Publications (13)46.08 Total impact
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ABSTRACT: We study the dynamical flavour dependence of the lattice estimates of the heavy meson decay constant in the static limit. We perform the analysis by considering negative flavour numbers and by extrapolating the results to positive values. We observe a sizeable flavour dependence which increases the quenched estimates. ROM2F9616 The knowledge of leptonic decay constants of heavy mesons enters the determination of the CabibboKobayashiMaskawa mixing angles. In particular, the value of the B meson decay constant constraints the shape of the unitarity triangle and sets the size of possible CP violation in B decays. Non perturbative estimates of this quantity can be obtained from lattice calculations which are still confronted with various sources of systematic errors. The presence in the dynamics of a heavy meson system of two very different mass scales implies that reasonable values for exploring the B meson dynamics with enough resolution for the heavy quark propagation and enough v...Physics Letters B 06/1998; · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We estimate the effects of dynamical fermions by extrapolating to positive flavour numbers the results from negative values obtained by adding to the pure gauge sector a fermion action where the fields obey a Bose statistics: the bermions. ROM2F9515 1 Introduction Dynamical fermion simulations require the calculation of statistical averages with the pure gauge measure modified by the fermion determinant. Its evaluation is at present the most time consuming step of lattice QCD simulations. In spite of the effort spent to evaluate quantum averages in the full theory, the results from these calculations when compared with those of the quenched approximation, where the fermion determinant is set to unity, appear to amount mainly to a shift in the values of the bare coupling fi. The size of the effect can be estimated by requiring that the lattice spacing of the pure gauge theory (G) matches the one of the full theory (GF = Gauge + Fermions) in perturbation theory: a GF (fi GF ) =...06/1998;  [Show abstract] [Hide abstract]
ABSTRACT: A method based on the Monte Carlo inversion of the Dirac operator on the lattice provides low noise results for the correlations entering the definition of the heavy meson decay constant in the static limit. The method is complementary to the usual method of smeared sources, avoids the systematic error arising from optimizing the size of the smearing volume and is more efficient for the values of lattice parameters that we have explored. ROM2F9610 The knowledge of leptonic decay constants of heavy mesons is crucial for the extraction of the CabibboKobayashiMaskawa mixing angles. In particular the value of the B meson decay constant constraints the shape of the unitarity triangle and sets the size of possible CP violation in B decays. Lattice calculations are attempting since a few years to provide non perturbative estimates of this quantity, but are still confronted with various sources of systematic errors. One of them originates from the presence in the dynamics of a heavy meso...Physics Letters B 06/1998; · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We make a quenched lattice simulation of hadron spectroscopy at beta=6.2 with the Wilson action nonperturbatively improved. With respect to the unimproved case, the estimate of the lattice spacing is less influenced by the choice of input hadron masses. We study also the effects of using an improved quark mass in the fits to the dependence of hadron masses upon quark masses.Physics Letters B 03/1998; · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: η′τ splitting in full QCD can be estimated extrapolating from negative to positive flavour numbers. Our results show a flavour dependence consistent with the Witten Veneziano formula based on the U(1) anomaly.Nuclear Physics B  Proceedings Supplements 01/1997; 53(1):338340. · 0.88 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We study the dynamical flavour dependence of the lattice estimates of the heavy meson decay constant in the static limit. We perform the analysis by considering negative flavour numbers and by extrapolating the results to positive values. We observe a sizeable flavour dependence which increases the quenched estimates.Physics Letters B 08/1996; · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We study dynamical fermion effects in lattice QCD at finite temperature. The method adopted is basically the extrapolation from negative flavour numbers already tested at zero temperature and based on the simulation of local bosonic theories, with an essential difference. With an appropriate choice of the boundary conditions on the bosonic fields, called “bermions”, it is possible to separate the Z3 breaking contribution of fermion loops to the effective action from the one conserving Z3: the former is simulated exactly at a fixed positive and even flavour number, while the extrapolation from negative flavour numbers is made only on the Z3 invariant part of the action. We test this approach by comparing our results on a 163 × 2 lattice with those from a hopping parameter expansion and our results on a 163 × 4 lattice with those of direct Monte Carlo simulations including the fermion determinant.Physics Letters B 07/1996; · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We perform an extrapolation from negative to positive flavour numbers of full QCD lattice estimates of the $\eta'$ mass. The extrapolations are carried out by keeping $\rho$ and $\pi$ masses at fixed values. We find an $\eta'$  $\pi$ splitting which shows a flavour dependence consistent with the Witten Veneziano formula based on the $U(1)$ anomaly. The quantitative splitting is consistent with the estimates made in the quenched approximation. Comment: 22 pages, uuencoded latex files, text + 8 figures05/1996;  [Show abstract] [Hide abstract]
ABSTRACT: A method based on the Monte Carlo inversion of the Dirac operator on the lattice provides low noise results for the correlations entering the definition of the heavy meson decay constant in the static limit. The method is complementary to the usual method of smeared sources, avoids the systematic error arising from optimizing the size of the smearing volume ans is more efficient for the values of lattice parameters that we have explored.Physics Letters B 01/1996; · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We perform an extrapolation from negative to positive flavour numbers of full QCD lattice estimates of the η′ mass. The extrapolations are carried out by keeping ϱ and π masses at fixed values. We find an η′π splitting which shows a flavour dependence consistent with the WittenVeneziano formula based on the U(1) anomaly. The quantitative splitting is consistent with the estimates made in the quenched approximation.Nuclear Physics B 01/1996; · 4.33 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We calculate the effects of including dynamical fermion loops in the lattice QCD estimates of meson decay constants, by extrapolating the results from negative flavour numbers after a suitable matching of the pion and rho mass. For moderately light quarks, the values of the decay constants not corrected for the renormalization constants increase with respect to their quenched values. Comment: 9 pages, uuencoded PS file, 2 figures includedPhysics Letters B 10/1995; · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We estimate the effects of dynamical fermions by extrapolating to positive flavour numbers the results from negative values obtained by adding to the pure gauge sector a fermion action where the fields obey a Bose statistics: the bermions.Nuclear Physics B 08/1995; · 4.33 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We propose to replace ordinary propagators in lattice operator correlations entering the determination of hadron masses with spacetime smeared propagators. These are defined as the inverse of the quadratic operator in the fermion action times its hermitian conjugate. We obtain a cleaner determination of hadron masses, comparable to the effect of using smeared operators. Comment: PS file replaced with uuencoded PS file, 9 pages with 5 figures includedPhysics Letters B 02/1995; · 4.57 Impact Factor
Publication Stats
62  Citations  
46.08  Total Impact Points  
Top Journals
Institutions

1995–1998

University of Rome Tor Vergata
 Dipartimento di Fisica
Roma, Latium, Italy
