Measurements of two- and four-particle angular correlations for charged particles emitted in pPb collisions are presented over a wide range in pseudorapidity and full azimuth. The data, corresponding to an integrated luminosity of approximately 31 inverse nanobarns, were collected during the 2013 LHC pPb run at a nucleon-nucleon center-of-mass energy of 5.02 TeV by the CMS experiment. The results are compared to 2.76 TeV semi-peripheral PbPb collision data, collected during the 2011 PbPb run, covering a similar range of particle multiplicities. The observed correlations are characterized by the near-side (abs(Delta(phi)~0) associated pair yields and the azimuthal anisotropy Fourier harmonics (v[n]). The second-order (v[2]) and third-order (v[3]) anisotropy harmonics are extracted using the two-particle azimuthal correlation technique. A four-particle correlation method is also applied to obtain the value of v[2] and further explore the multi-particle nature of the correlations. Both associated pair yields and anisotropy harmonics are studied as a function of particle multiplicity and transverse momentum. The associated pair yields, the four-particle v[2], and the v[3] become apparent at about the same multiplicity. A remarkable similarity in the v[3] signal as a function of multiplicity is observed between the pPb and PbPb systems. Predictions based on the color glass condensate and hydrodynamic models are compared to the experimental results

We report measurements of the primary charged-particle pseudorapidity density and transverse momentum distributions in p-Pb collisions at √ s NN = 5.02 TeV and investigate their correlation with experimental observables sensitive to the centrality of the collision. Centrality classes are defined by using different event-activity estimators, i.e., charged-particle multiplicities measured in three different pseudorapidity regions as well as the energy measured at beam rapidity (zero degree). The procedures to determine the centrality, quantified by the number of participants (N part ) or the number of nucleon-nucleon binary collisions (N coll ) are described. We show that, in contrast to Pb-Pb collisions, in p-Pb collisions large multiplicity fluctuations together with the small range of participants available generate a dynamical bias in centrality classes based on particle multiplicity. We propose to use the zero-degree energy, which we expect not to introduce a dynamical bias, as an alternative event-centrality estimator. Based on zero-degree energy-centrality classes, the N part dependence of particle production is studied. Under the assumption that the multiplicity measured in the Pb-going rapidity region scales with the number of Pb participants, an approximate independence of the multiplicity per participating nucleon measured at mid-rapidity of the number of participating nucleons is observed. Furthermore, at high-p T the p-Pb spectra are found to be consistent with the pp spectra scaled by N coll for all centrality classes. Our results represent valuable input for the study of the event-activity dependence of hard probes in p-Pb collisions and, hence, help to establish baselines for the interpretation of the Pb-Pb data.

Results are presented of a search for heavy particles decaying into two photons. The analysis is based on a 19.7 fb −1 sample of proton-proton collisions at √ s = 8 TeV collected with the CMS detector at the CERN LHC. The diphoton mass spectrum from 150 to 850 GeV is used to search for an excess of events over the background. The search is extended to new resonances with natural widths of up to 10% of the mass value. No evidence for new particle production is observed and limits at 95% confidence level on the production cross section times branching fraction to diphotons are determined. These limits are interpreted in terms of two-Higgs-doublet model parameters.The discovery of a standard model-like Higgs boson at the CERN LHC [1-4] opens a new phase in the understanding of the standard model (SM) of particle physics. The search for additional Higgs-like particles and the measurement of their properties provide complementary ways to test the validity of the SM and to test for the presence of physics beyond it. This analysis describes a search for new resonances in the diphoton invariant mass spectrum, using data corresponding to an integrated luminosity of 19.7 fb −1 collected with the CMS detector at a center-of-mass energy of 8 TeV at the CERN LHC. Despite the large nonresonant background, the diphoton decay mode provides a clean final-state topology that allows the mass of the decaying object to be reconstructed with high precision, exploiting the excellent performance of the electromagnetic calorimeter of the CMS experiment. The analysis searches for local excesses that could be due to the production of particles that decay into two photons with mass in the range from 150 to 850 GeV. Both narrow and wide resonances are investigated with natural widths ranging from 100 MeV to 10% of the resonance mass. This search covers the diphoton mass range above that investigated in [2,4]. The ATLAS experiment recently published a similar search for narrow resonances in the diphoton final state in the mass range between 65 and 600 GeV at a center-of-mass energy of 8 TeV [5]. Previous searches for resonant diphoton processes have been performed at the Tevatron by D0 [6] and CDF [7] at a center-of-mass energy of 1.96 TeV and by the ATLAS [8] and CMS [9] experiments at the LHC at a center-of-mass energy of 7 TeV. Several models of physics beyond the SM, such as the two-Higgs-doublet model (2HDM) [10], motivate the search for additional high-mass resonances in the diphoton channel. Generally, these models provide an extension of the Higgs sector, where a total of five Higgs bosons are predicted by the theory. The mass spectrum of the 2HDM can be split into two regions: a light SM-like Higgs boson h with mass around 125 GeV and the remaining physical Higgs bosons, H, a scalar, A, a pseudoscalar, and H ± , clustered at an equal or higher scale with m H ∼ m A ∼ m H ± .Under the assumption that the newly observed Higgs boson is the light CP-even Higgs scalar of the 2HDM, the consistency of its couplings with those predicted by th...

Midrapidity production of π ± , K ± , and (p)p measured by the ALICE experiment at the CERN Large Hadron Collider, in Pb-Pb and inelastic pp collisions at √ s NN = 5.02 TeV, is presented. The invariant yields are measured over a wide transverse momentum (p T) range from hundreds of MeV/c up to 20 GeV/c. The results in Pb-Pb collisions are presented as a function of the collision centrality, in the range 0-90%. The comparison of the p T-integrated particle ratios, i.e., proton-to-pion (p/π) and kaon-to-pion (K/π) ratios, with similar measurements in Pb-Pb collisions at √ s NN = 2.76 TeV show no significant energy dependence. Blast-wave fits of the p T spectra indicate that in the most central collisions radial flow is slightly larger at 5.02 TeV with respect to 2.76 TeV. Particle ratios (p/π , K/π) as a function of p T show pronounced maxima at p T ≈ 3 GeV/c in central Pb-Pb collisions. At high p T , particle ratios at 5.02 TeV are similar to those measured in pp collisions at the same energy and in Pb-Pb collisions at √ s NN = 2.76 TeV. Using the pp reference spectra measured at the same collision energy of 5.02 TeV, the nuclear modification factors for the different particle species are derived. Within uncertainties, the nuclear modification factor is particle species independent for high p T and compatible with measurements at √ s NN = 2.76 TeV. The results are compared to state-of-the-art model calculations, which are found to describe the observed trends satisfactorily.

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