Studies of Charm Quark Diffusion inside Jets Using Pb-Pb and pp Collisions at sqrt[s_{NN}]=5.02 TeV

The first study of charm quark diffusion with respect to the jet axis in heavy ion collisions is presented. The measurement is performed using jets with p_{T}^{jet}>60  GeV/c and D^{0} mesons with p_{T}^{D}>4  GeV/c in lead-lead (Pb-Pb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of sqrt[s_{NN}]=5.02  TeV, recorded by the CMS detector at the LHC. The radial distribution of D^{0} mesons with respect to the jet axis is sensitive to the production mechanisms of the meson, as well as to the energy loss and diffusion processes undergone by its parent parton inside the strongly interacting medium produced in Pb-Pb collisions. When compared to Monte Carlo event generators, the radial distribution in pp collisions is found to be well described by pythia, while the slope of the distribution predicted by sherpa is steeper than that of the data. In Pb-Pb collisions, compared to the pp results, the D^{0} meson distribution for 4<p_{T}^{D}<20  GeV/c hints at a larger distance on average with respect to the jet axis, reflecting a diffusion of charm quarks in the medium created in heavy ion collisions. At higher p_{T}^{D}, the Pb-Pb and pp radial distributions are found to be similar.

Measurement of the average very forward energy as a function of the track multiplicity at central pseudorapidities in proton-proton collisions at s = 13 TeV

The average total energy as well as its hadronic and electromagnetic components are measured with the CMS detector at pseudorapidities - 6.6 < η < - 5.2 in proton-proton collisions at a centre-of-mass energys = 13 TeV . The results are presented as a function of the charged particle multiplicity in the region | η | < 2 . This measurement is sensitive to correlations induced by the underlying event structure over a very wide pseudorapidity region. The predictions of Monte Carlo event generators commonly used in collider experiments and ultra-high energy cosmic ray physics are compared to the data. All generators considered overestimate the fraction of energy going into hadrons.

Azimuthal separation in nearly back-to-back jet topologies in inclusive 2- and 3-jet events in pp collisions at s = 13 Te

A measurement for inclusive 2- and 3-jet events of the azimuthal correlation between the two jets with the largest transverse momenta, Δ ϕ 12 , is presented. The measurement considers events where the two leading jets are nearly collinear ("back-to-back") in the transverse plane and is performed for several ranges of the leading jet transverse momentum. Proton-proton collision data collected with the CMS experiment at a center-of-mass energy of 13 Te and corresponding to an integrated luminosity of 35.9 fb - 1 are used. Predictions based on calculations using matrix elements at leading-order and next-to-leading-order accuracy in perturbative quantum chromodynamics supplemented with leading-log parton showers and hadronization are generally in agreement with the measurements. Discrepancies between the measurement and theoretical predictions are as large as 15%, mainly in the region177 ∘ < Δ ϕ 12 < 180 ∘ . The 2- and 3-jet measurements are not simultaneously described by any of models.

Measurement of exclusive ρ 770 0 photoproduction in ultraperipheral pPb collisions at s NN = 5.02 Te

Exclusiveρ 770 0 photoproduction is measured for the first time in ultraperipheral pPb collisions ats NN = 5.02 Te with the CMS detector. The cross section σ ( γ p → ρ 770 0 p ) is 11.0 ± 1.4 (stat) ± 1.0 (syst) μ b at ⟨ W γ p ⟩ = 92.6 Ge for photon-proton centre-of-mass energies W γ p between 29 and 213 Ge . The differential cross section d σ / d | t | is measured in the interval0.025 < | t | < 1 Ge 2 as a function of W γ p , where t is the squared four-momentum transfer at the proton vertex. The results are compared with previous measurements and theoretical predictions. The measured cross section σ ( γ p → ρ 770 0 p ) has a power-law dependence on the photon-proton centre-of-mass, consistent with electron-proton collision measurements performed at HERA. The W γ p dependence of the exponential slope of the differential cross section d σ / d | t | is also measured.

Study of the underlying event in top quark pair production in p p collisions at 13 Te

Measurements of normalized differential cross sections as functions of the multiplicity and kinematic variables of charged-particle tracks from the underlying event in top quark and antiquark pair production are presented. The measurements are performed in proton-proton collisions at a center-of-mass energy of 13 Te , and are based on data collected by the CMS experiment at the LHC in 2016 corresponding to an integrated luminosity of 35.9 fb - 1 . Events containing one electron, one muon, and two jets from the hadronization and fragmentation of b quarks are used. These measurements characterize, for the first time, properties of the underlying event in top quark pair production and show no deviation from the universality hypothesis at energy scales typically above twice the top quark mass.

