Thu·Dec 3, 2015Thursday·December 3, 2015

1. 01*

   Measurement of the Branching Ratio for the Beta Decay of ${}^{14}$O

   P.A. Voytas🇺🇸 · E.A. George🇺🇸 · G.W. Severin🇺🇸 · L. Zhan🇨🇳 · L.D. Knutson🇺🇸

   We present a new measurement of the branching ratio for the decay of ${}^{14}$O to the ground state of ${}^{14}$N. The experimental result, ${\lambda }_0/{\lambda }_{\mathrm{total}}=(4.934\pm 0.040(stat.)\pm 0.061(syst.))\times 10^{-3}$, is significantly smaller than previous determinations of this quantity. The new measurement allows an improved determination of the partial halflife for the superallowed $0^{+}\to 0^{+}$ Fermi decay to the ${}^{14}$N first excited state, which impacts the determination of the $V_{ud}$ element of the CKM matrix. With the new measurement in place, the corrected ${}^{14}$O $\mathcal{F}t$ value is in good agreement with the average $\mathcal{F}t$ for other superallowed $0^{+}\to 0^{+}$ Fermi decays.

   nucl-exPRC(2015)·15 citations
2. 02*

   Lifetime measurements of nuclei in few-electron ions

   Thomas Faestermann🇩🇪

   In this review lifetime measurements of ions with at most two electrons are summarized. Such highly ionized systems have been studied - until now - only in the Experimental Storage Ring of the GSI in Darmstadt. Emphasis is put on decays via the weak interaction. The first observations of beta-decay into bound atomic states are described as well as its time mirrored counterpart, the electron-capture decay. In the latter case the decays of hydrogen- and helium-like ions are compared with a surprising result. Further on, the observation of sinusoidal modulations of the decay rate in two-body decays is summarized. As a possible cause an interference due to the emission of neutrinos with different rest mass is discussed.

   nucl-exastro-ph.GAPhys.Scripta T(2015)·4 citations
3. 03*

   Measurements of long-range near-side angular correlations in $\sqrt{s_{\text{NN}}}=5$TeV proton-lead collisions in the forward region

   LHCb collaboration: R. Aaij🇨🇭 · C. Abellán Beteta🇨🇭 · B. Adeva🇪🇸 · M. Adinolfi🇬🇧 · A. Affolder🇬🇧 · Z. Ajaltouni🇫🇷 · S. Akar🇫🇷 · J. Albrecht🇩🇪 · F. Alessio🇨🇭 · M. Alexander🇬🇧 · S. Ali🇳🇱 · G. Alkhazov🇷🇺 and 724 other authors

   Two-particle angular correlations are studied in proton-lead collisions at a nucleon-nucleon centre-of-mass energy of $\sqrt{s_{\text{NN}}}=5$TeV, collected with the LHCb detector at the LHC. The analysis is based on data recorded in two beam configurations, in which either the direction of the proton or that of the lead ion is analysed. The correlations are measured in the laboratory system as a function of relative pseudorapidity, $\Delta \eta$, and relative azimuthal angle, $\Delta \varphi$, for events in different classes of event activity and for different bins of particle transverse momentum. In high-activity events a long-range correlation on the near side, $\Delta \varphi \approx 0$, is observed in the pseudorapidity range $2.0<\eta <4.9$. This measurement of long-range correlations on the near side in proton-lead collisions extends previous observations into the forward region up to $\eta =4.9$. The correlation increases with growing event activity and is found to be more pronounced in the direction of the lead beam. However, the correlation in the direction of the lead and proton beams are found to be compatible when comparing events with similar absolute activity in the direction analysed.

   nucl-exhep-exPLB(2016)·173 citations
4. 04*

   Observation of Large Enhancement of Charge Exchange Cross Sections with Neutron-Rich Carbon Isotopes

   I. Tanihata🇯🇵 · S. Terashima🇨🇳 · R. Kanungo🇨🇦 · F. Ameil🇩🇪 · J. Atkinson · Y. Ayyad🇯🇵 · D. Cortina-Gil🇪🇸 · I. Dillmann🇨🇦 · A. Estradé🇬🇧 · A. Evdokimov · F. Farinon🇩🇪 · H. Geissel🇩🇪 and 21 other authors

   Production cross sections of nitrogen isotopes from high-energy carbon isotopes on hydrogen and carbon targets have been measured for the first time for a wide range of isotopes. The fragment separator FRS at GSI was used to deliver C isotope beams. The cross sections of the production of N isotopes were determined by charge measurements of forward going fragments. The cross sections show a rapid increase with the number of neutrons in the projectile. Since the production of nitrogen is mostly due to charge exchange reactions below the proton separation energies, the present data suggests a concentration of Gamow-Teller and Fermi transition strength at low excitation energies for neutron-rich isotopes. It was also observed that the cross sections were enhanced much more strongly for neutron rich isotopes in the C-target data.

