10 research outputs found
Xi and AntiXi production in Pb+Pb collisions at 40 AGeV at CERN SPS
First results on the production of Xi and AntiXi hyperons in Pb+Pb
interactions at 40 AGeV are presented. The AntiXi/Xi ratio at midrapidity is
studied as a function of collision centrality. The ratio shows no significant
centrality dependence within statistical errors; it ranges from 0.07 to 0.15.
The AntiXi/Xi ratio for central Pb+Pb collisions increases strongly with the
collision energy.Comment: 6 pages, 6 figures, proceedings of SQM03, to be published in Journal
of Physics G; V2: changes in table 1 and figure
Omega and AntiOmega production in Pb+Pb and p+p collisions at 30, 40 and 158 AGeV
We report preliminary results on Omega and AntiOmega production in central
Pb+Pb collisions at 30, 40 and 158 AGeV and p + p interactions at 158 GeV. The
midrapidity AntiOmega/Omega ratio is estimated to be 0.45 +- 0.05 and 0.41 +-
0.18 for central Pb+Pb collisions at 158 and 40 AGeV, respectively. The
corresponding value for 158 GeV p+p interactions is 0.67 +- 0.62. For central
Pb+Pb collisions at 158 AGeV fully corrected distributions are obtained. The
inverse slope parameters of the transverse mass spectrum and total yields are
T(Omega) = 276 +- 23 MeV, = 0.47 +- 0.07 and T(AntiOmega) = 285 +- 39
MeV, = 0.15 +- 0.02.Comment: Contribution to the proceedings of "Strangeness in Quark Matter 2003"
(March 2003, Atlantic Beach NC, USA), to be published in Journal of Physics
G., 6 pages, 6 figure
Experimental Precision Tests for the Electroweak Standard Model
This paper contains a review of recent precision measurements of electroweak
observables and resulting tests of the electroweak Standard Model.Comment: 78 page
Prospects for Pentaquark Searches in Annihilations and Collisions
Recent strong experimental evidence of a narrow exotic S = +1 baryon
resonance, , suggests the existence of other exotic baryons. We
discuss the prospects of confirming earlier experimental evidence of
and the observation of additional hypothetical exotic baryons in
annihilations and collisions at LEP and B Factories
Rigidity dependent knee and cosmic ray induced high energy neutrino fluxes
Scenarios in which the knee of the cosmic ray spectrum depends on the
particle rigidities usually predict that the cosmic ray composition becomes
heavier above the knee and have associated a change in the spectral slope of
each individual nuclear component which is steeper than the change
() observed in the total spectrum. We show that this
implies that the very high energy ( eV) diffuse neutrino fluxes
produced by cosmic rays hitting the atmosphere or colliding with the
interstellar medium in the Galaxy will be significantly suppressed, making
their detection harder but also reducing the background for the search of other
(more challenging) astrophysical neutrino sources.Comment: 20 pages, 5 figure
Strangeness from 20 AGeV to 158 AGeV
New results from the energy scan programme of NA49, in particular kaon
production at 30 AGeV and phi production at 40 and 80 AGeV are presented. The
K+/pi+ ratio shows a pronounced maximum at 30 AGeV; the kaon slope parameters
are constant at SPS energies. Both findings support the scenario of a phase
transition at about 30 AGeV beam energy. The phi/pi ratio increases smoothly
with beam energy, showing an energy dependence similar to K-/pi-. The measured
particle yields can be reproduced by a hadron gas model, with chemical
freeze-out parameters on a smooth curve in the T-muB plane. The transverse
spectra can be understood as resulting from a rapidly expanding, locally
equilibrated source. No evidence for an earlier kinetic decoupling of heavy
hyperons is found.Comment: Contribution to the proceedings of "Strangeness in Quark Matter 2003"
(March 2003, Atlantic Beach NC, USA), to be published in Journal of Physics
G. 11 pages, 14 figure
Dark Matter and Higgs Mass in the CMSSM with Yukawa Quasi-Unification
We present an updated analysis of the constrained minimal supersymmetric
standard model with mu>0 supplemented by an `asymptotic' Yukawa coupling
quasi-unification condition, which allows an acceptable b-quark mass. Imposing
constraints from the cold dark matter abundance in the universe, B physics, the
muon anomalous magnetic moment, and the mass m_h of the lightest neutral
CP-even Higgs boson, we find that the lightest neutralino cannot act as a cold
dark matter candidate. This is mainly because the upper bound on the lightest
neutralino relic abundance from cold dark matter considerations, despite the
fact that this abundance is drastically reduced by neutralino-stau
coannihilations, is incompatible with the recent data on the branching ratio of
B_s --> mu^+ mu^-. Allowing for a different particle, such as the axino or the
gravitino, to be the lightest supersymmetric particle and, thus, constitute the
cold dark matter in the universe, we find that the predicted m_h's in our model
favor the range (119-126) GeV.Comment: 13 pages including 4 figures and 1 table, talk given by G. Lazarides
at the 7th International Workshop on the Dark Side of the Universe, KITPC,
Beijing, China, September 26-30, 2011 (to appear in the proceedings
Event shapes in e+e- annihilation and deep inelastic scattering
This article reviews the status of event-shape studies in e+e- annihilation
and DIS. It includes discussions of perturbative calculations, of various
approaches to modelling hadronisation and of comparisons to data.Comment: Invited topical review for J.Phys.G; 40 pages; revised version
corrects some nomenclatur
Search for promptly produced heavy quarkonium states in hadronic Z decays
A search has been made for direct production of heavy quarkonium states in more than 3 million hadronic Z 0 decays in the 1991-1994 DELPHI data. Prompt J/ψ, ψ(2 S) and Γ candidates have been searched for through their leptonic decay modes using criteria based on the kinematics and decay vertex positions. New upper limits are set at the 90% confidence level for Br(Z 0→(Qq)X)/Br(Z 0→ hadrons) for various strong production mechanisms of J/ψ and Γ; these range down to 0.9×10-4. The limits are set in the presence of a small excess (∼1% statistical probability of a background fluctuation) in the sum of candidates from prompt J/ψ, ψ(2 S), γ(1 S), γ(2 S) and γ(3 S) relative to the estimated background. © 1996 Springer-Verlag.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe