Lattice renormalisation of O(a) improved heavy-light operators: an addendum

The analytical expressions and the numerical values of the renormalisation constants of dimension 3 static-light currents are given at one-loop order of perturbation theory in the framework of Heavy Quark Effective Theory and with an improved gauge action: the static quark is described by the HYP-smeared action and the light quark is of Wilson kind. This completes a work started few years ago and is actually an intermediate step in the measurement of the decay constants $f_{B}$ and $f_{B_{s}}$ by the European Twisted Mass Collaboration [arXiv:1107.1441[hep-lat]].Comment: 5 pages, no figure

Fermion Masses and Mixings in a Minimal SO(10)X A_4 SUSY GUT

A SUSY SO(10) $\times A_4$ GUT model is constructed for fermion masses and mixing by introducing a minimal set of low dimensional Higgs representations needed to break the guage symmetry down to $SU(3)_c \times U(1)_{em}$. The hierarchy of fermion masses can be understood in the framework of $A_4$ symmetry. From the $A_4$-invariant superpotential, the "double lopsided" mass matrices for the charged leptons and the down quarks are obtained. It is shown that this structure leads to bi-large neutrino mixings simultaneously with small CKM mixing angles. An excellent fit to the masses and mixings of the quarks and leptons as well as to CP violation parameter is obtained. Moreover, the model predicts the neutrino mixing angle $\sin\theta_{13}\approx 0.15$.Comment: 19 pages, 4 figure

The continuum limit of the static-light meson spectrum

We investigate the continuum limit of the low lying static-light meson spectrum using Wilson twisted mass lattice QCD with N_f = 2 dynamical quark flavours. We consider three values of the lattice spacing a ~ 0.051 fm, 0.064 fm, 0.080 fm and various values of the pion mass in the range 280 MeV < m_PS < 640 MeV. We present results in the continuum limit for light cloud angular momentum j = 1/2, 3/2, 5/2 and for parity P = +, -. We extrapolate our results to physical quark masses, make predictions regarding the spectrum of B and B_s mesons and compare with available experimental results.Comment: 18 pages, 3 figure

Lattice renormalisation of O(a) improved heavy-light operators

The analytical expressions and the numerical values of the renormalisation constants of ${\cal O}(a)$ improved static-light currents are given at one-loop order of perturbation theory in the framework of Heavy Quark Effective Theory: the static quark is described by the HYP action and the light quark is described either with the Clover or the Neuberger action. These factors are relevant to extract from a lattice computation the decay constants $f_B$, $f_{B_S}$ and the set of bag parameters $B_i$ associated with $B-\bar{B}$ mixing phenomenology in the Standard Model and beyond.Comment: 16 pages, 2 figures, 4 tables; few comments and references added; version to be published in Phys Rev

Semileptonic B→D∗∗B \to D^{**} decays in Lattice QCD : a feasibility study and first results

We compute the decays ${B\to D^\ast_0}$ and ${B\to D^\ast_2}$ with finite masses for the $b$ and $c$ quarks. We first discuss the spectral properties of both the $B$ meson as a function of its momentum and of the $D^\ast_0$ and $D^\ast_2$ at rest. We compute the theoretical formulae leading to the decay amplitudes from the three-point and two-point correlators. We then compute the amplitudes at zero recoil of ${B\to D^\ast_0}$ which turns out not to be vanishing contrary to what happens in the heavy quark limit. This opens a possibility to get a better agreement with experiment. To improve the continuum limit we have added a set of data with smaller lattice spacing. The ${B\to D^\ast_2}$ vanishes at zero recoil and we show a convincing signal but only slightly more than 1 sigma from 0. In order to reach quantitatively significant results, we plan to fully exploit smaller lattice spacings as well as another lattice regularization.Comment: 31 pages with 15 figures ; sections 5 and 6 revised and update

B_s-\bar{B_s} mixing with a chiral light quark action

We study the $B^0_s-\bar{B^0_s}$ mixing amplitude in Standard Model by computing the relevant hadronic matrix element in the static limit of lattice HQET with the Neuberger light quark action. In the quenched approximation, and after matching to the $\bar{\rm MS}$ scheme in QCD, we obtain $B^{\bar{\rm MS}}_{B_s}(m_b)=0.940(16)(22)$.Comment: 6 pages, 3 figures, talk presented at Lattice 2005 (Heavy quark physics

Ghost-gluon coupling, power corrections and ΛMSˉ\Lambda_{\bar{MS}} from twisted-mass lattice QCD at Nf=2N_f=2

A non-perturbative calculation of the ghost-gluon running QCD coupling constant is performed using $N_f=2$ twisted-mass dynamical fermions. The extraction of $\Lambda_{\bar{MS}}$ in the chiral limit reveals the presence of a non-perturbative OPE contribution that is assumed to be dominated by a dimension-two \VEV{A^2} condensate. In this contest a novel method for calibrating the lattice spacing in lattice simulations is presented.Comment: 7 pages, 4 figures, XXVIII International Symposium on Lattice Field Theory 201

Average up/down, strange and charm quark masses with Nf=2 twisted mass lattice QCD

We present a high precision lattice calculation of the average up/down, strange and charm quark masses performed with Nf=2 twisted mass Wilson fermions. The analysis includes data at four values of the lattice spacing and pion masses as low as ~270 MeV, allowing for accurate continuum limit and chiral extrapolation. The strange and charm masses are extracted by using several methods, based on different observables: the kaon and the eta_s meson for the strange quark and the D, D_s and eta_c mesons for the charm. The quark mass renormalization is carried out non-perturbatively using the RI-MOM method. The results for the quark masses in the MSbar scheme read: m_ud(2 GeV)= 3.6(2) MeV, m_s(2 GeV)=95(6) MeV and m_c(m_c)=1.28(4) GeV. We also obtain the ratios m_s/m_ud=27.3(9) and m_c/m_s=12.0(3).Comment: 20 pages, 5 figures. Typos corrected in eqs. (15)-(17). Version published in Phys. Rev.