Nuclear Theory·nucl-th

Friday·October 11, 2019

9 papers—6 primary·3 cross-listed

07
Helicity-dependent generalization of the JIMWLK evolution
Florian Cougoulic🇺🇸 · Yuri V. Kovchegov🇺🇸
We generalize the JIMWLK evolution equation to include the small- $x$ evolution of helicity distributions. To derive helicity JIMWLK, we use the method devised by A.H. Mueller for the usual unpolarized JIMWLK, and apply it to the helicity evolution equations derived earlier. We obtain a functional evolution equation for the generalized JIMWLK weight functional. The functional now is a sum of a helicity-independent term and a helicity-dependent term. The kernel of the new evolution equation consists of the standard eikonal leading-order JIMWLK kernel plus new terms containing derivatives with respect to the sub-eikonal quark and gluon fields. The new kernel we derive can be used to generate the standard JIMWLK evolution and to construct small- $x$ evolution equations for flavor-singlet operators made of any number of light-cone Wilson lines along with one Wilson line containing sub-eikonal helicity-dependent local operator insertions (a "polarized Wilson line").
↳ hep-phnucl-thPRD(2019)·80 citations
08
New solutions of viscous relativistic hydrodynamics
Mate Csanad🇭🇺 · Marton I. Nagy🇭🇺 · Ze-Fang Jiang🇨🇳 · Tamas Csorgo🇭🇺
Relativistic hydrodynamics represents a powerful tool to investigate the time evolution of the strongly interacting quark gluon plasma created in ultrarelativistic heavy ion collisions. The equations are solved often numerically, and numerous analytic solutions also exist. However, the inclusion of viscous effects in exact, analytic solutions has received less attention. Here we utilize Hubble flow to investigate the role of bulk viscosity, and present different classes of exact, analytic solutions valid also in the presence of dissipative effects.
↳ hep-phnucl-thPhys.Part.Nucl.(2020)·1 citation
09
Diffractive photoproduction of $J / ψ$ and $Υ$ using holographic QCD: gravitational form factors and GPD of gluons in the proton
Kiminad A. Mamo🇺🇸 · Ismail Zahed🇺🇸
We present a holographic analysis of diffractive photoproducton of charmonium $J / ψ$ and upsilonium $Υ$ on a proton, considered as a bulk Dirac fermion, for all ranges of $s$ , i.e., from near threshold to very high energy. Using the bulk wave functions of the proton and vector mesons, within holographic QCD, and employing Witten diagrams in the bulk, we compute the diffractive photoproduction amplitude of $J / ψ$ and $Υ$ . The holographic amplitude shows elements of the strictures of vector meson dominance (VMD). It is dominated by the exchange of a massive graviton or $2^{++}$ glueball resonances near threshold, and its higher spin-j counterparts that reggeize at higher energies. Both the differential and total cross sections are controlled by the gravitational form factor $A (t)$ , and compare well to the recent results reported by the GlueX collaboration near threshold and the world data at large $s$ . The holographic gravitational form factors, including the D-term, which is due to the exchange of massive spin-0 glueballs, are in good agreement with lattice simulations. We use it to extract the holographic pressure and shear forces inside the proton. Finally, using a pertinent integral representation of the holographic gravitational form factor $A (t)$ near threshold, and its Pomeron counterpart way above threshold, we extract the generalized parton distribution (GPD) of gluons inside the proton at different resolutions.
↳ hep-phhep-thnucl-thPRD(2020)·139 citations

Affiliations

first authorsco-authorsvia INSPIRE

Helicity-dependent generalization of the JIMWLK evolution

New solutions of viscous relativistic hydrodynamics

Diffractive photoproduction of J/ψ and Υ using holographic QCD: gravitational form factors and GPD of gluons in the proton

Affiliations

Diffractive photoproduction of $J / ψ$ and $Υ$ using holographic QCD: gravitational form factors and GPD of gluons in the proton