Unified QCD determination of all pseudoscalar leptonic decay constants

Leptonic decay constants of all pseudoscalar mesons are determined in QCD by means of a new QCD sum-rule method. In the light meson and heavy quark limit the results are very similar and also agree with the well-known PCAC and scaling predictions respectively. The corrections to light meson pole dominance are generally small while those to the heavy quark limit are found to be sensitive to the binding energy (i.e. meson and quark mass differences). For standard values of quark masses we obtainf =132 MeV,f _k=161 MeV,f _B=128±28 MeV,f _D=175±13 MeV,f _Bs=144±30 MeV andf _Ds=193±12 MeV.Work supported by Bundesministerium für Forschung und Technologie (BMFT) under contract No. 06MZ758     

Quark mass dependence of pseudoscalar masses and decay constants on a lattice

Our previous calculations of the sea- and valence-quark mass dependence of the pseudoscalar meson masses and decay constants is repeated on a lattice, which allows for a better determination of the quantities in question. The conclusions are similar as before on the 16⁴ lattice [1]. The two light dynamical quark flavours we simulate have masses in the range m _s /4 < m _u,d < 2m _s /3. The sea quark mass dependence of and is well described by the next-to-leading order (NLO) chiral perturbation theory (ChPT) formulas and clearly shows the presence of chiral logarithms. The valence quark mass dependence requires the presence of NNLO contributions in partially quenched ChPT (PQChPT)--in addition to the NLO terms. The lattice artifacts in these quantities turn out to be small.Received: 19 March 2004, Published online: 24 August 2004     

Precise lattice constants determination of cubic crystals from x-ray powder diffractometric measurements

An analytical method for precise determination of lattice constants of cubic crystals, from x-ray diffractometric measurements, was formulated. The method minimizes both systematic and random errors and enables the estimation of the uncertainties in the constants. For higher precision, a weighting factor may also be used.The method was applied to diffractometric data from a Si powder standard reference material and was considered to be highly reliable for precise measurements.     

Precise hadron mass calculations from lattice QCD

By using scalar as opposed to spin-$\text{1}\text{2}$ quarks and treating spin effects perturbatively, the masses of the lowest lying 0^- and 1^- mesons above 1 GeV (the J/Ψ, η_c, D, D¹, F, F¹, and φ) are calculated to 1%. The masses of the K¹, ?, and K are respectively obtained to 3%, 8% and 30%. Certain (spin-averaged) linear combinations of baryon masses are also computed. The nucleon-delta result differs from experiment by 8%. For heavier baryons the error is smaller. Scalar lattice QCD seems to be a promising approach to the strong interactions.     

Weak decay constants of light and heavy pseudoscalar mesons

We investigate the weak leptonic decays of light and heavy pseudoscalar mesons in a relativistic quark model of independent quarks. We perform a static calculation of the decay constantf _M purely on grounds of simplicity. In order to minimize the possible uncertainty in the static calculation, we estimate the ratios of the decay constants which are found to be in good agreement, in the heavy flavor sector, with the predictions of other models available in the literature and existing experimental data. However, there is a noticeable discrepancy in the current prediction for pion decay constant which demonstrates the inherent limitations of the static approximation in the study of non-strange light mesons.     

A determination of the Cabibbo-Kobayashi-Maskawa parameter |V us| using KL decays

We present a determination of the Cabibbo-Kobayashi-Maskawa parameter |V(us)| based on new measurements of the six largest K(L) branching fractions and semileptonic form factors by the KTeV (E832) experiment at Fermilab. We find |V(us)|=0.2252+/-0.0008(KTeV)+/-0.0021(ext), where the errors are from KTeV measurements and from external sources. We also use the measured branching fractions to determine the CP violation parameter |eta(+-)|=(2.228+/-0.005(KTeV)+/-0.009(ext))x10(-3).     

B → F + X decay and pseudoscalar decay constants of explicitly flavored heavy mesons

If the current theoretical pictures of explicitly flavored heavy mesons are quantitatively correct, we expect that the branching ratio of B → $\text{F}$ + X (anything) may be 6 percent even in a conservative estimate. Accurate measurement of this branching ratio will determine the value of the pseudoscalar decay constant f_F, of the wave function at origin of the s wave $\text{c}$ s bound state in the potential picture, and help to clarify dynamical properties of heavy meson binding.     

