Nuclear Theory·nucl-th

Wednesday·November 11, 2015

8 papers—4 primary·4 cross-listed

05
(2+1)-flavor QCD Thermodynamics from the Gradient Flow
Etsuko Itou🇯🇵 · Hiroshi Suzuki🇯🇵 · Yusuke Taniguchi🇯🇵 · Takashi Umeda🇯🇵
Recently, we proposed a novel method to define and calculate the energy-momentum tensor (EMT) in lattice gauge theory on the basis of the Yang-Mills gradient flow [1]. In this proceedings, we summarize the basic idea and technical steps to obtain the bulk thermodynamic quantities in lattice gauge theory using this method for the quenched and $(2 + 1)$ -flavor QCD. The revised results of integration measure (trace anomaly) and entropy density of the quenched QCD with corrected coefficients are shown. Furthermore, we also show the flow time dependence of the parts of EMT including the dynamical fermions. This work is based on a joint-collaboration between FlowQCD and WHOT QCD.
↳ hep-lathep-phnucl-thPoS(2016)·9 citations
06
The effect of the chiral chemical potential on the chiral phase transition in the NJL model with different regularization schemes
Lang Yu🇨🇳 · Hao Liu🇨🇳 · Mei Huang🇨🇳
We study the chiral phase transition in the presence of the chiral chemical potential $μ_{5}$ using the two-flavor Nambu--Jona-Lasinio model. In particular, we analyze the reason why one can obtain two opposite behaviors of the chiral critical temperature as a function of $μ_{5}$ in the framework of different regularization schemes. We compare the modifications of the chiral condensate and the critical temperature due to $μ_{5}$ in different regularization schemes, analytically and numerically. Finally, we find that, for the conventional hard-cutoff regularization scheme, the increasing dependence of the critical temperature on the chiral chemical potential is an artifact, which is caused by the fact that it does not include complete contribution from the thermal fluctuations. When the thermal contribution is fully taken into account, the chiral critical temperature should decrease with $μ_{5}$ .
↳ hep-phhep-latnucl-thPRD(2016)·69 citations
07
Di-hadron fragmentation and mapping of the nucleon structure
Silvia Pisano🇮🇹 · Marco Radici🇮🇹
The fragmentation of a colored parton directly into a pair of colorless hadrons is a non-perturbative mechanism that offers important insights into the nucleon structure. Di-hadron fragmentation functions can be extracted from semi-inclusive electron-positron annihilation data. They also appear in observables describing the semi-inclusive production of two hadrons in deep-inelastic scattering of leptons off nucleons or in hadron-hadron collisions. When a target nucleon is transversely polarized, a specific chiral-odd di-hadron fragmentation function can be used as the analyzer of the net density of transversely polarized quarks in a transversely polarized nucleon, the so-called transversity distribution. The latter can be extracted through suitable single-spin asymmetries in the framework of collinear factorization, thus in a much simpler framework with respect to the traditional one in single-hadron fragmentation. At subleading twist, the same chiral-odd di-hadron fragmentation function provides the cleanest access to the poorly known twist-3 parton distribution $e (x)$ , which is intimately related to the mechanism of dynamical chiral symmetry breaking in QCD. When sensitive to details of transverse momentum dynamics of partons, the di-hadron fragmentation functions for a longitudinally polarized quark can be connected to the longitudinal jet handedness to explore possible effects due to $C P -$ violation of the QCD vacuum. In this review, we outline the formalism of di-hadron fragmentation functions, we discuss different observables where they appear and we present measurements and future worldwide plans.
↳ hep-phhep-exnucl-exnucl-thEPJA(2016)·21 citations
08
The pi0, eta, eta' -> gamma gamma*(Q^2) Decay Rates and Radii
A.M.Bernstein🇺🇸
The low $Q^{2}$ slopes of the the transition form factors provide a unique method to measure the sizes of the neutral pseudo-scalar mesons, since they do not have electromagnetic form factors. From the slope one obtains the "axial transition RMS radius" $R_{P S, A} = < r^{2} >$ for each PS meson. The present status of theory and experiment for these quantities are presented. A comparison of the $R_{P S, A}$ is presented along with the electromagnetic and scalar radii of the $π^{\pm}$ mesons and the proton. We observe the striking similarity of the values of axial transition radii of all of the pseudoscalar mesons to each other and to the charge radius of the $π^{\pm}$ . In the $Q^{2}$ = 0 limit the transition form factor is a measure of the pseudo-scalar meson radiative width (lifetime) and is a possible fourth (unexploited) method to perform such a measurement. The $π^{0} \to γ γ$ decay rate is a test of QCD at the confinement scale. There is a firm QCD prediction with a theoretical uncertainty of $≃$ 1 \% which calls for an experimental test at the same level of accuracy. There are three methods that have been utilized to perform this measurement and the present status of the experimental tests are outlined. The current accuracy is significantly less than the theoretical uncertainty. The efforts to improve this are briefly summarized.
↳ nucl-exhep-exhep-phnucl-thPoS(2016)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE

(2+1)-flavor QCD Thermodynamics from the Gradient Flow

The effect of the chiral chemical potential on the chiral phase transition in the NJL model with different regularization schemes

Di-hadron fragmentation and mapping of the nucleon structure

The pi0, eta, eta' -> gamma gamma*(Q^2) Decay Rates and Radii

Affiliations