Nuclear Theory·nucl-th

Friday·May 13, 2022

8 papers—2 primary·6 cross-listed

01
Quark formation and phenomenology in binary neutron-star mergers using V-QCD
Samuel Tootle🇩🇪 · Christian Ecker🇩🇪 · Konrad Topolski🇩🇪 · Tuna Demircik🇰🇷 · Matti Järvinen🇰🇷 · Luciano Rezzolla🇩🇪
Using full 3+1 dimensional general-relativistic hydrodynamic simulations of equal- and unequal-mass neutron-star binaries with properties that are consistent with those inferred from the inspiral of GW170817, we perform a detailed study of the quark-formation processes that could take place after merger. We use three equations of state consistent with current pulsar observations derived from a novel finite-temperature framework based on V-QCD, a non-perturbative gauge/gravity model for Quantum Chromodynamics. In this way, we identify three different post-merger stages at which mixed baryonic and quark matter, as well as pure quark matter, are generated. A phase transition triggered collapse already $≲ 10 ms$ after the merger reveals that the softest version of our equations of state is actually inconsistent with the expected second-long post-merger lifetime of GW170817. Our results underline the impact that multi-messenger observations of binary neutron-star mergers can have in constraining the equation of state of nuclear matter, especially in its most extreme regimes.
astro-ph.HEgr-qchep-phnucl-thSciPost Phys.(2022)·66 citations
02
Statistical correlations of nuclear quadrupole deformations and charge radii
Paul-Gerhard Reinhard · Witek Nazarewicz
Shape deformations and charge radii, basic properties of atomic nuclei, are influenced by both the global features of the nuclear force and the nucleonic shell structure. As functions of proton and neutron number, both quantities show regular patterns and, for nuclei away from magic numbers, they change very smoothly from nucleus to nucleus. In this paper, we explain how the local shell effects are impacting the statistical correlations between quadrupole deformations and charge radii in well-deformed even-even Er, Yb, and Hf isotopes. This implies, in turn, that sudden changes in correlations can be useful indicators of underlying shell effects. Our theoretical analysis is performed in the framework of self-consistent mean-field theory using quantified energy density functionals and density-dependent pairing forces. The statistical analysis is carried out by means of the linear least-square regression. The local variations of nuclear quadrupole deformations and charge radii, explained in terms of occupations individual deformed Hartree-Fock orbits, make and imprint on statistical correlations of computed observables. While the calculated deformations or charge radii are, in some cases, correlated with those of their even-even neighbors, the correlations seem to deteriorate rapidly with particle number. The statistical correlations between nuclear deformations and charge radii of different nuclei are affected by the underlying shell structure. Even for well deformed and superfluid nuclei for which these observables change smoothly, the correlation range usually does not exceed $Δ N = 4$ and $Δ Z = 4$ , i.e., it is rather short. This result suggests that the frequently made assumption of reduced statistical errors for the differences between smoothly-varying observables cannot be generally justified.
nucl-thPRC(2022)·11 citations
03
Search for baryon junctions in photonuclear processes and isobar collisions at RHIC
Nicole Lewis🇺🇸 · Wendi Lv🇨🇳 · Mason Alexander Ross🇺🇸 · Chun Yuen Tsang🇺🇸 · James Daniel Brandenburg🇺🇸 · Zi-Wei Lin🇺🇸 · Rongrong Ma🇺🇸 · Zebo Tang🇨🇳 · Prithwish Tribedy🇺🇸 · Zhangbu Xu🇺🇸
During the early development of Quantum Chromodynamics, it was proposed that baryon number could be carried by a non-perturbative Y-shaped topology of gluon fields, called the gluon junction, rather than by the valence quarks as in the QCD standard model. A puzzling feature of ultra-relativistic nucleus-nucleus collisions is the apparent substantial baryon excess in the midrapidity region that could not be adequately accounted for in most conventional models of quark and diquark transport. The transport of baryonic gluon junctions is predicted to lead to a characteristic exponential distribution of net-baryon density with rapidity and could resolve the puzzle. In this context we point out that the rapidity density of net-baryons near midrapidity indeed follows an exponential distribution with a slope of $- 0.61 \pm 0.03$ as a function of beam rapidity in the existing global data from A+A collisions at AGS, SPS and RHIC energies. To further test if quarks or gluon junctions carry the baryon quantum number, we propose to study the absolute magnitude of the baryon vs. charge stopping in isobar collisions at RHIC. We also argue that semi-inclusive photon-induced processes ( $γ + p$ /A) at RHIC kinematics provide an opportunity to search for the signatures of the baryon junction and to shed light onto the mechanisms of observed baryon excess in the mid-rapidity region in ultra-relativistic nucleus-nucleus collisions. Such measurements can be further validated in A+A collisions at the LHC and $e + p$ /A collisions at the EIC.
↳ hep-phnucl-exnucl-thEPJC(2024)·37 citations
04
Combining nonperturbative transverse momentum dependence with TMD evolution
J. O. Gonzalez-Hernandez🇮🇹 · T. C. Rogers🇺🇸 · N. Sato🇺🇸
Central to understanding the nonpertubative, intrinsic partonic nature of hadron structure are the concepts of transverse momentum dependent (TMD) parton distribution and fragmentation functions. A TMD factorization approach to the phenomenology of semi-inclusive processes that includes evolution, higher orders, and matching to larger transverse momentum, is ultimately necessary for reliably connecting with phenomenologically extracted nonperturbative structures, especially when widely different scales are involved. In this paper, we will address some of the difficulties that arise when phenomenological techniques that were originally designed for very high energy applications are extended to studies of hadron structures, and we will solidify the connection between standard high energy TMD implementations and the more intuitive, parton model based approaches to phenomenology that emphasize nonperturbative hadron structure. In the process, we will elaborate on differences between forward and backward TMD evolution, which in the context of this paper we call "bottom-up" and "top-down" approaches, and we will explain the advantages of a bottom-up strategy. We will also emphasize and clarify the role of the integral relations that connect TMD and collinear correlation functions. We will show explicitly how they constrain the nonperturbative " $g$ -functions" of standard Collins-Soper-Sterman (CSS) implementations of TMD factorization. This paper is especially targeted toward phenomenologists and model builders who are interested in merging specific nonperturbative models and calculations (including lattice QCD) with TMD factorization at large $Q$ . Our main result is a recipe for incorporating nonperturbative models into TMD factorization, and for constraining their parameters in a way that matches to perturbative QCD and evolution.
↳ hep-phhep-exnucl-exnucl-thPRD(2022)·23 citations
05
Towards the discovery of novel $B_{c}$ states: radiative and hadronic transitions
B. Martín-González🇪🇸 · P. G. Ortega🇪🇸 · D. R. Entem🇪🇸 · F. Fernández🇪🇸 · J. Segovia🇪🇸
The properties of the $B_{c}$ -meson family ( $c b ˉ$ ) are still not well determined experimentally because the specific mechanisms of formation and decay remain poorly understood. Unlike heavy quarkonia, i.e. the hidden heavy quark-antiquark sectors of charmonium ( $c c ˉ$ ) and bottomonium ( $b b ˉ$ ), the $B_{c}$ -mesons cannot annihilate into gluons and they are, consequently, more stable. The excited $B_{c}$ states, lying below the lowest strong-decay $B D$ -threshold, can only undergo through radiative decays and hadronic transitions to the $B_{c}$ ground state, which then decays weakly. As a result of this, a rich spectrum of narrow excited states below the $B D$ -threshold appear, whose total widths are two orders of magnitude smaller than those of the excited levels of charmonium and bottomonium. In a different article, we determined bottom-charmed meson masses using a non-relativistic constituent quark model which has been applied to a wide range of hadron physical observables, and thus the model parameters are completely constrained. Herein, continuing to our study of the $B_{c}$ sector, we calculate the relevant radiative decay widths and hadronic transition rates between $c b ˉ$ states which are below $B D$ -threshold. This shall provide the most promising signals for discovering excited $B_{c}$ states that are below the lowest strong-decay $B D$ -threshold. Finally, our results are compared with other models to measure the reliability of the predictions and point out differences.
↳ hep-phhep-exhep-latnucl-ex+1PRD(2022)·27 citations
06
Analysis of 2-Body Central Events for $^{129} X e +^{na t} S n$ from $8 A$ $M e V$ up to $18 A$ $M e V$ and for $^{129} X e +^{197} A u$ at $15 A$ $M e V$ and $18 A$ $M e V$
L. Manduci🇫🇷 · O. Lopez🇫🇷 · D. Durand🇫🇷 · R. Bougault🇫🇷 · E. Vient🇫🇷 · M. Pâlog🇫🇷 · B. Borderie🇫🇷 · I. Lombardo🇮🇹 · G. Verde🇫🇷
A study of medium-mass heavy-ion reactions leading to two fragments in the exit channel from barrier to 18A MeV is proposed. A special focus is made on fission and quasi-fission for events with two fragments ( $Z \geq 10$ ) in the exit channel selected. Reactions induced by $^{129} X e$ projectiles on $^{na t} S n$ and on $^{197} A u$ at energies ranging from $8 A$ MeV to $18 A$ MeV were analyzed. Using the fragment ( $Z \geq 10$ ) multiplicity equal to 2, fission and quasi-fission events were studied for the lowest beam energies using the fission fragment charge distributions, the total kinetic energy distribution (TKE) and its standard deviation $σ_{T K E}$ . For the lighter system it is still possible to observe fission events from incomplete fusion. At variance, for the heavier system, Xenon on gold target only quasi-fission is evidenced. The study of the events characterized by two fragments in the final channel shows that fission, related to fusion in the entrance channel, disappears around 20A MeV for both systems. At lower energies (8A, 12A and 15A MeV) for the Sn target, an evolution with increasing energies towards an asymmetric fission mode is displayed in the fragment charge distributions. This trend can be attributed to the increasing angular momentum as indicated by the out-of-plane angular distribution for light charged particles. The same effect is also observed in the case of the gold target at 15A MeV. However, for this heavier system, a strong memory of the entrance channel leading to quasi-fission is evidenced. A comparison with the Viola systematics, moreover, shows a deviation, greater for the heavier system than for $^{129} X e +^{na t} S n$ system. A complete understanding of the above results would certainly require precise model calculations at these energies.
↳ nucl-exnucl-th0 citations
07
The vector boson transverse momentum distributions
Ignazio Scimemi🇪🇸
The transverse momentum dependent distributions (TMD) are an essential part of the factorization theorems in vector boson production. They are non-perturbative, double scale dependent functions that asymptotically match onto collinear parton distributions functions (PDF). Once TMD are expressed using PDF, one observes that they are sensitive to the choice and quality of PDF sets (PDF bias). A solution to this problem is found and discussed. Nevertheless the main source of error on vector boson spectra still comes from PDF uncertainty propagation.
↳ hep-phhep-exnucl-exnucl-th1 citation
08
Aspects of univalence in holographic axion models
Matteo Baggioli🇨🇳 · Sebastian Grieninger🇪🇸 · Sašo Grozdanov🇬🇧 · Zhenkang Lu🇸🇪
Univalent functions are complex, analytic (holomorphic) and injective functions that have been widely discussed in complex analysis. It was recently proposed that the stringent constraints that univalence imposes on the growth of functions combined with sufficient analyticity conditions could be used to derive rigorous lower and upper bounds on hydrodynamic dispersion relation, i.e., on all terms appearing in their convergent series representations. The results are exact bounds on physical quantities such as the diffusivity and the speed of sound. The purpose of this paper is to further explore these ideas, investigate them in concrete holographic examples, and work towards a better intuitive understanding of the role of univalence in physics. More concretely, we study diffusive and sound modes in a family of holographic axion models and offer a set of observations, arguments and tests that support the applicability of univalence methods for bounding physical observables described in terms of effective field theories. Our work provides insight into expected `typical' regions of univalence, comparisons between the tightness of bounds and the corresponding exact values of certain quantities characterizing transport, tests of relations between diffusion and bounds that involve chaotic pole-skipping, as well as tests of a condition that implies the conformal bound on the speed of sound and a complementary condition that implies its violation.
↳ hep-thcond-mat.str-elmath-phmath.MP+2JHEP(2022)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE