ArcAdiA

An improved Standard Model prediction of BR(B →τν) and its implicationsfor New Physics

2010-02-24T23:00:00Z

An improved Standard Model prediction of BR(B →τν) and its implicationsfor New Physics Bona, Marcella; Ciuchini, Marco; Franco, Enrico; Lubicz, Vittorio; Martinelli, Guido; Parodi, Fabrizio; Pierini, Maurizio; Schiavi, Carlo; Silvestrini, Luca; Sordini, Viola; Stocchi, Achille; Tarantino, Cecilia; Vagnoni, Vincenzo 2010-02-25 Physics Letters B 687 61-69 The recently measured B →τν branching ratio allows to test the Standard Model by probing virtual effects of new heavy particles, such as a charged Higgs boson. The accuracy of the test is currently limited by the experimental error on BR(B → τν) and by the uncertainty on the parameters f B and |Vub|. The redundancy of the Unitarity Triangle fit allows to reduce the error on these parameters and thus to perform a more precise test of the Standard Model. Using the current experimental inputs, we obtain BR(B →τν)SM = (0.84±0.11)×10−4, to be compared with BR(B →τν)exp = (1.73±0.34)×10−4. The Standard Model prediction can be modified by New Physics effects in the decay amplitude as well as in the Unitarity Triangle fit. We discuss how to disentangle the two possible contributions in the case of minimal flavour violation at large tan β and generic loop-mediated New Physics. We also consider two specific models with minimal flavour violation: the Type-II Two Higgs Doublet Model and the Minimal Supersymmetric Standard Model.

Status of the Unitarity Triangle Analysis

2008-12-31T23:00:00Z

Status of the Unitarity Triangle Analysis Bona, Marcella; Ciuchini, Marco; Franco, Enrico; Lubicz, Vittorio; Martinelli, Guido; Parodi, Fabrizio; Pierini, Maurizio; Schiavi, Carlo; Silvestrini, Luca; Sordini, Viola; Stocchi, Achille; Tarantino, Cecilia; Vagnoni, Vincenzo 2009 160-163 We present an update of the Unitarity Triangle (UT) analysis, within the Standard Model (SM) and beyond. Within the SM the main novelties are the inclusion in eK of the contributions of x and fe 6= p /4 pointed out by A. J. Buras and D. Guadagnoli, and an accurate prediction of BR(B→tn), by using the indirect determination of |Vub| from the UT fit, which can be compared to the present experimental result. In the generalization of the UT analysis to investigate New Physics (NP) effects, the estimate of x is more delicate and only the effect of fe 6= p /4 has been included. We confirm an hint of NP in the Bs-¯Bs mixing at the 2.9s level, which makes a comparison with new experimental data certainly desired.

First evidence of new physics in b ↔ s transitions

2009-11-30T23:00:00Z

First evidence of new physics in b ↔ s transitions Bona, Marcella; Ciuchini, Marco; Franco, Enrico; Lubicz, Vittorio; Martinelli, Guido; Parodi, Fabrizio; Pierini, Maurizio; Schiavi, Carlo; Silvestrini, Luca; Sordini, Viola; Stocchi, Achille; Vagnoni, Vincenzo 2009-12 PMC Physics A 3 We combine all the available experimental information on Bs mixing, including the very recent tagged analyses of Bs → J/Ψϕ by the CDF and DØ collaborations. We find that the phase of the Bs mixing amplitude deviates more than 3σ from the Standard Model prediction. While no single measurement has a 3σ significance yet, all the constraints show a remarkable agreement with the combined result. This is a first evidence of physics beyond the Standard Model. This result disfavours New Physics models with Minimal Flavour Violation with the same significance.