Variations on a Higgs theme

We show how the $Z$ boson can be generated in gluon-gluon fusion and yield two photons, via $gg\to Z\to \gamma\gamma$, through massive fermion loops only, thereby contributing events to a candidate Higgs sample in the di-photon channel. A sub-leading contribution also exists from $q\bar q\to Z\to\gamma\gamma$ events. Assuming the Standard Model, the corresponding event rates are negligible at the LHC stages of 7, 8 TeV, given the luminosities collected therein (about 5 and 20 fb$^{-1}$, respectively). Conversely, at 14 TeV, the first process become accessible for luminosities of order 300 fb$^{-1}$. Finally, we show how additional fermion states entering such loops, in production, in decay or in both cases, could affect the predictions in this channel by curiously mimicking Higgs signals.Comment: 18 pages, 1 table, 4 figure

HERWIG: an event generator for e+e−e^+e^- Linear Colliders

I review all the new features of the HERWIG event generator which are relevant to Linear Collider (LC) physics starting from version 6.1Comment: 9 pages, latex, 4 figures; talk given at the International Workshop on Linear Colliders (LCWS2002), Jeju Island, Korea, 26-30 August 200

Detection of heavy charged Higgs bosons at future Linear Colliders via τ−νˉτH+\tau^-\bar\nu_\tau H^+ production

We show how a statistically significant signal of heavy charged Higgs bosons of a Type II Two-Higgs Doublet (2HDM) Model produced in association with tau-neutrino pairs can be established at future $e^+e^-$ Linear Colliders (LCs) in the $H^+\to t\bar b\to 4$ jet decay channel for large $\tan\beta$ in the M_{H^\pm}\gsim \sqrt s/2 mass regionComment: 6 pages, latex, 3 figures; talk given at the International Workshop on Linear Colliders (LCWS2002), Jeju Island, Korea, 26-30 August 2002; one reference added and one correcte

HERWIG: an event generator for MSSM processes

The HERWIG event generator was widely used throughout the workshop, particularly in the emulation of Supersymmetric and Higgs processes in the context of the Minimal Supersymmetric Standard Model. We briefly review here its main features in this respectComment: 5 pages, no figures, talk given at the `Seventh Workshop on High Energy Physics Phenomenology WHEPP-VII', Harish Chandra Research Institute, Allahabad, India, 4-15 January 2002 (to be published by PRAMANA - Journal of Physics

The B−LB-L Supersymmetric Standard Model with Inverse Seesaw at the Large Hadron Collider

We review the TeV scale $B-L$ extension of the Minimal Supersymmetric Standard Model (BLSSM) where an inverse seesaw mechanism of light neutrino mass generation is naturally implemented and concentrate on its hallmark manifestations at the Large Hadron Collider (LHC).Comment: 26 pages, 4 tables, 13 figures, to appear in Reports on Progress in Physic

A simple symmetry as a guide toward new physics beyond the Standard Model

There exists one experimental result that cannot be explained by the Standard Model (SM), the current theoretical framework for particle physics: non-zero masses for the neutrinos (elementary particles travelling close to light speed, electrically neutral and weakly interacting). The SM assumes that they are massless. Therefore, particle physicists are now exploring new physics beyond the SM. There is strong anticipation that we are about to unravel it, in the form of new matter and/or forces, at the Large Hadron Collider (LHC), presently running at CERN. We discuss a minimal extension of the SM, based on a somewhat larger version of its symmetry structure and particle content, that can naturally explain the existence of neutrino masses while also predicting novel signals accessible at the LHC, including a light Higgs boson, as evidenced by current data.Comment: 5 pages: version to be published in Frontiers in High-Energy and Astroparticle Physics following a change of title and minor changes to the tex

Heavy charged Higgs boson production at next generation γγ\gamma\gamma colliders

We investigate the scope of all relevant production modes of charged Higgs bosons in the MSSM, with mass larger than the one of the top quark, at future Linear Colliders operating in $\gamma\gamma$ mode at the TeV energy scale. Final states with one or two $H^\pm$ bosons are considered, as produced by both tree- and loop-level interactionsComment: 11 pages, latex, 6 figure

Searches for new particles at LEP: a summary report

We review the progress made at LEP in the quest for new particles.Comment: 10 pages, latex, 1 figure, summary talk given at `13th Convegno sulla Fisica al LEP (LEPTRE 2001)', Rome, Italy, 18-20 April 200

Higgs Sector of Non-minimal Supersymmetric Models at Future Hadron Colliders

We investigate the potential of current and planned hadron colliders operating at the TeV scale in disentangling the structure of the Higgs sector of non-minimal Supersymmetric extensions of the Standard Model with an extra gauge singlet. We assume universality of the soft Supersymmetry breaking terms at the GUT scale as well as a CP-even Higgs boson with mass around 115 GeV, as suggested by LEP. We find that mixing angles between the doublet and singlet Higgs states are always small. However, concrete prospects exist at both the Tevatron (Run II) and the Large Hadron Collider of detecting at least one neutral Higgs state with a dominant singlet component, in addition to those available from a doublet Higgs sector which is similar to the one of the Minimal Supersymmetric Standard Model.Comment: 4 pages, 2 figures, latex, contribution to the APS/DPF/DPB Summer Study on the `Future of Particle Physics (Snowmass 2001)', Snowmass, Colorado, 30 June - 21 July 200