Nuclear Theory·nucl-th

Thursday·June 11, 2020

15 papers—5 primary·10 cross-listed

06
[Submitted on 8 Jun 2020] (cross-list from hep-ph)
The anomalous magnetic moment of the muon in the Standard Model
T. Aoyama🇯🇵 · N. Asmussen🇬🇧 · M. Benayoun🇫🇷 · J. Bijnens🇸🇪 · T. Blum🇺🇸 · M. Bruno🇨🇭 · I. Caprini🇷🇴 · C. M. Carloni Calame🇮🇹 · M. Cè🇨🇭 · G. Colangelo🇨🇭 · F. Curciarello🇮🇹 · H. Czyż and 120 other authors
We review the present status of the Standard Model calculation of the anomalous magnetic moment of the muon. This is performed in a perturbative expansion in the fine-structure constant $α$ and is broken down into pure QED, electroweak, and hadronic contributions. The pure QED contribution is by far the largest and has been evaluated up to and including $O (α^{5})$ with negligible numerical uncertainty. The electroweak contribution is suppressed by $(m_{μ} / M_{W})^{2}$ and only shows up at the level of the seventh significant digit. It has been evaluated up to two loops and is known to better than one percent. Hadronic contributions are the most difficult to calculate and are responsible for almost all of the theoretical uncertainty. The leading hadronic contribution appears at $O (α^{2})$ and is due to hadronic vacuum polarization, whereas at $O (α^{3})$ the hadronic light-by-light scattering contribution appears. Given the low characteristic scale of this observable, these contributions have to be calculated with nonperturbative methods, in particular, dispersion relations and the lattice approach to QCD. The largest part of this review is dedicated to a detailed account of recent efforts to improve the calculation of these two contributions with either a data-driven, dispersive approach, or a first-principle, lattice-QCD approach. The final result reads $a_{μ}^{SM} = 116591810 (43) \times 1 0^{- 11}$ and is smaller than the Brookhaven measurement by 3.7 $σ$ . The experimental uncertainty will soon be reduced by up to a factor four by the new experiment currently running at Fermilab, and also by the future J-PARC experiment. This and the prospects to further reduce the theoretical uncertainty in the near future-which are also discussed here-make this quantity one of the most promising places to look for evidence of new physics.
Comments:
196 pages, 103 figures, version published in Phys. Rept., bib files for the citation references are available from: https://muon-gm2-theory.illinois.edu
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2006.04822 [pdf]
Phys.Rept.(2020)·1876 citations
07
[Submitted on 8 Jun 2020] (cross-list from astro-ph.SR)
129I and 247Cm in Meteorites Constrain the Last Astrophysical Source of Solar r-process Elements
Benoit Côté · Marius Eichler · Andrés Yagüe · Nicole Vassh · Matthew R. Mumpower · Blanka Világos · Benjámin Soós · Almudena Arcones · Trevor M. Sprouse · Rebecca Surman · Marco Pignatari · Maria K. Pető and 3 other authors
The composition of the early Solar System can be inferred from meteorites. Many elements heavier than iron were formed by the rapid neutron-capture process (r process), but the astrophysical sources where this occurred remain poorly understood. We demonstrate that the near-identical half-lives ( $≃$ 15.6 Myr) of the radioactive r-process nuclei 129I and 247Cm preserve their ratio, irrespective of the time between production and incorporation into the Solar System. We constrain the last r-process source by comparing the measured meteoritic 129I / 247Cm = 438 $\pm$ 184 to nucleosynthesis calculations based on neutron star merger and magneto-rotational supernova simulations. Moderately neutron-rich conditions, often found in merger disk ejecta simulations, are most consistent with the meteoritic value. Uncertain nuclear physics data limit our confidence in this conclusion.
Comments:
36 pages, 7 figures, 7 tables
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2006.04833 [pdf]
Science 26 Feb 2021: Vol. 371, Issue 6532…·2 citations
08
[Submitted on 9 Jun 2020] (cross-list from nucl-ex)
Pair invariant mass to isolate background in the search for the chiral magnetic effect in Au+Au collisions at $s_{_{NN}}$ = 200 GeV
STAR Collaboration: J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson · A. Aparin · E. C. Aschenauer · M. U. Ashraf and 352 other authors
Quark interactions with topological gluon configurations can induce local chirality imbalance and parity violation in quantum chromodynamics, which can lead to the chiral magnetic effect (CME) -- an electric charge separation along the strong magnetic field in relativistic heavy-ion collisions. The CME-sensitive azimuthal correlator observable ( $Δ γ$ ) is contaminated by background arising, in part, from resonance decays coupled with elliptic anisotropy ( $v_{2}$ ). We report here differential measurements of the correlator as a function of the pair invariant mass ( $m_{inv}$ ) in 20-50\% centrality Au+Au collisions at $s_{_{NN}}$ = 200 GeV by the STAR experiment at RHIC. Strong resonance background contributions to $Δ γ$ are observed. At large $m_{inv}$ where this background is significantly reduced, the $Δ γ$ value is found to be significantly smaller. An event-shape-engineering technique is deployed to determine the $v_{2}$ background shape as a function of $m_{inv}$ . We extract a $v_{2}$ -independent and $m_{inv}$ -averaged signal $Δ γ_{sig}$ = (0.03 $\pm$ 0.06 $\pm$ 0.08) $\times 1 0^{- 4}$ , or $(2 \pm 4 \pm 5) %$ of the inclusive $Δ γ (m_{inv} > 0.4$ GeV/ $c^{2}$ ) $= (1.58 \pm 0.02 \pm 0.02) \times 1 0^{- 4}$ , within pion $p_{T}$ = 0.2 - 0.8~\gevc and averaged over pseudorapidity ranges of $- 1 < η < - 0.05$ and $0.05 < η < 1$ . This represents an upper limit of $0.23 \times 1 0^{- 4}$ , or $15%$ of the inclusive result, at $95%$ confidence level for the $m_{inv}$ -integrated CME contribution.
Comments:
PRC published version
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2006.05035 [pdf]
PRC(2022)·36 citations
09
[Submitted on 7 Jun 2020] (cross-list from hep-ph)
Two-current correlations in the pion in the Nambu and Jona-Lasinio model
A.~Courtoy🇲🇽 · Santiago Noguera🇪🇸 · Sergio Scopetta🇮🇹
We present an analysis of two-current correlations for the pion in the Nambu--Jona-Lasinio model, with Pauli--Villars regularization. We provide explicit expressions in momentum space for two-current correlations corresponding to the zeroth component of the vector Dirac bilinear in the quark vertices, which has been evaluated on the lattice. The numerical results show a remarkable qualitative agreement with recent lattice data. The factorization approximation into one-body currents is discussed.
Comments:
19 pages, 9 figures. arXiv admin note: text overlap with arXiv:1909.09530
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2006.05300 [pdf]
EPJC(2020)·6 citations
10
[Submitted on 4 Jun 2020] (cross-list from hep-ph)
Transverse momentum dependent PDFs at N $^{3}$ LO
Markus A. Ebert🇺🇸 · Bernhard Mistlberger🇺🇸 · Gherardo Vita🇺🇸
We compute the quark and gluon transverse momentum dependent parton distribution functions at next-to-next-to-next-to-leading order (N $^{3}$ LO) in perturbative QCD. Our calculation is based on an expansion of the differential Higgs boson and Drell-Yan production cross sections about their collinear limit. This method allows us to employ cutting edge techniques for the computation of cross sections to extract the universal building blocks in question. The corresponding perturbative matching kernels for all channels are expressed in terms of simple harmonic polylogarithms up to weight five. As a byproduct, we confirm a previous computation of the soft function for transverse momentum factorization at N $^{3}$ LO. Our results are the last missing ingredient to extend the $q_{T}$ subtraction methods to N $^{3}$ LO and to obtain resummed $q_{T}$ spectra at N $^{3}$ LL $^{'}$ accuracy both for gluon as well as for quark initiated processes.
Comments:
12 pages + appendices, 4 awesome figures, important ancillary files. v2: journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2006.05329 [pdf]
JHEP(2020)·148 citations
11
[Submitted on 9 Jun 2020] (cross-list from physics.comp-ph)
Report from the A.I. For Nuclear Physics Workshop
Paulo Bedaque🇺🇸 · Amber Boehnlein🇺🇸 · Mario Cromaz🇺🇸 · Markus Diefenthaler🇺🇸 · Latifa Elouadrhiri🇺🇸 · Tanja Horn🇺🇸 · Michelle Kuchera🇺🇸 · David Lawrence🇺🇸 · Dean Lee🇺🇸 · Steven Lidia🇺🇸 · Robert McKeown🇺🇸 · Wally Melnitchouk🇺🇸 and 6 other authors
This report is an outcome of the workshop "AI for Nuclear Physics" held at Thomas Jefferson National Accelerator Facility on March 4-6, 2020. The workshop brought together 184 scientists to explore opportunities for Nuclear Physics in the area of Artificial Intelligence. The workshop consisted of plenary talks, as well as six working groups. The report includes the workshop deliberations and additional contributions to describe prospects for using AI across Nuclear Physics research.