High-precision determination of the pi, K, D, and Ds decay constants from lattice QCD

We determine D and D(s) decay constants from lattice QCD with 2% errors, 4 times better than experiment and previous theory: f(D(s))=241(3) MeV, f(D)=207(4) MeV, and fD(s))/f(D)=1.164(11). We also obtain f(K)/f(pi)=1.189(7) and (f(D(s))/f(D))/(f(K)/f(pi))=0.979(11). Combining with experiment gives V(us)=0.2262(14) and V(cs)/V(cd) of 4.43(41). We use a highly improved quark discretization on MILC gluon fields that include realistic sea quarks, fixing the u/d, s, and c masses from the pi, K, and eta(c) meson masses. This allows a stringent test against experiment for D and D(s) masses for the first time (to within 7 MeV).     

Chiral extrapolation and determination of low-energy constants from lattice data

We propose analytic approximations of chiral SU(3)$\mathit{SU}(3)$ amplitudes for the extrapolation of lattice data to the physical meson masses. The method allows the determination of NNLO low-energy constants in a controllable fashion. We test the approach with recent lattice data for the ratio FK/Fπ$F_K/F_{\pi }$ of meson decay constants.     

The relations between the decay constants of pseudoscalar mesons and the residues of the pomeron

The relations between the decay constants of pseudoscalar mesons and the residues of the pomeron are given. Based on these relations, it is shown that the relative scale between the couplings of the zero-mass Nambu-Goldstone bosons to the pomeron is determined by the spontaneous chiral symmetry breaking of the vacuum.     

Masses of S and P wave mesons and pseudoscalar decay constants using a confinement scheme

In the framework of relativistic harmonic confinement model for quarks and antiquarks, the masses of S- and P-wave mesons and pseudoscalar decay constants from light flavour to heavy flavour sectors are computed. The residual two-body Coulomb interaction and the spin-dependent interaction of the confined one gluon exchange effects (COGEP) such as spin-spin and spin-orbit interactions are perturbatively incorporated with the confinement energy to get the respective vector-pseudoscalar meson mass differences. Here we employ the same parametrization and model parameters as used in a recent study of low-lying hadron masses and leptonic decay widths. The results are being compared with the values obtained from other theoretical models and the experimental values.     

The leptonic decay constants of $$\bar Qq$$ mesons and the lattice resolution

We present a high statistics study of the leptonic decay constantf _P of heavy pseudoscalar mesons using propagating heavy Wilson quarks within the quenched approximation, on lattices covering sizes from about 0.7 fm to 2 fm. Varying between 5.74 and 6.26 we observe a sizeablea dependence off _P when one uses the quark field normalization that was suggested by Kronfeld and Mackenzie, compared with the weaker depence observed for the standard relativistic norm. The two schemes come into agreement when one extrapolates toa0. The extrapolations needed to reach the continuum quantityf _B introduce large errors and lead to the valuef _B =0.18(5) GeV in the quenched approximation. This suggests that much more effort will be needed to obtain an accurate lattice prediction forf _B .work supported in part by DFG grant Schi 257/3-1     

An evaluation of |V us | and precise tests of the Standard Model from world data on leptonic and semileptonic kaon decays

We present a global analysis of leptonic and semileptonic kaon decay data, including all recent results published by the BNL-E865, KLOE, KTeV, ISTRA+ and NA48 experiments. This analysis, in conjunction with precise lattice calculations of the hadronic matrix elements now available, leads to a very precise determination of |V _us | and allows us to perform several stringent tests of the Standard Model.     

Microscopic calculations of beta decay far from stability

Beta decay properties of nuclei far from stability are of decisive importance for the understanding of the element synthesis in the universe and the determination of the age of the universe by means of cosmochronometers. A new large scale microscopic calculation ofβ ^?-decay half-lives up to the neutron drip line is presented. This new approach uses the proton-neutron quasiparticle random phase approximation with a Gamow-Teller residual interaction.     

Determination of freeze-out conditions from lattice QCD calculations

Freeze-out conditions in Heavy Ion Collisions are generally determined by comparing experimental results for ratios of particle yields with theoretical predictions based on applications of the Hadron Resonance Gas model. We discuss here how this model dependent determination of freeze-out parameters may eventually be replaced by theoretical predictions based on equilibrium QCD thermodynamics.