Search for long-lived neutral heavy leptons in 400 GeV/c proton--nucleon interactions. [Upper limit for cross sections

Abstract

The production of long-lived neutral heavy leptons (L/sup 0/) was searched for in 400 GeV/c proton-nucleon interactions in a magnetized beam dump. It was required that the L/sup 0/'s be produced without accompanying muons of energy greater than 10 GeV, that they traverse the beam dump, and that they decay into charged particles in a 9.2 m long evacuated pipe whose front end was located 8.9 m downstream. These decay products were analyzed by a magnetic spectrometer employing multi-wire proportional chambers and scintillation counters. In a total flux of 2.8 x 10/sup 13/ protons incident on the beam dump, no evidence was found for such L/sup 0/'s. The upper limit on the cross section sigma for the production without accompanying muons of L/sup 0/'s with Feynman x = P/sub parallel//sup cm//P/sub max//sup cm/ approximately greater than 0.2 and theta/sub lab/ approximately less than 10 mr and with branching ratio B into two charged particles is sigmaB approximately less than 3.9 x 10/sup -35/ cm/sup 2//nucleon at the 90% confidence level for masses m/sub L/sup 0// approximately less than 1.0 GeV/c/sup 2/ and lifetimes between 10/sup -10/ and 10/sup -8/ seconds.