arXiv subjects

E. Gabrielli

Publications and source records attributed to E. Gabrielli.

59 records · Page 4Linked to original sources

arXiv1995

Constraints on supersymmetry from FCNC and CP violation

We consider FCNC and CP violating processes mediated by gluino exchange in generalized supersymmetric theories. We present the constraints on flavour (F) changing squark mass terms at the electroweak energy scale, focusing our analysis on $ΔF = 2$ transitions. Results are also given for $ΔF = 1$ CP conserving processes both in the hadronic and leptonic sectors, while we limit ourselves to some remarks on the relevance of box diagrams in the evaluation of $ε^{\prime}/ε$.

hep-ph↗

arXiv1995

Flavour changing neutral currents and CP violating processes in generalized supersymmetric theories

We consider supersymmetric extensions of the standard model with general non-universal soft breaking terms. We analyse in a model-independent way the constraints on these terms at the electroweak energy scale coming from gluino mediated flavour (F) changing neutral current and CP-violating processes. We have computed the complete $ΔF=1$ and $ΔF=2$ effective hamiltonian for gluino mediated processes, including for the first time the effect of box diagrams in the evaluation of $ε^{\prime}/ε$. We present numerical results for the constraints on these non-universal soft breaking terms for different values of the parameters, extending the analysis also to the leptonic sector. A comparison with previous results in the literature is given.

hep-ph↗

arXiv1994

Supersymmetric corrections to $ε^\prime /εat the leading order in QCD and QED

We study the corrections to $ε^\prime /ε$ in the minimal supersymmetric model at the leading order in QCD and QED. Supersymmetry can increase the standard model prediction for $ε^\prime /ε$ by at most 40\% for $m_t=174$ GeV, an enhancement which is indistinguishable from the present theoretical uncertainties. The most conspicuous effect of supersymmetry is a strong depletion of $ε^\prime /ε$. For certain choices of supersymmetric parameters, vanishing and even small negative values of $ε^\prime /ε$ can be obtained for the top quark in the CDF range.

hep-lat↗

arXiv1994

The Relevance of the Dipole Penguin Operators in $ε'/ε$

The standard model contribution to $ε'/ε$ of the magnetic- and electric-dipole penguin operators $Q_{11} = \frac{g_s}{16π^2} \, m_s \: \bar{s}\, σ_{μν} t^a G^{μν}_a (1-γ_5 )\, d $ and $Q_{12} = \frac{eQ_d}{16π^2}\, m_s \: \bar{s}\, σ_{μν} F^{μν} (1-γ_5 )\, d $ is discussed. While the electromagnetic penguin $Q_{12}$ seems to have a vanishingly small matrix element, we find that the gluonic dipole operator $Q_{11}$ may give a contribution to $ε'/ε$ comparable to that of other operators so far considered, and should therefore be consistently included in the analysis.

hep-ph↗

arXiv1993

Higgs Production in Association with a Vector Boson Pair at Future e+ e- Colliders

We study Higgs boson production in association with a pair of electroweak vector bosons ($WW,ZZ,Zγ$) at future $\epem$ colliders in the framework of the Standard Model. Total cross sections and distributions for the intermediate-mass Higgs are presented, with special emphasis on the Next Linear Collider (NLC) case operating at a centre-of-mass energy $\sqrt{s} \simeq 500$ GeV, where the cross sections turn out to be more favourable than in larger-$\sqrt{s}$ collisions. We find that with an integrated luminosity of 20 fb$^{-1}$ there is a sizeable event rate for the $HWW$ and $HZγ$ (with a high $p_T^γ$) channels, while a larger integrated luminosity is needed to study the $HZZ$ production. We take into account various backgrounds, notably top-pair and triple vector-boson production, and show ways to significantly reduce their effects.

hep-ph↗