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Register a new userNew-physics searches in $C!P$-violating $eta$ muonic decays
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Pablo Sanchez-Puertas
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In this work we investigate the possibility to observe $C!P$-violation in $eta$ decays containing muons at the proposed REDTOP experiment. Employing the SMEFT to parametrize the new-physics $C!P$-violating effects, we find that a single operator exists for which is possible to observe $C!P$-violation at REDTOP in $etatomu^+mu^-$ decays, while evading bounds from the neutron electric dipole moment and $D^-tomubar{ u}$
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Contributions to B - bar B mixing from physics beyond the standard model may be detected from CP-violating asymmetries in B decays. There exists the possibility of large new contributions that cannot be detected by first generation experiments because of a discrete ambiguity. Some possible strategies for resolving this are discussed.
A search for the $C!P$-violating strong decays $eta to pi^+pi^-$ and $eta^prime(958) to pi^+pi^-$ has been performed using approximately $2.5 times 10^{7}$ events of each of the decays $D^+ to pi^+pi^+pi^-$ and $D_s^+ to pi^+pi^+pi^-$, recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb$^{-1}$ of $pp$ collision data recorded during LHC Run 1 and 0.3 fb$^{-1}$ recorded in Run 2. No evidence is seen for $D^+_{(s)} to pi^+ eta^{(prime)}$ with $eta^{(prime)} to pi^+pi^-$, and upper limits at 90% confidence level are set on the branching fractions, $mathcal{B}(eta to pi^+pi^-) < 1.6 times 10^{-5}$ and $mathcal{B}(eta^prime to pi^+pi^-) < 1.8 times 10^{-5}$. The limit for the $eta$ decay is comparable with the existing one, while that for the $eta^prime$ is a factor of three smaller than the previous limit.
Review of prospects for discovery of new physics signals at LEP2. The areas covered include SUSY, exotic fermions, BESS models, leptoquarks, virtual effects and CP violating observables.
Motivated by recent measurements of the radiative decay rates of the emph{P}-wave spin singlet charmonium $h_c$ to the light meson $eta$ or $eta^prime$ by the BESIII Collaboration, we investigate the decay rates of these channels at order $alpha alpha_s^4$. The photon is radiated mainly from charm quark pairs in the lowest order Feynman diagrams, since the diagrams where a photon radiated from light quarks are suppressed by $alpha_s$ or the relative charm quark velocity $v$, due to Charge parity conservation. The form factors of two gluons to $eta$ or $eta^prime$ are employed, which are the major mechanism for $eta$ and $eta^prime$ productions. $eta(eta^prime)$ is treated as a light cone object when we consider that the parent charmonium mass is much heavier than that of the final light meson. We obtain the branching ratio ${cal B}(h_cto gammaeta^prime) = (1.94^{+0.70}_{-0.51})times 10^{-3}$ in the nonrelativistic QCD approach, which is in agreement with the BESIII measurement. The prediction of the branching ratio of $h_cto gammaeta$ is also within the range of experimental error after including the larger uncertainty of the total decay width $Gamma_{h_c}$. The applications of these formulae to the radiative decays to $eta(eta^prime)$ of the emph{P}-wave spin singlet bottomonium $h_b(nP)$ are presented. These studies will shed some light on the $eta - eta^prime$ mixing effects, the flavor SU(3) symmetry breaking, as well as the nonperturbative dynamics of charmonium and bottomonium.
While the LHC did not observe direct evidence for physics beyond the standard model, indirect hints for new physics were uncovered in the flavour sector in the decays $Bto K^*mu^+mu^-$, $Bto Kmu^+mu^-/Bto Ke^+e^-$, $B_stophimu^+mu^-$, $Bto D^{(*)}tau u$ and $htotau^pmmu^mp$. Each observable deviates from the SM predictions at the $2-3,sigma$ level only, but combining all $bto smu^+mu^-$ data via a global fit, one finds $4-5,sigma$ difference for NP compared to the SM and combining $Bto D^{*}tau u$ with $Bto Dtau u$ one obtains $3.9,sigma$. While $Bto D^{(*)}tau u$ and $htotaumu$ can be naturally explained by an extended Higgs sector, the $bto smu^+mu^-$ anomalies point at a $Z$ gauge boson. However, it is also possible to explain $Bto D^{(*)}tau u$ and $bto smu^+mu^-$ simultaneously with leptoquarks while their effect in $htotau^pmmu^mp$ is far too small to account for current data. Combining a 2HDM with a gauged $L_mu-L_tau$ symmetry allows for explaining the $bto smu^+mu^-$ anomalies in combination with $htotau^pmmu^mp$, predicting interesting correlations with $tauto3mu$. In the light of these deviations from the SM we also discuss the possibilities of observing lepton flavour violating $B$ decays (e.g. $Bto K^{(*)}tau^pmmu^mp$ and $B_stotau^pmmu^mp$).
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