Mon·Dec 3, 2018Monday·December 3, 2018

1. 01*

   Study of J/$\psi$ azimuthal anisotropy at forward rapidity in Pb-Pb collisions at $\sqrt{{\text{s}}_{\mathrm{NN}}}$ = 5.02 TeV

   ALICE Collaboration

   The second ($v_2$) and third ($v_3$) flow harmonic coefficients of J/$\psi$ mesons are measured at forward rapidity (2.5 $<$ $y$ $<$ 4.0) in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with the ALICE detector at the LHC. Results are obtained with the scalar product method and reported as a function of transverse momentum, $p_{\mathrm{T}}$, for various collision centralities. A positive value of J/$\psi$ $v_3$ is observed with 3.7$\sigma$ significance. The measurements, compared to those of prompt D${}^0$ mesons and charged particles at mid-rapidity, indicate an ordering with $v_{\mathrm{n}}$(J/$\psi$) $<v_{\mathrm{n}}$(D${}^0$) $<v_{\mathrm{n}}$(h${}^{\pm }$) (n = 2, 3) at low and intermediate $p_{\mathrm{T}}$ up to 6 GeV/$c$ and a convergence with $v_2$(J/$\psi$) $\approx v_2$(D${}^0$) $\approx v_2$(h${}^{\pm }$) at high $p_{\mathrm{T}}$ above 6-8 GeV/$c$. In semi-central collisions (5-40% and 10-50% centrality intervals) at intermediate $p_{\mathrm{T}}$ between 2 and 6 GeV/$c$, the ratio $v_3/v_2$ of J/$\psi$ mesons is found to be significantly lower (4.6$\sigma$) with respect to that of charged particles. In addition, the comparison to the prompt D${}^0$-meson ratio in the same $p_{\mathrm{T}}$ interval suggests an ordering similar to that of the $v_2$ and $v_3$ coefficients. The J/$\psi$ $v_2$ coefficient is further studied using the Event Shape Engineering technique. The obtained results are found to be compatible with the expected variations of the eccentricity of the initial-state geometry.

   nucl-exhep-exJHEP(2019)·37 citations
2. 02*

   Determination of hexadecapole (${\beta }_4$) deformation of the light-mass nucleus ${}^{24}$Mg using quasi-elastic measurement

   Y. K. Gupta · B. K. Nayak · U. Garg · N. Sensharma · Shahina · R. Gandhi · D. C. Biswas · M. Şenyiğit · K. B. Howard · W. Tan · P. D. O'Malley · K. Hagino and 17 other authors

   Quasi-elastic scattering measurements have been performed using ${}^{16}$O and ${}^{24}$Mg projectiles off ${}^{90}$Zr at energies around the Coulomb barrier. Experimental data have been analyzed in the framework of coupled channels (CC) calculations using the code CCFULL. The quasi-elastic scattering excitation function and derived barrier distribution for ${}^{16}$O + ${}^{90}$Zr reaction are well reproduced by the CC calculations using the vibrational coupling strengths for ${}^{90}$Zr reported in the literature. Using these vibrational coupling strengths, a Bayesian analysis is carried out for ${}^{24}$Mg + ${}^{90}$Zr reaction. The ${\beta }_2$ and ${\beta }_4$ values for ${}^{24}$Mg are determined to be $+0.43\pm 0.02$ and $-0.11\pm 0.02$, respectively. The ${\beta }_2$ parameter determined in the present work is in good agreement with results obtained using inelastic scattering probes. The hexadecapole deformation of ${}^{24}$Mg has been measured very precisely for the first time. Present results establish that quasi-elastic scattering could provide a useful probe to determine the ground state deformation of atomic nuclei.

   nucl-exnucl-thPLB(2020)·40 citations
3. 03*

   PEN experiment: a precise test of lepton universality

   C.J. Glaser · D. Pocanic · L.P. Alonzi · V.A. Baranov · W. Bertl · M. Bychkov · Yu.M. Bystritsky · E. Frlez · V.A. Kalinnikov · N.V. Khomutov · A.S. Korenchenko · S.M. Korenchenko and 17 other authors

   With few open channels and uncomplicated theoretical description, charged pion decays are uniquely sensitive to certain standard model (SM) symmetries, the universality of weak fermion couplings, and to aspects of pion structure and chiral dynamics. We review the current knowledge of the pion electronic decay ${\pi }^{+}\to e^{+}{\nu }_e(\gamma )$, or ${\pi }_{e2(\gamma )}$, and the resulting limits on non-SM processes. Focusing on the PEN experiment at the Paul Scherrer Institute (PSI), Switzerland, we examine the prospects for further improvement in the near term.

   ↳ hep-exhep-phnucl-ex13 citations
4. 04*

   ALICE Overwatch: Online monitoring and data quality assurance using HLT data

   R.J. Ehlers🇺🇸 · J.D. Mulligan🇺🇸

   ALICE Overwatch is a project started in late 2015 to provide augmented online monitoring and data quality assurance utilizing time-stamped QA histograms produced by the ALICE High Level Trigger. The system receives the data via ZeroMQ, stores it for later review, enriches it with detector specific functionality, and visualizes it via a web application. These provided capabilities are complementary to the existing Data Quality Monitoring system. In addition to basic visualization, additional processing options are accessible to the user, including requests for data within a particular time range or reprocessing of a particular run with different processing parameters. For example, the first ten minutes of a particular run could be investigated for a transient hot trigger channel. Due to similarities between the Overwatch architecture and that which will be used for Quality Control (QC) in LHC Run 3 and beyond, Overwatch will also be utilized to develop and test various QC components during LHC Run 2. Some of the areas of QC development include a new trending and alarm framework. We report on the project's design, development, and status.

   ↳ physics.ins-dethep-exnucl-exEPJ Web Conf.(2019)·4 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.