Mon·Oct 13, 2014Monday·October 13, 2014

1. 01*

   Beam-energy and system-size dependence of the space-time extent of the pion emission source produced in heavy ion collisions

   A. Adare · S. Afanasiev · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · H. Al-Bataineh · H. Al-Ta'ani · J. Alexander · M. Alfred · A. Angerami · K. Aoki and 611 other authors

   Two-pion interferometry measurements are used to extract the Gaussian radii $R_{\mathrm{out}}$, $R_{\mathrm{side}}$, and $R_{\mathrm{long}}$, of the pion emission sources produced in Cu$+$Cu and Au$+$Au collisions at several beam collision energies $\sqrt{s_{{}_{NN}}}$ at PHENIX. The extracted radii, which are compared to recent STAR and ALICE data, show characteristic scaling patterns as a function of the initial transverse size $\bar{R}$ of the collision systems and the transverse mass $m_T$ of the emitted pion pairs, consistent with hydrodynamiclike expansion. Specific combinations of the three-dimensional radii that are sensitive to the medium expansion velocity and lifetime, and the pion emission time duration show nonmonotonic $\sqrt{s_{{}_{NN}}}$ dependencies. The nonmonotonic behaviors exhibited by these quantities point to a softening of the equation of state that may coincide with the critical end point in the phase diagram for nuclear matter.

   nucl-ex37 citations
2. 02*

   Measurements of b-jet Nuclear Modification Factors in pPb and PbPb Collisions with CMS

   Kurt Jung (for the CMS Collaboration)🇺🇸

   We present measurements of the nuclear modification factors RAA and RpA(PYTHIA) of b jets in lead-lead and proton-lead collisions, respectively, using the CMS detector. Jets from b-quark fragmentations are found by exploiting the long lifetime of the b-quark through tagging methods using distributions of the secondary vertex displacement. From these, b-jet cross-sections are calculated and compared to the pp cross-section from the 2.76 TeV pp data collected in 2013 and to a PYTHIA simulation at 5.02 TeV, where these center-of-mass energies correspond to those of the PbPb and pPb data. We observe significant suppression for b jets in PbPb, and a RpA(PYTHIA) value consistent with unity for b jets in pPb. Results from both collision species show remarkable correspondence with inclusive-jet suppression measurements, indicating that mass-dependent energy-loss effects are negligible at pT values greater than around 50 GeV/c. We use 150 inverse {\mu}b of lead-lead data and 35 inverse nb of proton-lead data collected at the LHC.

   nucl-exNPA(2014)·6 citations
3. 03*

   First determination of the one-proton induced Non-Mesonic Weak Decay width of p-shell {\Lambda}-Hypernuclei

   M. Agnello🇮🇹 · L. Benussi🇮🇹 · M. Bertani🇮🇹 · H.C. Bhang🇰🇷 · G. Bonomi🇮🇹 · E. Botta🇮🇹 · T. Bressani🇮🇹 · S. Bufalino🇮🇹 · D. Calvo🇮🇹 · P. Camerini🇮🇹 · B. Dalena🇮🇹 · F. De Mori🇮🇹 and 15 other authors

   Previous studies of proton and neutron spectra from Non-Mesonic Weak Decay of eight Lambda-Hypernuclei (A = 5-16) have been revisited. New values of the ratio of the two-nucleon and the one-proton induced decay widths, Gamma_2N/Gamma_p, are obtained from single proton spectra, Gamma_2N/Gamma_p = 0.50 +/- 0.24, and from neutron and proton coincidence spectra, Gamma_2N/Gamma_p = 0.36 +/- 0.14stat +0.05sys -0.04sys , in full agreement with previously published ones. With these values, a method is developed to extract the one-proton induced decay width in units of the free Lambda decay width, Gamma_p/Gamma_Lambda, without resorting to Intra Nuclear Cascade models but by exploiting only experimental data, under the assumption of a linear dependence on A of the Final State Interaction contribution. This is the first systematic determination ever done and it agrees within the errors with recent theoretical calculations.

   nucl-exnucl-thPLB(2014)·15 citations
4. 04*

   Spectroscopy of Ba and Ba${}^{+}$ deposits in solid xenon for barium tagging in nEXO

   B. Mong🇨🇦 · S. Cook🇺🇸 · T. Walton🇺🇸 · C. Chambers🇺🇸 · A. Craycraft🇺🇸 · C. Benitez-Medina🇺🇸 · K. Hall🇺🇸 · W. Fairbank Jr.🇺🇸 · J.B. Albert🇺🇸 · D.J. Auty🇺🇸 · P.S. Barbeau🇺🇸 · V. Basque🇨🇦 and 64 other authors

   Progress on a method of barium tagging for the nEXO double beta decay experiment is reported. Absorption and emission spectra for deposits of barium atoms and ions in solid xenon matrices are presented. Excitation spectra for prominent emission lines, temperature dependence and bleaching of the fluorescence reveal the existence of different matrix sites. A regular series of sharp lines observed in Ba${}^{+}$ deposits is identified with some type of barium hydride molecule. Lower limits for the fluorescence quantum efficiency of the principal Ba emission transition are reported. Under current conditions, an image of $\le 10^4$ Ba atoms can be obtained. Prospects for imaging single Ba atoms in solid xenon are discussed.

   ↳ physics.atom-phhep-exnucl-exphysics.ins-detPRA(2015)·48 citations
5. 05*

   Fabrication and characterization of a lithium-glass-based composite neutron detector

   G.C. Rich🇺🇸 · K. Kazkaz🇺🇸 · H.P. Martinez · T. Gushue

   A novel composite, scintillating material intended for neutron detection and composed of small (1.5 mm) cubes of KG2-type lithium glass embedded in a matrix of scintillating plastic has been developed in the form of a 2.2 in.-diameter, 3.1 in.-tall cylindrical prototype loaded with $\left(5.82\pm 0.02\right)\%$ lithium glass by mass. The response of the material when exposed to ${}^{252}$Cf fission neutrons and various $\gamma$-ray sources has been studied; using the charge-integration method for pulse shape discrimination, good separation between neutron and $\gamma$-ray events is observed and intrinsic efficiencies of $\left(1.15\pm 0.16\right)\times 10^{-2}$ and $\left(2.28\pm 0.21\right)\times 10^{-4}$ for ${}^{252}$Cf fission neutrons and ${}^{60}$Co $\gamma$ rays are obtained; an upper limit for the sensitivity to ${}^{137}$Cs $\gamma$ rays is determined to be $<3.70\times 10^{-8}$. The neutron/$\gamma$ discrimination capabilities are improved in circumstances when a neutron capture signal in the lithium glass can be detected in coincidence with a preceding elastic scattering event in the plastic scintillator; with this coincidence requirement, the intrinsic efficiency of the prototype detector for ${}^{60}$Co $\gamma$ rays is $\left(2.42\pm 0.61\right)\times 10^{-6}$ while its intrinsic efficiency for unmoderated ${}^{252}$Cf fission neutrons is $\left(4.31\pm 0.59\right)\times 10^{-3}$. Through use of subregion-integration ratios in addition to the coincidence requirement, the efficiency for $\gamma$ rays from ${}^{60}$Co is reduced to $\left(7.15\pm 4.10\right)\times 10^{-7}$ while the ${}^{252}$Cf fission neutron efficiency becomes $\left(2.78\pm 0.38\right)\times 10^{-3}$.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2015)·6 citations
6. 06*

   Half-lives of $\alpha$ decay from natural nuclides and from superheavy elements

   Yibin Qian🇨🇳 · Zhongzhou Ren🇨🇳

   Recently, experimental researches on the $\alpha$ decay with long lifetime are one of hot topics in the contemporary nuclear physics [e.g. N. Kinoshita {\sl et al.} (2012) and J. W. Beeman {\sl et al.} (2012) ]. In this study, we have systematically investigated the extremely long-lived $\alpha$-decaying nuclei within a generalized density-dependent cluster model involving the experimental nuclear charge radii. In detail, the important density distribution of daughter nuclei is deduced from the corresponding experimental charge radii, leading to an improved $\alpha$-core potential in the quantum tunneling calculation of $\alpha$-decay width. Besides the excellent agreement between theory and experiment, predictions on half-lives of possible candidates for natural $\alpha$ emitters are made for future experimental detections. In addition, the recently confirmed $\alpha$-decay chain from ${}^{294}$117 is well described, including the attractive long-lived $\alpha$-decaying ${}^{270}$Db, i.e., a positive step towards the "island of stability" in the superheavy mass region.

   ↳ nucl-thnucl-exPLB(2014)·37 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.