Tue·Jul 22, 2014Tuesday·July 22, 2014

1. 01*

   Inverse-kinematics proton scattering on ${}^{50}$Ca: Determining effective charges using complementary probes

   L. A. Riley🇺🇸 · M. L. Agiorgousis🇺🇸 · T. R. Baugher🇺🇸 · D. Bazin🇺🇸 · M. Bowry🇬🇧 · P. D. Cottle🇺🇸 · F. G. DeVone🇺🇸 · A. Gade🇺🇸 · M. T. Glowacki🇺🇸 · K. W. Kemper🇺🇸 · E. Lunderberg🇺🇸 · D. M. McPherson🇺🇸 and 6 other authors

   We have performed measurements of the $0_{g.s.}^{+}\to 2_1^{+}$ excitations in the neutron-rich isotopes ${}^{48,50}$Ca via inelastic proton scattering on a liquid hydrogen target, using the GRETINA $\gamma$-ray tracking array. A comparison of the present results with those from previous measurements of the lifetimes of the $2_1^{+}$ states provides us the ratio of the neutron and proton matrix elements for the $0_{g.s.}^{+}\to 2_1^{+}$ transitions. These results allow the determination of the ratio of the proton and neutron effective charges to be used in shell model calculations of neutron-rich isotopes in the vicinity of ${}^{48}$Ca.

   nucl-exPRC(2014)·19 citations
2. 02*

   Event-by-event mean $p_{\mathrm{T}}$ fluctuations in pp and Pb-Pb collisions at the LHC

   ALICE Collaboration

   Event-by-event fluctuations of the mean transverse momentum of charged particles produced in pp collisions at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV, and Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV are studied as a function of the charged-particle multiplicity using the ALICE detector at the LHC. Dynamical fluctuations indicative of correlated particle emission are observed in all systems. The results in pp collisions show little dependence on collision energy. The Monte Carlo event generators PYTHIA and PHOJET are in qualitative agreement with the data. Peripheral Pb-Pb data exhibit a similar multiplicity dependence as that observed in pp. In central Pb-Pb, the results deviate from this trend, featuring a significant reduction of the fluctuation strength. The results in Pb--Pb are in qualitative agreement with previous measurements in Au-Au at lower collision energies and with expectations from models that incorporate collective phenomena.

   nucl-exhep-exEPJC(2014)·138 citations
3. 03*

   Giant Dipole Resonance as a Fingerprint of $\alpha$ Clustering Configurations in ${}^{12}$C and ${}^{16}$O

   W. B. He · Y. G. Ma🇨🇳 · X. G. Cao🇨🇳 · X. Z. Cai🇨🇳 · G. Q. Zhang🇨🇳

   It is studied how the $\alpha$ cluster degrees of freedom, such as $\alpha$ clustering configurations close to the $\alpha$ decay threshold in ${}^{12}$C and ${}^{16}$O, including the linear chain, triangle, square, kite, and tetrahedron, affect nuclear collective vibrations with a microscopic dynamical approach, which can describe properties of nuclear ground states well across the nuclide chart and reproduce the standard giant dipole resonance (GDR) of ${}^{16}$O quite nicely. It is found that the GDR spectrum is highly fragmented into several apparent peaks due to the $\alpha$ structure. The different $\alpha$ cluster configurations in ${}^{12}$C and ${}^{16}$O have corresponding characteristic spectra of GDR. The number and centroid energies of peaks in the GDR spectra can be reasonably explained by the geometrical and dynamical symmetries of $\alpha$ clustering configurations. Therefore, the GDR can be regarded as a very effective probe to diagnose the different $\alpha$ cluster configurations in light nuclei.

   ↳ nucl-thnucl-exPRL(2014)·144 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.