Nuclear Theory·nucl-th

Tuesday·July 2, 2024

22 papers—6 primary·16 cross-listed

07
Fudan Multi-purpose Active TArget Time Projection Chamber (fMeta-TPC) for Photonnuclear Reaction Experiments
Huang-Kai Wu · Xi-Yang Wang · Yu-Miao Wang · You-Jing Wang · De-Qing Fang · Wan-Bing He · Wei-Hu Ma · Xi-Guang Cao · Chang-Bo Fu · Xian-Gai Deng · Yu-Gang Ma
Active Target Time Projection Chambers (AT-TPCs) are state-of-the-art tools in the field of low-energy nuclear physics, particularly suitable for experiments using low-intensity radioactive ion beams or gamma rays. The Fudan Multi-purpose Active Target Time Projection Chamber (fMeta-TPC) with 2048 channels has been developed to study $α$ -clustering nuclei. {\fcb In this work, the focus is on the study of the photonuclear reaction with the Laser Compton Scattering (LCS) gamma source, especially for the decay of the highly excited $α$ -cluster state.} The design of fMeta-TPC is described and a comprehensive evaluation of its offline performance is performed by ultraviolet (UV) laser and $^{241}$ Am $α$ source. The result shows that the intrinsic angular resolution of the detector is within 0.30 $^{\circ}$ and has an energy resolution of 6.85\% for 3.0 MeV $α$ particles. The gain uniformity of the detector is about 10\% (RMS/Mean), tested by the $^{55}$ Fe X-ray source.
↳ physics.ins-detnucl-exnucl-thNucl.Sci.Tech.(2024)·7 citations
08
Neutrino emission in cold neutron stars: Bremsstrahlung and modified urca rates reexamined
Salvatore Bottaro🇮🇱 · Andrea Caputo🇨🇭 · Damiano Fiorillo🇩🇰
Neutrino emission in cold neutron stars is dominated by the modified urca (murca) process and nucleon-nucleon bremsstrahlung. The standard emission rates were provided by Friman and Maxwell in 1979, effectively based on a chiral Lagrangian framework with pion and rho meson exchange, supplemented by Landau parameters to describe short-range interactions. We reevaluate these rates within the same framework, correcting several errors and removing unnecessary simplifications, notably the triangular approximation - where the Fermi momenta of protons and leptons negligible compared to that of neutrons - in MURCA, and quantify their importance. The impact of rho meson exchange, previously argued to cancel with interference effects, is actually quite relevant. Altogether, the cooling rates are reduced by as much as a factor 2. We provide comprehensive analytical formulas encompassing all contributions, designed for straightforward numerical implementation. Our results are particularly relevant for studies of physics beyond the standard model, where the emission of new particles - such as axions - is typically computed within the same framework we adopt here.
↳ hep-phastro-ph.HEnucl-thJCAP(2024)·16 citations
09
Two-gluon one-photon vertex in a magnetic field and its explicit one-loop approximation in the intermediate field strength regime
Alejandro Ayala🇲🇽 · Santiago Bernal-Langarica🇲🇽 · Jorge Jaber-Urquiza🇲🇽 · José Jorge Medina-Serna🇲🇽
We find the general structure for the two-gluon one-photon vertex in the presence of a constant magnetic field. We show that, when accounting for the symmetries satisfied by the strong and electromagnetic interactions under parity, charge conjugation and gluon interchange, and for gluons and photons on mass-shell, there exist only three possible tensor structures that span the vertex. These correspond to external products of the polarization vectors for each of the particles in the vertex. We also explicitly compute the one-loop approximation to this vertex in the intermediate field strength regime, which is the most appropriate one to describe possible effects of the presence of a magnetic field to enhance photon emission during pre-equilibrium in peripheral relativistic heavy-ion collisions. We show that the most favored direction for the photon to propagate is in the plane transverse to the field, which is consistent with a positive contribution to $ν_{2}$ and may help to understand the larger than expected elliptic flow coefficient measured in this kind of reactions.
↳ hep-phnucl-thPRD(2024)·8 citations
10
Scattering Neutrinos, Spin Models, and Permutations
Duff Neill🇺🇸 · Hanqing Liu🇺🇸 · Joshua Martin🇺🇸 · Alessandro Roggero🇮🇹
We consider a class of Heisenberg all-to-all coupled spin models inspired by neutrino interactions in a supernova with $N$ degrees of freedom. These models are characterized by a coupling matrix that is relatively simple in the sense that there are only a few, relative to $N$ , non-trivial eigenvalues, in distinction to the classic Heisenberg spin-glass models, leading to distinct behavior in both the high-temperature and low-temperature regimes. When the momenta of the neutrinos are uniform and random in directions, we can calculate the large- $N$ partition function for the quantum Heisenberg model. In particular, the high-temperature partition function predicts a non-Gaussian density of states, providing interesting counter-examples showing the limits of general theorems on the density of states for quantum spin models. We can repeat the same argument for classical Heisenberg models, also known as rotor models, and we find the high-temperature expansion is completely controlled by the eigenvalues of the coupling matrix, and again predicts non-Gaussian behavior for the density of states as long as the number of eigenvalues does not scale linearly with $N$ . Indeed, we derive the amusing fact that these \emph{thermodynamic} partition functions are essentially the generating function for counting permutations in the high-temperature regime. Finally, for the case relevant to neutrinos in a supernova, we identify the low-temperature phase as a unique state with the direction of the momenta of the neutrino dictating its coherent state in flavor-space, a state we dub the "flavor-momentum-locked" state.
↳ hep-phcond-mat.stat-mechnucl-thquant-phPRResearch(2025)·12 citations
11
New Spin Structure Constraints on Hyperfine Splitting and Proton Size
David Ruth🇺🇸 · Karl Slifer🇺🇸 · Jian-Ping Chen🇺🇸 · Carl E. Carlson🇺🇸 · Franziska Hagelstein🇩🇪 · Vladimir Pascalutsa🇩🇪 · Alexandre Deur🇺🇸 · Sebastian Kuhn🇺🇸 · Marco Ripani🇮🇹 · Xiaochao Zheng🇺🇸 · Ryan Zielinski🇺🇸 · Chao Gu🇺🇸
The 1S hyperfine splitting in hydrogen is measured to an impressive ppt precision and will soon be measured to ppm precision in muonic hydrogen. The latter measurement will rely on theoretical predictions, which are limited by knowledge of the proton polarizability effect $Δ_{pol}$ . Data-driven evaluations of $Δ_{pol}$ have long been in significant tension with baryon chiral perturbation theory. Here we present improved results for $Δ_{pol}$ driven by new spin structure data, reducing the long-standing tension between theory and experiment and halving the dominating uncertainty in hyperfine splitting calculations.
↳ nucl-exnucl-thphysics.atom-phPLB(2024)·13 citations
12
Gluonic contributions to the pion parton distribution functions
Jiangshan Lan🇨🇳 · Chandan Mondal🇨🇳 · Xingbo Zhao🇨🇳 · Tobias Frederico🇧🇷 · James P. Vary🇺🇸
We investigate the role of a dynamical gluon in the pion within the Basis Light-Front Quantization (BLFQ) framework and compare it with the solution of the Minkowski space Bethe-Salpeter equation (BSE), focusing on contributions beyond the valence sector. We develop a framework to compute the quark-antiquark-gluon component of the pion, starting from its valence light-front wave function. Additionally, the quark and gluon parton distribution functions (PDFs) are derived by considering this higher Fock component in the pion state. The proposed operator, which acts on the valence state to produce the quark-antiquark-gluon component of the pion, is tested against results from BLFQ for its contribution to the quark and gluon PDFs, as well as with results from the BSE. In the BLFQ framework, we identify the effect of dynamical chiral symmetry breaking on the pion structure through the enhancement of the spin-flip matrix element. This enhancement is captured in the $∣ q q ˉ g ⟩$ component of the light-front wave function and the associated gluon PDF. We explicitly demonstrate an enhancement of the low- $x$ contribution in the quark PDF, which is associated with the large spin-flip matrix element, which also drives the $π - ρ$ mass splitting. The proposed framework also enables an exploration of the effect of the dressed gluon mass for a given valence state at the pion scale. We show that when the gluon mass vanishes, departing from the constituent gluon picture, it has a significant impact on the gluon PDF.
↳ hep-phnucl-thPRD(2025)·14 citations
13
Study of the $Ω_{ccc} Ω_{ccc}$ and $Ω_{bbb} Ω_{bbb}$ dibaryons in constituent quark model
Pablo Martín-Higueras🇪🇸 · David R. Entem🇪🇸 · Pablo G. Ortega🇪🇸 · Jorge Segovia🇪🇸 · Francisco Fernández🇪🇸
Dibaryons are the simplest system in which the baryon-baryon interaction, and hence the underlying quark-quark interaction, can be studied in a clear way. Although the only dibaryon known today is the deuteron (and possibly the $d^{*}$ ), fully heavy dibaryons are good candidates for bound states because in such systems the kinetic energy is small and the high symmetry of the wave function favours binding. In this study, the possible existence of $Ω_{ccc} Ω_{ccc}$ and $Ω_{bbb} Ω_{bbb}$ dibaryons is investigated in the framework of a constituent quark model that satisfactorily describes the deuteron, the $d^{*} (2380)$ and the $N N$ interaction. $J^{P} = 0^{+}$ candidates are found in both systems with binding energies of the order of MeV.
↳ hep-phhep-exhep-latnucl-thPRD(2025)·9 citations
14
Gamma decay of the $^{154}$ Sm Isovector Giant Dipole Resonance: Smekal-Raman Scattering as a Novel Probe of Nuclear Ground-State Deformation
J. Kleemann · N. Pietralla · U. Friman-Gayer · J. Isaak · O. Papst · K. Prifti · V. Werner · A. D. Ayangeakaa · T. Beck · G. Colò · M. L. Cortés · S. W. Finch and 10 other authors
Gamma decays of the isovector giant dipole resonance (GDR) of the deformed nucleus $^{154}$ Sm from $2_{1}^{+}$ -Smekal-Raman and elastic scattering were measured using linearly polarized, quasimonochromatic photon beams. The two scattering processes were disentangled through their distinct angular distributions. Their branching ratio and cross sections were determined at six excitation energies covering the $^{154}$ Sm GDR. Both agree with the predictions of the geometrical model for the GDR and establish $γ$ decay as an observable sensitive to the structure of the resonance. Consequently, the data place strong constraints on the nuclear shape, including the degree of triaxiality. The derived $^{154}$ Sm shape parameters $β = 0.2926 (26)$ and $γ = 5.0 (14)$ agree well with other measurements and recent Monte Carlo Shell-Model calculations.
↳ nucl-exnucl-thPRL(2025)·21 citations
15
QCD with background electromagnetic fields on the lattice: a review
Gergely Endrodi🇩🇪
This review provides a comprehensive summary of results on the physics of strongly interacting matter in the presence of background electromagnetic fields, obtained via numerical lattice simulations of the underlying theory, Quantum Chromodynamics (QCD). Lattice QCD has guided our understanding of magnetized quarks and gluons via landmark results on the phase diagram, the equation of state, the confinemenent mechanism, anomalous transport phenomena as well as many more fascinating effects. Some of the lattice results lead to completely new paradigms in the description of hot magnetized quark matter and provided useful insights to a broad high-energy particle physics community. Since the first lattice QCD simulations with background fields, this field has been established as an independent research direction. We present the current status and recent developments of this field, together with an outlook including open questions to be answered in the near future.
↳ hep-lathep-phhep-thnucl-thPPNP(2025)·77 citations
16
Lanczos, the transfer matrix, and the signal-to-noise problem
Michael L. Wagman🇺🇸
This work introduces a method for determining the energy spectrum of lattice quantum chromodynamics (LQCD) by applying the Lanczos algorithm to the transfer matrix and using a bootstrap generalization of the Cullum-Willoughby method to filter out spurious eigenvalues. Proof-of-principle analyses of the simple harmonic oscillator and the LQCD proton mass demonstrate that this method provides faster ground-state convergence than the "effective mass," which is related to the power-iteration algorithm. Lanczos provides more accurate energy estimates than multi-state fits to correlation functions with small imaginary times while achieving comparable statistical precision. Two-sided error bounds are computed for Lanczos results and guarantee that excited-state effects cannot shift Lanczos results far outside their statistical uncertainties.
↳ hep-lathep-phnucl-thPRL(2025)·43 citations
17
QCD Phase Diagram and the Finite Volume Fireball: A Model Study
Adiba Shaikh🇮🇳 · Ranjita K. Mohapatra🇮🇳 · Saumen Datta🇮🇳
Experimental investigations of the phase diagram of strongly interacting matter involve collisions of heavy ions at ultrarelativistic velocities. The medium created in such a collision is often of dimensions a few fermi, in particular in the Beam Energy Scan experiments. An understanding of the effect of the finite volume and the boundary is important for connecting the experimental results to the phase diagram. Using the Nambu Jona-Lasinio model, an effective theory for the chiral transition of quantum chromodynamics (QCD), we have studied the effect of the finite volume of the fireball on the transition line at finite temperature and density using the MIT boundary condition to mimic the condition that the system is deconfined inside. The shift of the transition temperature for finite volume and finite volume effect on number density and its susceptibilities are studied. The volume effects should be considered when looking for signatures of the phase diagram in experiments.
↳ hep-phnucl-thNPA(2025)·7 citations
18
Lattice QCD Calculation of $x$ -dependent Meson Distribution Amplitudes at Physical Pion Mass with Threshold Logarithm Resummation
Ian Cloet🇺🇸 · Xiang Gao🇺🇸 · Swagato Mukherjee🇺🇸 · Sergey Syritsyn🇺🇸 · Nikhil Karthik🇺🇸 · Peter Petreczky🇺🇸 · Rui Zhang🇺🇸 · Yong Zhao🇺🇸
We present a lattice quantum chromodynamics (QCD) calculation of the $x$ -dependent pion and kaon distribution amplitudes (DA) in the framework of large momentum effective theory. This calculation is performed on a fine lattice of $a = 0.076$ fm at physical pion mass, with the pion boosted to $1.8$ GeV and kaon boosted to $2.3$ GeV. We renormalize the matrix elements in the hybrid scheme and match to $MS$ with a subtraction of the leading renormalon in the Wilson-line mass. The perturbative matching is improved by resumming the large logarithms related to the small quark and gluon momenta in the soft-gluon limit. After resummation, we demonstrate that we are able to calculate a range of $x \in [x_{0}, 1 - x_{0}]$ with $x_{0} = 0.25$ for pion and $x_{0} = 0.2$ for kaon with theoretical systematic errors under control. The kaon DA is shown to be slighted skewed, and narrower than pion DA. Although the $x$ -dependence cannot be direct calculated beyond these ranges, we estimate higher moments of the pion and kaon DAs by complementing our calculation with short-distance factorization.
