Search

We derive relativistic hydrodynamic equations with a dynamical spin degree of freedom on the basis of an entropy-current analysis. The first and second laws of local thermodynamics constrain possible structures of the constitutive relations including a spin current and the antisymmetric part of the (canonical) energy-momentum tensor. Solving the obtained hydrodynamic equations within the linear-mode analysis, we find spin-diffusion modes, indicating that spin density is damped out after a characteristic time scale controlled by transport coefficients introduced in the antisymmetric part of the energy-momentum tensor in the entropy-current analysis. This is a consequence of mutual convertibility between spin and orbital angular momentum., 7 pages

Based on the chiral kinetic equations of motion, spin polarizations of various quarks, due to the magnetic field induced by spectator protons as well as the quark-antiquark vector interaction, are studied within a partonic transport approach. Although the magnetic field in QGP enhances the splitting of the spin polarizations of partons compared to the results under the magnetic field in vacuum, the spin polarizations of s and s ¯ quarks are also sensitive to the quark-antiquark vector interaction, challenging that the different Λ and Λ ¯ spin polarization is a good measure of the magnetic field in relativistic heavy-ion collisions. It is also found that there is no way to obtain the large splitting of the spin polarization between Λ and Λ ¯ at s N N = 7.7 GeV with partonic dynamics.

We calculate a class of polarized fermion string scattering amplitudes (PFSSA) at arbitrary mass levels. We discover that, in the hard scattering limit, the functional forms of the non-vanishing PFSSA at each fixed mass level are independent of the choices of spin polarizations. This result justifies and extends Gross conjecture on high energy string scattering amplitudes to the fermionic sector. In addition, this peculiar property of hard PFSSA is to be compared with the usual spin polarization dependence of the hard polarized fermion field theory scatterings., Comment: 15 pages, no figure

The concept of the Wigner function is used to construct a semi-classical kinetic theory describing the evolution of the axial-current phase-space density of spin-1/2 particles in the relaxation time approximation. The resulting approach can be used to study spin-polarization effects in relativistic matter, in particular, in heavy-ion collisions. An expression for the axial current based on the classical treatment of spin is also introduced and we show that it is consistent with earlier calculations using Wigner functions. Finally, we derive non-equilibrium corrections to the spin tensor, which are used to define, for the first time, the structure of spin transport coefficients in relativistic matter., 6 pages

We propose a new method, using the Andreev reflection at superconductors, to measure parity violation induced by the standard electroweak theory, which in turn constrains the possible parity-violating effects of new physics. The weak neutral currents induce parity-violating, marginal effective operators, though quite tiny, in superconductors. We estimate their effects on superconducting gaps and propose a method to measure the parity-violation from the spin polarization effect, when electrons or holes get Andreev-reflected at the interface between normal metal and a superconductor. Such polarization effects might be comparable to the atomic parity violation and thus naturally give an interesting bound on certain models of new physics, that couples to electrons, such as Majorana mass of active neutrinos or doubly charged Higgs., 11 pages, 6 figures. v2: minor changes, to appear in Physics Letters B

Recent STAR measurements suggest a difference in the global spin polarization between hyperons and anti-hyperons, especially at relatively low collision beam energy. One possible cause of this difference is the potential presence of in-medium magnetic field. In this study, we investigate the phenomenological viability of this interpretation. Using the AMPT model framework, we quantify the influence of different magnetic field evolution scenarios on the size of the polarization difference in a wide span of collision beam energies. We find that such difference is very sensitive to the lifetime of the magnetic field. For the same lifetime, the computed polarization difference only mildly depends on the detailed form of its evolution. Assuming magnetic polarization as the mechanism to enhance anti-hyperon signal while suppress hyperon signal, we phenomenologically extract an upper limit on the needed magnetic field lifetime in order to account for the experimental data. The so-obtained lifetime values are in a quite plausible ballpark and follow approximately the scaling relation of being inversely proportional to the beam energy. Possible implications on other magnetic field related effects are also discussed., 7 pages, 5 figures

Dense neutron matter with recently developed BSk19 and BSk21 Skyrme effective forces is considered in magnetic fields up to $10^{20}$ G at zero temperature. The breaking of the rotational symmetry by the magnetic field leads to the differentiation between the pressures along and perpendicular to the field direction which becomes significant in the fields $H>H_{th}\sim10^{18}$ G. The longitudinal pressure vanishes in the critical field $10^{18}, Comment: 7 pages, 3 figures; published online 7 December 2011

Theoretical studies of the deuteron beam transmission through the unpolarized target predict the appearance of tensor polarization in transmitted beam due to deuteron spin dichroism. If only nuclear interaction is taken into account when considering this phenomenon, the tensor polarization (spin dichroism) of transmitted beam has a positive sign which agree with conception of different “transverse dimensions” of deuteron in different spin state. However, the first experiments with deuteron with the energy of 5–20 MeV transmitting through unpolarized carbon target show that accumulated polarization in a deuteron beam firstly, has a negative sign and secondly, the increase in the target thickness (and primary deuteron energy) does not bring about the increase in the value of polarization. This can be explained by changing the sign of deuteron spin dichroism in the considered energy interval. In this Letter is shown that the account of the Coulomb interaction by means of the Coulomb-nuclear interference, can qualitatively explain behavior of deuteron spin dichroism in a carbon target in the energy interval from 5 to 20 MeV.

In inclusive deep-inelastic lepton-hadron scattering multi-photon exchange between the leptonic and the hadronic part of the process causes single spin asymmetries. The asymmetries exist for a polarized target as well as a polarized incoming or outgoing lepton, if the polarization vector has a component transverse with respect to the reaction plane. The spin dependent parts of the single polarized cross sections are suppressed like $\alpha_{em} m_{pol}/Q$ - where $m_{pol}$ denotes the mass of the polarized particle - compared to the leading terms of the cross section for unpolarized or double-polarized deep-inelastic scattering. Both the target and the beam spin asymmetry are evaluated in the parton model. In the calculation only quark-quark correlators are included. While this approximation turns out to be justified for the lepton spin asymmetries, it is not sufficient for the target asymmetry., Comment: 9 pages, 1 figure, minor changes, final version, to appear in Phys. Lett. B

The properties of spin polarized neutron matter are studied both at zero and finite temperature within the framework of the Brueckner--Hartree--Fock formalism, using the Argonne v18 nucleon-nucleon interaction. The free energy, energy and entropy per particle are calculated for several values of the spin polarization, densities and temperatures together with the magnetic susceptibility of the system. The results show no indication of a ferromagnetic transition at any density and temperature., Comment: 19 pages, 5 figures

We investigate the pseudoscalar transition form factors of nucleon for quasi-elastic scattering and \Delta resonance production in tau-neutrino nucleon scattering via the charged current interactions. Although the pseudoscalar form factors play an important role for the \tau production in neutrino-nucleon scattering, these are not known well. In this article, we examine their effects in quasi-elastic scattering and \Delta resonance production and find that the cross section, Q^{2} distribution, and spin polarization of the produced \tau^{\pm} leptons are quite sensitive to the pseudoscalar form factors., Comment: 7 pages, 3 figures

A general three quark bound state satisfying the Pauli principle, and conserving angular momentum and isospin, is used to investigate the spin structure of nucleons at high $x$. It is shown if {$F_{1n}/F_{1p}$$\to$1/4}, then both $A_{1p}$ and $A_{1n}$, as well as quark spin distribution $\Delta u/u$, will approach 1 as $x$$\to$1 in polarized deep inelastic scattering. The spin distribution $\Delta d/d$ does not approach 1, but is bound by the limits $-{1/3}\le\Delta d/d\le 0$ for any $x$., Comment: The quark function \phi(123) satisfies the constraint \phi(123)+\phi(213)=\phi(132)+\phi(231), which is less restrictive than the symmetry condition \phi(123)=\phi(132) originally stated. This means the constraint d\downarrow=u\uparrow does not hold at all x. (It still applies for x--> 1.) The main conclusions that \Delta u/u--> 1 as x--> 1, but -1/3

The semileptonic decays of polarised top quarks are analysed for a general chirality-conserving tbW vertex. We calculate double differential distributions for the charged lepton and the neutrino to order \alpha_s in the QCD coupling. We present these QCD corrections in terms of compact parameterisations that should be useful for the future investigation of the structure of the top decay vertex on the basis of large data samples., Comment: 7 pages, 2 figures, Latex

In this work we provide explicit calculations that support the conclusions stated in Phys. Rev. Lett. 111, 039102 (2013) (comment), regarding recent literature on transverse polarization. We also compare and contrast two methods of deriving spin sum rules., 11 pages, Latex

We study the gluon polarization contribution at the quark model renormalization scale to the proton spin, $\Gamma$, in the chiral bag model. It is evaluated by taking the expectation value of the forward matrix element of a local gluon operator in the axial gauge $A^+=0$. It is shown that the confining boundary condition for the color electric field plays an important role. When a solution satisfying the boundary condition for the color electric field, which is not the conventionally used but which we favor, is used, the $\Gamma$ has a positive value for {\it all} bag radii and its magnitude is comparable to the quark spin polarization. This results in a significant reduction in the relative fraction of the proton spin carried by the quark spin, which is consistent with the small flavor singlet axial current measured in the EMC experiments., Comment: Corrections to figures

We study the spin asymmetries of inclusive π + , π 0 , π − and η production in the interaction of polarized with non polarized protons, in the frame of a two components model. Particle production in the model is assumed to consist of conventional fragmentation plus recombination. We obtain a good description of experimental data. Thomas precession in the recombination process seems to be responsible for the single spin asymmetry.

In order to test modern theories of two-nucleon bound and scattering states, we have measured the spin polarization of ejectile protons in the electrodisintegration reaction d( e → ,e′ p → )n . Compared with spin-averaged observations, these observables offer the potential of enhanced sensitivity to details of the reaction process. The experiment was carried out in quasielastic kinematics ( q μ q μ =−2m p ω=−0.38 GeV2/c2). Protons were detected at two angles corresponding to neutron recoil momenta pr of 0 and 100 MeV/c. Full nonrelativistic calculations of the polarization transfer components sl and st, including leading order relativistic contributions, describe our measurements well, but calculations of the induced polarization sn at pr=100 MeV/c underpredict the experimental result.

Further progress in testing the structure of the electroweak interaction and in the precise determination of the weak coupling constants gA and gV by studying the decay of free polarized neutrons is presently limited by the accuracy to which the polarization of cold neutron beams can be measured. Current techniques of polarization analysis are based on neutron optical mirror reflection, and are systematically restricted to a precision of ≥0.25%. In this letter we introduce a new technique whereby systematic effects are strongly suppressed. The basic idea is to use an opaque spin filter, i.e., with analysing efficiency close to 100%, in analogy to an efficient polarizing foil in light optics. The method was successfully tested at the Institut Laue-Langevin in Grenoble in a comparison study, in which a well-defined neutron beam was analysed with two very different kinds of spin filters: a solid-state polarized proton target, using spin-dependent neutron scattering, and a spin filter of polarized 3 He gas, where spin-dependent neutron absorption is exploited. A difference in the neutron polarization of only 0.026(55)% was obtained, which demonstrates the power of the method.

The spin asymmetries in the momentum distributions of the neutron and proton in He-3 are obtained from a Faddeev calculation of the ground state. Both two- and three-body configurations are found to be important. Using a PWIA model and measurements of the spin asymmetries in (3)((p) over right arrow,2p) and (3)((p) over right arrow,pn) quasielastic scattering at 197 MeV the asymmetries in the momentum distributions are experimentally determined. Good agreement between theory and experiment is found up to initial nucleon momenta of 300 MeV/c.

Spin-polarized fragments 14B and 15B produced in intermediate-energy projectile fragmentation reactions were implanted in a Mg single crystal, and the electric quadrupole moments Q for 14B and 15B were determined by β-NMR spectroscopy. The results, |Q( 14 B)| = 29.84 ± 0.75 mb and |Q( 15 B)| = 38.01 ± 1.08 mb , are compared wi models. Shell-model calculations with 0ωω model space, using effective charges commonly accepted in this mass region, predict values about 40 % larger than the experimental Q (15B). Agreement is obtained when a much smaller effective charge for neutrons is employed. The Q (14B) sensitively reflects small admixture of the d 3 2 neutron configuration and, when combined with the previously obtained data for the magnetic moment, determines reliably the ground state wave function of 14B.

By making use of the phenomenon of ejectile spin polarization in the projectile fragmentation reaction as a tool to produce polarized radioactive nuclei, the magnetic moments of 14B and 15B have been determined by the β-NMR measurement, to be μ( 14 B ) = (1.185±0.005) μn and μ( 15 B ) = (2.659±0.015) μn where μn is the nuclear magneton. The comparison of the results with shell model calculations suggests that the single-particle energy of the neutron s 1 2 orbit shifts downwards considerably compared with the d 5 2 orbit in 14B, and also indicates the importance of Jπ = 2+ configurations of neutrons in the sd shell. Thus, it is demonstrated that the measurement of magnetic moments provides useful information on the nuclear structure in the newly accessible region of light-mass unstable nuclei.

In this paper we study experimental and theoretical aspects of the transverse spin polarization effects in τ + τ − production at LEP-I and at 10 GeV centre-of-mass energies. For this purpose QED and experimental cut-off effects have to be studied simultaneously and therefore a Monte Carlo technique is used. We present a method calculating the size of missing transverse spin effects in KORALZ and missing higher-order QED corrections in KORALB. Our aim is to determine the size of the related uncertainties for the two programs. Later, we discuss a transverse spin dependent observable and we show that with present statistics and systematics it can be measured at LEP. As an example of an experimental set-up we use the properties of the ALEPH detector. We discuss effects of the radiative corrections for our transverse spin correlation observable and for the visible total cross section.

A pair of spin rotators has been installed in the electron ring of HERA. Longitudinal spin polarizations up to 65% have been reached reproducibly during dedicated measurement time. This is the first time that longitudinal spin polarization has been produced in a high energy electron storage ring.

Ejectile spin polarization P in intermediate-energy projectile fragmentation has been measured for different targets and incident energies using the RIPS fragment separator at RIKEN. The observed P as a function of the fragment momentum shows a systematic change when the atomic number of the target or the incident energy is varied. Most remarkably, P does not vanish at the momentum corresponding to the beam velocity, indicating an important effect which has not been considered in the previously proposed model.

P - and T -odd interaction produces a spin distribution with the spins directed along the radius in spherically symmetric quantum systems. Due to the spin-dependent strong interaction this spin hedgehog contributes to P - and T -odd effects in neutron scattering, nuclear moments, etc. In deformed nuclei the P - and T -odd interaction produces a collective magnetic quadrupole moment. This moment induces P - and T -violating effects in atoms and molecules.

Spin polarization of projectile fragments 37 K and 39 Ca has been observed in 106 A MeV 40 Ca+ 197 Au collisions n ear the grazing angle. The fragment polarization was determined to be positive for points on the high momentum side of the distribution and negative for points on the low momentum side. At the highest energy, the spin polarization follows the same systematics observed at much lower energies, where it is believed that very different reaction mechanisms dominate. A simple fragmentation model explained the observed momentum dependence of the polarization quite well.

We estimate the contribution to the proton spin due to the orbital angular momentum of the pion cloud in a physical proton.

Discrete γ -ray transitions have been observed up to spin ∼30 in 122 Xe. A dramatic change in the mechanism by which this nucleus generates angular momentum is observed to occur above spin 20. The collective rotation of a prolate nucleus is replaced at high spin by a regime of non-collective single-particle states. Particularly favoured states are observed at high spin and by comparison with the predictions of the cranked Nilsson and Woods-Saxon models specific single-particle configurations are suggested. This gives information on the spectrum of single-particle states and the active orbitals which build high angular momentum states in this mass region.

In time-differential measurements it is shown that 1s electrons of single-electron 16O(3−) ions have their spin polarized on emergence from magnetized thin Fe foils into vacuum. The mean degree of polarization deduced, p 1 s =0.060(6) , is approximately half of what is observed inside the Fe foil.

The spin polarization, P , of 12 B ejectiles has been measured for projectile fragmentation reactions induced by a 40.6 MeV/u 14 N beam. Large values of P were observed, showing a characteristic dependence on the outgoing momentum including a sign change occurring at a momentum corresponding to the beam velocity. This behavior corresponds well with simple kinematical arguments based on projectile fragmentation models.

A Continuum limit of the two-dimensional ZN spin model is found and classical field equations are derived. It is also shown that in its first approximation this field theory reduces toe Villain form of the spin system.

Cross sections and polarization functions for elastic scattering of identical particles with spin 1 are compared in the relativistic (s,0)+(s− 1 2 , 1 2 ) invariant theory, for arbitrary spin, and the ( 1 2 , 1 2 ) invariant Proca theory. Heavy-ion scattering is suggested to test high spin theories.

The observation of the spin rotation of nuclei at high spin via unresolved γ-transitions using the transient magnetic field effect allows the determination of average g -factors 〈 g 〉 and yields information on average transition quadrupole moments 〈 Q t 〉 at high spin. The method is demonstrated in a first experiment with 162 Yb yielding 〈g〉=0.24(5) and 〈 Q t 〉=400(100)fm 2 for states with spins between 20 and 32.

The decay of the entry states in 158 Yb populated in the reactions of 149 MeV 20 Ne with 144,146 Nd has been investigated with the Spin Spectrometer gated by a Ge counter. The average excitation energy, the γ -ray spectra and the angular distributions as a function of multiplicity suggest a region of non-collective behavior at low spin. At higher spin collective characteristics are apparent, but between I ≈40 and 49 a strong stretched dipole component is seen. Above I ≈49 no additional dipole transitions are observed. These characteristics are discussed in terms of recent calculations.

The energies of the yrast levels extending up to I = 28 in even-even actinide nuclei were analyzed in terms of an angular velocity expansion E rot ( I ) = ∑ i =1 n α i ω I 2 i with n = 2−7 to test the application of this expansion to high spin. A strong ω 2 -dependence is observed for the Variable Moment of Inertia model (VMI) with two parameters α i ( ω 2 ), particularly at the higher spins. There is a marked difference in the ω 2 -dependence, of these parameters between the N = 142 and other nuclei studied in this region to indicate structure effects are present at the higher spin.

High-spin states in 150Sm have been investigated with the OSIRIS spectrometer. An alternating parity (octupole) band was found to develop above spin I = 8. A crossing of the positive-parity sequence of the outupole band with an aligned two-quasiparticle band has been observed around spin I = 16. It is suggested that above spin I = 16 reflection asymmetric and symmetric shapes coexist in 150Sm.

Magnetic transverse form factors of 12− and 14− states in 208Pb are calculated in a fully self-consistent manner utilizing the effective density dependent interaction D1. Reduction of the strength due to the RPA polarization and the ground state correlations is observed and found to be independent of the momentum transfer. Nuclear structure implications particular to two close lying 12− states are discussed.

λ hypernuclear states with spin polarization are shown to be populated through nucleon and γ decays of compound λ hypernuclei produced by resonant (π+, K+xnypγ) reactions. The low-lying Λ-hypernuclear states have the λ hyperon in the lowest 1 s 1 2 orbit. The intrinsic spin of Λ (sλ) is also shown to be well-polarized. These spin-oriented hypernuclear states useful for spectroscopic studies of hypernuclei such as electromagnetic moments and weak decays.

Utilizing the transient magnetic field interaction for nuclear recoils passing through an iron foil we have measured precessions for discrete γ -ray transitions in the reactions 24 Mg( 136 Xe, 4n) 156 Dy at 544, 570 and 650 MeV incident beam energy. The results are interpreted in terms of average g -factors for high spin regions in 156 Dy.

We compute the contribution induced by the chiral anomaly in the total helicity of fermionic constituents of a polarized hadron. We unify previous perturbative and nonperturbative determinations and we show that due to nonperturbative QCD effects the EMC measurements of polarized structure functions may be consistent with a large quark spin component, even in the absence of gluon polarization.

Odd-spin negative-parity states to spin 17 have been identified in 152Gd from in-beam spectra of (α, xn) reactions. The level scheme is well accounted for by a simple model coupling an octupole vibration to the transitional core.

Using the current-current interaction picture for elastic pp scattering, excellent fits are obtained for all data above 12Gev/ c which covers twelve orders of magnitude. It can fit all polarization data, and imply considerable structure in spin-dependent differential cross sections.

Spin polarization of residual nuclei was studied in ( 14 N , α) reactions by means of a γ-ray circular polarization measurement. Variations with target nucleus, scattering angle and Q-value were systematically investigated. The 197 Au ( 6 Li , α) reaction was investigated for comparison also. We argue the existence of competition between slow multi-step and fast direct- type processes in the ( 14 N , α) reactions on the basis of the observed polarization.

Internal waves, corresponding to the propagation of a projectile through the interior of a target nucleus, have been postulated to describe some features of elastic scattering. It is shown that the measurement of the spin polarization in α + 40 Ca inelastic scattering can confirm the existence of this very surprising phenomenon.

We investigate the stability, with respect to spin fluctuations, of neutron matter containing a small proton admixture. We establish conditions under which strongly ssymmetric nuclear matter could acquire a permanent magnetization. It is shown that, if the protons are localized, the system becomes unstable with respect to spin fluctuations for arbitrarily weak proton-neutron spin interactions. For non-localized protons, there exists a threshold value of the spin interaction above which the system can develop a spontaneous polarization.

The non-abelian spin 3 2 chiral gauge anomaly is evaluated both by topological and by explicit heat kernel methods. The result is three times the corresponding spin 1 2 anomaly. Reasons are given why this result was to be expected.

Effective and band moments of inertia are obtained from calculated discrete spin states for the nuclei 168 Hf, 166 Yb, 162 Yb and 160 Er. A comparison to recent experimental values indicates that a change to a large triaxial deformation occurs in one of the nuclei.