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Nuclear Theory·nucl-th

Thursday·February 23, 2017

9 papers—6 primary·3 cross-listed

All9Primary6Cross-lists3
  1. 07

    [Submitted on 21 Feb 2017] (cross-list from hep-ph)

    Twist-2 matching of transverse momentum dependent distributions

    Daniel Gutierrez-Reyes🇪🇸 · Ignazio Scimemi🇪🇸 · Alexey A. Vladimirov🇩🇪

    We systematically study the large- (or small-) matching of transverse momentum dependent (TMD) distributions to the twist-2 integrated parton distributions. Performing operator product expansion for a generic TMD operator at the next-to-leading order (NLO) we found the complete set of TMD distributions that match twist-2. These are unpolarized, helicity, transversity, pretzelosity and linearly polarized gluon distributions. The NLO matching coefficients for these distributions are presented. The pretzelosity matching coefficient is zero at the presented order, however, it is evident that it is non-zero in the following orders. This result offers a natural explanation of the small value of pretzelosity found in phenomenological fits. We also demonstrate that the cancellation of rapidity divergences by the leading order soft factor imposes the necessary requirement on the Lorentz structure of TMD operators, which is supported only by the TMD distributions of leading dynamical twist. Additionally, this requirement puts restrictions on the -definition in the dimensional regularization.

    Comments:
    7 pages; In v2 we correct a sign typo. Conclusions are unchanged
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1702.06558 [pdf]
    PLB(2017)·51 citations
  2. 08

    [Submitted on 22 Feb 2017] (cross-list from hep-ph)

    Multiplicity Dependence of Non-extensive Parameters for Strange and Multi-Strange Particles in Proton-Proton Collisions at TeV at the LHC

    Arvind Khuntia🇮🇳 · Sushanta Tripathy🇮🇳 · Raghunath Sahoo🇮🇳 · Jean Cleymans🇿🇦

    The transverse momentum () spectra in proton-proton collisions at = 7 TeV, measured by the ALICE experiment at the LHC are analyzed with a thermodynamically consistent Tsallis distribution. The information about the freeze-out surface in terms of freeze-out volume, temperature and the non-extenisivity parameter, , for , , and are extracted by fitting the spectra with Tsallis distribution function. The freeze-out parameters of these particles are studied as a function of charged particle multiplicity density (). In addition, we also study these parameters as a function of particle mass to see any possible mass ordering. The strange and multi-strange particles show mass ordering in volume, temperature, non-extensive parameter and also a strong dependence on multiplicity classes. It is observed that with increase in particle multiplicity, the non-extensivity parameter, decreases, which indicates the tendency of the produced system towards thermodynamic equilibration. The increase in strange particle multiplicity is observed to be due to the increase of temperature and not to the size of the freeze-out volume.

    Comments:
    Version similar to the published version in EPJA
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1702.06885 [pdf]
    EPJA(2017)·52 citations
  3. 09

    [Submitted on 22 Feb 2017] (cross-list from astro-ph.SR)

    The Core-Collapse Supernova Explosion Mechanism

    B. Müller (Queen's University Belfast, Monash University)🇬🇧

    The explosion mechanism of core-collapse supernovae is a long-standing problem in stellar astrophysics. We briefly outline the main contenders for a solution and review recent efforts to model core-collapse supernova explosions by means of multi-dimensional simulations. We discuss several suggestions for solving the problem of missing or delayed neutrino-driven explosions in three-dimensional supernova models, including -- among others -- variations in the microphysics and large seed perturbations in convective burning shells. Focusing on the neutrino-driven mechanism, we summarise currents efforts to predict supernova explosion and remnant properties based on first-principle models and on more phenomenological approaches.

    Comments:
    Invited review to appear in the International Astronomical Union Proceedings Serie (IAU Symposium 329, "The Lives and Death Throes of Massive Stars"). 8 pages, 2 figures
    Subjects:
    Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1702.06940 [pdf]
    IAU Symp.(2016)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE