Thu·Oct 11, 2018Thursday·October 11, 2018

1. 01*

   Effect of magnetic fields on pairs of oppositely charged particles in ultrarelativistic heavy-ion collisions

   Y. J. Ye🇨🇳 · Y. G. Ma🇨🇳 · A. H. Tang🇺🇸 · G. Wang🇺🇸

   The initial strong magnetic field produced in high-energy nuclear collisions will distort the distribution of the relative angle between oppositely charged particles within a pair. In this paper, two experimental observables are examined to quantify such effects: one based on the framework for detecting the hyperon global polarization, and the other based on the balance function. We also discuss the optimization of the signal, as well as the expected magnitude ranges for the two observables.

   nucl-exPRC(2019)·17 citations
2. 02*

   Precise measurement of ${\alpha }_K$ and ${\alpha }_T$ for the 39.8-keV $E$3 transition in ${}^{103}$Rh: Test of internal-conversion theory

   N. Nica · J.C. Hardy🇺🇸 · V.E. Iacob · V. Horvat · H.I. Park · T.A. Werke · K.J. Glennon · C.M. Folden III · V.I. Sabla🇺🇸 · J.B. Bryant · X.K. James · M.B. Trzhaskovskaya🇷🇺

   Neutron-activated sources of ${}^{103}$Ru and ${}^{103}$Pd both share the isomeric first-excited state in ${}^{103}$Rh as a daughter product. From independent measurements of both decays, we have measured the $K$-shell and total internal conversion coefficients, ${\alpha }_K$ and ${\alpha }_T$, for the 39.8-keV $E$3 transition, which de-excites that state in ${}^{103}$Rh, to be 141.1(23) and 1428(13), respectively. When compared with Dirac-Fock calculations, our new results disagree with the version of the theory that ignores the $K$-shell atomic vacancy, which is consistent with our conclusion drawn from a series of measurements on high multipolarity transitions in nuclei with higher $Z$. Calculations that include the atomic vacancy indicate that the transition actually has a small $M$4 component with mixing ratio $\delta$ = 0.023(5).

   nucl-exnucl-thPRC(2018)·3 citations
3. 03*

   The s-process nucleosynthesis in low mass stars: impact of the uncertainties in the nuclear physics determined by Monte Carlo variations

   G. Cescutti🇮🇹 · R. Hirschi🇬🇧 · N. Nishimura🇬🇧 · T. Rauscher🇬🇧 · J. den Hartogh · A. St. J. Murphy🇬🇧 · S. Cristallo🇮🇹

   We investigated the impact of uncertainties in neutron-capture and weak reactions (on heavy elements) on the s-process nucleosynthesis in low-mass stars using a Monte-Carlo based approach. We performed extensive nuclear reaction network calculations that include newly evaluated temperature-dependent upper and lower limits for the individual reaction rates. Our sophisticated approach is able to evaluate the reactions that impact more significantly the final abundances. We found that beta-decay rate uncertainties affect typically nuclides near s-process branchings, whereas most of the uncertainty in the final abundances is caused by uncertainties in neutron capture rates, either directly producing or destroying the nuclide of interest. Combined total nuclear uncertainties due to reactions on heavy elements are approximately 50%.

   ↳ astro-ph.SRnucl-exnucl-thSpringer Proc.Phys.(2019)·1 citation
4. 04*

   Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV

   CMS Collaboration

   Evidence for the light-by-light scattering process, $\gamma \gamma$ $\to$ $\gamma \gamma$, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390 $\mu$b${}^{-1}$ recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy E${}_{\mathrm{T}}^{\gamma }$ $>$ 2 GeV, pseudorapidity $|{\eta }^{\gamma }|$ $<$ 2.4, diphoton invariant mass $m^{\gamma \gamma }$ $>$ 5 GeV, diphoton transverse momentum $p_{\mathrm{T}}^{\gamma \gamma }$ $<$ 1 GeV, and diphoton acoplanarity below 0.01. After all selection criteria are applied, 14 events are observed, compared to expectations of 9.0 $\pm$ 0.9 (theo) events for the signal and 4.0 $\pm$ 1.2 (stat) for the background processes. The excess observed in data relative to the background-only expectation corresponds to a significance of 3.7 standard deviations, and has properties consistent with those expected for the light-by-light scattering signal. The measured fiducial light-by-light scattering cross section, ${\sigma }_{\mathrm{fid}}(\gamma \gamma$ $\to$ $\gamma \gamma )=$ 120 $\pm$ 46 (stat) $\pm$ 28 (syst) $\pm$ 12 (theo) nb, is consistent with the standard model prediction. The $m^{\gamma \gamma }$ distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the $\gamma \gamma$ $\to$ a $\to$ $\gamma \gamma$ process, in the mass range $m_{\mathrm{a}}=$ 5-90 GeV.

   ↳ hep-exnucl-exPLB(2019)·416 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.