Supersymmetric Contributions to Bs->K+K-

Inspired by the existing calculation of B->piK decays in supersymmetry (SUSY), we evaluate the dominant SUSY contributions to Bs->K+K-. We show that the observables of this process can be significantly modified in the presence of SUSY. In particular, the branching ratio can be increased considerably compared to the prediction of the standard model (SM). The effect is even more dramatic for the CP-violating asymmetries A_dir and A_mix. These asymmetries, expected to be small in the SM (A_dir is predicted to take only positive values), change drastically with SUSY contributions. The measurement of these observables can therefore be used to detect the presence of physics beyond the SM, and put constraints on its parameters.Comment: 17 pages, 2 figures. This new version contains one added reference and some minor style change

b→sb \to s Transitions in Family-dependent U(1)′U(1)^\prime Models

We analyze flavor-changing-neutral-current (FCNC) effects in the $b\to s$ transitions that are induced by family non-universal $U(1)'$ gauge symmetries. After systematically developing the necessary formalism, we present a correlated analysis for the $\Delta B =1, 2$ processes. We adopt a model-independent approach in which we only require family-universal charges for the first and second generations and small fermion mixing angles. We analyze the constraints on the resulting parameter space from $B_s - \bar B_s$ mixing and the time-dependent CP asymmetries of the penguin-dominated $B_d \to (\pi, \phi, \eta', \rho, \omega, f_0)K_S$ decays. Our results indicate that the currently observed discrepancies in some of these modes with respect to the Standard Model predictions can be consistently accommodated within this general class of models.Comment: 36 pages, 11 figure

First ADS analysis of B- -> D0K- decays in hadron collisions

Proceedings of DISCRETE 2010, Symposium on Prospects in the Physics of Discrete Symmetries, Rome (IT), 6-11 December 2010Comment: 7 pages, 5 figure

NNLO fermionic corrections to the charm quark mass dependent matrix elements in B -> X_s gamma

We compute the virtual O(alpha_s^2) fermionic contributions to the charm quark mass dependent matrix elements of the B -> X_s gamma decay. In the case of a massless quark loop insertion into the gluon propagator, our result obtained as an expansion in z=m_c^2/m_b^2 and an exact expression in terms of multi-fold MB integrals, confirms the findings of Bieri, Greub and Steinhauser [19]. We observe, however, large deviations in the case of a b-quark loop insertion.The charm quark loop shows smaller, but still noticeable differences.Comment: 11 pages, 3 figures, 1 tabl

Precision Flavour Physics with B→KννˉB\to K\nu\bar\nu and B→Kl+l−B\to Kl^+l^-

We show that a combined analysis of $B\to K\nu\bar\nu$ and $B\to Kl^+l^-$ allows for new physics tests practically free of form factor uncertainties. Residual theory errors are at the level of several percent. Our study underlines the excellent motivation for measuring these modes at a Super Flavour Factory.Comment: 26 pages, 2 figure

Prospects for the direct detection of neutralino dark matter in orbifold scenarios

We analyse the phenomenology of orbifold scenarios from the heterotic superstring, and the resulting theoretical predictions for the direct detection of neutralino dark matter. In particular, we study the parameter space of these constructions, computing the low-energy spectrum and taking into account the most recent experimental and astrophysical constraints, as well as imposing the absence of dangerous charge and colour breaking minima. In the remaining allowed regions the spin-independent part of the neutralino-proton cross section is calculated and compared with the sensitivity of dark matter detectors. In addition to the usual non universalities of the soft terms in orbifold scenarios due to the modular weight dependence, we also consider D-term contributions to scalar masses. These are generated by the presence of an anomalous U(1), providing more flexibility in the resulting soft terms, and are crucial in order to avoid charge and colour breaking minima. Thanks to the D-term contribution, large neutralino detection cross sections can be found, within the reach of projected dark matter detectors.Comment: 51 pages, 25 figure

Right-Handed New Physics Remains Strangely Beautiful

Current data on CP violation in B_d -> eta' K_S and B_d -> phi K_S, taken literally, suggest new physics contributions in b -> s transitions. Despite a claim to the contrary, we point out that right-handed operators with a single weak phase can account for both deviations thanks to the two-fold ambiguity in the extraction of the weak phase from the corresponding CP-asymmetry. This observation is welcome since large mixing in the right-handed sector is favored by many GUT models and frameworks which address the flavor puzzle. There are also interesting correlations with the B_s system which provide a way to test this scenario in the near future.Comment: 7 pages, 9 figures; published version: added 1 reference and 1 clarificatio

Lepton non-universality at LEP and charged Higgs

A recent analysis of the LEP data shows an interesting deviation from lepton universality in W boson decays. An excess at the level of 2.8 sigma is found in the tau mode branching ratio with respect to the other two modes. It is suggested that this seeming lepton non-universality might stem from pair production of charged Higgs bosons almost degenerate with W, that preferentially decay to heavy fermions. It is shown that the deviation can be reduced to 1.4 sigma in two Higgs doublet model I without any conflict with the existing direct or indirect constraints. This conclusion is largely independent of tan beta, the ratio of Higgs vacuum expectation values. This scenario can be tested at the forthcoming international linear collider.Comment: 16 pages, published version with minor change

Constraining the MSSM with universal gaugino masses and implication for searches at the LHC

Using a Markov chain Monte Carlo approach, we find the allowed parameter space of a MSSM model with seven free parameters. In this model universality conditions at the GUT scale are imposed on the gaugino sector. We require in particular that the relic density of dark matter saturates the value extracted from cosmological measurements assuming a standard cosmological scenario. We characterize the parameter space of the model that satisfies experimental constraints and illustrate the complementarity of the LHC searches, B-physics observables and direct dark matter searches for further probing the parameter space of the model. We also explore the different decay chains expected for the coloured particles that would be produced at LHC.Comment: 29 pages, 11 figure

Bs(d)0−Bˉs(d)0B^0_{s(d)} - \bar{B}^0_{s(d)} mixing and new physics effects in a top quark two-Higgs doublet model

We calculate the new physics contributions to the neutral $B_d^0$ and $B_s^0$ meson mass splitting $\Delta M_d$ and $\Delta M_s$ induced by the box diagrams involving the charged-Higgs bosons in the top quark two-Higgs doublet model (T2HDM). Using the precision data, we obtain the bounds on the parameter space of the T2HDM: (a) for fixed $M_H=400$ GeV and $\delta=[0^\circ,60^\circ]$, the upper bound on $\tan{\beta}$ is $\tan \beta \leq 30$ after the inclusion of major theoretical uncertainties; (b) for the case of $\tan{\beta} \leq 20$, a light charged Higgs boson with a mass around 300 GeV is allowed; and (c) the bounds on $\tan{\beta}$ and $M_H$ are strongly correlated: a smaller (larger) $\tan{\beta}$ means a lighter (heavier) charged Higgs boson.Comment: 11 pages, 2 EPS figures, RevTex, new references adde