Nuclear Theory·nucl-th

Tuesday·January 10, 2017

14 papers—7 primary·7 cross-listed

08
The hidden-charm multiquark states
Hua-Xing Chen🇨🇳 · Wei Chen🇨🇦 · Jun He🇨🇳 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳
Since 2003 many charmonium-like states were observed experimentally. Especially those charged charmonium-like $Z_{c}$ states and bottomonium-like $Z_{b}$ states cannot be accommodated within the naive quark model, which are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. In 2015, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this talk, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. We list the puzzles and theoretical challenges of these models when confronted with the experimental data. We also discuss possible future measurements which may distinguish the theoretical schemes on the underlying structures of the hidden-charm multiquark states.
↳ hep-phhep-exhep-latnucl-thPoS(2017)·1 citation
09
Proton rms-radii from low-q power expansions?
Ingo Sick🇨🇭 · Dirk Trautmann🇨🇭
Several recent publications claim that the proton charge {\em rms}-radius resulting from the analysis of electron scattering data restricted to {\em low} momentum transfer agrees with the radius determined from muonic hydrogen, in contrast to the radius resulting from analyses of the full (e,e) data set which is $0.04 f m$ larger. Here we show why these publications erroneously arrive at the low radii.
↳ nucl-exnucl-thPRC(2017)·26 citations
10
$ϕϕ$ and $J / ψ ϕ$ mass spectra in decay $B_{s}^{0} \to J / ψ ϕϕ$
A.A. Kozhevnikov🇷🇺
The mass spectra of the $ϕϕ$ and $J / ψ ϕ$ states in the decay $B_{s}^{0} \to J / ψ ϕϕ$ recently observed by LHCb are calculated in the model which takes into account the $J^{P} = 0^{+}, 0^{-}, 2^{+}$ intermediate resonances $R_{1}$ , $R_{2}$ in the $ϕϕ$ channel and the $J^{P} = 1^{+}$ ones, $X_{1}$ , $X_{2}$ , in the $J / ψ ϕ$ channel. When obtaining the expressions for the effective amplitudes and mass spectra, the approximate threshold kinematics of the decay is used essentially. The $R_{1} - R_{2}$ and $X_{1} - X_{2}$ mixings arising due to the common decay modes $ϕϕ$ and $J / ψ ϕ$ , respectively, are also taken into account. The obtained expressions for the mass spectra are applied for extracting the information about masses and coupling constants of the resonances in the $ϕϕ$ and $J / ψ ϕ$ final states.
↳ hep-phhep-exnucl-thPRD(2017)·2 citations
11
Spin-dependent sum rules connecting real and virtual Compton scattering verified
Vadim Lensky🇩🇪 · Vladimir Pascalutsa🇩🇪 · Marc Vanderhaeghen🇩🇪 · Chung Wen Kao🇹🇼
We present a detailed derivation of the two sum rules relating the spin polarizabilities measured in real, virtual, and doubly-virtual Compton scattering. For example, the polarizability $δ_{L T}$ , accessed in inclusive electron scattering, is related to the spin polarizability $γ_{E 1 E 1}$ and the slope of generalized polarizabilities $P^{(M 1, M 1) 1} - P^{(L 1, L 1) 1}$ , measured in, respectively, the real and the virtual Compton scattering. We verify these sum rules in different variants of chiral perturbation theory, discuss their empirical verification for the proton, and prospect their use in studies of the nucleon spin structure.
↳ hep-phnucl-exnucl-thPRD(2017)·14 citations
12
Search for the QCD Critical Point with Fluctuations of Conserved Quantities in Relativistic Heavy-Ion Collisions at RHIC : An Overview
Xiaofeng Luo🇨🇳 · Nu Xu🇨🇳
Fluctuations of conserved quantities, such as baryon, electric charge and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD critical point. In this paper, we review the experimental measurements of the cumulants (up to fourth order) of event-by-event net-proton (proxy for net-baryon), net-charge and net-kaon (proxy for net-strangeness) multiplicity distributions in Au+Au collisions at $s_{N N} = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, 200$ GeV from the first phase of beam energy scan program at the Relativistic Heavy-Ion Collider (RHIC). We also summarize the data analysis methods of suppressing the volume fluctuations, auto-correlations and the unified description of efficiency correction and error estimation. Based on theoretical and model calculations, we will discuss the characteristic signatures of critical point as well as backgrounds for the fluctuation observables in heavy-ion collisions. The physics implications and the future second phase of the beam energy scan (2019-2020) at RHIC will be also discussed.
↳ nucl-exhep-exhep-phnucl-thNucl.Sci.Tech.(2017)·550 citations
13
Strong isospin breaking at production of light scalars
N.N. Achasov🇷🇺 · G.N. Shestakov🇷🇺
It is discussed breaking the isotopic symmetry as the tool of studying the mechanism production and nature of light scalar mesons.
↳ hep-phhep-exnucl-thNucl.Part.Phys.Proc.(2017)·9 citations
14
Temperature dependence of shear viscosity of $S U (3)$ --gluodynamics within lattice simulation
Nikita Astrakhantsev🇷🇺 · Viktor Braguta🇷🇺 · Andrey Kotov🇷🇺
In this paper we study the shear viscosity temperature dependence of $S U (3)$ --gluodynamics within lattice simulation. To do so, we measure the correlation functions of energy-momentum tensor in the range of temperatures $T / T_{c} \in [0.9, 1.5]$ . To extract the values of shear viscosity we used two approaches. The first one is to fit the lattice data with some physically motivated ansatz for the spectral function with unknown parameters and then determine shear viscosity. The second approach is to apply the Backus-Gilbert method which allows to extract shear viscosity from the lattice data nonparametrically. The results obtained within both approaches agree with each other. Our results allow us to conclude that within the temperature range $T / T_{c} \in [0.9, 1.5]$ SU(3)--gluodynamics reveals the properties of a strongly interacting system, which cannot be described perturbatively, and has the ratio $η / s$ close to the value $1 / 4 π$ in $N = 4$ Supersymmetric Yang-Mills theory.
↳ hep-lathep-phhep-thnucl-thJHEP(2017)·108 citations

Affiliations

first authorsco-authorsvia INSPIRE

The hidden-charm multiquark states

Proton rms-radii from low-q power expansions?

ϕϕ and J/ψϕ mass spectra in decay Bs0​→J/ψϕϕ

Spin-dependent sum rules connecting real and virtual Compton scattering verified

Search for the QCD Critical Point with Fluctuations of Conserved Quantities in Relativistic Heavy-Ion Collisions at RHIC : An Overview

Strong isospin breaking at production of light scalars

Temperature dependence of shear viscosity of SU(3)--gluodynamics within lattice simulation

Affiliations

$ϕϕ$ and $J / ψ ϕ$ mass spectra in decay $B_{s}^{0} \to J / ψ ϕϕ$

Temperature dependence of shear viscosity of $S U (3)$ --gluodynamics within lattice simulation