Comments:
This version includes reference updates, improved figures and minor clarifications in the text
Subjects:
Computational Physics (physics.comp-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2006.05422 [pdf]
6 citations
12
[Submitted on 10 Jun 2020] (cross-list from nucl-ex)
Systematic reduction of the proton-removal cross section in neutron-rich medium-mass nuclei
J. Díaz-Cortés🇪🇸 · J. Benlliure🇪🇸 · J.L. Rodríguez-Sánchez🇪🇸 · H. Álvarez-Pol🇪🇸 · T. Aumann🇩🇪 · C.A. Bertulani🇺🇸 · B. Blank🇫🇷 · E. Casarejos🇪🇸 · D. Cortina-Gil🇪🇸 · D. Dragosavac🇪🇸 · V. Föhr🇩🇪 · A. Gargano🇮🇹 and 15 other authors
Single neutron- and proton-removal cross sections have been systematically measured for 72 medium-mass neutron-rich nuclei around Z=50 and energies around 900A MeV using the FRagment Separator (FRS) at GSI. Neutron-removal cross sections are described by considering the knock-out process together with initial- and final-state interactions. Proton-removal cross sections are, however, significantly smaller than predicted by the same calculations. The observed difference can be explained as due to the knockout of short-correlated protons in neutron-proton dominating pairs.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2006.05774 [pdf]
PLB(2020)·14 citations
13
[Submitted on 10 Jun 2020] (cross-list from hep-ph)
Chiral theory of nucleons and pions in the presence of an external gravitational field
H. Alharazin🇩🇪 · D. Djukanovic🇩🇪 · J. Gegelia🇩🇪 · M. V. Polyakov🇩🇪
We extend the standard second order effective chiral Lagrangian of pions and nucleons by considering the coupling to an external gravitational field. As an application we calculate one-loop corrections to the one-nucleon matrix element of the energy-momentum tensor to fourth order in chiral counting, and next-to-leading order tree-level amplitude of the pion-production in an external gravitational field. We discuss the relation of the obtained results to experimentally measurable observables. Our expressions for the chiral corrections to the nucleon gravitational form factors differ from those in the literature. That might require to revisit the chiral extrapolation of the lattice data on the nucleon gravitational form factors obtained in the past.
Comments:
11 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2006.05890 [pdf]
PRD(2020)·46 citations
14
[Submitted on 8 Jun 2020] (cross-list from cond-mat.other)
Two-channel approach to the average retarding force of metals for slow singly ionized projectiles
I. Nagy · I. Aldazabal
Based on the fundamental momentum-transfer theorem [Phys. Rev. Lett. 15, 11 (1965)] a novel contribution to the retarding force of metallic systems for slow intruders is derived. This contribution is associated with sudden charge-changing cycles during the path of projectiles. The sum of the novel and the well-known conventional contributions, both expressed in terms of scattering phase shifts, are used to discuss experimental data obtained for different targets. It is found that our two-channel modeling, with two nonlinear channels, improves the agreement between several data and theory and thus, as predictive modeling, can contribute to the desired convergence between experimental and theoretical attempts on the retarding force.
Subjects:
cond-mat.other (cond-mat.other); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2006.05903 [pdf]
PRA(2020)·0 citations
15
[Submitted on 10 Jun 2020] (cross-list from hep-ph)
Thermal properties of $π$ and $ρ$ meson
Fei Gao🇩🇪 · Minghui Ding🇮🇹
We computed the pole masses and decay constants of $π$ and $ρ$ meson at finite temperature in the framework of Dyson-Schwinger equations and Bethe-Salpeter equations approach. Below transition temperature, pion pole mass increases monotonously, while $ρ$ meson seems to be temperature independent. Above transition temperature, pion mass approaches the free field limit, whereas $ρ$ meson is about twice as large as that limit. Pion and the longitudinal projection of $ρ$ meson decay constants have similar behaviour as the order parameter of chiral symmetry, whereas the transverse projection of $ρ$ meson decay constant rises monotonously as temperature increases. The inflection point of decay constant and the chiral susceptibility get the same phase transition temperature. Though there is no access to the thermal width of mesons within this scheme, it is discussed by analyzing the Gell-Mann-Oakes-Renner (GMOR) relation in medium. These thermal properties of hadron observables will help us understand the QCD phases at finite temperature and can be employed to improve the experimental data analysis and heavy ion collision simulations.
Comments:
8 pages, 4 figures, matched the published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2006.05909 [pdf]
EPJC(2020)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE