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Register a new userD rare/forbidden decays at BESIII
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Ming-Gang Zhao
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In this document we present the latest result on rare/forbidden decays for D mesons at the BESIII experiment. Based on 2.92/fb data taken at the center-of-mass energy 3.773 GeV with the BESIII detector, the flavor-changing neutral current process of neutral D decays into two gammas is searched using a double tag technique, while the decays of charged D decays into a charged kaon/pion plus two electrons/positrons are studied based on a single tag method. The resulting upper limits are still above the Standard Model predictions.
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We present a search for nine lepton-number-violating and three lepton-flavor-violating neutral charm decays of the type $D^0rightarrow h^{prime -} h^{-}ell^{prime +} ell^{+}$ and $D^0rightarrow h^{prime -} h^{+}ell^{primepm} ell^{mp}$, where $h$ and $h^{prime}$ represent a $K$ or $pi$ meson and $ell$ and $ell^{prime}$ an electron or muon. The analysis is based on $468$ fb$^{-1}$ of $e^+e^-$ annihilation data collected at or close to the $Y(4S)$ resonance with the BaBar detector at the SLAC National Accelerator Laboratory. No significant signal is observed for any of the twelve modes and we establish 90% confidence level upper limits on the branching fractions in the range $(1.0 - 30.6)times 10^{-7}$. The limits are between one and three orders of magnitude times more stringent than previous measurements.
A search is performed for rare and forbidden charm decays of the form $D_{(s)}^+ to h^pm ell^+ ell^{(prime)mp}$, where $h^pm$ is a pion or kaon and $ell^{()pm}$ is an electron or muon. The measurements are performed using proton-proton collision data, corresponding to an integrated luminosity of $1.6text{fb}^{-1}$, collected by the LHCb experiment in 2016. No evidence is observed for the 25 decay modes that are investigated and $90%$ confidence level limits on the branching fractions are set between $1.4times10^{-8}$ and $6.4times10^{-6}$. In most cases, these results represent an improvement on existing limits by one to two orders of magnitude.
In 2009, the BESIII experiment has collected about 225M $jpsi$ and 106M $psip$ samples, both of which are the world largest on-peak charmonium production. Based on these dataset, BESIII has made great effort on the study of the charmonium decays, some important of which have been reviewed in this proceeding. In addition, a searching for new physics through the $CP/P$ violation process is reported.
The results on rare decay processes obtained by the LHCb experiment using 1.0 fb^(-1) of pp collisions collected in 2011 at a centre-of-mass energy of sqrt(s)=7 TeV are presented. Branching fractions, angular distributions, CP and isospin asymmetries are investigated to search for new physics effects.
The flavour changing neutral current decays can be interesting probes for searching for New Physics. Angular distributions of the decay $mathrm{B}^0 to mathrm{K}^{*0} mu^ +mu^-$ are studied using a sample of proton-proton collisions at $sqrt{s} = 8~mathrm{TeV}$ collected with the CMS detector at the LHC, corresponding to an integrated luminosity of $20.5~mathrm{fb}^{-1}$. An angular analysis is performed to determine $P_1$ and $P_5$, where $P_5$ is of particular interest due to recent measurements that indicate a potential discrepancy with the standard model. Based on a sample of 1397 signal events, $P_1$ and $P_5$ angular parameters are determined as a function of the dimuon invariant mass squared. The measurements are in agreement with standard model predictions.
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