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Nuclear Theory·nucl-th

Tuesday·March 26, 2019

15 papers—10 primary·5 cross-listed

All15Primary10Cross-lists5
  1. 11

    Simple non-perturbative resummation schemes beyond mean-field II: thermodynamics of scalar theory in 1+1 dimensions at arbitrary coupling

    Paul Romatschke🇺🇸

    Recently, non-perturbative approximate solutions were presented that go beyond the well-known mean-field resummation. In this work, these non-perturbative approximations are used to calculate finite temperature equilibrium properties for scalar theory in two dimensions such as the pressure, entropy density and speed of sound. Unlike traditional approaches, it is found that results are well-behaved for arbitrary temperature/coupling strength, are independent of the choice of the renormalization scale , and are apparently converging as the resummation level is increased. Results also suggest the presence of a possible analytic cross-over from the high-temperature to the low-temperature regime based on the change in the thermal entropy density.

    ↳ hep-thcond-mat.str-elhep-latnucl-thMod.Phys.Lett.A(2020)·12 citations
  2. 12

    Non-quadratic improved Hessian PDF reweighting and application to CMS dijet measurements at 5.02 TeV

    Kari J. Eskola🇫🇮 · Petja Paakkinen🇫🇮 · Hannu Paukkunen🇫🇮

    Hessian PDF reweighting, or "profiling", has become a widely used way to study the impact of a new data set on parton distribution functions (PDFs) with Hessian error sets. The available implementations of this method have resorted to a perfectly quadratic approximation of the initial function before inclusion of the new data. We demonstrate how one can take into account the first non-quadratic components of the original fit in the reweighting, provided that the necessary information is available. We then apply this method to the CMS measurement of dijet pseudorapidity spectra in proton-proton (pp) and proton-lead (pPb) collisions at 5.02 TeV. The measured pp dijet spectra disagree with next-to-leading order (NLO) theory calculations using the CT14 NLO PDFs, but upon reweighting the CT14 PDFs, these can be brought to a much better agreement. We show that the needed proton-PDF modifications also have a significant impact on the predictions for the pPb dijet distributions. Taking the ratio of the individual spectra, the proton-PDF uncertainties effectively cancel, giving a clean probe of the PDF nuclear modifications. We show that these data can be used to further constrain the EPPS16 nuclear PDFs and strongly support gluon nuclear shadowing at small and antishadowing at around .

    ↳ hep-phnucl-thEPJC(2019)·52 citations
  3. 13

    Nucleosynthesis in heavy-ion collisions at the LHC via the Saha equation

    Volodymyr Vovchenko🇩🇪 · Kai Gallmeister🇩🇪 · Jürgen Schaffner-Bielich🇩🇪 · Carsten Greiner🇩🇪

    The production of light (anti-)(hyper-)nuclei in heavy-ion collisions at the LHC is considered in the framework of the Saha equation, making use of the analogy between the evolution of the early universe after the Big Bang and that of "Little Bangs" created in the lab. Assuming that disintegration and regeneration reactions involving light nuclei proceed in relative chemical equilibrium after the chemical freeze-out of hadrons, their abundances are determined through the famous cosmological Saha equation of primordial nucleosynthesis and show no exponential dependence on the temperature typical for the thermal model. A quantitative analysis, performed using the hadron resonance gas model in partial chemical equilibrium, shows agreement with experimental data of the ALICE collaboration on d, He, H, and He yields for a very broad range of temperatures at MeV. The presented picture is supported by the observed suppression of resonance yields in central Pb-Pb collisions at the LHC.

    ↳ hep-phnucl-exnucl-thPLB(2020)·50 citations
  4. 14

    Excited-state quantum phase transitions in systems with two degrees of freedom: III. Interacting boson systems

    Michal Macek · Pavel Stránský · Amiram Leviatan · Pavel Cejnar

    The series of articles [Ann. Phys. 345, 73 (2014) and 356, 57 (2015)] devoted to excited-state quantum phase transitions (ESQPTs) in systems with degrees of freedom is continued by studying the interacting boson model of nuclear collective dynamics as an example of a truly many-body system. The intrinsic Hamiltonian formalism with angular momentum fixed to is used to produce a generic first-order ground-state quantum phase transition with an adjustable energy barrier between the competing equilibrium configurations. The associated ESQPTs are shown to result from various classical stationary points of the model Hamiltonian, whose analysis is more complex than in previous cases because of (i) a non-trivial decomposition to kinetic and potential energy terms and (ii) the boundedness of the associated classical phase space. Finite-size effects resulting from a partial separability of both degrees of freedom are analyzed. The features studied here are inherent in a great majority of interacting boson systems.

    ↳ quant-phnucl-thPRC(2019)·34 citations
  5. 15

    Interwoven limit cycles in the spectra of mass imbalanced many-boson system

    W. De Paula · A. Delfino · T. Frederico · Lauro Tomio

    The independence between few-body scales beyond the van der Waals universality is demonstrated for the extreme mass-imbalanced case of a specific many-boson system. This finding generalizes the scaling properties of universal tetramers to a broader class of heterogeneous few-boson systems. We assume two heavy atoms interacting with lighter ones at the unitary limit, using a particular case where no interactions are active between identical particles, by investigating the interwoven spectra of this many-body system for an arbitrary number of light bosons. A large mass-ratio between the particles allows us to treat this body system analytically, by solving an effective inverse-squared long-range interaction which is stablished for the two heavy bosons. For a cluster with light bosons (), we discuss the implications of the corresponding long-range potentials associated with different subsystem thresholds, implying in independent interwoven limit cycles for the correlation between the energies of excited body system. Our study with extreme mass-imbalanced few-boson bound states provides a fundamental understanding of the scaling behavior of their interwoven spectra. The novel insights enlarge the well-known Efimov physics paradigm and show the existence of different limit cycles, which could be probed by new experiments.

    ↳ quant-phnucl-thJ.Phys.B(2020)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE