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Register a new userMeasurement of the ratio of branching fractions of the decays $Lambda^0_b!topsi(2S) Lambda$ and $Lambda^0_b!to J/psi Lambda$
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Using $pp$ collisions corresponding to 3$,text{fb}^{-1}$ integrated luminosity, recorded by the LHCb experiment at centre-of-mass energies of 7 and 8$,text{TeV}$, the ratio of branching fractions begin{align*} mathcal{B}(Lambda^0_b!topsi(2S) Lambda )/mathcal{B}(Lambda^0_b!to J/psi Lambda)= 0.513 pm 0.023, (text{stat}) pm 0.016 , (text{syst}) pm 0.011, (mathcal{B}) end{align*} is determined. The first uncertainty is statistical, the second is systematic and the third is due to the external branching fractions used.
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A search for $C!P$ violation in $Lambda^0_b to p K^-$ and $Lambda^0_b to p pi^-$ decays is presented using a sample of $pp$ collisions collected with the LHCb detector and corresponding to an integrated luminosity of 3.0 fb$^{-1}$. The $C!P$-violating asymmetries are measured to be $A_{mathrm{CP}}^{pK^-} = -0.020 pm 0.013pm 0.019$ and $A_{mathrm{CP}}^{ppi^-} = -0.035 pm 0.017 pm 0.020 $, and their difference $A_{mathrm{CP}}^{pK^-}-A_{mathrm{CP}}^{ppi^-} = 0.014 pm 0.022 pm 0.010$, where the first uncertainties are statistical and the second systematic. These are the most precise measurements of such asymmetries to date.
The LHCb measurement of the lifetime ratio of the $Lambda^0_b$ to the $overline{B}^0$ meson is updated using data corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected using 7 and 8 TeV centre-of-mass energy $pp$ collisions at the LHC. The decay modes used are $overline{B}^0to J/psi p K^-$ and $overline{B}^0to J/psi pi^+ K^-$, where the $pi^+K^-$ mass is consistent with that of the $overline{K}^{*0}(892)$ meson. The lifetime ratio is determined with unprecedented precision to be $0.974pm0.006pm0.004$, where the first uncertainty is statistical and the second systematic. This result is in agreement with original theoretical predictions based on the heavy quark expansion. Using the current world average of the $overline{B}^0$ lifetime, the $Lambda^0_b$ lifetime is found to be $1.479 pm 0.009 pm 0.010$ ps.
Based on $4.481times10^8$ $psi(3686)$ events collected with the BESIII detector at BEPCII, the branching fraction of the isospin violating decay $psi(3686)rightarrowbar{Sigma}^{0}Lambda+c.c.$ is measured to be $(1.60 pm 0.31 pm 0.13~pm~0.58) times 10^{-6}$, where the first uncertainty is statistical, the second is systematic, and the third is the uncertainty arising from interference with the continuum. This result is significantly smaller than the measurement based on CLEO-c data sets. The decays $chi_{cJ} rightarrowLambdabar{Lambda}$ are measured via $psi(3686)rightarrowgammachi_{cJ}$, and the branching fractions are determined to be $mathcal{B}left(chi_{c0}rightarrowLambdabar{Lambda}right)=(3.64 pm 0.10 pm 0.10 pm 0.07)times 10^{-4}$, $mathcal{B}left(chi_{c1}rightarrowLambdabar{Lambda}right)=(1.31pm0.06 pm 0.06 pm0.03)times 10^{-4}$, $mathcal{B}left(chi_{c2}rightarrowLambdabar{Lambda}right)=(1.91pm0.08 pm 0.17 pm0.04)times 10^{-4}$, where the third uncertainties are systematic due to the $psi(3686) rightarrow gamma chi_{c J}$ branching fractions.
In this work, we report on a theoretical study of possible pentaquark states $Lambda^0_b(5912)$ and $Lambda^0_b(5920)$ in the $gamma{}pto{}Lambda_b^{0(*)}B^+$ reactions within an effective Lagrangian approach. In addition to the contributions from the $s$-channel nucleon pole and $t$-channel $bar{B}^{{*}-}$ exchange, the contact term contribution are also included. Our theoretical approach is based on the chiral unitary theory where the $Lambda^0_b(5912)$ and $Lambda^0_b(5920)$ resonances are dynamically generated. Within the coupling constants of the $Lambda^0_b(5912)$ and $Lambda^0_b(5920)$ to $bar{B}p$ and $bar{B}^{*}p$ channels obtained from chiral unitary theory, the total and differential cross sections of the $gamma{}pto{}Lambda_b^{0(*)}B^+$ are evaluated. Our calculation indicates that the cross section for $gamma{}pto{}Lambda_b^{0}(5912)B^{+}$ and $gamma{}pto{}Lambda_b^{0}(5920)B^{+}$ reactions are of the order of 0.0164 nb and 0.00527 nb,respectively. If measured in future experiments, such as Electron-Ion Collider in China (EicC) or US(US-EIC), the predicted total cross sections and specific features of the angular distributions can be used to test the (molecular) nature of the $Lambda^0_b(5912)$ and $Lambda^0_b(5920)$ that they may be pentaquark states.
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