F. Rapuano

Glueball masses and string tension in lattice QCD

We study glueball masses in lattice QCD. We present the first numerical determination of the mass of the lowest spin 2 state in the scaling region, and find that it is close to the lowest spin 0 state. We present very precise results for the string tension and for the spin 0 state, obtained by analyzing a large set of operators. We find that finite size effects are significant.

A measurement of the string tension near the continuum limit

Abstract The string tension has been measured at β =6 in the quenched approximation using a new technique for minimizing the statistical errors.

The Kaon B-parameter and K-π and K-ππ transition amplitudes on the lattice

We present the results of a computation of the K0−K0 and ΔI = 32 K−π and K−ππ amplitudes in lattice QCD. The numerical simulation has been done using the standard one-plaquette action and Wilson fermions, in the quenched approximation. Combining the tesults obtained at β = 6 on a 102 × 20 × 40 lattice with 30 configurations with those at β = 6.2 on a 163 × 48 lattice with 15 configurations, we have obtained for the kaon B-parameterBK0 − K0 = 0.65 ± 0.15 at μ = 3 GeV. We have also evaluated the ΔI = 32K−π and K−π weak hamiltonian matrix elements. The relevant renormalized operator O4 has been found to satisfy soft-pion theorems and chiral lagrangian relations at the 30% level, and this makes us confident about our results. We find (〈K+|HW|π+π0〉/mK) = (7 ± 2) × 10−8 to be compared with the experimental value of 3.7 × 10−8.

Nonperturbatively improved heavy - light mesons: Masses and decay constants

We present a study of the heavy-light spectrum and of the D- and B-meson decay constants. The results wer e obtained in the quenched approximation, by using the non-perturbatively improved Clover lattice action at beta=6.2, with a sample of 100 configurations, on a 24^3 x 64 lattice. After a careful analysis of th e systematic errors present in the extraction of the physical results, by assuming quite conservative discretization errors, we find f_Ds=231 +/- 12^{+6}_{-1} MeV, f_D = 211 +/- 14^{+0}_{-12} MeV, f_Ds/f_D=1.10(2), f_Bs = 204 +/- 16^{+28}_{-0} MeV, f_B = 179 +/- 18^{+26}_{-9} MeV, f_Bs/f_B=1.14(3)^{+0}_{-1}. Our results, which have smaller discretization errors than many previous estimates at fixed value of the lattice spacing

Light quenched hadron spectrum and decay constants on different lattices

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Hadron spectrum in quenched QCD on a 103 × 20 lattice

, support a large value of f_B in the quenched approximation.

Lattice calculation of D- and B-meson semileptonic decays, using the clover action at β = 6.0 on APE

In this paper we study O(2000) (quenched) lattice configurations from the APE collaboration, for different lattice volumes and for 6.0 \le beta \le 6.4 using both the Wilson and the SW-Clover fermion actions. We determine the light hadronic spectrum and meson decay constants and study the mesonic dispersion relation. We extract the hadronic variable J and the strange quark mass in the continuum at the next-to-leading order obtaining m_s^{MSbar}(mu=2 GeV) = 122 +/- 20 MeV. A study is made of their dependence on lattice spacing. We implement a newly developed technique to extract the inverse lattice spacing using data at the simulated values of the quark mass (i.e. at masses around the strange quark mass).In this paper we study (2000) (quenched) lattice configurations from the APE collaboration, for different lattice volumes and for 6.0 ⩽ β ⩽ 6.4 using both the Wilson and the SW-Clover fermion actions. We determine the light hadronic spectrum and meson decay constants and study the mesonic dispersion relation. We extract the hadronic variable J and the strange quark mass in the continuum at the next-to-leading order obtaining msMS(μ = 2 GeV) = 122 ± 20 MeV. A study is made of their dependence on lattice spacing. We implement a newly developed technique to extract the inverse lattice spacing using data at the simulated values of the quark mass (i.e. at masses around the strange quark mass).

Hadron spectroscopy in lattice QCD

Abstract We report the results of strange and light-quark hadron masses obtained by a simulation of QCD in the zero fermion loops approximation (quenching) on a 10 3 × 20 lattice. The results are sensibly different from those obtained on smaller lattices and show a definite improvement.

On the masses of the glueballs in pure SU(2) lattice gauge theory

Abstract We present the results of a high statistics lattice calculation of hadronic form factors relevant for D - and B -meson semi-leptonic decays into light pseudoscalar and vector mesons. The results have been obtained by averaging over 170 gauge field configurations, generated in the quenched approximation, at β = 6.0, on a 18 3 × 64 lattice, using the O ( α )-improved SW-Clover action. From the study of the matrix element 〈 K − |J μ |D 0 〉, we obtain f + (0) = 0.78 ± 0.08 and from the matrix element 〈 K ∗0 |J μ |D + 〉 we obtain V (0) = 1.08 ± 0.22, A i (0) = 0.67 ± 0.11 and A 2 (0) = 0.49 ± 0.34. We also obtain the ratios V(0) A 1 (0) = 1.6 ± 0.3 and A 2 (0) A 1 (0) = 0.7 ± 0.4 . Our predictions for the different form factors are in good agreement with the experimental data, although, in the case of A 2 (0), the errors are still too large to draw any firm conclusion. With the help of the Heavy Quark Effective Theory (HQET) we have also extrapolated the lattice results to B -meson decays. The form factors follow a behaviour compatible with the HQET predictions. Our results are in agreement with a previous lattice calculation, performed at β = 6.4, using the standard Wilson action.

The hadronic mass spectrum in quenched lattice QCD: β=5.7

Abstract A Monte Carlo computation of meson and hadron spectroscopy within lattice QCD is made. We give a detailed discussion of the statistical and systematic errors of the results and analyze the present limitations of our approach. The results are in agreement with the observed spectrum. We also estimate the values of up, down and strange quark masses.