Tue·Oct 9, 2018Tuesday·October 9, 2018

1. 01*

   Open charm measurements at CERN SPS energies with the new Vertex Detector of the NA61/SHINE experiment

   Anastasia Merzlaya (for the NA61/SHINE Collaboration)🇵🇱

   The heavy-ion programme of the NA61/SHINE experiment at the CERN SPS has been expanded to allow precise measurements of exotic particles with short lifetime. The study of open charm meson production is a sensitive tool for new detailed investigations of the properties of hot and dense matter formed in nucleus-nucleus collisions. In particular, it offers new possibilities for studies of such phenomena as in-medium parton energy loss and quarkonium dissociation and possible regeneration, thus providing new information to probe deconfinement. A new high resolution Vertex Detector was designed for the NA61/SHINE experiment for measurements of the very rare processes of open charm production in nucleus-nucleus collisions at the SPS. It will meet the challenges of track registration and of very precise spatial resolution in primary and secondary vertex reconstruction required for the identification of $D^0$ mesons. A small-acceptance version of the Vertex Detector, the SAVD (Small Acceptance Vertex Detector), was installed last year with a Pb target in the Pb beam of 150$A$ GeV/c momentum, and a modest set of data was collected. The main goal of the ongoing data analysis was to observe a signal from $D^0$ mesons. The status of this analysis will be presented, discussing a number of challenges related to the tracking in the inhomogeneous magnetic field, the matching of SAVD tracks to TPCs tracks, and the extraction of physics inresults.

   nucl-exphysics.ins-detKnE Energ.Phys.(2018)·6 citations
2. 02*

   Improving Light Yield Measurements for Low-Yield Scintillators

   J. B. Cumming🇺🇸 · S. Hans🇺🇸 · M. Yeh🇺🇸

   Light power spectra are introduced as a new tool for relative light yield (LY) determinations. Light event spectra have commonly been used for this purpose. Theoretical background supporting this change is provided. It is shown that the derivative of a light power spectrum can provide a reliable LY measurement at levels as low as 2% of those for high-yield liquid scintillators. Applications to light evolution in the PPO+LAB system and to water-based liquid scintillators are described.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2019)·14 citations
3. 03*

   Measurement of B${}_{\mathrm{s}}^0$ meson production in pp and PbPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV

   CMS Collaboration

   The production cross sections of B${}_{\mathrm{s}}^0$ mesons and charge conjugates are measured in proton-proton (pp) and PbPb collisions via the exclusive decay channel B${}_{\mathrm{s}}^0$ $\to$ ${\mu }^{+}{\mu }^{-}$K${}^{+}$K${}^{-}$ at a centre-of-mass energy of 5.02 TeV per nucleon pair and within the rapidity range $|y|$ $<$ 2.4 using the CMS detector at the LHC. The pp measurement is performed as a function of transverse momentum (p${}_{\mathrm{T}}$) of the B${}_{\mathrm{s}}^0$ meson in the range of 7 to 50 GeV/$c$ and is compared to the predictions of perturbative QCD calculations. The B${}_{\mathrm{s}}^0$ production yield in PbPb collisions is measured in two p${}_{\mathrm{T}}$ intervals, 7 to 15 and 15 to 50 GeV/$c$, and compared to the yield in pp collisions in the same kinematic region. The nuclear modification factor ($R_{\mathrm{AA}}$) is found to be 1.5 $\pm$ 0.6 (stat) $\pm$ 0.5 (syst) for 7-15 GeV/$c$, and 0.87 $\pm$ 0.30 (stat) $\pm$ 0.17 (syst) for 15-50 GeV/$c$, respectively. Within current uncertainties, the results are consistent with models of strangeness enhancement and a suppression as observed for the B${}^{+}$ mesons.

   ↳ hep-exnucl-exPLB(2019)·62 citations
4. 04*

   Time resolution and characteristic study of MWPC detectors with different Argon based gas

   Rajendra Nath Patra🇮🇳 · R. N. Singaraju🇮🇳 · S. Biswas🇮🇳 · T. K. Nayak🇮🇳 · Y. P. Viyogi🇮🇳

   A prototype of Multi-Wire Proportional Chambers (MWPC) has been fabricated for the study of its various characteristics. The detector contains gold-coated tungsten wires (20 $\mu m$ diameter) on the anode frame, with a pitch of 2.8 mm. The gap between the anode and the cathode is 3 mm and the gap between anode and read-out is also 3 mm. Detailed study of MWPC in terms of gain, energy and timing resolution and efficiency measurements have been performed. The detector has been operated using Ar/CO${}_2$ gas mixtures with 70:30 and 90:10 ratio. Energy spectrum of ${}^{55}$Fe X-ray source is obtained for the detector. The gain and energy resolution of the detector were calculated using X-ray spectrum. Time resolution is obtained $\sim$10 ns.