   nucl-exnucl-thPTEP(2016)·10 citations
5. 05*

   Population of 13Be in a Nucleon Exchange Reaction

   B.R. Marks · P.A. DeYoung🇺🇸 · J.K. Smith🇺🇸 · T. Baumann · J. Brown🇺🇸 · N. Frank🇺🇸 · J. Hinnefeld · M. Hoffman · M.D. Jones🇺🇸 · Z. Kohley🇺🇸 · A.N. Kuchera🇺🇸 · B. Luther🇺🇸 and 6 other authors

   The neutron-unbound nucleus 13Be was populated with a nucleon-exchange reaction from a 71 MeV/u secondary 13B beam. The decay energy spectrum was reconstructed using invariant mass spectroscopy based on 12Be fragments in coincidence with neutrons. The data could be described with an s-wave resonance at E = 0.73(9) MeV with a width of Gamma = 1.98(34) MeV and a d-wave resonance at E = 2.56(13) MeV with a width of Gamma = 2.29(73) MeV. The observed spectral shape is consistent with previous one-proton removal reaction measurements from 14B.

   nucl-exPRC(2015)·16 citations
6. 06*

   A search for cosmogenic production of $\beta$-neutron emitting radionuclides in water

   S. Dazeley🇺🇸 · M. Askins🇺🇸 · M. Bergevin🇺🇸 · A. Bernstein🇺🇸 · N. S. Bowden🇺🇸 · P. Jaffke🇺🇸 · S. D. Rountree🇺🇸 · T. M. Shokair🇺🇸 · M. Sweany🇺🇸

   Here we present the first results of WATCHBOY, a water Cherenkov detector designed to measure the yield of $\beta$-neutron emitting radionuclides produced by cosmic ray muons in water. In addition to the $\beta$-neutron measurement, we also provide a first look at isolating single-$\beta$ producing radionuclides following muon-induced hadronic showers as a check of the detection capabilities of WATCHBOY. The data taken over $207$ live days indicates a ${}^9$Li production yield upper limit of $1.9\times 10^{-7}{\mu }^{-1}{g}^{-1}{\mathrm{cm}}^2$ at $\sim 400$ meters water equivalent (m.w.e.) overburden at the $90\%$ confidence level. In this work the ${}^9$Li signal in WATCHBOY was used as a proxy for the combined search for ${}^9$Li and ${}^8$He production. This result will provide a constraint on estimates of antineutrino-like backgrounds in future water-based antineutrino detectors.

   nucl-exhep-exphysics.ins-detNucl.Instrum.Meth.A(2016)·19 citations
7. 07*

   Narrow Nucleon-$\psi (2S)$ Bound State and LHCb Pentaquarks

   Michael I. Eides🇺🇸 · Victor Yu.Petrov🇷🇺 · Maxim V. Polyakov🇷🇺

   We interpret the newly discovered pentaquark $P_c(4450)$ as a bound state of charmonium $\psi (2S)$ and the nucleon. The binding potential is due to charmonium-nucleon interaction that in the heavy quark approximation is proportional to the product of the charmonium chromoelectric polarizability and the nucleon energy-momentum distribution. We use the large $N_c$ expansion to estimate the quarkonium polarizability and calculate the nucleon properties in the framework of the mean-field picture of light baryons. Two almost degenerate states $J^P=(1/2{)}^{-}$ and $J^P=(3/2{)}^{-}$ are predicted at the position of the $P_c(4450)$ pentaquark. We find that the nucleon-$\psi (2S)$ bound state has a naturally narrow width in the range of tens of MeV. The unitary multiplet partners of the $P_c(4450)$ pentaquark and the generalization to $b\bar{b}$-nucleon pentaquark bound states are discussed.

   ↳ hep-phhep-exnucl-exPRD(2016)·99 citations
8. 08*

   Complex suppression patterns distinguish between major energy loss effects in Quark-Gluon Plasma

   Magdalena Djordjevic🇷🇸

   Interactions of high momentum partons with Quark-Gluon Plasma created in relativistic heavy-ion collisions provide an excellent tomography tool for this new form of matter. Recent measurements for charged hadrons and unidentified jets at the LHC show an unexpected flattening of the suppression curves at high momentum, exhibited when either momentum or the collision centrality is changed. Furthermore, a limited data available for B probes indicate a qualitatively different pattern, as nearly the same flattening is exhibited for the curves corresponding to two opposite momentum ranges. We here show that the experimentally measured suppression curves are well reproduced by our theoretical predictions, and that the complex suppression patterns are due to an interplay of collisional, radiative energy loss and the dead-cone effect. Furthermore, for B mesons, we predict that the uniform flattening of the suppression indicated by the limited dataset is in fact valid across the entire span of the momentum ranges, which will be tested by the upcoming experiments. Overall, the study presented here, provides a rare opportunity for pQCD theory to qualitatively distinguish between the major energy loss mechanisms at the same (nonintuitive) dataset.

