# First measurements of absolute branching fractions of the $\Xi_c^+$ baryon at Belle

## TL;DR

This paper reports the first absolute measurements of certain decay branching fractions of the $\\Xi_c^+$ baryon using data from the Belle detector, providing crucial normalization for future studies of this particle.

## Contribution

It provides the first absolute branching fraction measurements of $\\Xi_c^+$ decays and the $ar{B}^0$ decay to $\\Lambda_c^-$ and $\\Xi_c^+$, establishing a new standard for $\\Xi_c^+$ decay rates.

## Key findings

- Measured ${\cal B}(\Xi_c^+ \to \Xi^- \pi^+ \pi^+)$ as approximately 2.86%.
- Measured ${\cal B}(\Xi_c^+ \to p K^- \pi^+)$ as approximately 0.45%.
- Determined ${\cal B}(\bar{B}^0 \to \bar{\Lambda}_c^- \Xi_c^+)$ as approximately 1.16 x 10^{-3}.

## Abstract

We present the first measurements of the absolute branching fractions of $\Xi_c^+$ decays into $\Xi^- \pi^+ \pi^+$ and $p K^- \pi^+$ final states. Our analysis is based on a data set of $(772\pm 11)\times 10^{6}$ $B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We measure the absolute branching fraction of $\bar{B}^{0} \to \bar{\Lambda}_{c}^{-} \Xi_{c}^{+}$ with the $\Xi_c^+$ recoiling against $\bar{\Lambda}_c^-$ in $\bar{B}^0$ decays resulting in ${\cal B}(\bar{B}^{0} \to \bar{\Lambda}_{c}^{-} \Xi_{c}^{+}) = [1.16 \pm 0.42(\rm stat.) \pm 0.15(\rm syst.)] \times 10^{-3}$. We then measure the product branching fractions ${\cal B}(\bar{B}^{0} \to \bar{\Lambda}_c^- \Xi_c^+){\cal B}(\Xi_c^+ \to \Xi^- \pi^+ \pi^+)$ and ${\cal B}(\bar{B}^{0} \to \bar{\Lambda}_c^- \Xi_c^+){\cal B}(\Xi_c^+ \to p K^- \pi^+)$. Dividing these product branching fractions by $\bar{B}^{0} \to \bar{\Lambda}_{c}^{-} \Xi_{c}^{+}$ yields: ${\cal B}(\Xi_c^+ \to \Xi^- \pi^+ \pi^+) = [2.86 \pm 1.21(\rm stat.) \pm 0.38(\rm syst.)]\%$ and ${\cal B}(\Xi_c^+ \to p K^- \pi^+)=[0.45 \pm 0.21(\rm stat.) \pm 0.07(\rm syst.)]\%$. Our result for ${\cal B}(\Xi_c^+ \to \Xi^- \pi^+ \pi^+)$ can be combined with $\Xi_c^+$ branching fractions measured relative to $\Xi_c^+ \to \Xi^- \pi^+ \pi^+$ to set the absolute scale for many $\Xi_c^+$ branching fractions.