A Search for Longlived Neutral Heavy Leptons in 400-GeV/c Proton - Nucleon Interactions

Abstract

The production of long-lived neutra1 heavy leptons ($L^{\circ}$) was searched for in 400 GeV/c proton-nucleon interactions in a magnetized beamdump. It was required that the $L^{\circ}$'s be produced without accompanying muons of energy greater than 10 GeV, that they traverse the beamdump, and that they decay into charged partic1es 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 $10^{13}$ protons incident on the beamdump, no evidence was found for such $L^{\circ}$'s. The upper limit on the cross-section a for the production without accopanying muons of $L^{\circ}$'s with Feynman $x = P^{cm}_{ll}/P^{cm}_{max}$ 0.2 and $0_{1ab}$ $\lesssim$ 10 mr with branching ratio B into two charged particles is $\sigma$B $\lesssim$ 3.9 X $10^{35}$ $cm^2$/nucleon at the 90% confidence level for masses $m_L\circ$ $\lesssim$ 1.0 GeV/$c^2$ and lifetimes between $10^{-10}$ and $10^{-8}$ seconds