Giles Barr

Abstract:

HARP is a high-statistics, large solid angle experiment to measure hadron production using proton and pion beams with momenta between 1.5 and 15 GeV/c impinging on many different solid and liquid targets from low to high Z. The experiment, located in the T9 beam of the CERN PS, took data in 2001 and 2002. For the measurement of momenta of produced particles and for the identification of particle types, the experiment includes a large-angle spectrometer, based on a Time Projection Chamber and a system of Resistive Plate Chambers, and a forward spectrometer equipped with a set of large drift chambers, a threshold Cherenkov detector, a time-of-flight wall and an electromagnetic calorimeter. The large angle system uses a solenoidal magnet, while the forward spectrometer is based on a dipole magnet. Redundancy in particle identification has been sought, to enable the cross-calibration of efficiencies and to obtain a few percent overall accuracy in the cross-section measurements. Detector construction, operation and initial physics performances are reported. In addition, the full chain for data recording and analysis, from trigger to the software framework, is described. © 2006 Elsevier B.V. All rights reserved.

Abstract:

We present a measurement of the ratio of the decay rates Γ (KL → π⁺ π^-) / Γ (KL → π^± e^∓ ν), denoted as ΓK 2 π / ΓK e 3. The analysis is based on data taken during a dedicated run in 1999 by the NA48 experiment at the CERN SPS. Using a sample of 47 000 K2 π and five million Ke 3 decays, we find ΓK 2 π / ΓK e 3 = (4.835 ± 0.022stat . ± 0.016syst .) × 10^-3. From this we derive the branching ratio of the CP violating decay KL → π⁺ π^- and the CP violation parameter | η+ - |. Excluding the CP conserving direct photon emission component KL → π⁺ π^- γ, we obtain the results BR (KL → π⁺ π^-) = (1.941 ± 0.019) × 10^-3 and | η+ - | = (2.223 ± 0.012) × 10^-3. © 2006 Elsevier B.V. All rights reserved.

Abstract:

The double-differential production cross-section of positive pions, d ²σ^π+/d pdΩ, measured in the HARP experiment is presented. The incident particles are 8.9 GeV/c protons directed onto a beryllium target with a thickness of 5% of a nuclear interaction length. The measured cross-section has a direct impact on the prediction of neutrino fluxes for the MiniBooNE and SciBooNE experiments at Fermilab. After cuts, 13 million protons on target produced about 96000 reconstructed secondary tracks which were used in this analysis. Cross-section results are presented in the kinematic range 0.75∈GeV/c≤pπ≤ 6.5∈GeV/c and 30∈mrad≤θπ≤ 210∈mrad in the laboratory frame. © 2007 Springer-Verlag / Società Italiana di Fisica.

Abstract:

Starting from a survey of experimental measurements, we assign uncertainties to the two most critical inputs to the calculation of fluxes of unoscillated atmospheric neutrinos, the hadron production and the primary cosmic ray fluxes. We then propagate these uncertainties through the entire flux calculation to arrive at estimates of the uncertainties in the fluxes of neutrinos and of various ratios of neutrino fluxes. We find that there is indeed a significant cancellation of flux uncertainties when these ratios are made. The uncertainties as a function of neutrino energy will be presented.

Abstract:

The aspects of hadron simulation affecting the calculation of unoscillated atmospheric neutrino fluxes is discussed. The method of simulating the atmospheric cascades is described. An evaluation of the errors on the atmospheric neutrino fluxes and various experimentally convenient ratios is presented. A new measurement of hadron production with the NA49 experiment at CERN is briefly reported.