Static quark-antiquark potential

International Nuclear Information System (INIS)

Deo, B.B.; Barik, B.K.

1983-01-01

A heavy-quark--antiquark potential is suggested which connects asymptotic freedom and quark confinement in a unified manner by formal methods of field theory using some plausible assumptions. The potential has only one additional adjustable parameter B which is proportional to (M/sub q//m/sub q/), where M/sub q/ and m/sub q/ are the constituent and current quark masses, respectively

Partonic transverse momenta in non-relativistic hyper-central quark potential models

International Nuclear Information System (INIS)

Diakonos, F.K.; Kaplis, N.K.; Maintas, X.N.

2009-01-01

We investigate the impact of three-body forces on the transverse-momentum distribution of partons inside the proton. This is achieved by considering the three-body problem in a class of hyper-central quark potential models. Solving the corresponding Schroedinger equation, we determine the quark wave function in the proton and with appropriate transformations and projections we find the transverse-momentum distribution of a single quark. In each case the parameters of the quark potentials are adjusted in order to sufficiently describe observable properties of the proton. Using a factorization ansatz, we incorporate the obtained transverse-momentum distribution in a perturbative QCD scheme for the calculation of the cross-section for prompt photon production in pp collisions. A large set of experimental data is fitted using as a single free parameter the mean partonic transverse momentum. The dependence of left angle k T right angle on the collision characteristics (initial energy and transverse momentum of the final photon) is much smoother when compared with similar results found in the literature using a Gaussian distribution for the partonic transverse momenta. Within the considered class of hyper-central quark potentials the one with the weaker dependence on the hyper-radius is preferred for the description of the data since it leads to the smoothest mean partonic transverse-momentum profile. We have repeated all the calculations using a two-body potential of the same form as the optimal (within the considered class) hyper-central potential in order to check if the presence of three-body forces is supported by the experimental data. Our analysis indicates that three-body forces influence significantly the form of the parton transverse-momentum distribution and consequently lead to an improved description of the considered data. (orig.)

The universality of the confining potential and the running of the quasi-Coulombic potential constant in the independent-quark model

International Nuclear Information System (INIS)

Khruschev, V.V.; Savrin, V.I.; Semenov, S.V.

1999-01-01

Parameters of the QCD-motivated static potential and the quark masses are calculated on the basis of the 1 -- meson mass spectra in the framework of the relativistic independent-quark model based on the Dirac equation. The value of the confining potential parameter is found to be (0.20 ± 0.01) GeV 2 for interactions between quarks and antiquarks independently on their flavors. The flavor independence of the confining potential is justified on the 5 x 10 -2 accuracy level both for the heavy quarks and for the light ones. The values of parameter α s , which is a strength of the quasi-Coulombic potential are consistent with the QCD-motivated decrease of α s at small interaction range [ru

Coupling constants and the nonrelativistic quark model with charmonium potential

International Nuclear Information System (INIS)

Chaichian, M.; Koegerler, R.

1978-01-01

Hadronic coupling constants of the vertices including charm mesons are calculated in a nonrelativistic quark model. The wave functions of the mesons which enter the corresponding overlap integrals are obtained from the charmonium picture as quark-antiquark bound state solutions of the Schroedinger equation. The model for the vertices takes into account in a dynamical way the SU 4 breakings through different masses of quarks and different wave functions in the overlap integrals. All hadronic vertices involving scalar, pseudoscalar, vector, pseudovector and tensor mesons are calculated up to an overall normalization constant. Regularities among the couplings of mesons and their radial excitations are observed: i) Couplings decrease with increasing order of radial excitations; ii) In general they change sign if a particle is replaced by its next radial excitation. The k-dependence of the vertices is studied. This has potential importance in explaining the unorthodox ratios in different decay channels. Having got the hadronic couplings radiative transitions are obtained with the current coupled to mesons and their recurrences. The resulting width values are smaller than those conventionally obtained in the naive quark model. The whole picture is only adequate for nonrelativistic configurations, as for the members of the charmonium- or of the UPSILON-family and most calculations have been done for transitions among charmed states. To see how far nonrelativistic concepts can be applied, couplings of light mesons are also considered. (author)

'Relativistic' quark model for mesons with flavour-independent potential

International Nuclear Information System (INIS)

Kroesen, G.

1987-01-01

On the base of the Bethe-Salpeter equation in instantaneous approximation a unified model for the mass spectrum of the mesons was designed. The 'relativistic' structure of the Bethe-Salpeter equation allows a natural inclusion of the spin dependences and an extension of the model to small quark masses. The model contains as essential property two potential contributions where one represents the one-gluon exchange while the other represents the confinement potential. The annihilation of qanti q into gluons was not regarded. The spectrum and the amplitudes of the Bethe-Salpeter equation were solved approximatively in numerical way for the lowest states. The free parameters of the model were determined by a fit of the spectrum to a wellknown part of the meson spectrum. The results yield even at small quark masses a quantitatively good picture for all meson families. The result shows that the spectra of the heavy and light mesons can be described by a flavor-independent potential which contains 5 free parameters. Both the internal spin dependent structure and the absolute position of the families can so correctly be described. Especially the position of the D, D s , and B states and the position of the uanti u, danti d states can be simultaneously described by a constant C in the long-range part of the potential. The constant C is thereby essentially determined by the splitting between the Υ family and the B family repectively Ψ and D family. The 3 S 1- 3 D 1 respectively the 3 P 2 - 3 F 2 configuration mixing was regarded. The results show that this mixing is negligibly small. (orig./HSI) [de

Quark cluster model and confinement

International Nuclear Information System (INIS)

Koike, Yuji; Yazaki, Koichi

2000-01-01

How confinement of quarks is implemented for multi-hadron systems in the quark cluster model is reviewed. In order to learn the nature of the confining interaction for fermions we first study 1+1 dimensional QED and QCD, in which the gauge field can be eliminated exactly and generates linear interaction of fermions. Then, we compare the two-body potential model, the flip-flop model and the Born-Oppenheimer approach in the strong coupling lattice QCD for the meson-meson system. Having shown how the long-range attraction between hadrons, van der Waals interaction, shows up in the two-body potential model, we discuss two distinct attempts beyond the two-body potential model: one is a many-body potential model, the flip-flop model, and the other is the Born-Oppenheimer approach in the strong coupling lattice QCD. We explain how the emergence of the long-range attraction is avoided in these attempts. Finally, we present the results of the application of the flip-flop model to the baryon-baryon scattering in the quark cluster model. (author)

Quark potential of spontaneous strings

International Nuclear Information System (INIS)

German, G.; Kleinert, H.

1989-01-01

The authors present some recent developments in string models with an extrinsic curvature term in action. Particular emphasis is placed upon the static quark potential and on the thermal deconfinement properties of spontaneous strings

Magnetic moments of confined quarks and baryons in an independent-quark model based on Dirac equation with power-law potential

International Nuclear Information System (INIS)

Barik, N.; Das, M.

1983-01-01

The effect of confinement on the magnetic moment of a quark has been studied in a simple independent-quark model based on the Dirac equation with a power-law potential. The magnetic moments so obtained for the constituent quarks, which are found to be significantly different from their corresponding Dirac moments, are used in predicting the magnetic moments of baryons in the nucleon octet as well as those in the charmed and b-flavored sectors. We not only get an improved result for the proton magnetic moment, but the calculation for the rest of the nucleon octet also turns out to be in reasonable agreement with experiment. The overall predictions for the charmed and b-flavored baryons are also comparable with other model predictions

On equal constituent quark masses in different heavy quarkonia potential models

International Nuclear Information System (INIS)

Lewin, K.; Motz, G.

1989-01-01

In a representative number of more or less QCD-motivated QQ-bar potentials the simultaneous transformations of potentials V' j (r)=V i (r)-V i (r 0 ), m' Qi +1/2V j (r 0 ) (i -model index) introduce approximately equal constituent quark masses m' Qi ≅m Q (Q=b,c) for all considered models. The known model independence of m bi -m ci is explained and the influence of the transformation on data reproduction is studied. 16 refs.; 4 figs.; 1 tab

Quark-anti-quark potential in N=4 SYM

Energy Technology Data Exchange (ETDEWEB)

Gromov, Nikolay [Mathematics Department, King’s College London,The Strand, London WC2R 2LS (United Kingdom); St. Petersburg INP,Gatchina, 188 300, St.Petersburg (Russian Federation); Levkovich-Maslyuk, Fedor [Mathematics Department, King’s College London,The Strand, London WC2R 2LS (United Kingdom); Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden)

2016-12-22

We construct a closed system of equations describing the quark-anti-quark potential at any coupling in planar N=4 supersymmetric Yang-Mills theory. It is based on the Quantum Spectral Curve method supplemented with a novel type of asymptotics. We present a high precision numerical solution reproducing the classical and one-loop string predictions very accurately. We also analytically compute the first 7 nontrivial orders of the weak coupling expansion. Moreover, we study analytically the generalized quark-anti-quark potential in the limit of large imaginary twist to all orders in perturbation theory. We demonstrate how the QSC reduces in this case to a one-dimensional Schrodinger equation. In the process we establish a link between the Q-functions and the solution of the Bethe-Salpeter equation.

Quasinuclear colored quark model for hadrons

International Nuclear Information System (INIS)

Lipkin, H.J.

1978-09-01

Lectures are presented in which a quasinuclear constituent quark model in which constituent quarks are assumed to be made of constituent interacting with a two-body color-exchange logarithmic potential is considered. The color degree of freedom is discussed in detail. Some properties of the logarithmic potential and the definition of the quasinuclear model and its validity, and a comparison of some of its predictions with experiment are described. 31 references

Quark mass correction to the string potential

International Nuclear Information System (INIS)

Lambiase, G.; Nesterenko, V.V.

1995-01-01

A consistent method for calculating the interquark potential generated by the relativistic string with massive ends is proposed. In this approach the interquark potential in the model of the Nambu-Goto string with point-like masses at its ends is calculated. At first the calculation is done in the one-loop approximation and then the variational estimation is performed. The quark mass correction results in decreasing the critical distance (deconfinement radius). When quark mass decreases the critical distance also decreases. For obtaining a finite result under summation over eigenfrequencies of the Nambu-Goto string with massive ends a suitable mode-by-mode subtraction is proposed. This renormalization procedure proves to be completely unique. In the framework of the developed approach the one-loop interquark potential in the model of the relativistic string with rigidity is also calculated. 34 refs., 2 figs

Testing the constituent quark model in KN scattering

Energy Technology Data Exchange (ETDEWEB)

Lemaire, S. E-mail: lemaire@cenbg.in2p3.fr; Labarsouque, J.; Silvestre-Brac, B

2003-02-10

The kaon-nucleon S, P, D, F, G waves phase shifts have been calculated using a non-relativistic quark potential model and the resonating group method (RGM). The calculation has been performed using quark-quark potential which both includes gluon, pion and sigma exchanges and reproduces as well as possible the meson spectrum. The agreement obtained with the existing experimental phase shifts is quite poor. The results are also compared with a previous calculation based only on gluon exchanges at the quark level.

Testing the constituent quark model in KN scattering

International Nuclear Information System (INIS)

Lemaire, S.; Labarsouque, J.; Silvestre-Brac, B.

2003-01-01

The kaon-nucleon S, P, D, F, G waves phase shifts have been calculated using a non-relativistic quark potential model and the resonating group method (RGM). The calculation has been performed using quark-quark potential which both includes gluon, pion and sigma exchanges and reproduces as well as possible the meson spectrum. The agreement obtained with the existing experimental phase shifts is quite poor. The results are also compared with a previous calculation based only on gluon exchanges at the quark level

Strong interactions - quark models

International Nuclear Information System (INIS)

Goto, M.; Ferreira, P.L.

1979-01-01

The variational method is used for the PSI and upsilon family spectra reproduction from the quark model, through several phenomenological potentials, viz.: linear, linear plus coulomb term and logarithmic. (L.C.) [pt

Quark confinement potential and color Van der Waals force

International Nuclear Information System (INIS)

Zheng Yuming; Hua Daping; Liu Zuhua

1985-01-01

The color-analog Van der Waals force between two hadrons is studied by use of the coupling channel resonating group method in the framework of the Gaussian-type quark confinement potential. The problem of the boundary values for the two channel coupling differential equations is changed to the problem of the initial values. The equations are solved numerically by use of the Gear mehtod. The calculated results show that there is no color Van der Waals force between hadrons in the confinement potential model. This indicates that the confinement potential model not only can describe the internal structure of hadrons but also can be used to calculate the hadron-hadron interactions if the quark confinement potential is chosen properly

Y-Scaling in a simple quark model

International Nuclear Information System (INIS)

Kumano, S.; Moniz, E.J.

1988-01-01

A simple quark model is used to define a nuclear pair model, that is, two composite hadrons interacting only through quark interchange and bound in an overall potential. An ''equivalent'' hadron model is developed, displaying an effective hadron-hadron interaction which is strongly repulsive. We compare the effective hadron model results with the exact quark model observables in the kinematic region of large momentum transfer, small energy transfer. The nucleon reponse function in this y-scaling region is, within the traditional frame work sensitive to the nucleon momentum distribution at large momentum. We find a surprizingly small effect of hadron substructure. Furthermore, we find in our model that a simple parametrization of modified hadron size in the bound state, motivated by the bound quark momentum distribution, is not a useful way to correlate different observables

Quark confinement in a constituent quark model

International Nuclear Information System (INIS)

Langfeld, K.; Rho, M.

1995-01-01

On the level of an effective quark theory, we define confinement by the absence of quark anti-quark thresholds in correlation function. We then propose a confining Nambu-Jona-Lasinio-type model. The confinement is implemented in analogy to Anderson localization in condensed matter systems. We study the model's phase structure as well as its behavior under extreme conditions, i.e. high temperature and/or high density

Ellipsoidal bag model for heavy quark system

International Nuclear Information System (INIS)

Bi Pinzhen; Fudan Univ., Shanghai

1991-01-01

The ellipsoidal bag model is used to describe heavy quark systems such as Qanti Q, Qanti Qg and Q 2 anti Q 2 . Instead of two step model, these states are described by an uniform picture. The potential derived from the ellipsoidal bag for Qanti Q is almost equivalent to the Cornell potential. For a Q 2 anti Q 2 system with large quark pair separation, an improvement of 70 MeV is obtained comparing with the spherical bag. (orig.)

Studies on the quark confinement in a non-relativistic quark model

International Nuclear Information System (INIS)

Pfenninger, T.

1988-01-01

In the framework of the non-relativistic quark model we have studied several aspects of the description of the confinement by a confinement potential. A first consideration applied to the effects of the long-range color van-der-Waals forces on the nucleon-nucleon scattering. Regarding color dipole states as an additional closed channel in a dynamical and nonlocal resonating-group calculation we found a strong attraction. Additionally it was possible by means of the RGM kernels to derive an against earlier calculations improved color van-der-Waals potential in adiabatic approximation which regards correctly the internal kinetic and the confinement energy of the color octet states. This potential is not confined to large NN distances and shows asymptotically a 1/R 2 behaviour if it is based on a harmonic confinement. A further study applied to the question how far a possible vector character of the confinement, which is suggested by the elementary quark-gluon vertex, has effects on baryon properties and the NN interaction. Here it resulted that the vector confinement reacts in view of the model parameters very sensitively in the baryon properties whereas the scalar confinement did not show this dependence. In the NN scattering this vector confinement however plays a more secondary role. Because of the difficulties of the usual confinement potential with long-range color van-der-Waals forces we proposed in the last part a new potential and additional orthogonality relations for the quark wave functions in order to accomodate in the potential model to the string degrees of freedom. In scattering calculations we again studied the effects of the modification on the NN interaction. (orig./HSI) [de

Hot nuclear matter in the modified quark-meson coupling model with quark-quark correlations

International Nuclear Information System (INIS)

Zakout, I.; Jaqaman, H.R.

2000-01-01

Short-range quark-quark correlations in hot nuclear matter are examined within the modified quark-meson coupling (MQMC) model by adding repulsive scalar and vector quark-quark interactions. Without these correlations, the bag radius increases with the baryon density. However, when the correlations are introduced the bag size shrinks as the bags overlap. Also as the strength of the scalar quark-quark correlation is increased, the decrease of the effective nucleon mass M* N with the baryonic density is slowed down and tends to saturate at high densities. Within this model we study the phase transition from the baryon-meson phase to the quark-gluon plasma (QGP) phase with the latter modelled as an ideal gas of quarks and gluons inside a bag. Two models for the QGP bag parameter are considered. In one case, the bag is taken to be medium-independent and the phase transition from the hadron phase to QGP is found to occur at five to eight times ordinary nuclear matter density for temperatures less than 60 MeV. For lower densities, the transition takes place at a higher temperature, reaching up to 130 MeV at zero density. In the second case, the QGP bag parameter is considered to be medium-dependent as in the MQMC model for the hadronic phase. In this case, it is found that the phase transition occurs at much lower densities. (author)

Quark fragmentation function and the nonlinear chiral quark model

International Nuclear Information System (INIS)

Zhu, Z.K.

1993-01-01

The scaling law of the fragmentation function has been proved in this paper. With that, we show that low-P T quark fragmentation function can be studied as a low energy physocs in the light-cone coordinate frame. We therefore use the nonlinear chiral quark model which is able to study the low energy physics under scale Λ CSB to study such a function. Meanwhile the formalism for studying the quark fragmentation function has been established. The nonlinear chiral quark model is quantized on the light-front. We then use old-fashioned perturbation theory to study the quark fragmentation function. Our first order result for such a function shows in agreement with the phenomenological model study of e + e - jet. The probability for u,d pair formation in the e + e - jet from our calculation is also in agreement with the phenomenological model results

Quark-diquark model description for double charm baryons

International Nuclear Information System (INIS)

Majethiya, A.; Patel, B.; Vinodkumar, P. C.

2010-01-01

We report here the mass spectrum and magnetic moments of ccq(q (implied by) u, d, s) systems in the potential model framework by assuming the inter-quark potential as the colour coulomb plus power form with power index ν varying between 0.1 to 2.0. Here the two charm quarks are considered for the diquark states. The conventional one gluon exchange interaction has been employed to get the hyperfine and the fine structure between different states. We have predicted many low-lying states whose experimental verification can exclusively support the quark-diquark structure of the baryons. (authors)

Kaon-nucleon S-wave phase shifts in a QCD-motivated quark model

International Nuclear Information System (INIS)

Bender, I.; Dosch, H.G.

1982-01-01

We calculate kaon-nucleon central potentials and S-wave phase shifts for I = 0 and I = 1 in an QCD-motivated quark model. In our model the K-N interaction is derived from short-range perturbative quark-quark interactions. (orig.)

Models of quark bags and their consequences

International Nuclear Information System (INIS)

Bogolubov, P.N.

1977-01-01

The development of the first Dubna Quark Bag and the results obtained in this way are considered. The idea of the first Dubna Quark Bag is as follows: baryons are constructed of three quarks measons are constructed of two quarks, and each quark is interpreted as the Dirac particle which moves in a scalar square well. The so-called quasiindependent quark model is considered too. It is a simple quark model based on an analogy with the shell model for nuclei. The quarks are considered as moving in an arbitrary radially-symmetric field, and their one-particle wave function satisfies the usual Dirac equation. Such quark model can give at least the same results as the relativistic bag model. A possibility exists to improve the results of the relativistic quark model with the oscillator interaction between quarks. The results of the MIT-Bag model and the quasiindependent quark model coincide

Long-distance behavior of the quark-antiquark static potential. Application to light-quark mesons and heavy quarkonia

International Nuclear Information System (INIS)

Gonzalez, P.

2009-01-01

Screening effects from sea pairs on the quark-antiquark static potential are analyzed phenomenologically from the light-quark to the heavy-quark meson spectra. From the high excited light-quark meson spectrum, a universal form for the screened static potential is proposed. This potential is then successfully applied to heavy quarkonia. Our results suggest the assignment of X(4260) to the 4s state of charmonium and the possible existence of a 5s bottomonium resonance around 10748 MeV.

Kaon-Nucleon scattering in a constituent quark model

International Nuclear Information System (INIS)

Lemaire, S.

2002-06-01

We have investigated Kaon-Nucleon (KN) interaction in a constituent quark model in the momentum range for the Kaon between 0 and 1 GeV/c in the laboratory frame. This study has been motivated by the fact that in an approach relying on a boson exchange mechanism the Bonn group was forced, in order to obtain good agreement with I = 0 s-wave phase shifts, to add the exchange of a short range fictitious repulsive scalar meson. This need for repulsion, whose range (∼ 0.2 fm) is smaller than the nucleon radius, clearly shows that the quark substructure of the nucleons and K + mesons cannot be neglected. The Kaon-Nucleon phase shifts are calculated in a quark potential model using the resonating group method (RGM). We have to cope with a five body problem with antisymmetrization with respect to the four ordinary quarks of the Kaon-Nucleon system. One requirement of our approach is that the quark-quark interaction must give a quite good description of the hadron spectra. One goal of the present work aims at determining the influence of a relativistic kinematics, in this constituent quark model, for the calculation of KN phase shifts. We have also investigated s, p, d, f, g waves KN elastic phase shifts and we have included a spin-orbit term in the quark-quark interaction. Then we have studied the influence of medium and long range exchange mechanism in the quark quark interaction on KN phase shifts. (author)

Quark-diquark approximation of the three-quark structure of baryons in the quark confinement model

International Nuclear Information System (INIS)

Efimov, G.V.; Ivanov, M.A.; Lyubovitskij, V.E.

1990-01-01

Octet (1 + /2) and decuplet (3 + /2) of baryons as relativistic three-quark states are investigated in the quark confinement model (QCM), the relativistic quark model, based on some assumptions about hadronization and quark confinement. The quark-diquark approximation of the three-quark structure of baryons is proposed. In the framework of this approach the description of the main low-energy characteristics of baryons as magnetic moments, electromagnetic radii and form factors, ratio of axial and vector constants in semileptonic baryon octet decays, strong form factors and decay widths is given. The obtained results are in agreement with experimental data. 31 refs.; 4 figs.; 5 tabs

Octet baryons in the independent-quark-model approach based on the Dirac equation with a power-law potential

Energy Technology Data Exchange (ETDEWEB)

Barik, N; Das, M [Utkal Univ., Bhubaneswar (India). Dept. of Physics

1983-01-13

Several properties of octet baryons such as (i) the magnetic moment, (ii) (Gsub(A)/Gsub(v))sub(n) for neutron ..beta..-decay and (iii) the charge radius of the proton have been calculated in a simple independent-quark model under the assumption that the individual constituent quarks are confined, in first approximation, by a relativistic power-law potential Vsub(q)(r)=(1+..beta..) (asup(..nu..+1)rsup(..nu..)+V/sub 0/) with a, ..nu..>0. In view of the simplicity of the model, the results obtained are quite encouraging.

Octet baryons in the independent-quark-model approach based on the Dirac equation with a power-law potential

International Nuclear Information System (INIS)

Barik, N.; Das, M.

1983-01-01

Several properties of octet baryons such as (i) the magnetic moment, (ii) (Gsub(A)/Gsub(v))sub(n) for neutron #betta#-decay and (iii) the charge radius of the proton have been calculated in a simple independent-quark model under the assumption that the individual constituent quarks are confined, in first approximation, by a relativistic power-law potential Vsub(q)(r)=(1+#betta#) (asup(#betta#+1)rsup(#betta#)+V 0 ) with a, #betta#>0. In view of the simplicity of the model, the results obtained are quite encouraging. (orig.)

Interquark potential with finite quark mass from lattice QCD.

Science.gov (United States)

Kawanai, Taichi; Sasaki, Shoichi

2011-08-26

We present an investigation of the interquark potential determined from the q ̄q Bethe-Salpeter (BS) amplitude for heavy quarkonia in lattice QCD. The q ̄q potential at finite quark mass m(q) can be calculated from the equal-time and Coulomb gauge BS amplitude through the effective Schrödinger equation. The definition of the potential itself requires information about a kinetic mass of the quark. We then propose a self-consistent determination of the quark kinetic mass on the same footing. To verify the proposed method, we perform quenched lattice QCD simulations with a relativistic heavy-quark action at a lattice cutoff of 1/a≈2.1  GeV in a range 1.0≤m(q)≤3.6 GeV. Our numerical results show that the q ̄q potential in the m(q)→∞ limit is fairly consistent with the conventional one obtained from Wilson loops. The quark-mass dependence of the q ̄q potential and the spin-spin potential are also examined. © 2011 American Physical Society

A scalar-vector model of quark-antiquark interaction under linear confinement

International Nuclear Information System (INIS)

Chakrabarty, S.

1992-08-01

Considering the idea that the constituent quark mass is the dressed sum of current quark mass and dynamical quark mass, and using the standard values of current quark masses we obtain approximate values of constituent quark masses, which are then used in our extensively studied Bethe-Salpeter-reduced potential model. We find that the mass formulas become much simpler for linear potential ar with zero anomalous magnetic moment (λ), the values of scalar-vector fraction (η) and 'a' in the linear potential being (1/4) and (1/5) respectively. Also, some of the quantities can be related to each other and the match with experimental data is good. (author). 18 refs, 3 tabs

Nucleon quark distributions in a covariant quark-diquark model

Energy Technology Data Exchange (ETDEWEB)

Cloet, I.C. [Special Research Centre for the Subatomic Structure of Matter and Department of Physics and Mathematical Physics, University of Adelaide, SA 5005 (Australia) and Jefferson Lab, 12000 Jefferson Avenue, Newport News, VA 23606 (United States)]. E-mail: icloet@physics.adelaide.edu.au; 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; Thomas, A.W. [Jefferson Lab, 12000 Jefferson Avenue, Newport News, VA 23606 (United States)]. E-mail: awthomas@jlab.org

2005-08-18

Spin-dependent and spin-independent quark light-cone momentum distributions and structure functions are calculated for the nucleon. We utilize a modified Nambu-Jona-Lasinio model in which confinement is simulated by eliminating unphysical thresholds for nucleon decay into quarks. The nucleon bound state is obtained by solving the Faddeev equation in the quark-diquark approximation, where both scalar and axial-vector diquark channels are included. We find excellent agreement between our model results and empirical data.

Logarithmic correction in the deformed AdS5 model to produce the heavy quark potential and QCD beta function

International Nuclear Information System (INIS)

He Song; Huang Mei; Yan Qishu

2011-01-01

We study the holographic QCD model, which contains a quadratic term -σz 2 and a logarithmic term -c 0 log[(z IR -z)/z IR ] with an explicit infrared cutoff z IR in the deformed AdS 5 warp factor. We investigate the heavy-quark potential for three cases, i.e., with only a quadratic correction, with both quadratic and logarithmic corrections, and with only a logarithmic correction. We solve the dilaton field and dilation potential from the Einstein equation and investigate the corresponding beta function in the Guersoy-Kiritsis-Nitti framework. Our studies show that in the case with only a quadratic correction, a negative σ or the Andreev-Zakharov model is favored to fit the heavy-quark potential and to produce the QCD beta function at 2-loop level; however, the dilaton potential is unbounded in the infrared regime. One interesting observation for the case of positive σ is that the corresponding beta function exists in an infrared fixed point. In the case with only a logarithmic correction, the heavy-quark Cornell potential can be fitted very well, the corresponding beta function agrees with the QCD beta function at 2-loop level reasonably well, and the dilaton potential is bounded from below in the infrared. At the end, we propose a more compact model which has only a logarithmic correction in the deformed warp factor and has less free parameters.

The constituent quark model the spectrum of mesons

International Nuclear Information System (INIS)

Shojaei, M.R.; Rajabi, A.A.; Hasanabadi, H.

2007-01-01

Full text: We calculate exact solution of the Schroedinger equation analytically for a meson consisting of a quark and antiquark, considering the interaction potential between the particles as a combination of two potentials, a potential due to color charge and an oscillatory potential as confining potential. in this paper, first consider potential between quarks as a function of radios x, thus we assume this potential as a central potential. This potential is derived from that the central potential. This potential is derived from that the quark see itself under influence of another quark, in this case central potential is considered as: V(x)=ax 2 -c/x. Potential is obtained from interaction between a quark and an antiquary. The source of it is color charge and ax 2 potential plays confining potential. Because this potential shows oscillations of one quark to another quark in the distance x from it.. In addition to the above potentials we consider the spin-spin, spin - isospin and isospin - isospin interactions as perturbing potentials, and calculate the mass of the mesons for each potential separately finally using the equivalence of mass-energy we calculate the mass of the mesons

Quark models in hadron physics

International Nuclear Information System (INIS)

Phatak, Shashikant C.

2007-01-01

In this talk, we review the role played by the quark models in the study of interaction of strong, weak and electromagnetic probes with hadrons at intermediate and high momentum transfers. By hadrons, we mean individual nucleons as well as nuclei. We argue that at these momentum transfers, the structure of hadrons plays an important role. The hadron structure of the hadrons is because of the underlying quark structure of hadrons and therefore the quark models play an important role in determining the hadron structure. Further, the properties of hadrons are likely to change when these are placed in nuclear medium and this change should arise from the underlying quark structure. We shall consider some quark models to look into these aspects. (author)

Hadron structure in a simple model of quark/nuclear matter

International Nuclear Information System (INIS)

Horowitz, C.J.; Moniz, E.J.; Negele, J.W.

1985-01-01

We study a simple model for one-dimensional hadron matter with many of the essential features needed for examining the transition from nuclear to quark matter and the limitations of models based upon hadron rather than quark degrees of freedom. The dynamics are generated entirely by the quark confining force and exchange symmetry. Using Monte Carlo techniques, the ground-state energy, single-quark momentum distribution, and quark correlation function are calculated for uniform matter as a function of density. The quark confinement scale in the medium increases substantially with increasing density. This change is evident in the correlation function and momentum distribution, in qualitative agreement with the changes observed in deep-inelastic lepton scattering. Nevertheless, the ground-state energy is smooth throughout the transition to quark matter and is described remarkably well by an effective hadron theory based on a phenomenological hadron-hadron potential

Quark matter and quark stars at finite temperature in Nambu-Jona-Lasinio model

Energy Technology Data Exchange (ETDEWEB)

Chu, Peng-Cheng; Wang, Bin; Dong, Yu-Min; Jia, Yu-Yue; Wang, Shu-Mei; Ma, Hong-Yang [Qingdao Technological University, School of Science, Qingdao (China); Li, Xiao-Hua [University of South China, School of Nuclear Science and Technology, Hengyang (China); University of South China, Cooperative Innovation Center for Nuclear Fuel Cycle Technology and Equipment, Hengyang (China)

2017-08-15

We extend the SU(3) Nambu-Jona-Lasinio (NJL) model to include two types of vector interaction. Using these two types of vector interaction in NJL model, we study the quark symmetry free energy in asymmetric quark matter, the constituent quark mass, the quark fraction, the equation of state (EOS) for β-equilibrium quark matter, the maximum mass of QSs at finite temperature, the maximum mass of proto-quark stars (PQSs) along the star evolution, and the effects of the vector interaction on the QCD phase diagram. We find that comparing zero temperature case, the values of quark matter symmetry free energy get larger with temperature increasing, which will reduce the difference between the fraction of u, d and s quarks and stiffen the EoS for β-equilibrium quark matter. In particular, our results indicate that the maximum masses of the quark stars increase with temperature because of the effects of the quark matter symmetry free energy, and we find that the heating(cooling) process for PQSs will increase (decrease) the maximum mass within NJL model. (orig.)

Heavy-heavy-light quark potential in SU(3) lattice QCD

International Nuclear Information System (INIS)

Yamamoto, Arata; Suganuma, Hideo; Iida, Hideaki

2008-01-01

We perform the first study for the heavy-heavy-light quark (QQq) potential in SU(3) quenched lattice QCD with the Coulomb gauge. The calculations are done with the standard gauge and O(a)-improved Wilson fermion action on the 16 4 lattice at β=6.0. We calculate the energy of QQq systems as the function of the distance R between the two heavy quarks, and find that the QQq potential is well described with a Coulomb plus linear potential form up to the intermediate distance R≤0.8 fm. Compared to the static three-quark case, the effective string tension between the heavy quarks is significantly reduced by the finite-mass valence quark effect. This reduction is considered to be a general property for baryons

Test of quark fragmentation in the quark-parton model framework

International Nuclear Information System (INIS)

Derrick, M.; Barish, S.J.; Barnes, V.E.

1979-08-01

The hadronic system produced in charged-current antineutrino interactions is used to study fragmentation of the d-quark. Some problems encountered in separating the current quark-fragments are discussed. The fragmentation function for the current quark is in good agreement with the expectations of the naive quark-parton model and, in particular, there is no evidence of either a Q 2 - or x/sub BJ/-dependence. 10 references

Nucleon-nucleon interaction in the quark-compound-bag model

International Nuclear Information System (INIS)

Simonov, Yu.A.

1982-01-01

The NN potential is investigated in the framework of the quark-compound-bag model. The cluster decomposition of the total six-quark wave function are obtained. The resulting potential is nonlocal and energy dependent with coefficients which can be derived both phenomenologically and theoretically. Stringent conditions exist for those coefficients. As an example the NN potentials for the 3 S 1 and 1 S 0 states are presented. The properties of the wave functions are studied both in the configurational and momentum space

Baryons in the unquenched quark model

Energy Technology Data Exchange (ETDEWEB)

Bijker, R.; Díaz-Gómez, S. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, AP 70-543, 04510 Mexico DF (Mexico); Lopez-Ruiz, M. A. [Physics Department and Center for Exploration of Energy and Matter, Indiana University, Bloomington, IN 47408 (United States); Santopinto, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Genova, via Dodecaneso 33, I-16146 Italy (Italy)

2016-07-07

In this contribution, we present the unquenched quark model as an extension of the constituent quark model that includes the effects of sea quarks via a {sup 3}P{sub 0} quark-antiquark pair-creation mechanism. Particular attention is paid to the spin and flavor content of the proton, magnetic moments and β decays of octet baryons.

Constituent quarks as clusters in quark-gluon-parton model. [Total cross sections, probability distributions

Energy Technology Data Exchange (ETDEWEB)

Kanki, T [Osaka Univ., Toyonaka (Japan). Coll. of General Education

1976-12-01

We present a quark-gluon-parton model in which quark-partons and gluons make clusters corresponding to two or three constituent quarks (or anti-quarks) in the meson or in the baryon, respectively. We explicitly construct the constituent quark state (cluster), by employing the Kuti-Weisskopf theory and by requiring the scaling. The quark additivity of the hadronic total cross sections and the quark counting rules on the threshold powers of various distributions are satisfied. For small x (Feynman fraction), it is shown that the constituent quarks and quark-partons have quite different probability distributions. We apply our model to hadron-hadron inclusive reactions, and clarify that the fragmentation and the diffractive processes relate to the constituent quark distributions, while the processes in or near the central region are controlled by the quark-partons. Our model gives the reasonable interpretation for the experimental data and much improves the usual ''constituent interchange model'' result near and in the central region (x asymptotically equals x sub(T) asymptotically equals 0).

Large degeneracy of excited hadrons and quark models

International Nuclear Information System (INIS)

Bicudo, P.

2007-01-01

The pattern of a large approximate degeneracy of the excited hadron spectra (larger than the chiral restoration degeneracy) is present in the recent experimental report of Bugg. Here we try to model this degeneracy with state of the art quark models. We review how the Coulomb Gauge chiral invariant and confining Bethe-Salpeter equation simplifies in the case of very excited quark-antiquark mesons, including angular or radial excitations, to a Salpeter equation with an ultrarelativistic kinetic energy with the spin-independent part of the potential. The resulting meson spectrum is solved, and the excited chiral restoration is recovered, for all mesons with J>0. Applying the ultrarelativistic simplification to a linear equal-time potential, linear Regge trajectories are obtained, for both angular and radial excitations. The spectrum is also compared with the semiclassical Bohr-Sommerfeld quantization relation. However, the excited angular and radial spectra do not coincide exactly. We then search, with the classical Bertrand theorem, for central potentials producing always classical closed orbits with the ultrarelativistic kinetic energy. We find that no such potential exists, and this implies that no exact larger degeneracy can be obtained in our equal-time framework, with a single principal quantum number comparable to the nonrelativistic Coulomb or harmonic oscillator potentials. Nevertheless we find it plausible that the large experimental approximate degeneracy will be modeled in the future by quark models beyond the present state of the art

The quark bag model

International Nuclear Information System (INIS)

Hasenfratz, P.; Kuti, J.

1978-01-01

The quark bag model is reviewed here with particular emphasis on spectroscopic applications and the discussion of exotic objects as baryonium, gluonium, and the quark phase of matter. The physical vacuum is pictured in the model as a two-phase medium. In normal phase of the vacuum, outside hadrons, the propagation of quark and gluon fields is forbidden. When small bubbles in a second phase are created in the medium of the normal phase with a characteristic size of one fermi, the hadron constituent fields may propagate inside the bubbles in normal manner. The bubble (bag) is stabilized against the pressure of the confined hadron constituent fields by vacuum pressure and surface tension. Inside the bag the colored quarks and gluons are governed by the equations of quantum chromodynamics. (Auth.)

Approximating chiral quark models with linear σ-models

International Nuclear Information System (INIS)

Broniowski, Wojciech; Golli, Bojan

2003-01-01

We study the approximation of chiral quark models with simpler models, obtained via gradient expansion. The resulting Lagrangian of the type of the linear σ-model contains, at the lowest level of the gradient-expanded meson action, an additional term of the form ((1)/(2))A(σ∂ μ σ+π∂ μ π) 2 . We investigate the dynamical consequences of this term and its relevance to the phenomenology of the soliton models of the nucleon. It is found that the inclusion of the new term allows for a more efficient approximation of the underlying quark theory, especially in those cases where dynamics allows for a large deviation of the chiral fields from the chiral circle, such as in quark models with non-local regulators. This is of practical importance, since the σ-models with valence quarks only are technically much easier to treat and simpler to solve than the quark models with the full-fledged Dirac sea

Transversity quark distributions in a covariant quark-diquark model

Energy Technology Data Exchange (ETDEWEB)

Cloet, I.C. [Physics Division, Argonne National Laboratory, Argonne, IL 60439-4843 (United States)], E-mail: icloet@anl.gov; 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; Thomas, A.W. [Jefferson Lab, 12000 Jefferson Avenue, Newport News, VA 23606 (United States); College of William and Mary, Williamsburg, VA 23187 (United States)], E-mail: awthomas@jlab.org

2008-01-17

Transversity quark light-cone momentum distributions are calculated for the nucleon. We utilize a modified Nambu-Jona-Lasinio model in which confinement is simulated by eliminating unphysical thresholds for nucleon decay into quarks. The nucleon bound state is obtained by solving the relativistic Faddeev equation in the quark-diquark approximation, where both scalar and axial-vector diquark channels are included. Particular attention is paid to comparing our results with the recent experimental extraction of the transversity distributions by Anselmino et al. We also compare our transversity results with earlier spin-independent and helicity quark distributions calculated in the same approach.

P-matrix in the quark compound bag model

International Nuclear Information System (INIS)

Kalashnikova, Yu.S.; Narodetskij, I.M.; Veselov, A.I.

1983-01-01

Meaning of the P-matrix analysis is discussed within the quark compound bag (QCB) model. The most general version of this model is considered including the arbitrary coupling between quark and hadronic channels and the arbitrary smearipg of the surface interection region. The behaviour of P-matrix poles as functions of matching radius r,L0 is discussed for r 0 > + . In conclusion are presented the parameters of an illustrative set of NN potentials that has been obtained from the P-matrix fit to experimental data

Quark-antiquark potentials from QCD and quarkonium spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Laschka, Alexander

2012-12-11

This work examines the interaction between a heavy quark and its antiquark. By combining perturbative and non-perturbative methods, interaction potentials with an extended range of validity are derived from quantum chromodynamics. Using these potentials the spectra of the quarkonium bound states are calculated and compared with experimental results. This provides a new approach for determining the masses of the charm and bottom quark.

Properties of Doubly Heavy Baryons in the Relativistic Quark Model

International Nuclear Information System (INIS)

Ebert, D.; Faustov, R.N.; Galkin, V.O.; Martynenko, A.P.

2005-01-01

Mass spectra and semileptonic decay rates of baryons consisting of two heavy (b or c) and one light quark are calculated in the framework of the relativistic quark model. The doubly heavy baryons are treated in the quark-diquark approximation. The ground and excited states of both the diquark and quark-diquark bound systems are considered. The quark-diquark potential is constructed. The light quark is treated completely relativistically, while the expansion in the inverse heavy-quark mass is used. The weak transition amplitudes of heavy diquarks bb and bc going, respectively, to bc and cc are explicitly expressed through the overlap integrals of the diquark wave functions in the whole accessible kinematic range. The relativistic baryon wave functions of the quark-diquark bound system are used for the calculation of the decay matrix elements, the Isgur-Wise function, and decay rates in the heavy-quark limit

Exotic quarks in Twin Higgs models

Energy Technology Data Exchange (ETDEWEB)

Cheng, Hsin-Chia [Department of Physics, University of California, Davis,One Shields Avenue, Davis, CA 95616 (United States); Jung, Sunghoon [School of Physics, Korea Institute for Advanced Study,85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of); SLAC National Accelerator Laboratory,2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Salvioni, Ennio [Department of Physics, University of California, Davis,One Shields Avenue, Davis, CA 95616 (United States); Tsai, Yuhsin [Department of Physics, University of California, Davis,One Shields Avenue, Davis, CA 95616 (United States); Maryland Center for Fundamental Physics,Department of Physics, University of Maryland,College Park, MD 20742 (United States)

2016-03-14

The Twin Higgs model provides a natural theory for the electroweak symmetry breaking without the need of new particles carrying the standard model gauge charges below a few TeV. In the low energy theory, the only probe comes from the mixing of the Higgs fields in the standard model and twin sectors. However, an ultraviolet completion is required below ∼ 10 TeV to remove residual logarithmic divergences. In non-supersymmetric completions, new exotic fermions charged under both the standard model and twin gauge symmetries have to be present to accompany the top quark, thus providing a high energy probe of the model. Some of them carry standard model color, and may therefore be copiously produced at current or future hadron colliders. Once produced, these exotic quarks can decay into a top together with twin sector particles. If the twin sector particles escape the detection, we have the irreducible stop-like signals. On the other hand, some twin sector particles may decay back into the standard model particles with long lifetimes, giving spectacular displaced vertex signals in combination with the prompt top quarks. This happens in the Fraternal Twin Higgs scenario with typical parameters, and sometimes is even necessary for cosmological reasons. We study the potential displaced vertex signals from the decays of the twin bottomonia, twin glueballs, and twin leptons in the Fraternal Twin Higgs scenario. Depending on the details of the twin sector, the exotic quarks may be probed up to ∼ 2.5 TeV at the LHC and beyond 10 TeV at a future 100 TeV collider, providing a strong test of this class of ultraviolet completions.

CP violation for electroweak baryogenesis from mixing of standard model and heavy vector quarks

International Nuclear Information System (INIS)

McDonald, J.

1996-01-01

It is known that the CP violation in the minimal standard model is insufficient to explain the observed baryon asymmetry of the Universe in the context electroweak baryogenesis. In this paper we consider the possibility that the additional CP violation required could originate in the mixing of the standard model quarks and heavy vector quark pairs. We consider the baryon asymmetry in the context of the spontaneous baryogenesis scenario. It is shown that, in general, the CP-violating phase entering the mass matrix of the standard model and heavy vector quarks must be space dependent in order to produce a baryon asymmetry, suggesting that the additional CP violation must be spontaneous in nature. This is true for the case of the simplest models which mix the standard model and heavy vector quarks. We derive a charge potential term for the model by diagonalizing the quark mass matrix in the presence of the electroweak bubble wall, which turns out to be quite different from the fermionic hypercharge potentials usually considered in spontaneous baryogenesis models, and obtain the rate of baryon number generation within the wall. We find, for the particular example where the standard model quarks mix with weak-isodoublet heavy vector quarks via the expectation value of a gauge singlet scalar, that we can account for the observed baryon asymmetry with conservative estimates for the uncertain parameters of electroweak baryogenesis, provided that the heavy vector quarks are not heavier than a few hundred GeV and that the coupling of the standard model quarks to the heavy vector quarks and gauge singlet scalars is not much smaller than order of 1, corresponding to a mixing angle of the heavy vector quarks and standard model quarks not much smaller than order of 10 -1 . copyright 1996 The American Physical Society

The Quark's Model and Confinement

Science.gov (United States)

Novozhilov, Yuri V.

1977-01-01

Quarks are elementary particles considered to be components of the proton, the neutron, and others. This article presents the quark model as a mathematical concept. Also discussed are gluons and bag models. A bibliography is included. (MA)

Large Psub(tr) and quark-quark cross section in the dynamical model of factorizing quarks

International Nuclear Information System (INIS)

Kapshay, V.N.; Sidorov, A.V.; Skachkov, N.B.

1978-01-01

Dynamical model of factorizing quarks containing the quark mass as free model parameter was described. Model calculations were compared with the experimental data on the cross section of the inclusive πsup(o) meson production in the proton-proton interaction. It is shown that the results of the paper are in good agreement with experiments

Testing static quark-antiquark potentials with bottomonium

International Nuclear Information System (INIS)

Lichtenberg, D.B.; Predazzi, E.; Roncaglia, R.; Rosso, M.; Wills, J.G.

1989-01-01

We investigate the question of whether experimental data on the energy levels of bottomonium can discriminate between quark-antiquark potentials which are motivated by what we know about QCD and potentials which are purely phenomenological. We restrict ourselves to bottomonium because, of all the quarkonia observed thus far, bottomonium is the least relativistic and therefore the best testing ground for the static quarkonium potential. We consider two potentials whose functional form is motivated from perturbative QCD at short quark-antiquark separations and from nonperturbative lattice QCD at large separations. We also consider three strictly phenomenological potentials. We find that the best of the three phenomenological potentials, which has never been previously used, fits the spin-averaged data at least as well as the best of the QCD-motivated potentials. We propose further measurements on bottomium energy levels to provide additional tests. (orig.)

Quark interchange model of baryon interactions

Energy Technology Data Exchange (ETDEWEB)

Maslow, J.N.

1983-01-01

The strong interactions at low energy are traditionally described by meson field theories treating hadrons as point-like particles. Here a mesonic quark interchange model (QIM) is presented which takes into account the finite size of the baryons and the internal quark structure of hadrons. The model incorporates the basic quark-gluon coupling of quantum chromodynamics (QCD) and the MIT bag model for color confinement. Because the quark-gluon coupling constant is large and it is assumed that confinement excludes overlap of hadronic quark bags except at high momenta, a non-perturbative method of nuclear interactions is presented. The QIM allows for exchange of quark quantum numbers at the bag boundary between colliding hadrons mediated at short distances by a gluon exchange between two quarks within the hadronic interior. This generates, via a Fierz transformation, an effective space-like t channel exchange of color singlet (q anti-q) states that can be identified with the low lying meson multiplets. Thus, a one boson exchange (OBE) model is obtained that allows for comparison with traditional phenomenological models of nuclear scattering. Inclusion of strange quarks enables calculation of YN scattering. The NN and YN coupling constants and the nucleon form factors show good agreement with experimental values as do the deuteron low energy data and the NN low energy phase shifts. Thus, the QIM provides a simple model of strong interactions that is chirally invariant, includes confinement and allows for an OBE form of hadronic interaction at low energies and momentum transfers.

Quark interchange model of baryon interactions

International Nuclear Information System (INIS)

Maslow, J.N.

1983-01-01

The strong interactions at low energy are traditionally described by meson field theories treating hadrons as point-like particles. Here a mesonic quark interchange model (QIM) is presented which takes into account the finite size of the baryons and the internal quark structure of hadrons. The model incorporates the basic quark-gluon coupling of quantum chromodynamics (QCD) and the MIT bag model for color confinement. Because the quark-gluon coupling constant is large and it is assumed that confinement excludes overlap of hadronic quark bags except at high momenta, a non-perturbative method of nuclear interactions is presented. The QIM allows for exchange of quark quantum numbers at the bag boundary between colliding hadrons mediated at short distances by a gluon exchange between two quarks within the hadronic interior. This generates, via a Fierz transformation, an effective space-like t channel exchange of color singlet (q anti-q) states that can be identified with the low lying meson multiplets. Thus, a one boson exchange (OBE) model is obtained that allows for comparison with traditional phenomenological models of nuclear scattering. Inclusion of strange quarks enables calculation of YN scattering. The NN and YN coupling constants and the nucleon form factors show good agreement with experimental values as do the deuteron low energy data and the NN low energy phase shifts. Thus, the QIM provides a simple model of strong interactions that is chirally invariant, includes confinement and allows for an OBE form of hadronic interaction at low energies and momentum transfers

Important configurations in six-quark N-N states. II. Current quark model

International Nuclear Information System (INIS)

Stancu, F.; Wilets, L.

1989-01-01

Quark basis states constructed from molecular-type orbitals were shown previously to be more convenient to use than cluster model states for N-N processes. The usual cluster model representation omits configurations which emerge naturally in a molecular basis which contains the same number of spatial functions. The importance of the omitted states was demonstrated for a constituent quark model. The present work extends the study to the prototypical current quark model, namely the MIT bag. In order to test the expansion for short-range N-N interactions, the eigenstates and eigenenergies of six quarks in a spherical bag, including one-gluon exchange, are calculated. The lowest eigenenergies are lowered significantly with respect to the usual cluster model. This reaffirms the importance of dynamics for obtaining the needed short-range repulsion

A chiral quark model of the nucleon

International Nuclear Information System (INIS)

Wakamatsu, M.; Yoshiki, H.

1991-01-01

The baryon-number-one extended solution of a chiral quark lagrangian is obtained in the stationary-phase approximation with full inclusion of the sea-quark degrees of freedom. The collective quantization method is then applied to this static solution to obtain the nucleon (and Δ) state with the definite spin and isospin. A fundamental quantity appearing in this quantization procedure is the moment of inertia of the soliton system. We evaluate this quantity without recourse to the derivative expansion, by performing the necessary double sum over all the positive- and negative-energy quark orbitals in the mean field potential. Closed formulas are-derived for the nucleon (and Δ) matrix elements of arbitrary quark bilinear operators. These formulas are then used for calculating various nucleon observables in a nonperturbative manner with inclusion of the sea-quark effects. An especially interesting observable is the spin expectation value of the proton related to the recent EMC experiment. We derive the proton spin sum rule, and then explicitly evaluate the detailed contents of this sum rule. The proton spin analysis is shown to be particularly useful for clarifying the underlying dynamical content of the Skyrme model at quark level, thereby providing us with valuable information about its utility and limitation. (orig.)

The baryon-baryon interaction in a modified quark model

International Nuclear Information System (INIS)

Zhang Zongye; Faessler, Amand; Straub, U.; Glozman, L.Ya.

1994-01-01

The quark-cluster model with coupling constants constraint by chiral symmetry is extended to include strange quarks. In this model, besides the confinement and one-gluon exchange potentials, the pseudoscalar mesons and sigma (σ) meson exchanges are included as the nonperturbative effect. Using this interaction we studied the binding energy of the deuteron, the NN scattering phase shifts and the hyperon-nucleon cross sections in the framework of the resonating group method (RGM). The results are reasonably consistent with experiments. ((orig.))

Effective potential for heavy quark antiquark bound system

Energy Technology Data Exchange (ETDEWEB)

Barik, B K; Deo, B B

1985-12-01

A heavy quark antiquark potential is suggested connecting asymptotic freedom and quark confinement in a unified way. The ..cap alpha../sub g/(q/sup 2/) calculated using Borel summation technique with three loop agrees with the two loop ..beta..-function up to g/sup 2//4..pi.. -- 1.1 but changes appreciably after g/sup 2//4..pi.. = 1.5. The potential so derived satisfactorily explains the c overlined c and b overlined b spectrum. 13 refs., 4 figures, 3 tables.

Determination of quark-antiquark potentials and meson spectra

International Nuclear Information System (INIS)

Semay, C.; Silvestre-Brac, B.

1999-01-01

We determine two different sets of quark-antiquark potential to be used in a Schroedinger or a Salpeter type of equation. The central part contains QCD inspired components: the Coulomb like interaction, the confinement potential and an instanton interaction. It is supplemented with phenomenological relativistic corrections. The constituent quarks are characterized by a colour charge density. The parameters are determined by a minimization procedure on representative samples of mesons and the full spectra are calculated. Refs. 6, tabs. 2 (author)

Nucleon-nucleon interaction with quark exchanges and prediction to colour van der Waals potential

International Nuclear Information System (INIS)

Osman, A.

1985-11-01

The nucleon-nucleon interaction is considered by including the colour nucleon clusters. The nucleon-nucleon system is treated as a six-quark system. The obtained local potentials reduce the short-range repulsion. The resulted nucleon-nucleon potential by using a quark-quark potential well agrees with the central-force potentials. The phase shifts calculated by using these local potentials are in good agreement with those obtained from other methods. Introducing the quark-quark potential in the nucleon-nucleon interaction, leads to a colour van der Waals potential very strong compared with that predicted by experiments. (author)

Gravity dual corrections to the heavy quark potential at finite-temperature

International Nuclear Information System (INIS)

Grigoryan, Hovhannes R.; Kovchegov, Yuri V.

2011-01-01

We apply gauge/gravity duality to compute 1/N c 2 corrections to the heavy quark potentials of a quark-anti-quark pair (QQ-bar) and of a quark-quark pair (QQ) immersed into the strongly coupled N=4 SYM plasma. On the gravity side these corrections come from the exchanges of supergravity modes between two string worldsheets stretching from the UV boundary of AdS space to the black hole horizon in the bulk and smeared over S 5 . We find that the contributions to the QQ-bar potential coming from the exchanges of all of the relevant modes (such as dilaton, massive scalar, 2-form field, and graviton) are all attractive, leading to an attractive net QQ-bar potential. We show that at large separations r and/or high-temperature T the potential is of Yukawa-type, dominated by the graviton exchange, in agreement with earlier findings. On the other hand, at small-rT the QQ-bar potential scales as ∼(1/r)ln(1/rT). In the case of QQ potential the 2-form contribution changes sign and becomes repulsive: however, the net QQ potential remains attractive. At large-rT it is dominated by the graviton exchange, while at small-rT the QQ potential becomes Coulomb-like.

Subquark model of leptons and quarks

International Nuclear Information System (INIS)

Terazawa, Hidezumi.

1979-09-01

1) First, various subquark models so far proposed are briefly reviewed. Classifications of leptons and quarks in the models and their comparison are made. Our spinor-subquark model of leptons and quarks in which leptons and quarks are made of three subquarks of spin 1/2 is discussed in detail. 2) The possibility that guage bosons and Higgs scalars are also made of a subquark-antisubquark pair is discussed. 3) Exotic states of subquarks such as leptons and quarks of spin 3/2, exotic fermions, and exotic bosons are predicted in our model. 4) Subquark currents and their algebra are proposed. 5) Two unified subquark models of strong and electroweak interactions are discussed. The one is a gauge model and the other is a model of the Nambu-Jona-Lasinio type. 6) A subquark model of gravity and its supergrand unification is proposed. 7) An finally, a speculation is made on ''color-space correspondence''. (author)

Deformed baryons: constituent quark model vs. bag model

International Nuclear Information System (INIS)

Iwamura, Y.; Nogami, Y.

1985-01-01

Recently Bhaduri et al. developed a nonrelativistic constituent quark model for deformed baryons. In that model the quarks move in a deformable mean field, and the deformation parameters are determined by minimizing the quark energy subject to the constraint of volume conservation. This constraint is an ad hoc assumption. It is shown that, starting with a bag model, a model similar to that of Bhaduri et al. can be constructed. The deformation parameters are determined by the pressure balance on the bag surface. There is, however, a distinct difference between the two models with respect to the state dependence of the ''volume''. Implications of this difference are discussed

Revisiting the quasi-particle model of the quark-gluon plasma

International Nuclear Information System (INIS)

Bannur, V.M.

2007-01-01

The quasi-particle model of the quark-gluon plasma (QGP) is revisited here with a new method, different from earlier studies, one without the need of a temperature dependent bag constant and other effects such as confinement, effective degrees of freedom etc. Our model has only one system dependent parameter and shows a surprisingly good fit to the lattice results for the gluon plasma, and for 2-flavor, 3-flavor and (2+1)-flavor QGP. The basic idea is first to evaluate the energy density ε from the grand partition function of quasi-particle QGP, and then derive all other thermodynamic functions from ε. Quasi-particles are assumed to have a temperature dependent mass equal to the plasma frequency. Energy density, pressure and speed of sound at zero chemical potential are evaluated and compared with the available lattice data. We further extend the model to a finite chemical potential, without any new parameters, to obtain the quark density, quark susceptibility etc., and the model fits very well with the lattice results on 2-flavor QGP. (orig.)

The quark model and asymptotic freedom

International Nuclear Information System (INIS)

Anon.

1986-01-01

The authors stress that it is not their task to provide a detailed account of the quark model (this is given in many monographs and reviews). This chapter is merely a prolog to the complex contemporary problems of high-energy physics which form the main subject of the present monograph. The quark model is based on the idea that there exist hypothetical fundamental particles - quarks, which they shall denote by q-bar/sub i/ (the index i characterizes the type of quark). From these particles and their antiparticles one constructs bound states, which are identified with the known hadrons. It turns out that all the observed mesons can be constructed from a quark q/sub i/ and an antiquark q-bar/sub i/, while the baryons (antibaryons) can be constructed from three quarks (antiquarks). To make it possible to build up all the observed hadrons and their characteristics, the authors must postulate that the quarks (antiquarks) possess the following properties: 1) spin 1/2; 2) isospin. It is necessary to introduce isospin 1/2 for the construction of the nonstrange hadrons. It has been proposed to denote the quark with isospin projection tau/sub 3/ = 1/2 by the symbol u (from the English ''up'') and the quark with isospin projection tau/sub 3/ = -1/2 by the symbol d (from the English ''down'')

An effective potential for heavy quark antiquark bound system

International Nuclear Information System (INIS)

Barik, B.K.; Deo, B.B.

1985-01-01

A heavy quark antiquark potential is suggested connecting asymptotic freedom and quark confinement in a unified way. The α g (q 2 ) calculated using Borel summation technique with three loop agrees with the two loop β-function up to g 2 /4π ∼ 1.1 but changes appreciably after g 2 /4π = 1.5. The potential so derived satisfactorily explains the c overlined c and b overlined b spectrum. (author)

Nucleon-nucleon interaction with quark exchange and prediction of the color van der Waals potential

International Nuclear Information System (INIS)

Osman, A.

1988-01-01

The nucleon-nucleon interaction is considered by including the color nucleon clusters. The nucleon-nucleon system is treated as a six-quark system. The obtained local potentials reduce the short-range repulsion. The resulting nucleon-nucleon potential, using a quark-quark potential, agress well with the central-force potentials. The phase shifts calculated by using these local potentials are in good agreement with those obtained from other methods. Introducing the quark-quark potential in the nucleon-nucleon interaction leads to a color van der Waals potential much stronger than that implied by experiments

Variational approach to chiral quark models

Energy Technology Data Exchange (ETDEWEB)

Futami, Yasuhiko; Odajima, Yasuhiko; Suzuki, Akira

1987-03-01

A variational approach is applied to a chiral quark model to test the validity of the perturbative treatment of the pion-quark interaction based on the chiral symmetry principle. It is indispensably related to the chiral symmetry breaking radius if the pion-quark interaction can be regarded as a perturbation.

Leptonic decay of light vector mesons in an independent quark model

International Nuclear Information System (INIS)

Barik, N.; Dash, P.C.; Panda, A.R.

1993-01-01

Leptonic decay widths of light vector mesons are calculated in a framework based on the independent quark model with a scalar-vector harmonic potential. Assuming a strong correlation to exist between the quark-antiquark momenta inside the meson, so as to make their total momentum identically zero in the center-of-mass frame of the meson, we extract the quark and antiquark momentum distribution amplitudes from the bound quark eigenmode. Using the model parameters determined from earlier studies, we arrive at the leptonic decay widths of (ρ,ω,φ) as (6.26 keV, 0.67 keV, 1.58 keV) which are in very good agreement with the respective experimental data (6.77±0.32 keV, 0.6±0.02 keV, 1.37±0.05 keV)

Generalization of the quark rearrangement model

International Nuclear Information System (INIS)

Fields, T.; Chen, C.K.

1976-01-01

An extension and generalization of the quark rearrangement model of baryon annihilation is described which can be applied to all annihilation reactions and which incorporates some of the features of the highly successful quark parton model. Some p anti-p interactions are discussed

Charmonium suppression in a quark exchange model

International Nuclear Information System (INIS)

Martins, K.

1995-01-01

A diagrammatic approach to quark exchange processes in meson-meson scattering is applied to the case of inelastic reactions of the type (Q anti Q)+(q anti q)→(Q anti q)+(q anti Q), where Q and q refer to heavy and light quarks, respectively. This string-flip process is discussed as a microscopic mechanism for charmonium dissociation (absorption) in hadronic matter. The cross section for the reaction J/ψ+π→D+ anti D is calculated using a potential model. The behavior of a formed charmonium state in hadronic matter are discussed and consequences for ultrarelativistic hadron-nucleus and nucleus-nucleus collisions are discussed. (orig.)

Hadron matrix elements of quark operators in the relativistic quark model

Energy Technology Data Exchange (ETDEWEB)

Bando, Masako; Toya, Mihoko [Kyoto Univ. (Japan). Dept. of Physics; Sugimoto, Hiroshi

1979-07-01

General formulae for evaluating matrix elements of two- and four-quark operators sandwiched by one-hadron states are presented on the basis of the relativistic quark model. Observed hadronic quantities are expressed in terms of those matrix elements of two- and four-quark operators. One observes various type of relativistic expression for the matrix elements which in the non-relativistic case reduce to simple expression of the so-called ''the wave function at the origin /sup +/psi(0)/sup +/''.

Quark compound bag (QCB) model and nucleon-nucleon interaction

International Nuclear Information System (INIS)

Simonov, Yu.A.

1983-01-01

Quark degrees of freedom are treated in the NN system in the framework of the QCB model. The resulting QCB potential is in agreement with experimental data. P-matrix analysis inherent to the QCB model is discussed in detail. Applications of the QCB model are given including the weak NN interaction

Heavy baryons in the relativistic quark model

International Nuclear Information System (INIS)

Ebert, D.; Faustov, R.N.; Galkin, V.O.; Martynenko, A.P.; Saleev, V.A.

1996-07-01

In the framework of the relativistic quasipotential quark model the mass spectrum of baryons with two heavy quarks is calculated. The quasipotentials for interactions of two quarks and of a quark with a scalar and axial vector diquark are evaluated. The bound state masses of baryons with J P =1/2 + , 3/2 + are computed. (orig.)

Nucleon-nucleon forces in the quark compound bag model and few-nucleon systems

International Nuclear Information System (INIS)

Kalashnikova, Yu.S.; Narodetskij, I.M.

1984-01-01

Role of quark-gluon degrees of freedom is discussed in nucleon-nucleon scattering at low and intermediate energies. It is shown that the existence of six-quark hags fixes the form of NN potential at small distances, which leads to the P-matrix satisfying the criterion of Jaffe and Low. The dynamical model of three-nucleon system is discussed taking into accoint the contribution of six-quark bags

Quark condensates in nuclear matter in the global color symmetry model of QCD

International Nuclear Information System (INIS)

Liu Yuxin; Gao Dongfeng; Guo Hua

2003-01-01

With the global color symmetry model being extended to finite chemical potential, we study the density dependence of the local and nonlocal scalar quark condensates in nuclear matter. The calculated results indicate that the quark condensates increase smoothly with the increasing of nuclear matter density before the critical value (about 12ρ 0 ) is reached. It also manifests that the chiral symmetry is restored suddenly as the density of nuclear matter reaches its critical value. Meanwhile, the nonlocal quark condensate in nuclear matter changes nonmonotonously against the space-time distance among the quarks

A phenomenological and approximately flavour independent potential for quark-antiquark system

International Nuclear Information System (INIS)

Song Xiaotong.

1988-08-01

We proposed a phenomenological and flavour independent potential for quark-antiquark systems with equal or unequal masses. The potential has a Lorentz vector term motivated by empirical formula of leptonic width of vector meson at short distances and a Lorentz scalar part inspired by the result from lattice QCD responsible for quark confinement at large distances. Using this potential we calculated the energy levels, leptonic widths, radiative transition rates and hadronic decay rates of the (uu-bar), (dd-bar), (ss-bar), (cc-bar), (bb-bar) and (tt-bar) systems. The fine and hyperfine splittings of light and heavy quark-antiquark systems are also calculated. Most results agree fairly well with the experiment. (author). 46 refs, 5 figs, 13 tabs

Hyperon-nucleon interaction in the quark cluster model

International Nuclear Information System (INIS)

Straub, U.; Zhang Zongye; Braeuer, K.; Faessler, A.; Khadkikar, S.B.; Luebeck, G.

1988-01-01

The lambda-nucleon and sigma-nucleon interaction is described in the nonrelativistic quark cluster model. The SU(3) flavor symmetry breaking due to the different quark masses is taken into account, i.e. different wavefunctions for the light (up, down) and heavy (strange) quarks are used in flavor and orbital space. The six-quark wavefunction is fully antisymmetrized. The model hamiltonian contains gluon exchange, pseudoscalar meson exchange and a phenomenological σ-meson exchange. The six-quark scattering problem is solved within the resonating group method. The experimental lambda-nucleon and sigma-nucleon cross sections are well reproduced. (orig.)

Modern status of quark bag model

International Nuclear Information System (INIS)

Bogolyubov, P.N.; Dorokhov, A.E.

1987-01-01

A review contains a modern status of the bag model - a composite quark model of hadrons. The idea of quasi-independent quarks moving in a finite closed region of space is a basic feature of the model. Dubna's formulation of the model and its different versions (MIT, chiral model and others) are given in detail. The role of symmetric and physical principles of the model is underlined, a critical review of mass formulas is given, the relation of the bag model and the soliton-like models (in particular with the Skyrme model) is considered

On one pion exchange potential with quark exchange in the resonating group method

International Nuclear Information System (INIS)

Braeuer, K.; Faessler, A.; Fernandez, F.; Shimizu, K.

1985-01-01

The effect of quark exchange between different nucleons on the one pion exchange potential is studied in the framework of the resonating group method. The calculated phase shifts including the one pion exchange potential with quark exchange in addition to the one gluon plus sigma meson exchange are shown to be consistent with experiments. Especially the p-wave phase shifts are improved by taking into account the quark exchange on the one pion exchange potential. (orig.)

Quark confinement and the quark model

International Nuclear Information System (INIS)

Kuti, J.

1977-01-01

The CERN-JINR School of Physics is meant to give young experimental physicists and introduction to the theoretical aspects of recent advances in elementary particle physics. The purpose of the lectures contained in this paper is to discuss recent work on the quark model and its applications to hadron spectroscopy and some high-energy phenomena. (Auth.)

Wave-particle duality in a quark model

International Nuclear Information System (INIS)

Gudder, S.P.

1984-01-01

A quark model based on finite-dimensional quantum mechanics is presented. Observables associated with color, flavor, charge, and spin are considered. Using these observables, quark and baryon Hamiltonians are constructed. Wave-particle dualities in this model are pointed out. (Auth.)

NN interaction from bag-model quark interchange

Energy Technology Data Exchange (ETDEWEB)

Bakker, B.L.G.; Bozoian, M.; Maslow, J.N.; Weber, H.J.

1982-03-01

A partial-wave helicity-state analysis of elastic nucleon-nucleon scattering is carried out in momentum space. Its basis is a one- and two-boson exchange amplitude from a bag-model quark interchange mechanism. The resulting phase shifts and bound-state parameters of the deuteron are compared with other meson theoretic potentials and data up to laboratory energies of approx.350 MeV.

NN interaction from bag-model quark interchange

International Nuclear Information System (INIS)

Bakker, B.L.G.; Bozoian, M.; Maslow, J.N.; Weber, H.J.

1982-01-01

A partial-wave helicity-state analysis of elastic nucleon-nucleon scattering is carried out in momentum space. Its basis is a one- and two-boson exchange amplitude from a bag-model quark interchange mechanism. The resulting phase shifts and bound-state parameters of the deuteron are compared with other meson theoretic potentials and data up to laboratory energies of approx.350 MeV

A variational approach to chiral quark models

International Nuclear Information System (INIS)

Futami, Yasuhiko; Odajima, Yasuhiko; Suzuki, Akira.

1987-01-01

A variational approach is applied to a chiral quark model to test the validity of the perturbative treatment of the pion-quark interaction based on the chiral symmetry principle. It is indispensably related to the chiral symmetry breaking radius if the pion-quark interaction can be regarded as a perturbation. (author)

Quark compound Bag model for NN scattering up to 1 GeV

International Nuclear Information System (INIS)

Fasano, C.; Lee, T.S.H.

1987-01-01

A Quark Compound Bag model has been constructed to describe NN s-wave scattering up to 1 GeV. The model contains a vertex interaction H/sub D/leftrightarrow/NN/ for describing the excitation of a confined six-quark Bag state, and a meson-exchange interaction obtained from modifying the phenomenological core of the Paris potential. Explicit formalisms and numerical results are presented to reveal the role of the Bag excitation mechanism in determining the relative wave function, P- and S-matrix of NN scattering. We explore the merit as well as the shortcoming of the Quark Compound Bag model developed by the ITEP group. It is shown that the parameters of the vertex interaction H/sub D/leftrightarrow/NN/ can be more rigorously determined from the data if the notation of the Chiral/Cloudy Bag model is used to allow the presence of the background meson-exchange interaction inside Bag excitation region. The application of the model in the study of quark degrees of freedom in nuclei is discussed. 41 refs., 6 figs., 3 tabs

Top quark properties at ATLAS

CERN Document Server

Dilip, Jana

2008-01-01

The ATLAS potential for the study of the top quark properties and physics beyond the Standard Model in the top quark sector, is described. The measurements of the top quark charge, the spin and spin correlations, the Standard Model decay (t-> bW), rare top quark decays associated to flavour changing neutral currents (t-> qX with X = gluon, Z, photon) and ttbar resonances are discussed. The sensitivity of the ATLAS experiment is estimated for an expected luminosity of 1fb-1 at the LHC. The full simulation of the ATLAS detector is used. For the Standard Model measurements the expected precision is presented. For the tests of physics beyond the Standard Model, the 5 sigma discovery potential (in the presence of a signal) and the 95% Confidence Level (CL) limit (in the absence of a signal) are given.

Electromagnetic properties of baryons in the constituent quark model

International Nuclear Information System (INIS)

Warns, M.

1992-01-01

The electromagnetic properties of baryons are investigated in the framework of a relativized quark model. The model includes beyond the usual single quark transition ansatz relativistic effects due to the strong interaction and confinement forces between the quarks. Furthermore the center-of-mass motion of the three-quark system is separated off in a Lorentz-invariant way. All relativistic correction terms are obtained by expanding the corresponding relativistic expressions in powers of the quark velocity. In this way recoil effects on the electromagnetic interaction between the photon and the baryon could be explicitly studied. Using the harmonic oscillator wavefunctions with the configuration mixing from the Isgur-Karl model, the form factors of the nucleon and the electromagnetic transition amplitudes both for longitudinally and transversely polarized photons are calculated for the most important baryon resonances. An extension to baryons involving strange quarks is also considered. Comparisons are made with the results of the nonrelativistic quark model and with some other approaches. (orig.)

Gauging Non-local Quark Models

International Nuclear Information System (INIS)

Broniowski, W.

1999-09-01

The gauge effective quark model with non-local interactions is considered. It is shown how this approach regularize the theory in such a way that the anomalies are preserved and charges are properly quantized. With non-local interactions the effective action is finite to all orders in the loop expansion and there is no need to introduce the quark momentum cut-off parameter

Four-quark bound states

International Nuclear Information System (INIS)

Zouzou, S.

1986-01-01

In the framework of simple non-relativistic potential models, we examine the system consisting of two quarks and two antiquarks with equal or unequal masses. We search for possible bound states below the threshold for the spontaneous dissociation into two mesons. We solve the four body problem by empirical or systematic variational methods and we include the virtual meson-meson components of the wave function. With standard two-body potentials, there is no proliferation of multiquarks. With unequal quark masses, we obtain however exotic (anti Qanti Qqq) bound states with a baryonic antidiquark-quark-quark structure very analogous to the heavy flavoured (Q'qq) baryons. (orig.)

Gauge invariance and the quark-antiquark static potential

International Nuclear Information System (INIS)

Cahill, K.; Stump, D.R.

1979-01-01

We calculate the quark-antiquark static potential to order g 4 in temporal-gauge quantum chromodynamics by constructing a suitably general family of gauge-invariant qq-bar states and then selecting the one whose energy is minimal for a given qq-bar separation r. Our results agree with those of conventional perturbation theory. We study various ways in which quark confinement might arise from nonperturbative effects related to the Gribov ambiguity. We find that the presence of long-range gauge fields can change the asymptotic behavior of the Coulomb Green's function from r -1 to r/sup -1/2/. We illustrate this possibility by a simple example. After making some simplifying assumptions, we obtain a minimally confining potential V (r) that rises logarithmically for large r

Nucleon-nucleon interaction and the quark model

International Nuclear Information System (INIS)

Faessler, A.

1985-01-01

The NN phase shifts are calculated using the quark model with a QCD inspired quark-quark force. The short range part of the NN force is given by quark and gluon exchange. The long range part is described by π and σ-meson exchange. The data fitted in the model are five values connected with three quarks only: the nucleon mass, the Δ mass, the root mean square radius of the charge distribution of the proton including the pion cloud, the π-N and the σ-N coupling constant at zero momentum transfer. The 1 S and 3 S phase shifts are nicely reproduced. The short range repulsion is decisively influenced by the node in the [42] r relative wave function. Very important is the colour magnetic quark-quark force which enlarges the [42] r admixture. In the OBEP's the short range repulsion is connected with the exchange of the ω-meson. But to reproduce the short range repulsion one had to blow up the ω-N coupling constant by a factor 2 to 3 compared to flavour SU 3 . With quark and gluon exchange the best fit to the ω-N coupling constant lies close to the SU 3 flavour value. This fact strongly supports the notion that the real nature of the short range repulsion of the NN interaction have been found

Quark matter in a chiral chromodielectric model

International Nuclear Information System (INIS)

Broniowski, W.; Kutschera, M.; Cibej, M.; Rosina, M.

1989-03-01

Zero and finite temperature quark matter is studied in a chiral chromodielectric model with quark, meson and chromodielectric degrees of freedom. Mean field approximation is used. Two cases are considered: two-flavor and three-flavor quark matter. It is found that at sufficiently low densities and temperatures the system is in a chirally broken phase, with quarks acquiring effective masses of the order of 100 MeV. At higher densities and temperatures a chiral phase transition occurs and the quarks become massless. A comparison to traditional nuclear physics suggests that the chirally broken phase with massive quark gas may be the ground state of matter at densities of the order of a few nuclear saturation densities. 24 refs., 5 figs. (author)

Quark matter inside neutron stars in an effective chiral model

International Nuclear Information System (INIS)

Kotlorz, A.; Kutschera, M.

1994-02-01

An effective chiral model which describes properties of a single baryon predicts that the quark matter relevant to neutron stars, close to the deconfinement density, is in a chirally broken phase. We find the SU(2) model that pion-condensed up and down quark matter is preferred energetically at neutron star densities. It exhibits spin ordering and can posses a permanent magnetization. The equation of state of quark matter with chiral condensate is very well approximated by bag model equation of the state with suitably chosen parameters. We study quark cores inside neutron stars in this model using realistic nucleon equations of state. The biggest quark core corresponds to the second order phase transition to quark matter. Magnetic moment of the pion-condensed quark core is calculated. (author). 19 refs, 10 refs, 1 tab

The Model of Complex Structure of Quark

Science.gov (United States)

Liu, Rongwu

2017-09-01

In Quantum Chromodynamics, quark is known as a kind of point-like fundamental particle which carries mass, charge, color, and flavor, strong interaction takes place between quarks by means of exchanging intermediate particles-gluons. An important consequence of this theory is that, strong interaction is a kind of short-range force, and it has the features of ``asymptotic freedom'' and ``quark confinement''. In order to reveal the nature of strong interaction, the ``bag'' model of vacuum and the ``string'' model of string theory were proposed in the context of quantum mechanics, but neither of them can provide a clear interaction mechanism. This article formulates a new mechanism by proposing a model of complex structure of quark, it can be outlined as follows: (1) Quark (as well as electron, etc) is a kind of complex structure, it is composed of fundamental particle (fundamental matter mass and electricity) and fundamental volume field (fundamental matter flavor and color) which exists in the form of limited volume; fundamental particle lies in the center of fundamental volume field, forms the ``nucleus'' of quark. (2) As static electric force, the color field force between quarks has classical form, it is proportional to the square of the color quantity carried by each color field, and inversely proportional to the area of cross section of overlapping color fields which is along force direction, it has the properties of overlap, saturation, non-central, and constant. (3) Any volume field undergoes deformation when interacting with other volume field, the deformation force follows Hooke's law. (4) The phenomena of ``asymptotic freedom'' and ``quark confinement'' are the result of color field force and deformation force.

New quark model with weak triplet

International Nuclear Information System (INIS)

Suzuki, T.; Hori, S.; Yamada, E.; Yamanashi, K.; Abe, Y.

1976-01-01

We propose a new anomaly-free quark model with weak isotriplets for quarks. The ΔI=1/2 enhancement may be accounted for, the requirement of Golowich and Holstein being satisfied. There arises a mixing of left-handed charmed quarks with left-handed nucleonic ones - such mixing essentially gives an overall explanation of neutral-current effects, inclusive y distribution, the ratio sigma/sup T/(anti νd)/sigma/sup T/(νd), and copious dilepton events in ν and anti ν reactions

Color interaction of quarks and magnetic moments of baryons in the bag model

International Nuclear Information System (INIS)

Krivoruchenko, M.I.

1984-01-01

The purpose of the present study is to saccount for the quark interaction in the bag model by calculating corrections to the baryon magnetic moments related to the colour interaction of quarks. The quark-in-bag wave function to that holds the confinement linear boundary condition has been found in the first order for the external magnetic field. Corrections to the baryon magnetic moments are calculated. They are related to energy variations of colour electric and colour magnetic fields. Numerical data are presented and the structure of corrections in the SU-3 group approximation is discussed. The results are compared with the potential model and the experiment

Quark-diquark approximation of the three-quark structure of a nucleon and the NN phase shifts

International Nuclear Information System (INIS)

Efimov, G.V.; Ivanov, M.A.

1988-01-01

The quark-diquark approximations of the three-quark structure of a nucleon are considered in the framework of the quark confinement model (QCM) based on definite concepts of the hadronization and quark confinement. The static nucleon characteristics (magnetic moments, ratio G A /G V and strong meson-nucleon coupling constants) are calculated. The behaviour of the electromagnetic and strong nucleon form factors is obtained at the low energy (0≤0 2 =-q 2 2 , where q is a transfer momentum). The one-boson exchange potential is constructed and the NN-phase-shifts are computed. Our results are compared with experiment and the Bonn potential model. 45 refs.; 7 figs.; 3 tabs

Phenomenological aspects of nonrelativistic potential models

International Nuclear Information System (INIS)

Lucha, W.; Schoeberl, F.F.

1989-01-01

This review reports on the description of hardrons as bound states of quarks by nonrelativistic potential models. It contains a brief sketch of the way in which information on the form of the inter-quark potential may be gained from quantum chromodynamics, proofs of some general theorems related to the potential-model approach, a discussion of the significance of the treatment of bound states consisting of relativistically-moving constituents by the nonrelativistic Schroedinger formalism, as well as a brief survey of the motivations for the various proposed potential models. Finally, it illustrates the application of the developed theoretical framework at a few selected examples. 60 refs., 8 figs., 17 tabs. (Authors)

Diagrammatic group theory in quark models

International Nuclear Information System (INIS)

Canning, G.P.

1977-05-01

A simple and systematic diagrammatic method is presented for calculating the numerical factors arising from group theory in quark models: dimensions, casimir invariants, vector coupling coefficients and especially recoupling coefficients. Some coefficients for the coupling of 3 quark objects are listed for SU(n) and SU(2n). (orig.) [de

Vector-like quarks at the origin of light quark masses and mixing

Energy Technology Data Exchange (ETDEWEB)

Botella, Francisco J. [Universitat de Valencia-CSIC, Departament de Fisica Teorica and IFIC, Burjassot (Spain); Branco, G.C.; Nebot, Miguel; Rebelo, M.N.; Silva-Marcos, J.I. [Universidade de Lisboa, Departamento de Fisica and Centro de Fisica Teorica de Particulas (CFTP), Instituto Superior Tecnico (IST), Lisbon (Portugal)

2017-06-15

We show how a novel fine-tuning problem present in the Standard Model can be solved through the introduction of a Z{sub 6} flavour symmetry, together with three Q = -1/3 quarks, three Q = 2/3 quarks, as well as a complex singlet scalar. The Z{sub 6} symmetry is extended to the additional fields and it is an exact symmetry of the Lagrangian, only softly broken in the scalar potential, in order to avoid the domain-wall problem. Specific examples are given and a phenomenological analysis of the main features of the model is presented. It is shown that even for vector-like quarks with masses accessible at the LHC, one can have realistic quark masses and mixing, while respecting the strict constraints on processes arising from flavour changing neutral currents. The vector-like quark decay channels are also described. (orig.)

Relativistic form factors for hadrons with quark-model wave functions

International Nuclear Information System (INIS)

Stanley, D.P.; Robson, D.

1982-01-01

The relationship between relativistic form factors and quark-potential-model wave functions is examined using an improved version of an approach by Licht and Pagnamenta. Lorentz-contraction effects are expressed in terms of an effective hadron mass which varies as the square root of the number of quark constituents. The effective mass is calculated using the rest-frame wave functions from the mean-square momentum along the direction of the momentum transfer. Applications with the parameter-free approach are made to the elastic form factors of the pion, proton, and neutron using a Hamiltonian which simultaneously describes mesons and baryons. A comparison of the calculated radii for pions and kaons suggests that the measured kaon radius should be slightly smaller than the corresponding pion radius. The large negative squared charge radius for the neutron is partially explained via the quark model but a full description requires the inclusion of a small component of a pion ''cloud'' configuration. The problematic connection between the sizes of hadrons deduced from form factors and the ''measured'' values of average transverse momenta is reconciled in the present model

Second quantization approach to composite hadron interactions in quark models

International Nuclear Information System (INIS)

Hadjimichef, D.; Krein, G.; Veiga, J.S. da; Szpigel, S.

1995-11-01

Starting from the Fock space representation of hadron bound states in a quark model, a change of representation is implemented by a unitary transformation such that the composite hadrons are redescribed by elementary-particle field operators. Application of the unitary transformation to the microscopic quark Hamiltonian gives rise to effective hadron-hadron, hadron-quark, and quark-quark Hamiltonians. An effective baryon Hamiltonian is derived using a simple quark model. The baryon Hamiltonian is free of the post-prior discrepancy which usually plagues composite-particle effective interactions. (author). 13 refs., 1 fig

Bd0-bar Bd0 mixing and the prediction of the top-quark mass in an independent particle potential model

International Nuclear Information System (INIS)

Barik, N.; Das, P.; Panda, A.R.; Roy, K.C.

1993-01-01

Considering B d 0 -bar B d 0 mixing in a potential model of independent quarks by taking the effective interaction Hamiltonian of the standard Salam-Weinberg-Glashow model and subsequently diagonalizing the corresponding mass matrix with respect to B d 0 and bar B d 0 states, we obtain an expression for the mass difference ΔM Bd 0 in terms of the t-quark mass m t . Using the recent observation of the mixing parameter x d =0.72±0.15 by the ARGUS Collaboration, we predict the lower bound on the top-quark mass as m t ≥149 GeV. Further, a consideration of experimental mass difference ΔM Bd 0 =(4.0±0.8)x10 -13 GeV also leads to m t =167 -17 +16 GeV which is in agreement with the recent experimental bound as well as other theoretical predictions. However, such a prediction of m t that utilizes the experimental value of the CKM matrix element |V td | may not appear convincing in view of the large uncertainties in the measurement of |V td | so far reported. Therefore using the range of m t values within its bounds predicted from other independent works, we make a reasonable estimation of |V td |

Dihadron fragmentation functions in the quark-jet model: Transversely polarized quarks

Science.gov (United States)

Matevosyan, Hrayr H.; Kotzinian, Aram; Thomas, Anthony W.

2018-01-01

Within the most recent extension of the quark-jet hadronization framework, we explore the transverse-polarization-dependent dihadron fragmentation functions (DiFFs) H1∢ and H1⊥ of a quark into π+π- pairs. Monte Carlo (MC) simulations are employed to model polarized quark hadronization and calculate the corresponding number densities. These, in turn, are used to extract the Fourier cosine moments of the DiFFs H1∢ and H1⊥. A notable finding is that there are previously unnoticed apparent discrepancies between the definitions of the so-called interference DiFF (IFF) H1∢ , entering the cross sections for two-hadron semi-inclusive electroproduction, and those involved in the production of two pairs of hadrons from back-to-back jets in electron-positron annihilation. This manuscript completes the studies of all four leading-twist DiFFs for unpolarized hadron pairs within the quark-jet framework, following our previous work on the helicity-dependent DiFF G1⊥.

Chiral dynamics of baryons in the perturbative chiral quark model

Energy Technology Data Exchange (ETDEWEB)

Pumsa-ard, K.

2006-07-01

In this work we develop and apply variants of a perturbative chiral quark model (PCQM) to the study of baryonic properties dominantly in the low-energy region. In a first step we consider a noncovariant form of the PCQM, where confinement is modelled by a static, effective potential and chiral corrections are treated to second order, in line with similar chiral quark models. We apply the PCQM to the study of the electromagnetic form factors of the baryon octet. We focus in particular on the low-energy observables such as the magnetic moments, the charge and magnetic radii. In addition, the electromagnetic N-delta transition is also studied in the framework of the PCQM. In the chiral loop calculations we consider a quark propagator, which is restricted to the quark ground state, or in hadronic language to nucleon and delta intermediate states, for simplicity. We furthermore include the low-lying excited states to the quark propagator. In particular, the charge radius of the neutron and the transverse helicity amplitudes of the N-delta transition are considerably improved by this additional effect. In a next step we develop a manifestly Lorentz covariant version of the PCQM, where in addition higher order chiral corrections are included. The full chiral quark Lagrangian is motivated by and in analogy to the one of Chiral Perturbation Theory (ChPT). This Lagrangian contains a set of low energy constants (LECs), which are parameters encoding short distance effects and heavy degrees of freedom. We evaluate the chiral Lagrangian to order O(p{sup 4}) and to one loop to generate the dressing of the bare quark operators by pseudoscalar mesons. In addition we include the vector meson degrees of freedom in our study. Projection of the dressed quark operators on the baryonic level serves to calculate the relevant matrix elements. In a first application of this scheme, we resort to a parameterization of the valence quark form factors in the electromagnetic sector. Constraints

Effective potential models for hadrons

International Nuclear Information System (INIS)

Lucha, W.

1995-12-01

The aim of these lectures is to give a self-contained introduction to nonrelativistic potential models, to their formulation as well as to their possible applications. At the price of some lack of (in a mathematical sense) rigorous derivations, we try to give a feeling and understanding for the simplest conceivable method to extract the explicit form of the forces acting between quarks from the interplay between experimental observations and theoretical considerations. According to this spirit, we demonstrate, in detail, how to obtain the underlying Hamiltonian and how to determine the Lorentz structure of the quark-(anti-)quark interaction potential from well-established experimental facts. (author)

Diquark condensation and the quark-quark interaction

International Nuclear Information System (INIS)

Bloch, J. C. R.; Roberts, C. D.; Schmidt, S. M.

1999-01-01

We employ a bispinor gap equation to study superfluidity at nonzero chemical potential, μ≠0, in two- and three-color QCD, exploring the gap's sensitivity to the nature of the quark-quark interaction. The two-color theory, QC 2 D, is an excellent exemplar; the order of truncation of the quark-quark scattering kernel K has no qualitative impact, which allows a straightforward elucidation of the effects of μ when the coupling is strong. In the three-color theory the rainbow-ladder truncation admits diquark bound states, a defect that is eliminated by an improvement of K. The corrected gap equation describes a superfluid phase that is semiquantitatively similar to that obtained using the rainbow truncation. A model study suggests that the width of the superfluid gap and the transition point in QC 2 D provide reliable quantitative estimates of those quantities in QCD. (c) 1999 The American Physical Society

Strangeness content and structure function of the nucleon in a statistical quark model

CERN Document Server

Trevisan, L A; Tomio, L

1999-01-01

The strangeness content of the nucleon is determined from a statistical model using confined quark levels, and is shown to have a good agreement with the corresponding values extracted from experimental data. The quark levels are generated in a Dirac equation that uses a linear confining potential (scalar plus vector). With the requirement that the result for the Gottfried sum rule violation, given by the new muon collaboration (NMC), is well reproduced, we also obtain the difference between the structure functions of the proton and neutron, and the corresponding sea quark contributions. (27 refs).

Quark Model in the Quantum Mechanics Curriculum.

Science.gov (United States)

Hussar, P. E.; And Others

1980-01-01

This article discusses in detail the totally symmetric three-quark karyonic wave functions. The two-body mesonic states are also discussed. A brief review of the experimental efforts to identify the quark model multiplets is given. (Author/SK)

Kaon quark distribution functions in the chiral constituent quark model

Science.gov (United States)

Watanabe, Akira; Sawada, Takahiro; Kao, Chung Wen

2018-04-01

We investigate the valence u and s ¯ quark distribution functions of the K+ meson, vK (u )(x ,Q2) and vK (s ¯)(x ,Q2), in the framework of the chiral constituent quark model. We judiciously choose the bare distributions at the initial scale to generate the dressed distributions at the higher scale, considering the meson cloud effects and the QCD evolution, which agree with the phenomenologically satisfactory valence quark distribution of the pion and the experimental data of the ratio vK (u )(x ,Q2)/vπ (u )(x ,Q2) . We show how the meson cloud effects affect the bare distribution functions in detail. We find that a smaller S U (3 ) flavor symmetry breaking effect is observed, compared with results of the preceding studies based on other approaches.

Vector-like bottom quarks in composite Higgs models

DEFF Research Database (Denmark)

Gillioz, M.; Grober, R.; Kapuvari, A.

2014-01-01

Like many other models, Composite Higgs Models feature the existence of heavy vector-like quarks. Mixing effects between the Standard Model fields and the heavy states, which can be quite large in case of the top quark, imply deviations from the SM. In this work we investigate the possibility of ...

Various decays of some hadronic systems in constituent quark models

International Nuclear Information System (INIS)

Bonnaz, R.

2001-09-01

The topic of this study is the decay of mesons in constituent quark models. Those models as well as the various quark-antiquark interaction potentials are presented. Strong decay of a meson into two or three mesons is studied in the second part. The original 3 P o model is presented as well as the research of a vertex function γ(p) depending on the momentum for the created qq-bar pair. We show that a function γ(p) of constant+Gaussian type is superior than the constant usually used. The second part is dedicated to electromagnetic transitions studied through the emission of a real or a virtual photon. In the case of real photon emission, the different approximations found in the literature are reviewed and compared to the formalism going beyond the long wave length approximation. Mixing angles are tested for some mesons. In the case of virtual photon, the expression of decay width obtained by van Royen and Weisskopf is re-demonstrated and then improved by taking into account the quark momentum distribution inside the meson. An electromagnetic dressing of quarks is introduced that improves the results. All along this study, wave functions of various sophistication degrees are used. The results of decay widths are compared to a large bulk of experimental data. (author)

Quark-antiquark condensates in the hadronic phase

International Nuclear Information System (INIS)

Tawfik, A.; Toublan, D.

2005-01-01

We use a hadron resonance gas model to calculate the quark-antiquark condensates for light (up and down) and strange quark flavors at finite temperatures and chemical potentials. At zero chemical potentials, we find that at the temperature where the light quark-antiquark condensates entirely vanish the strange quark-antiquark condensate still keeps a relatively large fraction of its value in the vacuum. This is in agreement with results obtained in lattice simulations and in chiral perturbation theory at finite temperature and zero chemical potentials. Furthermore, we find that this effect slowly disappears at larger baryon chemical potential. These results might have significant consequences for our understanding of QCD at finite temperatures and chemical potentials. Concretely, our results imply that there might be a domain of temperatures where chiral symmetry is restored for light quarks, but still broken for strange quark that persists at small chemical potentials. This might have practical consequences for heavy ion collision experiments

Weak leptonic decay of light and heavy pseudoscalar mesons in an independent quark model

International Nuclear Information System (INIS)

Barik, N.; Dash, P.C.

1993-01-01

Weak leptonic decays of light and heavy pseudoscalar mesons are studied in a field-theoretic framework based on the independent quark model with a scalar-vector harmonic potential. Defining the quark-antiquark momentum distribution amplitude obtainable from the bound quark eigenmodes of the model with the assumption of a strong correlation between quark-antiquark momenta inside the decaying meson in its rest frame, we derive the partial decay width with correct kinematical factors from which we extract an expression for the pseudoscalar decay constants f M . Using the model parameters determined from earlier studies in the light-flavor sector and heavy-quark masses m c and m b from the hyperfine splitting of (D * ,D) and (B * ,B), we calculate the pseudoscalar decay constants. We find that while (f π ,f K )≡(138,157 MeV); (f D ,f Ds )≡(161,205 MeV), (f B ,f Bs )≡(122,154 MeV), and f Bc =221 MeV. We also obtain the partial decay widths and branching ratios for some kinematically allowed weak leptonic decay processes

A semiclassical model for quark jet fragmentation

International Nuclear Information System (INIS)

Andersson, B.; Gustafson, G.; Peterson, C.

1979-01-01

A semiclassical model is presented for the way the energy of a fast quark is transformed into observable hadrons. It reproduces the features of 1+1 dimensional QED (the Schwinger model) concerning a flat rapidity distribution in the central region. It also reproduces results from phenomenological considerations, which, based upon scaling, predict that meson formation in the fragmentation region can be described by an iterative scheme, implying a set of coupled integral equations. In particular the model predicts that the probability to find a meson containing the leading quark is independent of the Feynman scaling variable z. The iterative structure corresponds to a Brownian motion with relevance both to the cofinement problems and to the distribution of mass in the quark jet. (orig.) [de

Quarks in hadrons and nuclei and electromagnetic probes

International Nuclear Information System (INIS)

Faessler, Amand

1995-01-01

Deuteron properties and nuclear magnetic moments are studied in the non-relativistic quark cluster model. The quark cluster model is modified to include chiral symmetry. This reduces the number of parameters. The σ meson is exchanged between quarks and not as in earlier versions between nucleons. The charge monopole, quadrupole and magnetic-dipole form factors and the tensor polarization of the deuteron in this microscopic meson-quark cluster model are calculated. The deuteron wave function is derived from a microscopic 6-quark Hamiltonian which, in addition to a quadratic confinement potential, includes the one-pion and the one-gluon exchange potentials between quarks. The electromagnetic current operators are constructed on the quark level, i.e., the photon is coupled directly to the quarks. Aside from the one-body impulse current, pionic and gluonic exchange current corrections are included. Due to the Pauli principle on the quark level, new quark interchange terms arise in the one-body and two-body current matrix elements, that are not present on the nucleon level. While these additional quark exchange currents are small for low momentum transfers, we find that they appreciably influence the electromagnetic structure of the deuteron beyond a momentum transfer of q = 5fm -1 . (author)

Orbital angular momentum parton distributions in quark models

International Nuclear Information System (INIS)

Scopetta, S.; Vento, V.

2000-01-01

At the low energy, hadronic, scale we calculate Orbital Angular Momentum (OAM) twist-two parton distributions for the relativistic MIT bag model and for nonrelativistic quark models. We reach the scale of the data by leading order evolution in perturbative QCD. We confirm that the contribution of quarks and gluons OAM to the nucleon spin grows with Q 2 , and it can be relevant at the experimental scale, even if it is negligible at the hadronic scale, irrespective of the model used. The sign and shape of the quark OAM distribution at high Q 2 may depend strongly on the relative size of the OAM and spin distributions at the hadronic scale. Sizeable quark OAM distributions at the hadronic scale, as proposed by several authors, can produce the dominant contribution to the nucleon spin at high Q 2 . (author)

Beyond Standard Model searches with top quarks at ATLAS

International Nuclear Information System (INIS)

Chevalier, F.

2008-01-01

At the Lhc, the top quark is expected to provide a huge and clean signal. With about eight millions of expected top pairs and three millions of single top events produced per year in the low luminosity runs, and with a low level of backgrounds, the Lhc will open a new opportunity for precision measurements of the top quark properties and for exotic topology searches involving top quarks. As the ATLAS discovery potential on new physics with top quarks is being assessed with many analyses, this paper focuses on two particular topics: heavy neutral resonance and charged Higgs boson searches with top quarks. The analyses and the ATLAS expectations are described.

Single-particle spin-orbit potentials of the LAMBDA and SIGMA hyperons based on the quark-model G-matrix

CERN Document Server

Kohno, M; Fujita, T; Nakamoto, C; Suzuki, Y

2000-01-01

Using the SU sub 6 quark-model baryon-baryon interaction which was recently developed by the Kyoto-Niigata group, we calculate N N, LAMBDA N and SIGMA N G--matrices in ordinary nuclear matter. Following the Scheerbaum's prescription, the strength of the single-particle spin-orbit potential S sub B is quantitatively discussed. The S subLAMBDA becomes small because of the cancellation between spin-orbit and anti-symmetric spin-orbit components. The short-range correlation is found to further reduce S subLAMBDA.

A relativized quark model for radiative baryon transitions

International Nuclear Information System (INIS)

Warns, M.; Schroeder, H.; Pfeil, W.; Rollnik, H.

1989-03-01

In this paper we investigate the electromagnetic form factors of baryons and their resonances using the framework of a relativized constituent quark model. Beyond the usual single-quark transition ansatz, we incorporate relativistic corrections which are well-determined by the intrinsic strong interaction and confinement forces between the quarks. Furthermore we separate off for the compound three-quark system the relativistic center-of-mass motion by an approximately Lorentz-invariant approach. In this way for the first time recoil effects could be explicitly studied. Using the harmonic oscillator wavefunctions with the configuration mixing as derived in the Isgur-Karl model, after restoring gauge invariance our relativized interaction hamiltonian can be used to calculate the transversely and longitudinally polarized photon transition form factors of the baryons. (orig.)

Quark number density and susceptibility calculation with one correction in mean field potential

International Nuclear Information System (INIS)

Singh, S. Somorendro

2016-01-01

We calculate quark number density and susceptibility of a model which has one loop correction in mean field potential. The calculation shows continuous increasing in the number density and susceptibility up to the temperature T = 0.4 GeV. Then the value of number density and susceptibility approach to the lattice result for higher value of temperature. The result indicates that the calculated values of the model fit well and the result increase the temperature to reach the lattice data with the one loop correction in the mean field potential. (author)

The heavy quark-antiquark potential from lattice and perturbative QCD

OpenAIRE

Laschka, Alexander; Kaiser, Norbert; Weise, Wolfram

2009-01-01

The heavy quark-antiquark potential in perturbative QCD is subject to ambiguities. We show how to derive a well-defined and stable short-distance potential that can be matched to results from lattice QCD simulations at intermediate distances. The static potential as well as the order 1/m potential are discussed.

The quark-gluon model for particle production processes

International Nuclear Information System (INIS)

Volkovitskij, P.E.

1983-01-01

The quark-gluon model for hadronization of strings produced in soft and hard processes is suggested. The model is based on the distribution functions of valence quarks in hadrons which have correct Regge behaviour. The simplest case is discussed in which only the longitudinal degrees of freedom are taken into account

Confinement of quarks

International Nuclear Information System (INIS)

Nambu, J.

1978-01-01

Three quark models of hadron structure, which suggest an explanation of quarks confinement mechanism in hadrons are considered. Quark classifications, quark flawors and colours, symmetry model of hadron structure based on the colour theory of strong interaction are discussed. Diagrams of colour combinations of quarks and antiquarks, exchange of gluons, binding quarks in hadron. Quark confinement models based on the field theory, string model rotating and bag model are discussed. Diagrams of the colour charge distribution explaining the phenomena of infrared ''slavery'' and ultraviolet ''freedom'' are given. The models considered explain but some quark properties, creating prerequisites for the development of the consequent theory of hadron structure

KN s-wave phase shifts in a quark model with gluon and boson exchange at the quark level

International Nuclear Information System (INIS)

Silvestre-Brac, B.; Leandri, J.

1997-01-01

The kaon-nucleon s-wave phase shifts have been calculated in a quark potential model using the resonating group method (RGM). The interquark potential includes gluon, pion and sigma exchanges. The kaon and nucleon wave functions are expanded as a sum of Gaussian functions and the Hill-Wheeler (HW) equation is solved numerically. The I=0 phase shifts present too much attraction and in the I=1 channel too much repulsion is obtained. (orig.)

Quark Loop Effects on Dressed Gluon Propagator in Framework of Global Color Symmetry Model

Institute of Scientific and Technical Information of China (English)

ZONG Hong-Shi; SUN Wei-Min

2006-01-01

Based on the global color symmetry model (GCM), a method for obtaining the quark loop effects on the dressed gluon propagator in GCM is developed. In the chiral limit, it is found that the dressed gluon propagator containing the quark loop effects in the Nambu-Goldstone and Wigner phases are quite different. In solving the quark self-energy functions in the two different phases and subsequent study of bag constant one should use the above dressed gluon propagator as input. The above approach for obtaining the current quark mass effects on the dressed gluon propagator is quite general and can also be used to calculate the chemical potential dependence of the dressed gluon propagator.

Tetraquarks in a chiral constituent-quark model

International Nuclear Information System (INIS)

Vijande, J.; Fernandez, F.; Valcarce, A.; Silvestre-Brac, B.

2004-01-01

We analyze the possibility of heavy-light tetraquark bound states by means of a chiral constituent-quark model. The study is done in a variational approach. Special attention is paid to the contribution given by the different terms of the interacting potential and also to the role played by the different color channels. We find a stable state for both qq anti c anti c and qq anti b anti b configurations. Possible decay modes of these structures are analyzed. (orig.)

Tetraquarks in a chiral constituent-quark model

Energy Technology Data Exchange (ETDEWEB)

Vijande, J.; Fernandez, F.; Valcarce, A. [Grupo de Fisica Nuclear, Universidad de Salamanca, E-37008, Salamanca (Spain); Silvestre-Brac, B. [Institut des Sciences Nucleaires, 53 Avenue des Martyrs, F-38026, Grenoble Cedex (France)

2004-03-01

We analyze the possibility of heavy-light tetraquark bound states by means of a chiral constituent-quark model. The study is done in a variational approach. Special attention is paid to the contribution given by the different terms of the interacting potential and also to the role played by the different color channels. We find a stable state for both qq anti c anti c and qq anti b anti b configurations. Possible decay modes of these structures are analyzed. (orig.)

Superconvergent gluon propagator and the quark-antiquark potential

International Nuclear Information System (INIS)

Oehme, R.; Chicago Univ., IL; Chicago Univ., IL

1989-01-01

Superconvergence of the gluon propagator, together with the asymptotically negative sign of the discontinuity, imply that the structure function has a representation which corresponds to an approximately linear quark-antiquark potential, provided the number of flavors is less than ten. For more than ten flavors, there is no indication for a linear potential within this framework. The connection with metric confinement is emphasized. Possible dipole terms are considered briefly. (orig.)

Evaluation of the spectra of baryons containing two heavy quarks in a bag model

International Nuclear Information System (INIS)

He Daheng; Qian Ke; Ding Yibing; Li Xueqian; Shen Pengnian

2004-01-01

In this work, we evaluate the mass spectra of baryons which consist of two heavy quarks and one light quark in the MIT bag model. The two heavy quarks constitute a heavy scalar or axial-vector diquark. Concretely, we calculate the spectra of vertical bar q(QQ ' )> 1/2 and vertical bar q(QQ ' )> 3/2 where Q and Q ' stand for b and/or c quarks. Especially, for vertical bar q(bc)> 1/2 there can be a mixing between vertical bar q(bc) 0 > 1/2 and vertical bar q(bc) 1 > 1/2 where the subscripts 0 and 1 refer to the spin state of the diquark (bc), the mixing is not calculable in the framework of quantum mechanics as the potential model is employed, but can be evaluated by the quantum field theory. Our numerical results indicate that the mixing is sizable

Free-quark phases in dense stars

Energy Technology Data Exchange (ETDEWEB)

Keister, B D; Kisslinger, L S [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA). Dept. of Physics

1976-08-30

The possibility is examined that superdense matter can undergo a transition to a phase of free quarks within models which assume that the quark confinement potential is screened at high densities. The results imply that a phase of pure quarks of this type is unlikely to be found in stable stellar systems although they do not preclude the possible existence of a transition region which contains quarks and neutrons in equilibrium at the center of neutron stars.

Short range part of the NN interaction: Equivalent local potentials from quark exchange kernels

International Nuclear Information System (INIS)

Suzuk, Y.; Hecht, K.T.

1983-01-01

To focus on the nature of the short range part of the NN interaction, the intrinsically nonlocal interaction among the quark constituents of colorless nucleons is converted to an equivalent local potential using resonating group kernels which can be evaluated in analytic form. The WKB approximation based on the Wigner transform of the nonlocal kernels has been used to construct the equivalent potentials without recourse to the long range part of the NN interaction. The relative importance of the various components of the exchange kernels can be examined: The results indicate the importance of the color magnetic part of the exchange kernel for the repulsive part in the (ST) = (10), (01) channels, in particular since the energy dependence of the effective local potentials seems to be set by this term. Large cancellations of color Coulombic and quark confining contributions, together with the kinetic energy and norm exchange terms, indicate that the exact nature of the equivalent local potential may be sensitive to the details of the parametrization of the underlying quark-quark interaction. The equivalent local potentials show some of the characteristics of the phenomenological short range terms of the Paris potential

Phenomenology of heavy quark systems

International Nuclear Information System (INIS)

Gilman, F.J.

1987-03-01

The spectroscopy of heavy quark systems is examined with regards to spin independent and spin dependent potentials. It is shown that a qualitative picture exists of the spin-independent forces, and that a semi-quantitative understanding exists for the spin-dependent effects. A brief review is then given of the subject of the decays of hadrons containing heavy quarks, including weak decays at the quark level, and describing corrections to the spectator model

Electromagnetic properties of light and heavy baryons in the relativistic quark model

International Nuclear Information System (INIS)

Nicmorus Marinescu, Diana

2007-01-01

One of the main challenges of nowadays low-energy physics remains the description of the internal structure of hadrons, strongly connected to the electromagnetic properties of matter. In this vein, the success of the relativistic quark model in the analysis of the hadron structure constitutes a solid motivation for the study carried out throughout this work. The relativistic quark model is extended to the investigation of static electromagnetic properties of both heavy and light baryons. The bare contributions to the magnetic moments of the single-, double- and triple-heavy baryons are calculated. Moreover, the relativistic quark model allows the study of the electromagnetic properties of the light baryon octet incorporating meson cloud contributions in a perturbative manner. The long disputed values of the multipole ratios E2/M1 and C2/M1 and the electromagnetic form factors of the N→Δγ transition are successfully reproduced. The relativistic quark model can be viewed as a quantum field theory approach based on a phenomenological Lagrangian coupling light and heavy baryons to their constituent quarks. In our approach the baryon is a composite object of three constituent quarks, at least in leading order. The effective interaction Lagrangian is written in terms of baryon and constituent quark fields. The effective action preserves Lorentz covariance and gauge invariance. The main ingredients of the model are already introduced at the level of the interaction Lagrangian: the three-quark baryon currents, the Gaussian distribution of the constituent quarks inside the baryon and the compositeness condition which sets an upper limit for the baryon-quark vertex. The S-matrix elements are expressed by a set of Feynman quark-diagrams. The model contains only few parameters, namely, the cut-off parameter of the Gaussian quark distribution and the free quark propagator, which are unambiguously determined from the best fit to the data. The heavy quark limit within this

Electromagnetic properties of light and heavy baryons in the relativistic quark model

Energy Technology Data Exchange (ETDEWEB)

Nicmorus Marinescu, Diana

2007-06-14

One of the main challenges of nowadays low-energy physics remains the description of the internal structure of hadrons, strongly connected to the electromagnetic properties of matter. In this vein, the success of the relativistic quark model in the analysis of the hadron structure constitutes a solid motivation for the study carried out throughout this work. The relativistic quark model is extended to the investigation of static electromagnetic properties of both heavy and light baryons. The bare contributions to the magnetic moments of the single-, double- and triple-heavy baryons are calculated. Moreover, the relativistic quark model allows the study of the electromagnetic properties of the light baryon octet incorporating meson cloud contributions in a perturbative manner. The long disputed values of the multipole ratios E2/M1 and C2/M1 and the electromagnetic form factors of the N{yields}{delta}{gamma} transition are successfully reproduced. The relativistic quark model can be viewed as a quantum field theory approach based on a phenomenological Lagrangian coupling light and heavy baryons to their constituent quarks. In our approach the baryon is a composite object of three constituent quarks, at least in leading order. The effective interaction Lagrangian is written in terms of baryon and constituent quark fields. The effective action preserves Lorentz covariance and gauge invariance. The main ingredients of the model are already introduced at the level of the interaction Lagrangian: the three-quark baryon currents, the Gaussian distribution of the constituent quarks inside the baryon and the compositeness condition which sets an upper limit for the baryon-quark vertex. The S-matrix elements are expressed by a set of Feynman quark-diagrams. The model contains only few parameters, namely, the cut-off parameter of the Gaussian quark distribution and the free quark propagator, which are unambiguously determined from the best fit to the data. The heavy quark limit

NJL-jet model for quark fragmentation functions

International Nuclear Information System (INIS)

Ito, T.; Bentz, W.; Cloeet, I. C.; Thomas, A. W.; Yazaki, K.

2009-01-01

A description of fragmentation functions which satisfy the momentum and isospin sum rules is presented in an effective quark theory. Concentrating on the pion fragmentation function, we first explain why the elementary (lowest order) fragmentation process q→qπ is completely inadequate to describe the empirical data, although the crossed process π→qq describes the quark distribution functions in the pion reasonably well. Taking into account cascadelike processes in a generalized jet-model approach, we then show that the momentum and isospin sum rules can be satisfied naturally, without the introduction of ad hoc parameters. We present results for the Nambu-Jona-Lasinio (NJL) model in the invariant mass regularization scheme and compare them with the empirical parametrizations. We argue that the NJL-jet model, developed herein, provides a useful framework with which to calculate the fragmentation functions in an effective chiral quark theory.

Cumulative particle production in the quark recombination model

International Nuclear Information System (INIS)

Gavrilov, V.B.; Leksin, G.A.

1987-01-01

Production of cumulative particles in hadron-nuclear inteactions at high energies is considered within the framework of recombination quark model. Predictions for inclusive cross sections of production of cumulative particles and different resonances containing quarks in s state are made

Quark-hadron duality in meson physics

International Nuclear Information System (INIS)

Anisovich, V.V.

1994-01-01

Quark hadron dualism is discussed, based on observing the changes in the quark model characteristics after the inclusion into hadron degrees of freedom. A standard version of the potential model is presented. The potential which is responsible for the formation of mesons may be divided into two pieces: a short-range part for distances about 0.3 - 0.5 fm and a long-range part at distances more than 1 fm. (R.P.). 5 refs., 2 figs

Quark-hadron duality in meson physics

Energy Technology Data Exchange (ETDEWEB)

Anisovich, V.V. [Petersburg Nuclear Physics Inst., Gatchina (Russian Federation)

1994-12-31

Quark hadron dualism is discussed, based on observing the changes in the quark model characteristics after the inclusion into hadron degrees of freedom. A standard version of the potential model is presented. The potential which is responsible for the formation of mesons may be divided into two pieces: a short-range part for distances about 0.3 - 0.5 fm and a long-range part at distances more than 1 fm. (R.P.). 5 refs., 2 figs.

Non-leptonic decays in an extended chiral quark model

Energy Technology Data Exchange (ETDEWEB)

Eeg, J. O. [Dept. of Physics, Univ. of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo (Norway)

2012-10-23

We consider the color suppressed (nonfactorizable) amplitude for the decay mode B{sub d}{sup 0}{yields}{pi}{sup 0}{pi}{sup 0}. We treat the b-quark in the heavy quark limit and the energetic light (u,d,s) quarks within a variant of Large Energy Effective Theory combined with an extension of chiral quark models. Our calculated amplitude for B{sub d}{sup 0}{yields}{pi}{sup 0}{pi}{sup 0} is suppressed by a factor of order {Lambda}{sub QCD}/m{sub b} with respect to the factorized amplitude, as it should according to QCD-factorization. Further, for reasonable values of the (model dependent) gluon condensate and the constituent quark mass, the calculated nonfactorizable amplitude for B{sub d}{sup 0}{yields}{pi}{sup 0}{pi}{sup 0} can easily accomodate the experimental value. Unfortunately, the color suppressed amplitude is very sensitive to the values of these model dependent parameters. Therefore fine-tuning is necessary in order to obtain an amplitude compatible with the experimental result for B{sub d}{sup 0}{yields}{pi}{sup 0}{pi}{sup 0}.

Heavy-quark potential at finite temperature using the holographic correspondence

International Nuclear Information System (INIS)

Albacete, Javier L.; Kovchegov, Yuri V.; Taliotis, Anastasios

2008-01-01

We revisit the calculation of a heavy-quark potential in N=4 supersymmetric Yang-Mills theory at finite temperature using the AdS/CFT correspondence. As is widely known, the potential calculated in the pioneering works of Rey et al.[Nucl. Phys. B527, 171 (1998)] and Brandhuber et al.[Phys. Lett. B 434, 36 (1998)] is zero for separation distances r between the quark and the antiquark above a certain critical separation, at which the potential has a kink. We point out that by analytically continuing the string configurations into the complex plane, and using a slightly different renormalization subtraction, one obtains a smooth nonzero (negative definite) potential without a kink. The obtained potential also has a nonzero imaginary (absorptive) part for separations r>r c =0.870/πT. Most importantly, at large separations r the real part of the potential does not exhibit the exponential Debye falloff expected from perturbation theory and instead falls off as a power law, proportional to 1/r 4 for r>r 0 =2.702/πT.

Color superconductivity from the chiral quark-meson model

Science.gov (United States)

Sedrakian, Armen; Tripolt, Ralf-Arno; Wambach, Jochen

2018-05-01

We study the two-flavor color superconductivity of low-temperature quark matter in the vicinity of chiral phase transition in the quark-meson model where the interactions between quarks are generated by pion and sigma exchanges. Starting from the Nambu-Gorkov propagator in real-time formulation we obtain finite temperature (real axis) Eliashberg-type equations for the quark self-energies (gap functions) in terms of the in-medium spectral function of mesons. Exact numerical solutions of the coupled nonlinear integral equations for the real and imaginary parts of the gap function are obtained in the zero temperature limit using a model input spectral function. We find that these components of the gap display a complicated structure with the real part being strongly suppressed above 2Δ0, where Δ0 is its on-shell value. We find Δ0 ≃ 40MeV close to the chiral phase transition.

Light-flavor sea-quark distributions in the nucleon in the SU(3) chiral quark soliton model. I. Phenomenological predictions

International Nuclear Information System (INIS)

Wakamatsu, M.

2003-01-01

Theoretical predictions are given for the light-flavor sea-quark distributions in the nucleon including the strange quark ones on the basis of the flavor SU(3) version of the chiral quark soliton model. Careful account is taken of the SU(3) symmetry breaking effects due to the mass difference Δm s between the strange and nonstrange quarks, which is the only one parameter necessary for the flavor SU(3) generalization of the model. A particular emphasis of study is put on the light-flavor sea-quark asymmetry as exemplified by the observables d-bar(x)-u-bar(x),d-bar(x)/u-bar(x),Δu-bar(x)-Δd-bar(x) as well as on the particle-antiparticle asymmetry of the strange quark distributions represented by s(x)-s-bar(x),s(x)/s-bar(x),Δs(x)-Δs-bar(x) etc. As for the unpolarized sea-quark distributions, the predictions of the model seem qualitatively consistent with the available phenomenological information provided by the NMC data for d-bar(x)-u-bar(x), the E866 data for d-bar(x)/u-bar(x), the CCFR data and the fit of Barone et al. for s(x)/s-bar(x), etc. The model is shown to give several unique predictions also for the spin-dependent sea-quark distribution, such that Δs(x)<<Δs-bar(x) < or approx. 0 and Δd-bar(x)<0<Δu-bar(x), although the verification of these predictions must await more elaborate experimental investigations in the near future

Recursive model for the fragmentation of polarized quarks

Science.gov (United States)

Kerbizi, A.; Artru, X.; Belghobsi, Z.; Bradamante, F.; Martin, A.

2018-04-01

We present a model for Monte Carlo simulation of the fragmentation of a polarized quark. The model is based on string dynamics and the 3P0 mechanism of quark pair creation at string breaking. The fragmentation is treated as a recursive process, where the splitting function of the subprocess q →h +q' depends on the spin density matrix of the quark q . The 3P0 mechanism is parametrized by a complex mass parameter μ , the imaginary part of which is responsible for single spin asymmetries. The model has been implemented in a Monte Carlo program to simulate jets made of pseudoscalar mesons. Results for single hadron and hadron pair transverse-spin asymmetries are found to be in agreement with experimental data from SIDIS and e+e- annihilation. The model predictions on the jet-handedness are also discussed.

Gluon and quark jets in a recursive model motivated by quantum chromodynamics

International Nuclear Information System (INIS)

Sukhatme, U.P.

1979-01-01

We compute observable quantities like the multiplicity and momentum distributions of hadrons in gluon and quark jets in the framework of a recursive cascade model, which is strongly motivated by the fundamental interactions of QCD. Fragmentation occurs via 3 types of breakups: quark → meson + quark, gluon → meson + gluon, gluon → quark + antiquark. In our model gluon jets are softer than quark jets. The ratio of gluon jet to quark jet multiplicity is found to be 2 asymptotically, but much less at lower energies. Some phenomenological consequences for γ decay are discussed. (orig.)

KN interaction in a constituent quark model

International Nuclear Information System (INIS)

Labarsouque, J.; Leandri, J.; Silvestre Brac, B.

1997-01-01

The kaon-nucleon s-wave phase shift have been calculated in a quark potential model using the resonating group method. The Hill-Wheeler equation has been solved numerically without any parametrization of the KN relative wave-function. The I = 0 phase shift has been found in agreement with the experimental data. In the I = 1 channel too much repulsion has been obtained., probably due to the lack of medium-range boson exchange type attraction. In a second step, pion and sigma-type exchange have been incorporated in the calculation

Parity violating NN forcES in the quark compound bag model

International Nuclear Information System (INIS)

Simonov, Yu.A.

1982-01-01

Parity violation (PV) in the interaction is considered as due to the Weinberg-Salam quark-quark interaction inside the six-quark bag. The initial and final strong interaction is described within the same quark compound bag (QCB) model, where the NN coupling to the six quark QCB is defined from the NN experimental data. The resulting PV amplitude contains no free parameters and allows therefore an unambiguous test of the QCB model. An estimate of the 1 S 0 → 3 P 0 contribution to the proton-proton asymmetry is in a rough agreement with experimental data [ru

Quark model and high energy collisions

International Nuclear Information System (INIS)

Nyiri, J.; Kobrinsky, M.N.

1982-06-01

The aim of the present review is to show that the additive quark model describes well not only the static features of hadrons but also the interaction processes at high energies. Considerations of the hadron-hadron and hadron-nucleus interactions and of the hadron production in multiparticle production processes suggest serious arguments in favour of the nucleus-like hadron structure and show the possibility to apply the rules of quark statistics to the description of the secondary particle production. (author)

Quark model calculations of current correlators in the nonperturbative domain

International Nuclear Information System (INIS)

Celenza, L.S.; Shakin, C.M.; Sun, W.D.

1995-01-01

The authors study the vector-isovector current correlator in this work, making use of a generalized Nambu-Jona-Lasinio (NJL) model. In their work, the original NJL model is extended to describe the coupling of the quark-antiquark states to the two-pion continuum. Further, a model for confinement is introduced that is seen to remove the nonphysical cuts that appear in various amplitudes when the quark and antiquark go on mass shell. Quite satisfactory results are obtained for the correlator. The authors also use the correlator to define a T-matrix for confined quarks and discuss a rho-dominance model for that T-matrix. It is also seen that the Bethe-Salpeter equation that determines the rho mass (in the absence of the coupling to the two-pion continuum) has more satisfactory behavior in the generalized model than in the model without confinement. That improved behavior is here related to the absence of the q bar q cut in the basic quark-loop integral of the generalized model. In this model, it is seen how one may work with both quark and hadron degrees of freedom, with only the hadrons appearing as physical particles. 12 refs., 16 figs., 1 tab

Quarks

Energy Technology Data Exchange (ETDEWEB)

Shekhter, V [AN SSSR, Leningrad. Inst. Yadernoj Fiziki

1981-04-01

The history is described of the concept of quarks, ie., hypothetical particles of which,hadrons (strongly interacting particles) are believed to consist. The quark properties differ from those of known elementary particles. The electric charge of quarks is 1/3 and 2/3 of the electron charge and they obviously only exist inside hadrons. Quark existence is generally recognized because it has been confirmed by experimental verification of predictions made using a quark model.

A model of quarks with Δ(6N2) family symmetry

International Nuclear Information System (INIS)

Ishimori, Hajime; King, Stephen F.

2014-01-01

We propose a first model of quarks based on the discrete family symmetry Δ(6N 2 ) in which the Cabibbo angle is correctly determined by a residual Z 2 ×Z 2 subgroup, and the smaller quark mixing angles may be qualitatively understood from the model. The present model of quarks may be regarded as a first step towards formulating a complete model of quarks and leptons based on Δ(6N 2 ), in which the lepton mixing matrix is fully determined by a Klein subgroup. For example, the choice N=28 provides an accurate determination of both the reactor angle and the Cabibbo angle

Quark fragmentation functions in NJL-jet model

Science.gov (United States)

Bentz, Wolfgang; Matevosyan, Hrayr; Thomas, Anthony

2014-09-01

We report on our studies of quark fragmentation functions in the Nambu-Jona-Lasinio (NJL) - jet model. The results of Monte-Carlo simulations for the fragmentation functions to mesons and nucleons, as well as to pion and kaon pairs (dihadron fragmentation functions) are presented. The important role of intermediate vector meson resonances for those semi-inclusive deep inelastic production processes is emphasized. Our studies are very relevant for the extraction of transverse momentum dependent quark distribution functions from measured scattering cross sections. We report on our studies of quark fragmentation functions in the Nambu-Jona-Lasinio (NJL) - jet model. The results of Monte-Carlo simulations for the fragmentation functions to mesons and nucleons, as well as to pion and kaon pairs (dihadron fragmentation functions) are presented. The important role of intermediate vector meson resonances for those semi-inclusive deep inelastic production processes is emphasized. Our studies are very relevant for the extraction of transverse momentum dependent quark distribution functions from measured scattering cross sections. Supported by Grant in Aid for Scientific Research, Japanese Ministry of Education, Culture, Sports, Science and Technology, Project No. 20168769.

Vector and Axial-Vector Correlators in AN Instanton-Like Quark Model

Science.gov (United States)

Dorokhov, Alexander E.

The behavior of the vector Adler function at spacelike momenta is studied in the framework of a covariant chiral quark model with instanton-like quark-quark interaction. This function describes the transition between the high energy asymptotically free region of almost massless current quarks to the low energy hadronized regime with massive constituent quarks. The model reproduces the Adler function and V-A correlator extracted from the ALEPH and OPAL data on hadronic τ lepton decays, transformed into the Euclidean domain via dispersion relations. The leading order contribution from hadronic part of the photon vacuum polarization to the anomalous magnetic moment of the muon, aμ hvp(1), is estimated.

Diquark structure in heavy quark baryons in a geometric model

International Nuclear Information System (INIS)

Paria, Lina; Abbas, Afsar

1996-01-01

Using a geometric model to study the structure of hadrons, baryons having one, two and three heavy quarks have been studied here. The study reveals diquark structure in baryons with one and two heavy quarks but not with three heavy identical quarks. (author). 15 refs., 2 figs., 2 tabs

An algebraic model for quark mass matrices with heavy top

International Nuclear Information System (INIS)

Krolikowski, W.; Warsaw Univ.

1991-01-01

In terms of an intergeneration U(3) algebra, a numerical model is constructed for quark mass matrices, predicting the top-quark mass around 170 GeV and the CP-violating phase around 75 deg. The CKM matrix is nonsymmetric in moduli with |V ub | being very small. All moduli are consistent with their experimental limits. The model is motivated by the author's previous work on three replicas of the Dirac particle, presumably resulting into three generations of leptons and quarks. The paper may be also viewed as an introduction to a new method of intrinsic dynamical description of lepton and quark mass matrices. (author)

Physics of the Quark Model

Science.gov (United States)

Young, Robert D.

1973-01-01

Discusses the charge independence, wavefunctions, magnetic moments, and high-energy scattering of hadrons on the basis of group theory and nonrelativistic quark model with mass spectrum calculated by first-order perturbation theory. The presentation is explainable to advanced undergraduate students. (CC)

Heavy quark potential in a static and strong homogeneous magnetic field

Energy Technology Data Exchange (ETDEWEB)

Hasan, Mujeeb; Chatterjee, Bhaswar; Patra, Binoy Krishna [Indian Institute of Technology Roorkee, Department of Physics, Roorkee (India)

2017-11-15

We have investigated the properties of quarkonia in a thermal QCD medium in the background of strong magnetic field. For that purpose, we employ the Schwinger proper-time quark propagator in the lowest Landau level to calculate the one-loop gluon self-energy, which in the sequel gives the effective gluon propagator. As an artifact of strong magnetic field approximation (eB >> T{sup 2} and eB >> m{sup 2}), the Debye mass for massless flavors is found to depend only on the magnetic field which is the dominant scale in comparison to the scales prevalent in the thermal medium. However, for physical quark masses, it depends on both magnetic field and temperature in a low temperature and high magnetic field but the temperature dependence is very meager and becomes independent of the temperature beyond a certain temperature and magnetic field. With the above mentioned ingredients, the potential between heavy quark (Q) and anti-quark (anti Q) is obtained in a hot QCD medium in the presence of a strong magnetic field by correcting both short- and long-range components of the potential in the real-time formalism. It is found that the long-range part of the quarkonium potential is affected much more by magnetic field as compared to the short-range part. This observation facilitates us to estimate the magnetic field beyond which the potential will be too weak to bind Q anti Q together. For example, the J/ψ is dissociated at eB ∝ 10 m{sub π}{sup 2} and Υ is dissociated at eB ∝ 100 m{sub π}{sup 2} whereas its excited states, ψ{sup '} and Υ{sup '} are dissociated at smaller magnetic field eB = m{sub π}{sup 2}, 13 m{sub π}{sup 2}, respectively. (orig.)

Quark model and high energy collisions

CERN Document Server

Anisovich, V V; Nyíri, J; Shabelski, Yu M

2004-01-01

This is an updated version of the book published in 1985. QCD-motivated, it gives a detailed description of hadron structure and soft interactions in the additive quark model, where hadrons are regarded as composite systems of dressed quarks. In the past decade it has become clear that nonperturbative QCD, responsible for soft hadronic processes, may differ rather drastically from perturbative QCD. The understanding of nonperturbative QCD requires a detailed investigation of the experiments and the theoretical approaches. Bearing this in mind, the book has been rewritten paying special attenti

The half-skyrmion phase in a chiral-quark model

International Nuclear Information System (INIS)

Mantovani Sarti, Valentina; Vento, Vicente

2014-01-01

The Chiral Dilaton Model, where baryons arise as non-topological solitons built from the interaction of quarks and chiral mesons, shows in the high density low temperature regime a two phase scenario in the nuclear matter phase diagram. Dense soliton matter described by the Wigner–Seitz approximation generates a periodic potential in terms of the sigma and pion fields that leads to the formation of a band structure. The analysis up to three times nuclear matter density shows that soliton matter undergoes two separate phase transitions: a delocalization of the baryon number density leading to B=1/2 structures, as in skyrmion matter, at moderate densities, and quark deconfinement at larger densities. This description fits well into the so-called quarkyonic phase where, before deconfinement, nuclear matter should undergo structural changes involving the restoration of fundamental symmetries of QCD

The Top Quark as a Window to Beyond the Standard Model Physics

Energy Technology Data Exchange (ETDEWEB)

Yu, Chiu-Tien [Univ. of Wisconsin, Madison, WI (United States)

2013-01-01

The top quark was the last of the Standard Model quarks to be discovered, and is of considerable interest. The closeness of the top quark mass to the electroweak scale is suggestive that the top quark could be closely related to the mechanisms for electroweak symmetry breaking. Any new physics in electroweak symmetry breaking models could then preferentially couple to the top quark, making the top quark a promising probe for new physics. In this thesis, we will explore two aspects of the top quark as a harbinger to new physics: the top forward-backward asymmetry as seen at the Tevatron and the search for stops. In this thesis, we will discuss the Asymmetric Left-Right Model (ALRM), a model that is based on the gauge group $U'(1)\\times SU(2)\\times SU'(2)$ with couplings $g_1^\\prime, g_2^\\prime,$ and $g'$ associated with the fields $B',W,W'$, respectively, and show how this model can explain the top forward-backward asymmetry. We will then explore the scalar sector of the ALRM, and provide a specific Higgs mechanism that provides the masses for the $W'$ and $Z'$ bosons. The top forward-backward asymmetry is a test of invariance of charge-conjugation. Thus, we look at the $X$-gluon model, a model that was motivated by the top forward-backward asymmetry, and show that one can look at the longitudinal polarization of the top-quark to test parity conservation. Finally, we investigate searches for stop squarks, the supersymmetric partner of the top quark, at the Large Hadron Collider (LHC) using shape-based analyses.

Prediction of new Quarks, Generations and Quark Masses

Science.gov (United States)

Lach, Thedore

2002-04-01

The Standard model currently suggests no relationship between the quark and lepton masses. The CBM (model) of the nucleus has resulted in the prediction of two new quarks, an up quark mass of 237.31 MeV/c2 and a dn quark mass of 42.392 MeV/c2. These two new quarks help explain the numerical relationship between all the quark and lepton masses in a single function. The mass of each SNU-P (quark or lepton) is just the geometric mean of two related SNU-Ps, either in the same generation or in the same family. This numerology predicts the following masses for the electron family: 0.511000 (electron), 7.743828 (predicted), 117.3520, 1778.38, 26950.08 MeV. The resulting slope of these masses when plotted on semi log paper is "e" to 5 significant figures using the currently accepted mass for Tau. This theory suggests that all the "dn like" quarks have a mass of just 10X multiples of 4.24 MeV (the mass of the "d" quark). The first 3 "up like" quark masses are 38, 237 and 1500 MeV. This theory also predicts a new heavy generation with a lepton mass of 27 GeV, a "dn like" quark of 42.4 GeV, and an "up like" quark of 65 GeV. Significant evidence already exists for the existence of these quarks, and lepton.

The Mixed Quark-Gluon Condensate from the Global Color Symmetry Model

Institute of Scientific and Technical Information of China (English)

ZONG Hong-Shi; PING Jia-Lun; LU Xiao-Fu; WANG Fan; ZHAO En-Guang

2002-01-01

The mixed quark-gluon condensate from the global color symmetry model is derived. It is shown that themixed quark-gluon condensate depends explicitly on the gluon propagator. This interesting feature may be regarded asan additional constraint on the model of gluon propagator. The values of the mixed quark-gluon condensate from someansatz for the gluon propagator are compared with those determined from QCD sum rules.

Forward-backward asymmetry of the top quark in diquark models

International Nuclear Information System (INIS)

Arhrib, Abdesslam; Benbrik, Rachid; Chen, Chuan-Hung

2010-01-01

Motivated by the recent unexpected large forward-backward asymmetry of the top-quark observed by D0 and CDF at the Tevatron, we investigate a possible explanation for the anomaly within the framework of diquark models. In the diquark models, the top-quark pair production is mediated by the u-channel diagram. It is found that the color-triplet diquark can generate the forward-backward asymmetry of 20% when the constraint from the cross section of the top-quark pair production is taken into account.

Extended particle model with quark confinement and charmonium spectroscopy

International Nuclear Information System (INIS)

Hasenfratz, Peter; Kuti, Julius; Szalay, A.S.

Extended particle like vector gluon bubbles /bags/ are introduced which are stabilized against free expansion by a surface tension of volume tension. Since quraks are coupled to the gluon field, they are confined to the inside of the gluon bag without any further mechanism. Only color singlet gluon bags are allowed. Nonlinear boundary conditions are not imposed on the quark field in the model. A massless abelian gauge confined by a surface tension is first considered; in a four-dimensional relativistic picture the surface of the gauge field bubble appears as a tube with a three dimensional surface. As a first application, the model is used to study bound states of heavy charmed quarks (charmonium). Similar to the Born-Oppenheimer approximation in molecular physics, heavy charmed quarks are treated as nonrelativistic in their motion whereas the gluon bag and light quarks (u,d,s) are treated in an adiabatic approximation

Transverse momentum correlations of quarks in recursive jet models

Science.gov (United States)

Artru, X.; Belghobsi, Z.; Redouane-Salah, E.

2016-08-01

In the symmetric string fragmentation recipe adopted by PYTHIA for jet simulations, the transverse momenta of successive quarks are uncorrelated. This is a simplification but has no theoretical basis. Transverse momentum correlations are naturally expected, for instance, in a covariant multiperipheral model of quark hadronization. We propose a simple recipe of string fragmentation which leads to such correlations. The definition of the jet axis and its relation with the primordial transverse momentum of the quark is also discussed.

Quark model and QCD

International Nuclear Information System (INIS)

Anisovich, V.V.

1989-06-01

Using the language of the quarks and gluons for description of the soft hadron physics it is necessary to take into account two characteristic phenomena which prevent one from usage of QCD Lagrangian in the straightforward way, chiral symmetry breaking, and confinement of colour particles. The topics discussed in this context are: QCD in the domain of soft processes, phenomenological Lagrangian for soft processes and exotic mesons, spectroscopy of low-lying hadrons (mesons, baryons and mesons with heavy quarks - c,b -), confinement forces, spectral integration over quark masses. (author) 3 refs.; 19 figs.; 3 tabs

Possible D(*) anti D(*) and B(*) anti B(*) molecular states in the extended constituent quark models

International Nuclear Information System (INIS)

Yang, You-Chang; Tan, Zhi-Yun; Ping, Jialun; Zong, Hong-Shi

2017-01-01

The possible neutral D (*) anti D (*) and B (*) anti B (*) molecular states are studied in the framework of the constituent quark models, which is extended by including the s-channel one-gluon exchange. Using different types of quark-quark potentials, we solve the four-body Schroedinger equation by means of the Gaussian expansion method. The bound states of D (*) anti D (*) with J PC = 1 ++ , 2 ++ and B (*) anti B (*) with J PC = 0 ++ , 1 +- , 1 ++ , 2 ++ are obtained. The molecular states D* anti D with J PC = 1 ++ and B* anti B with J PC = 1 +- are good candidates for X(3872) and Z 0 b (10610), respectively. The dependence of the results on the model parameters is also discussed. (orig.)

KN phase shifts in a constituent quark model

International Nuclear Information System (INIS)

Lemaire, S.; Labarsouque, J.; Silvestre-Brac, B.

2001-01-01

In a first step, the I=1 and I=0 kaon-nucleon s-wave phase shifts have been calculated in a quark potential model using the resonating group method (RGM) and a relativistic kinematics. The spinless Salpeter equation has been solved numerically using the Fourier grid hamiltonian method. The results have been compared to the nonrelativistic ones. For each isospin channel the phase shifts obtained are not so far from the nonrelativistic results. Then, K-nucleon p, d, f, g-waves phase shifts have been calculated using a nonrelativistic kinematics

H-particle stability in the nonrelativistic quark model

International Nuclear Information System (INIS)

Silvestre-Brac, B.; Carbonell, J.; Gignoux, C.

1987-01-01

The H particle with quark content (uuddss) is presented as a good candidate to be stable with respect to strong interactions. In the framework of a nonrelativistic potential model, the binding energy is calculated by a full dynamical approach using a resonating group trial wave function. The center-of-mass motion and the Pauli principle are correctly treated. Sophisticated baryon wave functions are employed and the equation of motion is solved with six coupled channels including radial excited baryon states. The effect of breaking SU(3)-flavor symmetry is discussed in detail

Quarkonium states in an anisotropic quark-gluon plasma

Energy Technology Data Exchange (ETDEWEB)

Guo Yun

2009-09-10

In this work we study the properties of quarkonium states in a quark-gluon plasma which, due to expansion and non-zero viscosity, exhibits a local anisotropy in momentum space. We determine the hard-loop resummed gluon propagator in an anisotropic QCD plasma in general linear gauges and define a potential between heavy quarks from the Fourier transform of its static limit. This potential which arises due to one-gluon exchange describes the force between a quark and anti-quark at short distances. It is closer to the vacuum potential as compared to the isotropic Debye screened potential which indicates the reduced screening in an anisotropic QCD plasma. In addition, angular dependence appears in the potential; we find that there is stronger attraction on distance scales on the order of the inverse Debye mass for quark pairs aligned along the direction of anisotropy than for transverse alignment. The potential at long distances, however, is non-perturbative and modeled as a QCD string which is screened at the same scale as the Coulomb field. At asymptotic separation the potential energy is non-zero and inversely proportional to the temperature. With a phenomenological potential model which incorporates the different behaviors at short and long distances, we solve the three-dimensional Schroedinger equation. Our numerical results show that quarkonium binding is stronger at non-vanishing viscosity and expansion rate, and that the anisotropy leads to polarization of the P-wave states. Furthermore, we determine viscosity corrections to the imaginary part of the heavy-quark potential in the weak-coupling hard-loop approximation. The imaginary part is found to be smaller (in magnitude) than at vanishing viscosity. This implies a smaller decay width of quarkonium bound states in an anisotropic plasma. (orig.)

Quarkonium states in an anisotropic quark-gluon plasma

International Nuclear Information System (INIS)

Guo Yun

2009-01-01

In this work we study the properties of quarkonium states in a quark-gluon plasma which, due to expansion and non-zero viscosity, exhibits a local anisotropy in momentum space. We determine the hard-loop resummed gluon propagator in an anisotropic QCD plasma in general linear gauges and define a potential between heavy quarks from the Fourier transform of its static limit. This potential which arises due to one-gluon exchange describes the force between a quark and anti-quark at short distances. It is closer to the vacuum potential as compared to the isotropic Debye screened potential which indicates the reduced screening in an anisotropic QCD plasma. In addition, angular dependence appears in the potential; we find that there is stronger attraction on distance scales on the order of the inverse Debye mass for quark pairs aligned along the direction of anisotropy than for transverse alignment. The potential at long distances, however, is non-perturbative and modeled as a QCD string which is screened at the same scale as the Coulomb field. At asymptotic separation the potential energy is non-zero and inversely proportional to the temperature. With a phenomenological potential model which incorporates the different behaviors at short and long distances, we solve the three-dimensional Schroedinger equation. Our numerical results show that quarkonium binding is stronger at non-vanishing viscosity and expansion rate, and that the anisotropy leads to polarization of the P-wave states. Furthermore, we determine viscosity corrections to the imaginary part of the heavy-quark potential in the weak-coupling hard-loop approximation. The imaginary part is found to be smaller (in magnitude) than at vanishing viscosity. This implies a smaller decay width of quarkonium bound states in an anisotropic plasma. (orig.)

Inverted radiative hierarchy of quark masses

International Nuclear Information System (INIS)

Berezhiani, Z.G.; Rattazzi, R.

1992-01-01

Inverted radiative hierarchy of quark masses is investigated. The authors suggest that the mass hierarchy is first generated in a sector of heavy isosinglet fermions due to radiative effects and then projected in the inverted way to the usual quarks by means of a universal seesaw. The simple left-right symmetric gauge model is presented with the P- and CP-parities and the exact isotopical symmetry which are softly (or spontaneously) broken in the Higgs potential. This approach naturally explains the observed pattern of quark masses and mixing, providing the quantitatively correct formula for the Cabibbo angle. Top quark is predicted to be in the 90-150 GeV range

Deeply virtual Compton scattering in a relativistic quark model

Energy Technology Data Exchange (ETDEWEB)

Spitzenberg, T.

2007-09-15

This thesis is mainly concerned with a model calculation for generalized parton distributions (GPDs). We calculate vectorial- and axial GPDs for the N{yields}N and N{yields}{delta} transition in the framework of a light front quark model. This requires the elaboration of a connection between transition amplitudes and GPDs. We provide the first quark model calculations for N{yields}{delta} GPDs. The examination of transition amplitudes leads to various model independent consistency relations. These relations are not exactly obeyed by our model calculation since the use of the impulse approximation in the light front quark model leads to a violation of Poincare covariance. We explore the impact of this covariance breaking on the GPDs and form factors which we determine in our model calculation and find large effects. The reference frame dependence of our results which originates from the breaking of Poincare covariance can be eliminated by introducing spurious covariants. We extend this formalism in order to obtain frame independent results from our transition amplitudes. (orig.)

Chemical Potentials of Quarks Extracted from Particle Transverse Momentum Distributions in Heavy Ion Collisions at RHIC Energies

International Nuclear Information System (INIS)

Zhao, Hong; Liu, Fu-Hu

2014-01-01

In the framework of a multisource thermal model, the transverse momentum distributions of charged particles produced in nucleus-nucleus (A-A) and deuteron-nucleus (d-A) collisions at relativistic heavy ion collider (RHIC) energies are investigated by a two-component revised Boltzmann distribution. The calculated results are in agreement with the PHENIX experimental data. It is found that the source temperature increases obviously with increase of the particle mass and incident energy, but it does not show an obvious change with the collision centrality. Then, the values of chemical potentials for up, down, and strange quarks can be obtained from the antiparticle to particle yield ratios in a wide transverse momentum range. The relationship between the chemical potentials of quarks and the transverse momentum with different centralities is investigated, too

Unpolarized structure functions and the parton distributions for nucleon in an independent quark model

International Nuclear Information System (INIS)

Barik, N.; Mishra, R.N.

2001-01-01

Considering the nucleon as consisting entirely of its valence quarks confined independently in a scalar-vector harmonic potential; unpolarized structure functions F 1 (x, μ 2 ) and F 2 (x, μ 2 ) are derived in the Bjorken limit under certain simplifying assumptions; from which valence quark distribution functions u v (x, μ 2 ) and d v (x, μ 2 ) are appropriately extracted satisfying the normalization constraints. QCD-evolution of these input distributions from a model scale of μ 2 = 0.07 GeV 2 to a higher Q 2 scale of Q 0 2 = 15 GeV 2 yields xu v (x, Q 0 2 ) and xd v (x, Q 0 2 ) in good agreement with experimental data. The gluon and sea-quark distributions such as G (x, Q 0 2 ) and q s (x, Q 0 2 ) are dynamically generated with a reasonable qualitative agreement with the available data; using the leading order renormalization group equations with appropriate valence-quark distributions as the input. (author)

Model for dynamical chiral symmetry breaking and quark condensate

International Nuclear Information System (INIS)

Nekrasov, M.L.; Rochev, V.E.

1986-01-01

In the framework of the model, proposed earlier to describe nonperturbative QCD, the singularity of the type 1/k 4 in the gluon propagator is shown to result in dynamical chiral symmetry breaking and appearance of quark condensate. The value, obtained for quark condensate, is close to the phenomenological one

Hyperon-nucleon and hyperon-hyperon interaction in the quark cluster model

International Nuclear Information System (INIS)

Straub, U.

1988-01-01

The nonrelativistic quark cluster model is used for the description of the hyperon-nucleon and hyperon-hyperon interaction. The different mass of the quarks is consistently regarded in the Hamiltonian and in the shape of the spatial wave functions of the quarks. The six-quark wave function is completely antisymmetrisized. By means of the resonating-group method the dynamic equations for the determination of the binding and scattering states of the six-quark problem are formulated. The corresponding resonating-group kernels are explicitely given. We calculate the lambda-nucleon and sigma-nucleon interaction. The sigma-nucleon scattering in the isospin (T=3/2) channel can be treated in a one-channel calculation. The sigma-nucleon (T=1/2) interaction and the lambda-nucleon interaction are studied in a coupled two-channel calculation. From a fit of the experimental lambda-nucleon interaction cross section the strength of the sigma-meson exchange is determined. The calculation of the sigma-nucleon scattering follows then completely parameterless. The agreement of the theory with the experiment is good. Subsequently the cluster model with this parameter is applied to the dihyperon which is a possibly bound state of two up quarks, two down quarks, and two strange quarks. We solve for this a coupled three-channel calculation. The cluster model presented here gives a binding energy of the dihyperon of (20±5) MeV below the lambda-lambda threshold. The mass of the dihyperon is predicted by this as (2211±5) MeV. (orig.) [de

Quark shell model using projection operators

International Nuclear Information System (INIS)

Ullah, N.

1988-01-01

Using the projection operators in the quark shell model, the wave functions for proton are calculated and expressions for calculating the wave function of neutron and also magnetic moment of proton and neutron are derived. (M.G.B.)

1/M corrections to baryonic form factors in the quark model

International Nuclear Information System (INIS)

Cheng, H.; Tseng, B.

1996-01-01

Weak current-induced baryonic form factors at zero recoil are evaluated in the rest frame of the heavy parent baryon using the nonrelativistic quark model. Contrary to previous similar work in the literature, our quark model results do satisfy the constraints imposed by heavy quark symmetry for heavy-heavy baryon transitions at the symmetric point v·v'=1 and are in agreement with the predictions of the heavy quark effective theory for antitriplet-antitriplet heavy baryon form factors at zero recoil evaluated to order 1/m Q . Furthermore, the quark model approach has the merit that it is applicable to any heavy-heavy and heavy-light baryonic transitions at maximum q 2 . Assuming a dipole q 2 behavior, we have applied the quark model form factors to nonleptonic, semileptonic, and weak radiative decays of the heavy baryons. It is emphasized that the flavor suppression factor occurring in many heavy-light baryonic transitions, which is unfortunately overlooked in most literature, is very crucial towards an agreement between theory and experiment for the semileptonic decay Λ c →Λe + ν e . Predictions for the decay modes Λ b →J/ψΛ, Λ c →pφ, Λ b →Λγ, Ξ b →Ξγ, and for the semileptonic decays of Λ b , Ξ b, c, and Ω b are presented. copyright 1996 The American Physical Society

From the standard model to composite quarks and leptons

International Nuclear Information System (INIS)

Harari, H.

1981-01-01

An updated version of lectures delivered at the SLAC Summer Institute, 1980 is presented. Part I describes the present status of the standard model and gives a short survey of topics such as extensions of the electroweak group, grand unification, the generation puzzle and the connection between quark masses and generalized Cabibbo angles. Part II is devoted to the possibility that quarks and leptons are composite. The general theoretical difficulties are described and several published models are reviewed, including the dynamical rishon model. (H.K.)

Pion polarizability in a chiral quark model

International Nuclear Information System (INIS)

Volkov, M.K.; Ebert, D.

1981-01-01

It is shown that the pion polarizability calculated in a chiral model with quark loops agrees exactly with the analogous quantity found in a chiral meson-baryon model. The results of a paper by Llanta and Tarrach are discussed critically

Minkowski space pion model inspired by lattice QCD running quark mass

Energy Technology Data Exchange (ETDEWEB)

Mello, Clayton S. [Instituto Tecnológico de Aeronáutica, DCTA, 12.228-900 São José dos Campos, SP (Brazil); Melo, J.P.B.C. de [Laboratório de Física Teórica e Computacional – LFTC, Universidade Cruzeiro do Sul, 01506-000 São Paulo, SP (Brazil); Frederico, T., E-mail: tobias@ita.br [Instituto Tecnológico de Aeronáutica, DCTA, 12.228-900 São José dos Campos, SP (Brazil)

2017-03-10

The pion structure in Minkowski space is described in terms of an analytic model of the Bethe–Salpeter amplitude combined with Euclidean Lattice QCD results. The model is physically motivated to take into account the running quark mass, which is fitted to Lattice QCD data. The pion pseudoscalar vertex is associated to the quark mass function, as dictated by dynamical chiral symmetry breaking requirements in the limit of vanishing current quark mass. The quark propagator is analyzed in terms of a spectral representation, and it shows a violation of the positivity constraints. The integral representation of the pion Bethe–Salpeter amplitude is also built. The pion space-like electromagnetic form factor is calculated with a quark electromagnetic current, which satisfies the Ward–Takahashi identity to ensure current conservation. The results for the form factor and weak decay constant are found to be consistent with the experimental data.

Minkowski space pion model inspired by lattice QCD running quark mass

Directory of Open Access Journals (Sweden)

Clayton S. Mello

2017-03-01

Full Text Available The pion structure in Minkowski space is described in terms of an analytic model of the Bethe–Salpeter amplitude combined with Euclidean Lattice QCD results. The model is physically motivated to take into account the running quark mass, which is fitted to Lattice QCD data. The pion pseudoscalar vertex is associated to the quark mass function, as dictated by dynamical chiral symmetry breaking requirements in the limit of vanishing current quark mass. The quark propagator is analyzed in terms of a spectral representation, and it shows a violation of the positivity constraints. The integral representation of the pion Bethe–Salpeter amplitude is also built. The pion space-like electromagnetic form factor is calculated with a quark electromagnetic current, which satisfies the Ward–Takahashi identity to ensure current conservation. The results for the form factor and weak decay constant are found to be consistent with the experimental data.

Study of light baryons in the three-quark-cluster model: Exact calculations

International Nuclear Information System (INIS)

Silvestre-Brac, B.; Gignoux, C.

1985-01-01

Within the nonrelativistic model, all the baryons built with three quarks of flavors, u, d, and s (N,Δ,Λ,Σ,Ψ,Ω) are studied with the Bhaduri-Cohler-Nogami potential. It is shown that the free-parameter simplest model is able to reproduce most of the experimental properties and allows the extraction of the rare effects which need a more elaborate model. The validity of the description in terms of a harmonic-oscillator basis is also tested

Non-uniform chiral phase in effective chiral quark models

International Nuclear Information System (INIS)

Sadzikowski, M.; Broniowski, W.

2000-01-01

We analyze the phase diagram in effective chiral quark models (the Nambu-Jona-Lasinio model, the σ-model with quarks) and show that at the mean-field level a phase with a periodically-modulated chiral fields separates the usual phases with broken and restored chiral symmetry. A possible signal of such a phase is the production of multipion jets travelling in opposite directions, with individual pions having momenta of the order of several hundred MeV. This signal can be interpreted in terms of disoriented chiral condensates. (author)

Bootstrap procedure in the quasinuclear quark model

International Nuclear Information System (INIS)

Anisovich, V.V.; Gerasyuta, S.M.; Keltuyala, I.V.

1983-01-01

The scattering amplitude for quarks (dressed quarks of a single flavour, and three colours) is obtained by means of a bootstrap procedure with introdUction of an initial paint-wise interaction due to a heavy gluon exchange. The obtained quasi-nuclear model (effective short-range interaction in the S-wave states) has reasonable properties: there exist colourless meson states Jsup(p)=0sup(-), 1 - ; there are no bound states in coloured channels, a virtual diquark level Jsup(p)=1sup(+) appears in the coloured state anti 3sub(c)

Dark matter admixed strange quark stars in the Starobinsky model

Science.gov (United States)

Lopes, Ilídio; Panotopoulos, Grigoris

2018-01-01

We compute the mass-to-radius profiles for dark matter admixed strange quark stars in the Starobinsky model of modified gravity. For quark matter, we assume the MIT bag model, while self-interacting dark matter inside the star is modeled as a Bose-Einstein condensate with a polytropic equation of state. We numerically integrate the structure equations in the Einstein frame, adopting the two-fluid formalism, and we treat the curvature correction term nonperturbatively. The effects on the properties of the stars of the amount of dark matter as well as the higher curvature term are investigated. We find that strange quark stars (in agreement with current observational constraints) with the highest masses are equally affected by dark matter and modified gravity.

Polarized heavy baryon production in quark-diquark model considering two different scenarios

Energy Technology Data Exchange (ETDEWEB)

Moosavi Nejad, S.M. [Yazd University, Faculty of Physics, Yazd (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), School of Particles and Accelerators, Tehran (Iran, Islamic Republic of); Delpasand, M. [Yazd University, Faculty of Physics, Yazd (Iran, Islamic Republic of)

2017-09-15

At sufficiently large transverse momentum, the dominant production mechanism for heavy baryons is actually the fragmentation. In this work, we first study the direct fragmentation of a heavy quark into the unpolarized triply heavy baryons in the leading order of perturbative QCD. In a completely different approach, we also analyze the two-stage fragmentation of a heavy quark into a scalar diquark followed by the fragmentation of such a scalar diquark into a triply heavy baryon: quark-diquark model of baryons. The results of this model are in acceptable agreement with those obtained through a full perturbative regime. Relying on the quark-diquark model and considering two different scenarios we determine the spin-dependent fragmentation functions of polarized heavy baryons in such a way that a vector or a pseudoscalar heavy diquark is an intermediate particle between the initial heavy quark and the final state baryon. (orig.)

Nuclear forces and quark degrees of freedom

International Nuclear Information System (INIS)

Lacombe, M.; Loiseau, B.; Vinh Mau, R.; Demetriou, P.; Pantis, C.

1999-01-01

Attempts to derive the NN forces from the quark and gluon degrees of freedom have been made so far in the framework of the nonrelativistic quark-cluster model (QCM). The justification of such a model is based on the remarkable success in describing the static properties of single hadrons. In the earlier calculations, the NN s-wave phase shifts obtained with the QCM show that the model produces repulsive NN forces at short distances, which constitutes a success for the model, but fails to provide the intermediate range attraction indispensable for binding nucleons in nuclei. This drawback is amended within the context of these models, at the expense of introducing by hand intermediate-range attraction through meson-exchange potentials between quarks or/and between nucleons (quark clusters). This procedure improves the results for the phase shifts and it is often concluded that the QCM provides a good description of the short-range (SR) part of the NN potential. In our opinion, the above procedure does not provide a rigorous test of the validity of the quark-cluster model. In order to get a clear-cut conclusion one should consider the QCM in association with an accurate and well founded model for the long-medium-range (LR+MR) forces. For these reason we study a NN interaction model which satisfies this requirement. In this model, the LR+MR parts are given by the Paris NN potential and the SR part by the QCM. The quality of the model is then tested by confronting directly its predictions with data on observables rather then, as it is usually done, with phase shifts. We compute all the observables for pp and np scattering at energies below the pion production threshold for different QCM versions corresponding to different qq interactions. The results are then compared with the existing world set data. Preliminary results show that the agreement with experiment is not good. (authors)

Search for heavy resonances decaying to heavy-flavor quarks at ATLAS

CERN Document Server

Lin, Kuan-yu; The ATLAS collaboration

2018-01-01

Searches for new resonances whose decay contain top quarks and/or b-quarks cover a wide range of beyond the Standard Model (SM) physics. These searches offer great potential as well as significant challenges in reconstructing and identifying the decay products as well as modeling the SM background. 2 recent results: W' and top-quark pair resonance searching will be presented.

Valence QCD: Connecting QCD to the quark model

International Nuclear Information System (INIS)

Liu, K.F.; Dong, S.J.; Draper, T.; Sloan, J.; Leinweber, D.; Woloshyn, R.M.

1999-01-01

A valence QCD theory is developed to study the valence quark properties of hadrons. To keep only the valence degrees of freedom, the pair creation through the Z graphs is deleted in the connected insertions, whereas the sea quarks are eliminated in the disconnected insertions. This is achieved with a new 'valence QCD' Lagrangian where the action in the time direction is modified so that the particle and antiparticle decouple. It is shown in this valence version of QCD that the ratios of isovector to isoscalar matrix elements (e.g., F A /D A and F S /D S ratios) in the nucleon reproduce the SU(6) quark model predictions in a lattice QCD calculation. We also consider how the hadron masses are affected on the lattice and discover new insights into the origin of dynamical mass generation. It is found that, within statistical errors, the nucleon and the Δ become degenerate for the quark masses we have studied (ranging from 1 to 4 times the strange mass). The π and ρ become nearly degenerate in this range. It is shown that valence QCD has the C, P, T symmetries. The lattice version is reflection positive. It also has the vector and axial symmetries. The latter leads to a modified partially conserved axial Ward identity. As a result, the theory has a U(2N F ) symmetry in the particle-antiparticle space. Through lattice simulation, it appears that this is dynamically broken down to U q (N F )xU bar q (N F ). Furthermore, the lattice simulation reveals spin degeneracy in the hadron masses and various matrix elements. This leads to an approximate U q (2N F )xU bar q (2N F ) symmetry which is the basis for the valence quark model. In addition, we find that the masses of N, Δ,ρ,π,a 1 , and a 0 all drop precipitously compared to their counterparts in the quenched QCD calculation. This is interpreted as due to the disappearance of the 'constituent' quark mass which is dynamically generated through tadpole diagrams. The origin of the hyperfine splitting in the baryon is

Top quark pair production and modeling via QCD in CMS

CERN Document Server

Gonzalez Fernandez, Juan Rodrigo

2017-01-01

Measurements of the inclusive and differential top quark pair ($\\textrm{t}\\bar{\\textrm{t}}$) production cross section at centre-of-mass energies of 13 TeV and 5.02 TeV are presented, performed using CMS data collected in 2015 and 2016. The inclusive cross section is measured in the lepton+jets, dilepton and fully hadronic channels. Top quark pair differential cross sections are measured and are given as functions of various kinematic observables of (anti)top quark, the $\\textrm{t}\\bar{\\textrm{t}}$ system, and of the jets and leptons in the final state. Furthermore, the multiplicity and kinematic distributions of the additional jets produced in $\\textrm{t}\\bar{\\textrm{t}}$ events are also investigated and its modeling is compared for several generators. A new tune of parameters is developed for some of the generators. In addition, first measurements of top quark pair production with additional b quarks in the final state are presented. Furthermore, searches for four top quark production in CMS are also present...

A fermion-boson composite model of quarks and leptons

Directory of Open Access Journals (Sweden)

Yoshio Koide

1983-01-01

Full Text Available Quark and lepton masses and flavor-mixing angles are estimated on the basis of a fermion-boson composite model where the (u, d, (c, s and (t, b quarks are assigned to the diagonal elements π8, η8 and η1, respectively, in3 × 3* = 8 + 1 of the SU(3-generation symmetry.

A chiral quark model for meson electroproduction in the S11 partial wave

International Nuclear Information System (INIS)

Golli, B.; Sirca, S.

2011-01-01

We calculate the meson scattering and electroproduction amplitudes in the S11 partial wave in a coupled-channel approach that incorporates quasi-bound quark-model states. Using the quark wave functions and the quark-meson interaction from the Cloudy Bag Model, we obtain a good overall agreement with the available experimental results for the partial widths of the N(1535) and the N(1650) resonances as well as for the pion, eta and kaon electroproduction amplitudes. Our model is consistent with the N(1535) resonance being dominantly a genuine three-quark state rather than a quasi-bound state of mesons and baryons. (orig.)

The effect of dynamical quark mass on the calculation of a strange quark star's structure

Institute of Scientific and Technical Information of China (English)

Gholam Hossein Bordbar; Babak Ziaei

2012-01-01

We discuss the dynamical behavior of strange quark matter components,in particular the effects of density dependent quark mass on the equation of state of strange quark matter.The dynamical masses of quarks are computed within the Nambu-Jona-Lasinio model,then we perform strange quark matter calculations employing the MIT bag model with these dynamical masses.For the sake of comparing dynamical mass interaction with QCD quark-quark interaction,we consider the one-gluon-exchange term as the effective interaction between quarks for the MIT bag model.Our dynamical approach illustrates an improvement in the obtained equation of state values.We also investigate the structure of the strange quark star using TolmanOppenheimer-Volkoff equations for all applied models.Our results show that dynamical mass interaction leads to lower values for gravitational mass.

Top quark pair production and top quark properties at CDF

Energy Technology Data Exchange (ETDEWEB)

Moon, Chang-Seong [INFN, Pisa

2016-06-02

We present the most recent measurements of top quark pairs production and top quark properties in proton-antiproton collisions with center-of-mass energy of 1.96 TeV using CDF II detector at the Tevatron. The combination of top pair production cross section measurements and the direct measurement of top quark width are reported. The test of Standard Model predictions for top quark decaying into $b$-quarks, performed by measuring the ratio $R$ between the top quark branching fraction to $b$-quark and the branching fraction to any type of down quark is shown. The extraction of the CKM matrix element $|V_{tb}|$ from the ratio $R$ is discussed. We also present the latest measurements on the forward-backward asymmetry ($A_{FB}$) in top anti-top quark production. With the full CDF Run II data set, the measurements are performed in top anti-top decaying to final states that contain one or two charged leptons (electrons or muons). In addition, we combine the results of the leptonic forward-backward asymmetry in $t\\bar t$ system between the two final states. All the results show deviations from the next-to-leading order (NLO) standard model (SM) calculation.

Superoperators in the dual model with coloured quarks

International Nuclear Information System (INIS)

Manida, S.N.

1978-01-01

The derivation of the dual model with coloured quarks is considered. The model is represented as a superoperator generalization of the Bardakci-Halpern model. It is shown that the three-regeon vertex of the model appears to be more compact and transparent

and density-dependent quark mass model

Indian Academy of Sciences (India)

Since a fair proportion of such dense proto stars are likely to be ... the temperature- and density-dependent quark mass (TDDQM) model which we had em- ployed in .... instead of Tc ~170 MeV which is a favoured value for the ud matter [26].

The Bayesian reconstruction of the in-medium heavy quark potential from lattice QCD and its stability

Science.gov (United States)

Burnier, Yannis; Kaczmarek, Olaf; Rothkopf, Alexander

2016-01-01

We report recent results of a non-perturbative determination of the static heavy-quark potential in quenched and dynamical lattice QCD at finite temperature. The real and imaginary part of this complex quantity are extracted from the spectral function of Wilson line correlators in Coulomb gauge. To obtain spectral information from Euclidean time numerical data, our study relies on a novel Bayesian prescription that differs from the Maximum Entropy Method. We perform simulations on quenched 323 × Nτ (β = 7.0, ξ = 3.5) lattices with Nτ = 24, …, 96, which cover 839MeV ≥ T ≥ 210MeV. To investigate the potential in a quark-gluon plasma with light u,d and s quarks we utilize Nf = 2 + 1 ASQTAD lattices with ml = ms/20 by the HotQCD collaboration, giving access to temperatures between 286MeV ≥ T ≥ 148MeV. The real part of the potential exhibits a clean transition from a linear, confining behavior in the hadronic phase to a Debye screened form above deconfinement. Interestingly its values lie close to the color singlet free energies in Coulomb gauge at all temperatures. We estimate the imaginary part on quenched lattices and find that it is of the same order of magnitude as in hard-thermal loop perturbation theory. From among all the systematic checks carried out in our study, we discuss explicitly the dependence of the result on the default model and the number of datapoints.

Mass spectrum of low-lying baryons in the ground state in a relativistic potential model of independent quarks with chiral symmetry

International Nuclear Information System (INIS)

Barik, N.; Dash, B.K.

1986-01-01

Under the assumption that baryons are an assembly of independent quarks, confined in a first approximation by an effective potential U(r) = 1/2(1+γ 0 )(ar 2 +V 0 ) which presumably represents the nonperturbative gluon interactions, the mass spectrum of the low-lying ground-state baryons has been calculated by considering perturbatively the contributions of the residual quark-pion coupling arising out of the requirement of chiral symmetry and that of the quark-gluon coupling due to one-gluon exchange over and above the necessary center-of-mass correction. The physical masses of the baryons so obtained agree quite well with the corresponding experimental value. The strong coupling constant α/sub c/ = 0.58 required here to describe the QCD mass splittings is quite consistent with the idea of treating one-gluon-exchange effects in lowest-order perturbation theory

CP-violating top quark couplings at future linear $e^+e^-$ colliders

CERN Document Server

Bernreuther, Werner; Garcia Garcia, Ignacio; Perello Rosello, Martin; Poeschl, Roman; Richard, Francois; Ros, Eduardo; Vos, Marcel

2017-01-01

We study the potential of future lepton colliders to probe violation of the CP symmetry in the top quark sector. In certain extensions of the Standard Model, such as the two-Higgs-doublet model (2HDM), sizeable anomalous top quark dipole moments can arise, that may be revealed by a precise measurement of top quark pair production. We present results from detailed Monte Carlo studies for the ILC at 500 GeV and CLIC at 380 GeV and use parton level simulations to explore the potential of high-energy operation. We find that precise measurements in $e^+e^- \\rightarrow t \\bar{t}$ production with subsequent decay to lepton plus jets final states can provide sufficient sensitivity to detect Higgs-boson-induced CP violation in a viable two-Higgs-doublet model. The potential of a linear $e^+e^-$ collider to detect CP-violating electric and weak dipole form factors of the top quark exceeds the prospects of the HL-LHC by over an order of magnitude.

CP-violating top quark couplings at future linear e^+e^- colliders

Science.gov (United States)

Bernreuther, W.; Chen, L.; García, I.; Perelló, M.; Poeschl, R.; Richard, F.; Ros, E.; Vos, M.

2018-02-01

We study the potential of future lepton colliders to probe violation of the CP symmetry in the top quark sector. In certain extensions of the Standard Model, such as the two-Higgs-doublet model (2HDM), sizeable anomalous top quark dipole moments can arise, which may be revealed by a precise measurement of top quark pair production. We present results from detailed Monte Carlo studies for the ILC at 500 GeV and CLIC at 380 GeV and use parton-level simulations to explore the potential of high-energy operation. We find that precise measurements in e^+e^- → t\\bar{t} production with subsequent decay to lepton plus jets final states can provide sufficient sensitivity to detect Higgs-boson-induced CP violation in a viable two-Higgs-doublet model. The potential of a linear e^+e^- collider to detect CP-violating electric and weak dipole form factors of the top quark exceeds the prospects of the HL-LHC by over an order of magnitude.

Pseudoscaler meson masses in the quark model

International Nuclear Information System (INIS)

Karl, G.

1976-10-01

Pseudoscaler meson masses and sum rules are compared in two different limits of a quark model with 4 quarks. The conventional limit corresponds to a heavy c anti c state and generalizes ideal mixing in a nonet. The second limit corresponds to a missing SU 4 unitary singlet and appears more relevant to the masses of π, K, eta, eta'. If SU 3 is broken only by the mass difference between the strange and nonstrange quarks, the physical masses imply that the u anti u, d anti d and s anti s pairs account only for 33% of the composition of the eta'(960), while for the eta(548) this fraction is 86%. If some of the remaining matter is in the form of the constituents of J/psi, the relative proportion of the relative decays J/psi → eta γ vs J/psi → etaγ is accounted for in satisfactory agreement with experiment. (author)

Interactions between baryon octets by quark model

Energy Technology Data Exchange (ETDEWEB)

Nakamoto, S. [Suzuka National College of Technology, Suzuka, Mie (Japan); Fujiwara, Y. [Kyoto Univ., Faculty of Science, Kyoto (Japan); Suzuki, Y. [Niigata Univ., Faculty of Science, Niigata (Japan); Kohno, M. [Kyushu Dental College, Kita-kyushu, Fukuoka (Japan)

2003-03-01

Interactions between the baryon octets are studied by using the two spin flavor SU{sub 6} quark models, namely fss2 and FSS. In all channels, results that can be systematically understood along with the flavor symmetry are obtained. Effect of the channel coupling in the {sup 1}S{sub 0} state of the system of strangeness-2 shows a tendency to be weak in the system of isospin 0 while strong in the system of isospin 1. It is shown that this tendency is due to the competitive contributions of the color magnetic term and the effective meson exchange potential to the transition potential. Flavor symmetry breaking weakens both the repulsive force in the short range and the attractive force in the intermediate range. It is revealed that the overall qualitative behavior is determined as the result of the competitive effect of those interactions. (S. Funahashi)

A gauge model with eight quarks

International Nuclear Information System (INIS)

Ragiadakos, C.

1977-01-01

A gauge model with eight quarks, on the basis of the SU(2)U(1) gauge group, containing the Weinberg-Salam-GIM model is proposed. It may explain the ratio of the neutral current and charged current found at Gargamelle and HPWF, the large y anomaly and, with a convenient introduction of the leptonic sector, the energetic trimuons observed recently in neutrino nucleon collisions

Duality and quarks

International Nuclear Information System (INIS)

Volkov, D.V.; Zheltukhin, A.A.; Pashnev, A.I.

1975-01-01

As it has shown, the study of vacuum transitions in dual models makes it possible to establish certain relations between duality, on the one hand, and the quark structure of resonances and the internal symmetries, on the other. In the case of Veneziano model the corresponding quark structure of resonances is determined by the infinity number of quarks of increasing mass. The intercents of the main trajectory and all adopted trajectories are additive with respect to squares of mass-forming quarks. The latter circumstance results in a number of important consequences: the presence of quadratic mass formulas for resonance states; the exact SU(infinity)-symmetry for the three-resonance coupling constants; the validity of Adler's self-consistency principle for external particles composed of different quarks and anti-quarks, etc

On the quark-antiquark potential at short distances

International Nuclear Information System (INIS)

Altevogt, P.

1994-12-01

We investigate the static quark-antiquark potential up to distances of 8 lattice units for pure SU(2) gauge theory on lattices with anisotropic couplings. The action is the Wilson action with a coupling fro time-like plaquettes which differs from those for space-like ones. Numerical simulations are performed in a large range of β. The potential is obtained by fitting 'cooled' Wilson loops with up to 4 exponential terms. An interpolation of the potentials by a sum of a perturbative term, a linear term and by lattice artifacts shows poor scaling in comparison with the isotropic case. If the coupling in the time-like region is reduced, the linear term is much smaller than in the isotropic case, and vice versa. Consequences for the bag picture for hadrons are discussed. (orig.)

Decay constants in the heavy quark limit in models a la Bakamjian and Thomas

International Nuclear Information System (INIS)

Morenas, V.; Le Yaouanc, A.; Oliver, L.; Pene, O.; Raynal, J.C.

1997-07-01

In quark models a la Bakamjian and Thomas, that yield covariance and Isgur-Wise scaling of form factors in the heavy quark limit, the decay constants f (n) and f 1/2 (n) of S-wave and P-wave mesons composed of heavy and light quarks are computed. Different Ansaetze for the dynamics of the mass operator at rest are discussed. Using phenomenological models of the spectrum with relativistic kinetic energy and regularized short distance part the decay constants in the heavy quark limit are calculated. The convergence of the heavy quark limit sum rules is also studied. (author)

Modified quark-meson coupling model for nuclear matter

International Nuclear Information System (INIS)

Jin, X.; Jennings, B.K.

1996-01-01

The quark-meson coupling model for nuclear matter, which describes nuclear matter as nonoverlapping MIT bags bound by the self-consistent exchange of scalar and vector mesons, is modified by introducing medium modification of the bag constant. We model the density dependence of the bag constant in two different ways: One invokes a direct coupling of the bag constant to the scalar meson field, and the other relates the bag constant to the in-medium nucleon mass. Both models feature a decreasing bag constant with increasing density. We find that when the bag constant is significantly reduced in nuclear medium with respect to its free-space value, large canceling isoscalar Lorentz scalar and vector potentials for the nucleon in nuclear matter emerge naturally. Such potentials are comparable to those suggested by relativistic nuclear phenomenology and finite-density QCD sum rules. This suggests that the reduction of bag constant in nuclear medium may play an important role in low- and medium-energy nuclear physics. copyright 1996 The American Physical Society

A quark structure of hadrons and nuclei

International Nuclear Information System (INIS)

Chakrabarty, S.; Deoghuria, S.

1992-08-01

In this review we look into the recent understanding of mesons, baryons and nuclei as few quark bound states within the framework of quantum chromodynamics (QCD). In particular, we have reviewed our understanding of the nature of confining interaction, the spin - dependence of colour forces and the role of non-perturbative effects in the study of quark forces in the potential model approach. We also give a comparative study of results obtained by several potential models with reference to the experimental data. We find that although the Lorentz nature of confinement and the nature of spin-dependent colour forces have been better understood now, only a partial understanding of these problems are obtained so far. Our study reveals that properties of baryons could be explained by the same potential model which successfully describe the mesons. However, the nuclei require chiral symmetry and non-perturbative methods for their description. We also discuss the relation between constituent, current and dynamical quark masses. We conclude that QCD motivated approaches have shown much success in explaining many results on hadronic and nuclear data. (author). 212 refs, 14 tabs

Electromagnetic moments of hadrons and quarks in a hybrid model

International Nuclear Information System (INIS)

Gerasimov, S.B.

1989-01-01

Magnetic moments of baryons are analyzed on the basis of general sum rules following from the theory of broken symmetries and quark models including the relativistic effects and hadronic corrections due to the meson exchange currents. A new sum rule is proposed for the hyperon magnetic moments, which is in accord with the most precise new data and also with a theory of the electromagnetic ΛΣ 0 mixing. The numerical values of the quark electromagnetic moments are obtained within a hybrid model treating the pion cloud effects through the local coupling of the pion field with the constituent massive quarks. Possible sensitivity of the weak neutral current magnetic moments to violation of the Okubo-Zweig-Izuki rule is emphasized nand discussed. 39 refs.; 1 fig

Studies on top-quark Monte Carlo modelling for Top2016

CERN Document Server

The ATLAS collaboration

2016-01-01

This note summarises recent studies on Monte Carlo simulation setups of top-quark pair production used by the ATLAS experiment and presents a new method to deal with interference effects for the $Wt$ single-top-quark production which is compared against previous techniques. The main focus for the top-quark pair production is on the improvement of the modelling of the Powheg generator interfaced to the Pythia8 and Herwig7 shower generators. The studies are done using unfolded data at centre-of-mass energies of 7, 8, and 13 TeV.

Quark model calculation of charmed baryon production by neutrinos

International Nuclear Information System (INIS)

Avilez, C.; Kobayashi, T.; Koerner, J.G.

1976-11-01

We study the neutrino production of 25 low-lying charmed baryon resonances in the four flavour quark model. The mass difference of ordinary and charmed quarks is explicitly taken into account. The quark model is used to determine the spectrum of the charmed baryon resonances and the q 2 = 0 values of the weak current transition matrix elements. These transition matrix elements are then continued to space-like q 2 -values by a generalized meson dominance ansatz for a set of suitably chosen invariant form factors. We find that the production of the L = 0 states C 0 , C 1 and C 1 * is dominant, with the C 0 produced most copiously. For L = 1, 2 the Jsup(P) = 3/2 - 5/2 + charm states are dominant. We give differential cross sections, total cross sections and energy integrated total cross sections using experimental neutrino fluxes. (orig./BJ) [de

Interplay Between Quark-Antiquark and Diquark Condensates in Vacuum in a Two-Flavor Nambu-Jona-Lasinio Model

Institute of Scientific and Technical Information of China (English)

ZHOU Bang-Rong

2007-01-01

By means of a relativistic effective potential, we analytically research competition between the quarkLasinio (NJL) model and obtain the Gs-Hs phase diagram, where Gs and Hs are the respective four-fermion coupling constants in scalar quark-antiquark channel and scalar color anti-triplet diquark channel. The results show that, in the that there is no diquark condensates in the vacuum of QCD, will also impose a real restriction to any given two-flavor NJL model which is intended to simulate QCD, i.e. in such model the resulting snallest ratio Gs/Hs after the Fierz transformations in the Hartree approximation must be larger than 2/3. A few phenomenological QCD-like NJL models are checked and analyzed.

Bulk viscosity of hot dense Quark matter in the PNJL model

International Nuclear Information System (INIS)

Xiao Shisong; Guo Panpan; Zhang Le; Hou Defu

2014-01-01

Starting from the Kubo formula and the QCD low energy theorem, we study the the bulk viscosity of hot dense quark matter in the PNJL model from the equation of state. We show that the bulk viscosity has a sharp peak near the chiral phase transition, and that the ratio of bulk viscosity over entropy rises dramatically in the vicinity of the phase transition. These results agree with those from the lattice and other model calculations. In addition, we show that the increase of chemical potential raises the bulk viscosity. (authors)

The calculation of multiquark hadrons by the quark model baryon, meson and multiquark states

International Nuclear Information System (INIS)

Takeuchi, Sachiko; Takizawa, Makoto; Yasui, Shigehiro

2011-01-01

The 1st new hadron summer school related with the new science field, 'the comprehensive research of new hadron states searched by variable flavor number scheme', was held on August 18-20, 2010. This report is one of the 'quark model' lectures. The chapter 1 describes following problems: 1. The background and the significance as a phenomenological theory of the constituent quark model. 2. The introduction of the quark model. 3. The summary of the properties of hadrons in which the quark model can apply to three quarks (qqq) and, one quark and antiquark (q - q) configurations, but is difficult to apply to some configurations. 4. A brief summary of exotic hadrons and recent problems. In chapter 2, the introduction and some exercises of the stochastic variational method are reported as a technique of solving spatial part of multiquark states. In the chapter 3, spins and color parts in multiquark states are calculated. The group theory is applied to calculate the eigenvalues of the Casimir operators of SU(2), SU(3) and SU(6). In the problems of being unable to apply Casimir operators, the direct matrix diagonalization method, m-scheme, is employed for interacting quarks and for the interaction involving quark mass. To find the attractive interaction in tetraquark (QQqq-bar) state is given as an exercise problem. (Y. Kazumata)

Quarks degrees of freedom and deuteron static moments

International Nuclear Information System (INIS)

Kalashnikova, Yu.S.; Narodetskij, I.M.; Veselov, A.I.

1985-01-01

The probability of the six-quark bag part of the deuteron is defined within recently formulated quark compound bag (QCB) model.An upper limit of about 1% for admixture of the confined bag in the deuteron is found for the QCB potential supplied by the long range Paris interaction. The six-quark bag corrections to the static multipole moments of the deuteron are estimated to be < or approximately 1% for μsub(α) and < or approximately 6% for Qsub(d)

Quark model and high-energy nuclear experiments

International Nuclear Information System (INIS)

Bialas, A.

1979-05-01

Theoretical aspects of the measurements of production of low transverse momentum secondaries in high-energy hadron-nucleus and nucleus-nucleus collisions are discussed. Applications of the quark model to those processes are discussed in some detail. 58 references

Quark model and high-energy nuclear experiments

Energy Technology Data Exchange (ETDEWEB)

Bialas, A.

1979-05-01

Theoretical aspects of the measurements of production of low transverse momentum secondaries in high-energy hadron-nucleus and nucleus-nucleus collisions are discussed. Applications of the quark model to those processes are discussed in some detail. 58 references.

Systematics of quark mass matrices in the standard electroweak model

International Nuclear Information System (INIS)

Frampton, P.H.; Jarlskog, C.; Stockholm Univ.

1985-01-01

It is shown that the quark mass matrices in the standard electroweak model satisfy the empirical relation M = M' + O(lambda 2 ), where M(M') refers to the mass matrix of the charge 2/3 (-1/3) quarks normalized to the largest eigenvalue, msub(t) (msub(b)), and lambda = Vsub(us) approx.= 0.22. (orig.)

Quark self-energy beyond the mean field at finite temperature

International Nuclear Information System (INIS)

Zhuang, P.

1995-01-01

The Nambu--Jona-Lasinio model, an effective low-energy model of QCD, is extended to the next to the leading order in the 1/N c expansion at finite temperature and density. The contributions to the quark self-energy and the constituent quark mass from the meson dressing are considered in a perturbative approach about the mean field. In particular, the temperature dependence of the quark mass is shown numerically at zero chemical potential. The correction to the quark mass from the meson dressing amounts to 20% compared to the result of the leading order at low temperature, and rapidly approaches zero at high temperature

Hadron interactions in quark models

International Nuclear Information System (INIS)

Narodetskij, I.M.

1987-01-01

Some recent developments on the study of quark degrees of freedom in hadron scattering at intermediate energy are reviewed. Physical foundations of the P-matrix approach and the Quark Compound Bag method are discussed including applications to pion-pion, pion-nucleon, nucleon-nucleon and three-nucleon systems

Perturbative study of the QCD phase diagram for heavy quarks at nonzero chemical potential: Two-loop corrections

Science.gov (United States)

Maelger, J.; Reinosa, U.; Serreau, J.

2018-04-01

We extend a previous investigation [U. Reinosa et al., Phys. Rev. D 92, 025021 (2015), 10.1103/PhysRevD.92.025021] of the QCD phase diagram with heavy quarks in the context of background field methods by including the two-loop corrections to the background field effective potential. The nonperturbative dynamics in the pure-gauge sector is modeled by a phenomenological gluon mass term in the Landau-DeWitt gauge-fixed action, which results in an improved perturbative expansion. We investigate the phase diagram at nonzero temperature and (real or imaginary) chemical potential. Two-loop corrections yield an improved agreement with lattice data as compared to the leading-order results. We also compare with the results of nonperturbative continuum approaches. We further study the equation of state as well as the thermodynamic stability of the system at two-loop order. Finally, using simple thermodynamic arguments, we show that the behavior of the Polyakov loops as functions of the chemical potential complies with their interpretation in terms of quark and antiquark free energies.

Prediction of new Quarks, Generations & low Mass Quarks

Science.gov (United States)

Lach, Theodore

2003-04-01

The CBM (model) of the nucleus has resulted in the prediction of two new quarks, an "up" quark of mass 237.31 MeV/c2 and a "dn" quark of mass 42.392 MeV/c2. These two new predicted quarks helped to determine that the masses of the quarks and leptons are all related by a geometric progression relationship. The mass of each quark or lepton is just the "geometric mean" of two related elementary particles, either in the same generation or in the same family. This numerology predicts the following masses for the electron family: 0.511000 (electron), 7.74 (predicted), 117.3, 1778.4 (tau), 26950.1 MeV. The geometric ratio of this progression is 15.154 (e to the power e). The mass of the tau in this theory agrees very well with accepted values. This theory suggests that all the "dn like" quarks have a mass of just 10X multiples of 4.24 MeV (the mass of the "d" quark). The first 3 "up like" quark masses are 38, 237.31 and 1500 MeV. This theory also predicts a new heavy generation with a lepton mass of 27 GeV, a "dn like" quark of 42.4 GeV, and an "up like" quark of 65 GeV. Significant evidence already exists for the existence of these new quarks, and lepton. Ref. Masses of the Sub-Nuclear Particles, nucl-th/ 0008026, @ http://xxx.lanl.gov. Infinite Energy, Vol 5, issue 30.

E1 transitions in the Harari quark model

International Nuclear Information System (INIS)

Kamath, S.G.

1976-10-01

The radiative decays psi(3.684)→γchi(sup(3)P sub(J)) and chi(sup(3)Psub(J)→chipsi(3.1) have been analyzed within the framework of the Harari quark model. The spatial matrix elements describing these L=1 to L=0 transitions have been estimated from the A 2 (1310)→ chirho(770) mode by applying U(6) symmetry at the quark level. The resulting decay widths, which compare very well with experimental data, have subsequently been used to determine the SU(3)sub(H) assignments for the chi states

Thermodynamic potential with condensate fields in an SU(2) model of QCD

International Nuclear Information System (INIS)

Ebert, D.

1996-06-01

We calculate the thermodynamic potential of the quark-gluon plasma in an SU(2) model of QCD, taking into account the gluon condensate configuration with a constant A 4 -potential and a uniform chromomagnetic field H. Within this scheme the interplay of condensate fields, as well as the role of quarks in the possible dynamical stabilization of the system is investigated. (orig.)

Flavor-singlet axial-vector current in quark model within background field

International Nuclear Information System (INIS)

Chen Kun; Yan Mulin

1993-01-01

The flavor-singlet axial-vector current is calculated in a quark model within pseudoscalar background-field through the Seeley-DeWitt coefficients. This current is responsible for the quark spin content of proton and is of O(1) in the large-N e expansion

Composite model for quarks and leptons

International Nuclear Information System (INIS)

Harari, H.

1982-12-01

We discuss the motivation for constructing composite models for quarks and leptons, the hopes we have for a successful model and the difficulties encountered, so far, in this field. This paper corresponds to the contents of lectures given at the SLAC Summer Institute (August 1982), at the DESY Workshop on ''Electroweak Interactions at High Energies'' (September 1982) and at the Solvay Conference at the University of Texas, Austin, Texas (November 1982). (author)

Unpolarized structure functions and the parton distributions for nucleon in an independent quark model

Energy Technology Data Exchange (ETDEWEB)

Barik, N [Dept. of Physics, Utkal Univ., Bhubaneswar (India); Mishra, R N [Dept. of Physics, Dhenkanal College, Dhenkanal (India)

2001-04-01

Considering the nucleon as consisting entirely of its valence quarks confined independently in a scalar-vector harmonic potential; unpolarized structure functions F{sub 1} (x, {mu}{sup 2}) and F{sub 2} (x, {mu}{sup 2}) are derived in the Bjorken limit under certain simplifying assumptions; from which valence quark distribution functions u{sub v} (x, {mu}{sup 2}) and d{sub v} (x, {mu}{sup 2}) are appropriately extracted satisfying the normalization constraints. QCD-evolution of these input distributions from a model scale of {mu}{sup 2} = 0.07 GeV{sup 2} to a higher Q{sup 2} scale of Q{sub 0}{sup 2} = 15 GeV{sup 2} yields xu{sub v} (x, Q{sub 0}{sup 2}) and xd{sub v} (x, Q{sub 0}{sup 2}) in good agreement with experimental data. The gluon and sea-quark distributions such as G (x, Q{sub 0}{sup 2}) and q{sub s} (x, Q{sub 0}{sup 2}) are dynamically generated with a reasonable qualitative agreement with the available data; using the leading order renormalization group equations with appropriate valence-quark distributions as the input. (author)

On the quark structure of resonance states in dual models

International Nuclear Information System (INIS)

Volkov, D.V.; Zheltukhin, A.A.; Pashnev, A.I.

1975-01-01

It is shown using as an example the Veneziano dual model, that each particular dual model already contains a certain latent quark structure unambiauously determined by internal properties of the dual model. To prove this degeneration of the resonance state spectrum is studied by introducing an additional disturbing interaction into the model being considered. Induced transitions of particles into a vacuum act as such an additional disturbance. This method complements the known factorization method of Fubini, Gordon and Veneziano and turns out to be free from an essential limitation of the latter connected with implicit assumption about the basence of internal additive laws of conservation in the model. By using the method of induced transitions of particles into a vacuum it has been possible to show that the resonance state spectrum is indeed more degenerated than it should be expected from the factorization theorem, and that the supplementary degeneration corresponds to the quark model with an infinite number of quarks of the increasing mass. Structures of some terms of the dual amplitude expansion over the degrees of the constant of the induced transition of particles to vacuum are considered; it is shown that the summation of this expansion may be reduced to a solution of a certain integral equation. On the basis of the integral equation obtained an integral representation ofr dual amplitudes is established. The problems related with degeneration of resonance states and with determination of additive quantum numbers leading to the quark interpretation of the degeneration being considered are discussed

Transport coefficients of Quark-Gluon plasma with full QCD potential

Science.gov (United States)

J. P., Prasanth; Bannur, Vishnu M.

2018-05-01

The shear viscosity η, bulk viscosity ζ and their ratio with the entropy density, η / s, ζ / s have been studied in a quark-gluon plasma (QGP) within the cluster expansion method. The cluster expansion method allows us to include the interaction between the partons in the deconfined phase and to calculate the equation of state of quark-gluon plasma. It has been argued that the interactions present in the equation of state, the modified Cornell potential significantly contributes to the viscosity. The results obtained within our approaches agree with lattice quantum chromodynamics (LQCD) equation of state. We obtained η / s ≈ 0 . 128 within the temperature range T /Tc ∈ [ 0 . 9 , 1 . 5 ] which is very close to the theoretical lower bound η / s ≥ 1 /(4 π) in Yang-Mills theory. We also demonstrate that the effects of ζ / s at freezeout are possibly large.

Model uncertainties in top-quark physics

CERN Document Server

Seidel, Markus

2014-01-01

The ATLAS and CMS collaborations at the Large Hadron Collider (LHC) are studying the top quark in pp collisions at 7 and 8 TeV. Due to the large integrated luminosity, precision measurements of production cross-sections and properties are often limited by systematic uncertainties. An overview of the modeling uncertainties for simulated events is given in this report.

Study of dibaryon states containing three different types of quarks

International Nuclear Information System (INIS)

Leandri, J.; Silvestre-Brac, B.

1997-01-01

Previously we have shown, in a simple chromomagnetic model, that including heavy quarks in the dibaryon sector can lead to favorable configurations for stability against decay into two baryons. In this study we investigate a reduced set of favorable candidates that have emerged from our previous works. We use a non-relativistic quark model with quarks interacting through a QCD-inspired potential, which has been tested previously in meson and baryon spectroscopy. A variational procedure is performed using a great number of Gaussian functions containing all the possibilities for colour, isospin, and spin components. (author)

The Quark - A Decade Later

Science.gov (United States)

Dakin, James T.

1974-01-01

Reviews theoretical principles underlying the quark model. Indicates that the agreement with experimental results and the understanding of the quark-quark force are two hurdles for the model to survive in the future. (CC)

Gluon condensation and modelling of quark confinement in QCD-motivated Nambu-Jona-Lasinio model

International Nuclear Information System (INIS)

Bel'kov, A.A.; Ebert, D.; Emel'yanenko, A.V.

1992-01-01

The possibility of modelling of a quark propagator without poles realizing quark confinement is considered on the basis of a nonperturbative gluon propagator including gluon condensation and a dynamical gluon mass. The property of spontaneous chiral symmetry breaking is retained providing us with a reasonable pattern of low-lying meson properties. 2 figs.; 1 tab

Exact solutions to a schematic nuclear quark model and colorless superconductivity

DEFF Research Database (Denmark)

Bohr, Henrik; da Providencia, Joao

2008-01-01

Exact solutions are found to the equations of a standard nuclear quark model exemplified by the Bonn model which is defined in terms of an effective pairing force. We show, by symmetry arguments, that, in general, the ground state of this model is not color neutral. In particular, color-neutral s......Exact solutions are found to the equations of a standard nuclear quark model exemplified by the Bonn model which is defined in terms of an effective pairing force. We show, by symmetry arguments, that, in general, the ground state of this model is not color neutral. In particular, color...

In quest of a relativistic constituent quark model - some constructive remarks

International Nuclear Information System (INIS)

Hofsaess, T.; Schierholz, G.

1978-01-01

The set-up of a relativistic constituent quark model in four dimensions is one of the outstanding problems in particle physics. For the time being this involves a great deal of model building which, very probably, will not change in the near future. In this paper we shall offer some general remarks which might help putting such models into shape. Most of the earlier attempts are found controversial. In particular, a conventional quark constituent interpretation could not be recovered. (orig.) [de

Quark matter revisited with non-extensive MIT bag model

Energy Technology Data Exchange (ETDEWEB)

Cardoso, Pedro H.G.; Nunes da Silva, Tiago; Menezes, Debora P. [Universidade Federal de Santa Catarina, Departamento de Fisica, CFM, Florianopolis (Brazil); Deppman, Airton [Instituto de Fisica da Universidade de Sao Paulo, Sao Paulo (Brazil)

2017-10-15

In this work we revisit the MIT bag model to describe quark matter within both the usual Fermi-Dirac and the Tsallis statistics. We verify the effects of the non-additivity of the latter by analysing two different pictures: the first order phase transition of the QCD phase diagram and stellar matter properties. While the QCD phase diagram is visually affected by the Tsallis statistics, the resulting effects on quark star macroscopic properties are barely noticed. (orig.)

Quark bags, P-matrix and nucleon-nucleon scattering

International Nuclear Information System (INIS)

Narodetskij, I.M.

1984-01-01

This paper is an extended version of the talk given at IX European Conference on Few Body Problems in Physics, Tbilisi, 1984. It reviews recent developments of the quark compound bag (QCB) model including explicit examples of the QCB nucleon-nucleon potentials, description of the deuteron properties, calculation of the six quark admixture in the deuteron and applications to the three-nucleon system

Topology of magnetic fields in particle physics, implications on the quark model

Energy Technology Data Exchange (ETDEWEB)

Jehle, H.

1977-01-01

The flux-loop model of quarks is considered covering electomagnetic gauge invariance, flux quantization, topological conditions for the magnetic field, the extended source model, the electric field, linkage of loop forms, topology and motion of flux loop forms, coalial loops of hadrons having weak interactions, magnetic moments of hadrons, strong interactions, some remarks about string models, and the implications of he topological quark model on the ground and excited states of mesons. 80 references. (JFP)

Pion polarizability in nonlocal quark model

International Nuclear Information System (INIS)

Efimov, G.V.; Okhlopkova, V.A.

1978-01-01

The γγ→ππ amplitude was calculated in nonlocal quark model in the fourth order on the perturbation theory. The coefficients of electric[a) and magnetic polarizability (β) determined are equal in magnitude and opposite in sign αsub(π+-)=βsub(π+-)=+0.014α/msub(π)sup(3), αsub(πsup(0))=-βsub(πsup(0))=-0.07α/msub(π)sup(3). The results have been compared with calculations in other models

QCD topological susceptibility from the nonlocal chiral quark model

Science.gov (United States)

Nam, Seung-Il; Kao, Chung-Wen

2017-06-01

We investigate the quantum chromodynamics (QCD) topological susceptibility χ by using the semi-bosonized nonlocal chiral-quark model (SB-NLχQM) for the leading large- N c contributions. This model is based on the liquid-instanton QCD-vacuum configuration, in which SU(3) flavor symmetry is explicitly broken by the finite current-quark mass ( m u,d, m s) ≈ (5, 135) MeV. To compute χ, we derive the local topological charge-density operator Q t( x) from the effective action of SB-NLχQM. We verify that the derived expression for χ in our model satisfies the Witten- Veneziano (WV) and the Leutwyler-Smilga (LS) formulae, and the Crewther theorem in the chiral limit by construction. Once the average instanton size and the inter-instanton distance are fixed with ρ¯ = 1/3 fm and R¯ = 1 fm, respectively, all the other parameters are determined self-consistently within the model. We obtain χ = (167.67MeV)4, which is comparable with the empirical value χ = (175±5MeV)4 whereas it turns out that χ QL = (194.30MeV)4 in the quenched limit. Thus, we conclude that the value of χ will be reduced around 10 20% by the dynamical-quark contribution.

Equation of state for neutron matter in the Quark Compound Bag model

Science.gov (United States)

Krivoruchenko, M. I.

2017-11-01

The equation of state for neutron matter is derived in the framework of the Quark Compound Bag model, in which the nucleon-nucleon interaction is generated by the s-channel exchange of six-quark Jaffe-Low primitives.

Incorporating pion effects into the naive quark model

International Nuclear Information System (INIS)

Nogami, Y.; Ohtuska, N.

1982-01-01

A hybrid of the naive nonrelativistic quark model and the Chew-Low model is proposed. The pion is treated as an elementary particle which interacts with the ''bare baryon'' or ''baryon core'' via the Chew-Low interaction. The baryon core, which is the source of the pion interaction, is described by the naive nonrelativistic quark model. It turns out that the baryon-core radius has to be as large as 0.8 fm, and consequently the cutoff momentum Λ for the pion interaction is < or approx. =3m/sub π/, m/sub π/ being the pion mass. Because of this small Λ (as compared with Λapprox. nucleon mass in the old Chew-Low model) the effects of the pion cloud are strongly suppressed. The baryon masses, baryon magnetic moments, and the nucleon charge radii can be reproduced quite well. However, we found it singularly difficult to fit the axial-vector weak decay constant g/sub A/

Consideration of the vacuum of QCD in a composite quark model. Strange hadrons

International Nuclear Information System (INIS)

Dorokhov, A.E.; Kochelev, N.I.

1986-01-01

The method of inclusion of QCD vacuum condensates within the quark composite model is generalized to the case of hadrons containing strange quarks. The mass formula for such hadrons is obtained. The mass of strange quark is defined by analysing the energy spectrum of hadron ground states. The mixing angles of pseudoscalar mesons are estimated

Generation labels in composite models for quarks and leptons

International Nuclear Information System (INIS)

Harari, H.; Seiberg, N.

1981-03-01

Models in which quarks and leptons are approximately massless composites of fundamental massless fermions which are confined by a hypercolor force are considered. The fundamental Lagrangian exhibits an axial U(1)sub(X) symmetry which is broken by hypercolor instantons, leaving a conserved discrete subgroup. It is proposed that the distinction between different generations of quarks and leptons is given by the X-number. The resulting generation labelling scheme does not lead to massless Goldstone bosons or to new anomalies and is based on a quantum number which is already contained in the theory. The dynamical rishon model is described as an illustrative example. (H.K.)

Semileptonic Decays of Heavy Omega Baryons in a Quark Model

International Nuclear Information System (INIS)

Muslema Pervin; Winston Roberts; Simon Capstick

2006-01-01

The semileptonic decays of (Omega) c and (Omega) b are treated in the framework of a constituent quark model developed in a previous paper on the semileptonic decays of heavy Λ baryons. Analytic results for the form factors for the decays to ground states and a number of excited states are evaluated. For (Omega) b to (Omega) c the form factors obtained are shown to satisfy the relations predicted at leading order in the heavy-quark effective theory at the non-recoil point. A modified fit of nonrelativistic and semirelativistic Hamiltonians generates configuration-mixed baryon wave functions from the known masses and the measured Λ c + → Λe + ν rate, with wave functions expanded in both harmonic oscillator and Sturmian bases. Decay rates of (Omega) b to pairs of ground and excited (Omega) c states related by heavy-quark symmetry calculated using these configuration-mixed wave functions are in the ratios expected from heavy-quark effective theory, to a good approximation. Our predictions for the semileptonic elastic branching fraction of (Omega) Q vary minimally within the models we use. We obtain an average value of (84 ± 2%) for the fraction of (Omega) c → Ξ (*) decays to ground states, and 91% for the fraction of (Omega) c → (Omega) (*) decays to the ground state (Omega). The elastic fraction of (Omega) b → (Omega) c ranges from about 50% calculated with the two harmonic-oscillator models, to about 67% calculated with the two Sturmian models

Inclusive production of large-p/sub T/ protons and quark-quark elastic scattering

International Nuclear Information System (INIS)

Chen, C.K.

1978-01-01

A proton-formation process in combination with hard quark-quark scattering is capable of explaining the observed large-p/sub T/ single-proton inclusive production data. This model implies that the inclusive production of two large-p/sub T/ protons at opposite directions is dominated by large-angle elastic scattering of two up quarks, and becomes an ideal place to study elastic quark-quark scattering. This two-proton inclusive production process is also ideal for the study of the spin structure of quark-quark elastic scattering, so the assumptions of pure vector-type quark-quark interaction and of colored quarks can be checked empirically. The consistency of applying the quark-elastic-scattering idea to large-angle elastic proton-proton scattering and to the inclusive production of large-p/sub T/ protons is also demonstrated

General structure of democratic mass matrix of quark sector in E{sub 6} model

Energy Technology Data Exchange (ETDEWEB)

Ciftci, R., E-mail: rciftci@cern.ch [Ankara (Turkey); Çiftci, A. K., E-mail: abbas.kenan.ciftci@cern.ch [Ankara University, Ankara (Turkey)

2016-03-25

An extension of the Standard Model (SM) fermion sector, which is inspired by the E{sub 6} Grand Unified Theory (GUT) model, might be a good candidate to explain a number of unanswered questions in SM. Existence of the isosinglet quarks might explain great mass difference of bottom and top quarks. Also, democracy on mass matrix elements is a natural approach in SM. In this study, we have given general structure of Democratic Mass Matrix (DMM) of quark sector in E6 model.

Gravitational form factors and angular momentum densities in light-front quark-diquark model

Energy Technology Data Exchange (ETDEWEB)

Kumar, Narinder [Indian Institute of Technology Kanpur, Department of Physics, Kanpur (India); Mondal, Chandan [Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China); Sharma, Neetika [I K Gujral Punjab Technical University, Department of Physical Sciences, Jalandhar, Punjab (India); Panjab University, Department of Physics, Chandigarh (India)

2017-12-15

We investigate the gravitational form factors (GFFs) and the longitudinal momentum densities (p{sup +} densities) for proton in a light-front quark-diquark model. The light-front wave functions are constructed from the soft-wall AdS/QCD prediction. The contributions from both the scalar and the axial vector diquarks are considered here. The results are compared with the consequences of a parametrization of nucleon generalized parton distributions (GPDs) in the light of recent MRST measurements of parton distribution functions (PDFs) and a soft-wall AdS/QCD model. The spatial distribution of angular momentum for up and down quarks inside the nucleon has been presented. At the density level, we illustrate different definitions of angular momentum explicitly for an up and down quark in the light-front quark-diquark model inspired by AdS/QCD. (orig.)

Building the nucleus from quarks: The cloudy bag model and the quark description of the nucleon-nucleon wave functions

International Nuclear Information System (INIS)

Miller, G.A.

1984-01-01

In the Cloudy Bag Model hadrons are treated as quarks confined in an M.I.T. bag that is surrounded by a cloud of pions. Computations of the charge and magnetism distributions of nucleons and baryons, pion-nucleon scattering, and the strong and electromagnetic decays of mesons are discussed. Agreement with experimental results is excellent if the nucleon bag radius is in the range between 0.8 and 1.1 fm. Underlying qualitative reasons which cause the pionic corrections to be of the obtained sizes are analyzed. If bags are of such reasonably large sizes, nucleon bags in nuclei will often come into contact. As a result one needs to consider whether explicit quark degrees of freedom are relevant for Nuclear Physics. To study such possibilities a model which treats a nucleus as a collection of baryons, pions and six-quark bags is discussed. In particular, the short distance part of a nucleon-nucleon wave function is treated as six quarks confined in a bag. This approach is used to study the proton-proton weak interaction, the asymptotic D to S state ratio of the deuteron, the pp → dπ reaction, the charge density of /sup 3/He, magnetic moments of /sup 3/He and /sup 3/H and, the /sup 3/He-/sup 3/H binding energy difference. It is found that quark effects are very relevant for understanding nuclear properties

Pion polarizability in a chiral quark model

International Nuclear Information System (INIS)

Ebert, D.; Volkov, M.K.

1981-01-01

The pion polarizability is calculated in a chiral meson-quark model at the one-loop level. The results are in complete agreement with earlier ones obtained within a chiral meson-baryon theory. A critical discussion of a recent paper by Llanta and Tarrach is given. (orig.)

Pion polarizability in a chiral quark model

International Nuclear Information System (INIS)

Volkov, M.K.; Ehbert, D.

1981-01-01

The pion polarizability is calculated in a chiral meson- quark model at the one-loop level. The results are in complete agreement with earlier ones obtained within a chiral meson-baryon theory. A critical discussion of a recent paper by Llanta and Tarrach is given [ru

Top quark decays in extended models

International Nuclear Information System (INIS)

Gaitan, R.; Cabral-Rosetti, L.G.

2011-01-01

We evaluate the FCNC decays t → H 0 + c at tree-level and t → γ + c at one-loop level in the context of Alternative Left-Right symmetric Models (ALRM) with extra isosinglet heavy fermions; in the first case, FCNC decays occurs at tree-level and they are only suppressed by the mixing between ordinary top and charm quarks. (author)

Heavy mesons spectroscopy and new quarks

International Nuclear Information System (INIS)

Carvalho, H.F. de.

1977-12-01

The spectroscopy of new heavy mesons with masses above 2.8 GeV in the context of the asymptoticallty free gauge theories is analysed. To this end a power -law confinement potential is chosen. It is shown that the charmonium spectroscopy is best described by a potential where the exponent is around 0.5. It is observed that the spin-spin interaction is problematic. A possible interpretation of the γ resonances in the neighbourhood of 10 GeV is also discussed. The possible consequences of the existence of heavy quarks beyond charm with special reference to the processes initiated by neutral currents is also discussed. The present results on processes initiated by neutral current effects does not require introduction of right-handed heavy quarks beyond charm. Inclusion of the sea-quark contribution improves the agreements of the results of the Salam-Weinberg model with the recently observed results from CERN where 'ν anomaly' was not seen. The recently discovered γ resonances probably indicate the existence of heavy quarks probably with left handed coupling. Some preliminary study of this possibility was also carried out. (Author) [pt

The baryonic spectrum in a constituent quark model including a three-body force

International Nuclear Information System (INIS)

Desplanques, B.; Gignoux, C.; Silvestre-Brac, B.; Gonzalez, P.; Navarro, J.; Noguera, S.

1992-01-01

We analyze, within a non-relativistic quark model, the low energy part of the baryonic spectrum in the octet and decuplet flavour representations. The relevance of a strong Coulomb potential is emphasized in order to explain its general features. The addition of a three-body force allows to solve the 'Roper puzzle', giving a consistent explanation to its relative position in the spectrum. (orig.)

Effective field theory and the quark model

International Nuclear Information System (INIS)

Durand, Loyal; Ha, Phuoc; Jaczko, Gregory

2001-01-01

We analyze the connections between the quark model (QM) and the description of hadrons in the low-momentum limit of heavy-baryon effective field theory in QCD. By using a three-flavor-index representation for the effective baryon fields, we show that the 'nonrelativistic' constituent QM for baryon masses and moments is completely equivalent through O(m s ) to a parametrization of the relativistic field theory in a general spin-flavor basis. The flavor and spin variables can be identified with those of effective valence quarks. Conversely, the spin-flavor description clarifies the structure and dynamical interpretation of the chiral expansion in effective field theory, and provides a direct connection between the field theory and the semirelativistic models for hadrons used in successful dynamical calculations. This allows dynamical information to be incorporated directly into the chiral expansion. We find, for example, that the striking success of the additive QM for baryon magnetic moments is a consequence of the relative smallness of the non-additive spin-dependent corrections

Color-flavor locked strange quark matter in a mass density-dependent model

International Nuclear Information System (INIS)

Chen Yuede; Wen Xinjian

2007-01-01

Properties of color-flavor locked (CFL) strange quark matter have been studied in a mass-density-dependent model, and compared with the results in the conventional bag model. In both models, the CFL phase is more stable than the normal nuclear matter for reasonable parameters. However, the lower density behavior of the sound velocity in this model is completely opposite to that in the bag model, which makes the maximum mass of CFL quark stars in the mass-density-dependent model larger than that in the bag model. (authors)

Quark mass correction to chiral separation effect and pseudoscalar condensate

Energy Technology Data Exchange (ETDEWEB)

Guo, Er-dong [State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,Chinese Academy of Sciences,Beijing 100190 (China); Kavli Institute of Theoretical Physics China, Chinese Academy of Sciences,Beijing 100190 (China); Lin, Shu [School of Physics and Astronomy, Sun Yat-Sen University,No 2 University Road, Zhuhai 519082 (China)

2017-01-25

We derived an analytic structure of the quark mass correction to chiral separation effect (CSE) in small mass regime. We confirmed this structure by a D3/D7 holographic model study in a finite density, finite magnetic field background. The quark mass correction to CSE can be related to correlators of pseudo-scalar condensate, quark number density and quark condensate in static limit. We found scaling relations of these correlators with spatial momentum in the small momentum regime. They characterize medium responses to electric field, inhomogeneous quark mass and chiral shift. Beyond the small momentum regime, we found existence of normalizable mode, which possibly leads to formation of spiral phase. The normalizable mode exists beyond a critical magnetic field, whose magnitude decreases with quark chemical potential.

Nuclear matter from effective quark-quark interaction.

Science.gov (United States)

Baldo, M; Fukukawa, K

2014-12-12

We study neutron matter and symmetric nuclear matter with the quark-meson model for the two-nucleon interaction. The Bethe-Bruckner-Goldstone many-body theory is used to describe the correlations up to the three hole-line approximation with no extra parameters. At variance with other nonrelativistic realistic interactions, the three hole-line contribution turns out to be non-negligible and to have a substantial saturation effect. The saturation point of nuclear matter, the compressibility, the symmetry energy, and its slope are within the phenomenological constraints. Since the interaction also reproduces fairly well the properties of the three-nucleon system, these results indicate that the explicit introduction of the quark degrees of freedom within the considered constituent quark model is expected to reduce the role of three-body forces.

Leading Twist TMDs in a Light-Front Quark-Diquark Model for Proton

Science.gov (United States)

Maji, Tanmay; Chakrabarti, Dipankar

2018-05-01

We present p_{\\perp } variation (fixed x) of the leading-twist T-even transverse momentum dependent parton distributions (TMDs) of a proton in a light-front quark-diquark model at μ ^2=2.4 and 20 GeV^2. The quark densities for unpolarized and transversely polarized proton are also presented. We observe a Soffer bound for TMDs in this model.

Results of the naive quark model

International Nuclear Information System (INIS)

Gignoux, C.

1987-10-01

The hypotheses and limits of the naive quark model are recalled and results on nucleon-nucleon scattering and possible multiquark states are presented. Results show that with this model, ropers do not come. For hadron-hadron interactions, the model predicts Van der Waals forces that the resonance group method does not allow. Known many-body forces are not found in the model. The lack of mesons shows up in the absence of a far reaching force. However, the model does have strengths. It is free from spuriousness of center of mass, and allows a democratic handling of flavor. It has few parameters, and its predictions are very good [fr

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

A QCD derivation of the additive quark model from two and three gluon exchanges

International Nuclear Information System (INIS)

Lipkin, H.J.

1982-06-01

The contributions to the Pomeron from two and three gluon exchanges are shown to give the correct combinatorial factors for the additive quark model relation between meson and baryon Pomeron couplings, even though two-quark and three-quark operators are involved. Similar results hold for the contributions to hadron masses from three-gluon vertices as well as one-gluon exchange. The color algebra reduces the multiquark couplings to a linear function of quark number. (author)

On the limits of application of the nolocal quark model

International Nuclear Information System (INIS)

Efimov, G.V.; Ivanov, M.A.; Novitsyn, E.A.; Ryabtsev, A.D.

1983-01-01

The possibility of application of the nolocal quark model (NQM) to the physics of mesons, containin charmed quarks, is considered. A method for description of states with identical quantum numbers is suggested. I' order to distinguish between such states different quark currents are introduced with additional condition of ''o thogonality'' implied. The latter allows one to neglect nondiagonal off-shell matrix elements in compositeness conditi ' for coupling constants. In the framework of NQM with ditional assumptions mentioned several decay widths of vector charmonium states have been computed, namely lepton c widths of J/psi(3100), psi'(3685) and psi(3770) an the decay width into charmed D-mesons psi(3770) → D nti D. It is shown that the two-parametric freedom of the m del is not sufficient to fit the experimental data. It is co'cluded that the revision of basic concepts of NQM is nec ssary in physics of mesons containing c-quarks

Measurements and searches with top quarks

International Nuclear Information System (INIS)

Peters, Reinhild Yvonne

2008-01-01

In 1995 the last missing member of the known families of quarks, the top quark, was discovered by the CDF and D0 experiments at the Tevatron, a proton-antiproton collider at Fermilab near Chicago. Until today, the Tevatron is the only place where top quarks can be produced. The determination of top quark production and properties is crucial to understand the Standard Model of particle physics and beyond. The most striking property of the top quark is its mass--of the order of the mass of a gold atom and close to the electroweak scale--making the top quark not only interesting in itself but also as a window to new physics. Due to the high mass, much higher than of any other known fermion, it is expected that the top quark plays an important role in electroweak symmetry breaking, which is the most prominent candidate to explain the mass of particles. In the Standard Model, electroweak symmetry breaking is induced by one Higgs field, producing one additional physical particle, the Higgs boson. Although various searches have been performed, for example at the Large Electron Positron Collider (LEP), no evidence for the Higgs boson could yet be found in any experiment. At the Tevatron, multiple searches for the last missing particle of the Standard Model are ongoing with ever higher statistics and improved analysis techniques. The exclusion or verification of the Higgs boson can only be achieved by combining many techniques and many final states and production mechanisms. As part of this thesis, the search for Higgs bosons produced in association with a top quark pair (t(bar t)H) has been performed. This channel is especially interesting for the understanding of the coupling between Higgs and the top quark. Even though the Standard Model Higgs boson is an attractive candidate, there is no reason to believe that the electroweak symmetry breaking is induced by only one Higgs field. In many models more than one Higgs boson are expected to exist, opening even more channels

Results on top-quark physics and top-quark-like signatures by CMS

Science.gov (United States)

Chabert, Eric; CMS Collaboration

2017-07-01

This report reviews the results obtained by the CMS Collaboration on top quark physics, focusing on the latest ones based on p-p collisions provided by the LHC at \\sqrt{s}=13{{TeV}} during Run II. It covers measurements of single-top, top quark pairs and associated productions as well as measurements of top quark properties. Finally several beyond the standard model searches involving top quark in the final states are presented, such as searches for supersymmetry in the third generation, heavy resonances decaying into a top quark pair, or dark matter produced in association to a single-top or a top quark pair.

A new parametric equation of state and quark stars

International Nuclear Information System (INIS)

Na Xuesen; Xu Renxin

2011-01-01

It is still a matter of debate to understand the equation of state of cold matter with supra-nuclear density in compact stars because of unknown non-perturbative strong interaction between quarks. Nevertheless, it is speculated from an astrophysical view point that quark clusters could form in cold quark matter due to strong coupling at realistic baryon densities. Although it is hard to calculate this conjectured matter from first principles, one can expect that the inter-cluster interaction will share some general features with the nucleon- nucleon interaction successfully depicted by various models. We adopt a two-Gaussian component soft-core potential with these general features and show that quark clusters can form stable simple cubic crystal structure if we assume that the wave function of quark clusters have a Gaussian form. With this parametrization, the Tolman-Oppenheimer-Volkoff equation is solved with reasonably constrained parameter space to give mass-radius relations of crystalline solid quark stars. With baryon number densities truncated at 2n 0 at surface and the range of the interaction fixed at 2 fm we can reproduce similar mass-radius relations to that obtained with bag model equations of state. The maximum mass ranges from ∼ 0.5 solar mass to approx.> 3 solar mass . The recently measured high pulsar mass (approx.> 2 solar mass ) is then used to constrain the parameters of this simple interaction potential. (authors)

Properties of the Top Quark

Energy Technology Data Exchange (ETDEWEB)

Wicke, Daniel; /Wuppertal U., Dept. Math.

2009-08-01

The aim of particle physics is the understanding of elementary particles and their interactions. The current theory of elementary particle physics, the Standard Model, contains twelve different types of fermions which (neglecting gravity) interact through the gauge bosons of three forces. In addition a scalar particle, the Higgs boson, is needed for theoretical consistency. These few building blocks explain all experimental results found in the context of particle physics, so far. Nevertheless, it is believed that the Standard Model is only an approximation to a more complete theory. First of all the fourth known force, gravity, has withstood all attempts to be included until now. Furthermore, the Standard Model describes several features of the elementary particles like the existence of three families of fermions or the quantisation of charges, but does not explain these properties from underlying principles. Finally, the lightness of the Higgs boson needed to explain the symmetry breaking is difficult to maintain in the presence of expected corrections from gravity at high scales. This is the so called hierarchy problem. In addition astrophysical results indicate that the universe consists only to a very small fraction of matter described by the Standard Model. Large fractions of dark energy and dark matter are needed to describe the observations. Both do not have any correspondence in the Standard Model. Also the very small asymmetry between matter and anti-matter that results in the observed universe built of matter (and not of anti-matter) cannot be explained until now. It is thus an important task of experimental particle physics to test the predictions of the Standard Model to the best possible accuracy and to search for deviations pointing to necessary extensions or modifications of our current theoretical understanding. The top quark was predicted to exist by the Standard Model as the partner of the bottom quark. It was first observed in 1995 by the

Properties of the Top Quark

International Nuclear Information System (INIS)

Wicke, Daniel

2009-01-01

The aim of particle physics is the understanding of elementary particles and their interactions. The current theory of elementary particle physics, the Standard Model, contains twelve different types of fermions which (neglecting gravity) interact through the gauge bosons of three forces. In addition a scalar particle, the Higgs boson, is needed for theoretical consistency. These few building blocks explain all experimental results found in the context of particle physics, so far. Nevertheless, it is believed that the Standard Model is only an approximation to a more complete theory. First of all the fourth known force, gravity, has withstood all attempts to be included until now. Furthermore, the Standard Model describes several features of the elementary particles like the existence of three families of fermions or the quantisation of charges, but does not explain these properties from underlying principles. Finally, the lightness of the Higgs boson needed to explain the symmetry breaking is difficult to maintain in the presence of expected corrections from gravity at high scales. This is the so called hierarchy problem. In addition astrophysical results indicate that the universe consists only to a very small fraction of matter described by the Standard Model. Large fractions of dark energy and dark matter are needed to describe the observations. Both do not have any correspondence in the Standard Model. Also the very small asymmetry between matter and anti-matter that results in the observed universe built of matter (and not of anti-matter) cannot be explained until now. It is thus an important task of experimental particle physics to test the predictions of the Standard Model to the best possible accuracy and to search for deviations pointing to necessary extensions or modifications of our current theoretical understanding. The top quark was predicted to exist by the Standard Model as the partner of the bottom quark. It was first observed in 1995 by the

Hidden Fine Tuning In The Quark Sector Of Little Higgs Models

CERN Document Server

Grinstein, Benjamin; Uttayarat, Patipan

2010-01-01

In Little Higgs models a collective symmetry prevents the higgs from acquiring a quadratically divergent mass at one loop. We have previously shown that the couplings in the Littlest Higgs model introduced to give the top quark a mass do not naturally respect the collective symmetry. We extend our previous work showing that the problem is generic: it arises from the fact that the would be collective symmetry of any one top quark mass term is broken by gauge interactions.

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

Instanton vacuum at finite density of quark matter

International Nuclear Information System (INIS)

Molodtsov, S.V.; Zinovjev, G.M.

2002-01-01

We study light quark interactions in the instanton liquid at finite quark/baryon number density analyzing chiral and diquark condensates and investigate the behaviors of quark dynamical mass and both condensates together with instanton liquid density as a function of quark chemical potential. We conclude the quark impact (estimated in the tadpole approximation) on the instanton liquid could shift color superconducting phase transition to higher values of the chemical potential bringing critical quark matter density to the values essentially higher than conventional nuclear one

Multi-Quarks and Two-Baryon Interaction in Lattice QCD

International Nuclear Information System (INIS)

Okiharu, F.; Suganuma, H.; Takahashi, T. T.; Doi, T.

2006-01-01

We study multi-quark (3Q,4Q,5Q) systems in lattice QCD. We perform the detailed studies of multi-quark potentials in lattice QCD to clarify the inter-quark interaction in multi-quark systems. We find that all the multi-quark potentials are well described by the OGE Coulomb plus multi-Y-type linear potential, i.e., the multi-Y Ansatz. For multi-quark systems, we observe lattice QCD evidences of 'flip-flop', i.e., flux-tube recombination. These lattice QCD studies give an important bridge between elementary particle physics and nuclear physics

Nucleon spin-flavor structure in the SU(3)-breaking chiral quark model

International Nuclear Information System (INIS)

Song, X.; McCarthy, J.S.; Weber, H.J.

1997-01-01

The SU(3) symmetric chiral quark model, which describes interactions between quarks, gluons, and the Goldstone bosons, explains reasonably well many aspects of the flavor and spin structure of the proton, except for the values of f 3 /f 8 and Δ 3 /Δ 8 . Introducing the SU(3)-breaking effect suggested by the mass difference between the strange and nonstrange quarks, we find that this discrepancy can be removed and better overall agreement obtained. copyright 1997 The American Physical Society

Quark spin-flavor layered structure with condensed π/sup 0/ field in Chiral bag model

International Nuclear Information System (INIS)

Tamagaki, R.; Tatsumi, T.

1984-01-01

In order to understand predispositions of high density matter, a new phase possibly arising from the neutron matter under π/sup 0/ condensation is studied in chiral bag model, as a facet in which both quark and pion degrees of freedom are incorporated in a well-developed situation of π/sup 0/ condensation. The aspects of this phase are characterized by the periodic layered structure of the two-dimensional quark matter with a specific spin-flavor order the π/sup 0/ field existent as the Nambu-Goldstone mode between the adjacent layers. Such quark configuration is caused due to the pion-quark coupling at the layer (bag) surface which drastically lowers quark energy. Energy properties of the system are examined, and it is shown that the one-gluon-exchange contribution provides the repulsive effect to prevent the layered structure from collapsing. This model provides an example which can be solved nonperturbatively in the chiral bag model and suggests the possibility of an intermediate stage which may appear prior to the phase transition to uniform quark matter

Faddeev approach in three-quark systems

International Nuclear Information System (INIS)

Kuperin, Yu.A.; Kvintsinskij, A.A.; Merkur'ev, S.P.; Novozhilov, V.Yu.

1985-01-01

Calculations of baryon static properties represent a noval field where the Faddeev differential equations are applied. The mass spectra and were functions of baryons from multiplets of spin-partity Jsup(P)=1/2 + , 3/2 + are investigated in non-relativistic quark model. The structure parameters characterizing the ''quality'' of the baryon wave functions, i.e. charge radii, electromagnetic form factors quark distribution functions, are calculated. It is shown that the majority of the popular qq-potentials do not give ''high quality'' wave functions in spite of the good fit for the hadron masses

Quark-nuclear hybrid star equation of state with excluded volume effects

Science.gov (United States)

Kaltenborn, Mark Alexander Randolph; Bastian, Niels-Uwe Friedrich; Blaschke, David Bernhard

2017-09-01

A two-phase description of the quark-nuclear matter hybrid equation of state that takes into account the effect of excluded volume in both the hadronic and the quark-matter phases is introduced. The nuclear phase manifests a reduction of the available volume as density increases, leading to a stiffening of the matter. The quark-matter phase displays a reduction of the effective string tension in the confining density functional from available volume contributions. The nuclear equation of state is based upon the relativistic density-functional model DD2 with excluded volume. The quark-matter equation of state is based upon a quasiparticle model derived from a relativistic density-functional approach and will be discussed in greater detail. The interactions are decomposed into mean scalar and vector components. The scalar interaction is motivated by a string potential between quarks, whereas the vector interaction potential is motivated by higher-order interactions of quarks leading to an increased stiffening at high densities. As an application, we consider matter under compact star constraints of electric neutrality and β equilibrium. We obtain mass-radius relations for hybrid stars that form a third family, disconnected from the purely hadronic star branch, and fulfill the 2 M⊙ constraint.

Mass spectrum of vector mesons in the relativistic model of quasi-independent quarks

International Nuclear Information System (INIS)

Savrin, V.I.; Khrushchev, V.V.; Semenov, S.V.

1988-01-01

Mass values of mesons with J PC =1 -- built of u-, d-, s-, c-, b-quarks in S-states have been found with the help of numerical solutions of Dirac equation. The potential entering the equation consists of the scalar linear potential and the Coulomb vector one. The main contribution into spectra dependence on the radial quantum number for light quarks is shown to give the cnfinement scalar flavour independent potential: V c (r)=κ 2 r, at parameter value κ∼ 0.42 GeV. The calculated mass values are in agreement with ∼ 5% accuracy with the data for well established mesons

Unlocking color and flavor in superconducting strange quark matter

International Nuclear Information System (INIS)

Alford, Mark; Berges, Juergen; Rajagopal, Krishna

1999-01-01

We explore the phase diagram of strongly interacting matter with massless u and d quarks as a function of the strange quark mass m s and the chemical potential μ for baryon number. Neglecting electromagnetism, we describe the different baryonic and quark matter phases at zero temperature. For quark matter, we support our model-independent arguments with a quantitative analysis of a model which uses a four-fermion interaction abstracted from single-gluon exchange. For any finite m s , at sufficiently large μ we find quark matter in a color-flavor-locked state which leaves a global vector-like SU(2) color+L+R symmetry unbroken. As a consequence, chiral symmetry is always broken in sufficiently dense quark matter. As the density is reduced, for sufficiently large m s we observe a first-order transition from the color-flavor-locked phase to color superconducting phase analogous to that in two-flavor QCD. At this unlocking transition chiral symmetry is restored. For realistic values of m s our analysis indicates that chiral symmetry breaking may be present for all densities down to those characteristic of baryonic matter. This supports the idea that quark matter and baryonic matter may be continuously connected in nature. We map the gaps at the quark Fermi surfaces in the high density color-flavor-locked phase onto gaps at the baryon Fermi surfaces at low densities

CP-violating top quark couplings at future linear e{sup +}e{sup -} colliders

Energy Technology Data Exchange (ETDEWEB)

Bernreuther, W. [RWTH Aachen University, Institut fuer Theoretische Teilchenphysik und Kosmologie, Aachen (Germany); Chen, L. [RWTH Aachen University, Institut fuer Theoretische Teilchenphysik und Kosmologie, Aachen (Germany); Max-Planck-Institut fuer Physik, Muenchen (Germany); Garcia, I. [Instituto de Fisica Corpuscular (IFIC, UVEG/CSIC), Valencia (Spain); CERN, Geneva (Switzerland); Perello, M.; Ros, E.; Vos, M. [Instituto de Fisica Corpuscular (IFIC, UVEG/CSIC), Valencia (Spain); Poeschl, R.; Richard, F. [Centre Scientifique d' Orsay, Laboratoire de l' Accelerateur Lineaire (LAL), Orsay (France)

2018-02-15

We study the potential of future lepton colliders to probe violation of the CP symmetry in the top quark sector. In certain extensions of the Standard Model, such as the two-Higgs-doublet model (2HDM), sizeable anomalous top quark dipole moments can arise, which may be revealed by a precise measurement of top quark pair production. We present results from detailed Monte Carlo studies for the ILC at 500 GeV and CLIC at 380 GeV and use parton-level simulations to explore the potential of high-energy operation. We find that precise measurements in e{sup +}e{sup -} → t anti t production with subsequent decay to lepton plus jets final states can provide sufficient sensitivity to detect Higgs-boson-induced CP violation in a viable two-Higgs-doublet model. The potential of a linear e{sup +}e{sup -} collider to detect CP-violating electric and weak dipole form factors of the top quark exceeds the prospects of the HL-LHC by over an order of magnitude. (orig.)

Search for vector-like quarks and excited quarks at CMS

CERN Document Server

Rauco, Giorgia

2017-01-01

We present the results of the latest searches for new hypothetical heavy quarks using proton-proton collisions data collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV. Vector-like quarks are postulated to solve the hierarchy problem and stabilize the Higgs mass and they are not constrained by the Higgs discovery and electroweak measurements, as for the case of a fourth generation of fermions. They can either be produced singly or pair-wise and their decays result in a variety of final states, containing massive standard model quarks and bosons (Z, W, H). Being these new particles expected to be appearing at the TeV scale, they give rise to boosted topologies, in which jet substructures techniques play a fundamental role. An alternative type of heavy quark resonance are the excited quarks, which are predicted by the compositeness model, being their evidence a clear signature of the composite structure of the ordinary matter. Their decay leads to the corresponding ordinary qua...

The proton's spin: A quark model perspective

International Nuclear Information System (INIS)

Close, F.E.

1989-01-01

Magnetic moments and g A /g V provide information on the correlations among quark spins and flavors in the proton. I compare this information with the deep inelastic polarized data from EMC which has been claimed to show that very little of the proton's spin is due to the quarks. The possibility that there is significant polarization of strange quarks within protons is discussed. 38 refs

Super-hypernuclei in the quark-shell model, 2

International Nuclear Information System (INIS)

Terazawa, Hidezumi.

1989-07-01

By following the previous paper, where the quark-shell model of nuclei in quantum chromodynamics is briefly reviewed, a short review of the MIT bag model of nuclei is presented for comparison and a simple estimate of the Hλ ('hexalambda') mass is also made for illustration. Furthermore, an even shorter review of the 'nucleon cluster model' of nuclei is presented for further comparison. (J.P.N.)

Sivers function in constituent quark models

CERN Document Server

Scopetta, S.; Fratini, F.; Vento, V.

2008-01-01

A formalism to evaluate the Sivers function, developed for calculations in constituent quark models, is applied to the Isgur-Karl model. A non-vanishing Sivers asymmetry, with opposite signs for the u and d flavor, is found; the Burkardt sum rule is fulfilled up to 2 %. Nuclear effects in the extraction of neutron single spin asymmetries in semi-inclusive deep inelastic scattering off 3He are also evaluated. In the kinematics of JLab, it is found that the nuclear effects described by an Impulse Approximation approach are under control.

Ground-state triply and doubly heavy baryons in a relativistic three-quark model

International Nuclear Information System (INIS)

Martynenko, A.P.

2008-01-01

Mass spectra of the ground-state baryons consisting of three or two heavy (b or c) and one light (u,d,s) quarks are calculated in the framework of the relativistic quark model and the hyperspherical expansion. The predictions of masses of the triply and doubly heavy baryons are obtained by employing the perturbation theory for the spin-independent and spin-dependent parts of the three-quark Hamiltonian

Quark approach to Santilli's conjecture on hadronic structure - II

International Nuclear Information System (INIS)

Animalu, A.O.E.

1982-08-01

In this paper, we continue an earlier investigation of an exactly soluble relativistic Bohr-type model of the internal structure of the proton (three-quark baryon system) and the pion (quark-antiquark meson system), based on a realization of Santilli's conjecture that the hadronic constituents are extended (non-pointlike) objects. The model is abstracted from an expansion of a Yukawa-type potential between the valence quarks and a massive core, in which the meson or gluon exchange term has the effect of reducing the effective Bohr radius for binding to a value less than the radius of the strong charge sphere (or Compton wavelength) of each constituent, so that appreciable overlap of charge volumes occurs, to within a typical distance of order 0.25F or 1/(800 MeV) in qqq-system, and order 1/(1200 MeV) in qq-bar-system, which are comparable to gluon masses, msub(G) approx.= 800 to 1200 MeV, required by the lattice QCD and the MIT Bag Model. Based on the assumptions that the ground state of the proton has 1s 2 2s valence quark configuration, the non-strange quark mass is msub(p)/3, and the dimensionless strong coupling constant of the Yukawa-type potential is g 2 =1, the mass of the proton core is determined self-consistently to be 2470 MeV, exactly balancing the quark binding energy so that the valence quarks appear free. The model correctly predicts the masses of the well-known resonant states of the proton with Jsup(P)=1/2 + as excited states associated with the configuration 1s2s 2 and predicts an upper bound (spectroscopic limit) for the mass of the excited states of the proton in ns 2 ms configuration, as n→infinity and m→infinity, to be 3409 MeV. Based on a generalization of the model to qq-bar-systems, an upper bound (spectroscopic limit) for the mass of qq-bar in ns 2 configuration, as n→infinity, is found to be 3096 MeV, which is the mass of the J/psi-meson. The relation of the model to violation of time-reversal invariance (T-symmetry) by non

Electromagnetic polarisabilities of the proton in an independent particle potential model

International Nuclear Information System (INIS)

Barik, N.; Panda, A.R.

1996-01-01

We consider the electric and magnetic polarisabilities of the proton including the valence quark as well as pion dressing effects in an independent quark model with an effective scalar-vector harmonic potential which renders the solvability of relativistic Dirac equations for confined quarks, and has in fact acted as an alternative to the cloudy bag model (CBM). This model which has been applied successfully to a variety of hadronic problems is also observed here to yield the electromagnetic polarisabilities of the proton satisfactorily without any free parameters. The electric and magnetic polarisabilities, including valence quark core and pion cloud effects, obtained here as anti α P =14.074.10 -4 fm 3 and anti β P =3.155.10 -4 fm 3 , are well within the uncertainties of their experimental measurements of (10.9±2.2±1.4).10 -4 fm 3 and (3.3±2.2±1.4).10 -4 fm 3 , respectively and are also in agreement with other model estimations. (orig.)

Electromagnetic polarisabilities of the proton in an independent particle potential model

Energy Technology Data Exchange (ETDEWEB)

Barik, N [Utkal Univ., Bhubaneswer (India). P.G. Dept. of Phys.; Dash, B K [Utkal Univ., Bhubaneswer (India). P.G. Dept. of Phys.; Das, P [Department of Physics, Kendrapara College, Kendrapara-754211 (India); Panda, A R [Department of Physics, Kendrapara College, Kendrapara-754211 (India)

1996-08-19

We consider the electric and magnetic polarisabilities of the proton including the valence quark as well as pion dressing effects in an independent quark model with an effective scalar-vector harmonic potential which renders the solvability of relativistic Dirac equations for confined quarks, and has in fact acted as an alternative to the cloudy bag model (CBM). This model which has been applied successfully to a variety of hadronic problems is also observed here to yield the electromagnetic polarisabilities of the proton satisfactorily without any free parameters. The electric and magnetic polarisabilities, including valence quark core and pion cloud effects, obtained here as anti {alpha}{sub P}=14.074.10{sup -4} fm{sup 3} and anti {beta}{sub P}=3.155.10{sup -4} fm{sup 3}, are well within the uncertainties of their experimental measurements of (10.9{+-}2.2{+-}1.4).10{sup -4} fm{sup 3} and (3.3{+-}2.2{+-}1.4).10{sup -4} fm{sup 3}, respectively and are also in agreement with other model estimations. (orig.).

Hadron spectra and quarks

International Nuclear Information System (INIS)

Gasiorowicz, S.; Rosner, J.L.

1982-01-01

The quark model began as little more than a quantum-number counting device. After a brief period during which quarks only played a symmetry role, serious interest in quark dynamics developed. The marriage of the principle of local gauge invariance and quarks has been astonishingly productive. Although many questions still need to be be answered, there is little doubt that the strong, weak and electroweak interactions of matter are described by gauge theories of interactions of the quarks. This review is focussed on the successes

On the H particle stability in the non relativistic quark model

International Nuclear Information System (INIS)

Silvestre-Brac, B.; Carbonell, J.; Gignoux, C.

1987-05-01

The H particle with quark content (uuddss) is presented as a good candidate to be stable with respect to strong interactions. In the framework of a non relativistic potential model, the binding energy is calculated by a full dynamical approach using a resonating group trial wave function. The center of mass motion and the Pauli principle are correctly treated. Sophisticated baryon wave functions are employed and the equation of motion is solved with six coupled channels including radial excited baryon states. The effect of breaking SU(3) flavour symmetry is discussed in detail

Quantum chromodynamic quark model study of hadron and few hadron systems

International Nuclear Information System (INIS)

Ji, Chueng-Ryong.

1990-10-01

This report details research progress and results obtained during the five month period July 1, 1990 to November 30, 1990. The research project, entitled ''Quantum Chromodynamic Quark Model Study of Hadron and Few Hadron Systems,'' is supported by grant FG05-90ER40589 between North Carolina State University and the United States Department of Energy. This is a research program addressing theoretical investigations of hadron structure and reactions using quantum chromodynamic quark models. The new, significant research results are briefly summarized in the following sections

Chiral quark model with relativistic kinematics

International Nuclear Information System (INIS)

Garcilazo, H.; Valcarce, A.

2003-01-01

The nonstrange baryon spectrum is studied within a three-body model that incorporates relativistic kinematics. We found that the combined effect of relativistic kinematics together with the pion exchange between quarks is able to reverse the order of the first positive- and negative-parity nucleon excited states as observed experimentally. Including the chiral partner of the pion (the σ meson) leads to an overall good description of the spectrum

Chiral quark model with relativistic kinematics

OpenAIRE

Garcilazo, H.; Valcarce, A.

2003-01-01

The non-strange baryon spectrum is studied within a three-body model that incorporates relativistic kinematics. We found that the combined effect of relativistic kinematics together with the pion exchange between quarks is able to reverse the order of the first positive- and negative-parity nucleon excited states as observed experimentally. Including the chiral partner of the pion (the $\\sigma$ meson) leads to an overall good description of the spectrum.

Successes and failures of the constituent quark model

International Nuclear Information System (INIS)

Lipkin, H.J.

1982-01-01

Our approach considers the model as a possible bridge between QCD and the experimental data and examines its predictions to see where these succeed and where they fail. We also attempt to improve the model by looking for additional simple assumptions which give better fits to the experimental data. But we avoid complicated models with too many ad hoc assumptions and too many free parameters; these can fit everything but teach us nothing. We define our constituent quark model by analogy with the constituent electron model of the atom and the constituent nucleon model of the nucleus. In the same way that an atom is assumed to consist only of constituent electrons and a central Coulomb field and a nucleus is assumed to consist only of constituent nucleons hadrons are assumed to consist only of their constituent valence quarks with no bag, no glue, no ocean, nor other constituents. Although these constituent models are oversimplified and neglect other constituents we push them as far as we can. Atomic physics has photons and vacuum polarization as well as constituent electrons, but the constituent model is adequate for calculating most features of the spectrum when finer details like the Lamb shift are neglected. 54 references

Mass spectra and wave functions of meson systems and the covariant oscillator quark model as an expansion basis

International Nuclear Information System (INIS)

Oda, Ryuichi; Ishida, Shin; Wada, Hiroaki; Yamada, Kenji; Sekiguchi, Motoo

1999-01-01

We examine mass spectra and wave functions of the nn-bar, cc-bar and bb-bar meson systems within the framework of the covariant oscillator quark model with the boosted LS-coupling scheme. We solve nonperturbatively an eigenvalue problem for the squared-mass operator, which incorporates the four-dimensional color-Coulomb-type interaction, by taking a set of covariant oscillator wave functions as an expansion basis. We obtain mass spectra of these meson systems, which reproduce quite well their experimental behavior. The resultant manifestly covariant wave functions, which are applicable to analyses of various reaction phenomena, are given. Our results seem to suggest that the present model may be considered effectively as a covariant version of the nonrelativistic linear-plus-Coulomb potential quark model. (author)

Adler function and hadronic contribution to the muon g-2 in a nonlocal chiral quark model

International Nuclear Information System (INIS)

Dorokhov, Alexander E.

2004-01-01

The behavior of the vector Adler function at spacelike momenta is studied in the framework of a covariant chiral quark model with instantonlike quark-quark interaction. This function describes the transition between the high-energy asymptotically free region of almost massless current quarks to the low-energy hadronized regime with massive constituent quarks. The model reproduces the Adler function and V-A correlator extracted from the ALEPH and OPAL data on hadronic τ lepton decays, transformed into the Euclidean domain via dispersion relations. The leading order contribution from the hadronic part of the photon vacuum polarization to the anomalous magnetic moment of the muon, a μ hvp(1) , is estimated

Hadron-quark phase transition in dense stars

International Nuclear Information System (INIS)

Grassi, F.

1987-10-01

An equation of state is computed for a plasma of one flavor quarks interacting through some phenomenological potential, at zero temperature. Assuming that the confining potential is scalar and color-independent, it is shown that the quarks undergo a first-order mass phase transition. In addition, due to the way screening is introduced, all the thermodynamic quantities computed are independent of the actual shape of the interquark potential. This equation of state is then generalized to a several quark flavor plasma and applied to the study of the hadron-quark phase transition inside a neutron star. 45 refs., 4 figs

When is a heavy quark not a parton? Charged Higgs production and heavy quark mass effects in the QCD-based parton model

International Nuclear Information System (INIS)

Olness, F.I.; Tung, Wu-Ki

1989-10-01

Applications of the QCD-based parton model to new physics processes involving heavy partons are illustrated using charged Higgs production. The naive parton model predictions are found to over-estimate the actual cross section by a factor of 2 to 5. The role of the top quark as a ''parton'' is examined, and the energy range over which heavy quarks (or other particles) should or should not be naturally treated as ''partons'' is delineated. 12 refs., 5 figs

Quarkonium spectroscopy in a potential model with vacuum-polarization corrections

International Nuclear Information System (INIS)

Barik, N.; Jena, S.N.

1980-01-01

We consider a potential model taking long-distance vacuum-polarization corrections as suggested by Poggio and Schnitzer, which enables one to interpolate between cc-bar, bb-bar, and tt-bar systems. Taking special care for the accuracy of the numerical integration near the origin, we have developed a numerical method to obtain the heavy-quark--antiquark bound states along with their leptonic widths. We obtain the above flavor-independent potential giving good agreement with the so-called experimental mass splitting of the 1S-2S states of the psi and UPSILON family with reasonable values of the quark-gluon coupling constant α/sub s/, which do not deviate very much from the quantum-chromodynamics value. We obtain some of the bound states of the hypothetical tt-bar family and observe that the effect of screening of the potential due to the vacuum-polarization cloud decreases with increase of the mass of the heavy quark forming the quarkonium

Lowest-lying even-parity anti B{sub s} mesons: heavy-quark spin-flavor symmetry, chiral dynamics, and constituent quark-model bare masses

Energy Technology Data Exchange (ETDEWEB)

Albaladejo, M.; Fernandez-Soler, P.; Nieves, J.; Ortega, P.G. [Centro Mixto CSIC-Universidad de Valencia, Instituto de Fisica Corpuscular (IFIC), Institutos de Investigacion de Paterna, Aptd. 22085, Valencia (Spain)

2017-03-15

The discovery of the D{sup *}{sub s0}(2317) and D{sub s1}(2460) resonances in the charmed-strange meson spectra revealed that formerly successful constituent quark models lose predictability in the vicinity of two-meson thresholds. The emergence of non-negligible effects due to meson loops requires an explicit evaluation of the interplay between Q anti q and (Q anti q)(q anti q) Fock components. In contrast to the c anti s sector, there is no experimental evidence of J{sup P} = 0{sup +}, 1{sup +} bottom-strange states yet. Motivated by recent lattice studies, in this work the heavy-quark partners of the D{sub s0}{sup *}(2317) and D{sub s1}(2460) states are analyzed within a heavy meson chiral unitary scheme. As a novelty, the coupling between the constituent quark-model P-wave anti B{sub s} scalar and axial mesons and the anti B{sup (*)}K channels is incorporated employing an effective interaction, consistent with heavy-quark spin symmetry, constrained by the lattice energy levels. (orig.)

QCD-motivated Nambu-Jona-Lasinio model with quark and gluon condensates

International Nuclear Information System (INIS)

Ebert, D.; Volkov, M.K.

1991-01-01

We present a systematic study of the role of the nonperturbative gluon condensate arising in a QCD-motivated NJL model. The effects of the gluon condensate on induced meson couplings, the pion decay constant, quark condensate and mass formulae are investigated. An interesting result is the change of the scale Λ of chiral symmetry breaking and of the universal four-quark coupling κ. (orig.)

Maximum Mass of Hybrid Stars in the Quark Bag Model

Science.gov (United States)

Alaverdyan, G. B.; Vartanyan, Yu. L.

2017-12-01

The effect of model parameters in the equation of state for quark matter on the magnitude of the maximum mass of hybrid stars is examined. Quark matter is described in terms of the extended MIT bag model including corrections for one-gluon exchange. For nucleon matter in the range of densities corresponding to the phase transition, a relativistic equation of state is used that is calculated with two-particle correlations taken into account based on using the Bonn meson-exchange potential. The Maxwell construction is used to calculate the characteristics of the first order phase transition and it is shown that for a fixed value of the strong interaction constant αs, the baryon concentrations of the coexisting phases grow monotonically as the bag constant B increases. It is shown that for a fixed value of the strong interaction constant αs, the maximum mass of a hybrid star increases as the bag constant B decreases. For a given value of the bag parameter B, the maximum mass rises as the strong interaction constant αs increases. It is shown that the configurations of hybrid stars with maximum masses equal to or exceeding the mass of the currently known most massive pulsar are possible for values of the strong interaction constant αs > 0.6 and sufficiently low values of the bag constant.

Semileptonic Decays of Heavy Lambda Baryons in a Quark Model

Energy Technology Data Exchange (ETDEWEB)

Winston Roberts; Muslema Pervin; Simon Capstick

2005-03-01

The semileptonic decays of {Lambda}{sub c} and {Lambda}{sub b} are treated in the framework of a constituent quark model. Both nonrelativistic and semirelativistic Hamiltonians are used to obtain the baryon wave functions from a fit to the spectra, and the wave functions are expanded in both the harmonic oscillator and Sturmian bases. The latter basis leads to form factors in which the kinematic dependence on q{sup 2} is in the form of multipoles, and the resulting form factors fall faster as a function of q{sup 2} in the available kinematic ranges. As a result, decay rates obtained in the two models using the Sturmian basis are significantly smaller than those obtained using the harmonic oscillator basis. In the case of the {Lambda}{sub c}, decay rates calculated using the Sturmian basis are closer to the experimentally reported rates. However, we find a semileptonic branching fraction for the {Lambda}{sub c} to decay to excited {Lambda}* states of 11% to 19%, in contradiction with what is assumed in available experimental analyses. Our prediction for the {Lambda}{sub b} semileptonic decays is that decays to the ground state {Lambda}{sub c} provide a little less than 70% of the total semileptonic decay rate. For the decays {Lambda}{sub b} {yields} {Lambda}{sub c}, the analytic form factors we obtain satisfy the relations expected from heavy-quark effective theory at the non-recoil point, at leading and next-to-leading orders in the heavy-quark expansion. In addition, some features of the heavy-quark limit are shown to naturally persist as the mass of the heavy quark in the daughter baryon is decreased.

Pion polarizability in a chiral quark model

International Nuclear Information System (INIS)

Volkov, M.K.; Ehbert, D.

1980-01-01

The pion polarizability is calculated in a chiral meson-quark model at the one-loop level. The results are in complete agreement with earlier ones obtained within a chiral meson-baryon theory. A critical discussion of a recent paper by Lanta and Tarrach is given. The results of the paper give evidence to the nonlinear chiral Lagrangian favour

Search for the fourth standard model family fermions and E6 quarks at μ+μ- colliders

International Nuclear Information System (INIS)

Ciftci, A.K.; Ciftci, R.; Sultansoy, S.

2002-01-01

The potential of μ + μ - colliders to investigate the fourth standard model family fermions predicted by flavor democracy is analyzed. It is shown that muon colliders are advantageous for both pair production of fourth family fermions and resonance production of fourth family quarkonia. Also, isosinglet quark production at μ + μ - colliders is investigated

Radiative leptonic B{sub c} decay in the relativistic independent quark model

Energy Technology Data Exchange (ETDEWEB)

Barik, N [Department of Physics, Utkal University, Bhubaneswar-751004 (India); Naimuddin, Sk; Dash, P C [Department of Physics, Prananath Autonomous College, Khurda-752057 (India); Kar, Susmita [Department of Physics, North Orissa University, Baripada-757003 (India)

2008-12-01

The radiative leptonic decay B{sub c}{sup -}{yields}{mu}{sup -}{nu}{sub {mu}}{gamma} is analyzed in its leading order in a relativistic independent quark model based on a confining potential in an equally mixed scalar-vector harmonic form. The branching ratio for this decay in the vanishing lepton mass limit is obtained as Br(B{sub c}{yields}{mu}{nu}{sub {mu}}{gamma})=6.83x10{sup -5}, which includes the contributions of the internal bremsstrahlung and structure-dependent diagrams at the level of the quark constituents. The contributions of the bremsstrahlung and the structure-dependent diagrams, as well as their additive interference parts, are compared and found to be of the same order of magnitude. Finally, the predicted photon energy spectrum is observed here to be almost symmetrical about the peak value of the photon energy at E-tilde{sub {gamma}}{approx_equal}(M{sub B{sub c}}/4), which may be quite accessible experimentally at LHC in near future.

Multimesonic decays of charmonium states in the statistical quark model

International Nuclear Information System (INIS)

Montvay, I.; Toth, J.D.

1978-01-01

The data known at present of multimesonic decays of chi and psi states are fitted in a statistical quark model, in which the matrix elements are assumed to be constant and resonances as well as both strong and second order electromagnetic processes are taken into account. The experimental data are well reproduced by the model. Unknown branching ratios for the rest of multimesonic channels are predicted. The fit leaves about 40% for baryonic and radiative channels in the case of J/psi(3095). The fitted parameters of the J/psi decays are used to predict the mesonic decays of the pseudoscalar eta c. The statistical quark model seems to allow the calculation of competitive multiparticle processes for the studied decays. (D.P.)

The spin predictions of the relativistic quark model for baryon decuplet production

CERN Document Server

Montvay, István

1973-01-01

Single-quark scattering contributions are considered in the case of ground-state decuplet baryon production. It is shown within the framework of an explicitly covariant approach that the spin consequences of the quark additivity assumption hold in the t-channel helicity frame independently of much of the details of the model. (12 refs).

Hadronic physics of q anti q light quark mesons, quark molecules and glueballs

International Nuclear Information System (INIS)

Lindenbaum, S.J.

1980-10-01

A brief introduction reviews the development of QCD and defines quark molecules and glueballs. This review is concerned primarily with u, d, and s quarks, which provide practically all of the cross section connected with hadronic interactions. The following topics form the bulk of the paper: status of quark model classification for conventional u, d, s quark meson states; status of multiquark or quark molecule state predictions and experiments; glueballs and how to find them; and the OZI rule in decay and production and how glueballs might affect it. 17 figures, 1 table

The p-antip annihilation in the quark model

International Nuclear Information System (INIS)

Niskanen, J.A.

1988-05-01

After a concise review of the N-antiN annihilation in the quark rearrangement and 3 P 0 annihilation models, preliminary results are given for the case with an additional term where a q-antiq pair with the gluon quantum number 3 S 1

Indirect handle on the down-quark Yukawa coupling.

Science.gov (United States)

Goertz, Florian

2014-12-31

To measure the Yukawa couplings of the up and down quarks, Yu,d, seems to be far beyond the capabilities of current and (near) future experiments in particle physics. By performing a general analysis of the potential misalignment between quark masses and Yukawa couplings, we derive predictions for the magnitude of induced flavor-changing neutral currents (FCNCs), depending on the shift in the physical Yukawa coupling of first-generation quarks. We find that a change of more than 50% in Yd would generically result in ds transitions in conflict with kaon physics. This could already be seen as evidence for a nonvanishing direct coupling of the down quark to the newly discovered Higgs boson. The nonobservation of certain--already well-constrained--processes is thus turned into a powerful indirect measure of otherwise basically unaccessible physical parameters of the effective standard model. Similarly, improvements in limits on FCNCs in the up-type quark sector can lead to valuable information on Yu.

Comment on ``Brown dwarfs, quark stars, and quark-hadron phase transition``

Energy Technology Data Exchange (ETDEWEB)

Kubis, S.; Kutschera, M. [Institute of Nuclear Physics, Cracow (Poland)

1995-12-01

It is shown that the cosmological quark-hadron phase transition within the Lee-Wick model with a high degree of supercooling cannot be completed. No quark stars could be produced in this scenario. (author). 2 refs.

Comment on ''Brown dwarfs, quark stars, and quark-hadron phase transition''

International Nuclear Information System (INIS)

Kubis, S.; Kutschera, M.

1995-12-01

It is shown that the cosmological quark-hadron phase transition within the Lee-Wick model with a high degree of supercooling cannot be completed. No quark stars could be produced in this scenario. (author). 2 refs

Deep Learning Techniques for Top-Quark Reconstruction

CERN Document Server

Naderi, Kiarash

2017-01-01

Top quarks are unique probes of the standard model (SM) predictions and have the potential to be a window for physics beyond the SM (BSM). Top quarks decay to a $Wb$ pair, and the $W$ can decay in leptons or jets. In a top pair event, assigning jets to their correct source is a challenge. In this study, I studied different methods for improving top reconstruction. The main motivation was to use Deep Learning Techniques in order to enhance the precision of top reconstruction.

On the effective quark potential in baryons

International Nuclear Information System (INIS)

Gromes, D.

1977-01-01

The splitting of the non-strange members of the first excited level [70,1 - ] 1 of baryon resonances is analysed. The spin-dependent forces (spin-spin, spin-orbit, tensor) are supposed to arise from the Coulomb term due to one-gluon exchange, from the long-range linearly rising part of the potential, and from additional 'hard-core' spin-spin terms which may be generated by higher-order graphs contributing to the qq kernel. For the long range part it is assumed either that it comes from a superposition of a vector and a scalar kernel of the form epsilon(γsup(μ) X γsub(μ) X 1) + (1 - epsilon)(1 X 1 X 1) (+ permutations), or, alternatively, that it arises from a vector exchange with an anomalous moment kappa in the quark-gluon vertex. Values of epsilon approximately 0 or kappa approximately -1 turn out to be favoured. The strong coupling constant and the slope of the linear potential come out in the correct order of magnitude. Very large hard-core spin-spin terms are needed. This fact makes the determination of the effective potential from the underlying theory of quantum chromodynamics as well as the phenomenological analysis of the observed spectra rather problematic. (Auth.)

Vector Susceptibility of QCD Vacuum from an Effective Quark-Quark Interaction

Institute of Scientific and Technical Information of China (English)

ZONG Hong-Shi; QI Shi; CHEN Wei; WU Xiao-Hua

2003-01-01

.A new approach for calculating vacuum susceptibilities from an effective quark-quark interaction model is derived. As a special case, the vector vacuum susceptibility is calculated. A comparison with the results of the previous approaches is given.

Quark-quark interactions

International Nuclear Information System (INIS)

Jacob, M.

1982-01-01

This chapter discusses interactions only at the constituent level, as observed in hadron-hadron collisions. It defines quarks and gluons as constituents of the colliding hadrons, reviews some applications of perturbative OCD, discussing in turn lepton pair production, which in lowest order approximation corresponds to the Drell-Yan process. It investigates whether quark-quark interactions could not lead to some new color structure different from those prevalent for known baryons and mesons, which could be created in hadron interactions, and whether color objects (not specifically quarks or gluons) could not appear as free particles. Discussed is perturbative QCD in hadron collisions; the quark approach to soft processes; and new color structures. It points out that perturbative QCD has been at the origin of much progress in the understanding of hadron interactions at the constituent level

A diquark model for baryons containing one heavy quark

International Nuclear Information System (INIS)

Ebert, D.; Feldmann, T.; Kettner, C.; Reinhardt, H.

1995-06-01

We present a phenomenological ansatz for coupling a heavy quark with two light quarks to form a heavy baryon. The heavy quark is treated in the heavy mass limit, and the light quark dynamics is approximated by propagating scalar and axial vector 'diquarks'. The resulting effective lagrangian, which incorporates heavy quark and chiral symmetry, describes interactions of heavy baryons with Goldstone bosons in the low energy region. As an application, the Isgur-Wise formfactors are estimated. (orig.)

Consequences of a description of the nucleon and delta spectra in terms of a non-relativistic quark-potential model with oscillator variational states

International Nuclear Information System (INIS)

Harvey, M.

1984-01-01

General conditions are derived for matrix elements of a quark-confining potential that is assumed to yield the nucleon and delta spectra with oscillator variational states. Parameters are given for a particular functional form of the confining potential under various fitting criteria to the baryon spectra; this form is to be used in subsequent calculations of the nuclear force. (orig.)

Baryons in and beyond the quark-diquark model

International Nuclear Information System (INIS)

Eichmann, G.; Alkofer, R.; Krassnigg, A.; Fischer, C. S.; Nicmorus, D.

2011-01-01

We examine the nucleon's electromagnetic form factors in a Poincare-covariant Faddeev framework. The three-quark core contributions to the form factors are obtained by employing a quark-diquark approximation. We implement the self-consistent solution for the quark-photon vertex from its inhomogeneous Bethe-Salpeter equation. We find that the resulting transverse parts which add to the Ball-Chiu vertex have no significant impact on nucleon magnetic moments. The current-quark mass evolution of the form factors agrees with results from lattice QCD.

From hot lattice QCD to cold quark stars

International Nuclear Information System (INIS)

Schulze, Robert

2011-01-01

A thermodynamic model of the quark-gluon plasma using quasiparticle degrees of freedom based on the hard thermal loop self-energies is introduced. It provides a connection between an established phenomenological quasiparticle model - following from the former using a series of approximations - and QCD - from which the former is derived using the Cornwall-Jackiw-Tomboulis formalism and a special parametrization of the running coupling. Both models allow for an extrapolation of first-principle QCD results available at small chemical potentials using Monte-Carlo methods on the lattice to large net baryon densities with remarkably similar results. They are used to construct equations of state for heavy-ion collider experiments at SPS and FAIR as well as quark and neutron star interiors. A mixed-phase construction allows for a connection of the SPS equation of state to the hadron resonance gas. An extension to the weak sector is presented as well as general stability and binding arguments for compact stellar objects are developed. From the extrapolation of the most recent lattice results the existence of bound pure quark stars is not suggested. However, quark matter might exist in a hybrid phase in cores of neutron stars. (orig.)

From hot lattice QCD to cold quark stars

Energy Technology Data Exchange (ETDEWEB)

Schulze, Robert

2011-02-22

A thermodynamic model of the quark-gluon plasma using quasiparticle degrees of freedom based on the hard thermal loop self-energies is introduced. It provides a connection between an established phenomenological quasiparticle model - following from the former using a series of approximations - and QCD - from which the former is derived using the Cornwall-Jackiw-Tomboulis formalism and a special parametrization of the running coupling. Both models allow for an extrapolation of first-principle QCD results available at small chemical potentials using Monte-Carlo methods on the lattice to large net baryon densities with remarkably similar results. They are used to construct equations of state for heavy-ion collider experiments at SPS and FAIR as well as quark and neutron star interiors. A mixed-phase construction allows for a connection of the SPS equation of state to the hadron resonance gas. An extension to the weak sector is presented as well as general stability and binding arguments for compact stellar objects are developed. From the extrapolation of the most recent lattice results the existence of bound pure quark stars is not suggested. However, quark matter might exist in a hybrid phase in cores of neutron stars. (orig.)

QCD-motivated Nambu-Jona-Lasinio model with quark and gluon condensates

International Nuclear Information System (INIS)

Ebert, D.; Volkov, M.K.

1991-01-01

A systematic study of the role of the nonperturbative gluon condensate arising in a QCD-motivated Nambu-Jona-Lasinio model is presented. The effects of the gluon condensate on induced meson couplings, the pion decay constant, quark condensate and mass formulae are investigated. An interesting result is the change of the scale Λ of chiral symmetry breaking and of the universal four-quark coupling constant κ. 20 refs

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

A path integral for heavy-quarks in a hot plasma

CERN Document Server

Beraudo, A.; Faccioli, P.; Garberoglio, G.; 10.1016/j.nuclphysa.2010.06.007

2010-01-01

We propose a model for the propagation of a heavy-quark in a hot plasma, to be viewed as a first step towards a full description of the dynamics of heavy quark systems in a quark-gluon plasma, including bound state formation. The heavy quark is treated as a non relativistic particle interacting with a fluctuating field, whose correlator is determined by a hard thermal loop approximation. This approximation, which concerns only the medium in which the heavy quark propagates, is the only one that is made, and it can be improved. The dynamics of the heavy quark is given exactly by a quantum mechanical path integral that is calculated in this paper in the Euclidean space-time using numerical Monte Carlo techniques. The spectral function of the heavy quark in the medium is then reconstructed using a Maximum Entropy Method. The path integral is also evaluated exactly in the case where the mass of the heavy quark is infinite; one then recovers known results concerning the complex optical potential that controls the ...

The A=3 Nolen-Schiffer anomaly and the up-down quark mass difference

International Nuclear Information System (INIS)

Encinosa, M.; Robson, D.

1990-01-01

A recently proposed nonrelativistic many-body quark model is used to generate class III nucleon-nucleon potentials in a Born-Oppenheimer approach. These potentials, when treated in first-order perturbation theory with a simple ansatz for the three-nucleon wave function, allow us to make an estimate of the 3 He- 3 H mass difference. For accepted values of the constituent up-down quark mass difference we find that approximately sixty percent of the A=3 Nolen-Schiffer anomaly can be accounted for solely from the up-down quark kinetic energy difference. (orig.)

Heavy mesons in the bootstrap quark model

International Nuclear Information System (INIS)

Gerasyuta, S.M.; Sarantsev, A.V.

1990-01-01

In the frame of an approach developed for light quarks the scattering amplitudes of heavy quarks qQ-bar→qQ-bar→,QQ-bar→QQ-bar (q=u,d,s; Q=c,b,t) are calculated. The obtained mass values of the lowest c,b-mesons multiplets (J P =0 - ,1 - ,0 + ) are in a good agreement with the experimental ones. The masses of the new heavy particles with the t-quark are predicted. 46 refs.; 4 figs.; 5 tabs

Chromostatics of two-quark systems

International Nuclear Information System (INIS)

Milton, K.A.; Palmer, W.F.; Pinsky, S.S.

1981-01-01

An estimate for the mean-field potential between two heavy quarks (qq) is studied using Adler's chromostatics. To do so, the pseudocolor charge algebra is worked out for the qq system in SU(n) of color, which had not been correctly presented previously. Using the leading-logarithm, renormalization group improved Euclidean action for the gluon fields, it is found the mean-field potential depends crucially on the algebraic properties of the sources, and that while the quark-anti-quark (q anti q) system possesses an at-least-linear potential, as Adler showed, the qq system has infinite energy, and hence is decoupled from the physical spectrum. The physical states exhibit color screening

Fluctuation instability of the Dirac Sea in quark models of strong interactions

Science.gov (United States)

Zinovjev, G. M.; Molodtsov, S. V.

2016-03-01

A number of exactly integrable (quark) models of quantum field theory that feature an infinite correlation length are considered. An instability of the standard vacuum quark ensemble, a Dirac sea (in spacetimes of dimension higher than three), is highlighted. It is due to a strong ground-state degeneracy, which, in turn, stems from a special character of the energy distribution. In the case where the momentumcutoff parameter tends to infinity, this distribution becomes infinitely narrow and leads to large (unlimited) fluctuations. A comparison of the results for various vacuum ensembles, including a Dirac sea, a neutral ensemble, a color superconductor, and a Bardeen-Cooper-Schrieffer (BCS) state, was performed. In the presence of color quark interaction, a BCS state is unambiguously chosen as the ground state of the quark ensemble.

Fluctuation instability of the Dirac Sea in quark models of strong interactions

International Nuclear Information System (INIS)

Zinovjev, G. M.; Molodtsov, S. V.

2016-01-01

A number of exactly integrable (quark) models of quantum field theory that feature an infinite correlation length are considered. An instability of the standard vacuum quark ensemble, a Dirac sea (in spacetimes of dimension higher than three), is highlighted. It is due to a strong ground-state degeneracy, which, in turn, stems from a special character of the energy distribution. In the case where the momentumcutoff parameter tends to infinity, this distribution becomes infinitely narrow and leads to large (unlimited) fluctuations. A comparison of the results for various vacuum ensembles, including a Dirac sea, a neutral ensemble, a color superconductor, and a Bardeen–Cooper–Schrieffer (BCS) state, was performed. In the presence of color quark interaction, a BCS state is unambiguously chosen as the ground state of the quark ensemble.

Fluctuation instability of the Dirac Sea in quark models of strong interactions

Energy Technology Data Exchange (ETDEWEB)

Zinovjev, G. M., E-mail: Gennady.Zinovjev@cern.ch [National Academy of Sciences of Ukraine, Bogolyubov Institute for Theoretical Physics (Ukraine); Molodtsov, S. V. [Joint Institute for Nuclear Research (Russian Federation)

2016-03-15

A number of exactly integrable (quark) models of quantum field theory that feature an infinite correlation length are considered. An instability of the standard vacuum quark ensemble, a Dirac sea (in spacetimes of dimension higher than three), is highlighted. It is due to a strong ground-state degeneracy, which, in turn, stems from a special character of the energy distribution. In the case where the momentumcutoff parameter tends to infinity, this distribution becomes infinitely narrow and leads to large (unlimited) fluctuations. A comparison of the results for various vacuum ensembles, including a Dirac sea, a neutral ensemble, a color superconductor, and a Bardeen–Cooper–Schrieffer (BCS) state, was performed. In the presence of color quark interaction, a BCS state is unambiguously chosen as the ground state of the quark ensemble.

Relativistic wave functions of two spin 1/2 quarks in a model with QCD interaction

International Nuclear Information System (INIS)

Skachkov, N.B.; Solovtsov, I.L.

1981-01-01

Within the hamiltonian formulation of quantum field theory an equation is obtained for the vertex and wave functions of a composite system of two spin 1/2 quarks. Exact solutions are found for the relativistic potential having in the momentum representation the ''asymptotically-free'' behaviour at large values of momentum transfer Q 2 . It is shown that within the given model the π-meson wave function has zero at a finite distance corresponding to the point of discontinuity of the effective potential [ru

The strange quark contribution to the neutron electric dipole moment in multi-Higgs doublet models

International Nuclear Information System (INIS)

He, Xiao Gang; McKeller, H.J.; Pakvasa, S.

1990-09-01

The strange quark contribution to the neutron electric dipole moment was studied and compared with other contributions in multi-Higgs doublet models. It was found that the strange quark contribution is significant because the strange quark color dipole moment is larger than that of the down (up) quark by a factor m s /m d (m s /m u ). In the case of neutral Higgs it can be the dominant contribution to the neutron electric dipole moment. 18 refs

Qq(Q-bar)(q-bar)' states in chiral SU(3) quark model

International Nuclear Information System (INIS)

Zhang Haixia; Zhang Min; Zhang Zongye

2007-01-01

We study the masses of Qq(Q-bar)(q-bar)' states with J PC =0 ++ , 1 ++ , 1 +- and 2 ++ in the chiral SU(3) quark model, where Q is the heavy quark (c or b) and q(q') is the light quark (u,d or s). According to our numerical results, it is improbable to make the interpretation of [cn(c-bar)(n-bar)] 1 ++ and [cn(c-bar)(n-bar)] 2 ++ (n=u,d) states as X(3872) and Y(3940), respectively. However, it is interesting to find the tetraquarks in the bq(b-bar)(q-bar)' system. (authors)

Heavy hadron spectroscopy: A quark model perspective

International Nuclear Information System (INIS)

Vijande, J.; Valcarce, A.; Caramés, T.F.; Garcilazo, H.

