Mon·Oct 6, 2014Monday·October 6, 2014

1. 01*

   Shell structure of potassium isotopes deduced from their magnetic moments

   J. Papuga🇧🇪 · M.L. Bissell🇧🇪 · K. Kreim🇩🇪 · C. Barbieri🇬🇧 · K. Blaum🇩🇪 · M. De Rydt🇧🇪 · T. Duguet🇫🇷 · R.F. Garcia Ruiz🇧🇪 · H. Heylen🇧🇪 · M. Kowalska🇨🇭 · R. Neugart🇩🇪 · G. Neyens🇧🇪 and 6 other authors

   \item[Background] Ground-state spins and magnetic moments are sensitive to the nuclear wave function, thus they are powerful probes to study the nuclear structure of isotopes far from stability. \item[Purpose] Extend our knowledge about the evolution of the $1/2^{+}$ and $3/2^{+}$ states for K isotopes beyond the $N=28$ shell gap. \item[Method] High-resolution collinear laser spectroscopy on bunched atomic beams. \item[Results] From measured hyperfine structure spectra of K isotopes, nuclear spins and magnetic moments of the ground states were obtained for isotopes from $N=19$ up to $N=32$. In order to draw conclusions about the composition of the wave functions and the occupation of the levels, the experimental data were compared to shell-model calculations using SDPF-NR and SDPF-U effective interactions. In addition, a detailed discussion about the evolution of the gap between proton $1d_{3/2}$ and $2s_{1/2}$ in the shell model and {\it{ab initio}} framework is also presented. \item[Conclusions] The dominant component of the wave function for the odd-$A$ isotopes up to ${}^{45}$K is a $\pi 1d_{3/2}^{-1}$ hole. For ${}^{47,49}$K, the main component originates from a $\pi 2s_{1/2}^{-1}$ hole configuration and it inverts back to the $\pi 1d_{3/2}^{-1}$ in ${}^{51}$K. For all even-$A$ isotopes, the dominant configuration arises from a $\pi 1d_{3/2}^{-1}$ hole coupled to a neutron in the $\nu 1f_{7/2}$ or $\nu 2p_{3/2}$ orbitals. Only for ${}^{48}$K, a significant amount of mixing with $\pi 2s_{1/2}^{-1}\otimes \nu (pf)$ is observed leading to a $I^{\pi }=1^{-}$ ground state. For ${}^{50}$K, the ground-state spin-parity is $0^{-}$ with leading configuration $\pi 1d_{3/2}^{-1}\otimes \nu 2p_{3/2}^{-1}$.

   nucl-exnucl-thPRC(2014)·52 citations
2. 02*

   Hadronic observables from a hadronic rescattering model in $Pb+Pb$ collisions at $\sqrt{s_{NN}}=2.76$ TeV

   J. T. Buxton🇺🇸 · T. J. Humanic🇺🇸

   We employ a simple kinematic model based on the superposition of $p+p$ collisions, relativistic kinematics, and final-state hadronic rescattering to calculate a number of hadronic observables in $\sqrt{s_{NN}}=2.76$ TeV $Pb+Pb$ collisions. The current model is similar to those used in previous studies, but includes an additional procedure ("squeeze procedure") which modifies the model pseudorapidity distribution to better represent the experimental data. In addition, we vary the model hadronization time ($\tau$ = 0.1, 0.2, 0.3 fm/c) to gain a better understanding of our systematic uncertainty. We find that the simple model describes the overall data reasonably well qualitatively, and in some cases quantitatively. Furthermore, the model is found to be robust in the sense that using the squeeze procedure and small variations of the hadronization proper time do not significantly affect our results.

   nucl-exnucl-th0 citations
3. 03*

   Lee-Yang zero distribution of high temperature QCD and Roberge-Weiss phase transition

   Keitaro Nagata🇯🇵 · Kouji Kashiwa🇯🇵 · Atsushi Nakamura🇯🇵 · Shinsuke M. Nishigaki🇯🇵

   Canonical partition functions and Lee-Yang zeros of QCD at finite density and high temperature are studied. Recent lattice simulations have confirmed that the free energy of QCD is a quartic function of quark chemical potential at temperature slightly above pseudo-critical temperature $T_c$, as in the case with a gas of free massless fermions. We present analytic derivation of the canonical partition functions and Lee-Yang zeros for this type of free energy using the saddle point approximation. We also perform lattice QCD simulation in a canonical approach using the fugacity expansion of the fermion determinant, and carefully examine its reliability. By comparing the analytic and numerical results, we conclude that the canonical partition functions follow the Gaussian distribution of the baryon number, and the accumulation of Lee-Yang zeros of these canonical partition functions exhibit the first-order Roberge-Weiss phase transition. We discuss the validity and applicable range of the result and its implications both for theoretical and experimental studies.

   ↳ hep-lathep-exhep-phnucl-exPRD(2015)·42 citations
4. 04*

   Production, characterization and operation of ${}^{76}$Ge enriched BEGe detectors in GERDA

   M. Agostini🇩🇪 · M. Allardt🇩🇪 · E. Andreotti🇧🇪 · A.M. Bakalyarov🇷🇺 · M. Balata🇮🇹 · I. Barabanov🇷🇺 · N. Barros🇩🇪 · L. Baudis🇨🇭 · C. Bauer🇩🇪 · N. Becerici-Schmidt🇩🇪 · E. Bellotti🇮🇹 · S. Belogurov🇷🇺 and 100 other authors

   The GERmanium Detector Array (GERDA) at the Gran Sasso Underground Laboratory (LNGS) searches for the neutrinoless double beta decay (0{\nu}{\beta}{\beta}) of ${}^{76}$Ge. Germanium detectors made of material with an enriched ${}^{76}$Ge fraction act simultaneously as sources and detectors for this decay. During Phase I of the experiment mainly refurbished semi-coaxial Ge detectors from former experiments were used. For the upcoming Phase II, 30 new ${}^{76}$Ge enriched detectors of broad energy germanium (BEGe)-type were produced. A subgroup of these detectors has already been deployed in GERDA during Phase I. The present paper reviews the complete production chain of these BEGe detectors including isotopic enrichment, purification, crystal growth and diode production. The efforts in optimizing the mass yield and in minimizing the exposure of the ${}^{76}$Ge enriched germanium to cosmic radiation during processing are described. Furthermore, characterization measurements in vacuum cryostats of the first subgroup of seven BEGe detectors and their long-term behavior in liquid argon are discussed. The detector performance fulfills the requirements needed for the physics goals of GERDA Phase~II.

   ↳ physics.ins-dethep-exnucl-exEPJC(2015)·85 citations
5. 05*

   The structure of rotational bands in alpha-cluster nuclei

   Roelof Bijker🇲🇽

   In this contribution, I discuss an algebraic treatment of alpha-cluster nuclei based on the introduction of a spectrum generating algebra for the relative motion of the alpha-clusters. Particular attention is paid to the discrete symmetry of the geometric arrangement of the alpha-particles, and the consequences for the structure of the rotational bands in the 12C and 16O nuclei.

   ↳ nucl-thnucl-exEPJ Web Conf.(2015)·3 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.