Determination of the mass of the W boson

Previous studies of the physics potential of LEP2 indicated that with the design luminosity of 500 inverse picobarn one may get a direct measurement of the mass of the W-boson with a precision in the range 30 - 50 MeV. This report presents an updated evaluation of the estimated error on the mass of the W-boson based on recent simulation work and improved theoretical input. The most efficient experimental methods which will be used are also described

Radiation damage effect on avalanche photodiodes

Avalanche Photodiodes have been chosen as photon sensors for the electromagnetic calorimeter of the CMS experiment at the LHC. These sensors should operate in the 4T magnetic field of the experiment. Because of the high neutron radiation in the detector extensive studies have been done by the CMS collaboration on the APD neutron radiation damage. The characteristics of these devices after irradiation have been analized, with particular attention to the quantum efficiency and the dark current. The recovery of the radiation induced dark current has been studied carefully at room temperature and at slightly lower and higher temperatures. The temperature dependence of the defects decay-time has been evaluated

Study of vector mesons in dimuon production in a large kinematic region in p-W and S-W interactions at 200Gev/nucleons

Results are presented on rho + omega, phi and J/psi production in p-W and (32)S-W interactions at 200 GeV/c/nucleon measured via the dimuon decay in a large kinematic region. The data are normalized to the charged particle multiplicity in the same rapidity interval. They have been collected using the HELIOS/3 muon spectrometer at the CERN SPS. The ratio B sigma(phi)(B sigma(rho) + B sigma(omega)), where B is the relevant resonance mu mu branching fraction, increases between proton and sulphur projectiles, and is somewhat enhanced going from peripheral to central S-W interactions. This results from an increase in the number of produced phi's per charged particle. The ratio is measured in different intervals of p tau and rapidity. It is not clearly dependent on pr, but is larger at higher rapidities. J/psi production, likewise normalized to charged multiplicity, is significantly lower in S-W compared to p-W interactions

Excess of continuum dimuon production at masses between threshold and the J/Ψ in S-W interactions at 200-GeV/c/nucleon

Results are presented on dimuon production for invariant masses ranging from the dimuon threshold up to the J/Psi meson. Proton-tungsten and sulphur-tungsten interactions at 200 GeV/c/nucleon were measured over a large kinematic region, using the HELIOS/3 dimuon spectrometer at the CERN SPS. In the continuum regions between the dimuon threshold and the rho/omega mesons, and between the phi and J/Psi mesons, an excess is observed in S-W interactions relative to minimum bias p-W interactions. The observed excess is continuous over the explored mass range and has no apparent resonant structure. In the low mass region the dimuon yield increases by (76 +/- 4)% of the corresponding p-W dimuon spectrum, whereas in the higher mass region the excess amounts to 2.4 +/- 0.3 times the p-W yield. The observed excess for the low mass region follows an exponential transverse mass distribution with an average inverse slope parameter T of (190 +/- 5) MeV/c(2), constant for all but the lowest charged multiplicity interval and consistent with the slope of the excess in the higher mass region. In the invariant mass range of 1.35-2.5 GeV/c(2) the continuum dimuon mass distribution observed in p-W interactions can be quantitatively understood as a sum of three expected contributions (vector meson decays, semileptonic charm decays and Drell-Yan process), but both in central and in minimum bias S-W interactions an excess is observed with respect to these sources which does not depend on centrality, nor very strongly on the transverse momentum

Electroweak parameters of the z0 resonance and the standard model

Contains fulltext : 124399.pdf (publisher's version ) (Open Access

INCLUSIVE NEGATIVE PARTICLE p(T) SPECTRA IN P - NUCLEUS AND NUCLEUS-NUCLEUS COLLISIONS AT 200-GeV PER NUCLEON

The HELIOS experiment has measured inclusivep ⊥ spectra of negative particles in the rapidity region 1.0 is found to be approximately constant up to the highest accessible values of E ⊥