Nuclear Theory·nucl-th

Tuesday·August 6, 2024

11 papers—6 primary·5 cross-listed

01
Jet-Induced Enhancement of Deuteron Production in $pp$ and $p$ -Pb Collisions at the LHC
Yi-Heng Feng🇨🇳 · Che Ming Ko🇺🇸 · Yu-Gang Ma🇨🇳 · Kai-Jia Sun🇨🇳 · Xin-Nian Wang🇨🇳 · Zhong Yang🇨🇳 · Song Zhang🇨🇳
Jet-associated deuteron production in $pp$ collisions at $s = 13$ TeV and $p$ -Pb collisions at $s_{N N} = 5.02$ TeV is studied in the coalescence model by using the phase-space information of proton and neutron pairs from a multiphase transport (AMPT) model at the kinetic freezeout. In the low transverse momentum ( $p_{T}$ ) region $p_{T} / A < 1.5$ GeV/ $c$ , where $A$ is the mass number of a nucleus, the in-jet coalescence factor $B_{2}^{In-jet}$ for deuteron production, given by the ratio of the in-jet deuteron number to the square of the in-jet proton number, is found to be larger than the coalescence factor $B_{2}$ in the medium perpendicular to the jet by a factor of about 10 in $pp$ collisions and of 25 in $p -$ Pb collisions, which are consistent with the ALICE measurements at the LHC. Such large low-momentum enhancements mainly come from coalescence of nucleons inside the jet with the medium nucleons. Coalescence of nucleons inside the jet dominates deuteron production only at the higher $p_{T}$ region of $p_{T} / A ≳ 4$ GeV/ $c$ , where both the yield ratio $d / p$ of deuteron to proton numbers and the $B_{2}$ are also significantly larger in the jet direction than in the direction perpendicular to the jet due to the strong collinear correlation among particles produced from jet fragmentation. Studying jet-associated deuteron production in relativistic nuclear collisions thus opens up a new window to probe the phase-space structure of nucleons inside jets.
nucl-thhep-phPLB(2024)·9 citations
02
Ternary fission with the emission of long-range $α$ particles in fission of the heaviest nuclei
J. Khuyagbaatar
The most probable outcome of the ternary fission is the emission of two heavy fragments and one light-charged particle. In about 90\%, these are $α$ particles, which often referred to as the long-range alpha (LRA). Such decay has been extensively studied over decades in various heavy fissioning systems. The probability of such a process has been found to be about (2-4) $\times 1 0^{- 3}$ relative to binary fission. The experimental data showed an increasing trend in the probability of such a process with an increase in fissility parameter within the range of 35 - 39. In the last decades, a region of the heaviest nuclei has been substantially expanded in both proton and neutron numbers. This includes neutron-deficient heavy and superheavy nuclei with fissility parameters, which are significantly exceeding the aforementioned range. In the present work, the currently available experimental data on the probability of the LRA emission, which is a representative of ternary fission, are discussed. The probabilities of LRA emission were calculated within the various empirical approaches, including the presently suggested semi-empirical expression. The latter one was derived on the basis of the $α$ -decay property of the fissioning nucleus. The results of all approaches discussed show that the probabilities of LRA emission are substantial (up to a percentage) in the fission of neutron-deficient heavy and superheavy nuclei.
nucl-thnucl-exPRC(2024)·4 citations
03
The $p Λ$ and $pp Λ$ correlation functions
E. Garrido🇪🇸 · A. Kievsky🇮🇹 · M. Gattobigio🇫🇷 · M. Viviani🇮🇹 · L.E. Marcucci🇮🇹 · R. Del Grande🇩🇪 · L. Fabbietti🇩🇪 · D. Melnichenko🇩🇪
In this work we present the study of $p Λ$ and $pp Λ$ scattering processes using femtoscopic correlation functions. This observable has been recently used to access the low-energy interaction of hadrons emitted in the final state of high-energy collisions, delivering unprecedented precision information of the interaction among strange hadrons. The formalism for particle pairs is well established and it relates the measured correlation functions with the scattering wave function and the emission source. In the present work we analyze the $N N Λ$ scattering in free space and relate the corresponding wave function to the $pp Λ$ correlation measurement performed by the ALICE collaboration. The three-body problem is solved using the hyperspherical adiabatic basis. Regarding the $p Λ$ and $pp Λ$ interactions, different models are used and their impact on the correlation function is studied. The three body force considered in this work is anchored to describe the binding energy of the hypertriton and to give a good description of the two four-body hypernuclei. As a main result we have observed a huge, low-energy peak in the $pp Λ$ correlation function, mainly produced by the $J^{π} = 1/ 2^{+}$ three-body state. The study of this peak from an experimental as well as a theoretical point of view will provide important constraints to the two- and three-body interactions.
nucl-thhep-exhep-phnucl-exPRC(2024)·18 citations
04
Correlation of neutrinoless double-beta decay nuclear matrix elements with nucleon-nucleon phase shifts
A. Belley🇨🇦 · J. Pitcher🇨🇦 · T. Miyagi🇯🇵 · S. R. Stroberg🇺🇸 · J. D. Holt🇨🇦
We present an ab initio study of the correlation between nuclear matrix elements of neutrinoless double-beta ( $0 ν β β$ ) decay and nucleon-nucleon scattering phase shifts in the $^{1} S_{0}$ channel. Starting from thirty-four statistically weighted interactions derived from chiral effective field theory, we apply the valence-space in-medium similarity renormalization group to calculate nuclear matrix elements in four key experimental isotopes. Comparing with the $^{1} S_{0}$ -channel phase shifts given from each interaction, in all cases we observe a strong correlation for scattering energies above 75 MeV. Furthermore, a global sensitivity analysis, enabled by newly developed machine-learning emulators, confirms that the nuclear matrix elements of the decay depend primarily on the $C_{1 S 0}$ low-energy constant, which is associated with the phase shifts in that partial wave. These results provide the first clear correlation between $0 ν β β$ decay nuclear matrix elements and a measured observable and will therefore serve as a crucial component in ongoing and future refinements of ab initio uncertainty estimates.
nucl-thhep-exhep-phnucl-exPRC(2026)·12 citations
05
A critical assessment of the current implementations of the Generator Coordinate Method
Aurel Bulgac
The generator coordinate method (GCM) was introduced in nuclear physics by Wheeler and independently by Peierls and their collaborators in 1950s and it is still one of the most used approximations for treating nuclear large-amplitude collective motion. GCM was inspired by similar methods introduced in molecular and condensed-matter physics in the late 1920s, after the Schrödinger equation became the tool of choice to describe quantum phenomena. The interest in the 1983 extension of GCM suggested by Reinhard, Cusson, and Goeke, which includes the internal excitations (absent in the initial GCM formulation), was revived in recent years. Unfortunately, this newer version of the time-dependent GCM framework has flaws that prevent it from describing correctly many anticipated features, in particular interference and entanglement, which can play an important role in fission and many-nucleon transfer reactions. I present here an alternative formulation, the enhanced GCM (eGCM), which is free of the difficulties encountered in previous GCM implementations and which is relevant for fission and many-nucleon transfer in heavy-ion reactions, and which can be used in either static or time-dependent eGCM formulations. In the eGCM framework, the corresponding many-body wave functions have a much more complex structure, and this framework is equivalent to a configuration-interaction approach in the continuum for nuclear reactions. The eGCM is aimed at being used in the microscopic description of heavy-ion reactions and fission in particular. ....
nucl-thPRC(2026)·4 citations
06
Bayesian analysis of nucleon-nucleon scattering data in pionless effective field theory
J. M. Bub🇺🇸 · M. Piarulli🇺🇸 · R. J. Furnstahl🇺🇸 · S. Pastore🇺🇸 · D. R. Phillips🇺🇸
We perform Bayesian model calibration of two-nucleon ( $N N$ ) low-energy constants (LECs) appearing in an $N N$ interaction based on pionless effective field theory (EFT). The calibration is carried out for potentials constructed using naive dimensional analysis in $N N$ relative momenta ( $p$ ) up to next-to-leading order [NLO, $O (p^{2})$ ] and next-to-next-to-next-to-leading order [N3LO, $O (p^{4})$ ]. We consider two classes of pionless EFT potential: one that acts in all partial waves and another that is dominated by $s$ -wave physics. The two classes produce broadly similar results for calibrations to $N N$ data up to $E_{lab} = 5$ MeV. Our analysis accounts for the correlated uncertainties that arise from the truncation of the pionless EFT. We simultaneously estimate both the EFT LECs and the parameters that quantify the truncation error. This permits the first quantitative estimates of the pionless EFT breakdown scale, $Λ_{b}$ : the 95% intervals are $Λ_{b} \in [50.11, 63.03]$ MeV at NLO and $Λ_{b} \in [72.27, 88.54]$ MeV at N3LO. Invoking naive dimensional analysis for the $N N$ potential, therefore, does not lead to consistent results across orders in pionless EFT. This exemplifies the possible use of Bayesian tools to identify inconsistencies in a proposed EFT power counting.
nucl-thphysics.data-anPRC(2025)·17 citations
07
Old neutron stars as a new probe of relic neutrinos and sterile neutrino dark matter
Saurav Das🇺🇸 · P. S. Bhupal Dev🇺🇸 · Takuya Okawa🇺🇸 · Amarjit Soni🇺🇸
We study the kinetic cooling (heating) of old neutron stars due to coherent scattering with relic neutrinos (sterile neutrino dark matter) via Standard Model neutral-current interactions. We take into account several important physical effects, such as gravitational clustering, coherent enhancement, neutron degeneracy and Pauli blocking. We find that the anomalous cooling of nearby neutron stars due to relic neutrino scattering might actually be observable by current and future telescopes operating in the optical to near-infrared frequency band, such as the James Webb Space Telescope (JWST), provided there is a large local relic overdensity that is still allowed. Similarly, the anomalous heating of neutron stars due to coherent scattering with keV-scale sterile neutrino dark matter, could also be observed by JWST or future telescopes, which would probe hitherto unexplored parameter space in the sterile neutrino mass-mixing plane.
↳ hep-phastro-ph.HEastro-ph.SRnucl-thPRD(2025)·15 citations
08
Linearized fluctuating hydrodynamics via random polynomials
Farid Taghinavaz🇮🇷 · Giorgio Torrieri🇧🇷
We argue that an ensemble of backgrounds best understands hydrodynamic dispersion relations in a medium with few degrees of freedom and is therefore subject to strong thermal fluctuations. In the linearized regime, dispersion relations become describeable by polynomials with random coefficients. We give a short review of this theory and perform a numerical study of the distribution of the roots of polynomials whose coefficients are of the order of a Knudsen series but fluctuate in accordance with canonical fluctuations of temperature. We find that, remarkably, the analytic structure of the poles of fluctuating dispersion relations is very different from deterministic ones, particularly regarding the distribution of imaginary parts with respect to real components. We argue that this provides evidence that hydrodynamic behavior persists, and is enhanced, by non-perturbative background fluctuations.
↳ hep-thhep-phnucl-thPRD(2024)·3 citations
09
Calculation of Some Integrals over Gaussian Measure with Nuclear Covariance Operator in Separable Hilbert Space
Nikita A. Ignatyuk🇷🇺 · Anna A. Ogarkova🇷🇺 · Stanislav L. Ogarkov🇷🇺
The main purpose of this paper is to construct convergent series for the approximate calculation of certain integrals over the Gaussian measure with a nuclear covariance operator, nonlocal propagator, in separable Hilbert space. Such series arise, for example, in the model with the interaction Lagrangian $sinh^{2 (p + 1)} φ$ , where $p \in N$ and $φ$ is the scalar field, although the problem can be solved in general form for a fairly wide class of Lagrangians: an even, strictly convex, continuous, non-negative function with a single zero value for $φ = 0$ and for $∣ φ ∣ \to + \infty$ growing faster than $φ^{2}$ . We strictly define the scattering matrix, $S$ -matrix, at the zero value of the classical field, argument of the $S$ -matrix, of such a theory in terms of the corresponding integral, find the iterated expansion for the integrand (the Gaussian measure doesn't expand) over two orthonormal bases of functions, prove the validity of summation and integration interchange and thus find the expansion of the $S$ -matrix at the zero value of the classical field into the iterated series in powers of the interaction action. The individual terms of the resulting series have the form of a canonical partition function (CPF), and the methods of statistical physics are applicable to them. In particular, we express them in terms of Bell polynomials. It is important to note that such iterated series cannot be reduced to the perturbation theory (PT) series, since in the proposed model the latter diverges as $e^{n^{2}}$ , where $n \in N$ is the PT order. Along the way, we provide detailed mathematical background, including Beppo Levi's monotone convergence theorem (MCT) and Henri Lebesgue's dominated convergence theorem (DCT), without which the presented calculation would be significantly more complex.
↳ hep-thcond-mat.stat-mechmath-phmath.MP+10 citations
10
A possible evidence of pion condensation
Wei Zhu🇨🇳 · Yu-Chen Tang🇨🇳 · Lei Feng🇨🇳 · Feng-yao Hou🇨🇳
This work demonstrates that once a large number of pion is condensed in a high-energy hadron collision, the gamma-ray spectrum from $π^{0}$ decay takes on a typical broken power-law shape, which has been documented in many astronomical observations, but we have not yet recognized it. We show that this pion condensation is caused by a large number of soft gluons condensed in protons.
↳ hep-phastro-ph.HEcond-mat.othernucl-thCommun.Theor.Phys.(2025)·0 citations
11
The Fate of Weakly Bound Light Nuclei in Central Collider Experiments: a Challenge in Favor of a Late Continuous Decoupling Mechanism
Jörn Knoll🇩🇪
Arguments are presented that the reaction products of central high energy nuclear collisions up to collider energies can rigorously be interpreted in terms of a continuous decoupling mechanism based on continuous equations of motion. The various aspects of the collision dynamics are investigate in terms of the individual decoupling processes. Thereby each observed particle decouples during its own temporal decoupling window. This includes a ``very late'' decoupling of the faintly bound Hypertritons observed in recent ALICE experiments. The success of the strategy is based upon 200 years old wisdom and leads to a revised interpretation of the entire decoupling process.
↳ hep-phnucl-thPLB(2024)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE