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Register a new userExplaining B decays anomalies in SUSY models
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Recent measurements of certain B decays indicate deviations from Standard Model (SM) predictions. We show that Supersymmetric effects can increase the Branching Ratios (BRs) of both $Bto D {tau} { u}_{tau}$ and $Bto D^ast {tau} { u}_{tau}$ with respect to the SM rates, thereby approaching their newest experimentally measured values.
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We study supersymmetric (SUSY) effects on $C_7(mu_b)$ and $C_7(mu_b)$ which are the Wilson coefficients (WCs) for $b to s gamma$ at b-quark mass scale $mu_b$ and are closely related to radiative $B$-meson decays. The SUSY-loop contributions to $C_7(mu_b)$ and $C_7(mu_b)$ are calculated at leading order (LO) in the Minimal Supersymmetric Standard Model (MSSM) with general quark-flavour violation (QFV). For the first time we perform a systematic MSSM parameter scan for the WCs $C_7(mu_b)$ and $C_7(mu_b)$ respecting all the relevant constraints, i.e. the theoretical constraints from vacuum stability conditions and the experimental constraints, such as those from $K$- and $B$-meson data and electroweak precision data, as well as recent limits on SUSY particle masses and the 125 GeV Higgs boson data from LHC experiments. From the parameter scan we find the following: (1) The MSSM contribution to Re($C_7(mu_b)$) can be as large as $sim pm 0.05$, which could correspond to about 3$sigma$ significance of New Physics (NP) signal in the future LHCb and Belle II experiments. (2) The MSSM contribution to Re($C_7(mu_b)$) can be as large as $sim -0.08$, which could correspond to about 4$sigma$ significance of NP signal in the future LHCb and Belle II experiments. (3) These large MSSM contributions to the WCs are mainly due to (i) large scharm-stop mixing and large scharm/stop involved trilinear couplings, (ii) large sstrange-sbottom mixing and large sstrange-sbottom involved trilinear couplings and (iii) large bottom Yukawa coupling $Y_b$ for large $tanbeta$ and large top Yukawa coupling $Y_t$. In case such large NP contributions to the WCs are really observed in the future experiments at Belle II and LHCb Upgrade, this could be the imprint of QFV SUSY (the MSSM with general QFV).
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.
The direct searches for Beyond Standard Model (BSM) particles have been constraining their mass scale to the extent where it is now becoming consensual that such particles are likely to be above the energy reach of the LHC. Meanwhile, the studies of indirect probes of BSM physics, with all their diversity, have been progressing both in accurracy and in setting up observables with reduced theoretical uncertainties. The observation of flavour anomalies in $b$ hadron decays represents an important part of the program of indirect detection of BSM physics. Several benchmark analyses involving leptonic or semileptonic decays are presented, with an emphasis on intriguing patterns which are systematic in their trend, though not individually significant yet.
We study a class of DFSZ-like models for the QCD axion that can address observed anomalies in stellar cooling. Stringent constraints from SN1987A and neutron stars are avoided by suppressed couplings to nucleons, while axion couplings to electrons and photons are sizable. All axion couplings depend on few parameters that also control the extended Higgs sector, in particular lepton flavor-violating couplings of the Standard Model-like Higgs boson $h$. This allows us to correlate axion and Higgs phenomenology, and we find that that ${rm BR}(h to tau e)$ can be as large as the current experimental bound of 0.22%, while ${rm BR} (h to mu mu)$ can be larger than in the Standard Model by up to 70%. Large parts of the parameter space will be tested by the next generation of axion helioscopes such as the IAXO experiment.
$tau$ leptons emitted in cascade decays of supersymmetric particles are polarized. The polarization may be exploited to determine spin and mixing properties of the neutralinos and stau particles involved.
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