Nuclear Theory·nucl-th

Monday·February 1, 2021

7 papers—1 primary·6 cross-listed

01
[Submitted on 28 Jan 2021]
Dispersive analysis of low energy $γ^{*} N \to π N$ process
Xiong-Hui Cao (Peking U. and Peking U., SKLNPT)🇨🇳 · Yao Ma (Peking U. and Peking U., SKLNPT)🇨🇳 · Han-Qing Zheng (Peking U. and Peking U., SKLNPT and CICQM, Beijing)🇨🇳
We use a dispersion representation based on unitarity and analyticity to study the low energy $γ^{*} N \to π N$ process in the $S_{11}$ channel. Final state interactions among the $π N$ system are critical to this analysis. The left-hand part of the partial wave amplitude is imported from $O (p^{2})$ chiral perturbation theory result. On the right-hand part, the final state interaction is calculated through Omnès formula in $S$ wave. It is found that a good numerical fit can be achieved with only one subtraction parameter, and the eletroproduction experimental data of multipole amplitudes $E_{0 +}, S_{0 +}$ in the energy region below $Δ (1232)$ are well described when the photon virtuality $Q^{2} \leq 0.1 GeV^{2}$ .
Comments:
30 pages, 11 figures, 3 tables; to match the published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2101.12576 [pdf]
PRD(2021)·9 citations
02
[Submitted on 28 Jan 2021] (cross-list from hep-ph)
Measures of pion and kaon structure from generalised parton distributions
Jin-Li Zhang🇨🇳 · Khépani Raya🇨🇳 · Lei Chang🇨🇳 · Zhu-Fang Cui🇨🇳 · José Manuel Morgado🇪🇸 · Craig D. Roberts🇨🇳 · José Rodríguez-Quintero🇪🇸
Pion and kaon structural properties provide insights into the emergence of mass within the Standard Model and attendant modulations by the Higgs boson. Novel expressions of these effects, in impact parameter space and in mass and pressure profiles, are exposed via $π$ and $K$ generalised parton distributions, built using the overlap representation from light-front wave functions constrained by one-dimensional valence distribution functions that describe available data. Notably, e.g. $K$ pressure profiles are spatially more compact than $π$ profiles and both achieve near-core pressures of similar magnitude to that found in neutron stars.
Comments:
9 pages, 6 figures, 2 tables. Accepted for publication in Phys. Lett. B
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:
2101.12286 [pdf]
PLB(2021)·42 citations
03
[Submitted on 29 Jan 2021] (cross-list from nucl-ex)
Cumulants and Correlation Functions of Net-proton, Proton and Antiproton Multiplicity Distributions in Au+Au Collisions at energies available at the BNL Relativistic Heavy Ion Collider
STAR Collaboration: M. S. Abdallah · J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson · A. Aparin and 379 other authors
We report a systematic measurement of cumulants, $C_{n}$ , for net-proton, proton and antiproton multiplicity distributions, and correlation functions, $κ_{n}$ , for proton and antiproton multiplicity distributions up to the fourth order in Au+Au collisions at $s_{NN}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4 and 200 GeV. The $C_{n}$ and $κ_{n}$ are presented as a function of collision energy, centrality and kinematic acceptance in rapidity, $y$ , and transverse momentum, $p_{T}$ . The data were taken during the first phase of the Beam Energy Scan (BES) program (2010 -- 2017) at the BNL Relativistic Heavy Ion Collider (RHIC) facility. The measurements are carried out at midrapidity ( $∣ y ∣ <$ 0.5) and transverse momentum 0.4 $<$ $p_{T}$ $<$ 2.0 GeV/ $c$ , using the STAR detector at RHIC. We observe a non-monotonic energy dependence ( $s_{NN}$ = 7.7 -- 62.4 GeV) of the net-proton $C_{4}$ / $C_{2}$ with the significance of 3.1 $σ$ for the 0-5\% central Au+Au collisions. This is consistent with the expectations of critical fluctuations in a QCD-inspired model. Thermal and transport model calculations show a monotonic variation with $s_{NN}$ . For the multiparticle correlation functions, we observe significant negative values for a two-particle correlation function, $κ_{2}$ , of protons and antiprotons, which are mainly due to the effects of baryon number conservation. Furthermore, it is found that the four-particle correlation function, $κ_{4}$ , of protons plays a role in determining the energy dependence of proton $C_{4} / C_{1}$ below 19.6 GeV, which cannot be understood by the effect of baryon number conservation.
Comments:
34 pages, 25 figures, 8 tables
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2101.12413 [pdf]
PRC(2021)·226 citations
04
[Submitted on 27 Jan 2021] (cross-list from hep-ph)
Modern status of heavy quark sum rules in QCD
Stephan Narison (LUPM-CNRS/Univ Montpellier, FR and iHEPMAD-Univ. Antananarivo, MG)🇫🇷
