D. G. Michael

Performance of Hamamatsu 64-anode photomultipliers for use with wavelength—shifting optical fibres

Hamamatsu R5900-00-M64 and R7600-00-M64 photomultiplier tubes will be used with wavelength-shifting optical fibres to read out scintillator strips in the MINOS near detector. We report on measurements of the gain, efficiency, linearity, crosstalk, and dark noise of 232 of these PMTs, of which 219 met MINOS requirements.

The MINOS experiment

The MINOS (Main Injector Neutrino Oscillation Search) experiment will use the Main Injector neutrino beam to make high-precision oscillation measurements on all possible oscillation channels relevant to the atmospheric neutrino problem. Construction of the detector and the beamline are underway. Data acquisition with atmospheric neutrinos will begin in 2002 while the first beam neutrinos are expected in late 2004. While waiting for the beam neutrinos, MINOS will provide the first measurement oil the oscillation properties of atmospheric anti-neutrinos compared to neutrinos. This is possible due to the magnetic field in the detector.

Comparisons of the MINOS near and far detector readout systems at a test beam

MINOS is a long baseline neutrino oscillation experiment that uses two detectors separated by 734 km. The readout systems used for the two detectors are different and have to be independently calibrated. To verify and make a direct comparison of the calibrated response of the two readout systems, test beam data were acquired using a smaller calibration detector. This detector was simultaneously instrumented with both readout systems and exposed to the CERN PS T7 test beam. Differences in the calibrated response of the two systems are shown to arise from differences in response non-linearity, photomultiplier tube crosstalk, and threshold effects at the few percent level. These differences are reproduced by the Monte Carlo (MC) simulation to better than 1% and a scheme that corrects for these differences by calibrating the MC to match the data in each detector separately is presented. The overall difference in calorimetric response between the two readout systems is shown to be consistent with zero to a precision of 1.3% in data and 0.3% in MC with no significant energy dependence.

Update on Minos

The MINOS (Main Injector Neutrino Oscillation Search) experiment will use the Main Injector neutrino beam to make high-precision oscillation measurements on all possible oscillation channels relevant to the atmospheric neutrino problem. Construction of the detector and the beamline are underway. Data acquisition with atmospheric neutrinos will begin in 2002 while the first beam neutrinos are expected in 2004.

Charge properties in glass-electrode resistive plate counters

Abstract We have measured the charge response to single cosmic-ray muons passing through a glass-electrode resistive plate counter under several different operating conditions. Under appropriate conditions, we find that the width of the charge response is better than measured using streamer tubes. The best observed response is approximately Gaussian with FWHM peak = 0.24 with only a small high-charge tail. A well-timed, narrow charge integration gate is essential to remove undesired charge spreading effects from afterpulsing.

Plans for long-baseline neutrino oscillation experiments

Several new experiments have been proposed to address the suggestion of neutrino oscillations from the atmospheric neutrino problem. In order to be sensitive to oscillations arising from Δm2 in the region of 10−3eV2 to 10−1eV2 oscillation pathlengths on the order of 10–1000 times longer than those previously used are required; hence the name “long-baseline” experiments. General features of such experiments are discussed and then some details of the specific proposals are presented.

Upward-going muons in MACRO

The first 6 months of running with the full length of the lower structure of MACRO with both scintillator and streamer tubes operational has been completed. Combined with 2.5 years of running with 16 of the lower detector, roughly 5 million muon events have been analyzed looking for upward going muons by using time information in the scintillator counters. The symmetry of the detector hardware and analysis are exploited to check the acceptance and efficiency for upgoing muon events by studying all downgoing muon events in the data runs used for this analysis. The total number of upgoing muons observed in these running periods was 68 ± 8stat ± 7sys which compares to an expected number of events of 81 ± 12sys. The flux of upgoing muons as a function of zenith angle is shown compared to MC expectation. A search has been made for astrophysical point sources of neutrinos. No point sources of neutrinos have been observed.

Searching for oscillations of atmospheric and accelerator neutrinos with GeNIUS

Abstract A very large (17KT) fine-grained sampling calorimeter is discussed for use in studying contained events induced by atmospheric or accelerator neutrinos for the purpose of searching for neutrino oscillations. The ratio of neutral current to charged current events can be used to rule out a large region of the currently allowed parameter space with accelerator and atmospheric neutrinos providing complimentary measurements.

Muon measurements with MACRO

The large size, good pointing resolution and fine grain of the MACRO detector make it a powerful tool for studying interactions of very high energy cosmic rays through the high energy muons (E≳1.3 TeV) resulting from decays of energetic pions and kaons. Results are presented on muon astronomy, cosmic ray composition studies and interaction model studies.

Neutrino Oscillations at Proton Accelerators

Data from many different experiments have started to build a first glimpse of the phenomenology associated with neutrino oscillations. Results on atmospheric and solar neutrinos are particularly clear while a third result from LSND suggests a possibly very complex oscillation phenomenology. As impressive as the results from current experiments are, it is clear that we are just getting started on a long-term experimental program to understand neutrino masses, mixings and the physics which produce them. A number of exciting fundamental physics possibilities exist, including that neutrino oscillations could demonstrate CP or CPT violation and could be tied to exotic high-energy phenomena including strings and extra dimensions. A complete exploration of oscillation phenomena demands many experiments, including those possible using neutrino beams produced at high energy proton accelerators. Most existing neutrino experiments are statistics limited even though they use gigantic detectors. High intensity proton beams are essential for producing the intense neutrino beams which we need for next generation neutrino oscillation experiments.