Nuclear Theory·nucl-th

Friday·June 18, 2021

13 papers—6 primary·7 cross-listed

07
An effective field theory of the Delta-resonance
Juan Carlos Criado🇬🇧 · Abdelhak Djouadi🇪🇪 · Niko Koivunen🇪🇪 · Kristjan Müürsepp🇪🇪 · Martti Raidal🇪🇪 · Hardi Veermäe🇪🇪
We present an effective field theory of the $Δ$ -resonance as an interacting Weinberg's $(3/2, 0) \oplus (0, 3/2)$ field in the multi-spinor formalism. We derive its interactions with nucleons $N$ , pions $π$ and photons $γ$ , and compute the $Δ$ -resonance cross-sections in pion-nucleon scattering and pion photo-production. The theory contains only the physical spin-3/2 degrees of freedom. Thus, it is intrinsically consistent at the Hamiltonian level and, unlike the commonly used Rarita-Schwinger framework, does not require any additional ad hoc manipulation of couplings or propagators. The symmetries of hadronic physics select a unique operator for each coupling $N π Δ$ and $γ π Δ$ . The proposed framework can be extended to also describe other higher-spin hadronic resonances.
↳ hep-phnucl-th5 citations
08
Quantum Monte Carlo studies of a trimer scaling function with microscopic two- and three-body interactions
Lucas Madeira · Tobias Frederico · Stefano Gandolfi · Lauro Tomio · Marcelo T. Yamashita
We present an energy scaling function to predict, in a specific range, the energy of bosonic trimers with large scattering lengths and finite range interactions, which is validated by quantum Monte Carlo calculations using microscopic Hamiltonians with two- and three-body potentials. The proposed scaling function depends on the scattering length, effective range, and a reference energy, which we chose as the trimer energy at unitarity. We obtained the scaling function as a limit cycle from the solution of the renormalized zero-range model with effective range corrections. We proposed a simple parametrization of the energy scaling function. Besides the intrinsic interest in theoretical and experimental investigations, this scaling function allows one to probe Efimov physics with only the trimer ground states, which may open opportunities to identify Efimov trimers whenever access to excited states is limited.
↳ physics.atom-phcond-mat.quant-gasnucl-thPRA(2021)·4 citations
09
Diquark properties from full QCD lattice simulations
Anthony Francis🇨🇭 · Philippe de Forcrand🇨🇭 · Randy Lewis🇨🇦 · Kim Maltman🇨🇦
We study diquarks on the lattice in the background of a static quark, in a gauge-invariant formalism with quark masses down to almost physical $m_{π}$ . We determine mass differences between diquark channels as well as diquark-quark mass differences. The lightest and next-to-lightest diquarks have "good" scalar, $3 ˉ_{F}$ , $3 ˉ_{c}$ , $J^{P} = 0^{+}$ , and "bad" axial vector, $6_{F}$ , $3 ˉ_{c}$ , $J^{P} = 1^{+}$ , quantum numbers, and a bad-good mass difference for $u d$ flavors, $198 (4) MeV$ , in excellent agreement with phenomenological determinations. Quark-quark attraction is found only in the "good" diquark channel. We extract a corresponding diquark size of $\sim 0.6 fm$ and perform a first exploration of the "good" diquark shape, which is shown to be spherical. Our results provide quantitative support for modeling the low-lying baryon spectrum using good light diquark effective degrees of freedom.
↳ hep-lathep-phnucl-thJHEP(2022)·42 citations
10
Dispersion relation analysis of the radiative corrections to $g_{A}$ in the neutron $β$ -decay
Mikhail Gorchtein🇩🇪 · Chien-Yeah Seng🇩🇪
We present the first and complete dispersion relation analysis of the inner radiative corrections to the axial coupling constant $g_{A}$ in the neutron $β$ -decay. Using experimental inputs from the elastic form factors and the spin-dependent structure function $g_{1}$ , we determine the contribution from the $γ W$ -box diagram to a precision better than $1 0^{- 4}$ . Our calculation indicates that the inner radiative corrections to the Fermi and the Gamow-Teller matrix element in the neutron $β$ -decay are almost identical, i.e. the ratio $λ = g_{A} / g_{V}$ is almost unrenormalized. With this result, we predict the bare axial coupling constant to be { $g ˚_{A} = - 1.2754 (13)_{exp} (2)_{RC}$ } based on the PDG average $λ = - 1.2756 (13)$
↳ hep-phhep-latnucl-exnucl-thJHEP(2021)·45 citations
11
Search for the chiral magnetic effect via charge-dependent azimuthal correlations relative to spectator and participant planes in Au+Au collisions at $s_{N N}$ = 200 GeV
STAR Collaboration: M. S. Abdallah · J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson · A. Aparin and 377 other authors
The chiral magnetic effect (CME) refers to charge separation along a strong magnetic field due to imbalanced chirality of quarks in local parity and charge-parity violating domains in quantum chromodynamics. The experimental measurement of the charge separation is made difficult by the presence of a major background from elliptic azimuthal anisotropy. This background and the CME signal have different sensitivities to the spectator and participant planes, and could thus be determined by measurements with respect to these planes. We report such measurements in Au+Au collisions at a nucleon-nucleon center-of-mass energy of 200 GeV at the Relativistic Heavy-Ion Collider. It is found that the charge separation, with the flow background removed, is consistent with zero in peripheral (large impact parameter) collisions. Some indication of finite CME signals is seen in mid-central (intermediate impact parameter) collisions. Significant residual background effects may, however, still be present.
↳ nucl-exhep-exhep-phnucl-thPRL(2022)·61 citations
12
Inclusive Production of Heavy Quarkonia in pNRQCD
Nora Brambilla🇩🇪 · Hee Sok Chung🇩🇪 · Antonio Vairo🇩🇪
We develop a formalism for computing inclusive production cross sections of heavy quarkonia based on the nonrelativistic QCD and the potential nonrelativistic QCD effective field theories. Our formalism applies to strongly coupled quarkonia, which include excited charmonium and bottomonium states. Analogously to heavy quarkonium decay processes, we express nonrelativistic QCD long-distance matrix elements in terms of quarkonium wavefunctions at the origin and universal gluonic correlators. Our expressions for the long-distance matrix elements are valid up to corrections of order $1/ N_{c}^{2}$ . These expressions enhance the predictive power of the nonrelativistic effective field theory approach to inclusive production processes by reducing the number of nonperturbative unknowns, and make possible first-principle determinations of long-distance matrix elements once the gluonic correlators are known. Based on this formalism, we compute the production cross sections of $P$ -wave charmonia and bottomonia at the LHC, and find good agreement with measurements.
↳ hep-phhep-exhep-latnucl-thJHEP(2021)·34 citations
13
A Neutron Star is born
Débora Peres Menezes🇧🇷
A neutron star was first detected as a pulsar in 1967. It is one of the most mysterious compact objects in the universe, with a radius of the order of 10 km and masses that can reach two solar masses. In fact, neutron stars are star remnants, a kind of stellar zombies (they die, but do not disappear). In the last decades, astronomical observations yielded various contraints for the neutron star masses and finally, in 2017, a gravitational wave was detected (GW170817). Its source was identified as the merger of two neutron stars coming from NGC 4993, a galaxy 140 million light years away from us. The very same event was detected in $γ$ -ray, x-ray, UV, IR, radio frequency and even in the optical region of the electromagnetic spectrum, starting the new era of multi-messenger astronomy. To understand and describe neutron stars, an appropriate equation of state that satisfies bulk nuclear matter properties is necessary. GW170817 detection contributed with extra constraints to determine it. On the other hand, magnetars are the same sort of compact objects, but bearing much stronger magnetic fields that can reach up to 10 $^{15}$ G on the surface as compared with the usual 10 $^{12}$ G present in ordinary pulsars. While the description of ordinary pulsars is not completely established, describing magnetars poses extra challenges. In this paper, I give an overview on the history of neutron stars and on the development of nuclear models and show how the description of the tiny world of the nuclear physics can help the understanding of the cosmos, especially of the neutron stars.
↳ astro-ph.HEnucl-thUniverse(2021)·42 citations

Affiliations

first authorsco-authorsvia INSPIRE

An effective field theory of the Delta-resonance

Quantum Monte Carlo studies of a trimer scaling function with microscopic two- and three-body interactions

Diquark properties from full QCD lattice simulations

Dispersion relation analysis of the radiative corrections to gA​ in the neutron β-decay

Search for the chiral magnetic effect via charge-dependent azimuthal correlations relative to spectator and participant planes in Au+Au collisions at sNN​​ = 200 GeV

Inclusive Production of Heavy Quarkonia in pNRQCD

A Neutron Star is born

Affiliations

Dispersion relation analysis of the radiative corrections to $g_{A}$ in the neutron $β$ -decay

Search for the chiral magnetic effect via charge-dependent azimuthal correlations relative to spectator and participant planes in Au+Au collisions at $s_{N N}$ = 200 GeV