We briefly report the modern status of heavy quark sum rules (HQSR) based on stability criteria by emphasizing the recent progresses for determining the QCD parameters (alpha_s, m_{c,b} and gluon condensates)where their correlations have been taken into account. The results: alpha_s(M_Z)=0.1181(16)(3), m_c(m_c)=1286(16) MeV, m_b(m_b)=4202(7) MeV,<alpha_s G^2> = (6.49+-0.35)10^-2 GeV^4, < g^3 G^3 >= (8.2+-1.0) GeV^2 <alpha_s G^2> and the ones from recent light quark sum rules are summarized in Table 2. One can notice that the SVZ value of <alpha_s G^2> has been underestimated by a factor 1.6, <g^3 G^3> is much bigger than the instanton model estimate, while the four-quark condensate which mixes under renormalization is incompatible with the vacuum saturation which is phenomenologically violated by a factor (2~4). The uses of HQSR for molecules and tetraquarks states are commented.
Comments:
8 pages in 2-column format, 5 figures, 2 Tables. Mini-Review talk given at QCD20-35 years later, 23th International Conference in QCD (27-30 october 2020, Montpellier-FR)
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2101.12579 [pdf]
Nucl.Part.Phys.Proc.(2021)·8 citations
05
[Submitted on 29 Jan 2021] (cross-list from cond-mat.quant-gas)
Energies and widths of Efimov states in the three-boson continuum
A. Deltuva
Three-boson Efimov physics is well known in the bound-state regime, but far less in the three-particle continuum at negative two-particle scattering length where Efimov states evolve into resonances. They are studied solving rigorous three-particle scattering equations for transition operators in the momentum space. The dependence of the three-boson resonance energy and width on the two-boson scattering length is studied with several force models. The universal limit is determined numerically considering highly excited states; simple parametrizations for the resonance energy and width in terms of the scattering length are established. Decreasing the attraction, the resonances rise not much above the threshold but broaden rapidly and become physically unobservable, evolving into subthreshold resonances. Finite-range effects are studied and related to those in the bound-state regime.
Comments:
6 pages, 5 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
2101.12654 [pdf]
PRC(2020)·11 citations
06
[Submitted on 29 Jan 2021] (cross-list from hep-ph)
Fluctuations of order parameter in an $S U (N_{c})$ effective model
Pok Man Lo🇵🇱 · Krzysztof Redlich🇵🇱 · Chihiro Sasaki🇵🇱
We investigate features of the deconfinement phase transition in an $S U (N_{c})$ gauge theory as revealed by fluctuations of the order parameter. The tool of choice is an effective model built from one-loop expressions of the field determinants of gluon and ghost, in the presence of a Polyakov loop background field. We show that the curvature masses associated with the Cartan angles, which serve as a proxy to study the $A_{0}$ -gluon screening mass, show a characteristic dip in the vicinity of the transition temperature. The strength of the observables, which reflects a competition between the confining and the deconfining forces, is sensitive to assumptions of dynamics, thus provides an interesting link between the $Z (N_{c})$ vacuum structure and the properties of gluon and ghost propagators.
Comments:
15 pages, 6 figures, typos. corrected, version appear in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2101.12663 [pdf]
PRD(2021)·12 citations
07
[Submitted on 29 Jan 2021] (cross-list from hep-lat)
Path integral contour deformations for observables in $S U (N)$ gauge theory
William Detmold🇺🇸 · Gurtej Kanwar🇺🇸 · Henry Lamm🇺🇸 · Michael L. Wagman🇺🇸 · Neill C. Warrington🇺🇸
Path integral contour deformations have been shown to mitigate sign and signal-to-noise problems associated with phase fluctuations in lattice field theories. We define a family of contour deformations applicable to $S U (N)$ lattice gauge theory that can reduce sign and signal-to-noise problems associated with complex actions and complex observables. For observables, these contours can be used to define deformed observables with identical expectation value but different variance. As a proof-of-principle, we apply machine learning techniques to optimize the deformed observables associated with Wilson loops in two dimensional $S U (2)$ and $S U (3)$ gauge theory. We study loops consisting of up to 64 plaquettes and achieve variance reduction of up to 4 orders of magnitude.
Comments:
25 pages, 12 figures
Subjects:
High Energy Physics — Lattice (hep-lat); Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
arXiv:
2101.12668 [pdf]
PRD(2021)·47 citations

Affiliations

first authorsco-authorsvia INSPIRE

Dispersive analysis of low energy γ∗N→πN process

Measures of pion and kaon structure from generalised parton distributions

Cumulants and Correlation Functions of Net-proton, Proton and Antiproton Multiplicity Distributions in Au+Au Collisions at energies available at the BNL Relativistic Heavy Ion Collider

Modern status of heavy quark sum rules in QCD

Energies and widths of Efimov states in the three-boson continuum

Fluctuations of order parameter in an SU(Nc​) effective model

Path integral contour deformations for observables in SU(N) gauge theory

Affiliations

Dispersive analysis of low energy $γ^{*} N \to π N$ process

Fluctuations of order parameter in an $S U (N_{c})$ effective model

Path integral contour deformations for observables in $S U (N)$ gauge theory