28,796 papers in this slice of arXiv.
Nicholas J. Benoit, Chiho Nonaka, Hidetoshi Taya
We study non-perturbative quark-antiquark pair production and the subsequent quark dynamics in the earliest glasma stage of relativistic heavy-ion collisions. For that, we develop a new model, WAGASHI (Wong-precessing Anisotropic Glasma And ScHwinger-produced Initial-conditions), which combines classical Yang-Mills glasma evolution, Wong-equation transport, and Schwinger pair production on an event-by-event basis. We find that a sizeable number of quarks, comparable to the final hadron yields, are produced already during the glasma stage and subsequently undergo substantial momentum broadening and spin randomization, suggesting a significant contribution toward the early equilibration of the quark-gluon plasma. We also determine the event-by-event distributions of baryon number, electric charge, strangeness, and spin polarization in Pb-Pb and O-O collisions at LHC energies, finding particularly large fluctuations in the smaller O-O system. These results provide dynamical initial conditions for the subsequent hydrodynamic evolution of the quark-gluon plasma.
Guangping Chen, Wenmin Deng, Ganlong Ding +3
Starting from the 1+1 dimensional (one spatial and one temporal dimension) Dirac equation, we employ the Wentzel-Kramers-Brillouin (WKB) approximation to derive the corresponding relativistic penetration probability. The derivation shows that the semiclassical momentum is determined by the Schrödinger-equivalent potential Ueff(r)=S(r)+mEV(r)+2mS2(r)−V2(r), instead of the simple sum of scalar and vector potentials S(r)+V(r), which has been adopted widely in the studies of relativistic quantum tunneling. We then quantify the relativistic dynamical effects in proton emission by comparing the results obtained with Ueff(r) and those obtained with S(r)+V(r). Incorporating Ueff(r) systematically reduces the penetration probability and the assault frequency, and consequently increases the predicted half-life. The relativistic dynamical effect becomes more pronounced with higher orbital angular momentum and can reach about 84% in the half-life of 144Tm.
Bao-An Li, Xavier Grundler
We investigate how future high-precision neutron star (NS) radius measurements encode microscopic information about the dense-matter equation of state (EOS), focusing on a possible first-order hadron--quark phase transition and the resulting mass--radius topology. Within a Bayesian framework using meta-model EOSs with nine microscopic parameters, we analyze mock radius measurements R1.4=11.9±σR km with σR=0.9 and 0.1 km for canonical NSs. We introduce inverse EOS--radius mappings that give the posterior mean of each EOS parameter as a function of R1.4. Their slope measures radius sensitivity, while their curvature determines the leading precision dependence of the posterior mean through the Jensen expansion. Resolving the mappings into four mass--radius topologies, Connected, Disconnected, Both, and No-Quark-Matter, reveals a clear hierarchy of information. The symmetry-energy parameters L (slope) and Ksym (curvature) are strongly encoded in R1.4 and their posterior means shift appreciably with improved radius precision, whereas the higher-order hadronic parameters show stronger topology dependence. Among the transition parameters, the transition density ρt is the most strongly encoded in R1.4, while the energy-density jump and quark-matter sound speed are more strongly associated with the topology of the full mass--radius sequence. Since the different topologies have strongly overlapping R1.4 distributions, even precise radius measurements cannot by themselves identify the topology or uniquely determine the high-density transition properties. These results provide a parameter-dependent hierarchy for assessing the scientific return of future high-precision radius measurements and complementary probes of high-density
A. L. Conley, M. Spieker, R. Aggarwal +15
We report new data from a 150Nd(p,t)148Nd experiment performed at the John D. Fox Accelerator Laboratory of Florida State University. In total, 54 excited states of 148Nd were observed up to an excitation energy of 3500 keV. In this work, we focus on
Bo-Wen Xiao, Yuxiang Zhao, Jian Zhou
The Electron-Ion Collider in China (EicC), a cutting-edge facility under development, aims to unveil the internal structure of nucleons and nuclei by leveraging collisions of high-intensity polarized electrons and ions (polarized protons, polarized deuterons, polarized 3He, and unpolarized heavy ions up to Uranium) at center-of-mass energies of 15-20 GeV and luminosity of (2-4)×1033cm−2s−1. Its primary physics objectives include 3D tomography of nucleon spin and momentum structure, fundamental questions regarding the origin of nucleon mass, partonic structure of nuclei and parton interactions with the nuclear environment, and exploration of exotic hadronic states. In this paper, we review the physics potential of the EicC and highlight its unique capabilities for advancing precision nucleon structure studies by combining its specialized kinematic coverage and high luminosity. Since traditional topics like 3D nucleon structure have already been well-covered by several extensive reviews, we have deliberately dedicated significant space to recent progress in nucleon mass decomposition, nucleon energy-energy correlation, quantum information, and artificial intelligence applications in high-energy nuclear physics, which have been emerging rapidly and attracted a tremendous amount of attention in the community.
