2018 JINST 13 P05011 8.5 Measurement of the data-to-simulation scale factors as a function of the discriminator value 76 8.6 Comparison of the measured data-to-simulation scale factors 79 9 Measurement of the tagging efficiency for boosted topologies 82 9.1 Comparison of data with simulation 82 9.2 Efficiency for subjets 83 9.2.1 Misidentification probability 83 9.2.2 Measurement of the b tagging efficiency 84 9.3 Efficiency of the double-b tagger 86 9.3.1 Measurement of the double-b tagging efficiency 86 9.3.2 Measurement of the misidentification probability for top quarks 87

A statistical combination of several searches for the electroweak production of charginos and neutralinos is presented. All searches use proton-proton collision data at √ s = 13 TeV, recorded with the CMS detector at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb −1 . In addition to the combination of previous searches, a targeted analysis requiring three or more charged leptons (electrons or muons) is presented, focusing on the challenging scenario in which the difference in mass between the two least massive neutralinos is approximately equal to the mass of the Z boson. The results are interpreted in simplified models of chargino-neutralino or neutralino pair production. For chargino-neutralino production, in the case when the lightest neutralino is massless, the combination yields an observed (expected) limit at the 95% confidence level on the chargino mass of up to 650 (570) GeV, improving upon the individual analysis limits by up to 40 GeV. If the mass difference between the two least massive neutralinos is approximately equal to the mass of the Z boson in the chargino-neutralino model, the targeted search requiring three or more leptons obtains observed and expected exclusion limits of around 225 GeV on the second neutralino mass and 125 GeV on the lightest neutralino mass, improving the observed limit by about 60 GeV in both masses compared to the previous CMS result. In the neutralino pair production model, the combined observed (expected) exclusion limit on the neutralino mass extends up to 650-750 (550-750) GeV, depending on the branching fraction assumed. This extends the observed exclusion achieved in the individual analyses by up to 200 GeV. The combined result additionally excludes some intermediate gaps in the mass coverage of the individual analyses.

A measurement is performed of the cross section of top quark pair production in association with a W or Z boson using proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb −1 , collected by the CMS experiment in 2016. The measurement is performed in the same-sign dilepton, three-and four-lepton final states. The production cross sections are measured to be σ(ttW) = 0.77 +0.12 −0.11 (stat) +0.13 −0.12 (syst) pb and σ(ttZ) = 0.99 +0.09 −0.08 (stat) +0.12 −0.10 (syst) pb. The expected (observed) signal significance for the ttW production in same-sign dilepton channel is found to be 4.5 (5.3) standard deviations, while for the ttZ production in three-and four-lepton channels both the expected and the observed significances are found to be in excess of 5 standard deviations. The results are in agreement with the standard model predictions and are used to constrain the Wilson coefficients for eight dimension-six operators describing new interactions that would modify ttW and ttZ production. states to simultaneously extract these cross sections. Furthermore, the results are interpreted in the context of an effective field theory to constrain the Wilson coefficients [9], which parameterize the strength of new physics interactions, for a set of selected dimension-six operators that might signal the presence of NP contributions in ttW and ttZ production. The CMS detectorThe central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. Forward calorimeters extend the pseudorapidity (η) coverage provided by the barrel and endcap detectors. Muons are detected in gas-ionization chambers embedded in the steel magnetic fluxreturn yoke outside the solenoid. A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in Ref. [10]. Events of interest are selected using a two-tiered trigger system [11]. The first level, composed of custom hardware processors, uses information from the calorimeters and muon detectors to select events, while the second level selects events by running a version of the full event reconstruction software optimized for fast processing on a farm of computer processors. Event and object selectionEvents are selected by online triggers that require the presence of at least one electron or muon, with transverse momentum, p T , greater than 27 or 24 GeV, respectively. The selection efficiencies for the signal and background events that pass all requirements are found to be greater than 95 and 98% for the dilepton analysis and for the three-and four-lepton analyses, respectively.The Monte Carlo (MC) simulations are used to estimate som...

A search for the standard model (SM) Higgs boson (H) decaying to bb when produced in association with an electroweak vector boson is reported for the following processes: Z(νν)H, W(µν)H, W(eν)H, Z(µµ)H, and Z(ee)H. The search is performed in data samples corresponding to an integrated luminosity of 35.9 fb −1 at √ s = 13 TeV recorded by the CMS experiment at the LHC during Run 2 in 2016. An excess of events is observed in data compared to the expectation in the absence of a H → bb signal. The significance of this excess is 3.3 standard deviations, where the expectation from SM Higgs boson production is 2.8. The signal strength corresponding to this excess, relative to that of the SM Higgs boson production, is 1.2 ± 0.4. When combined with the Run 1 measurement of the same processes, the signal significance is 3.8 standard deviations with 3.8 expected. The corresponding signal strength, relative to that of the SM Higgs boson, is 1.06 +0.31 −0.29 . used at NLO with the FxFx merging scheme [51] for the diboson background samples. The same generator is used at LO accuracy with the MLM matching scheme [52] for the W+jets and Z+jets in inclusive and b-quark enriched configurations, as well as the QCD multijet sample. The tt [53] production process, as well as the single top quark sample for the t-channel [54], are produced with POWHEG v2. The single top quark samples for the tW-[55] and s-channel [56] are instead produced with POWHEG v1. The production cross sections for the signal samples are rescaled to next-to-next-to-leading order (NNLO) QCD + NLO electroweak accuracy combining the VHNNLO [57-59], VH@NNLO [60, 61] and HAWK v2.0 [62] generators as described in the documentation produced by the LHC Working Group on Higgs boson cross sections [63], and they are applied as a function of the vector boson transverse momentum (p T ). The production cross sections for the tt samples are rescaled to the NNLO with the next-to-next-to-leading-log (NNLL) prediction obtained with TOP++ v2.0 [64], while the W+jets and Z+jets samples are rescaled to the NLO cross sections using MADGRAPH5 aMC@NLO. The parton distribution functions (PDFs) used to produce the NLO samples are the NLO NNPDF3.0 set [65], while the LO NNPDF3.0 set is used for the LO samples. For parton showering and hadronization the POWHEG and MADGRAPH5 aMC@NLO samples are interfaced with PYTHIA 8.212 [66]. The PYTHIA8 parameters for the underlying event description correspond to the CUETP8M1 tune derived in Ref. [67] based on the work described in Ref. [68].During the 2016 data-taking period the LHC instantaneous luminosity reached approximately 1.5 × 10 34 cm −2 s −1 and the average number of pp interactions per bunch crossing was approximately 23. The simulated samples include these additional pp interactions, referred to as pileup interactions (or pileup), that overlap with the event of interest in the same bunch crossing. TriggersSeveral triggers are used to collect events with final-state objects consistent with the signal processes in the channels under consider...

A search for narrow vector resonances decaying into quark-antiquark pairs is presented. The analysis is based on data collected in proton-proton collisions at √ s = 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb −1 . The hypothetical resonance is produced with sufficiently high transverse momentum that its decay products are merged into a single jet with two-prong substructure. A signal would be identified as a peak over a smoothly falling background in the distribution of the invariant mass of the jet, using novel jet substructure techniques. No evidence for such a resonance is observed within the mass range of 50-300 GeV. Upper limits at 95% confidence level are set on the production cross section, and presented in a mass-coupling parameter space. The limits further constrain simplified models of dark matter production involving a mediator interacting between quarks and dark matter particles through a vector or axial-vector current. In the framework of these models, the results are the most sensitive to date, extending for the first time the search region to masses below 100 GeV. [28][29][30][31][32][33][34][35] Collaborations have mostly focused on the production of heavy particles. For resonance masses below 1 TeV, the sensitivity is limited by high trigger thresholds and by the large expected backgrounds, notably from SM events consisting of jets produced through the strong interaction, referred to here as QCD multijet events.These difficulties can be avoided by an approach focused on the events where at least one high transverse momentum (p T ) jet from initial-state radiation (ISR) is produced in association with a light resonance decaying into a qq pair. The ISR requirement provides enough energy in the event to satisfy the trigger, either by the ISR jet or by the resonance itself. The minimum p T of the resonance considered in this search is sufficiently high that the hadronization products of the daughter quarks merge and are reconstructed as a -1 - JHEP01(2018)097single, large-radius jet. The only previous search in this topology to place constraints on resonance masses below 300 GeV was by the CMS Collaboration, applying this technique to data collected at the LHC in 2015 [36].In the current paper, the results of a search for leptophobic vector resonances (Z ) decaying to quark-antiquark pairs in pp collisions at √ s = 13 TeV are reported, using data collected by the CMS detector in 2016, corresponding to an integrated luminosity of 35.9 fb −1 . The search is performed by looking for a narrow resonance peak in the continuous jet mass distribution. The analysis exploits a new substructure variable that is decorrelated from the jet mass and p T and preserves the shape of the jet mass distribution used in the search. The jet is required to have the two-prong substructure expected from the signal. The dominant background from SM QCD multijet production is estimated from a signal-depleted control region created by inverting the substructure requir...