like region [-μ 2 , - infinity[. A phenomenological μ dependent upper bound for the exponent of the first non leading logarithmic correction is deduced. Restrictions and problems of the method are discussed
Strong CP violation and the neutron electric dipole form factor
International Nuclear Information System (INIS)
Kuckei, J.; Dib, C.; Faessler, A.; Gutsche, T.; Kovalenko, S. G.; Lyubovitskij, V. E.; Pumsa-ard, K.
2007-01-01
We calculate the neutron electric dipole form factor induced by the CP-violating θ term of QCD within a perturbative chiral quark model which includes pion and kaon clouds. On this basis, we derive the neutron electric dipole moment and the electron-neutron Schiff moment. From the existing experimental upper limits on the neutron electric dipole moment, we extract constraints on the θ parameter and compare our results with other approaches
Massive three-loop form factor in the planar limit
Energy Technology Data Exchange (ETDEWEB)
Henn, Johannes [PRISMA Cluster of Excellence, Johannes Gutenberg University,Staudingerweg 9, 55099 Mainz (Germany); Smirnov, Alexander V. [Research Computing Center, Moscow State University,119991 Moscow (Russian Federation); Smirnov, Vladimir A. [Skobeltsyn Institute of Nuclear Physics of Moscow State University,119991 Moscow (Russian Federation); Institut für Theoretische Teilchenphysik, Karlsruhe Institute of Technology (KIT),Wolfgang-Gaede Straße 1, 76128 Karlsruhe (Germany); Steinhauser, Matthias [Institut für Theoretische Teilchenphysik, Karlsruhe Institute of Technology (KIT),Wolfgang-Gaede Straße 1, 76128 Karlsruhe (Germany)
2017-01-17
We compute the three-loop QCD corrections to the massive quark-anti-quark-photon form factors F{sub 1} and F{sub 2} in the large-N{sub c} limit. The analytic results are expressed in terms of Goncharov polylogarithms. This allows for a straightforward numerical evaluation. We also derive series expansions, including power suppressed terms, for three kinematic regions corresponding to small and large invariant masses of the photon momentum, and small velocities of the heavy quarks.
Helicity non-conserving form factor of the proton
Energy Technology Data Exchange (ETDEWEB)
Voutier, E.; Furget, C.; Knox, S. [Universite Joseph Fourier, Grenoble (France)] [and others
1994-04-01
The study of the hadron structure in the high Q{sup 2} range contributes to the understanding of the mechanisms responsible for the confinement of quarks and gluons. Among the numerous experimental candidates sensitive to these mechanisms, the helicity non-conserving form factor of the proton is a privileged observable since it is controlled by non-perturbative effects. The authors investigate here the feasibility of high Q{sup 2} measurements of this form factor by means of the recoil polarization method in the context of the CEBAF 8 GeV facility. For that purpose, they discuss the development of a high energy proton polarimeter, based on the H({rvec p},pp) elastic scattering, to be placed at the focal plane of a new hadron spectrometer. It is shown that this experimental method significantly improves the knowledge of the helicity non-conserving form factor of the proton up to 10 GeV{sup 2}/c{sup 2}.
Meson Transition Form Factors in Light-Front Holographic QCD
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC; Cao, Fu-Guang; /Massey U.; de Teramond, Guy F.; /Costa Rica U.
2011-06-22
We study the photon-to-meson transition form factors (TFFs) F{sub M{gamma}}(Q{sup 2}) for {gamma}{gamma}* {yields} M using light-front holographic methods. The Chern-Simons action, which is a natural form in 5-dimensional anti-de Sitter (AdS) space, leads directly to an expression for the photon-to-pion TFF for a class of confining models. Remarkably, the predicted pion TFF is identical to the leading order QCD result where the distribution amplitude has asymptotic form. The Chern-Simons form is local in AdS space and is thus somewhat limited in its predictability. It only retains the q{bar q} component of the pion wavefunction, and further, it projects out only the asymptotic form of the meson distribution amplitude. It is found that in order to describe simultaneously the decay process {pi}{sup 0} {yields} {gamma}{gamma} and the pion TFF at the asymptotic limit, a probability for the q{bar q} component of the pion wavefunction P{sub q{bar q}} = 0.5 is required; thus giving indication that the contributions from higher Fock states in the pion light-front wavefunction need to be included in the analysis. The probability for the Fock state containing four quarks (anti-quarks) which follows from analyzing the hadron matrix elements, P{sub q{bar q}q{bar q}} {approx} 10%, agrees with the analysis of the pion elastic form factor using light-front holography including higher Fock components in the pion wavefunction. The results for the TFFs for the {eta} and {eta}{prime} mesons are also presented. The rapid growth of the pion TFF exhibited by the BABAR data at high Q{sup 2} is not compatible with the models discussed in this article, whereas the theoretical calculations are in agreement with the experimental data for the {eta} and {eta}{prime} TFFs.
Volfson, Boris
2013-09-01
The hypothesis of transition from a chaotic Dirac Sea, via highly unstable positronium, into a Simhony Model of stable face-centered cubic lattice structure of electrons and positrons securely bound in vacuum space, is considered. 13.75 Billion years ago, the new lattice, which, unlike a Dirac Sea, is permeable by photons and phonons, made the Universe detectable. Many electrons and positrons ended up annihilating each other producing energy quanta and neutrino-antineutrino pairs. The weak force of the electron-positron crystal lattice, bombarded by the chirality-changing neutrinos, may have started capturing these neutrinos thus transforming from cubic crystals into a quasicrystal lattice. Unlike cubic crystal lattice, clusters of quasicrystals are "slippery" allowing the formation of centers of local torsion, where gravity condenses matter into galaxies, stars and planets. In the presence of quanta, in a quasicrystal lattice, the Majorana neutrinos' rotation flips to the opposite direction causing natural transformations in a category comprised of three components; two others being positron and electron. In other words, each particle-antiparticle pair "e-" and "e+", in an individual crystal unit, could become either a quasi- component "e- ve e+", or a quasi- component "e+ - ve e-". Five-to-six six billion years ago, a continuous stimulation of the quasicrystal aetherial lattice by the same, similar, or different, astronomical events, could have triggered Hebbian and anti-Hebbian learning processes. The Universe may have started writing script into its own aether in a code most appropriate for the quasicrystal aether "hardware": Eight three-dimensional "alphabet" characters, each corresponding to the individual quasi-crystal unit shape. They could be expressed as quantum Turing machine qubits, or, alternatively, in a binary code. The code numerals could contain terminal and nonterminal symbols of the Chomsky's hierarchy, wherein, the showers of quanta, forming the
Neutron charge radius and the neutron electric form factor
International Nuclear Information System (INIS)
Gentile, T. R.; Crawford, C. B.
2011-01-01
For nearly forty years, the Galster parametrization has been employed to fit existing data for the neutron electric form factor, G E n , vs the square of the four-momentum transfer, Q 2 . Typically this parametrization is constrained to be consistent with experimental data for the neutron charge radius. However, we find that the Galster form does not have sufficient freedom to accommodate reasonable values of the radius without constraining or compromising the fit. In addition, the G E n data are now at sufficient precision to motivate a two-parameter fit (or three parameters if we include thermal neutron data). Here we present a modified form of a two-dipole parametrization that allows this freedom and fits both G E n (including recent data at both low and high four-momentum transfer) and the charge radius well with simple, well-defined parameters. Analysis reveals that the Galster form is essentially a two-parameter approximation to the two-dipole form but becomes degenerate if we try to extend it naturally to three parameters.
Shot noise in systems with semi-Dirac points
International Nuclear Information System (INIS)
Zhai, Feng; Wang, Juan
2014-01-01
We calculate the ballistic conductance and shot noise of electrons through a two-dimensional stripe system (width W ≫ length L) with semi-Dirac band-touching points. We find that the ratio between zero-temperature noise power and mean current (the Fano factor) is highly anisotropic. When the transport is along the linear-dispersion direction and the Fermi energy is fixed at the semi-Dirac point, the Fano factor has a universal value F = 0.179 while a minimum conductivity exists and scales with L 1∕2 . Along the parabolic dispersion direction, the Fano factor at the semi-Dirac point has a contact-independent limit exceeding 0.9, which varies weakly with L due to the common-path interference of evanescent waves. Our findings suggest a way to discern the type of band-touching points
LHCb: LHCbDirac is a DIRAC extension to support LHCb specific workflows
Stagni, Federico
2012-01-01
We present LHCbDIRAC, an extension of the DIRAC community Grid solution to handle the LHCb specificities. The DIRAC software has been developed for many years within LHCb only. Nowadays it is a generic software, used by many scientific communities worldwide. Each community wanting to take advantage of DIRAC has to develop an extension, containing all the necessary code for handling their specific cases. LHCbDIRAC is an actively developed extension, implementing the LHCb computing model and workflows. LHCbDIRAC extends DIRAC to handle all the distributed computing activities of LHCb. Such activities include real data processing (reconstruction, stripping and streaming), Monte-Carlo simulation and data replication. Other activities are groups and user analysis, data management, resources management and monitoring, data provenance, accounting for user and production jobs. LHCbDIRAC also provides extensions of the DIRAC interfaces, including a secure web client, python APIs and CLIs. While DIRAC and LHCbDIRAC f...
Maxwell-Like Equations for Free Dirac Electrons
Bruce, S. A.
2018-03-01
In this article, we show that the wave equation for a free Dirac electron can be represented in a form that is analogous to Maxwell's electrodynamics. The electron bispinor wavefunction is explicitly expressed in terms of its real and imaginary components. This leads us to incorporate into it appropriate scalar and pseudo-scalar fields in advance, so that a full symmetry may be accomplished. The Dirac equation then takes on a form similar to that of a set of inhomogeneous Maxwell's equations involving a particular self-source. We relate plane wave solutions of these equations to waves corresponding to free Dirac electrons, identifying the longitudinal component of the electron motion, together with the corresponding Zitterbewegung ("trembling motion").
Dirac vacuum: Acceleration and external-field effects
International Nuclear Information System (INIS)
Jauregui, R.; Torres, M.; Hacyan, S.
1991-01-01
The quantization of the massive spin-1/2 field in Rindler coordinates is considered, including the effects of a background magnetic field. We calculate the expectation values of conserved quantities such as the stress-energy tensor, current density, and spin distribution, as detected by an accelerated observer. The ratio of the energy and particle densities is given by a Fermi-Dirac distribution, but the spectrum of these quantities takes in general a complicated form that cannot be simply interpreted as a thermal spectrum. For the free-particle case the spectrum of the energy-stress tensor has a Fermi-Dirac form only in the massless limit. In the presence of the magnetic field the Dirac vacuum is magnetized and exhibits plasmalike properties
Inverse scattering scheme for the Dirac equation at fixed energy
International Nuclear Information System (INIS)
Leeb, H.; Lehninger, H.; Schilder, C.
2001-01-01
Full text: Based on the concept of generalized transformation operators a new hierarchy of Dirac equations with spherical symmetric scalar and fourth component vector potentials is presented. Within this hierarchy closed form expressions for the solutions, the potentials and the S-matrix can be given in terms of solutions of the original Dirac equation. Using these transformations an inverse scattering scheme has been constructed for the Dirac equation which is the analog to the rational scheme in the non-relativistic case. The given method provides for the first time an inversion scheme with closed form expressions for the S-matrix for non-relativistic scattering problems with central and spin-orbit potentials. (author)
Granular superconductor in a honeycomb lattice as a realization of bosonic Dirac material
Banerjee, S.; Fransson, J.; Black-Schaffer, A. M.; Ågren, H.; Balatsky, A. V.
2016-04-01
We examine the low-energy effective theory of phase oscillations in a two-dimensional granular superconducting sheet where the grains are arranged in a honeycomb lattice structure. Using the example of graphene, we present evidence for the engineered Dirac nodes in the bosonic excitations: the spectra of the collective bosonic modes cross at the K and K' points in the Brillouin zone and form Dirac nodes. We show how two different types of collective phase oscillations are obtained and that they are analogous to the Leggett and the Bogoliubov-Anderson-Gorkov modes in a two-band superconductor. We show that the Dirac node is preserved in the presence of an intergrain interaction, despite induced changes of the qualitative features of the two collective modes. Finally, breaking the sublattice symmetry by choosing different on-site potentials for the two sublattices leads to a gap opening near the Dirac node, in analogy with fermionic Dirac materials. The Dirac node dispersion of bosonic excitations is thus expanding the discussion of the conventional Dirac cone excitations to the case of bosons. We call this case as a representative of bosonic Dirac materials (BDM), similar to the case of Fermionic Dirac materials extensively discussed in the literature.
Relativistic form factors for clusters with nonrelativistic wave functions
International Nuclear Information System (INIS)
Mitra, A.N.; Kumari, I.
1977-01-01
Using a simple variant of an argument employed by Licht and Pagnamenta (LP) on the effect of Lorentz contraction on the elastic form factors of clusters with nonrelativistic wave functions, it is shown how their result can be generalized to inelastic form factors so as to produce (i) a symmetrical appearance of Lorentz contraction effects in the initial and final states, and (ii) asymptotic behavior in accord with dimensional scaling theories. A comparison of this result with a closely analogous parametric form obtained by Brodsky and Chertok from a propagator chain model leads, with plausible arguments, to the conclusion of an effective mass M for the cluster, with M 2 varying as the number n of the quark constituents, instead of as n 2 . A further generalization of the LP formula is obtained for an arbitrary duality-diagram vertex, again with asymptotic behavior in conformity with dimensional scaling. The practical usefulness of this approach is emphasized as a complementary tool to those of high-energy physics for phenomenological fits to data up to moderate values of q 2
Quasi-Dirac neutrino oscillations
Anamiati, Gaetana; Fonseca, Renato M.; Hirsch, Martin
2018-05-01
Dirac neutrino masses require two distinct neutral Weyl spinors per generation, with a special arrangement of masses and interactions with charged leptons. Once this arrangement is perturbed, lepton number is no longer conserved and neutrinos become Majorana particles. If these lepton number violating perturbations are small compared to the Dirac mass terms, neutrinos are quasi-Dirac particles. Alternatively, this scenario can be characterized by the existence of pairs of neutrinos with almost degenerate masses, and a lepton mixing matrix which has 12 angles and 12 phases. In this work we discuss the phenomenology of quasi-Dirac neutrino oscillations and derive limits on the relevant parameter space from various experiments. In one parameter perturbations of the Dirac limit, very stringent bounds can be derived on the mass splittings between the almost degenerate pairs of neutrinos. However, we also demonstrate that with suitable changes to the lepton mixing matrix, limits on such mass splittings are much weaker, or even completely absent. Finally, we consider the possibility that the mass splittings are too small to be measured and discuss bounds on the new, nonstandard lepton mixing angles from current experiments for this case.
Forms and factors of peer violence and victimisation
Directory of Open Access Journals (Sweden)
Dinić Bojana
2014-01-01
Full Text Available The main aim of this study was to explore the latent structure of violence and victimisation based on the factor analysis of the Peer Violence and Victimisation Questionnaire (PVVQ, as well as to examine the correlates of violence and victimisation. The sample included 649 secondary school students (61.8% male from the urban area. Besides the PVVQ, the Aggressiveness questionnaire AVDH was administered. Based on parallel analysis, three factors were extracted in the violence domain, as well as in the victimisation domain of the PVVQ. The factors were interpreted as a physical, verbal and relational form of violence and victimisation, which is in line with common classifications. The correlations of those forms with the aggressiveness dimensions were positive. The relationships with gender, school grade and school achievement referred to the importance of interaction effects between the mentioned characteristics of students and the tendency towards violence or being exposed to it. The main result is that boys from lower school grades and students with lower school achievement in general, are more prone to manifesting physical violence and more often are the target of physical violence. These groups of students are the target groups for preventive programs. The resulting effects indicated the complexity of the violence phenomenon and pointed to the need to consider the wider context of student’s characteristics in the determination of violence. [Projekat Ministarstva nauke Republike Srbije, br. 179037 i br. 179053
Dispersive analysis of the scalar form factor of the nucleon
Hoferichter, M.; Ditsche, C.; Kubis, B.; Meißner, U.-G.
2012-06-01
Based on the recently proposed Roy-Steiner equations for pion-nucleon ( πN) scattering [1], we derive a system of coupled integral equations for the π π to overline N N and overline K K to overline N N S-waves. These equations take the form of a two-channel Muskhelishvili-Omnès problem, whose solution in the presence of a finite matching point is discussed. We use these results to update the dispersive analysis of the scalar form factor of the nucleon fully including overline K K intermediate states. In particular, we determine the correction {Δ_{σ }} = σ ( {2M_{π }^2} ) - {σ_{{π N}}} , which is needed for the extraction of the pion-nucleon σ term from πN scattering, as a function of pion-nucleon subthreshold parameters and the πN coupling constant.
Baryon octet electromagnetic form factors in a confining NJL model
Directory of Open Access Journals (Sweden)
Manuel E. Carrillo-Serrano
2016-08-01
Full Text Available Electromagnetic form factors of the baryon octet are studied using a Nambu–Jona-Lasinio model which utilizes the proper-time regularization scheme to simulate aspects of colour confinement. In addition, the model also incorporates corrections to the dressed quarks from vector meson correlations in the t-channel and the pion cloud. Comparison with recent chiral extrapolations of lattice QCD results shows a remarkable level of consistency. For the charge radii we find the surprising result that rEp
CEBAF at higher energies and the kaon electromagnetic form factor
Energy Technology Data Exchange (ETDEWEB)
Baker, O.K.
1994-04-01
The electromagnetic production of strangeness, the physics of exciting systems having strangeness degrees of freedom (production of hadrons with one or more strange constituent quarks) using electromagnetic probes (real or virtual photons), is one of the frontier areas of research which will be investigated at the Continuous Electron Beam Accelerator Facility (CEBAF) when it becomes operational. CEBAF is expected to have an important impact upon this field of research using its specialized set of detection instruments and high quality electron beam. This paper focusses upon one aspect of the associated production of strangeness - the determination of the kaon electromagnetic form factor at high squared momentum transfers.
Light trapping and circularly polarization at a Dirac point in 2D plasma photonic crystals
Li, Qian; Hu, Lei; Mao, Qiuping; Jiang, Haiming; Hu, Zhijia; Xie, Kang; Wei, Zhang
2018-03-01
Light trapping at the Dirac point in 2D plasma photonic crystal has been obtained. The new localized mode, Dirac mode, is attributable to neither photonic bandgap nor total internal reflection. It exhibits a unique algebraic profile and possesses a high-Q factor resonator of about 105. The Dirac point could be modulated by tuning the filling factor, plasma frequency and plasma cyclotron frequency, respectively. When a magnetic field parallel to the wave vector is applied, Dirac modes for right circularly polarized and left circularly polarized waves could be obtained at different frequencies, and the Q factor could be tuned. This property will add more controllability and flexibility to the design and modulation of novel photonic devices. It is also valuable for the possibilities of Dirac modes in photonic crystal containing other kinds of metamaterials.
Dispersionless wave packets in Dirac materials
Czech Academy of Sciences Publication Activity Database
Jakubský, Vít; Tušek, M.
2017-01-01
Roč. 378, MAR (2017), s. 171-182 ISSN 0003-4916 R&D Projects: GA ČR(CZ) GJ15-07674Y; GA ČR GA17-01706S Institutional support: RVO:61389005 Keywords : quantum systems * wave packets * dispersion * dirac materials Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics ( physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 2.465, year: 2016
The Dirac medals of the ICTP. 1993
Energy Technology Data Exchange (ETDEWEB)
NONE
1996-12-31
The Dirac Medals of the International Centre for Theoretical Physics (ICTP) were instituted in 1985. These are awarded yearly to outstanding physicists, on Dirac`s birthday - 8th August- for contributions to theoretical physics. The document includes the lectures of the three Dirac Medalists for 1993: Professor Sergio Ferrara, Professor Daniel Z. Freedman, and Professor Peter van Nieuwenhuizen. A separate abstract was prepared for each lecture
The pion form factor within the hidden local symmetry model
International Nuclear Information System (INIS)
Benayoun, M.; David, P.; DelBuono, L.; Leruste, P.; O'Connell, H.B.
2003-01-01
We analyze a pion form factor formulation which fulfills the Analyticity requirement within the Hidden Local Symmetry (HLS) Model. This implies an s-dependent dressing of the ρ-γ VMD coupling and an account of several coupled channels. The corresponding function F π (s) provides nice fits of the pion form factor data from s=-0.25 to s=1 GeV 2 . It is shown that the coupling to KK has little effect, while ωπ 0 improves significantly the fit probability below the φ mass. No need for additional states like ρ(1450) shows up in this invariant-mass range. All parameters, except for the subtraction polynomial coefficients, are fixed from the rest of the HLS phenomenology. The fits show consistency with the expected behaviour of F π (s) at s=0 up to O(s 2 ) and with the phase shift data on δ 1 1 (s) from threshold to somewhat above the φ mass. The ω sector is also examined in relation with recent data from CMD-2. (orig.)
Analytical and unitary approach in mesons electromagnetic form factor applications
International Nuclear Information System (INIS)
Liptaj, A.
2010-07-01
In the dissertation thesis we address several topics related to the domain of particle physics. All of them represent interesting open problems that can be connected to the elastic or transition electromagnetic form factors of mesons, the form factors being the main objects of our interest. Our ambition is to contribute to the solution of these problems and use for that purpose known analytic properties of the form factors and the unitarity condition. These two tools are very powerful in the low energy domain (such as bound states of partons), where the perturbative QCD looses its validity. This is the motivation for construction of the unitary and analytic (U and A) models of studied form factors, that enable us to get the majority of our results. We use the U and A model to evaluate the contribution of the processes e"+e"- → Pγ, P = π"0, η, η to the muon magnetic anomaly a_μ in the lowest order of the hadronic vacuum polarization. For the contribution a_μ"h"a"d","L"O (π"+π"-) we demonstrate, that the use of the model leads to a dramatic error reduction with respect to the results of other authors. We also get a shift in the central value in the 'correct' direction, that brings the theoretical value closer to the experimental one. This results encourages us to use the model also for the evaluation of a_μ"h"a"d","L"O (P_γ). These contributions are smaller, however the precision of the experiment makes their evaluation necessary. We further use the U and A model of the transition form factors of π"0, η and η"' mesons to predict the partial decay widths of these particles Γ_π_"0_→_γ_γ and Γ_η_→_γ_γ and Γ_η_"'_→_γ_γ. In this way we make an independent cross check of the PDG table values. We find an agreement in the case of Γ_η_→_γ_γ and Γ_η_"'_→_γ_γ, even a smaller uncertainty for Γ_η_"'_→_γ_γ. In the case of Γ_π_"0_→_γ_γ we find a disagreement that points to an interesting problem. We wonder whether it could be
Measurement of the $\\Lambda_{b}^{0}$ Decay Form Factor
Abdallah, J; Adam, W; Adzic, P; Albrecht, T; Alderweireld, T; Alemany-Fernandez, R; Allmendinger, T; Allport, P P; Amaldi, Ugo; Amapane, N; Amato, S; Anashkin, E; Andreazza, A; Andringa, S; Anjos, N; Antilogus, P; Apel, W D; Arnoud, Y; Ask, S; Åsman, B; Augustin, J E; Augustinus, A; Baillon, Paul; Ballestrero, A; Bambade, P; Barbier, R; Bardin, Dimitri Yuri; Barker, G; Baroncelli, A; Battaglia, Marco; Baubillier, M; Becks, K H; Begalli, M; Behrmann, A; Ben-Haim, E; Benekos, N C; Benvenuti, Alberto C; Bérat, C; Berggren, M; Berntzon, L; Bertrand, D; Besançon, M; Besson, N; Bloch, D; Blom, M; Bluj, M; Bonesini, M; Boonekamp, M; Booth, P S L; Borisov, G; Botner, O; Bouquet, B; Bowcock, T J V; Boyko, I; Bracko, M; Brenner, R; Brodet, E; Brückman, P; Brunet, J M; Bugge, L; Buschmann, P; Calvi, M; Camporesi, T; Canale, V; Carena, F; Castro, N; Cavallo, F R; Chapkin, M M; Charpentier, P; Checchia, P; Chierici, R; Shlyapnikov, P; Chudoba, J; Chung, S U; Cieslik, K; Collins, P; Contri, R; Cosme, G; Cossutti, F; Costa, M J; Crawley, B; Crennell, D J; Cuevas-Maestro, J; D'Hondt, J; Dalmau, J; Da Silva, T; Da Silva, W; Della Ricca, G; De Angelis, A; de Boer, Wim; De Clercq, C; De Lotto, B; De Maria, N; De Min, A; De Paula, L S; Di Ciaccio, Lucia; Di Simone, A; Doroba, K; Drees, J; Dris, M; Eigen, G; Ekelöf, T J C; Ellert, M; Elsing, M; Espirito-Santo, M C; Fanourakis, G K; Fassouliotis, D; Feindt, M; Fernández, J; Ferrer, A; Ferro, F; Flagmeyer, U; Föth, H; Fokitis, E; Fulda-Quenzer, F; Fuster, J A; Gandelman, M; García, C; Gavillet, P; Gazis, E N; Gokieli, R; Golob, B; Gómez-Ceballos, G; Gonçalves, P; Graziani, E; Grosdidier, G; Grzelak, K; Guy, J; Haag, C; Hallgren, A; Hamacher, K; Hamilton, K; Haug, S; Hauler, F; Hedberg, V; Hennecke, M; Herr, H; Hoffman, J; Holmgren, S O; Holt, P J; Houlden, M A; Hultqvist, K; Jackson, J N; Jarlskog, G; Jarry, P; Jeans, D; Johansson, E K; Johansson, P D; Jonsson, P; Joram, C; Jungermann, L; Kapusta, F; Katsanevas, S; Katsoufis, E C; Kernel, G; Kersevan, Borut P; Kerzel, U; Kiiskinen, A P; King, B T; Kjaer, N J; Kluit, P; Kokkinias, P; Kourkoumelis, C; Kuznetsov, O; Krumshtein, Z; Kucharczyk, M; Lamsa, J; Leder, G; Ledroit, F; Leinonen, L; Leitner, R; Lemonne, J; Lepeltier, V; Lesiak, T; Liebig, W; Liko, D; Lipniacka, A; Lopes, J H; López, J M; Loukas, D; Lutz, P; Lyons, L; MacNaughton, J; Malek, A; Maltezos, S; Mandl, F; Marco, J; Marco, R; Maréchal, B; Margoni, M; Marin, J C; Mariotti, C; Markou, A; Martínez-Rivero, C; Masik, J; Mastroyiannopoulos, N; Matorras, F; Matteuzzi, C; Mazzucato, F; Mazzucato, M; McNulty, R; Meroni, C; Meyer, W T; Myagkov, A; Migliore, E; Mitaroff, W A; Mjörnmark, U; Moa, T; Moch, M; Mönig, K; Monge, R; Montenegro, J; Moraes, D; Moreno, S; Morettini, P; Müller, U; Münich, K; Mulders, M; Mundim, L M; Murray, W; Muryn, B; Myatt, Gerald; Myklebust, T; Nassiakou, M; Navarria, Francesco Luigi; Nawrocki, K; Nicolaidou, R; Nikolenko, M; Oblakowska-Mucha, A; Obraztsov, V F; Olshevskii, A G; Onofre, A; Orava, Risto; Österberg, K; Ouraou, A; Oyanguren, A; Paganoni, M; Paiano, S; Palacios, J P; Palka, H; Papadopoulou, T D; Pape, L; Parkes, C; Parodi, F; Parzefall, U; Passeri, A; Passon, O; Peralta, L; Perepelitsa, V F; Perrotta, A; Petrolini, A; Piedra, J; Pieri, L; Pierre, F; Pimenta, M; Piotto, E; Podobnik, T; Poireau, V; Pol, M E; Polok, G; Poropat, P; Pozdnyakov, V; Pukhaeva, N; Pullia, Antonio; Rames, J; Ramler, L; Read, A; Rebecchi, P; Rehn, J; Reid, D; Reinhardt, R; Renton, P B; Richard, F; Rídky, J; Rivero, M; Rodríguez, D; Romero, A; Ronchese, P; Rosenberg, E I; Roudeau, Patrick; Rovelli, T; Ruhlmann-Kleider, V; Ryabtchikov, D; Sadovskii, A; Salmi, L; Salt, J; Savoy-Navarro, A; Schwickerath, U; Segar, A; Sekulin, R L; Siebel, M; Sissakian, A N; Smadja, G; Smirnova, O G; Sokolov, A; Sopczak, A; Sosnowski, R; Spassoff, Tz; Stanitzki, M; Stocchi, A; Strauss, J; Stugu, B; Szczekowski, M; Szeptycka, M; Szumlak, T; Tabarelli de Fatis, T; Taffard, A C; Tegenfeldt, F; Timmermans, J; Tkatchev, L G; Tobin, M; Todorovova, S; Tomé, B; Tonazzo, A; Tortosa, P; Travnicek, P; Treille, D; Tristram, G; Trochimczuk, M; Troncon, C; Turluer, M L; Tyapkin, I A; Tyapkin, P; Tzamarias, S; Uvarov, V; Valenti, G; van Dam, P; Van Eldik, J; Van Lysebetten, A; Van Remortel, N; Van Vulpen, I B; Vegni, G; Veloso, F; Venus, W A; Verdier, P; Verzi, V; Vilanova, D; Vitale, L; Vrba, V; Wahlen, H; Washbrook, A J; Weiser, C; Wicke, D; Wickens, J H; Wilkinson, G; Winter, M; Witek, M; Yushchenko, O P; Zalewska-Bak, A; Zalewski, Piotr; Zavrtanik, D; Zhuravlov, V; Zimin, N I; Zinchenko, A I; Zupan, M
2004-01-01
The form factor of Lambda_b^0 baryons is estimated using 3.46 10^6 hadronic Z decays collected by the DELPHI experiment between 1992 and 1995. Charmed Lambda_c^+ baryons fully reconstructed in the pK-pi+, pK0_S, and Lambda pi+pi+pi- modes, are associated to a lepton with opposite charge in order to select Lambda_b^0 -> Lambda_c^+ l^- anti-nu_l decays. From a combined likelihood and event rate fit to the distribution of the Isgur-Wise variable w, and using the Heavy Quark Effective Theory (HQET), the slope of the b-baryon form factor is measured to be: rho-hat^2 = 2.03 +/- 0.46 (stat) ^{+0.72}_{-1.00} (syst). The exclusive semileptonic branching fraction Br(Lambda_b^0 -> Lambda_c^+ l^- anti-nu_l) can be derived from rho-hat^2 and is found to be (5.0^{+1.1}_{-0.8} (stat) ^{+1.6}_{-1.2} (syst))%. Limits on other branching fractions are also obtained.
Small form factor optical fiber connector evaluation for harsh environments
Ott, Melanie N.; Thomes, W. Joe, Jr.; Chuska, Richard F.; Switzer, Robert; Blair, Diana E.
2011-09-01
For the past decade NASA programs have utilized the Diamond AVIM connector for optical fiber assemblies on space flight instrumentation. These connectors have been used in communications, sensing and LIDAR systems where repeatability and high performance are required. Recently Diamond has released a smaller form factor optical fiber connector called the "Mini-AVIM" which although more compact still includes the tight tolerances and the ratcheting feature of the heritage AVIM. NASA Goddard Space Flight Center Photonics Group in the Parts, Packaging and Assembly Technologies Office has been performing evaluations of this connector to determine how it compares to the performance of the AVIM connector and to assess its feasibility for harsh environmental applications. Vibration and thermal testing were performed on the Mini-AVIM with both multi-mode and single-mode optical fiber using insitu optical transmission monitoring. Random vibration testing was performed using typical launch condition profiles for most NASA missions but extended to 35 Grms, which is much higher than most requirements. Thermal testing was performed incrementally up to a range of -55°C to +125°C. The test results include both unjacketed fiber and cabled assembly evaluations. The data presented here indicate that the Mini-AVIM provides a viable option for small form factor applications that require a high performance optical fiber connector.
A Dirac algebraic approach to supersymmetry
International Nuclear Information System (INIS)
Guersey, F.
1984-01-01
The power of the Dirac algebra is illustrated through the Kaehler correspondence between a pair of Dirac spinors and a 16-component bosonic field. The SO(5,1) group acts on both the fermion and boson fields, leading to a supersymmetric equation of the Dirac type involving all these fields. (author)
Adaptive Multigrid Algorithm for the Lattice Wilson-Dirac Operator
International Nuclear Information System (INIS)
Babich, R.; Brower, R. C.; Rebbi, C.; Brannick, J.; Clark, M. A.; Manteuffel, T. A.; McCormick, S. F.; Osborn, J. C.
2010-01-01
We present an adaptive multigrid solver for application to the non-Hermitian Wilson-Dirac system of QCD. The key components leading to the success of our proposed algorithm are the use of an adaptive projection onto coarse grids that preserves the near null space of the system matrix together with a simplified form of the correction based on the so-called γ 5 -Hermitian symmetry of the Dirac operator. We demonstrate that the algorithm nearly eliminates critical slowing down in the chiral limit and that it has weak dependence on the lattice volume.
Zero-energy eigenstates for the Dirac boundary problem
International Nuclear Information System (INIS)
Hortacsu, M.; Rothe, K.D.; Schroer, B.
1980-01-01
As an alternative to the method of spherical compactification for the Dirac operator in instanton background fields we study the correct method of 'box-quantization': the Atiyah-Patodi-Singer spectral boundary condition. This is the only self-adjoint boundary condition which respects the charge conjugation property and the γ 5 symmetry, apart form the usual breaking due to zero modes. We point out the relevance of this approach to the computation of instanton determinants and other problems involving Dirac spinors. (orig.)
Dirac equation and optical wave propagation in one dimension
Energy Technology Data Exchange (ETDEWEB)
Gonzalez, Gabriel [Catedras CONACYT, Universidad Autonoma de San Luis Potosi (Mexico); Coordinacion para la Innovacion y la Aplicacion de la Ciencia y la Tecnologia, Universidad Autonoma de San Luis Potosi (Mexico)
2018-02-15
We show that the propagation of transverse electric (TE) polarized waves in one-dimensional inhomogeneous settings can be written in the form of the Dirac equation in one space dimension with a Lorentz scalar potential, and consequently perform photonic simulations of the Dirac equation in optical structures. In particular, we propose how the zero energy state of the Jackiw-Rebbi model can be generated in an optical set-up by controlling the refractive index landscape, where TE-polarized waves mimic the Dirac particles and the soliton field can be tuned by adjusting the refractive index. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Hadron spectroscopy and form factors at quark level
International Nuclear Information System (INIS)
Chakrabarty, S.; Gupta, K.K.; Singh, N.N.; Mitra, A.N.
1988-01-01
The theoretical status of hadrons as quark composites is examined from the point of view of a simultaneous understanding of their on-shell (mass spectra) and off-shell (form factors, transition amplitudes) properties. Greater stress is laid on light quark systems which are more sensitive to the confinement regime, and more prone to relativistic effects than on heavy quarkonia (on which many reviews exist). Two broad theoretical approaches obeying Lorentz and gauge invariance are identified: (i) QCD sum rules as a means of extrapolation from high to low energies; and (ii) dynamical equations for providing a microcausal link in the opposite direction (from low to high energies). The latter represents the major focus of attention in this article, with the Bethe-Salpeter Equation (BSE) providing a formal plank for a comparative assessment of several models. The Null-plane ansatz which facilitates the reduction of the 4-D BSE to a covariant 3-D form also provides the language for its comparison with other covariant 3-D equations. In particular, attention is drawn to the interesting possibility of reconstructing the 4-D BS wave function from its 3-D form (in a two-tier fashion) as a practical tool for generating higher Fock-space components (qq effects) in the BS wave function, and (more interestingly) for a clean separation between soft and hard QCD effects. To illustrate one such practical tool for an integrated view of different hadronic sectors within a single framework, the results of a two-tier BS model are presented in respect of qq-bar, qqq, gg, ggg, gqq-bar states and compared with experiment as well as with the results of other contemporary models. The N.R Resonating Group Method, which becomes necessary for bigger (six-quark) systems is briefly discussed from the point of view of its compatibility with a relativistic form of quark dynamics motivated from the BSC. (Author)
Interlayer magnetoresistance in multilayer Dirac electron systems: motion and merging of Dirac cones
Assili, Mohamed; Haddad, Sonia
2013-01-01
We theoretically study the effect of the motion and the merging of Dirac cone on the interlayer magnetoresistance in multilayer graphene like systems. This merging, which could be induced by a uniaxial strain, gives rise in monolayer Dirac electron system to a topological transition from a semi-metallic phase to an insulating phase where Dirac points disappear. Based on a universal Hamiltonian proposed to describe the motion and the merging of Dirac points in two dimensional Dirac electron cr...
A new derivation of Dirac's magnetic monopole strength
International Nuclear Information System (INIS)
Panat, P V
2003-01-01
A new derivation of the strength of Dirac's magnetic monopole is presented which does not require an explicit form of the magnetic induction in terms of g, the magnetic pole strength. The derivation essentially uses a modification of Faraday's law of induction and quantization of angular momentum
Dirac, Prof. Paul Adrien Maurice
Indian Academy of Sciences (India)
Home; Fellowship. Fellow Profile. Elected: 1935 Honorary. Dirac, Prof. Paul Adrien Maurice Nobel Laureate (Physics) - 1933. Date of birth: 8 August 1902. Date of death: 20 October 1984. YouTube; Twitter; Facebook; Blog. Academy News. IAS Logo. 29th Mid-year meeting. Posted on 19 January 2018. The 29th Mid-year ...
Dirac, Jordan and quantum fields
International Nuclear Information System (INIS)
Darrigol, O.
1985-01-01
The case of two principal physicists of quantum mechanics is specially chose: Paul Dirac and Pascual Jordan. They gave a signification and an importance very different to the notion of quantum field, and in particular to the quantized matter wave one. Through their formation and motivation differences, such as they are expressed in their writings, this deep difference is tentatively understood [fr
about the Dirac Delta Function(?)
Indian Academy of Sciences (India)
V Balakrishnan is in the. Department of ... and sweet as befits this impatient age. It said (in its en- ... to get down to real work by shutting down the system and reverting to ... the Dirac delta function" - but do note the all-important question mark in ...
Pion form factor in QCD at intermediate momentum transfers
Braun, V. M.; Khodjamirian, A.; Maul, M.
2000-04-01
We present a quantitative analysis of the electromagnetic pion form factor in the light-cone sum rule approach, including radiative corrections and higher-twist effects. The comparison to the existing data favors the asymptotic profile of the pion distribution amplitude and allows us to estimate the deviation: [∫du/uφπ(u)]/[∫du/uφasπ(u)]=1.1+/-0.1 at the scale of 1 GeV. Special attention is paid to the precise definition and interplay of soft and hard contributions at intermediate momentum transfer, and to the matching of the sum rule to the perturbative QCD prediction. We observe a strong numerical cancellation between the soft (end-point) contribution and power-suppressed hard contributions of higher twist, so that the total nonperturbative correction to the usual PQCD result turns out to be of the order of 30% for Q2~1 GeV2.
Five-meson VDM fits to the nucleon form factors
International Nuclear Information System (INIS)
Mehrotra, S.; Roos, M.
1975-01-01
Nucleon electromagnetic form factor data in the spacelike and the timelike regions are fitted with a VDM sum of (up to five) isovector and isoscalar pole terms. Finite width effects are included in the rho and the rhosup(,) terms. The effects of including the rhosup(,) and the psi(3105) are studied. Good fits are found only when the rhosup(,) is allowed to have a too low mass (1.2-1.4 GeV) and when in addition some of the couplings or other derived quantities disagree with other estimates. It is concluded that VDM is unable to describe the data unless one introduces a number of yet unknown mesons, such as ωsup(,), phisup(,), rhosup(,)(1.2), etc. (author)
Form factors and related quantities in clothed-particle representation
Directory of Open Access Journals (Sweden)
Shebeko Alexander
2017-01-01
Full Text Available We show new applications of the notion of clothed particles in quantum field theory. Its realization by means of the clothing procedure put forward by Greenberg and Schweber allows one to express the total Hamiltonian H and other generators of the Poincaré group for a given system of interacting fields through the creation (annihilation operators for the so-called clothed particles with physical (observed properties. Here such a clothed particle representation is used to calculate the matrix elements (shortly, form factors of the corresponding Nöther current operators sandwiched between the H eigenstates. Our calculations are performed with help of an iterative technique suggested by us earlier when constructing the NN → πNN transition operators. As an illustration, we outline some application of our approach in the spinor quantum electrodynamics.
Finite-lattice form factors in free-fermion models
International Nuclear Information System (INIS)
Iorgov, N; Lisovyy, O
2011-01-01
We consider the general Z 2 -symmetric free-fermion model on the finite periodic lattice, which includes as special cases the Ising model on the square and triangular lattices and the Z n -symmetric BBS τ (2) -model with n = 2. Translating Kaufman's fermionic approach to diagonalization of Ising-like transfer matrices into the language of Grassmann integrals, we determine the transfer matrix eigenvectors and observe that they coincide with the eigenvectors of a square lattice Ising transfer matrix. This allows us to find exact finite-lattice form factors of spin operators for the statistical model and the associated finite-length quantum chains, of which the most general is equivalent to the XY chain in a transverse field
Electric form factor of the proton through recoil polarization
International Nuclear Information System (INIS)
Punjabi, V.
2000-01-01
The electromagnetic form factors of the nucleon, G E and G M , describe the charge and current distribution inside the nucleon and thus are quite intimately related to its structure. Jefferson Lab experiment 93-027 measured P l and Pt, the longitudinal and transverse recoil proton polarization, respectively, for the 1 H(e-vector,e'p-vector) reaction in the four-momentum transfer squared range of 0.5 to 3.5 GeV 2 , using the Hall A facility with two high resolution spectrometers and a Focal Plane Polarimeter. The ratio G Ep /G Mp is directly proportional to the ratio P t /P l . These data have unprecedented precision, and show for the first time that the Q 2 dependence of G Ep and G Mp is very different. (author)
Meson Form Factors and Deep Exclusive Meson Production Experiments
Energy Technology Data Exchange (ETDEWEB)
Horn, Tanja [The Catholic Univ. of America, Washington, DC (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2017-05-01
Pion and kaon electroproduction data play a unique role in Nature and our understanding of them is essential for explaining hadron structure. Precision longitudinaltransverse separated pion and kaon cross sections are of particular interest. They allow for the extraction of meson form factors and validation of understanding of hard exclusive and semi-inclusive reactions (π+, K+, π0, γ) towards 3D hadron imaging and potential future flavor decomposition. We review recent data and present prospects for deep exclusive pion and kaon electroproduction at the 12 GeV Jefferson Lab including the prospects to use projected charged- and neutral pion data to further determine the spin, charge-parity and flavor of GPDs, including the helicity-flip GPDs.
Conformal anomaly of generalized form factors and finite loop integrals
Chicherin, Dmitry
2017-01-01
We reveal a new mechanism of conformal symmetry breaking at Born level. It occurs in generalized form factors with several local operators and an on-shell state of massless particles. The effect is due to hidden singularities on collinear configurations of the momenta. This conformal anomaly is different from the holomorphic anomaly of amplitudes. We present a number of examples in four and six dimensions. We find an application of the new conformal anomaly to finite loop momentum integrals with one or more massless legs. The collinear region around a massless leg creates a contact anomaly, made visible by the loop integration. The anomalous conformal Ward identity for an $\\ell-$loop integral is a 2nd-order differential equation whose right-hand side is an $(\\ell-1)-$loop integral. We show several examples, in particular the four-dimensional scalar double box.
Current correlators and form factors in the resonance region
Energy Technology Data Exchange (ETDEWEB)
Rosell, I. [Departamento de Ciencias Fisicas, Matematicas y de la Computacion, Universidad CEU Cardenal Herrera, c/Sant Bartomeu 55, E-46115 Alfara del Patriarca, Valencia (Spain); IFIC, Universitat de Valencia - CSIC, Apt. Correus 22085, E-46071 Valencia (Spain)
2009-01-15
Within Resonance Chiral Theory and in the context of QCD current correlators at next-to-leading order in 1/N{sub C}, we have analyzed the two-body form factors which include resonances as a final state. The short-distance constraints have been studied. One of the main motivations is the estimation of the chiral low-energy constants at subleading order, that is, keeping full control of the renormalization scale dependence. As an application we show the resonance estimation of some coupling, L{sub 10}{sup r}({mu}{sub 0})=(-4.4{+-}0.9).10{sup -3} and C{sub 87}{sup r}({mu}{sub 0})=(3.1{+-}1.1).10{sup -5}.
Disconnected-Sea Quarks Contribution to Nucleon Electromagnetic Form Factors
Sufian, Raza Sabbir
We present comprehensive analysis of the light and strange disconnected-sea quarks contribution to the nucleon electric and magnetic form factors. The lattice QCD estimates of strange quark magnetic moment GsM (0) = -0.064(14)(09) microN and the mean squared charge radius E = -0.0043(16)(14) fm2 are more precise than any existing experimental measurements and other lattice calculations. The lattice QCD calculation includes ensembles across several lattice volumes and lattice spacings with one of the ensembles at the physical pion mass. We have performed a simultaneous chiral, infinite volume, and continuum extrapolation in a global fit to calculate results in the continuum limit. We find that the combined light-sea and strange quarks contribution to the nucleon magnetic moment is -0.022(11)(09) microN and to the nucleon mean square charge radius is -0.019(05)(05) fm 2. The most important outcome of this lattice QCD calculation is that while the combined light-sea and strange quarks contribution to the nucleon magnetic moment is small at about 1%, a negative 2.5(9)% contribution to the proton charge radius and a relatively larger positive 16.3(6.1)% contribution to the neutron charge radius come from the sea quarks in the nucleon. For the first time, by performing global fits, we also give predictions of the light-sea and strange quarks contributions to the nucleon electric and magnetic form factors at the physical point and in the continuum and infinite volume limits in the momentum transfer range of 0 ≤ Q2 ≤ 0.5 GeV2.
Dirac Magnons in Honeycomb Ferromagnets
Directory of Open Access Journals (Sweden)
Sergey S. Pershoguba
2018-01-01
Full Text Available The discovery of the Dirac electron dispersion in graphene [A. H. Castro Neto, et al., The Electronic Properties of Graphene, Rev. Mod. Phys. 81, 109 (2009RMPHAT0034-686110.1103/RevModPhys.81.109] led to the question of the Dirac cone stability with respect to interactions. Coulomb interactions between electrons were shown to induce a logarithmic renormalization of the Dirac dispersion. With a rapid expansion of the list of compounds and quasiparticle bands with linear band touching [T. O. Wehling, et al., Dirac Materials, Adv. Phys. 63, 1 (2014ADPHAH0001-873210.1080/00018732.2014.927109], the concept of bosonic Dirac materials has emerged. We consider a specific case of ferromagnets consisting of van der Waals-bonded stacks of honeycomb layers, e.g., chromium trihalides CrX_{3} (X=F, Cl, Br and I, that display two spin wave modes with energy dispersion similar to that for the electrons in graphene. At the single-particle level, these materials resemble their fermionic counterparts. However, how different particle statistics and interactions affect the stability of Dirac cones has yet to be determined. To address the role of interacting Dirac magnons, we expand the theory of ferromagnets beyond the standard Dyson theory [F. J. Dyson, General Theory of Spin-Wave Interactions, Phys. Rev. 102, 1217 (1956PHRVAO0031-899X10.1103/PhysRev.102.1217, F. J. Dyson, Thermodynamic Behavior of an Ideal Ferromagnet, Phys. Rev. 102, 1230 (1956PHRVAO0031-899X10.1103/PhysRev.102.1230] to the case of non-Bravais honeycomb layers. We demonstrate that magnon-magnon interactions lead to a significant momentum-dependent renormalization of the bare band structure in addition to strongly momentum-dependent magnon lifetimes. We show that our theory qualitatively accounts for hitherto unexplained anomalies in nearly half-century-old magnetic neutron-scattering data for CrBr_{3} [W. B. Yelon and R. Silberglitt, Renormalization of Large-Wave-Vector Magnons in
Dirac Magnons in Honeycomb Ferromagnets
Pershoguba, Sergey S.; Banerjee, Saikat; Lashley, J. C.; Park, Jihwey; Ågren, Hans; Aeppli, Gabriel; Balatsky, Alexander V.
2018-01-01
The discovery of the Dirac electron dispersion in graphene [A. H. Castro Neto, et al., The Electronic Properties of Graphene, Rev. Mod. Phys. 81, 109 (2009), 10.1103/RevModPhys.81.109] led to the question of the Dirac cone stability with respect to interactions. Coulomb interactions between electrons were shown to induce a logarithmic renormalization of the Dirac dispersion. With a rapid expansion of the list of compounds and quasiparticle bands with linear band touching [T. O. Wehling, et al., Dirac Materials, Adv. Phys. 63, 1 (2014), 10.1080/00018732.2014.927109], the concept of bosonic Dirac materials has emerged. We consider a specific case of ferromagnets consisting of van der Waals-bonded stacks of honeycomb layers, e.g., chromium trihalides CrX3 (X =F , Cl, Br and I), that display two spin wave modes with energy dispersion similar to that for the electrons in graphene. At the single-particle level, these materials resemble their fermionic counterparts. However, how different particle statistics and interactions affect the stability of Dirac cones has yet to be determined. To address the role of interacting Dirac magnons, we expand the theory of ferromagnets beyond the standard Dyson theory [F. J. Dyson, General Theory of Spin-Wave Interactions, Phys. Rev. 102, 1217 (1956), 10.1103/PhysRev.102.1217, F. J. Dyson, Thermodynamic Behavior of an Ideal Ferromagnet, Phys. Rev. 102, 1230 (1956), 10.1103/PhysRev.102.1230] to the case of non-Bravais honeycomb layers. We demonstrate that magnon-magnon interactions lead to a significant momentum-dependent renormalization of the bare band structure in addition to strongly momentum-dependent magnon lifetimes. We show that our theory qualitatively accounts for hitherto unexplained anomalies in nearly half-century-old magnetic neutron-scattering data for CrBr3 [W. B. Yelon and R. Silberglitt, Renormalization of Large-Wave-Vector Magnons in Ferromagnetic CrBr3 Studied by Inelastic Neutron Scattering: Spin-Wave Correlation
Ward, Thomas
2013-10-01
A new electromagnetic neutral-current quark mixing matrix, analog to the well-known Cabibbo-Kobayashi-Maskawa (CKM) weak charge-current matrix, is proposed to account for the strange quark content of the neutron and proton and part of the anomalous axial vector magnetic moments. The EM-CKM matrix is shown to be equivalent to the weak-CKM matrix following an EM to weak gauge symmetry transformation, demonstrating the universality of the Standard Model (SM) CKM quark mixing matrix. The electric and magnetic form factors are reformulated using a new QCD three quark nucleon gyromagnetic factor, Dirac and Pauli form factors and anomalous kappa factors. The old 1943 Jauch form factors which have been systematically used and developed for many years is shown to be in stark disagreement with the new global set of experimental polarized electron-proton scattering data whereas the reformulated SM parameter set of this study is shown to agree very well, lending strong support for this new EM SM approach.
Graphene based d-character Dirac Systems
Li, Yuanchang; Zhang, S. B.; Duan, Wenhui
From graphene to topological insulators, Dirac material continues to be the hot topics in condensed matter physics. So far, almost all of the theoretically predicted or experimentally observed Dirac materials are composed of sp -electrons. By using first-principles calculations, we find the new Dirac system of transition-metal intercalated epitaxial graphene on SiC(0001). Intrinsically different from the conventional sp Dirac system, here the Dirac-fermions are dominantly contributed by the transition-metal d-electrons, which paves the way to incorporate correlation effect with Dirac-cone physics. Many intriguing quantum phenomena are proposed based on this system, including quantum spin Hall effect with large spin-orbital gap, quantum anomalous Hall effect, 100% spin-polarized Dirac fermions and ferromagnet-to-topological insulator transition.
Dirac electronics states in graphene systems: optical spectroscopy studies
Czech Academy of Sciences Publication Activity Database
Orlita, Milan; Potemski, M.
2010-01-01
Roč. 25, č. 6 (2010), 063001/1-063001/22 ISSN 0268-1242 R&D Projects: GA AV ČR KAN400100652 Institutional research plan: CEZ:AV0Z10100521 Keywords : graphene * Dirac fermions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.323, year: 2010
Qualitative analysis of trapped Dirac fermions in graphene
Czech Academy of Sciences Publication Activity Database
Jakubský, Vít; Krejčiřík, David
2014-01-01
Roč. 349, OCT (2014), s. 268-287 ISSN 0003-4916 R&D Projects: GA ČR(CZ) GA14-06818S Institutional support: RVO:61389005 Keywords : graphene * Dirac fermion * confinement * Varitional principle Subject RIV: BE - Theoretical Physics Impact factor: 2.103, year: 2014
IEEE 1588 Time Synchronization Board in MTCA.4 Form Factor
Jabłoński, G.; Makowski, D.; Mielczarek, A.; Orlikowski, M.; Perek, P.; Napieralski, A.; Makijarvi, P.; Simrock, S.
2015-06-01
Distributed data acquisition and control systems in large-scale scientific experiments, like e.g. ITER, require time synchronization with nanosecond precision. A protocol commonly used for that purpose is the Precise Timing Protocol (PTP), also known as IEEE 1588 standard. It uses the standard Ethernet signalling and protocols and allows obtaining timing accuracy of the order of tens of nanoseconds. The MTCA.4 is gradually becoming the platform of choice for building such systems. Currently there is no commercially available implementation of the PTP receiver on that platform. In this paper, we present a module in the MTCA.4 form factor supporting this standard. The module may be used as a timing receiver providing reference clocks in an MTCA.4 chassis, generating a Pulse Per Second (PPS) signal and allowing generation of triggers and timestamping of events on 8 configurable backplane lines and two front panel connectors. The module is based on the Xilinx Spartan 6 FPGA and thermally stabilized Voltage Controlled Oscillator controlled by the digital-to-analog converter. The board supports standalone operation, without the support from the host operating system, as the entire control algorithm is run on a Microblaze CPU implemented in the FPGA. The software support for the card includes the low-level API in the form of Linux driver, user-mode library, high-level API: ITER Nominal Device Support and EPICS IOC. The device has been tested in the ITER timing distribution network (TCN) with three cascaded PTP-enabled Hirschmann switches and a GPS reference clock source. An RMS synchronization accuracy, measured by direct comparison of the PPS signals, better than 20 ns has been obtained.
DIRAC pilot framework and the DIRAC Workload Management System
International Nuclear Information System (INIS)
Casajus, Adrian; Graciani, Ricardo; Paterson, Stuart; Tsaregorodtsev, Andrei
2010-01-01
DIRAC, the LHCb community Grid solution, has pioneered the use of pilot jobs in the Grid. Pilot Jobs provide a homogeneous interface to an heterogeneous set of computing resources. At the same time, Pilot Jobs allow to delay the scheduling decision to the last moment, thus taking into account the precise running conditions at the resource and last moment requests to the system. The DIRAC Workload Management System provides one single scheduling mechanism for jobs with very different profiles. To achieve an overall optimisation, it organizes pending jobs in task queues, both for individual users and production activities. Task queues are created with jobs having similar requirements. Following the VO policy a priority is assigned to each task queue. Pilot submission and subsequent job matching are based on these priorities following a statistical approach.
DIRAC pilot framework and the DIRAC Workload Management System
Energy Technology Data Exchange (ETDEWEB)
Casajus, Adrian; Graciani, Ricardo [Universitat de Barcelona (Spain); Paterson, Stuart [CERN (Switzerland); Tsaregorodtsev, Andrei, E-mail: adria@ecm.ub.e, E-mail: graciani@ecm.ub.e, E-mail: stuart.paterson@cern.c, E-mail: atsareg@in2p3.f [CPPM Marseille (France)
2010-04-01
DIRAC, the LHCb community Grid solution, has pioneered the use of pilot jobs in the Grid. Pilot Jobs provide a homogeneous interface to an heterogeneous set of computing resources. At the same time, Pilot Jobs allow to delay the scheduling decision to the last moment, thus taking into account the precise running conditions at the resource and last moment requests to the system. The DIRAC Workload Management System provides one single scheduling mechanism for jobs with very different profiles. To achieve an overall optimisation, it organizes pending jobs in task queues, both for individual users and production activities. Task queues are created with jobs having similar requirements. Following the VO policy a priority is assigned to each task queue. Pilot submission and subsequent job matching are based on these priorities following a statistical approach.
Exact solution of the N-dimensional generalized Dirac-Coulomb equation
International Nuclear Information System (INIS)
Tutik, R.S.
1992-01-01
An exact solution to the bound state problem for the N-dimensional generalized Dirac-Coulomb equation, whose potential contains both the Lorentz-vector and Lorentz-scalar terms of the Coulomb form, is obtained. 24 refs. (author)
Asymptotic analysis of fundamental solutions of Dirac operators on even dimensional Euclidean spaces
International Nuclear Information System (INIS)
Arai, A.
1985-01-01
We analyze the short distance asymptotic behavior of some quantities formed out of fundamental solutions of Dirac operators on even dimensional Euclidean spaces with finite dimensional matrix-valued potentials. (orig.)
Integrable couplings of the multi-component Dirac hierarchy and its Hamiltonian structure
International Nuclear Information System (INIS)
Li Zhu; Dong Huanhe
2008-01-01
Integrable couplings of the multi-component Dirac hierarchy is obtained by use of the vector loop algebra G ∼ M , then the Hamiltonian structure of the above system is given by the quadratic-form identity
Exact symplectic structures and a classical model for the Dirac electron
International Nuclear Information System (INIS)
Rawnsley, J.
1992-01-01
We show how the classical model for the Dirac electron of Barut and coworkers can be obtained as a Hamiltonian theory by constructing an exact symplectic form on the total space of the spin bundle over spacetime. (orig.)
Microscopic models for hadronic form factors and vertex functions
International Nuclear Information System (INIS)
Santhanam, I.; Bhatnagar, S.; Mitra, A.N.
1990-01-01
We review the status of nucleon (N) and few-nucleon form factors (f.f.'s) from the view-point of a gradual unfolding of successively inner degrees of freedom (d.o.f.) with increase in q 2 . To this end we focus attention on the problem of a microscopic formulation of hadronic vertex functions (v.f.) from the point of view of their key role in understanding the physics of a large variety of few-hadron reactions on the one hand, and their practical usefulness in articulating the internal dynamics of hadron and few-hadron systems on the other hand. The criterion of an integrated view from low-energy spectroscopy to high-q 2 amplitudes is employed to emphasize the desirability of formulations in terms of relativistic dynamical equations based on Lorentz and gauge invariance in preference to phenomenological models, which often require additional assumptions beyond their original premises to extend their applicability domains. In this respect, the practical possibilities of the Bethe-Salpeter equation (BSE) in articulating the necessary dynamical ingredients are emphasized on a two-tier basis, the basis constants (3) being pre-determined from the mass spectral data (1 st stage) in preparation for the construction of the hadron-quark vertex functions (2 nd stage). An explicit construction is outlined for meson-quark and baryon-quark vertex functions as well as of meson-nucleon vertex functions in a stepwise fashion. The role of the latter as basic parameter-free ingredients is discussed for possible use in the more serious treatment in the current literature of quark-meson level (α) and meson-isobar (β) d.o.f. in 2-N and 3-N form factor studies. Since most of these studies are characterized by the use of RGM techniques at the six-quark level, a comparative discussion is also given of several contemporary RGM based models. Finally, the concrete prospects for employing such hardon-quark vertex functions for evaluating pp-bar annihilation amplitudes are briefly indicated
Factorization of heavy-to-light form factors in soft-collinear effective theory
Beneke, Martin; Feldmann, Th.
2004-01-01
Heavy-to-light transition form factors at large recoil energy of the light meson have been conjectured to obey a factorization formula, where the set of form factors is reduced to a smaller number of universal form factors up to hard-scattering corrections. In this paper we extend our previous investigation of heavy-to-light currents in soft-collinear effective theory to final states with invariant mass Lambda^2 as is appropriate to exclusive B meson decays. The effective theory contains soft modes and two collinear modes with virtualities of order m_b*Lambda (`hard-collinear') and Lambda^2. Integrating out the hard-collinear modes results in the hard spectator-scattering contributions to exclusive B decays. We discuss the representation of heavy-to-light currents in the effective theory after integrating out the hard-collinear scale, and show that the previously conjectured factorization formula is valid to all orders in perturbation theory. The naive factorization of matrix elements in the effective theory ...
Nucleon form factors and hidden symmetry in holographic QCD
International Nuclear Information System (INIS)
Hong, D.K.; Rho, M.; Yee, H.-U.; Yi, P.
2007-10-01
The vector dominance of the electromagnetic (EM) form factors both for mesons and baryons arises naturally in holographic QCD, where both the number of colors and the 't Hooft coupling are taken to be very large, offering a bona-fide derivation of the notion of vector dominance. The crucial ingredient for this is the infinite tower of vector mesons in the approximations made which share features that are characteristic of the quenched approximation in lattice QCD. We approximate the infinite sum by contributions from the lowest four vector mesons of the tower which turn out to saturate the charge and magnetic moment sum rules within a few % and compute them totally free of unknown parameters for momentum transfers Q 2 approx.= 1 GeV 2 . We identify certain observables that can be reliably computed within the approximations and others that are not, and discuss how the improvement of the latter can enable one to bring holographic QCD closer to QCD proper. (author)
Conformal anomaly of generalized form factors and finite loop integrals
Chicherin, Dmitry; Sokatchev, Emery
2018-04-01
We reveal a new mechanism of conformal symmetry breaking at Born level. It occurs in generalized form factors with several local operators and an on-shell state of massless particles. The effect is due to hidden singularities on collinear configurations of the momenta. This conformal anomaly is different from the holomorphic anomaly of amplitudes. We present a number of examples in four and six dimensions. We find an application of the new conformal anomaly to finite loop momentum integrals with one or more massless legs. The collinear region around a massless leg creates a contact anomaly, made visible by the loop integration. The anomalous conformal Ward identity for an ℓ-loop integral is a 2nd-order differential equation whose right-hand side is an (ℓ - 1)-loop integral. It could serve as a new useful tool to find/test analytic expressions for conformal integrals. We illustrate this point with several examples of known integrals. We propose a new differential equation for the four-dimensional scalar double box.
Measurements of the nucleon form factors at large momentum transfers
International Nuclear Information System (INIS)
Andivahis, L.; Bosted, P.; Lung, A.; Arnold, R.; Keppel, C.; Rock, S.; Spengos, M.; Szalata, Z.; Tao, L.; Stuart, L.; Dietrich, F.; Alster, J.; Lichtenstadt, J.; Chang, C.; Dodge, W.; Gearhart, R.; Kuhn, S.; Gomez, J.; Griffioen, K.; Hicks, R.; Miskimen, R.; Peterson, G.; Rokni, S.; Hyde-Wright, C.; Swartz, K.; Petratos, G.; Sakumoto, W.
1992-12-01
New measurements of the electric G E (Q 2 ) and magnetic G M (Q 2 ) form factors of the nucleons are reported. The proton data cover the Q 2 range from 1.75 to 8.83 (GeV/c) 2 and the neutron data from 1.75 to 4.00 (GeV/c) 2 , more than doubling the range of previous data. Scaled by the dipole fit, G D (Q 2 ), the results for G Mp (Q 2 )/μ p G D (Q 2 ) decrease smoothly from 1.05 to 0.92, while G Ep (Q 2 )/G D (Q 2 ) is consistent with unity. The preliminary results for Gm.(Q2)1 GD(Q2) consistent with unity, while F En 2 is consistent with zero at all values of Q 2 . Comparisons are made to QCD Sum Rule, diquark, constituent quark, and VMD models, none of which agree with all of the new data
Baryon form factors at high momentum transfer and generalized parton distributions
International Nuclear Information System (INIS)
Stoler, Paul
2002-01-01
Nucleon form factors at high momentum transfer t are treated in the framework of generalized parton distributions (GPD's). The possibility of obtaining information about parton high transverse momentum components by application of GPD's to form factors is discussed. This is illustrated by applying an ad hoc 2-body parton wave function to elastic nucleon form factors F 1 and F 2 , the N→Δ transition magnetic form factor G M * , and the wide angle Compton scattering form factor R 1
DIRAC in Large Particle Physics Experiments
Stagni, F.; Tsaregorodtsev, A.; Arrabito, L.; Sailer, A.; Hara, T.; Zhang, X.; Consortium, DIRAC
2017-10-01
The DIRAC project is developing interware to build and operate distributed computing systems. It provides a development framework and a rich set of services for both Workload and Data Management tasks of large scientific communities. A number of High Energy Physics and Astrophysics collaborations have adopted DIRAC as the base for their computing models. DIRAC was initially developed for the LHCb experiment at LHC, CERN. Later, the Belle II, BES III and CTA experiments as well as the linear collider detector collaborations started using DIRAC for their computing systems. Some of the experiments built their DIRAC-based systems from scratch, others migrated from previous solutions, ad-hoc or based on different middlewares. Adaptation of DIRAC for a particular experiment was enabled through the creation of extensions to meet their specific requirements. Each experiment has a heterogeneous set of computing and storage resources at their disposal that were aggregated through DIRAC into a coherent pool. Users from different experiments can interact with the system in different ways depending on their specific tasks, expertise level and previous experience using command line tools, python APIs or Web Portals. In this contribution we will summarize the experience of using DIRAC in particle physics collaborations. The problems of migration to DIRAC from previous systems and their solutions will be presented. An overview of specific DIRAC extensions will be given. We hope that this review will be useful for experiments considering an update, or for those designing their computing models.
DIRAC: Secure web user interface
International Nuclear Information System (INIS)
Casajus Ramo, A; Sapunov, M
2010-01-01
Traditionally the interaction between users and the Grid is done with command line tools. However, these tools are difficult to use by non-expert users providing minimal help and generating outputs not always easy to understand especially in case of errors. Graphical User Interfaces are typically limited to providing access to the monitoring or accounting information and concentrate on some particular aspects failing to cover the full spectrum of grid control tasks. To make the Grid more user friendly more complete graphical interfaces are needed. Within the DIRAC project we have attempted to construct a Web based User Interface that provides means not only for monitoring the system behavior but also allows to steer the main user activities on the grid. Using DIRAC's web interface a user can easily track jobs and data. It provides access to job information and allows performing actions on jobs such as killing or deleting. Data managers can define and monitor file transfer activity as well as check requests set by jobs. Production managers can define and follow large data productions and react if necessary by stopping or starting them. The Web Portal is build following all the grid security standards and using modern Web 2.0 technologies which allow to achieve the user experience similar to the desktop applications. Details of the DIRAC Web Portal architecture and User Interface will be presented and discussed.
Nucleon Structure and Hyperon Form Factors from Lattice QCD.
Energy Technology Data Exchange (ETDEWEB)
Lin,H.W.
2007-06-11
In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point. to be 1.23(5), consistent with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(2G), consistent with the Adelaide-JLab Collaboration's result. The hyperon {Sigma} and {Xi} axial coupling constants are also performed for the first time in a lattice calculation, g{sub {Sigma}{Sigma}} = 0.441(14) and g{sub {Xi}{Xi}} = -0.277(11).
Nucleon Structure and hyperon form factors from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Lin, Huey-Wen
2007-06-11
In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point to be 1.23(5), consistant with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(26), consistent with the Adelaide-JLab Collaboration's result. The hyperon Sigma and Xi axial coupling constants are also performed for the first time in a lattice calculation, g_SigmaSigma = 0.441(14) and g_XiXi = -0.277(11).
Dirac fermions in nontrivial topology black hole backgrounds
International Nuclear Information System (INIS)
Gozdz, Marek; Nakonieczny, Lukasz; Rogatko, Marek
2010-01-01
We discuss the behavior of the Dirac fermions in a general spherically symmetric black hole background with a nontrivial topology of the event horizon. Both massive and massless cases are taken into account. We will conduct an analytical study of intermediate and late-time behavior of massive Dirac hair in the background of a black hole with a global monopole and dilaton black hole pierced by a cosmic string. In the case of a global monopole swallowed by a static black hole, the intermediate late-time behavior depends on the mass of the Dirac field, the multiple number of the wave mode, and the global monopole parameter. The late-time behavior is quite independent of these factors and has a decay rate proportional to t -5/6 . As far as the black hole pierced by a cosmic string is concerned, the intermediate late-time behavior depends only on the hair mass and the multipole number of the wave mode, while the late-time behavior dependence is the same as in the previous case. The main modification stems from the topology of the S 2 sphere pierced by a cosmic string. This factor modifies the eigenvalues of the Dirac operator acting on the transverse manifold.
Double Dirac cones in phononic crystals
Li, Yan
2014-07-07
A double Dirac cone is realized at the center of the Brillouin zone of a two-dimensional phononic crystal (PC) consisting of a triangular array of core-shell-structure cylinders in water. The double Dirac cone is induced by the accidental degeneracy of two double-degenerate Bloch states. Using a perturbation method, we demonstrate that the double Dirac cone is composed of two identical and overlapping Dirac cones whose linear slopes can also be accurately predicted from the method. Because the double Dirac cone occurs at a relatively low frequency, a slab of the PC can be mapped onto a slab of zero refractive index material by using a standard retrieval method. Total transmission without phase change and energy tunneling at the double Dirac point frequency are unambiguously demonstrated by two examples. Potential applications can be expected in diverse fields such as acoustic wave manipulations and energy flow control.
Data Management System of the DIRAC Project
Haen, Christophe; Tsaregorodtsev, Andrei
2015-01-01
The DIRAC Interware provides a development framework and a complete set of components for building distributed computing systems. The DIRAC Data Management System (DMS) offers all the necessary tools to ensure data handling operations for small and large user communities. It supports transparent access to storage resources based on multiple technologies, and is easily expandable. The information on data files and replicas is kept in a File Catalog of which DIRAC offers a powerful and versatile implementation (DFC). Data movement can be performed using third party services including FTS3. Bulk data operations are resilient with respect to failures due to the use of the Request Management System (RMS) that keeps track of ongoing tasks. In this contribution we will present an overview of the DIRAC DMS capabilities and its connection with other DIRAC subsystems such as the Transformation System. The DIRAC DMS is in use by several user communities now. The contribution will present the experience of the LHCb exper...
The DIRAC Data Management System (poster)
Haen, Christophe
2015-01-01
The DIRAC Interware provides a development framework and a complete set of components for building distributed computing systems. The DIRAC Data Management System (DMS) offers all the necessary tools to ensure data handling operations for small and large user communities. It supports transparent access to storage resources based on multiple technologies, and is easily expandable. The information on data files and replicas is kept in a File Catalog of which DIRAC offers a powerful and versatile implementation (DFC). Data movement can be performed using third party services including FTS3. Bulk data operations are resilient with respect to failures due to the use of the Request Management System (RMS) that keeps track of ongoing tasks. In this contribution we will present an overview of the DIRAC DMS capabilities and its connection with other DIRAC subsystems such as the Transformation System. The DIRAC DMS is in use by several user communities now. The contribution will present the experience of the LHCb exper...
Double Dirac cones in phononic crystals
Li, Yan; Wu, Ying; Mei, Jun
2014-01-01
A double Dirac cone is realized at the center of the Brillouin zone of a two-dimensional phononic crystal (PC) consisting of a triangular array of core-shell-structure cylinders in water. The double Dirac cone is induced by the accidental degeneracy of two double-degenerate Bloch states. Using a perturbation method, we demonstrate that the double Dirac cone is composed of two identical and overlapping Dirac cones whose linear slopes can also be accurately predicted from the method. Because the double Dirac cone occurs at a relatively low frequency, a slab of the PC can be mapped onto a slab of zero refractive index material by using a standard retrieval method. Total transmission without phase change and energy tunneling at the double Dirac point frequency are unambiguously demonstrated by two examples. Potential applications can be expected in diverse fields such as acoustic wave manipulations and energy flow control.
Cytokinin response factors regulate PIN-FORMED auxin transporters
Czech Academy of Sciences Publication Activity Database
Šimášková, M.; O'Brien, J.A.; Khan, M.; Van Noorden, G.; Ötvös, K.; Vieten, A.; De Clercq, E.; Van Haperen, J.M.A.; Cuesta, C.; Hoyerová, Klára; Vanneste, S.; Marhavý, P.; Wabnik, K.; Van Breusegem, F.; Nowack, M.; Murphy, A.; Friml, J.; Weijers, D.; Beeckman, T.; Benková, E.
2015-01-01
Roč. 6, NOV (2015), s. 8717 ISSN 2041-1723 Institutional support: RVO:61389030 Keywords : ARABIDOPSIS -THALIANA * ROOT-MERISTEM * TRANSCRIPTION FACTORS Subject RIV: ED - Physiology Impact factor: 11.329, year: 2015
Conservative flight with a varying load factor and closed form ...
Indian Academy of Sciences (India)
Conservative flight performance of an aircraft with constant load factor was analysed by ... Within the frame work of flat earth hypotheses the equations of motion of an aircraft as obtained by ..... load factor function if this inequality holds good.
Local energy decay of massive Dirac fields in the 5D Myers-Perry metric
International Nuclear Information System (INIS)
Daudé, Thierry; Kamran, Niky
2012-01-01
We consider massive Dirac fields evolving in the exterior region of a five-dimensional Myers-Perry black hole and study their propagation properties. Our main result states that the local energy of such fields decays in a weak sense at late times. We obtain this result in two steps: first, using the separability of the Dirac equation, we prove the absence of a pure point spectrum for the corresponding Dirac operator; second, using a new form of the equation adapted to the local rotations of the black hole, we show by a Mourre theory argument that the spectrum is absolutely continuous. This leads directly to our main result. (paper)
The Dirac medals of the ICTP. 1993
International Nuclear Information System (INIS)
1995-01-01
The Dirac Medals of the International Centre for Theoretical Physics (ICTP) were instituted in 1985. These are awarded yearly to outstanding physicists, on Dirac's birthday - 8th August- for contributions to theoretical physics. The document includes the lectures of the three Dirac Medalists for 1993: Professor Sergio Ferrara, Professor Daniel Z. Freedman, and Professor Peter van Nieuwenhuizen. A separate abstract was prepared for each lecture
LHCbDIRAC as Apache Mesos microservices
Haen, Christophe; Couturier, Benjamin
2017-01-01
The LHCb experiment relies on LHCbDIRAC, an extension of DIRAC, to drive its offline computing. This middleware provides a development framework and a complete set of components for building distributed computing systems. These components are currently installed and run on virtual machines (VM) or bare metal hardware. Due to the increased workload, high availability is becoming more and more important for the LHCbDIRAC services, and the current installation model is showing its limitations. A...
Dirac Magnon Nodal Loops in Quasi-2D Quantum Magnets.
Owerre, S A
2017-07-31
In this report, we propose a new concept of one-dimensional (1D) closed lines of Dirac magnon nodes in two-dimensional (2D) momentum space of quasi-2D quantum magnetic systems. They are termed "2D Dirac magnon nodal-line loops". We utilize the bilayer honeycomb ferromagnets with intralayer coupling J and interlayer coupling J L , which is realizable in the honeycomb chromium compounds CrX 3 (X ≡ Br, Cl, and I). However, our results can also exist in other layered quasi-2D quantum magnetic systems. Here, we show that the magnon bands of the bilayer honeycomb ferromagnets overlap for J L ≠ 0 and form 1D closed lines of Dirac magnon nodes in 2D momentum space. The 2D Dirac magnon nodal-line loops are topologically protected by inversion and time-reversal symmetry. Furthermore, we show that they are robust against weak Dzyaloshinskii-Moriya interaction Δ DM magnon edge modes.
Radiationless Zitterbewegung of Dirac particles and mass formula
International Nuclear Information System (INIS)
Noboru Hokkyo.
1987-06-01
The Zitterbewegung of the Dirac particle is given a visual representation by solving the two-component difference form of the Dirac equation. It is seen that the space-time trajectory of a Dirac particle can be pictured as a correlated whole of a network of zigzags of left- and right-handed chiral neutrino-like line elements. These zigzags can feel the curl of the external electromagnetic vector potential and give rise to the spin magnetic interaction, confirming Schroedinger's earlier intuitive picture of the spin as the orbital angular momentum of the Zitterbewegung. The network of zigzags associated with an electron splits and reunites in passing through the slits in the electron beam interference experiment. It is proposed to interpret Nambu's empirical mass formula m n =(n/2)137m e =(n/2)((h/2π)/cL), n=integer, as a radiationless condition for the Zitterbewegung of the hadronic Dirac particle of the linear spatial extension of the order of the classical electron radius L=e 2 /m e c 2 . (author). 20 refs, 4 figs
LHCbDIRAC as Apache Mesos microservices
Haen, Christophe; Couturier, Benjamin
2017-10-01
The LHCb experiment relies on LHCbDIRAC, an extension of DIRAC, to drive its offline computing. This middleware provides a development framework and a complete set of components for building distributed computing systems. These components are currently installed and run on virtual machines (VM) or bare metal hardware. Due to the increased workload, high availability is becoming more and more important for the LHCbDIRAC services, and the current installation model is showing its limitations. Apache Mesos is a cluster manager which aims at abstracting heterogeneous physical resources on which various tasks can be distributed thanks to so called “frameworks” The Marathon framework is suitable for long running tasks such as the DIRAC services, while the Chronos framework meets the needs of cron-like tasks like the DIRAC agents. A combination of the service discovery tool Consul together with HAProxy allows to expose the running containers to the outside world while hiding their dynamic placements. Such an architecture brings a greater flexibility in the deployment of LHCbDirac services, allowing for easier deployment maintenance and scaling of services on demand (e..g LHCbDirac relies on 138 services and 116 agents). Higher reliability is also easier, as clustering is part of the toolset, which allows constraints on the location of the services. This paper describes the investigations carried out to package the LHCbDIRAC and DIRAC components into Docker containers and orchestrate them using the previously described set of tools.
Two-dimensional spin-orbit Dirac point in monolayer HfGeTe
Guan, Shan; Liu, Ying; Yu, Zhi-Ming; Wang, Shan-Shan; Yao, Yugui; Yang, Shengyuan A.
2017-10-01
Dirac points in two-dimensional (2D) materials have been a fascinating subject of research, with graphene as the most prominent example. However, the Dirac points in existing 2D materials, including graphene, are vulnerable against spin-orbit coupling (SOC). Here, based on first-principles calculations and theoretical analysis, we propose a new family of stable 2D materials, the HfGeTe-family monolayers, which host so-called spin-orbit Dirac points (SDPs) close to the Fermi level. These Dirac points are special in that they are formed only under significant SOC, hence they are intrinsically robust against SOC. We show that the existence of a pair of SDPs are dictated by the nonsymmorphic space group symmetry of the system, which are very robust under various types of lattice strains. The energy, the dispersion, and the valley occupation around the Dirac points can be effectively tuned by strain. We construct a low-energy effective model to characterize the Dirac fermions around the SDPs. Furthermore, we find that the material is simultaneously a 2D Z2 topological metal, which possesses nontrivial Z2 invariant in the bulk and spin-helical edge states on the boundary. From the calculated exfoliation energies and mechanical properties, we show that these materials can be readily obtained in experiment from the existing bulk materials. Our result reveals HfGeTe-family monolayers as a promising platform for exploring spin-orbit Dirac fermions and topological phases in two-dimensions.
Basic quantum mechanics for three Dirac equations in a curved spacetime
International Nuclear Information System (INIS)
Arminjon, Mayeul
2010-01-01
We study the basic quantum mechanics for a fully general set of Dirac matrices in a curved spacetime by extending Pauli's method. We further extend this study to three versions of the Dirac equation: the standard (Dirac-Fock-Weyl or DFW) equation, and two alternative versions, both of which are based on the recently proposed linear tensor representations of the Dirac field (TRD). We begin with the current conservation: we show that the latter applies to any solution of the Dirac equation, if the field of Dirac matrices γμ satisfies a specific PDE. This equation is always satisfied for DFW with its restricted choice for the γμ matrices. It similarly restricts the choice of the γμ matrices for TRD. However, this restriction can be achieved. The frame dependence of a general Hamiltonian operator is studied. We show that in any given reference frame with minor restrictions on the spacetime metric, the axioms of quantum mechanics impose a unique form for the Hilbert space scalar product. Finally, the condition for the general Dirac Hamiltonian operator to be Hermitian is derived in a general curved spacetime. For DFW, the validity of this hermeticity condition depends on the choice of the γμ matrices. (author)
International Nuclear Information System (INIS)
Karbstein, Felix
2009-01-01
We introduce a new method for dealing with fermionic quantum field theories amenable to a mean-field-type approximation. In this work we focus on the relativistic Hartree approximation. Our aim is to integrate out the Dirac sea and derive a no-sea effective theory'' with positive energy single particle states only. As the derivation of the no-sea effective theory involves only standard Feynman diagrams, our approach is quite general and not restricted to particular space-time dimensions. We develop and illustrate the approach in the ''large N'' limit of the Gross-Neveu model family in 1+1 dimensions. As the Gross-Neveu model has been intensely studied and several analytical solutions are known for this model, it is an ideal testing ground for our no-sea effective theory approach. The chiral Gross-Neveu model, also referred to as 1+1 dimensional Nambu-Jona-Lasinio model, turns out to be of particular interest. In this case, we explicitly derive a consistent effective theory featuring both elementary ''π meson'' fields and (positive energy) ''quark'' fields, starting from a purely fermionic quantum field theory. In the second part of this work, we apply our approach to the Walecka model in 1+1 and 3+1 dimensions. As the Dirac sea caused considerable difficulties in attempts to base nuclear physics on field theoretic models like the Walecka model, mean-field calculations were typically done without the sea. We confront several of these mean-field theory results with our no-sea effective theory approach. The potential of our approach is twofold. While the no-sea effective theory can be utilized to provide new analytical insights in particular parameter regimes, it also sheds new light on more fundamental issues as the explicit emergence of effective, Dirac-sea induced multi-fermion interactions in an effective theory with positive energy states only. (orig.)
Solar test of Dirac's large number hypothesis. [multiplicative creation model for solar evolution
Chin, C.-W.; Stothers, R.
1975-01-01
An investigation is conducted regarding the implications of Dirac's theories (1973, 1974) concerning the creation of new matter. It is found that Dirac's theory of multiplicative creation, but not his theory of additive creation, is not in contradiction with known facts about the sun. According to the theory of additive creation, matter is formed uniformly throughout space. The concept of multiplicative creation implies that existing matter multiplies itself in proportion to the amount of matter already present.
Solution of the Lorentz-Dirac equation based on a new momentum expression
Yan, C C
1998-01-01
The Lorentz-Dirac equation is solved based on a new momentum expression given by p sup a =1/c sup 2 (u submu p supmu)u sup a +k du sup a /d tau. This new momentum expression is the form proposed by Barut modified to satisfy the condition imposed by Dirac. The solution turns out to be well behaved without violating causality or causing runaway. (author)
Dirac tensor with heavy photon
Energy Technology Data Exchange (ETDEWEB)
Bytev, V.V.; Kuraev, E.A. [Joint Institute of Nuclear Research, Moscow (Russian Federation). Bogoliubov Lab. of Theoretical Physics; Scherbakova, E.S. [Hamburg Univ. (Germany). 1. Inst. fuer Theoretische Physik
2012-01-15
For the large-angles hard photon emission by initial leptons in process of high energy annihilation of e{sup +}e{sup -} {yields} to hadrons the Dirac tensor is obtained, taking into account the lowest order radiative corrections. The case of large-angles emission of two hard photons by initial leptons is considered. This result is being completed by the kinematics case of collinear hard photons emission as well as soft virtual and real photons and can be used for construction of Monte-Carlo generators. (orig.)
Forms and factors of peer violence and victimisation
Dinić Bojana; Sokolovska Valentina; Milovanović Ilija; Oljača Milan
2014-01-01
The main aim of this study was to explore the latent structure of violence and victimisation based on the factor analysis of the Peer Violence and Victimisation Questionnaire (PVVQ), as well as to examine the correlates of violence and victimisation. The sample included 649 secondary school students (61.8% male) from the urban area. Besides the PVVQ, the Aggressiveness questionnaire AVDH was administered. Based on parallel analysis, three factors were extra...
Matter density distributions and elastic form factors of some two ...
Indian Academy of Sciences (India)
Ahmed N Abdullah
2017-08-31
Aug 31, 2017 ... include the proton, neutron and matter density distributions, the corresponding rms radii, the binding energy per nucleon and the charge form ... the nuclear structure models based on the experimental data for stable nuclei ... Most exotic nuclei are so short lived that they cannot be used as targets at rest.
Iso-vector form factors of the delta and nucleon in QCD sum rules
International Nuclear Information System (INIS)
Ozpineci, A.
2012-01-01
Form factors are important non-perturbative properties of hadrons. They give information about the internal structure of the hadrons. In this work, iso-vector axial-vector and iso-vector tensor form factors of the nucleon and the iso-vector axial-vector Δ→N transition form factor calculations in QCD Sum Rules are presented.
Two neutron transfer form factor for the reaction 42Ca(p,t)40Ca
International Nuclear Information System (INIS)
Meyer, R.H.
1978-01-01
In an attempt to better interpret experimental data concerning the two-neutron pickup process 42 Ca(p,t) 40 Ca, a detailed study of the form factors associated with the reaction is carried out. A set of coupled integro-differential equations describing these form factors is derived, starting from a microscopic, model-independent Hamiltonian. These equations allow contributions to the form factors from hole terms as well as from the particle and so-called ''continuum'' states, which were previously studied. An approximate solution of the form factor equations is obtained by neglecting the coupling terms and expressing the form factor in terms of a set of Sturmian states. Form factors for the transition to the 40 Ca ground state (O 1 + ) are calculated using various sets of Sturmian states. The inclusion of hole states is found to have a major effect upon both the shape of the form factor and the size of the related cross section. Finally, a comparison is made between the O 1 + form factors calculated using Sturmian states and a O 1 + form factor obtained using Sturmian states and a O 1 + form factor obtained using the coexistence model. It is found that a form factor based on Sturmian particle and hole states is very similar to the form factor obtained from the coexistence model calculation
The Dirac equation in classical statistical mechanics
International Nuclear Information System (INIS)
Ord, G.N.
2002-01-01
The Dirac equation, usually obtained by 'quantizing' a classical stochastic model is here obtained directly within classical statistical mechanics. The special underlying space-time geometry of the random walk replaces the missing analytic continuation, making the model 'self-quantizing'. This provides a new context for the Dirac equation, distinct from its usual context in relativistic quantum mechanics
Dirac and Weyl semimetals with holographic interactions
Jacobs, V.P.J.
2015-01-01
Dirac and Weyl semimetals are states of matter exhibiting the relativistic physics of, respectively, the Dirac and Weyl equation in a three-dimensional bulk material. These three-dimensional semimetals have recently been realized experimentally in various crystals. Theoretically, especially the
A fractional Dirac equation and its solution
International Nuclear Information System (INIS)
Muslih, Sami I; Agrawal, Om P; Baleanu, Dumitru
2010-01-01
This paper presents a fractional Dirac equation and its solution. The fractional Dirac equation may be obtained using a fractional variational principle and a fractional Klein-Gordon equation; both methods are considered here. We extend the variational formulations for fractional discrete systems to fractional field systems defined in terms of Caputo derivatives. By applying the variational principle to a fractional action S, we obtain the fractional Euler-Lagrange equations of motion. We present a Lagrangian and a Hamiltonian for the fractional Dirac equation of order α. We also use a fractional Klein-Gordon equation to obtain the fractional Dirac equation which is the same as that obtained using the fractional variational principle. Eigensolutions of this equation are presented which follow the same approach as that for the solution of the standard Dirac equation. We also provide expressions for the path integral quantization for the fractional Dirac field which, in the limit α → 1, approaches to the path integral for the regular Dirac field. It is hoped that the fractional Dirac equation and the path integral quantization of the fractional field will allow further development of fractional relativistic quantum mechanics.
New solitons connected to the Dirac equation
International Nuclear Information System (INIS)
Grosse, H.
1984-01-01
Imposing isospectral invariance for the one dimensional Dirac operator leads to systems of nonlinear partial differential equations. By constructing reflectionless potentials of the Dirac equation we obtain a new type of solitons for a system of modified Korteweg-de Vries equations. (Author)
Semi-Dirac points in phononic crystals
Zhang, Xiujuan; Wu, Ying
2014-01-01
of rubber, in which the acoustic wave velocity is lower than that in water, the semi-Dirac dispersion can be characterized by an effective medium theory. The effective medium parameters link the semi-Dirac point to a topological transition in the iso
The Dirac-Kaehler equation and fermions on the lattice
International Nuclear Information System (INIS)
Becher, P.
1982-05-01
The geometrical description of spinor fields by E. Kaehler is used to formulate a consistent lattice approximation of fermions. The relation to free simple Dirac fields as well as to Susskind's description of lattice fermions is clarified. The first steps towards a quantized interacting theory are given. The correspondence between the calculus of differential forms and concepts of algebraic topology is shown to be a useful method for a completely analogous treatment of the problems in the continuum and on the lattice. (orig.)
LHCbDIRAC as Apache Mesos microservices
Couturier, Ben
2016-01-01
The LHCb experiment relies on LHCbDIRAC, an extension of DIRAC, to drive its offline computing. This middleware provides a development framework and a complete set of components for building distributed computing systems. These components are currently installed and ran on virtual machines (VM) or bare metal hardware. Due to the increased load of work, high availability is becoming more and more important for the LHCbDIRAC services, and the current installation model is showing its limitations. Apache Mesos is a cluster manager which aims at abstracting heterogeneous physical resources on which various tasks can be distributed thanks to so called "framework". The Marathon framework is suitable for long running tasks such as the DIRAC services, while the Chronos framework meets the needs of cron-like tasks like the DIRAC agents. A combination of the service discovery tool Consul together with HAProxy allows to expose the running containers to the outside world while hiding their dynamic placements. Such an arc...
Dirac operators on coset spaces
International Nuclear Information System (INIS)
Balachandran, A.P.; Immirzi, Giorgio; Lee, Joohan; Presnajder, Peter
2003-01-01
The Dirac operator for a manifold Q, and its chirality operator when Q is even dimensional, have a central role in noncommutative geometry. We systematically develop the theory of this operator when Q=G/H, where G and H are compact connected Lie groups and G is simple. An elementary discussion of the differential geometric and bundle theoretic aspects of G/H, including its projective modules and complex, Kaehler and Riemannian structures, is presented for this purpose. An attractive feature of our approach is that it transparently shows obstructions to spin- and spin c -structures. When a manifold is spin c and not spin, U(1) gauge fields have to be introduced in a particular way to define spinors, as shown by Avis, Isham, Cahen, and Gutt. Likewise, for manifolds like SU(3)/SO(3), which are not even spin c , we show that SU(2) and higher rank gauge fields have to be introduced to define spinors. This result has potential consequences for string theories if such manifolds occur as D-branes. The spectra and eigenstates of the Dirac operator on spheres S n =SO(n+1)/SO(n), invariant under SO(n+1), are explicitly found. Aspects of our work overlap with the earlier research of Cahen et al
Recruitment of bloom-forming cyanobacteria and its driving factors ...
African Journals Online (AJOL)
Based on most of the literature, this paper reviewed the progress made in following aspects: cognition to cyanobacteria recruitment, various traps for studying cyanobacteria recruitment in lakes, recruitment patterns of some species of cyanobacteria, and the driving factors for recruitment. Additionally, perspective studies of ...
On Charge Conjugation, Chirality and Helicity of the Dirac and Majorana Equation for Massive Leptons
Directory of Open Access Journals (Sweden)
Eckart Marsch
2015-04-01
Full Text Available We revisit the charge-conjugation operation for the Dirac equation in its chiral representation. A new decomposition of the Dirac spinor field is suggested and achieved by means of projection operators based on charge conjugation, which is discussed here in a non-standard way. Thus, two separate two-component Majorana-type field equations for the eigenfields of the charge-conjugation operator are obtained. The corresponding free fields are entirely separated without a gauge field, but remain mixed and coupled together through an electromagnetic field term. For fermions that are charged and, thus, subjected to the gauge field of electrodynamics, these two Majorana fields can be reassembled into a doublet, which is equivalent to a standard four-component Dirac spinor field. In this way, the Dirac equation is retained in a new guise, which is fully equivalent to that equation in its chiral form.
Finster, Felix; Smoller, Joel; Yau, Shing-Tung
We consider for j=1/2, 3/2,... a spherically symmetric, static system of (2j+1) Dirac particles, each having total angular momentum j. The Dirac particles interact via a classical gravitational and electromagnetic field. The Einstein-Dirac-Maxwell equations for this system are derived. It is shown that, under weak regularity conditions on the form of the horizon, the only black hole solutions of the EDM equations are the Reissner-Nordstrom solutions. In other words, the spinors must vanish identically. Applied to the gravitational collapse of a "cloud" of spin-1/2-particles to a black hole, our result indicates that the Dirac particles must eventually disappear inside the event horizon.
Energy Technology Data Exchange (ETDEWEB)
Karbstein, Felix
2009-07-08
We introduce a new method for dealing with fermionic quantum field theories amenable to a mean-field-type approximation. In this work we focus on the relativistic Hartree approximation. Our aim is to integrate out the Dirac sea and derive a no-sea effective theory'' with positive energy single particle states only. As the derivation of the no-sea effective theory involves only standard Feynman diagrams, our approach is quite general and not restricted to particular space-time dimensions. We develop and illustrate the approach in the ''large N'' limit of the Gross-Neveu model family in 1+1 dimensions. As the Gross-Neveu model has been intensely studied and several analytical solutions are known for this model, it is an ideal testing ground for our no-sea effective theory approach. The chiral Gross-Neveu model, also referred to as 1+1 dimensional Nambu-Jona-Lasinio model, turns out to be of particular interest. In this case, we explicitly derive a consistent effective theory featuring both elementary ''{pi} meson'' fields and (positive energy) ''quark'' fields, starting from a purely fermionic quantum field theory. In the second part of this work, we apply our approach to the Walecka model in 1+1 and 3+1 dimensions. As the Dirac sea caused considerable difficulties in attempts to base nuclear physics on field theoretic models like the Walecka model, mean-field calculations were typically done without the sea. We confront several of these mean-field theory results with our no-sea effective theory approach. The potential of our approach is twofold. While the no-sea effective theory can be utilized to provide new analytical insights in particular parameter regimes, it also sheds new light on more fundamental issues as the explicit emergence of effective, Dirac-sea induced multi-fermion interactions in an effective theory with positive energy states only. (orig.)
AEMnSb2 (AE=Sr, Ba): a new class of Dirac materials
International Nuclear Information System (INIS)
Farhan, M Arshad; Lee, Geunsik; Shim, Ji Hoon
2014-01-01
The Dirac fermions of Sb square net in AEMnSb 2 (AE=Sr, Ba) are investigated by using first-principles calculation. BaMnSb 2 contains Sb square net layers with a coincident stacking of Ba atoms, exhibiting Dirac fermion behavior. On the other hand, SrMnSb 2 has a staggered stacking of Sr atoms with distorted zig-zag chains of Sb atoms. Application of hydrostatic pressure on the latter induces a structural change from a staggered to a coincident arrangement of AE ions accompanying a transition from insulator to a metal containing Dirac fermions. The structural investigations show that the stacking type of cation and orthorhombic distortion of Sb layers are the main factors to decide the crystal symmetry of the material. We propose that the Dirac fermions can be obtained by controlling the size of cation and the volume of AEMnSb 2 compounds. (fast track communication)
Paul Dirac: the purest soul in physics
International Nuclear Information System (INIS)
Berry, M.
1998-01-01
Paul Dirac published the first of his papers on ''The Quantum Theory of the Electron'' seventy years ago this month. Published in the Proceedings of the Royal Society (London) in February and March 1928, the papers contained one of the greatest leaps of imagination in 20th century physics. The Dirac equation, derived in those papers, is one of the most important equations in physics. Dirac showed that the simplest wave satisfying the requirements of quantum mechanics and relativity was not a simple number but had four components. He found that the logic that led to the theory was, although deeply sophisticated, in a sense beautifully simple. Much later, when someone asked him ''How did you find the Dirac equation?'' he is said to have replied: ''I found it beautiful''. In addition to explaining the magnetic and spin properties of the electron, the equation also predicts the existence of antimatter. Because Dirac was a quiet man - famously quiet, indeed - he is not well known outside physics, although this is slowly changing. In 1995 a plaque to Dirac was unveiled at Westminster Abbey in London and last year Institute of Physics Publishing, which is based in Bristol, named its new building Dirac House. In this article the author recalls the achievements of the greatest physicists of the 20th century. (UK)
Dirac fermions in blue-phosphorus
International Nuclear Information System (INIS)
Li, Yuanchang; Chen, Xiaobin
2014-01-01
We propose that Dirac cones can be engineered in phosphorene with fourfold-coordinated phosphorus atoms. The key is to separate the energy levels of the in-plane (s, p x , and p y ) and out-of-plane (p z ) oribtals through the sp 2 configuration, yielding respective σ- and π-character Dirac cones, and then quench the latter. As a proof-of-principle study, we create σ-character Dirac cones in hydrogenated and fluorinated phosphorene with a honeycomb lattice. The obtained Dirac cones are at K-points, slightly anisotropic, with Fermi velocities of 0.91 and 1.23 times that of graphene along the ΓK and KM direction, and maintain good linearity up to ∼2 eV for holes. A substantive advantage of a σ-character Dirac cone is its convenience in tuning the Dirac gap via in-plane strain. Our findings pave the way for development of high-performance electronic devices based on Dirac materials. (letter)
Dirac cones in isogonal hexagonal metallic structures
Wang, Kang
2018-03-01
A honeycomb hexagonal metallic lattice is equivalent to a triangular atomic one and cannot create Dirac cones in its electromagnetic wave spectrum. We study in this work the low-frequency electromagnetic band structures in isogonal hexagonal metallic lattices that are directly related to the honeycomb one and show that such structures can create Dirac cones. The band formation can be described by a tight-binding model that allows investigating, in terms of correlations between local resonance modes, the condition for the Dirac cones and the consequence of the third structure tile sustaining an extra resonance mode in the unit cell that induces band shifts and thus nonlinear deformation of the Dirac cones following the wave vectors departing from the Dirac points. We show further that, under structure deformation, the deformations of the Dirac cones result from two different correlation mechanisms, both reinforced by the lattice's metallic nature, which directly affects the resonance mode correlations. The isogonal structures provide new degrees of freedom for tuning the Dirac cones, allowing adjustment of the cone shape by modulating the structure tiles at the local scale without modifying the lattice periodicity and symmetry.
Benoit-Lévy, Aurélien; Chardin, Gabriel
2014-05-01
We study an unconventional cosmology, in which we investigate the consequences that antigravity would pose to cosmology. We present the main characteristics of the Dirac-Milne Universe, a cosmological model where antimatter has a negative active gravitational mass. In this non-standard Universe, separate domains of matter and antimatter coexist at our epoch without annihilation, separated by a gravitationally induced depletion zone. We show that this cosmology does not require a priori the Dark Matter and Dark Energy components of the standard model of cosmology. Additionally, inflation becomes an unnecessary ingredient. Investigating this model, we show that the classical cosmological tests such as primordial nucleosynthesis, Type Ia supernovæ and Cosmic Microwave Background are surprisingly concordant.
International Nuclear Information System (INIS)
Liang Aiji; Chen Chaoyu; Wang Zhijun; Shi Youguo; Feng Ya; Yi Hemian; Xie Zhuojin; He Shaolong; He Junfeng; Peng Yingying; Liu Yan; Liu Defa; Hu Cheng; Zhao Lin; Liu Guodong; Dong Xiaoli; Zhang Jun; Nakatake, M; Iwasawa, H; Shimada, K
2016-01-01
The three-dimensional (3D) Dirac semimetals have linearly dispersive 3D Dirac nodes where the conduction band and valence band are connected. They have isolated 3D Dirac nodes in the whole Brillouin zone and can be viewed as a 3D counterpart of graphene. Recent theoretical calculations and experimental results indicate that the 3D Dirac semimetal state can be realized in a simple stoichiometric compound A 3 Bi ( A = Na, K, Rb). Here we report comprehensive high-resolution angle-resolved photoemission (ARPES) measurements on the two cleaved surfaces, (001) and (100), of Na 3 Bi. On the (001) surface, by comparison with theoretical calculations, we provide a proper assignment of the observed bands, and in particular, pinpoint the band that is responsible for the formation of the three-dimensional Dirac cones. We observe clear evidence of 3D Dirac cones in the three-dimensional momentum space by directly measuring on the k x – k y plane and by varying the photon energy to get access to different out-of-plane k z s. In addition, we reveal new features around the Brillouin zone corners that may be related with surface reconstruction. On the (100) surface, our ARPES measurements over a large momentum space raise an issue on the selection of the basic Brillouin zone in the (100) plane. We directly observe two isolated 3D Dirac nodes on the (100) surface. We observe the signature of the Fermi-arc surface states connecting the two 3D Dirac nodes that extend to a binding energy of ∼150 meV before merging into the bulk band. Our observations constitute strong evidence on the existence of the Dirac semimetal state in Na 3 Bi that are consistent with previous theoretical and experimental work. In addition, our results provide new information to clarify on the nature of the band that forms the 3D Dirac cones, on the possible formation of surface reconstruction of the (001) surface, and on the issue of basic Brillouin zone selection for the (100) surface. (rapid communication)
The Dirac equation and its solutions
Energy Technology Data Exchange (ETDEWEB)
Bagrov, Vladislav G. [Tomsk State Univ., Tomsk (Russian Federation). Dept. of Quantum Field Theroy; Gitman, Dmitry [Sao Paulo Univ. (Brazil). Inst. de Fisica; P.N. Lebedev Physical Institute, Moscow (Russian Federation); Tomsk State Univ., Tomsk (Russian Federation). Faculty of Physics
2013-07-01
The Dirac equation is of fundamental importance for relativistic quantum mechanics and quantum electrodynamics. In relativistic quantum mechanics, the Dirac equation is referred to as one-particle wave equation of motion for electron in an external electromagnetic field. In quantum electrodynamics, exact solutions of this equation are needed to treat the interaction between the electron and the external field exactly. In particular, all propagators of a particle, i.e., the various Green's functions, are constructed in a certain way by using exact solutions of the Dirac equation.
The Dirac equation and its solutions
Bagrov, Vladislav G
2014-01-01
Dirac equations are of fundamental importance for relativistic quantum mechanics and quantum electrodynamics. In relativistic quantum mechanics, the Dirac equation is referred to as one-particle wave equation of motion for electron in an external electromagnetic field. In quantum electrodynamics, exact solutions of this equation are needed to treat the interaction between the electron and the external field exactly.In particular, all propagators of a particle, i.e., the various Green's functions, are constructed in a certain way by using exact solutions of the Dirac equation.
Counter-diabatic driving for Dirac dynamics
Fan, Qi-Zhen; Cheng, Xiao-Hang; Chen, Xi
2018-03-01
In this paper, we investigate the fast quantum control of Dirac equation dynamics by counter-diabatic driving, sharing the concept of shortcut to adiabaticity. We systematically calculate the counter-diabatic terms in different Dirac systems, like graphene and trapped ions. Specially, the fast and robust population inversion processes are achieved in Dirac system, taking into account the quantum simulation with trapped ions. In addition, the population transfer between two bands can be suppressed by counter-diabatic driving in graphene system, which might have potential applications in opt-electric devices.
Quantum geometry of the Dirac fermions
International Nuclear Information System (INIS)
Korchemskij, G.P.
1989-01-01
The bosonic path integral formalism is developed for Dirac fermions interacting with a nonabelian gauge field in the D-dimensional Euclidean space-time. The representation for the effective action and correlation functions of interacting fermions as sums over all bosonic paths on the complex projective space CP 2d-1 , (2d=2 [ D 2] is derived where all the spinor structure is absorbed by the one-dimensional Wess-Zumino term. It is the Wess-Zumino term that ensures all necessary properties of Dirac fermions under quantization. i.e., quantized values of the spin, Dirac equation, Fermi statistics. 19 refs
The Dirac equation and its solutions
International Nuclear Information System (INIS)
Bagrov, Vladislav G.; Gitman, Dmitry; P.N. Lebedev Physical Institute, Moscow; Tomsk State Univ., Tomsk
2013-01-01
The Dirac equation is of fundamental importance for relativistic quantum mechanics and quantum electrodynamics. In relativistic quantum mechanics, the Dirac equation is referred to as one-particle wave equation of motion for electron in an external electromagnetic field. In quantum electrodynamics, exact solutions of this equation are needed to treat the interaction between the electron and the external field exactly. In particular, all propagators of a particle, i.e., the various Green's functions, are constructed in a certain way by using exact solutions of the Dirac equation.
Scalar potentials and the Dirac equation
International Nuclear Information System (INIS)
Bergerhoff, B.; Soff, G.
1994-01-01
The Dirac equation is solved for various types of scalar potentials. Energy eigenvalues and normalized bound-state wave functions are calculated analytically for a scalar 1/r-potential as well as for a mixed scalar and Coulomb 1/r-potential. Also continuum wave functions for positive and negative energies are derived. Similarly, we investigate the solutions of the Dirac equation for a scalar square-well potential. Relativistic wave functions for scalar Yukawa and exponential potentials are determined numerically. Finally, we also discuss solutions of the Dirac equation for scalar linear and quadratic potentials which are frequently used to simulate quark confinement. (orig.)
Self-Assembled Si(111) Surface States: 2D Dirac Material for THz Plasmonics.
Wang, Z F; Liu, Feng
2015-07-10
Graphene, the first discovered 2D Dirac material, has had a profound impact on science and technology. In the last decade, we have witnessed huge advances in graphene related fundamental and applied research. Here, based on first-principles calculations, we propose a new 2D Dirac band on the Si(111) surface with 1/3 monolayer halogen coverage. The sp(3) dangling bonds form a honeycomb superstructure on the Si(111) surface that results in an anisotropic Dirac band with a group velocity (∼10(6) m/s) comparable to that in graphene. Most remarkably, the Si-based surface Dirac band can be used to excite a tunable THz plasmon through electron-hole doping. Our results demonstrate a new way to design Dirac states on a traditional semiconductor surface, so as to make them directly compatible with Si technology. We envision this new type of Dirac material to be generalized to other semiconductor surfaces with broad applications.
Meson widths and form factor at intermediate momentum transfer in nonperturbative QCD
International Nuclear Information System (INIS)
Ioffe, B.L.; Smilga, A.V.
1982-01-01
A general method is proposed for the QCD based calculations of form factors at intermediate momentum transfer Q 2 and of the partial widths of the low-lying meson resonances. The basic idea is to use the QCD sum rules for the vertex functions. With this method the pion electromagnetic form factor along with electromagnetic form factors of rho- and A 1 mesons and transition form factors γπ → A 1 at 0.5 2 2 are calculated. The widths rho+2π and A 1 → rhoπ are also determined. +.he results are in a good agreement with experiment
Calculation of the Nucleon Axial Form Factor Using Staggered Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Meyer, Aaron S. [Fermilab; Hill, Richard J. [Perimeter Inst. Theor. Phys.; Kronfeld, Andreas S. [Fermilab; Li, Ruizi [Indiana U.; Simone, James N. [Fermilab
2016-10-14
The nucleon axial form factor is a dominant contribution to errors in neutrino oscillation studies. Lattice QCD calculations can help control theory errors by providing first-principles information on nucleon form factors. In these proceedings, we present preliminary results on a blinded calculation of $g_A$ and the axial form factor using HISQ staggered baryons with 2+1+1 flavors of sea quarks. Calculations are done using physical light quark masses and are absolutely normalized. We discuss fitting form factor data with the model-independent $z$ expansion parametrization.
Electromagnetic form factors of the ρ meson in light cone QCD sum rules
International Nuclear Information System (INIS)
Aliev, T.M.; Savci, M.
2004-01-01
We investigate the electromagnetic form factors of the ρ meson in light cone QCD sum rules. We find that the ratio of the magnetic and charge form factors is larger than 2 at all values of Q 2 (Q 2 ≥0.5 GeV 2 ). The values of the individual form factors at fixed values of Q 2 predicted by the light cone QCD sum rules are quite different compared to the results of other approaches. These results can be checked in the future, when more precise data on ρ meson form factors is available
Up- and Down-Quark Contributions to the Nucleon Form Factors
Directory of Open Access Journals (Sweden)
Qattan I. A.
2014-03-01
Full Text Available Recent measurements of the neutron s electric to magnetic form factors ratio, Rn = µnGnE/GnM, up to 3.4 (GeV/c2 combined with existing Rp = µpGpE/GpM measurements in the same Q2 range allowed, for the first time, a separation of the up- and downquark contributions to the form factors at high Q2, as presented by Cates, et al.. Our analysis expands on the original work by including additional form factor data, applying two-photon exchange (TPE corrections, and accounting for the uncertainties associated with all of the form factor measurements.
Dirac equation in magnetic-solenoid field
Energy Technology Data Exchange (ETDEWEB)
Gavrilov, S.P. [Dept. Fisica e Quimica, UNESP, Campus de Guaratingueta (Brazil); Gitman, D.M.; Smirnov, A.A. [Instituto de Fisica, Universidade de Sao Paulo (Brazil)
2004-07-01
We consider the Dirac equation in the magnetic-solenoid field (the field of a solenoid and a collinear uniform magnetic field). For the case of Aharonov-Bohm solenoid, we construct self-adjoint extensions of the Dirac Hamiltonian using von Neumann's theory of deficiency indices. We find self-adjoint extensions of the Dirac Hamiltonian and boundary conditions at the AB solenoid. Besides, for the first time, solutions of the Dirac equation in the magnetic-solenoid field with a finite radius solenoid were found. We study the structure of these solutions and their dependence on the behavior of the magnetic field inside the solenoid. Then we exploit the latter solutions to specify boundary conditions for the magnetic-solenoid field with Aharonov-Bohm solenoid. (orig.)
SU(4) proprerties of the Dirac equation
International Nuclear Information System (INIS)
Linhares, C.A.; Mignaco, J.A.
1985-09-01
The Dirac equation in four dimensions has an intimate connection with the representations of the group SU(4). This connection is shown in detail and subsequent properties are displayed in the continuum as well as in the lattice description [pt
On the level order for Dirac operators
International Nuclear Information System (INIS)
Grosse, H.
1987-01-01
We start from the Dirac operator for the Coulomb potential and prove within first order perturbation theory that degenerate levels split in a definite way depending on the sign of the Laplacian of the perturbing potential. 9 refs. (Author)
New and old symmetries of the Maxwell and Dirac equations
International Nuclear Information System (INIS)
Fushchich, V.I.; Nikitin, A.G.
1983-01-01
The symmetry properties of Maxwell's equations for the electromagnetic field and also of the Dirac and Kemmer-Duffin-Petiau equations are analyzed. In the framework of a ''non-Lie'' approach it is shown that, besides the well-known invariance with respect to the conformal group and the Heaviside-Larmor-Rainich transformations, Maxwell's equations have an additional symmetry with respect to the group U(2)xU(2) and with respect to the 23-dimensional Lie algebra A 23 . The transformations of the additional symmetry are given by nonlocal (integro-differential) operators. The symmetry of the Dirac equation in the class of differential and integro-differential transformations is investigated. It is shown that this equation is invariant with respect to an 18-parameter group, which includes the Poincare group as a subgroup. A 28-parameter invariance group of the Kemmer-Duffin-Petiau equation is found. Finite transformations of the conformal group for a massless field with arbitrary spin are obtained. The explicit form of conformal transformations for the electromagnetic field and also for the Dirac and Weyl fields is given
On new and old symmetries of Maxwell and Dirac equations
International Nuclear Information System (INIS)
Fushchich, V.I.; Nikitin, A.G.
1983-01-01
Symmetry properties of the Maxwell equation for the electromagnetic field are analysed as well as of the Dirac and Kemmer-Duffin-Petiau one. In the frame of the non-geometrical approach it is demonstrated, that besides to the well-known invariance under the conformal group and Heaviside-Larmor-Rainich transformation, Maxwell equation possess the additional symmetry under the group U(2)xU(2) and under the 23-dimensional Lie algebra A 23 . The additional symmetry transformations are realized by the non-local (integro-differential) operators. The symmetry of the Dirac. equation under the differential and integro-differential transformations is investio.ated. It is shown that this equation is invariant under the 18-parametrical group, which includes the Poincare group as a subgroup. The 28-parametrical invariance group of the Kemmer-Duffin-Petiau equation is found. The finite conformal group transformations for a massless field of any spin are obtained. The explicit form of the conformal transformations for the electromagnetic field as well as for the Dirac and Weyl fields is given
Data acquisition software for DIRAC experiment
International Nuclear Information System (INIS)
Ol'shevskij, V.G.; Trusov, S.V.
2000-01-01
The structure and basic processes of data acquisition software of DIRAC experiment for the measurement of π + π - atom life-time are described. The experiment is running on PS accelerator of CERN. The developed software allows one to accept, record and distribute to consumers up to 3 Mbytes of data in one accelerator supercycle of 14.4 s duration. The described system is used successfully in the DIRAC experiment starting from 1998 year
Deuteron stripping reactions using dirac phenomenology
Hawk, E. A.; McNeil, J. A.
2001-04-01
In this work deuteron stripping reactions are studied using the distorted wave born approximation employing dirac phenomenological potentials. In 1982 Shepard and Rost performed zero-range dirac phenomenological stripping calculations and found a dramatic reduction in the predicted cross sections when compared with similar nonrelativistic calculations. We extend the earlier work by including full finite range effects as well as the deuteron's internal D-state. Results will be compared with traditional nonrelativistic approaches and experimental data at low energy.
Solvable linear potentials in the Dirac equation
International Nuclear Information System (INIS)
Dominguez-Adame, F.; Gonzalez, M.A.
1990-01-01
The Dirac equation for some linear potentials leading to Schroedinger-like oscillator equations for the upper and lower components of the Dirac spinor have been solved. Energy levels for the bound states appear in pairs, so that both particles and antiparticles may be bound with the same energy. For weak coupling, the spacing between levels is proportional to the coupling constant while in the strong limit those levels are depressed compared to the nonrelativistic ones
Leptons as systems of Dirac particles
International Nuclear Information System (INIS)
Borstnik, N.M.; Kaluza, M.
1988-03-01
Charged leptons are treated as systems of three equal independent Dirac particles in an external static effective potential which has a vector and a scalar term. The potential is constructed to reproduce the experimental mass spectrum of the charged leptons. The Dirac covariant equation for three interacting particles is discussed in order to comment on the magnetic moment of leptons. (author). 9 refs, 2 figs, 4 tabs
Dirac equation on a curved surface
Energy Technology Data Exchange (ETDEWEB)
Brandt, F.T., E-mail: fbrandt@usp.br; Sánchez-Monroy, J.A., E-mail: antosan@usp.br
2016-09-07
The dynamics of Dirac particles confined to a curved surface is examined employing the thin-layer method. We perform a perturbative expansion to first-order and split the Dirac field into normal and tangential components to the surface. In contrast to the known behavior of second order equations like Schrödinger, Maxwell and Klein–Gordon, we find that there is no geometric potential for the Dirac equation on a surface. This implies that the non-relativistic limit does not commute with the thin-layer method. Although this problem can be overcome when second-order terms are retained in the perturbative expansion, this would preclude the decoupling of the normal and tangential degrees of freedom. Therefore, we propose to introduce a first-order term which rescues the non-relativistic limit and also clarifies the effect of the intrinsic and extrinsic curvatures on the dynamics of the Dirac particles. - Highlights: • The thin-layer method is employed to derive the Dirac equation on a curved surface. • A geometric potential is absent at least to first-order in the perturbative expansion. • The effects of the extrinsic curvature are included to rescue the non-relativistic limit. • The resulting Dirac equation is consistent with the Heisenberg uncertainty principle.
Mathe, Z.; Casajus Ramo, A.; Lazovsky, N.; Stagni, F.
2015-12-01
For many years the DIRAC interware (Distributed Infrastructure with Remote Agent Control) has had a web interface, allowing the users to monitor DIRAC activities and also interact with the system. Since then many new web technologies have emerged, therefore a redesign and a new implementation of the DIRAC Web portal were necessary, taking into account the lessons learnt using the old portal. These new technologies allowed to build a more compact, robust and responsive web interface that enables users to have better control over the whole system while keeping a simple interface. The web framework provides a large set of “applications”, each of which can be used for interacting with various parts of the system. Communities can also create their own set of personalised web applications, and can easily extend already existing ones with a minimal effort. Each user can configure and personalise the view for each application and save it using the DIRAC User Profile service as RESTful state provider, instead of using cookies. The owner of a view can share it with other users or within a user community. Compatibility between different browsers is assured, as well as with mobile versions. In this paper, we present the new DIRAC Web framework as well as the LHCb extension of the DIRAC Web portal.
Dirac Fermions in an Antiferromagnetic Semimetal
Tang, Peizhe; Zhou, Quan; Xu, Gang; Zhang, Shou-Cheng; Shou-Cheng Zhang's Group Team, Prof.
Analogues of the elementary particles have been extensively searched for in condensed matter systems for both scientific interest and technological applications. Recently, massless Dirac fermions were found to emerge as low energy excitations in materials now known as Dirac semimetals. All the currently known Dirac semimetals are nonmagnetic with both time-reversal symmetry and inversion symmetry "". Here we show that Dirac fermions can exist in one type of antiferromagnetic systems, where both and "" are broken but their combination "" is respected. We propose orthorhombic antiferromagnet CuMnAs as a candidate, analyze the robustness of the Dirac points under symmetry protections, and demonstrate its distinctive bulk dispersions as well as the corresponding surface states by ab initio calculations. Our results provide a possible platform to study the interplay of Dirac fermion physics and magnetism. We acknowledge the DOE, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under contract DE-AC02-76SF00515, NSF under Grant No.DMR-1305677 and FAME, one of six centers of STARnet.
Form factors in quantum integrable models with GL(3)-invariant R-matrix
Energy Technology Data Exchange (ETDEWEB)
Pakuliak, S., E-mail: pakuliak@theor.jinr.ru [Laboratory of Theoretical Physics, JINR, 141980 Dubna, Moscow Reg. (Russian Federation); Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Moscow Reg. (Russian Federation); Institute of Theoretical and Experimental Physics, 117259 Moscow (Russian Federation); Ragoucy, E., E-mail: eric.ragoucy@lapth.cnrs.fr [Laboratoire de Physique Théorique LAPTH, CNRS and Université de Savoie, BP 110, 74941 Annecy-le-Vieux Cedex (France); Slavnov, N.A., E-mail: nslavnov@mi.ras.ru [Steklov Mathematical Institute, Moscow (Russian Federation)
2014-04-15
We study integrable models solvable by the nested algebraic Bethe ansatz and possessing GL(3)-invariant R-matrix. We obtain determinant representations for form factors of off-diagonal entries of the monodromy matrix. These representations can be used for the calculation of form factors and correlation functions of the XXX SU(3)-invariant Heisenberg chain.
Recoil of the pion-surrounded nucleon bag and axial form factors
International Nuclear Information System (INIS)
Klabucar, D.; Picek, I.
1984-03-01
A recent method of boosting the bag is extended to the pion-surrounded nucleon bag and developed for the calculation of low-energy nucleon form factors. The usefulness of the method is illustrated by the induced pseudoscalar form factor where both the inclusion of the pion field and the non-vanishing momentum transfer are necessary. (Auth.)
Gluing operation and form factors of local operators in N = 4 Super Yang-Mills theory
Bolshov, A. E.
2018-04-01
The gluing operation is an effective way to get form factors of both local and non-local operators starting from different representations of on-shell scattering amplitudes. In this paper it is shown how it works on the example of form factors of operators from stress-tensor operator supermultiplet in Grassmannian and spinor helicity representations.
Viability of Dirac phase leptogenesis
International Nuclear Information System (INIS)
Anisimov, Alexey; Blanchet, Steve; Di Bari, Pasquale
2008-01-01
We discuss the conditions for a non-vanishing Dirac phase δ and mixing angle θ 13 , sources of CP violation in neutrino oscillations, to be uniquely responsible for the observed matter–antimatter asymmetry of the Universe through leptogenesis. We show that this scenario, that we call δ-leptogenesis, is viable when the degenerate limit for the heavy right-handed (RH) neutrino spectrum is considered. We derive an interesting joint condition on sinθ 13 and the absolute neutrino mass scale that can be tested in future neutrino oscillation experiments. In the limit of the hierarchical heavy RH neutrino spectrum, we strengthen the previous result that δ-leptogenesis is only very marginally allowed, even when the production from the two heavier RH neutrinos is taken into account. An improved experimental upper bound on sinθ 13 and/or an account of quantum kinetic effects could completely rule out this option in the future. Therefore, δ-leptogenesis can be also regarded as motivation for models with degenerate heavy neutrino spectrum
48 CFR 247.372 - DD Form 1654, Evaluation of Transportation Cost Factors.
2010-10-01
... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false DD Form 1654, Evaluation... Transportation in Supply Contracts 247.372 DD Form 1654, Evaluation of Transportation Cost Factors. Contracting personnel may use the DD Form 1654 to furnish information to the transportation office for development of...
Effects of the d-state quarks on the nucleon electric form factors
International Nuclear Information System (INIS)
Oh, Y.J.; Kong, K.J.; Cheon, I.T.
1987-11-01
Considering the d-orbital excitation of a quark in the bag, we calculate the nucleon electric form factors in the cloudy bag model. In these calculations, we have taken into account the πNN, πΔN and πγ form factors though neglecting the c.m. correction. It turns out that the neutron charge form factor is very sensitive to the d-state quark admixture in the overall region of the momentum transfer but the proton charge form factor remains unchanged. Taking the d-state quark admixture in the intermediate state baryons, we can obtain the nucleon rms radii in remarkable agreement with the experimental values. We also investigate the roles of Δ particles in the nucleon charge form factors. (author). 20 refs, 10 figs
Future Measurements of the Nucleon Elastic Electromagnetic Form Factors at Jefferson Lab
Gilfoyle, Gerard
2018-01-01
The elastic, electromagnetic form factors are fundamental observables that describe the internal structure of protons, neutrons, and atomic nuclei. Jefferson Lab in the United States has completed the 12 GeV Upgrade that will open new opportunities to study the form factors. A campaign to measure all four nucleon form factors (electric and magnetic ones for both proton and neutron) has been approved consisting of seven experiments in Halls A, B, and C. The increased energy of the electron beam will extend the range of precision measurements to higher Q2 for all four form factors together. This combination of measurements will allow for the decomposition of the results into their quark components and guide the development of a QCD-based understanding of nuclei in the non-perturbative regime. I will present more details on the 12 GeV Upgrade, the methods used to measure the form factors, and what we may learn.
Separating form factor and nuclear model effects in quasielastic neutrino-nucleus scattering
Wieske, Joseph
2017-09-01
When studying neutrino oscillations an understanding of charged current quasielastic (CCQE) neutrino-nucleus scattering is imperative. This interaction depends on a nuclear model as well as knowledge of form factors. In the past, CCQE data from the MiniBooNE experiment was analyzed assuming the Relativistic Fermi Gas (RFG) nuclear model, an axial dipole form factor in, and using the the z-expansion for the axial form factor in. We present the first analysis that combines a non-RFG nuclear model, in particular the Correlated Fermi Gas nuclear model (CFG) of, and the z expansion for the axial form factor. This will allow us to separate form factor and nuclear model effects in CCQE scattering. This project was supported through the Wayne State University REU program under NSF Grant PHY-1460853 and by the DOE Grant DE-SC0007983.
Skyrme-model πNN form factor and nucleon-nucleon interaction
International Nuclear Information System (INIS)
Holzwarth, G.; Machleidt, R.
1997-01-01
We apply the strong πNN form factor, which emerges from the Skyrme model, in the two-nucleon system using a one-boson-exchange (OBE) model for the nucleon-nucleon (NN) interaction. Deuteron properties and phase parameters of NN scattering are reproduced well. In contrast to the form factor of monopole shape that is traditionally used in OBE models, the Skyrme form factor leaves low-momentum transfers essentially unaffected while it suppresses the high-momentum region strongly. It turns out that this behavior is very appropriate for models of the NN interaction and makes it possible to use a soft pion form factor in the NN system. As a consequence, the πN and the NN systems can be described using the same πNN form factor, which is impossible with the monopole. copyright 1997 The American Physical Society
The scalar and electromagnetic form factors of the nucleon in dispersively improved Chiral EFT
Energy Technology Data Exchange (ETDEWEB)
Alarcon, Jose Manuel [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2018-04-01
We present a method for calculating the nucleon form factors of G-parity-even operators. This method combines chiral effective field theory (χEFT) and dispersion theory. Through unitarity we factorize the imaginary part of the form factors into a perturbative part, calculable with χEFT, and a non-perturbative part, obtained through other methods. We consider the scalar and electromagnetic (EM) form factors of the nucleon. The results show an important improvement compared to standard chiral calculations, and can be used in analysis of the low-energy properties of the nucleon.
Heavy-to-light form factors for non-relativistic bound states
International Nuclear Information System (INIS)
Bell, G.; Feldmann, Th.
2007-01-01
We investigate transition form factors between non-relativistic QCD bound states at large recoil energy. Assuming the decaying quark to be much heavier than its decay product, the relativistic dynamics can be treated according to the factorization formula for heavy-to-light form factors obtained from the heavy-quark expansion in QCD. The non-relativistic expansion determines the bound-state wave functions to be Coulomb-like. As a consequence, one can explicitly calculate the so-called 'soft-overlap' contribution to the transition form factor
Remarks on electromagnetic form factors of hadrons in the quark model
International Nuclear Information System (INIS)
Vainshtein, A.I.; Zakharov, V.I.
1977-01-01
Relations between the transversal and longitudinal parts of elastic and quasielastic form factors are studied within the quark model. It is shown that for an even number of the constituent quarks the longitudinal part dominates while for an odd number the transversal part is the largest one. Consequences form this result are considered for deuteron form factor and for matrix elements of the electromagnetic transitions between π, rho, A 1 mesons
First-principles study of Dirac and Dirac-like cones in phononic and photonic crystals
Mei, Jun; Wu, Ying; Chan, C. T.; Zhang, Zhao-Qing
2012-01-01
By using the k•p method, we propose a first-principles theory to study the linear dispersions in phononic and photonic crystals. The theory reveals that only those linear dispersions created by doubly degenerate states can be described by a reduced Hamiltonian that can be mapped into the Dirac Hamiltonian and possess a Berry phase of -π. Linear dispersions created by triply degenerate states cannot be mapped into the Dirac Hamiltonian and carry no Berry phase, and, therefore should be called Dirac-like cones. Our theory is capable of predicting accurately the linear slopes of Dirac and Dirac-like cones at various symmetry points in a Brillouin zone, independent of frequency and lattice structure. © 2012 American Physical Society.
First-principles study of Dirac and Dirac-like cones in phononic and photonic crystals
Mei, Jun
2012-07-24
By using the k•p method, we propose a first-principles theory to study the linear dispersions in phononic and photonic crystals. The theory reveals that only those linear dispersions created by doubly degenerate states can be described by a reduced Hamiltonian that can be mapped into the Dirac Hamiltonian and possess a Berry phase of -π. Linear dispersions created by triply degenerate states cannot be mapped into the Dirac Hamiltonian and carry no Berry phase, and, therefore should be called Dirac-like cones. Our theory is capable of predicting accurately the linear slopes of Dirac and Dirac-like cones at various symmetry points in a Brillouin zone, independent of frequency and lattice structure. © 2012 American Physical Society.
The neutron electric form factor to Q² = 1.45 (GeV/c)²
Energy Technology Data Exchange (ETDEWEB)
Plaster, Bradley [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
2004-02-01
The nucleon elastic electromagnetic form factors are fundamental quantities needed for an understanding of nucleon and nuclear electromagnetic structure. The evolution of the Sachs electric and magnetic form factors with Q^{2}, the square of the four-momentum transfer, is related to the distribution of charge and magnetization within the nucleon. High precision measurements of the nucleon form factors are essential for stringent tests of our current theoretical understanding of confinement within the nucleon. Measurements of the neutron form factors, in particular, those of the neutron electric form factor, have been notoriously difficult due to the lack of a free neutron target and the vanishing integral charge of the neutron. Indeed, a precise measurement of the neutron electric form factor has eluded experimentalists for decades; however, with the advent of high duty-factor polarized electron beam facilities, experiments employing polarization degrees of freedom have finally yielded the first precise measurements of this fundamental quantity. Following a general overview of the experimental and theoretical status of the nucleon form factors, a detailed description of an experiment designed to extract the neutron electric form factor from measurements of the neutron's recoil polarization in quasielastic 2H(e, e')1H scattering is presented. The experiment described here employed the Thomas Jefferson National Accelerator Facility's longitudinally polarized electron beam, a magnetic spectrometer for detection of the scattered electron, and a neutron polarimeter designed specifically for this experiment. Measurements were conducted at three Q^{2} values of 0.45, 1.13, and 1.45 (GeV/c)^{2}, and the final results extracted from an analysis of the data acquired in this experiment are reported and compared with recent theoretical predictions for the nucleon form factors.
A Factor Analytic Study of the Coopersmith Self-Esteem Inventory Adult Short Form.
Haines, Janet; Wilson, George V.
1988-01-01
A factor analysis was conducted on the Coopersmith Self-Esteem Inventory-Adult Short Form using 237 college students and 43 female office workers in Australia. Factors were found corresponding with three of the four subscales: general self, social self-peers, and home-parents (family). No factor related to the school-academic (work) subscale. (SLD)
Nucleon electromagnetic form factors using lattice simulations at the physical point
International Nuclear Information System (INIS)
Alexandrou, C.; Cyprus Univ., Nicosia; Constantinou, M.; Hadjiyiannakou, K.; Kallidonis, C.; Koutsou, G.; Jansen, K.; Vaquero Aviles-Casco, A.
2017-01-01
We present results for the nucleon electromagnetic form factors using an ensemble of maximally twisted mass clover-improved fermions with pion mass of about 130 MeV. We use multiple sink-source separations and three analysis methods to probe ground-state dominance. We evaluate both the connected and disconnected contributions to the nucleon matrix elements. We find that the disconnected quark loop contributions to the isoscalar matrix elements are small giving an upper bound of up to 2% of the connected and smaller than its statistical error. We present results for the isovector and isoscalar electric and magnetic Sachs form factors and the corresponding proton and neutron form factors. By fitting the momentum dependence of the form factors to a dipole form or to the z-expansion we extract the nucleon electric and magnetic radii, as well as, the magnetic moment. We compare our results to experiment as well as to other recent lattice QCD calculations.
Nucleon electromagnetic form factors using lattice simulations at the physical point
Energy Technology Data Exchange (ETDEWEB)
Alexandrou, C. [The Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center; Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Constantinou, M. [Temple Univ., Philadelphia, PA (United States). Dept. of Physics; Hadjiyiannakou, K.; Kallidonis, C.; Koutsou, G. [The Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center; Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Vaquero Aviles-Casco, A. [Utah Univ., Salt Lake City, UT (United States). Dept. of Physics and Astronomy
2017-09-20
We present results for the nucleon electromagnetic form factors using an ensemble of maximally twisted mass clover-improved fermions with pion mass of about 130 MeV. We use multiple sink-source separations and three analysis methods to probe ground-state dominance. We evaluate both the connected and disconnected contributions to the nucleon matrix elements. We find that the disconnected quark loop contributions to the isoscalar matrix elements are small giving an upper bound of up to 2% of the connected and smaller than its statistical error. We present results for the isovector and isoscalar electric and magnetic Sachs form factors and the corresponding proton and neutron form factors. By fitting the momentum dependence of the form factors to a dipole form or to the z-expansion we extract the nucleon electric and magnetic radii, as well as, the magnetic moment. We compare our results to experiment as well as to other recent lattice QCD calculations.
Semi-Dirac points in phononic crystals
Zhang, Xiujuan
2014-01-01
A semi-Dirac cone refers to a peculiar type of dispersion relation that is linear along the symmetry line but quadratic in the perpendicular direction. It was originally discovered in electron systems, in which the associated quasi-particles are massless along one direction, like those in graphene, but effective-mass-like along the other. It was reported that a semi-Dirac point is associated with the topological phase transition between a semi-metallic phase and a band insulator. Very recently, the classical analogy of a semi-Dirac cone has been reported in an electromagnetic system. Here, we demonstrate that, by accidental degeneracy, two-dimensional phononic crystals consisting of square arrays of elliptical cylinders embedded in water are also able to produce the particular dispersion relation of a semi-Dirac cone in the center of the Brillouin zone. A perturbation method is used to evaluate the linear slope and to affirm that the dispersion relation is a semi-Dirac type. If the scatterers are made of rubber, in which the acoustic wave velocity is lower than that in water, the semi-Dirac dispersion can be characterized by an effective medium theory. The effective medium parameters link the semi-Dirac point to a topological transition in the iso-frequency surface of the phononic crystal, in which an open hyperbola is changed into a closed ellipse. This topological transition results in drastic change in wave manipulation. On the other hand, the theory also reveals that the phononic crystal is a double-zero-index material along the x-direction and photonic-band-edge material along the perpendicular direction (y-direction). If the scatterers are made of steel, in which the acoustic wave velocity is higher than that in water, the effective medium description fails, even though the semi-Dirac dispersion relation looks similar to that in the previous case. Therefore different wave transport behavior is expected. The semi-Dirac points in phononic crystals described in
Dirac matrices for Chern-Simons gravity
Energy Technology Data Exchange (ETDEWEB)
Izaurieta, Fernando; Ramirez, Ricardo; Rodriguez, Eduardo [Departamento de Matematica y Fisica Aplicadas, Universidad Catolica de la Santisima Concepcion, Alonso de Ribera 2850, 4090541 Concepcion (Chile)
2012-10-06
A genuine gauge theory for the Poincare, de Sitter or anti-de Sitter algebras can be constructed in (2n- 1)-dimensional spacetime by means of the Chern-Simons form, yielding a gravitational theory that differs from General Relativity but shares many of its properties, such as second order field equations for the metric. The particular form of the Lagrangian is determined by a rank n, symmetric tensor invariant under the relevant algebra. In practice, the calculation of this invariant tensor can be reduced to the computation of the trace of the symmetrized product of n Dirac Gamma matrices {Gamma}{sub ab} in 2n-dimensional spacetime. While straightforward in principle, this calculation can become extremely cumbersome in practice. For large enough n, existing computer algebra packages take an inordinate long time to produce the answer or plainly fail having used up all available memory. In this talk we show that the general formula for the trace of the symmetrized product of 2n Gamma matrices {Gamma}{sub ab} can be written as a certain sum over the integer partitions s of n, with every term being multiplied by a numerical cofficient {alpha}{sub s}. We then give a general algorithm that computes the {alpha}-coefficients as the solution of a linear system of equations generated by evaluating the general formula for different sets of tensors B{sup ab} with random numerical entries. A recurrence relation between different coefficients is shown to hold and is used in a second, 'minimal' algorithm to greatly speed up the computations. Runtime of the minimal algorithm stays below 1 min on a typical desktop computer for up to n = 25, which easily covers all foreseeable applications of the trace formula.
An experimental survey of the factors that affect leaching from low-level radioactive waste forms
International Nuclear Information System (INIS)
Dougherty, D.R.; Pietrzak, R.F.; Fuhrmann, M.; Colombo, P.
1988-09-01
This report represents the results of an experimental survey of the factors that affect leaching from several types of solidified low-level radioactive waste forms. The goal of these investigations was to determine those factors that accelerate leaching without changing its mechanism(s). Typically, although not in every case,the accelerating factors include: increased temperature, increased waste loading (i.e., increased waste to binder ratio), and decreased size (i.e., decreased waste form volume to surface area ratio). Additional factors that were studied were: increased leachant volume to waste form surface area ratio, pH, leachant composition (groundwaters, natural and synthetic chelating agents), leachant flow rate or replacement frequency and waste form porosity and surface condition. Other potential factors, including the radiation environment and pressure, were omitted based on a survey of the literature. 82 refs., 236 figs., 13 tabs
Strain engineering of Dirac cones in graphyne
Energy Technology Data Exchange (ETDEWEB)
Wang, Gaoxue; Kumar, Ashok; Pandey, Ravindra, E-mail: pandey@mtu.edu [Department of Physics, Michigan Technological University, Houghton, Michigan 49931 (United States); Si, Mingsu [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)
2014-05-26
6,6,12-graphyne, one of the two-dimensional carbon allotropes with the rectangular lattice structure, has two kinds of non-equivalent anisotropic Dirac cones in the first Brillouin zone. We show that Dirac cones can be tuned independently by the uniaxial compressive strain applied to graphyne, which induces n-type and p-type self-doping effect, by shifting the energy of the Dirac cones in the opposite directions. On the other hand, application of the tensile strain results into a transition from gapless to finite gap system for the monolayer. For the AB-stacked bilayer, the results predict tunability of Dirac-cones by in-plane strains as well as the strain applied perpendicular to the plane. The group velocities of the Dirac cones show enhancement in the resistance anisotropy for bilayer relative to the case of monolayer. Such tunable and direction-dependent electronic properties predicted for 6,6,12-graphyne make it to be competitive for the next-generation electronic devices at nanoscale.
Asymptotic behavior of composite-particle form factors and the renormalization group
International Nuclear Information System (INIS)
Duncan, A.; Mueller, A.H.
1980-01-01
Composite-particle form factors are studied in the limit of large momentum transfer Q. It is shown that in models with spinor constituents and either scalar or gauge vector gluons, the meson electromagnetic form factor factorizes at large Q 2 and is given by independent light-cone expansions on the initial and final meson legs. The coefficient functions are shown to satisfy a Callan-Symanzik equation. When specialized to quantum chromodynamics, this equation leads to the asymptotic formula of Brodsky and Lepage for the pion electromagnetic form factor. The nucleon form factors G/sub M/(Q 2 ), G/sub E/(Q 2 ) are also considered. It is shown that momentum flows which contribute to subdominant logarithms in G/sub M/(Q 2 ) vitiate a conventional renormalization-group interpretation for this form factor. For large Q 2 , the electric form factor G/sub E/(Q 2 ) fails to factorize, so that a renormalization-group treatment seems even more unlikely in this case
Lattice approximation of gauge theories with Dirac Kaehler fermions
International Nuclear Information System (INIS)
Joos, H.
1988-01-01
A program which tries to overcome the systematic difficulties caused by the lattice fermion problem by the consideration of models which describe Dirac fields by differential forms is reported. In the first lecture the formalism is developped and applied to the formulation of geometric QCD and of a Geometric Standard Model. The second lecture treats the characteristic symmetry problems which appear in the lattice approximation of geometric field theories. In the last lecture strong coupling dynamics of geometric QCD are considered with the final aim of a derivation of the quark model for the hadron spectrum. (author) [pt
International Nuclear Information System (INIS)
Theussl, L.; Noguera, S.; Amghar, A.; Desplanques, B.
2003-01-01
The effect of different boost expressions, pertinent to the instant, front and point forms of relativistic quantum mechanics, is considered for the calculation of the ground-state form factor of a two-body system in simple scalar models. Results with a Galilean boost as well as an explicitly covariant calculation based on the Bethe-Salpeter approach are given for comparison. It is found that the present so-called point-form calculations of form factors strongly deviate from all the other ones. This suggests that the formalism which underlies them requires further elaboration. A proposition in this sense is made. (author)
A measurement of the space-like pion electromagnetic form factor
International Nuclear Information System (INIS)
Amendolia, S.R.; Badelek, B.; Batignani, G.; Bedeschi, F.; Bertolucci, E.; Bettoni, D.; Bosisio, L.; Bradaschia, C.; Dell'Orso, M.; Fidecaro, F.; Foa, L.; Focardi, E.; Giazotto, A.; Giorgi, M.A.; Marrocchesi, P.S.; Menzione, A.; Ristori, L.; Scribano, A.; Tonelli, G.; Triggiani, G.; Codino, A.; Enorini, M.; Fabbri, F.L.; Laurelli, P.; Satta, L.; Spillantini, P.; Zallo, A.
1986-01-01
The pion form factor has been measured in the space-like q 2 region 0.014 to 0.26 (GeV/c) 2 by scattering 300 GeV pions from the electrons of a liquid hydrogen target. A detailed description is given of the apparatus, data analysis and corrections to the data. The mean square charge radius extracted from the data is model-dependent. We find that a form which includes a realistic description of the form factor phase gives a similar result to the naive pole form, and conclude π 2 >=0.439±0.008 fm 2 . (orig.)
Measurement of the form factor in the decay K+ → π0e+vsub(e)
International Nuclear Information System (INIS)
Martyn, H.U.
1974-01-01
Following an introduction into the theory of the K(l3) decay, the fundamentals for the measuring methods of the form factor are derived. The choice of the quantity of nuclear events, the problems of the detection probabilities and of the background, and the form factor analysis are dealt with in detail. The analysis shows that the form factor can be very well described by a linear parametrization. The upper limits for scalar and tensorial interaction contributions are given; these results confirm the validity of the V-A theory also for strangeness-changing decays. (BJ/LH) [de
Strange mesons and kaon-to-pion transition form factors from holography
International Nuclear Information System (INIS)
Abidin, Zainul; Carlson, Carl E.
2009-01-01
We present a calculation of the K l3 transition form factors using the AdS/QCD correspondence. We also solidify and extend our ability to calculate quantities in the flavor-broken versions of AdS/QCD. The normalization of the form factors is a crucial ingredient for extracting |V us | from data, and the results obtained here agree well with results from chiral perturbation theory and lattice gauge theory. The slopes and curvature of the form factors agree well with the data, and with what results are available from other methods of calculation.
The B → D*lv form factor at zero recoil
International Nuclear Information System (INIS)
Simone, J.N.; Hashimoto, S.; El-Khadra, A.X.; Kronfeld, A.S.; Mackenzie, P.B.; Ryan, S.M.
2000-01-01
We describe a model independent lattice QCD method for determining the deviation from unity for h A1 (1), the B → D*lv form factor at zero recoil. We extend the double ratio method previously used to determine the B → Dlv form factor. The bulk of statistical and systematic errors cancel in the double ratios we consider, yielding form factors which promise to reduce present theoretical uncertainties in the determination of parallel V cb parallel. We present results from a prototype calculation at a single lattice spacing corresponding to β = 5.7
Delta and Omega electromagnetic form factors in a Dyson-Schwinger/Bethe-Salpeter approach
Energy Technology Data Exchange (ETDEWEB)
Diana Nicmorus, Gernot Eichmann, Reinhard Alkofer
2010-12-01
We investigate the electromagnetic form factors of the Delta and the Omega baryons within the Poincare-covariant framework of Dyson-Schwinger and Bethe-Salpeter equations. The three-quark core contributions of the form factors are evaluated by employing a quark-diquark approximation. We use a consistent setup for the quark-gluon dressing, the quark-quark bound-state kernel and the quark-photon interaction. Our predictions for the multipole form factors are compatible with available experimental data and quark-model estimates. The current-quark mass evolution of the static electromagnetic properties agrees with results provided by lattice calculations.
On form factors of the conjugated field in the non-linear Schroedinger model
Energy Technology Data Exchange (ETDEWEB)
Kozlowski, K.K.
2011-05-15
Izergin-Korepin's lattice discretization of the non-linear Schroedinger model along with Oota's inverse problem provides one with determinant representations for the form factors of the lattice discretized conjugated field operator. We prove that these form factors converge, in the zero lattice spacing limit, to those of the conjugated field operator in the continuous model. We also compute the large-volume asymptotic behavior of such form factors in the continuous model. These are in particular characterized by Fredholm determinants of operators acting on closed contours. We provide a way of defining these Fredholm determinants in the case of generic paramaters. (orig.)
On the large-Q2 behavior of the pion transition form factor
Directory of Open Access Journals (Sweden)
Gernot Eichmann
2017-11-01
Full Text Available We study the transition of non-perturbative to perturbative QCD in situations with possible violations of scaling limits. To this end we consider the singly- and doubly-virtual pion transition form factor π0→γγ at all momentum scales of symmetric and asymmetric photon momenta within the Dyson–Schwinger/Bethe–Salpeter approach. For the doubly virtual form factor we find good agreement with perturbative asymptotic scaling laws. For the singly-virtual form factor our results agree with the Belle data. At very large off-shell photon momenta we identify a mechanism that introduces quantitative modifications to Efremov–Radyushkin–Brodsky–Lepage scaling.
Interaction between droplets in a ternary microemulsion evaluated by the relative form factor method
International Nuclear Information System (INIS)
Nagao, Michihiro; Seto, Hideki; Yamada, Norifumi L.
2007-01-01
This paper describes the concentration dependence of the interaction between water droplets coated by a surfactant monolayer using the contrast variation small-angle neutron scattering technique. In the first part, we explain the idea of how to extract a relatively model free structure factor from the scattering data, which is called the relative form factor method. In the second part, the experimental results for the shape of the droplets (form factor) are described. In the third part the relatively model free structure factor is shown, and finally the concentration dependence of the interaction potential between droplets is discussed. The result indicates the validity of the relative form factor method, and the importance of the estimation of the model free structure factor to discuss the nature of structure formation in microemulsion systems
Interlayer magnetoresistance in multilayer Dirac electron systems: motion and merging of Dirac cones
International Nuclear Information System (INIS)
Assili, M; Haddad, S
2013-01-01
We theoretically study the effect of the motion and the merging of Dirac cones on the interlayer magnetoresistance in multilayer graphene-like systems. This merging, which can be induced by a uniaxial strain, gives rise in a monolayer Dirac electron system to a topological transition from a semi-metallic phase to an insulating phase whereby Dirac points disappear. Based on a universal Hamiltonian, proposed to describe the motion and the merging of Dirac points in two-dimensional Dirac electron crystals, we calculate the interlayer conductivity of a stack of deformed graphene-like layers using the Kubo formula in the quantum limit where only the contribution of the n = 0 Landau level is relevant. A crossover from a negative to a positive interlayer magnetoresistance is found to take place as the merging is approached. This sign change of the magnetoresistance can also result from a coupling between the Dirac valleys, which is enhanced as the magnetic field amplitude increases. Our results describe the behavior of the magnetotransport in the organic conductor α-(BEDT) 2 I 3 and in a stack of deformed graphene-like systems. The latter can be simulated by optical lattices or microwave experiments in which the merging of Dirac cones can be observed. (paper)
Interlayer magnetoresistance in multilayer Dirac electron systems: motion and merging of Dirac cones
Assili, M.; Haddad, S.
2013-09-01
We theoretically study the effect of the motion and the merging of Dirac cones on the interlayer magnetoresistance in multilayer graphene-like systems. This merging, which can be induced by a uniaxial strain, gives rise in a monolayer Dirac electron system to a topological transition from a semi-metallic phase to an insulating phase whereby Dirac points disappear. Based on a universal Hamiltonian, proposed to describe the motion and the merging of Dirac points in two-dimensional Dirac electron crystals, we calculate the interlayer conductivity of a stack of deformed graphene-like layers using the Kubo formula in the quantum limit where only the contribution of the n = 0 Landau level is relevant. A crossover from a negative to a positive interlayer magnetoresistance is found to take place as the merging is approached. This sign change of the magnetoresistance can also result from a coupling between the Dirac valleys, which is enhanced as the magnetic field amplitude increases. Our results describe the behavior of the magnetotransport in the organic conductor α-(BEDT)2I3 and in a stack of deformed graphene-like systems. The latter can be simulated by optical lattices or microwave experiments in which the merging of Dirac cones can be observed.
Assili, M; Haddad, S
2013-09-11
We theoretically study the effect of the motion and the merging of Dirac cones on the interlayer magnetoresistance in multilayer graphene-like systems. This merging, which can be induced by a uniaxial strain, gives rise in a monolayer Dirac electron system to a topological transition from a semi-metallic phase to an insulating phase whereby Dirac points disappear. Based on a universal Hamiltonian, proposed to describe the motion and the merging of Dirac points in two-dimensional Dirac electron crystals, we calculate the interlayer conductivity of a stack of deformed graphene-like layers using the Kubo formula in the quantum limit where only the contribution of the n = 0 Landau level is relevant. A crossover from a negative to a positive interlayer magnetoresistance is found to take place as the merging is approached. This sign change of the magnetoresistance can also result from a coupling between the Dirac valleys, which is enhanced as the magnetic field amplitude increases. Our results describe the behavior of the magnetotransport in the organic conductor α-(BEDT)2I3 and in a stack of deformed graphene-like systems. The latter can be simulated by optical lattices or microwave experiments in which the merging of Dirac cones can be observed.
Dirac operator on spaces with conical singularities
International Nuclear Information System (INIS)
Chou, A.W.
1982-01-01
The Dirac operator on compact spaces with conical singularities is studied via the separation of variables formula and the functional calculus of the Dirac Laplacian on the cone. A Bochner type vanishing theorem which gives topological obstructions to the existence of non-negative scalar curvature k greater than or equal to 0 in the singular case is proved. An index formula relating the index of the Dirac operator to the A-genus and Eta-invariant similar to that of Atiyah-Patodi-Singer is obtained. In an appendix, manifolds with boundary with non-negative scalar curvature k greater than or equal to 0 are studied, and several new results on constructing complete metrics with k greater than or equal to on them are obtained
LHCb: Monitoring the DIRAC Distribution System
Nandakumar, R; Santinelli, R
2009-01-01
DIRAC is the LHCb gateway to any computing grid infrastructure (currently supporting WLCG) and is intended to reliably run large data mining activities. The DIRAC system consists of various services (which wait to be contacted to perform actions) and agents (which carry out periodic activities) to direct jobs as required. An important part of ensuring the reliability of the infrastructure is the monitoring and logging of these DIRAC distributed systems. The monitoring is done collecting information from two sources - one is from pinging the services or by keeping track of the regular heartbeats of the agents, and the other from the analysis of the error messages generated by both agents and services and collected by the logging system. This allows us to ensure that he components are running properly and to collect useful information regarding their operations. The process status monitoring is displayed using the SLS sensor mechanism which also automatically allows one to plot various quantities and also keep ...
DIRAC - Distributed Infrastructure with Remote Agent Control
Tsaregorodtsev, A; Closier, J; Frank, M; Gaspar, C; van Herwijnen, E; Loverre, F; Ponce, S; Graciani Diaz, R.; Galli, D; Marconi, U; Vagnoni, V; Brook, N; Buckley, A; Harrison, K; Schmelling, M; Egede, U; Bogdanchikov, A; Korolko, I; Washbrook, A; Palacios, J P; Klous, S; Saborido, J J; Khan, A; Pickford, A; Soroko, A; Romanovski, V; Patrick, G N; Kuznetsov, G; Gandelman, M
2003-01-01
This paper describes DIRAC, the LHCb Monte Carlo production system. DIRAC has a client/server architecture based on: Compute elements distributed among the collaborating institutes; Databases for production management, bookkeeping (the metadata catalogue) and software configuration; Monitoring and cataloguing services for updating and accessing the databases. Locally installed software agents implemented in Python monitor the local batch queue, interrogate the production database for any outstanding production requests using the XML-RPC protocol and initiate the job submission. The agent checks and, if necessary, installs any required software automatically. After the job has processed the events, the agent transfers the output data and updates the metadata catalogue. DIRAC has been successfully installed at 18 collaborating institutes, including the DataGRID, and has been used in recent Physics Data Challenges. In the near to medium term future we must use a mixed environment with different types of grid mid...
DIRAC - The Distributed MC Production and Analysis for LHCb
Tsaregorodtsev, A
2004-01-01
DIRAC is the LHCb distributed computing grid infrastructure for MC production and analysis. Its architecture is based on a set of distributed collaborating services. The service decomposition broadly follows the ARDA project proposal, allowing for the possibility of interchanging the EGEE/ARDA and DIRAC components in the future. Some components developed outside the DIRAC project are already in use as services, for example the File Catalog developed by the AliEn project. An overview of the DIRAC architecture will be given, in particular the recent developments to support user analysis. The main design choices will be presented. One of the main design goals of DIRAC is the simplicity of installation, configuring and operation of various services. This allows all the DIRAC resources to be easily managed by a single Production Manager. The modular design of the DIRAC components allows its functionality to be easily extended to include new computing and storage elements or to handle new tasks. The DIRAC system al...
Meson form factors and covariant three-dimensional formulation of composite model
International Nuclear Information System (INIS)
Skachkov, N.B.; Solovtsov, I.L.
1978-01-01
An approach is developed which is applied in the framework of the relativistic quark model to obtain explicit expressions for meson form factors in terms of covariant wave functions of the two-quark system. These wave functions obey the two-particle quasipotential equation in which the relative motion of quarks is singled out in a covariant way. The exact form of the wave functions is found using the transition to the relativistic configurational representation with the help of the harmonic analysis on the Lorentz group instead of the usual Fourier expansion and then solving the relativistic difference equation thus obtained. The expressions found for form factors are transformed into the three-dimensional covariant form which is a direct geometrical relativistic generalization of analogous expressions of the nonrelativistic quantum mechanics and provides the decrease of the meson form factor by the Fsub(π)(t) approximately t -1 law as -t infinity, in the Coulomb field
Relativistic corrections to the form factors of Bc into P-wave orbitally excited charmonium
Zhu, Ruilin
2018-06-01
We investigated the form factors of the Bc meson into P-wave orbitally excited charmonium using the nonrelativistic QCD effective theory. Through the analytic computation, the next-to-leading order relativistic corrections to the form factors were obtained, and the asymptotic expressions were studied in the infinite bottom quark mass limit. Employing the general form factors, we discussed the exclusive decays of the Bc meson into P-wave orbitally excited charmonium and a light meson. We found that the relativistic corrections lead to a large correction for the form factors, which makes the branching ratios of the decay channels B (Bc ± →χcJ (hc) +π± (K±)) larger. These results are useful for the phenomenological analysis of the Bc meson decays into P-wave charmonium, which shall be tested in the LHCb experiments.
Applicability of perturbative QCD and NLO power corrections for the pion form factor
International Nuclear Information System (INIS)
Yeh Tsungwen
2002-01-01
As is well recognized, the asymptotic of the perturbative QCD prediction for the pion form factor is much smaller than the upper end of the data. We investigate this problem. We first evaluate the next-to-leading-order (NLO) power correction for the pion form factor. The corrected form factor contains nonperturbative parameters which are determined from a χ 2 fit to the data. Interpreting these parameters leads to the fact that the involved strong interaction coupling constant should be identified as an effective coupling constant under a nonperturbative QCD vacuum. If the scale associated with the effective coupling constant is identified as 2 Q 2 , then Q 2 , the momentum transfer square for the pion form factor to be measured, can have a value about 1 GeV 2 , and , the averaged momentum fraction variable, can locate around 0.5. This circumstance is consistent with the asymptotic model for the pion wave function
Study of the electromagnetic form factors of Helium-3 and Tritium nuclei by electron scattering
International Nuclear Information System (INIS)
Amroun, A.
1989-01-01
Accurate measurements of the tritium electromagnetic form factor demonstrated that, when the exchange currents are included, the theoretical and the experimental data are in agreement. Similar calculations carried out on helium-3 were not satisfactory. In this investigation, a new electromagnetic form factor of helium-3 is measured. The transfer zone of the diffraction spectra concerning the first minimum and the second maximum is considered. The aim of the study is to test on both nuclei the validity and the uncertainties of the models. The scattering of electrons on helium-3 is analyzed. The experiment was performed in the Saclay linear accelerator. The isoscalar and isovector form factors could be differentiated. By comparing the theoretical and the experimental data, it is demonstrated that the use of three body forces in the calculations has no effect on the form factor results [fr
The proton electromagnetic form factor F2 and quark orbital angular ...
Indian Academy of Sciences (India)
Protein; electromagnetic form factors; perturbative QCD; quark orbital angular momentum. ... Failures of the ASD approach to correctly predict ex- perimental ... The success of the formalism is the correct prediction of the Q2 scaling behavior of ...
The three-loop form factor in N=4 super Yang-Mills theory
Energy Technology Data Exchange (ETDEWEB)
Gehrmann, Thomas [Universitaet Zuerich (Switzerland); Henn, Johannes [IAS Princeton (United States); Huber, Tobias [Universitaet Siegen (Germany)
2012-07-01
We present the calculation of the Sudakov form factor in N=4 super Yang-Mills theory to the three-loop order. At leading colour, the latter is expressed in terms of planar and non-planar loop integrals. We show that it is possible to choose a representation in which each loop integral has uniform transcendentality in the Riemann {zeta}-function. We comment on the expected exponentiation of the infrared divergences and the values of the three-loop cusp and collinear anomalous dimensions in dimensional regularisation. We also compare the form factor in N=4 super Yang-Mills to the leading transcendentality pieces of the quark and gluon form factor in QCD. Finally, we investigate the ultraviolet properties of the form factor in D>4 dimensions.
Inelastic magnetic electron scattering form factors of the 26 Mg nucleus
Indian Academy of Sciences (India)
Magnetic electron scattering (3) form factors with core polarization effects, ... to 3+ states of the 26Mg nucleus have been studied using shell model calculations. ... The wave functions of the radial single-particle matrix elements have been ...
Constraints on the [Formula: see text] form factor from analyticity and unitarity.
Ananthanarayan, B; Caprini, I; Kubis, B
Motivated by the discrepancies noted recently between the theoretical calculations of the electromagnetic [Formula: see text] form factor and certain experimental data, we investigate this form factor using analyticity and unitarity in a framework known as the method of unitarity bounds. We use a QCD correlator computed on the spacelike axis by operator product expansion and perturbative QCD as input, and exploit unitarity and the positivity of its spectral function, including the two-pion contribution that can be reliably calculated using high-precision data on the pion form factor. From this information, we derive upper and lower bounds on the modulus of the [Formula: see text] form factor in the elastic region. The results provide a significant check on those obtained with standard dispersion relations, confirming the existence of a disagreement with experimental data in the region around [Formula: see text].
Virtual photons in the pion form factors and the energy-momentum tensor
Energy Technology Data Exchange (ETDEWEB)
Kubis, Bastian E-mail: b.kubis@fz-juelich.de; Meissner, Ulf-G. E-mail: ulf-g.meissner@fz-juelich.de
2000-05-22
We evaluate the vector and scalar form factor of the pion in the presence of virtual photons at next-to-leading order in two-flavor chiral perturbation theory. We also consider the scalar and tensor pion form factors of the energy-momentum tensor. We find that the intrinsic electromagnetic corrections are very small for the vector as well as the charged pion scalar form factor. The scalar radius of the neutral pion is reduced by two percent. We perform infrared regularization by considering electron-positron annihilation into pions and the decay of a light Higgs boson into a pion pair. We discuss the detector resolution dependent contributions to the various form factors and pion radii.
Constraints on the ωπ form factor from analyticity and unitarity
International Nuclear Information System (INIS)
Ananthanarayan, B.; Caprini, I.; Kubis, B.
2014-01-01
Motivated by the discrepancies noted recently between the theoretical calculations of the electromagnetic ωπ form factor and certain experimental data, we investigate this form factor using analyticity and unitarity in a framework known as the method of unitarity bounds. We use a QCD correlator computed on the spacelike axis by operator product expansion and perturbative QCD as input, and exploit unitarity and the positivity of its spectral function, including the two-pion contribution that can be reliably calculated using high-precision data on the pion form factor. From this information, we derive upper and lower bounds on the modulus of the ωπ form factor in the elastic region. The results provide a significant check on those obtained with standard dispersion relations, confirming the existence of a disagreement with experimental data in the region around 0.6 GeV. (orig.)
Virtual photons in the pion form factors and the energy-momentum tensor
International Nuclear Information System (INIS)
Kubis, Bastian; Meissner, Ulf-G.
2000-01-01
We evaluate the vector and scalar form factor of the pion in the presence of virtual photons at next-to-leading order in two-flavor chiral perturbation theory. We also consider the scalar and tensor pion form factors of the energy-momentum tensor. We find that the intrinsic electromagnetic corrections are very small for the vector as well as the charged pion scalar form factor. The scalar radius of the neutral pion is reduced by two percent. We perform infrared regularization by considering electron-positron annihilation into pions and the decay of a light Higgs boson into a pion pair. We discuss the detector resolution dependent contributions to the various form factors and pion radii
Constraints on the ωπ form factor from analyticity and unitarity
Energy Technology Data Exchange (ETDEWEB)
Ananthanarayan, B. [Indian Institute of Science, Centre for High Energy Physics, Bangalore (India); Caprini, I. [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, Magurele (Romania); Kubis, B. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen-und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Bonn (Germany)
2014-12-01
Motivated by the discrepancies noted recently between the theoretical calculations of the electromagnetic ωπ form factor and certain experimental data, we investigate this form factor using analyticity and unitarity in a framework known as the method of unitarity bounds. We use a QCD correlator computed on the spacelike axis by operator product expansion and perturbative QCD as input, and exploit unitarity and the positivity of its spectral function, including the two-pion contribution that can be reliably calculated using high-precision data on the pion form factor. From this information, we derive upper and lower bounds on the modulus of the ωπ form factor in the elastic region. The results provide a significant check on those obtained with standard dispersion relations, confirming the existence of a disagreement with experimental data in the region around 0.6 GeV. (orig.)
Model for next-to-leading order threshold resummed form factors
International Nuclear Information System (INIS)
Aglietti, Ugo; Ricciardi, Giulia
2004-01-01
We present a model for next-to-leading order resummed threshold form factors based on a timelike coupling recently introduced in the framework of small x physics. Improved expressions for the form factors in N-space are obtained which are not plagued by Landau-pole singularities, as the included absorptive effects - usually neglected - act as regulators. The physical reason is that, because of faster decay of gluon jets, there is not enough resolution time to observe the Landau pole. Our form factors reduce to the standard ones when the absorptive parts related to the coupling are neglected. The inverse transform from N-space to x-space can be done directly without any prescription and we obtain analytical expressions for the form factors, which are well defined in all x-space
Electric form factors of the octet baryons from lattice QCD and chiral extrapolation
International Nuclear Information System (INIS)
Shanahan, P.E.; Thomas, A.W.; Young, R.D.; Zanotti, J.M.; Pleiter, D.; Stueben, H.
2014-03-01
We apply a formalism inspired by heavy baryon chiral perturbation theory with finite-range regularization to dynamical 2+1-flavor CSSM/QCDSF/UKQCD Collaboration lattice QCD simulation results for the electric form factors of the octet baryons. The electric form factor of each octet baryon is extrapolated to the physical pseudoscalar masses, after finite-volume corrections have been applied, at six fixed values of Q 2 in the range 0.2-1.3 GeV 2 . The extrapolated lattice results accurately reproduce the experimental form factors of the nucleon at the physical point, indicating that omitted disconnected quark loop contributions are small. Furthermore, using the results of a recent lattice study of the magnetic form factors, we determine the ratio μ p G E p /G M p . This quantity decreases with Q 2 in a way qualitatively consistent with recent experimental results.
Effects of Velocity-Dependent Force on the Magnetic Form Factors of Odd-Z Nuclei
International Nuclear Information System (INIS)
Tie-Kuang, Dong; Zhong-Zhou, Ren
2008-01-01
We investigate the effects of the velocity-dependent force on the magnetic form factors and magnetic moments of odd-Z nuclei. The form factors are calculated with the harmonic-oscillator wavefunctions. It is found that the contributions of the velocity-dependent force manifest themselves in the very large momentum transfer region (q ≥ 4fm- 1 ). In the low and medium q region the contributions of the velocity-dependent force are very small compared with those without this force. However, in the high-q region the contributions of the velocity-dependent force are larger than the normal form factors. The diffraction structures beyond the existing experimental data are found after the contributions of the velocity-dependent force are included. The formula of the correction to the single particle magnetic moment due to the velocity-dependent force is reproduced exactly in the long-wavelength limit (q = 0) of the M1 form factor
Asymptotic dynamics of QCD, coherent states and the quark form factor
International Nuclear Information System (INIS)
Steiner, F.; Dahmen, H.D.
1980-05-01
The method of asymptotic dynamics for large times developed by Kulish and Fadde'ev for QED is applied to QCD. We study the solution and calculate the on shell quark form factor in leading logarithmic order. (orig.)
Su(4) properties of the Dirac-Kaehler equation
International Nuclear Information System (INIS)
Linhares, C.A.; Mignaco, J.A.
1991-01-01
We use the Dirac-Kaehler formalism in the space of differential forms (endowed with a Clifford product) to study the SU(4) symmetry related to the description of spin-1/2 particles found previously in the usual matrix treatment. We show that differential forms may be taken as the generators spanning the algebra of the SU(4) group and how the operations of this group can be related to a change of frame of reference in the algebra. We demonstrate that minimal left ideals of the algebra constitute irreducible representations for spin-1/2 particles for Clifford operation from the left, and exhibit how these ideals are related via space inversion, time reversal and their product. We also consider the dual space of minimal right ideals and show how the Dirac-Kaehler differential operator acts from the right, leaving the minimal right ideals invariant. This allows the introduction of an adjoint form and through the definition of a suitable scalar product, of conserved currents. We emphasize the relevance of all these features to the problem of proliferation of fermion species in the continuum limit of the lattice formalism. (author)
Cloud flexibility using DIRAC interware
International Nuclear Information System (INIS)
Albor, Víctor Fernandez; Miguelez, Marcos Seco; Silva, Juan Jose Saborido; Pena, Tomas Fernandez; Muñoz, Victor Mendez; Diaz, Ricardo Graciani
2014-01-01
Communities of different locations are running their computing jobs on dedicated infrastructures without the need to worry about software, hardware or even the site where their programs are going to be executed. Nevertheless, this usually implies that they are restricted to use certain types or versions of an Operating System because either their software needs an definite version of a system library or a specific platform is required by the collaboration to which they belong. On this scenario, if a data center wants to service software to incompatible communities, it has to split its physical resources among those communities. This splitting will inevitably lead to an underuse of resources because the data centers are bound to have periods where one or more of its subclusters are idle. It is, in this situation, where Cloud Computing provides the flexibility and reduction in computational cost that data centers are searching for. This paper describes a set of realistic tests that we ran on one of such implementations. The test comprise software from three different HEP communities (Auger, LHCb and QCD phenomelogists) and the Parsec Benchmark Suite running on one or more of three Linux flavors (SL5, Ubuntu 10.04 and Fedora 13). The implemented infrastructure has, at the cloud level, CloudStack that manages the virtual machines (VM) and the hosts on which they run, and, at the user level, the DIRAC framework along with a VM extension that will submit, monitorize and keep track of the user jobs and also requests CloudStack to start or stop the necessary VM's. In this infrastructure, the community software is distributed via the CernVM-FS, which has been proven to be a reliable and scalable software distribution system. With the resulting infrastructure, users are allowed to send their jobs transparently to the Data Center. The main purpose of this system is the creation of flexible cluster, multiplatform with an scalable method for software distribution for
Cloud flexibility using DIRAC interware
Fernandez Albor, Víctor; Seco Miguelez, Marcos; Fernandez Pena, Tomas; Mendez Muñoz, Victor; Saborido Silva, Juan Jose; Graciani Diaz, Ricardo
2014-06-01
Communities of different locations are running their computing jobs on dedicated infrastructures without the need to worry about software, hardware or even the site where their programs are going to be executed. Nevertheless, this usually implies that they are restricted to use certain types or versions of an Operating System because either their software needs an definite version of a system library or a specific platform is required by the collaboration to which they belong. On this scenario, if a data center wants to service software to incompatible communities, it has to split its physical resources among those communities. This splitting will inevitably lead to an underuse of resources because the data centers are bound to have periods where one or more of its subclusters are idle. It is, in this situation, where Cloud Computing provides the flexibility and reduction in computational cost that data centers are searching for. This paper describes a set of realistic tests that we ran on one of such implementations. The test comprise software from three different HEP communities (Auger, LHCb and QCD phenomelogists) and the Parsec Benchmark Suite running on one or more of three Linux flavors (SL5, Ubuntu 10.04 and Fedora 13). The implemented infrastructure has, at the cloud level, CloudStack that manages the virtual machines (VM) and the hosts on which they run, and, at the user level, the DIRAC framework along with a VM extension that will submit, monitorize and keep track of the user jobs and also requests CloudStack to start or stop the necessary VM's. In this infrastructure, the community software is distributed via the CernVM-FS, which has been proven to be a reliable and scalable software distribution system. With the resulting infrastructure, users are allowed to send their jobs transparently to the Data Center. The main purpose of this system is the creation of flexible cluster, multiplatform with an scalable method for software distribution for several
Extrapolation of π-meson form factor, zeros in the analyticity domain
International Nuclear Information System (INIS)
Morozov, P.T.
1978-01-01
The problem of a stable extrapolation from the cut to an arbitrary interior of the analyticity domain for the pion form factor is formulated and solved. As it is shown a stable solution can be derived if module representations with the Karleman weight function are used as the analyticity conditions. The case when the form factor has zeros is discussed. If there are zeros in the complex plane they must be taken into account when determining the extrapolation function
Measurement of the energy dependence of the form factor $f_{+}$ in $K^{0}_{e3}$ decay
Apostolakis, Alcibiades J; Backenstoss, Gerhard; Bargassa, P; Behnke, O; Benelli, A; Bertin, V; Blanc, F; Bloch, P; Carlson, P J; Carroll, M; Cawley, E; Chertok, M B; Danielsson, M; Dejardin, M; Derré, J; Ealet, A; Eleftheriadis, C; Fetscher, W; Fidecaro, Maria; Filipcic, A; Francis, D; Fry, J; Gabathuler, Erwin; Gamet, R; Gerber, H J; Go, A; Haselden, A; Hayman, P J; Henry-Coüannier, F; Hollander, R W; Jon-And, K; Kettle, P R; Kokkas, P; Kreuger, R; Le Gac, R; Leimgruber, F; Mandic, I; Manthos, N; Marel, Gérard; Mikuz, M; Miller, J; Montanet, François; Müller, A; Nakada, Tatsuya; Pagels, B; Papadopoulos, I M; Pavlopoulos, P; Polivka, G; Rickenbach, R; Roberts, B L; Ruf, T; Schäfer, M; Schaller, L A; Schietinger, T; Schopper, A; Tauscher, Ludwig; Thibault, C; Touchard, F; Touramanis, C; van Eijk, C W E; Vlachos, S; Weber, P; Wigger, O; Wolter, M; Zavrtanik, D; Zimmerman, D
2000-01-01
Neutral-kaon decays to \\pielnu\\ % recorded by the CPLEAR experimentwere analysed to determine the $q^2$ dependence of the \\Kzet\\ electroweak form factor $f_+$. Based on $365\\,612$ events,this form factor was found to have a linear dependence on $q^2$with a slope $\\lambda_+ = 0.0245 \\pm 0.0012_{\\text{stat}} \\pm 0.0022_{\\text{syst}}$.
The spin-dependent neutralino-nucleus form factor for 127I
International Nuclear Information System (INIS)
Ressell, M.T.
1996-01-01
We present the results of detailed shell model calculations of the spin-dependent elastic form factor for the nucleus 127 I. the calculations were performed in extremely large model spaces which adequately describe the configuration mixing in this nucleus. Good agreement between the calculated and experimental values of the magnetic moment are found. Other nuclear observables are also compared to experiment. The dependence of the form factor upon the model space and effective interaction is discussed
Relativistic two-fermion equations with form factors and anomalous magnetic moment interactions
International Nuclear Information System (INIS)
Ahmed, S.
1977-04-01
Relativistic equations for two-fermion systems are derived from quantum field theory taking into account the form factors of the particles. When the q 2 dependence of the form factors is disregarded, in the static approximation, the two-fermion equations with Coulomb and anomalous magnetic moment interactions are obtained. Separating the angular variables, a sixteen-component relativistic radial equation are finally given
Proton and neutron charge form factors in soliton model with dilaton-quarkonium fields
International Nuclear Information System (INIS)
Magar, E.N.; Nikolaev, V.A.; Tkachev, O.G.; Novozhilov, V.Yu.
1997-01-01
Nucleon electromagnetic form factors are considered in the framework of the generalized Skyrme model with dilaton-quarkonium fields. In our first publication we got big discrepancy between calculated form factors and dipole approximation formula. Here we have reasonably good accordance between them in finite impulse region after vector meson dominance has been taken into account. Omega- and rho-mesons have been included only into hadron structure of the photon
Stationary solutions of the Maxwell-Dirac and the Klein-Gordon-Dirac equations
International Nuclear Information System (INIS)
Esteban, M.J.; Georgiev, V.; Sere, E.
1995-01-01
The Maxwell-Dirac system describes the interaction of an electron with its own electromagnetic field. We prove the existence of soliton-like solutions of Maxwell-Dirac in (3+1)-Minkowski space-time. The solutions obtained are regular, stationary in time, and localized in space. They are found by a variational method, as critical points of an energy functional. This functional is strongly indefinite and presents a lack of compactness. We also find soliton-like solutions for the Klein-Gordon-Dirac system, arising in the Yukawa model. (author). 32 refs
Quantized Dirac field interacting with a classical Maxwell field
International Nuclear Information System (INIS)
Kolsrud, M.
1987-10-01
The S operator for the quantized and the s matrix for the unquantized Dirac field, both fields interacting with an unquantized Maxwell field, are shown to be related in the following way: S=exp(-ic†kc) and s=exp(-ik). Here c is the column matrix of the particle operators, and k is a Hermitian matrix. With splitting of c into an electron and a positron part, a corresponding factorization of S is performed. Exact expressions for the probability amplitude for various electron and/or positron processes are then obtained
Minimax rational approximation of the Fermi-Dirac distribution
Moussa, Jonathan E.
2016-10-01
Accurate rational approximations of the Fermi-Dirac distribution are a useful component in many numerical algorithms for electronic structure calculations. The best known approximations use O(log(βΔ)log(ɛ-1)) poles to achieve an error tolerance ɛ at temperature β-1 over an energy interval Δ. We apply minimax approximation to reduce the number of poles by a factor of four and replace Δ with Δocc, the occupied energy interval. This is particularly beneficial when Δ ≫ Δocc, such as in electronic structure calculations that use a large basis set.
All-Metallic Vertical Transistors Based on Stacked Dirac Materials
Wang, Yangyang; Ni, Zeyuan; Liu, Qihang; Quhe, Ruge; Zheng, Jiaxin; Ye, Meng; Yu, Dapeng; Shi, Junjie; Yang, Jinbo; Lu, Jing
2014-01-01
It is an ongoing pursuit to use metal as a channel material in a field effect transistor. All metallic transistor can be fabricated from pristine semimetallic Dirac materials (such as graphene, silicene, and germanene), but the on/off current ratio is very low. In a vertical heterostructure composed by two Dirac materials, the Dirac cones of the two materials survive the weak interlayer van der Waals interaction based on density functional theory method, and electron transport from the Dirac ...
On Huygens' principle for Dirac operators associated to electromagnetic fields
Directory of Open Access Journals (Sweden)
CHALUB FABIO A.C.C.
2001-01-01
Full Text Available We study the behavior of massless Dirac particles, i.e., solutions of the Dirac equation with m = 0 in the presence of an electromagnetic field. Our main result (Theorem 1 is that for purely real or imaginary fields any Huygens type (in Hadamard's sense Dirac operators is equivalent to the free Dirac operator, equivalence given by changes of variables and multiplication (right and left by nonzero functions.
Dirac equations for generalised Yang-Mills systems
International Nuclear Information System (INIS)
Lechtenfeld, O.; Nahm, W.; Tchrakian, D.H.
1985-06-01
We present Dirac equations in 4p dimensions for the generalised Yang-Mills (GYM) theories introduced earlier. These Dirac equations are related to the self-duality equations of the GYM and are checked to be elliptic in a 'BPST' background. In this background these Dirac equations are integrated exactly. The possibility of imposing supersymmetry in the GYM-Dirac system is investigated, with negative results. (orig.)
A framework for unified Dirac gauginos
Directory of Open Access Journals (Sweden)
Benakli Karim
2017-01-01
Full Text Available We identify the Minimal Dirac Gaugino Supersymmetric Standard Model (MDGSSM as the minimal field content with Dirac gauginos allowing unification of gauge coupling. We stress that its parameter space describes also other most popular models as the MSSM, NMSSM and MRSSM. We discuss the generation of trilinear couplings in models of gauge mediation that has been overlooked in the past. We study the different source of Higgs mixings and constraints from the ƿ parameter. Finally, we provide new experimental limits on the masses of the scalar octets.
Dirac particle tunneling from black rings
International Nuclear Information System (INIS)
Jiang Qingquan
2008-01-01
Recent research shows that Hawking radiation can be treated as a quantum tunneling process, and Hawking temperatures of Dirac particles across the horizon of a black hole can be correctly recovered via the fermion tunneling method. In this paper, motivated by the fermion tunneling method, we attempt to apply the analysis to derive Hawking radiation of Dirac particles via tunneling from black ring solutions of 5-dimensional Einstein-Maxwell-dilaton gravity theory. Finally, it is interesting to find that, as in the black hole case, fermion tunneling can also result in correct Hawking temperatures for the rotating neutral, dipole, and charged black rings.
Kapitza–Dirac effect with traveling waves
International Nuclear Information System (INIS)
Hayrapetyan, Armen G; Götte, Jörg B; Grigoryan, Karen K; Petrosyan, Rubik G
2015-01-01
We report on the possibility of diffracting electrons from light waves traveling inside a dielectric medium. We show that, in the frame of reference which moves with the group velocity of light, the traveling wave acts as a stationary diffraction grating from which electrons can diffract, similar to the conventional Kapitza–Dirac effect. To characterize the Kapitza–Dirac effect with traveling light waves, we make use of the Hamiltonian Analogy between electron optics and quantum mechanics and apply the Helmholtz–Kirchhoff theory of diffraction. (fast track communication)
Are Dirac electrons faster than light?
International Nuclear Information System (INIS)
De Angelis, G.F.
1986-01-01
This paper addresses the problem of path integral solutions of the Dirac equation. The path integral construction of the Dirac propagator which extends Fynman's checkerboard rule in more than one space dimension is discussed. A distinguished feature of such extension is the fact that the speed of a relativistic electron is actually greater than the speed of light when the space has more than one dimension. A technique employed in obtaining an extension to higher space dimension is described which consists in comparing continuity equations of quantum mechanical origin with forward Kolmogorov equations for suitable chosen classes of random processes
Landau quantization and quasiparticle interference in the three-dimensional Dirac semimetal Cd₃As₂.
Jeon, Sangjun; Zhou, Brian B; Gyenis, Andras; Feldman, Benjamin E; Kimchi, Itamar; Potter, Andrew C; Gibson, Quinn D; Cava, Robert J; Vishwanath, Ashvin; Yazdani, Ali
2014-09-01
Condensed-matter systems provide a rich setting to realize Dirac and Majorana fermionic excitations as well as the possibility to manipulate them for potential applications. It has recently been proposed that chiral, massless particles known as Weyl fermions can emerge in certain bulk materials or in topological insulator multilayers and give rise to unusual transport properties, such as charge pumping driven by a chiral anomaly. A pair of Weyl fermions protected by crystalline symmetry effectively forming a massless Dirac fermion has been predicted to appear as low-energy excitations in a number of materials termed three-dimensional Dirac semimetals. Here we report scanning tunnelling microscopy measurements at sub-kelvin temperatures and high magnetic fields on the II-V semiconductor Cd3As2. We probe this system down to atomic length scales, and show that defects mostly influence the valence band, consistent with the observation of ultrahigh-mobility carriers in the conduction band. By combining Landau level spectroscopy and quasiparticle interference, we distinguish a large spin-splitting of the conduction band in a magnetic field and its extended Dirac-like dispersion above the expected regime. A model band structure consistent with our experimental findings suggests that for a magnetic field applied along the axis of the Dirac points, Weyl fermions are the low-energy excitations in Cd3As2.
Meson form factors and covariant three-dimensional formulation of the composite model
International Nuclear Information System (INIS)
Skachkov, N.B.; Solovtsov, I.L.
1979-01-01
An apparatus is developed which allows within the relativistic quark model, to find explicit expressions for meson form factors in terms of the wave functions of two-quark system that obey the covariant two-particle quasipotential equation. The exact form of wave functions is obtained by passing to the relativistic configurational representation. As an example, the quark Coulomb interaction is considered
Proton electromagnetic form factors: present status and future perspectives at PANDA
Directory of Open Access Journals (Sweden)
Tomasi-Gustafsson E.
2015-01-01
Full Text Available Data and models on electromagnetic proton form factors are reviewed, highlighting the contribution foreseen by the PANDA collaboration. Electromagnetic hadron form factors contain essential information on the internal structure of hadrons. Precise and surprising data have been obtained at electron accelerators, applying the polarization method in electron-proton elastic scattering. At electron-positron colliders, using initial state radiation, BABAR measured proton time-like form factors in a wide time-like kinematical region and the BESIII collaboration will measure very precisely proton and neutron form factors in the threshold region. In the next future an antiproton beam with momentum up to 15 GeV/c will be available at FAIR (Darmstadt. Measurements of the reaction p̅ + p → e+ + e− by the PANDA collaboration will contribute to the individual determination of electric and magnetic form factors in the time-like region of momentum transfer squared, as well as to their first determination in the unphysical region (below the kinematical threshold, through the reaction p̅ + p → e+ + e− + π0. From the discussion on feasibility studies at PANDA, we focus on the consequences of such measurements in view of an unified description of form factors in the full kinematical region. We present models which have the necessary analytical requirements and apply to the data in the whole kinematical region.
Light meson form factors at high Q2 from lattice QCD
Koponen, Jonna; Zimermmane-Santos, André; Davies, Christine; Lepage, G. Peter; Lytle, Andrew
2018-03-01
Measurements and theoretical calculations of meson form factors are essential for our understanding of internal hadron structure and QCD, the dynamics that bind the quarks in hadrons. The pion electromagnetic form factor has been measured at small space-like momentum transfer |q2| theory is applicable. This leaves a gap in the intermediate Q2 where the form factors are not known. As a part of their 12 GeV upgrade Jefferson Lab will measure pion and kaon form factors in this intermediate region, up to Q2 of 6 GeV2. This is then an ideal opportunity for lattice QCD to make an accurate prediction ahead of the experimental results. Lattice QCD provides a from-first-principles approach to calculate form factors, and the challenge here is to control the statistical and systematic uncertainties as errors grow when going to higher Q2 values. Here we report on a calculation that tests the method using an ηs meson, a 'heavy pion' made of strange quarks, and also present preliminary results for kaon and pion form factors. We use the nf = 2 + 1 + 1 ensembles made by the MILC collaboration and Highly Improved Staggered Quarks, which allows us to obtain high statistics. The HISQ action is also designed to have small dicretisation errors. Using several light quark masses and lattice spacings allows us to control the chiral and continuum extrapolation and keep systematic errors in check. Warning, no authors found for 2018EPJWC.17506016.
Cutting through form factors and cross sections of non-protected operators in N=4 SYM
International Nuclear Information System (INIS)
Nandan, Dhritiman; Sieg, Christoph; Wilhelm, Matthias; Yang, Gang
2015-01-01
We study the form factors of the Konishi operator, the prime example of non-protected operators in N=4 SYM theory, via the on-shell unitarity method. Since the Konishi operator is not protected by supersymmetry, its form factors share many features with amplitudes in QCD, such as the occurrence of rational terms and of UV divergences that require renormalization. A subtle point is that this operator depends on the spacetime dimension. This requires a modification when calculating its form factors via the on-shell unitarity method. We derive a rigorous prescription that implements this modification to all loop orders and obtain the two-point form factor up to two-loop order and the three-point form factor to one-loop order. From these form factors, we construct an IR-finite cross-section-type quantity, namely the inclusive decay rate of the (off-shell) Konishi operator to any final (on-shell) state. Via the optical theorem, it is connected to the imaginary part of the two-point correlation function. We extract the Konishi anomalous dimension up to two-loop order from it.
New exact solutions of the Dirac equation. 8
International Nuclear Information System (INIS)
Bagrov, V.G.; Gitman, D.M.; Zadorozhnyj, V.N.; Sukhomlin, N.B.; Shapovalov, V.N.
1978-01-01
The paper continues the investigation into the exact solutions of the Dirac, Klein-Gordon, and Lorentz equations for a charge in an external electromagnetic field. The fields studied do not allow for separation of variables in the Dirac equation, but solutions to the Dirac equation are obtained
Kondo effect in three-dimensional Dirac and Weyl systems
Mitchell, Andrew K.; Fritz, Lars
2015-01-01
Magnetic impurities in three-dimensional Dirac and Weyl systems are shown to exhibit a fascinatingly diverse range of Kondo physics, with distinctive experimental spectroscopic signatures. When the Fermi level is precisely at the Dirac point, Dirac semimetals are in fact unlikely candidates for a
Dirac cones beyond the honeycomb lattice : a symmetry based approach
Miert, G. van; de Morais Smith, Cristiane
2016-01-01
Recently, several new materials exhibiting massless Dirac fermions have been proposed. However, many of these do not have the typical graphene honeycomb lattice, which is often associated with Dirac cones. Here, we present a classification of these different two-dimensional Dirac systems based on
Huygens' Principle, Dirac Operators, and Rational Solutions of the AKNS Hierarchy
International Nuclear Information System (INIS)
Chalub, Fabio A. C. C.; Zubelli, Jorge P.
2005-01-01
We prove that rational solutions of the AKNS hierarchy of the form q=σ/τ and r=ρ/τ, where (σ,τ,ρ) are certain Schur functions, naturally yield Dirac operators of strict Huygens' type, i.e., the support of their fundamental solutions is the surface of the light-cone. This strengthens the connection between the theory of completely integrable systems and Huygens' principle by extending to the Dirac operators and the rational solutions of the AKNS hierarchy a classical result of Lagnese and Stellmacher concerning perturbations of wave operators
Generating {mu} and B{mu} in models with Dirac gauginos
Energy Technology Data Exchange (ETDEWEB)
Benakli, Karim [CNRS, UPMC Univ. Paris 06 (France). Lab. de Physique Theorique et Hautes Energies; Goodsell, Mark D. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Maier, Ann-Kathrin [SB-EPFL, Lausanne (Switzerland). Laboratoire de Physique de la Matiere Complexe
2011-04-15
We consider the extension of the Minimal Supersymmetric Standard Model by Dirac masses for the gauginos. We study the possibility that the same singlet S that pairs up with the bino, to form a Dirac fermion, is used to generate {mu} and B{mu} terms through its vacuum expectation value. For this purpose, we assume that, in the Higgs potential, the necessary R-symmetry breaking originates entirely from a superpotential term ({kappa})/(3)S{sup 3} and discuss the implications for the spectrum of the model. (orig.)
The half-filled Landau level: The case for Dirac composite fermions
Geraedts, Scott D.; Zaletel, Michael P.; Mong, Roger S. K.; Metlitski, Max A.; Vishwanath, Ashvin; Motrunich, Olexei I.
2016-04-01
In a two-dimensional electron gas under a strong magnetic field, correlations generate emergent excitations distinct from electrons. It has been predicted that “composite fermions”—bound states of an electron with two magnetic flux quanta—can experience zero net magnetic field and form a Fermi sea. Using infinite-cylinder density matrix renormalization group numerical simulations, we verify the existence of this exotic Fermi sea, but find that the phase exhibits particle-hole symmetry. This is self-consistent only if composite fermions are massless Dirac particles, similar to the surface of a topological insulator. Exploiting this analogy, we observe the suppression of 2kF backscattering, a characteristic of Dirac particles. Thus, the phenomenology of Dirac fermions is also relevant to two-dimensional electron gases in the quantum Hall regime.
Large leptonic Dirac CP phase from broken democracy with random perturbations
Ge, Shao-Feng; Kusenko, Alexander; Yanagida, Tsutomu T.
2018-06-01
A large value of the leptonic Dirac CP phase can arise from broken democracy, where the mass matrices are democratic up to small random perturbations. Such perturbations are a natural consequence of broken residual S3 symmetries that dictate the democratic mass matrices at leading order. With random perturbations, the leptonic Dirac CP phase has a higher probability to attain a value around ± π / 2. Comparing with the anarchy model, broken democracy can benefit from residual S3 symmetries, and it can produce much better, realistic predictions for the mass hierarchy, mixing angles, and Dirac CP phase in both quark and lepton sectors. Our approach provides a general framework for a class of models in which a residual symmetry determines the general features at leading order, and where, in the absence of other fundamental principles, the symmetry breaking appears in the form of random perturbations.
Dirac gap-induced graphene quantum dot in an electrostatic potential
Giavaras, G.; Nori, Franco
2011-04-01
A spatially modulated Dirac gap in a graphene sheet leads to charge confinement, thus enabling a graphene quantum dot to be formed without the application of external electric and magnetic fields [G. Giavaras and F. Nori, Appl. Phys. Lett. 97, 243106 (2010)]. This can be achieved provided the Dirac gap has a local minimum in which the states become localized. In this work, the physics of such a gap-induced dot is investigated in the continuum limit by solving the Dirac equation. It is shown that gap-induced confined states couple to the states introduced by an electrostatic quantum well potential. Hence the region in which the resulting hybridized states are localized can be tuned with the potential strength, an effect which involves Klein tunneling. The proposed quantum dot may be used to probe quasirelativistic effects in graphene, while the induced confined states may be useful for graphene-based nanostructures.
Reduced Dirac equation and Lamb shift as off-mass-shell effect in quantum electrodynamics
International Nuclear Information System (INIS)
Ni Guang-Jiong; Xu Jian-Jun; Lou Sen-Yue
2011-01-01
Based on the accurate experimental data of energy-level differences in hydrogen-like atoms, especially the 1S—2S transitions of hydrogen and deuterium, the necessity of introducing a reduced Dirac equation with reduced mass as the substitution of original electron mass is stressed. Based on new cognition about the essence of special relativity, we provide a reasonable argument for the reduced Dirac equation to have two symmetries, the invariance under the (newly defined) space-time inversion and that under the pure space inversion, in a noninertial frame. By using the reduced Dirac equation and within the framework of quantum electrodynamics in covariant form, the Lamb shift can be evaluated (at one-loop level) as the radiative correction on a bound electron staying in an off-mass-shell state—-a new approach eliminating the infrared divergence. Hence the whole calculation, though with limited accuracy, is simplified, getting rid of all divergences and free of ambiguity. (general)
High energy approximations for nuclear knockout form factors at small momentum transfer
International Nuclear Information System (INIS)
Amado, R.D.; Cannata, F.; Dedonder, J.P.
1985-01-01
We obtain an explicit approximate expression for the nucleon knockout form factor at small momentum transfer induced by a scalar probe in a single particle model in terms of the momentum space bound state wave function. Our form preserves the orthogonality constraint without using explicitly the final state scattering wave function. We examine the leading large momentum behavior of the momentum space wave function and of correction terms to our expression for the form factor in the case where the bound state is an s state
Single-Spin Polarization Effects and the Determination of Timelike Proton Form Factors
Energy Technology Data Exchange (ETDEWEB)
Brodsky, S
2003-10-24
We show that measurements of the proton's polarization in e{sup +}e{sup -} {yields} p{bar p} strongly discriminate between analytic forms of models which fit the proton form factors in the spacelike region. In particular, the single-spin asymmetry normal to the scattering plane measures the relative phase difference between the timelike G{sub E} and G{sub M} form factors. The expected proton polarization in the timelike region is large, of order of several tens of percent.
Cui, Lixia; Lin, Wenwen; Oei, Tian P. S.
2011-01-01
This study investigated cross-cultural differences in the factor structure and psychometric properties of the Young Schema Questionnaire (short form; YSQ-SF). The participants were 712 Chinese undergraduate students. The total sample was randomly divided into two sub-samples. Exploratory Factor Analysis (EFA) was conducted on questionnaire results…
Spontaneous magnetization of quantum XY-chain from finite chain form-factor
International Nuclear Information System (INIS)
Iorgov, N.Z.
2010-01-01
Using the explicit factorized formulas for matrix elements (form-factors) of the spin operators between vectors of the Hamiltonian of a finite quantum XY-chain in a transverse field, the spontaneous magnetization for σ x and σ y is re-derived in a simple way.
Multilevel Confirmatory Factor Analysis of the Teacher My Class Inventory-Short Form
Villares, Elizabeth; Mariani, Melissa; Sink, Christopher A.; Colvin, Kimberly
2016-01-01
Researchers analyzed data from elementary teachers (N = 233) to further establish the psychometric soundness of the Teacher My Class Inventory-Short Form. Supporting previous psychometric research, confirmatory factor analyses findings supported the factorial validity of the hypothesized five-factor solution. Internal reliability estimates were…
Jagiellonian University Study of Hadronic Hydrogen-like Atoms in the DIRAC Experiment at PS CERN
Afanasyev, L
2017-01-01
Production of hadronic hydrogen-like atoms at high-energy collisions and method of their observation are considered. Main results of the DIRAC experiment on observation and lifetime measurement of atoms formed by pairs of charged pion–pion and pion–kaon are presented.
Electromagnetic and axial-vector form factors of the quarks and nucleon
Dahiya, Harleen; Randhawa, Monika
2017-11-01
In light of the improved precision of the experimental measurements and enormous theoretical progress, the nucleon form factors have been evaluated with an aim to understand how the static properties and dynamical behavior of nucleons emerge from the theory of strong interactions between quarks. We have analyzed the vector and axial-vector nucleon form factors (GE,Mp,n(Q2) and GAp,n(Q2)) using the spin observables in the chiral constituent quark model (χCQM) which has made a significant contribution to the unraveling of the internal structure of the nucleon in the nonperturbative regime. We have also presented a comprehensive analysis of the flavor decomposition of the form factors (GEq(Q2), GMq(Q2) and GAq(Q2) for q = u,d,s) within the framework of χCQM with emphasis on the extraction of the strangeness form factors which are fundamental to determine the spin structure and test the chiral symmetry breaking effects in the nucleon. The Q2 dependence of the vector and axial-vector form factors of the nucleon has been studied using the conventional dipole form of parametrization. The results are in agreement with the available experimental data.
Charge form factors and alpha-cluster internal structure of 12C
International Nuclear Information System (INIS)
Luk'yanov, V.K.; Zemlyanaya, E.V.; Kadrev, D.N.; Antonov, A.N.; Spasova, K.; Anagnostatos, G.S.; Ginis, P.; Giapitzakis, J.
1999-01-01
The transition densities and form factors of 0 + , 2 + , and 3 - states in 12 C are calculated in alpha-cluster model using the triangle frame with clusters in the vertices. The wave functions of nucleons in the alpha clusters are taken as they were obtained in the framework of the models used for the description of the 4 He form factor and momentum distribution which are based on the one-body density matrix construction. They contain effects of the short-range NN correlations, as well as the d-shell admixtures in 4 He. Calculations and the comparison with the experimental data show that visible effects on the form and magnitude of the 12 C form factors take place, especially at relatively large momentum transfers
International Nuclear Information System (INIS)
Massen, S. E.; Garistov, V. P.; Grypeos, M. E.
1996-01-01
The effects of nuclear surface fluctuations on harmonic oscillator elastic charge form factor of light nuclei are investigated, simultaneously approximating the short-range correlations through a Jastrow correlation factor. Inclusion of the surface fluctuation effects within this description, by truncating the cluster expansion at the two-body part, is found to improve somewhat the fit to the elastic charge form-factor of 16 O and 40 Ca. However, the convergence of the cluster expansion is expected to deteriorate. An additional finding is that surface-fluctuation correlations produce a drastic change in the asymptotic behaviour of the point-proton form-factor, which now falls off quite slowly (i.e. as const.q -4 ) at large values of the momentum transfer q
The NE11 experiment at SLAC and the neutron form factors
International Nuclear Information System (INIS)
Stuart, L.M.; Lung, A.; Bosted, P.E.
1993-05-01
The neutron electromagnetic form factors G En and G Mn , which reflect the charge and magnetization distributions within the neutron, are of fundamental importance for understanding nucleon structure, and are necessary for calculations of processes involving the electromagnetic interaction with complex nuclei. These quantities are functions of Q 2 , the four-momentum transfer squared. SLAC experiment NE11 has measured these form factors out to a Q 2 of 4.0 (GeV/c) 2 with high precision, and the results have been recently published. This paper provides some additional details on the extraction of G Mn and G En from the NE11 measurements. Several formalisms have been developed over the years which attempt to understand the nucleon form factors using basic physical principles. Vector Meson Dominance (VMD) models are based on superpositions of photon couplings to various vector mesons. These models generally involve free parameters which are fit to form factor data at low Q 2 , and are not expected to be valid at high Q 2 . For asymptotically large Q 2 , dimensional scaling methods and perturbative Quantum Chromodynamics (pQCD) predict form factor behavior at large Q 2 , but they do not make absolute magnitude predictions. To describe the form factor behavior at intermediate values of Q 2 , a hybrid model by Gari and Kruempelmann (GK) uses VMD constraints at low Q 2 and pQCD constraints at high Q 2 . Free parameters in the model are adjusted to fit existing form factor data. Other approaches include the use of QCD sum rules to make absolute predictions, diquark models, and relativistic constituent quark models
Sulkosky, V.; Jin, G.; Long, E.; Zhang, Y.-W.; Mihovilovic, M.; Kelleher, A.; Anderson, B.; Higinbotham, D. W.; Širca, S.; Allada, K.; Annand, J. R. M.; Averett, T.; Bertozzi, W.; Boeglin, W.; Bradshaw, P.; Camsonne, A.; Canan, M.; Cates, G. D.; Chen, C.; Chen, J.-P.; Chudakov, E.; De Leo, R.; Deng, X.; Deur, A.; Dutta, C.; El Fassi, L.; Flay, D.; Frullani, S.; Garibaldi, F.; Gao, H.; Gilad, S.; Gilman, R.; Glamazdin, O.; Golge, S.; Gomez, J.; Hansen, J.-O.; Holmstrom, T.; Huang, J.; Ibrahim, H.; de Jager, C. W.; Jensen, E.; Jiang, X.; Jones, M.; Kang, H.; Katich, J.; Khanal, H. P.; King, P.; Korsch, W.; LeRose, J.; Lindgren, R.; Lu, H.-J.; Luo, W.; Markowitz, P.; Meekins, D.; Meziane, M.; Michaels, R.; Moffit, B.; Monaghan, P.; Muangma, N.; Nanda, S.; Norum, B. E.; Pan, K.; Parno, D.; Piasetzky, E.; Posik, M.; Punjabi, V.; Puckett, A. J. R.; Qian, X.; Qiang, Y.; Qui, X.; Riordan, S.; Saha, A.; Sawatzky, B.; Shabestari, M.; Shahinyan, A.; Shoenrock, B.; John, J. St.; Subedi, R.; Tobias, W. A.; Tireman, W.; Urciuoli, G. M.; Wang, D.; Wang, K.; Wang, Y.; Watson, J.; Wojtsekhowski, B.; Ye, Z.; Zhan, X.; Zhang, Y.; Zheng, X.; Zhao, B.; Zhu, L.; Jefferson Lab Hall A Collaboration
2017-12-01
Background: Measurements of the neutron charge form factor, GEn, are challenging because the neutron has no net charge. In addition, measurements of the neutron form factors must use nuclear targets which require accurately accounting for nuclear effects. Extracting GEn with different targets and techniques provides an important test of our handling of these effects. Purpose: The goal of the measurement was to use an inclusive asymmetry measurement technique to extract the neutron charge form factor at a four-momentum transfer of 1 (GeV/c ) 2 . This technique has very different systematic uncertainties than traditional exclusive measurements and thus serves as an independent check of whether nuclear effects have been taken into account correctly. Method: The inclusive quasielastic reaction 3He ⃗(e ⃗,e') was measured at Jefferson Laboratory. The neutron electric form factor, GEn, was extracted at Q2=0.98 (GeV/c ) 2 from ratios of electron-polarization asymmetries measured for two orthogonal target spin orientations. This Q2 is high enough that the sensitivity to GEn is not overwhelmed by the neutron magnetic contribution, and yet low enough that explicit neutron detection is not required to suppress pion production. Results: The neutron electric form factor, GEn, was determined to be 0.0414 ±0.0077 (stat)±0.0022 (syst) , providing the first high-precision inclusive extraction of the neutron's charge form factor. Conclusions: The use of the inclusive quasielastic 3He ⃗(e ⃗,e') with a four-momentum transfer near 1 (GeV/c ) 2 has been used to provide a unique measurement of GEn. This new result provides a systematically independent validation of the exclusive extraction technique results and implies that the nuclear corrections are understood. This is contrary to the proton form factor where asymmetry and differential cross section measurements have been shown to have large systematic differences.
Dirac's aether in relativistic quantum mechanics
International Nuclear Information System (INIS)
Petroni, N.C.; Bari Univ.; Vigier, J.P.
1984-01-01
The paper concerns Dirac's aether model, based on a stochastic covariant distribution of subquantum motions. Stochastic derivation of the relativistic quantum equations; deterministic nonlocal interpretation of the Aspect-Rapisarda experiments on the EPR paradox; and photon interference with itself; are all discussed. (U.K.)
Dirac's minimum degree condition restricted to claws
Broersma, Haitze J.; Ryjacek, Z.; Schiermeyer, I.
1997-01-01
Let G be a graph on n 3 vertices. Dirac's minimum degree condition is the condition that all vertices of G have degree at least . This is a well-known sufficient condition for the existence of a Hamilton cycle in G. We give related sufficiency conditions for the existence of a Hamilton cycle or a
International Nuclear Information System (INIS)
Ferreira, P.L.; Alcaras, J.A.C.
1980-01-01
The group theoretical properties of the Dirac groups of rank n are discussed together with the properties and construction of their IR's. The cases n even and n odd show distinct features. Furthermore, for n odd, the cases n=4K+1 and n=4K+3 exhibit some different properties too. (Author) [pt
Higher dimensional supersymmetric quantum mechanics and Dirac ...
Indian Academy of Sciences (India)
We exhibit the supersymmetric quantum mechanical structure of the full 3+1 dimensional Dirac equation considering `mass' as a function of coordinates. Its usefulness in solving potential problems is discussed with speciﬁc examples. We also discuss the `physical' signiﬁcance of the supersymmetric states in this formalism.
Applications of Dirac's Delta Function in Statistics
Khuri, Andre
2004-01-01
The Dirac delta function has been used successfully in mathematical physics for many years. The purpose of this article is to bring attention to several useful applications of this function in mathematical statistics. Some of these applications include a unified representation of the distribution of a function (or functions) of one or several…
On Kaehler's geometric description of dirac fields
International Nuclear Information System (INIS)
Goeckeler, M.; Joos, H.
1983-12-01
A differential geometric generalization of the Dirac equation due to E. Kaehler seems to be an appropriate starting point for the lattice approximation of matter fields. It is the purpose of this lecture to illustrate several aspects of this approach. (orig./HSI)
SU(4) properties of the Dirac equation
International Nuclear Information System (INIS)
Linhares, C.A.; Mignaco, J.A.
1988-01-01
The Dirac equation in four dimensions has an intimate connection with the representations of the group SU(4). This connection is shown in detail and subsequente properties are displayed in the continuum as well as in the lattice description. (author) [pt
The Dirac operator on the Fuzzy sphere
International Nuclear Information System (INIS)
Grosse, H.
1994-01-01
We introduce the Fuzzy analog of spinor bundles over the sphere on which the non-commutative analog of the Dirac operator acts. We construct the complete set of eigenstates including zero modes. In the commutative limit we recover known results. (authors)
Mass and oscillations of Dirac neutrinos
International Nuclear Information System (INIS)
Collot, J.
1989-01-01
In the most economical extension of the standard model, we have presented the theory of massive Dirac neutrinos. We have particularly emphasized that, in this model, a complete analogy between quarks and leptons can be erected and predicts neutrino flavor oscillations. We have reviewed the last experimental results concerning kinetic neutrino mass experiments and neutrino oscillation investigations
First level trigger of the DIRAC experiment
International Nuclear Information System (INIS)
Afanas'ev, L.G.; Karpukhin, V.V.; Kulikov, A.V.; Gallas, M.
2001-01-01
The logic of the first level trigger of the DIRAC experiment at CERN is described. A parallel running of different trigger modes with tagging of events and optional independent prescaling is realized. A CAMAC-based trigger system is completely computer controlled
Evolution kernel for the Dirac field
International Nuclear Information System (INIS)
Baaquie, B.E.
1982-06-01
The evolution kernel for the free Dirac field is calculated using the Wilson lattice fermions. We discuss the difficulties due to which this calculation has not been previously performed in the continuum theory. The continuum limit is taken, and the complete energy eigenfunctions as well as the propagator are then evaluated in a new manner using the kernel. (author)
Probabilistic solution of the Dirac equation
International Nuclear Information System (INIS)
Blanchard, P.; Combe, P.
1985-01-01
Various probabilistic representations of the 2, 3 and 4 dimensional Dirac equation are given in terms of expectation with respect to stochastic jump processes and are used to derive the nonrelativistic limit even in the presence of an external electromagnetic field. (orig.)
Poisson geometry from a Dirac perspective
Meinrenken, Eckhard
2018-03-01
We present proofs of classical results in Poisson geometry using techniques from Dirac geometry. This article is based on mini-courses at the Poisson summer school in Geneva, June 2016, and at the workshop Quantum Groups and Gravity at the University of Waterloo, April 2016.
Interfacial Dirac cones from alternating topological invariant superlattice structures of Bi2Se3.
Song, Jung-Hwan; Jin, Hosub; Freeman, Arthur J
2010-08-27
When the three-dimensional topological insulators Bi2Se3 and Bi2Te3 have an interface with vacuum, i.e., a surface, they show remarkable features such as topologically protected and spin-momentum locked surface states. However, for practical applications, one often requires multiple interfaces or channels rather than a single surface. Here, for the first time, we show that an interfacial and ideal Dirac cone is realized by alternating band and topological insulators. The multichannel Dirac fermions from the superlattice structures open a new way for applications such as thermoelectric and spintronics devices. Indeed, utilizing the interfacial Dirac fermions, we also demonstrate the possible power factor improvement for thermoelectric applications.
A Route to Dirac Liquid Theory: A Fermi Liquid Description for Dirac Materials
Gochan, Matthew; Bedell, Kevin
Since the pioneering work developed by L.V. Landau sixty years ago, Fermi Liquid Theory has seen great success in describing interacting Fermi systems. While much interest has been generated over the study of non-Fermi Liquid systems, Fermi Liquid theory serves as a formidable model for many systems and offers a rich amount of of results and insight. The recent classification of Dirac Materials, and the lack of a unifying theoretical framework for them, has motivated our study. Dirac materials are a versatile class of materials in which an abundance of unique physical phenomena can be observed. Such materials are found in all dimensions, with the shared property that their low-energy fermionic excitations behave as massless Dirac fermions and are therefore governed by the Dirac equation. The most popular Dirac material, graphene, is the focus of this work. We present our Fermi Liquid description of Graphene. We find many interesting results, specifically in the transport and dynamics of the system. Additionally, we expand on previous work regarding the Virial Theorem and its impact on the Fermi Liquid parameters in graphene. Finally, we remark on viscoelasticity of Dirac Materials and other unusual results that are consequences of AdS-CFT.
The GridPP DIRAC project - DIRAC for non-LHC communities
Bauer, D; Currie, R; Fayer, S; Huffman, A; Martyniak, J; Rand, D; Richards, A
2015-01-01
The GridPP consortium in the UK is currently testing a multi-VO DIRAC service aimed at non-LHC VOs. These VOs (Virtual Organisations) are typically small and generally do not have a dedicated computing support post. The majority of these represent particle physics experiments (e.g. NA62 and COMET), although the scope of the DIRAC service is not limited to this field. A few VOs have designed bespoke tools around the EMI-WMS & LFC, while others have so far eschewed distributed resources as they perceive the overhead for accessing them to be too high. The aim of the GridPP DIRAC project is to provide an easily adaptable toolkit for such VOs in order to lower the threshold for access to distributed resources such as Grid and cloud computing. As well as hosting a centrally run DIRAC service, we will also publish our changes and additions to the upstream DIRAC codebase under an open-source license. We report on the current status of this project and show increasing adoption of DIRAC within the non-LHC communiti...
The GridPP DIRAC project - DIRAC for non-LHC communities
Bauer, D.; Colling, D.; Currie, R.; Fayer, S.; Huffman, A.; Martyniak, J.; Rand, D.; Richards, A.
2015-12-01
The GridPP consortium in the UK is currently testing a multi-VO DIRAC service aimed at non-LHC VOs. These VOs (Virtual Organisations) are typically small and generally do not have a dedicated computing support post. The majority of these represent particle physics experiments (e.g. NA62 and COMET), although the scope of the DIRAC service is not limited to this field. A few VOs have designed bespoke tools around the EMI-WMS & LFC, while others have so far eschewed distributed resources as they perceive the overhead for accessing them to be too high. The aim of the GridPP DIRAC project is to provide an easily adaptable toolkit for such VOs in order to lower the threshold for access to distributed resources such as Grid and cloud computing. As well as hosting a centrally run DIRAC service, we will also publish our changes and additions to the upstream DIRAC codebase under an open-source license. We report on the current status of this project and show increasing adoption of DIRAC within the non-LHC communities.