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تسجيل مستخدم جديدSearch for the $Lambda_b rightarrow Lambda eta^prime$ and $Lambda_b rightarrow Lambda eta$ decays with the LHCb detector
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A search is performed for the as yet unobserved baryonic $Lambda_b rightarrow Lambda eta^prime$ and $Lambda_b rightarrow Lambda eta$ decays with 3$fb^{-1}$ of proton-proton collision data recorded by the LHCb experiment. The $B^0 rightarrow K_S^0 eta^prime$ decay is used as a normalisation channel. No significant signal is observed for the $Lambda_b rightarrow Lambda eta^prime$ decay. An upper limit is found on the branching fraction of $mathcal{B}(Lambda_b rightarrow Lambda eta^prime)<3.1times10^{-6}$} at 90% confidence level. Evidence is seen for the presence of the $Lambda_b rightarrow Lambda eta$ decay at the level of $3sigma$ significance, with a branching fraction $mathcal{B}(Lambda_b rightarrow Lambda eta)=(9.3^{+7.3}_{-5.3})times10^{-6}$}.
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We report the results of the first search for the decay $B_s^0 rightarrow eta^prime eta$ using $121.4~textrm{fb}^{-1}$ of data collected at the $Upsilon(5S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We observ
e no significant signal and set a 90% confidence-level upper limit of %$7.1 times 10^{-5}$ $6.5 times 10^{-5}$ on the branching fraction of this decay.
In the Standard Model (SM) charmless hadronic decays $B_s^0 rightarrow eta^prime eta$ proceed via tree-level $bto u$ and penguin $bto s$ transitions. Penguin transitions are sensitive to Beyond-the-Standard-Model (BSM) physics scenarios and could aff
ect the branching fractions and {it CP} asymmetries in such decays. Once branching fractions for two-body decays $B_s to etaeta, etaeta^{prime}, eta^{prime}eta^{prime} $ are measured, and the theoretical uncertainties are reduced, it would be possible to extract {it CP} violating parameters from the data using the formalism based on SU(3)/U(3) symmetry. To achieve this goal, at least four of these six branching fractions need to be measured. Only the branching fraction for $B_s^0 to eta^{prime}eta^{prime}$ has been measured so far.
We study the hadronic decays of $Lambda_{c}^{+}$ to the final states $Sigma^{+}eta$ and $Sigma^+eta^prime$, using an $e^{+}e^{-}$ annihilation data sample of 567 pb$^{-1}$ taken at a center-of-mass energy of 4.6 GeV with the BESIII detector at the BE
PCII collider. We find evidence for the decays $Lambda_{c}^{+}rightarrowSigma^{+}eta$ and $Sigma^+eta^prime$ with statistical significance of $2.5sigma$ and $3.2sigma$, respectively. Normalizing to the reference decays $Lambda_c^+toSigma^+pi^0$ and $Sigma^+omega$, we obtain the ratios of the branching fractions $frac{{mathcal B}(Lambda_c^+toSigma^+eta)}{{mathcal B}(Lambda_c^+toSigma^+pi^0)}$ and $frac{{mathcal B}(Lambda_c^+toSigma^+eta^prime)}{{mathcal B}(Lambda_c^+toSigma^+omega)}$ to be $0.35 pm 0.16 pm 0.03$ and $0.86 pm 0.34 pm 0.07$, respectively. The upper limits at the 90% confidence level are set to be $frac{{mathcal B}(Lambda_c^+toSigma^+eta)}{{mathcal B}(Lambda_c^+toSigma^+pi^0)}<0.58$ and $frac{{mathcal B}(Lambda_c^+toSigma^+eta^prime)}{{mathcal B}(Lambda_c^+toSigma^+omega)}<1.2$. Using BESIII measurements of the branching fractions of the reference decays, we determine $mathcal B({Lambda_{c}^{+}rightarrowSigma^{+}eta})=(0.41pm0.19pm0.05)%$ ($<0.68%$) and $mathcal B({Lambda_{c}^{+}rightarrowSigma^{+}eta})=(1.34pm0.53pm0.21)%$ ($<1.9%$). Here, the first uncertainties are statistical and the second systematic. The obtained branching fraction of $Lambda_c^+toSigma^+eta$ is consistent with the previous measurement, and the branching fraction of $Lambda_{c}^{+}rightarrowSigma^{+}eta^{prime}$ is measured for the first time.
Based on a sample of $1.31 times 10^9$ $J/psi$ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays $eta^prime rightarrow pi^+pi^-pi^0$ and $eta^prime rightarrow pi^0pi^0pi^0$ is performed. A significant $P
$-wave contribution from $eta^prime rightarrow rho^{pm} pi^{mp}$ is observed for the first time in $eta^prime rightarrow pi^+pi^-pi^0$. The branching fraction is determined to be ${mathcal B}(eta^prime rightarrow rho^{pm}pi^{mp})=(7.44pm0.60pm1.26pm1.84)times 10^{-4}$, where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant $S$-wave component, there is a significant $sigma$ meson component. The branching fractions of the combined $S$-wave components are determined to be ${mathcal B}(eta^prime rightarrow pi^+pi^-pi^0)_S=(37.63pm0.77pm2.22pm4.48)times 10^{-4}$ and ${mathcal B}(eta^prime rightarrow pi^0pi^0pi^0)=(35.22pm0.82pm2.54)times 10^{-4}$, respectively. The latter one is consistent with previous BESIII measurements.
A search for $CP$ violation in $D^{pm}rightarrow eta^{prime} pi^{pm}$ and $D^{pm}_{s}rightarrow eta^{prime} pi^{pm}$ decays is performed using proton-proton collision data, corresponding to an integrated luminosity of $3$ fb$^{-1}$, recorded by the L
HCb experiment at centre-of-mass energies of $7$ and $8$ TeV. The measured $CP$-violating charge asymmetries are $A_{CP}(D^{pm} rightarrow eta^{prime} pi^{pm})=(-0.61pm 0.72 pm 0.53 pm 0.12)%$ and $A_{CP}(D^{pm}_{s}rightarrow eta^{prime} pi^{pm})=(-0.82pm 0.36 pm 0.22 pm 0.27)%$, where the first uncertainties are statistical, the second systematic, and the third are the uncertainties on the $A_{CP}(D^{pm} rightarrow K^0_S pi^{pm})$ and $A_{CP}(D^{pm}_{s}rightarrow phi pi^{pm})$ measurements used for calibration. The results represent the most precise measurements of these asymmetries to date.
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