Nuclear Theory·nucl-th

Wednesday·November 30, 2022

14 papers—6 primary·8 cross-listed

01
Directed flow in a baryonic fireball
Tribhuban Parida🇮🇳 · Sandeep Chatterjee🇮🇳
Directed flow of identified hadrons in a baryon rich fireball is an interesting observable as it is expected to probe several physics aspects: the initial three dimensional baryon profile in the thermalised fireball that can be treated as an input for the hydrodynamic evolution, the nature of baryon dissipation current and baryon transport coefficients, the QCD equation of state at finite baryon densities as well as the nature of phase transition between the quark gluon and hadronic phases. Particularly, the mid-rapidity slope of the rapidity dependence of directed flow of protons have been proposed as a sensitive observable to several of these physics aspects while a consistent description of the splitting in directed flow of baryon and its anti-particle has been a challenge. In this work, we propose a suitable ansatz of the initial condition for baryon deposition. When such a baryon deposition ansatz is coupled to a tilted fireball, we manage to find parameter space that can describe the directed flow of identified hadrons including the elusive baryon antibaryon splitting of directed flow. Further, we demonstrate that future measurements of baryon antibaryon directed flow at larger rapidities have the potential to constrain the baryon diffusion coefficient.
nucl-th12 citations
02
QRPA calculations for M1 transitions with the noniterative finite amplitude method and the application to neutron radiative capture cross sections
Hirokazu Sasaki · Toshihiko Kawano · Ionel Stetcu
We derive the equations of quasiparticle random-phase approximation (QRPA) based on the finite amplitude method (FAM) with the Hartree-Fock+BCS (HF+BCS) single-particle states, and calculate the magnetic dipole (M1) transition for deformed gadolinium isotopes. Our QRPA calculation shows both large spin-flip transitions in the 5 to 10 MeV excitation energy and the low energy orbital transition that would correspond to the M1 scissors mode observed in nuclear experiments. Then, we calculate neutron capture reactions based on the statistical Hauser-Feshbach theory with the photoabsorption cross sections given by QRPA. We find that the capture cross section is enhanced due to the contribution from the low energy M1 transition although the calculated capture cross section still underestimates the experimental data. This issue in the calculated capture cross section could be improved by uncertainties of low energy E1 transition neglected in our QRPA calculation.
nucl-thnucl-exPRC(2023)·8 citations
03
Normal ordering of three-nucleon interactions for ab initio calculations of heavy nuclei
K. Hebeler · V. Durant · J. Hoppe · M. Heinz · A. Schwenk · J. Simonis · A. Tichai
Three-nucleon (3N) interactions are key for an accurate solution of the nuclear many-body problem. However, fully taking into account 3N forces constitutes a computational challenge and hence approximate treatments are commonly employed. The method of normal ordering has proven to be a powerful tool that allows to systematically include 3N interactions in an efficient way, but traditional normal-ordering frameworks require the representation of 3N interactions in a large single-particle basis, typically necessitating a truncation of 3N matrix elements. While this truncation has only a minor impact for light and medium-mass nuclei, its effects become sizable for heavier systems and hence limit the scope of \textit{ab initio} calculations. In this work, we present a novel normal-ordering framework that allows to circumvent this limitation by performing the normal ordering directly in a Jacobi basis. We discuss in detail the new framework, benchmark it against established results, and present calculations for ground-state energies and charge radii of heavy nuclei, such as $^{132}$ Sn and $^{208}$ Pb.
nucl-thPRC(2023)·47 citations
04
The 3D structure of anisotropic flow in small collision systems at the Relativistic Heavy Ion Collider
Wenbin Zhao🇺🇸 · Sangwook Ryu🇺🇸 · Chun Shen🇺🇸 · Björn Schenke🇺🇸
We present (3+1)D dynamical simulations of asymmetric nuclear collisions at the Relativistic Heavy Ion Collider (RHIC). Employing a dynamical initial state model coupled to (3+1)D viscous relativistic hydrodynamics, we explore the rapidity dependence of anisotropic flow in the RHIC small system scan at 200 GeV center of mass energy. We calibrate parameters to describe central $^{3}$ He+Au collisions and make extrapolations to d+Au and p+Au collisions. Our calculations demonstrate that approximately 50% of the $v_{3} (p_{T})$ difference between the measurements by the STAR and PHENIX Collaborations can be explained by the use of reference flow vectors from different rapidity regions. This emphasizes the importance of longitudinal flow decorrelation for anisotropic flow measurements in asymmetric nuclear collisions, and the need for (3+1)D simulations. We also present results for the beam energy dependence of particle spectra and anisotropic flow in d+Au collisions.
nucl-thhep-phnucl-exPRC(2023)·60 citations
05
Probing initial baryon stopping and equation of state with rapidity-dependent directed flow of identified particles
Lipei Du🇨🇦 · Chun Shen🇺🇸 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
Using a (3+1)-dimensional hybrid framework with parametric initial conditions, we study the rapidity-dependent directed flow $v_{1} (y)$ of identified particles, including pions, kaons, protons, and lambdas in heavy-ion collisions. Cases involving Au+Au collisions are considered, performed at $s_{NN}$ ranging from 7.7 to 200 GeV. The dynamics in the beam direction is constrained using the measured pseudo-rapidity distribution of charged particles and the net proton rapidity distribution. Within this framework, the directed flow of mesons is driven by the sideward pressure gradient from the tilted source, and that of baryons mainly due to the initial asymmetric baryon distribution with respect to the beam axis driven by the transverse expansion. Our approach successfully reproduces the rapidity- and beam energy-dependence of $v_{1}$ for both mesons and baryons. We find that the $v_{1} (y)$ of baryons has strong constraining power on the initial baryon stopping, and together with that of mesons, the directed flow probes the equation of state of the dense nuclear matter at finite chemical potentials.
nucl-thhep-phnucl-exPRC(2023)·42 citations
06
Lee-Yang-inspired functional including contributions to fourth order in effective field theory
Jérémy Bonnard🇫🇷
In the last years, a new family of energy density functionals directly inspired by effective field theory (EFT) has been developed, among which the ELYO (extended Lee-Yang Orsay) functional. In this paper, a new extension of ELYO that includes the recently calculated fourth-order EFT terms is presented. Compared to the previous version, the description of neutron-drop energies slightly degrades for a harmonic trap $ℏ ω = 10$ MeV -- yet remaining reasonable -- , but improves for $ℏ ω = 5$ MeV. Furthermore, the obtained neutron effective mass agrees significantly better with \textit{ab-initio} estimates.
nucl-thJ.Phys.Conf.Ser.(2023)·0 citations
07
Quenching jets increases their flavor
Chathuranga Sirimanna🇺🇸 · Ismail Soudi🇺🇸 · Gojko Vujanovic🇺🇸 · Wen-Jing Xing🇨🇳 · Shanshan Cao🇨🇳 · Abhijit Majumder🇺🇸
The widespread notion that jets quenched in a Quark-Gluon-Plasma (QGP) are similar in their parton flavor composition to jets in vacuum is critically examined. We demonstrate that while the soft to semi-hard [low to intermediate transverse momentum ( $p_{T}$ )] sector of vacuum jets are predominantly bosonic i.e., composed of gluons, \emph{sufficiently} quenched jets can have an intermediate momentum sector that is predominantly fermionic, dominated by quarks and antiquarks. We demonstrate, using leading order perturbative QCD processes, that the rate of flavor conversion from a gluon traversing the QGP as part of a jet, to a quark or antiquark, versus the reverse process, grows steadily with falling $p_{T}$ . Simple diagrammatic estimates are followed by a variety of realistic simulations in static media. The relation of this increase in flavor to the observed baryon enhancement at intermediate $p_{T}$ is studied in a fully realistic simulation.
