Nuclear Theory·nucl-th

Wednesday·September 25, 2024

15 papers—4 primary·11 cross-listed

01
Field redefinition and its impact in relativistic hydrodynamics
Sayantani Bhattacharyya🇬🇧 · Sukanya Mitra🇮🇳 · Shuvayu Roy🇮🇳 · Rajeev Singh🇮🇳
In this paper, we explore the impact of field redefinition on the spectrum of linearized perturbations in relativistic hydrodynamics. We observe that the spectrum of hydrodynamics modes is never affected by the local field redefinition, however, the spectrum of the non-hydrodynamic modes is affected. Through an appropriate all-order redefinition, non-hydrodynamic modes can be eliminated, leading to a new frame where the spectrum contains only hydrodynamic modes. We also observe that the resulting stress-energy tensor may have an infinite series in momentum space, with a convergence radius linked to the eliminated non-hydrodynamic mode. In certain special cases, higher-order terms in the stress-energy tensor under field redefinition may cancel, indicating that non-hydrodynamic modes are mere artefacts of the fluid variable choice and hold no physical significance, even if they appear to violate physical constraints. Using a special toy example, we find a criterion to distinguish between physical and unphysical non-hydrodynamic modes.
nucl-thgr-qchep-phhep-thPRD(2025)·11 citations
02
Nucleon thermalization hindered by isospin symmetry: Violation of eigenstate thermalization hypothesis in atomic nuclei
Dong Bai · Zhongzhou Ren
Bohr's compound nucleus theory is one of the most important models in nuclear physics, with far-reaching applications in nuclear science and technology. This model generally assumes that the participating nucleons attain a thermal equilibrium characterized by the microcanonical ensemble before subsequent decays. However, from a theoretical viewpoint, it remains uncertain whether this assumption is universally valid. In this Letter, we critically examine this longstanding assumption through the lens of the eigenstate thermalization hypothesis (ETH), a cornerstone of the modern quantum thermalization theory. Utilizing the time-dependent configuration interaction shell model, it is found that, in certain cases, the long-time averages of nucleon occupation numbers can exhibit significant deviations from the microcanonical ensemble averages, in contrast to the conventional expectation. We attribute this discrepancy primarily to the violation of the ETH in the presence of isospin symmetry and discover that incorporating a substantial isospin-breaking term into the shell-model Hamiltonian can effectively restore the nucleon thermalization.
nucl-th0 citations
03
Multicomponent Fermi systems at low densities
C.J. Pethick · A. Schwenk
We calculate, to second order in the scattering length between two fermions, the Landau quasiparticle interaction for a low-density mixture of two fermion species with unequal densities at temperature zero. From the Landau parameters we evaluate the energy density and find agreement with the result of Kanno, Prog. Theor. Phys. 44, 813 (1970). The calculations are then extended to the case of two fermion components with different total densities, each with two spin components, a situation of interest in nuclear physics and astrophysics, where the species are neutrons and protons. An interesting finding is that, for low proton concentrations, $x ≪ 1$ , the leading term in the energy density, beyond the $x^{5/3}$ contribution from the kinetic energy and the $x^{2}$ one due to the two-body interaction in the mean-field approximation, varies as $x^{7/3} ln x$ . This is to be contrasted with the higher powers of $x$ implicit in many phenomenological energy-density functionals employed in nuclear physics, such as those of the Skyrme type.
nucl-thastro-ph.HEcond-mat.quant-gasPRC(2025)·0 citations
04
Equilibrium expectations for non-Gaussian fluctuations near a QCD critical point
Jamie M. Karthein🇺🇸 · Maneesha Sushama Pradeep🇺🇸 · Krishna Rajagopal🇺🇸 · Mikhail Stephanov🇺🇸 · Yi Yin🇨🇳
With the highly anticipated results from the Beam Energy Scan II program at RHIC being recently revealed, an understanding of particle-number fluctuations and their significance as a potential signature of a possible QCD critical point is crucial. Early works that embarked on this endeavor sought to estimate the fluctuations due to the presence of a critical point assuming they stay in equilibrium. From these results came the proposal to focus efforts on higher, non-Gaussian, moments of the event-by-event distributions, in particular of the number of protons. These non-Gaussian moments are especially sensitive to critical fluctuations, as their magnitudes are proportional to high powers of the critical correlation length. As the equation of state provides key input for hydrodynamical simulations of heavy-ion collisions, we estimate equilibrium fluctuations from the BEST equation of state (EoS) that includes critical features from the 3D Ising Model. In particular, the proton factorial cumulants and their dependence on non-universal mapping parameters is investigated within the BEST EoS. Furthermore, the correlation length, as a central quantity for the assessment of fluctuations in the vicinity of a critical point, is also calculated in a consistent manner with the scaling equation of state. An understanding of the equilibrium estimates of proton factorial cumulants will be useful for further comparison to estimates of out-of-equilibrium fluctuations in order to determine the magnitude of the observable fluctuations to be expected in heavy-ion collision experiments, in which the time spent near a critical point is short.
nucl-thhep-phEPJ Web Conf.(2025)·4 citations
05
Nucleon Gravitational Form Factors
Z.-Q. Yao🇨🇳 · Y.-Z. Xu🇪🇸 · D. Binosi🇮🇹 · Z.-F. Cui🇨🇳 · M. Ding🇨🇳 · K. Raya🇪🇸 · C. D. Roberts🇨🇳 · J. Rodríguez-Quintero🇪🇸 · S. M. Schmidt🇩🇪
A symmetry-preserving analysis of strong interaction quantum field equations is used to complete a unified treatment of pion, kaon, nucleon electromagnetic and gravitational form factors. Findings include a demonstration that the pion near-core pressure is roughly twice that in the proton, so both are significantly greater than that of a neutron star; parton species separations of the nucleon's three gravitational form factors, in which, inter alia, the glue-to-quark ratio for each form factor is seen to take the same constant value, independent of momentum transfer; and a determination of proton radii orderings, with the mechanical (normal force) radius being less than the mass-energy radius, which is less than the proton charge radius. This body of predictions should prove useful in an era of anticipated experiments that will enable them to be tested.
↳ hep-phhep-exhep-latnucl-ex+1EPJA(2025)·60 citations
06
Partial-wave projection of relativistic three-body amplitudes
Raúl A. Briceño🇩🇪 · Caroline S. R. Costa🇺🇸 · Andrew W. Jackura🇺🇸
We derive the integral equations for partial-wave projected three-body scattering amplitudes, starting from the integral equations for three-body amplitudes developed for lattice QCD analyses. The results, which hold for generic three-body systems of spinless particles, build upon the recently derived partial-wave projected one-particle exchange, a primary component of the relativistic framework proven to satisfy S matrix unitarity. We derive simplified expressions for factorizable short-distance interactions, $K_{3}$ , in two equivalent formalisms - one symmetric under particle interchange and one asymmetric. For the asymmetric case, we offer parameterizations useful for amplitude analysis. Finally, we examine toy models for $3 π$ systems at unphysically heavy pion masses with total isospins 0,1, and 2.
↳ hep-phhep-lathep-thnucl-thPRD(2025)·20 citations
07
Twist-2 distribution amplitudes of $a_{0} (980)$ and $a_{0} (1450)$
Wei Hong🇨🇳 · Di Gao🇨🇳 · Yanjun Sun🇨🇳
We investigate the twist-2 distribution amplitudes of the scalar mesons $a_{0} (980)$ and $a_{0} (1450)$ in the two-quark picture. The moments of these scalar mesons are obtained up to the third order with QCD sum rules method. With these moments, the first two Gegenbauer coefficients are determined and utilized to analyze the twist-2 distribution amplitudes. Our numerical results indicate that the meson $a_{0} (980)$ favors a conventional two-quark ground state. The paper concludes with an examination of the form factors for the transitions $B / D \to a_{0}$ .
↳ hep-phnucl-thNPA(2025)·3 citations
08
Second-order chiral kinetic theory from Wigner function approach
Shi-Zheng Yang🇨🇳 · Shu-Xiang Ma🇨🇳 · Jian-Hua Gao🇨🇳
We present a systematic method to derive the chiral kinetic theory from the Wigner equations based on quantum field theory order by order. We take special effort to derive the chiral kinetic theory in seven-dimensional phase space from the eight-dimensional chiral kinetic theory. We give the seven-dimensional chiral kinetic theory up to second order of semiclassical expansion. We find some new second-order contributions compared with other approaches.
↳ hep-phhep-thnucl-thPRD(2025)·3 citations
09
Improving target neutron momentum reconstruction using MINER $ν$ A $π^{0}$ data
R K Pradhan🇮🇳 · R Lalnuntluanga🇮🇳 · A Giri🇮🇳
With the neutrino experiments advancing toward high-precision measurements and greater emphasis on reducing systematic uncertainties, improving the single-pion production models, a major component of the hadronic activity observed in the neutrino oscillation experiments, into the Monte Carlo simulations is crucial. This work presents the predictions of the struck nucleon's Fermi motion by analyzing the charged-current neutral pion production on carbon nucleus in MINER $ν$ A. A minimal variation of GENIE and NuWro based on their default models shows an improvement in the prediction of single $π^{0}$ production. The prediction describes the data more accurately in the higher-momentum tail; however, discrepancies between the predictions and data below the Fermi peak highlight the limitations in current nuclear models used in the Monte Carlo generators.
↳ hep-phhep-exnucl-thPRD(2025)·3 citations
10
Evidence of collinear factorization breaking due to collinear-to-soft Glauber exchanges for a $2 \to 3$ exclusive process at leading twist
Saad Nabeebaccus🇫🇷 · Jakob Schoenleber🇩🇪 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷
We exhibit an exclusive process, namely the photoproduction of a $π^{0} γ$ pair with large invariant mass, which violates collinear factorization. We explicitly demonstrate that this is due to the fact that there exists diagrams with gluon exchange in $t$ channel, contributing at the leading power, for which Glauber gluons are trapped. This is caused by the pinching of the contour integration of both the plus and minus light-cone components of the Glauber gluon momentum. We argue that this leads to the observed ``endpoint-like'' divergence of the convolution integral at leading order and leading power when collinear factorization is naïvely assumed.
↳ hep-phnucl-thPRD(2025)·15 citations
11
Going against the flow: Revealing the QCD degrees of freedom in hadronic collisions
Christian Bierlich🇸🇪 · Peter Christiansen🇸🇪 · Gösta Gustafson🇸🇪 · Leif Lönnblad🇸🇪 · Robin Törnkvist🇪🇸 · Korinna Zapp🇸🇪
In collisions between heavy nuclei, such as those at the Large Hadron Collider (LHC) at CERN, hydrodynamic models have successfully related measured azimuthal momentum anisotropies to the transverse shape of the collision region. For an elliptically shaped interaction area, the hydrodynamic pressure gradient is greater along the minor axis, resulting in increased particle momentum in that direction - a phenomenon known as positive elliptic flow. In this paper, we demonstrate that in smaller systems, such as proton-proton and peripheral ion-ion collisions, microscopic models for final state interactions, can produce anisotropies where the elliptic flow is negative - that is, the momentum is largest along the major axis, contrary to hydrodynamic predictions. We present results from two distinct microscopic models: one based on repulsion between string-like fields and another based on effective kinetic theory. Negative elliptic flow is a solid prediction of the string interaction model while in the model based on kinetic theory it is linked to a finite interaction range. Consequently, an experimental determination of the sign of elliptic flow, will provide novel insights into the degrees of freedom governing strong nuclear interactions in high-energy collisions and the way in which they interact.
↳ hep-phnucl-thPLB(2026)·4 citations
12
Phase-transition-induced collapse of proto-compact stars and its implication for supernova explosions
Xu-Run Huang🇵🇰 · Shuai Zha🇨🇦 · Ming-chung Chu🇵🇰 · Evan P. O'Connor🇯🇵 · Lie-Wen Chen🇨🇳
A hadron-quark phase transition (PT) may trigger supernova explosions during stellar core collapse. However, both success and failure have occurred in previous attempts to explode dying stars via this mechanism. We systematically explore the outcomes of the PT-induced collapse of mock proto-compact stars (PCSs) with a constant entropy and lepton fraction, with spherically symmetric general relativistic hydrodynamic simulations and a controlled series of hybrid equations of state. Our results reveal the qualitative dependence of successful and failed explosions on the PT and quark matter characteristics. A small portion ( $\sim 0.04% - 1%$ ) of the released binding energy $Δ E_{B}$ transforms into the diagnostic explosion energy $E_{exp, diag}$ , which saturates at $\sim 6 \times 1 0^{51}$ erg near the black hole formation. Note that our $E_{exp, diag}$ represents an upper limit of the final explosion energies in realistic supernova simulations. We draw the phase diagrams indicative of the possible fates of supernova explosions driven by hadron-quark PTs, where the control parameters are the onset density, energy gap of the PT, and the quark matter speed of sound. Our findings can guide further self-consistent investigations on PT-driven core-collapse supernovae and help identify hadron-quark PT-induced PCS collapse from future observations.
↳ astro-ph.HEnucl-thApJ(2025)·23 citations
13
Testing gravity with the latent heat of neutron star matter
Pablo Navarro Moreno🇪🇸 · Aneta Wojnar🇪🇸 · Felipe J. Llanes-Estrada🇪🇸
The Seidov limit is a bound on the maximum latent heat that a presumed first-order phase transition of neutron-star matter can have before its excess energy density, not compensated by additional pressure, results in gravitational collapse. Because latent heat forces an apparent nonanalytic behaviour in plots correlating physical quantities (kinks in two-dimensional, ridges in three-dimensional ones), it can be constrained by data. As the onset of collapse depends on the intensity of gravity, testing for sudden derivative changes and, if they are large, breaching the Seidov limit would reward with two successive discoveries: such a phase transition (which could stem from hadron matter but also from a gravitational phase transition), and a modification of General Relativity (thus breaking the matter/gravity degeneracy). We illustrate the point with $f (R) = R + α R^{2}$ metric gravity.
↳ gr-qcnucl-thJCAP(2025)·3 citations
14
Probing the equation of state of neutron stars using neutrino oscillations
Siddhartha Bandyopadhyay🇮🇳 · Golam Mortuza Hossain🇮🇳
We study the phenomena of neutrino oscillations and flavour mixing by incorporating the gravitational effects through the Dirac equation in curved spacetime inside a spherically symmetric star. We show that the flavour transition probabilities of the neutrinos depend on the interior spacetime metric as they propagate out of the star. As a consequence, we show that one could distinguish between different possible equation of states of nuclear matter even for an isolated neutron star if one could determine the flavour composition of emitted neutrinos near the stellar surface.
↳ gr-qcastro-ph.HEhep-phnucl-thPRD(2025)·2 citations
15
Heavy $K^{*}$ mesons with open charm from $K D^{(*)} D^{*}$ interactions
Xiu-Lei Ren🇩🇪 · K. P. Khemchandani🇧🇷 · A. Martínez Torres🇧🇷
In view of the recent discovery of $T_{cc}$ , which can be described as a $D D^{*}$ molecular state, we perform a study of the $K D D^{*}$ system, and its extension to studying $K D^{*} D^{*}$ , where $D^{*} D^{*}$ is bound as a spin 1 $T_{cc}$ -like state, to search for the possible existence of exotic mesons with the open flavors $ccs$ being part of their quark configuration. Considering the additional attractive interactions present in the $K D$ and $K D^{*}$ subsystems, where the states $D_{s 0}^{*} (2317)$ and $D_{s 1} (2460)$ are generated, we solve the Faddeev equations considering the fixed-center approximation for the mentioned three-body systems and find the existence of two doubly charmed $K^{*}$ -like mesons, $K_{cc}^{*} (4309)$ and $K_{cc}^{*} (4449)$ , with quantum numbers $I (J^{P}) = 1/2 (1^{-})$ . Considering the respective three-body thresholds of the two systems, both $K_{cc}$ -states are bound by around $60$ MeV. An experimental confirmation will bring evidence for the existence of a degree of exoticity beyond charm +2.
↳ hep-phnucl-thEPJC(2024)·7 citations

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