0000000001019159
AUTHOR
Ph. Boucaud
showing 19 related works from this author
Non-perturbatively renormalised light quark masses from a lattice simulation with Nf=2
2006
Abstract We present results for the light quark masses obtained from a lattice QCD simulation with N f = 2 degenerate Wilson dynamical quark flavours. The sea quark masses of our lattice, of spacing a ≃ 0.06 fm , are relatively heavy, i.e., they cover the range corresponding to 0.60 ≲ M P / M V ≲ 0.75 . After implementing the non-perturbative RI-MOM method to renormalise quark masses, we obtain m ud MS ¯ ( 2 GeV ) = 4.3 ± 0.4 −0 +1.1 MeV , and m s MS ¯ ( 2 GeV ) = 101 ± 8 −0 +25 MeV , which are about 15% larger than they would be if renormalised perturbatively. In addition, we show that the above results are compatible with those obtained in a quenched simulation with a similar lattice.
A Wilson-Yukawa Model with undoubled chiral fermions in 2D
1997
We consider the fermion spectrum in the strong coupling vortex phase of a lattice fermion-scalar model with a global $U(1)_L\times U(1)_R$, in 2D, in the context of a recently proposed two-cutoff lattice formulation. The fermion doublers are made massive by a strong Wilson-Yukawa coupling, but in contrast with the standard formulation of these models, in which the light fermion spectrum was found to be massive and vectorlike, we find massless undoubled fermions with chiral quantum numbers at finite lattice spacing. When the global symmetry is gauged, this model is expected to give rise to a chiral gauge theory.
Matrix elements of decays
2004
We present a numerical computation of matrix elements of ?I = 3/2 K ? ?? decays by using Wilson fermions. In order to extrapolate to the physical point we work at unphysical kinematics and we resort to Chiral Perturbation Theory at the next-to-leading order. In particular we explain the case of the electroweak penguins 07,8 which can contribute significantly in the theoretical prediction of sol|??/?. The study is done at ? = 6.0 on a 243 × 64 lattice.
Light meson physics from maximally twisted mass lattice QCD
2009
40 pages, 5 figures, 8 tables, 3 appendix.-- PACS: 11.15.Ha; 12.38.Gc; 12.39.Fe
On the zero crossing of the three-gluon vertex
2016
We report on new results on the infrared behaviour of the three-gluon vertex in quenched Quantum Chormodynamics, obtained from large-volume lattice simulations. The main focus of our study is the appearance of the characteristic infrared feature known as 'zero crossing', the origin of which is intimately connected with the nonperturbative masslessness of the Faddeev-Popov ghost. The appearance of this effect is clearly visible in one of the two kinematic configurations analyzed, and its theoretical origin is discussed in the framework of Schwinger-Dyson equations. The effective coupling in the momentum subtraction scheme that corresponds to the three-gluon vertex is constructed, revealing t…
Kaon weak matrix elements with Wilson fermions
2002
We present results of several numerical studies with Wilson fermions relevant for kaon physics. We compute the B_K parameter by using two different methods and extrapolate to the continuum limit. Our preliminary result is B_K(2 GeV)=0.66(7). Delta I=3/2 K->pi pi matrix elements are obtained by using the next-to-leading order expressions derived in chiral perturbation theory in which the low energy constants are determined by the lattice results computed at unphysical kinematics. From the simulation at beta=6.0 our (preliminary) results read: _{I=2}=0.14(1)(1) GeV^3 and _{I=2}=0.69(6)(6) GeV^3.
K --> pi pi matrix elements beyond the leading-order chiral expansion
2002
We propose an approach for calculating $K\to\pi\pi$ decays to the next-to-leading order in chiral expansion. A detailed numerical study of this approach is being performed.
Matrix elements of (delta S=2) operators with Wilson fermions
2002
We test the recent proposal of using the Ward identities to compute the K0-K0bar mixing amplitude with Wilson fermions, without the problem of spurious lattice subtractions. From our simulations, we observe no difference between the results obtained with and without subtractions. In addition, from the standard study of the complete set of (delta S=2) operators, we quote the following (preliminary) results (in the MS(NDR) scheme): Bk(2 GeV)=0.70(10), < O7^{3/2}>_{K->pi pi} = 0.10(2)(1) GeV^3, < O8^{3/2}>_{K->pi pi} = 0.49(6)(0) GeV^3.
BK from the lattice with Wilson quarks
2004
We report our results for the bag-parameter BK obtained from the quenched simulations on the lattice with Wilson fermions at three values of the lattice spacing. We implemented the method by which no subtraction of the mixing with other four-fermion dS=2 operators is needed. Our final result, in terms of the renormalisation group invariant bag-parameter, is BK = 0.96 +/- 0.10.
Light hadron spectrum, renormalization constants and light quark masses with two dynamical fermions
2004
The results of a preliminary partially quenched (N_f=2) study of the light hadron spectrum, renormalization constants and light quark masses are presented. Numerical simulations are carried out with the LL-SSOR preconditioned Hybrid Monte Carlo with two degenerate dynamical fermions, using the plaquette gauge action and the Wilson quark action at beta = 5.8. Finite volume effects have been investigated employing two lattice volumes: 16^3 x 48 and 24^3 x 48. Configurations have been generated at four values of the sea quark mass corresponding to M_{PS}/M_V ~ 0.6 - 0.8.
Three-gluon Green functions: low-momentum instanton dominance and zero-crossing
2016
International audience; We will report on a some efforts recently made in order to gain a better understanding of some IR properties of the 3-point gluon Green function by following both lattice and continuum QCD approaches.
Semi-leptonic Decays of Heavy Flavours on a Fine Grained Lattice
1994
We present the results of a numerical calculation of semi-leptonic form factors relevant for heavy flavour meson decays into light mesons, at $\beta=6.4$ on a $24^3 \times 60$ lattice, using the Wilson action in the quenched approximation. We obtain $f^+_K(0)=0.65\pm 0.18$, $V(0)=0.95\pm 0.34$, $A_1(0)=0.63\pm 0.14 $ and $A_2(0)=0.45\pm 0.33 $. We also obtain $A_1(q^2_{max})=0.62\pm 0.09$, $V(0)/A_1(0)=1.5\pm 0.28 $ and $A_2(0)/A_1(0)=0.7\pm 0.4$. The results for $f^+_K(0)$, $V(0)$ and $A_1(0)$ are consistent with the experimental data and with previous lattice determinations with larger lattice spacings. In the case of $A_2(0)$ the errors are too large to draw any firm conclusion. We have …
An exploratory lattice study of Delta I=3/2 K ->pi pi decays at next-to-leading order in the chiral expansion
2005
We present the first direct evaluation of Delta I = 3/2K -> pi pi matrix elements with the aim of determining all the low-energy constants at NLO in the chiral expansion. Our numerical investigation demonstrates that it is indeed possible to determine the K -> pi pi matrix elements directly for the masses and momenta used in the simulation with good precision. In this range however, we find that the matrix elements do not satisfy the predictions of NLO chiral perturbation theory. For the chiral extrapolation we therefore use a hybrid procedure which combines the observed polynomial behavior in masses and momenta of our lattice results, with NLO chiral perturbation theory at lower masses. In…
Dynamical twisted mass fermions with light quarks: simulation and analysis details
2008
In a recent paper [hep-lat/0701012] we presented precise lattice QCD results of our European Twisted Mass Collaboration (ETMC). They were obtained by employing two mass-degenerate flavours of twisted mass fermions at maximal twist. In the present paper we give details on our simulations and the computation of physical observables. In particular, we discuss the problem of tuning to maximal twist, the techniques we have used to compute correlators and error estimates. In addition, we provide more information on the algorithm used, the autocorrelation times and scale determination, the evaluation of disconnected contributions and the description of our data by means of chiral perturbation theo…
Matrix elements of Delta I=3/2 K ->pi pi decays
2004
We present a numerical computation of matrix elements of DeltaI = 3/2 K --> pipi decays by using Wilson fermions. In order to extrapolate to the physical point we work at unphysical kinematics and we resort to Chiral Perturbation Theory at the next-to-leading order. In particular we explain the case of the electroweak penguins O-7,O-8 which can contribute significantly in the theoretical prediction of epsilon'/epsilon. The study is done at beta = 6.0 on a 24(3) x 64 lattice.
Non-perturbatively renormalised light quark masses from a lattice simulation with N(f) = 2
2006
We present results for the light quark masses obtained from a lattice QCD simulation with N-f = 2 degenerate Wilson dynamical quark flavours. The sea quark masses of our lattice, of spacing a similar or equal to 0.06 fm, are relatively heavy, i.e., they cover the range corresponding to 0.60 less than or similar to M-p/M-V less than or similar to 0.75. After implementing the non-perturbative RI-MOM method to renormalise quark masses, we obtain m(ud)((MS) over bar)(2 GeV)= 4.3 +/- 0.4(-0)(+1.1) MeV, and m(s)((MS) over bar)(2 GeV) = 101 +/- 8(-0)(+25) MeV, which are about 15% larger than they would be if renormalised perturbatively. In addition, we show that the above results are compatible wi…
Dynamical twisted mass fermions with light quarks
2007
We present results of dynamical simulations with 2 flavours of degenerate Wilson twisted mass quarks at maximal twist in the range of pseudo scalar masses from 300 to 550 MeV. The simulations are performed at one value of the lattice spacing a \lesssim 0.1 fm. In order to have O(a) improvement and aiming at small residual cutoff effects, the theory is tuned to maximal twist by requiring the vanishing of the untwisted quark mass. Precise results for the pseudo scalar decay constant and the pseudo scalar mass are confronted with chiral perturbation theory predictions and the low energy constants F, \bar{l}_3 and \bar{l}_4 are evaluated with small statistical errors.
Extraction of K --> pi pi matrix elements with Wilson fermions
2001
We present the status of a lattice calculation for the K-->pipi matrix elements of the (delta S=1) effective weak Hamiltonian, directly with two pion in the final state. We study the energy shift of two pion in a finite volume both in the I=0 and I=2 channels. We explain a method to avoid the Goldstone pole contamination in the computation of renormalization constants for (delta I=3/2) operators. Finally we show some preliminary results for the matrix elements of (delta I=1/2) operators. Our quenched simulation is done at beta=6.0, with Wilson fermions, on a (24^3 X 64) lattice.
K-0-(K)over-bar(0) mixing with Wilson fermions without subtractions
2000
By using suitable Ward identities, we show that it is possible to compute K-0-(K) over bar(0) mixing without subtracting the terms generated by explicit chiral symmetry breaking present in Wilson-like lattice actions. The accuracy in the determination of the amplitudes is of O(a), which is the best one attainable in the absence of improvement.