ArcAdiA

Kaon oscillations in the Standard Model and Beyond using Nf=2 dynamical quarks

2008-12-31T23:00:00Z

Kaon oscillations in the Standard Model and Beyond using Nf=2 dynamical quarks Bertone, Valerio; Dimopoulos, Petros; Frezzotti, Roberto; Gimenez, Vicent; Lubicz, Vittorio; Mescia, Federico; Palao, David; Papinutto, Mauro; Rossi, Giancarlo; Simula, Silvano; Vladikas, Anastassios 2009 1-7 We compute non-perturbatively the B-parameters of the complete basis of four-fermion operators needed to study the Kaon oscillations in the SM and in its supersymmetric extension. We perform numerical simulations with two dynamical maximally twisted sea quarks at three values of the lattice spacing on configurations generated by the ETMC. Unwanted operator mixings and O(a) discretization effects are removed by discretizing the valence quarks with a suitable Osterwalder-Seiler variant of the Twisted Mass action. Operators are renormalized non-perturbatively in the RI/MOM scheme. Our preliminary result for BK(RGI) is 0.73(3)(3).

A proposal for B-physics on current lattices

2010-04-11T22:00:00Z

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.

fB and fBs with maximally twisted Wilson fermions

2009-12-31T23:00:00Z

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.

Electromagnetic Form Factor of the Pion from Twisted-mass Lattice QCD at Nf=2

2009-03-31T22:00:00Z

Electromagnetic Form Factor of the Pion from Twisted-mass Lattice QCD at Nf=2 Frezzotti, Roberto; Lubicz, Vittorio; Simula, Silvano 2009-04 Physical Review D 79 074506 We present a lattice calculation of the electromagnetic form factor of the pion obtained using the tree-level Symanzik improved gauge action with two flavors of dynamical twisted Wilson quarks. The simulated pion masses range approximately from 260 to 580 MeV, and the lattice box sizes are chosen in order to guarantee that Mpi*L>~4. Accurate results for the form factor are obtained using all-to-all quark propagators evaluated by a stochastic procedure. The momentum dependence of the pion form factor is investigated up to values of the squared four-momentum transfer Q^2~=0.8 GeV^2 and, thanks to the use of twisted boundary conditions, down to Q^2~=0.05 GeV^2. Volume and discretization effects on the form factor appear to be within the statistical errors. Our results for the pion mass, decay constant and form factor are analyzed using (continuum) chiral perturbation theory at next-to-next-to-leading order. The extrapolated value of the pion charge radius is _phys=0.456±0.030(stat)±0.024(syst) in nice agreement with the experimental result. The extrapolated values of the pion form factor agree very well with the experimental data up to Q^2~=0.8 GeV^2 within uncertainties which become competitive with the experimental errors for Q^2>~0.3 GeV^2. The relevant low-energy constants appearing in the chiral expansion of the pion form factor are extracted from our lattice data, which come essentially from a single lattice spacing, adding the experimental value of the pion scalar radius in the fitting procedure. Our findings are in nice agreement with the available results of chiral perturbation theory analyses of pi-pi scattering data as well as with other analyses of our collaboration.

Pseudoscalar decay constants of kaon and D-mesons from Nf=2 twisted mass Lattice QCD

2009-06-30T22:00:00Z

Pseudoscalar decay constants of kaon and D-mesons from Nf=2 twisted mass Lattice QCD ETM, Collaboration; Blossier, Benoit; Dimopoulos, Petros; Frezzotti, Roberto; Haas, Benjamin; Herdoiza, Gregorio; Jansen, Karl; Lubicz, Vittorio; Mescia, Federico; Palao, David; Shindler, Andrea; Simula, Silvano; Tarantino, Cecilia; Urbach, Carsten 2009-07 Journal of High Energy Physics 07 043 We present the results of a lattice QCD calculation of the pseudoscalar meson decay constants fπ, fK, fD and fDs, performed with Nf=2 dynamical fermions. The simulation is carried out with the tree-level improved Symanzik gauge action and with the twisted mass fermionic action at maximal twist. We have considered for the final analysis three values of the lattice spacing, a = 0.10 fm, 0.09 fm and 0.07 fm, with pion masses down to mπ = 270 MeV. Our results for the light meson decay constants are fK = 158.1(2.4) MeV and fK/fπ = 1.210(18). From the latter ratio, by using the experimental determination of Γ(K → μbar nuμ(γ))/Γ(π → μbar nuμ(γ)) and the average value of |Vud| from nuclear beta decays, we obtain |Vus| = 0.2222(34), in good agreement with the determination from semileptonic Kl3 decays and the unitarity constraint. For the D and Ds meson decay constants we obtain fD = 197(9) MeV, fDs = 244(8) MeV and fDs/fD = 1.24(3). Our result for fD is in good agreement with the CLEO experimental measurement. For fDs our determination is smaller than the PDG 2008 experimental average but in agreement with a recent improved measurement by CLEO at the 1.4 σ level.

f_B and f_Bs with maximally twisted Wilson fermions

2008-12-31T23:00:00Z

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.

Pseudoscalar decay constants of kaon and D-mesons from N-f=2 twisted mass Lattice QCD

2009-06-30T22:00:00Z

Pseudoscalar decay constants of kaon and D-mesons from N-f=2 twisted mass Lattice QCD Blossier, Benoît; Dimopoulos, Pedro; Frezzotti, Roberto; Haas, Benjamin; Herdoiza, Gregorio; Jansen, Karl; Lubicz, Vittorio; Mescia, Federico; Palao, David; Shindler, Andrea; Simula, Silvano; Tarantino, Cecilia; Urbach, Carsten; Wenger, Urs 2009-07 Journal of high energy physics 2009 043 We present the results of a lattice QCD calculation of the pseudoscalar meson decay constants f(pi), f(K), f(D) and f(Ds), performed with N-f =2 dynamical fermions. The simulation is carried out with the tree-level improved Symanzik gauge action and with the twisted mass fermionic action at maximal twist. We have considered for the final analysis three values of the lattice spacing, a similar or equal to 0.10 fm, 0.09 fm and 0.07 fm, with pion masses down to m(pi) similar or equal to 270 MeV. Our results for the light meson decay constants are f(K) =158.1(2.4) MeV and f(K)/f(pi) = 1.210(18). From the latter ratio, by using the experimental determination of Gamma(K -> munu(mu)(gamma))/Gamma(pi -> mu nu(mu)(gamma)) and the average value of vertical bar V-ud vertical bar from nuclear beta decays, we obtain vertical bar V-us vertical bar = 0.2222(34), in good agreement with the determination from semileptonic K-13 decays and the unitarity constraint. For the D and D-s meson decay constants we obtain f(D) =197(9) MeV, f(Ds) = 244(8) MeV and f(Ds)/f(D) = 1.24(3). Our result for f(D) is in good agreement with the CLEO experimental measurement. For f(Ds) our determination is smaller than the PDG 2008 experimental average but in agreement with a recent improved measurement by CLEO at the 1.4 sigma level.