Related papers: Alpha_s with GAPP
We point out that an apparent discrepancy between the values of $\alpha_s(M_z)$ as determined from low versus high energy experiments can be explained if an electrically neutral coloured fermion exists which slows down the running of the…
The leptonic decays of the tau lepton provide relevant tests on the structure of the weak currents and the universality of their couplings to the gauge bosons. The hadronic tau decay modes constitute an ideal tool for studying low--energy…
There are some indications from recent determinations of the strong coupling constant alpha_s and the gluon condensate that the Operator Product Expansion may not be accurate enough to describe non-perturbative effects in hadronic tau…
A $\theta$ term, which couples to topological charge, is added to the lattice $CP^{N-1}$ model. The strong-coupling character expansion is developed. The series for the free energy and mass gap are respectively computed to tenth order and…
We present an explicit demonstration that a determination of the strong coupling constant $\alpha_s(m_Z)$ from deep-inelastic scattering and hadron collider data without a simultaneous determination of the parton distribution functions…
We examine gauge coupling unification and prediction for $\alpha_s (M_Z)$ in minimal flipped SU(5) with gauge-mediated supersymmetry breaking. We include threshold corrections at weak scale, messenger scale and unification scale, and…
We use analytic continuation to extend the gauge/gravity duality nonperturbative description of the strong force coupling into the transition, near-perturbative, regime where perturbative effects become important. By excluding the…
The first complete calculation of the quadratic quark mass correction to the correlator of the two currents relevant for the strangeness-changing semihadronic tau-decay rate is presented including its real part at the four-loop level. This…
The brief overview of the definite determinations of the QCD coupling constant $\alpha_s$ from the characteristics of deep-inelastic scattering processes is given.
We present a new analysis of $\alpha_s$ from hadronic $\tau$ decays based on the recently revised ALEPH data. The analysis is based on a strategy which we previously applied to the OPAL data. We critically compare our strategy to the one…
We apply analytic perturbation theory to the inclusive decay of a $\tau$ lepton into hadrons. It is shown that the resulting analyticity of the coupling constant strongly influences the value of the QCD $\Lambda$-parameter extracted from…
The jet cross-section and structure-function measurements done with the ZEUS detector to extract the strong coupling constant and to test its energy-scale dependence are summarised. The values of alphas thus obtained and the HERA average…
Theoretical predictions for particle production cross sections and decays at colliders rely heavily on perturbative Quantum Chromodynamics (QCD) calculations, expressed as an expansion in powers of the strong coupling constant $\alpha_s$.…
The tau hadronic width provides a determination of the strong coupling constant alpha_s at low energies, since it can be related to a weighted integral of the Adler function in the complex energy plane. Using Operator Product Expansion, one…
We revisit the determination of alpha_s(m_tau) using a fit to inclusive tau hadronic spectral moments in light of (1) the recent calculation of the fourth-order perturbative coefficient K_4 in the expansion of the Adler function, (2) new…
Axion-like particles (ALPs) are well-motivated examples of light, weakly coupled particles in theories beyond the Standard Model. In this work, we study long-lived ALPs coupled exclusively to leptons in the mass range between $2 m_e$ and…
We present a strong coupling constant extraction at Next-to-Leading Order QCD accuracy using ATLAS Z+2,3,4 jets data. This is the first extraction using processes with a dependency to high powers of the coupling constant. We obtain values…
The prospects for a determination of the strong coupling constant $\alpha_s$ via scaling violations of fragmentation functions in deeply inelastic scattering are studied. The statistical error in the case of an integrated luminosity of $250…
By reanalyzing the influence of the anomalous $Z\bar t t$ couplings on the $Z\rightarrow b\bar b$ decay process, we pointed out the ambiguity in the conventional treatment of the effective Lagrangian approach, because of the possible…
We compute the matching relation for the strong coupling constant within the framework of QCD up to four-loop order. This allows a consistent five-loop running (once the $\beta$ function is available to this order) taking into account…