Nuclear Theory·nucl-th

Tuesday·February 7, 2017

16 papers—9 primary·7 cross-listed

10
Angular Momentum Conservation Law in Light-Front Quantum Field Theory
Kelly Yu-Ju Chiu🇺🇸 · Stanley J. Brodsky🇺🇸
We prove the Lorentz invariance of the angular momentum conservation law and the helicity sum rule for relativistic composite systems in the light-front formulation. We explicitly show that $j^{3}$ , the $z$ -component of the angular momentum remains unchanged under Lorentz transformations generated by the light-front kinematical boost operators. The invariance of $j^{3}$ under Lorentz transformations is a feature unique to the front form. Applying the Lorentz invariance of the angular quantum number in the front form, we obtain a selection rule for the orbital angular momentum which can be used to eliminate certain interaction vertices in QED and QCD. We also generalize the selection rule to any renormalizable theory and show that there exists an upper bound on the change of orbital angular momentum in scattering processes at any fixed order in perturbation theory.
↳ hep-thnucl-thPRD(2017)·27 citations
11
Review of experimental and theoretical status of the proton radius puzzle
Richard J. Hill🇨🇦
The discrepancy between the measured Lamb shift in muonic hydrogen and expectations from electron-proton scattering and regular hydrogen spectroscopy has become known as the proton radius puzzle, whose most "mundane" resolution requires a $> 5 σ$ shift in the value of the fundamental Rydberg constant. I briefly review the status of spectroscopic and scattering measurements, recent theoretical developments, and implications for fundamental physics.
↳ hep-phnucl-thphysics.atom-phEPJ Web Conf.(2017)·43 citations
12
World-line construction of a covariant chiral kinetic theory
Niklas Mueller🇩🇪 · Raju Venugopalan🇺🇸
We discuss a novel world-line framework for computations of the Chiral Magnetic Effect (CME) in ultrarelativistic heavy-ion collisions. Starting from the fermion determinant in the QCD effective action, we show explicitly how its real part can be expressed as a supersymmetric world-line action of spinning, colored, Grassmanian particles in background fields. Restricting ourselves for simplicity to spinning particles, we demonstrate how their constrained Hamiltonian dynamics arises for both massless and massive particles. In a semi-classical limit, this gives rise to the covariant generalization of the Bargmann-Michel-Telegdi equation; the derivation of the corresponding Wong equations for colored particles is straightforward. In a previous letter we outlined how Berry's phase arises in a non-relativistic adiabatic limit for massive particles. We extend the discussion here to systems with a finite chemical potential. We discuss a path integral formulation of the relative phase in the fermion determinant that places it on the same footing as the real part. We construct the corresponding anomalous world-line axial vector current and show in detail how the chiral anomaly appears. Our work provides a systematic framework for a relativistic kinetic theory of chiral fermions in the fluctuating topological backgrounds that generate the CME in a deconfined quark-gluon plasma. We outline some further applications of this framework in many-body systems.
↳ hep-phhep-thnucl-thPRD(2017)·89 citations
13
Cooling of neutron stars with stiff stellar matter
H. Grigorian · D. N. Voskresensky · D. Blaschke
Recent evidence for high masses ( $\sim 2 M_{⊙}$ ) pulsars PSR J1614-2230 and PSR J0348-0432 requires neutron star matter to have a stiff equation of state (EoS). The thermal evolution of compact stars (CS) with stiff hadronic EoS necessitates the application of the "nuclear medium cooling" scenario with a selection of appropriate proton gap profiles together with in-medium effects (like pion softening) on cooling mechanisms in order to achieve a satisfactory explanation of all existing observational data for the temperature-age relation of CS. Here we focus on two examples from \cite{Grigorian:2016leu} for a stiff hadronic EoS without (DD2 EoS) and with (DD2vex) excluded volume correction.
↳ astro-ph.HEnucl-thActa Phys.Polon.Supp.(2017)·1 citation
14
Characterizing the mechanism(s) of heavy element synthesis
W. Loveland
A review of the current state of our understanding of complete fusion reaction mechanisms is presented, from the perspective of an experimentalist. For complete fusion reactions, the overall uncertainties in predicting heavy element synthesis cross sections are examined in terms of the uncertainties associated with the calculations of capture cross sections, fusion probabilities and survival probabilities.
↳ nucl-exnucl-thEPJA Web of Conferences 131, 04003 (2016)·0 citations
15
Concurrent application of ANC and THM to assess the $^{13} C (α, n)^{16} O$ absolute cross section at astrophysical energies and possible consequences for neutron production in low-mass AGB stars
Oscar Trippella · Marco La Cognata
The $^{13} C (α, n)^{16} O$ reaction is considered to be the main neutron source responsible for the production of heavy nuclides (from $Sr$ to $Bi$ ) through slow $n$ -capture nucleosynthesis ( $s$ -process) at low temperatures during the asymptotic giant branch (AGB) phase of low mass stars ( $≲ 3 - 4 M_{⊙}$ , or LMSs). In recent years, several direct and indirect measurements have been carried out to determine the cross section at the energies of astrophysical interest (around $190 \pm 40 keV$ ). However, they yield inconsistent results causing a highly uncertain reaction rate and affecting the neutron release in LMSs. In this work we have combined two indirect approaches, the asymptotic normalization coefficient (or ANC) and the Trojan Horse Method (THM), to unambiguously determine the absolute value of the $^{13} C (α, n)^{16} O$ astrophysical factor. Therefore, we have determined a very accurate reaction rate to be introduced into astrophysical models of $s$ -process nucleosynthesis in LMSs. Calculations using such recommended rate have shown limited variations in the production of those neutron-rich nuclei (with $86 \leq A \leq 209$ ) receiving contribution only by slow neutron captures.
↳ astro-ph.SRnucl-exnucl-thApJ(2017)·34 citations
16
Baryon interactions from lattice QCD with physical masses -- Overview and $S = 0, - 4$ sectors --
Takumi Doi🇯🇵 · Sinya Aoki🇯🇵 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Takumi Iritani🇯🇵 · Noriyoshi Ishii🇯🇵 · Takaya Miyamoto🇯🇵 · Keiko Murano🇯🇵 · Hidekatsu Nemura🇯🇵 · Kenji Sasaki🇯🇵
Nuclear forces and hyperon forces are studied by lattice QCD. Simulations are performed with (almost) physical quark masses, $m_{π} ≃ 146$ MeV and $m_{K} ≃ 525$ MeV, where $N_{f} = 2 + 1$ nonperturbatively $O (a)$ -improved Wilson quark action with stout smearing and Iwasaki gauge action are employed on the lattice of $(96 a)^{4} ≃ (8.1 \mbox f m)^{4}$ with $a^{- 1} ≃ 2.3$ GeV. In this report, we give the overview of the theoretical framework and present the numerical results for two-nucleon forces ( $S = 0$ ) and two- $Ξ$ forces ( $S = - 4$ ). Central forces are studied in $^{1} S_{0}$ channel, and central and tensor forces are obtained in $^{3} S_{1}$ - $^{3} D_{1}$ coupled channel analysis.
↳ hep-lathep-phnucl-thPoS(2017)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE

Angular Momentum Conservation Law in Light-Front Quantum Field Theory

Review of experimental and theoretical status of the proton radius puzzle

World-line construction of a covariant chiral kinetic theory

Cooling of neutron stars with stiff stellar matter

Characterizing the mechanism(s) of heavy element synthesis

Concurrent application of ANC and THM to assess the 13C(α,n)16O absolute cross section at astrophysical energies and possible consequences for neutron production in low-mass AGB stars

Baryon interactions from lattice QCD with physical masses -- Overview and S=0,−4 sectors --

Affiliations

Concurrent application of ANC and THM to assess the $^{13} C (α, n)^{16} O$ absolute cross section at astrophysical energies and possible consequences for neutron production in low-mass AGB stars

Baryon interactions from lattice QCD with physical masses -- Overview and $S = 0, - 4$ sectors --