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Nuclear Theory·nucl-th

Wednesday·July 26, 2017

10 papers—5 primary·5 cross-listed

All10Primary5Cross-lists5
  1. 06

    DPS in CGC: Double Quark Production and Effects of Quantum Statistics

    Alex Kovner🇨🇱 · Amir H. Rezaeian🇨🇱

    We consider forward inclusive production of two quarks in the high energy p-A collisions in the CGC formalism. We demonstrate that the production cross-section is determined by the convolution of the proton generalized double transverse momentum-dependent distribution (2GTMD) functions with two independent eikonal scattering amplitudes: the product of two dipoles and a quadrupole. We explicitly demonstrate that the quadrupole amplitude term accounts for all the (initial and final state) effects of quantum statistics for identical fermions, and the correlations due to these effects. We also demonstrate that the effects due to quantum statistics (entirely encoded in the quadrupole) are parametrically leading contributions to the correlated particle production at large . For non-identical quarks the quadrupole term also leads to correlated production which has characteristics similar to the HBT effect.

    ↳ hep-phhep-exnucl-exnucl-thPRD(2017)·33 citations
  2. 07

    Nucleon form factors in dispersively improved Chiral Effective Field Theory I: Scalar form factor

    J. M. Alarcón🇺🇸 · C. Weiss🇺🇸

    We propose a method for calculating the nucleon form factors (FFs) of -parity-even operators by combining Chiral Effective Field Theory (EFT) and dispersion analysis. The FFs are expressed as dispersive integrals over the two-pion cut at . The spectral functions are obtained from the elastic unitarity condition and expressed as products of the complex partial-wave amplitudes and the timelike pion FF. EFT is used to calculate the ratio of the partial-wave amplitudes and the pion FF, which is real and free of rescattering in the -channel ( method). The rescattering effects are then incorporated by multiplying with the squared modulus of the empirical pion FF. The procedure results in a marked improvement compared to conventional EFT calculations of the spectral functions. We apply the method to the nucleon scalar FF and compute the scalar spectral function, the scalar radius, the -dependent FF, and the Cheng-Dashen discrepancy. Higher-order chiral corrections are estimated through the low-energy constants. Results are in excellent agreement with dispersion-theoretical calculations. We elaborate several other interesting aspects of our method. The results show proper scaling behavior in the large- limit of QCD because the EFT calculation includes and intermediate states. The squared modulus of the timelike pion FF required by our method can be extracted from Lattice QCD calculations of vacuum correlation functions of the operator at large Euclidean distances. Our method can be applied to the nucleon FFs of other operators of interest, such as the isovector-vector current, the energy-momentum tensor, and twist-2 QCD operators (moments of generalized parton distributions).

    ↳ hep-phhep-latnucl-thPRC(2017)·31 citations
  3. 08

    Multi-angle calculation of the matter-neutrino resonance near an accretion disk

    Shashank Shalgar🇺🇸

    We perform a numerical study of the matter-neutrino resonance in a multi-angle calculation in the vicinity of an accretion disk. We assume thermally distributed neutrino and anti-neutrino fields emitted by two-dimensional disk that is homogeneous and isotropic; the electrons are assumed to be at constant density. We compare the the result of this computation to that obtained using single-angle approximation. We investigate the robustness of matter-neutrino resonance in environment surrounding accretion disks by progressively relaxing the single angle approximation. We find that the multi-angle results in the present simplified model do not support a robust resonance mechanism as suggested by the single angle treatment. We also discuss the context under which matter-neutrino resonance may be important in future studies.

    ↳ hep-phastro-ph.HEnucl-thJCAP(2018)·20 citations
  4. 09

    Entrainment in Superfluid Neutron Star Crusts: Hydrodynamic Description and Microscopic Origin

    N. Chamel

    In spite of the absence of viscous drag, the neutron superfluid permeating the inner crust of a neutron star cannot flow freely, and is entrained by the nuclear lattice similarly to laboratory superfluid atomic gases in optical lattices. The role of entrainment on the neutron superfluid dynamics is reviewed. For this purpose, a minimal hydrodynamical model of superfluidity in neutron-star crusts is presented. This model relies on a fully four-dimensionally covariant action principle. The equivalence of this formulation with the more traditional approach is demonstrated. In addition, the different treatments of entrainment in terms of dynamical effective masses or superfluid density are clarified. The nuclear energy density functional theory employed for the calculations of all the necessary microscopic inputs is also reviewed, focusing on superfluid properties. In particular, the microscopic origin of entrainment and the different methods to estimate its importance are discussed.

    ↳ astro-ph.HEcond-mat.quant-gasnucl-thJ.Low Temp.Phys.(2017)·44 citations
  5. 10

    Entropy Production During Hadronization of a Quark-Gluon Plasma

    Tamas S. Biro🇭🇺 · Zsolt Schram🇭🇺 · Laszlo Jenkovszky🇺🇦

    We revisit the physical pictures for the hadronization of quark-gluon plasma, concentrating on the problem of entropy production during processes where the number of degrees of freedom is seemingly reduced due to color confinement. Based on observations on Regge trajectories we propose not having an infinite tower of hadronic resonances. We discuss possible entropy production mechanisms far from equilibrium in terms of stochastic dynamics.

    ↳ hep-phcond-mat.stat-mechnucl-thEPJA(2018)·5 citations

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