948 research outputs found

    Evidence for flow in pPb collisions at 5 TeV from v2 mass splitting

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    We show that a fluid dynamical scenario describes quantitatively the observed mass splitting of the elliptical flow coefficients v2 for pions, kaons, and protons. This provides a strong argument in favor of the existence of a fluid dynamical expansion in pPb collisions at 5TeV

    Compulsory Community Care for the Mentally Ill

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    At the present time, the benefits of community care are limited to voluntary patients, but they should be extended to involuntary patients as well. This paper discusses the need for compulsory community care and the steps taken to meet this need in a few states and in Britain. Finally, it proposes legislation which could cope with the problems of providing community care for the civilly committed

    Jets, Bulk Matter, and their Interaction in Heavy Ion Collisions at Several TeV

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    We discuss a theoretical scheme that accounts for bulk matter, jets, and the interaction between the two. The aim is a complete description of particle production at all transverse momentum (ptp_{t}) scales. In this picture, the hard initial scatterings result in mainly longitudinal flux tubes, with transversely moving pieces carrying the ptp_{t} of the partons from hard scatterings. These flux tubes constitute eventually both bulk matter (which thermalizes and flows) and jets. We introduce a criterion based on parton energy loss to decide whether a given string segment contributes to the bulk or leaves the matter to end up as a jet of hadrons. Essentially low ptp_{t} segments from inside the volume will constitute the bulk, high ptp_{t} segments (or segments very close to the surface) contribute to the jets. The latter ones appear after the usual flux tube breaking via q-qbar production (Schwinger mechanism). Interesting is the transition region: Intermediate ptp_{t} segments produced inside the matter close to the surface but having enough energy to escape, are supposed to pick up q-qbar pairs from the thermal matter rather than creating them via the Schwinger mechanism. This represents a communication between jets and the flowing bulk matter (fluid-jet interaction). Also very important is the interaction between jet hadrons and the soft hadrons from the fluid freeze-out. We employ the new picture to investigate Pb-Pb collisions at 2.76 TeV. We discuss the centrality and ptp_{t} dependence of particle production and long range dihadron correlations at small and large ptp_{t}

    Hypernuclei, dibaryon and antinuclei production in high energy heavy ion collisions: Thermal production vs. Coalescence

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    We study the production of (hyper-)nuclei and di-baryons in most central heavy Ion collisions at energies of Elab=1160AE_{lab}=1-160 A GeV. In particular we are interested in clusters produced from the hot and dense fireball. The formation rate of strange and non-strange clusters is estimated by assuming thermal production from the intermediate phase of the UrQMD-hydro hybrid model and alternatively by the coalescence mechanism from a hadronic cascade model. Both model types are compared in detail. For most energies we find that both approaches agree in their predictions for the yields of the clusters. Only for very low beam energies, and for di-baryons including Ξ\Xi's, we observe considerable differences. We also study the production of anti-matter clusters up to top RHIC energies and show that the observation of anti-4He^4He and even anti-Λ4He^4_{\Lambda}He is feasible. We have found a considerable qualitative difference in the energy dependence of the strangeness population factor RHR_H when comparing the thermal production with the coalescence results.Comment: 9 pages, 8 figures and 2 tables, version accepted by PL

    Association between recurrent bacterial vaginosis and Helicobacter pylori infection: a case report

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    Background: Nearly one in three women in the United States are affected by bacterial vaginosis at some point in their life, with more than fifty percent experiencing recurrent symptoms within 12 months. Case: A 36 year old G9P2072 with 1 year history of recurrent bacterial vaginosis despite repeated treatments with local and systemic metronidazole, metronidazole suppression, and probiotic therapy had relief of bacterial vaginosis following triple antibiotic therapy for Helicobacter pylori. She remains asymptomatic for both bacterial vaginosis and Helicobacter pylori at 6 month follow up. Discussion: We present a woman with recurrent bacterial vaginosis who had sudden relief of her symptoms following treatment for Helicobacter pylori. While association should not be construed as causation, similar pathogenesis may warrant investigation of H pylori as a potential cause of the complex change in the vaginal flora leading to bacterial vaginosis

    Production of Theta(1540) and Xi Pentaquark States in Proton-Proton Interactions

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    The production of strange pentaquark states (e.g. Theta baryons and Xi^-- states) in hadronic interactions within a Gribov-Regge approach is explored. In this approach the Theta^+(1540) and the Xi Pentaquark are produced by disintegration of remnants formed by the exchange of pomerons between the two protons. We predict the rapidity and transverse momentum distributions as well as the 4 pi multiplicity of the Theta^+, Xi^--, Xi^-, Xi^0 and Xi^+ for sqrt{s} = 17 GeV (SPS) and 200 GeV (RHIC). For both energies more than 10^{-3} Theta^+ and more than 10^{-5} Xi per pp event should be observed by the present experiments.Comment: Predictions for Xi Pentaquarks added. Phys. Lett. B in prin

    UrQMD calculations of two-pion HBT correlations in p+p and Pb+Pb collisions at LHC energies

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    Two-pion Hanbury-Brown-Twiss (HBT) correlations for p+p and central Pb+Pb collisions at the Large-Hadron-Collider (LHC) energies are investigated with the ultra-relativistic quantum molecular dynamics model combined with a correlation afterburner. The transverse momentum dependence of the Pratt-Bertsch HBT radii RlongR_{long}, RoutR_{out}, and RsideR_{side} is extracted from a three-dimensional Gaussian fit to the correlator in the longitudinal co-moving system. In the p+p case, the dependence of correlations on the charged particle multiplicity and formation time is explored and the data allows to constrain the formation time in the string fragmentation to τf0.8\tau_f \leq 0.8 fm/c. In the Pb+Pb case, it is found that RoutR_{out} is overpredicted by nearly 50%. The LHC results are also compared to data from the STAR experiment at RHIC. For both energies we find that the calculated Rout/RsideR_{out}/R_{side} ratio is always larger than data, indicating that the emission in the model is less explosive than observed in the data.Comment: 9 pages, 4 figures, 1 table. Talk given by Qingfeng Li at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS

    Baryonic contributions to the dilepton spectra in relativistic heavy ion collisions

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    We investigate the baryonic contributions to the dilepton yield in high energy heavy ion collisions within the context of a transport model. The relative contribution of the baryonic and mesonic sources are examined. It is observed that most dominant among the baryonic channels is the decay of N*(1520) and mostly confined in the region below the rho peak. In a transport theory implementation we find the baryonic contribution to the lepton pair yield to be small.Comment: 11 pages, 8 figure

    Probing the density dependence of the symmetry potential in intermediate energy heavy ion collisions

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    Based on the ultrarelativistic quantum molecular dynamics (UrQMD) model, the effects of the density-dependent symmetry potential for baryons and of the Coulomb potential for produced mesons are investigated for neutron-rich heavy ion collisions at intermediate energies. The calculated results of the Delta-/Delta++ and pi -/pi + production ratios show a clear beam-energy dependence on the density-dependent symmetry potential, which is stronger for the pi -/pi + ratio close to the pion production threshold. The Coulomb potential of the mesons changes the transverse momentum distribution of the pi -/pi + ratio significantly, though it alters only slightly the pi- and pi+ total yields. The pi- yields, especially at midrapidity or at low transverse momenta and the p-/pi+ ratios at low transverse momenta, are shown to be sensitive probes of the density-dependent symmetry potential in dense nuclear matter. The effect of the density-dependent symmetry potential on the production of both, K0 and K+ mesons, is also investigated
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