Accelerator Neutrinos

Abstract:

In the HARP experiment the large-angle spectrometer is using a cylindrical TPC as main tracking and particle identification detector. The momentum scale of reconstructed tracks in the TPC is the most important systematic error for the majority of kinematic bins used for the HARP measurements of the double-differential production cross-section of charged pions in proton interactions on nuclear targets at large angle. The HARP TPC operated with a number of hardware shortfalls and operational mistakes. Thus it was important to control and characterize its momentum calibration. While it was not possible to enter a direct particle beam into the sensitive volume of the TPC to calibrate the detector, a set of physical processes and detector properties were exploited to achieve a precise calibration of the apparatus. In the following we recall the main issues concerning the momentum measurement in the HARP TPC, and describe the cross-checks made to validate the momentum scale. As a conclusion, this analysis demonstrates that the measurement of momentum is correct within the published precision of 3%. © 2008 IOP Publishing Ltd and SISSA.

Abstract:

We present the first measurement of σ(gg→tt̄)/ σ(pp̄→tt̄). We use 0.96fb-1 of s=1.96TeV pp̄ collision data recorded with the CDF II detector at Fermilab. Using charged particles with low transverse momentum in tt̄ events, we find σ(gg→ tt̄)/σ(pp̄→tt̄)=0.07±0.14(stat)±0. 07(syst), corresponding to a 95% confidence level upper limit of 0.33, in agreement with the standard model next-to-leading-order prediction of 0.15±0.05. © 2008 The American Physical Society.

Abstract:

MINOS is a long baseline neutrino oscillation experiment. Protons from the Fermilab main injector are used to generate an intense muon neutrino beam, which is directed at the Soudan underground laboratory in Northern Minnesota. The result from two years of running with a total exposure of 2.5 × 10 20 protons on target from the NuMI beam is reported. We made a preliminary measurement by comparing the event rate and energy spectra of charge current muon neutrino interactions in the two detectors, which are 1 and 735 km from the neutrino production target. The data is consistent with νμ to ντ oscillation in the so-called atmospheric parameter range with Δm2 = (2.38+0.20-0.16) * 10-3eV2 and sin2 2θ = 1-0.08. Copyright © 2008, by INFN.