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Nuclear Theory·nucl-th

Friday·May 13, 2022

8 papers—2 primary·6 cross-listed

All8Primary2Cross-lists6
  1. 03

    [Submitted on 12 May 2022] (cross-list from hep-ph)

    Search for baryon junctions in photonuclear processes and isobar collisions at RHIC

    Nicole Lewis🇺🇸 · Wendi Lv🇨🇳 · Mason Alexander Ross🇺🇸 · Chun Yuen Tsang🇺🇸 · James Daniel Brandenburg🇺🇸 · Zi-Wei Lin🇺🇸 · Rongrong Ma🇺🇸 · Zebo Tang🇨🇳 · Prithwish Tribedy🇺🇸 · Zhangbu Xu🇺🇸

    During the early development of Quantum Chromodynamics, it was proposed that baryon number could be carried by a non-perturbative Y-shaped topology of gluon fields, called the gluon junction, rather than by the valence quarks as in the QCD standard model. A puzzling feature of ultra-relativistic nucleus-nucleus collisions is the apparent substantial baryon excess in the midrapidity region that could not be adequately accounted for in most conventional models of quark and diquark transport. The transport of baryonic gluon junctions is predicted to lead to a characteristic exponential distribution of net-baryon density with rapidity and could resolve the puzzle. In this context we point out that the rapidity density of net-baryons near midrapidity indeed follows an exponential distribution with a slope of as a function of beam rapidity in the existing global data from A+A collisions at AGS, SPS and RHIC energies. To further test if quarks or gluon junctions carry the baryon quantum number, we propose to study the absolute magnitude of the baryon vs. charge stopping in isobar collisions at RHIC. We also argue that semi-inclusive photon-induced processes (/A) at RHIC kinematics provide an opportunity to search for the signatures of the baryon junction and to shed light onto the mechanisms of observed baryon excess in the mid-rapidity region in ultra-relativistic nucleus-nucleus collisions. Such measurements can be further validated in A+A collisions at the LHC and /A collisions at the EIC.

    Comments:
    12 pages, 6 figures, Submitted to EPJC
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2205.05685 [pdf]
    EPJC(2024)·37 citations
  2. 04

    [Submitted on 11 May 2022] (cross-list from hep-ph)

    Combining nonperturbative transverse momentum dependence with TMD evolution

    J. O. Gonzalez-Hernandez🇮🇹 · T. C. Rogers🇺🇸 · N. Sato🇺🇸

    Central to understanding the nonpertubative, intrinsic partonic nature of hadron structure are the concepts of transverse momentum dependent (TMD) parton distribution and fragmentation functions. A TMD factorization approach to the phenomenology of semi-inclusive processes that includes evolution, higher orders, and matching to larger transverse momentum, is ultimately necessary for reliably connecting with phenomenologically extracted nonperturbative structures, especially when widely different scales are involved. In this paper, we will address some of the difficulties that arise when phenomenological techniques that were originally designed for very high energy applications are extended to studies of hadron structures, and we will solidify the connection between standard high energy TMD implementations and the more intuitive, parton model based approaches to phenomenology that emphasize nonperturbative hadron structure. In the process, we will elaborate on differences between forward and backward TMD evolution, which in the context of this paper we call "bottom-up" and "top-down" approaches, and we will explain the advantages of a bottom-up strategy. We will also emphasize and clarify the role of the integral relations that connect TMD and collinear correlation functions. We will show explicitly how they constrain the nonperturbative "-functions" of standard Collins-Soper-Sterman (CSS) implementations of TMD factorization. This paper is especially targeted toward phenomenologists and model builders who are interested in merging specific nonperturbative models and calculations (including lattice QCD) with TMD factorization at large . Our main result is a recipe for incorporating nonperturbative models into TMD factorization, and for constraining their parameters in a way that matches to perturbative QCD and evolution.

    Comments:
    41 pages, 12 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2205.05750 [pdf]
    PRD(2022)·23 citations
  3. 05

    [Submitted on 12 May 2022] (cross-list from hep-ph)

    Towards the discovery of novel states: radiative and hadronic transitions

    B. Martín-González🇪🇸 · P. G. Ortega🇪🇸 · D. R. Entem🇪🇸 · F. Fernández🇪🇸 · J. Segovia🇪🇸

    The properties of the -meson family () are still not well determined experimentally because the specific mechanisms of formation and decay remain poorly understood. Unlike heavy quarkonia, i.e. the hidden heavy quark-antiquark sectors of charmonium () and bottomonium (), the -mesons cannot annihilate into gluons and they are, consequently, more stable. The excited states, lying below the lowest strong-decay -threshold, can only undergo through radiative decays and hadronic transitions to the ground state, which then decays weakly. As a result of this, a rich spectrum of narrow excited states below the -threshold appear, whose total widths are two orders of magnitude smaller than those of the excited levels of charmonium and bottomonium. In a different article, we determined bottom-charmed meson masses using a non-relativistic constituent quark model which has been applied to a wide range of hadron physical observables, and thus the model parameters are completely constrained. Herein, continuing to our study of the sector, we calculate the relevant radiative decay widths and hadronic transition rates between states which are below -threshold. This shall provide the most promising signals for discovering excited states that are below the lowest strong-decay -threshold. Finally, our results are compared with other models to measure the reliability of the predictions and point out differences.

    Comments:
    13 pages, 9 tables. arXiv admin note: text overlap with arXiv:1601.05093
    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:
    2205.05950 [pdf]
    PRD(2022)·27 citations
  4. 06

    [Submitted on 12 May 2022] (cross-list from nucl-ex)

    Analysis of 2-Body Central Events for from up to and for at and

    L. Manduci🇫🇷 · O. Lopez🇫🇷 · D. Durand🇫🇷 · R. Bougault🇫🇷 · E. Vient🇫🇷 · M. Pâlog🇫🇷 · B. Borderie🇫🇷 · I. Lombardo🇮🇹 · G. Verde🇫🇷

    A study of medium-mass heavy-ion reactions leading to two fragments in the exit channel from barrier to 18A MeV is proposed. A special focus is made on fission and quasi-fission for events with two fragments () in the exit channel selected. Reactions induced by projectiles on and on at energies ranging from MeV to MeV were analyzed. Using the fragment () multiplicity equal to 2, fission and quasi-fission events were studied for the lowest beam energies using the fission fragment charge distributions, the total kinetic energy distribution (TKE) and its standard deviation . For the lighter system it is still possible to observe fission events from incomplete fusion. At variance, for the heavier system, Xenon on gold target only quasi-fission is evidenced. The study of the events characterized by two fragments in the final channel shows that fission, related to fusion in the entrance channel, disappears around 20A MeV for both systems. At lower energies (8A, 12A and 15A MeV) for the Sn target, an evolution with increasing energies towards an asymmetric fission mode is displayed in the fragment charge distributions. This trend can be attributed to the increasing angular momentum as indicated by the out-of-plane angular distribution for light charged particles. The same effect is also observed in the case of the gold target at 15A MeV. However, for this heavier system, a strong memory of the entrance channel leading to quasi-fission is evidenced. A comparison with the Viola systematics, moreover, shows a deviation, greater for the heavier system than for system. A complete understanding of the above results would certainly require precise model calculations at these energies.

    Comments:
    12 pages, 13 figures, submitted to PRC
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2205.05968 [pdf]
    0 citations
  5. 07

    [Submitted on 12 May 2022] (cross-list from hep-ph)

    The vector boson transverse momentum distributions

    Ignazio Scimemi🇪🇸

    The transverse momentum dependent distributions (TMD) are an essential part of the factorization theorems in vector boson production. They are non-perturbative, double scale dependent functions that asymptotically match onto collinear parton distributions functions (PDF). Once TMD are expressed using PDF, one observes that they are sensitive to the choice and quality of PDF sets (PDF bias). A solution to this problem is found and discussed. Nevertheless the main source of error on vector boson spectra still comes from PDF uncertainty propagation.

    Comments:
    Proceedings of Rencontres de Moriond 2022, QCD, 19-26 march 2022
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2205.05997 [pdf]
    1 citation
  6. 08

    [Submitted on 12 May 2022] (cross-list from hep-th)

    Aspects of univalence in holographic axion models

    Matteo Baggioli🇨🇳 · Sebastian Grieninger🇪🇸 · Sašo Grozdanov🇬🇧 · Zhenkang Lu🇸🇪

    Univalent functions are complex, analytic (holomorphic) and injective functions that have been widely discussed in complex analysis. It was recently proposed that the stringent constraints that univalence imposes on the growth of functions combined with sufficient analyticity conditions could be used to derive rigorous lower and upper bounds on hydrodynamic dispersion relation, i.e., on all terms appearing in their convergent series representations. The results are exact bounds on physical quantities such as the diffusivity and the speed of sound. The purpose of this paper is to further explore these ideas, investigate them in concrete holographic examples, and work towards a better intuitive understanding of the role of univalence in physics. More concretely, we study diffusive and sound modes in a family of holographic axion models and offer a set of observations, arguments and tests that support the applicability of univalence methods for bounding physical observables described in terms of effective field theories. Our work provides insight into expected `typical' regions of univalence, comparisons between the tightness of bounds and the corresponding exact values of certain quantities characterizing transport, tests of relations between diffusion and bounds that involve chaotic pole-skipping, as well as tests of a condition that implies the conformal bound on the speed of sound and a complementary condition that implies its violation.

    Comments:
    v2: minor revision, matching the published version
    Subjects:
    High Energy Physics — Theory (hep-th); Strongly Correlated Electrons (cond-mat.str-el); Mathematical Physics (math-ph); math.MP (math.MP); nlin.CD (nlin.CD); Nuclear Theory (nucl-th)
    arXiv:
    2205.06076 [pdf]
    JHEP(2022)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE