Nuclear Theory·nucl-th

Tuesday·February 1, 2022

21 papers—12 primary·9 cross-listed

13
Spin relaxation rate for heavy quarks in weakly coupled QCD plasma
Masaru Hongo🇺🇸 · Xu-Guang Huang🇨🇳 · Matthias Kaminski🇺🇸 · Mikhail Stephanov🇺🇸 · Ho-Ung Yee🇺🇸
We compute the relaxation rate of the spin density of heavy quarks in a perturbative QCD plasma to leading-log order in the coupling constant $g$ . The spin relaxation rate $Γ_{s}$ in spin hydrodynamics is shown to be $Γ_{s} \sim g^{4} lo g (1/ g) T (T / M)^{2}$ in the heavy-quark limit $T / M ≪ 1$ , which is smaller than the relaxation rate of other non-hydrodynamic modes by additional powers of $T / M$ . We demonstrate three different methods to evaluate the spin relaxation rate: 1) the Green-Kubo formula in the spin hydrodynamic regime, 2) the spin density correlation function in the strict hydrodynamic limit, and 3) quantum kinetic theory of the spin distribution function in momentum space. We highlight the interesting differences between these methods, while they are ultimately connected to each other by the underlying Ward-Takahashi identity for the non-conserved spin density.
↳ hep-thhep-phnucl-thJHEP(2022)·48 citations
14
Cooking pasta with Lie groups
S.L. Cacciatori🇮🇹 · F. Canfora🇨🇱 · M. Lagos🇨🇱 · F. Muscolino🇮🇹 · A. Vera🇨🇱
We extend the (gauged) Skyrme model to the case in which the global isospin group (which usually is taken to be $S U (N)$ ) is a generic compact connected Lie group $G$ . We analyze the corresponding field equations in (3+1) dimensions from a group theory point of view. Several solutions can be constructed analytically and are determined by the embeddings of three dimensional simple Lie groups into $G$ , in a generic irreducible representation. These solutions represent the so-called nuclear pasta state configurations of nuclear matter at low energy. We employ the Dynkin explicit classification of all three dimensional Lie subgroups of exceptional Lie group to classify all such solutions in the case $G$ is an exceptional simple Lie group, and give all ingredients to construct them explicitly. As an example, we construct the explicit solutions for $G = G_{2}$ . We then extend our ansatz to include the minimal coupling of the Skyrme field to a $U (1)$ gauge field. We extend the definition of the topological charge to this case and then concentrate our attention to the electromagnetic case. After imposing a "free force condition" on the gauge field, the complete set of coupled field equations corresponding to the gauged Skyrme model minimally coupled to an Abelian gauge field is reduced to just one linear ODE keeping alive the topological charge. We discuss the cases in which such ODE belongs to the (Whittaker-)Hill and Mathieu types.
↳ hep-thastro-ph.SRmath-phmath.MP+1NPB(2022)·20 citations
15
Backward timelike Compton scattering to decipher the photon content of the nucleon
Bernard Pire🇫🇷 · Kirill M. Semenov-Tian-Shansky🇷🇺 · Alisa A. Shaikhutdinova🇷🇺 · Lech Szymanowski🇵🇱
The exclusive photoproduction off nucleon of a large invariant mass lepton pair in the backward region specified by the small Mandelstam variable $- u$ is discussed in the framework of collinear QCD factorization. The amplitude is factorized in terms of photon-to-nucleon Transition Distribution Amplitudes (TDAs) which encode the photon content of the nucleon. Model estimates of these new non-perturbative objects are described and the corresponding cross sections calculated. The background due to the electromagnetic Bethe-Heitler process is shown to be negligible in the kinematical regime of interest.
↳ hep-phhep-exnucl-exnucl-thEPJC(2022)·11 citations
16
Strong CP problem, electric dipole moment, and fate of the axion
Gerrit Schierholz🇩🇪
Three hard problems! In this talk I investigate the long-distance properties of quantum chromodynamics in the presence of a topological theta term. This is done on the lattice, using the gradient flow to isolate the long-distance modes in the functional integral measure and tracing it over successive length scales. It turns out that the color fields produced by quarks and gluons are screened, and confinement is lost, for vacuum angles theta > 0, thus providing a natural solution of the strong CP problem. This solution is compatible with recent lattice calculations of the electric dipole moment of the neutron, while it excludes the axion extension of the Standard Model.
↳ hep-lathep-phhep-thnucl-thSciPost Phys.Proc.(2022)·2 citations
17
Signatures of the spin Hall effect in hot and dense QCD matter
Baochi Fu🇨🇳 · Longgang Pang🇨🇳 · Huichao Song🇨🇳 · Yi Yin🇨🇳
