Orbital Angular Momentum and Generalized Transverse Momentum Distribution
Zhao, Yong; Liu, Keh-Fei; Yang, Yibo
2015-01-01
We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of X. S. Chen et al. are the same as those derived from generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally, and discuss the strat...
Wigner distributions and quark orbital angular momentum
Cedric LorceOrsay, IPN and Orsay, LPT; Barbara Pasquini(Pavia U. and INFN, Pavia)
2015-01-01
We discuss the quark phase-space or Wigner distributions of the nucleon which combine in a single picture all the information contained in the generalized parton distributions and the transverse-momentum dependent parton distributions. In particular, we present results for the distribution of unpolarized quarks in a longitudinally polarized nucleon obtained in a light-front constituent quark model. We show how the quark orbital angular momentum can be extracted from the Wigner distributions a...
Quark Wigner distributions and orbital angular momentum
We study the Wigner functions of the nucleon which provide multidimensional images of the quark distributions in phase space. These functions can be obtained through a Fourier transform in the transverse space of the generalized transverse-momentum dependent parton distributions. They depend on both the transverse position and the three-momentum of the quark relative to the nucleon, and therefore combine in a single picture all the information contained in the generalized parton distributions and the transverse-momentum dependent parton distributions. We focus the discussion on the distributions of unpolarized/longitudinally polarized quark in an unpolarized/longitudinally polarized nucleon. In this way, we can study the role of the orbital angular momentum of the quark in shaping the nucleon and its correlations with the quark and nucleon polarizations. The quark orbital angular momentum is also calculated from its phase-space average weighted with the Wigner distribution of unpolarized quarks in a longitudinally polarized nucleon. The corresponding results obtained within different light-cone quark models are compared with alternative definitions of the quark orbital angular momentum, as given in terms of generalized parton distributions and transverse-momentum dependent parton distributions.
Orbital angular momentum and generalized transverse momentum distribution
Zhao, Yong; Liu, Keh-Fei; Yang, Yi-Bo
2016-03-01
We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of Chen et al. are the same as those whose matrix elements correspond to the moments of generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally and discuss the strategies of calculating them in lattice QCD.
Orbital Angular Momentum and Generalized Transverse Momentum Distribution
Zhao, Yong; Yang, Yibo
2015-01-01
We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of X. S. Chen et al. are the same as those derived from generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally, and discuss the strategies of calculating them in lattice QCD.
Parton Transverse Momentum and Orbital Angular Momentum Distributions
Rajan, Abha; Courtoy, Aurore; Engelhardt, Michael; Liuti, Simonetta
2016-01-01
The quark orbital angular momentum component of proton spin, $L_q$, can be defined in QCD as the integral of a Wigner phase space distribution weighting the cross product of the quark's transverse position and momentum. It can also be independently defined from the operator product expansion for the off-forward Compton amplitude in terms of a twist-three generalized parton distribution. We provide an explicit link between the two definitions, connecting them through their dependence on parton...
Parton Transverse Momentum and Orbital Angular Momentum Distributions
Rajan, Abha; Engelhardt, Michael; Liuti, Simonetta
2016-01-01
The quark orbital angular momentum component of proton spin, $L_q$, can be defined in QCD as the integral of a Wigner phase space distribution weighting the cross product of the quark's transverse position and momentum. It can also be independently defined from the operator product expansion for the off-forward Compton amplitude in terms of a twist-three generalized parton distribution. We provide an explicit link between the two definitions, connecting them through their dependence on partonic intrinsic transverse momentum. Connecting the definitions provides the key for correlating direct experimental determinations of $L_q$, and evaluations through Lattice QCD calculations. The direct observation of quark orbital angular momentum does not require transverse spin polarization, but can occur using longitudinally polarized targets.
Angular momentum distributions in subbarrier fusion reactions
Interest in subbarrier heavy-ion fusion was stimulated by the realization that subbarrier fusion cross sections were enhanced by many orders of magnitude over what would be expected from quantum mechanical one-dimensional barrier penetration. This review focuses on the angular momentum (spin) distributions in heavy-ion fusion reactions. Experimental probes, theoretical considerations, and a comparison of experimental results with model calculations are given. 86 refs., 10 figs
Quark Orbital-Angular-Momentum Distribution in the Nucleon
Hoodbhoy, Pervez; Ji, Xiangdong; Lu, Wei
1998-01-01
We introduce gauge-invariant quark and gluon angular momentum distributions after making a generalization of the angular momentum density operators. From the quark angular momentum distribution, we define the gauge-invariant and leading-twist quark {\\it orbital} angular momentum distribution $L_q(x)$. The latter can be extracted from data on the polarized and unpolarized quark distributions and the off-forward distribution $E(x)$ in the forward limit. We comment upon the evolution equations o...
Partons Transverse Momentum and Orbital Angular Momentum Distributions
Liuti, Simonetta; Rajan, Abha; Courtoy, Aurore; Engelhardt, Michael
2015-10-01
We discuss the two definitions of partonic orbital angular momentum given by Ji and by Jaffe and Manohar, respectively. It is by now established that the two definitions are described by the same generalized transverse momentum distribution, F14, while they differ through their gauge link structure. They can also be both described in terms of a twist three generalized parton distribution, G2 which can be measured in DVCS type experiments. Here, starting from nonlocal, kT unintegrated, off-forward matrix elements, instead of the standard OPE, we show how G2 can be written as the sum of twist two, quark mass, and interaction dependent (twist three) terms, thus emphasizing the role of quark intrinsic transverse momentum and off-shellness. The twist two term in particular is given by the kT2 moment of F14. We therefore uncover a relation/sum rule connecting the two definitions of orbital angular momentum, F14 and G2. We explore both the spin and the intrinsic transverse momentum/transverse space correlations as well as the gauge link structure behind the two decomposition frameworks, which are necessary to extract orbital angular momentum from experiment.
Quark orbital-angular-momentum distribution in the nucleon
Hoodbhoy, P.; Ji, X.; Lu, W. [Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)
1999-01-01
We introduce gauge-invariant quark and gluon angular momentum distributions after making a generalization of the angular momentum density operators. From the quark angular momentum distribution, we define the gauge-invariant and leading-twist quark {ital orbital} angular momentum distribution L{sub q}(x). The latter can be extracted from data on the polarized and unpolarized quark distributions and the off-forward distribution E(x) in the forward limit. We comment upon the evolution equations obeyed by this as well as other orbital distributions considered in the literature. {copyright} {ital 1998} {ital The American Physical Society}
Quark orbital-angular-momentum distribution in the nucleon
We introduce gauge-invariant quark and gluon angular momentum distributions after making a generalization of the angular momentum density operators. From the quark angular momentum distribution, we define the gauge-invariant and leading-twist quark orbital angular momentum distribution Lq(x). The latter can be extracted from data on the polarized and unpolarized quark distributions and the off-forward distribution E(x) in the forward limit. We comment upon the evolution equations obeyed by this as well as other orbital distributions considered in the literature. copyright 1998 The American Physical Society
Quark Wigner Distributions and Orbital Angular Momentum
Lorce, Cédric; Pasquini, B.
2011-01-01
We study the Wigner functions of the nucleon which provide multidimensional images of the quark distributions in phase space. These functions can be obtained through a Fourier transform in the transverse space of the generalized transverse-momentum dependent parton distributions. They depend on both the transverse position and the three-momentum of the quark relative to the nucleon, and therefore combine in a single picture all the information contained in the generalized parton distributions...
Orbital Angular Momentum Parton Distributions in Light-Front Dynamics
Cano, F.; Faccioli, P.; Scopetta, S.; Traini, M.(Dipartimento di Fisica, Università degli studi di Trento and INFN — TIFPA, Via Sommarive 14, I-38123, Povo (Trento), Italy)
2000-01-01
We study the quark angular momentum distribution in the nucleon within a light-front covariant quark model. Special emphasis is put into the orbital angular momentum: a quantity which is very sensitive to the relativistic treatment of the spin in a light-front dynamical approach. Discrepancies with the predictions of the low-energy traditional quark models where relativistic spin effects are neglected, are visible also after perturbative evolution to higher momentum scales. Orbital angular mo...
Observables for Quarks and Gluons Orbital Angular Momentum Distributions
Liuti, Simonetta; Courtoy, Aurore; Goldstein, Gary R.; Hernandez, J. Osvaldo Gonzalez; Rajan, Abha
2015-02-01
We discuss the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term - Ji decomposition - or a canonical term - Jaffe-Manohar decomposition. Orbital angular momentum has been connected in each decomposition to a different observable, a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and a twist three Generalized Parton Distribution (GPD) for the kinetic term. While the latter appears as an azimuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments.
Evolution Equations for Higher Moments of Angular Momentum Distributions
Haegler, P.; Schaefer, A
1998-01-01
Based on a sumrule for the nucleon spin we expand quark and gluon orbital angular momentum operators and derive an evolution matrix for higher moments of the corresponding distributions. In combination with the spin-dependent DGLAP-matrix we find a complete set of spin and orbital angular momentum evolution equations.
Phase-space distributions and orbital angular momentum
Pasquini B.
2014-06-01
Full Text Available We review the concept of Wigner distributions to describe the phase-space distributions of quarks in the nucleon, emphasizing the information encoded in these functions about the quark orbital angular momentum.
Phase-space distributions and orbital angular momentum
Pasquini B.; Lorcé C.
2014-01-01
We review the concept of Wigner distributions to describe the phase-space distributions of quarks in the nucleon, emphasizing the information encoded in these functions about the quark orbital angular momentum.
Generalized Parton Distributions Describing Partonic Orbital Angular Momentum
Liuti, Simonetta; Engelhardt, Michael; Rajan, Abha; Courtoy, Aurore
2015-04-01
We discuss orbital angular momentum in QCD, in particular, its observability, and its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic and a canonical definition, respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist three Generalized Parton Distributions (GPDs), and it is therefore readily observable in Deeply Virtual Compton Scattering experiments. On the other hand, canonical angular momentum is defined in terms of a Generalized Transverse Momentum Distribution (GTMD) and it can be therefore observed in scattering processes involving an additional hadronic reaction plane. A comparison between the two definitions can be performed by extending to GTMDs the techniques previously developed for lattice calculations of Transverse Momentum Distributions (TMDs) evaluating the matrix elements of quark bilocal operators containing a staple-shaped Wilson connection. This work was funded in part by U.S. D.O.E. Grant DE-FG02-01ER4120.
On the Observability of the Quark Orbital Angular Momentum Distribution
Courtoy, Aurore; Hernandez, J Osvaldo Gonzalez; Liuti, Simonetta; Rajan, Abha
2013-01-01
We argue that due to Parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions -- the generalized transverse momentum distributions -- that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon, can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated to orbital angular momentum %to deeply virtual Compton scattering provide observables related to orbital angular momentum and are related to the target-spin asymmetry in deeply virtual Compton scattering, already mea...
On the observability of the quark orbital angular momentum distribution
Courtoy, Aurore, E-mail: aurore.courtoy@ulg.be [IFPA, AGO Department, Université de Liège, Bât. B5, Sart Tilman, B-4000 Liège (Belgium); Laboratori Nazionali di Frascati, INFN, Frascati (Italy); Goldstein, Gary R., E-mail: gary.goldstein@tufts.edu [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Osvaldo Gonzalez Hernandez, J., E-mail: jog4m@virginia.edu [Istituto Nazionale di Fisica Nucleare (INFN) – Sezione di Torino, via P. Giuria, 1, 10125 Torino (Italy); Liuti, Simonetta, E-mail: sl4y@virginia.edu [University of Virginia – Physics Department, 382 McCormick Rd., Charlottesville, VA 22904 (United States); Laboratori Nazionali di Frascati, INFN, Frascati (Italy); Rajan, Abha, E-mail: ar5xc@virginia.edu [University of Virginia – Physics Department, 382 McCormick Rd., Charlottesville, VA 22904 (United States)
2014-04-04
We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions – the generalized transverse momentum distributions – that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light-cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated with orbital angular momentum are related to the target-spin asymmetry in deeply virtual Compton scattering, already measured at HERMES.
On the observability of the quark orbital angular momentum distribution
We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions – the generalized transverse momentum distributions – that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light-cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated with orbital angular momentum are related to the target-spin asymmetry in deeply virtual Compton scattering, already measured at HERMES.
On the observability of the quark orbital angular momentum distribution
Courtoy, Aurore; Goldstein, Gary R.; Osvaldo Gonzalez Hernandez, J.; Liuti, Simonetta; Rajan, Abha
2014-04-01
We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions - the generalized transverse momentum distributions - that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light-cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated with orbital angular momentum are related to the target-spin asymmetry in deeply virtual Compton scattering, already measured at HERMES.
Spin and Orbital Angular Momentum Distribution Functions of the Nucleon
Wakamatsu, M.; Watabe, T
1999-01-01
A theoretical prediction is given for the spin and orbital angular momentum distribution functions of the nucleon within the framework of an effective quark model of QCD, i.e. the chiral quark soliton model. An outstanding feature of the model is that it predicts fairly small quark spin fraction of the nucleon $\\Delta \\Sigma \\simeq 0.35$, which in turn dictates that the remaining 65% of the nucleon spin is carried by the orbital angular momentum of quarks and antiquarks at the model energy sc...
Twist Three Generalized Parton Distributions for Orbital Angular Momentum
Rajan, Abha
2016-01-01
We study the orbital angular momentum contribution to the spin structure of the proton. It is well known that the quark and gluon spin contributions do not add up to the proton spin. We motivate the connection between the Generalized Transverse Momentum Distribution (GTMD) $F_{14}$, and orbital angular momentum by exploring the underlying quark proton helicity amplitude structure. The twist three Generalized Parton Distribution (GPD) $\\tilde{E}_{2T}$, was shown to connect to OAM. We study these functions using a diquark model calculation. The GTMD $F_{14}$ is unique in that it can describe both Jaffe-Manohar and Ji OAM depending on choice of gauge link, i.e. whether final state interactions are included or not. We perform a calculation of $F_{14}$ in both scenarios.
Experimental orbital angular momentum based quantum key distribution through turbulence
Goyal, Sandeep; Roux, Filippus S; Konrad, Thomas; Forbes, Andrew
2014-01-01
Using an experimental setup that simulates a turbulent atmosphere, we study the secret key rate for quantum key distribution protocols in orbital angular momentum based free space quantum communication. The quantum key distribution protocols under consideration include the Ekert 91 protocol for different choices of mutually unbiased bases and the six-state protocol. We find that the secret key rate of these protocols decay to zero roughly at the same scale where the entanglement of formation decays to zero.
Experimental orbital angular momentum based quantum key distribution through turbulence
Goyal, Sandeep; Ibrahim, Alpha Hamadou; Roux, Filippus S.; Konrad, Thomas; Forbes, Andrew
2014-01-01
Using an experimental setup that simulates a turbulent atmosphere, we study the secret key rate for quantum key distribution protocols in orbital angular momentum based free space quantum communication. The quantum key distribution protocols under consideration include the Ekert 91 protocol for different choices of mutually unbiased bases and the six-state protocol. We find that the secret key rate of these protocols decay to zero roughly at the same scale where the entanglement of formation ...
Wigner distribution and orbital angular momentum of a proton
Chakrabarti, D.; Maji, T.; Mondal, C.; Mukherjee, A.
2016-01-01
The Wigner distributions for u and d quarks in a proton are calculated using the light front wave functions (LFWFs) of the scalar quark-diquark model for nucleon constructed from the soft-wall AdS/QCD correspondence. We present a detail study of the quark orbital angular momentum(OAM) and its correlation with quark spin and proton spin. The quark density distributions, considering the different polarizations of quarks and proton, in transverse momentum plane as well as in transverse impact pa...
Accessing the quark orbital angular momentum with Wigner distributions
Cedric LorceIPNO and LPT, Orsay; Barbara Pasquini(Pavia U. and INFN, Pavia)
2015-01-01
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wig...
Wigner distribution and orbital angular momentum of a proton
Chakrabarti, D; Mondal, C; Mukherjee, A
2016-01-01
The Wigner distributions for u and d quarks in a proton are calculated using the light front wave functions (LFWFs) of the scalar quark-diquark model for nucleon constructed from the soft-wall AdS/QCD correspondence. We present a detail study of the quark orbital angular momentum(OAM) and its correlation with quark spin and proton spin. The quark density distributions, considering the different polarizations of quarks and proton, in transverse momentum plane as well as in transverse impact parameter plane are presented for both u and d quarks.
Accessing the quark orbital angular momentum with Wigner distributions
Lorce, Cedric [IPNO, Universite Paris-Sud, CNRS/IN2P3, 91406 Orsay, France and LPT, Universite Paris-Sud, CNRS, 91406 Orsay (France); Pasquini, Barbara [Dipartimento di Fisica, Universita degli Studi di Pavia, Pavia, Italy and Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia (Italy)
2013-04-15
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wigner distributions. We discuss the concept of Wigner distributions in the context of quantum field theory and show how they are related to the GPDs and the TMDs. We summarize the different definitions discussed in the literature for the quark OAM and show how they can in principle be extracted from the Wigner distributions.
Accessing the quark orbital angular momentum with Wigner distributions
Cedric, Lorce
2012-01-01
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wigner distributions. We discuss the concept of Wigner distributions in the context of quantum field theory and show how they are related to the GPDs and the TMDs. We summarize the different definitions discussed in the literature for the quark OAM and show how they can in principle be extracted from the Wigner distributions.
Accessing the quark orbital angular momentum with Wigner distributions
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wigner distributions. We discuss the concept of Wigner distributions in the context of quantum field theory and show how they are related to the GPDs and the TMDs. We summarize the different definitions discussed in the literature for the quark OAM and show how they can in principle be extracted from the Wigner distributions.
Orbital angular momentum from marginals of quadrature distributions
Sanchez-Soto, L. L.; Klimov, A. B.; de la Hoz, P.; Rigas, I.; J. Rehacek; Hradil, Z.; Leuchs, G.
2013-01-01
We set forth a method to analyze the orbital angular momentum of a light field. Instead of using the canonical formalism for the conjugate pair angle-angular momentum, we model this latter variable by the superposition of two independent harmonic oscillators along two orthogonal axes. By describing each oscillator by a standard Wigner function, we derive, via a consistent change of variables, a comprehensive picture of the orbital angular momentum. We compare with previous approaches and show...
Statistical mechanics of collisionless orbits. IV. Distribution of angular momentum
It has been shown in previous work that DARKexp, which is a theoretically derived, maximum entropy, one shape parameter model for isotropic collisionless systems, provides very good fits to simulated and observed dark matter halos. Specifically, it fits the energy distribution, N(E), and the density profiles, including the central cusp. Here, we extend DARKexp N(E) to include the distribution in angular momentum, L 2, for spherically symmetric systems. First, we argue, based on theoretical, semi-analytical, and simulation results, that while dark matter halos are relaxed in energy, they are not nearly as relaxed in angular momentum, which precludes using maximum entropy to uniquely derive N(E, L 2). Instead, we require that when integrating N(E, L 2) over squared angular momenta one retrieves the DARKexp N(E). Starting with a general expression for N(E, L 2) we show how the distribution of particles in L 2 is related to the shape of the velocity distribution function, VDF, and velocity anisotropy profile, β(r). We then demonstrate that astrophysically realistic halos, as judged by the VDF shape and β(r), must have linear or convex distributions in L 2, for each separate energy bin. The distribution in energy of the most bound particles must be nearly flat, and become more tilted in favor of radial orbits for less bound particles. These results are consistent with numerical simulations and represent an important step toward deriving the full distribution function for spherically symmetric dark matter halos.
