QCD corrections to e+e−→u dˉ s cˉe^+ e^- \to u~\bar d~s~\bar c at Lep 2 and the Next Linear Collider: CC11 at O(\alpha_s)

QCD one-loop corrections to the full gauge invariant set of electroweak diagrams describing the hadronic process $e^+ e^- \to u~\bar d~s~\bar c$ are computed. Four-jet shape variables for $WW$ events are studied at next-to-leading order and the effects of QCD corrections on the determination of the $W$--mass in the hadronic channel at Lep 2 and NLC is discussed. We compare the exact calculation with a ``naive''approach to strong radiative corrections which has been widely used in the literature.Comment: 10 pages, 4 ps figures, requires axodra

Higgs Production in Charged Current Six Fermion Processes at Future e+e−e^+e^- Colliders

We study higgs physics at future $e^+e^-$ colliders taking into account the full set of Feynman diagrams for six fermion final states, which are produced for higgs masses near or above the two $W$'s threshold. In particular we examine events where one isolated lepton or two isolated leptons of different flavours signal the presence of two $\rm W^*$'s. For these charged current processes, a detailed analysis of the relevance of irreducible and QCD background shows that appropriate cuts are generally sufficient to deal with it in the case of reconstructed or missing higgs mass distributions. These latter are however affected by a non negligible distortion and shift of the maximum.Comment: Latex, 16 pages, 8 Ps figures included. Revised version. One fig. added, qcd curve in fig.5 corrected, various changes in the tex

CC10 at O(αs){\cal O}(\alpha_s ): QCD corrections to e+e−→μ−νˉμudˉe^+ e^- \to \mu^- \bar \nu_\mu u \bar d at LEP2 and the Next Linear Collider

QCD one-loop corrections to the semileptonic process $e^+ e^- \to \mu^- \bar \nu_\mu u \bar d$ are computed. We compare the exact calculation with a ``naive'' approach to strong radiative corrections which has been widely used in the literature and discuss the phenomenological relevance of QCD contributions for LEP2 and NLC physics.Comment: 10 LaTex pages, 3 figs using Axodraw.sty, 3 ps figure

bbˉW+W−b \bar b W^+ W^- production at hadron colliders. Top signal and irreducible backgrounds

We compute complete tree level matrix elements for $gg , q \bar q \rightarrow b \bar b W^+W^-$. We analyze the irreducible backgrounds to top signal at the Tevatron and at the LHC. Their contribution to the total cross section is about $5 \%$ at the LHC, due to single resonant channels. Several distributions with contributions from signal and backgrounds are presented.Comment: 13 LaTex pages, 2 figs using feynman.sty, 5 ps figure

NLO QCD corrections to the production of off--shell WW pairs at e+e−e^+ e^- colliders

QCD corrections to e^+e^- \ra WW \ra q_1 \bar q_1 q_2 \bar q_2 are computed and presented in a form which allows to impose realistic cuts on the structure of the observed events. QCD radiation substantially modifies the jet--jet invariant mass distributions from which the value of the $W$ mass will be extracted. When the range of allowed jet--jet masses is restricted, as it has been proposed in order to suppress non--$WW$ backgrounds, the total cross section is also deeply affected. If all events are forced to four jets, combining the two partons with smallest invariant mass, and the reconstructed masses are required to satisfy $\left| M_{Ri} -M_W \right| \le 10$ GeV $i$=1,2 the lowest order cross section can be reduced by more than 40\%.Comment: One ref. fixed. 15 LaTex pages, 2 figs in a uuencoded gz-compressed tar fil

Semileptonic six fermion processes at future e+e−e^+ e^- colliders: signal and irreducible background for top and WWZ physics

We compute several total and differential cross sections relevant to top and WWZ physics at future $e^+e^-$ colliders taking into account the full set of Feynman diagrams for six fermion final states. We also include in our calculations initial state radiation and beamstrahlung effects, and the most important QCD corrections in an approximate (naive) form. We compare such a complete approach with "production x decay" approximation and we suggest that in many physical studies the former is needed.Comment: 28 pages including 8 figures (7 ps). Latex. Uses Axodraw. Minor changes and some typos correcte