Nuclear Theory·nucl-th

Monday·September 4, 2023

9 papers—4 primary·5 cross-listed

01
Calculation of microscopic nuclear level densities based on covariant density functional theory
Kun-Peng Geng · Peng-Xiang Du · Jian Li · Dong-Liang Fang
A microscopic method for calculating nuclear level density (NLD) based on the covariant density functional theory (CDFT) is developed. The particle-hole state density is calculated by combinatorial method using the single-particle levels schemes obtained from the CDFT. Then the level densities are obtained by taking into account collective effects such as vibration and rotation. Our results are compared with those from other NLD models, including phenomenological, microstatistical, and non-relativistic HFB combinatorial models. The comparison suggests that the general trends among these models are basically the same, except for some deviations from different NLD models. In addition, the NLDs of the CDFT combinatorial method with normalization are compared with experimental data, including the observed cumulative number of levels at low excitation energy and the measured NLDs. Compared with the existing experimental data, the CDFT combinatorial method can give reasonable results.
nucl-thNucl.Sci.Tech.(2023)·17 citations
02
$^{16}$ O spectral function from coupled-cluster theory: applications to lepton-nucleus scattering
Joanna E. Sobczyk🇩🇪 · Sonia Bacca🇩🇪
We calculate the $^{16}$ O spectral function by combining coupled-cluster theory with a Gaussian integral transform and by expanding the integral kernel in terms of Chebyshev polynomials to allow for a quantification of the theoretical uncertainties. We perform an analysis of the spectral function and employ it to predict lepton-nucleus scattering. Our results well describe the $^{16}$ O electron scattering data in the quasi-elastic peak for momentum transfers $∣ q ∣ ⪆ 500$ MeV and electron energies up to 1.2 GeV, extending therefore the so-called first principles approach to lepton-nucleus cross sections well into the relativistic regime. To prove the applicability of this method to neutrino-nucleus cross sections, we implement our $^{16}$ O spectral functions in the NuWro Monte Carlo event generator and provide a comparison with recently published T2K neutrino data.
nucl-thhep-phPRC(2024)·16 citations
03
Dilepton polarization as a signature of plasma anisotropy
Maurice Coquet🇫🇷 · Xiaojian Du🇫🇷 · Jean-Yves Ollitrault🇪🇸 · Soeren Schlichting🇫🇷 · Michael Winn🇩🇪
We propose the angular distribution of lepton pairs produced in ultrarelativistic heavy-ion collisions as a probe of thermalization of the quark-gluon plasma. We focus on dileptons with invariant masses large enough that they are produced through quark-antiquark annihilation in the early stages of the collision. The angular distribution of the lepton in the rest frame of the pair then reflects the angular distribution of quark momenta. At early times, the transverse pressure of the quark-gluon plasma is larger than its longitudinal pressure as a result of the fast longitudinal expansion, which results in an oblate lepton distribution. By contrast, direct (Drell-Yan) production by quarks and antiquarks from incoming nuclei, whose momenta are essentially longitudinal, results in a prolate distribution. As the invariant mass increases, Drell-Yan gradually becomes the dominant source of dilepton production, and the lepton distribution evolves from oblate to prolate. The invariant mass at which the transition occurs is highly sensitive to the equilibration time of the quark-gluon plasma or, equivalently, the shear viscosity over entropy ratio $η / s$ in the early stages of the collision.
nucl-thhep-exhep-phnucl-exPRL(2024)·27 citations
04
Bayesian location of the QCD critical point from a holographic perspective
Mauricio Hippert🇺🇸 · Joaquin Grefa🇺🇸 · T. Andrew Manning🇺🇸 · Jorge Noronha🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Israel Portillo Vazquez🇺🇸 · Claudia Ratti🇺🇸 · Romulo Rougemont🇧🇷 · Michael Trujillo🇺🇸
A fundamental question in QCD is the existence of a phase transition at large doping of quarks over antiquarks. We present the first prediction of a QCD critical point (CP) from a Bayesian analysis constrained by first principle results at zero doping. We employ the gauge/gravity duality to map QCD onto a theory of dual black holes. Predictions for the CP location in different realizations of the model overlap at one sigma. Even if many prior samples do not include a CP, one is found in nearly 100\% of posterior samples, indicating a strong preference for a CP.
nucl-thhep-phhep-thnucl-exPRD(2024)·121 citations
05
Semi-inclusive direct photon+jet and $π^{0}$ +jet correlations measured in $p + p$ and central Au+Au collisions at $s_{NN} = 200$ GeV
The STAR Collaboration
The STAR experiment at RHIC reports new measurements of jet quenching based on the semi-inclusive distribution of charged-particle jets recoiling from direct photon ( $γ_{dir}$ ) and neutral pion ( $π^{0}$ ) triggers in pp and central Au+Au collisions at $s_{NN} = 200$ GeV, for triggers in the range $9 < E_{T}^{trig} < 20$ GeV. The datasets have integrated luminosities of 3.9 $nb^{- 1}$ for Au+Au and 23 $pb^{- 1}$ for pp collisions. Jets are reconstructed using the anti- $k_{T}$ algorithm with resolution parameters $R$ =0.2 and 0.5. The large uncorrelated jet background in central Au+Au collisions is corrected using a mixed-event approach, which enables precise charged-particle jet measurements at low transverse momentum $p_{T, jet}^{ch}$ and large $R$ . Recoil-jet distributions are reported in the range $p_{T, jet}^{ch} < 25$ \gev. Comparison of the distributions measured in pp and Au+Au collisions reveals strong medium-induced jet yield suppression for $R = 0.2$ , with markedly less suppression for $R = 0.5$ . Comparison is also made to theoretical models incorporating jet quenching. These data provide new insight into the mechanisms underlying jet quenching and the angular dependence of medium-induced jet-energy transport, and provide new constraints on modelling such effects.
↳ nucl-exhep-exhep-phnucl-thPRC(2025)·21 citations
06
Measurement of in-medium jet modification using direct photon+jet and $π^{0}$ +jet correlations in $p + p$ and central Au+Au collisions at $s_{NN} = 200$ GeV
STAR Collaboration
The STAR Collaboration presents measurements of the semi-inclusive distribution of charged-particle jets recoiling from energetic direct-photon ( $γ_{dir}$ ) and neutral-pion ( $π^{0}$ ) triggers in p+p and central Au+Au collisions at $s_{NN}$ GeV over a broad kinematic range, for jet resolution parameters $R$ =0.2 and 0.5. Medium-induced jet yield suppression is observed to be larger for $R$ =0.2 than for 0.5, reflecting the angular range of jet energy redistribution due to quenching. The predictions of model calculations incorporating jet quenching are not fully consistent with the observations. These results provide new insight into the physical origins of jet quenching.
↳ nucl-exhep-exhep-phnucl-thPRL(2025)·21 citations
07
Correlation function for the $T_{bb}$ state: Determination of the binding, scattering lengths, effective ranges and molecular probabilities
A. Feijoo🇪🇸 · L. R. Dai🇨🇳 · L. M. Abreu🇧🇷 · E. Oset🇪🇸
We perform a study of the $B^{*+} B^{0}, B^{* 0} B^{+}$ correlation functions using an extension of the local hidden gauge approach which provides the interaction from the exchange of light vector mesons and gives rise to a bound state of these components in $I = 0$ with a binding energy of about $21$ ~MeV. After that, we face the inverse problem of determining the low energy observables, scattering length and effective range for each channel, the possible existence of a bound state, and, if found, the couplings of such a state to each $B^{*+} B^{0}, B^{* 0} B^{+}$ component as well as the molecular probabilities of each of the channels. We use the bootstrap method to determine these magnitudes and find that, with errors in the correlation function typical of present experiments, we can determine all these magnitudes with acceptable precision. In addition, the size of the source function of the experiment from where the correlation functions are measured can be also determined with a high precision.
↳ hep-phnucl-thPRD(2024)·30 citations
08
Schwinger-Keldysh effective field theory for stable and causal relativistic hydrodynamics
Akash Jain🇳🇱 · Pavel Kovtun🇨🇦
We construct stable and causal effective field theories (EFTs) for describing statistical fluctuations in relativistic diffusion and relativistic hydrodynamics. These EFTs are fully non-linear, including couplings to background sources, and enable us to compute n-point time-ordered correlation functions including the effects of statistical fluctuations. The EFTs we construct are inspired by the Maxwell-Cattaneo model of relativistic diffusion and Müller-Israel-Stewart model of relativistic hydrodynamics respectively, and have been derived using both the Martin-Siggia-Rose and Schwinger-Keldysh formalisms. The EFTs non-linearly realise the dynamical Kubo-Martin-Schwinger (KMS) symmetry, which ensures that n-point correlation functions and interactions in the theory satisfy the appropriate fluctuation-dissipation theorems. Since these EFTs typically admit ultraviolet sectors that are not fixed by the low-energy infrared symmetries, we find that they simultaneously admit multiple realisations of the dynamical KMS symmetry. We also comment on certain obstructions to including statistical fluctuations in the recently-proposed stable and causal Bemfica-Disconzi-Noronha-Kovtun model of relativistic hydrodynamics.
↳ hep-thcond-mat.stat-mechhep-phnucl-th+1JHEP(2024)·39 citations
09
Relativistic hydrodynamic fluctuations from an effective action: causality, stability, and the information current
Nicki Mullins🇺🇸 · Mauricio Hippert🇺🇸 · Lorenzo Gavassino🇺🇸 · Jorge Noronha🇺🇸
Causality is necessary for retarded Green's functions to remain retarded in all inertial frames in relativity, which ensures that dissipation of fluctuations is a Lorentz invariant concept. For first-order BDNK theories with stochastic fluctuations, introduced via the Schwinger-Keldysh formalism, we show that imposing causality and stability leads to correlation functions of hydrodynamic fluctuations that only display the expected physical properties at small frequencies and wavenumber, i.e., within the expected regime of validity of the first-order approach. For second-order theories of Israel and Stewart type, constructed using the information current such that entropy production is always non-negative, a stochastic formulation is presented using the Martin-Siggia-Rose approach where imposing causality and stability leads to correlators with the desired properties. We also show how Green's functions can be determined from such an action. We identify a $Z_{2}$ symmetry, analogous to the Kubo-Martin-Schwinger symmetry, under which this Martin-Siggia-Rose action is invariant. This modified Kubo-Martin-Schwinger symmetry provides a new guide for the effective action formulation of hydrodynamic systems with dynamics not solely governed by conservation laws. Furthermore, this symmetry ensures that the principle of detailed balance is valid in a covariant manner. We employ the new symmetry to further clarify the connection between the Schwinger-Keldysh and Martin-Siggia-Rose approaches, establishing a precise link between these descriptions in second-order theories of relativistic hydrodynamics. Finally, the modified Kubo-Martin-Schwinger symmetry is used to determine the corresponding action describing diffusion in Israel-Stewart theories in a general hydrodynamic frame.
↳ hep-thhep-phnucl-thPRD(2023)·31 citations

Affiliations

first authorsco-authorsvia INSPIRE