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).

Vector and scalar form factors for K- and D-mesonsemileptonic decays from twisted mass fermionswith Nf = 2

2008-12-31T23:00:00Z

Vector and scalar form factors for K- and D-mesonsemileptonic decays from twisted mass fermionswith Nf = 2 Di Vita, Stefano; Haas, Benjamin; Lubicz, Vittorio; Mescia, Federico; Simula, Silvano; Tarantino, Cecilia 2009 257-264 We present lattice results for the formfactors relevant in the K→p ℓnℓ and D→p ℓnℓ semileptonic decays, obtained from simulations with two flavors of dynamical twisted-mass fermions and pion masses as light as 260 MeV. For K →p ℓn decays we discuss the estimates of the main sources of systematic uncertainties, including the quenching of the strange quark, leading to our final result f+(0) = 0.9560(57)stat.(62)syst.. Combined with the latest experimental data, our value of f+(0) implies for the CKMmatrix element |Vus| the value 0.2267(5)exp.(20) f+(0) consistent with the first-row CKM unitarity. For D →p ℓnℓ decays the application of Heavy Meson Chiral Perturbation Theory allows to extrapolate our results for both the scalar and the vector form factors at the physical point with quite good accuracy, obtaining a nice agreement with the experimental data. In particular at zero-momentumtransfer we obtain f+(0) = 0.64(5). A preliminary analysis of the discretization effects is presented and discussed.

K ->pi l nu semileptonic form factors from two-flavor lattice QCD

2009-11-30T23:00:00Z

K ->pi l nu semileptonic form factors from two-flavor lattice QCD Lubicz, Vittorio; Mescia, Federico; Simula, Silvano; Tarantino, Cecilia 2009-12 Physical review D 80 111502 We present new lattice results of the K ->pi l nu semileptonic formfactors obtained from simulations with two flavors of dynamicaltwisted-mass fermions, using pion masses as light as 260 MeV. Our mainresult is f(+)(0)=0.9560(84), which, combined with the latestexperimental data for K-l3 decays, leads to|V-us|=0.2267(5)(exp)(20)(f+)(0). Using the PDG(2008) determinations of|V-ud| and |V-ub| our result implies for the unitarity relation|V-ud|(2)+|V-us|(2)+|V-ub|(2)=1.0004(15). For the O(p(6)) term of thechiral expansion of f(+)(0) we get Delta f equivalent tof(+)(0)-1-f(2)=-0.0214(84).

An estimate of the B --> K* γ Decay Form Factor

2007-03-31T22:00:00Z

An estimate of the B --> K* γ Decay Form Factor Becirevic, Damir; Lubicz, Vittorio; Mescia, Federico 2007-04 Nuclear Physics B 769 31-43 We present the results of a lattice QCD calculation of the form factor relevant to B→K*γ decay. Our final value, T(0) = 0.24 +/- 0.03 (+0.04/-0.01), is obtained in the quenched approximation, and by extrapolating T(q2=0;H--> K*)MH^(3/2) from the directly accessed H-heavy mesons to the meson B. We also show that the extrapolation from B→K*γ* (q2≠0) to B→K*γ (q2=0), leads to a result consistent with the one quoted above. On the other hand, our results are not accurate enough to solve the SU(3) flavor breaking effects in the form factor and we quote TB→K*(0)/TB→ρ(0)=1.2(1), as our best estimate.

K ->pi l nu semileptonic form factors from two-flavor lattice QCD

2009-12-29T23:00:00Z

K ->pi l nu semileptonic form factors from two-flavor lattice QCD Lubicz, Vittorio; Mescia, Federico; Simula, Silvano; Tarantino, Cecilia 2009-12-30 Physical Review D 80 111502 We present new lattice results of the K ->pi l nu semileptonic form factors obtained from simulations with two flavors of dynamicaltwisted-mass fermions, using pion masses as light as 260 MeV. Our main result is f(+)(0)=0.9560(84), which, combined with the latest experimental data for Kl3 decays, leads to |Vus|=0.2267(5)(exp)(20)(f+(0)). Using the PDG(2008) determinations of|Vud| and |Vub| our result implies for the unitarity relation |Vud|^2+|Vus|^2+|Vub|^2=1.0004(15). For the O(p^6) term of the chiral expansion of f+(0) we get Delta f = f+(0)-1-f2=-0.0214(84).

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.

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.