Measurement of the Moments of the Hadronic Invariant Mass Distribution in Semileptonic B Decays

TL;DR

This study measures the moments of the hadronic invariant mass distribution in semileptonic B decays to determine fundamental parameters of Heavy Quark Effective Theory, aiding in the precise extraction of CKM matrix elements.

Contribution

It provides the first measurement of the moments of the hadronic mass distribution in B decays, extracting non-perturbative parameters without assumptions on D** resonance structure.

Findings

Measured the first two moments of the hadronic mass distribution.

Determined the non-perturbative parameters Lambda and lambda_1.

Provided precise values for the moments of the D** component.

Abstract

Using 180 pb^-1 of data collected with the CDF II detector at the Tevatron, we measure the first two moments of the hadronic invariant mass-squared distribution in charmed semileptonic B decays. From these we determine the non-perturbative Heavy Quark Effective Theory parameters Lambda and lambda_1, used to relate the B meson semileptonic branching ratio to the CKM matrix element |V_cb|. For a minimum lepton momentum of 0.7 GeV/c in the B rest frame me measure the first two moments of the D** --> D(*) pi component to be <m^2_D**> = (5.83 +/- 0.16(stat) +/- 0.08(syst)) GeV^2, <(m^2_D** - <m^2_D**>)^2> = (1.30 +/- 0.69(stat) +/- 0.22(syst)) GeV^4. Combining these with the discrete mass terms from the D and D* mesons, we find the total moments to be <M^2_Xc> - mbar_D^2 = (0.467 +/- 0.038_(stat) +/- 0.068(syst)) GeV^2, <(M^2_Xc - <M^2_Xc>)^2> = (1.05 +/- 0.26(stat) +/- 0.13(syst)) GeV^4, where mbar_D is the spin-averaged D mass. The systematic error is dominated by the uncertainties in the world-average branching ratios used to combine the D, D* and D** contributions. The analysis makes no assumptions about the shape or resonant structure of the D** --> D(*) pi invariant mass distribution.