25 research outputs found
DIANE multiparticle transport code
No full textDIANE is the general Monte Carlo code developed at CEA-DAM. DIANE is a 3D multiparticle multigroup code. DIANE includes automated biasing techniques and is optimized for massive parallel calculations
Measurement of the Lambda polarization in nu(mu) charged current interactions in the NOMAD experiment
No full textThe Lambda polarization in upsilon (mu) charged current interactions has been measured in the NOMAD experiment. The event sample (8087 reconstructed Lambda 's) is more than an order of magnitude larger than that of previous bubble chamber experiments, while the quality of event reconstruction is comparable. We observe negative polarization along the W-boson direction which is enhanced in the target fragmentation region: P-x(x(F) lt 0) = -0.21 +/- 0.04(stat) +/- 0.02(sys). In the current fragmentation region we find P-x(x(F) gt 0) = -0.09 +/- 0.06(stat) +/- 0.03(sys). These results provide a test of different models describing the nucleon spin composition and the spin transfer mechanisms. A significant transverse polarization tin the direction orthogonal to the Lambda production plane! has been observed for the first time in a neutrino experiment: P-y = -0.22 +/- 0.03(stat) +/- 0.01(sys). The dependence of the absolute value of P-y on the Lambda transverse momentum with respect to the hadronic jet direction is in qualitative agreement with the resuits from unpolarized hadron-hadron experiments
Limit on νe→ντ oscillations from the NOMAD experiment
No full textIn the context of a two-flavour approximation we reinterpret the published NOMAD limit on nu(mu) --> nu(tau) oscillations in terms of nu(e) --> nu(tau) oscillations. At 90% C.L. we obtain sin2(2)theta(e tau) < 5.2 X 10(-2) for large Delta m(2), while for sin2(2)theta(e tau) = 1 the confidence region includes Delta m(2) < 11 eV(2)/c(4)
Inclusive production of ρ0(770), f0(980) and f2(1270) mesons in νμ charged current interaction
No full textThe inclusive production of the meson resonances p(0)(770), f(0)(980) and f(2)(1270) in neutrino- nucleus charged current interactions has been studied with the NOMAD detector exposed to the wide band neutrino beam generated by 450 GeV protons at the CERN SPS. For the first time the f0(980) meson is observed in neutrino interactions. The statistical significance of its observation is 6 standard deviations. The presence of f(2)(1270) in neutrino interactions is reliably established, The average multiplicity of these three resonances is measured as a function of several kinematic variables, The experimental results are compared to the multiplicities obtained from a simulation based on the Lund model, In addition, the average multiplicity of rho (0)(770) in antineutrino-nucleus interactions is measured
Precision measurement of scaled momentum, charge multiplicity, and thrust in v<sub>μ</sub>N and <span style="text-decoration: overline">V</span><sub>μ</sub>N interactions
No full textWe report the first precision measurements of the scaled momentum, the charge multiplicity, and the thrust of hadronic jets in the Breit frame in Deep Inelastic Scattering v<sub>μ</sub>N and <span style="text-decoration: overline">V</span><sub>μ</sub>N charged current events over the Q<sup>2</sup> range from 1 to 100 GeV<sup>2</sup>. The neutrino data, obtained in the NOMAD experiment at the CERN SPS, extend the Q<sup>2</sup>-evolution of these parameters by two orders of magnitude, and with commensurate precision, when compared to those reported by the ep and e<sup>+</sup>e<sup>−</sup> experiments
Search for a new gauge boson in π<sup>0</sup> decays
No full textA search was made for a new light gauge boson which might be produced in decay from neutral pions generated by 450-GeV protons in the CERN SPS neutrino target. Th e X's would penetrate the downstream shielding and be observed in the NOMAD detector via the Primakoff effect, in the process of conversion in the external Coulomb field of a nucleus.\ With protons on target, 20 candidate events with energy between 8 and 140 GeV were found from the analysis of neutrino data.\ This number is in agreement with the e xpectation of 18.12.8 background events from standard neutrino processes.\ A new 90 upper limit on the branching ratio (3.3~to~1.9) for masses ranging from 0 to 120 MeV/c is obtained.A search was made for a new light gauge boson which might be produced in decay from neutral pions generated by 450-GeV protons in the CERN SPS neutrino target. The X's would penetrate the downstream shielding and be observed in the NOMAD detector via the Primakoff effect, in the process of conversion in the external Coulomb field of a nucleus. With protons on target, 20 candidate events with energy between 8 and 140 GeV were found from the analysis of neutrino data. This number is in agreement with the expectation of 18.12.8 background events from standard neutrino processes. A new 90% C.L. upper limit on the branching ratio for masses ranging from 0 to 120 MeV/c^2 is obtained.A search was made for a new light gauge boson which might be produced in decay from neutral pions generated by 450-GeV protons in the CERN SPS neutrino target. The X's would penetrate the downstream shielding and be observed in the NOMAD detector via the Primakoff effect, in the process of conversion in the external Coulomb field of a nucleus. With protons on target, 20 candidate events with energy between 8 and 140 GeV were found from the analysis of neutrino data. This number is in agreement with the expectation of 18.12.8 background events from standard neutrino processes. A new 90% C.L. upper limit on the branching ratio for masses ranging from 0 to 120 MeV/c^2 is obtained.A search was made for a new light gauge boson X which might be produced in π 0 → γ + X decay from neutral pions generated by 450 GeV protons in the CERN SPS neutrino target. The X's would penetrate the downstream shielding and be observed in the NOMAD detector via the Primakoff effect, in the process of X → π 0 conversion in the external Coulomb field of a nucleus. With 1.45×10 18 protons on target, 20 candidate events with energy between 8 and 140 GeV were found from the analysis of neutrino data. This number is in agreement with the expectation of 18.1±2.8 background events from standard neutrino processes. A new 90 % C.L. upper limit on the branching ratio Br ( π 0 → γ + X )< (3.3 to 1.9)×10 −5 for X masses ranging from 0 to 120 MeV/ c 2 is obtained
Search for heavy neutrinos mixing with tau neutrinos
No full textWe report on a search for heavy neutrinos ( nu /sub 4/) produced in the decay D/sub s/ to tau nu /sub 4/ at the SPS proton target followed by the decay nu /sub 4/ to nu /sub tau /e/sup +/e/sup -/ in the NOMAD detector. Both decays are expected to occur if nu /sub 4/ is a component of nu /sub tau /. From the analysis of the data collected during the 1996-1998 runs with 4.1*10/sup 19/ protons on target, a single candidate event consistent with background expectations was found. This allows to derive an upper limit on the mixing strength between the heavy neutrino and the tau neutrino in the nu /sub 4/ mass range from 10 to 190 MeV. Windows between the SN1987 A and big bang nucleosynthesis lower limits and our result are still open for future experimental searches. The results obtained are used to constrain an interpretation of the time anomaly observed in the KARMEN1 detector
The NOMAD experiment at the CERN SPS
No full textThe NOMAD experiment is a short base-line search for ν<sub>μ</sub> − ν<sub>τ</sub> oscillations in the CERN neutrino beam. The ν<sub>τ</sub>'s are searched for through their charged current interactions followed by the observation of the resulting τ− through its electronic, muonic or hadronic decays. These decays are recognized using kinematical criteria necessitating the use of a light target which enables the reconstruction of individual particles produced in the neutrino interactions. This paper describes the various components of the NOMAD detector: the target and muon drift chambers, the electromagnetic and hadronic calorimeters, the preshower and transition radiation detectors and the veto and trigger scintillation counters. The beam and data acquisition system are also described. The quality of the reconstruction and individual particles is demonstrated through the ability of NOMAD to observe K<sub>s</sub><sup>0</sup>'s, Λ<sup>0</sup>'s and π<sup>0</sup>'s. Finally, the observation of τ− through its electronic decay being one of the most promising channels in the search, the identification of electrons in NOMAD is discussed
Neutrino production of opposite sign dimuons in the NOMAD experiment
No full textThe NOMAD Collaboration presents a study of opposite sign dimuon events in the framework of leading order QCD. A total of 2714 neutrino- and 115 antineutrino-induced opposite sign dimuon events with E/sub mu 1/,E/sub mu 2/ gt 4.5 GeV, 15 lt E/sub nu / lt 300 GeV and Q/sup 2/ gt 1 (GeV/c)/sup 2/ are observed in the front-calorimeter of NOMAD during the 1995 and 1996 runs. The analysis yields a value for the charm quark mass of m/sub c/=1.3/sub -0.3-0.3//sup +0.3+0.3/ GeV/c/sup 2/ and for the average semileptonic branching ratio of B/sub c/=0.095/sub -0.007-0.013//sup +0.007+0.014/. The ratio of the strange to non-strange sea in the nucleon is measured to be kappa =0.48/sub -0.07-0.12//sup +0.09+0.17/. The measured rate of charm-induced dimuon relative to single muon, as a function of neutrino energy, is consistent with the slow rescaling hypothesis of heavy quark production
Inclusive production of ρ<sup>0</sup>(770), f<sub>0</sub>(980) and f<sub>2</sub>(1270) mesons in ν<sub>μ</sub> charged current interactions
No full textThe inclusive production of the meson resonances ρ<sup>0</sup>(770), f<sub>0</sub>(980) and f<sub>2</sub>(1270) in neutrino–nucleus charged current interactions has been studied with the NOMAD detector exposed to the wide band neutrino beam generated by 450 GeV protons at the CERN SPS. For the first time the f<sub>0</sub>(980) meson is observed in neutrino interactions. The statistical significance of its observation is 6 standard deviations. The presence of f<sub>2</sub>(1270) in neutrino interactions is reliably established. The average multiplicity of these three resonances is measured as a function of several kinematic variables. The experimental results are compared to the multiplicities obtained from a simulation based on the Lund model. In addition, the average multiplicity of ρ<sup>0</sup>(770) in antineutrino–nucleus interactions is measured
