Determination Of Quark Masses Research Articles

Hard gluon radiation and the top mass value from CDF

The effect of hard gluon radiation on the top quark mass determination at Tevatron energies is studied. An expectation value 〈 Δm 〉 for the correction implied on m top is defined, and it is shown that the hard gluon effect is of the order of GeV. Quantitative numerical results are obtained on the basis of the complete higher order matrix elements for production and decay of the top quark.

Precise determination of the top quark and Higgs masses in the reduced standard theory for electroweak and strong interactions

Using the latest experimental data, we recalculate the top quark and Higgs masses, m t and m h , on the basis of the reduction of coupling constants in the standard theory for electroweak and strong interactions. The reduced standard theory predicts m t =99.2±5.7 GeV and m h =64.6±0.9 GeV, where the uncertainty mostly originates from that of the QCD coupling constant.

Scalar densities and baryon mass differences in lattice QCD with Wilson fermions

We compute the normalization constant and the proton matrix elements of the scalar quark densities on a 10 3 × 20 lattice, at β = 6.0, in the quenched approximation and for three values of the Wilson parameter: K = 0.1515, 0.1530, 0.1545. The normalization constant is in agreement with a new Ward identity derived in this paper. In terms of the usual D and F terms of the baryon octet mass differences, we find D F = −0.4 ± 0.2 , in agreement with the experimental value ( D F ) exp = −0.3 . We observe that D F decreases in absolute value for large quark mass, as suggested by the constituent quark model. Using a previous lattice determination of quark masses, we find M Ξ − M p = 210 ± 60 MeV, to be compared with the measured value ( Ξ − m p = 380 MeV. We also determine the nucleon σ-term to be σ = 15 ± 4 MeV.

Model independent determination of QCD quark masses

The method of approximate analytic continuation by duality (ACD), which permits to extrapolate a two-point function from its asymptotic QCD form down to Q 2 = 0, is used to determine the value of the light quark masses in QCD. For the value of the four-quark condensate advocated by Shifman, Vainshtein and Zakharov we obtain ( m u + m d) = (21 ± 2) MeV at Q 2 = 1 GeV 2.

Determination of light quark masses

Using the finite energy sum rule or the Shifman-Vainshtein-Zakharov technique for the scalar correlation function, it is shown that m ̂ d − m ̂ u = 10 MeV (for Λ QCD = 150 MeV and three flavours) where the m ̂ 's are the invariant masses. Using ( m ̂ d − m ̂ u ) ( m ̂ d + m ̂ u ) = 0.29 we deduced that m ̂ d = 22 MeV . The question of the determination of the sum of the light quark masses with the pseudoscalar correlation function is discussed.

Counting rules and determination of quark masses in chiralSU 4⊗SU 4

A «current quark» mass counting rule is derived from the Gell-Mann-Oakes-Renner model for the breaking of chiralSU4⊗SU4. We obtain from the counting rule a «current quark» mass ratiomc/ms≈10.0. Making further use of theSU4 version of Leutwyler's sum rule for pseudoscalar-meson wave functions, we arrive atms≈mc/10≈≈111 MeV,md≈5.7 MeV andmu≈3.4 MeV.

KL→2μ,KL→2γ, and quark masses in gauge models

Experimental knowledge of the decay rates for ${K}_{L}\ensuremath{\rightarrow}2\ensuremath{\mu}$ and ${K}_{L}\ensuremath{\rightarrow}2\ensuremath{\gamma}$ is combined with theoretical understanding of strangeness-changing neutral-current effects in unified gauge models of the weak and electromagnetic interactions for a determination of quark masses. Given that the Weinberg parameter ${sin}^{2}{\ensuremath{\theta}}_{W}$ is between 0.3 and 0.4, the mass of the proton quark becomes roughly 900 MeV, while that of the "charmed" quark is about 5 GeV.

Deep-Inelastic Scattering, the Subtraction of Divergent Sum Rules, and Chiral-Symmetry Breaking in the Gluon Model

The formal light-cone properties of commutators involving current divergences are studied in the gluon model. Relations are derived which make it possible (in principle) to distinguish the vector- from the (pseudo) scalar-gluon model. In the vector-gluon model these relations provide an experimental determination of the bare quark masses. The additional assumption that the residues of any $\ensuremath{\alpha}=0$ fixed poles in current scattering amplitudes are polynomials in ${q}^{2}$ makes it possible to relate the $\ensuremath{\sigma}$ term in pion-nucleon scattering to convergent integrals over neutrino-scattering structure functions; the polynomial assumption dictates a prescription for subtracting a (linearly) divergent sum rule derived previously. The same technique generates subtracted sum rules for the (neutrino- and spin-dependent) structure functions ${W}_{3}$ and ${G}_{2}$. With the parton-model assumption that the leading scaling behavior of current-divergence and divergence-divergence scattering is given by free-field theory, it is possible to relate fixed-pole residues in $\mathrm{ep}$, $\mathrm{en}$, $\ensuremath{\nu}p$, and $\ensuremath{\nu}n$ scattering, deep-inelastic data, the $\ensuremath{\sigma}$ term, baryon mass differences, and the bare quark masses; approximate values for the bare quark masses and the parameter ${\ensuremath{\mu}}_{0}$ can be obtained.