PaperPanorama

Nuclear Theory·nucl-th

Tuesday·December 15, 2020

16 papers11 primary·5 cross-listed

  1. 12

    Explainable machine learning of the underlying physics of high-energy particle collisions

    Yue Shi Lai🇺🇸 · Duff Neill🇺🇸 · Mateusz Płoskoń🇺🇸 · Felix Ringer🇺🇸

    We present an implementation of an explainable and physics-aware machine learning model capable of inferring the underlying physics of high-energy particle collisions using the information encoded in the energy-momentum four-vectors of the final state particles. We demonstrate the proof-of-concept of our White Box AI approach using a Generative Adversarial Network (GAN) which learns from a DGLAP-based parton shower Monte Carlo event generator. We show, for the first time, that our approach leads to a network that is able to learn not only the final distribution of particles, but also the underlying parton branching mechanism, i.e. the Altarelli-Parisi splitting function, the ordering variable of the shower, and the scaling behavior. While the current work is focused on perturbative physics of the parton shower, we foresee a broad range of applications of our framework to areas that are currently difficult to address from first principles in QCD. Examples include nonperturbative and collective effects, factorization breaking and the modification of the parton shower in heavy-ion, and electron-nucleus collisions.

    hep-phnucl-exnucl-thPLB(2022)·36 citations
  2. 13

    Symmetry energy investigation with pion production from Sn+Sn systems

    G. Jhang · J. Estee · J. Barney · G. Cerizza · M. Kaneko · J. W. Lee · W. G. Lynch · T. Isobe · M. Kurata-Nishimura · T. Murakami · C. Y .Tsang · M. B. Tsang and 68 other authors

    In the past two decades, pions created in the high density regions of heavy ion collisions have been predicted to be sensitive at high densities to the symmetry energy term in the nuclear equation of state, a property that is key to our understanding of neutron stars. In a new experiment designed to study the symmetry energy, the multiplicities of negatively and positively charged pions have been measured with high accuracy for central Sn+Sn, Sn+Sn, and Sn+Sn collisions at with the SRIT Time Projection Chamber. While the uncertainties of individual pion multiplicities are measured to 4\%, those of the charged pion multiplicity ratios are measured to 2\%. We compare these data to predictions from seven major transport models. The calculations reproduce qualitatively the dependence of the multiplicities and their ratios on the total neutron to proton number in the colliding systems. However, the predictions of the transport models from different codes differ too much to allow extraction of reliable constraints on the symmetry energy from the data. This finding may explain previous contradictory conclusions on symmetry energy constraints obtained from pion data in Au+Au system. These new results call for better understanding of the differences among transport codes, and new observables that are more sensitive to the density dependence of the symmetry energy.

    nucl-exnucl-thPLB(2021)·69 citations
  3. 14

    The strongly intensive observable in pp collisions at LHC energies in the string fusion model

    V.V. Vechernin🇷🇺 · S.N. Belokurova🇷🇺

    The properties of the strongly intensive variable characterizing correlations between the number of particles in two separated rapidity interval in pp interactions at LHC energies are studied in the framework of the string fusion model. We perform the MC simulations of string distributions in the impact parameter plane to take into account the experimental conditions of pp collisions. We account the string fusion processes, leading to the formation of string clusters, embedding a finite lattice (a grid) in the impact parameter plane. As a result, we found the dependence of this variable both on the distance between the centers of the observation windows and their width for the minbias pp collisions at several initial energies. Analyzing these dependencies we can extract the important information on the properties of string clusters. We show that in pp collisions at LHC energies the string fusion effects have a significant impact on the behavior of this strongly intensive variable. The role of these effects is increasing with the initial energy and centrality of collisions. In particular, we found that the increase of this variable with initial energy takes place due to the growth of the portion of the fused string clusters in string configurations arising in pp interactions.

    hep-phnucl-thJ.Phys.Conf.Ser.(2020)·11 citations
  4. 15

    Octet and decuplet baryon self-energies in relativistic SU(3) chiral effective theory

    P. M. Copeland🇺🇸 · Chueng-Ryong Ji🇺🇸 · W. Melnitchouk🇺🇸

    The self-energies of the full set of flavor SU(3) octet and decuplet baryons are computed within a relativistic chiral effective theory framework. The leading nonanalytic chiral behavior is derived for the octet and decuplet masses, and a finite-range regularization consistent with Lorentz and gauge invariance is applied to account for the finite size of the baryons. Using a four-dimensional dipole form factor, the relative importance of various meson-baryon loop contributions to the self-energies is studied numerically as a function of the dipole range parameter and meson mass, and comparison is made between the relativistic results and earlier approximations within the heavy baryon limit.

    hep-phnucl-thPRD(2021)·5 citations
  5. 16

    Chemical potential on the lattice: Universal or Unique?

    Rajiv V. Gavai🇩🇪

    Lattice techniques are the most reliable ones to investigate non-perturbative aspects of quantum chromodynamics (QCD) such as its phase diagram in the temperature-baryon density plane. They are, however, well-known to be beset with a variety of problems as one increases the density. We address here the old question of placing the baryonic (quark) chemical potential on the lattice. We point out that it may have important consequences for the current and future experimental searches of QCD critical point.

    hep-lathep-phnucl-th1 citation

Affiliations

first authorsco-authorsvia INSPIRE