Tue·Sep 19, 2017Tuesday·September 19, 2017

1. 01*

   New determination of proton spectroscopic factors and reduced widths for ${}^8$Be states in the $16.5-18.0$ MeV excitation energy region via the study of the ${}^7$Li(${}^3$He,d)${}^8$Be transfer reaction at E${}_{lab}$ $=20$ MeV

   A. Belhout (1) S. Ouichaoui (1) · H. Beaumevieille (1) · A. Bouchemha (1) G. Bogaert (2) · S. Fortier (3) · J. Kiener (2) · A. Lefebvre-Schuhl (2) · J. M. Maison (3) · L. Rosier (3) J. Rotbard (3) · V. Tatischeff (2) · J.P. Thibaud (2) · J. Vernotte (3) ((1) Universite des Sciences et de la Technologie Houari Boumediene (USTHB), Faculte de Physique, Algeria, (2) Centre de Sciences Nucleaires et des Sciences de la Mati`ere (CSNSM), IN2P3/CNRS-Universite de Paris XI, France, (3) Institut de Physique Nucleaire, IN2P3/CNRS-Universite de Paris XI, France)

   The angular distributions of ${}^8$Be states in the excitation energy region, E${}_x$ $\sim$($16.5-18.2$) MeV, produced in the ${}^7$Li(${}^3$He,d)${}^8$Be proton transfer reaction have been measured at the Orsay 14.8$-$MV tandem accelerator for ${}^3$He${}^{2+}$ ion bombarding energy, E${}_{lab}$ $=20$ MeV, and forward anglular range, ${\theta }_{lab}=5^{\circ }-50^{\circ }$. A high energy resolution detection system composed of a split-pole magnetic spectrometer and a $\Delta E-E$,\ position-sensitive drift chamber was used to record the energy spectra of outgoing deuterons. The measured cross section data for the direct reaction component have been separated from the compound nucleus one, then analyzed in the framework of the non local, FR-DWBA theory. New values of the $C^{2}S$ and ($S_{p1/2},$ $S_{p3/2})$ proton absolute and partial spectroscopic factors and related ${\gamma }_p^2(a)$\ proton reduced widths versus the p $+$ ${}^7$Li channel radius have been extracted for the $2^{+}(16.626)$ and $2^{+}(16.922),T=0+1$ isospin-mixed loosely bound states of astrophysical interest and the $1^{+}(17.640)$, $T=1$ unbound state of ${}^8$Be. They are compared to sparse earlier experimental values and to shell-model predicted ones from the literature, and are discussed. In particular, the status of the spectroscopic information on the $2^{+}$ isospin-mixed doublet is reviewed and up-dated. The application in nuclear astrophysics of the DWBA derived results is emphasised.

   nucl-exPRC(2017)·2 citations
2. 02*

   A laser excitation scheme for ${}^{229\text{m}}$Th

   Lars von der Wense · Benedict Seiferle · Simon Stellmer · Johannes Weitenberg · Georgy Kazakov · Adriana Pálffy🇩🇪 · Peter G. Thirolf

   Direct laser excitation of the lowest known nuclear excited state in ${}^{229}$Th has been a longstanding objective. It is generally assumed that reaching this goal would require a considerably reduced uncertainty of the isomer's excitation energy compared to the presently adopted value of $(7.8\pm 0.5)$ eV. Here we present a direct laser excitation scheme for ${}^{229\text{m}}$Th, which circumvents this requirement. The proposed excitation scheme makes use of already existing laser technology and therefore paves the way for nuclear laser spectroscopy. In this concept, the recently experimentally observed internal-conversion decay channel of the isomeric state is used for probing the isomeric population. A signal-to-background ratio of better than $10^4$ and a total measurement time of less than three days for laser scanning appear to be achievable.

   nucl-exPRL(2017)·34 citations
3. 03*

   The search for magnetic-induced charged currents in Pb--Pb collisions with ALICE

   Jacopo Margutti (for the ALICE Collaboration)🇳🇱

   In non-central heavy-ion collisions unprecedented strong magnetic fields, of the order of 10${}^{18}$ Gauss, are expected to be produced. The interplay of such fields with QCD anomalies in the Quark--Gluon Plasma (QGP) has been predicted to lead to a number of interesting phenomena, such as the Chiral Magnetic Effect (CME). While several experimental observations are partially consistent with predictions of a CME signal, it is hard to distinguish them unambiguously from a combination of more mundane phenomena present in the anisotropic expansion of the QGP. This makes it imperative to establish that the early-time magnetic field has observable consequences not related to the anomalous QCD effects on final-state charged particles and to calibrate its strength. We test a recent prediction of a pure electromagnetic effect, which may arise in heavy-ion collisions. The varying magnetic field would induce a current within the QGP, which is expected to leave a very peculiar imprint on final-state particles: a contribution to directed flow which is asymmetric both in charge and pseudorapidity. We report the measurement of the charge dependence of directed flow with respect to the spectator plane for unidentified charged particles in Pb--Pb collisions at $\sqrt{s_{\text{NN}}}=5.02$ TeV.

   nucl-ex7 citations
4. 04*

   Lévy-stable two-pion Bose-Einstein correlations in $\sqrt{s_{{}_{NN}}}=200$ GeV Au$+$Au collisions

   A. Adare · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · J. Alexander · M. Alfred · H. Al-Ta'ani · A. Angerami · K. Aoki · N. Apadula · Y. Aramaki and 436 other authors

   We present a detailed measurement of charged two-pion correlation functions in 0%-30% centrality $\sqrt{s_{{}_{NN}}}=200$ GeV Au$+$Au collisions by the PHENIX experiment at the Relativistic Heavy Ion Collider. The data are well described by Bose-Einstein correlation functions stemming from Lévy-stable source distributions. Using a fine transverse momentum binning, we extract the correlation strength parameter $\lambda$, the Lévy index of stability $\alpha$ and the Lévy length scale parameter $R$ as a function of average transverse mass of the pair $m_T$. We find that the positively and the negatively charged pion pairs yield consistent results, and their correlation functions are represented, within uncertainties, by the same Lévy-stable source functions. The $\lambda (m_T)$ measurements indicate a decrease of the strength of the correlations at low $m_T$. The Lévy length scale parameter $R(m_T)$ decreases with increasing $m_T$, following a hydrodynamically predicted type of scaling behavior. The values of the Lévy index of stability $\alpha$ are found to be significantly lower than the Gaussian case of $\alpha =2$, but also significantly larger than the conjectured value that may characterize the critical point of a second-order quark-hadron phase transition.

   nucl-exPRC(2018)·88 citations
5. 05*

   Experimental techniques and performance of $\Lambda$-hypernuclear spectroscopy with the $(e,e^{\prime }{K}^{+})$ reaction

   T. Gogami🇯🇵 · C. Chen🇺🇸 · Y. Fujii🇯🇵 · O. Hashimoto🇯🇵 · M. Kaneta🇯🇵 · D. Kawama🇯🇵 · T. Maruta🇯🇵 · A. Matsumura🇯🇵 · S. Nagao🇯🇵 · S. N. Nakamura🇯🇵 · Y. Okayasu🇯🇵 · J. Reinhold🇺🇸 and 4 other authors

   The missing-mass spectroscopy of $\Lambda$ hypernuclei via the $(e,e^{\prime }{K}^{+})$ reaction has been developed through experiments at JLab Halls A and C in the last two decades. For the latest experiment, E05-115 in Hall C, we developed a new spectrometer system consisting of the HKS and HES; resulting in the best energy resolution ($E_{\Lambda }\simeq 0.5$-MeV FWHM) and $B_{\Lambda }$ accuracy ($B_{\Lambda }\le 0.2$ MeV) in $\Lambda$-hypernuclear reaction spectroscopy. This paper describes the characteristics of the $(e,e^{\prime }{K}^{+})$ reaction compared to other reactions and experimental methods. In addition, the experimental apparatus, some of the important analyses such as the semi-automated calibration of absolute energy scale, and the performance achieved in E05-115 are presented.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2018)·17 citations
6. 06*

   Line shape analysis of the K$\beta$ transition in muonic hydrogen

   D.S. Covita🇵🇹 · D.F. Anagnostopoulos🇬🇷 · H. Fuhrmann🇦🇹 · H. Gorke🇩🇪 · D. Gotta🇩🇪 · A. Gruber🇦🇹 · A. Hirtl🇦🇹 · T. Ishiwatari🇦🇹 · P. Indelicato🇫🇷 · T.S. Jensen🇨🇭 · E.-O. Le Bigot🇫🇷 · V.E. Markushin🇨🇭 and 10 other authors

   The K$\beta$ transition in muonic hydrogen was measured with a high-resolution crystal spectrometer. The spectrum is shown to be sensitive to the ground-state hyperfine splitting, the corresponding triplet-to-singlet ratio, and the kinetic energy distribution in the $3p$ state. The hyperfine splitting and triplet-to-singlet ratio are found to be consistent with the values expected from theoretical and experimental investigations and, therefore, were fixed accordingly in order to reduce the uncertainties in the further reconstruction of the kinetic energy distribution. The presence of high-energetic components was established and quantified in both a phenomenological, i.e. cascade-model-free fit, and in a direct deconvolution of the Doppler broadening based on the Bayesian approach.

   ↳ physics.atom-phnucl-exEur.Phys.J.D(2018)·10 citations
7. 07*

   The MCUCN simulation code for ultracold neutron physics

   G. Zsigmond🇨🇭

   Ultracold neutrons (UCN) have very low kinetic energies 0-300 neV, thereby can be stored in specific material or magnetic confinements for many hundreds of seconds. This makes them a very useful tool in probing fundamental symmetries of nature (for instance charge-parity violation by neutron electric dipole moment experiments) and contributing important parameters for the Big Bang nucleosynthesis (neutron lifetime measurements). Improved precision experiments are in construction at new and planned UCN sources around the world. MC simulations play an important role in the optimization of such systems with a large number of parameters, but also in the estimation of systematic effects, in benchmarking of analysis codes, or as part of the analysis. The MCUCN code written at PSI has been extensively used for the optimization of the UCN source optics and in the optimization and analysis of (test) experiments within the nEDM project based at PSI. In this paper we present the main features of MCUCN and interesting benchmark and application examples.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2018)·26 citations
8. 08*

   Stopping powers and energy loss straggling for MeV protons in a kapton polyimide thin film

   S. Damache (Division de Physique, CRNA)🇩🇿 · S. Djaroum (Division de Technologie Nucléaire, CRNB) · S. Ouichaoui (Université des Sciences et Technologie H. Boumediene (USTHB), Faculté de Physique) · L. Amari (Université des Sciences et Technologie H. Boumediene (USTHB), Faculté de Physique) · D. Moussa (Université des Sciences et Technologie H. Boumediene (USTHB), Faculté de Physique)🇩🇿

   The energy loss and energy loss straggling widths have been measured in transmission for MeV protons traversing a thin kapton polyimide foil. In a prior step, the thickness and non-uniformity of the target foil were carefully investigated. The overall relative uncertainties in the stopping power and energy loss straggling variance data amount, respectively, to less than 2% and 8%. The experimental data show to be in excellent agreement with available previous ones and with those compiled in the ICRU-49 report. They are fully consistent with the predictions of Sigmund-Schinner's binary collision theory of electronic stopping over the whole proton energy range explored. An average deviation of ~2.5% relative to values calculated by the SRIM-2008 code, likely due to effects of valence electrons involving the , and bonds, is however observed at low proton velocities. The measured energy loss straggling data, which are unique to our knowledge, are found to be in good agreement with values derived by the classical Bohr formula for keV but they significantly exceed Bohr's collisional energy loss straggling at lower proton velocities where target electrons can no longer be considered as free. They also show to be consistent with the predictions of the Bethe-Livingston and Sigmund-Schinner theories over the low proton velocity region ( keV). However, they are significantly overestimated by these theories over the intermediate and high proton velocity regions, which may be due to bunching effect by inner shell electrons of the polymer target. Besides, our energy loss straggling data are in better overall consistency with the Yang, O'Connor and Wang empirical formula for keV, while deviations above the latter amounting up to ~18% are observed at lower proton velocities. Keywords: Swift protons; Kapton polyimide; Stopping power; Energy loss straggling; Binary collision theory.

   ↳ physics.ins-detnucl-ex0 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.