2013-01-01

We present recent results of hadron spectroscopy and hadron–hadron interaction from the perspective of constituent quark models. We pay special attention to the role played by higher order Fock space components in the hadron spectra and the connection of this extension with the hadron–hadron interaction. The main goal of our description is to obtain a coherent understanding of the low-energy hadron phenomenology without enforcing any particular model, to constrain its characteristics and learn about low-energy realization of the theory

Difficulties for SU(N) quark models of the new particles

International Nuclear Information System (INIS)

Colglazier, E.W.; Barnes, K.J.; Hey, A.J.; Zia, R.K.

1975-01-01

If preliminary experimental results on the new particles are confirmed and if conventional theoretical prejudices are accepted, it is shown that Harari's SU(6) model is the minimal N-quark model (with hidden color) which can accommodate these constraints. (author)

Baryon magnetic moments in the quark model and pion cloud contributions

International Nuclear Information System (INIS)

Sato, Toshiro; Sawada, Shoji

1981-01-01

Baryon magnetic moment is studied paying attention to the effects of pion cloud which is surrounding the 'bare' baryon whose magnetic moment is given by the quark model with broken SU(6) symmetry. The precisely measured nucleon magnetic moments are reproduced by the pion cloud contributions from the distance larger than 1.4 fm. The effects of pion cloud on the hyperon magnetic moments are also discussed. It is shown that the pion cloud contributions largely reduce the discrepancies between the quark model predictions and the recent accurate experimental data on the hyperon magnetic moments. (author)

Chiral Quark-Meson model of N and DELTA with vector mesons

International Nuclear Information System (INIS)

Broniowski, W.; Banerjee, M.K.

1985-10-01

Vector mesons rho, A 1 and ω are introduced in the Chiral Quark-Meson Theory (CQMT) of N and Δ. We propose a new viewpoint for developing CQMT from QCD at the mean-field level. The SU(2) x SU(2) chiral Lagrangian incorporates universal coupling. Accordingly, rho is coupled to the conserved isospin current, A to the partially conserved axial-vector current (PCAC), and ω to the conserved baryon current. As a result the only parameter of the model not directly related to experiment is the quark-pion coupling constant. A fully self-consistent mean-field solution to the model is found for fields in the hedgehog ansatz. The vector mesons play a very important role in the system. They contribute significantly to the values of observables and produce a high-quality fit to many data. The classical stability of the system with respect to hedgehog excitations is analyzed through the use of the Quark-Meson RPA equations (QMRPA)

Soap opera: the sad tale of the quark

International Nuclear Information System (INIS)

Lipkin, H.

1984-01-01

The history of quark physics is briefly reviewed, followed by an introduction to quantum chromodynamics, leading terms, and the OZI rule. The basic physics of hadron structure as revealed by experiment is then discussed, followed by the models used to treat it. The two complementary models are the quasinuclear colored quark model and the quark-parton model. Another model for orthogonal physical properties is the bag model. Several applications of the constituent quark model are considered, including hadron masses, spin physics, and multiquark physics. The theoretical basis and phenomenology of the OZI rule forbids processes described by disconnected quark line diagrams

Light-cone quark model with spin force for the nucleon and Δ(1232)

International Nuclear Information System (INIS)

Weber, H.J.

1992-01-01

Electromagnetic structure functions for the nucleon, static observables for the nucleon and N→D(1232) transition form factors are calculated in a relativistic constituent quark model on the light cone. The model simulates the main effect of the spin force between quarks in terms of smaller (and lighter) scalar ud diquarks in the nucleon. The polarized proton structure function is found to agree with the EMC data. (orig.)

Axial charges of octet and decuplet baryons in a perturbative chiral quark model

Science.gov (United States)

Liu, X. Y.; Samart, D.; Khosonthongkee, K.; Limphirat, A.; Xu, K.; Yan, Y.

2018-05-01

Using the perturbative chiral quark model (PCQM), we investigate and predict in this work axial charges gAB of octet and decuplet N , Σ , Ξ , Δ , Σ*, and Ξ* baryons, considering both the ground and excited states in the quark propagator. The PCQM predictions are in good agreement with the experimental data, lattice-QCD values, and other approaches. In addition, the study reveals that the meson cloud is influential in the PCQM, contributing around 30% to the total values of gAB, and the meson cloud contribution to gAB stems mainly from the diagrams with the ground-state quark propagator while the excited intermediate quark states reduce gAB by 10-20%.

The quark mass spectrum in the Universal Seesaw model

International Nuclear Information System (INIS)

Ranfone, S.

1993-03-01

In the context of a Universal Seesaw model implemented in a left-right symmetric theory, we show that, by allowing the two left-handed doublet Higgs fields to develop different vacuum-expectation-values (VEV's), it is possible to account for the observed structure of the quark mass spectrum without the need of any hierarchy among the Yukawa couplings. In this framework the top-quark mass is expected to be of the order of its present experimental lower bound, m t ≅ 90 to 100 GeV. Moreover, we find that, while one of the Higgs doublets gets essentially the standard model VEV of approximately 250 GeV, the second doublet is expected to have a much smaller VEV, of order 10 GeV. The identification of the large mass scale of the model with the Peccei-Quinn scale fixes the mass of the right-handed gauge bosons in the range 10 7 to 10 10 GeV, far beyond the reach of present collider experiments. (author)

Possible D{sup (*)} anti D{sup (*)} and B{sup (*)} anti B{sup (*)} molecular states in the extended constituent quark models

Energy Technology Data Exchange (ETDEWEB)

Yang, You-Chang [Nanjing University, Department of Physics, Nanjing (China); Zunyi Normal University, School of Physics and Electronic Science, Zunyi (China); Institute of Theoretical Physics, CAS, State Key Laboratory of Theoretical Physics, Beijing (China); Tan, Zhi-Yun [Zunyi Normal University, School of Physics and Electronic Science, Zunyi (China); Ping, Jialun [Nanjing Normal University, Department of Physics, Nanjing (China); Zong, Hong-Shi [Nanjing University, Department of Physics, Nanjing (China); Institute of Theoretical Physics, CAS, State Key Laboratory of Theoretical Physics, Beijing (China)

2017-09-15

The possible neutral D{sup (*)} anti D{sup (*)} and B{sup (*)} anti B{sup (*)} molecular states are studied in the framework of the constituent quark models, which is extended by including the s-channel one-gluon exchange. Using different types of quark-quark potentials, we solve the four-body Schroedinger equation by means of the Gaussian expansion method. The bound states of D{sup (*)} anti D{sup (*)} with J{sup PC} = 1{sup ++}, 2{sup ++} and B{sup (*)} anti B{sup (*)} with J{sup PC} = 0{sup ++}, 1{sup +-}, 1{sup ++}, 2{sup ++} are obtained. The molecular states D* anti D with J{sup PC} = 1{sup ++} and B* anti B with J{sup PC} = 1{sup +-} are good candidates for X(3872) and Z{sup 0}{sub b}(10610), respectively. The dependence of the results on the model parameters is also discussed. (orig.)

Quark Physics without Quarks: A Review of Recent Developments in S-Matrix Theory.

Science.gov (United States)

Capra, Fritjof

1979-01-01

Reviews the developments in S-matrix theory over the past five years which have made it possible to derive results characteristic of quark models without any need to postulate the existence of physical quarks. In the new approach, the quark patterns emerge as a consequence of combining the general S-matrix principles with the concept of order.…

A quark-antiquark formation model for meson production in low transverse momentum hadron-hadron reactions

International Nuclear Information System (INIS)

Friebel, W.; Kriegel, U.; Nahnhauer, R.

1979-01-01

Introducing quark transverse momenta and masses it is proposed a 3-dimensional generalization of the quark recombination and the quark fusion model for meson production in low transverse momentum hadron-hadron reactions. A consistent description of vector meson production in proton-proton and proton-antiproton reactions from 12 - 405 GeV/c has been achieved. (author)

Effects of renormalizing the chiral SU(2) quark-meson model

Science.gov (United States)

Zacchi, Andreas; Schaffner-Bielich, Jürgen

2018-04-01

We investigate the restoration of chiral symmetry at finite temperature in the SU(2) quark-meson model, where the mean field approximation is compared to the renormalized version for quarks and mesons. In a combined approach at finite temperature, all the renormalized versions show a crossover transition. The inclusion of different renormalization scales leave the order parameter and the mass spectra nearly untouched but strongly influence the thermodynamics at low temperatures and around the phase transition. We find unphysical results for the renormalized version of mesons and the combined one.

Search for vector like quarks and heavy resonances decaying to top quarks

CERN Document Server

Camincher, Clement; The ATLAS collaboration

2017-01-01

Vector like quarks appear in many theories beyond the Standard Model as a way to cancel the mass divergence for the Higgs boson. The current status of the ATLAS searches for the production of vector like quarks will be reviewed for proton-proton collisions at 13 TeV. This presentation will address the analysis techniques, in particular the selection criteria, the background modeling and the related experimental uncertainties. The phenomenological implications of the obtained results will also be discussed. Searches for new resonances that decay either to pairs of top quarks or a top and a b-quark will be presented. The searches are performed with the ATLAS experiment at the LHC using proton-proton collision data collected in 2015 and 2016 with a centre-of-mass energy of 13 TeV. The invariant mass spectrum of hypothetical resonances are examined for local excesses or deficits that are inconsistent with the Standard Model prediction.

Ruling out exotic models of b quark decay

International Nuclear Information System (INIS)

Chen, A.; Goldberg, M.; Horwitz, N.; Jawahery, A.; Jibaly, M.; Kooy, H.; Lipari, P.; Moneti, G.C.; Van Hecke, H.; Alam, M.S.; Csorna, S.E.; Fridman, A.; Mestayer, M.; Panvini, R.S.; Andrews, D.; Avery, P.; Berkelman, K.; Cassel, D.G.; DeWire, J.W.; Ehrlich, R.; Ferguson, T.; Galik, R.; Gilchriese, M.G.D.; Gittelman, B.; Hartill, D.L.; Herrup, D.; Herzlinger, M.; Holner, S.; Ito, M.; Kandaswamy, J.; Kistiakowsky, V.; Kreinick, D.L.; Kubota, Y.; Mistry, N.B.; Morrow, F.; Nordberg, E.; Ogg, M.; Perchonok, R.; Plunckett, R.; Silverman, A.; Stein, P.C.; Stone, S.; Weber, D.; Wilcke, R.; Sadoff, A.J.; Bebek, C.; Haggerty, J.; Hassard, J.; Hempstead, M.; Izen, J.M.; MacKay, W.W.; Pipkin, F.M.; Rohlf, J.; Wilson, R.; Kagan, H.; Chadwick, K.; Chauveau, J.; Ganci, P.; Gentile, T.; Guida, J.A.; Kass, R.; Melissinos, A.C.; Olsen, S.L.; Parkhurst, G.; Poling, R.; Rosenfeld, C.; Rucinski, G.; Thorndike, E.H.; Green, J.; Hicks, R.G.; Sannes, F.; Skubic, P.; Snyder, A.; Stone, R.

1983-01-01

We consider three broad classes of nonstandard models for b quark decay: (1) b->llq with charged or neutral leptons of arbitrary flavor; (2) b->lanti qanti q; and (3) b->qa - where a - is a Higgs boson or hyperpion. For these classes of models we have calculated the charged energy fraction and the inclusive yields of electrons, muons, protons, and lambdas. We demonstrate that these model predictions are inconsistent with CLEO measurements at the T(4S). (orig.)

Unified approach to the study of light and heavy mesons in the frameworkof the vacuum-polarization-corrected potential model

International Nuclear Information System (INIS)

Barik, N.; Jena, S.N.

1981-01-01

Phenomenological evidence from meson spectroscopy is presented to support the view that a unified description of bound light- and heavy-quark systems is possible within the scope of a nonrelativistic-potential-model approach. The vacuum-polarization-corrected potential with its confinement part in the form of an approximately equal admixture of vector and scalar components is found to be a suitable one for the purpose. The overall systematics of the predictions based on this potential model for the meson masses, fine-hyperfine splittings, leptonic decay widths, and the Regge slopes are observed to be consistent with the premise that the forces between quarks and antiquarks are independent of the quark flavors

Strange star candidates revised within a quark model with chiral mass scaling

Institute of Scientific and Technical Information of China (English)

Ang Li; Guang-Xiong Peng; Ju-Fu Lu

2011-01-01

We calculate the properties of static strange stars using a quark model with chiral mass scaling. The results are characterized by a large maximum mass (～ 1.6 M⊙) and radius (～ 10 km). Together with a broad collection of modern neutron star models, we discuss some recent astrophysical observational data that could shed new light on the possible presence of strange quark matter in compact stars. We conclude that none of the present astrophysical observations can prove or confute the existence of strange stars.

Lepton and quark generations in the geometrical Rishon model

International Nuclear Information System (INIS)

Elbaz, E.; Uschersohn, J.; Meyer, J.

1981-12-01

We propose a concrete representation of leptons and quarks in different generations in the geometrical approach to the rishon model where rishons behave as the fundamental representations of the SU(3)sub(C) x SU(3)sub(H) group. The model allows a unified description of both hadronic and leptonic decays of elementary particles

Quark Yukawa pattern from spontaneous breaking of flavour SU(3) 3

Science.gov (United States)

Nardi, Enrico

2015-10-01

A SU(3)Q × SU(3)u × SU(3)d invariant scalar potential breaking spontaneously the quark flavour symmetry can explain the Standard Model flavour puzzle. The approximate alignment in flavour space of the vacuum expectation values of the up and down 'Yukawa fields' results as a dynamical effect. The observed quark mixing angles, the weak CP violating phase, and hierarchical quark masses can be all reproduced at the cost of introducing additional (auxiliary) scalar multiplets, but without the need of introducing hierarchical parameters.

Charge asymmetry in e+e- → γ + hadrons: New tests of the quark-parton model and fractional charge

International Nuclear Information System (INIS)

Brodsky, S.J.; Carlson, C.E.; Suaya, R.

1976-01-01

We consider the process e + e - → γ + h + X, where h is a hadron and γ is a hard photon, and show how it can be used to test the quark-parton model. Detailed formulas are given for the cross sections, which in the quark-parton model are products of cross sections for e + e - → γμanti μ and quark breakup functions. We focus on the asymmetry between h and h-bar production, and display sum rules and ratio tests which measure the quark charge, the quark Compton amplitude, and the large-x behavior of the quark breakup function. The asymmetry is calculated for the muon case, and is about 100% for the forward direction

Bag-model motivated NN potentials and the three-nucleon system

International Nuclear Information System (INIS)

Grach, I.L.; Narodetskij, I.M.

1986-01-01

Few examples are presented of the short-range energy-dependent NN potentials derived in the quark compound bag model which satisfy the classical causality condition and show that for the radii of the NN interactions b=1.35-1.40 fm these potentials reproduce the trinucleon binding energy

The Top Quark, QCD, And New Physics.

Science.gov (United States)

Dawson, S.

2002-06-01

The role of the top quark in completing the Standard Model quark sector is reviewed, along with a discussion of production, decay, and theoretical restrictions on the top quark properties. Particular attention is paid to the top quark as a laboratory for perturbative QCD. As examples of the relevance of QCD corrections in the top quark sector, the calculation of e{sup+}e{sup -}+ t{bar t} at next-to-leading-order QCD using the phase space slicing algorithm and the implications of a precision measurement of the top quark mass are discussed in detail. The associated production of a t{bar t} pair and a Higgs boson in either e{sup+}e{sup -} or hadronic collisions is presented at next-to-leading-order QCD and its importance for a measurement of the top quark Yulrawa coupling emphasized. Implications of the heavy top quark mass for model builders are briefly examined, with the minimal supersymmetric Standard Model and topcolor discussed as specific examples.

The discovery of the top quark

International Nuclear Information System (INIS)

Sinervo, P.K.

1995-12-01

The top quark and the Higgs boson are the heaviest elementary particles predicted by the standard model. The four lightest quark flavours, the up, down, strange and charm quarks, were well-established by the mid-1970's. The discovery in 1977 of the Τ resonances, a new family of massive hadrons, required the introduction of the fifth quark flavour. Experimental and theoretical studies have indicated that this quark also has a heavier partner, the top quark

The Discovery of the Top Quark

Science.gov (United States)

Sinervo, P.K.

1995-12-01

The top quark and the Higgs boson are the heaviest elementary particles predicted by the standard model. The four lightest quark flavours, the up, down, strange and charm quarks, were well-established by the mid-1970's. The discovery in 1977 of the {Tau} resonances, a new family of massive hadrons, required the introduction of the fifth quark flavour. Experimental and theoretical studies have indicated that this quark also has a heavier partner, the top quark.

Enhancement of new physics signal sensitivity with mistagged charm quarks

Directory of Open Access Journals (Sweden)

Doojin Kim

2016-07-01

Full Text Available We investigate the potential for enhancing search sensitivity for signals having charm quarks in the final state, using the sizable bottom-mistagging rate for charm quarks at the LHC. Provided that the relevant background processes contain light quarks instead of charm quarks, the application of b-tagging on charm quark-initiated jets enables us to reject more background events than signal ones due to the relatively small mistagging rate for light quarks. The basic idea is tested with two rare top decay processes: i t→ch→cbb¯ and ii t→bH+→bb¯c where h and H+ denote the Standard Model-like higgs boson and a charged higgs boson, respectively. The major background source is a hadronic top quark decay such as t→bW+→bs¯c. We test our method with Monte Carlo simulation at the LHC 14 TeV, and find that the signal-over-background ratio can be increased by a factor of O(6–7 with a suitably designed (heavy flavor tagging algorithm and scheme.

Angular correlations in top quark decays in standard model extensions

International Nuclear Information System (INIS)

Batebi, S.; Etesami, S. M.; Mohammadi-Najafabadi, M.

2011-01-01

The CMS Collaboration at the CERN LHC has searched for the t-channel single top quark production using the spin correlation of the t-channel. The signal extraction and cross section measurement rely on the angular distribution of the charged lepton in the top quark decays, the angle between the charged lepton momentum and top spin in the top rest frame. The behavior of the angular distribution is a distinct slope for the t-channel single top (signal) while it is flat for the backgrounds. In this Brief Report, we investigate the contributions which this spin correlation may receive from a two-Higgs doublet model, a top-color assisted technicolor (TC2) and the noncommutative extension of the standard model.

Quark confinement

International Nuclear Information System (INIS)

Joos, H.

1976-07-01

The main topics of these lectures are: phenomenological approach to quark confinement, standard Lagrangian of hadrondynamics, Lagrangian field theory and quark confinement, classical soliton solutions in a simple model, quantization of extended systems, colour charge screening and quantization on a lattice and remarks on applications. A survey of the scientific publications listed according to the topics until 26 March 1976 is supplemented. (BJ) [de

Parton distributions and EMC ratios of the 6Li nucleus in the constituent quark exchange model

Science.gov (United States)

Modarres, M.; Hadian, A.

2017-10-01

While the constituent quark model (CQM), in which the quarks are assumed to be the complex objects, is used to calculate the parton distribution functions of the iso-scalar lithium-6 (6Li) nucleus, the u-d constituent quark distribution functions of the 6Li nucleus are evaluated from the valence quark exchange formalism (VQEF) for the A = 6 iso-scalar system. After computing the valence quark, sea quark, and gluon distribution functions in the constituent quark exchange model (CQEM, i.e., CQM +VQEF), the nucleus structure function is calculated for the 6Li nucleus at the leading order (LO) and the next-to-leading-order (NLO) levels to extract the European muon collaboration (EMC) ratio, at different hard scales, using the standard Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGALP) evolution equations. The outcomes are compared with those of our previous works and the available NMC experimental data, and various physical points are discussed. It is observed that the present EMC ratios are considerably improved compared with those of our previous works, in which only the valence quark distributions were considered to calculate the EMC ratio, and are closer to the NMC data. Finally, it is concluded that at a given appropriate hard scale, the LO approximation may be enough for calculating the nucleus EMC ratio.

Composite quarks and their magnetic moments

International Nuclear Information System (INIS)

Parthasarathy, R.

1980-08-01

A composite quark model based on the symmetry group SU(10)sub(flavour) x SU(10)sub(colour) with the assumption of mass non-degenerate sub-quarks is considered. Magnetic moments of quarks and sub-quarks are obtained from the observed nucleon magnetic moments. Using these quark and sub-quark magnetic moments, a satisfactory agreement for the radiative decays of vector mesons (rho,ω) is obtained. The ratio of the masses of the sub-quarks constituting the u,d,s quarks are found to be Msub(p)/Msub(n) = 0.3953 and Msub(p)/Msub(lambda) = 0.596, indicating a mass hierarchy Msub(p) < Msub(n) < Msub(lambda) for the sub-quarks. (author)

Heavy quarks and leptons

International Nuclear Information System (INIS)

Azimov, Ya.I.; Khoze, V.A.

1979-01-01

Experimental results which proved the reality of quarks are reviewed along with further experiments broadening the representation of quarks and leptons and providing the basis to develop the theory of elementary particles. The discovery of the J/psi particle is noted to give rise to the discovery of c-quark, the existance of which is confirmed by the discovery of charmed hadrons. The main aspects of quantum chromodynamics explaining the mechanism of strong interaction of quarks are considered along with those of the Weinberg-Salam theory proposed to describe weak and electromagnetic interactions of quarks and leptons. Experimental data testifying to the existance of heavy tausup(+-) leptons are presented. The history of discovery of γ mesons and of a new heavier b-quark is described. Perspectives for studying elementary particles are discussed. Further studies of γ mesons, discovery and investigation of charmed particles are noted to be immediate tasks along with the search for manifestation of t-quark considered to be a partner of b-quark from the viewpoint of the Weinberg-Salam model

Towards a new paradigm for quark-lepton unification

Energy Technology Data Exchange (ETDEWEB)

Smith, Christopher [Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-Alpes, CNRS/IN2P3,53 avenue des Martyrs, 38026 Grenoble Cedex (France)

2017-05-03

The quark and charged lepton mass patterns upset their naïve unification. In this paper, a new approach to solve this problem is proposed. Model-independently, we find that a successful unification can be achieved. A mechanism is identified by which the large top quark mass renders its third-generation leptonic partner very light. This state is thus identified with the electron. We then construct a toy model to implement dynamically this mechanism, using tree-level exchanges of vector leptons to relate the quark and charged lepton flavor structures. In a supersymmetric context, this same mechanism splits the squark masses, and third generation squarks end up much lighter than the others. Finally, the implementation of this mechanism in SU(5) GUT permits to avoid introducing any flavor structure beyond the two minimal Yukawa couplings, ensuring the absence of unknown mixing matrices and their potentially large impact on FCNC.

Searches for exotic heavy quarks decaying into a W-Boson and a b-Quark with the ATLAS experiment

CERN Document Server

Nektarijevic, Snezana

In this thesis, searches for two hypothetical heavy quarks are presented: the fourth Standard Model generation up-type quark t’, and the vector-like quark T, predicted by the new physics models involving extra dimensions or a composite Higgs boson. Both searches assume pair production of the heavy quarks decaying to a W-boson and a b-quark, and are performed in final states with one electron or muon, at least three jets, and significant missing transverse energy. The first search employs the kinematic fitting of the reconstructed quark mass, while the second relies on the artificial neural network method. In both searches no excess of data over the Standard Model expectation is observed, resulting in observed lower bounds on the quark masses of mt’>404 GeV and mT>618 GeV. Both searches are based on proton-proton collision data at 7 TeV centre-of-mass energy collected by the ATLAS experiment at CERN’s Large Hadron Collider in 2011.

QCD mixing effects in a gauge invariant quark model for photo- and electroproduction of baryon resonances

International Nuclear Information System (INIS)

Zhenping Li; Close, F.E.

1990-03-01

The photo and electroproduction of baryon resonances has been calculated using the Constituent Quark Model with chromodynamics consistent with O(υ 2 /c 2 ) for the quarks. We find that the successes of the nonrelativistic quark model are preserved, some problems are removed and that QCD mixing effects may become important with increasing q 2 in electroproduction. For the first time both spectroscopy and transitions receive a unified treatment with a single set of parameters. (author)

Hadronization of quark-diquark model for nucleon structure and nuclear force by path integral

International Nuclear Information System (INIS)

Nagata, Keitaro

2003-01-01

One of the central issues of the hadron physics is how to interpret the properties and the origin of nuclear force. Nuclear force is in principle the manifestation of dynamics of quarks and gluons but no trial has been successful yet in describing the nuclear force by using QCD, the fundamental theory of the strong interactions. Phenomenon related to the chiral symmetry and the spontaneous breaking of the chiral symmetry is one of the important phenomena for the understanding of hadron physics. Nambu-Jona-Lasinio (NJL) model is one of the quark system models to explain the phenomena concerning the chiral symmetry. Although the method to deduce the Lagrangian describing mesons by applying the path integral to NJL model has been well known as the bosonization, it has been difficult to extend it to baryons because baryons are three-body system. In this paper, a method is reported to deduce Lagrangian which describes baryon-meson from quark-diquark Lagrangian by assuming that baryons are the bound states of quark and diquark. (S. Funahashi)

Charm-quarks and new elementary particles

International Nuclear Information System (INIS)

Petersen, J.L.

1978-01-01

This is the first part of an extensive paper which discusses: the Nobel prize in physics 1976; discovery of the J/psi-particle; elementary particles and elementary building blocks; the four reciprocal effects; gauge theories; quark-antiquark reciprocal effects; the high-energy approximation; a simple quark-antiquark potential; and quark diagrams and the Zweig rule. (Auth.)

SU(3)xSU(2) color symmetry and Usub(B)(1)xSUsub(f)(4) quark model of hadrons

International Nuclear Information System (INIS)

Khrushchov, V.V.

1982-01-01

A quark model with a generalized color group SUsub(c)(3)xSU'sub(c)(2) is treated in the framework of the SUsub(f)(4)xUsub(B)(1) symnetry of strong interactions. The model contains twelve standard u, d, s, c quarks and new quarks belonging to representation 6 of the SU(4) group. The properties of new quarks are considered with respect to the color group and some properties of the exotic states, predicted by the model are presented

Semileptonic (Λb → Λc eV) decay in a field theoretic quark model

International Nuclear Information System (INIS)

Das, R.K.; Panda, A.R.; Sahoo, R.K.; Swain, M.R.

2002-01-01

The semileptonic decay width of heavy baryons such as (Λ b → Λ c eV) has been estimated in the framework of a nonrelativistic field theoretic quark model where four component quark field operators along with a harmonic oscillator wave function are used to describe translationally invariant hadronic states. The present estimation does not make an explicit use of heavy quark symmetry and has a reasonable agreement with the experimentally measured decay width, polarisation ratio and form factors with the harmonic oscillator radii and quark momentum distribution inside the hadron as free parameters. (author)

Ratio of a strange quark mass ms to up or down quark mass mu,d predicted by a quark propagator in the framework of the chiral perturbation theory

International Nuclear Information System (INIS)

Peng Jinsong; Meng Chengju; Pan Jihuan; Yuan Tongquan; Zhou Lijuan; Ma Weixing

2013-01-01

Based on the fully dressed quark propagator and chiral perturbation theory, we study the ratio of the strange quark mass m s to up or down quark mass m u,d . The ratio is related to the determination of quark masses which are fundamental input parameters of QCD Lagrangian in the Standard Model of particle physics and can not be directly measured since the quark is confined within a hadron. An accurate determination of these QCD free parameters is extremely important for both phenomenological and theoretical applications. We begin with a brief introduction to the non-perturbation QCD theory, and then study the mass ratio in the framework of the chiral perturbation theory (χPT) with a parameterized fully dressed quark propagator which describes confining fully dressed quark propagation and is analytic everywhere in the finite complex p 2 -plane and has no Lehmann representation so there are no quark production thresholds in any theoretical calculations of observable data. Our prediction for the ratio m s /m u,d is consistent with other model predictions such as Lattice QCD, instanton model, QCD sum rules and the empirical values used widely in the literature. As a by-product of this study, our theoretical results, together with other predictions of physical quantities that used this quark propagator in our previous publications, clearly show that the parameterized form of the fully dressed quark propagator is an applicable and reliable approximation to the solution of the Dyson-Schwinger Equation of quark propagator in the QCD. (authors)

Exotic hadron production in a quark combination model

International Nuclear Information System (INIS)

Han Wei; Shao Fenglan; Li Shiyuan; Shang Yonghui; Yao Tao

2009-01-01

The philosophy on production of exotic hadrons (multiquark states) in the framework of the quark combination model is investigated, taking f 0 (980) as an example. The production rate and p T spectra of f 0 (980) considered as (ss) or (sqsq), respectively, are calculated and compared in Au+Au collisions at √(s NN )=200 GeV. The unitarity of various combination models, when open for exotic hadron production, is addressed.

Electroweak amplitudes in chiral quark models

International Nuclear Information System (INIS)

Fiolhais, Manuel

2004-01-01

After referring to some basic features of chiral models for baryons, with quarks and mesons, we describe how to construct model states representing physical baryons. We consider soliton models such as the Linear Sigma Model or the Chromodielectric Model, and bag models such as the Cloudy Bag Model. These models are solved approximately using variational approaches whose starting point is a mean-field description. We go beyond the mean-field description by introducing quantum fluctuations in the mesonic degrees of freedom. This is achieved, in a first step, by using a quantum state to represent meson clouds and, secondly, by performing an angular momentum and isospin projection from the mean-field state (actually a coherent state). Model states for baryons (nucleon, Delta, Roper) constructed in this way are used to determine several physical properties. I this seminar we paid a particular attention to the nucleon-delta electromagnetic and weak transition, presenting the model predictions for the electromagnetic and axial amplitudes

Low-lying 1/2-hidden strange pentaquark states in the constituent quark model

Institute of Scientific and Technical Information of China (English)

Hui Li; Zong-Xiu Wu; Chun-Sheng An; Hong Chen

2017-01-01

We investigate the spectrum of the low-lying 1/2-hidden strange pentaquark states,employing the constituent quark model,and looking at two ways within that model of mediating the hyperfine interaction between quarks-Goldstone boson exchange and one gluon exchange.Numerical results show that the lowest 1/2-hidden strange pentaquark state in the Goldstone boson exchange model lies at ～ 1570 MeV,so this pentaquark configuration may form a notable component in S11(1535) if the Goldstone boson exchange model is applied.This is consistent with the prediction that S11 (1535) couples very strongly to strangeness channels.

Finite Nuclei in the Quark-Meson Coupling Model.

Science.gov (United States)

Stone, J R; Guichon, P A M; Reinhard, P G; Thomas, A W

2016-03-04

We report the first use of the effective quark-meson coupling (QMC) energy density functional (EDF), derived from a quark model of hadron structure, to study a broad range of ground state properties of even-even nuclei across the periodic table in the nonrelativistic Hartree-Fock+BCS framework. The novelty of the QMC model is that the nuclear medium effects are treated through modification of the internal structure of the nucleon. The density dependence is microscopically derived and the spin-orbit term arises naturally. The QMC EDF depends on a single set of four adjustable parameters having a clear physics basis. When applied to diverse ground state data the QMC EDF already produces, in its present simple form, overall agreement with experiment of a quality comparable to a representative Skyrme EDF. There exist, however, multiple Skyrme parameter sets, frequently tailored to describe selected nuclear phenomena. The QMC EDF set of fewer parameters, derived in this work, is not open to such variation, chosen set being applied, without adjustment, to both the properties of finite nuclei and nuclear matter.

Interactions of heavy quarks in quantum chromodynamics

International Nuclear Information System (INIS)

Dine, M.

1978-01-01

The interactions of heavy quarks in quantum chromodynamics (QCD) are analyzed in detail. The problem of extracting instantaneous interaction potentials from quantum field theory is first reviewed, in the context of simple models. How such a potential for a fermion-antifermion system may be extracted is indicated. After a review of the quantization of non-Abelian gauge theories in Coulomb gauge, the interaction of a heavy quark-antiquark (Q anti Q) pair is considered. A Ward identity relating the Coulomb-gluon-fermion vertex to the fermion self-energy is derived. This identity is used to prove the mass independence of the static potential. The potential is shown to be infrared finite through two loops, and its general structure in perturbation theory is indicated. At three loops, divergences associated with long-lived intermediate states appear. A method to resolve this problem for static sources is given, but the result cannot readily be identified as a potential appropriate to the description of a Q anti Q bound state. This problem is discussed in detail. Then the spin-dependent interactions in these systems are analyzed. It is shown that the spin-dependent potentials depend in a nontrivial way on the quark mass. The phenomenological implications of these results are considered. In conclusion, the implications of the results for nonperturbative attacks on the potential problem are discussed. The importance of source-field correlations is stressed. The limitations of schemes introduced recently to compute spin-dependent forces due to instantons are illustrated

Static properties of the nucleon octet in a relativistic potential model with center-of-mass correction

International Nuclear Information System (INIS)

Barik, N.; Dash, B.K.; Das, M.

1985-01-01

The static properties, such as magnetic moment, charge radius, and axial-vector coupling constants, of the quark core of baryons in the nucleon octet have been studied in an independent-quark model based on the Dirac equation with equally mixed scalar-vector potential in harmonic form in the current quark mass limit. The results obtained with the corrections due to center-of-mass motion are in reasonable agreement with experimental values

Effects of dynamical quarks in UKQCD simulations

International Nuclear Information System (INIS)

Allton, Chris

2002-01-01

Recent results from the UKQCD Collaboration's dynamical simulations are presented. The main feature of these ensembles is that they have a fixed lattice spacing and volume, but varying sea quark mass from infinite (corresponding to the quenched simulation) down to roughly that of the strange quark mass. The main aim of this work is to uncover dynamical quark effects from these 'matched' ensembles. We obtain some evidence of dynamical quark effects in the static quark potential with less effects in the hadronic spectrum

Covariant introduction of quark spin into the dual resonance model

International Nuclear Information System (INIS)

Iroshnikov, G.S.

1979-01-01

A very simple method of insertion of a quark spin into the dual resonance model of hadron interaction is proposed. The method is suitable for amplitudes with an arbitrary number of particles. The amplitude of interaction of real particles is presented as a product of contribution of oscillatory excitations in the (q anti q) system and of a spin factor. The latter is equal to the trace of the product of the external particle wave functions constructed from structural quarks and satisfying the relativistic Bargman-Wigner equations. Two examples of calculating the meson interaction amplitudes are presented

Constituent gluons and the static quark potential

Energy Technology Data Exchange (ETDEWEB)

Greensite, Jeff [San Francisco State Univ., CA (United States); Szczepaniak, Adam P. [Indiana Univ., Bloomington, IN (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

2016-04-01

We suggest that Hamiltonian matrix elements between physical states in QCD might be approximated, in Coulomb gauge, by "lattice-improved" tree diagrams; i.e. tree diagram contributions with dressed ghost, transverse gluon, and Coulomb propagators obtained from lattice simulations. Such matrix elements can be applied to a variational treatment of hadronic states which include constituent gluons. As an illustration and first application of this hybrid approach, we derive a variational estimate of the heavy quark potential for distances up to 2.5 fm. The Coulomb string tension in SU(3) gauge theory is about a factor of four times greater than the asymptotic string tension. In our variational approach, using for simplicity a single variational parameter, we can reduce this overshoot by nearly the factor required. The building blocks of our approach are Coulomb gauge propagators, and in this connection we present new lattice results for the ghost and transverse gluon propagators in position space.

Strange sea quark effects for low lying baryons

International Nuclear Information System (INIS)

Upadhyay, A.; Batra, Meenakshi

2013-01-01

Assuming hadrons as an ensemble of quark-gluon Fock states, contributions from sea quarks and gluons can be studied in detail for ground state baryons. Spin crisis of nucleons say that only a small fraction of proton spin is carried by valence quarks. Rest part is distributed among gluons and sea which includes both strange and non-strange quark-anti-quark pairs. This necessitates the study of strange sea quark contribution for other baryons too due to higher mass and presence of strange quark in valence part. Recent studies have also studied strange sea contribution for baryons using different models. We implement the statistical modeling techniques to compute strange sea quark content for baryon octet. Statistical model has already been applied to study sea quark content for nucleons in the form of scalar, vector and tensor sea. In our present work the same idea has been extended for strange sea to probe the structure in more detail. (author)

KN s-wave phase shifts in the non-relativistic quark model

International Nuclear Information System (INIS)

Silvestre-Brac, B.; Labarsouque, J.

1995-01-01

The I=1 and 0 kaon-nucleon s-wave phase shifts have been calculated in a quark potential model using the resonating group method (RGM). The Hill-Wheeler equation has been solved numerically without any parametrization of the KN relative wave-function. The kaon and the nucleon wave-functions have been expanded as sums of several well-chosen gaussian functions, and the sensitivity of the results to the number of terms was analyzed carefully. The I=0 phase shifts are in agreement with the experimental data. In the I=1 channel too much repulsion is obtained, probably due to the lack of medium-range boson exchange type attraction. ((orig.))

Two-Quark Condensate Changes with Quark Current Mass

International Nuclear Information System (INIS)

Lu Changfang; Lue Xiaofu; Wu Xiaohua; Zhan Yongxin

2009-01-01

Using the Schwinger-Dyson equation and perturbation theory, we calculate the two-quark condensates for the light quarks u, d, strange quark s and a heavy quark c with their current masses respectively. The results show that the two-quark condensate will decrease when the quark mass increases, which hints the chiral symmetry may be restored for the heavy quarks.

Strange Quark Matter Status and Prospects

Science.gov (United States)

Sandweiss, J.

2004-01-01

The existence of quark states with more than three quarks is allowed in QCD. The stability of such quark matter states has been studied with lattice QCD and phenomenological bag models, but is not well constrained by theory. The addition of strange quarks to the system allows the quarks to be in lower energy states despite the additional mass penalty. There is additional stability from reduced Coulomb repulsion. SQM is expected to have a low Z/A. Stable or metastable massive multiquark states contain u, d, and s quarks.

Pion-cloud corrections to the relativistic S + V harmonic potential model

International Nuclear Information System (INIS)

Palladino, B.E.; Ferreira, P.L.

1988-01-01

Pionic corrections to the mass spectrum of low-lying s-wave baryons are incorporated in a relativistic independent quark model with equally mixed Lorentz scalar and vector harmonic potentials. (M.W.O.) [pt