Associated Production Of Gu→(?)_i(?)_j~+ At LHC

The Standard Model (SM) in particle physics has achieved enormous success, but we still consider it as an effective theory at Fermi scale (- 246 GeV) of some fundamental theory. Therefore, people have proposed many new physics models beyond the SM, such as the Minimal Supersymmetric Standard Model (MSSM), which is the simplest supersymmetric (SUSY) extension of the SM. The MSSM does not introduce any new gauge interactions, and only includes basic particle spectrum. Especially, some SUSY breaking models just introduce several extra parameters, which endows them with strong ability of theoretical predictions. So searching for new particles predicted by SUSY theory is one of the main goals of the CERN Large Hadron Collider (LHC) experiments, and if SUSY really exists, they certainly can been detected at LHC.After a brief summary of elementary theoretical structures of the MSSM, we mainly study the associated production of down squarks and charginos at the LHC in next-to-leading order (NLO) QCD including SUSY QCD. Here we calculate the contributions from virtual self-energy, vertex and box corrections as well as real gluon emission and the processes with a massless quark in final state.Our calculations indicate that(1) In most of parameter space allowed by current experimental data, the total cross sectionsof both d₁χ₁⁺ and d₁χ₂⁺ associated productions can reach 100 fb, and especially for d₁χ₂⁺, the cross section can exceed 1 pb. This means that if SUSY is correct, we will find abundant events of these two processes at the LHC.(2) The NLO QCD corrections in general enhance the leading order (LO) results significantly,which can reach thirty percent.(3) The masses of u, d quarks are so small that they can be neglected in our calculations, the dependence of the cross sections and the NLO QCD corrections on the parameter tanβis therefore small. (4) The dependence of the NLO cross sections on the renormalization/factorization scale is greatly reduced compared to the leading order case, which means higher confidence in predictions based on the NLO results.