Nuclear Theory·nucl-th
17 papers—8 primary·9 cross-listed
The recent lattice QCD calculations of the neutron and proton electric dipole moments (EDMs) and the CP-violating coupling constant due to the term are reviewed. Progress towards nucleon EDM calculations, including the Weinberg three-gluon operator, and the quark chromoelectric dipole moment operator and their renormalization, is also discussed.
Carlota Andres🇺🇸 · Fabio Dominguez🇪🇸 · Jack Holguin🇬🇧 · Cyrille Marquet🇫🇷 · Ian Moult🇺🇸
Collider experiments involving nuclei provide a direct means of studying exotic states of nuclear matter. Recent measurements of energy correlators in both proton-nucleus (p-A) and nucleus-nucleus (A-A) collisions reveal sizable modifications, attributable to nuclear effects, compared to proton-proton (p-p) collisions. Energy correlators, and their associated light-ray operator product expansion (OPE), allow scaling behaviors of the measured spectrum to be directly mapped to properties of the underlying quantum field theory. Here, we demonstrate for the first time how this mapping occurs in nuclear collisions, and highlight how the light-ray OPE characterizes leading nuclear effects. We show that the leading modification to the energy correlator distribution is characterized by an enhancement of the expectation value of twist-4 light-ray operators, resulting in a scaling for the ratio of the two-point correlator in nuclear matter to that in vacuum of up to quantum corrections. We verify that this leading twist-4 correction accurately describes recent A-A and p-A data, and is thus sufficient to capture the scaling behavior within the angular range measured for jet radii used in nuclear experiments. Our light-ray OPE based approach lays the groundwork for a rigorous characterization of nuclear modification to energy correlator observables.
Zhen-Ni Xu🇨🇳 · Daniele Binosi🇮🇹 · Chen Chen🇨🇳 · Khépani Raya🇨🇳 · Craig D. Roberts🇨🇳 · José Rodríguez-Quintero🇨🇳
Using available information from Drell-Yan data on pion and kaon structure functions, an approach is described which enables the development of pointwise profiles for all pion and kaon parton distribution functions (DFs) without reference to theories of hadron structure. The key steps are construction of structure-function-constrained probability-weighted ensembles of valence DF replicas and use of an evolution scheme for parton DFs that is all-orders exact. The DFs obtained express qualitatively sound features of light-meson structure, e.g., the effects of Higgs boson couplings into QCD and the size of heavy-quark momentum fractions in light hadrons. In order to improve the results, additional and more precise data on the -quark-in-kaon, , to -quark-in-pion, , DF ratio would be necessary. Of greater value would be extraction of alone, thereby avoiding inference from the ratio: currently, the data-based form of is materially influenced by results for .
Zi-Yue Zheng · Jin-Biao Wei · Huan Chen · Xiao-Ping Zheng · G. F. Burgio · H.-J. Schulze
We investigate nonradial -mode oscillations of hybrid neutron stars in full general relativity, employing hybrid equations of state describing a nuclear outer core and a pasta-phase transition to a quark-matter core. The validity of various universal relations is confirmed for those stars. Prospects of observations are also discussed.
Sebastian M. Dawid🇺🇸 · Andrew W. Jackura🇺🇸 · Adam P. Szczepaniak🇺🇸
We propose a new model-independent method for determining hadronic resonances from lattice QCD. The formalism is derived from the general principles of unitarity and analyticity, as encoded in the representation of a partial-wave two-body amplitude. The associated quantization condition relates the finite-volume spectrum to the infinite-volume numerator, , used to reconstruct the scattering amplitude from dispersive relations. Unlike the original Lüscher condition, this new formalism is valid for energies coinciding with the left-hand cuts from arbitrary one- and multi-particle exchanges.
Sabarnya Mitra🇩🇪 · Frithjof Karsch🇩🇪 · Sipaz Sharma🇩🇪
In order to quantify the universal properties of the chiral phase transition in (2+1)-flavor QCD, we make use of an improved, renormalized order parameter for chiral symmetry breaking which is obtained as a suitable difference of the -flavor light quark chiral condensate and its corresponding light quark susceptibility. Having no additive ultraviolet as well as multiplicative logarithmic divergences, we use ratios of this order parameter constructed from its values for two different light quark masses. We show that this facilitates determining in a parameter-independent manner, the chiral phase transition temperature and the associated critical exponent which, for sufficiently small values of the light quark masses, controls the quark mass dependence of the order parameter at . We present first results of these calculations from our numerical analysis performed with staggered fermions on lattices.
Jin Hu🇨🇳
We provide an exact analytical solution to the nonlinear relativistic Boltzmann equation for a homogeneous, anisotropically scattering massless gas. Utilizing a BKW-like trial solution, we cast the Boltzmann equation into a set of nonlinear coupled equations for scalar moments, based on which the analytical solution is derived. One remarkable feature of our analytical solution lies in the nontrivial scattering angle dependence. We also show that this analytical solution admits a stable fixed point corresponding to the equilibrium solution as long as the parameters are physically feasible. Furthermore, a clear correspondence between our solution and the BKW solution pertaining to nonrelativistic Maxwell molecules is established, thereby clarifying the non-existence of a BKW-type solution in the relativistic domain for massive particles.
M. McCann · L. P. Mulholland · Z. Xiong · C. A. Ramsbottom · C. P. Ballance · O. Just · A. Bauswein · G. Martínez-Pinedo · F. McNeill · S. A. Sim
A large number of R-matrix calculations of electron impact excitation for heavy elements (Z > 70) have been performed in recent years for applications in fusion and astrophysics research. With the expanding interest in heavy ions due to kilonova (KN) events such as AT2017gfo and AT2023vfi, this new data can be utilised for the diagnosis and study of observed KN spectra. In this work recently computed electron-impact excitation effective collision strengths are used, for the first three ionisation stages of tungsten (W, Z = 74), platinum (Pt, Z = 78) and gold (Au, Z = 79), to construct basic collisional radiative models tailored for the late stage nebular phases of KN. Line luminosities are calculated at a range of electron temperatures and densities and the strengths of these lines for a representative ion mass are compared. For the case of W III, these optically thin intensities are additionally used to constrain the mass of this ion in both AT2017gfo and AT2023vfi. Comparing with theoretical predictions of nucleosynthesis yields from neutron-star merger simulations, broad agreement with the inferred ion masses of W is found. Furthermore, we highlight the value of W measurements by showing that the abundance of other groups of elements and outflow properties are constrained by exploiting theoretically motivated correlations between the abundance of W and that of lanthanides or third r-process peak elements. Based on simple estimates, we also show that constraints on the distribution of tungsten in the ejecta may be accessible through the line shape, which may also yield information on the neutron-star merger remnant evolution.
We discuss the role of gluon dynamics in physics and in nucleon resonances where excitations of gluonic potentials may also be important. Interesting phenomenology includes a possible narrow near threshold resonance in photoproduction and whether the parity doublets observed in the higher mass nucleon resonance spectrum might be hinting at a possible second minimum in the confinement potential corresponding to supercritical confinement.
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