Nuclear Theory·nucl-th

Friday·November 4, 2016

3 papers—2 primary·1 cross-listed

01
Rapidity correlations test stochastic hydrodynamics
Christopher Zin🇺🇸 · Sean Gavin🇺🇸 · George Moschelli🇺🇸
We show that measurements of the rapidity dependence of transverse momentum correlations can be used to determine the characteristic time $τ_{π}$ that dictates the rate of isotropization of the stress energy tensor, as well as the shear viscosity $ν = η / s T$ . We formulate methods for computing these correlations using second order dissipative hydrodynamics with noise. Current data are consistent with $τ_{π} / ν \sim 10$ but targeted measurements can improve this precision.
nucl-thJ.Phys.Conf.Ser.(2017)·0 citations
02
Improvements and Testing Practical Expressions for Photon Strength Functions of E1 Gamma-Transitions
Vladimir Plujko · Oleksandr Gorbachenko · Igor Kadenko · Kateryna Solodovnyk
Analytical expression for the E1 photon strength functions (PSF) is modified to account for the low-energy enhancement due to nuclear structure effects (presence of low-energy state (LES)). A closed-form expression of the E1 PSF function includes response of two nuclear states: LES and giant diplole resonance (GDR). Expression for the nuclear response function on electromagnetic field is based on a model of excitation of two coupled damped states. These approach is tested for different data sets for spherical nuclei. Impact on PSF shape of coupling between LES and GDR excitations is considered.
nucl-thEPJ Web Conf.(2017)·2 citations
03
Effects of $Z_{b}$ states and bottom meson loops on $Υ (4 S) \to Υ (1 S, 2 S) π^{+} π^{-}$ transitions
Yun-Hua Chen🇩🇪 · Martin Cleven🇪🇸 · Johanna T. Daub🇩🇪 · Feng-Kun Guo🇨🇳 · Christoph Hanhart🇩🇪 · Bastian Kubis🇩🇪 · Ulf-G. Meißner🇩🇪 · Bing-Song Zou🇨🇳
We study the dipion transitions $Υ (4 S) \to Υ (n S) π^{+} π^{-}$ $(n = 1, 2)$ . In particular, we consider the effects of the two intermediate bottomoniumlike exotic states $Z_{b} (10610)$ and $Z_{b} (10650)$ as well as bottom meson loops. The strong pion-pion final-state interactions, especially including channel coupling to $K K ˉ$ in the $S$ -wave, are taken into account model-independently by using dispersion theory. Based on a nonrelativistic effective field theory we find that the contribution from the bottom meson loops is comparable to those from the chiral contact terms and the $Z_{b}$ -exchange terms. For the $Υ (4 S) \to Υ (2 S) π^{+} π^{-}$ decay, the result shows that including the effects of the $Z_{b}$ -exchange and the bottom meson loops can naturally reproduce the two-hump behavior of the $π π$ mass spectra. Future angular distribution data are decisive for the identification of different production mechanisms. For the $Υ (4 S) \to Υ (1 S) π^{+} π^{-}$ decay, we show that there is a narrow dip around 1 GeV in the $π π$ invariant mass distribution, caused by the final-state interactions. The distribution is clearly different from that in similar transitions from lower $Υ$ states, and needs to be verified by future data with high statistics. Also we predict the decay width and the dikaon mass distribution of the $Υ (4 S) \to Υ (1 S) K^{+} K^{-}$ process.
↳ hep-phhep-exnucl-thPRD(2017)·55 citations

Affiliations

first authorsco-authorsvia INSPIRE

Rapidity correlations test stochastic hydrodynamics

Improvements and Testing Practical Expressions for Photon Strength Functions of E1 Gamma-Transitions

Effects of Zb​ states and bottom meson loops on Υ(4S)→Υ(1S,2S)π+π− transitions

Affiliations

Effects of $Z_{b}$ states and bottom meson loops on $Υ (4 S) \to Υ (1 S, 2 S) π^{+} π^{-}$ transitions