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Nuclear Theory·nucl-th

Wednesday·April 26, 2023

9 papers—3 primary·6 cross-listed

All9Primary3Cross-lists6
  1. 04

    [Submitted on 24 Apr 2023] (cross-list from hep-ph)

    Probing gluon saturation via diffractive jets in ultra-peripheral nucleus-nucleus collisions

    E. Iancu🇫🇷 · A.H. Mueller🇺🇸 · D.N. Triantafyllopoulos🇮🇹 · S.Y. Wei🇨🇳

    We argue that semi-inclusive photo-production of a pair of hard jets via coherent diffraction in nucleus-nucleus ultra-peripheral collisions at high energy is a golden channel to study gluon saturation. The dominant contribution is the diffractive production of three jets in an asymmetric configuration. Two of the jets are hard and propagate at nearly central pseudo-rapidities. The third jet is semi-hard, with transverse momentum comparable to the nuclear saturation momentum, and is well separated in pseudo-rapidity from the hard dijets. The emission of the semi-hard jet allows for strong scattering, thus avoiding the "higher-twist" suppression of the exclusive dijet production due to colour transparency. We compute the trijet cross-section using the diffractive TMD factorisation which emerges from the CGC effective theory at high energy. The cross-section is controlled by gluon saturation, which leaves its imprints on the structure of the final state, notably on the rapidity distribution.

    Comments:
    23 pages, 9 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2304.12401 [pdf]
    EPJC(2023)·29 citations
  2. 05

    [Submitted on 24 Apr 2023] (cross-list from hep-ph)

    Polarised parton distribution functions and proton spin

    Peng Cheng🇨🇳 · Yang Yu🇨🇳 · Hui-Yu Xing🇨🇳 · Chen Chen🇨🇳 · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇨🇳

    Supposing there exists an effective charge which defines an evolution scheme for both unpolarised and polarised parton distribution functions (DFs) that is all-orders exact and using Ansätze for hadron-scale proton polarised valence quark DFs, constrained by flavour-separated axial charges and insights from perturbative quantum chromodynamics, predictions are delivered for all proton polarised DFs at the scale GeV. The pointwise behaviour of the predicted DFs and, consequently, their moments, compare favourably with results inferred from data. Notably, flavour-separated singlet polarised DFs are small. On the other hand, the polarised gluon DF, , is large and positive. Using our result, we predict and that experimental measurements of the proton flavour-singlet axial charge should return .

    Comments:
    8 pages, 6 figures, 3 tables
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2304.12469 [pdf]
    PLB(2023)·29 citations
  3. 06

    [Submitted on 24 Apr 2023] (cross-list from hep-ph)

    Ultra-peripheral nuclear collisions

    C. A. Bertulani🇺🇸

    This article presents a very brief review of the physics of Ultra-Peripheral Collisions (UPC) at the Large Hadron Collider (LHC) and other nuclear facilities. I discuss several processes of interest such as electron-position pair production, the anti-hydrogen atom, giant resonances, exotic meson production and parton distribution functions.

    Comments:
    10 pages, 12 figures, Proceedings of the 44th Symposium on Nuclear Physics, Cocoyoc, Mexico, January 2023 - Additional comments and references
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2304.12475 [pdf]
    J.Phys.Conf.Ser.(2023)·5 citations
  4. 07

    [Submitted on 24 Apr 2023] (cross-list from hep-ph)

    Double Parton Distributions from Euclidean Lattice

    Jian-Hui Zhang🇨🇳

    We show that double parton distributions, which are important in describing double parton scattering processes in hadron collisions, can be directly computed from correlations of equal-time nonlocal Euclidean operators on the lattice in the large hadron momentum limit. We demonstrate this by taking the unpolarized color singlet quark double parton distribution as an example, and present a factorization formula connecting the corresponding lightcone and Euclidean correlations. This opens a new possibility of studying multiparton interactions on the Euclidean lattice.

    Comments:
    5 pages, 1 figure, typos corrected
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    2304.12481 [pdf]
    14 citations
  5. 08

    [Submitted on 25 Apr 2023] (cross-list from hep-ph)

    An Augmented QCD Phase Portrait: Mapping Quark-Hadron Deconfinement for Hot, Dense, Rotating Matter under Magnetic Field

    Gaurav Mukherjee🇮🇳 · D. Dutta🇮🇳 · D. K. Mishra🇮🇳

    The quark-hadron transition that happens in ultra-relativistic heavy-ion collisions is expected to be influenced by the effects of rotation and magnetic field, both present due to the geometry of a generic non-head-on impact. We augment the conventional -- planar phase diagram for QCD matter by extending it to a multi-dimensional domain spanned by temperature , baryon chemical potential , external magnetic field and angular velocity . Using two independent approaches, one from a rapid rise in entropy density and another dealing with a dip in the squared speed of sound, we identify deconfinement in the framework of a modified statistical hadronization model. We find that the deconfinement temperature decreases nearly monotonically with increasing and with the most prominent drop (by nearly to MeV) in occurring when all the three quasi-control (via collision energy and centrality) parameters are simultaneously tuned to finite values that are typically achievable in present and upcoming heavy-ion colliders.

    Comments:
    7 pages, 4 figures, Accepted for publication in PLB
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2304.12643 [pdf]
    PLB(2023)·14 citations
  6. 09

    [Submitted on 25 Apr 2023] (cross-list from hep-th)

    Charged participants and their electromagnetic fields in an expanding fluid

    Ashutosh Dash🇩🇪 · Ankit Kumar Panda🇮🇳

    We investigate the space-time dependence of electromagnetic fields produced by charged participants in an expanding fluid. To address this problem, we need to solve the Maxwell's equations coupled to the hydrodynamics conservation equation, specifically the relativistic magnetohydrodynamics (RMHD) equations, since the charged participants move with the flow. To gain analytical insight, we approximate the problem by solving the equations in a fixed background Bjorken flow, onto which we solve Maxwell's equations. The dynamical electromagnetic fields interact with the fluid's kinematic quantities such as the shear tensor and the expansion scalar, leading to additional non-trivial coupling. We use mode decomposition of Green's function to solve the resulting non-linear coupled wave equations. We then use this function to calculate the electromagnetic field for two test cases: a point source and a transverse charge distribution. The results show that the resulting magnetic field vanishes at very early times, grows, and eventually falls at later times.

    Comments:
    13 pages, 5 figures. Minor revisions and a new figure showing domain of influence added
    Subjects:
    High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Fluid Dynamics (physics.flu-dyn)
    arXiv:
    2304.12977 [pdf]
    PLB(2024)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE