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

Jet production in PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV was studied with the Compact Muon Solenoid (CMS) detector at the LHC, using a data sample corresponding to an integrated luminosity of 6.7 μb −1 . Jets are reconstructed using the energy deposited in the CMS calorimeters and studied as a function of collision centrality. With increasing collision centrality, a striking imbalance in dijet transverse momentum is observed, consistent with jet quenching. The observed effect extends from the lower cutoff used in this study (jet p T = 120 GeV/c) up to the statistical limit of the available data sample (jet p T ≈ 210 GeV/c). Correlations of charged particle tracks with jets indicate that the momentum imbalance is accompanied by a softening of the fragmentation pattern of the second most energetic, away-side jet. The dijet momentum balance is recovered when integrating low transverse momentum particles distributed over a wide angular range relative to the direction of the away-side jet.

The spectra of strange hadrons are measured in proton-proton collisions, recorded by the CMS experiment at the CERN LHC, at centre-of-mass energies of 0.9 and 7 TeV. The K 0 S , Λ, and Ξ − particles and their antiparticles are reconstructed from their decay topologies and the production rates are measured as functions of rapidity and transverse momentum, p T . The results are compared to other experiments and to predictions of the Pythia Monte Carlo program. The p T distributions are found to differ substantially from the Pythia results and the production rates exceed the predictions by up to a factor of three.

A search for new physics is performed based on events with jets and a pair of isolated, same-sign leptons. The results are obtained using a sample of proton-proton collision data collected by the CMS experiment at a centre-of-mass energy of 8 TeV at the LHC, corresponding to an integrated luminosity of 19.5 fb −1 . In order to be sensitive to a wide variety of possible signals beyond the standard model, multiple search regions defined by the missing transverse energy, the hadronic energy, the number of jets and bquark jets, and the transverse momenta of the leptons in the events are considered. No excess above the standard model background expectation is observed and constraints are set on a number of models for new physics, as well as on the same-sign top-quark pair and quadruple-top-quark production cross sections. Information on event selection efficiencies is also provided, so that the results can be used to confront an even broader class of new physics models. 8 Limits on models of new physics and on rare SM processes 109 Information for additional model testing 19 Summary 22The CMS collaboration 27 IntroductionIn the standard model (SM), proton-proton collision events having a final state with isolated leptons of the same sign are extremely rare. Searches for anomalous production of same-sign dileptons can therefore be very sensitive to new physics processes that produce this signature copiously. These include supersymmetry (SUSY) [1][2][3], universal extra dimensions [4], pair production of T 5/3 particles (fermionic partners of the top quark) [5], heavy Majorana neutrinos [6], and same-sign top-quark pair production [7,8]. In SUSY, for example, same-sign dileptons occur naturally with the production of gluino pairs, when each gluino decays to a top quark and a top anti-squark, with the anti-squark further decaying into a top anti-quark and a neutralino. In this paper we describe searches for new physics with same-sign dileptons (ee, eµ, and µµ) and hadronic jets, with or without accompanying missing transverse energy (E miss T ). Our choice of signatures is driven by the following considerations. New physics signals with large cross sections are likely to be produced by strong interactions, and we thus expect significant hadronic activity in conjunction with the two leptons. Astrophysical evidence for dark matter [9] suggests considering SUSY models with R-parity conservation, which provides an excellent dark matter candidate -a stable lightest supersymmetric particle -1 -JHEP01(2014)163 JHEP01 (2014)163 (LSP) that escapes detection. Therefore, a search for this signature involves sizable E miss T due to undetected LSPs. Nevertheless, we also consider signatures without significant E miss T in order to be sensitive to SUSY models with R-parity violation (RPV) [10] which imply an unstable LSP. Beyond these general guiding principles, the choice of signatures is made independently of any particular physics model and, as a result, these signatures can be applied also to probe non-supersymmetric ex...

Angular distributions of the decay B 0 → K * 0 µ + µ − are studied using a sample of proton-proton collisions at √ s = 8 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 20.5 fb −1 . An angular analysis is performed to determine the P 1 and P 5 parameters, where the P 5 parameter is of particular interest because of recent measurements that indicate a potential discrepancy with the standard model predictions. Based on a sample of 1397 signal events, the P 1 and P 5 parameters are determined as a function of the dimuon invariant mass squared. The measurements are in agreement with predictions based on the standard model.