Tue·Apr 21, 2015Tuesday·April 21, 2015

1. 01*

   Selecting specific initial configuration using spectator neutrons in U+U collisions

   Vipul Bairathi🇮🇳 · Md. Rihan Haque🇮🇳 · Bedangadas Mohanty🇮🇳

   We present a method to select events with specific initial configuration, namely body-tip, in heavy-ion collisions using deformed Uranium nuclei. We propose to use asymmetry in spectator neutron numbers to filter out these body-tip events from the unbiased configurations in U+U collisions. We have used a variable S_eta to differentiate between the body-tip and unbiased configurations. We have calculated the second order azimuthal anisotropy, namely elliptic flow (v2), for this body-tip configuration in the framework of a transport model and found it to be consistently lower compared to that in unbiased configurations as we expected. The purity of selecting such events in a real experiment is also discussed.

   nucl-exhep-phnucl-thPRC(2015)·14 citations
2. 02*

   Experimental constraints on the $\gamma$-ray strength function in ${}^{90}$Zr using partial cross sections of the ${}^{89}$Y(p,$\gamma$)${}^{90}$Zr reaction

   L. Netterdon🇩🇪 · A. Endres🇩🇪 · S. Goriely🇧🇪 · J. Mayer🇩🇪 · P. Scholz🇩🇪 · M. Spieker🇩🇪 · A. Zilges🇩🇪

   Partial cross sections of the ${}^{89}$Y(p,$\gamma$)${}^{90}$Zr reaction have been measured to investigate the $\gamma$-ray strength function in the neutron-magic nucleus ${}^{90}$Zr. For five proton energies between $E_p=3.65$ MeV and $E_p=4.70$ MeV, partial cross sections for the population of seven discrete states in ${}^{90}$Zr have been determined by means of in-beam $\gamma$-ray spectroscopy. Since these $\gamma$-ray transitions are dominantly of $E1$ character, the present measurement allows an access to the low-lying dipole strength in ${}^{90}$Zr. A $\gamma$-ray strength function based on the experimental data could be extracted, which is used to describe the total and partial cross sections of this reaction by Hauser-Feshbach calculations successfully. Significant differences with respect to previously measured strength functions from photoabsorption data point towards deviations from the Brink-Axel hypothesis relating the photo-excitation and de-excitation strength functions.

   nucl-exPLB(2015)·34 citations
3. 03*

   The cosmic ray muon tomography facility based on large scale MRPC detector

   Xuewu Wang🇨🇳 · Ming Zeng🇨🇳 · Zhi Zeng🇨🇳 · Yi Wang🇨🇳 · Ziran Zhao🇨🇳 · Xiaoguang Yue🇨🇳 · Zhifei Luo🇨🇳 · Hengguan Yi🇨🇳 · Baihui Yu🇨🇳 · Jianping Cheng🇨🇳

   Cosmic ray muon tomography is a novel technology to detect high-Z material. A prototype of TUMUTY with 73.6 cm x 73.6 cm large scale position sensitive MRPC detectors has been developed and is introduced in this paper. Three test kits have been tested and image is reconstructed using MAP algorithm. The reconstruction results show that the prototype is working well and the objects with complex structure and small size (20 mm) can be imaged on it, while the high-Z material is distinguishable from the low-Z one. This prototype provides a good platform for our further studies of the physical characteristics and the performances of cosmic ray muon tomography.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2015)·18 citations
4. 04*

   Microscopic study of low-lying spectra of $\Lambda$ hypernuclei based on a beyond-mean-field approach with covariant energy density functional

   H. Mei🇯🇵 · K. Hagino🇯🇵 · J.M. Yao🇯🇵 · T. Motoba🇯🇵

   We present a detailed formalism of the microscopic particle-rotor model for hypernuclear low-lying states based on a covariant density functional theory. In this method, the hypernuclear states are constructed by coupling a hyperon to low-lying states of the core nucleus, which are described by the generator coordinate method (GCM) with the particle number and angular momentum projections. We apply this method to study in detail the low-lying spectrum of ${}_{\Lambda }^{13}$C and ${}_{\Lambda }^{21}$Ne hypernuclei. We also briefly discuss the structure of ${}_{\Lambda }^{155}$Sm as an example of heavy deformed hypernuclei. It is shown that the low-lying excitation spectrum with positive parity states of the hypernuclei, which are dominated by $\Lambda$ hyperon in $s$-orbital coupled to the core states, are similar to that for the corresponding core states, while the electric quadrupole transition strength, $B(E2)$, from the 2${}_1^{+}$ state to the ground state is reduced according to the mass number of the hypernuclei. Our study indicates that the energy splitting between the first 1/2${}^{-}$ and 3/2${}^{-}$ hypernuclear states is generally small for all the hypernuclei which we study. However, their configurations depend much on the properties of a core nucleus, in particular on the sign of deformation parameter. That is, the first $1/2^{-}$ and $3/2^{-}$ states in ${}_{\Lambda }^{13}$C are dominated by a single configuration with $\Lambda$ particle in the $p$-wave orbits and thus providing good candidates for a study of the $\Lambda$ spin-orbit splitting. On the other hand, those states in the other hypernuclei exhibit a large configuration mixing and thus their energy difference cannot be interpreted as the spin-orbit splitting for the $p$-orbits.

   ↳ nucl-thnucl-exPRC(2015)·35 citations
5. 05*

   Electromagnetic Structure of Few-Nucleon Ground States

   L.E. Marcucci🇮🇹 · F. Gross🇺🇸 · M.T. Pena🇵🇹 · M. Piarulli🇺🇸 · R. Schiavilla🇺🇸 · I. Sick🇨🇭 · A. Stadler🇵🇹 · J.W. Van Orden🇺🇸 · M. Viviani🇮🇹

   Experimental form factors of the hydrogen and helium isotopes, extracted from an up-to-date global analysis of cross sections and polarization observables measured in elastic electron scattering from these systems, are compared to predictions obtained in three different theoretical approaches: the first is based on realistic interactions and currents, including relativistic corrections (labeled as the conventional approach); the second relies on a chiral effective field theory description of the strong and electromagnetic interactions in nuclei (labeled $\chi$EFT); the third utilizes a fully relativistic treatment of nuclear dynamics as implemented in the covariant spectator theory (labeled CST). For momentum transfers below $Q\lesssim 5$ fm${}^{-1}$ there is satisfactory agreement between experimental data and theoretical results in all three approaches. However, at $Q\gtrsim 5$ fm${}^{-1}$, particularly in the case of the deuteron, a relativistic treatment of the dynamics, as is done in the CST, is necessary. The experimental data on the deuteron $A$ structure function extend to $Q\simeq 12$ fm${}^{-1}$, and the close agreement between these data and the CST results suggests that, even in this extreme kinematical regime, there is no evidence for new effects coming from quark and gluon degrees of freedom at short distances.

   ↳ nucl-thnucl-exJ.Phys.G(2016)·67 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.