↳ hep-lathep-exhep-phnucl-thPRD(2024)·27 citations
19
Magnetic Polarisability of Octet Baryons via Lattice QCD
Thomas Kabelitz (1) · Ryan Bignell (2) · Waseem Kamleh (1) · Derek Leinweber (1) ((1) University of Adelaide · (2) Trinity College)
Drawing on recent advances in lattice-QCD background-field techniques, the magnetic polarisability of octet baryons is calculated from the first principles of QCD. The results are presented in the context of new constituent quark-model calculations providing a framework for understanding the lattice results and a direct comparison with simulation results at unphysical quark masses. Using smeared quark sources, low-lying Laplacian eigenmode projection and final-state Landau mode projection, considerable attention is devoted to ensuring single-state isolation in the lattice correlation functions. We also introduce new weighting methods to reduce the sensitivity to correlation-function fits, averaging over many fits based on merit drawn from the full correlated $χ^{2}$ of the fits. The techniques are implemented on the $3 2^{3} \times 64$ , 2+1-flavour dynamical-fermion lattices provided by the PACS-CS collaboration following the introduction of uniform magnetic fields quantised to the lowest nontrivial values available. After some fine tuning of the constituent quark model parameters, we find the model captures the patterns observed in the lattice QCD results very well, providing important insights into the physics underpinning the magnetic polarisabilities. Finally, comparison with the most recent results from experiment proceeds through an effective field theory formalism which incorporates estimates of finite-volume corrections and small electro-quenching corrections as the results are brought to the physical point. We find excellent agreement with experiment where available, including the proton and neutron polarisabilities.
↳ hep-lathep-phnucl-thPRD(2024)·4 citations
20
Relevance of the coupled channels in the $ϕ$ p and $ρ^{0}$ p Correlation Functions
A. Feijoo🇩🇪 · M. Korwieser🇩🇪 · L. Fabbietti🇩🇪
The vector meson-baryon interaction in a coupled channel scheme is revisited within the correlation function framework. As illustrative cases to reveal the important role played by the coupled channels, we focus on the $ϕ$ p and $ρ^{0}$ p systems given their complex dynamics and the presence of quasi-bound states or resonances in the vicinity of their thresholds. We show that the $ϕ$ p femtoscopic data provide novel information about a $N^{*}$ state present in the experimental region and anticipate the relevance of a future $ρ^{0}$ p correlation function measurement in order to pin down the $S = 0, Q = + 1$ vector meson-baryon interaction as well as to disclose the characterizing features of the $N^{*} (1700)$ state.
↳ hep-phnucl-thPRD(2025)·38 citations
21
Effects of saturation and fluctuating hotspots for flow observables in ultrarelativistic heavy-ion collisions
Henry Hirvonen🇫🇮 · Mikko Kuha🇫🇮 · Jussi Auvinen🇫🇮 · Kari J. Eskola🇫🇮 · Yuuka Kanakubo🇫🇮 · Harri Niemi🇫🇮
We investigate the effects of saturation dynamics on midrapidity flow observables by adding fluctuating hotspots into the novel Monte Carlo EKRT (MC-EKRT) event generator for high-energy nuclear collisions. We demonstrate that the intensity of the saturation effects significantly affects the ratio between the flow coefficients $v_{3}$ and $v_{2}$ at the LHC. Adding a hotspot substructure to the nucleons enhances the saturation effects and improves the agreement with the measured data. We show that the collision-energy dependence of the flow coefficients obtained using the MC-EKRT initial states with hotspots is improved in comparison with the earlier event-by-event EKRT model. In addition, we present the results for the charged hadron multiplicity distribution in Pb+Pb collisions at the LHC, and show that the minijet-multiplicity originating fluctuations of the saturation scale included in MC-EKRT, as well as the presence of hotspots, are necessary for describing the measured large-multiplicity tail in the distribution.
↳ hep-phnucl-thPRC(2024)·6 citations
22
Precise determination of the $η Λ$ scattering length and effective range and relationship to the $Λ (1670)$ resonance
Man-Yu Duan🇪🇸 · Melahat Bayar🇹🇷 · Eulogio Oset🇪🇸
We use the Belle data on the $K^{-} p$ mass distribution of the $Λ_{c}^{+} \to p K^{-} π^{+}$ reaction near the $η Λ$ threshold to determine the $η Λ$ scattering length and effective range. We show that from these data alone we can determine the value of $a$ with better precision than so far determined, and the value of $r_{0}$ for the first time. The addition of the $K^{-} p \to η Λ$ data allows us to improve the precision of these magnitudes, with errors smaller than $15%$ . We also determine with high precision the pole position of the $Λ (1670)$ .
↳ hep-phnucl-thPLB(2024)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE