Nuclear Theory·nucl-th

Tuesday·December 22, 2020

10 papers—5 primary·5 cross-listed

01
[Submitted on 21 Dec 2020]
Generator coordinate method with a conjugate momentum: application to the particle number projection
N. Hizawa · K. Hagino · K. Yoshida
We discuss an extension of the generator coordinate method (GCM) by taking simultaneously a collective coordinate and its conjugate momentum as generator coordinates. To this end, we follow the idea of the dynamical GCM (DGCM) proposed by Goeke and Reinhard. We first show that the DGCM method can be regarded as an extension of the double projection method for the center of mass motion. As an application of DGCM, we then investigate the particle number projection, for which we not only carry out an integral over the gauge angle as in the usual particle number projection but also take a linear superposition of BCS states which have different mean particle numbers. We show that the ground state energy is significantly lowered by such effect, especially for magic nuclei for which the pairing gap is zero in the BCS approximation. This suggests that the present method makes a good alternative to the variation after projection (VAP) method, as the method is much simpler than the VAP.
Comments:
9 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Superconductivity (cond-mat.supr-con)
arXiv:
2012.11123 [pdf]
PRC(2021)·14 citations
02
[Submitted on 21 Dec 2020]
A formalism for the study of $K^{+} π Σ$ photoproduction in the $Λ^{*} (1405)$ region
Peter C. Bruns🇨🇿
We present a formalism for the low-energy analysis of the $γ p \to K^{+} π Σ$ photoproduction reaction in the $Λ^{*} (1405)$ resonance region. In particular, the constraints arising from unitarity, gauge invariance and chiral perturbation theory are discussed in some detail.
Comments:
Fixed some typos for v2
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2012.11298 [pdf]
9 citations
03
[Submitted on 21 Dec 2020]
Polarization of $Λ (1405)$ in the $γ p \to K^{+} π Σ$ reaction
Ke Wang🇨🇳 · Bo-Chao Liu🇨🇳
In this paper, we study the polarization of the $Λ (1405)$ in the $γ p \to K^{+} π Σ$ reaction within an effective Lagrangian approach and isobar model. In our model, the $Λ (1405)$ is excited through the t-channel $K / K^{*}$ exchanges and u-channel hyperon exchange. Compared to previous studies, we also include the contribution from a contact term, which is necessary for our model to interpret the polarization of the $Λ (1405)$ . In addition, we also discuss the possibility to verify the proposed two-pole structure of the $Λ (1405)$ using the polarization data. We find that the polarization of the $Λ (1405)$ or the polarization of the final $Σ$ in this reaction is sensitive to the invariant mass $M_{π Σ}$ . Thus the measurement of the dependence of the $Λ (1405)$ polarization on the $M_{π Σ}$ can offer valuable information about the pole structure of the $Λ (1405)$ .
Comments:
8 pages, 7 figures. Version accepted by PLB
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2012.11379 [pdf]
PLB(2021)·1 citation
04
[Submitted on 21 Dec 2020]
Update of the Three-fluid Hydrodynamics-based Event Simulator: light-nuclei production in heavy-ion collisions
M. Kozhevnikova🇷🇺 · Yu. B. Ivanov🇷🇺 · Iu. Karpenko🇨🇿 · D. Blaschke🇵🇱 · O. Rogachevsky🇷🇺
We present an update of the event generator based on the three-fluid dynamics (3FD), complemented by Ultra-relativistic Quantum Molecular Dynamics (UrQMD) for the late stage of the nuclear collision~-- the three-fluid Hydrodynamics-based Event Simulator Extended by UrQMD final State interactions (THESEUS). Two modifications are introduced. The THESEUS table of hadronic resonances is made consistent with that of the underlying 3FD model. The main modification is that the generator is extended to simulate the light-nuclei production in relativistic heavy-ion collisions, on the equal basis with hadrons. These modifications are illustrated by applications to the description of available experimental data. The first run of the updated generator revealed a good reproduction of the NA49 data on the light nuclei. The reproduction is achieved without any extra parameters, while the coalescence approach in 3FD requires special tuning of the coalescence coefficients for each light nucleus separately.
Comments:
8 pages, 3 figures, version published in PRC
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2012.11438 [pdf]
PRC(2021)·15 citations
05
[Submitted on 21 Dec 2020]
Collective flow at SIS energies within a hadronic transport approach: Influence of light nuclei formation and equation of state
Justin Mohs🇩🇪 · Martha Ege🇩🇪 · Hannah Elfner🇩🇪 · Markus Mayer🇩🇪
