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Register a new userNew Physics Effects in CP-Violating B Decays
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Lincoln Wolfenstein
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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.
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At present, there are several measurements of $B$ decays that exhibit discrepancies with the predictions of the SM, and suggest the presence of new physics (NP) in $b to s mu^+ mu^-$ transitions. Many NP models have been proposed as explanations. These involve the tree-level exchange of a leptoquark (LQ) or a flavor-changing $Z$ boson. In this paper we examine whether it is possible to distinguish the various models via CP-violating effects in $B to K^{(*)} mu^+ mu^-$. Using fits to the data, we find the following results. Of all possible LQ models, only three can explain the data, and these are all equivalent as far as $b to s mu^+ mu^-$ processes are concerned. In this single LQ model, the weak phase of the coupling can be large, leading to some sizeable CP asymmetries in $B to K^{(*)} mu^+ mu^-$. There is a spectrum of $Z$ models; the key parameter is $g_L^{mumu}$, which describes the strength of the $Z$ coupling to $mu^+mu^-$. If $g_L^{mumu}$ is small (large), the constraints from $B^0_s$-${bar B}^0_s$ mixing are stringent (weak), leading to a small (large) value of the NP weak phase, and corresponding small (large) CP asymmetries. We therefore find that the measurement of CP-violating asymmetries in $B to K^{(*)} mu^+ mu^-$ can indeed distinguish among NP $b to s mu^+ mu^-$ models
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 $B_stotau^pmmu^mp$).
We report theoretical results of the electric dipole moment (EDM) of $^{210}$Fr which arises from the interaction of the EDM of an electron with the internal electric field in an atom and the scalar-pseudoscalar electron-nucleus interaction; the two dominant sources of CP violation in this atom. Employing the relativistic coupled-cluster theory, we evaluate the enhancement factors for these two CP violating interactions to an accuracy of about 3% and analyze the contributions of the many-body effects. These two quantities in combination with the projected sensitivity of the $^{210}$Fr EDM experiment provide constraints on new physics beyond the Standard Model. Particularly, we demonstrate that their precise values are necessary to account for the effect of the bottom quark in models in which the Higgs sector is augmented by nonstandard Yukawa interactions such as the two-Higgs doublet model.
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 $D^-tomubar{ u}$
At the present time, there are a number of measurements of $B$-decay observables that disagree with the predictions of the standard model. These discrepancies have been seen in processes governed by two types of decay: (i) $b to s mu^+ mu^-u$ and (ii) $b to c tau^- {bar u}$. In this talk, I review the experimental results, as well as the proposed new-physics explanations. We may be seeing the first signs of physics beyond the standard model.
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