↳ hep-phnucl-exnucl-thPRC(2023)·14 citations
08
A solvable quantum field theory with asymptotic freedom in 3+1 dimensions
Paul Romatschke🇺🇸
Recently, Ai, Bender and Sarkar gave a prescription on how to obtain $P T$ -symmetric field theory results from an analytic continuation of Hermitian field theories. I perform this analytic continuation for the massless (critical) O(N) model with quartic interaction in 3+1 dimensions. In the large N limit, this theory is exactly solvable, and has negative $β$ -function in the ultraviolet, and a stable bound state in the infrared. The coupling diverges at a scale $Λ_{c}$ , but can be continued into the far infrared. At finite temperature, the theory exhibits two phases separated by a second-order phase transition near $T_{c} ≃ Λ_{c} / e$ .
↳ hep-thhep-phnucl-thInt.J.Mod.Phys.A(2023)·28 citations
09
QED as a many-body theory of worldlines: II. All-order S-matrix formalism
Xabier Feal🇪🇸 · Andrey Tarasov🇺🇸 · Raju Venugopalan🇺🇸
In arXiv:2206.04188, we developed a first-quantized worldline formalism for all-order computations of amplitudes in QED. In particular, we demonstrated in this framework an all-order proof of the infrared safety of the Faddeev-Kulish (FK) S-matrix for virtual exchanges in the scattering of charged fermions. In this work, we extend the worldline formalism for both the Dyson and FK S-matrix to consider further the emission and absorption of arbitrary numbers of photons. We show how Low's theorem follows in this framework and derive Weinberg's theorem for the exponentiation of IR divergences. In particular, we extend our all-order proof of the IR safety of the FK S-matrix to both virtual exchanges and real photon emissions. We argue that the worldline approach leads to a modern Wilsonian interpretation of the IR safety of the FK S-matrix and provides a novel template for the treatment of IR divergences in real-time problems. Using Grassmannian integration methods, we derive a simple and powerful result for N-th rank vacuum polarization tensors. Applications of these methods will be discussed in follow-up work.
↳ hep-thhep-phnucl-thPRD(2023)·10 citations
10
Radiative corrections to inverse muon decay for accelerator neutrinos
Oleksandr Tomalak🇺🇸 · Kaushik Borah🇺🇸 · Richard J. Hill🇺🇸 · Kevin S. McFarland🇺🇸 · Daniel Ruterbories🇺🇸
Inverse muon decay ( $ν_{μ} e^{-} \to ν_{e} μ^{-}$ ) is a promising tool to constrain neutrino fluxes with energies $E_{ν} \geq 10.9 GeV$ . Radiative corrections introduce percent-level distortions to energy spectra of outgoing muons and depend on experimental details. In this paper, we calculate radiative corrections to the scattering processes $ν_{μ} e^{-} \to ν_{e} μ^{-}$ and $ν ˉ_{e} e^{-} \to ν ˉ_{μ} μ^{-}$ . We present the muon energy spectrum for both channels, double-differential distributions in muon energy and muon scattering angle and in photon energy and photon scattering angle, and the photon energy spectrum for the dominant $ν_{μ} e^{-} \to ν_{e} μ^{-}$ process. Our results clarify and extend the region of applicability of previous results in the literature for the double differential distribution in muon energy and photon energy, and in the muon energy spectrum with a radiated photon above a threshold energy. We provide analytic expressions for single, double and triple differential cross sections, and discuss how radiative corrections modify experimentally interesting observable distributions.
↳ hep-phhep-exnucl-exnucl-thPRD(2023)·5 citations
11
Patterns of gauge symmetry in the background field method
A. C. Aguilar🇧🇷 · M. N. Ferreira🇪🇸 · D. Ibañez🇪🇸 · B. M. Oliveira🇧🇷 · J. Papavassiliou🇪🇸
The correlation functions of Yang-Mills theories formulated in the background field method satisfy linear Slavnov-Taylor identities, which are naive generalizations of simple tree level relations, with no deformations originating from the ghost sector of the theory. In recent years, a stronger version of these identities has been found to hold at the level of the background gluon self-energy, whose transversality is enforced separately for each special block of diagrams contributing to the gluon Schwinger-Dyson equation. In the present work we demonstrate by means of explicit calculations that the same distinct realization of the Slavnov-Taylor identity persists in the case of the background three-gluon vertex. The analysis is carried out at the level of the exact Schwinger-Dyson equation for this vertex, with no truncations or simplifying assumptions. The demonstration entails the contraction of individual vertex diagrams by the relevant momentum, which activates Slavnov-Taylor identities of vertices and multi-particle kernels nested inside these graphs; the final result emerges by virtue of a multitude of extensive cancellations, without the need of performing explicit integrations. In addition, we point out that background Ward identities amount to replacing derivatives of propagators by zero-momentum background-gluon insertions, in exact analogy to standard properties of Abelian gauge theories. Finally, certain potential applications of these results are briefly discussed.
↳ hep-thhep-lathep-phnucl-thEPJC(2023)·3 citations
12
Dirac Kondo effect under magnetic catalysis
Koichi Hattori🇨🇳 · Daiki Suenaga🇯🇵 · Kei Suzuki🇯🇵 · Shigehiro Yasui🇯🇵
We develop a mean-field theory of a novel Kondo effect emerging in systems without a Fermi surface, which instead emerges under strong magnetic fields. We determine the magnitude of the Kondo condensate which is a particle pairing composed of conducting Dirac fermions and localized impurities. We focus on the competition between the Kondo effect and the energy gap formation that stems from the pairing among the Dirac fermions leading to the dynamical chiral symmetry breaking. We find that this competition induces a quantum critical point. We also investigate finite-temperature effects. This system at vanishing fermion density can be studied with Monte Carlo lattice simulations which do not suffer from the sign problem.
↳ hep-phcond-mat.mes-hallcond-mat.str-elhep-lat+1PRB(2023)·4 citations
13
$D_{1} (2420)$ and its interactions with a kaon: open charm states with strangeness
Brenda B. Malabarba🇧🇷 · K. P. Khemchandani🇧🇷 · A. Martinez Torres🇧🇷 · E. Oset🇪🇸
In this work we present an attempt to describe the $X_{1} (2900)$ found by the LHCb collaboration, in the experimental data on the invariant mass spectrum of $D^{-} K^{+}$ , as a three-meson molecular state of the $K ρ D ˉ$ system. We discuss that the interactions in all the subsystems are attractive in nature, with the $ρ D ˉ$ interaction generating $D ˉ_{1} (2420)$ and the $K ρ$ resonating as $K_{1} (1270)$ . We find that the system can form a three-body state but with a mass higher than that of $X_{1} (2900)$ . We investigate the $K ρ D$ system too, finding that the three-body dynamics generates an isoscalar state, which can be related to $D_{s 1}^{*} (2860)$ , and an exotic isovector state. This latter state has a mass similar to that of the $X_{0} (2900)$ and $X_{1} (2900)$ states found by LHCb, but a very small width ( $\sim 7.4 \pm 0.9$ MeV) and necessarily requires more than two quarks to describe its properties. We hope that our findings will encourage experimental investigations of the isovector $K ρ D$ state. Finally, in the pursuit of finding a description for $X_{1} (2900)$ , we study the $π K ˉ^{*} D^{*}$ system where $K ˉ^{*} D^{*}$ forms $0^{+}$ , $1^{+}$ and $2^{+}$ states. We do not find a state which can be associated with $X_{1} (2900)$ .
↳ hep-phnucl-thPRD(2023)·7 citations
14
Quark-Hadron Transition and Entanglement
Berndt Müller🇺🇸 · Andreas Schäfer🇩🇪
The dual holographic description has enjoyed many successes in explaining fundamental properties of the early stages of relativistic heavy ion collisions up to the formation of a minimal-viscosity quark-gluon fluid. However, there have been few attempts to extend its application beyond this stage. Here we explore the prospects for such an extension beyond the time of hadronization. Our discussion makes use of recent insights into the duality of entanglement properties of field theory states in the edge of Anti-de Sitter space and non-trivial topologies of horizons in the bulk, often referred to as ER = EPR duality. We discuss this topic from the point of view of heavy-ion phenomenology, review several relevant concepts, and map out a path toward combining them into a comprehensive, at least semiquantitative description of relativistic heavy ion collisions. We outline possible next steps in this direction.
↳ hep-phnucl-th11 citations

Affiliations

first authorsco-authorsvia INSPIRE