Nuclear Theory·nucl-th

Thursday·February 7, 2019

5 papers—3 primary·2 cross-listed

01
Thick-Restart Block Lanczos Method for Large-Scale Shell-Model Calculations
Noritaka Shimizu · Takahiro Mizusaki · Yutaka Utsuno · Yusuke Tsunoda
We propose a thick-restart block Lanczos method, which is an extension of the thick-restart Lanczos method with the block algorithm, as an eigensolver of the large-scale shell-model calculations. This method has two advantages over the conventional Lanczos method: the precise computations of the near-degenerate eigenvalues, and the efficient computations for obtaining a large number of eigenvalues. These features are quite advantageous to compute highly excited states where the eigenvalue density is rather high. A shell-model code, named KSHELL, equipped with this method was developed for massively parallel computations, and it enables us to reveal nuclear statistical properties which are intensively investigated by recent experimental facilities. We describe the algorithm and performance of the KSHELL code and demonstrate that the present method outperforms the conventional Lanczos method.
nucl-thphysics.comp-phComput.Phys.Commun.(2019)·400 citations
02
Effects of drag induced radiation and multi-stage evolution on heavy quark energy loss
Abhijit Majumder🇺🇸 · Shanshan Cao🇺🇸 · Chun Shen🇺🇸 · Guang-You Qin🇨🇳
Heavy quarks serve as ideal probes of the QGP properties produced in energetic nuclear collisions, and provide a unique opportunity to study the mass effects on parton energy loss. We develop a multi-stage approach for heavy quark evolution inside the QGP, in which heavy quarks first undergo a rare-scattering multiple-emission evolution at momenta large compared to their mass (sensitive only to the transverse diffusion coefficient $q^$ ), and then evolve through a single-scattering induced emission (Gunion-Bertsch) stage at momenta comparable to their mass [sensitive to not only $q^$ , but also the longitudinal drag $e^$ and diffusion $e^_{2}$ coefficients]. This multi-stage approach is coupled to a (2+1)-D viscous hydrodynamic model for a quantitative investigation of charm vs. beauty quark energy loss inside the QGP. Based on this approach, we find that drag induced radiation has a considerable impact on the energy loss of intermediate $p_{T}$ massive beauty quarks. This effect increases the suppression of B mesons and narrows the difference between the $R_{AA}$ of B and D mesons. Our results are consistent with the experimental data at the LHC and contribute to a more quantitative understanding of the transverse momentum dependence of the mass hierarchy of parton energy loss inside the QGP.
nucl-thhep-phPoS(2019)·0 citations
03
Complex-energy analysis of proton-proton fusion
David Gaspard · Jean-Marc Sparenberg · Quentin Wenda · Daniel Baye
An analysis of the astrophysical $S$ factor of the proton-proton weak capture ( $p + p \to^{2} H + e^{+} + ν_{e}$ ) is performed on a large energy range covering solar-core and early Universe temperatures. The measurement of $S$ being physically unachievable, its value relies on the theoretical calculation of the matrix element $Λ$ . Surprisingly, $Λ$ reaches a maximum near $0.13 MeV$ that has been unexplained until now. A model-independent parametrization of $Λ$ valid up to about $5 MeV$ is established on the basis of recent effective-range functions. It provides an insight into the relationship between the maximum of $Λ$ and the proton-proton resonance pole at $(- 140 - 467 i) keV$ from analytic continuation. In addition, this parametrization leads to an accurate evaluation of the derivatives of $Λ$ , and hence of $S$ , in the limit of zero energy.
nucl-thPRC(2019)·2 citations
04
Comparison of AMD calculations with experimental data for peripheral collisions of 93Nb+93Nb,116Sn at 38 MeV/nucleon
S.Piantelli · A.Olmi · P.R.Maurenzig · A.Ono · M.Bini · G.Casini · G.Pasquali · A.Mangiarotti · G.Poggi · A.A.Stefanini · S.Barlini · A.Camaiani and 4 other authors
Experimental data concerning binary events in peripheral collisions for the systems 93Nb+93Nb and 93Nb+116Sn at 38 MeV/nucleon, collected with the Fiasco setup, are compared with calculations performed with the dynamic code AMD, coupled with the statistical code Gemini used as an afterburner. The comparison focuses on the properties of the quasiprojectile (QP) and on the total multiplicities of the emitted light charged particles. A good reproduction of the average mass ratio, charge Z and c.m. angle of the QP is obtained in the examined impact parameter range (b~7-12 fm). Concerning the light charged particles, a general agreement is found for the total emitted charge, while some discrepancy remains for the multiplicities of the various species, especially for the protons which are always overestimated by the calculations.
↳ nucl-exnucl-thPRC(2019)·26 citations
05
A dispersive analysis of the pion vector form factor and $τ^{-} \to K^{-} K_{S} ν_{τ}$ decay
Sergi Gonzàlez-Solís🇨🇳 · Pablo Roig🇲🇽
We explore the potential of a combined analysis of the decays $τ^{-} \to π^{-} π^{0} ν_{τ}$ and $τ^{-} \to K^{-} K_{S} ν_{τ}$ in the determination of the $ρ (1450)$ and $ρ (1700)$ resonance properties in the frame of resonance Chiral Theory supplemented by dispersion relations. On the one hand, we take advantage of the very precise data on the modulus squared of the pion vector form factor $∣ F_{V}^{π} ∣^{2}$ obtained by Belle to carry out a very dedicated analysis of the region where these resonances come up into play. Our study provides an improved treatment of the systematic theoretical errors and, as a most important result, we conclude that they dominate over the fit uncertainties in the determination of the $ρ (1450)$ and $ρ (1700)$ pole parameters and tend to be larger than in other determinations quoted in the literature where these errors were ignored or underestimated. The results of our analysis are summarized in numerical tables for the form factor modulus and phase, including both statistical and systematic errors, that can be found as ancillary material of this paper. As a byproduct, we also determine the low-energy observables of the pion vector form factor and the $ρ$ -pole position. On the other hand, we benefit from the recent experimental data for the transition $τ^{-} \to K^{-} K_{S} ν_{τ}$ released by BaBar to perform a first analysis of its decay spectrum and discuss the role of these resonances in this decay. We point out that higher-quality data on the $K^{-} K_{S}$ decay channel will allow compete with the $∣ F_{V}^{π} ∣^{2}$ ones and improve the determination of the $ρ (1450)$ and $ρ (1700)$ resonance parameters as a result of a combined analysis. We hope our study to be of interest for present and future experimental analysis of these decays.
↳ hep-phhep-exnucl-thEPJC(2019)·66 citations

Affiliations

first authorsco-authorsvia INSPIRE

Thick-Restart Block Lanczos Method for Large-Scale Shell-Model Calculations

Effects of drag induced radiation and multi-stage evolution on heavy quark energy loss

Complex-energy analysis of proton-proton fusion

Comparison of AMD calculations with experimental data for peripheral collisions of 93Nb+93Nb,116Sn at 38 MeV/nucleon

A dispersive analysis of the pion vector form factor and τ−→K−KS​ντ​ decay

Affiliations

A dispersive analysis of the pion vector form factor and $τ^{-} \to K^{-} K_{S} ν_{τ}$ decay