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تسجيل مستخدم جديدProbing unparticle theory via lepton flavor violating process $J/psito ll$ at BESIII
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The lepton flavor violating process $J/psito ll (l eq l)$ serves as an ideal place to probe the unparticle theory. Such process can only occur at loop level in the Standard model (SM), so that should be very suppressed, by contrast in unparticle scenario, it happens at tree level and its contribution may be sizable for practical measurement. Moreover, the BESIII will offer the largest database on $J/psi$ which makes more accurate measurements possible. Furthermore, for such purely leptonic decays background is relatively low and signal would be cleaner. Our work carefully investigates the possibility of observing such processes from both theoretical and experimental aspects.
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A search for the charged lepton flavor violating decay $J/psito e^{pm}tau^{mp}$ with $tau^{mp} to pi^{mp}pi^0 u_{tau}$ is performed with about $10$ billion $J/ psi$ events collected with the BESIII detector at the BEPCII. No significant signal is obs
erved, and an upper limit is set on the branching fraction $mathcal{B}(J/psito e^{pm}tau^{mp})<7.5times10^{-8}$ at the 90$%$ confidence level. This improves the previously published limit by two orders of magnitude.
We search for the lepton-flavor-violating decay of the $J/psi$ into an electron and a muon using $(225.3pm2.8)times 10^{6}$ $J/psi$ events collected with the BESIII detector at the BEPCII collider. Four candidate events are found in the signal region
, consistent with background expectations. An upper limit on the branching fraction of $mathcal{B}(J/psi to emu)< 1.5 times 10^{-7}$ (90% C.L.) is obtained.
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Using a data sample of $1.31 times 10^{9}$ $J/psi$ events accumulated with the BESIII detector, the decay $J/psito pbar{p}phi$ is studied via two decay modes, $phito K^{0}_{S}K^{0}_{L}$ and $phito K^{+}K^{-}$. The branching fraction of $J/psito pbar{
p}phi$ is measured to be $mathcal{B}(J/psito pbar{p}phi)=[5.23pm0.06(mbox{stat})pm0.33(mbox{syst})]times10^{-5}$, which agrees well with a previously published measurement, but with a significantly improved precision. No evident enhancement near the $pbar{p}$ mass threshold, denoted as $X(pbar{p})$, is observed, and the upper limit on the branching fraction of $J/psito X(pbar{p})phito pbar{p}phi$ is determined to be $mathcal{B}(J/psito X(pbar{p})phito pbar{p}phi)<2.1times10^{-7}$ at the 90% confidence level.
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