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.

Pseudorapidity (η) distributions of charged particles produced in proton-proton collisions at a centre-of-mass energy of 8 TeV are measured in the ranges |η| < 2.2 and 5.3 < |η| < 6.4 covered by the CMS and TOTEM detectors, respectively. The data correspond to an integrated luminosity of L = 45 µb −1 . Measurements are presented for three event categories. The most inclusive category is sensitive to 91-96 % of the total inelastic proton-proton cross section. The other two categories are disjoint subsets of the inclusive sample that are either enhanced or depleted in single diffractive dissociation events. The data are compared to models used to describe high-energy hadronic interactions. None of the models considered provide a consistent description of the measured distributions.

The first LHC pp collisions at centre-of-mass energies of 0.9 and 2.36 TeV were recorded by the CMS detector in December 2009. The trajectories of charged particles produced in the collisions were reconstructed using the all-silicon Tracker and their momenta were measured in the 3.8 T axial magnetic field. Results from the Tracker commissioning are presented including studies of timing, efficiency, signal-to-noise, resolution, and ionization energy. Reconstructed tracks are used to benchmark the performance in terms of track and vertex resolutions, reconstruction of decays, estimation of ionization energy loss, as well as identification of photon conversions, nuclear interactions, and heavy-flavour decays.

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A search for the standard model Higgs boson decaying to a W-boson pair at the LHC is reported. The event sample corresponds to an integrated luminosity of 4.9 fb −1 and 19.4 fb −1 collected with the CMS detector in pp collisions at √ s = 7 and 8 TeV, respectively. The Higgs boson candidates are selected in events with two or three charged leptons. An excess of events above background is observed, consistent with the expectation from the standard model Higgs boson with a mass of around 125 GeV. The probability to observe an excess equal or larger than the one seen, under the background-only hypothesis, corresponds to a significance of 4.3 standard deviations for m H = 125.6 GeV. The observed signal cross section times the branching fraction to WW for m H = 125.6 GeV is 0.72 +0.20 −0.18 times the standard model expectation. The spin-parity J P = 0 + hypothesis is favored against a narrow resonance with J P = 2 + or J P = 0 − that decays to a W-boson pair. This result provides strong evidence for a Higgs-like boson decaying to a W-boson pair. Finding such a signal in the complex environment of a hadron collider is not straightforward. A complete reconstruction of all the final-state particles is not possible because of the presence of neutrinos which are not directly detected. Kinematic observables such as the opening angle between the two charged leptons in the transverse plane, the dilepton mass, and the transverse mass of the system of the two leptons and the neutrinos, can be used to distinguish not only the Higgs boson signal from background processes with similar signature [17,18], but also between the SM Higgs boson hypothesis and other narrow exotic resonances with different spin or parity. Phenomenological studies of the amplitudes for the decay of a Higgs or an exotic boson into the WW final state demonstrate a good sensitivity to distinguish between the SM Higgs boson hypothesis (spin-parity 0 + ) and a spin-2 resonance, which couples to the bosons through minimal couplings, referred to as 2 + min [19]. Some sensitivity has also been shown with this final state to distinguish between the 0 + and the pseudoscalar 0 − boson hypotheses. Keywords: Hadron-Hadron Scattering, Higgs physics-1 - JHEP01(2014)096Searches for the SM Higgs boson in the H → WW final state at the LHC have previously been performed using data at √ s = 7 TeV by CMS [20][21][22], excluding the presence of the SM Higgs boson at the 95% CL in the mass range 129-270 GeV, and by ATLAS [23], excluding the mass range 133-261 GeV. Using their full dataset at 7 and 8 TeV, ATLAS have reported a H → WW signal with a statistical significance of 3.8 standard deviations [24] as well as evidence for the spin zero nature of the Higgs boson [25].This paper reports a measurement of the production and properties of the Higgs boson in the WW decay channel using the entire dataset collected by the CMS experiment during the 2011 and 2012 LHC running period. Various production modes, using events with two or three charged leptons ( ), electrons o...