Nuclear Theory·nucl-th

Wednesday·May 15, 2019

8 papers—3 primary·5 cross-listed

01
[Submitted on 13 May 2019]
Symmetry, symmetry breaking, and pion parton distributions
Minghui Ding🇨🇳 · Khepani Raya🇲🇽 · Daniele Binosi🇮🇹 · Lei Chang🇨🇳 · C. D. Roberts🇺🇸 · S. M. Schmidt🇩🇪
Pion valence, glue and sea distributions are calculated using a continuum approach to the two valence-body bound-state problem. Since the framework is symmetry preserving, physical features of the distributions are properly expressed. The analysis reveals that the emergent phenomenon of dynamical chiral symmetry breaking causes a hardening of the valence-quark distribution function, $q^{π} (x)$ . Nevertheless, this distribution exhibits the $x ≃ 1$ behaviour predicted by quantum chromodynamics (QCD). At the scale $ζ_{2} := 2$ GeV, the following momentum fractions are predicted: $⟨ x_{valence} ⟩ = 0.48 (3)$ , $⟨ x_{glue} ⟩ = 0.41 (2)$ , $⟨ x_{sea} ⟩ = 0.11 (2)$ . Evolving to $ζ = 5.2$ GeV, the result for $q^{π} (x)$ agrees with that computed using lattice QCD. These outcomes should both spur improved analyses of existing experiments and stimulate efforts to obtain new data on the pion distribution functions using available and envisioned facilities.
Comments:
13 pages, 7 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1905.05208 [pdf]
PRD(2020)·129 citations
02
[Submitted on 13 May 2019]
Extracting free-space observables from trapped interacting clusters
Xilin Zhang
The energy spectrum of two short-range interacting particles in a harmonic potential trap has previously been related to free-space scattering phase shifts. But the existing formula for this purpose is exact only in the limit of an infinitely shallow trap. Here we provide a systematically improved formula---describing the low-energy dynamics---that enables the use of finite traps. This paves the way for extracting nuclear scattering phase shifts from {\it ab initio} nuclear many-body structure calculations, a long-sought goal in nuclear physics. The derivation establishes effective field theory as a powerful framework for studying the connection between structure information of a trapped system (with two or more sub-clusters) and continuum physics in the fields of both nuclear and condensed-matter physics.
Comments:
12 Pages, 5 figures. Version 3---close to publication version---has more figures included
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); Nuclear Experiment (nucl-ex)
arXiv:
1905.05275 [pdf]
PRC(2020)·31 citations
03
[Submitted on 13 May 2019]
Thermodynamic Geometry of Nambu -- Jona Lasinio model
P. Castorina🇮🇹 · D. Lanteri🇮🇹 · S. Mancani🇮🇹
The formalism of Riemannian geometry is applied to study the phase transitions in Nambu -Jona Lasinio (NJL) model. Thermodynamic geometry reliably describes the phase diagram, both in the chiral limit and for finite quark masses. The comparison between the geometrical study of NJL model and of (2+1) Quantum Chromodynamics at high temperature and small baryon density shows a clear connection between chiral symmetry restoration/breaking and deconfinement/confinement regimes.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1905.05296 [pdf]
Eur.Phys.J.Plus(2020)·9 citations
04
[Submitted on 13 May 2019] (cross-list from hep-ph)
The Photon and Light $1^{--}$ Mesons
R.S. Longacre🇺🇸
In this paper we look into the world data related to the photon and the connection to light mesons with the same spin parity quantum number as the photon $J^{p} = 1^{-}$ .
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1905.05259 [pdf]
0 citations
05
[Submitted on 14 May 2019] (cross-list from nucl-ex)
Hyperon I: Study of the $Λ (1405)$
A.V. Anisovich🇩🇪 · A.V. Sarantsev🇩🇪 · V.A. Nikonov🇩🇪 · V. Burkert🇺🇸 · R.A. Schumacher🇺🇸 · U. Thoma🇩🇪 · E. Klempt🇩🇪
Low-energy data on the three charge states in $γ p \to K^{+} (Σ π)$ from CLAS at JLab, on $K^{-} p \to π^{0} π^{0} Λ$ and $π^{0} π^{0} Σ$ from the Crystal Ball at BNL, bubble chamber data on $K^{-} p \to π^{-} π^{+} π^{\pm} Σ^{\mp}$ , low-energy total cross sections on $K^{-}$ induced reactions, and data on the $K^{-} p$ atom are fitted with the BnGa partial-wave-analysis program. We find that the data can be fitted well with just one isoscalar spin-1/2 negative-parity pole, the $Λ (1405)$ , and background contributions.
Comments:
9 pages, 10 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1905.05456 [pdf]
8 citations
06
[Submitted on 14 May 2019] (cross-list from hep-ph)
Compton Scattering off Pions and Electromagnetic Polarizabilities
Murray Moinester🇮🇱 · Stefan Scherer🇩🇪
The electric ( $α_{π}$ ) and magnetic ( $β_{π}$ ) Compton polarizabilities of both the charged and the neutral pion are of fundamental interest in the low-energy sector of quantum chromodynamics (QCD). Pion polarizabilities affect the shape of the $γ π \to γ π$ Compton scattering angular distribution at back scattering angles and $γ γ \to π π$ absolute cross sections. Theory derivations are given of the $γ π \to γ π$ Compton scattering differential cross section, dispersion relations, and sum rules in terms of the polarizabilities. We review experimental charged and neutral polarizability studies and theoretical predictions. The $π^{0}$ polarizabilities were deduced from DESY Crystal Ball $γ γ \to π^{0} π^{0}$ data, but with large uncertainties. The charged pion polarizabilities were deduced most recently from (1) radiative pion Primakoff scattering $π^{-} Z \to π^{-} Z γ$ at CERN COMPASS, (2) two-photon pion pair production $γ γ \to π^{+} π^{-}$ at SLAC Mark II, and (3) radiative pion photoproduction $γ p \to γ π^{+} n$ from the proton at MAMI in Mainz. A stringent test of chiral perturbation theory (ChPT) is possible based on comparisons of precision experimental charged pion polarizabilities with ChPT predictions. Only the CERN COMPASS charged pion polarizability measurement has acceptably small uncertainties. Its value $α_{π^{\pm}} - β_{π^{\pm}} = (4.0 \pm 1.8) \times 1 0^{- 4} fm^{3}$ agrees well with the two-loop ChPT prediction $α_{π^{\pm}} - β_{π^{\pm}} = (5.7 \pm 1.0) \times 1 0^{- 4} fm^{3}$ , strengthening the identification of the pion with the Goldstone boson of chiral symmetry breaking in QCD.
Comments:
64 pages, 13 figures, preprint of a review article submitted for consideration in International Journal of Modern Physics A o̧pyright} [2019] [copyright World Scientific Publishing Company] [https://www.worldscientific.com/worldscinet/ijmpa]
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1905.05640 [pdf]
Int.J.Mod.Phys.A(2019)·24 citations
07
[Submitted on 14 May 2019] (cross-list from hep-ph)
Heavy quarkonium suppression beyond the adiabatic limit
Jacob Boyd🇺🇸 · Thomas Cook🇺🇸 · Ajaharul Islam🇺🇸 · Michael Strickland🇺🇸
Many prior studies of in-medium quarkonium suppression have implicitly made use of an adiabatic approximation in which it was assumed that the heavy quark potential is a slowly varying function of time. In the adiabatic limit, one can separately determine the in-medium breakup rate and the medium time evolution, folding these together only at the end of the calculation. In this paper, we relax this assumption by solving the 3d Schrodinger equation in real-time in order to compute quarkonium suppression dynamically. We compare results obtained using the adiabatic approximation with real-time calculations for both harmonic oscillator and realistic complex heavy quark potentials. Using the latter, we find that, for the Upsilon(1s), the difference between the adiabatic approximation and full real-time evolution is at the few percent level, however, for the Upsilon(2s), we find that the correction can be as large as 18% in low temperature regions. For the J/Psi, we find a larger difference between the dynamical evolution and the adiabatic approximation, with the error reaching approximately 36%.
Comments:
28 pages, 9 figures, 1 table; v2 - typos fixed, numerical benchmarks added; published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1905.05676 [pdf]
PRD(2019)·24 citations
08
[Submitted on 14 May 2019] (cross-list from hep-ph)
Hadronization within the Non-Extensive Approach and the Evolution of the Parameters
Keming Shen🇭🇺 · Gergely Gábor Barnaföldi🇭🇺 · Tamás Sándor Biró🇭🇺
We review transverse momentum distributions of various identified charged particles stemming from high energy collisions fitted by various non-extensive distributions as well as by the usual Boltzmann-Gibbs statistics. We investigate the best-fit formula with the obtained $χ^{2} / n df$ values. We find that the physical mass and $s$ scaling become more explicit with heavier produced hadrons in both proton-proton and heavy-ion collisions. The spectral shape parameters, in particular the temperature $T$ and the non-extensive Tsallis parameter $q$ , do exhibit an almost linear dependence with the centrality-dependence in heavy-ion collisions.
Comments:
18 pages, 13 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1905.05736 [pdf]
EPJA(2019)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE