Nuclear Theory·nucl-th

Wednesday·July 10, 2024

15 papers—6 primary·9 cross-listed

01
Viscous damping of r-modes and emission of gravitational waves
Debasis Atta🇮🇳 · D. N. Basu🇮🇳
The Rossby mode (r-mode) perturbation in pulsars as a steady gravitational wave (GW) source has been explored. The effect of a rigid crust on viscous damping and dissipation rate in the boundary layer between fluid core and crust has been studied. The intensity of the emitted GWs in terms of the strain tensor amplitude has been estimated with the approximation of slow rotation using equation of state derived from the APR and Skyrme effective interactions with Brussels-Montreal parameter sets. The core of the neutron star has been considered to be $β$ -equilibrated nuclear matter containing neutrons, protons, electrons and muons, surrounded by a solid crust. Calculations have been made for critical frequencies, the time evolution and the rate of change of the spin frequencies across a broad spectrum of pulsar masses.
nucl-thPramana(2025)·2 citations
02
Angular anisotropy in prefission neutron spectra and PFNS of $^{240}$ Pu $(n, F)$
V.M. Maslov
Angular anisotropy of secondary neutrons was evidenced in neutron emission spectra (NES) of $^{239}$ Pu+n in 1972, and prompt fission neutron spectra (PFNS) of $^{239}$ Pu $(n, F)$ in 2019, it might be predicted for $^{240}$ Pu(n,F) PFNS now. In case of NES angular anisotropy is due to direct excitation of collective levels and pre-equilibrium/semi-direct (states in the continuum are excited) mechanism of neutron emission of first neutron in (n,nX) reaction, while in case of PFNS it is due to exclusive spectra of pre-fission neutrons of (n, xnf) reactions. In $^{239}$ Pu $(n, x n f)$ and $^{240}$ Pu(n,xnf) reactions observed PFNS envision different response to the emission of first pre-fission neutron in forward or backward semi-spheres with respect to the momentum of incident neutrons. Since energies of (n,nf) neutrons and their average values depend on angle of emission theta with respect to the incident neutron momentum, the observed PFNS, average prompt fission neutron multiplicity, fission cross section, average total kinetic energy TKE, etc. also would be quite dependent on angle theta. Exclusive spectra of (n, xnf) neutrons at theta of 90 degrees are consistent with $^{240}$ Pu(n, F)( $^{239}$ Pu $(n, F)$ , $^{239}$ Pu $(n, 2 n)$ ) observed cross sections and neutron emission spectra of $^{239}$ Pu+n interaction at En up to 20 MeV. The correlations of the angular anisotropy of PFNS with the relative contribution of the $(n, n f)$ fission chance to the observed fission cross section and angular anisotropy of pre-fission neutron emission are ascertained.
nucl-thnucl-ex0 citations
03
Electron scattering cross section for light nuclei within the unified electroweak theory
Vo Minh Truong · Nguyen Quang Hung
We employ the multipole expansion within the unified electroweak theory to develop a complete calculation method of the electron scattering cross section for light nuclei. The specific calculations for 6,7Li and 7Be nuclei indicate that the conventional impulse approximation can be applied to the electron-nucleus scattering only when the incident electron energy does not exceed twice the nucleon mass. In addition, the quasi-elastic scattering cross section of 7Li in the excitation from its ground state to the nearest excited state and that of elastic scattering in the ground state are independently treated, whereas they have not been separately measured in experiments. The obtained scattering cross sections corresponding to an appropriate adjustment of the harmonic oscillator parameter along with the V-A structure interpret reasonably well the available experimental data at MeV energies and provide predictive information at GeV energies. This gives new perspectives in studying the structure of nuclei and the weak interactions via electron or lepton scattering at high (GeV) energies, considering nuclei rather than quarks.
nucl-thhep-phPRC(2024)·0 citations
04
A Method to Constrain Preferential Emission and Spectator Dynamics in Heavy-Ion Collisions
Vipul Bairathi🇨🇱 · Somadutta Bhatta🇺🇸
Longitudinal particle production in heavy-ion collisions is influenced both by preferential emission from participating nucleons and by the breakup of spectator matter, yet quantifying these effects experimentally remains challenging. We introduce a Pearson correlation between spectator and charged-particle forward-backward asymmetries as an experimental probe of these phenomena. Using Au+Au collisions at $s_{N N} = 200$ GeV simulated with A Multi-Phase Transport (AMPT) model, we validate that this correlator provides a robust, pseudorapidity-differential measure of the influence of preferential emission on the longitudinal structure of particle production. We further demonstrate that the correlation strength is sensitive to fluctuations in spectator number, which in experiments arise from evaporation and fragmentation of the spectator remnants. The proposed observable therefore offers a data-driven handle for constraining models of preferential emission and spectator breakup, thereby improving our understanding of the mechanisms that shape the final-state longitudinal distributions in heavy-ion collisions.
nucl-thhep-exhep-phnucl-exPRC(2026)·0 citations
05
Quantum Monte Carlo calculations of electron scattering from $^{12} C$ in the Short-Time Approximation
Lorenzo Andreoli · Garrett B. King · Saori Pastore · Maria Piarulli · Joseph Carlson · Stefano Gandolfi · Robert B. Wiringa
The Short-Time approximation is a method introduced to evaluate electroweak nuclear response for systems with $A \geq 12$ , extending the reach of first-principle many-body Quantum Monte Carlo calculations. Using realistic two- and three-body nuclear interactions and consistent one- and two-body electromagnetic currents, we calculate longitudinal and transverse response densities and response functions of $^{12} C$ . We compare the resulting cross sections with experimental data for electron-nucleus scattering, finding good agreement.
nucl-thPRC(2024)·16 citations
06
Enhanced $ψ^{'}$ yield and $ψ^{'} / (J / ψ)$ yield ratio as a possible signature of QGP formation in high multiplicity $p + p$ collisions
Partha Bagchi🇮🇳 · Arpan Das🇮🇳 · Ananta P. Mishra🇮🇳 · Ankit Kumar Panda🇮🇳
Suppression in the yield of quarkonia (heavy quark-antiquark bound states) has been considered one of the important signatures of the formation of the thermalized deconfined partonic matter, also known as the Quark Gluon Plasma (QGP), in Relativistic Heavy Ion Collision Experiments (RHICE). Traditionally, the in-medium dissociation of quarkonium states has been presented by implicitly assuming an adiabatic approximation, which considers that the heavy quark Hamiltonian changes slowly over time owing to change in the medium. However, in high multiplicity smaller systems, such as in $p + p$ collisions, the early development of transverse flow resulting from the finite transverse size of the locally thermalized medium may cause the quarkonium states to undergo a non-adiabatic evolution. It has been argued that in the presence of such a non-adiabatic evolution, the suppression of heavy quark-antiquark bound state yields may not reliably indicate QGP formation~\cite{Bagchi:2023vfv}. We propose that, rather than concentrating on the suppression of $J / ψ$ yields, the enhancement in the yield ratio of $ψ^{'}$ to $J / ψ$ (i.e., $ψ^{'} / (J / ψ)$ ), along with an increase in $ψ^{'}$ yield, should be considered as a probe of QGP formation for small systems. Our findings, based on realistic modeling of the time evolution of small systems, suggest that the yield ratio $ψ^{'} / (J / ψ)$ and the yield of $ψ^{'}$ increase as a function of hydrodynamization temperature incorporating the non-adiabatic transitions in high multiplicity $p + p$ collisions.
nucl-thhep-ph1 citation
07
Explanation of the excesses in associated di-photon production at 152 GeV in 2HDM
Sumit Banik🇨🇭 · Andreas Crivellin🇨🇭
Statistically significant excesses exist at around 152 GeV in associated di-photon production ( $γ γ + X$ ) in the sidebands of SM Higgs analyses of ATLAS (using the full run-2 dataset). They are most pronounced in the single- $τ$ , missing-transverse-energy, four-jet and $⩾ 1 ℓ + ⩾ 1 b$ -jet channels ( $\approx 3 σ$ ) and can be explained by the Drell-Yan production of new Higgs bosons, i.e. $pp \to W^{*} \to H^{\pm} H^{0}$ . We first examine the excesses in a simplified model approach, considering that $H^{\pm}$ decays to $τ ν$ , $W Z$ or $t b$ . Both the $τ ν$ and $t b$ decay modes individually lead to a significance of $⪅ 4 σ$ while for $W Z$ one can obtain at most $3.5 σ$ . This is because the decays of $W Z$ lead to multiple leptons contributing to the two-lepton channel which does not show an excess at 152 GeV. Next, we consider two-Higgs-doublet models where the charged Higgs does not decay to $W Z$ at tree-level, finding a significance of $⪆ 4 σ$ for a branching ratio of the new neutral Higgs to photons of $\approx$ 2%. Even though this branching fraction is quite sizable, it can be obtained in composite models or via the Lagrangian term $λ_{6} H_{1}^{†} H_{1} H_{2}^{†} H_{1} + h.c.$ breaking the commonly imposed $Z_{2}$ symmetry.
↳ hep-phhep-exnucl-thJHEP(2024)·14 citations
08
Circularly polarized photon emission from magnetized chiral plasmas
Xinyang Wang🇨🇳 · Igor A. Shovkovy🇺🇸
We investigate the emission of circularly polarized photons from a magnetized quark-gluon plasma with nonzero quark-number and chiral charge chemical potentials. These chemical potentials qualitatively influence the differential emission rates of circularly polarized photons. A nonzero net electric charge density, induced by quark-number chemical potentials, enhances the overall emission of one circular polarization over the other, while a nonzero chiral charge density introduces a spatial asymmetry in the emission with respect to reflection in the transverse plane. The signs of the electrical and chiral charge densities determine which circular polarization dominates overall and whether the emission preferentially aligns with or opposes the magnetic field. Based on these findings, we propose that polarized photon emission is a promising observable for characterizing the quark-gluon plasma produced in heavy-ion collisions.
↳ hep-phnucl-thPRD(2024)·10 citations
09
Net-Proton Number Cumulants in Strongly and Weakly Coupled QGP
Kiminad A. Mamo🇺🇸
We provide a description of the QCD phase diagram across different energy regimes. Without any adjustable free parameters fitted to lattice or experimental data, we demonstrate that the net-proton number cumulant ratios from the Beam Energy Scan-I (BES-I) central ( $0 - 5%$ ) Au+Au collision experiments at RHIC, for center-of-mass energies $s \geq 39 GeV$ , are well described by the $dynamical soft-wall$ AdS black hole model, indicating the formation of a strongly coupled quark-gluon plasma (sQGP) dominated by gluons in the large $N_{c}$ limit. We identify a critical point at $μ_{B} = 247 MeV$ or $s = 16 GeV$ in this model, where net-proton cumulant ratios show non-monotonic variation. However, for $s < 39 GeV$ , the recent BES-II data does not exhibit the expected variation due to the critical point, suggesting instead a transition to a nearly-cold ( $μ_{B} ≫ T$ ) weakly coupled QGP (wQGP), for $s < 7.7 GeV$ , dominated by valence quarks. This prediction can be tested by the upcoming STAR Fixed-Target experimental data.
↳ hep-phhep-thnucl-exnucl-th1 citation
10
Tractable $a$ $priori$ Dimensionality Reduction for Quantum Dynamics
Patrick Cook
In this short letter, I present a powerful application in dimensionality reduction of the lesser-used Jacobi-Davidson algorithm for the generalized eigenvalue decomposition. When combined with matrix-free implementations of relevant operators, this technique allows for the computation of the dynamics of an arbitrary quantum state to be done in $O (n)$ time, where $n$ is the size of the original Hilbert space.
↳ quant-phnucl-thphysics.comp-ph1 citation
11
Electromagnetic and two-photon transition form factors of the pseudoscalar mesons: An algebraic model computation
I. M. Higuera-Angulo🇲🇽 · R. J. Hernández-Pinto🇲🇽 · K. Raya🇪🇸 · A. Bashir🇲🇽
We compute electromagnetic and two-photon transition form factors of ground-state pseudoscalar mesons: $π, K, η_{c}, η_{b}$ . To this end, we employ an algebraic model based upon the coupled formalism of Schwinger-Dyson and Bethe-Salpeter equations. Within this approach, the dressed quark propagator and the relevant Bethe-Salpeter amplitude encode the internal structure of the corresponding meson. Electromagnetic properties of the meson are probed via the quark-photon interaction. The algebraic model employed by us unifies the treatment of all ground-state pseudoscalar mesons. Its parameters are carefully fitted performing a global analysis of existing experimental data including the knowledge of the charge radii of the mesons studied. We then compute and predict electromagnetic and two-photon transition form factors for a wide range of probing photon momentum-squared which is of direct relevance to the experimental observations carried out thus far or planned at different hadron physics facilities such as the Thomas Jefferson National Accelerator Facility (JLab) and the forthcoming Electron-Ion Collider. We also present comparisons with other theoretical models and approaches and lattice quantum chromodynamics.
↳ hep-phhep-thnucl-thPRD(2024)·10 citations
12
Unveiling the Secrets of Vortex Neutron Decay
Wei Kou🇨🇳 · Bing'ang Guo🇨🇳 · Xurong Chen🇨🇳
Investigation of decay and scattering processes of particles in a vortex state offers a novel and promising approach for probing particle structure. Our study reveals distinct properties of vortex neutron decay, which deviate from those of classical plane-wave neutron decay. We present the energy-angle distributions of the final-state electron and antineutrino in unpolarized vortex neutrons, as well as angle distributions integrated over their energies. Notably, we provide theoretical calculations of the decay behavior of neutrons with varying vortex cone angles and initial energies. We propose that identifying the vortex state of the initial neutron can be achieved by analyzing the angular and energy distributions of the final-state particles, introducing new degrees of freedom for studying weak interactions and neutron decay kinematics that have been previously overlooked in particle physics. This timely investigation takes advantage of recent advancements in vortex neutron preparation and analysis, opening up new avenues for exploring the fundamental properties of matter.
↳ hep-phnucl-thPLB(2025)·3 citations
13
A NICER View of the Nearest and Brightest Millisecond Pulsar: PSR J0437 $\unicode x 2013$ 4715
Devarshi Choudhury🇳🇱 · Tuomo Salmi🇳🇱 · Serena Vinciguerra🇳🇱 · Thomas E. Riley🇳🇱 · Yves Kini🇳🇱 · Anna L. Watts🇳🇱 · Bas Dorsman🇳🇱 · Slavko Bogdanov🇺🇸 · Sebastien Guillot🇫🇷 · Paul S. Ray🇺🇸 · Daniel J. Reardon🇦🇺 · Ronald A. Remillard🇺🇸 and 8 other authors
We report Bayesian inference of the mass, radius and hot X-ray emitting region properties - using data from the Neutron Star Interior Composition ExploreR (NICER) - for the brightest rotation-powered millisecond X-ray pulsar PSR J0437 $\unicode x 2013$ 4715. Our modeling is conditional on informative tight priors on mass, distance and binary inclination obtained from radio pulsar timing using the Parkes Pulsar Timing Array (PPTA) (Reardon et al. 2024), and we use NICER background models to constrain the non-source background, cross-checking with data from XMM-Newton. We assume two distinct hot emitting regions, and various parameterized hot region geometries that are defined in terms of overlapping circles; while simplified, these capture many of the possibilities suggested by detailed modeling of return current heating. For the preferred model identified by our analysis we infer a mass of $M = 1.418 \pm 0.037$ M $_{⊙}$ (largely informed by the PPTA mass prior) and an equatorial radius of $R = 11.3 6_{- 0.63}^{+ 0.95}$ km, each reported as the posterior credible interval bounded by the 16% and 84% quantiles. This radius favors softer dense matter equations of state and is highly consistent with constraints derived from gravitational wave measurements of neutron star binary mergers. The hot regions are inferred to be non-antipodal, and hence inconsistent with a pure centered dipole magnetic field.
↳ astro-ph.HEastro-ph.SRnucl-thApJL(2024)·395 citations
14
Constraining the dense matter equation of state with new NICER mass-radius measurements and new chiral effective field theory inputs
Nathan Rutherford🇺🇸 · Melissa Mendes🇩🇪 · Isak Svensson🇩🇪 · Achim Schwenk🇩🇪 · Anna L. Watts🇳🇱 · Kai Hebeler🇩🇪 · Jonas Keller🇩🇪 · Chanda Prescod-Weinstein🇺🇸 · Devarshi Choudhury🇳🇱 · Geert Raaijmakers🇳🇱 · Tuomo Salmi🇳🇱 · Patrick Timmerman🇳🇱 and 3 other authors
Pulse profile modeling of X-ray data from NICER is now enabling precision inference of neutron star mass and radius. Combined with nuclear physics constraints from chiral effective field theory ( $χ$ EFT), and masses and tidal deformabilities inferred from gravitational wave detections of binary neutron star mergers, this has lead to a steady improvement in our understanding of the dense matter equation of state (EOS). Here we consider the impact of several new results: the radius measurement for the 1.42 $M_{⊙}$ pulsar PSR J0437 $-$ 4715 presented by Choudhury et al. (2024), updates to the masses and radii of PSR J0740 $+$ 6620 and PSR J0030 $+$ 0451, and new $χ$ EFT results for neutron star matter up to 1.5 times nuclear saturation density. Using two different high-density EOS extensions -- a piecewise-polytropic (PP) model and a model based on the speed of sound in a neutron star (CS) -- we find the radius of a 1.4 $M_{⊙}$ (2.0 $M_{⊙}$ ) neutron star to be constrained to the 95% credible ranges $12.2 8_{- 0.76}^{+ 0.50}$ km ( $12.3 3_{- 1.34}^{+ 0.70}$ km) for the PP model and $12.0 1_{- 0.75}^{+ 0.56}$ km ( $11.5 5_{- 1.09}^{+ 0.94}$ km) for the CS model. The maximum neutron star mass is predicted to be $2.1 5_{- 0.16}^{+ 0.14}$ $M_{⊙}$ and $2.0 8_{- 0.16}^{+ 0.28}$ $M_{⊙}$ for the PP and CS model, respectively. We explore the sensitivity of our results to different orders and different densities up to which $χ$ EFT is used, and show how the astrophysical observations provide constraints for the pressure at intermediate densities. Moreover, we investigate the difference $R_{2.0} - R_{1.4}$ of the radius of 2 $M_{⊙}$ and 1.4 $M_{⊙}$ neutron stars within our EOS inference.
↳ astro-ph.HEastro-ph.SRnucl-exnucl-thApJL(2024)·122 citations
15
Charged current weak production of $Δ (1232)$ induced by electrons and positrons
A. Fatima🇮🇳 · M. Sajjad Athar🇮🇳 · S. K. Singh🇮🇳
The charged current weak production of $Δ (1232)$ from the free proton target induced by the electron/positron in the intermediate energy range corresponding to the beam energy available at JLab and Mainz, has been studied. The results for the differential scattering cross section $\frac{d σ}{d Q ^{2}}$ , the angular distribution $\frac{d σ}{d Ω _{Δ}}$ , and the total scattering cross section $σ (E_{e})$ for both the electron and positron induced processes are presented, for the various energies in the range of 0.5--4~GeV. The cross section $σ (E_{e})$ is found to be of the order of $1 0^{- 39}$ ~cm $^{2}$ for the electron/positron energies in the few GeV range. The availability of electron/positron beams having well defined energy and direction with very high luminosity of the order of $1 0^{38} - 1 0^{39}$ ~cm $^{- 2}$ ~sec $^{- 1}$ , makes it possible to observe the weak charged current production of $Δ (1232)$ and determine the axial vector form factors $C_{i}^{A} (Q^{2}); (i = 3 - 5)$ . The sensitivity of the differential cross section $\frac{d σ}{d Q ^{2}}$ to the subdominant form factors $C_{3}^{A} (Q^{2})$ and $C_{4}^{A} (Q^{2})$ is found to be strong enough, especially in the low $Q^{2}$ region, which can be used to determine them phenomenologically and to test the various theoretical models proposed to calculate them.
↳ hep-phhep-exnucl-thPRD(2024)·3 citations

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