Improved Measurement of the Form Factors in the Decay Lambda_c^+ --> Lambda e^+ nu_e

TL;DR

This study precisely measures the form factors and decay asymmetry in Lambda_c^+ decays using the CLEO detector, providing insights into the weak decay dynamics and CP symmetry.

Contribution

It presents the first detailed four-dimensional analysis of Lambda_c^+ decay form factors and tests for CP violation with improved accuracy.

Findings

Measured form factor ratio R = -0.31 +/- 0.05(stat) +/- 0.04(syst)

Determined pole mass M_{pole} = 2.21 +/- 0.08(stat) +/- 0.14(syst) GeV/c^2

Found no evidence for CP violation, A_{Lambda_c} = 0.00 +/- 0.03(stat) +/- 0.01(syst) +/- 0.02

Abstract

Using the CLEO detector at the Cornell Electron Storage Ring, we have studied the distribution of kinematic variables in the decay Lambda_c^+ -> Lambda e^+ nu_e. By performing a four-dimensional maximum likelihood fit, we determine the form factor ratio, R = f_2/f_1 = -0.31 +/- 0.05(stat) +/- 0.04(syst), the pole mass, M_{pole} = (2.21 +/- 0.08(stat) +/- 0.14(syst)) GeV/c^2, and the decay asymmetry parameter of the Lambda_c, alpha_{Lambda_c} = -0.86 +/- 0.03(stat) +/- 0.02(syst), for <q^2> = 0.67 (GeV/c^2)^2. We compare the angular distributions of the Lambda_c^+ and Lambda_c^- and find no evidence for CP-violation: A_{Lambda_c} = (alpha_{Lambda_c^+} + alpha_{Lambda_c^-})/ (alpha_{Lambda_c^+} - alpha_{Lambda_c^-}) = 0.00 +/- 0.03(stat) +/- 0.01(syst) +/- 0.02, where the third error is from the uncertainty in the world average of the CP-violating parameter, A_{Lambda}, for Lambda -> p pi^-.