Giles Barr

Abstract:

In the context of time-of-flight measurements, the timing at the departure and arrival locations is obviously critical to the outcome of the experiment. In the case of neutrino time-of-flight experiments, the locations are many hundreds of kilometers apart with synchronization requirements of nanoseconds for several months at a time. In addition to the already stringent set of requirements outlined above, the locations of the origin of the particle beam and the detector need to be precisely determined. NIST and USNO have provided the MINOS (Main Injector Neutrino Oscillation Search) collaboration with both hardware and expertise to synchronize the two sites of the experiment, the accelerator at Fermilab in Batavia, IL and the Soudan Mine in northern Minnesota. Two GPS receivers are installed at each location where the local clocks are commercial Cesium clocks. Two more GPS receivers are constantly traveling between locations (including NIST in Boulder, CO) to provide multiple differential calibrations of the fixed receivers. The availability of the TWTFST equipment from USNO allowed for one comparison between the GPS and TWSTFT for the link between the locations, providing an independent means of determining the accuracy of the synchronization. Several months of continuous GPS data are now available, including the two-way calibration instance and several differential GPS calibrations. The results of data processing yielded synchronization stability below one nanosecond with accuracy at the nanosecond level over several months. © (2012) by the Institute of Navigation. All rights reserved.

Abstract:

This paper reports measurements of atmospheric neutrino and antineutrino interactions in the MINOS Far Detector, based on 2553 live-days (37.9kton-years) of data. A total of 2072 candidate events are observed. These are separated into 905 contained-vertex muons and 466 neutrino-induced rock-muons, both produced by charged-current ν μ and ν ̄μ interactions, and 701 contained-vertex showers, composed mainly of charged-current ν e and ν ̄e interactions and neutral-current interactions. The curvature of muon tracks in the magnetic field of the MINOS Far Detector is used to select separate samples of ν μ and ν ̄μ events. The observed ratio of ν ̄μ to ν μ events is compared with the MonteCarlo (MC) simulation, giving a double ratio of Rν̄/νdata/ Rν̄/νMC=1.03±0.08(stat)±0.08(syst). The ν μ and ν ̄μ data are separated into bins of L/E resolution, based on the reconstructed energy and direction of each event, and a maximum likelihood fit to the observed L/E distributions is used to determine the atmospheric neutrino oscillation parameters. This fit returns 90% confidence limits of |Δm2|=(1.9±0.4)×10 -3eV2 and sin22θ>0.86. The fit is extended to incorporate separate ν μ and ν ̄μ oscillation parameters, returning 90% confidence limits of |Δm2|-|Δm ̄2|=0.6- 0.8+2.4×10 -3eV2 on the difference between the squared-mass splittings for neutrinos and antineutrinos. © 2012 American Physical Society.

Abstract:

The pi-zero detector (POD) is one of the subdetectors that makes up the off-axis near detector for the Tokai-to-Kamioka (T2K) long baseline neutrino experiment. The primary goal for the POD is to measure the relevant cross-sections for neutrino interactions that generate π0s, especially the cross-section for neutral current π0 interactions, which are one of the dominant sources of background to the νμ→ νe appearance signal in T2K. The POD is composed of layers of plastic scintillator alternating with water bags and brass sheets or lead sheets and is one of the first detectors to use Multi-Pixel Photon Counters (MPPCs) on a large scale. © 2012 Elsevier B.V. All rights reserved.

Abstract:

We report an improved measurement of ν ̄μ disappearance over a distance of 735 km using the MINOS detectors and the Fermilab Main Injector neutrino beam in a ν ̄μ-enhanced configuration. From a total exposure of 2.95×1020 protons on target, of which 42% have not been previously analyzed, we make the most precise measurement of Δm ̄2=[2.62-0.28+0.31(stat)±0. 09(syst)]×10 -3eV2 and constrain the ν ̄μ mixing angle sin2(2θ̄)>0.75 (90% C.L.). These values are in agreement with Δm2 and sin2(2θ) measured for ν μ, removing the tension reported in. © 2012 American Physical Society.