Nuclear Theory·nucl-th

Thursday·November 23, 2017

7 papers—1 primary·6 cross-listed

02
Hadron tomography by generalized distribution amplitudes in pion-pair production process $γ^{*} γ \to π^{0} π^{0}$ and gravitational form factors for pion
S. Kumano🇯🇵 · Qin-Tao Song🇯🇵 · O. V. Teryaev🇯🇵
Hadron tomography can be investigated by three-dimensional structure functions such as generalized parton distributions (GPDs), transverse-momentum-dependent parton distributions, and generalized distribution amplitudes (GDAs). Here, we extract the GDAs, which are $s$ - $t$ crossed quantities of the GPDs, from cross-section measurements of hadron-pair production process $γ^{*} γ \to π^{0} π^{0}$ at KEKB. This work is the first attempt to obtain the GDAs from the actual experimental data. The GDAs are expressed by a number of parameters and they are determined from the data of $γ^{*} γ \to π^{0} π^{0}$ by including intermediate scalar- and tensor-meson contributions to the cross section. Our results indicate that the dependence of parton-momentum fraction $z$ in the GDAs is close to the asymptotic one. The timelike gravitational form factors $Θ_{1}$ and $Θ_{2}$ are obtained from our GDAs, and they are converted to the spacelike ones by the dispersion relation.From the spacelike $Θ_{1}$ and $Θ_{2}$ , gravitational densities of the pion are calculated. Then, we obtained the mass (energy) radius and the mechanical (pressure and shear force) radius from $Θ_{2}$ and $Θ_{1}$ , respectively. They are calculated as $⟨ r^{2} ⟩_{mass} = 0.32 \sim 0.39$ fm, whereas the mechanical radius is larger $⟨ r^{2} ⟩_{mech} = 0.82 \sim 0.88$ fm. This is the first report on the gravitational radius of a hadron from actual experimental measurements. It is interesting to find the possibility that the gravitational mass and mechanical radii could be different from the experimental charge radius $⟨ r^{2} ⟩_{charge} = 0.672 \pm 0.008$ fm for the charged pion.
↳ hep-phhep-exhep-latnucl-thPRD(2018)·174 citations
03
One-loop corrections to light cone wave functions: the dipole picture DIS cross section
H. Hänninen🇫🇮 · T. Lappi🇫🇮 · R. Paatelainen🇫🇮
We develop methods needed to perform loop calculations in light cone perturbation theory using a helicity basis, refining the method introduced in our earlier work. In particular this includes implementing a consistent way to contract the four-dimensional tensor structures from the helicity vectors with d-dimensional tensors arising from loop integrals, in a way that can be fully automatized. We demonstrate this explicitly by calculating the one-loop correction to the virtual photon to quark-antiquark dipole light cone wave function. This allows us to calculate the deep inelastic scattering cross section in the dipole formalism to next-to-leading order accuracy. Our results, obtained using the four dimensional helicity scheme, agree with the recent calculation by Beuf using conventional dimensional regularization, confirming the regularization scheme independence of this cross section.
↳ hep-phnucl-thAnnals Phys.(2018)·91 citations
04
Tetraquark mixing framework for isoscalar resonances in light mesons
Hungchong Kim🇰🇷 · K. S. Kim🇰🇷 · Myung-Ki Cheoun🇰🇷 · Makoto Oka🇯🇵
Recently, a tetraquark mixing framework has been proposed for light mesons and applied more or less successfully to the isovector resonances, $a_{0} (980), a_{0} (1450)$ , as well as to the isodoublet resonances, $K_{0}^{*} (800), K_{0}^{*} (1430)$ . In this work, we present a more extensive view on the mixing framework and extend this to the isoscalar resonances, $f_{0} (500)$ , $f_{0} (980)$ , $f_{0} (1370)$ , $f_{0} (1500)$ . Tetraquarks in this framework can have two spin configurations containing either spin-0 diquark or spin-1 diquark and each configuration forms a nonet in flavor space. The two spin configurations are found to mix strongly through the color-spin interactions. Their mixtures, which diagonalize the hyperfine masses, can generate the physical resonances constituting the two nonets, which, in fact, coincide roughly with the experimental observation. We identify that $f_{0} (500)$ , $f_{0} (980)$ are the isoscalar members in the light nonet, and $f_{0} (1370)$ , $f_{0} (1500)$ are the similar members in the heavy nonet. This means that the spin configuration mixing, as it relates the corresponding members in the two nonets, can generate $f_{0} (500), f_{0} (1370)$ among the members in light mass, and $f_{0} (980), f_{0} (1500)$ in heavy mass. The complication arises because the isoscalar members of each nonet are subject to an additional flavor mixing known as OZI rule so that $f_{0} (500), f_{0} (980)$ , and similarly $f_{0} (1370), f_{0} (1500)$ , are the mixture of two isoscalar members belonging to an octet and a singlet in SU $_{f}$ (3). The tetraquark mixing framework including the flavor mixing is tested for the isoscalar resonances in terms of the mass splitting and the fall-apart decay modes.
↳ hep-phhep-exnucl-thPRD(2018)·27 citations
05
Medium effects on the electrical conductivity of a hot pion gas
Snigdha Ghosh · Sukanya Mitra · Sourav Sarkar
The electromagnetic response of an interacting system of pions has been studied at finite temperature. The corresponding transport parameter i.e. electrical conductivity has been estimated by solving the relativistic transport equation in presence of a finite electric field employing the Chapman-Enskog technique where the collision term has been treated in the relaxation time approximation. The scattering amplitudes of charged pions modeled by $ρ$ and $σ$ meson exchange using an effective Lagrangian have been obtained at finite temperature by introducing self-energy corrections in the thermal propagators in the real time formalism. The temperature behavior of electrical conductivity for a hot pion gas shows significant quantitative enhancement due to the inclusion of medium effects in scattering.
↳ hep-phnucl-thNPA(2018)·16 citations
06
Pion Condensation by Rotation in a Magnetic field
Yizhuang Liu🇺🇸 · Ismail Zahed🇺🇸
We show that the combined effects of a rotation plus a magnetic field can cause charged pion condensation. We suggest that this phenomenon may yield to observable effects in current heavy ion collisions at collider energies, where large magnetism and rotations are expected in off-central collisions.
↳ hep-phhep-thnucl-exnucl-thPRL(2018)·81 citations
07
MagnetoHydrodynamics with chiral anomaly: phases of collective excitations and instabilities
Koichi Hattori🇨🇳 · Yuji Hirono🇺🇸 · Ho-Ung Yee🇺🇸 · Yi Yin🇺🇸
We study the relativistic hydrodynamics with chiral anomaly and dynamical electromagnetic fields, namely Chiral MagnetoHydroDynamics (CMHD). We formulate CMHD as a low-energy effective theory based on a generalized derivative expansion. We demonstrate that the modification of ordinary MagnetoHydroDynamics (MHD) due to chiral anomaly can be obtained from the second law of thermodynamics and is tied to chiral magnetic effect. We further study the real-time properties of chiral fluid by solving linearized CMHD equations. We discover a remarkable "transition" at an intermediate axial chemical potential $μ_{A}$ between a stable Chiral fluid at low $μ_{A}$ and an unstable Chiral fluid at large $μ_{A}$ . We summarize this transition in a "phase diagram" in terms of $μ_{A}$ and the angle of the wavevector relative to the magnetic field. In the unstable regime, there are four collective modes carrying both magnetic and fluid helicity, in contrary to MHD waves which are unpolarized. The half of the helical modes grow exponentially in time, indicating the instability, while the other half become dissipative.
↳ hep-thcond-mat.mes-hallhep-phnucl-thPRD(2019)·63 citations

Affiliations

first authorsco-authorsvia INSPIRE

Hadron tomography by generalized distribution amplitudes in pion-pair production process γ∗γ→π0π0 and gravitational form factors for pion

One-loop corrections to light cone wave functions: the dipole picture DIS cross section

Tetraquark mixing framework for isoscalar resonances in light mesons

Medium effects on the electrical conductivity of a hot pion gas

Pion Condensation by Rotation in a Magnetic field

MagnetoHydrodynamics with chiral anomaly: phases of collective excitations and instabilities

Affiliations

Hadron tomography by generalized distribution amplitudes in pion-pair production process $γ^{*} γ \to π^{0} π^{0}$ and gravitational form factors for pion