Statistical mechanics of collisionless orbits. IV. Distribution of angular momentum
Williams, Liliya L. R. [School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States); Hjorth, Jens; Wojtak, Radosław, E-mail: llrw@astro.umn.edu, E-mail: jens@dark-cosmology.dk, E-mail: wojtak@dark-cosmology.dk [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark)
2014-03-01
It has been shown in previous work that DARKexp, which is a theoretically derived, maximum entropy, one shape parameter model for isotropic collisionless systems, provides very good fits to simulated and observed dark matter halos. Specifically, it fits the energy distribution, N(E), and the density profiles, including the central cusp. Here, we extend DARKexp N(E) to include the distribution in angular momentum, L {sup 2}, for spherically symmetric systems. First, we argue, based on theoretical, semi-analytical, and simulation results, that while dark matter halos are relaxed in energy, they are not nearly as relaxed in angular momentum, which precludes using maximum entropy to uniquely derive N(E, L {sup 2}). Instead, we require that when integrating N(E, L {sup 2}) over squared angular momenta one retrieves the DARKexp N(E). Starting with a general expression for N(E, L {sup 2}) we show how the distribution of particles in L {sup 2} is related to the shape of the velocity distribution function, VDF, and velocity anisotropy profile, β(r). We then demonstrate that astrophysically realistic halos, as judged by the VDF shape and β(r), must have linear or convex distributions in L {sup 2}, for each separate energy bin. The distribution in energy of the most bound particles must be nearly flat, and become more tilted in favor of radial orbits for less bound particles. These results are consistent with numerical simulations and represent an important step toward deriving the full distribution function for spherically symmetric dark matter halos.
Quark Orbital Angular Momentum
Burkardt Matthias
2015-01-01
Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asy...
Orbital Angular Momentum Parton Distributions in Quark Models
Scopetta, S.; Vento, V.
1999-01-01
At the low energy, {\\sl hadronic}, scale we calculate Orbital Angular Momentum (OAM) twist-two parton distributions for the relativistic MIT bag model and for non-relativistic 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. Th...
Nucleon form factors, generalized parton distributions and quark angular momentum
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale μ=2 GeV to be Juv=0.230+0.009-0.024 and Jdv=-0.004+0.010-0.016.
DISTRIBUTION OF ACCRETING GAS AND ANGULAR MOMENTUM ONTO CIRCUMPLANETARY DISKS
We investigate gas accretion flow onto a circumplanetary disk from a protoplanetary disk in detail by using high-resolution three-dimensional nested-grid hydrodynamic simulations, in order to provide a basis of formation processes of satellites around giant planets. Based on detailed analyses of gas accretion flow, we find that most of gas accretion onto circumplanetary disks occurs nearly vertically toward the disk surface from high altitude, which generates a shock surface at several scale heights of the circumplanetary disk. The gas that has passed through the shock surface moves inward because its specific angular momentum is smaller than that of the local Keplerian rotation, while gas near the midplane in the protoplanetary disk cannot accrete to the circumplanetary disk. Gas near the midplane within the planet's Hill sphere spirals outward and escapes from the Hill sphere through the two Lagrangian points L1 and L2. We also analyze fluxes of accreting mass and angular momentum in detail and find that the distributions of the fluxes onto the disk surface are well described by power-law functions and that a large fraction of gas accretion occurs at the outer region of the disk, i.e., at about 0.1 times the Hill radius. The nature of power-law functions indicates that, other than the outer edge, there is no specific radius where gas accretion is concentrated. These source functions of mass and angular momentum in the circumplanetary disk would provide us with useful constraints on the structure and evolution of the circumplanetary disk, which is important for satellite formation.
Angular momentum of disc galaxies with a lognormal density distribution
Marr, John Herbert
2015-01-01
Whilst most galaxy properties scale with galaxy mass, similar scaling relations for angular momentum are harder to demonstrate. A lognormal (LN) density distribution for disc mass provides a good overall fit to the observational data for disc rotation curves for a wide variety of galaxy types and luminosities. In this paper, the total angular momentum J and energy $\\vert{}$E$\\vert{}$ were computed for 38 disc galaxies from the published rotation curves and plotted against the derived disc masses, with best fit slopes of 1.683$\\pm{}$0.018 and 1.643$\\pm{}$0.038 respectively, using a theoretical model with a LN density profile. The derived mean disc spin parameter was $\\lambda{}$=0.423$\\pm{}$0.014. Using the rotation curve parameters V$_{max}$ and R$_{max}$ as surrogates for the virial velocity and radius, the virial mass estimator $M_{disc}\\propto{}R_{max}V_{max}^2$ was also generated, with a log-log slope of 1.024$\\pm{}$0.014 for the 38 galaxies, and a proportionality constant ${\\lambda{}}^*=1.47\\pm{}0.20\\time...
Drell-Yan Lepton Angular Distribution at Small Transverse Momentum
Boer, D; Boer, Daniel; Vogelsang, Werner
2006-01-01
We investigate the dependence of the Drell-Yan cross section on lepton polar and azimuthal angles, as generated by the lowest-order QCD annihilation and Compton processes. We focus in particular on the azimuthal-angular distributions, which are of the form cos(phi) and cos(2phi). At small transverse momentum q_T of the lepton pair, q_T << Q, with Q the pair mass, these terms are known to be suppressed relative to the phi-independent part of the Drell-Yan cross section by one or two powers of the transverse momentum. Nonetheless, as we show, like the phi-independent part they are subject to large logarithmic corrections, whose precise form however depends on the reference frame chosen. These logarithmic contributions ultimately require resummation to all orders in the strong coupling. We discuss the potential effects of resummation on the various angular terms in the cross section and on the Lam-Tung relation.
Nucleon form factors, generalized parton distributions and quark angular momentum
Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kroll, Peter [Bergische Univ., Wuppertal (Germany). Fachbereich Physik; Regensburg Univ. (Germany). Institut fuer Theoretische Physik
2013-02-15
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale {mu}=2 GeV to be J{sup u}{sub v}=0.230{sup +0.009}{sub -0.024} and J{sup d}{sub v}=-0.004{sup +0.010}{sub -0.016}.
Quark Orbital Angular Momentum
Burkardt Matthias
2015-01-01
Full Text Available Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.
On the observability of the quark orbital angular momentum distribution
Courtoy, Aurore; Goldstein, Gary R.; Hernandez, J. Osvaldo Gonzalez; Liuti, Simonetta; Rajan, Abha(University of Virginia – Physics Department, 382 McCormick Rd., Charlottesville, VA 22904, USA)
2014-01-01
We argue that due to Parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions -- the generalized transverse momentum distributions -- that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon, can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light cone operators projections in the ...
Defining the Observables for Quarks and Gluons Orbital Angular Momentum Distributions
We present a critical discussion of the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term, generally associated with the Ji decomposition, and a canonical term from the Jaffe Manohar decomposition. Orbital angular momentum has been connected to a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and to a twist three Generalized Parton Distribution for the kinetic term. We argue that while the latter appears as an azimuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments. (author)
Defining the Observables for Quarks and Gluons Orbital Angular Momentum Distributions
Liuti, S.; Courtoy, A.; Goldstein, G. R.; Gonzalez Hernandez, J. O.; Rajan, A.
2015-09-01
We present a critical discussion of the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term, generally associated with the Ji decomposition, and a canonical term from the Jaffe Manohar decomposition. Orbital angular momentum has been connected to a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and to a twist three Generalized Parton Distribution for the kinetic term. We argue that while the latter appears as an azymuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments.
Quark phase-space distributions and orbital angular momentum
Cédric LorcéOrsay, IPN and Orsay, LPT; Barbara Pasquini(Pavia U. and INFN, Pavia)
2012-01-01
We discuss the Wigner functions of the nucleon which provide multi-dimensional images of the quark distributions in phase space. They combine in a single picture all the information contained in the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs). In particular, we present results for the distribution of unpolarized quarks in a longitudinally polarized nucleon obtained in a light-cone constituent quark model. We show how quark orbital ...
The quark orbital angular momentum from Wigner distributions and light-cone wave functions
Lorce, Cédric; Pasquini, Barbara; Xiong, Xiaonu; Yuan, Feng
2012-01-01
We investigate the quark orbital angular momentum of the nucleon in the absence of gauge-field degrees of freedom, by using the concept of the Wigner distribution and the light-cone wave functions of the Fock state expansion of the nucleon. The quark orbital angular momentum is obtained from the phase-space average of the orbital angular momentum operator weighted with the Wigner distribution of unpolarized quarks in a longitudinally polarized nucleon. We also derive the light-cone wave funct...
Quark Wigner Distributions and Orbital Angular Momentum in Light-front Dressed Quark Model
Mukherjee, Asmita; Ojha, Vikash Kumar
2014-01-01
We calculate the Wigner functions for a quark target dressed with a gluon. These give a combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs). We calculate and compare the different definitions of quark orbital angular momentum in this model. We compare our results with other model calculations.
Partonic orbital angular momentum
Arash, Firooz; Taghavi-Shahri, Fatemeh; Shahveh, Abolfazl
2013-04-01
Ji's decomposition of nucleon spin is used and the orbital angular momentum of quarks and gluon are calculated. We have utilized the so called valon model description of the nucleon in the next to leading order. It is found that the average orbital angular momentum of quarks is positive, but small, whereas that of gluon is negative and large. Individual quark flavor contributions are also calculated. Some regularities on the total angular momentum of the quarks and gluon are observed.
Quark Orbital Angular Momentum
Burkardt, Matthias
2016-06-01
Generalized parton distributions provide information on the distribution of quarks in impact parameter space. For transversely polarized nucleons, these impact parameter distributions are transversely distorted and this deviation from axial symmetry leads on average to a net transverse force from the spectators on the active quark in a DIS experiment. This force when acting along the whole trajectory of the active quark leads to transverse single-spin asymmetries. For a longitudinally polarized nucleon target, the transverse force implies a torque acting on the quark orbital angular momentum (OAM). The resulting change in OAM as the quark leaves the target equals the difference between the Jaffe-Manohar and Ji OAMs.
Quark Orbital Angular Momentum
Burkardt, Matthias
2016-03-01
Generalized parton distributions provide information on the distribution of quarks in impact parameter space. For transversely polarized nucleons, these impact parameter distributions are transversely distorted and this deviation from axial symmetry leads on average to a net transverse force from the spectators on the active quark in a DIS experiment. This force when acting along the whole trajectory of the active quark leads to transverse single-spin asymmetries. For a longitudinally polarized nucleon target, the transverse force implies a torque acting on the quark orbital angular momentum (OAM). The resulting change in OAM as the quark leaves the target equals the difference between the Jaffe-Manohar and Ji OAMs.
Hazak, G.; Zarmi, Y.; Zinamon, Z.
1981-06-01
The detailed structure of electron momentum distribution in relativistic diodes is studied. It is proven that in most of the diode region the momentum distribution is isotropic in fluid rest frame, with azimuthal temperature which, in general, is much larger than the cathode temperature. A diode model based on these conclusions is presented. The model allows for a continuum of electron trajectories at each point. In various limits the results are reduced to well-known cold fluid model results.
Towards a Direct Measurement of the Quark Orbital Angular Momentum Distribution
Liuti, Simonetta; Engelhardt, Michael; Rajan, Abha
2015-01-01
We discuss two different definitions of partonic orbital angular momentum given in the literature in terms of the Fourier transform of a Wigner distribution, $F_{14}$, and a twist three generalized parton distribution, $\\tilde{E}_{2T}$, respectively. We derive a relation between the two definitions which reflects their specific spin and intrinsic transverse momentum/transverse space correlations as well as their gauge link structure.
Effect of Orbital Angular Momentum on Valence-Quark Helicity Distributions
Avakian, Harut; Brodsky, Stanley J.; Deur, Alexandre; Yuan, Feng
2007-01-01
We study the quark helicity distributions at large x in perturbative QCD, taking into account contributions from the valence Fock states of the nucleon which have nonzero orbital angular momentum. These states are necessary to have a nonzero anomalous magnetic moment. We find that the quark orbital angular momentum contributes a large logarithm to the negative helicity quark distributions in addition to its power behavior, scaling as (1-x)^5\\log^2(1-x) in the limit of x\\to 1. Our analysis sho...
Fourier relationship between angular position and optical orbital angular momentum
Yao, E.; Franke-Arnold, S.; Courtial, J.; Barnett, S.; Padgett, M. J.
2006-01-01
We demonstrate the Fourier relationship between angular position and angular momentum for a light mode. In particular we measure the distribution of orbital angular momentum states of light that has passed through an aperture and verify that the orbital angular momentum distribution is given by the complex Fourier-transform of the aperture function. We use spatial light modulators, configured as diffractive optical components, to define the initial orbital angular momentum state of the beam, ...
Quiescence and late time activity in collapsars due to critical angular momentum distributions
Lopez-Camara, D
2010-01-01
Even thought a large amount of long gamma ray bursts (LGRBs) present quiescent periods, their origin remains unclear. In this talk, it is shown how different angular momentum distributions, as a function of the stellar radius), can lead to neutrino luminosity variability and the possibility of quiescent epochs in LGRBs.
ZHANG Yi-Xin; CANG Ji
2009-01-01
Effects of atmospheric turbulence tilt, defocus, astigmatism and coma aberrations on the orbital angular mo-mentum measurement probability of photons propagating in weak turbulent regime are modeled with Rytov approximation. By considering the resulting wave as a superposition of angular momentum eigenstates, the or-bital angular momentum measurement probabilities of the transmitted digit axe presented. Our results show that the effect of turbulent tilt aberration on the orbital angular momentum measurement probabilities of photons is the maximum among these four kinds of aberrations. As the aberration order increases, the effects of turbulence aberrations on the measurement probabilities of orbital angular momentum generally decrease, whereas the effect of turbulence defoens can be ignored. For tilt aberration, as the difference between the measured orbital angular momentum and the original orbital angular momentum increases, the orbital angular momentum measurement probabifity decreases.
Effects of atmospheric turbulence tilt, defocus, astigmatism and coma aberrations on the orbital angular momentum measurement probability of photons propagating in weak turbulent regime are modeled with Rytov approximation. By considering the resulting wave as a superposition of angular momentum eigenstates, the orbital angular momentum measurement probabilities of the transmitted digit are presented. Our results show that the effect of turbulent tilt aberration on the orbital angular momentum measurement probabilities of photons is the maximum among these four kinds of aberrations. As the aberration order increases, the effects of turbulence aberrations on the measurement probabilities of orbital angular momentum generally decrease, whereas the effect of turbulence defocus can be ignored. For tilt aberration, as the difference between the measured orbital angular momentum and the original orbital angular momentum increases, the orbital angular momentum measurement probability decreases. (fundamental areas of phenomenology (including applications))
For many years the Institute of Physics has published books on hot topics based on a collection of reprints from different journals, including some remarks by the editors of each volume. The book on Optical Angular Momentum, edited by L Allen, S M Barnett and M J Padgett, is a recent addition to the series. It reproduces forty four papers originally published in different journals and in a few cases it provides direct access to works not easily accessible to a web navigator. The collection covers nearly a hundred years of progress in physics, starting from an historic 1909 paper by Poynting, and ending with a 2002 paper by Padgett, Barnett and coworkers on the measurement of the orbital angular momentum of a single photon. The field of optical angular momentum has expanded greatly, creating an interdisciplinary attraction for researchers operating in quantum optics, atomic physics, solid state physics, biophysics and quantum information theory. The development of laser optics, especially the control of single mode sources, has made possible the specific design of optical radiation modes with a high degree of control on the light angular momentum. The editors of this book are important figures in the field of angular momentum, having contributed to key progress in the area. L Allen published an historical paper in 1999, he and M J Padgett (together with M Babiker) produced few years ago a long review article which is today still the most complete basic introduction to the angular momentum of light, while S M Barnett has contributed several high quality papers to the progress of this area of physics. The editors' choice provides an excellent overview to all readers, with papers classified into eight different topics, covering the basic principles of the light and spin and orbital angular momentum, the laboratory tools for creating laser beams carrying orbital angular momentum, the optical forces and torques created by laser beams carrying angular momentum on
Angular momentum distributions for {sup 16}O + {sup 144}Nd
Duchene, G.; Romain, P.; Beck, F.A.; Benet, P.; Disdier, D.; Haas, B.; Lott, B.; Rauch, V.; Scheibling, F.; Vivien, J.P. [Strasbourg-1 Univ., 67 (France). Centre de Recherches Nucleaires]|[Strasbourg-1 Univ., 67 (France); Basu, S.K. [Bhabha Atomic Research Centre, Calcutta (India). Variable Energy Cyclotron Project; Bozek, E.; Zuber, K. [Institute of Nuclear Physics, Cracow (Poland); Di Gregorio, D.E.; Fernandez-Niello, J. [Comision Nacional de Energia Atomica, Buenos Aires (Argentina). Dept. de Fisica
1992-12-31
Fusion cross sections have been measured for the system {sup 16} O + {sup 144} Nd at bombarding energies in the range 67 MeV {<=}E{sub lab} {<=} 90 MeV by detecting directly evaporation residues in Si detectors and in the range 60 MeV {<=}E{sub lab}{<=} 75 MeV by off-line detection of the K X-rays emitted by the radioactive evaporation residues and daughters. In order to obtain the spin distributions in the compound system gamma-ray multiplicity distributions for the most important neutron evaporation channels were also measured using a 4{pi} - BaF{sub 2} array, in conjunction with Ge detectors. Results are compared with calculations based on models that consider fluctuations in barrier height due to ground state zero point vibrations as well as couplings to various inelastic and transfer channels.
Angular momentum distributions for 16O+144Nd
Fusion cross sections have been measured for the system 16O+144Nd at bombarding energies in the range 67 MeV≤Elab≤90 MeV by detecting directly evaporation residues in Si detectors and in the range 60 MeV≤Elab≤75 MeV by off-line detection of the K x rays emitted by the radioactive evaporation residues and daughters. In order to obtain the spin distributions in the compound system gamma-ray multiplicity distributions for the most important neutron evaporation channels were also measured using a 4π BaF2 array, in conjunction with Ge detectors. Results are compared with calculations based on models that consider fluctuations in barrier height due to ground-state zero-point vibrations as well as couplings to various inelastic and transfer channels
Orbital angular momentum effects
This paper reports that in the context of the parton model description of baryon structure orbital angular momentum effects have long been considered negligible. However, recent results obtained within the framework of QCD and presented in this talk indicate that a substantial fraction of the baryon spin may be carried as orbital angular momentum of its constituents. These results are of particular relevance in the light of new data on the spin structure of the proton recently published by the EMC collaboration
Rotations and angular momentum
This paper is devoted to the analysis of rotational invariance and the properties of angular momentum in quantum mechanics. In particular, the problem of addition of angular momenta is treated in detail, and tables of Clebsch-Gordan coefficients are included
Probability distribution of primordial angular momentum and formation of massive black holes
Susa, H; Tanaka, T; Hajime Susa; Misao Sasaki; Takahiro Tanaka
1994-01-01
Abstract{ We consider the joint probability distribution function for the mass contrast and angular momentum of over-density regions on the proto- galactic scale and investigate the formation of massive black holes at redshift z\\gsim10. We estimate the growth rate of the angular momentum by the linear perturbation theory and the decay rate by the Compton drag and apply the Press-Schechter theory to obtain the formation rate of massive black holes, assuming the full reionization of the universe at z=z_{ion}\\gg 10. We find the correlation between the mass contrast and angular momentum vanishes in the linear theory. However, application of the Press-Schechter theory introduces a correlation between the mass contrast and angular momentum of bound objects. Using thus obtained probability distribution, we calculate the mass fraction of black holes with M\\sim10^6-10^8M_{\\odot} in the universe. We find that it crucially depends on the reionization epoch z_{ion}. Specifically, for the standard CDM power spectrum with ...
Inner Engine Shutdown from Transitions in the Angular Momentum Distribution in Collapsars
Batta, Aldo
2016-01-01
For the collapsar scenario to be effective in the production of Gamma Ray Bursts, the infalling star's angular momentum $J(r)$ must be larger than the critical angular momentum needed to form an accretion disk around a blackhole (BH), namely $J_{\\rm crit} = 2r_{g}c$ for a Schwarzschild BH. By means of 3D SPH simulations, here we study the collapse and accretion onto black holes of spherical rotating envelopes, whose angular momentum distribution has transitions between supercritical ($J>J_{\\rm crit}$) and subcritical ($J
Inner engine shutdown from transitions in the angular momentum distribution in collapsars
Batta, Aldo; Lee, William H.
2016-06-01
For the collapsar scenario to be effective in the production of gamma ray bursts (GRBs), the infalling star's angular momentum J(r) must be larger than the critical angular momentum needed to form an accretion disc around a black hole (BH), namely Jcrit = 2rgc for a Schwarzschild BH. By means of 3D smoothed particle hydrodynamics simulations, here we study the collapse and accretion on to BHs of spherical rotating envelopes, whose angular momentum distribution has transitions between supercritical (J > Jcrit) and subcritical (J 2D hydrodynamical simulations, we find that a substantial amount of subcritical material fed to the accretion disc, lingers around long enough to contribute significantly to the energy loss rate. Increasing the amount of angular momentum in the subcritical material increases the time spent at the accretion disc, and only when the bulk of this subcritical material is accreted before it is replenished by a massive outermost supercritical shell, the inner engine experiences a shutdown. Once the muffled accretion disc is provided again with enough supercritical material, the shutdown will be over and a quiescent time in the long GRB produced afterwards could be observed.
Effect of Orbital Angular Momentum on Valence-Quark Helicity Distributions
Harut Avakian; Stanley J. Brodsky; Alexandre Deur; Feng Yuan
2007-08-01
We study the quark helicity distributions at large x in perturbative QCD, taking into account contributions from the valence Fock states of the nucleon which have nonzero orbital angular momentum. These states are necessary to have a nonzero anomalous magnetic moment. We find that the quark orbital angular momentum contributes a large logarithm to the negative helicity quark distributions in addition to its power behavior, scaling as (1-x)^5\\log^2(1-x) in the limit of x\\to 1. Our analysis shows that the ratio of the polarized over unpolarized down quark distributions, \\Delta d/d, will still approach 1 in this limit. By comparing with the experimental data, we find that this ratio should cross zero at x\\approx 0.75.
Retrieving orbital angular momentum distribution of light with plasmonic vortex lens
Zhou, Hailong; Dong, Jianji; Zhang, Jihua; Zhang, Xinliang
2016-06-01
We utilize a plasmonic vortex lens (PVL) to retrieve the orbital angular momentum (OAM) distribution of light. The OAM modes are coupled to the surface plasmon polaritons (SPPs) in the form of various Bessel functions respectively. By decomposing the interference pattern of SPPs into these Bessel functions, we can retrieve the relative amplitude and the relative phase of input OAM modes simultaneously. Our scheme shows advantage in integration and can measure hybrid OAM states by one measurement.
Angular momentum distribution during the collapse of primordial star-forming clouds
Dutta, Jayanta
2015-01-01
It is generally believed that angular momentum is distributed during the gravitational collapse of the primordial star forming cloud. However, so far there has been little understanding of the exact details of the distribution. We use the modified version of the Gadget-2 code, a three-dimensional smoothed-particle hydrodynamics simulation, to follow the evolution of the collapsing gas in both idealized as well as more realistic minihalos. We find that, despite the lack of any initial turbulence and magnetic fields in the clouds the angular momentum profile follows the same characteristic power-law that has been reported in studies that employed fully self-consistent cosmological initial conditions. The fit of the power-law appears to be roughly constant regardless of the initial rotation of the cloud. We conclude that the specific angular momentum of the self-gravitating rotating gas in the primordial minihalos maintains a scaling relation with the gas mass as $L \\propto M^{1.125}$. We also discuss the plausi...
Dang, N Dinh; Kmiecik, M; Maj, A
2013-01-01
The line shapes of giant dipole resonance (GDR) in the decay of the compound nucleus $^{88}$Mo, which is formed after the fusion-evaporation reaction $^{48}$Ti + $^{40}$Ca at various excitation energies $E^{*}$ from 58 to 308 MeV, are generated by averaging the GDR strength functions predicted within the phonon damping model (PDM) using the empirical probabilities for temperature and angular momentum. The average strength functions are compared with the PDM strength functions calculated at the mean temperature and mean angular momentum, which are obtained by averaging the values of temperature and angular momentum using the same temperature and angular-momentum probability distributions, respectively. It is seen that these two ways of generating the GDR linear line shape yield very similar results. It is also shown that the GDR width approaches a saturation at angular momentum $J\\geq$ 50$\\hbar$ at $T=$ 4 MeV and at $J\\geq$ 70$\\hbar$ at any $T$.
Wigner Functions and Quark Orbital Angular Momentum
Mukherjee Asmita; Nair Sreeraj; Ojha Vikash Kumar
2014-01-01
Wigner distributions contain combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs). We report on a recent model calculation of the Wigner distributions for the quark and their relation to the orbital angular momentum.
Wigner Functions and Quark Orbital Angular Momentum
Mukherjee Asmita
2015-01-01
Full Text Available Wigner distributions contain combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs and transverse momentum dependent parton distributions (TMDs. We report on a recent model calculation of the Wigner distributions for the quark and their relation to the orbital angular momentum.
Angular momentum projected semiclassics
Hasse, Rainer W.
1987-06-01
By using angular momentum projected plane waves as wave functions, we derive semiclassical expressions for the single-particle propagator, the partition function, the nonlocal density matrix, the single-particle density and the one particle-one hole level density for fixed angular momentum and fixed z-component or summed over the z-components. Other quantities can be deduced from the propagator. In coordinate space ( r, r') the relevant quantities depend on |r-r'| instead of | r- r'| and in Wigner space ( R, P) they become proportional to the angular momentum constraints δ(| R × P|/ h̵-l) and δ( R × P) z/ h̵-m) . As applications we calculate the single-particle and one-particle-one hole level densities for harmonic oscillator and Hill-Wheeler box potentials and the imaginary part of the optical potential and its volume integral with an underlying harmonic oscillator potential and a zero range two-body interaction.
Six-State Quantum Key Distribution Using Photons with Orbital Angular Momentum
LI Jun-Lin; WANG Chuan
2010-01-01
@@ A new implementation of high-dimensional quantum key distribution (QKD) protocol is discussed. Using three mutual unbiased bases, we present a d-level six-state QKD protocol that exploits the orbital angular momentum with the spatial mode of the light beam. The protocol shows that the feature of a high capacity since keys are encoded using photon modes in d-level Hilbert space. The devices for state preparation and measurement are also discussed. This protocol has high security and the alignment of shared reference frames is not needed between sender and receiver.
A Large-alphabet Quantum Key Distribution Protocol Using Orbital Angular Momentum Entanglement
Zhao, Sheng-Mei; Gong, Long-Yan; Li, Yong-Qiang; Yang, Hua; Sheng, Yu-Bo; Cheng, Wei-Wen
2013-06-01
We experimentally demonstrate a quantum key distribution protocol using entangled photon pairs in orbital angular momentum (OAM). Here Alice uses a fixed phase hologram to modulate her OAM state on one photon with a spatial light modulator (SLM), while Bob uses the designed N different phase holograms for his N-based keys on the other photon with his SLM. With coincidences, Alice can fully retrieve the keys sent by Bob without reconciliation. We report the experiment results with N = 3 and OAM eigenmodes |l = ±1>, and discuss the security from the light path and typical attacks.
The angular distributions for dileptons arising from decays of a virtual photon and the Z0 produced in hadronic collisions are calculated at large mass and finite transverse momentum of dileptons in the lowest order of the quantum chromodynamics and the Weinberg-Salam model with three fermion generations. Numerical evaluation for coefficients of the distributions is carried out for anti pp collision at √s=540 GeV and pp at √s=800 GeV in different (helicity, Gottfried-Jackson and Collins-Soper) reference frames. Coefficients of parity violating terms in the distributions exhibit clean signs of the Z0-boson, while those of parity conserving terms are quite insensitive to the presence of the Z0-boson. (author)
Orbital angular momentum and the parton model
Ratcliffe, P.G.
1987-06-25
The role of orbital angular momentum is discussed within the framework of the parton model. It is shown that a consistent interpretation of the Altarelli-Parisi equations governing the Q/sup 2/-evolution of helicity-weighted parton distributions necessitates the assumption that partons carry a large orbital angular momentum, contrary to popular belief. In developing the arguments presented, the Altarelli-Parisi formalism is extended to include orbital angular momentum dependence.
The properties of the transverse momenta and angular distributions of hadrons produced in muon-proton scattering with first-order quantum-chromodynamics calculations. The quantum-chromodynamics prediction for the Q2 dependence of the average hadron transverse momentum squared agrees with the data provided a constant term is added in quadrature to the prediction. This additive term is attributed to the intrinsic transverse momentum of the quarks in the nucleon and to the transverse momentum inherent in quark fragmentation
Angular momentum analysis of rotational transfer of superthermal relative velocity distributions
Whiteley, T.W.J.; McCaffery, A.J. [Sussex Univ., Brighton (United Kingdom). School of Molecular Sciences
1996-12-02
An angular momentum (AM) theory is developed to calculate the relative populations of final rotational states after collision between a diatomic molecule and an atom having a narrow, superthermal velocity distribution as produced by, e.g. photolysis of a precursor species. Probability densities are derived from semiclassical expressions for energy and angular momentum assuming the classically impulsive limit with the repulsive wall modelled by a hard ellipsoid. The treatment given is general and therefore applies to molecules in which the centre-of-mass does not coincide with the centre of the potential coordinates. A transfer function for RT is derived and applied to the H + CO system. Analysis of the data allows the anisotropy to be extracted which is in good agreement with an ab initio potential surface. The method described allows one to rapidly assess the contributions from the elliptical core of the potential and from other features of the potential, and would permit more sophisticated representations of the topology to be incorporated. (Author).
The Orbital Angular Momentum Sum Rule
Aslan, Fatma; Burkardt, Matthias
2015-10-01
As an alternative to the Ji sum rule for the quark angular momentum, a sum rule for the quark orbital angular momentum, based on a twist-3 generalized parton distribution, has been suggested. We study the validity of this sum rule in the context of scalar Yukawa interactions as well as in QED for an electron.
Orbital angular momentum microlaser
Miao, Pei; Zhang, Zhifeng; Sun, Jingbo; Walasik, Wiktor; Longhi, Stefano; Litchinitser, Natalia M.; Feng, Liang
2016-07-01
Structured light provides an additional degree of freedom for modern optics and practical applications. The effective generation of orbital angular momentum (OAM) lasing, especially at a micro- and nanoscale, could address the growing demand for information capacity. By exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser producing a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. The polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes.
Orbital angular momentum microlaser.
Miao, Pei; Zhang, Zhifeng; Sun, Jingbo; Walasik, Wiktor; Longhi, Stefano; Litchinitser, Natalia M; Feng, Liang
2016-07-29
Structured light provides an additional degree of freedom for modern optics and practical applications. The effective generation of orbital angular momentum (OAM) lasing, especially at a micro- and nanoscale, could address the growing demand for information capacity. By exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser producing a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. The polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes. PMID:27471299
This work demonstrates that the quantum mechanical moments of a state described by the density matrix correspond to discrete spherical harmonic moments of the classical multipole expansion of the spatial distribution of the angular momentum vectors. For the diagonal density matrix elements, this work exploits the fact that the quantum mechanical vector coupling (Clebsch-Gordan) coefficients become increasingly accurate discrete representations of spherical harmonics as j increases. A Schwinger-type basis accounts for nonaxially symmetric angular distributions, which result in nonzero off-diagonal elements of the density matrix. The resulting discrete minimum uncertainty picture of the classical moments has a stringent equivalence with the quantum mechanical one for all j and provides an unambiguous connection for the classical and quantum moments in the large j limit. The equivalence is numerically tested for simple models, and there is a satisfying equivalence even for small j. Applications, implications, and extensions are indicated, and the relevance of this work for the interpretation of classical mechanical simulations of inelastic and reactive molecular collisions will be documented elsewhere
Pretzelosity TMD and Quark Orbital Angular Momentum
Lorce, Cédric; Pasquini, B.
2015-01-01
We study the connection between the quark orbital angular momentum and the pretzelosity transverse-momentum dependent parton distribution function. We discuss the origin of this relation in quark models, identifying as key ingredient for its validity the assumption of spherical symmetry for the nucleon in its rest frame. Finally we show that the individual quark contributions to the orbital angular momentum obtained from this relation can not be interpreted as the intrinsic contributions, but...
Lopez-Camara, D; Ramirez-Ruiz, E
2009-01-01
The rotation rate in pre-supernova cores is an important ingredient which can profoundly affect the post-collapse evolution and associated energy release in supernovae and long gamma ray bursts (LGRBs). Previous work has focused on whether the specific angular momentum is above or below the critical value required for the creation of a centrifugally supported disk around a black hole. Here, we explore the effect of the distribution of angular momentum with radius in the star, and show that qualitative transitions between high and low angular momentum flow, corresponding to high and low luminosity accretion states, can effectively be reflected in the energy output through neutrinos, leading to variability and the possibility of quiescent times in LGRBs.
Achromatic orbital angular momentum generator
Bouchard, Frédéric; Mand, Harjaspreet; Mirhosseini, Mohammad; Karimi, Ebrahim; Boyd, Robert W
2014-01-01
We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of \\textit{two glued hollow axicons}, is used to introduce a nonuniform rotation of polarisation into a linearly polarised input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming be...
MBL Experiment in Angular Momentum
Gluck, Paul
2002-04-01
Among the series of beautiful take-home experiments designed by A.P. French and J.G. King for MIT students, the one on angular momentum studies the loss and conservation of angular momentum using a small dc motor as generator. Here we describe a version of the experiment that increases its accuracy, enables students to perform detailed rotational dynamics calculations, and sharpens the ability to isolate the region where the collision occurs.
Angular momentum in subbarrier fusion
We have measured the ratio of the isomer to ground-state yields of 137Ce produced in the fusion reactions 128Te(12C,3n), 133Cs(7Li,3n), 136Ba(3He,2n), 136Ba(4He,3n), and 137Ba(3He,3n), from energies above the Coulomb barrier to energies typically 20--30% below the barrier by observing the delayed x- and γ-ray emission. We deduce the average angular momentum, , from the measured isomer ratios with a statistical model. In the first three reactions we observe that the values of exhibit the behavior predicted for low energies and the expected variation with the reduced mass of the entrance channel. We analyze these data and the associated cross sections with a barrier penetration model that includes the coupling of inelastic channels. Measurements of average angular momenta and cross sections made on other systems using the γ-multiplicity and fission-fragment angular correlation techniques are then analyzed in a similar way with this model. The discrepancies with theory for the γ-multiplicity data show correlations in cross section and angular momentum that suggest a valid model can be found. The measurements of angular momentum using the fission fragment angular correlation technique, however, do not appear reconcilable with the energy dependence of the cross sections. This systematic overview suggests, in particular, that our current understanding of the relationship of angular momentum and anisotropy in fission fragment angular correlations is incomplete. 26 refs
The effect of the mass asymmetry of the input channel on the compound nuclei spin distribution. The 16O + 144Nd and 80Se + 80Se reactions produce the same 160Er compound nucleus in the 38 to 68 MeV energy range. In certain cases, the incident energies required to form the compound nucleus, at the same excitation energies, are very close to the Coulomb barrier. In the experimental device, the 'Chateau de Cristal' multidetector and additional sensors are used. The angular momentum distribution of the different evaporation products are measured by gamma spectrometry techniques. The fusion cross sections are measured by the time-of-flight technique. Theoretical predictions and experimental results concerning the distribution of the compound nucleus angular momentum are compared
Orbital angular momentum is dependent on polarization
Li, Chun-Fang
2009-01-01
It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that originates from the former part is spin, and the angular momentum that originates from the latter part is orbital angular momentum. Expressions for the spin and orbital angular momentum are given in terms of the electric vector in reciprocal space. The spin and or...
Goyal, Sandeep K.; Hamadou Ibrahim, Alpha; Roux, Filippus S.; Konrad, Thomas; Forbes, Andrew
2016-06-01
Using an experimental setup that simulates a turbulent atmosphere, we study the secret key rate for quantum key distribution (QKD) protocols in orbital angular momentum based free space quantum communication. The QKD protocols under consideration include the Ekert 91 protocol for different choices of mutually unbiased bases and the six-state protocol. We find that the secret key rate of these protocols decay to zero, roughly at the same scale where the entanglement of formation decays to zero.
Using an experimental setup that simulates a turbulent atmosphere, we study the secret key rate for quantum key distribution (QKD) protocols in orbital angular momentum based free space quantum communication. The QKD protocols under consideration include the Ekert 91 protocol for different choices of mutually unbiased bases and the six-state protocol. We find that the secret key rate of these protocols decay to zero, roughly at the same scale where the entanglement of formation decays to zero. (paper)
Achromatic orbital angular momentum generator
Bouchard, Frédéric; Mirhosseini, Mohammad; Karimi, Ebrahim; Boyd, Robert W
2014-01-01
We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of \\textit{two glued hollow axicons}, is used to introduce a nonuniform rotation of polarisation into a linearly polarised input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam's polarisation, and by conservation of total angular momentum thereby generates a well-defined value of OAM. Our device is broadband, since the phase shift due to total internal reflection is nearly independent of wavelength. We verify the broad-band behaviour by measuring the conversion efficiency of the device for three different wavelengths corresponding to the RGB colours, red, green and blue. An average conversion efficiency of $95\\%$ for these three different wavelengths is observed. %, which confirms its wavelen...
Li, Yang; Lan, Pengfei; Xie, Hui; He, Mingrui; Zhu, Xiaosong; Zhang, Qingbin; Lu, Peixiang
2015-11-01
We perform time-dependent calculation of strong-field ionization of neon, initially prepared in 2p(-1) and 2p(+1) states, with intense near-circularly polarized laser pulses. By solving the three-dimensional time-dependent Schrödinger equation, we find clear different offset angles of the maximum in the photoelectron momentum distribution in the polarization plane of the laser pulses for the two states. We provide clear interpretation that this different angular offset is linked to the sign of the magnetic quantum number, thus it can be used to map out the orbital angular momentum of the initial state. Our results provide a potential tool for studying orbital symmetry in atomic and molecular systems. PMID:26561149
Quantum theory of angular momentum
This monograph pertains to the angular momentum coupling and recoupling coefficients and their relation to generalized hypergeometric functions; their q-generalization; their polynomial zeros; their relation to orthogonal polynomials; and their numerical computation. The book builds on standard textbook material on Angular Momentum Theory and leads the reader to the recent developments in the selected topics. Fortran programs for the computation of the 3-j, 6-j and 9-j coefficients are included for use by atomic, molecular and nuclear physicists/chemists. (orig.)
Polarized Parton Distribution, Orbital Angular Momentum, and the Violation of a8
Arash, Firooz; Taghavi-Shahri, Fatemeh
2009-03-01
We use the so-called valon model, to describe the spin structure of the nucleon. We show that about 40% of the nucleon spin is carried by the polarized valence quarks. The remaining part comes from the gluon polarization and the orbital angular momentum. It is shown that the sea quark contributions to the spin of any hadron is simply marginal and consistent with zero. We also found that the value of a8 is substantially smaller than the value inferred from hyperon—β decay, suggesting that full SU(3) symmetric assumption needs to be reconsidered. New and emerging experimental data tend to support this finding. Finally, we show that within the model presented here the experimental data on the polarized structure functions g1p,n,d are reproduced.
