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We summarize the results of two recent searches for flavor-changing neutral current, lepton-flavor violating, and lepton-number violating decays of D+, Ds, and D0 mesons (and their antiparticles) into modes containing muons and electrons.…
Following the intriguing hints of deviations from the Standard Model in rare B meson decays, searches for rare and forbidden decays of charm hadrons become a hot topic again. We present recent results on Flavour Changing Neutral Current…
LHCb, bolstered up by the 10^12 b-hadrons produced yearly, is an excellent place to study rare B decays. The B_s to mu^+ mu^- decay, generated by flavour-changing neutral current, is strongly suppressed within the Standard Model (SM).…
We report a fully inclusive measurement of the flavor changing neutral current decay $B\to X_s\gamma$ in the energy range $1.7 \GeV\le E^\mathrm{c.m.s}_\gamma\le 2.8 \GeV$, covering 97% of the total spectrum, where c.m.s is the center of…
We investigate the potential effects of the scalar flavour changing neutral currents that are generated e.g. in supersymmetry with $\tan\beta\gg1$ in the $b\to sl^+l^-$ transitions. Using the experimental upper limit on…
We study the decay width and forward-backward asymmetry of the lepton pair for the inclusive decay b --> s \tau^+ \tau^- in the two Higgs doublet model with three level flavor changing neutral currents (model III) and analyse the…
A short overview of motivations and successes of two-body exchange currents between constituent quarks for electromagnetic hadron observables like charge radii, magnetic and quadrupole moments is given. We then predict and analyze exchange…
Branching fraction and effective lifetime measurements of the rare decay $B^0_s\to\mu^+\mu^-$ and searches for the decays $B^0\to\mu^+\mu^-$ and $B^0_s\to\mu^+\mu^-\gamma$ are reported using proton-proton collision data collected with the…
We examine the decays $t\rightarrow c\gamma$ and $c Z^0$ in the Standard Model with an extra scalar doublet and no discrete symmetry preventing tree-level flavour changing neutral currents. The Yukawa couplings of the new scalars are…
LHCb has reported deviations from the Standard Model in $b\to s\mu^+\mu^-$ transitions for which a new neutral gauge boson is a prime candidate for an explanation. As this gauge boson has to couple in a flavour non-universal way to muons…
A search for flavor-changing neutral current interactions of the top quark (t) and the Higgs boson (H) is presented. The search is based on proton-proton collision data collected in 2016-2018 at a center-of-mass energy of 13 TeV with the…
The semileptonic $B_{(s)} \rightarrow T(J^P=2^-)l^+l^-$ decays induced by flavor changing neural currents are investigated within the light cone QCD sum rule method. We apply the $B$ meson distribution amplitudes up to twist-4 and calculate…
Leptophobic Z' gauge bosons can appear in models with an E_6 gauge symmetry. We show that flavour-changing neutral currents can be generated in some of these models due to the mixing of the ordinary d_R, s_R and b_R quark fields with the…
We present a search for the rare decays B+ -> K+ nu nubar and B0 -> K0 nu nubar using 459 million BBbar pairs collected with the BaBar detector at the SLAC National Accelerator Laboratory. Flavor-changing neutral-current decays such as…
Inspired by the discrepancies observed in the $b\to s\ell^+\ell^-$ neutral current decays, we study the decay channel $B_c\to D_s^{(\ast)} \,\ell^+\ell^-$ ($\ell=\mu,\tau$), which is based on the same flavor changing neutral current (FCNC)…
We investigate the bounds on axionlike states from flavor-changing neutral current b->s decays, assuming the axion couples to the standard model through mixing with the Higgs sector. Such GeV-scale axions have received renewed attention in…
Semileptonic B meson decays induced by $b \to s(d) l^+ l^-$ flavour changing neutral current (FCNC) transitions are very important to probe the quark-flavour sector of the standard model (SM) and also offer a probe to test new physics (NP).…
We are reporting on a search for flavour-changing neutral current decays $D^0 \to \mu^+ \mu^-$ and $D^0 \to e^+ e^-$, and for lepton-flavour violating decays $D^0 \to e^\pm \mu^\mp$, the measurement of $D^+_{(s)} \to K_S^0 \pi^+$ and…
Flavor changing neutral current and CP violating processes are discussed in the minimal supergravity model. The constraint on charged Higgs mass from the new measurement of the inclusive branching ratio of the $b\rightarrow s\gamma$ process…
We study the neutral current flavour changing rare decay mode $B\to K \gamma \gamma $ within the framework of Standard Model, including the long distance contributions. It is found that these long distance contributions can larger than the…