Measurement of differential cross sections for inclusive isolated-photon and photon+jet production in proton-proton collisions at s = 13 TeV

Measurements of inclusive isolated-photon and photon+jet production in proton-proton collisions ats = 13 TeV are presented. The analysis uses data collected by the CMS experiment in 2015, corresponding to an integrated luminosity of 2.26fb - 1 . The cross section for inclusive isolated photon production is measured as a function of the photon transverse energy in a fiducial region. The cross section for photon+jet production is measured as a function of the photon transverse energy in the same fiducial region with identical photon requirements and with the highest transverse momentum jet. All measurements are in agreement with predictions from next-to-leading-order perturbative QCD.

Measurement of differential cross sections for Z boson production in association with jets in proton-proton collisions at s = 13 TeV

The production of a Z boson, decaying to two charged leptons, in association with jets in proton-proton collisions at a centre-of-mass energy of 13TeV is measured. Data recorded with the CMS detector at the LHC are used that correspond to an integrated luminosity of 2.19fb -1 . The cross section is measured as a function of the jet multiplicity and its dependence on the transverse momentum of the Z boson, the jet kinematic variables (transverse momentum and rapidity), the scalar sum of the jet momenta, which quantifies the hadronic activity, and the balance in transverse momentum between the reconstructed jet recoil and the Z boson. The measurements are compared with predictions from four different calculations. The first two merge matrix elements with different parton multiplicities in the final state and parton showering, one of which includes one-loop corrections. The third is a fixed-order calculation with next-to-next-to-leading order accuracy for the process with a Z boson and one parton in the final state. The fourth combines the fully differential next-to-next-to-leading order calculation of the process with no parton in the final state with next-to-next-to-leading logarithm resummation and parton showering.

Measurement of the top quark mass with lepton+jets final states using p p collisions at s = 13 TeV

The mass of the top quark is measured using a sample of t t ¯ events collected by the CMS detector using proton-proton collisions ats = 13 TeV at the CERN LHC. Events are selected with one isolated muon or electron and at least four jets from data corresponding to an integrated luminosity of 35.9fb - 1 . For each event the mass is reconstructed from a kinematic fit of the decay products to a t t ¯ hypothesis. Using the ideogram method, the top quark mass is determined simultaneously with an overall jet energy scale factor (JSF), constrained by the mass of the W boson in q q ¯ ' decays. The measurement is calibrated on samples simulated at next-to-leading order matched to a leading-order parton shower. The top quark mass is found to be 172.25 ± 0.08 (stat+JSF) ± 0.62 (syst) GeV . The dependence of this result on the kinematic properties of the event is studied and compared to predictions of different models of t t ¯ production, and no indications of a bias in the measurements are observed.

Observation of the Z→ψℓ^{+}ℓ^{-} Decay in pp Collisions at sqrt[s]=13 TeV

This Letter presents the observation of the rare Z boson decay Z→ψℓ^{+}ℓ^{-}. Here, ψ represents contributions from direct J/ψ and ψ(2S)→J/ψX, ℓ^{+}ℓ^{-} is a pair of electrons or muons, and the J/ψ meson is detected via its decay to μ^{+}μ^{-}. The sample of proton-proton collision data, collected by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, corresponds to an integrated luminosity of 35.9  fb^{-1}. The signal is observed with a significance in excess of 5 standard deviations. After subtraction of the ψ(2S)→J/ψX contribution, the ratio of the branching fraction of the exclusive decay Z→J/ψℓ^{+}ℓ^{-} to the decay Z→μ^{+}μ^{-}μ^{+}μ^{-} within a fiducial phase space is measured to be B(Z→J/ψℓ^{+}ℓ^{-})/B(Z→μ^{+}μ^{-}μ^{+}μ^{-})=0.67±0.18(stat)±0.05(syst).

Measurement of charged particle spectra in minimum-bias events from proton-proton collisions at s = 13 TeV

Pseudorapidity, transverse momentum, and multiplicity distributions are measured in the pseudorapidity range | η | < 2.4 for charged particles with transverse momenta satisfyingp T > 0.5 GeV in proton-proton collisions at a center-of-mass energy ofs = 13 TeV . Measurements are presented in three different event categories. The most inclusive of the categories corresponds to an inelastic p p data set, while the other two categories are exclusive subsets of the inelastic sample that are either enhanced or depleted in single diffractive dissociation events. The measurements are compared to predictions from Monte Carlo event generators used to describe high-energy hadronic interactions in collider and cosmic-ray physics.

Constraining Gluon Distributions in Nuclei Using Dijets in Proton-Proton and Proton-Lead Collisions at sqrt[s_{NN}]=5.02 TeV

The pseudorapidity distributions of dijets as functions of their average transverse momentum (p_{T}^{ave}) are measured in proton-lead (pPb) and proton-proton (pp) collisions. The data samples were collected by the CMS experiment at the CERN LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. A significant modification of the pPb spectra with respect to the pp spectra is observed in all p_{T}^{ave} intervals investigated. The ratios of the pPb and pp distributions are compared to next-to-leading order perturbative quantum chromodynamics calculations with unbound nucleon and nuclear parton distribution functions (PDFs). These results give the first evidence that the gluon PDF at large Bjorken x in lead ions is strongly suppressed with respect to the PDF in unbound nucleons.

Measurement of prompt and nonprompt charmonium suppression in PbPb collisions at 5.02 TeV

The nuclear modification factors of J / ψ and ψ (2S) mesons are measured in PbPb collisions at a centre-of-mass energy per nucleon pair of s NN = 5.02 TeV . The analysis is based on PbPb and p p data samples collected by CMS at the LHC in 2015, corresponding to integrated luminosities of 464 μ b - 1 and 28 pb -1 , respectively. The measurements are performed in the dimuon rapidity range of | y | < 2.4 as a function of centrality, rapidity, and transverse momentum ( p T ) from p T = 3 GeV / c in the most forward region and up to 50 GeV / c . Both prompt and nonprompt (coming from b hadron decays) J / ψ mesons are observed to be increasingly suppressed with centrality, with a magnitude similar to the one observed at s NN = 2.76 TeV for the two J / ψ meson components. No dependence on rapidity is observed for either prompt or nonprompt J / ψ mesons. An indication of a lower prompt J / ψ meson suppression at p T > 25 GeV / c is seen with respect to that observed at intermediate p T . The prompt ψ (2S) meson yield is found to be more suppressed than that of the prompt J / ψ mesons in the entire p T range.

Search for the X(5568) State Decaying into B_{s}^{0}π^{±} in Proton-Proton Collisions at sqrt[s]=8 TeV

A search for resonancelike structures in the B_{s}^{0}π^{±} invariant mass spectrum is performed using proton-proton collision data collected by the CMS experiment at the LHC at sqrt[s]=8  TeV, corresponding to an integrated luminosity of 19.7  fb^{-1}. The B_{s}^{0} mesons are reconstructed in the decay chain B_{s}^{0}→J/ψϕ, with J/ψ→μ^{+}μ^{-} and ϕ→K^{+}K^{-}. The B_{s}^{0}π^{±} invariant mass distribution shows no statistically significant peaks for different selection requirements on the reconstructed B_{s}^{0} and π^{±} candidates. Upper limits are set on the relative production rates of the X(5568) and B_{s}^{0} states times the branching fraction of the decay X(5568)^{±}→B_{s}^{0}π^{±}. In addition, upper limits are obtained as a function of the mass and the natural width of possible exotic states decaying into B_{s}^{0}π^{±}.

Measurement of associated Z + charm production in proton-proton collisions at s = 8 TeV

A study of the associated production of a Z boson and a charm quark jet ( Z + c ), and a comparison to production with a b quark jet ( Z + b ), in p p collisions at a centre-of-mass energy of 8TeV are presented. The analysis uses a data sample corresponding to an integrated luminosity of 19.7fb - 1 , collected with the CMS detector at the CERN LHC. The Z boson candidates are identified through their decays into pairs of electrons or muons. Jets originating from heavy flavour quarks are identified using semileptonic decays of c or b flavoured hadrons and hadronic decays of charm hadrons. The measurements are performed in the kinematic region with two leptons withp T ℓ > 20 GeV ,| η ℓ | < 2.1 , 71 < m ℓ ℓ < 111 GeV , and heavy flavour jets withp T jet > 25 GeV and| η jet | < 2.5 . The Z + c production cross section is measured to be σ ( p p → Z + c + X ) B ( Z → ℓ + ℓ - ) = 8.8 ± 0.5 (stat) ± 0.6 (syst) pb . The ratio of the Z + c and Z + b production cross sections is measured to be σ ( p p → Z + c + X ) / σ ( p p → Z + b + X ) = 2.0 ± 0.2 (stat) ± 0.2 (syst) . The Z + c production cross section and the cross section ratio are also measured as a function of the transverse momentum of the Z boson and of the heavy flavour jet. The measurements are compared with theoretical predictions.

Search for standard model production of four top quarks with same-sign and multilepton final states in proton-proton collisions at s = 13 TeV

A search for standard model production of four top quarks ( t t ¯ t t ¯ ) is reported using events containing at least three leptons ( e , μ ) or a same-sign lepton pair. The events are produced in proton-proton collisions at a center-of-mass energy of 13TeV at the LHC, and the data sample, recorded in 2016, corresponds to an integrated luminosity of 35.9fb - 1 . Jet multiplicity and flavor are used to enhance signal sensitivity, and dedicated control regions are used to constrain the dominant backgrounds. The observed and expected signal significances are, respectively, 1.6 and 1.0 standard deviations, and the t t ¯ t t ¯ cross section is measured to be 16 . 9 - 11.4 + 13.8 fb , in agreement with next-to-leading-order standard model predictions. These results are also used to constrain the Yukawa coupling between the top quark and the Higgs boson to be less than 2.1 times its expected standard model value at 95% confidence level.

Measurement of the differential cross section and charge asymmetry for inclusive [Formula: see text] production at [Formula: see text] TeV

The differential cross section and charge asymmetry for inclusive [Formula: see text] production at [Formula: see text] are measured as a function of muon pseudorapidity. The data sample corresponds to an integrated luminosity of 18.8[Formula: see text] recorded with the CMS detector at the LHC. These results provide important constraints on the parton distribution functions of the proton in the range of the Bjorken scaling variable x from [Formula: see text] to [Formula: see text].

Search for Narrow Resonances in Dijet Final States at sqrt[s]=8 TeV with the Novel CMS Technique of Data Scouting

A search for narrow resonances decaying into dijet final states is performed on data from proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 18.8  fb^{-1}. The data were collected with the CMS detector using a novel technique called data scouting, in which the information associated with these selected events is much reduced, permitting collection of larger data samples. This technique enables CMS to record events containing jets at a rate of 1 kHz, by collecting the data from the high-level-trigger system. In this way, the sensitivity to low-mass resonances is increased significantly, allowing previously inaccessible couplings of new resonances to quarks and gluons to be probed. The resulting dijet mass distribution yields no evidence of narrow resonances. Upper limits are presented on the resonance cross sections as a function of mass, and compared with a variety of models predicting narrow resonances. The limits are translated into upper limits on the coupling of a leptophobic resonance Z_{B}^{'} to quarks, improving on the results obtained by previous experiments for the mass range from 500 to 800 GeV.

Measurements of the [Formula: see text][Formula: see text] production cross sections in the [Formula: see text] channel in proton-proton collisions at [Formula: see text] and [Formula: see text] and combined constraints on triple gauge couplings

Measurements of the [Formula: see text][Formula: see text] production cross sections in proton-proton collisions at center-of-mass energies of 7 and 8[Formula: see text] are presented. Candidate events for the leptonic decay mode [Formula: see text], where [Formula: see text] denotes an electron or a muon, are reconstructed and selected from data corresponding to an integrated luminosity of 5.1 (19.6)[Formula: see text] at 7 (8)[Formula: see text] collected with the CMS experiment. The measured cross sections, [Formula: see text] at 7[Formula: see text], and [Formula: see text] at 8[Formula: see text], are in good agreement with the standard model predictions with next-to-leading-order accuracy. The selected data are analyzed to search for anomalous triple gauge couplings involving the [Formula: see text][Formula: see text] final state. In the absence of any deviation from the standard model predictions, limits are set on the relevant parameters. These limits are then combined with the previously published CMS results for [Formula: see text][Formula: see text] in 4[Formula: see text] final states, yielding the most stringent constraints on the anomalous couplings.

Constraints on the pMSSM, AMSB model and on other models from the search for long-lived charged particles in proton-proton collisions at [Formula: see text]

Stringent limits are set on the long-lived lepton-like sector of the phenomenological minimal supersymmetric standard model (pMSSM) and the anomaly-mediated supersymmetry breaking (AMSB) model. The limits are derived from the results presented in a recent search for long-lived charged particles in proton-proton collisions, based on data collected by the CMS detector at a centre-of-mass energy of 8 TeV at the Large Hadron Collider. In the pMSSM parameter sub-space considered, 95.9 % of the points predicting charginos with a lifetime of at least 10 ns are excluded. These constraints on the pMSSM are the first obtained at the LHC. Charginos with a lifetime greater than 100 ns and masses up to about 800 GeV in the AMSB model are also excluded. The method described can also be used to set constraints on other models.

Search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks using a matrix element method

A search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks is presented. Events with hadronic jets and one or two oppositely charged leptons are selected from a data sample corresponding to an integrated luminosity of 19.5[Formula: see text] collected by the CMS experiment at the LHC in [Formula: see text] collisions at a centre-of-mass energy of 8[Formula: see text]. In order to separate the signal from the larger [Formula: see text]  + jets background, this analysis uses a matrix element method that assigns a probability density value to each reconstructed event under signal or background hypotheses. The ratio between the two values is used in a maximum likelihood fit to extract the signal yield. The results are presented in terms of the measured signal strength modifier, [Formula: see text], relative to the standard model prediction for a Higgs boson mass of 125[Formula: see text]. The observed (expected) exclusion limit at a 95 % confidence level is [Formula: see text] (3.3), corresponding to a best fit value [Formula: see text].

Measurement of J/ψ and ψ(2S) Prompt Double-Differential Cross Sections in pp Collisions at sqrt[s]=7 TeV

The double-differential cross sections of promptly produced J/ψ and ψ(2S) mesons are measured in pp collisions at sqrt[s]=7 TeV, as a function of transverse momentum p_{T} and absolute rapidity |y|. The analysis uses J/ψ and ψ(2S) dimuon samples collected by the CMS experiment, corresponding to integrated luminosities of 4.55 and 4.90 fb^{-1}, respectively. The results are based on a two-dimensional analysis of the dimuon invariant mass and decay length, and extend to p_{T}=120 and 100 GeV for the J/ψ and ψ(2S), respectively, when integrated over the interval |y|<1.2. The ratio of the ψ(2S) to J/ψ cross sections is also reported for |y|<1.2, over the range 10<p_{T}<100 GeV. These are the highest p_{T} values for which the cross sections and ratio have been measured.