   ↳ nucl-thnucl-exPLB(2016)·6 citations
9. 09*

   Reconstructing the direction of reactor antineutrinos via electron scattering in Gd-doped water Cherenkov detectors

   D. Hellfeld🇺🇸 · S. Dazeley🇺🇸 · A. Bernstein🇺🇸 · C. Marianno🇺🇸

   The potential of elastic antineutrino-electron scattering in a Gd-doped water Cherenkov detector to determine the direction of a nuclear reactor antineutrino flux was investigated using the recently proposed WATCHMAN antineutrino experiment as a baseline model. The expected scattering rate was determined assuming a 13-km standoff from a 3.758-GWt light water nuclear reactor and the detector response was modeled using a Geant4-based simulation package. Background was estimated via independent simulations and by scaling published measurements from similar detectors. Background contributions were estimated for solar neutrinos, misidentified reactor-based inverse beta decay interactions, cosmogenic radionuclides, water-borne radon, and gamma rays from the photomultiplier tubes (PMTs), detector walls, and surrounding rock. We show that with the use of low background PMTs and sufficient fiducialization, water-borne radon and cosmogenic radionuclides pose the largest threats to sensitivity. Directional sensitivity was then analyzed as a function of radon contamination, detector depth, and detector size. The results provide a list of experimental conditions that, if satisfied in practice, would enable antineutrino directional reconstruction at 3$\sigma$ significance in large Gd-doped water Cherenkov detectors with greater than 10-km standoff from a nuclear reactor.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2017)·17 citations
10. 10*

    Antimatter ${}_{\Lambda }^4$H Hypernucleus Production and the ${}_{\Lambda }^3$H/${}^3$He Puzzle in Relativistic Heavy-Ion Collisions

    Kai-Jia Sun🇨🇳 · Lie-Wen Chen🇨🇳

    We show that the measured yield ratio ${}_{\Lambda }^3$H/${}^3$He (${}_{\overline{\Lambda }}^3\overline{\text{H}}$/${}^3\overline{\text{He}}$) in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV and in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV can be understood within a covariant coalescence model if (anti-)$\Lambda$ particles freeze out earlier than (anti-)nucleons but their relative freezeout time is closer at $\sqrt{s_{NN}}=2.76$ TeV than at $\sqrt{s_{NN}}=200$ GeV. The earlier (anti-)$\Lambda$ freezeout can significantly enhance the yield of (anti)hypernucleus ${}_{\Lambda }^4$H (${}_{\overline{\Lambda }}^4\overline{\text{H}}$), leading to that ${}_{\overline{\Lambda }}^4\overline{\text{H}}$ has a comparable abundance with ${}^4\overline{\text{He}}$ and thus provides an easily measured antimatter candidate heavier than ${}^4\overline{\text{He}}$. The future measurement on ${}_{\Lambda }^4$H (${}_{\overline{\Lambda }}^4\overline{\text{H}}$) would be very useful to understand the (anti-)$\Lambda$ freezeout dynamics and the production mechanism of (anti)hypernuclei in relativistic heavy-ion collisions.

    ↳ nucl-thastro-ph.COhep-phnucl-exPRC(2016)·31 citations
11. 11*

    Vibration-induced field fluctuations in a superconducting magnet

    J. W. Britton · B. C. Sawyer · J. G. Bohnet · H. Uys · M. J. Biercuk · J. J. Bollinger

    Superconducting magnets enable precise control of nuclear and electron spins, and are used in experiments that explore biological and condensed matter systems, and fundamental atomic particles. In high-precision applications, a common view is that that slow (<1 Hz) drift of the homogeneous magnetic field limits control and measurement precision. We report on previously undocumented higher-frequency field noise (10 Hz to 200 Hz) that limits the coherence time of 9Be+ electron-spin qubits in the 4.46 T field of a superconducting magnet. We measure a spin-echo T2 coherence time of ~6 ms for the 9Be+ electron-spin resonance at 124 GHz, limited by part-per-billion fractional fluctuations in the magnet's homogeneous field. Vibration isolation of the magnet improved T2 to ~50 ms.

    ↳ quant-phcond-mat.supr-connucl-exphysics.atom-phPRA(2016)·20 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.