The spin Hall effect (SHE) is a generation of spin polarization for moving spin carriers in materials under an external electric field and has been observed in semiconductors, metals, and insulators at or below room temperature. Recent theoretical analyses show that spin Hall current can be induced by the baryon chemical potential gradient which plays the role of the analogous electric field and which becomes sizable in the fireballs created in heavy-ion collisions at beam energy of $O (10)$ ~GeV. In this letter, we study this important mechanism for spin polarization generation that has not been systematically explored before and predict the signature of the SHE in those collisions using a (3+1)~D viscous hydrodynamic model MUSIC with AMPT initial condition. We propose to use the second Fourier coefficients of the net spin polarization of Lambda hyperon as sensitive probes to search for the SHE. Those SHE observables show a qualitative difference in both the sign and beam energy dependence for the situations with and without the SHE. Future experimental observation of these distinct qualitative features would provide strong evidence for the existence of the SHE in the hot and dense QCD matter at trillions of degrees.
↳ hep-phnucl-thPRC(2026)·43 citations
18
An overview of recent STAR jet measurements
Nihar Ranjan Sahoo (for the STAR collaboration)🇨🇳
These proceedings discuss recent jet measurements by the STAR experiment at RHIC to study jet substructure in p+p and jet quenching in Au+Au collisions at $s_{NN}$ = 200 GeV. Furthermore, STAR's future plans for precision jet measurements with the upcoming data-taking periods in 2023-2025 are presented.
↳ nucl-exhep-exhep-phnucl-thIJMPE(2024)·0 citations
19
Coherent photoproduction of heavy quarkonia on nuclei
B.Z. Kopeliovich🇨🇱 · M. Krelina🇨🇿 · J. Nemchik🇨🇿 · I.K. Potashnikova🇨🇱
The differential cross section of coherent photo-production of heavy quarkonia on nuclear targets is calculated within the QCD color dipole formalism. The higher-twist nuclear shadowing corresponding to the $Q ˉ Q$ Fock component of the photon, is calculated including the correlation between dipole orientation $r$ and impact parameter of a collision $b$ , which is related to the transverse momentum transfer via Fourier transform. We also included the leading twist gluon shadowing corresponding to higher Fock components of the photon containing gluons, which have specifically short coherence time, especially for multi-gluon components, even at very high energies. The contribution of such fluctuating gluonic dipole is calculated employing the path-integral technique. Our results are in good agreement with recent ALICE data on charmonium production in ultra-peripheral nuclear collisions.
↳ hep-phnucl-thPRD(2022)·11 citations
20
Artificial atoms from cold bosons in one dimension
Fabian Brauneis🇩🇪 · Timothy G Backert🇩🇪 · Simeon I Mistakidis🇺🇸 · Mikhail Lemeshko🇦🇹 · Hans-Werner Hammer🇩🇪 · Artem G Volosniev🇦🇹
We investigate the ground-state properties of weakly repulsive one-dimensional bosons in the presence of an attractive zero-range impurity potential. First, we derive mean-field solutions to the problem on a finite ring for the two asymptotic cases: (i) all bosons are bound to the impurity and (ii) all bosons are in a scattering state. Moreover, we derive the critical line that separates these regimes in the parameter space. In the thermodynamic limit, this critical line determines the maximum number of bosons that can be bound by the impurity potential, forming an artificial atom. Second, we validate the mean-field results using the flow equation approach and the multi-layer multi-configuration time-dependent Hartree method for atomic mixtures. While beyond-mean-field effects destroy long-range order in the Bose gas, the critical boson number is unaffected. Our findings are important for understanding such artificial atoms in low-density Bose gases with static and mobile impurities.
↳ cond-mat.quant-gasnucl-thquant-phNew J.Phys.(2022)·10 citations
21
Evolutions in first-order viscous hydrodynamics
Hans Bantilan🇬🇧 · Yago Bea🇬🇧 · Pau Figueras🇬🇧
Motivated by the physics of the quark-gluon plasma created in heavy-ion collision experiments, we use holography to study the regime of applicability of various theories of relativistic viscous hydrodynamics. Using the microscopic description provided by holography of a system that relaxes to equilibrium, we obtain initial data with which we perform real-time evolutions in 2+1 dimensional conformal fluids using the first-order viscous relativistic hydrodynamics theory of Bemfica, Disconzi, Noronha and Kovtun (BDNK), BRSSS and ideal hydrodynamics. By initializing the hydrodynamics codes at different times, we can check the constitutive relations and assess the predictive power and accuracy of each of these theories.
↳ hep-thastro-ph.HEgr-qcnucl-th+1JHEP(2022)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE