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Nuclear Theory·nucl-th

Friday·September 12, 2025

11 papers—9 primary·2 cross-listed

All11Primary9Cross-lists2
  1. 10

    [Submitted on 10 Sept 2025] (cross-list from hep-ph)

    Constraining the Resolution Length of Quark-Gluon Plasma with New Jet Substructure Measurements

    Arjun Srinivasan Kudinoor🇺🇸 · Daniel Pablos🇪🇸 · Krishna Rajagopal🇺🇸

    We show that recent measurements of substructure-dependent jet suppression constrain the value of the resolution length of the droplets of quark-gluon plasma (QGP) formed in heavy ion collisions. This resolution length, , is defined such that the medium can only resolve partons within a jet shower that are separated by more than . We first use Hybrid Model calculations to reproduce ALICE measurements of the scaled Soft Drop angle for anti- jets reconstructed from charged-particle tracks. We find that the narrowing of the -distribution in PbPb collisions compared to pp collisions that is seen in the ALICE data rules out a picture of fully coherent energy loss () where each entire parton shower loses energy to the plasma as if it were a single unresolved colored object. We then use Hybrid Model calculations to reproduce ATLAS measurements of , the Soft Drop angle obtained by applying the Soft Drop grooming procedure to all charged-particle tracks in jets reconstructed from skinny subjets. Our analysis demonstrates that the ATLAS measurements of for such jets as a function of are inconsistent with a picture of fully incoherent energy loss () in which every splitting in a parton shower is immediately resolved by the plasma. We find that our Hybrid Model calculations agree best with the ATLAS measurements if QGP has a finite, nonzero, resolution length . For the first time, jet substructure measurements are constraining the resolution length of QGP from below, as well as from above.

    Comments:
    8 passionate pages, 3 fascinating figures, and substantive supplemental material
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2509.08881 [pdf]
    6 citations
  2. 11

    [Submitted on 10 Sept 2025] (cross-list from hep-ph)

    Microscopic calculation of two-particle-two-hole meson-exchange currents in Ar and asymmetric scaling properties for neutrino and electron scattering

    V.L. Martinez-Consentino🇪🇸 · J. Segovia🇪🇸 · J.E. Amaro🇪🇸

    We present a microscopic calculation of two particle-two hole meson exchange current response functions in asymmetric nuclei, with particular emphasis on the Ar nucleus. Employing a relativistic mean-field and relativistic Fermi gas framework, we compute the nuclear response for Ar and compare it with that of the symmetric Ca nucleus, analyzing the role of proton-neutron imbalance. The model incorporates distinct proton and neutron Fermi momenta to accurately capture the nuclear dynamics of systems with . Our results indicate that using Ca as a proxy for Ar leads to a systematic error of approximately 10\%. Additionally, we propose an asymmetric scaling formula to obtain the 2p2h response for arbitrary nuclei from the C response, improving the description of asymmetric nuclei. Finally, we benchmark our predictions against inclusive electron scattering and neutrino cross sections.

    Comments:
    16 pages, 9 figures. Article revised. Accepted in Phys. Rev. D
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2509.08916 [pdf]
    PRD(2025)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE