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Nuclear Theory·nucl-th

Monday·June 19, 2023

7 papers—3 primary·4 cross-listed

All7Primary3Cross-lists4
  1. 01

    [Submitted on 15 Jun 2023]

    The paradox of coherent photoproduction in incoherent interactions

    Spencer R. Klein🇺🇸

    The Good-Walker (GW) paradigm relates coherent and incoherent exclusive reactions to the average target configuration and its nucleonic and partonic fluctuations. In it, coherent photoproduction occurs when the target remains in the ground state, while, in incoherent photoproduction, the target breaks up. However, the GW paradigm fails to explain the observation of coherent vector meson photoproduction accompanied by nuclear breakup in ultra-peripheral collisions (UPCs) , and in peripheral relativistic heavy-ion collisions. In the latter, hundreds of particles can be created. This writeup will explore this paradox, and also present an alternate, semi-classical approach toward coherent production: adding the amplitudes with an appropriate propagator. The semi-classical approach explains the transverse momentum dependence of exclusive vector meson production in UPCs, but does not address the target final state. I will address these two approaches, and suggest possible future work to resolve the paradox \cite{Klein:2023zlf}.

    Comments:
    5 pages; presented at Deep Inelastic Scattering 2023
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2306.09494 [pdf]
    1 citation
  2. 02

    [Submitted on 15 Jun 2023]

    Open charm phenomenology with a multi-stage approach to relativistic heavy-ion collisions

    Mayank Singh🇺🇸 · Manu Kurian🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

    We study open charm flavor observables in Pb+Pb collision at TeV within the MARTINI framework. The space-time expansion of the quark-gluon plasma is described using the hydrodynamical approach-MUSIC with IP-Glasma initial conditions. The model parameters, including the viscous coefficients, were obtained from a recent Bayesian model-to-data comparison. We evolve heavy quarks in this background using Langevin dynamics while incorporating their collisional and radiative processes in the medium. The sensitivity of charm observables to the IP-Glasma initial state, bulk evolution, and centrality of the collision is studied. We find that the elliptic flow of open charm flavor has a strong dependence on the fluctuating initial conditions in addition to the strength of the interaction of heavy quarks with the medium constituents. Within this framework, the nuclear suppression factor and elliptic flow of D-mesons act as efficient probes to study the initial stages of heavy-ion collisions, transport coefficients associated with QGP medium as well as heavy quark interactions.

    Comments:
    7 pages, 4 figures; Version published in Phys. Rev. C
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2306.09514 [pdf]
    PRC(2023)·28 citations
  3. 03

    [Submitted on 16 Jun 2023]

    Early-times Yang-Mills dynamics and the characterization of strongly interacting matter with statistical learning

    Matthew R. Heffernan🇨🇦 · Charles Gale🇨🇦 · Sangyong Jeon🇨🇦 · Jean-François Paquet🇺🇸

    In ultrarelativistic heavy-ion collisions, a plasma of deconfined quarks and gluons is formed within fm/c of the nuclei's impact. The complex dynamics of the collision before fm/c is often described with parametric models, which affect the predictivity of calculations. In this work, we perform a systematic analysis of LHC measurements from Pb-Pb collisions, by combining an \emph{ab-initio} model of the early stage of the collisions with a hydrodynamic model of the plasma. We obtain state-of-the-art constraints on the shear and bulk viscosity of quark-gluon plasma. We mitigate the additional cost of the ab-initio initial conditions by combining Bayesian model averaging with transfer learning, allowing us to account for important theoretical uncertainties in the hydrodynamics-to-hadron transition. We show that, despite the apparent strong constraints on the shear viscosity, metrics that balance the model's predictivity with its degree of agreement with data do not prefer a temperature-dependent specific shear viscosity over a constant value. We validate the model by comparing with discriminating observables not used in the calibration, finding excellent agreement.

    Comments:
    7 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2306.09619 [pdf]
    PRL(2024)·41 citations

Affiliations

first authorsco-authorsvia INSPIRE