The Scientific and Technical Research Council of Turkey, and Turkish Atomic Energy Authorit

Recent results of the searches for Supersymmetry in final states with one or two leptons at CMS are presented. Many Supersymmetry scenarios, including the Constrained Minimal Supersymmetric extension of the Standard Model (CMSSM), predict a substantial amount of events containing leptons, while the largest fraction of Standard Model background events -which are QCD interactions -gets strongly reduced by requiring isolated leptons. The analyzed data was taken in 2011 and corresponds to an integrated luminosity of approximately L = 1 fb −1 . The center-of-mass energy of the pp collisions was √ s = 7 TeV.

New sets of parameters (“tunes”) for the underlying-event (UE) modelling of the pythia8, pythia6 and herwig++ Monte Carlo event generators are constructed using different parton distribution functions. Combined fits to CMS UE proton–proton () data at and to UE proton–antiproton () data from the CDF experiment at lower , are used to study the UE models and constrain their parameters, providing thereby improved predictions for proton–proton collisions at 13. In addition, it is investigated whether the values of the parameters obtained from fits to UE observables are consistent with the values determined from fitting observables sensitive to double-parton scattering processes. Finally, comparisons are presented of the UE tunes to “minimum bias” (MB) events, multijet, and Drell–Yan ( lepton-antilepton+jets) observables at 7 and 8, as well as predictions for MB and UE observables at 13.

This paper describes the CMS trigger system and its performance during Run 1 of the LHC. The trigger system consists of two levels designed to select events of potential physics interest from a GHz (MHz) interaction rate of proton-proton (heavy ion) collisions. The first level of the trigger is implemented in hardware, and selects events containing detector signals consistent with an electron, photon, muon, τ lepton, jet, or missing transverse energy. A programmable menu of up to 128 object-based algorithms is used to select events for subsequent processing. The trigger thresholds are adjusted to the LHC instantaneous luminosity during data taking in order to restrict the output rate to 100 kHz, the upper limit imposed by the CMS readout electronics. The second level, implemented in software, further refines the purity of the output stream, selecting an average rate of 400 Hz for offline event storage. The objectives, strategy and performance of the trigger system during the LHC Run 1 are described.

Searches for invisible decays of the Higgs boson are presented. The data collected with the CMS detector at the LHC correspond to integrated luminosities of 5.1, 19.7, and 2.3 fb −1 at centre-of-mass energies of 7, 8, and 13 TeV, respectively. The search channels target Higgs boson production via gluon fusion, vector boson fusion, and in association with a vector boson. Upper limits are placed on the branching fraction of the Higgs boson decay to invisible particles, as a function of the assumed production cross sections. The combination of all channels, assuming standard model production, yields an observed (expected) upper limit on the invisible branching fraction of 0.24 (0.23) at the 95% confidence level. The results are also interpreted in the context of Higgs-portal dark matter models. [6,7]. More generally, invisible Higgs boson decays can be realised through interactions between the Higgs boson and dark matter (DM) [8]. In Higgs-portal models [9][10][11][12], the Higgs boson acts as a mediator between SM and DM particles allowing for direct production of DM at the LHC. Furthermore, cosmological models proposing that the Higgs boson played a central role in the evolution of the early universe motivate the study of the relationship between the Higgs boson and DM [13, 14].Direct searches for invisible decays of the Higgs boson increase the sensitivity to the invisible Higgs boson width beyond the indirect constraints. The typical signature at the LHC is a large missing transverse momentum recoiling against a distinctive visible system. Previous searches by the ATLAS and CMS Collaborations have targeted Higgs boson production in association with a vector boson (VH, where V denotes W or Z) [15][16][17] or with jets consistent with a vector boson fusion (VBF, via qq → qqH) topology [17, 18]. A combination of direct searches for invisible Higgs boson decays in qqH and VH production, by the ATLAS Collaboration, yields an upper limit of 0.25 on the Higgs boson invisible branching fraction, B(H → inv), at the 95% confidence level [19]. Additionally, searches by the ATLAS Collaboration for DM in events with missing transverse momentum accompanied by jets have been interpreted in the context of Higgs boson production via gluon fusion and subsequent decay to invisible particles [20].In this paper, results from a combination of searches for invisible decays of the Higgs boson using data collected during 2011, 2012, and 2015 are presented. The searches target the qqH, VH, and ggH production modes. The searches for the VH production mode include searches targeting ZH production, in which the Z boson decays to a pair of leptons (either e + e − or µ + µ − ) or bb, and searches for both the ZH and WH production modes, in which the W or Z boson decays to light-flavour jets. Additional sensitivity is achieved in this analysis by including a search targeting gluon fusion production where the Higgs boson is produced accompanied by a gluon jet (gg → gH). The diagrams for the qqH, VH, and ggH Higgs boson production pr...