Collective flow observables are known to be a sensitive tool to gain insights on the equation of state of nuclear matter from heavy-ion collision observations. Towards more quantitative constraints one has to carefully assess other influences on the collective behaviour. In this work a hadronic transport approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is applied to study the first four anisotropic flow coefficients in Au+Au collisions at $E_{lab} = 1.23 A$ GeV in the context of the recently measured data by the HADES collaboration. In particular, the formation of light nuclei is important in this energy regime. Two different approaches are contrasted to each other: A clustering algorithm inspired by coalescence as well as microscopic formation of deuterons via explicit cross-sections. The sensitivity of directed and elliptic flow observables to the strength of the Skyrme mean field is explored. In addition, it is demonstrated that the rapidity-odd $v_{3}$ coefficient is practically zero in this energy regime and the ratio of $v_{4} / v_{2}^{2}$ is close to the value of 0.5 expected from hydrodynamic behaviour. This study establishes the current understanding of collective behaviour within the SMASH approach and lays the ground for future more quantitative constraints on the equation of state of nuclear matter within improved mean field calculations.
Comments:
Tables for all plotted calculations can be found in the anc folder
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2012.11454 [pdf]
PRC(2022)·41 citations
06
[Submitted on 20 Dec 2020] (cross-list from nucl-ex)
International Workshop on Next Generation Gamma-Ray Source
C. R. Howell🇺🇸 · M. W. Ahmed🇺🇸 · A. Afanasev🇺🇸 · D. Alesini🇮🇹 · J. R. M. Annand🇬🇧 · A. Aprahamian🇺🇸 · D. L. Balabanski🇷🇴 · S. V. Benson🇺🇸 · A. Bernstein🇺🇸 · C. R. Brune🇺🇸 · J. Byrd🇺🇸 · B. E. Carlsten🇺🇸 and 41 other authors
A workshop on The Next Generation Gamma-Ray Sources sponsored by the Office of Nuclear Physics at the Department of Energy, was held November 17--19, 2016 in Bethesda, Maryland. The goals of the workshop were to identify basic and applied research opportunities at the frontiers of nuclear physics that would be made possible by the beam capabilities of an advanced laser Compton beam facility. To anchor the scientific vision to realistically achievable beam specifications using proven technologies, the workshop brought together experts in the fields of electron accelerators, lasers, and optics to examine the technical options for achieving the beam specifications required by the most compelling parts of the proposed research programs. An international assembly of participants included current and prospective $γ$ -ray beam users, accelerator and light-source physicists, and federal agency program managers. Sessions were organized to foster interactions between the beam users and facility developers, allowing for information sharing and mutual feedback between the two groups. The workshop findings and recommendations are summarized in this whitepaper.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Accelerator Physics (physics.acc-ph)
arXiv:
2012.10843 [pdf]
J.Phys.G(2022)·35 citations
07
[Submitted on 21 Dec 2020] (cross-list from hep-ph)
\boldmath{ $Υ$ } and \boldmath{ $η_{b}$ } mass shifts in nuclear matter
G. N. Zeminiani🇧🇷 · J. J. Cobos-Martinez🇲🇽 · K. Tsushima🇧🇷
We estimate the $Υ$ , $η_{b}$ and $B^{*}$ meson mass shifts in symmetric nuclear matter. The interest is, whether the strengths of the bottomonium-(nuclear matter) and charmonium-(nuclear matter) interactions are similar or different. This is because, each ( $J /Ψ, Υ$ ) and ( $η_{c}, η_{b}$ ) meson group is usually assumed to have very similar properties based on the heavy charm and bottom quark masses. The estimate for the $Υ$ is made using an SU(5) effective Lagrangian and the anomalous coupling one, by studying the $B B$ , $B B^{*}$ , and $B^{*} B^{*}$ meson loop contributions for the self-energy. As for the $η_{b}$ , we include the $B B^{*}$ and $B^{*} B^{*}$ meson loop contributions in the self-energy. The in-medium masses of the $B$ and $B^{*}$ mesons appearing in the self-energy are calculated by the quark-meson coupling model. An analysis on the $B B$ , $B B^{*}$ , and $B^{*} B^{*}$ meson loops in the $Υ$ mass shift is made by comparing with the corresponding $D D, D D^{*}$ , and $D^{*} D^{*}$ meson loops for the $J /Ψ$ mass shift. Our prediction for the $η_{b}$ mass shift is made including only the lowest order $B B^{*}$ meson loop. The $Υ$ mass shift, with including only the $B B$ loop, is predicted to be -16 to -22 MeV at the nuclear matter saturation density using the $Υ B B$ coupling constant determined by the vector meson dominance model with the experimental data, while the $η_{b}$ mass shift is predicted to be -75 to -82 MeV with the SU(5) universal coupling constant determined by the $Υ B B$ coupling constant. Our results show an appreciable difference between the bottomonium-(nuclear matter) and charmonium-(nuclear matter) interaction strengths. We also study the $Υ$ and $η_{b}$ mass shifts in a heavy quark (heavy meson) symmetry limit.
Comments:
19 pages, 9 figures (21 eps.files for figures), version to appear in EPJA
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2012.11381 [pdf]
EPJA(2021)·24 citations
08
[Submitted on 21 Dec 2020] (cross-list from hep-ph)
Reweighted nuclear PDFs using Heavy-Flavor Production Data at the LHC: nCTEQ15_rwHF & EPPS16_rwHF
Aleksander Kusina🇵🇱 · Jean-Philippe Lansberg🇫🇷 · Ingo Schienbein🇫🇷 · Hua-Sheng Shao🇫🇷
We present the reweighting of two sets of nuclear PDFs, nCTEQ15 and EPPS16, using a selection of experimental data on heavy-flavor meson [D0, J/psi, J/psi from B and Upsilon(1S)] production in proton-lead collisions at the LHC which were not used in the original determination of these nuclear PDFs. The reweighted PDFs exhibit significantly smaller uncertainties thanks to these new heavy-flavor constraints. We present a comparison with another selection of data from the LHC and RHIC which were not included in our reweighting procedure. The comparison is overall very good and serves as a validation of these reweighted nuclear PDF sets, which we dub nCTEQ15_rwHF & EPPS16_rwHF. This indicates that the LHC and forward RHIC heavy-flavor data can be described within the standard collinear factorization framework with the same (universal) small-x gluon distribution. We discuss how we believe such reweighted PDFs should be used as well as the limitations of our procedure.
Comments:
Latex, 20 pages, 20 figures, 1 table; v2: a few references added
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2012.11462 [pdf]
PRD(2021)·38 citations
09
[Submitted on 21 Dec 2020] (cross-list from nucl-ex)
Measurement of the Ar(e,e $^{'}$ p) and Ti(e,e $^{'}$ p) cross sections in Jefferson Lab Hall A
L. Gu🇺🇸 · D. Abrams🇺🇸 · A. M. Ankowski🇺🇸 · L. Jiang🇺🇸 · B. Aljawrneh🇺🇸 · S. Alsalmi🇸🇦 · J. Bane🇺🇸 · A. Batz🇺🇸 · S. Barcus🇺🇸 · M. Barroso🇺🇸 · O. Benhar🇮🇹 · V. Bellini🇮🇹 and 49 other authors
The E12-14-012 experiment, performed in Jefferson Lab Hall A, has collected exclusive electron-scattering data (e,e $^{'}$ p) in parallel kinematics using natural argon and natural titanium targets. Here, we report the first results of the analysis of the data set corresponding to beam energy of 2,222 MeV, electron scattering angle 21.5 deg, and proton emission angle -50 deg. The differential cross sections, measured with $\sim$ 4% uncertainty, have been studied as a function of missing energy and missing momentum, and compared to the results of Monte Carlo simulations, obtained from a model based on the Distorted Wave Impulse Approximation.
Comments:
14 pages, 8 figures (submitted to PRC)
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2012.11466 [pdf]
PRC(2021)·22 citations
10
[Submitted on 21 Dec 2020] (cross-list from hep-ph)
nCTEQ15HIX -- Extending nPDF Analyses into the High- $x$ , Low $Q^{2}$ Region
E.P. Segarra🇺🇸 · T. Ježo🇩🇪 · A. Accardi🇺🇸 · P. Duwentäster🇩🇪 · O. Hen🇺🇸 · T.J. Hobbs🇺🇸 · C. Keppel🇺🇸 · M. Klasen🇩🇪 · K. Kovařík🇩🇪 · A. Kusina🇵🇱 · J.G. Morfín🇺🇸 · K.F. Muzakka🇩🇪 and 3 other authors
We use the nCTEQ analysis framework to investigate nuclear Parton Distribution Functions (nPDFs) in the region of large x and intermediate-to-low $Q$ , with special attention to recent JLab Deep Inelastic Scattering data on nuclear targets. This data lies in a region which is often excluded by $W$ and $Q$ cuts in global nPDF analyses. As we relax these cuts, we enter a new kinematic region, which requires new phenomenology. In particular, we study the impact of i) target mass corrections, ii) higher twist corrections, iii) deuteron corrections, and iv) the shape of the nuclear PDF parametrization at large- $x$ close to one. Using the above tools, we produce a new nPDF set (named nCTEQ15HIX) which yields a good description of the new JLab data in this challenging kinematic region, and displays reduced uncertainties at large $x$ , in particular for up and down quark flavors.
Comments:
25 pages, 19 figures, 6 tables, 1 auxiliary data file. Version 02: include journal updates
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2012.11566 [pdf]
PRD(2021)·49 citations

Affiliations

first authorsco-authorsvia INSPIRE