arXiv subjects

Alessandro Vicini

Publications and source records attributed to Alessandro Vicini.

40 records · Page 3Linked to original sources

arXiv2004

Two-loop renormalization of the electric charge in the Standard Model

We discuss the renormalization of the electric charge at the two-loop level in the Standard Model of the electroweak interactions. We explicitly calculate the expression of the complete on-shell two-loop counterterm using the Background Field Method and discuss the advantages of this computational approach. We consider the related quantity $\hat e(μ)$, defined in the $\ms$ renormalization scheme and present numerical results for different values of the scale $μ$. We find that the full 2-loop electroweak corrections contribute more than 10 parts in units $10^{-5}$ to the $Δ\hatα(\mz^2)$ parameter, obtaining $\hatα^{-1}(\mz)= 128.12 \pm 0.05$ for $Δα_{had}(\mz^2) =0.027572 \pm 0.000359$.

hep-ph↗

arXiv2003

The electric charge at the two-loop level in the Standard Model and the precision measurements of Delta alpha_{had}

The complete calculation of the 2-loop electroweak corrections to the renormalization of the electric charge in the Standard Model allows to discuss in detail the value of the MSbar effective coupling $\hat e(m_Z)$. We discuss the phenomenological impact of these results in view of the increasing accuracy in the measurements of the cross-section of the reaction e+e- -->hadrons at low energies.

hep-ph↗

arXiv2001

Gauge invariant decomposition of 1-loop multiparticle scattering amplitudes

A simple algorithm is presented to decompose any 1-loop amplitude for scattering processes of the class 2 fermions -> 4 fermions into a fixed number of gauge-invariant form factors. The structure of the amplitude is simpler than in the conventional approaches and its numerical evaluation is made faster. The algorithm can be efficiently applied also to amplitudes with several thousands of Feynman diagrams.

hep-ph↗

arXiv2000

A screening mechanism for extra W and Z gauge bosons

We generalize a previous construction of a fermiophobic model to the case of more than one extra $W$ and $Z$ gauge bosons. We focus in particular on the existence of screening configurations and their implication on the gauge boson mass spectrum. One of these configurations allows for the existence of a set of relatively light new gauge bosons, without violation of the quite restrictive bounds coming from the $ρ_{\rm NC}$ parameter. The links with Bess and degenerate Bess models are also discussed. Also the signal given here by this more traditional gauge extension of the SM could help to disentangle it from the towers of Kaluza-Klein states over $W$ and $Z$ gauge bosons in extra dimensions.

hep-ph↗