The physics potential of the LHC

This talk is a short overview of the physics potential of the LHC with emphasis on Higgs search and SUSY search. First I review why LHC with the ATLAS and CMS detectors is expected to give a decisive test of the electroweak symmetry breaking mechanism of the Standard Model. Then I consider the Higgs sector of the Standard Model (SM). Finally the search for supersymmetry is discussed within the framework of various implementation of the Minimal Supersymmetric Standard Model (MSSM).Comment: Talk given at the meeting Beyond The Standard Model V, Balholm, Norway April 29 -- May 4, 1997, 10 pages, 2 figure

Bread and Butter Standard Model

Lectures given at the International School of Subnuclear Physics: 37th Course: Basics and Highlights of Fundamental Physics, Erice, Italy, 29 Aug - 7 Sep 1999

One-loop radiative corrections to the helicity amplitudes of QCD processes involving four quarks and one gluon

We present analytic results for the one-loop corrections of the helicity amplitudes of the QCD five-parton subprocesses involving four quarks and one gluon obtained with a standard Feynman diagram calculation using dimensional reduction.Comment: 9 pages LaTeX, ETH-TH/94-14, KLTE-DTP/94-

Two photons plus jet al LHC: the NNLO contribution from the gg initiated process

The production of the Standard Model Higgs boson of mass ~ 100-140 GeV at the LHC likely gives clear signals in the $\gamma \gamma$ (1) and in the $\gamma \gamma jet$ (2) channels. The quantitative evaluation of the background to channel (1) is very hard since the next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) QCD corrections are large. In particular, the contributions of the NNLO QCD subprocess $gg -> \gamma \gamma$ to inclusive $\gamma\gamma$ production is comparable to the contribution of the leading order subprocess $q\bar{q} -> \gamma \gamma$. The quantitative description of the background to channel (1), therefore, requires to calculate all corrections up to the NNNLO level. In this letter we present results on the contribution of the NNLO QCD subprocess $gg -> g \gamma \gamma$ to the production rate of channel (2). We have found that in this case this NNLO contribution is less than 20% of the Born contribution. Since the NNLO contributions will likely be dominated by this subprocess one can argue that in the case of channel (2) - contrary to the case of channel (1)- a quantitative description of the background can be achieved already at next-to-leading order accuracy.Comment: 7 pages, two figures include

Singular terms of helicity amplitudes at one-loop in QCD and the soft limit of the cross sections of multi-parton processes

We describe a general method that enables us to obtain all the singular terms of helicity amplitudes of n-parton processes at one loop. The algorithm uses helicity amplitudes at tree level and simple color algebra. We illustrate the method by calculating the singular part of the one loop helicity amplitudes of all $2\to 3$ parton subprocesses. The results are used to derive the soft gluon limit of the cross sections of all $2\to 4$ parton scattering subprocesses which provide a useful initial condition for the angular ordering approximation to coherent multiple soft gluon emission, incorporated in existing Monte Carlo simulation programs.Comment: Latex,13 pages, ETH-TH/94-

Diffractive Higgs Production at the LHC

We use diffractive parton distributions obtained from fits to the diffractive structure function measured at HERA to predict cross sections for single diffractive Higgs production at the LHC. The dominant background processes are also considered. Although some 5% - 15% of Higgs events are predicted to be diffractive in this model, the ratio of signal to background is not significantly improved.Comment: 14 pages, LaTeX, incl. 6 postscript figures, uses epsf.st

One-loop corrections to five-parton amplitudes with external photons

Recently the calculations of all five-parton one-loop QCD amplitudes have been completed. In this letter we describe how to get the corresponding amplitudes with one gluon replaced by a photon and we give the explicit results for the process 0 \to 2q 2Q 1\y.Comment: 7 pages, late