Lambda_b Ratio of Branching Fractions

We summarize here the blessed results for the measurement of the ratio of branching fractions:

BR(&Lambdab0 &rarr &Lambdac+ &mu-&nu ) /BR(&Lambdab0 &rarr &Lambdac+ &pi-) = 16.6 ± 3.0(stat.) ± 1.0(syst.) +2.6-3.4(PDG) ± 0.3(EBR) ,

where the first uncertainty is statistical, the second uncertainty is due to CDF internal systematics, the third is from uncertainties on external input summarized by the particle data group (branching fractions) and forth uncertainties are on estimated branching ratios, respectively. As a test of the technique, we also measure the ratio of branching fractions:

BR(B0 &rarr D- &mu+&nu ) /BR(B0 &rarr D- &pi+) = 9.9 ± 1.0(stat.) ± 0.6(syst.) ± 0.4(PDG) ± 0.5(EBR)

BR(B0 &rarr D*- &mu+&nu ) /BR(B0 &rarr D*- &pi+) = 16.5 ± 2.3(stat.) ± 0.6(syst.) ± 0.5(PDG) ± 0.8(EBR)

As part of this analysis, we measure the relative branching fractions of the following new &Lambdab0 semileptonic decay modes:

BR(&Lambdab0 &rarr &Lambdac(2595)+ &mu-&nu ) /BR(&Lambdab0 &rarr &Lambdac+ &mu-&nu) = 0.126 ± 0.033(stat.)+0.047-0.038(syst.)
BR(&Lambdab0 &rarr &Lambdac(2625)+ &mu-&nu ) /BR(&Lambdab0 &rarr &Lambdac+ &mu-&nu) = 0.210 ± 0.042(stat.)+0.071-0.050(syst.)
BR(&Lambdab0 &rarr &Sigmac(2455)&pi- &mu-&nu ) /BR(&Lambdab0 &rarr &Lambdac+ &mu-&nu) = 0.054 ± 0.022(stat.)+0.021-0.018(syst.)

These results have been re-blessed for submission to PRD at the B-physics meeting on Thursday, September 11 2008.

Analysis Description:

A brief description of the analysis is contained in a PostScript file.

Figures:

Click on the figures below for a larger version. Encapsulated PostScript versions of each figure may be obtained by clicking on the (EPS) in the caption.


Figure 1: Invariant mass of D+ &pi-. The D+ is reconstructed from the decay D+ &rarr K- &pi+ &pi+. The red curve is the result of a fit to a signal and background model. Various mis-reconstructed backgrounds from B-meson and &Lambdab0 decays are indicated by the filled histograms.(EPS)
Figure 2: Invariant mass of K-&pi+ &pi+. The red curve is the result of a fit to a signal and background model. Mis-reconstructed backgrounds are indicated by the filled histograms. All events in the distribution contain a muon which has an impact parameter, with respect to the beam line, larger than 120 microns. (EPS)



Figure 3: Invariant mass of D*+&pi-. The D*+ is reconstructed from the decay D*+ &rarr D0 &pi+, D0 &rarr K- &pi+. The red curve is the result of a fit to a signal and background model. Various mis-reconstructed backgrounds from B-meson decays are indicated by the filled histograms. (EPS)
Figure 4: Invariant mass difference M(K-&pi+&pi+) - M(K-&pi+). The red curve is the result of a fit to a signal and background model. All events in the distribution contain a muon which has an impact parameter, with respect to the beam line, larger than 120 microns. (EPS)



Figure 5: Invariant mass of &Lambdac+&pi-. The red curve is the result of a fit to a signal and background model. Backgrounds from other B-hadron decays are indicated by the filled histograms. (EPS)
Figure 6: Invariant mass of p K- &pi+. The red curve is the result of a fit to a signal and background model. All events in the distribution contain a muon which has an impact parameter, with respect to the beam line, larger than 120 microns. (EPS)



Figure 7: Invariant mass difference, M(&Lambdac+ &pi+ &pi-) - M(&Lambdac+), for &Lambdac+ events containing a muon which has an impact parameter, with respect to the beam line, larger than 120 microns. Peaks for both the &Lambdac(2595)+ (lower delta M) and the &Lambdac(2625)+ (higher delta M) are evident. (EPS)
Figure 8: Invariant mass difference, M(&Lambdac+ &pi-) - M(&Lambdac+), for &Lambdac+ events containing a muon which has an impact parameter, with respect to the beam line, larger than 120 microns. A peak for the &Sigmac(2455)0 is evident. (EPS)

Figure 9: Invariant mass difference, M(&Lambdac+ &pi+) - M(&Lambdac+), for &Lambdac+ events containing a muon which has an impact parameter, with respect to the beam line, larger than 120 microns. A peak for the &Sigmac(2455)++ is evident. (EPS)
Figure 10: Comparison of the B0 and &Lambdab0 Pt spectra measured in data (top) and ratio of Pt(&Lambdab)/Pt(B0) (bottom). The B0 spectrum was normalize to the area of the &Lambdab spectrum. The ratio indicates that the Pt(&Lambdab) distribution is softer (more events at lower Pt) than the Pt(B0) distribution. (EPS)



Figure 16: Ratio of branching fractions for B0 &rarr D+ modes for various subsets of the data. The band represents the result from the full data sample. All uncertainties are statistical only. (EPS)
Figure 17: Ratio of branching fractions for B0 &rarr D*+ modes for various subsets of the data. The band represents the result from the full data sample. All uncertainties are statistical only. (EPS)
Figure 18: Ratio of branching fractions for &Lambdab &rarr &Lambdac+ modes for various subsets of the data. The band represents the result from the full data sample. All uncertainties are statistical only. (EPS)

Tables:

Click on the Tables below for a larger version. PostScript, PDF, or TEX versions of each Table may be obtained by clicking on the (PS, PDF, TEX) in the caption.

Table 1: Summary of statistical and systematic uncertainties for B0 to D+ and B0 to D*+ ratio of branching ratio measurements. ( PS PDF TEX )
Table 2: Summary of statistical and systematic uncertainties for &Lambdab0 ratio of branching ratio measurement. ( PS PDF TEX )