Wed·May 4, 2016Wednesday·May 4, 2016

1. 01*

   Aspects of the momentum dependence of the equation of state and of the residual $NN$ cross section, and their effects on nuclear stopping

   Z. Basrak🇭🇷 · P. Eudes🇫🇷 · V. de la Mota🇫🇷

   With the semiclassical Landau-Vlasov transport model we studied the stopping observable $R_E$, the energy-based isotropy ratio, for the ${}^{129}$Xe\,+\,${}^{120}$Sn reaction at beam energies spanning 12$A$ to 100$A$ MeV. We investigated the impacts of the nonlocality of the nuclear mean field, of the in-medium modified nucleon-nucleon ($NN$) cross section and of the reaction centrality. A fixed set of model parameters yields $R_E$ values that favorably compare with the experimental ones, but only for energies below the Fermi energy $E_F$. Above $E_F$ agreement is readily possible, but by a smooth evolution with energy of the parameter that controls the in-medium modification of $NN$ cross section. By comparing the simulation correction factor $\mathcal{F}$ applied to the free $NN$ cross section with the one deduced from experimental data [Phys.\ Rev.\ C\,{\bf 90}, 064602 (2014)], we infer that the zero-range mean field almost entirely reproduces it. Also, in accordance with what has been deduced from experimental data, around $E_F$ a strong reduction of the free $NN$ cross section is found. In order to test the impact of sampling central collisions by multiplicity an event generator (HIPSE) was used. We obtain that high multiplicity events are spread over a broad impact parameter range, but it turns out that this has a small effect on the observable $R_E$ and, thus, on $\mathcal{F}$ as well.

   nucl-exnucl-thPRC(2016)·23 citations
2. 02*

   Search for neutrinoless double beta decay

   Igor Ostrovskiy🇺🇸 · Kevin O'Sullivan🇺🇸

   We review current experimental efforts to search for neutrinoless double beta decay (0$\nu \beta \beta$). A description of the selected leading experiments is given and the strongest recent results are compared in terms of achieved background indexes and limits on effective Majorana mass. A combined limit is also shown. The second part of the review covers next generation experiments, highlighting the challenges and new technologies that may be necessary to achieve a justifiable discovery potential. A potential synergy with direct dark matter searches, which could be an especially prudent strategy in case the axial vector coupling constant is quenched in 0$\nu \beta \beta$ decay, is emphasized.

   ↳ hep-exnucl-exphysics.ins-detMod.Phys.Lett.A(2016)·29 citations
3. 03*

   Algebraic benchmark for prolate-oblate coexistence in nuclei

   A. Leviatan🇮🇱 · D. Shapira🇺🇸

   We present a symmetry-based approach for prolate-oblate and spherical-prolate-oblate shape coexistence, in the framework of the interacting boson model of nuclei. The proposed Hamiltonian conserves the SU(3) and $\overline{\mathrm{SU}(3)}$ symmetry for the prolate and oblate ground bands and the U(5) symmetry for selected spherical states. Analytic expressions for quadrupole moments and $E2$ rates involving these states are derived and isomeric states are identified by means of selection rules.

   ↳ nucl-thnucl-exquant-phPRC(2016)·23 citations
4. 04*

   Development of the MICROMEGAS Detector for Measuring the Energy Spectrum of Alpha Particles by using a 241-Am Source

   Do Yoon Kim🇰🇷 · Cheolmin Ham🇰🇷 · Jae Won Shin🇰🇷 · Tae-Sun Park🇰🇷 · Seung-Woo Hong🇰🇷 · Samuel Andriamonje🇨🇭 · Yacine Kadi🇨🇭 · Claudio Tenreiro🇨🇱

   We have developed MICROMEGAS (MICRO MEsh GASeous) detectors for detecting {\alpha} particles emitted from an 241-Am standard source. The voltage applied to the ionization region of the detector is optimized for stable operation at room temperature and atmospheric pressure. The energy of {\alpha} particles from the 241-Am source can be varied by changing the flight path of the {\alpha} particle from the 241 Am source. The channel numbers of the experimentally-measured pulse peak positions for different energies of the {\alpha} particles are associated with the energies deposited by the alpha particles in the ionization region of the detector as calculated by using GEANT4 simulations; thus, the energy calibration of the MICROMEGAS detector for {\alpha} particles is done. For the energy calibration, the thickness of the ionization region is adjusted so that {\alpha} particles may completely stop in the ionization region and their kinetic energies are fully deposited in the region. The efficiency of our MICROMEGAS detector for {\alpha} particles under the present conditions is found to be ~ 97.3 %.

   ↳ physics.ins-detnucl-exJ.Korean Phys.Soc.(2016)·3 citations
5. 05*

   Characterization of PARIS LaBr${}_3$(Ce)-NaI(Tl) phoswich detectors upto $E_{\gamma }$ $\sim$ 22 MeV

   C. Ghosh🇮🇳 · V. Nanal🇮🇳 · R.G. Pillay🇮🇳 · Anoop K.V🇮🇳 · N. Dokania🇮🇳 · Sanjoy Pal🇮🇳 · M.S. Pose🇮🇳 · G. Mishra🇮🇳 · P.C. Rout🇮🇳 · Suresh Kumar🇮🇳 · Deepak Pandit🇮🇳 · Debasish Mondal🇮🇳 and 7 other authors

   In order to understand the performance of the PARIS (Photon Array for the studies with Radioactive Ion and Stable beams) detector, detailed characterization of two individual phoswich (LaBr${}_3$(Ce)-NaI(Tl)) elements has been carried out. The detector response is investigated over a wide range of $E_{\gamma }$ = 0.6 to 22.6 MeV using radioactive sources and employing ${}^{11}B(p,\gamma )$ reaction at $E_p$ = 163 keV and $E_p$ = 7.2 MeV. The linearity of energy response of the LaBr${}_3$(Ce) detector is tested upto 22.6 MeV using three different voltage dividers. The data acquisition system using CAEN digitizers is set up and optimized to get the best energy and time resolution. The energy resolution of $\sim$ 2.1% at $E_{\gamma }$ = 22.6~MeV is measured for the configuration giving best linearity upto high energy. Time resolution of the phoswich detector is measured with a ${}^{60}$Co source after implementing CFD algorithm for the digitized pulses and is found to be excellent (FWHM $\sim$ 315~ps). In order to study the effect of count rate on detectors, the centroid position and width of the $E_{\gamma }$ = 835~keV peak were measured upto 220 kHz count rate. The measured efficiency data with radioactive sources are in good agreement with GEANT4 based simulations. The total energy spectrum after the add-back of energy signals in phoswich components is also presented.

   ↳ physics.ins-detnucl-exJINST(2016)·15 citations
6. 06*

   Transverse pion structure beyond leading twist in constituent models

   C. Lorcé (Ecole Polytechnique, CPHT)🇫🇷 · B. Pasquini (Pavia U. & INFN, Pavia)🇮🇹 · P. Schweitzer (Connecticut U. and Tubingen U.)🇺🇸

   The understanding of the pion structure as described in terms of transverse-momentum dependent parton distribution functions (TMDs) is of importance for the interpretation of currently ongoing Drell-Yan experiments with pion beams. In this work we discuss the description of pion TMDs beyond leading twist in a pion model formulated in the light-front constituent framework. For comparison, we also review and derive new results for pion TMDs in the bag and spectator models.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2016)·48 citations
7. 07*

   Multidimensionally-constrained covariant density functional theories --- nuclear shapes and potential energy surfaces

   Shan-Gui Zhou🇨🇳

   The intrinsic nuclear shapes deviating from a sphere not only manifest themselves in nuclear collective states but also play important roles in determining nuclear potential energy surfaces (PES's) and fission barriers. In order to describe microscopically and self-consistently nuclear shapes and PES's with as many shape degrees of freedom as possible included, we developed multidimensionally-constrained covariant density functional theories (MDC-CDFTs). In MDC-CDFTs, the axial symmetry and the reflection symmetry are both broken and all deformations characterized by ${\beta }_{\lambda \mu }$ with even $\mu$ are considered. We have used the MDC-CDFTs to study PES's and fission barriers of actinides, the non-axial octupole $Y_{32}$ correlations in $N=150$ isotones and shapes of hypernuclei. In this Review we will give briefly the formalism of MDC-CDFTs and present the applications to normal nuclei.

   ↳ nucl-thnucl-exPhys.Scripta(2016)·133 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.