Thu·Dec 17, 2015Thursday·December 17, 2015

1. 01*

   Radiative Decay of Neutron-Unbound Intruder States in ${}^{19}$O

   R.Dungan🇺🇸 · S.L. Tabor🇺🇸 · Vandana Tripathi · A.Volya🇺🇸 · K.Kravvaris · B.Abromeit · D.D.Caussyn🇺🇸 · S.Morrow🇺🇸 · J.J. Parker IV · P.-L. Tai · J.M. VonMoss

   The ${}^9$Be(${}^{14}$C, $\alpha$$\gamma$) reaction at E${}_{Lab}$=30 and 35 MeV was used to study excited states of ${}^{19}$O. The Florida State University (FSU) $\gamma$ detector array was used to detect $\gamma$ radiation in coincidence with charged particles detected and identified with a silicon $\Delta$E-E particle telescope. Gamma decays have been observed for the first time from six states ranging from 368 to 2147 keV above the neutron separation energy (S${}_n$=3962 keV) in ${}^{19}$O. The $\gamma$ decaying states are interspersed among states previously observed to decay by neutron emission. The ability of electromagnetic decay to compete successfully with neutron decay is explained in terms of neutron angular momentum barriers and small spectroscopic factors implying higher spin and complex structure for these intruder states. These results illustrate the need for complementary experimental approaches to best illuminate the complete nuclear structure.

   nucl-exPRC(2016)·8 citations
2. 02*

   Measurement of neutral mesons in pp and Pb-Pb collisions at mid-rapidity with ALICE

   Astrid Morreale (the ALICE collaboration)🇫🇷

   One of the key signatures of the Quark-Gluon Plasma (QGP), is the modification of hadron transverse momentum differential cross-sections in heavy-ion collisions (HIC) as compared to proton-proton (pp) collisions. Suppression of hadron production at high transverse momenta (\pt)~in HIC has been explained by the energy loss of the partons produced in the hard scattering processes which traverse the deconfined quantum chromodynamic (QCD) matter. The dependence of the observed suppression on the \pt~ of the measured hadron towards higher \pt~ is an important input for the theoretical understanding of jet quenching effects in the QGP and the nature of the energy loss. The ALICE experiment at the Large Hadron Collider (LHC) performs measurements of neutral meson inclusive spectra at mid-rapidity in a wide \pt~ range in $pp$, $p$-Pb and Pb-Pb collisions. Neutral mesons (${\pi }^0$, $\eta$, $\omega$) are reconstructed via complementary methods, using the ALICE electromagnetic calorimeters, PHOS and EMCal, and by the central tracking system, identifying photons converted into $e^{+}{e}^{-}$ pairs in the material of the inner barrel detectors (TPC and ITS). In this presentation, an overview of current ${\pi }^0$ and $\eta$ measurements by the ALICE experiment in HIC and pp collisions will be given.

   nucl-exNPA(2016)·7 citations
3. 03*

   Fluctuations of conserved charges in relativistic heavy ion collisions: An introduction

   Masayuki Asakawa🇯🇵 · Masakiyo Kitazawa🇯🇵

   Bulk fluctuations of conserved charges measured by event-by-event analysis in relativistic heavy ion collisions are observables which are believed to carry significant amount of information on the hot medium created by the collisions. Active studies have been done recently experimentally, theoretically, and on the lattice. In particular, non-Gaussianity of the fluctuations has acquired much attention recently. In this review, we give a pedagogical introduction to these issues, and survey recent developments in this field of research. Starting from the definition of cumulants, basic concepts in fluctuation physics, such as thermal fluctuations in statistical mechanics and time evolution of fluctuations in diffusive systems, are described. Phenomena which are expected to occur in finite temperature and/or density QCD matter and their measurement by event-by-event analyses are also elucidated.

   ↳ nucl-thhep-phnucl-exPPNP(2016)·166 citations
4. 04*

   Electromagnetic selection rules in the triangular alpha-cluster model of 12C

   G.Stellin🇩🇪 · L.Fortunato🇮🇹 · A.Vitturi🇮🇹

   After recapitulating the procedure to find the bands and the states occurring in the ${\mathcal{D}}_{3h}$ alpha-cluster model of ${}^{12}$C in which the clusters are placed at the vertexes of an equilateral triangle, we obtain the selection rules for electromagnetic transitions. While the alpha cluster structure leads to the cancellation of E1 transitions, the approximations carried out in deriving the roto-vibrational hamiltonian lead to the disappearance of M1 transitions. Furthermore, although in general the lowest active modes are E2, E3, $\cdots$ and M2, M3, $\cdots$, the cancellation of M2, M3 and M5 transitions between certain bands also occurs, as a result of the application of group theoretical techniques drawn from molecular physics. These implications can be very relevant for the spectroscopic analysis of $\gamma$-ray spectra of ${}^{12}$C.

   ↳ nucl-thnucl-exphysics.atm-clusJ.Phys.G(2016)·16 citations
5. 05*

   Heavy-flavour production in high-energy d-Au and p-Pb collisions

   Andrea Beraudo🇮🇹 · Arturo De Pace🇮🇹 · Marco Monteno🇮🇹 · Marzia Nardi🇮🇹 · Francesco Prino🇮🇹

   Soft-hadron measurements in high-energy collisions of small systems like p-Pb and d-Au show peculiar qualitative features (long-range rapidity correlations, flattening of the $p_T$-spectra with increasing hadron mass and centrality, non-vanishing Fourier harmonics in the azimuthal particle distributions) suggestive of the formation of a strongly-interacting medium displaying a collective behaviour, with a hydrodynamic flow as a response to the pressure gradients in the initial conditions. Hard observables (high-$p_T$ jet and hadron spectra) on the other hand, within the current large systematic uncertainties, appear only midly modified with the respect to the benchmark case of minimum-bias p-p collisions. What should one expect for heavy-flavour particles, initially produced in hard processes but tending, in the nucleus-nucleus case, to approach kinetic equilibrium with the rest of the medium? This is the issue we address in the present study, showing how the current experimental findings are compatible with a picture in which the formation of a hot medium even in proton-nucleus collisions modifies the propagation and hadronization of heavy-flavour particles.

   ↳ hep-phnucl-exnucl-thJHEP(2016)·76 citations
6. 06*

   Charged-Particle Multiplicity Distributions over a Wide Pseudorapidity Range in Proton-Proton Collisions with ALICE

   Valentina Zaccolo (for the ALICE Collaboration)🇩🇰

   Multiplicity distributions of charged particles for pp collisions at LHC Run 1 energies, from $\sqrt{s}=$ 0.9 to 8 TeV are measured over a wide pseudorapidity range ($-3.4<\eta <5.0$) for the first time. The results are obtained using the Forward Multiplicity Detector and the Silicon Pixel Detector within ALICE. The results are compared to Monte Carlo simulations, and to the IP-Glasma model.

   ↳ hep-exnucl-exNPA(2016)·10 citations
7. 07*

   The Trigger System for the External Target Experiment in CSR of HIRFL

   Min Li🇺🇸 · Lei Zhao🇨🇳 · Jin Xin Liu🇨🇳 · Yi Ming Lu · Shu Bin Liu🇨🇳 · Qi An🇨🇳

   A trigger system was designed for the external target experiment in the Cooling Storage Ring (CSR) of the Heavy Ion Research Facility in Lanzhou (HIRFL). Considering that different detectors are scattered in a large area, the trigger system is designed based on a master-slave structure and fiber-based serial data transmission technique. The trigger logic is organized in hierarchies, and flexible reconfiguration of the trigger function is achieved based on command register access or overall field-programmable gate array (FPGA) logic on-line reconfiguration controlled by remote computers. We also conducted tests to confirm the function of the trigger electronics, and the results indicate that this trigger system works well.

   ↳ physics.ins-detnucl-exCPC(2016)·4 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.