Nuclear Experiment·nucl-ex
9 papers—4 primary·5 cross-listed·reconstructed*
WA98 Collaboration
Measurements of direct photon production in p+Pb and p+C collisions at are presented. Upper limits on the direct photon yield as a function of are derived and compared to the results for Pb+Pb collisions at GeV. The production of the meson, which is an important input to the direct photon signal extraction, has been determined in the channel for p+C collisions at .
Wenqin Xu (for the STAR Collaboration)🇺🇸
We present preliminary results of Non-Photonic Electron (NPE) production, NPE-hadron azimuthal correlation as well as NPE elliptic flow studies at midrapidity using a data set with high statistics and low photon conversion background from collisions at GeV collected at RHIC in Run 2010.
W. Trautmann · A. S. Botvina · J. Brzychczyk · N. Buyukcizmeci · I. N. Mishustin · P. Pawlowski · ALADIN2000 Collaboration
The neutron emission in the fragmentation of stable and radioactive Sn and La projectiles of 600 MeV per nucleon has been studied with the Large Neutron Detector LAND coupled to the ALADIN forward spectrometer at SIS. A cluster-recognition algorithm is used to identify individual particles within the hit distributions registered with LAND. The obtained momentum distributions are extrapolated over the full phase space occupied by the neutrons from the projectile-spectator source. The mean multiplicities of spectator neutrons reach values of up to 12 and depend strongly on the isotopic composition of the projectile. An effective source temperature of T approx. 3 - 4 MeV is deduced from the transverse momentum distributions. For the interpretation of the data, calculations with the Statistical Multifragmentation Model for a properly chosen ensemble of excited sources were performed. The possible modification of the liquid-drop parameters of the fragment description in the hot environment is studied, and a significant reduction of the symmetry-term coefficient is found necessary to simultaneously reproduce the neutron multiplicities and the mean neutron-to-proton ratios <N>/Z of Z <= 10 fragments. Because of the similarity of the freeze-out conditions with those encountered in supernova scenarios, this is of astrophysical interest.
T. Ishiwatari · M. Bazzi · G. Beer · C. Berucci · L. Bombelli · A.M. Bragadireanu · M. Cargnelli · A. Clozza · G. Corradi · C. Curceanu (Petrascu) · A. d'Uffizi · C. Fiorini and 29 other authors
The strong-interaction shift of kaonic 3He and 4He 2p states was measured using gaseous targets for the first time in the SIDDHARTA experiment. The determined shift of kaonic 4He is much smaller than the values obtained in the experiments performed in 70's and 80's. Thus, the problems in kaonic helium (the "kaonic helium puzzle") was definitely solved by our measurements. The first observation of the kaonic 3He X-rays was also achieved. The shift both of kaonic 3He and 4He was found to be as small as a few eV.
Ulrich W. Heinz🇺🇸 · J. Scott Moreland (Ohio State)🇺🇸
Due to gluon saturation, the growth of the inelastic nucleon-nucleon cross section with increasing collision energy sqrt(s) results in a broadening of the nucleon's density distribution in position space. This leads to a natural smoothing of the initial energy density distribution in the transverse plane of the matter created near midrapidity in heavy-ion collisions. We study this effect for fluctuating initial conditions generated with the Monte Carlo Kharzeev-Levin-Nardi (MC-KLN) model for Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). We argue that at the LHC viscous hydrodynamics is applicable at earlier times than at RHIC, not only because of the higher temperature but also since the length scale over which the initial pressure fluctuates increases with collision energy.
A. M. Sandorfi🇺🇸 · B. Dey🇺🇸 · A. Sarantsev🇩🇪 · L. Tiator🇩🇪 · R. Workman🇺🇸
A new generation of complete experiments in pseudoscalar meson photo-production is being pursued at several laboratories. While new data are emerging, there is some confusion regarding definitions of asymmetries and the conventions used in partial wave analyses (PWA). We present expressions for constructing asymmetries as coordinate-system independent ratios of cross sections, along with the names used for these ratios by different PWA groups. (This update reflects a recent change in the definition of an asymmetry as used by one group.)
The LHC brings nuclear collisions to the TeV scale for the first time and the first data show the qualitative differences of this new regime. The corresponding phase-space available encompasses completely uncharted regions of QCD in which high-density or high-temperature domains can be identified. Proton-nucleus runs are essential for a complete interpretation of the data and for the study of new regimes dominated by large occupation numbers in the hadronic wave function. I comment here the physics opportunities for p+Pb runs at the LHC and d+Au runs at RHIC and the corresponding needs in view of the new Pb+Pb data from the LHC.
Hadrons proceeding from quasi-real photo-production are one of the many probes accesible at the Common Muon Proton Apparatus for Structure and Spectroscopy (COMPASS) at CERN. These hadrons provide information on the scattering between photon and partons through \gamma-gluon(g) direct channels as well as q-g resolved processes. Comparisons of unpolarized differential cross section measurements to next-to-leading order (NLO) pQCD calculations are essential to develop our understanding of proton-proton and lepton-nucleon scattering at varying center of mass energies. These measurements are important to asses the applicability of NLO pQCD in interpreting polarized processes. In this talk we will present the unidentified charged separated hadron cross-sections measured by the COMPASS experiment at center of mass energy of \sqrt{s}=17GeV, low Q^{2} (Q^{2}<0.1GeV^{2}/c^{2}) and high transverse momenta (p_{T}>1.0 GeV/c.)
R. Acciarri · M. Antonello · F. Boffelli · M. Cambiaghi · N. Canci · F. Cavanna · A.G. Cocco · N. Deniskina · F. Di Pompeo · G. Fiorillo · C. Galbiati · L. Grandi and 17 other authors
Liquified noble gases are widely used as a target in direct Dark Matter searches. Signals from scintillation in the liquid, following energy deposition from the recoil nuclei scattered by Dark Matter particles (e.g. WIMPs), should be recorded down to very low energies by photosensors suitably designed to operate at cryogenic temperatures. Liquid Argon based detectors for Dark Matter searches currently implement photo multiplier tubes for signal read-out. In the last few years PMTs with photocathodes operating down to liquid Argon temperatures (87 K) have been specially developed with increasing Quantum Efficiency characteristics. The most recent of these, Hamamatsu Photonics Mod. R11065 with peak QE up to about 35%, has been extensively tested within the R&D program of the WArP Collaboration. During these testes the Hamamatsu PMTs showed superb performance and allowed obtaining a light yield around 7 phel/keVee in a Liquid Argon detector with a photocathodic coverage in the 12% range, sufficient for detection of events down to few keVee of energy deposition. This shows that this new type of PMT is suited for experimental applications, in particular for new direct Dark Matter searches with LAr-based experiments.
* 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.