Search for high mass dijet resonances with a new background prediction method in proton-proton collisions at √ s = 13 TeV The CMS collaboration

A search is presented for long-lived charged particles that decay within the CMS detector and produce the signature of a disappearing track. A disappearing track is an isolated track with missing hits in the outer layers of the silicon tracker, little or no energy in associated calorimeter deposits, and no associated hits in the muon detectors. This search uses data collected with the CMS detector in 2015 and 2016 from protonproton collisions at a center-of-mass energy of 13 TeV at the LHC, corresponding to an integrated luminosity of 38.4 fb −1 . The results of the search are interpreted in the context of the anomaly-mediated supersymmetry breaking model. The data are consistent with the background-only hypothesis. Limits are set on the product of the cross section for direct production of charginos and their branching fraction to a neutralino and a pion, as a function of the chargino mass and lifetime. At 95% confidence level, charginos with masses below 715 (695) GeV are excluded for a lifetime of 3 (7) ns, as are charginos with lifetimes from 0.5 to 60 ns for a mass of 505 GeV. These are the most stringent limits using a disappearing track signature on this signal model for chargino lifetimes above ≈0.7 ns.

A search for supersymmetry is presented based on proton-proton collision events containing identified hadronically decaying top quarks, no leptons, and an imbalance p miss T in transverse momentum. The data were collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 35.9 fb −1 . Search regions are defined in terms of the multiplicity of bottom quark jet and top quark candidates, the p miss T , the scalar sum of jet transverse momenta, and the m T2 mass variable. No statistically significant excess of events is observed relative to the expectation from the standard model. Lower limits on the masses of supersymmetric particles are determined at 95% confidence level in the context of simplified models with top quark production. For a model with direct top squark pair production followed by the decay of each top squark to a top quark and a neutralino, top squark masses up to 1020 GeV and neutralino masses up to 430 GeV are excluded. For a model with pair production of gluinos followed by the decay of each gluino to a top quark-antiquark pair and a neutralino, gluino masses up to 2040 GeV and neutralino masses up to 1150 GeV are excluded. These limits extend previous results. Published in Physical Review D asThe CMS detector is built around a superconducting solenoid of 6 m internal diameter, which provides 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 Event reconstructionEvents are reconstructed using the particle-flow (PF) algorithm [30], which reconstructs charged hadrons, neutral hadrons, photons, electrons, and muons using information from all subdetectors. Electron and muon candidates are subjected to additional requirements [31,32] to im- B The CMS Collaboration

A search for a heavy resonance decaying into a top quark and antiquark (tt) pair is performed using proton-proton collisions at √ s = 13 TeV. The search uses the data set collected with the CMS detector in 2016, which corresponds to an integrated luminosity of 35.9 fb −1 . The analysis considers three exclusive final states and uses reconstruction techniques that are optimized for top quarks with high Lorentz boosts, which requires the use of nonisolated leptons and jet substructure techniques. No significant excess of events relative to the expected yield from standard model processes is observed. Upper limits on the production cross section of heavy resonances decaying to a tt pair are calculated. Limits are derived for a leptophobic topcolor Z resonance with widths of 1, 10, and 30%, relative to the mass of the resonance, and exclude masses up to 3.80, 5.25, and 6.65 TeV, respectively. Kaluza-Klein excitations of the gluon in the Randall-Sundrum model are excluded up to 4.55 TeV. To date, these are the most stringent limits on tt resonances. This paper is organized the following way. Section 2 provides a description of the CMS detector. The reconstruction and identification of electrons, muons, and jets are described in Section 3. Section 3 also gives an overview of the t tagging algorithms used. The data sets and triggering techniques are described in Section 4. The simulated Monte Carlo (MC) samples used in the analysis are discussed in Section 5. Section 6 describes the event selection for the three different channels. Section 7 describes the evaluation of the SM background processes. Systematic uncertainties affecting the signal and background shapes and normalization are discussed in Section 8. The statistical analysis and the results are given in Sections 9 and 10, respectively, and a summary is presented in Section 11. The CMS detectorThe central feature of the CMS detector 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. In addition to the barrel and endcap detectors, CMS has extensive forward calorimetry. Muons are detected by four layers of gas-ionization detectors embedded in the steel flux-return yoke of the magnet. The inner tracker measures charged-particle trajectories within the pseudorapidity range |η| < 2.5, and provides an impact parameter resolution of approximately 15 µm. A two-stage trigger system [34] selects pp collision events of interest for use in physics analyses. 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. [35]. Event reconstructionThe CMS event reconstruction uses a particle-flow (PF) technique that aggregates input from all subdetectors for event reconstruction [36]. Typical examples of P...

Search for an exotic decay of the Higgs boson to a pair of light pseudoscalars in the final state of two muons and two τ leptons in proton-proton collisions at √ s = 13 TeVThe CMS Collaboration * Abstract A search for exotic Higgs boson decays to light pseudoscalars in the final state of two muons and two τ leptons is performed using proton-proton collision data recorded by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV in 2016, corresponding to an integrated luminosity of 35.9 fb −1 . Masses of the pseudoscalar boson between 15.0 and 62.5 GeV are probed, and no significant excess of data is observed above the prediction of the standard model. Upper limits are set on the branching fraction of the Higgs boson to two light pseudoscalar bosons in different types of two-Higgs-doublet models extended with a complex scalar singlet.Signal processes, for both h → aa → 2µ2τ and h → aa → 4τ, are generated using the MADGRAPH5 aMC@NLO 2.2.2 generator [23] with its implementation of the 2HDM and the NMSSM, in gluon fusion and vector boson fusion production. They are simulated at leading order (LO) in perturbative quantum chromodynamics (QCD) with the MLM jet matching and merging scheme [24]. The generator is interfaced with PYTHIA 8.212[25] to model the parton showering and fragmentation as well as the decay of the τ leptons. The CUETP8M1 tune [26] is chosen for the PYTHIA parameters controlling the description of the underlying event. The ZZ background from quark-antiquark annihilation is generated at next-to-LO (NLO) in perturbative QCD with POWHEG v2.0 [27][28][29], while the gg → ZZ process is generated at LO with MCFM 7.0 [30]. The set of parton distribution functions is NLO NNPDF3.0 for NLO samples, and LO NNPDF3.0 for LO samples [31]. The fully differential cross section for the qq → ZZ process has been computed at next-to-NLO (NNLO) [32], and the NNLO/NLO K-factor is applied to the POWHEG sample as a function of the invariant mass of the Z boson pair. Rare processes, such as triboson, ttZ, or SM Higgs boson production, have a negligible contribution to the signal region because they typically have a larger invariant mass of the four leptons in the final state.Simulated samples include additional pp interactions per bunch crossing (pileup), and are reweighted so as to match the pileup distribution observed in data. Generated events are processed through a simulation of the CMS detector based on GEANT4 [33].The reconstruction of events relies on the particle-flow (PF) algorithm [34], which combines the information from the CMS subdetectors to identify and reconstruct the particles emerging from pp collisions: charged and neutral hadrons, photons, muons, and electrons. Combinations of these PF objects are used to reconstruct higher-level objects such as jets or τ h candidates. The reconstructed vertex with the largest value of summed physics-object p 2 T is taken to be the primary pp interaction vertex, where p T denotes the transverse momentum. The physics