   ↳ physics.ins-dethep-exnucl-exSpringer Proc.Phys.(2018)·0 citations
5. 05*

   Predictions of nuclear $\beta$-decay half-lives with machine learning and their impacts on $r$ process

   Z. M. Niu🇨🇳 · H. Z. Liang🇯🇵 · B. H. Sun🇨🇳 · W. H. Long🇨🇳 · Y. F. Niu🇷🇴

   Nuclear $\beta$ decay is a key process to understand the origin of heavy elements in the universe, while the accuracy is far from satisfactory for the predictions of $\beta$-decay half-lives by nuclear models up to date. In this letter, we pave a novel way to accurately predict $\beta$-decay half-lives with the machine-learning based on the Bayesian neural network, in which the known physics has been explicitly embedded, including the ones described by the Fermi theory of $\beta$ decay, and the dependence of half-lives on pairing correlations and decay energies. The other potential physics, which is not clear or even missing in nuclear models nowadays, will be learned by the Bayesian neural network. The results well reproduce the experimental data with a very high accuracy and further provide reasonable uncertainty evaluations in half-life predictions. These accurate predictions for half-lives with uncertainties are essential for the $r$-process simulations.

   ↳ nucl-thastro-ph.SRnucl-exPRC(2019)·128 citations
6. 06*

   Uncertainty quantification in nuclear shell model

   Sota Yoshida🇯🇵 · Noritaka Shimizu🇯🇵 · Tomoaki Togashi🇯🇵 · Takaharu Otsuka🇯🇵

   The uncertainty quantifications of theoretical results are of great importance to make meaningful comparisons of those results with experimental data and to make predictions in experimentally unknown regions. By quantifying uncertainties, one can make more solid statements about, e.g., origins of discrepancy in some quantities between theory and experiment. We propose a novel method for uncertainty quantification for the effective interactions of nuclear shell-model calculations as an example. The effective interaction is specified by a set of parameters, and its probability distribution in the multi-dimensional parameter space is considered. This enables us to quantify the agreement with experimental data in a statistical manner and the resulting confidence intervals show unexpectedly large variations. Moreover, we point out that a large deviation of the confidence interval for the energy in shell-model calculations from the corresponding experimental data can be used as an indicator of some exotic property, e.g. alpha clustering, etc. Other possible applications and impacts are also discussed.

   ↳ nucl-thnucl-exPRC(2018)·24 citations
7. 07*

   Characteristic study of a quadruple GEM detector and its comparison with a triple GEM detector

   Rajendra Nath Patra🇮🇳 · Rama Narayan Singaraju🇮🇳 · Saikat Biswas🇮🇳 · Yogendra P. Viyogi🇮🇳 · Tapan K. Nayak🇮🇳

   A quadruple GEM detector has been assembled in a standalone configuration and operated using Ar and CO${}_2$ gas mixtures in proportions of 70:30 and 90:10. Detailed performance study of the detector has been made by using ${}^{106}$Ru-Rh $\beta$-source and X-ray spectrum of ${}^{55}$Fe source. Results of these measurements are presented in terms of gain, efficiency, energy and time resolutions and also compared with our earlier triple GEM results. The energy resolution has been found to be somewhat worse compared with that of the triple-GEM detector. Effect of drift field on electron transparency and time resolution has been studied in detail.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2018)·5 citations
8. 08*

   $N\Omega$ dibaryon from lattice QCD near the physical point

   Takumi Iritani🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Faisal Etminan🇮🇷 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Noriyoshi Ishii🇯🇵 · Takaya Miyamoto🇯🇵 · Kenji Sasaki🇯🇵

   The nucleon($N$)-Omega($\Omega$) system in the S-wave and spin-2 channel (${}^5$S${}_2$) is studied from the (2+1)-flavor lattice QCD with nearly physical quark masses ($m_{\pi }\simeq 146$~MeV and $m_K\simeq 525$~MeV). The time-dependent HAL QCD method is employed to convert the lattice QCD data of the two-baryon correlation function to the baryon-baryon potential and eventually to the scattering observables. The $N\Omega$(${}^5$S${}_2$) potential, obtained under the assumption that its couplings to the D-wave octet-baryon pairs are small, is found to be attractive in all distances and to produce a quasi-bound state near unitarity: In this channel, the scattering length, the effective range and the binding energy from QCD alone read $a_0=5.30(0.44){(}_{-0.01}^{+0.16})$~fm, $r_{\mathrm{eff}}=1.26(0.01){(}_{-0.01}^{+0.02})$~fm, $B=1.54(0.30){(}_{-0.10}^{+0.04})$~MeV, respectively. Including the extra Coulomb attraction, the binding energy of $p{\Omega }^{-}$(${}^5$S${}_2$) becomes $B_{p{\Omega }^{-}}=2.46(0.34){(}_{-0.11}^{+0.04})$~MeV. Such a spin-2 $p{\Omega }^{-}$ state could be searched through two-particle correlations in $p$-$p$, $p$-nucleus and nucleus-nucleus collisions.

   ↳ hep-lathep-exhep-phnucl-ex+1PLB(2019)·157 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.