M. Spira

SQUARK AND GLUINO PRODUCTION AT HADRON COLLIDERS

We have determined the theoretical predictions for the cross-sections of squark and gluino production at p¯ p and pp colliders (Tevatron and LHC) in next-to-leading order of supersymmetric QCD. By reducing the dependence on the renormalization/factorization scale considerably, the theoretically predicted values for the cross-sections are much more stable if these higher-order corrections are implemented. If squarks and gluinos are discovered, this improved stability translates into a reduced error on the masses, as extracted experimentally from the size of the production cross-sections. The cross-sections increase significantly if the next-to-leading order corrections are included at a renormalization/factorization scale near the average mass of the produced massive particles. This rise results in improved lower bounds on squark and gluino masses. By contrast, the shape of the transverse-momentum and rapidity distributions remains nearly unchanged when the next-to-leading order corrections are included.

Stop production at hadron colliders

Abstract Stop particles are expected to be the lightest squarks in supersymmetric theories and the search for these particles is an important experimental task. We therefore present the cross sections for the production processes p p /pp → t 1 t 1 and t 2 t 2 at Tevatron and LHC energies in next-to-leading order supersymmetric QCD. The corrections stabilize the theoretical predictions for the cross sections, and they are positive, thus raising the cross sections to values above the leading-order predictions. Mixed t 1 t 2 / t 1 t 2 pairs can only be generated in higher orders at strongly suppressed rates.

Soft Gluon Radiation in Higgs Boson Production at the LHC

We examine the contributions of soft gluons to the Higgs production cross section at the LHC in the Standard Model and its minimal supersymmetric extension. The soft gluon radiation effects of this reaction share many features with the Drell-Yan process, but arise at lowest order from a purely gluonic initial state. We provide an extension of the conventional soft gluon resummation formalism to include a new class of contributions which we argue to be universal, and resum these and the usual Sudakov effects to all orders. The effect of these new terms is striking: only if they are included, does the expansion of the resummed cross section to next-to-leading order reproduce the exact result to within a few percent for the full range of Higgs boson masses. We use our resummed cross section to derive next-to-next-to-leading order results, and their scale dependence. Moreover, we demonstrate the importance of including the novel contributions in the resummed Drell-Yan process.

QCD Effects in Higgs Physics

Higgs boson production at the LHC within the Standard Model and its minimal supersymmetric extension is reviewed. The predictions for decay rates and production cross sections are updated by choosing the present value of the top quark mass and recent parton density sets. Moreover, all relevant higher order corrections, some of which have been obtained only recently, are included in a consistent way.

Pair production of neutral Higgs particles in gluon-gluon collisions

Abstract Pair production processes of neutral Higgs particles will allow us to study the trilinear Higgs couplings at future high-energy colliders. Several mechanisms give rise to multi-Higgs final states in hadron interactions. In the present paper we investigate Higgs pair production in gluon-gluon collisions. After recapitulating pair production in the Standard Model, the analysis of the cross sections is carried out in detail for the neutral Higgs particles in the minimal supersymmetric extension.

Production of MSSM Higgs bosons in photon–photon collisions

Abstract The heavy neutral Higgs bosons H,A in the minimal supersymmetric extension of the Standard Model can be produced as single resonances at high-energy γγ colliders. We have studied the prospects of the search for these particles in b b and neutralino-pair final states. The Higgs bosons can be found with masses up to 70–80% of the initial e±e− collider energy for medium values of tg β , i.e., in areas of the supersymmetric parameter space not accessible at other colliders.

PAIR PRODUCTION OF SCALAR LEPTOQUARKS AT THE FERMILAB TEVATRON

We present the cross section for pair production of scalar leptoquarks LQ in p{ovr p} collisions, p+{ovr p}{r_arrow}LQ+{ovr LQ}+X , at the Fermilab Tevatron in next-to-leading order QCD. Including the higher-order corrections stabilizes the theoretical prediction and increases the size of the cross section for renormalization/factorization scales close to the mass of the leptoquarks. This leads to a rise of the lower bound on the mass of scalar leptoquarks by up to 15GeV with respect to earlier analyses. {copyright} {ital 1997} {ital The American Physical Society}

HIGLU and HDECAY: Programs for Higgs boson production at the LHC and Higgs boson decay widths

Abstract The total cross section for neutral Higgs boson production via the gluon fusion mechanism including NLO (two-loop) QCD corrections can be calculated numerically with the program HIGLU within the Standard Model (SM) as well as its minimal supersymmetric extension (MSSM). The program HDECAY determines the decay widths and branching ratios of the Higgs bosons within the SM and the MSSM, including the dominant higher-order corrections. The program is able to calculate the branching ratios of the MSSM Higgs bosons into standard and supersymmetric particles.

Production of Charged Higgs Boson Pairs in Gluon{Gluon Collisions

Abstract The search for charged Higgs bosons, which are predicted in supersymmetric theories, is difficult at hadron colliders if the mass is large. In this paper we present the theoretical set-up for the production of charged Higgs-boson pairs at the LHC in gluon-gluon collisions: pp → gg → H + H − . When established experimentally, the trilinear couplings between charged and neutral CP -even Higgs bosons, H + H − H 0 and H + H − H 0 , can be measured.

Electroweak symmetry breaking and higgs physics

We present an introduction to electroweak symmetry breaking and Higgs physics within the Standard Model and supersymmetric extensions. A brief overview will also be given on strong interactions of the electroweak gauge bosons in alternative scenarios. In addition to the theoretical basis, the present experimental status of Higgs physics and implications for future experiments at the LHC and lepton colliders are discussed.