Jet momentum dependence of jet quenching in PbPb collisions at √sNN = 2.76 TeV

Dijet production in PbPb collisions at a nucleon–nucleon center-of-mass energy of 2.76 TeV is studied with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 150 μb−1 is analyzed. Jets are reconstructed using combined information from tracking and calorimetry, using the anti-kT algorithm with R = 0.3. The dijet momentum balance and angular correlations are studied as a function of collision centrality and leading jet transverse momentum. For the most peripheral PbPb collisions, good agreement of the dijet momentum balance distributions with pp data and reference calculations at the same collision energy is found, while more central collisions show a strong imbalance of leading and subleading jet transverse momenta attributed to the jet-quenching effect. The dijets in central collisions are found to be more unbalanced than the reference, for leading jet transverse momenta up to the highest values studied

Study of the production of charged pions, kaons, and protons in pPb collisions at √sNN = 5.02TeV

Spectra of identified charged hadrons are meas√ ured in pPb collisions with the CMS detector at the LHC at sNN = 5.02 TeV. Charged pions, kaons, and protons in the transverse-momentum range pT ≈ 0.1–1.7 GeV/c and laboratory rapidity |y| \u3c 1 are identified via their energy loss in the silicon tracker. The average pT increases with particle mass and the charged multiplicity of the event. The increase of the average pT with charged multiplicity is greater for heavier hadrons. Comparisons to Monte Carlo event generators reveal that Epos Lhc, which incorporates additional hydrodynamic evolution of the created system, is able to reproduce most of the data features, unlike Hijing and Ampt. The pT spectra and integrated yields are also compared to those measured in pp and PbPb collisions at various energies. The average transverse momentum and particle ratio measurements indicate that particle production at LHC energies is strongly correlated with event particle multiplicity

Search for the pair production of third-generation squarks with two-body decays to a bottom or charm quark and a neutralino in proton–proton collisions at √s=13 TeV

Results are presented from a search for the pair production of third-generation squarks in proton–proton collision events with two-body decays to bottom or charm quarks and a neutralino, which produces a significant imbalance in the transverse momentum. The search is performed using a sample of proton–proton collision data at √s=13 TeV recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9fb−1. No statistically significant excess of events is observed beyond the expected contribution from standard model processes. Exclusion limits are set in the context of simplified models of bottom or top squark pair production. Models with bottom squark masses up to 1220 GeV are excluded at 95% confidence level for light neutralinos, and models with top squark masses of 510 GeV are excluded assuming that the mass splitting between the top squark and the neutralino is small

Measurements of tt cross sections in association with b jets and inclusive jets and their ratio using dilepton final states in pp collisions at √s=13 TeV

The cross sections for the production of ttbb and ttjj events and their ratio σttbb/σttjj are measured using data corresponding to an integrated luminosity of 2.3fb−1 collected in pp collisions at √s = 13 TeV with the CMS detector at the LHC. Events with two leptons (e or μ) and at least four reconstructed jets, including at least two identified as b quark jets, in the final state are selected. In the full phase space, the measured ratio is 0.022 ± 0.003(stat) ± 0.006(syst), the cross section σttbb is 4.0 ± 0.6(stat) ±1.3(syst) pb and σttjj is 184 ± 6(stat) ± 33(syst) pb. The measurements are compared with the standard model expectations obtained from a powheg simulation at next-to-leading-order interfaced with pythia

CMS: Measurement of double-differential cross sections for top quark pair production in pp collisions at √s = 8 TeV and impact on parton distribution functions

Normalized double-differential cross sections for top quark pair (tt) production are measured in pp collisions at a centre-of-mass energy of 8 TeV with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7 fb−1. The measurement is performed in the dilepton e±μ∓ final state. The tt cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and tt system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions are used. The inclusion of the measured tt cross sections in a fit of parametrized parton distribution functions is shown to have significant impact on the gluon distribution

CMS: Observation of long-range, near-side angular correlations in proton-proton collisions at the LHC

Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7TeV are presented, using data collected with the CMS detector over a broad range of pseudorapidity (n) and azimuthal angle (?). Short-range correlations in [?]n, which are studied in minimum bias events, are characterized using a simple \independent cluster parametrization in order to quantify their strength (cluster size) and their extent in n (cluster decay width). Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 nb-1 data set at 7TeV. In high multiplicity events, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate pT of 1-3 GeV/c, 2.0 \u3c |[?]n| \u3c 4.8 and [?][?] [?]0. This is the first observation of such a long-range, near-side feature in two-particle correlation functions in pp or pp collisions

CMS: Search for heavy resonances decaying to a top quark and a bottom quark in the lepton+jets final state in proton–proton collisions at 13TeV

A search is presented for narrow heavy resonances decaying to a top quark and a bottom quark using data collected by the CMS experiment at √s=13TeV in 2016. The data set analyzed corresponds to an integrated luminosity of 35.9fb−1. Final states that include a single lepton (e, μ), multiple jets, and missing transverse momentum are analyzed. No evidence is found for the production of a W\u27 boson, and the production of right-handed W\u27 bosons is excluded at 95% confidence level for masses up to 3.6TeV depending on the scenario considered. Exclusion limits for W\u27 bosons are also presented as a function of their coupling strength to left-and right-handed fermions. These limits on a W\u27 boson decaying via a top and a bottom quark are the most stringent published to date

CMS: Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at p [?] = 0.9 and 2.36TeV

Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at [?] = 0.9 and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive interactions, the average charged-hadron transverse momentum is measured to be 0:46 ± 0:01 (stat.) ± 0.01 (syst.) GeV/c at 0.9 TeV and 0:50 ± 0:01 (stat.) ± 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between -2:4 and +2:4. At these energies, the measured pseudorapidity densities in the central region, dNch/dn||n|\u3c0.5, are 3.48±0.02 (stat.) ± 0.13 (syst.) and 4.47±0.04 (stat.) ± 0.16 (syst.), respectively. The results at 0.9 TeV are in agreement with previous measurements and confirm the expectation of near equal hadron production in pp and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date

Search for new phenomena with the MT2 variable in the all-hadronic final state produced in proton–proton collisions at √s = 13TeV

A search for new phenomena is performed using events with jets and significant transverse momentum imbalance, as inferred through the MT2 variable. The results are based on a sample of proton–proton collisions collected in 2016 at a center-of-mass energy of 13 TeV with the CMS detector and corresponding to an integrated luminosity of 35.9 fb−1. No excess event yield is observed above the predicted standard model background, and the results are interpreted as exclusion limits at 95% confidence level on the masses of predicted particles in a variety of simplified models of R-parity conserving supersymmetry. Depending on the details of the model, 95% confidence level lower limits on the gluino (light-flavor squark) masses are placed up to 2025 (1550) GeV. Mass limits as high as 1070 (1175) GeV are set on the masses of top (bottom) squarks. Information is provided to enable re-interpretation of these results, including model-independent limits on the number of non-standard model events for a set of simplified, inclusive search regions

Search for resonant and nonresonant Higgs boson pair production in the bb\u3ci\u3elvlv\u3c/i\u3e final state in proton-proton collisions at √s = 13 TeV

Searches for resonant and nonresonant pair-produced Higgs bosons (HH) decaying respectively into lvlv, through either W or Z bosons, and bb are presented. The analyses are based on a sample of proton-proton collisions at √s = 13TeV, collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb-1. Data and predictions from the standard model are in agreement within uncertainties. For the standard model HH hypothesis, the data exclude at 95% confidence level a product of the production cross section and branching fraction larger than 72 fb, corresponding to 79 times the standard model prediction. Constraints are placed on different scenarios considering anomalous couplings, which could affect the rate and kinematics of HH production. Upper limits at 95% confidence level are set on the production cross section of narrow width spin-0 and spin-2 particles decaying to Higgs boson pairs, the latter produced with minimal gravity-like coupling