A Search for Lambda sub-b in pi- - A Collisions at 515 GeV/c

الأصل · EN

An extensive analysis was performed on 8.0 pb-1 of dimuon data produced in pi- - A collisions at 515 GeV/c to search for Lambdab events in the decay channel Lambdab --> J/psi Lambda⁰, with J/psi --> mu+ mu- and Lambda⁰ --> p pi- (and for the conjugate reactions). The data was collected by the Fermilab fixed target experiments E672 and E706. Several cuts were applied to the Lambda⁰ (and anti-Lambda⁰) to make a clean Lambda⁰ (and anti-Lambda⁰) data sample. Among the cuts there was a K⁰ₛ mass cut, in which if the Lambda⁰ --> p pi- (or conjugate reaction) had the mass of the K⁰ₛ under the hypothesis of both tracks being pi+ pi-, the Lambda⁰ (or anti-Lambda⁰) candidates were rejected. The results show 2 events in the Lambdab mass region. Using the E672/E706 measurement of the bbbar cross-section, and considering the 2 Lambdab event candidates as signal with zero background, an upper limit to F(Lambdab) * Br(Lambdab --> J/psi Lambda⁰) was found to be less than 6.2x10-2 at 90 % C. L. An upper limit was also calculate without using the K⁰ₛ mass cut for the Lambda⁰ s (and anti-Lambda⁰ s), and again, requiring that the J/psi s originate from secondary vertices, giving that F(Lambdab) * Br(Lambdab --> J/psi Lambda⁰) < 3.1x10-2 at 90 % C. L. and F(Lambdab) * Br(Lambdab --> J/psi Lambda⁰) < 3.2x10-2 at 90 % C.L., respectively.