ArcAdiA

A proposal for B-physics on current lattices

2011-12-22T13:34:34Z

A proposal for B-physics on current lattices Blossier, Benoit; Dimopoulos, Petros; Frezzotti, Roberto; Herdoiza, Gregorio; Jansen, Karl; Lubicz, Vittorio; Martinelli, Guido; Michael, Chris; Rossi, Giancarlo; Shindler, Andrea; Simula, Silvano; Tarantino, Cecilia; Urbach, Carsten 2010-04-12 JHEP 2010 1-25 A method to extract B-physics parameters (b-quark mass and fB, fBs decay constants) from currently available lattice data is presented and tested. The approach is based on the idea of constructing appropriate ratios of heavy-light meson masses and decay constants, respectively, possessing a precisely known static limit, and evaluating them at various pairs of heavy quark masses around the charm. Via a smooth interpolation in the heavy quark mass from the easily accessible charm region to the asymptotic point, B-physics parameters are computed with a few percent (statistical + systematic) error using recently produced Nf = 2 maximally twisted Wilson fermions data.

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

2011-12-22T13:34:34Z

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.

fB and fBs with maximally twisted Wilson fermions

2011-12-22T13:39:36Z

fB and fBs with maximally twisted Wilson fermions Blossier, Benoit; Dimopoulos, Petros; Frezzotti, Roberto; Herdoiza, Gregorio; Jansen, Karl; Lubicz, Vittorio; Martinelli, Guido; Michael, Chris; Rossi, Giancarlo; Sanfilippo, Francesco; Shindler, Andrea; Simula, Silvano; Tarantino, Cecilia; Urbach, Carsten; Wagner, Marc 2010 151-158 We present a lattice QCD calculation of the heavy-light decay constants fB and fBs performed with Nf = 2 maximally twisted Wilson fermions, at four values of the lattice spacing. The decay constants have been also computed in the static limit and the results are used to interpolate the observables between the charmand the infinite-mass sectors, thus obtaining the value of the decay constants at the physical b quark mass. Our preliminary results are fB = 191(14)MeV, fBs = 243(14)MeV, fBs/ fB = 1.27(5). They are in good agreement with those obtained with a novel approach, recently proposed by our Collaboration (ETMC), based on the use of suitable ratios having an exactly known static limit.

Status of the Unitarity Triangle Analysis

2011-12-22T13:39:36Z

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

2011-12-22T13:34:55Z

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.

f_B and f_Bs with maximally twisted Wilson fermions

2011-12-22T13:39:36Z

f_B and f_Bs with maximally twisted Wilson fermions ETM Collaboration; Blossier, Benoit; Dimopoulos, Petros; Frezzotti, Roberto; Herdoiza, Gregorio; Jansen, Karl; Lubicz, Vittorio; Martinelli, Guido; Michael, Chris; Rossi, Giancarlo; Sanfilippo, Francesco; Shindler, Andrea; Simula, Silvano; Tarantino, Cecilia; Urbach, Carsten; Wagner, Marc 2009 151 We present a lattice QCD calculation of the heavy-light decay constants f_B and f_Bs performed with Nf=2 maximally twisted Wilson fermions, at four values of the lattice spacing. The decay constants have been also computed in the static limit and the results are used to interpolate the observables between the charm and the infinite-mass sectors, thus obtaining the value of the decay constants at the physical b quark mass. Our preliminary results are f_B=191(14) MeV, f_Bs=243(14) MeV, f_Bs/f_B=1.27(5). They are in good agreement with those obtained with a novel approach, recently proposed by our Collaboration (ETMC), based on the use of suitable ratios having an exactly known static limit.