Nuclear Theory·nucl-th

Wednesday·October 16, 2024

8 papers—1 primary·7 cross-listed

01
Calculable Microscopic Theory for $^{12}$ C( $α$ , $γ$ ) $^{16}$ O Cross Section near Gamow Window II
Yasuyuki Suzuki
A microscopic approach to the $^{12}$ C $(α, γ)^{16}$ O radiative-capture reaction near the Gamow window has been proposed by Y. Suzuki, Few-Body Syst. {\bf 62}, 2 (2021). The important ingredients of the approach include the following: (1) The states of $^{12}$ C and $^{16}$ O relevant to the reaction are described by fully microscopic 3\, $α$ -particle and 4\, $α$ -particle configurations. (2) The isovector electric dipole transition is accounted for through the isospin impurity of the constituent $α$ -particles. (3) The relative motion among the $α$ -particles is expanded in terms of correlated-Gaussian basis functions. A calculation of the radiative-capture cross section demands double angular-momentum projections, that is, the angular momentum of $^{12}$ C consisting of 3 $α$ -particles and the orbital angular momentum for $^{12}$ C $- α$ relative motion. Advancing the previous formulation based on the single angular-momentum projection, I carry out the double projection and present all the formulas needed for the cross section calculation.
nucl-thFew Body Syst.(2024)·0 citations
02
Solving the Lindblad equation with methods from computational fluid dynamics
Jan Rais · Adrian Koenigstein · Niklas Zorbach · Carsten Greiner
Liouvillian dynamics describes the evolution of a density operator in closed quantum systems. One extension towards open quantum systems is provided by the Lindblad equation. It is applied to various systems and energy regimes in solid state physics as well as also in nuclear physics. A main challenge is that analytical solutions for the Lindblad equation are only obtained for harmonic system potentials or two-level systems. For other setups one has to rely on numerical methods. In this work, we propose to use a method from computational fluid dynamics, the Kurganov-Tadmor central (finite volume) scheme, to numerically solve the Lindblad equation in position-space representation. We will argue, that this method is advantageous in terms of the efficiency concerning initial conditions, discretization, and stability. On the one hand, we study, the applicability of this scheme by performing benchmark tests. Thereby we compare numerical results to analytic solutions and discuss aspects like boundary conditions, initial values, conserved quantities, and computational efficiency. On the other hand, we also comment on new qualitative insights to the Lindblad equation from its reformulation in terms of an advection-diffusion equation with source/sink terms.
↳ quant-phnucl-thPRE(2025)·7 citations
03
From Supernovae to Neutron Stars: A Systematic Approach to Axion Production at Finite Density
Konstantin Springmann🇩🇪 · Michael Stadlbauer🇩🇪 · Stefan Stelzl🇨🇭 · Andreas Weiler🇩🇪
We present a systematic study of QCD axion production in environments with finite baryon density and temperature, implying significant changes to axion phenomenology. Within heavy baryon chiral perturbation theory, we derive the effective Lagrangian describing axion interactions with nucleons and mesons up to next-to-leading-order in the chiral expansion. We focus on corrections to the axion-nucleon couplings from higher orders and finite density. These couplings are modified by up to an order of magnitude near nuclear saturation density, significantly impacting axion production in supernovae and neutron stars. Density-dependent corrections enhance the axion luminosity in supernovae by an order of magnitude, strengthening current best bounds by a factor of three. We stress the importance of including all axion production channels up to a given chiral order for a consistent luminosity calculation and classify the missing contributions up to the third chiral order. The modified axion-nucleon couplings also affect neutron star cooling rates via axion emission. A re-evaluation of existing neutron star cooling bounds, constrained to regions where perturbative control is reliable, weakens these bounds by a factor of four. Lastly, our results have implications for terrestrial axion searches that rely on precise knowledge of axion-nucleon couplings.
↳ hep-phastro-ph.HEnucl-thJHEP(2025)·42 citations
04
Quasielastic Lepton-Nucleus Scattering and the Correlated Fermi Gas Model
Gil Paz🇺🇸
The future neutrino research program will require improved precision. A major source of uncertainty is the interaction of neutrinos with nuclei that serve as targets for such experiments. Broadly speaking, this interaction often depends, e.g., for Charge-Current Quasi-Elastic (CCQE) scattering, on the combination of "nucleon physics" expressed by form factors and "nuclear physics" expressed by a nuclear model. It is important to get a good handle on both. This talk presents a fully analytic implementation of the Correlated Fermi Gas (CFG) Model for CCQE electron-nuclei and neutrino-nuclei scattering. The implementation is used to compare separately form factors and nuclear model effects for both electron-carbon and neutrino-carbon scattering data.
↳ hep-phhep-exhep-latnucl-ex+1PoS(2025)·0 citations
05
Universal Mass Equation for Equal-Quantum Excited-States Sets I
L. David Roper (VPI)🇺🇸 · Igor Strakovsky (GWU)🇺🇸
The masses of fifteen baryon sets and twenty-four meson sets of three or more equal-quantum excited states, using Breit-Wigner PDG masses and their uncertainties at fixed $J^{P}$ for baryons and $J^{P C}$ for mesons, are fitted by a simple two-parameter logarithmic function, $M_{n} = α L n (n) + β$ , where $n$ is the level of radial excitation. The conjecture is made that accurately measured masses of all equal-quantum baryons (including LHCb exotic $P_{c c ˉ}^{+}$ s) and meson excited states (including $s s ˉ$ , $s c ˉ$ , $c c ˉ$ , $c b ˉ$ , and $b b ˉ$ states) are related by the logarithmic function used here; at least for the mass range of currently known excited states. The baryon ``star'' rating case is evaluated. The Cornell potential is an example of how a logarithmic behavior can be explained by an appropriate potential. Thus, a ``universal mass equation'' (UME) for equal-quantum excited-state sets is presented.
↳ hep-phhep-exnucl-exnucl-thEPJA(2025)·10 citations
06
Non-diagonal DVCS and transition GPDs: A unified framework for spinless hadron case $γ^{*} π \to γ π π$
Sangyeong Son🇰🇷 · Kirill M. Semenov-Tian-Shansky🇰🇷
Hadron-to-two-hadron transition generalized parton distributions (GPDs) extend the concept of hadron-to-resonance transition GPDs and provide a unified description of non-diagonal hard exclusive reactions in the generalized Bjorken limit. We present the formalism for the case of spinless hadrons addressing the non-diagonal deeply virtual Compton scattering $γ^{*} π \to γ π π$ in terms of $π \to π π$ transition GPDs, which generalize GPDs for $π \to f_{0}, ρ, f_{2}, \dots$ transitions. We work out the basic properties of $π \to π π$ transition GPDs and establish the soft pion theorems at the $2 π$ production threshold. We construct the partial wave expansion of $π \to π π$ transition GPDs in the two-pion decay angles and employ the dispersive approach to constrain $π \to π π$ transition GPDs in terms of $π π$ -scattering phases with help of the Omnès representation. We estimate the $e^{-} π^{+} \to e^{-} γ π^{+} π^{0}$ cross section in the kinematics of the JLab@12 GeV incorporating the isolated $ρ (770)$ resonance state and work out the angular distributions of the cross section, specifying the observables sensitive to the polarization states of the produced $ρ (770)$ resonance.
↳ hep-phnucl-thJHEP(2025)·4 citations
07
Constraints on neutrino-Majoron couplings using SN1987A data
Pilar Iváñez-Ballesteros (APC, Paris)🇫🇷 · M. Cristina Volpe (APC, Paris)🇫🇷
Neutrino decay to a lighter neutrino and a massless or almost massless (pseudo)scalar Goldstone boson remains of wide interest, as in the search for ultralight dark matter or for neutrinoless double beta-decay, and for its implications in astrophysics and cosmology. Neutrino interactions with Majorons can affect the dynamics of supernovae and impact the emitted neutrino flux. Using a three-neutrino framework and detailed supernova simulations, we perform the first likelihood analysis of the 24 neutrino events from SN1987A, including nonradiative decay in matter to a massless (pseudo)scalar boson like a Majoron. Focusing on the induced spectral distortions, we present bounds on the neutrino-Majoron couplings, as a function of the lightest neutrino mass, that are either complementary or competitive with current ones.
↳ hep-phastro-ph.HEastro-ph.SRhep-ex+2PRD(2025)·9 citations
08
Hadron-quark hybrid model, modular transformation and Roberge-Weiss transition
Hiroaki Kouno🇯🇵 · Riki Oshima🇯🇵 · Motoi Tachibana🇯🇵 · Kouji Kashiwa🇯🇵
In the framework of modular transformations, we reformulate the recently proposed hadron-quark hybrid model when the imaginary baryonic chemical potential is introduced. As a result, we can consider the torus, which is characterized by the complex number densities of baryons (antibaryons) and quarks (antiquarks). We apply this model to analyze the Roberge-Weiss transition. It is shown that the torus vanishes at the baryonic chemical potential where the Roberge-Weiss transition appears because the number density of baryons (antibaryons) is not linearly independent of the number density of quarks (antiquarks). When the temperature T is lower than the Roberge-Weiss transition temperature TRW, the torus shrinks smoothly to the one-dimensional object at the Roberge-Weiss transition point, but the discontinuity does not appear. On the other hand, the discontinuity of the geometrical object appears when T>TRW. We also calculate the modulus of the torus and transform it into the fundamental region. The transformed moduli are symmetric below TRW, but the symmetry is broken above TRW.
↳ hep-phhep-latnucl-thPRD(2025)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE