Search results for "Particle physics"
showing 10 items of 6826 documents
Coherent ψ(2S) photo-production in ultra-peripheral Pb Pb collisions at sNN=2.76 TeV
2015
We have performed the first measurement of the coherent ψ(2S) photo-production cross section in ultraperipheral Pb–Pb collisions at the LHC. This charmonium excited state is reconstructed via the ψ(2S) → l +l − and ψ(2S) → J/ψπ+π− decays, where the J/ψ decays into two leptons. The analysis is based on an event sample corresponding to an integrated luminosity of about 22 μb−1. The cross section for coherent ψ(2S) production in the rapidity interval −0.9 < y < 0.9 is dσcoh ψ(2S)/dy = 0.83±0.19 stat+syst mb. The ψ(2S) to J/ψ coherent cross section ratio is 0.34+0.08 −0.07(stat + syst). The obtained results are compared to predictions from theoretical models.
Measurement of the mass and width of the charmed meson D∗+ (2010)
1992
Abstract Using a high-resolution silicon vertex detector we have observed a very clean signal of 127 D∗+. After a careful study of the experimental resolution of our apparatus we have measured m( D ∗++ )−m( D 0 ) = 145.39±0.06±0.03 MeV . We have also obtained a 90% CL upper limit to γ(D∗+) of 131 keV.
Nuclear effects in neutrino production of Δ at intermediate energies
1998
Abstract The neutrino production of Δ in 16 O has been studied at intermediate energies relevant to atmospheric neutrino experiments. The Δ production cross sections with electrons or muons in the final state is found to be reduced due to nuclear effects. This reduction is even larger for the accompanying one pion production cross sections. The ratio of electron to muon production cross sections, however, does not show any significant dependence on nuclear medium effects.
Measurement of the proton and deuteron structure functions, F2p and F2d, and of the ratio
1997
The muon-proton and muon-deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q(2) < 75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results are based on the full data set collected by the New Muon Collaboration, including the data taken with a small angle trigger. The extracted values of the structure functions F-2(p) and F-2(d) are in good agreement with those from other experiments. The data cover a sufficient range of y to allow the determination of the ratio of the longitudinally to transversely polarised virtual photon absorption cross sections, R = sigma(L)/sigma(T), for 0.002 < x < 0.12. The …
Limits on the mass of the lightest supersymmetric particle at LEP
2003
Abstract The results of searches for charginos, neutralinos and sleptons in data collected by the four LEP experiments up to center-of-mass energies of 209 GeV have been used to extract limits on the mass of the lightest neutralino within a constrained MSSM and the mSUGRA model.
Analysis of the 2νββ decay and muon capture reactions for the mass A = 46 and A = 48 nuclei using the nuclear shell model
2005
We discuss the two-neutrino double-beta decays of 46Ca and 48Ca by using the nuclear shell model with well-tested two-body interactions. We also discuss the ordinary muon-capture (OMC) reaction on the final nuclei, 46Ti and 48Ti, of these decays. The OMC leads to the virtual states of the intermediate nuclei, 46Sc and 48Sc, in these double-beta decays.
Strangeness of the nucleon
2005
Abstract Strangeness observables of the nucleon are discussed. Emphasis is put on the strange vector form factors as they are measured in current parity violating electron scattering experiments. Recent results are presented and the evidence for non-vanishing strangeness contributions is shown.
Cosmological promising parameters of stau in the minimal supersymmetric standard model
2009
We find that we can account for the possible descrepancy of the primordial abundance of 7 Li between the observation and the prediction of the Big-Bang Nucleosynthesis in a scenario of the Big-Bang Nucleosynthesis with the Minimal Supersymmetric Standard Model. This scenario is consistent with a stau-neutralino coannihilation scenario to explain the relic abundance of dark matter. The solution to the discrepancy is given by taking the values of parameters; the mass of the neutralino as 300 GeV and the mass difference between the stau and the neutralino as (100 – 120) MeV.
A more sensitive search for νμ→ντ oscillations in NOMAD
1999
With additional data and improved algorithms, we have enhanced the sensitivity of our appearance search for $\numunutau$ oscillations in the NOMAD detector in the CERN-SPS wide-band neutrino beam. The search uses kinematic criteria to identify $\nutau$ charged current interactions followed by decay of the $\tau^-$ to one of several decay modes. Our ``blind'' analyses of deep-inelastic scattering data taken in 1996 and 1997, combined with consistent reanalyses of previously reported 1995 data, yield no oscillation signal. For the two-family oscillation scenario, we present the contour outlining a 90\% C.L. confidence region in the $\sin^22\theta_{\mu \tau} - \Delta m^2$ plane. At large $\Del…
First results from MAMI
1993
Abstract The 100% duty factor electron accelerator MAMI (Mainzer Mikrotron) has gone into operation. First experiments with quasi-monochromatic real photons have been performed. First results, mostly preliminary, are presented.