T. Hu, Z. Akbar, V. Crede +147
We report on the differential cross sections dσ/dt, the unpolarized spin-density matrix elements ρ000, ρ1−10
Iris Likmeta
Anisotropic flow measurements in heavy-ion collisions are sensitive to the spatial distribution of the initial state, and quark-gluon plasma transport properties such as the shear viscosity to entropy density ratio (η/s). State-of-the-art relativistic hydrodynamic models successfully describe such flow measurements over a wide centrality range. However, the hydrodynamic description of anisotropic flow deviates from the experimental data in ultra-central collisions (UCC), where the average geometric anisotropy of the system becomes small and fluctuations dominate the initial-state geometry. This discrepancy constitutes the UCC puzzle, as the expected hierarchy of flow harmonics is not fully reproduced by current modeling approaches. Probing towards ultra-central collisions, effects on flow fluctuations due to the initial spatial anisotropies are suppressed. The measured flow can be explained by quantum fluctuations on the energy distribution of 208Pb nuclei. An octupole deformation of the 208
The Muon g-2 Collaboration, :, D. P. Aguillard +193
A limit on the permanent electric dipole moment (EDM) of the positive muon is presented based on data from the Fermilab Muon g-2 Experiment taken between 2019 and 2020. The tracking detectors measure the average vertical decay angle of positrons from muon decays, enabling a search for an interaction between a possible muon EDM dμ and the lab-frame magnetic field. The result, dμ=(−0.35±0.19stat±0.34sys)×10−19 e⋅cm, is consistent with zero and sets a new direct limit on the muon EDM of ∣dμ∣<1.10×10−19 e⋅cm at the 95 percent confidence level.
Wulf Krümpelmann, Yong-Hui Lin, Ulf-G. Meißner
The Gari--Krümpelmann (GK) model provided one of the first semiphenomenological descriptions of the electromagnetic nucleon form-factors over a wide range of momentum transfer. It combined vector-meson dominance at low and intermediate momentum transfer with perturbative-QCD constraints at large momentum transfer. The present work extends this framework by including the dispersive two-pion continuum explicitly in the isovector channel. The two-pion contribution is taken from modern dispersive analyses and embedded into the intrinsic high-Q2 structure of the GK ansatz. The physical ρ dynamics is then interpreted as part of the correlated two-pion spectral function. The direct coupling terms remain essential for the transition to the asymptotic regime. This gives a cleaner separation between long-range continuum dynamics, coherent vector-meson contributions, and direct quark-current dynamics. With just 5 parameters, we can describe the large body on form-factor data and differential cross sections from electron-proton scattering in the space-like region.
Massimiliano Bazzi, Francesco Clozza, Carlo Guaraldo +38
The study of the strong interaction among hadrons at low energies remains one of the key challenges in fundamental physics because of its non-perturbative nature, which makes theoretical descriptions strongly dependent on experimental input. Although substantial progress has been made for systems involving up and down quarks, theoretical models in the strangeness sector continue to face limitations due to the lack of experimental data. Kaonic atoms provide a powerful tool to study the low-energy strong interaction with strangeness through the energy shifts and widths induced on their lowest atomic levels. In this context, kaonic deuterium X-ray spectroscopy has long represented one of the major open challenges in hadronic-atom physics because of its extremely low X-ray yield. This measurement is particularly important because it gives access to the experimentally inaccessible K−n interaction at threshold energy. Here, we report the first observation of kaonic deuterium X-ray transitions, performed with the SIDDHARTA-2 experiment at the DAΦNE collider. We determine the strong-interaction shift and width of the 1s level to be ε1s=−810.9±24.5(stat)±2.1(syst)eV and Γ1s=812±97(stat)±33(syst)eV, respectively. This measurement constitutes the most precise experimental determination of the K−d strong interaction at threshold and allows discrimination among competing theoretical models. Combined with the kaonic hydrogen measurement, this result provides the experimental input required to determine the isospin-dependent K−N scattering lengths, with implications for the description of the nature of the first predicted hadronic molecular state, the Λ(1405), and neutron-rich matter.
Suraj Prasad, Aditya Nath Mishra, Guy Paić +1
We investigate the geometrical and thermodynamical aspects of particle production in pp collisions over a broad center-of-mass energy, ranging from s=62.4 GeV to 13 TeV using PYTHIA8. We study the azimuthal dependence of charged-particle production relative to the leading particle. This includes the study of the Tsallis--Pareto parameters extracted from the charged-particle transverse-momentum spectra in fixed Δφ intervals relative to the leading charged particle. The simultaneous analysis of charged-particle multiplicity and event topology demonstrates that the underlying event (UE) dominated region can be extended beyond the conventional transverse side region across RHIC and LHC energies. To further disentangle effects from soft and hard particle production mechanisms, the study is performed in different transverse spherocity and charged-particle flattenicity classes. We demonstrate that the UE region extends beyond the conventional transverse region, validating an enlarged angular interval of 40∘≲∣Δφ∣≲140∘ from RHIC to LHC energies. Event-shape selections reveal that jetty events consistently exhibit larger q and lower Ts than isotropic events. The Δφ profiles of charged-particle multiplicity and transverse spherocity remain universal in shape across collision energies despite the strong increase in overall event activity, whereas the Tsallis parameters retain a residual, leading-particle-driven energy dependence in the near- and away-side regions.
Zhi-Guo He, Guanghui Li, Yang Liu +3
The dihadron fragmentation function (DiFF) of a linearly polarized gluon has not yet been accessed experimentally, leaving an important aspect of spin-dependent gluon hadronization unexplored. We show that, at leading order, the color-singlet decay channel of the P-wave bottomonium state χb0 produces two energetic gluons with correlated linear polarizations. Within collinear factorization, their fragmentation into separate dihadron pairs generates an Artru--Collins-type angular correlation that provides the first direct probe of the linearly polarized gluon DiFF, while the corresponding semi-inclusive decay rate constrains the unpolarized gluon DiFF. A spectator-model benchmark indicates percent-level asymmetries, potentially within reach of existing Belle data. A dedicated Belle II data set would substantially improve the statistical precision, enabling more stringent constraints on the kinematic dependence of the linearly polarized gluon DiFF.
S. Ipsita Sahoo, Sanjeebani Biswal, D. Dutta +1
A large vorticity produced in non-central ultra-relativistic heavy-ion collisions induces an effective chemical potential in both partonic and hadronic matter, thereby influencing the quark-hadron transition and its associated properties. In this work, we investigate the influence of rotation on hadron yields within the framework of Hadron Resonance Gas (HRG) model. Our results show that vorticity significantly modifies hadron yields and their ratios. Most notably, rotation enhances the p/π+ ratio while suppressing the K+/π+ ratio, suggesting that these observables may serve as sensitive probes of the rotational properties of the medium created in heavy-ion collisions. To quantify the effect of rotation, the calculated dependence of the p/π+ ratio on vorticity is compared with the centrality dependence of the p/π ratio measured by the ALICE collaboration in Pb+Pb collisions at sNN = 5.02 TeV. From this comparison, we estimate the maximum vorticity produced at freeze-out for different collision centralities. In case of peripheral collisions, the freeze-out vorticity (ω) is found to reach an upper bound value of approximately 0.088 GeV, whereas for central collisions it is about 0.028 GeV. Furthermore, we investigate the effect of rotation on fluctuations of conserved quantities and their correlations. This study provides a quantitative framework for assessing the role of rotation in the thermodynamics of hadronic matter and its phenomenological consequences for heavy-ion collisions.
E. Craig Dukes, Ralf Ehrlich, Daniel Lee +4
Scintillator counters employing embedded wavelength-shifting fibers have been used in particle physics experiments for several decades. Such counters have been produced with square, rectangular, and triangular profiles. An advantage of arrays of triangular counters is that their position resolution can be greatly enhanced by interpolation between adjacent counters using their relative light yields. We report here on a testbeam study of the position resolution of such a scintillator hodoscope and compare the results to a simulation. We find an order of magnitude improvement in the position resolution over that found by simply using the fiber separation.
Grégoire Pihan, Roman Poberezhniuk, Volodymyr A. Kuznietsov +1
We present, to our knowledge, the first Bayesian extraction of baryon number susceptibilities of QCD matter at finite baryon density from heavy-ion collision data on proton number cumulants. The framework embeds arbitrary equation-of-state susceptibilities χnB into realistic hydrodynamic particlization hypersurfaces through maximum-entropy freeze-out, maps the resulting (anti)baryon fluctuations onto protons, applies the experimental kinematic acceptance, and accounts for exact baryon number conservation. Applying the framework to measurements of (net-)proton number fluctuations in 0--5% central Au-Au collisions from the RHIC Beam Energy Scan in the collider mode, we extract, at each collision energy, the second-order susceptibility normalized by the hadron resonance gas value, χ2B/χˉ2B, and the higher-order susceptibility ratios χ3B/χ1B and χ4B/χ2B. We obtain tight constraints on χ2B, with extracted values in quantitative agreement with lattice QCD based estimates along the chemical freeze-out line for μB≲300 MeV. At larger μB, the extracted values indicate an enhancement of baryon number fluctuations relative to the noncritical lattice-based extrapolation and HRG baseline considered here. The third- and fourth-order susceptibilities are only weakly constrained. In particular, we find that the observed nonmonotonic collision-energy dependence of the proton factorial cumulant ratio C^3/C^1 can be described without irreducible three- or four-baryon correlations. This behavior emerges from the interplay between the energy dependence of χ2B and exact baryon number conservation.
Sandeep Puri, Noah D'Amico, Andrew Gillespie +4
We report experimental and computational investigations of a collision-cascade mechanism to induce deuterium-deuterium (D-D) fusion. Evidence of neutron production was observed from a pressurized deuterium target exposed to energetic alpha particles emitted by a 210Po source. A 5-mCi 210Po alpha source was placed within a chamber containing pressurized deuterium gas, and neutron emission was monitored for 18 h using two Mirion SN-S 3He neutron detectors. Alpha particles incident on pressurized deuterium gas produced an average excess of ∼74 neutrons after background subtraction, corresponding to a fusion neutron rate of ∼2.24 n/s. With LiD in the pressurized deuterium, the average excess increased to 268 neutrons, corresponding to 8.1 n/s. Since D-D fusion branches into two equally likely pathways, these correspond to a fusion rate near 4.5 and 16.2 fusions per second, respectively. MCNP simulations incorporating experimental geometry, source activity, and detector configuration predicted neutron yields within 5.4% of the measured values and reproduced the detector response within experimental uncertainty. The tight agreement between measured and simulated neutron counts suggests that energetic alpha-particle interactions within the deuterium may contribute to measurable D-D fusion reactions through the D(d,n)3He channel.
Y. G. Lee, J. Kim, T. Zhao +1
We present constraints on the nuclear equation of state (EOS) from microscopic asymmetric matter calculations at zero temperature based on chiral nucleon-nucleon and three-nucleon interactions. The constraints include the saturation point, the isospin dependence of the incompressibility, and the symmetry energy, as well as the crust-core transition density of neutron-star matter. To quantify and propagate correlated uncertainties from noisy many-body calculations to derived observables, we introduce GPDiff, an efficient JAX-based Python package for multivariate Gaussian process (GP) regression with automatic differentiation. After training, GPDiff enables joint predictions of the EOS and derivatives of arbitrary order with respect to the input variables, including mixed partial derivatives. In this initial application, we analyze recent high-order many-body perturbation theory calculations of asymmetric matter up to about twice saturation density and explore nonstationary change-surface kernels, a class of input-dependent kernels, for modeling the EOS. GPDiff is broadly applicable to microscopic nuclear EOS calculations at zero and finite temperature and provides a versatile package for GP-based uncertainty quantification and inference of the nuclear EOS.
Bui Minh Loc, Hoang Thai An, Nguyen Le Anh +2
Octupole deformation in atomic nuclei is of interest for both nuclear structure and precision tests of fundamental symmetries, but identifying regions of octupole collectivity remains challenging. We analyze low-energy spectra of odd-mass nuclei and uncover a previously unrecognized empirical regularity that serves as a signature of octupole collectivity in neighboring even-even systems. The observed patterns, which can be understood within a core-coupling picture, are consistent with previous theoretical studies and lead to predictions for neutron-rich and proton-deficient nuclei. These findings provide a simple empirical guide for identifying promising candidates for future experiments and microscopic calculations.
V. V. Gauzshtein, A. I. Fix, V. I. Ivanov +30
We present measurements of the tensor analyzing power T20 in the reaction γd→pn at photon energies Eγ=350
Vladimir Khachatryan, Riad Suleiman, Alberto Accardi +27
A breakthrough in fundamental physics experiments measuring particle spin precession may happen if spin-transparent storage rings become adopted tools for such experiments. We present a new design of highly specialized table-sized storage rings, which use low-energy polarized electron beams and Mott polarimetry. Based on the spin transparency ansatz, the spin precession stemming from the magnetic dipole moment is canceled at any beam energy after an electron's turn along the periodic orbit in the ring. Meanwhile, a spin precession induced by the fundamental physics of interest, e.g., the electron's permanent electric dipole moment (EDM) and/or ultralight-dark-matter-mediated forces such as axions, will accumulate. However, capitalizing on such types of rings is not only desirable for measurements of EDMs and axion searches relevant to CP violation and matter-antimatter asymmetry in the Universe, but may also find very promising applications in quantum computing.