Inverse cascades of angular momentum
Most theoretical and computational studies of turbulence in Navier-Stokes fluids and/or guiding-centre plasmas have been carried out in the presence of spatially periodic boundary conditions. In view of the frequently reproduced result that two-dimensional and/or MHD decaying turbulence leads to structures comparable in length scae to a box dimension, it is natural to ask if periodic boundary conditions are an adequate representation of any physical situation. Here, we study, computationally, the decay of two-dimensional turbulence in a Navier-Stokes fluid or guiding-centre plasma in the presence of circular no-slip rigid walls. The method is wholly spectral, and relies on a Galerkin approximation by a set of functions that obey two boundary conditions at the wall radius (analogues of the Chandrasekhar-Reid functions). It is possible to explore Reynolds numbers up to the order of 1250, based on an RMS velocity and a box radius. It is found that decaying turbulence is altered significantly by the no-slip boundaries. First, strong boundary layers serve as sources of vorticity and enstrophy and enhance the early-time energy decay rate, for a given Reynolds number, well above the periodic boundary condition values. More importantly, angular momentum turns out to be an even more slowly decaying ideal invariant than energy, and to a considerable extent governs the dynamics of the decay. Angular momentum must be taken into account, for example, in order to achieve quantitative agreement with the prediction of maximum entropy, or 'most probable', states. These are predictions of conditions that are established after several eddy turnover times but before the energy has decayed away. Angular momentum will cascade to lower azimuthal mode numbers, even if absent there initially, and the angular momentum modal spectrum is eventually dominated by the lowest mode available. When no initial angular momentum is present, no behaviour that suggests the likelihood of inverse cascades
Spin Angular Momentum Imparted by Gravitational Waves
Sharif, M.
2007-01-01
Following the demonstration that gravitational waves impart linear momentum, it is argued that if they are polarized they should impart angular momentum to appropriately placed 'test rods' in their path. A general formula for this angular momentum is obtained and used to provide expressions for the angular momentum imparted by plane and cylindrical gravitational waves.
Dynamical birth and thermal death of angular momentum in heavy ion reactions
Dynamical and equilibrium angular momentum fractionation as well as equilibrium angular momentum distributions associated with a variety of collective modes of the intermediate complex are described. (orig.)
An orbital angular momentum spectrometer for electrons
Harvey, Tyler; Grillo, Vincenzo; McMorran, Benjamin
2016-05-01
With the advent of techniques for preparation of free-electron and neutron orbital angular momentum (OAM) states, a basic follow-up question emerges: how do we measure the orbital angular momentum state distribution in matter waves? Control of both the energy and helicity of light has produced a range of spectroscopic applications, including molecular fingerprinting and magnetization mapping. Realization of an analogous dual energy-OAM spectroscopy with matter waves demands control of both initial and final energy and orbital angular momentum states: unlike for photons, final state post-selection is necessary for particles that cannot be annihilated. We propose a magnetic field-based mechanism for quantum non-demolition measurement of electron OAM. We show that OAM-dependent lensing is produced by an operator of form U =exp iLzρ2/ℏb2 where ρ =√{x2 +y2 } is the radial position operator, Lz is the orbital angular momentum operator along z, and b is the OAM dispersion length. We can physically realize this operator as a term in the time evolution of an electron in magnetic round lens. We discuss prospects and practical challenges for implementation of a lensing orbital angular momentum measurement. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under the Early Career Research Program Award # DE-SC0010466.
Time-resolved orbital angular momentum spectroscopy
Noyan, Mehmet A.; Kikkawa, James M. [Department of Physics and Astronomy, The University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)
2015-07-20
We introduce pump-probe magneto-orbital spectroscopy, wherein Laguerre-Gauss optical pump pulses impart orbital angular momentum to the electronic states of a material and subsequent dynamics are studied with 100 fs time resolution. The excitation uses vortex modes that distribute angular momentum over a macroscopic area determined by the spot size, and the optical probe studies the chiral imbalance of vortex modes reflected off the sample. First observations in bulk GaAs yield transients that evolve on time scales distinctly different from population and spin relaxation, as expected, but with surprisingly large lifetimes.
Time-resolved orbital angular momentum spectroscopy
We introduce pump-probe magneto-orbital spectroscopy, wherein Laguerre-Gauss optical pump pulses impart orbital angular momentum to the electronic states of a material and subsequent dynamics are studied with 100 fs time resolution. The excitation uses vortex modes that distribute angular momentum over a macroscopic area determined by the spot size, and the optical probe studies the chiral imbalance of vortex modes reflected off the sample. First observations in bulk GaAs yield transients that evolve on time scales distinctly different from population and spin relaxation, as expected, but with surprisingly large lifetimes
Malik, Mehul; Rodenburg, Brandon; Mirhosseini, Mohammad; Leach, Jonathan; Lavery, Martin P J; Padgett, Miles J; Boyd, Robert W
2012-01-01
We describe an experimental implementation of a free-space 11-dimensional quantum key distribution (QKD) system using orbital angular momentum (OAM) modes. This QKD system has a maximum theoretical channel capacity of log2(11) = 3.46 bits/photon. The effects of Kolmogorov thin-phase turbulence on the OAM channel capacity of this QKD system are quantified. We find that increasing the turbulence leads to a degradation of the channel capacity of the OAM channel. We are able to mitigate the effects of turbulence by increasing the spacing between detected modes.
Angular-momentum-bearing modes in fission
The angular-momentum-bearing degrees of freedom involved in the fission process are identified and their influence on experimental observables is discussed. The excitation of these modes is treated in the ''thermal'' limit, and the resulting distributions of observables are calculated. Experiments demonstrating the role of these modes are presented and discussed. 61 refs., 12 figs
Zhao, Y M; Yoshinaga, N
2002-01-01
In this paper, we discuss the angular momentum distribution in the ground states of many-body systems interacting via a two-body random ensemble. Beginning with a few simple examples, a simple approach to predict P(I)'s, angular momenta I ground state (g.s.) probabilities, of a few solvable cases, such as fermions in a small single-j shell and d boson systems, is given. This method is generalized to predict P(I)'s of more complicated cases, such as even or odd number of fermions in a large single-j shell or a many-j shell, d-boson, sd-boson or sdg-boson systems, etc. By this method we are able to tell which interactions are essential to produce a sizable P(I) in a many-body system. The g.s. probability of maximum angular momentum $I_{max}$ is discussed. An argument on the microscopic foundation of our approach, and certain matrix elements which are useful to understand the observed regularities, are also given or addressed in detail. The low seniority chain of 0 g.s. by using the same set of two-body interact...
Angular momentum in QGP holography
Brett McInnes
2014-10-01
Full Text Available The quark chemical potential is one of the fundamental parameters describing the quark–gluon plasma produced by sufficiently energetic heavy-ion collisions. It is not large at the extremely high temperatures probed by the LHC, but it plays a key role in discussions of the beam energy scan programmes at the RHIC and other facilities. On the other hand, collisions at such energies typically (that is, in peripheral collisions give rise to very high values of the angular momentum density. Here we explain that holographic estimates of the quark chemical potential of a rotating sample of plasma can be very considerably improved by taking the angular momentum into account.
Orbital angular momentum in phase space
Rigas, I.; Sanchez-Soto, L. L.; Klimov, A. B.; Rehacek, J.; Hradil, Z.
2010-01-01
A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented. Special attention is paid to the problems linked to rotational periodicity and angular-momentum discreteness.
Achromatic orbital angular momentum generator
We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of two glued hollow axicons, is used to introduce a nonuniform rotation of polarization into a linearly polarized input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam's polarization, and by conservation of total angular momentum thereby generates a well-defined value of OAM. Our device is broadband, since the phase shift due to total internal reflection is nearly independent of wavelength. We verify the broad-band behaviour by measuring the conversion efficiency of the device for three different wavelengths corresponding to the RGB colours, red, green and blue. An average conversion efficiency of 95% for these three different wavelengths is observed. This device may find applications in imaging from micro- to astronomical systems where a white vortex beam is needed. (paper)
Angular Momentum Decomposition for an Electron
Burkardt, Matthias; BC, Hikmat
2008-01-01
We calculate the orbital angular momentum of the `quark' in the scalar diquark model as well as that of the electron in QED (to order $\\alpha$). We compare the orbital angular momentum obtained from the Jaffe-Manohar decomposition to that obtained from the Ji relation and estimate the importance of the vector potential in the definition of orbital angular momentum.
Angular momentum of non-paraxial light beam: Dependence of orbital angular momentum on polarization
Li, Chun-Fang
2009-01-01
It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that is associated with the former part is spin, and the angular momentum that is associated with the latter part is orbital angular momentum. Expressions for the spin and orbital angular momentum are given in terms of the electric vector in reciprocal space. The spin ...
Plate tectonics conserves angular momentum
C. Bowin
2009-03-01
Full Text Available A new combined understanding of plate tectonics, Earth internal structure, and the role of impulse in deformation of the Earth's crust is presented. Plate accelerations and decelerations have been revealed by iterative filtering of the quaternion history for the Euler poles that define absolute plate motion history for the past 68 million years, and provide an unprecedented precision for plate angular rotation variations with time at 2-million year intervals. Stage poles represent the angular rotation of a plate's motion between adjacent Euler poles, and from which the maximum velocity vector for a plate can be determined. The consistent maximum velocity variations, in turn, yield consistent estimates of plate accelerations and decelerations. The fact that the Pacific plate was shown to accelerate and decelerate, implied that conservation of plate tectonic angular momentum must be globally conserved, and that is confirmed by the results shown here (total angular momentum ~1.4 E+27 kgm^{2}s^{−1}. Accordingly, if a plate decelerates, other plates must increase their angular momentums to compensate. In addition, the azimuth of the maximum velocity vectors yields clues as to why the "bend" in the Emperor-Hawaiian seamount trend occurred near 46 Myr. This report summarizes processing results for 12 of the 14 major tectonic plates of the Earth (except for the Juan de Fuca and Philippine plates. Plate accelerations support the contention that plate tectonics is a product of torques that most likely are sustained by the sinking of positive density anomalies due to phase changes in subducted gabbroic lithosphere at depth in the upper lower mantle (above 1200 km depth. The tectonic plates are pulled along by the sinking of these positive mass anomalies, rather than moving at near constant velocity on the crests of convection cells driven by rising heat. These results imply that spreading centers are primarily passive reactive
On the "initial" Angular Momentum of Galaxies
Abel, T; Hernquist, L E; Abel, Tom; Croft, Rupert C.; Hernquist, Lars
2001-01-01
Spherical density profiles and specific angular momentum profiles of Dark Matter halos found in cosmological N-body simulations have been measured extensively. The distribution of the total angular momentum of dark matter halos is also used routinely in semi-analytic modeling of the formation of disk galaxies. However, it is unclear whether the initial (i.e. at the time the halo is assembled) angular momentum distributions of baryons is related to the dark matter at all. Theoretical models for ellipticities in weak lensing studies often rely on an assumed correlation of the angular momentum vectors of dark matter and gas in galaxies. Both of these assumptions are shown to be in reasonable agreement with high resolution cosmological smoothed particle hydrodynamical simulations that follow the dark matter as long as only adiabatic gas physics are included. However, we argue that in more realistic models of galaxy formation one expects pressure forces to play a significant role at turn--around. Consequently the ...
The mass and angular momentum distribution of simulated massive galaxies to large radii
Wu, Xufen; Naab, Thorsten; Oser, Ludwig; Martinez-Valpuesta, Inma; Hilz, Michael; Churazov, Eugene; Lyskova, Natalya
2012-01-01
We study the mass distributions, circular velocity curves (CVCs), line-of-sight kinematics and angular momenta out to many Re for a sample of 42 cosmological zoom simulations of massive galaxies. In order to reduce the particle noise at large radii, we temporally smooth the observables of the simulated galaxies in a static potential. The mass of the simulated galaxies is parametrised by vcirc at r=5Re. We find: (i) The projected stellar density distributions at large radii can be well fitted by S'ersic functions. The S'ersic indices range from 3 to 13 and correlate with stellar mass and galaxy size (low n, low mass, small size). (ii) The dark matter halo density profiles are consistent with simple power-law models, corresponding to flat dark matter CVCs for lower-mass systems, and rising CVCs for high-mass halos. (iii) The massive systems have nearly flat total CVCs at large radii, while the less massive systems have mildly decreasing CVCs. The slope of the CVC at large radii correlates with S'ersic index and...
Quantitative measurement of orbital angular momentum in electron microscopy
Clark, L; Guzzinati, G; Verbeeck, J
2014-01-01
Electron vortex beams have been predicted to enable atomic scale magnetic information measurement, via transfer of orbital angular momentum. Research so far has focussed on developing production techniques and applications of these beams. However, methods to measure the outgoing orbital angular momentum distribution are also a crucial requirement towards this goal. Here, we use a method to obtain the orbital angular momentum decomposition of an electron beam, using a multi-pinhole interferometer. We demonstrate both its ability to accurately measure orbital angular momentum distribution, and its experimental limitations when used in a transmission electron microscope.
Angular momentum transfer in deep inelastic scattering
The measured γ-ray multiplicities as a function of exit channel kinetic energy and mass asymmetry for the reactions Au, Ho, Ag + 620 MeV Kr are compared with a diffusion calculation based exclusively upon particle transfer and which reproduces the Z distributions as well as the angular distributions as function of Z. The model correctly predicts the energy and Z dependence of the γ-ray multiplicities, thus lending support to the one-body model on one hand and to the angular-momentum fractionation along the mass asymmetry coordinate on the other
Phonons with orbital angular momentum
Ayub, M. K. [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan); National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Ali, S. [National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)
2011-10-15
Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.
Phonons with orbital angular momentum
Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.
Identification of Observables for Quark and Gluon Orbital Angular Momentum
Courtoy, Aurore; Hernandez, J Osvaldo Gonzalez; Liuti, Simonetta; Rajan, Abha
2014-01-01
A new debate has recently arisen on the subject of orbital angular momentum in QCD, in particular on its observability and on its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic and a canonical definition, respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist three generalized parton distributions, and it is therefore more readily observable, while, due to parity constraints, canonical angular momentum, if defined as suggested in the literature in terms of generalized transverse momentum distributions, cannot be observed in scattering processes involving a single hadronic reaction plane.
Matter waves with angular momentum
Bracher, C; Kleber, M; Bracher, Christian; Kramer, Tobias; Kleber, Manfred
2003-01-01
An alternative description of quantum scattering processes rests on inhomogeneous terms amended to the Schr\\"odinger equation. We detail the structure of sources that give rise to multipole scattering waves of definite angular momentum, and introduce pointlike multipole sources as their limiting case. Partial wave theory is recovered for freely propagating particles. We obtain novel results for ballistic scattering in an external uniform force field, where we provide analytical solutions for both the scattering waves and the integrated particle flux. As an illustration of the theory, we predict some properties of vortex-bearing atom laser beams outcoupled from a rotating Bose--Einstein condensate under the influence of gravity.
The difficulty of measuring orbital angular momentum
Preece, D; Nieminen, T. A.; Asavei, T.; Heckenberg, N. R.; Rubinsztein-Dunlop, H.
2011-01-01
Light can carry angular momentum as well as energy and momentum; the transfer of this angular momentum to an object results in an optical torque. The development of a rotational analogue to the force measurement capability of optical tweezers is hampered by the difficulty of optical measurement of orbital angular momentum. We present an experiment with encouraging results, but emphasise the difficulty of the task.
The difficulty of measuring orbital angular momentum
D. Preece
2011-09-01
Full Text Available Light can carry angular momentum as well as energy and momentum; the transfer of this angular momentum to an object results in an optical torque. The development of a rotational analogue to the force measurement capability of optical tweezers is hampered by the difficulty of optical measurement of orbital angular momentum. We present an experiment with encouraging results, but emphasise the difficulty of the task.
Quantitative measurement of orbital angular momentum in electron microscopy
Clark, L.; Béché, A.; Guzzinati, G.; Verbeeck, J.
2014-01-01
Abstract: Electron vortex beams have been predicted to enable atomic scale magnetic information measurement, via transfer of orbital angular momentum. Research so far has focused on developing production techniques and applications of these beams. However, methods to measure the outgoing orbital angular momentum distribution are also a crucial requirement towards this goal. Here, we use a method to obtain the orbital angular momentum decomposition of an electron beam, using a multipinhole int...
Parton Orbital Angular Momentum and Final State Interactions
Burkardt, Matthias
2012-01-01
Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar.We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asym...
Quark Orbital Angular Momentum and Final State Interactions
Burkardt, Matthias
2014-01-01
Definitions of orbital angular momentum based on Wigner distributions are used to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. The difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive d...
Do waves carrying orbital angular momentum possess azimuthal linear momentum?
Speirits, Fiona C.; Barnett, Stephen M.
2013-01-01
All beams are a superposition of plane waves, which carry linear momentum in the direction of propagation with no net azimuthal component. However, plane waves incident on a hologram can produce a vortex beam carrying orbital angular momentum that seems to require an azimuthal linear momentum, which presents a paradox. We resolve this by showing that the azimuthal momentum is not a true linear momentum but the azimuthal momentum density is a true component of the linear momentum density.
Alignment of wave functions for angular momentum projection
Taniguchi, Yasutaka
2016-01-01
Angular momentum projection is used to obtain eigen states of angular momentum from general wave functions. Multi-configuration mixing calculation with angular momentum projection is an important microscopic method in nuclear physics. For accurate multi-configuration mixing calculation with angular momentum projection, concentrated distribution of $z$ components $K$ of angular momentum in the body-fixed frame ($K$-distribution) is favored. Orientation of wave functions strongly affects $K$-distribution. Minimization of variance of $\\hat{J}_z$ is proposed as an alignment method to obtain wave functions that have concentrated $K$-distribution. Benchmark calculations are performed for $\\alpha$-$^{24}$Mg cluster structure, triaxially superdeformed states in $^{40}$Ar, and Hartree-Fock states of some nuclei. The proposed alignment method is useful and works well for various wave functions to obtain concentrated $K$-distribution.
The fission of 210Po, produced by three different nuclear reactions (209Bi + p, 206Pb + α and 198Pt + 12C), has been studied in detail in order to establish the dependence of various scission-point properties on the excitation energy and angular-momentum distribution of the fissioning nucleus. Excitation energies of 31, 44 and 57 MeV were chosen so as to give reasonable fission cross-sections, while avoiding a large contribution from second chance fission. The experiments were conducted on a beam line of the Harwell Variable Energy Cyclotron. The mean-fragment total-kinetic-energy release was found to be dependent on the 210Po excitation energy and angular-momentum distribution. The variances of the total-kinetic energy and mass distributions were found to be a strongly dependent on excitation energy but not on angular momentum. The experimental results of this work were found to be in good agreement with the theoretical liquid-drop-model calculations of Nix and Swiatecki. (author)
Wilson lines and orbital angular momentum
Lorcé, Cédric
2012-01-01
We present an explicit realization of the Chen et al. approach to the proton spin decomposition in terms of Wilson lines, generalizing the light-front gauge-invariant extensions discussed recently by Hatta. Particular attention is drawn to the residual gauge freedom by further separating the pure-gauge term into contour and residual terms. Contrarily to a recent claim, we show that the Wigner distributions do not give access to the kinetic orbital angular momentum. Finally, we confirm from twist-2 arguments that the advanced, retarded and antisymmetric light-front canonical orbital angular momenta are the same.
Orbital angular momentum-entanglement frequency transducer
Zhou, Zhi-Yuan; Liu, Shi-Long; Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Dong, Ming-xin; Shi, Bao-Sen; Guo, Guang-Can
2016-01-01
Entanglement is a vital resource for realizing many tasks such as teleportation, secure key distribution, metrology and quantum computations. To effectively build entanglement between different quantum systems and share information between them, a frequency transducer to convert between quantum states of different wavelengths while retaining its quantum features is indispensable. Information encoded in the photons orbital angular momentum OAM degrees of freedom is preferred in harnessing the ...
The pretzelosity TMD and quark orbital angular momentum
Lorce, C. [IPNO, Universite Paris-Sud, CNRS/IN2P3, 91406 Orsay (France); LPT, Universite Paris-Sud, CNRS, 91406 Orsay (France); Pasquini, B., E-mail: pasquini@pv.infn.it [Dipartimento di Fisica, Universita degli Studi di Pavia, Pavia (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia (Italy)
2012-04-12
We study the connection between the quark orbital angular momentum and the pretzelosity transverse-momentum dependent parton distribution function. We discuss the origin of this relation in quark models, identifying as key ingredient for its validity the assumption of spherical symmetry for the nucleon in its rest frame. Finally we show that the individual quark contributions to the orbital angular momentum obtained from this relation cannot be interpreted as the intrinsic contributions, but include the contribution from the transverse centre of momentum which cancels out only in the total orbital angular momentum.
The pretzelosity TMD and quark orbital angular momentum
We study the connection between the quark orbital angular momentum and the pretzelosity transverse-momentum dependent parton distribution function. We discuss the origin of this relation in quark models, identifying as key ingredient for its validity the assumption of spherical symmetry for the nucleon in its rest frame. Finally we show that the individual quark contributions to the orbital angular momentum obtained from this relation cannot be interpreted as the intrinsic contributions, but include the contribution from the transverse centre of momentum which cancels out only in the total orbital angular momentum.
Does high harmonic generation conserve angular momentum?
Fleischer, Avner; Diskin, Tzvi; Sidorenko, Pavel; Cohen, Oren
2013-01-01
High harmonic generation (HHG) is a unique and useful process in which infrared or visible radiation is frequency up converted into the extreme ultraviolet and x ray spectral regions. As a parametric process, high harmonic generation should conserve the radiation energy, momentum and angular momentum. Indeed, conservation of energy and momentum have been demonstrated. Angular momentum of optical beams can be divided into two components: orbital and spin (polarization). Orbital angular momentum is assumed to be conserved and recently observed deviations were attributed to propagation effects. On the other hand, conservation of spin angular momentum has thus far never been studied, neither experimentally nor theoretically. Here, we present the first study on the role of spin angular momentum in extreme nonlinear optics by experimentally generating high harmonics of bi chromatic elliptically polarized pump beams that interact with isotropic media. While observing that the selection rules qualitatively correspond...
Photoionization with Orbital Angular Momentum Beams
Picón, A.; Mompart, J.; de Aldana, J. R. Vázquez; Plaja, L.; Calvo, G. F.; Roso, L.
2010-01-01
Intense laser ionization expands Einstein's photoelectric effect rules giving a wealth of phenomena widely studied over the last decades. In all cases, so far, photons were assumed to carry one unit of angular momentum. However it is now clear that photons can possess extra angular momentum, the orbital angular momentum (OAM), related to their spatial profile. We show a complete description of photoionization by OAM photons, including new selection rules involving more than one unit of angula...
Quantum formulation of fractional orbital angular momentum
Götte, Jörg B; Franke-Arnold, Sonja; Zambrini, Roberta; Barnett, Stephen M.
2007-01-01
The quantum theory of rotation angles (S. M. Barnett and D. T. Pegg, Phys. Rev. A, 41, 3427-3425 (1990)) is generalised to non-integer values of the orbital angular momentum. This requires the introduction of an additional parameter, the orientation of a phase discontinuity associated with fractional values of the orbital angular momentum. We apply our formalism to the propagation of light modes with fractional orbital angular momentum in the paraxial and non-paraxial regime.
Orbital angular momentum in phase space
Research highlights: → We propose a comprehensive Weyl-Wigner formalism for the canonical pair angle-angular momentum. → We present a simple and useful toolkit for the practitioner. → We derive simple evolution equations in terms of a star product in the semiclassical limit. - Abstract: A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented. Special attention is paid to the problems linked to rotational periodicity and angular-momentum discreteness.
Quark and gluon orbital angular momentum: Where are we?
Lorcé, Cédric
2016-01-01
The orbital angular momentum of quarks and gluons contributes significantly to the proton spin budget and attracted a lot of attention in the recent years, both theoretically and experimentally. We summarize the various definitions of parton orbital angular momentum together with their relations with parton distributions functions. In particular, we highlight current theoretical puzzles and give some prospects.
Anomalous Magnetic Moments and Quark Orbital Angular Momentum
Burkardt, M.; Schnell, G.(University of the Basque Country UPV/EHU, 48080 Bilbao, Spain)
2005-01-01
We derive an inequality for the distribution of quarks with non-zero orbital angular momentum, and thus demonstrate, in a model-independent way, that a non-vanishing anomalous magnetic moment requires both a non-zero size of the target as well as the presence of wave function components with quark orbital angular momentum L_z>0.
Quark and Gluon Orbital Angular Momentum: Where Are We?
Lorcé, Cédric; Liu, Keh-Fei
2016-06-01
The orbital angular momentum of quarks and gluons contributes significantly to the proton spin budget and attracted a lot of attention in the recent years, both theoretically and experimentally. We summarize the various definitions of parton orbital angular momentum together with their relations with parton distributions functions. In particular, we highlight current theoretical puzzles and give some prospects.
Quark and Gluon Orbital Angular Momentum: Where Are We?
Lorcé, Cédric; Liu, Keh-Fei
2016-02-01
The orbital angular momentum of quarks and gluons contributes significantly to the proton spin budget and attracted a lot of attention in the recent years, both theoretically and experimentally. We summarize the various definitions of parton orbital angular momentum together with their relations with parton distributions functions. In particular, we highlight current theoretical puzzles and give some prospects.
The Angular Momentum of the Solar System
Cang, Rongquin; Guo, Jianpo; Hu, Juanxiu; He, Chaoquiong
2016-05-01
The angular momentum of the Solar System is a very important physical quantity to the formation and evolution of the Solar System. Previously, the spin angular momentum of the Sun and the orbital angular momentum of the Eight Giant Planets were only taken into consideration, when researchers calculated the angular momentum of the Solar System. Nowadays, it seems narrow and conservative. Using Eggleton's code, we calculate the rotational inertia of the Sun. Furthermore, we obtain that the spin angular momentum of the Sun is 1.8838 x 10^41 kg m^2 s^-1. Besides the spin angular momentum of the Sun and the orbital angular momentum of the Eight Giant Planets, we also account for the orbital angular momentum of the Asteroid Belt, the Kuiper Belt, the Oort Cloud, the Ninth Giant Planet and the Solar Companion. We obtain that the angular momentum of the whole Solar System is 3.3212 x 10^45 kg m^2 s^-1.
Controlling neutron orbital angular momentum.
Clark, Charles W; Barankov, Roman; Huber, Michael G; Arif, Muhammad; Cory, David G; Pushin, Dmitry A
2015-09-24
The quantized orbital angular momentum (OAM) of photons offers an additional degree of freedom and topological protection from noise. Photonic OAM states have therefore been exploited in various applications ranging from studies of quantum entanglement and quantum information science to imaging. The OAM states of electron beams have been shown to be similarly useful, for example in rotating nanoparticles and determining the chirality of crystals. However, although neutrons--as massive, penetrating and neutral particles--are important in materials characterization, quantum information and studies of the foundations of quantum mechanics, OAM control of neutrons has yet to be achieved. Here, we demonstrate OAM control of neutrons using macroscopic spiral phase plates that apply a 'twist' to an input neutron beam. The twisted neutron beams are analysed with neutron interferometry. Our techniques, applied to spatially incoherent beams, demonstrate both the addition of quantum angular momenta along the direction of propagation, effected by multiple spiral phase plates, and the conservation of topological charge with respect to uniform phase fluctuations. Neutron-based studies of quantum information science, the foundations of quantum mechanics, and scattering and imaging of magnetic, superconducting and chiral materials have until now been limited to three degrees of freedom: spin, path and energy. The optimization of OAM control, leading to well defined values of OAM, would provide an additional quantized degree of freedom for such studies. PMID:26399831
Orbital angular momentum in /sup 3/He-A-italic
Balatskii-breve, A.V.; Mineev, V.P.
1985-12-01
The intrinsic angular momentum in the A-italic phase of superfluid /sup 3/He is found in terms of the response to the angular velocity of rotation. It is shown that in the weak-coupling approximation at an arbitrary temperature and with allowance for the Fermi-liquid renormalization the intrinsic angular momentum is small in accordance with the smallness of the asymmetry in the distribution of particles and holes.
Identification of Observables for Quark and Gluon Orbital Angular Momentum
Courtoy, Aurore; Goldstein, Gary R.; Hernandez, J. Osvaldo Gonzalez; Liuti, Simonetta; Rajan, Abha(University of Virginia – Physics Department, 382 McCormick Rd., Charlottesville, VA 22904, USA)
2014-01-01
A new debate has recently arisen on the subject of orbital angular momentum in QCD, in particular on its observability and on its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic and a canonical definition, respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist three generalized parton distributions, and it is therefore more readily observable, while, due to parity constr...
Nonzero orbital angular momentum superfluidity in ultracold Fermi gases
Iskin, M.; de Melo, C. A. R. Sá
2006-01-01
We analyze the evolution of superfluidity for nonzero orbital angular momentum channels from the Bardeen-Cooper-Schrieffer (BCS) to the Bose-Einstein condensation (BEC) limit in three dimensions. First, we analyze the low energy scattering properties of finite range interactions for all possible angular momentum channels. Second, we discuss ground state ($T = 0$) superfluid properties including the order parameter, chemical potential, quasiparticle excitation spectrum, momentum distribution, ...
Orbital Angular Momentum in the Nucleon
Garvey, Gerald T.
2010-01-01
Analysis of the measured value of the integrated \\bar{d}-\\bar{u} asymmetry (Ifas = 0.147+-0.027) in the nucleon show it to arise from nucleon fluctuations into baryon plus pion. Requiring angular momentum conservation in these fluctuations shows the associated orbital angular momentum is equal to the value of the flavor asymmetry.
Detecting orbital angular momentum in radio signals
Then, H.; Thidé, B.; Mendonça, J T; Carozzi, T.D.; Bergman, J.; Baan, W. A.; Mohammadi, S. (Siawoosh); Eliasson, B.
2008-01-01
Electromagnetic waves with an azimuthal phase shift are known to have a well defined orbital angular momentum. Different methods that allow for the detection of the angular momentum are proposed. For some, we discuss the required experimental setup and explore the range of applicability.
Quark angular momentum in a spectator model
We investigate the quark angular momentum in a model with the nucleon being a quark and a spectator. Both scalar and axial-vector spectators are included. We perform the calculations in the light-cone formalism where the parton concept is well defined. We calculate the quark helicity and canonical orbital angular momentum. Then we calculate the gravitational form factors which are often related to the kinetic angular momentums, and find that even in a no gauge field model we cannot identify the canonical angular momentums with half the sum of gravitational form factors. In addition, we examine the model relation between the orbital angular momentum and pretzelosity, and find it is violated in the axial-vector case
Quark angular momentum in a spectator model
Tianbo Liu
2015-02-01
Full Text Available We investigate the quark angular momentum in a model with the nucleon being a quark and a spectator. Both scalar and axial-vector spectators are included. We perform the calculations in the light-cone formalism where the parton concept is well defined. We calculate the quark helicity and canonical orbital angular momentum. Then we calculate the gravitational form factors which are often related to the kinetic angular momentums, and find that even in a no gauge field model we cannot identify the canonical angular momentums with half the sum of gravitational form factors. In addition, we examine the model relation between the orbital angular momentum and pretzelosity, and find it is violated in the axial-vector case.
Physical Angular Momentum Separation for QED
Sun, Weimin
2016-01-01
We study the non-uniqueness problem of the gauge-invariant angular momentum separation for the case of QED, which stems from the recent controversy concerning the proper definitions of the orbital angular momentum and spin operator of the individual parts of a gauge field system. For the free quantum electrodynamics without matter, we show that the basic requirement of Euclidean symmetry selects a unique physical angular momentum separation scheme from the multitude of the possible angular momentum separation schemes constructed using the various Gauge Invariant Extentions. Based on these results, we propose a set of natural angular momentum separation schemes for the case of interacting QED by invoking the formalism of asymptotic fields. Some perspectives on such a problem for the case of QCD are briefly discussed.
Generalized Uncertainty Principle and Angular Momentum
Bosso, Pasquale
2016-01-01
Various models of quantum gravity suggest a modification of the Heisenberg's Uncertainty Principle, to the so-called Generalized Uncertainty Principle, between position and momentum. In this work we show how this modification influences the theory of angular momentum in Quantum Mechanics. In particular, we compute Planck scale corrections to angular momentum eigenvalues, the Hydrogen atom spectrum, the Stern-Gerlach experiment and the Clebsch-Gordan coefficients. We also examine effects of the Generalized Uncertainty Principle on multi-particle systems.
Radio beam vorticity and orbital angular momentum
Thidé, Bo; Tamburini, Fabrizio; Mari, Elettra; Romanato, Filippo; Barbieri, Cesare
2011-01-01
It has been known for a century that electromagnetic fields can transport not only energy and linear momentum but also angular momentum. However, it was not until twenty years ago, with the discovery in laser optics of experimental techniques for the generation, detection and manipulation of photons in well-defined, pure orbital angular momentum (OAM) states, that twisted light and its pertinent optical vorticity and phase singularities began to come into widespread use in science and technol...
Topological Orbital Angular Momentum Hall Current
Hu, Jiangping
2005-01-01
We show that there is a fundamental difference between spin Hall current and orbital angular momentum Hall current in Rashba- Dresselhaus spin orbit coupling systems. The orbital angular momentum Hall current has a pure topological contribution which is originated from the existence of magnetic flux in momentum space while there is no such topological nature for the spin Hall current. Moreover, we show that the orbital Hall conductance is always larger than the spin Hall conductance in the pr...
Angular momentum distributions for [sup 16]O+[sup 144]Nd
Duchene, G.; Romain, P.; Beck, F.A.; Benet, P.; Disdier, D.; Haas, B.; Lott, B.; Rauch, V.; Scheibling, F.; Vivien, J.P. (Centre de Recherches Nucleaires, Institut National de Physique Nucleaire et de Physique des Particules, Universite Louis Pasteur, BP 20, 67037 Strasbourg CEDEX (France)); Basu, S.K. (Variable Energy Cyclotron Centre, Bhabha Atomic Research Centre, I/AF Bidhan Nagar, Calcutta 700064 (India)); Bozek, E.; Zuber, K. (Institute of Nuclear Physics Krakow, 30-342 Krakow (Poland)); Di Gregorio, D.; Fernandez-Niello, J. (Departamento de Fisica, Comision Nacional de Energia Atomica, 1429 Buenos Aires (Argentina))
1993-05-01
Fusion cross sections have been measured for the system [sup 16]O+[sup 144]Nd at bombarding energies in the range 67 MeV[le][ital E][sub lab][le]90 MeV by detecting directly evaporation residues in Si detectors and in the range 60 MeV[le][ital E][sub lab][le]75 MeV by off-line detection of the K x rays emitted by the radioactive evaporation residues and daughters. In order to obtain the spin distributions in the compound system gamma-ray multiplicity distributions for the most important neutron evaporation channels were also measured using a 4[pi] BaF[sub 2] array, in conjunction with Ge detectors. Results are compared with calculations based on models that consider fluctuations in barrier height due to ground-state zero-point vibrations as well as couplings to various inelastic and transfer channels.
A simple approach to the angular momentum distribution in the ground states of many-body systems
Zhao, Y M; Yoshinaga, N
2002-01-01
We propose a simple approach to predict the angular momentum I ground state (I g.s.) probabilities of many-body systems that does not require the diagonalization of hamiltonians with random interactions. This method is found to be applicable to {\\bf all} cases that have been discussed: even and odd fermion systems (both in single-j and many-j shells), and boson (both sd and sdg) systems. A simple relation for the highest angular momentum g.s. probability is found. Furthermore, it is suggested for the first time that the 0g.s. dominance in boson systems and in even-fermion systems is given by two-body interactions with specific features.
Angular momentum evolution of galaxies in EAGLE
Lagos, Claudia del P; Stevens, Adam R H; Cortese, Luca; Padilla, Nelson D; Davis, Timothy A; Contreras, Sergio; Croton, Darren
2016-01-01
We use EAGLE to study the specific angular momentum of galaxies, j, at z1.2, and then increase as lstars~a. Galaxy mergers reduce lstars by a factor of 2-3. These tracks are driven by both the evolution of the total jstars but also its radial distribution. Regardless of the aperture used to measure j, two distinct channels leading to low jstars in galaxies at z=0 are identified: (i) galaxy mergers, and (ii) early formation of most of the stars.
Multi-modal study of angular momentum distribution of fission fragments as a result of bending modes
The average angular momentum of the primary fission fragments as a function of their masses was calculated using the wave function of the bending mode excitation at the scission point. The scission configuration was assumed to be determined by the prescission shapes of fissioning nucleus within the multimodal fission model. Results in 235U(nth, f) is in good agreement with the recent experimental data. (author)
The physics of angular momentum radio
Thidé, B; Then, H; Someda, C G; Ravanelli, R A
2014-01-01
Wireless communications, radio astronomy and other radio science applications are mainly implemented with techniques built on top of the electromagnetic linear momentum (Poynting vector) physical layer. As a supplement and/or alternative to this conventional approach, techniques rooted in the electromagnetic angular momentum physical layer have been advocated, and promising results from proof-of-concept radio communication experiments using angular momentum were recently published. This sparingly exploited physical observable describes the rotational (spinning and orbiting) physical properties of the electromagnetic fields and the rotational dynamics of the pertinent charge and current densities. In order to facilitate the exploitation of angular momentum techniques in real-world implementations, we present a systematic, comprehensive theoretical review of the fundamental physical properties of electromagnetic angular momentum observable. Starting from an overview that puts it into its physical context among ...
Efficient separation of light's orbital angular momentum
Mirhosseini, Mohammad; Shi, Zhimin; Boyd, Robert W
2013-01-01
The orbital angular momentum (OAM) of light is an attractive degree of freedom for fundamentals studies in quantum mechanics. In addition, the discrete unbounded state-space provided by OAM has been used to enhance classical and quantum communications. The ability to unambiguously measure the OAM of single photons is a key part of all such experiments. However, state-of-the-art methods for sorting OAM modes are limited to a separation efficiency of about 80 percent. Here we demonstrate a method which uses a series of complex optical transformations to enable the measurement of light's OAM with a separation efficiency of more than 92 percent. Further, we demonstrate the separation of modes in the angular position basis, which is mutually unbiased with respect to the OAM basis. The high degree of certainty makes our approach particularly attractive for quantum key distribution systems employing spatial encoding.
Angular momentum conservation for dynamical black holes
Hayward, Sean A.
2006-01-01
Angular momentum can be defined by rearranging the Komar surface integral in terms of a twist form, encoding the twisting around of space-time due to a rotating mass, and an axial vector. If the axial vector is a coordinate vector and has vanishing transverse divergence, it can be uniquely specified under certain generic conditions. Along a trapping horizon, a conservation law expresses the rate of change of angular momentum of a general black hole in terms of angular momentum densities of ma...
Quark Orbital Angular Momentum and Final State Interactions
Burkardt, Matthias
2014-01-01
Definitions of orbital angular momentum based on Wigner distributions are used to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. The difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.
Mass and Angular Momentum in General Relativity
Jaramillo, J L
2010-01-01
We present an introduction to mass and angular momentum in General Relativity. After briefly reviewing energy-momentum for matter fields, first in the flat Minkowski case (Special Relativity) and then in curved spacetimes with or without symmetries, we focus on the discussion of energy-momentum for the gravitational field. We illustrate the difficulties rooted in the Equivalence Principle for defining a local energy-momentum density for the gravitational field. This leads to the understanding of gravitational energy-momentum and angular momentum as non-local observables that make sense, at best, for extended domains of spacetime. After introducing Komar quantities associated with spacetime symmetries, it is shown how total energy-momentum can be unambiguously defined for isolated systems, providing fundamental tests for the internal consistency of General Relativity as well as setting the conceptual basis for the understanding of energy loss by gravitational radiation. Finally, several attempts to formulate q...
Orbital angular momentum exchange in post-collision interaction
Burgt, P.J.M. van der; Eck, J. van; Heideman, H.G.M.
1985-03-14
The authors have measured the angular distribution of electrons ejected by the He**(2s/sup 2/)/sup 1/S autoionising state after its electron impact excitation via the He/sup -/(2s2p/sup 2/)/sup 2/D resonance. Taking into account interference with electrons from the direct ionisation of helium, analysis of this angular distribution provides evidence for angular momentum exchange between ejected and scattered electrons during the post-collision interaction.
Gravitational waves carrying orbital angular momentum
Bialynicki-Birula, Iwo; Bialynicka-Birula, Zofia
2016-02-01
Spinorial formalism is used to map every electromagnetic wave into the gravitational wave (within the linearized gravity). In this way we can obtain the gravitational counterparts of Bessel, Laguerre-Gauss, and other light beams carrying orbital angular momentum.
Angular Momentum Acquisition in Galaxy Halos
Stewart, Kyle R; Bullock, James S; Maller, Ariyeh H; Diemand, Juerg; Wadsley, James; Moustakas, Leonidas A
2013-01-01
We use high-resolution cosmological hydrodynamic simulations to study the angular momentum acquisition of gaseous halos around Milky Way sized galaxies. We find that cold mode accreted gas enters a galaxy halo with ~70% more specific angular momentum than dark matter averaged over cosmic time (though with a very large dispersion). In fact, we find that all matter has a higher spin parameter when measured at accretion than when averaged over the entire halo lifetime, and is well characterized by \\lambda~0.1, at accretion. Combined with the fact that cold flow gas spends a relatively short time (1-2 dynamical times) in the halo before sinking to the center, this naturally explains why cold flow halo gas has a specific angular momentum much higher than that of the halo and often forms "cold flow disks". We demonstrate that the higher angular momentum of cold flow gas is related to the fact that it tends to be accreted along filaments.
Gravitational waves carrying orbital angular momentum
Bialynicki-Birula, Iwo
2015-01-01
Spinorial formalism is used to map every electromagnetic wave into the gravitational wave (within the linearized gravity). In this way we can obtain the gravitational counterparts of Bessel, Laguerre-Gauss, and other light beams carrying orbital angular momentum.
On the relation between angular momentum and angular velocity
Silva, J. P.; Tavares, J. M.
2007-01-01
Students of mechanics usually have difficulties when they learn about the rotation of a rigid body. These difficulties are rooted in the relation between angular momentum and angular velocity, because these vectors are not parallel, and we need in general to utilize a rotating frame of reference or a time dependent inertia tensor. We discuss a series of problems that introduce both difficulties.
Multipolar expansion of orbital angular momentum modes
Molina-Terriza, Gabriel
2008-01-01
In this letter a general method for expanding paraxial beams into multipolar electromagnetic fields is presented. This method is applied to the expansion of paraxial modes with orbital angular momentum (OAM), showing how the paraxial OAM is related to the general angular momentum of an electromagnetic wave. This method can be extended to quasi-paraxial beams, i.e. highly focused laser beams. Some applications to the control of electronic transitions in atoms are discussed.
Orbital angular momentum of partially coherent beams
Serna Galán, Julio; Movilla Serrano, Jesús María
2001-01-01
The definition of the orbital angular momentum established for coherent beams is extended to partially coherent beams, expressed in terms of two elements of the beam matrix. This extension is justified by use of the Mercer expansion of partially coherent fields. General Gauss-Schell-model fields are considered, and the relation between the twist; parameter and the orbital angular momentum is analyzed. © 2001 Optical Society of America.
Entanglement of Polarization and Orbital Angular Momentum
Bhatti, Daniel; von Zanthier, Joachim; Agarwal, Girish S.
2015-01-01
We investigate two-photon entangled states using two important degrees of freedom of the electromagnetic field, namely orbital angular momentum (OAM) and spin angular momentum. For photons propagating in the same direction we apply the idea of $\\textit{entanglement duality}$ and develop schemes to do $\\textit{entanglement sorting}$ based either on OAM or polarization. In each case the entanglement is tested using appropriate witnesses. We finally present generalizations of these ideas to thre...
Angular Momentum and Galaxy Formation Revisited
Romanowsky, Aaron J.; Fall, S. Michael
2012-12-01
-M sstarf scaling relations. This provides a physical motivation for characterizing galaxies most basically with two parameters: mass and bulge-to-disk ratio. Next, in an approach complementary to numerical simulations, we construct idealized models of angular momentum content in a cosmological context, using estimates of dark matter halo spin and mass from theoretical and empirical studies. We find that the width of the halo spin distribution cannot account for the differences between spiral and elliptical j sstarf, but that the observations are reproduced well if these galaxies simply retained different fractions of their initial j complement (~60% and ~10%, respectively). We consider various physical mechanisms for the simultaneous evolution of j sstarf and M sstarf (including outflows, stripping, collapse bias, and merging), emphasizing that the vector sum of all such processes must produce the observed j sstarf-M sstarf relations. We suggest that a combination of early collapse and multiple mergers (major or minor) may account naturally for the trend for ellipticals. More generally, the observed variations in angular momentum represent simple but fundamental constraints for any model of galaxy formation.
Quark Orbital Angular Momentum and Exclusive Processes at HERMES
A first attempt for a model-dependent extraction of the orbital angular momentum of quarks in the nucleon has been made, based on HERMES data on exclusive processes and their description in terms of generalized parton distributions. An overview of the HERMES data on hard exclusive electroproduction of real photons (Deeply-Virtual Compton Scattering) and mesons is given, focusing on the measurements relevant to the extraction of quark orbital angular momentum
Quark Orbital Angular Momentum and Exclusive Processes at HERMES
Ellinghaus, F.
2006-11-01
A first attempt for a model-dependent extraction of the orbital angular momentum of quarks in the nucleon has been made, based on HERMES data on exclusive processes and their description in terms of generalized parton distributions. An overview of the HERMES data on hard exclusive electroproduction of real photons (Deeply-Virtual Compton Scattering) and mesons is given, focusing on the measurements relevant to the extraction of quark orbital angular momentum.
Relaxation times for angular momentum in damped nuclear reactions
The evolution of the angular momentum distribution in damped nuclear reactions is discussed within the framework of the nucleon exchange transport model. First order equations are derived for the time evolution of the mean values and covariances of the spin variables. Solutions are given for 1400 MeV 165Ho + 165Ho reactions at various values of total angular momentum and total kinetic energy loss. Spin dispersions are well described by the calculations
Experimental determination of high angular momentum states
The current knowledge of the atomic nucleus structure is summarized. A short abstract of the nuclear properties at high angular momentum and a more detailed description of the experimental methods used in the study of high angular momenta is made. (L.C.)
Angular momentum decomposition of Richardson's pairs
The angular momentum decomposition of pairs obtained using Richardson's exact solution of the pairing Hamiltonian for the deformed 174Yb nucleus are displayed. The probabilities for low angular momenta of the collective pairs are strikingly different from the ones obtained in the BCS ground state
Ramsey, G.P.; Qui, J.; Richards, D.; Sivers, D.
1989-01-01
New data from the European Muon Collaboration (EMC) on the spin-spin asymmetry in deep-inelastic lepton-proton scattering suggests that the total spin carried by valence quarks in a polarized proton may be approximately canceled by a strong negative polarization of the sea of q-barq pairs. The evolution in Q/sup 2/ of the fraction of proton spin carried by gluons depends on the initial spin fractions and it is possible to avoid the introduction of large orbital angular momentum by adopting a ''hybrid'' quark-Skyrme picture of the proton suggested by the EMC results.
Orbital angular momentum of general astigmatic modes
We present an operator method to obtain complete sets of astigmatic Gaussian solutions of the paraxial wave equation. In case of general astigmatism, the astigmatic intensity and phase distribution of the fundamental mode differ in orientation. As a consequence, the fundamental mode has a nonzero orbital angular momentum, which is not due to phase singularities. Analogous to the operator method for the quantum harmonic oscillator, the corresponding astigmatic higher-order modes are obtained by repeated application of raising operators on the fundamental mode. The nature of the higher-order modes is characterized by a point on a sphere, in analogy with the representation of polarization on the Poincare sphere. The north and south poles represent astigmatic Laguerre-Gaussian modes, similar to circular polarization on the Poincare sphere, while astigmatic Hermite-Gaussian modes are associated with points on the equator, analogous to linear polarization. We discuss the propagation properties of the modes and their orbital angular momentum, which depends on the degree of astigmatism and on the location of the point on the sphere
Orbital angular momentum induced beam shifts
Hermosa N.; Merano M.; Aiello A.; Woerdman J.P.
2011-01-01
We present experiments on Orbital Angular Momentum (OAM) induced beam shifts in optical reflection. Specifically, we observe the spatial Goos-H\\"anchen shift in which the beam is displaced parallel to the plane of incidence and the angular Imbert-Fedorov shift which is a transverse angular deviation from the geometric optics prediction. Experimental results agree well with our theoretical predictions. Both beam shifts increase with the OAM of the beam; we have measured these for OAM indices u...
Quark Orbital Angular Momentum from Lattice QCD
N. Mathur; Dong, S. J.; Liu, K. F.; Mankiewicz, L.; Mukhopadhyay, N. C.
1999-01-01
We calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice. The disconnected insertion is estimated stochastically which employs the $Z_2$ noise with an unbiased subtraction. This reduced the error by a factor of 4 with negligible overhead. The total quark contribution to the proton spin is found to be $0.30 \\pm 0.07$. From this and the quark spin content we deduce the quark orbital angular momentum to be $0.17 \\pm 0.06$ wh...
The angular momentum built up in the fragment nuclei during a damped nuclear reaction is subsequently lost through decay. Since the decay is very fast, the only way to learn about the angular momentum accumulated in the nuclei is to observe the sequential decay products. The present investigation aims at providing precise methods for calculating properties of the sequential decay on the basis of primary spin distributions calculated with the transfer theory
Localizing the Angular Momentum of Linear Gravity
Butcher, Luke M; Hobson, Michael; 10.1103/PhysRevD.86.084012
2012-01-01
In a previous article [Phys. Rev. D 82 104040 (2010)], we derived an energy-momentum tensor for linear gravity that exhibited positive energy density and causal energy flux. Here we extend this framework by localizing the angular momentum of the linearized gravitational field, deriving a gravitational spin tensor which possesses similarly desirable properties. By examining the local exchange of angular momentum (between matter and gravity) we find that gravitational intrinsic spin is localized, separately from orbital angular momentum, in terms of a gravitational spin tensor. This spin tensor is then uniquely determined by requiring that it obey two simple physically motivated algebraic conditions. Firstly, the spin of an arbitrary (harmonic-gauge) gravitational plane wave is required to flow in the direction of propagation of the wave. Secondly, the spin tensor of any transverse-traceless gravitational field is required to be traceless. (The second condition ensures that local field redefinitions suffice to ...
Quark orbital angular momentum from lattice QCD
Mathur, N.; Dong, S. J.; Liu, K. F.; Mankiewicz, L.; Mukhopadhyay, N. C.
2000-12-01
We calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice with the quenched approximation. The disconnected insertion is estimated stochastically which employs the Z{sub 2} noise with an unbiased subtraction. This reduced the error by a factor of 3--4 with negligible overhead. The total quark contribution to the proton spin is found to be 0.30{+-}0.07. From this and the quark spin content we deduce the quark orbital angular momentum to be 0.17{+-}0.06 which is {approx}34% of the proton spin. We further predict that the gluon angular momentum is 0.20{+-}0.07; i.e., {approx}40% of the proton spin is due to the glue.
Quark orbital angular momentum from lattice QCD
Liu, K.F.
2000-01-10
The authors calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice. The disconnected insertion is estimated stochastically which employs the Z{sub 2} noise with an unbiased subtraction. This reduced the error by a factor of 4 with negligible overhead. The total quark contribution to the proton spin is found to be 0.30{+-}0.07. From this and the quark spin content the authors deduce the quark orbital angular momentum to be 0.17{+-}0.06 which is {approximately} 34% of the proton spin. The authors further predict that the gluon angular momentum to be 0.20{+-}0.07, i. e. {approximately} 40% of the proton spin is due to the glue.
Quark orbital angular momentum from lattice QCD
The authors calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice. The disconnected insertion is estimated stochastically which employs the Z2 noise with an unbiased subtraction. This reduced the error by a factor of 4 with negligible overhead. The total quark contribution to the proton spin is found to be 0.30±0.07. From this and the quark spin content the authors deduce the quark orbital angular momentum to be 0.17±0.06 which is ∼ 34% of the proton spin. The authors further predict that the gluon angular momentum to be 0.20±0.07, i. e. approximately 40% of the proton spin is due to the glue
Quark orbital angular momentum from lattice QCD
We calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice with the quenched approximation. The disconnected insertion is estimated stochastically which employs the Z2 noise with an unbiased subtraction. This reduced the error by a factor of 3--4 with negligible overhead. The total quark contribution to the proton spin is found to be 0.30±0.07. From this and the quark spin content we deduce the quark orbital angular momentum to be 0.17±0.06 which is ∼34% of the proton spin. We further predict that the gluon angular momentum is 0.20±0.07; i.e., ∼40% of the proton spin is due to the glue
Radio beam vorticity and orbital angular momentum
Thidé, Bo; Mari, Elettra; Romanato, Filippo; Barbieri, Cesare
2011-01-01
It has been known for a century that electromagnetic fields can transport not only energy and linear momentum but also angular momentum. However, it was not until twenty years ago, with the discovery in laser optics of experimental techniques for the generation, detection and manipulation of photons in well-defined, pure orbital angular momentum (OAM) states, that twisted light and its pertinent optical vorticity and phase singularities began to come into widespread use in science and technology. We have now shown experimentally how OAM and vorticity can be readily imparted onto radio beams. Our results extend those of earlier experiments on angular momentum and vorticity in radio in that we used a single antenna and reflector to directly generate twisted radio beams and verified that their topological properties agree with theoretical predictions. This opens the possibility to work with photon OAM at frequencies low enough to allow the use of antennas and digital signal processing, thus enabling software con...
The origin of angular momentum in dark matter halos
Vitvitska, M; Kravtsov, A V; Bullock, J S; Wechsler, R H; Primack, Joel R
2002-01-01
We propose a new explanation for the origin of angular momentum in galaxies and their dark halos, in which the halos obtain their spin through the cumulative acquisition of angular momentum from satellite accretion. In our model, the build-up of angular momentum is a random walk process associated with the mass assembly history of the halo's major progenitor. We assume no correlation between the angular momenta of accreted objects. Using the extended Press-Schechter approximation, we calculate the growth of mass, angular momentum, and spin parameter $\\lambda$ for many halos. Our random walk model reproduces the key features of the angular momentum of halos found in N-body simulations: a lognormal distribution in $\\lambda$ with an average of $ \\approx 0.04$, independent of mass and redshift. The evolution of the spin parameter in individual halos in this model is quite different from the steady increase with time of angular momentum in the tidal torque picture. We find both in N-body simulations and in our ran...
The role of angular momentum conservation law in statistical mechanics
I.M. Dubrovskii
2008-01-01
Within the limits of Khinchin ideas [A.Y. Khinchin, Mathematical Foundation of Statistical Mechanics. NY, Ed. Dover, 1949] the importance of momentum and angular momentum conservation laws was analyzed for two cases: for uniform magnetic field and when magnetic field is absent. The law of momentum conservation does not change the density of probability distribution in both cases, just as it is assumed in the conventional theory. It is shown that in systems where the kinetic energy depends onl...
Martiny, Christian; Abu-Samha, Mahmoud; Madsen, Lars Bojer
2009-01-01
We solve the three-dimensional time-dependent Schrödinger equation for a three-cycle circularly polarized laser pulse interacting with an atom. The photoelectron momentum distributions show counterintuitive shifts, similar to those observed in a recent experiment (Eckle et al 2008 Science 322 1525...
Cen, Renyue
2015-01-01
We reason that, without physical fine-tuning, neither the supermassive black holes (SMBHs) nor the stellar bulges can self-regulate or inter-regulate by driving away already fallen cold gas to produce the observed correlation between them. We suggest an alternative scenario where the observed mass ratios of the SMBHs to bulges reflect the angular momentum distribution of infallen gas such that the mass reaching the stable accretion disc is a small fraction of that reaching the bulge region, averaged over the cosmological time scales. We test this scenario using high resolution, large-scale cosmological hydrodynamic simulations (without AGN feedback), assuming the angular momentum distribution of gas landing in the bulge region to yield a Mestel disc that is supported by independent simulations resolving the Bondi radii of SMBHs. A mass ratio of $0.1-0.3\\%$ between the very low angular momentum gas that free-falls to the sub-parsec region to accrete to the SMBH and the overall star formation rate is found. Thi...
Wang, Le; Zhao, Sheng-Mei; Gong, Long-Yan; Cheng, Wei-Wen
2015-12-01
In this paper, we propose a measurement-device-independent quantum-key-distribution (MDI-QKD) protocol using orbital angular momentum (OAM) in free space links, named the OAM-MDI-QKD protocol. In the proposed protocol, the OAM states of photons, instead of polarization states, are used as the information carriers to avoid the reference frame alignment, the decoy-state is adopted to overcome the security loophole caused by the weak coherent pulse source, and the high efficient OAM-sorter is adopted as the measurement tool for Charlie to obtain the output OAM state. Here, Charlie may be an untrusted third party. The results show that the authorized users, Alice and Bob, could distill a secret key with Charlie’s successful measurements, and the key generation performance is slightly better than that of the polarization-based MDI-QKD protocol in the two-dimensional OAM cases. Simultaneously, Alice and Bob can reduce the number of flipping the bits in the secure key distillation. It is indicated that a higher key generation rate performance could be obtained by a high dimensional OAM-MDI-QKD protocol because of the unlimited degree of freedom on OAM states. Moreover, the results show that the key generation rate and the transmission distance will decrease as the growth of the strength of atmospheric turbulence (AT) and the link attenuation. In addition, the decoy states used in the proposed protocol can get a considerable good performance without the need for an ideal source. Project supported by the National Natural Science Foundation of China (Grant Nos. 61271238 and 61475075), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20123223110003), the Natural Science Research Foundation for Universities of Jiangsu Province of China (Grant No. 11KJA510002), the Open Research Fund of Key Laboratory of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education, China (Grant No. NYKL2015011), and the
Probing Parton Orbital Angular Momentum in Longitudinally Polarized Nucleon
Ji, Xiangdong; Xiong, Xiaonu; Yuan, Feng
2012-01-01
While the total orbital angular momentum (OAM) of a definite quark flavor in a longitudinally-polarized nucleon can be obtained through a sum rule involving twist-two generalized parton distribution (GPDs), its distribution as a function of parton momentum in light-front coordinates is more complicated to define and measure because it involves intrinsically twist-three effects. In this paper, we consider two different parton OAM distributions. The first is manifestly gauge invariant, and its ...
Effects of Angular Momentum on Halo Profiles
Lentz, Erik W; Rosenberg, Leslie J
2016-01-01
The near universality of DM halo density profiles provided by N-body simulations has proven to be robust against changes in total mass density, power spectrum, and some forms of initial velocity dispersion. In this letter we study the effects of coherently spinning up an isolated DM-only progenitor on halo structure. Halos with spins within several standard deviations of the simulated mean ($\\lambda \\lesssim 0.20$) produce profiles with negligible deviations from the universal form. Only when the spin becomes quite large ($\\lambda \\gtrsim 0.20$) do departures become evident. The angular momentum distribution also exhibits a near universal form, which is also independent of halo spin up to $\\lambda \\lesssim 0.20$. A correlation between these epidemic profiles and the presence of a strong bar in the virialized halo is also observed. These bar structures bear resemblance to the radial orbit instability in the rotationless limit.
Orbital angular momentum-entanglement frequency transducer
Zhou, Zhi-Yuan; Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Dong, Ming-Xin; Shi, Bao-Sen; Guo, Guang-Can
2016-01-01
Entanglement is a vital resource for realizing many tasks such as teleportation, secure key distribution, metrology and quantum computations. To effectively build entanglement between different quantum systems and share information between them, a frequency transducer to convert between quantum states of different wavelengths while retaining its quantum features is indispensable. Information encoded in the photons orbital angular momentum OAM degrees of freedom is preferred in harnessing the information carrying capacity of a single photon because of its unlimited dimensions. A quantum transducer, which operates at wavelengths from 1558.3 nm to 525 nm for OAM qubits, OAMpolarization hybrid entangled states, and OAM entangled states, is reported for the first time. Nonclassical properties and entanglements are demonstrated following the conversion process by performing quantum tomography, interference, and Bell inequality measurements. Our results demonstrate the capability to create an entanglement link betwe...
Orbital angular momentum photonic quantum interface
Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Shi, Bao-Sen; Guo, Guang-Can
2014-01-01
High dimensional orbital angular momentum (OAM) light states are very important in enhancing the information carrying capacity in optical communications and quantum key distributions. Light at wavelengths of fiber communication windows or free space communication windows are suitable for long distance quantum communication, but most quantum processing tasks are performed in the visible wavelength ranges. The interface to bridge the wavelength gap of single photon with Gaussian shape has been realized, however, to create such interface for OAM-carrying light is a great challenge. We report the demonstration of such an interface to frequency up-conversion of herald single photon OAM state from 1560nm to 525nm with high efficiency by using nonlinear crystal in an external cavity. We show that different single photon OAM light shapes are observed directly by using single photon counting camera and the single photon entangled property is retained in the conversion process.
Ghost Imaging Using Orbital Angular Momentum
We present a novel encoding scheme in a ghost-imaging system using orbital angular momentum. In the signal arm, object spatial information is encoded as a phase matrix. For an N-grey-scale object, different phase matrices, varying from 0 to π with increment π/N, are used for different greyscales, and then they are modulated to a signal beam by a spatial light modulator. According to the conservation of the orbital angular momentum in the ghost imaging system, these changes will give different coincidence rates in measurement, and hence the object information can be extracted in the idler arm. By simulations and experiments, the results show that our scheme can improve the resolution of the image effectively. Compared with another encoding method using orbital angular momentum, our scheme has a better performance for both characters and the image object. (fundamental areas of phenomenology(including applications))
Chirality and angular momentum in optical radiation
Coles, Matt M
2012-01-01
This paper develops, in precise quantum electrodynamic terms, photonic attributes of the "optical chirality density", one of several measures long known to be conserved quantities for a vacuum electromagnetic field. The analysis lends insights into some recent interpretations of chiroptical experiments, in which this measure, and an associated chirality flux, have been treated as representing physically distinctive "superchiral" phenomena. In the fully quantized formalism the chirality density is promoted to operator status, whose exploration with reference to an arbitrary polarization basis reveals relationships to optical angular momentum and helicity operators. Analyzing multi-mode beams with complex wave-front structures, notably Laguerre-Gaussian modes, affords a deeper understanding of the interplay between optical chirality and optical angular momentum. By developing theory with due cognizance of the photonic character of light, it emerges that only the spin angular momentum of light is engaged in such...
Ghost Imaging Using Orbital Angular Momentum
赵生妹; 丁建; 董小亮; 郑宝玉
2011-01-01
We present a novel encoding scheme in a ghost-imaging system using orbital angular momentum. In the signal arm, object spatial information is encoded as a phase matrix. For an N-grey-scale object, different phase matrices, varying from 0 to K with increment n/N, are used for different greyscales, and then they are modulated to a signal beam by a spatial light modulator. According to the conservation of the orbital angular momentum in the ghost imaging system, these changes will give different coincidence rates in measurement, and hence the object information can be extracted in the idler arm. By simulations and experiments, the results show that our scheme can improve the resolution of the image effectively. Compared with another encoding method using orbital angular momentum, our scheme has a better performance for both characters and the image object.%We present a novel encoding scheme in a ghost-imaging system using orbital angular momentum.In the signal arm,object spatial information is encoded as a phase matrix.For an N-grey-scale object,different phase matrices,varying from 0 to π with increment π/N,are used for different greyscales,and then they are modulated to a signal beam by a spatial light modulator.According to the conservation of the orbital angular momentum in the ghost imaging system,these changes will give different coincidence rates in measurement,and hence the object information can be extracted in the idler arm.By simulations and experiments,the results show that our scheme can improve the resolution of the image effectively.Compared with another encoding method using orbital angular momentum,our scheme has a better performance for both characters and the image object.
Karim, Md Tanveer; Briceno, Cesar; Vivas, A Katherina; Raetz, Stefanie; Mateu, Cecilia; Downes, Juan Jose; Calvet, Nuria; Hernandez, Jesus; Neuhauser, Ralph; Mugrauer, Markus; Takahashi, Hidenori; Tachihara, Kengo; Chini, Rolf; Cruz-Dias, Gustavo A; Aarnio, Alicia; James, David J; Hackstein, Moritz
2016-01-01
Most existing studies of the angular momentum evolution of young stellar populations have focused on the youngest (1-3 Myr) T Tauri stars. In contrast, the angular momentum distributions of older T Tauri stars (4-10 Myr) have been less studied, even though they hold key insight to understanding stellar angular momentum evolution at a time when protoplanetary disks have largely dissipated and when models therefore predict changes in the rotational evolution that can in principle be tested. We present a study of photometric variability among 1,974 confirmed T Tauri members of various sub-regions of the Orion OB1 association, and with ages spanning 4-10 Myr, using optical time-series from three different surveys. For 564 of the stars (~32% of the weak-lined T Tauri stars and ~13% of the classical T Tauri stars in our sample) we detect statistically significant periodic variations which we attribute to the stellar rotation periods, making this one of the largest samples of T Tauri star rotation periods yet publis...
Wilson lines and orbital angular momentum
We present an explicit realization of the Chen et al. approach to the proton spin decomposition in terms of Wilson lines, generalizing the light-front gauge-invariant extensions discussed recently by Hatta. Particular attention is drawn to the residual gauge freedom by further separating the pure-gauge term into contour and residual terms. We show that the kinetic orbital angular momentum operator can be expressed in terms of the Wigner operator only when the momentum variable is integrated over. Finally, we confirm from twist-2 arguments that the advanced, retarded and antisymmetric light-front canonical orbital angular momenta are the same
Wilson lines and orbital angular momentum
Lorcé, Cédric, E-mail: cedric.lorce@googlemail.com [IPNO, Université Paris-Sud, CNRS/IN2P3, 91406 Orsay (France); LPT, Université Paris-Sud, CNRS, 91406 Orsay (France)
2013-02-12
We present an explicit realization of the Chen et al. approach to the proton spin decomposition in terms of Wilson lines, generalizing the light-front gauge-invariant extensions discussed recently by Hatta. Particular attention is drawn to the residual gauge freedom by further separating the pure-gauge term into contour and residual terms. We show that the kinetic orbital angular momentum operator can be expressed in terms of the Wigner operator only when the momentum variable is integrated over. Finally, we confirm from twist-2 arguments that the advanced, retarded and antisymmetric light-front canonical orbital angular momenta are the same.
Angular momentum and the electromagnetic top
GIANFRANCO SPAVIERI; GEORGE T GILLIES
2016-08-01
The electric charge–magnetic dipole interaction is considered. If $\\Gamma_{\\rm em}$ is the electromagnetic and $\\Gamma_{\\rm mech}$ the mechanical angular momentum, the conservation law for the total angular momentum $\\Gamma_{\\rm tot}$ holds: $\\Gamma_{\\rm tot}$ =$\\Gamma_{\\rm em}$ + $\\Gamma_{\\rm mech}$ = ${\\rm const.}$, but when the dipole moment varies with time, $\\Gamma_{\\rm mech}$ is not conserved. We show that the non-conserved $\\Gamma_{\\rm mech}$ of such a macroscopic isolated system might be experimentally observable. With advanced technology, the strength of the interaction hints to the possibility of novel applications for gyroscopes, such as the electromagnetic top.
Orbital angular momentum in the nucleons
Lorcé, Cédric
2014-01-01
In the last decade, it has been realized that the orbital angular momentum of partons inside the nucleon plays a major role. It contributes significantly to nucleon properties and is at the origin of many asymmetries observed in spin physics. It is therefore of paramount importance to determine this quantity if we want to understand the nucleon internal structure and experimental observables. This triggered numerous discussions and controversies about the proper definition of orbital angular momentum and its extraction from experimental data. We summarize the present situation and discuss recent developments in this field.
On the vector model of angular momentum
Saari, Peeter
2016-09-01
Instead of (or in addition to) the common vector diagram with cones, we propose to visualize the peculiarities of quantum mechanical angular momentum by a completely quantized 3D model. It spotlights the discrete eigenvalues and noncommutativity of components of angular momentum and corresponds to outcomes of measurements—real or computer-simulated. The latter can be easily realized by an interactive worksheet of a suitable program package of algebraic calculations. The proposed complementary method of visualization helps undergraduate students to better understand the counterintuitive properties of this quantum mechanical observable.
Orbital angular momentum in the nucleons
Lorcé, Cédric
2014-01-01
In the last decade, it has been realized that the orbital angular momentum of partons inside the nucleon plays a major role. It contributes significantly to nucleon properties and is at the origin of many asymmetries observed in spin physics. It is therefore of paramount importance to determine this quantity if we want to understand the nucleon internal structure and experimental observables. This triggered numerous discussions and controversies about the proper definition of orbital angular ...
Wilson lines and orbital angular momentum
Lorce, Cédric
2013-01-01
We present an explicit realization of the Chen et al. approach to the proton spin decomposition in terms of Wilson lines, generalizing the light-front gauge-invariant extensions discussed recently by Hatta. Particular attention is drawn to the residual gauge freedom by further separating the pure-gauge term into contour and residual terms. We show that the kinetic orbital angular momentum operator can be expressed in terms of the Wigner operator only when the momentum variable is integrated o...
Non-Colinearity of Angular Velocity and Angular Momentum
Burr, A. F.
1974-01-01
Discusses the principles, construction, and operation of an apparatus which serves to demonstrate the non-colinearity of the angular velocity and momentum vectors as well as the inertial tensors. Applications of the apparatus to teaching of advanced undergraduate mechanics courses are recommended. (CC)
Dual electromagnetism: helicity, spin, momentum and angular momentum
The dual symmetry between electric and magnetic fields is an important intrinsic property of Maxwell equations in free space. This symmetry underlies the conservation of optical helicity and, as we show here, is closely related to the separation of spin and orbital degrees of freedom of light (the helicity flux coincides with the spin angular momentum). However, in the standard field-theory formulation of electromagnetism, the field Lagrangian is not dual symmetric. This leads to problematic dual-asymmetric forms of the canonical energy–momentum, spin and orbital angular-momentum tensors. Moreover, we show that the components of these tensors conflict with the helicity and energy conservation laws. To resolve this discrepancy between the symmetries of the Lagrangian and Maxwell equations, we put forward a dual-symmetric Lagrangian formulation of classical electromagnetism. This dual electromagnetism preserves the form of Maxwell equations, yields meaningful canonical energy–momentum and angular-momentum tensors, and ensures a self-consistent separation of the spin and orbital degrees of freedom. This provides a rigorous derivation of the results suggested in other recent approaches. We make the Noether analysis of the dual symmetry and all the Poincaré symmetries, examine both local and integral conserved quantities and show that only the dual electromagnetism naturally produces a complete self-consistent set of conservation laws. We also discuss the observability of physical quantities distinguishing the standard and dual theories, as well as relations to quantum weak measurements and various optical experiments. (paper)
Photon Orbital Angular Momentum and Mass in a Plasma Vortex
Tamburini, F; Sponselli, A.; Thidé, B.; Mendonça, J. T.
2010-01-01
We analyse the Anderson-Higgs mechanism of photon mass acquisition in a plasma and study the contribution to the mass from the orbital angular momentum acquired by a beam of photons when it crosses a spatially structured charge distribution. To this end we apply Proca-Maxwell equations in a static plasma with a particular spatial distribution of free charges, notably a plasma vortex, that is able to impose orbital angular momentum (OAM) onto light. In addition to the mass acquisition of the c...
Photon Orbital Angular Momentum in Astrophysics
Harwit, Martin
2003-01-01
Astronomical observations of the orbital angular momentum of photons, a property of electromagnetic radiation that has come to the fore in recent years, have apparently never been attempted. Here, I show that measurements of this property of photons have a number of astrophysical applications.
Critical gravitational collapse with angular momentum
Gundlach, Carsten
2016-01-01
We derive a theoretical model of mass and angular momentum scaling in type-II critical collapse with rotation. We focus on the case where the critical solution has precisely one, spherically symmetric, unstable mode. We demonstrate excellent agreement with numerical results for critical collapse of a rotating radiation fluid, which falls into this case.
Cisneros, G. Andrés; Piquemal, Jean-Philip; Darden, Thomas A.
2006-11-01
The simulation of biological systems by means of current empirical force fields presents shortcomings due to their lack of accuracy, especially in the description of the nonbonded terms. We have previously introduced a force field based on density fitting termed the Gaussian electrostatic model-0 (GEM-0) J.-P. Piquemal et al. [J. Chem. Phys. 124, 104101 (2006)] that improves the description of the nonbonded interactions. GEM-0 relies on density fitting methodology to reproduce each contribution of the constrained space orbital variation (CSOV) energy decomposition scheme, by expanding the electronic density of the molecule in s-type Gaussian functions centered at specific sites. In the present contribution we extend the Coulomb and exchange components of the force field to auxiliary basis sets of arbitrary angular momentum. Since the basis functions with higher angular momentum have directionality, a reference molecular frame (local frame) formalism is employed for the rotation of the fitted expansion coefficients. In all cases the intermolecular interaction energies are calculated by means of Hermite Gaussian functions using the McMurchie-Davidson [J. Comput. Phys. 26, 218 (1978)] recursion to calculate all the required integrals. Furthermore, the use of Hermite Gaussian functions allows a point multipole decomposition determination at each expansion site. Additionally, the issue of computational speed is investigated by reciprocal space based formalisms which include the particle mesh Ewald (PME) and fast Fourier-Poisson (FFP) methods. Frozen-core (Coulomb and exchange-repulsion) intermolecular interaction results for ten stationary points on the water dimer potential-energy surface, as well as a one-dimensional surface scan for the canonical water dimer, formamide, stacked benzene, and benzene water dimers, are presented. All results show reasonable agreement with the corresponding CSOV calculated reference contributions, around 0.1 and 0.15kcal/mol error for
Angular momentum transfer in incomplete fusion
B S Tomar; K Surendra Babu; K Sudarshan; R Tripathi; A Goswami
2005-02-01
Isomeric cross-section ratios of evaporation residues formed in 12C+93Nb and 16O + 89Y reactions were measured by recoil catcher technique followed by off-line -ray spectrometry in the beam energy range of 55.7-77.5 MeV for 12C and 68-81 MeV for 16O. The isomeric cross-section ratios were resolved into that for complete and incomplete fusion reactions. The angular momentum of the intermediate nucleus formed in incomplete fusion was deduced from the isomeric cross-section ratio by considering the statistical de-excitation of the incompletely fused composite nucleus. The data show that incomplete fusion is associated with angular momenta slightly smaller than critical angular momentum for complete fusion, indicating the deeper interpenetration of projectile and target nuclei than that in peripheral collisions.
Angular momentum alignment in molecular beam scattering
It is shown how the angular momentum alignment in a molecular beam can be determined using laser-induced fluorescence in combination with precession of the angular momenta in a magnetic field. After a general analysis of the method, some results are presented to illustrate the possibilities of the method. Experimental data are presented on the alignment production for Na2 molecules that made a collision induced angular momentum transition. Magnitude as well as direction of the alignment have been determined for scattering with several scattering partners and for a large number of scattering angles and transitions. The last chapter deals with the total alignment production in a final J-state, i.e. without state selection of the initial rotational state. (orig.)
Martiny, Christian; Abu-Samha, Mahmoud; Madsen, Lars Bojer
2010-01-01
We solve the three-dimensional time-dependent Schrödinger equation for a few-cycle circularly polarized femtosecond laser pulse that interacts with an oriented target exemplified by an argon atom, initially in a 3px or 3py state. The photoelectron momentum distributions show distinct signatures of....... Furthermore, we show that ionization by a circularly polarized pulse completely maps out the angular nodal structure of the initial state, thus providing a potential tool for studying orbital symmetry in individual systems or during chemical reactions....
Ezhilov, Aleksei; The ATLAS collaboration
2016-01-01
The ATLAS collaboration has performed precision measurements sensitive to the transverse momentum of the Z/gamma* bosons, both directly through the transverse momentum of the di-lepton pair and through the angular decorrelation as measured in the phi* observable. These measurements are sensitive to soft resummation effects and hard jet emissions for small and large momentum transfers, respectively, probing QCD in a unique way. The studies carried out with 20.3 /fb of data at a center-of-mass energy of 8TeV probe a wide di-lepton invariant mass region from 12 GeV to 150 GeV, both integrated and differential in the di-lepton rapidity. The measurements are compared to a variety of resummation calculations and parton shower Monte Carlos at up to NNLO+NNLL as well as fixed order predictions at NNLO QCD including NLO electroweak corrections. The precision measurement of angular distributions of the Drell-Yan lepton pairs around the Z-boson mass peak provide a stringent test of the underlying QCD dynamic of the Z-bo...
Quark orbital angular momentum in the Wandzura-Wilczek approximation
Haegler, Ph.Ph.; Mukherjee, A.; Schaefer, A
2004-02-26
We show that quark orbital angular momentum is directly related to off-forward correlation functions which include intrinsic transverse momentum corresponding to a derivative with respect to the transverse coordinates. Its possible contribution to scattering processes is therefore of higher twist and vanishes in the forward limit. The relation of OAM to other twist 2 and 3 distributions known in the literature is derived and formalized by an unintegrated sum rule.
The role of angular momentum conservation law in statistical mechanics
I.M. Dubrovskii
2008-12-01
Full Text Available Within the limits of Khinchin ideas [A.Y. Khinchin, Mathematical Foundation of Statistical Mechanics. NY, Ed. Dover, 1949] the importance of momentum and angular momentum conservation laws was analyzed for two cases: for uniform magnetic field and when magnetic field is absent. The law of momentum conservation does not change the density of probability distribution in both cases, just as it is assumed in the conventional theory. It is shown that in systems where the kinetic energy depends only on particle momenta canonically conjugated with Cartesian coordinates being their diagonal quadric form,the angular momentum conservation law changes the density of distribution of the system only in case the full angular momentum of a system is not equal to zero. In the gas of charged particles in a uniform magnetic field the density of distribution also varies if the angular momentum is zero [see Dubrovskii I.M., Condensed Matter Physics, 2206, 9, 23]. Two-dimensional gas of charged particles located within a section of an endless strip filled with gas in magnetic field is considered. Under such conditions the angular momentum is not conserved. Directional particle flows take place close to the strip boundaries, and, as a consequence, the phase trajectory of the considered set of particles does not remain within the limited volume of the phase space. In order to apply a statistical thermodynamics method, it was suggested to consider near-boundary trajectories relative to a reference system that moves uniformly. It was shown that if the diameter of an orbit having average thermal energy is much smaller than a strip width, the corrections to thermodynamic functions are small depending on magnetic field. Only the average velocity of near-boundary particles that form near-boundary electric currents creating the paramagnetic moment turn out to be essential.
Numerical Solution of the Evolution Equation for Orbital Angular Momentum of Partons in the Nucleon
Martin, O.; Hagler, P.; Schafer, A.
1998-01-01
The evolution of orbital angular momentum distributions within the radiative parton model is studied. We use different scenarios for the helicity weighted parton distributions and consider a broad range of input distributions for orbital angular momentum. In all cases we are lead to the conclusion that the absolute value of the average angular momentum per parton peaks at relatively large $x\\approx 0.1$ for perturbatively accessible scales. Furthermore, in all scenarios considered here the av...
Creation of orbital angular momentum states with chiral polaritonic lenses.
Dall, Robert; Fraser, Michael D; Desyatnikov, Anton S; Li, Guangyao; Brodbeck, Sebastian; Kamp, Martin; Schneider, Christian; Höfling, Sven; Ostrovskaya, Elena A
2014-11-14
Controlled transfer of orbital angular momentum to an exciton-polariton Bose-Einstein condensate spontaneously created under incoherent, off resonant excitation conditions is a long-standing challenge in the field of microcavity polaritonics. We demonstrate, experimentally and theoretically, a simple and efficient approach to the generation of nontrivial orbital angular momentum states by using optically induced potentials-chiral polaritonic lenses. These lenses are produced by a structured optical pump with a spatial distribution of intensity that breaks the chiral symmetry of the system. PMID:25432029
DARK MATTER ANGULAR MOMENTUM PROFILE FROM THE JEANS EQUATION
Cosmological simulations of dark matter (DM) structures have shown that the equilibrated DM structures have a fairly small angular momentum. It appears from these N-body simulations that the radial profile of the angular momentum has an almost universal behavior, even if the different DM structures have experienced very different formation and merger histories. We suggest a perturbed Jeans equation, which includes a rotational term. This is done under a reasonable assumed form of the change in the distribution function. By conjecturing that the (new) subdominant rotation term must be proportional to the (old) dominant mass term, we find a clear connection, which is in rather good agreement with the results of recent high-resolution simulations. We also present a new connection between the radial profiles of the angular momentum and the velocity anisotropy, which is also in fair agreement with numerical findings. Finally, we show how the spin parameter λ increases as a function of radius.
Orbital angular momentum exchange in cylindrical-lens mode converters
Padgett, M J; Allen, L [Department of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom)
2002-04-01
Cylindrical-lens mode converters (Beijersbergen M W, Allen L, van der Veen H E L O and Woerdman J P 1993 Opt. Commun. 96 123-32) are used to transform between Hermite-Gaussian and Laguerre-Gaussian modes with a resulting transfer of angular momentum to the light beam and a corresponding torque on the lenses. By numerically analysing both the total and local angular momentum of the light beam, we explain the origin of this torque and confirm that is not evenly distributed between the lenses. We also confirm that any vortex contained within the beam may change sign even when the orbital angular momentum of the beam remains constant.
Valley-contrasting orbital angular momentum in photonic valley crystals
Chen, Xiaodong; Dong, Jianwen
2016-01-01
Valley, as a degree of freedom, has been exploited to realize valley-selective Hall transport and circular dichroism in two-dimensional layered materials. On the other hand, orbital angular momentum of light with helical phase distribution has attracted great attention for its unprecedented opportunity to optical communicagtions, atom trapping, and even nontrivial topology engineering. Here, we reveal valley-contrasting orbital angular momentum in all-dielectric photonic valley crystals. Selective excitation of valley chiral bulk states is realized by sources carrying orbital angular momentum with proper chirality. Valley dependent edge states, predictable by nonzero valley Chern number, enable to suppress the inter-valley scattering along zigzag boundary, leading to broadband robust transmission in Z-shape bend without corner morphological optimization. Our work may open up a new door towards the discovery of novel quantum states and the manipulation of spin-orbit interaction of light in nanophotonics.
Generation of the Stigmatic Beam with Orbital Angular Momentum
高春清; 魏光辉; Horst WEBER
2001-01-01
The stigmatic beam with orbital angular momentum is generated by transforming the Hermite-Gaussian beamof a diode-pumped Nd:YAG laser through a rotated cylindrical optical system. Behind the transformation optics,the output beam has an intensity distribution of ring shape and a twist phase. The beam transformation istheoretically calculated and the result has been confirmed in the experiments.
Phenomenological determination of the orbital angular momentum.
Ramsey, G. P.; High Energy Physics; Loyola Univ.
2009-01-01
Measurements involving the gluon spin, {Delta}G(x, t) and the corresponding asymmetry, A(x,t) = {Delta}G(x,t)/G(x,t) play an important role in quantitative understanding of proton structure. We have modeled the asymmetry perturbatively and calculated model corrections to obtain information about non-perturbative spin-orbit effects. These models are consistent with existing COMPASS and HERMES data on the gluon asymmetry. The J{sub z} = 1/2 sum rule is used to generate values of orbital angular momentum at LO and NLO. For models consistent with data, the orbital angular momentum is small. Our studies specify accuracy that future measurements should achieve to constrain theoretical models for nucleon structure.
A Stern-Gerlach-like approach to electron orbital angular momentum measurement
Harvey, Tyler R
2016-01-01
Many methods now exist to prepare free electrons into orbital angular momentum states, and the predicted applications of these electron states as probes of materials and scattering processes are numerous. The development of electron orbital angular momentum measurement techniques has lagged behind. We show that coupling between electron orbital angular momentum and a spatially varying magnetic field produces an angular momentum-dependent focusing effect. We propose a design for an orbital angular momentum measurement device built on this principle. As the method of measurement is non-interferometric, the device works equally well for mixed, superposed and pure final orbital angular momentum states. The energy and orbital angular momentum distributions of inelastically scattered electrons may be simultaneously measurable with this technique.
Arbitrary orbital angular momentum of photons
Pan, Yue; Gao, Xu-Zhen; Ren, Zhi-Cheng; Wang, Xi-Lin; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian
2015-01-01
Orbital angular momentum (OAM) of photons, as a new fundamental degree of freedom, has excited a great diversity of interest, because of a variety of emerging applications. Arbitrarily tunable OAM has gained much attention, but its creation remains still a tremendous challenge. We demonstrate the realization of well-controlled arbitrary OAM in both theory and experiment. We present the concept of general OAM, which extends the OAM carried by the scalar vortex field to the OAM carried by the a...
Quark Orbital Angular Momentum in the Baryon
Song, Xiaotong
2000-01-01
Analytical and numerical results, for the orbital and spin content carried by different quark flavors in the baryons, are given in the chiral quark model with symmetry breaking. The reduction of the quark spin, due to the spin dilution in the chiral splitting processes, is transferred into the orbital motion of quarks and antiquarks. The orbital angular momentum for each quark flavor in the proton as a function of the partition factor $\\kappa$ and the chiral splitting probability $a$ is shown...
Orbital angular momentum photonic quantum interface
Zhou, Zhi-Yuan; Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Shi, Bao-Sen; Guo, Guang-Can
2014-01-01
Light carrying orbital angular momentum (OAM) has great potential in enhancing the information channel capacity in both classical and quantum optical communications. Long distance optical communication requires the wavelengths of light are situated in the low-loss communication windows, but most quantum memories currently being developed for use in a quantum repeater work at different wavelengths, so a quantum interface to bridge the wavelength gap is necessary. So far, such an interface for ...
Orbital angular momentum entanglement in turbulence
Ibrahim, Alpha Hamadou; Roux, Filippus S.; McLaren, Melanie; Konrad, Thomas; Forbes, Andrew
2013-01-01
The turbulence induced decay of orbital angular momentum (OAM) entanglement between two photons is investigated numerically and experimentally. To compare our results with previous work, we simulate the turbulent atmosphere with a single phase screen based on the Kolmogorov theory of turbulence. We consider two different scenarios: in the first only one of the two photons propagates through turbulence, and in the second both photons propagate through uncorrelated turbulence. Comparing the ent...
Four-photon orbital angular momentum entanglement
Hiesmayr, B. C.; De Dood, M.J.A.; Löffler, W.
2015-01-01
Quantum entanglement shared between more than two particles is essential to foundational questions in quantum mechanics, and upcoming quantum information technologies. So far, up to 14 two-dimensional qubits have been entangled, and an open question remains if one can also demonstrate entanglement of higher-dimensional discrete properties of more than two particles. A promising route is the use of the photon orbital angular momentum (OAM), which enables implementation of novel quantum informa...
Angular Momentum in Loop Quantum Gravity
Bojowald, Martin
2000-01-01
An angular momentum operator in loop quantum gravity is defined using spherically symmetric states as a non-rotating reference system. It can be diagonalized simultaneously with the area operator and has the familiar spectrum. The operator indicates how the quantum geometry of non-rotating isolated horizons can be generalized to rotating ones and how the recent computations of black hole entropy can be extended to rotating black holes.
Angular Momentum of Dark Matter Black Holes
Frampton, Paul H.
2016-01-01
The putative black holes which may constitute all the dark matter are described by a Kerr metric with only two parameters, mass M and angular momentum J. There has been little discussion of J since it plays no role in the upcoming attempt at detection by microlensing. Nevertheless J does play a central role in understanding the previous lack of detection, especially of CMB distortion. We explain why bounds previously derived from lack of CMB distortion are too strong for primordial black hole...
A practical formula for the radiated angular momentum
Lousto, Carlos O.; Zlochower, Yosef
2007-01-01
We present a simple formula for the radiated angular momentum based on a spin-weighted spherical harmonic decomposition of the Weyl scalar psi_4 representing outgoing radiation in the Kinnersley tetrad. We test our formula by measuring the radiated angular momentum from three simulations of non-spinning equal-mass black-hole binary with orbital angular momentum aligned along the x, y, and z axes respectively. We find that the radiated angular momentum agrees with the differences in the remnan...
Angular momentum nonconservation and conservation in quasiclassical Positronium
Lush, David C.
2010-01-01
It is shown that due to Thomas precession, angular momentum is not generally a constant of the motion in a quasiclassical model of the Positronium atom consisting of circular-orbiting point charges with intrinsic spin and associated magnetic moment. Despite absence of externally-applied torque, angular momentum is a constant of the motion only if the electron and positron intrinsic angular momentum vector components perpendicular to the orbital angular momentum are antiparallel and of equal m...
Angular momentum of a strongly focussed Gaussian beam
Nieminen, Timo A.; Heckenberg, Norman R.; Rubinsztein-Dunlop, Halina
2004-01-01
A circularly polarized rotationally symmetric paraxial laser beams carries hbar angular momentum per photon as spin. Focussing the beam with a rotationally symmetric lens cannot change this angular momentum flux, yet the focussed beam must have spin less than hbar per photon. The remainder of the original spin is converted to orbital angular momentum, manifesting itself as a longitudinal optical vortex at the focus. This demonstrates that optical orbital angular momentum can be generated by a...
Orbital and field angular momentum in the nucleon
Singleton, D; Dzhunushaliev, V.
1998-01-01
The nucleon spin problem raises experimental and theoretical questions regarding the contribution of the orbital angular momentum of the quarks to the total spin of the nucleon. In this article we examine the commutation relationships of various operators that contribute to the total angular momentum of the nucleon. We find that the sum of the orbital plus gluon field angular momentum should satisfy the angular momentum commutators, at least up to the one-loop level. This requirement on the s...
On angular momentum operator in quantum field theory
Iliev, Bozhidar Z.
2002-01-01
Relations between two definitions of (total) angular momentum operator, as a generator of rotations and in the Lagrangian formalism, are explored in quantum field theory. Generally, these definitions result in different angular momentum operators, which are suitable for different purposes in the theory. From the spin and orbital angular momentum operators (in the Lagrangian formalism) are extracted additive terms which are conserved operators and whose sum is the total angular momentum operator.
Orbital angular momentum density of a general Lorentz–Gauss vortex beam
Zhou, Guoquan; Ji, Zhiyue; Ru, Guoyun
2016-07-01
Based on the vectorial Rayleigh–Sommerfeld integral formulae, the analytical expression of a general Lorentz–Gauss vortex beam with an arbitrary topological charge is derived in free space. By using the analytical expressions of the electromagnetic field beyond the paraxial approximation, the orbital angular momentum density of a general Lorentz–Gauss vortex beam can be calculated. The effects of the linearly polarized angle and the topological charge on the three components of the orbital angular momentum density are investigated in the reference plane. The two transversal components of the orbital angular momentum are composed of two lobes with the same areas and opposite signs. The longitudinal component of the orbital angular momentum density is composed of four lobes with the same areas. The sign of the orbital angular momentum density in a pair of lobes is positive, and that of the orbital angular momentum density in the other pair of lobes is negative. Moreover, the negative magnitude of the orbital angular momentum density is larger than the positive magnitude of the orbital angular momentum density. The linearly polarized angle affects not only the shape and the location of the lobes, but also the magnitude of the three components of the orbital angular momentum density. With increasing the topological charge, the distribution of the orbital angular momentum density expands, the magnitude of the orbital angular momentum density increases, and the shape of the lobe also slightly changes.
AUTHOR|(INSPIRE)INSPIRE-00367680; The ATLAS collaboration
2016-01-01
The ATLAS collaboration has performed precision measurements sensitive to the transverse mo- mentum of the Z/γ∗ bosons, both directly through the transverse momentum of the dilepton pair and through the angular decorrelation as measured in the φ∗ observable. These measurements are sensitive to soft resummation effects and hard jet emissions for small and large momentum transfers, respectively, probing QCD in a unique way. The studies carried out with 20.3 fb−1 of data at a center-of-mass energy of 8 TeV probe a wide dilepton invariant mass region from 12 GeV to 150 GeV, both integrated and differential in the dilepton rapidity. The measurements are compared to a variety of resummation calculations and parton shower Monte Carlos at up to NNLO+NNLL as well as fixed order predictions at NNLO QCD including NLO electroweak corrections. The precision measurement of angular distributions of the Drell-Yan lepton pairs around the Z-boson mass peak provide a stringent test of the underlying QCD dynamic of the Z...
A critique of the angular momentum sum rules and a new angular momentum sum rule
Bakker, B L G; Trueman, T L
2004-01-01
We show that the expressions in the literature for the tensorial structure of the hadronic matrix elements of the angular momentum operators J are incorrect. Given this disagreement with the published results, we have taken pains to derive the correct expressions in three different ways, two involving explicit physical wave packets and the third, totally independent, based upon the rotational properties of the state vectors. Surprisingly it turns out that the results are very sensitive to the type of relativistic spin state used to describe the motion of the particle i.e. whether a canonical (i.e. boost) state or a helicity state is utilized. We present results for the matrix elements of the angular momentum operators, valid in an arbitrary Lorentz frame, both for helicity states and canonical states. These results are relevant for the construction of angular momentum sum rules, relating the angular momentum of a nucleon to the spin and orbital angular momentum of its constituents. Moreover, we show that it i...
Influence of the angular momentum on nuclear fission
Tanikawa, Masashi [Tokyo Univ. (Japan). Faculty of Science
1996-03-01
The effects of the angular momentum on the mechanism of nuclear fission are studied about the reaction systems of compound nucleus of {sup 210}P and {sup 239}Np by the time-of-flight (TOF) method. The reaction systems in this work are {sup 209}Bi+P, {sup 206}Pb+{alpha}, {sup 206}Po+{alpha}, {sup 198}Pt+{sup 12}C, {sup 238}U+P and {sup 232}Th+{sup 7}Li. Target was prepared by vacuum evaporating of each about 100 {mu}g/cm{sup 2} of {sup 209}Bi, {sup 206}Pb and {sup 198}Pt on 10 {mu}g/cm{sup 2} of carbon film. On compound nucleus {sup 210}Po, {sup 210}Po fissions at Ex=45McV but it fissions after 1 or 2 neutrons emission at higher excited energy (Ex=57 MeV). TKE shows almost the same values except higher value of {sup 209}Bi+P. The decreasing tendency of width of TKE distribution with increasing the angular momentum is found at the first time in this work. The effect of the angular momentum on the fission is small in the case of low angular momentum. On the compound nucleus {sup 239}Np, the effects are shown at the asymmetric fission part of the mass distribution. (S.Y.)
Energy, momentum and angular momentum conservations in de Sitter gravity
Lu, Jia-An
2016-08-01
In de Sitter (dS) gravity, where gravity is a gauge field introduced to realize the local dS invariance of the matter field, two kinds of conservation laws are derived. The first kind is a differential equation for a dS-covariant current, which unites the canonical energy-momentum (EM) and angular momentum (AM) tensors. The second kind presents a dS-invariant current which is conserved in the sense that its torsion-free divergence vanishes. The dS-invariant current unites the total (matter plus gravity) EM and AM currents. It is well known that the AM current contains an inherent part, called the spin current. Here it is shown that the EM tensor also contains an inherent part, which might be observed by its contribution to the deviation of the dust particle’s world line from a geodesic. All the results are compared to the ordinary Lorentz gravity.
Angular Momentum of Dark Matter Black Holes
Frampton, Paul H
2016-01-01
The putative black holes which may constitute all the dark matter are described by a Kerr metric with only two parameters, mass M and angular momentum J. There has been little discussion of J since it plays no role in the upcoming attempt at detection by microlensing. Nevertheless J does play a central role in understanding the previous lack of detection, especially of CMB distortion. We explain why bounds previously derived from lack of CMB distortion are too strong for primordial black holes with J non-vanishing. Almost none of the dark matter black holes can be from stellar collapse, and nearly all are primordial, to avoid excessive CMB distortion.
Orbital angular momentum of mixed vortex beams
Bouchal, Z.; Kollárová, V.; Zemánek, Pavel; Čižmár, Tomáš
Bellingham : SPIE, 2007, 660907:1-7. ISBN 978-0-8194-6748-5. ISSN 0277-786X. [Czech-Polish-Slovak Conference Wave and Quantum Aspects of Contemporary Optics /15./. Liberec (CZ), 11.09.2006-15.09.2006] R&D Projects: GA MŠk(CZ) LC06007; GA MPO FT-TA2/059 Institutional research plan: CEZ:AV0Z20650511 Keywords : optical vortices * orbital angular momentum * spatial light modulator Subject RIV: BH - Optics, Masers, Lasers
Spin-orbit coupling and the conservation of angular momentum
Hnizdo, V.
2011-01-01
In nonrelativistic quantum mechanics, the total (i.e. orbital plus spin) angular momentum of a charged particle with spin that moves in a Coulomb plus spin-orbit-coupling potential is conserved. In a classical nonrelativistic treatment of this problem, in which the Lagrange equations determine the orbital motion and the Thomas equation yields the rate of change of the spin, the particle's total angular momentum in which the orbital angular momentum is defined in terms of the kinetic momentum ...
Beam moments and angular momentum in non-uniformly polarized beams
Serna, Julio; Piquero, Gemma
2009-05-01
The angular momentum of non-uniformly totally polarized beams is investigated using methods from the beam characterization approach. The relationship between the elements of the beam matrix for the two components of the field and the angular momentum is given. The unconventional distribution of the polarization across the beam profile could result in contributions to both the spin and orbital terms of the angular momentum. To illustrate this, a particular example with a vortex beam is considered.
Blanc, Thompson S. Le; Covey, Kevin R.; Stassun, Keivan G.
2011-01-01
Theoretical work suggests that a young star's angular momentum and rotation rate may be strongly influenced by magnetic interactions with its circumstellar disk. A generic prediction of these 'disk-locking' (DL) theories is that a disk-locked star will be forced to co-rotate with the Keplerian angular velocity of the inner edge of the disk. These theories have also been interpreted to suggest a correlation between young stars' rotation periods and the structural properties of their disks, suc...