Precise predictions for supersymmetric particle production at the LHC

One of the main objectives of the Large Hadron Collider (LHC) is the search for physics beyond the Standard Model. Among the most promising candidates is the Minimal Supersymmetric Standard Model (MSSM) which postulates the existence of further particles. Since none of these supersymmetric particles have been found yet, their mass limits have been shifted to high values. Hence, with the available energy of the LHC they would always be produced close to their production threshold. This leads to predictions for cross sections which are characterized by the presence of dominant logarithmic terms stemming from multiple soft gluon emission. These contributions spoil the convergence of the perturbative series and require a resummation to predict reliable results in these critical kinematical phase space regions. As the attention of experimental searches has been shifted towards electroweak supersymmetric particle production at the LHC, we update in this thesis our predictions for direct slepton pair production at proton-proton collision to next-to-leading order (NLO) matched to resummation at the next-to-leading logarithmic (NLL) accuracy. As a benchmark scenario we choose simplified models which have the advantage of only containing a few relevant physical parameters. They are now commonly adopted by the experimental collaborations for slepton and electroweak gaugino searches. We find that the scale dependence is drastically reduced by including NLL corrections, especially for large slepton masses. For increasing mass limits we hint towards the significance of next-to-next-to-leading logarithmic contributions to the cross section. By using modern Monte Carlo techniques we reanalyze ATLAS and CMS results for slepton searches for different assumptions about the compositions of the sleptons and their neutralino decay products. We observe similar mass limits for selectrons and smuons as both collaborations and find that masses for left-handed (right-handed) selectrons and smuons up to 175 GeV (150 GeV) and 130 GeV (100 GeV), respectively, are excluded for an almost massless lightest neutralino. For a compressed spectrum of the supersymmetric particles no limits can be derived as the signal electrons are too soft to be detected. In addition, we point out that a distinction between the flavor and the left- and right-handed components of the sleptons should be considered in future analyses, whereas the neutralino composition is irrelevant for our simplified models. In the second part of this thesis we investigate the associated production of gluinos and electroweak gauginos. As the gluinos are required to be heavy due to the mass limits their direct pair production at the LHC could be beyond its reach. However, their associated production with the relatively light electroweak gauginos might be a possibility to produce gluinos at the LHC. For this reason, we generalize the previously obtained NLO results to non-degenerate squark masses and add NLL contributions. We present analytical results for the soft anomalous dimension and the hard matching coefficient function. For our chosen benchmark scenario NLL corrections increase the NLO cross section by 7 to 20% for central scale choices and gluino masses of 3 to 6 TeV, respectively, and reduce its scale dependence typically from up to ±12% to below ±3%.