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Register a new userPolarization in $Xi_c^0$ decays
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Measurements on the weak decay asymmetry parameters of charmed baryon, say $Xi_c$, provide more information on the $W$-emission and $W$-exchange mechanisms controlled by the strong and weak interactions. Taking advantage of the spin polarization in the charmed baryon decays, we investigate the possibility to measure the weak decay asymmetry parameters in the $e^{+}e^{-}to Xi_c^0barXi_c^0$ process. We analyze the transverse polarization spontaneously produced in this process and spin transfer in the subsequent $Xi_c$ decays. The sensitivity to measure the asymmetry parameters are estimated for the decay $Xi_ctoXi pi$.
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We report the first observation of the Cabibbo-suppressed decays $Xi_c^0rightarrow Xi^- K^+$, $Xi_c^0raLambda K^+ K^-$ and $Xi_c^0rightarrow Lambda phi$, using a data sample of $711, mathrm{fb}^{-1}$ collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We measure the ratios of branching fractions to be $frac{{cal B}(Xi_c^0ra Xi^- K^+)}{{cal B}(Xi^0_craXi^-pi^+)}=(2.75pm 0.51pm 0.25)times 10^{-2}$, $frac{{cal B}(Xi_c^0raLambda K^+ K^-)}{{cal B}(Xi_c^0rightarrowXi^- pi^+)}=(2.86pm 0.61pm 0.24)times 10^{-2}$ and $frac{{cal B}(Xi_c^0ra Lambdaphi)}{{cal B}(Xi^0_craXi^-pi^+)}=(3.43pm 0.58pm 0.32)times 10^{-2}$, where the first uncertainty is statistical and the second is systematic.
We report measurements of the lifetimes of the $Lambda_c^+$, $Xi_c^+$ and $Xi_c^0$ charm baryons using proton-proton collision data at center-of-mass energies of 7 and 8tev, corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected by the LHCb experiment. The charm baryons are reconstructed through the decays $Lambda_c^+to pK^-pi^+$, $Xi_c^+to pK^-pi^+$ and $Xi_c^0to pK^-K^-pi^+$, and originate from semimuonic decays of beauty baryons. The lifetimes are measured relative to that of the $D^+$ meson, and are determined to be begin{align*} tau_{Lambda_c^+} &= 203.5pm1.0pm1.3pm1.4~{rm fs}, ewline tau_{Xi_c^+} &= 456.8pm3.5pm2.9pm3.1~{rm fs}, ewline tau_{Xi_c^0} &= 154.5pm1.7pm1.6pm1.0~{rm fs}, end{align*} where the uncertainties are statistical, systematic, and due to the uncertainty in the $D^+$ lifetime. The measurements are approximately 3--4 times more precise than the current world average values. The $Lambda_c^+$ and $Xi_c^+$ lifetimes are in agreement with previous measurements; however, the $Xi_c^0$ baryon lifetime is approximately 3.3 standard deviations larger than the world average value.
Using a data sample of 980 ${rm fb}^{-1}$ of $e^+e^-$ annihilation data taken with the Belle detector operating at the KEKB asymmetric-energy $e^+e^-$ collider, we report the results of a study of excited $Xi_c$ states that decay, via the emission of photons and/or charged pions, into $Xi_c^0$ or $Xi_c^+$ ground state charmed-strange baryons. We present new measurements of the masses of all members of the $Xi_c^{prime}$, $Xi_c(2645)$, $Xi_c(2790)$, $Xi_c(2815)$, and $Xi_c(2980)$ isodoublets, measurements of the intrinsic widths of those that decay strongly, and evidence of previously unknown transitions.
The first observation of the $Omega_b^-toXi_c^+ K^- pi^-$ decay is reported using proton-proton collision data at centre-of-mass energies of $7$, $8$ and $13,mathrm{TeV}$ collected by the LHCb experiment, corresponding to an integrated luminosity of $9,mathrm{fb}^{-1}$. Four excited $Omega_c^0$ baryons are observed in the $Xi_c^+ K^-$ mass projection of the $Omega_b^-toXi_c^+ K^- pi^-$ decays with significance exceeding five standard deviations. Their relative production rates, masses and natural widths are measured, and a test of spin hypotheses is performed. Moreover, the branching ratio of $Omega_b^-toXi_c^+ K^- pi^-$ is measured relative to the $Omega_b^-to Omega_c^0 pi^-$ decay mode and a precise measurement of the $Omega_b^-$ mass of $6044.3 pm 1.2 pm 1.1^{,+0.19}_{,-0.22},mathrm{MeV}$ is obtained.
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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