Nuclear Theory·nucl-th

Wednesday·July 15, 2020

17 papers—9 primary·8 cross-listed

10
Valence parton distribution of pion from lattice QCD: Approaching continuum
Xiang Gao🇺🇸 · Luchang Jin🇺🇸 · Christos Kallidonis🇺🇸 · Nikhil Karthik🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Charles Shugert🇺🇸 · Sergey Syritsyn🇺🇸 · Yong Zhao🇺🇸
We present a high-statistics lattice QCD determination of the valence parton distribution function (PDF) of the pion, with a mass of 300 MeV, using two very fine lattice spacings of $a = 0.06$ fm and 0.04 fm. We reconstruct the $x$ -dependent PDF, as well as infer the first few even moments of the PDF using leading-twist 1-loop perturbative matching framework. Our analyses use both RI-MOM and ratio-based schemes to renormalize the equal-time bi-local quark-bilinear matrix elements of pions boosted up to 2.4 GeV momenta. We use various model-independent and model-dependent analyses to infer the large- $x$ behavior of the valence PDF. We also present technical studies on lattice spacing and higher-twist corrections present in the boosted pion matrix elements.
↳ hep-lathep-exhep-phnucl-ex+1PRD(2020)·124 citations
11
Why is LaMET an effective field theory for partonic structure?
Xiangdong Ji🇺🇸
Partons are effective degrees of freedom describing the structure of hadrons involved in high-energy collisions. Familiar theories of partons are QCD light-front quantization and soft-collinear effective theory, both of which are intrinsically Minkowskian and appear unsuitable for classical Monte Carlo simulations. A ``new'' form of the parton theory has been formulated in term of the old-fashioned, Feynman's infinite momentum frame, in which the parton degrees of freedom are filtered through infinite-momentum external states. The partonic structure of hadrons is then related to the matrix elements of static (equal-time) correlators in the state $∣ P^{z} = \infty ⟩$ . This representation lays the foundation of large-momentum effective theory (LaMET) which approximates parton physics through a systematic $M / P^{z}$ expansion of the lattice QCD matrix elements at a finite but large momentum $P^{z}$ , and removes the residual logarithmic- $P^{z}$ dependence by the standard effective-field-theory matching and running.
↳ hep-phhep-lathep-thnucl-thAAPPS Bull.(2020)·23 citations
12
Hyperfine structure of $^{173} Yb^{+}$ : toward resolving the $^{173} Yb$ nuclear octupole moment puzzle
Di Xiao · Jiguang Li · Wesley C. Campbell · Thomas Dellaert · Patrick McMillin · Anthony Ransford · Conrad Roman · Andrei Derevianko
Hyperfine structure (HFS) of atomic energy levels arises due to interactions of atomic electrons with a hierarchy of nuclear multipole moments, including magnetic dipole, electric quadrupole and higher rank moments. Recently, a determination of the magnetic octupole moment of the $^{173} Yb$ nucleus was reported from HFS measurements in neutral $^{173} Yb$ [PRA 87, 012512 (2013)], and is four orders of magnitude larger than the nuclear theory prediction. Considering this substantial discrepancy between the spectroscopically extracted value and nuclear theory, here we propose to use an alternative system to resolve this tension, a singly charged ion of the same $^{173} Yb$ isotope. Utilizing the substantial suite of tools developed around $Yb^{+}$ for quantum information applications, we propose to extract nuclear octupole and hexadecapole moments from measuring hyperfine splittings in the extremely long lived first excited state ( $4 f^{13} (^{2} F^{o}) 6 s^{2}$ , $J = 7/2$ ) of $^{173} Yb^{+}$ . We present results of atomic structure calculations in support of the proposed measurements.
↳ physics.atom-phnucl-thPRA(2020)·10 citations
13
Hydrodynamization in systems with detailed transverse profiles
Aleksi Kurkela🇨🇭 · Seyed Farid Taghavi🇩🇪 · Urs Achim Wiedemann🇨🇭 · Bin Wu🇨🇭
The observation of fluid-like behavior in nucleus-nucleus, proton-nucleus and high-multiplicity proton-proton collisions motivates systematic studies of how different measurements approach their fluid-dynamic limit. We have developed numerical methods to solve the ultra-relativistic Boltzmann equation for systems of arbitrary size and transverse geometry. Here, we apply these techniques for the first time to the study of azimuthal flow coefficients $v_{n}$ including non-linear mode-mode coupling and to an initial condition with realistic event-by-event fluctuations. We show how both linear and non-linear response coefficients extracted from $v_{n}$ develop as a function of opacity from free streaming to perfect fluidity. We note in particular that away from the fluid-dynamic limit, the signal strength of linear and non-linear response coefficients does not reduce uniformly, but that their hierarchy and relative size shows characteristic differences.
↳ hep-phnucl-thPLB(2020)·40 citations
14
Shear viscosity of classical Yang-Mills field
Hidefumi Matsuda🇯🇵 · Teiji Kunihiro🇯🇵 · Berndt Müller🇺🇸 · Akira Ohnishi🇯🇵 · Toru T. Takahashi🇯🇵
We investigate the shear viscosity $η$ of the classical Yang-Mills (CYM) field on a lattice by using the Green-Kubo formula, where the shear viscosity is calculated from the time-correlation function of the energy-momentum tensor in equilibrium. Dependence of the shear viscosity $η (g, T)$ on the coupling $g$ and temperature $T$ is represented by a scaling function $f_{η} (g^{2} T)$ as $η (g, T) = T f_{η} (g^{2} T)$ due to the scaling-invariant property of the CYM. The explicit functional form of $f_{η} (g^{2} T)$ is successfully determined from the calculated shear viscosity: It turns out that $η (g, T)$ of the CYM field is proportional to $1/ g^{1.10 - 1.88}$ at weak coupling, which is a weaker dependence on $g$ than that in the leading-order perturbation theory but consistent with that of the "anomalous viscosity" $η \propto 1/ g^{1.5}$ under the strong disordered field. The obtained shear viscosity is also found to be roughly consistent with that estimated through the analysis of the anisotropy of the pressure of the CYM dynamics in the expanding geometry with recourse to a hydrodynamic equation.
↳ hep-phhep-latnucl-thPRD(2020)·5 citations
15
James Chadwick: ahead of his time
Gerhard Ecker
James Chadwick is known for his discovery of the neutron. Many of his earlier findings and ideas in the context of weak and strong nuclear forces are much less known. This biographical sketch attempts to highlight the achievements of a scientist who paved the way for contemporary subatomic physics.
↳ physics.hist-phhep-exhep-phnucl-ex+10 citations
16
Multi-particle quantum-statistical correlation functions in a Hubble-expanding hadron gas
Mate Csanad🇭🇺 · Antal Jakovac🇭🇺 · Sandor Lokos🇭🇺 · Ayon Mukherjee🇭🇺 · Srikanta Kumar Tripathy🇭🇺
Quantum-statistical correlation measurements in high-energy physics represent an important tool to obtain information about the space-time structure of the particle-emitting source. There are several final state effects which may modify the measured femtoscopic correlation functions. One of these may be the interaction of the investigated particles with the expanding hadron gas, consisting of the other final state particles. This may cause the trajectories - and hence the phases - of the quantum-correlated pairs to be modified compared to free streaming. The resulting effect and could be interpreted as an Aharonov-Bohm-like phenomenon, in the sense that the possible paths of a quantum-correlated pair represent a closed loop, with an internally present field caused by the hadron gas. In this paper, the possible role of the effect in heavy-ion experiments is presented with analytical calculations and a simple numerical model. The modification of the strength of multi-particle Bose-Einstein correlation functions is investigated, and the is found that in case of sufficiently large source density, this effect may play a non-negligible role.
↳ hep-phnucl-thGribov-90 Memorial Volume, pp. 261-273 (2…·4 citations
17
Dark Nucleosynthesis: Cross-sections and Astrophysical Signals
Rakhi Mahbubani🇬🇧 · Michele Redi🇮🇹 · Andrea Tesi🇮🇹
We investigate dark matter bound-state formation and its implication for indirect-detection experiments. We focus on the case where dark matter is a baryon of a strongly-coupled dark sector and provide generic formulae for the formation of shallow nuclear bound states on emission of photons, and W and Z gauge bosons. These processes can occur via electric and magnetic transitions, and give rise to indirect signals that are testable in monochromatic and diffuse photon measurements by Fermi and HESS. We also study the validity of factorizing the bound-state formation cross section into a short-distance nuclear part multiplied by Sommerfeld-enhancement factors. We find that the short-distance nuclear potential often violates factorization, modifying in particular the location of the peaks associated with zero-energy bound states. Finally we revisit bound-state formation of a (weakly-coupled) Minimal DM quintuplet including isospin-breaking effects, and find it gives rise to indirect-detection signals that are compatible with current bounds.
↳ hep-phastro-ph.COnucl-thJCAP(2021)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE