Nuclear Theory·nucl-th

Monday·June 5, 2023

11 papers—3 primary·8 cross-listed

04
Hadron transverse momentum distributions in the Tsallis statistics with escort probabilities
A.S. Parvan🇷🇺
The exact and approximate hadron transverse momentum distributions for the Fermi-Dirac, Bose-Einstein and Maxwell-Boltzmann statistics of particles in the framework of the Tsallis statistics with escort probabilities (the Tsallis-3 statistics) have been derived. The classical and quantum transverse momentum distributions in the zeroth term approximation and the quantum transverse momentum distributions in the factorization approximation introduced in the zeroth term approximation were found. The transverse momentum distributions in the zeroth term approximation and in the factorization approximation of the zeroth term approximation are the same in the Tsallis-3, Tsallis-2 and $q$ -dual statistics. The well-known classical phenomenological Tsallis distribution exactly coincides with the classical transverse momentum distribution of the Tsallis-3 statistics in the zeroth term approximation for which the entropy of system is zero in the whole range of state variables. However, the quantum phenomenological Tsallis distribution does not coincide with either the exact or approximate transverse momentum distributions of the Tsallis-3 statistics. The exact Tsallis-3 classical distribution and the classical phenomenological Tsallis distribution were applied to describe the experimental spectra of the charged pions produced in the proton-proton collisions at high energies. The values of the parameters $(T, q)$ for both these model distributions differ in the whole energy range. Thus, the classical phenomenological Tsallis distribution is an unsatisfactory approximation for the exact classical transverse momentum distribution of the Tsallis-3 statistics.
↳ hep-phnucl-thJ.Phys.G(2023)·7 citations
05
Proton charge radius extraction from muon scattering at MUSE using dispersively improved chiral effective field theory
F. Gil-Domínguez🇪🇸 · J. M. Alarcón🇪🇸 · C. Weiss🇺🇸
The MUSE experiment at Paul Scherrer Institute will perform the first measurement of low-energy muon-proton elastic scattering (muon lab momenta 115-210 MeV) with the aim of determining the proton charge radius. We study the prospects for the proton radius extraction using the theoretical framework of Dispersively Improved Chiral Effective Field Theory (DI $χ$ EFT). It connects the proton radii with the finite- $Q^{2}$ behavior of the form factors through complex analyticity and enables the use of data up to $Q^{2} \sim$ 0.1 GeV $^{2}$ for radius extraction. We quantify the sensitivity of the $μ p$ cross section to the proton charge radius, the theoretical uncertainty of the cross section predictions, and the size of two-photon exchange corrections. We find that the optimal kinematics for radius extraction at MUSE is at momenta 210 MeV and $Q^{2} \sim$ 0.05-0.08 GeV $^{2}$ . We compare the performance of electron and muon scattering in the same kinematics. As a byproduct, we obtain explicit predictions for the $μ p$ and $e p$ cross sections at MUSE as functions of the assumed value of the proton radius.
↳ hep-phhep-exnucl-exnucl-thPRD(2023)·6 citations
06
Combined analysis of the $γ n \to K^{0} Σ^{0}$ and $γ n \to K^{+} Σ^{-}$ reactions
Neng-Chang Wei🇨🇳 · Ai-Chao Wang🇨🇳 · Fei Huang🇨🇳
The recently released data on differential cross sections for $γ n \to K^{0} Σ^{0}$ from the A2 and BGOOD Collaborations are used to examine the theoretical model constructed in our previous work [Phys. Rev. D \textbf{105}, 094017 (2022)] for $γ n \to K^{+} Σ^{-}$ , and it is found that the model predictions are able to qualitatively reproduce the A2 data but fail to describe the BGOOD data. Then, a combined analysis of the $γ n \to K^{0} Σ^{0}$ and $γ n \to K^{+} Σ^{-}$ reactions is performed to revise the theoretical model. Due to the inconsistency problem, the A2 and BGOOD data are included in fits separately. In the case of including the A2 data, both the data for $γ n \to K^{0} Σ^{0}$ and $γ n \to K^{+} Σ^{-}$ can be fairly well described, and the contributions from the $N (1710) 1/ 2^{+}$ , $N (1880) 1/ 2^{+}$ , $N (1900) 3/ 2^{+}$ , and $Δ (1920) 3/ 2^{+}$ resonances are found to dominate the reactions in the lower energy region. While in the case of including the BGOOD data, although most of the data for the $γ n \to K^{+} Σ^{-}$ reaction can be described with the exception of some noticeable discrepancies on beam asymmetries at lower energies, the BGOOD data for $γ n \to K^{0} Σ^{0}$ can be only qualitatively described, and the contributions from the $N (1710) 1/ 2^{+}$ , $N (1900) 3/ 2^{+}$ , and $Δ (1910) 1/ 2^{+}$ resonances are found to dominate the reactions in the lower energy region. In both cases, the $t$ -channel $K^{*} (892)$ exchange is found to play a crucial role at forward angles in the higher energy region. Further precise measurements of data for $γ n \to K^{0} Σ^{0}$ are called on to disentangle the discrepancies between the data sets from the A2 and BGOOD Collaborations.
↳ hep-phnucl-thPRD(2023)·7 citations
07
Corrections to Local Density Approximation for superfluid trapped fermionic atoms from the Wigner-Kirkwood $ℏ$ expansion
Peter Schuck🇫🇷 · Michael Urban🇫🇷 · Xavier Viñas🇪🇸
A semiclassical second-order differential equation for the inhomogeneous local gap $Δ (r)$ is derived from a strict second-order $ℏ$ expansion of the anomalous pairing tensor and compared with a similar equation given by Simonucci et al. The second-order normal density matrix is given as well. Several extra gradient terms are revealed. Second-order expressions at finite temperature are given for the first time. The corresponding Ginzburg-Landau equation is presented and it is shown that, compared to the equation of Baranov and Petrov, an extra second-order gradient term is present. Applications to the pairing gap in cold atoms in a harmonic trap are presented.
↳ cond-mat.quant-gasnucl-thEPJA(2023)·3 citations
08
Equation Generator for Equation-of-Motion Coupled Cluster Assisted by Computer Algebra System
Raúl Quintero-Monsebaiz · Pierre-François Loos
We present an equation generator algorithm that utilizes second-quantized operators in normal order with respect to a correlated or non-correlated reference and the corresponding Wick theorem. The algorithm proposed here, written with \textsc{mathematica}, enables the generation of non-redundant strings of second-quantized operators that, after classification, are directly assigned to intermediate quantities used to construct the coupled-cluster (CC) effective Hamiltonian. We demonstrate the capabilities of the algorithm by computing the CC amplitude equations and various blocks of the equation-of-motion CC effective Hamiltonian. A comprehensive description of this four-step algorithm is provided alongside concrete examples.
↳ physics.chem-phcond-mat.mtrl-scicond-mat.str-elnucl-thAIP Adv.(2023)·1 citation
09
Combining lattice QCD and phenomenological inputs on generalised parton distributions at moderate skewness
Michael Joseph Riberdy🇫🇷 · Hervé Dutrieux🇫🇷 · Cédric Mezrag🇫🇷 · Paweł Sznajder🇵🇱
We present a systematic study demonstrating the impact of lattice QCD data on the extraction of generalised parton distributions (GPDs). For this purpose, we use a previously developed modelling of GPDs based on machine learning techniques fulfilling the theoretical requirements of polynomiality, a form of positivity constraint and known reduction limits. A special care is given to estimate the uncertainty stemming from the ill-posed character of the connection between GPDs and the experimental processes usually considered to constrain them, like deeply virtual Compton scattering (DVCS). Mock lattice QCD data inputs are included in a Bayesian framework to the prior model which is fitted to reproduce the most experimentally accessible information of a phenomenological model by Goloskov and Kroll. We highlight the impact of the precision, correlation and kinematic coverage of lattice data on GPD extraction at moderate $ξ$ which has only been brushed in the literature so far, paving the way for a joint extraction of GPDs.
↳ hep-phhep-latnucl-thEPJC(2024)·25 citations
10
Helicity Evolution at Small $x$ : Revised Asymptotic Results at Large $N_{c} & N_{f}$
Daniel Adamiak🇺🇸 · Yuri V. Kovchegov🇺🇸 · Yossathorn Tawabutr🇺🇸
We present a numerical solution of the revised version of the small- $x$ helicity evolution equations at large $N_{c}$ and $N_{f}$ . (Here $N_{c}$ and $N_{f}$ are the numbers of quark colors and flavors, respectively.) The evolution equations are double-logarithmic in the Bjorken $x$ variable, resumming powers of $α_{s} ln^{2} (1/ x)$ with $α_{s}$ the strong coupling constant. The large- $N_{c} & N_{f}$ evolution we consider includes contributions of small- $x$ quark emissions and is thus more realistic than the large- $N_{c}$ one, which only involves gluon emissons. The evolution equations are written for the so-called ``polarized dipole amplitudes", which are related to the helicity distribution functions and the $g_{1}$ structure function. Unlike the previously reported solution of the earlier version of helicity evolution equations at large $N_{c} & N_{f}$ , our solution does not exhibit periodic oscillations in $ln (1/ x)$ for $N_{f} < 2 N_{c}$ , while only showing occasional sign reversals. For $N_{f} = 2 N_{c}$ , we report oscillations with $ln (1/ x)$ , similar to those found earlier. We determine the intercept of our evolution for $N_{f} < 2 N_{c}$ as well as the parameters of the oscillatory behavior for $N_{f} = 2 N_{c}$ . We compare our results to the existing resummation and finite-order calculations for helicity-dependent quantities in the literature.
↳ hep-phnucl-thPRD(2023)·36 citations
11
Impacts of the $^{12} C (α, γ)^{16} O$ reaction rate on $^{56} Ni$ nucleosynthesis in pair-instability supernovae
Hiroki Kawashimo · Ryo Sawada · Yudai Suwa · Takashi J. Moriya · Ataru Tanikawa · Nozomu Tominaga
Nuclear reactions are key to our understanding of stellar evolution, particularly the $^{12} C (α, γ)^{16} O$ rate, which is known to significantly influence the lower and upper ends of the black hole (BH) mass distribution due to pair-instability supernovae (PISNe). However, these reaction rates have not been sufficiently determined. We use the $MESA$ stellar evolution code to explore the impact of uncertainty in the $^{12} C (α, γ)^{16} O$ rate on PISN explosions, focusing on nucleosynthesis and explosion energy by considering the high resolution of the initial mass. Our findings show that the mass of synthesized radioactive nickel ( $^{56} Ni$ ) and the explosion energy increase with $^{12} C (α, γ)^{16} O$ rate for the same initial mass, except in the high-mass edge region. With a high (about twice the $STARLIB$ standard value) rate, the maximum amount of nickel produced falls below 70 $M_{⊙}$ , while with a low rate (about half of the standard value) it increases up to 83.9 $M_{⊙}$ . These results highlight that carbon "preheating" plays a crucial role in PISNe by determining core concentration when a star initiates expansion. Our results also suggest that the onset of the expansion, which means the end of compression, competes with collapse caused by helium photodisintegration, and the maximum mass that can lead to an explosion depends on the $^{12} C (α, γ)^{16} O$ reaction rate.
↳ astro-ph.SRastro-ph.HEnucl-thMNRAS(2024)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE