A BACKGROUND-FREE DETECTOR FOR COSMIC-RAY SHOWERS IN THE ATMOSPHERE

A detector of new design is planned to detect Cherenkov light in high energy cosmic ray showers. It is based on the detection of the middle-UV radiation by TMAE photosensitive chambers, giving detailed imaging of the shower, combined with the beneficial background screening of the ozone in the upper atmosphere. This allows us to greatly improve the duty-cycle, the sensitivity and the range of observations with respect to traditional Cherenkov experiments in the visible. A further advantage is the achievable big angular aperture which makes it possible to search for new sources with an efficiency similar to extensive air shower experiments. Details of the technique and achievable physics goals are presented

Upper limits on D+/- and B+/- decays to two leptons plus pi +/- or K+/-

Data taken by the Mark II detector at the SLAC e+e- storage ring PEP was used to search for exclusive decays of D and B mesons into two charged leptons plus a charged pion or kaon. All possible charge and lepton combinations consistent with charge conservation were considered and no evidence for any signals was found. We obtain upper limits for the various branching ratios ranging from 2.5×10-3 to 9.2×10-3, at a 90% confidence level. Some of these limits can be used to constrain leptoquark masses in various models. © 1990 The American Physical Society

Determination of alpha s from energy-energy correlations in e+e- annihilation at 29 GeV.

We have studied the energy-energy correlation in e+e- annihilation into hadrons at s =29 GeV using the Mark II detector at the SLAC storage ring PEP. We find to O(s2) that s=0.1580.0030.008 if hadronization is described by string fragmentation. Independent fragmentation schemes give s=0.100.14, and give poor agreement with the data. A leading-log shower fragmentation model is found to describe the data well. © 1988 The American Physical Society

Upper limits on D+/- and B+/- decays to two leptons plus pi +/- or K+/-

Data taken by the Mark II detector at the SLAC e+e- storage ring PEP was used to search for exclusive decays of D and B mesons into two charged leptons plus a charged pion or kaon. All possible charge and lepton combinations consistent with charge conservation were considered and no evidence for any signals was found. We obtain upper limits for the various branching ratios ranging from 2.5×10-3 to 9.2×10-3, at a 90% confidence level. Some of these limits can be used to constrain leptoquark masses in various models. © 1990 The American Physical Society

Measurement of the B0-meson lifetime.

We report a measurement of the lifetime of the B0 meson based upon 29-GeV e+e- annihilation data taken with the Mark II detector at the SLAC storage ring PEP. The B0 mesons are tagged by their decays into D*- and D*+, where the D*- is tagged by its decay into -D 0. We reconstruct the decay vertices of 15 B0-meson candidates and measure the B0 lifetime to be 1.20-0.360.14+0.52+0.16 psec. © 1990 The American Physical Society

Search for elastic nondiagonal lepton-pair production in e+e- annihilation at sqrt s =29 GeV.

We have searched for the annihilation of e+e- into the exclusive channels e and at s =29 GeV, using 226 and 133 pb-1, respectively, of data taken with the Mark II detector at the SLAC storage ring PEP. The resulting candidate sample is compatible with the expected background from pair production. Our analysis yields 95%-C.L. cross-section limits of e/<1.8×10-3 and /<6.1×10-3, where is the QED cross section for production of a lepton pair. This is the first high-Q2 test of lepton-flavor conservation involving leptons. © 1991 The American Physical Society

A BACKGROUND-FREE DETECTOR FOR COSMIC-RAY SHOWERS IN THE ATMOSPHERE

A detector of new design is planned to detect Cherenkov light in high energy cosmic ray showers. It is based on the detection of the middle-UV radiation by TMAE photosensitive chambers, giving detailed imaging of the shower, combined with the beneficial background screening of the ozone in the upper atmosphere. This allows us to greatly improve the duty-cycle, the sensitivity and the range of observations with respect to traditional Cherenkov experiments in the visible. A further advantage is the achievable big angular aperture which makes it possible to search for new sources with an efficiency similar to extensive air shower experiments. Details of the technique and achievable physics goals are presented