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Stefano Moretti

Publications and source records attributed to Stefano Moretti.

297 records · Page 17Linked to original sources
arXiv1996

The process $e^+e^-\to b\bar bW^+W^-$ at the Next Linear Collider in the Minimal Supersymmetric Standard Model

The complete matrix element for $e^+e^-\rightarrow b\bar b W^+W^-$ is computed at tree-level within the Minimal Supersymmetric Standard Model. Rates of interest to phenomenological analyses at the Next Linear Collider are given. In particular, we study: - $t\bar t$ production and decay $t\bar t\ar (bW^+)(\bar bW^-)$; - $ZH$ production followed by $Z\ar b\bar b$ and $H\ar W^+W^-$; - $AH$ production followed by $A\ar b\bar b$ and $H\ar W^+W^-$; - $hW^+W^-$ production followed by $h\ar b\bar b$. Top and Higgs finite width effects are included, as well as all those of the irreducible backgrounds.

hep-ph↗
arXiv1996

Standard Model Higgs boson production and hard photon radiation in $e^+e^-\to μ^+μ^- b\bar bγ$ events at LEP II and Next Linear Collider

We study at LEP II and Next Linear Collider energies Higgs production via the bremsstrahlung channel $e^+e^-\ar ZH$, with $Z\ar μ^+μ^-$ and $H\ar b\bar b$, and the corresponding irreducible background, in presence of hard photon radiation, both from the initial and the final state. We carry out an analysis that includes the computation of all the relevant contributions to the complete tree--level matrix element for $e^+e^-\ar μ^+μ^- b\bar bγ$ and makes use of the one at leading order $e^+e^-\ar μ^+μ^- b\bar b$ interfaced with electron structure functions. We concentrate on the case of mass degeneracy $M_H\approx M_Z$, for which next--to--leading electromagnetic contributions can modify the content of $b\bar b$--pairs coming from $H$ and $Z$ decays. A brief discussion concerning the case $M_H\not\approx M_Z$ is also given.

hep-ph↗
arXiv1995

Intermediate mass standard model Higgs boson at the proposed CERN LEP$\otimes$LHC $ep$ collider

The production of the \sm\ Higgs $ϕ$ with intermediate mass at the proposed CERN LEP$\otimes$LHC $ep$ collider in $γq(\bar q)\rightarrow W^\pmϕq'(\bar q')$, $γq(\bar q)\rightarrow Z^0ϕq(\bar q)$ and $gγ\rightarrow q\bar qϕ$ events is studied. This is done for all possible (massive) flavours of the quarks $q(q')$ and using photons generated via Compton back--scattering of laser light. We study signatures in which the Higgs decays to $b\bar b$--pairs and the electroweak vector bosons $W^\pm$ and $Z^0$ decay either hadronically or leptonically. All possible backgrounds to these signals are also computed. Flavour identification on $b$--jets is assumed. Explicit formulae for the helicity amplitudes of the above processes are given.

hep-ph↗
arXiv1995

Intermediate mass Higgs bosons of the Minimal Supersymmetric Standard Model at the proposed CERN LEP$\otimes$LHC $ep$ collider

The production of the \mssm\ Higgs bosons $H^0,h^0,A^0$ and $H^\pm$, in the intermediate mass range of the $A^0$, at two different values of $\tanβ$, is studied at the possible CERN LEP$\otimes$LHC $ep$ collider, through $γp$ interactions, by photons generated via Compton back--scattering of laser light. Signatures in which $H^0,h^0,A^0\ar b\bar b$ and $H^\pm\ar τν_τ$ are considered. Flavour identification on $b$--jets is assumed. Backgrounds to Higgs signals are computed. Explicit formulae for the helicity amplitudes of the Higgs processes are given.

hep-ph↗
arXiv1995

Finite width and irreducible background effects to $t\bar t$ production at $γγ$ Next Linear Colliders

We study the complete process \phphbbww\ using exact matrix element computations at tree-level, at a $\sqrt s=500$ GeV \eeb\ linear collider of the next generation. Incoming photons produced via back-scattering of laser light are considered. Sizable effects due to the finite width of the top quark as well as to the irreducible background to $t\bar t$ production and decay are predicted.

hep-ph↗
arXiv1995

Heavy Higgs production and decay via $e^+e^-\to Z^0 H^0 \to b\bar bZ^0Z^0$ and irreducible backgrounds at Next Linear Colliders

The complete matrix element for $e^+e^-\ar b\bar bZ^0Z^0$ has been computed at tree--level and applied to $Z^0H^0$--production followed by $Z^0\ar b\bar b$ and $H^0\ar Z^0Z^0$, including all the irreducible background, at Next Linear Colliders. We find that, assuming flavour identification of the $Z^0$--decay products, this channel, together with $e^+e^-\ar b\bar bW^+W^-$ in which $Z^0H^0\ar (b\bar b)(W^+W^-$), can be important for the study of the parameters of the Standard Model Higgs boson over the heavy mass range $2M_{Z^0}\Ord M_{H^0}\Ord 2{m_t}$.

hep-ph↗
arXiv1994

Heavy Quark Production at $e^+ e^-$ Colliders in Multijet Events and a New Method of Computing Helicity Amplitudes

Heavy quark production in multijet events at $e^+e^-$ colliders is studied at tree level. Total production rates are given and compared with the corresponding results for massless quarks. A new method of computing helicity amplitudes is briefly sketched. Talk presented at the XXIXth Rencontres de Moriond, QCD and High Energy Hadronic Interactions, Meribel, France, March 19-26 1994.

hep-ph↗
arXiv1994

Intermediate mass Higgs bosons at TeV $eγ$ colliders in the ${\cal {MSSM}}$

We study the cross sections for the production of intermediate mass Higgs bosons via the reactions $e^-γ\rightarrow ν_eW^-Φ^0$, $e^-γ\rightarrow ν_eH^-Φ^0$, $e^-γ\rightarrow e^-Z^0Φ^0$ and $e^-γ\rightarrow e^-H^+H^-$ in the Minimal Supersymmetric Standard Model (with $Φ^0=H^0,h^0$ and, where possible, $A^0$) at TeV energies, taking into account $b$--tagging capabilities. We find that the rates for $e^-γ\rightarrow ν_eW^-Φ^0$ are large enough to permit the discovery of at least one between $h^0$ and $H^0$ over the whole intermediate mass range of $M_{A^0}$, at all $\tanβ$, using the $(jj)(b\bar b)$ final state. The ${\cal {CP}}$-odd neutral $A^0$ and the charged $H^\pm$'s can be detected via the processes $e^-γ\rightarrow ν_eH^-A^0$, with $A^0\rightarrow b\bar b$, and $e^-γ\rightarrow e^-H^+H^-$, resorting to the leptonic decay $H^\pm\rightarrow ν_ττ^+(\barν_ττ^-)$, but only for $M_{A^0}\approx60$ GeV. Finally, we present explicit formulae for the helicity amplitudes of these processes.

hep-ph↗