Search

Neutrino‐electron elastic scattering was observed at LAMPF with a 15‐ton fine‐grained tracking calorimeter exposed to electron‐neutrinos from muon decay at rest. The measured νee−→νee− elastic scattering cross section, 10.0±1.5(stat)±0.09(syst)×10−45 cm−2×(Eν(MeV)), gives a model independent measurement of the strength of the destructive interference between the charged and neutral currents, I=−1.07±0.21, that agrees well with the standard model (SM) prediction I=−1.08. The agreement between the measured electroweak parameters and SM expectations is used to place limits on neutrino properties, such as neutrino flavor‐changing neutral currents and neutrino electromagnetic moments, and on the masses of hypothetical new bosons that would interact with leptons.

In this paper we describe a new proposed water‐Cerenkov detector called MILAGRO, for observing cosmic gamma rays over a broad energy range of 1–1000 TeV. This detector will have an angular resolution better than 0.5° and an energy threshold near 1 TeV.

The 11 ‘‘in‐phase’’ source events from the 1986 muon‐rich bursts associated with Hercules X‐1 (previously reported by this group) have been studied for indications of further anomalous behavior. The most significant effect observed resulted from an analysis of the showerfront time‐structures of these events. This analysis was then applied a priori to the rest of the source day, where an additional ∼9 signal events are expected to remain. The same effect was observed at a chance probability level of ∼0.1%.

A new method of searching for UHE point source has been developed. With a data sample of 150 million events, we have surveyed the sky for point sources over 3314 locations (1.4°

A small pilot experiment to examine the use of the water‐Cerenkov technique for air shower detection was installed near the center of the CYGNUS air shower array. Preliminary results showing general agreement with simulations are presented. Thus, the technique promises to offer significant advances for VHE‐UHE γ‐ray astronomy.

A preliminary search is made for continuously pulsed, and burst, emission from the Crab pulsar or its nebula at ultra‐high energies using the CYGNUS air shower experiment. No evidence is found for pulsed emission over the entire data set of 1,075 days searched. A 90% confidence upper limit for the flux of cosmic rays at the interpulse phase is 6.9×10−14 cm−2s−1 above 50 TeV. A single day (JD=2447644.5,UTC=66700s to JD=2447645.5,UTC=11200s), is found to have a 4.1 σ excess corresponding to a chance probability of 2.2%; no evidence of the pulsar period is found on this day.

We report here the preliminary results of our observations of the sporadic X‐binary system 4U0115+63. The CYGNUS air shower array has been collecting data since April 1986. No significant excess is seen from the direction of this source, nor any correlation with its 24‐day orbital period. A 90% confidence‐level upper limit on the flux from 4U0115+63 is 2.8×10−13 cm−2 s−1 above 50 TeV. This flux limit is considerably lower than those reported by other UHE experiments. Search for periodicity at the neutron star frequency is in progress.

Data from the CYGNUS extensive air shower experiment at Los Alamos, NM has been analyzed to study the angular resolution of the array, and to search for point sources in the galaxy. Results on searches for steady emission from Cyg X‐3, Her X‐1 and the Crab nebula are presented.