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Nuclear Theory·nucl-th

Wednesday·September 6, 2023

26 papers—14 primary·12 cross-listed

All26Primary14Cross-lists12
  1. 15

    [Submitted on 31 Aug 2023] (cross-list from nucl-ex)

    Upper Limit on the Chiral Magnetic Effect in Isobar Collisions at the Relativistic Heavy-Ion Collider

    STAR Collaboration: M. I. Abdulhamid · B. E. Aboona · J. Adam · J. R. Adams · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · A. Aitbaev · I. Alekseev · E. Alpatov · A. Aparin and 345 other authors

    The chiral magnetic effect (CME) is a phenomenon that arises from the QCD anomaly in the presence of an external magnetic field. The experimental search for its evidence has been one of the key goals of the physics program of the Relativistic Heavy-Ion Collider. The STAR collaboration has previously presented the results of a blind analysis of isobar collisions (, ) in the search for the CME. The isobar ratio () of CME-sensitive observable, charge separation scaled by elliptic anisotropy, is close to but systematically larger than the inverse multiplicity ratio, the naive background baseline. This indicates the potential existence of a CME signal and the presence of remaining nonflow background due to two- and three-particle correlations, which are different between the isobars. In this post-blind analysis, we estimate the contributions from those nonflow correlations as a background baseline to , utilizing the isobar data as well as Heavy Ion Jet Interaction Generator simulations. This baseline is found consistent with the isobar ratio measurement, and an upper limit of 10% at 95% confidence level is extracted for the CME fraction in the charge separation measurement in isobar collisions at GeV.

    Comments:
    8 pages, 4 figures
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2308.16846 [pdf]
    PRResearch(2024)·25 citations
  2. 16

    [Submitted on 1 Sept 2023] (cross-list from hep-ph)

    Jet quenching in anisotropic flowing matter

    Matvey V. Kuzmin🇷🇺 · Xoán Mayo López🇪🇸 · Jared Reiten🇺🇸 · Andrey V. Sadofyev🇪🇸

    We study the interplay between the flow and hydrodynamic gradients in jet quenching at first order in opacity. We find that the mixed flow-gradient contributions in jet quenching are enhanced by the medium length, and survive in the eikonal limit, dominating over other medium evolution effects. The resulting modification to the jet quenching parameter and energy loss rate can be substantial, leading to ample phenomenological implications. We also compute the leading corrections to the jet broadening due to the flow velocity gradients, and consider the leading gradient effects in the medium-induced branching for general kinematics, extending the recent considerations of jets in inhomogeneous media. These results can be straightforwardly coupled to matter simulations, providing new opportunities for jet tomography in heavy-ion collisions.

    Comments:
    36 pages, 6 figures, published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2309.00683 [pdf]
    PRD(2024)·43 citations
  3. 17

    [Submitted on 2 Sept 2023] (cross-list from nucl-ex)

    Side Ridge in Ar + KCl Collisions at 1.8 GeV/nucleon with Reaction-Plane Deblurring

    Pawel Danielewicz · Herbert Stroebele · Pierre Nzabahimana

    Reaction-plane deblurring is applied to the triple-differential distributions of protons, deuterons and negatively charged pions from central Ar + KCl collisions at 1.8 GeV/nucleon, measured with the LBL-GSI Streamer Chamber, to yield distributions relative to the true reaction plane of the collisions. Within the reaction plane and in the forward cm rapidity region a side ridge away from the beam axis is observed: the distributions peak away from the beam direction for protons and deuterons but not for pions. These findings are consistent with a source of particles moving at an in-plane transverse velocity of ~0.1 c. Transport pBUU calculations yield results in semi-quantitative agreement with those from the data.

    Comments:
    5 pages, 3 figures
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2309.00813 [pdf]
    PRC(2023)·3 citations
  4. 18

    [Submitted on 2 Sept 2023] (cross-list from astro-ph.HE)

    Electrical conductivity of warm neutron star crust in magnetic fields: Neutron-drip regime

    Arus Harutyunyan · Armen Sedrakian · Narine T. Gevorgyan · Mekhak V. Hayrapetyan

    We compute the anisotropic electrical conductivity tensor of the inner crust of a compact star at non-zero temperature by extending a previous work on the conductivity of the outer crust. The physical scenarios, where such crust is formed, involve proto-neutron stars born in supernova explosions, binary neutron star mergers and accreting neutron stars. The temperature-density range studied covers the transition from a non-degenerate to a highly degenerate electron gas and assumes that the nuclei form a liquid, i.e., the temperature is above the melting temperature of the lattice of nuclei. The electronic transition probabilities include (a) the dynamical screening of electron-ion interaction in the hard-thermal-loop approximation for the QED plasma, (b) the correlations of the ionic component in a one-component plasma, and (c) finite nuclear size effects. The conductivity tensor is obtained from the Boltzmann kinetic equation in relaxation time approximation accounting for the anisotropies introduced by a magnetic field. The sensitivity of the results towards the matter composition of the inner crust is explored by using several compositions of the inner crust which were obtained using different nuclear interactions and methods of solving the many-body problem. The standard deviation of relaxation time and components of the conductivity tensor from the average are below except close to crust-core transition, where non-spherical nuclear structures are expected. Our results can be used in dissipative magneto-hydrodynamics (MHD) simulations of warm compact stars.

    Comments:
    13 pages, 13 figures, 5 tables
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    2309.00893 [pdf]
    PRC(2024)·9 citations
  5. 19

    [Submitted on 4 Sept 2023] (cross-list from astro-ph.HE)

    The proto-neutron star inner crust in a multi-component plasma approach

    H. Dinh Thi🇫🇷 · A. F. Fantina🇫🇷 · F. Gulminelli🇫🇷

    Proto-neutron stars (PNS) are born hot, with temperatures exceeding a few times K. In these conditions, the PNS crust is expected to be made of a Coulomb liquid composed of an ensemble of different nuclear species. We perform a study of the beta-equilibrated PNS crust in the liquid phase in a self-consistent multi-component plasma (MCP) approach, thus allowing us to consistently calculate the impurity parameter, often taken as a free parameter in cooling simulations. We developed a self-consistent MCP approach at finite temperature using a compressible liquid-drop description of the ions, with surface parameters adjusted to reproduce experimental masses. The treatment of the ion centre-of-mass motion was included through a translational free-energy term accounting for in-medium effects. The results of self-consistent MCP calculations are systematically compared with those performed in a perturbative and in the one-component plasma treatment. We show that the inclusion of non-linear mixing terms arising from the ion centre-of-mass motion leads to a breakdown of the ensemble equivalence between the one-component and MCP approach. Our findings illustrate that the abundance of light nuclei becomes important, eventually dominating the distribution at higher density and temperature. This is reflected in the impurity parameter, which, in turn, may have a potential impact on NS cooling. For practical applications, we also provide a fitting formula for the impurity parameter in the PNS inner crust. Our results obtained within a self-consistent MCP approach show important differences in the prediction of the PNS composition with respect to those obtained with a one-component or a perturbative MCP approximation, particularly in the deeper region of the crust. This highlights the importance of a full, self-consistent MCP calculation for reliable predictions of the PNS crust composition.

    Comments:
    16 pages, 15 figures, accepted for publication in Astronomy and Astrophysics
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    2309.01527 [pdf]
    Astron.Astrophys.(2023)·10 citations
  6. 20

    [Submitted on 4 Sept 2023] (cross-list from astro-ph.HE)

    Unified equations of state for cold non-accreting neutron stars with Brussels-Montreal functionals. IV. Role of the symmetry energy in pasta phases

    N. N. Shchechilin · N. Chamel · J. M. Pearson

    Our previous investigation of neutron-star crusts, based on the functional BSk24, led to a substantial reduction of the pasta mantle when Strutinsky integral and pairing corrections were added on top of the fourth-order extended Thomas-Fermi method (ETF). Here, our earlier calculations are widened to a larger set of functionals within the same family, and we find that the microscopic corrections weaken significantly the influence of the symmetry energy. In particular, the correlation observed at the pure ETF level between the density for the onset of pasta formation and the symmetry energy vanishes, not only for the coefficient but also for the symmetry-energy values at the relevant densities. Moreover, the inclusion of microscopic corrections results in a much lower abundance of pasta for all functionals.

    Comments:
    11 pages, 4 figures
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    2309.01591 [pdf]
    PRC(2023)·20 citations
  7. 21

    [Submitted on 5 Sept 2023] (cross-list from nucl-ex)

    Nuclear charge radii of silicon isotopes

    Kristian König · Julian C. Berengut · Anastasia Borschevsky · Alex Brinson · B. Alex Brown · Adam Dockery · Serdar Elhatisari · Ephraim Eliav · Ronald F. Garcia Ruiz · Jason D. Holt · Bai-Shan Hu · Jonas Karthein and 11 other authors

    The nuclear charge radius of Si was determined using collinear laser spectroscopy. The experimental result was confronted with ab initio nuclear lattice effective field theory, valence-space in-medium similarity renormalization group, and mean field calculations, highlighting important achievements and challenges of modern many-body methods. The charge radius of Si completes the radii of the mirror pair Ar - Si, whose difference was correlated to the slope of the symmetry energy in the nuclear equation of state. Our result suggests \,MeV, which agrees with complementary observables.

    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2309.02037 [pdf]
    PRL(2024)·51 citations
  8. 22

    [Submitted on 5 Sept 2023] (cross-list from hep-ph)

    Hadronization dynamics from the spectral representation of the gauge invariant quark propagator

    Caroline S. R. Costa🇺🇸 · Alberto Accardi🇺🇸 · Andrea Signori🇮🇹

    Using the spectral representation of the quark propagator we study the Dirac decomposition of the gauge invariant quark propagator, whose imaginary part describes the hadronization of a quark as this interacts with the vacuum. We then demonstrate the formal gauge invariance of the so-called jet mass, that is of the coefficient of the chiral-odd part of the gauge invariant propagator, that can be expressed in any gauge as the first moment of the chiral-odd quark spectral function. This is therefore revealed to be a \textit{bona fide} QCD observable encoding aspects of the dynamical mass generation in the QCD vacuum, and is furthermore experimentally measurable in specific twist-3 longitudinal-transverse asymmetries in DIS and in semi-inclusive electron-positron collisions. In light-like axial gauges, we also obtain a new sum rule for the spectral function associated with the gauge fixing vector. We finally present a gauge-dependent formula that connects the second moment of the chiral-even coefficient of the quark spectral function to invariant mass generation and final state rescattering in the hadronization of a quark. Finding twist-4 experimental observables sensitive to this quantity is left for future work.

    Comments:
    Contribution to DIS2023: XXX International Workshop on Deep-Inelastic Scattering and Related Subjects, Michigan State University, USA, 27-31 March 2023
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2309.02118 [pdf]
    0 citations
  9. 23

    [Submitted on 5 Sept 2023] (cross-list from hep-ph)

    Acceleration of a polarized neutron by internal weak nuclear forces

    M. Donaire🇪🇸

    It is proven that a polarized neutron gets accelerated by internal nuclear forces along the coherent rotation of its spin. The net force upon the neutron arises from the weak nuclear interactions between its quarks. It is the result of the simultaneous breaking of parity symmetry by the chiral interactions between the neutron's quarks, and of time-reversal symmetry along the inversion of their spins. The variation of the neutron's kinetic momentum is accompanied with the transfer of an equivalent momentum to the fields of the Z and W bosons that mediate the interactions, in the opposite direction. The effect is linear in Fermi's constant. Using the simplest hadron models, an upper bound of the order of meters per second is estimated for the velocity variation of the polarized neutron along the spin-flip process.

    Comments:
    15-page article + 12-page appendix + 1 figure
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2309.02293 [pdf]
    1 citation
  10. 24

    [Submitted on 5 Sept 2023] (cross-list from astro-ph.HE)

    Nontrivial features in the speed of sound inside neutron stars

    Debora Mroczek · M. Coleman Miller · Jacquelyn Noronha-Hostler · Nicolas Yunes

    Measurements of neutron star masses, radii, and tidal deformability have direct connections to nuclear physics via the equation of state (EoS), which for the cold, catalyzed matter in neutron star cores is commonly represented as the pressure as a function of energy density. Microscopic models with exotic degrees of freedom display nontrivial structure in the speed of sound () in the form of first-order phase transitions and bumps, oscillations, and plateaus in the case of crossovers and higher-order phase transitions. We present a procedure based on Gaussian processes to generate an ensemble of EoSs that include nontrivial features. Using a Bayesian analysis incorporating measurements from X-ray sources, gravitational wave observations, and perturbative QCD results, we show that these features are compatible with current constraints. We investigate the possibility of a global maximum in that occurs within the densities realized in neutron stars -- implying a softening of the EoS and possibly an exotic phase in the core of massive stars -- and find that such a global maximum is consistent with, but not required by, current constraints.

    Comments:
    Version submitted to PRD, 31 pages, 9 figures
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
    arXiv:
    2309.02345 [pdf]
    PRD(2024)·70 citations
  11. 25

    [Submitted on 5 Sept 2023] (cross-list from nucl-ex)

    Implications of correlations and fluctuations in small systems

    Debasish Das🇮🇳

    The small collision systems like p+p and p+A collisions have shown new features like A+A collisions in the relativistic regime. These new aspects in small systems which have altered our research and understanding on the two-particle correlation measurements have been provided. Additionally, a critical observation of the fluctuation measurements provides new ways to infer such novel happening in the small collision systems. The ongoing and future endeavors towards the new measurements are also discussed.

    Comments:
    Published in Int. J. of Mod. Phys. A
    Subjects:
    Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2309.02364 [pdf]
    Int.J.Mod.Phys.A(2022)·1 citation
  12. 26

    [Submitted on 5 Sept 2023] (cross-list from hep-ph)

    SU(3) parity doubling in cold neutron star matter

    Eduardo S. Fraga🇧🇷 · Rodrigo da Mata🇧🇷 · Jürgen Schaffner-Bielich🇩🇪

    We present a phenomenological model to investigate the chiral phase transition characterized by parity doubling in dense, beta equilibrated, cold matter. Our model incorporates effective interactions constrained by SU(3) relations and considers baryonic degrees of freedom. By constraining the model with astrophysical data and nuclear matter properties, we find a first-order phase transition within realistic values of the slope parameter L. The inclusion of the baryon octet and negative parity partners, along with a chiral-invariant mass , allows for a non-massless chiral symmetric phase. Through exploration of parameter space, we identify parameter sets satisfying mass and radius constraints without requiring a partonic phase. The appearance of the parity partner of the nucleon, the N(1535) resonance, suppresses strangeness, pushing hyperonization to higher densities. We observe a mild first-order phase transition to the chirally restored phase, governed by . Our calculations of surface tension highlight its strong dependence on . The existence of mixed phases is ruled out since they become energetically too costly. We compare stars with metastable and stable cores using both branches of the equation of state. Despite limited lifespans due to low surface tension values, phase conversion and star contraction could impact neutron stars with masses around 1.3 solar masses or more. We discuss some applications of this model in its non-zero temperatures generalization and scenarios beyond beta equilibrium that can provide insights into core-collapse supernovae, proto-neutron star evolution, and neutron star mergers. Core-collapse supernovae dynamics, influenced by chiral symmetry restoration and exotic hadronic states, affect explosion mechanisms and nucleosynthesis.

    Comments:
    22 pages, 10 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    2309.02368 [pdf]
    PRD(2023)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE