Measurement of $\sigma(\Lambda_b)/\sigma(B^0) \times BR(\Lambda_b\to\Lambda_c\pi^-) / BR(B^0\to D^+\pi^-)$ in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV

TL;DR

This paper reports the first observation of the decay $ ext{Lambda}_b o ext{Lambda}_c o p K^- o ext{pi}^+ ext{K}^- ext{pi}^+$ in proton-antiproton collisions at 1.96 TeV, measuring the ratio of production cross sections times branching ratios.

Contribution

It provides the first measurement of the ratio of $ ext{Lambda}_b$ to $B^0$ production cross sections times their decay branching ratios at Tevatron energies.

Findings

Measured ratio: 0.82 ± 0.08 (stat) ± 0.11 (syst) ± 0.22 (BR)

First observation of $ ext{Lambda}_b o ext{Lambda}_c o p K^- ext{pi}^+$ decay

Normalized to $B^0 o D^+ o ext{pi}^+ K^- ext{pi}^+$ decay

Abstract

We present the first observation of the baryon decay $\Lambda_b\to\Lambda_c\pi^-$ followed by $\Lambda_c\to p K^-\pi^+$ in 106 pb-1 of $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV in the CDF experiment. In order to reduce systematic error, the measured rate for $\Lambda_b$ decay is normalized to the kinematically similar meson decay $B^0\to D^+\pi^-$ followed by $D^+\to\pi^+K^-\pi^+$. We report the ratio of production cross sections ($\sigma$) times the ratio of branching fractions (BR) for the momentum region integrated above $p_T > 6$ GeV/c and pseudorapidity range $|\eta| < 1.3$: $\sigma(p\bar{p}\to \Lambda_b X) / \sigma (p\bar{p}\to B^0 X) \times BR(\Lambda_b\to\Lambda_c\pi^-) / BR(B^0\to D^+\pi^-) = 0.82 \pm 0.08(stat) \pm 0.11(syst) \pm 0.22 (BR(\Lambda_c\to p K^-\pi^+))$.