Nuclear Theory·nucl-th
6 papers—2 primary·4 cross-listed
This is a review of selected recent developments in finite-temperature lattice QCD. The focus is on the properties of the chiral crossover region, deconfinement and fluctuations of conserved charges, the equation of state, properties of heavy quarkonia and reconstruction of spectral functions.
Thomas D. Cohen🇺🇸 · Brian Mc Peak🇺🇸 · Bendeguz Offertaler🇺🇸
Nucleon-antinucleon annihilation in the large limit of QCD in the Witten regime of fixed velocity is considered with a focus on the spin and isospin dependence of the annihilation cross-section. In general, time-reversal and isospin invariance restricts the annihilation cross-section to depend on 6 independent energy-dependent terms. At large , a spin-flavor symmetry emerges in the theory that acts to further restrict the dependence of the annihilation cross-section to three of these terms; the other terms amount to corrections. Assuming dominance of the leading order terms, several identities are derived that relate annihilation in different spin-isospin channels. A key prediction is that for unpolarized nucleons in Witten kinematics, the proton-antiproton annihilation cross-section should be equal to the proton-antineutron annihilation cross-section up to corrections of relative order . Unpolarized nucleon-antinucleon annihilation data appears to be consistent with this expectation.
Takahiro M. Doi🇯🇵 · Krzysztof Redlich🇵🇱 · Chihiro Sasaki🇵🇱 · Hideo Suganuma🇯🇵
We investigate correlations of the Polyakov loop fluctuations with eigenmodes of the lattice Dirac operator. Their analytic relations are derived on the temporally odd-number size lattice with the normal non-twisted periodic boundary condition for the link-variables. We find that the low-lying Dirac modes yield negligible contributions to the Polyakov loop fluctuations. This property is confirmed to be valid in confined and deconfined phase by numerical simulations in SU(3) quenched QCD. These results indicate that there is no direct, one-to-one correspondence between confinement and chiral symmetry breaking in QCD in the context of different properties of the Polyakov loop fluctuation ratios.
I.V. Anikin🇷🇺 · V.M. Braun🇩🇪 · N. Offen🇩🇪
Following the 12 GeV upgrade, a dedicated experiment is planned with the Hall B CLAS12 detector at Jefferson Lab, with the aim to study electroproduction of nucleon resonances at high photon virtualities up to GeV. In this work we present a QCD-based approach to the theoretical interpretation of these upcoming results in the framework of light-cone sum rules that combine perturbative calculations with dispersion relations and duality. The form factors are thus expressed in terms of light-front wave functions at small transverse separations, called distribution amplitudes. The distribution amplitudes can therefore be determined from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations. The results of the corresponding next-to-leading order calculation are presented and compared with the existing data. We find that the form factors are dominated by the twist-four distribution amplitudes that are related to the -wave three-quark wave functions of the , i.e. to contributions of orbital angular momentum.
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