Giles Barr

Abstract:

The velocity of a ∼3GeV neutrino beam is measured by comparing detection times at the near and far detectors of the MINOS experiment, separated by 734 km. A total of 473 far detector neutrino events was used to measure (v-c)/c=5.1±2.9×10-5 (at 68% C.L.). By correlating the measured energies of 258 charged-current neutrino events to their arrival times at the far detector, a limit is imposed on the neutrino mass of mν<50MeV/c2 (99% C.L.). © 2007 The American Physical Society.

Abstract:

The 5.4 kton MINOS far detector has been taking charge-separated cosmic ray muon data since the beginning of August, 2003 at a depth of 207 m.w.e. in the Soudan Underground Laboratory, Minnesota, USA. The data with both forward and reversed magnetic field running configurations were combined to minimize systematic errors in the determination of the underground muon charge ratio. When averaged, two independent analyses find the charge ratio underground to be Nμ+/Nμ-=1.374±0.004(stat)-0.010+0.012(sys). Using the map of the Soudan rock overburden, the muon momenta as measured underground were projected to the corresponding values at the surface in the energy range 1-7 TeV. Within this range of energies at the surface, the MINOS data are consistent with the charge ratio being energy independent at the 2 standard deviation level. When the MINOS results are compared with measurements at lower energies, a clear rise in the charge ratio in the energy range 0.3-1.0 TeV is apparent. A qualitative model shows that the rise is consistent with an increasing contribution of kaon decays to the muon charge ratio. © 2007 The American Physical Society.

Abstract:

A measurement of the double-differential cross-section for the production of charged pions in proton-tantalum collisions emitted at large angles from the incoming beam direction is presented. The data were taken in 2002 with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12 GeV/c hitting a tantalum target with a thickness of 5% of a nuclear interaction length. The angular and momentum range covered by the experiment (100 MeV/c ≤ p< 800 MeV/c and 0.35 rad ≤ θ< 2.15 rad) is of particular importance for the design of a neutrino factory. The produced particles were detected using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. Track recognition, momentum determination and particle identification were all performed based on the measurements made with the TPC. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results are shown for the double-differential cross-sections d 2σ/dpdθ at four incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c and 12 GeV/c). In addition, the pion yields within the acceptance of typical neutrino factory designs are shown as a function of beam momentum. The measurement of these yields within a single experiment eliminates most systematic errors in the comparison between rates at different beam momenta and between positive and negative pion production. © 2007 Springer-Verlag / Società Italiana di Fisica.

Abstract:

We found 140 neutrino-induced muons in 854.24 live days in the MINOS far detector, which has an acceptance for neutrino-induced muons of 6.91×106cm2sr. We looked for evidence of neutrino disappearance in this data set by computing the ratio of the number of low momentum muons to the sum of the number of high momentum and unknown momentum muons for both data and Monte Carlo expectation in the absence of neutrino oscillations. The ratio of data and Monte Carlo ratios, R, is R=0.65-0.12+0.15(stat)±0.09(syst), a result that is consistent with an oscillation signal. A fit to the data for the oscillation parameters sin 22θ23 and Δm232 excludes the null oscillation hypothesis at the 94% confidence level. We separated the muons into μ- and μ+ in both the data and Monte Carlo events and found the ratio of the total number of μ- to μ+ in both samples. The ratio of those ratios, R^CPT, is a test of CPT conservation. The result R^CPT=0.72-0.18+0.24(stat)-0. 04+0.08(syst) is consistent with CPT conservation. © 2007 The American Physical Society.

Abstract:

The beam and detector, used for the NA48 experiment, devoted to the measurement of Re (ε{lunate}′ / ε{lunate}), and for the NA48/1 experiment on rare KS and neutral hyperon decays, are described. © 2007 Elsevier B.V. All rights reserved.