First Measurement of the Ratio of Branching Fractions B(Lambda_b to Lambda_c mu nu)/B(Lambda_b to Lambda_c pi)

TL;DR

This paper reports the first measurement of the ratio of branching fractions for Lambda_b decays to Lambda_c mu nu and Lambda_c pi, using data from the Fermilab Tevatron, and includes new measurements of several semileptonic decay modes.

Contribution

It provides the first measurement of the ratio of Lambda_b to Lambda_c mu nu and pi branching fractions, along with new semileptonic decay measurements and a comparison of Lambda_b and B0 transverse momentum distributions.

Findings

Measured B(Lambda_b to Lambda_c mu nu)/B(Lambda_b to Lambda_c pi) = 16.6 ± 3.0 (stat) ± 1.0 (syst)

First observation of four new Lambda_b semileptonic decay modes

Lambda_b baryons have a different transverse momentum distribution compared to B0 mesons.

Abstract

The analysis uses data from an integrated luminosity of approximately 172 pb-1 of ppbar collisions at sqrt(s)=1.96 TeV, collected with the CDF II detector at the Fermilab Tevatron. The Lambda_b and B0 relative branching fractions are measured to be: B(Lambda_b to Lambda_c+ mu nu)/B(Lambda_b to Lambda_c+ pi) = 16.6 +- 3.0 (stat) +- 1.0 (syst) +2.6 -3.4 (PDG) +- 0.3 (EBR), B(B0 to D+ mu nu)/B(B0 to D+ pi) = 9.9 +- 1.0 (stat) +- 0.6 (syst) +- 0.4 (PDG) +- 0.5 (EBR), B(B0 to D*+ mu nu)/B(B0 to D*+ pi) = 16.5 +- 2.3 (stat) +- 0.6 (syst) +- 0.5 (PDG) +- 0.8 (EBR) This article also presents measurements of the branching fractions of four new Lambda_b semileptonic decays: Lambda_b to Lambda_c(2595)+ mu nu, Lambda_b to Lambda_c(2625)+ mu nu, Lambda_b to Sigma_c(2455)0 pi mu nu, Lambda_b to Sigma_c(2455)++ pi mu nu, relative to the branching fraction of the Lambda_b to Lambda_c mu nu decay. Finally, the transverse-momentum distribution of Lambda_b baryons produced in p-pbar collisions is measured and found to be significantly different from that of B0 mesons.