Evidence for the strangeness-changing weak decay $\Xi_b^-\to\Lambda_b^0\pi^-$

Abstract : Using a $pp$ collision data sample corresponding to an integrated luminosity of 3.0~fb$^{-1}$, collected by the LHCb detector, we present the first search for the strangeness-changing weak decay $\Xi_b^-\to\Lambda_b^0\pi^-$. No $b$ hadron decay of this type has been seen before. A signal for this decay, corresponding to a significance of 3.2 standard deviations, is reported. The relative rate is measured to be ${{f_{\Xi_b^-}}\over{f_{\Lambda_b^0}}}{\cal{B}}(\Xi_b^-\to\Lambda_b^0\pi^-) = (5.7\pm1.8^{+0.8}_{-0.9})\times10^{-4}$, where $f_{\Xi_b^-}$ and $f_{\Lambda_b^0}$ are the $b\to\Xi_b^-$ and $b\to\Lambda_b^0$ fragmentation fractions, and ${\cal{B}}(\Xi_b^-\to\Lambda_b^0\pi^-)$ is the branching fraction. Assuming $f_{\Xi_b^-}/f_{\Lambda_b^0}$ is bounded between 0.1 and 0.3, the branching fraction ${\cal{B}}(\Xi_b^-\to\Lambda_b^0\pi^-)$ would lie in the range from $(0.57\pm0.21)\%$ to $(0.19\pm0.07)\%$.
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Submitted on : Wednesday, October 14, 2015 - 10:22:50 AM
Last modification on : Monday, June 3, 2019 - 1:38:03 PM

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R. Aaij, Y. Amhis, S. Barsuk, M. Borsato, O. Kochebina, et al.. Evidence for the strangeness-changing weak decay $\Xi_b^-\to\Lambda_b^0\pi^-$. Physical Review Letters, American Physical Society, 2015, 115, pp.241801. ⟨10.1103/PhysRevLett.115.241801⟩. ⟨in2p3-01215379⟩

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