J. L. Stone

Indications of neutrino oscillation in a 250 km long-baseline experiment.

The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.

Neutrino measurements with the IMB director

The measure fraction of muon-like, single-track, atmospheric neutrino events over a 7.7 kton-yr exposure of IMB is 0.36±0.02(stat)±0.02(syst) as compared to an expectation of 0.51±0.01(stat)±0.05(syst). No significant dependence of this fraction on zenith angle or momentum is seen. In addition, upward-going muons from higher energy atmospheric neutrino interactions are used to search for vμ oscillations into vτ by comparing the measured rate with the expected rate from a conservative flux calculation. The ratio of upward-going muons which stop in the detector to those which exit is also used to search for deviations from the expected energy spectrum. No evidence for oscillations is found in either analysis. Finally, a search is made for an astrophysical component to the detected neutrino flux from both energetic point sources and gamma-ray bursts and also for a possible seasonal variation of the high energy neutrino flux due to atmospheric density changes. No evidence for any of these effects if found.

The macro detector at the Gran Sasso Laboratory

Abstract The MACRO detector is presently under construction, its installation at Gran Sasso being planned to start in September 1987. It is a large area detector, the acceptance for isotropic particle fluxes being around 10 000 m 2 sr, designed to search for rare phenomena in the cosmic radiation. It makes use of three detection techniques: liquid scintillator counters, plastic streamer tubes, and track-etch. It will perform a search for GUT monopoles (or any supermassive charged penetrating particle), a survey of cosmic point sources of HE gammas and neutrinos, a systematic study of the penetrating cosmic ray muons, and will be sensitive to neutrino bursts from gravitational stellar collapses in the Galaxy.

Study of penetrating cosmic ray muons and search for large scale anisotropies at the Gran Sasso Laboratory

Abstract The MACRO detector, located in the underground Gran Sasso Laboratory, had its initial data run from February 27 to May 30, 1989, using the first supermodule (SΩ∼800 m 2 sr ) . Approximately 245 000 muon events were recorded. Here are reported the results of the analysis of penetrating muons which determine the measured vertical muon flux at depths greater than 3000 m.w.e. In addition the data have been used to search for large scale anisotropies.

Up-down asymmetry of neutral current events as a diagnostic for νμ−νst versus νμ−ντ oscillations

Abstract We show that the asymmetry in the neutral current events (e.g. νN → νNπ 0 ) can be used to discriminate between ν μ − ν τ and ν μ − ν st mixing as being responsible for the atmospheric neutrino anomaly. Specifically, A N vanishes for ν μ − ν τ mixing and is about 2/3 A μ for ν μ − ν st mixing. We also comment on the possibility of mixing of all three neutrinos (i.e. ν μ − ν τ − ν st ) which can give a muon asymmetry as large as 1/2.

Calibration of the IMB detector

The IMB detector (named after its founding institutions: University of California, Irvine, the University of Michigan and Brookhaven National Laboratory) collected data on a wide range of phenomena for over eight years. It was the first and the largest of the ring imaging water Cherenkov detectors. The detector consisted of 8000 metric tons of ultra-pure water instrumented with 2048 photomultiplier tubes (PMTs). The PMTs were placed on the roof, floor, and walls of the detector in a lattice of approximately 1 m spacing. It made measurements of contained events that ranged in energy from 15 MeV up to 1.5 GeV. This paper describes the calibration of the IMB detector. This procedure was accurate and stable over a wide range of physical variables. It was used with little change throughout the entire eight-year lifetime of the experiment. The IMB calibration is a model for future large-scale detectors that employ the water Cherenkov technique.

Tracking Performance of the Scintillating Fiber Detector in the K2K Experiment

The K2K long-baseline neutrino oscillation experiment uses a Scintillating Fiber Detector (SciFi) to reconstruct charged particles produced in neutrino interactions in the near detector. We describe the track reconstruction algorithm and the performance of the SciFi after 3 years of operation.

A search for neutrino and gamma ray burst temporal correlations with the IMB detector

If Gamma Ray Bursts (GRBs) are associated with a stellar collapse‐like phenomenon then it is resonable to expect neutrino production to occur at the source. We have performed a temporal correlation analysis with GRBs using the IMB low‐energy neutrino dataset during 809 days of livetime between 1986 and 1990. No correlations were observed placing a 90%. C.L. limit of 0.046 ν interactions per GRB. The dependence of the GRB distances to neutrino yield using volume and shell distribution models is discussed. Lower limits are derived which exclude galactic stellar collapse‐like models.

TEXAS: a calorimeter-based high-rate detector for the SSC

Abstract The conceptual design for a novel SSC detector that focuses on calorimetry is presented. The physics goals include searches for elementary scalars of low mass (MH 600 GeV), for heavy supersymmetric matter, for compositeness and for strong vector-boson interactions. Examples of the relevant signatures are H → γγ; H → ZZ ∗ ; H → lvq q , llvv, llq q ; g g → E T miss + > 2 jets ; and a jet excess at high pT. These goals may be achieved with high precision, fast, compensated and hermetic calorimetry, optimized for electrons, photons, and jets. The design allows for total hermeticity to η = 5.5 missing energy. All the goals require operation at high luminosity and the additional concerns of γ-γ and jet-jet separation, as well as survival in a high radiation environment, are addressed by an unusually large inner radius of the detector. The detector concept consists of the following few and well defined components: a scintillating fiber tracking system incorporating an imaging preradiator, a projective, finely segmented, thick scintillator calorimeter; and a muon TRD trigger and spectrometer.

Status report of the macro experiment at gran sasso

Abstract The half of the MACRO detector, a large area Monopole, Astrophysics, Cosmic Ray Observatory is nearly completed in Hall B of the Gran Sasso Laboratory. One supermodule is already taken data and the remainder will be activated in few months. A general overview of the MACRO detector, together with its physics capabilities as far as the search for point sources of high energy neutrino is concerned, will be presented.