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First measurements of absolute branching fractions of $Xi_c^0$ at Belle

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 نشر من قبل Chengping Shen
 تاريخ النشر 2018
  مجال البحث
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We present the first measurements of absolute branching fractions of $Xi_c^0$ decays into $Xi^- pi^+$, $Lambda K^- pi^+$, and $p K^- K^- pi^+$ final states. The measurements are made using a data set comprising $(772pm 11)times 10^{6}$ $Bbar{B}$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We first measure the absolute branching fraction for $B^- to bar{Lambda}_c^- Xi_c^0$ using a missing-mass technique; the result is ${cal B}(B^- to bar{Lambda}_c^- Xi_c^0) = (9.51 pm 2.10 pm 0.88) times 10^{-4}$. We subsequently measure the product branching fractions ${cal B}(B^- to bar{Lambda}_c^- Xi_c^0){cal B}(Xi_c^0 to Xi^- pi^+)$, ${cal B}( B^- to bar{Lambda}_c^- Xi_c^0) {cal B}(Xi_c^0 to Lambda K^- pi^+)$, and ${cal B}( B^- to bar{Lambda}_c^- Xi_c^0) {cal B}(Xi_c^0 to p K^- K^- pi^+)$ with improved precision. Dividing these product branching fractions by the result for $B^- to bar{Lambda}_c^- Xi_c^0$ yields the following branching fractions: ${cal B}(Xi_c^0 to Xi^- pi^+)= (1.80 pm 0.50 pm 0.14)%$, ${cal B}(Xi_c^0 to Lambda K^- pi^+)=(1.17 pm 0.37 pm 0.09)%$, and ${cal B}(Xi_c^0 to p K^- K^- pi^+)=(0.58 pm 0.23 pm 0.05)%.$ For the above branching fractions, the first uncertainties are statistical and the second are systematic. Our result for ${cal B}(Xi_c^0 to Xi^- pi^+)$ can be combined with $Xi_c^0$ branching fractions measured relative to $Xi_c^0 to Xi^- pi^+$ to yield other absolute $Xi_c^0$ branching fractions.

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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 $(772pm 11)times 10^{6}$ $Bbar{B}$ 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.
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