arXiv subjects

A. Ferroglia

Publications and source records attributed to A. Ferroglia.

44 records · Page 3Linked to original sources

arXiv2004

Bounds on M_W, M_t, Sin^2 theta_eff^lept

Assuming that the Standard Model is correct and taking into account the lower bound on M_H from direct searches, we discuss bounds on M_W, M_top, and Sin^2 theta_eff_lept at various confidence levels. This permits to identify theoretically favored ranges for these important parameters in the Standard Model framework, regardless of other observables. As an illustration of possible future developments, a hypothetical benchmark scenario, involving shifts less then 1 sigma in the experimental central values, is discussed.

hep-ph↗

arXiv2004

The electroweak form factor \hatκ(q^2) and the running of \sin^2 \hatθ_W

Gauge independent form factors ρ^(e; e) and \hatκ^(e; e)(q^2) for Moller scattering at s << m_W^2 are derived. It is pointed out that \hatκ^(e; e) is very different from its counterparts in other processes. The relation between the effective parameter \hatκ^(e; e)(q^2,μ) \sin^2 \hatθ_W(μ) and \sin^2 θ_eff is derived in a scale-independent manner. A gauge and process-independent running parameter \sin^2 \hatθ_W (q^2), based on the pinch-technique self-energy a_{γZ} (q^2), is discussed for all q^2 values. At q^2=0 it absorbs very accurately the Czarnecki-Marciano calculation of the Moller scattering asymmetry at low s values, and at q^2 = m^2_Z it is rather close to \sin^2 θ_eff. The q^2 dependence of \sin^2 \hatθ_W (q^2) is displayed in the space and time-like domains.

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arXiv2003

Two-Loop Vertices in Quantum Field Theory: Infrared Convergent Scalar Configurations

A comprehensive study is performed of general massive, scalar, two-loop Feynman diagrams with three external legs. Algorithms for their numerical evaluation are introduced and discussed, numerical results are shown for all different topologies, and comparisons with analytical results, whenever available, are performed. An internal cross-check, based on alternative procedures, is also applied. The analysis of infrared divergent configurations, as well as the treatment of tensor integrals, will be discussed in two forthcoming papers.

hep-ph↗

arXiv2002

All-Purpose Numerical Evaluation of One-Loop Multi-Leg Feynman Diagrams

A detailed investigation is presented of a set of algorithms which form the basis for a fast and reliable numerical integration of one-loop multi-leg (up to six) Feynman diagrams, with special attention to the behavior around (possibly) singular points in phase space. No particular restriction is imposed on kinematics, and complex masses (poles) are allowed.

hep-ph↗

arXiv2002

Simple Formulae for Sin^2 theta_eff^lept, M_W, Gamma_l, and their Physical Applications

The calculation of the partial widths of the Z boson in the effective scheme is discussed. Simple formulae for Sin^2 theta_eff^lept, M_W, and Gamma_l in the on-shell, MS, and effective renormalization schemes are presented. Their domain of validity extends to low M_H values probed by current experiments, and to the range of Delta alpha_hadr results from recent calculations. Physical applications of these formulae are illustrated. A comparative analysis of the above mentioned schemes is presented. The paper includes a discussion of the discrepancy of the Sin^2 theta_eff^lept values derived from the leptonic and hadronic sectors and of the shortcomings of theoretical error estimates of Sin^2 theta_eff^lept based solely on those affecting M_W.

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arXiv2001

Novel Approach to Renormalize the Electroweak Sector of the Standard Model

We discuss a novel approach to renormalize the Electroweak Sector of the Standard Model, in which \sin^2θ_{eff}, measured at the Z^0 peak, is identified with the basic renormalized electroweak mixing parameter. This approach shares the desirable convergence properties of the MS scheme and provides a framework for calculations that are strictly independent of the electroweak scale in finite orders of perturbation theory. We illustrate the method with updated precise calculations of \sin^2θ_{eff} and M_W, as functions of M_H, and comment on the implications of these calculations for the Higgs boson search and the theoretical prediction of M_W.

hep-ph↗

arXiv2001

Scale-Independent Calculation of $\sin^2 θ_{eff}^{lept}$

We present a calculation of the electroweak mixing parameter $\sin^2 θ_{eff}^{lept}$ that incorporates known higher order effects, shares the desirable convergence properties of the $\bar{MS}$ scheme, and has the important theoretical advantage of being strictly independent of the electroweak scale in finite orders of perturbation theory . We also show how this formulation can be extended to the calculation of the W mass $M_W$. The results provide accurate, scale-independent evaluations of these important parameters, as functions of the Higgs boson mass $M_H$, and are compared with previous calculations in order to analyze the scheme and scale dependence of the electroweak corrections.

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arXiv1999

Considerations Concerning the Radiative Corrections to Muon Decay in the Fermi and Standard Theories

The FAC, PMS, and BLM optimization methods are applied to the QED corrections to the muon lifetime in the Fermi V-A theory. The FAC and PMS scales are close to m_e, while the BLM scale nearly concides with the geometric average \sqrt{m_e m_μ}. The optimized expressions are employed to estimate the third order coefficient in the α(m_μ) expansion and the theoretical error of the perturbative series. Using arguments based on effective field theory and a simple examination of Feynman diagrams, it is shown that, if contributions of O(αm_μ^2/M_W^2) are neglected, the corrections to muon decay in the SM factorize into the QED correction of the Fermi V-A theory and the electroweak amplitude g^2/(1-Δr), both of which are strictly scale-independent. We use the results to clarify how the QED corrections to muon decay and the Fermi constant G_F should be used in the SM, and what is the natural choice of scales if running couplings are employed.

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