Nuclear Theory·nucl-th

Monday·April 23, 2018

8 papers—4 primary·4 cross-listed

05
$J / ψ \to γ η^{'} π^{+} π^{-}$ and the structure observed around the $p ˉ p$ threshold
Ling-Yun Dai🇨🇳 · Johann Haidenbauer🇩🇪 · Ulf-G. Meißner🇩🇪
We analyze the origin of the structure observed in the reaction $J / ψ \to γ η^{'} π^{+} π^{-}$ for $η^{'} π^{+} π^{-}$ invariant masses close to the antiproton-proton ( $p ˉ p$ ) threshold, commonly associated with the $X (1835)$ resonance. Specifically, we explore the effect of a possible contribution from the two-step process $J / ψ \to γ N ˉ N \to γ η^{'} π^{+} π^{-}$ . The calculation is performed in distorted-wave Born approximation which allows an appropriate inclusion of the $N ˉ N$ interaction in the transition amplitude. The $N ˉ N$ amplitude itself is generated from a corresponding potential recently derived within chiral effective field theory. We are able to reproduce the measured spectra for the reactions $J / ψ \to γ p ˉ p$ and $J / ψ \to γ η^{'} π^{+} π^{-}$ for invariant masses around the $p ˉ p$ threshold. The structure seen in the $η^{'} π^{+} π^{-}$ spectrum emerges as a threshold effect due to the opening of the $p ˉ p$ channel.
↳ hep-phnucl-thPRD(2018)·20 citations
06
Nucleon Mass Sum Rule Violation in QCD and Confinement
Gouranga C Nayak🇺🇸
In this paper we show that for a nucleon at rest if the quarks and/or antiquarks are in motion inside the nucleon producing chromo-magnetic field then the mass sum rule in QCD is violated when the confinement potential energy at large distance $r$ rises linearly with $r$ (or faster). Hence we find that the mass of the nucleon at rest is not equal to the mass-energy of all the quarks plus antiquarks plus gluons inside the nucleon if there exists chromo-magnetic field inside the nucleon and the confinement potential energy at large distance $r$ rises linearly with $r$ (or faster).
↳ hep-phhep-latnucl-th3 citations
07
Partial-Wave Analysis of $γ p \to K^{+} Λ$ using a multichannel framework
B. C. Hunt🇺🇸 · D. M. Manley🇺🇸
Results from a partial-wave analysis of the reaction $γ p \to K^{+} Λ$ are presented. The reaction is dominated by the $S_{11} (1650)$ and $P_{13} (1720)$ resonances at low energies and by $P_{13} (1900)$ at higher energies. There are small contributions from all amplitudes up to and including $G_{17}$ , with $F_{17}$ necessary for obtaining a good fit of several of the spin observables. We find evidence for $P_{11}$ (1880), $D_{13}$ (2120), and $D_{15}$ (2080) resonances, as well as a possible $F_{17}$ resonance near 2300 MeV, which is expected from quark-model predictions. Some predictions for $γ n \to K^{0} Λ$ are also included.
↳ nucl-exnucl-thPRC(2019)·20 citations
08
Elliptic flow and $R_{AA}$ of D mesons at FAIR comparing the UrQMD hybrid model and the coarse-graining approach
Gabriele Inghirami🇩🇪 · Hendrik van Hees🇩🇪 · Stephan Endres🇩🇪 · Juan M. Torres-Rincon🇺🇸 · Marcus Bleicher🇩🇪
We present a study of the elliptic flow and $R_{AA}$ of D and anti-D mesons in Au+Au collisions at FAIR energies. We propagate the charm quarks and the D mesons following a previously applied Langevin dynamics. The evolution of the background medium is modeled in two different ways: (I) we use the UrQMD hydrodynamics + Boltzmann transport hybrid approach including a phase transition to QGP and (II) with the coarse-graining approach employing also an equation of state with QGP. The latter approach has previously been used to describe di-lepton data at various energies very successfully. This comparison allows us to explore the effects of partial thermalization and viscous effects on the charm propagation. We explore the centrality dependencies of the collisions, the variation of the decoupling temperature and various hadronization parameters. We find that the initial partonic phase is responsible for the creation of most of the D mesons elliptic flow and that the subsequent hadronic interactions seem to play only a minor role. This indicates that D mesons elliptic flow is a smoking gun for a partonic phase at FAIR energies. However, the results suggest that the magnitude and the details of the elliptic flow strongly depend on the dynamics of the medium and on the hadronization procedure, which is related to the medium properties as well. Therefore, even at FAIR energies the charm quark might constitute a very useful tool to probe the Quark-Gluon Plasma and investigate its physics.
↳ hep-phhep-exnucl-thEPJC(2019)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE

J/ψ→γη′π+π− and the structure observed around the pˉ​p threshold

Nucleon Mass Sum Rule Violation in QCD and Confinement

Partial-Wave Analysis of γp→K+Λ using a multichannel framework

Elliptic flow and RAA​ of D mesons at FAIR comparing the UrQMD hybrid model and the coarse-graining approach

Affiliations

$J / ψ \to γ η^{'} π^{+} π^{-}$ and the structure observed around the $p ˉ p$ threshold

Partial-Wave Analysis of $γ p \to K^{+} Λ$ using a multichannel framework

Elliptic flow and $R_{AA}$ of D mesons at FAIR comparing the UrQMD hybrid model and the coarse-graining approach