We present a search for ten baryon-number violating decay modes of ? hyperons using the CLAS detector at Jefferson Laboratory. Nine of these decay modes result in a single meson and single lepton in the final state (? → m?) and conserve either the sum or the difference of baryon and lepton number (? ± L). The tenth decay mode (? → p¯?+) represents a difference in baryon number of two units and no difference in lepton number. Furthermore, we observe no significant signal and set upper limits on the branching fractions of these reactions in the range (4 – 200) x 107 at the 90% confidence level.

Bringing together leading researchers from particle physics, astrophysics, and cosmology, Lepton and Baryon Number Violation in Particle Physics, Astrophysics and Cosmology presents reviews of current theoretical ideas, experimental results, and future perspectives in this topical field. The book covers areas related to baryon number (B) and lepton number (L) violation in particle physics, nuclear physics, rare decays, and cosmology. The main topics include B and L violation and grand unified theories; B and L violation in the early universe, cosmology, and astrophysics; Lepton family number violation; and B and L violation and collider physics.

The authors have searched for the violation of baryon number B and lepton number L in the (B-L)-conserving modes {tau}{sup -} {yields} {bar {Lambda}}{sup 0}{pi}{sup -} and {tau}{sup -} {yields} {bar {Lambda}}{sup 0}K{sup -} as well as the (B-L)-violating modes {tau}{sup -} {yields} {Lambda}{sup 0}{pi}{sup -} and {tau}{sup -} {yields} {Lambda}{sup 0}K{sup -} using 237 fb{sup -1} of data collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage ring. They do not observe any signal and determine preliminary upper limits on the branching fractions {Beta}({tau}{sup -} {yields} {bar {Lambda}}{sup 0}{pi}{sup -})

We present a search for ten baryon-number violating decay modes of $\Lambda$ hyperons using the CLAS detector at Jefferson Laboratory. Nine of these decay modes result in a single meson and single lepton in the final state ($\Lambda \rightarrow m \ell$) and conserve either the sum or the difference of baryon and lepton number ($B \pm L$). The tenth decay mode ($\Lambda \rightarrow \bar{p}\pi^+$) represents a difference in baryon number of two units and no difference in lepton number. We observe no significant signal and set upper limits on the branching fractions of these reactions in the range $(4-200)\times 10^{-7}$ at the $90\%$ confidence level.

Searches for B mesons decaying to final states containing a baryon and a lepton are performed, where the baryon is either [Lambda]{sub c} or [Lambda] and the lepton is a muon or an electron. These decays violate both baryon and lepton number and would be a signature of physics beyond the standard model. No significant signal is observed in any of the decay modes, and upper limits in the range (3.2 - 520) x 10−8 are set on the branching fractions at the 90% confidence level.