Search for decays of stopped long-lived particles produced in proton-proton collisions at [Formula: see text]

A search has been performed for long-lived particles that could have come to rest within the CMS detector, using the time intervals between LHC beam crossings. The existence of such particles could be deduced from observation of their decays via energy deposits in the CMS calorimeter appearing at times that are well separated from any proton-proton collisions. Using a data set corresponding to an integrated luminosity of 18.6[Formula: see text] of 8[Formula: see text] proton-proton collisions, and a search interval corresponding to 281 h of trigger livetime, 10 events are observed, with a background prediction of [Formula: see text] events. Limits are presented at 95 % confidence level on gluino and top squark production, for over 13 orders of magnitude in the mean proper lifetime of the stopped particle. Assuming a cloud model of R-hadron interactions, a gluino with mass [Formula: see text]1000[Formula: see text] and a top squark with mass [Formula: see text]525[Formula: see text] are excluded, for lifetimes between 1 [Formula: see text]s and 1000[Formula: see text]. These results are the most stringent constraints on stopped particles to date.

Search for monotop signatures in proton-proton collisions at √s=8 TeV

Results are presented from a search for new decaying massive particles whose presence is inferred from an imbalance in transverse momentum and which are produced in association with a single top quark that decays into a bottom quark and two light quarks. The measurement is performed using 19.7  fb^{-1} of data from proton-proton collisions at a center-of-mass energy of 8 TeV, collected with the CMS detector at the CERN LHC. No deviations from the standard model predictions are observed and lower limits are set on the masses of new invisible bosons. In particular, scalar and vector particles, with masses below 330 and 650 GeV, respectively, are excluded at 95% confidence level, thereby substantially extending a previous limit published by the CDF Collaboration.

Measurement of prompt ψ(2S) to J/ψ yield ratios in Pb-Pb and p-p collisions at sqrt[sNN]=2.76 TeV

The ratio between the prompt ψ(2S) and J/ψ yields, reconstructed via their decays into μ+ μ-, is measured in Pb-Pb and p-p collisions at sqrt[sNN]=2.76  TeV. The analysis is based on Pb-Pb and p-p data samples collected by CMS at the Large Hadron Collider, corresponding to integrated luminosities of 150  μb(-1) and 5.4  pb(-1), respectively. The double ratio of measured yields (Nψ(2S)/N(J/ψ))(Pb-Pb)/(Nψ(2S)/N(J/ψ))(p-p) is computed in three Pb-Pb collision centrality bins and two kinematic ranges: one at midrapidity, |y|<1.6, covering the transverse momentum range 6.5<pT<30  GeV/c, and the other at forward rapidity, 1.6<|y|<2.4, extending to lower pT values, 3<pT<30  GeV/c. The centrality-integrated double ratio changes from 0.45±0.13(stat)±0.07(syst) in the first range to 1.67±0.34(stat)±0.27(syst) in the second. This difference is most pronounced in the most central collisions.

Measurement of differential cross sections for the production of a pair of isolated photons in pp collisions at [Formula: see text]

A measurement of differential cross sections for the production of a pair of isolated photons in proton-proton collisions at [Formula: see text] is presented. The data sample corresponds to an integrated luminosity of 5.0[Formula: see text] collected with the CMS detector. A data-driven isolation template method is used to extract the prompt diphoton yield. The measured cross section for two isolated photons, with transverse energy above 40 and 25[Formula: see text] respectively, in the pseudorapidity range [Formula: see text], [Formula: see text] and with an angular separation [Formula: see text], is [Formula: see text][Formula: see text]. Differential cross sections are measured as a function of the diphoton invariant mass, the diphoton transverse momentum, the azimuthal angle difference between the two photons, and the cosine of the polar angle in the Collins-Soper reference frame of the diphoton system. The results are compared to theoretical predictions at leading, next-to-leading, and next-to-next-to-leading order in quantum chromodynamics.

Searches for electroweak production of charginos, neutralinos, and sleptons decaying to leptons and W, Z, and Higgs bosons in pp collisions at 8 TeV

Searches for the direct electroweak production of supersymmetric charginos, neutralinos, and sleptons in a variety of signatures with leptons and [Formula: see text], [Formula: see text], and Higgs bosons are presented. Results are based on a sample of proton-proton collision data collected at center-of-mass energy [Formula: see text] with the CMS detector in 2012, corresponding to an integrated luminosity of 19.5 [Formula: see text]. The observed event rates are in agreement with expectations from the standard model. These results probe charginos and neutralinos with masses up to 720 [Formula: see text], and sleptons up to 260 [Formula: see text], depending on the model details.

Evidence of b-jet quenching in PbPb collisions at √(s(NN))=2.76 TeV

The production of jets associated to bottom quarks is measured for the first time in PbPb collisions at a center-of-mass energy of 2.76 TeV per nucleon pair. Jet spectra are reported in the transverse momentum (p(T)) range of 80-250  GeV/c, and within pseudorapidity |η|<2. The nuclear modification factor (R(AA)) calculated from these spectra shows a strong suppression in the b-jet yield in PbPb collisions relative to the yield observed in pp collisions at the same energy. The suppression persists to the largest values of p(T) studied, and is centrality dependent. The R(AA) is about 0.4 in the most central events, similar to previous observations for inclusive jets. This implies that jet quenching does not have a strong dependence on parton mass and flavor in the jet p(T) range studied.

Measurement of top quark-antiquark pair production in association with a W or Z boson in pp collisions at [Formula: see text][Formula: see text]

A measurement of the cross section for the production of top quark-antiquark pairs ([Formula: see text]) in association with a vector boson V (W or Z) in proton-proton collisions at [Formula: see text][Formula: see text] is presented. The results are based on a dataset corresponding to an integrated luminosity of 19.5 fb[Formula: see text] recorded with the CMS detector at the LHC. The measurement is performed in three leptonic (e and [Formula: see text]) channels: a same-sign dilepton analysis targeting [Formula: see text] events, and trilepton and four-lepton analyses designed for [Formula: see text] events. In the same-sign dilepton channel, the [Formula: see text] cross section is measured as [Formula: see text], corresponding to a significance of 1.6 standard deviations over the background-only hypothesis. Combining the trilepton and four-lepton channels, a direct measurement of the [Formula: see text] cross section, [Formula: see text], is obtained with a significance of 3.1 standard deviations. The measured cross sections are compatible with standard model predictions within their experimental uncertainties. The inclusive [Formula: see text] process is observed with a significance of 3.7 standard deviations from the combination of all three leptonic channels.

Measurement of jet multiplicity distributions in [Formula: see text] production in pp collisions at [Formula: see text]

The normalised differential top quark-antiquark production cross section is measured as a function of the jet multiplicity in proton-proton collisions at a centre-of-mass energy of 7[Formula: see text] at the LHC with the CMS detector. The measurement is performed in both the dilepton and lepton+jets decay channels using data corresponding to an integrated luminosity of 5.0[Formula: see text]. Using a procedure to associate jets to decay products of the top quarks, the differential cross section of the [Formula: see text] production is determined as a function of the additional jet multiplicity in the lepton+jets channel. Furthermore, the fraction of events with no additional jets is measured in the dilepton channel, as a function of the threshold on the jet transverse momentum. The measurements are compared with predictions from perturbative quantum chromodynamics and no significant deviations are observed.

Search for invisible decays of Higgs bosons in the vector boson fusion and associated ZH production modes

A search for invisible decays of Higgs bosons is performed using the vector boson fusion and associated ZH production modes. In the ZH mode, the Z boson is required to decay to a pair of charged leptons or a [Formula: see text] quark pair. The searches use the 8 [Formula: see text] pp collision dataset collected by the CMS detector at the LHC, corresponding to an integrated luminosity of up to 19.7 [Formula: see text]. Certain channels include data from 7 [Formula: see text] collisions corresponding to an integrated luminosity of 4.9 [Formula: see text]. The searches are sensitive to non-standard-model invisible decays of the recently observed Higgs boson, as well as additional Higgs bosons with similar production modes and large invisible branching fractions. In all channels, the observed data are consistent with the expected standard model backgrounds. Limits are set on the production cross section times invisible branching fraction, as a function of the Higgs boson mass, for the vector boson fusion and ZH production modes. By combining all channels, and assuming standard model Higgs boson cross sections and acceptances, the observed (expected) upper limit on the invisible branching fraction at [Formula: see text] [Formula: see text] is found to be 0.58 (0.44) at 95 % confidence level. We interpret this limit in terms of a Higgs-portal model of dark matter interactions.

Observation of the associated production of a single top quark and a W boson in pp collisions at sqrt[s] = 8 TeV

The first observation of the associated production of a single top quark and a W boson is presented. The analysis is based on a data set corresponding to an integrated luminosity of 12.2 fb(-1) of proton-proton collisions at sqrt[s] = 8 TeV recorded by the CMS experiment at the LHC. Events with two leptons and a jet originating from a b quark are selected. A multivariate analysis based on kinematic and topological properties is used to separate the signal from the dominant tt background. An excess consistent with the signal hypothesis is observed, with a significance which corresponds to 6.1 standard deviations above a background-only hypothesis. The measured production cross section is 23.4 ± 5.4 pb, in agreement with the standard model prediction.

Study of the production of charged pions, kaons, and protons in pPb collisions at [Formula: see text]5.02[Formula: see text]

Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the LHC at [Formula: see text]. Charged pions, kaons, and protons in the transverse-momentum range [Formula: see text]-1.7[Formula: see text] and laboratory rapidity [Formula: see text] are identified via their energy loss in the silicon tracker. The average [Formula: see text] increases with particle mass and the charged multiplicity of the event. The increase of the average [Formula: see text] 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 [Formula: see text] 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.

Measurement of inclusive W and Z boson production cross sections in pp collisions at sqrt[s] = 8 TeV

A measurement of total and fiducial inclusive W and Z boson production cross sections in pp collisions at sqrt[s] = 8 TeV is presented. Electron and muon final states are analyzed in a data sample collected with the CMS detector corresponding to an integrated luminosity of 18.2 ± 0.5 pb(-1). The measured total inclusive cross sections times branching fractions are σ(pp → WX)×B(W → ℓν) = 12.21 ± 0.03(stat) ± 0.24(syst) ± 0.32(lum) nb and σ(pp → ZX) × B(Z → ℓ+ℓ-) = 1.15 ± 0.01(stat) ± 0.02(syst) ± 0.03(lum) nb for the dilepton mass in the range of 60-120 GeV. The measured values agree with next-to-next-to-leading-order QCD cross section calculations. Ratios of cross sections are reported with a precision of 2%. This is the first measurement of inclusive W and Z boson production in proton-proton collisions at sqrt[s] = 8 TeV.

Search for top-quark partners with charge 5/3 in the same-sign dilepton final state

A search for the production of heavy partners of the top quark with charge 5/3 is performed in events with a pair of same-sign leptons. The data sample corresponds to an integrated luminosity of 19.5 fb(-1) and was collected at sqrt[s] = 8 TeV by the CMS experiment. No significant excess is observed in the data above the expected background, and the existence of top-quark partners with masses below 800 GeV is excluded at a 95% confidence level, assuming they decay exclusively to tW. This is the first limit on these particles from the LHC, and it is significantly more restrictive than previous limits.

Search for flavor-changing neutral currents in top-quark decays t → Zq in pp collisions at sqrt[s] = 8 TeV

A search for flavor-changing neutral currents in top-quark decays t → Zq is performed in events produced from the decay chain tt → Zq+Wb, where both vector bosons decay leptonically, producing a final state with three leptons (electrons or muons). A data set collected with the CMS detector at the LHC is used, corresponding to an integrated luminosity of 19.7 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV. No excess is seen in the observed number of events relative to the standard model prediction; thus, no evidence for flavor-changing neutral currents in top-quark decays is found. A combination with a previous search at 7 TeV excludes a t → Zq branching fraction greater than 0.05% at the 95% confidence level.

Search for top squark and Higgsino production using diphoton Higgs boson decays

Results are presented of a search for a "natural" supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top quark (the top squark) and the Higgs boson (Higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two b-quark jets. In 19.7  fb-1 of proton-proton collision data at s=8  TeV, recorded in the CMS experiment, no evidence of a signal is found and lower limits at the 95% confidence level are set, excluding the top squark mass below 360 to 410 GeV, depending on the Higgsino mass.

Measurement of the top-quark mass in all-jets [Formula: see text] events in pp collisions at [Formula: see text] TeV

The mass of the top quark is measured using a sample of [Formula: see text] candidate events with at least six jets in the final state. The sample is selected from data collected with the CMS detector in pp collisions at [Formula: see text] TeV in 2011 and corresponds to an integrated luminosity of 3.54 [Formula: see text]. The mass is reconstructed for each event employing a kinematic fit of the jets to a [Formula: see text] hypothesis. The top-quark mass is measured to be [Formula: see text] GeV. A combination with previously published measurements in other decay modes by CMS yields a mass of [Formula: see text] GeV.

Search for top squarks in R-parity-violating supersymmetry using three or more leptons and b-tagged jets

A search for anomalous production of events with three or more isolated leptons and bottom-quark jets produced in pp collisions at √s=8 TeV is presented. The analysis is based on a data sample corresponding to an integrated luminosity of 19.5 fb(-1) collected by the CMS experiment at the LHC in 2012. No excess above the standard model expectations is observed. The results are interpreted in the context of supersymmetric models with signatures that have low missing transverse energy arising from light top-squark pair production with R-parity-violating decays of the lightest supersymmetric particle. In two models with different R-parity-violating couplings, top squarks are excluded below masses of 1020 GeV and 820 GeV when the lightest supersymmetric particle has a mass of 200 GeV.

Search for supersymmetry in hadronic final states with missing transverse energy using the variables αT and b-quark multiplicity in pp collisions at [Formula: see text]

An inclusive search for supersymmetric processes that produce final states with jets and missing transverse energy is performed in pp collisions at a centre-of-mass energy of 8 TeV. The data sample corresponds to an integrated luminosity of 11.7 fb-1 collected by the CMS experiment at the LHC. In this search, a dimensionless kinematic variable, αT, is used to discriminate between events with genuine and misreconstructed missing transverse energy. The search is based on an examination of the number of reconstructed jets per event, the scalar sum of transverse energies of these jets, and the number of these jets identified as originating from bottom quarks. No significant excess of events over the standard model expectation is found. Exclusion limits are set in the parameter space of simplified models, with a special emphasis on both compressed-spectrum scenarios and direct or gluino-induced production of third-generation squarks. For the case of gluino-mediated squark production, gluino masses up to 950-1125 GeV are excluded depending on the assumed model. For the direct pair-production of squarks, masses up to 450 GeV are excluded for a single light first- or second-generation squark, increasing to 600 GeV for bottom squarks.

Inclusive search for supersymmetry using razor variables in pp collisions at √s=7 TeV

An inclusive search is presented for new heavy particle pairs produced in √s=7 TeV proton-proton collisions at the LHC using 4.7±0.1 fb(-1) of integrated luminosity. The selected events are analyzed in the 2D razor space of M(R), an event-by-event indicator of the heavy particle mass scale, and R, a dimensionless variable related to the missing transverse energy. The third-generation sector is probed using the event heavy-flavor content. The search is sensitive to generic supersymmetry models with minimal assumptions about the superpartner decay chains. No excess is observed in the number of events beyond that predicted by the standard model. Exclusion limits are derived in the CMSSM framework as well as for simplified models. Within the CMSSM parameter space considered, gluino masses up to 800 GeV and squark masses up to 1.35 TeV are excluded at 95% confidence level depending on the model parameters. The direct production of pairs of top or bottom squarks is excluded for masses as high as 400 GeV.

Search for physics beyond the standard model in events with τ leptons, jets, and large transverse momentum imbalance in pp collisions at [Formula: see text]

A search for physics beyond the standard model is performed with events having one or more hadronically decaying τ leptons, highly energetic jets, and large transverse momentum imbalance. The data sample corresponds to an integrated luminosity of 4.98 fb-1 of proton-proton collisions at [Formula: see text] collected with the CMS detector at the LHC in 2011. The number of observed events is consistent with predictions for standard model processes. Lower limits on the mass of the gluino in supersymmetric models are determined.

Measurement of masses in the [Formula: see text] system by kinematic endpoints in pp collisions at [Formula: see text]

A simultaneous measurement of the top-quark, W-boson, and neutrino masses is reported for [Formula: see text] events selected in the dilepton final state from a data sample corresponding to an integrated luminosity of 5.0 fb-1 collected by the CMS experiment in pp collisions at [Formula: see text]. The analysis is based on endpoint determinations in kinematic distributions. When the neutrino and W-boson masses are constrained to their world-average values, a top-quark mass value of [Formula: see text] is obtained. When such constraints are not used, the three particle masses are obtained in a simultaneous fit. In this unconstrained mode the study serves as a test of mass determination methods that may be used in beyond standard model physics scenarios where several masses in a decay chain may be unknown and undetected particles lead to underconstrained kinematics.

Search for a standard-model-like Higgs boson with a mass in the range 145 to 1000 GeV at the LHC

A search for a standard-model-like Higgs boson in the H→WW and H→ZZ decay channels is reported, for Higgs boson masses in the range 145 Collapse

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Search for supersymmetry in pp collisions at [Formula: see text] TeV in events with a single lepton, jets, and missing transverse momentum

Results are reported from a search for new physics processes in events containing a single isolated high-transverse-momentum lepton (electron or muon), energetic jets, and large missing transverse momentum. The analysis is based on a 4.98 fb-1 sample of proton-proton collisions at a center-of-mass energy of 7 TeV, obtained with the CMS detector at the LHC. Three separate background estimation methods, each relying primarily on control samples in the data, are applied to a range of signal regions, providing complementary approaches for estimating the background yields. The observed yields are consistent with the predicted standard model backgrounds. The results are interpreted in terms of limits on the parameter space for the constrained minimal supersymmetric extension of the standard model, as well as on cross sections for simplified models, which provide a generic description of the production and decay of new particles in specific, topology based final states.

ELECTRONIC SUPPLEMENTARY MATERIAL

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Measurement of associated production of vector bosons and top quark-antiquark pairs in pp collisions at sqrt[s]=7 TeV

The first measurement of vector-boson production associated with a top quark-antiquark pair in proton-proton collisions at sqrt[s] = 7  TeV is presented. The results are based on a data set corresponding to an integrated luminosity of 5.0  fb(-1), recorded by the CMS detector at the LHC in 2011. The measurement is performed in two independent channels through a trilepton analysis of ttZ events and a same-sign dilepton analysis of ttV (V = W or Z) events. In the trilepton channel a direct measurement of the ttZ cross section σ(ttZ) = 0.28(-0.11)(+0.14) (stat)(-0.03)(+0.06) (syst)  pb is obtained. In the dilepton channel a measurement of the ttV cross section yields σ(ttV) = 0.43(-0.15)(+0.17) (stat)(-0.07)(+0.09) (syst)  pb. These measurements have a significance, respectively, of 3.3 and 3.0 standard deviations from the background hypotheses and are compatible, within uncertainties, with the corresponding next-to-leading order predictions of 0.137(-0.016)(+0.012) and 0.306(-0.053)(+0.031)  pb.