The Scientific and Technical Research Council of Turkey, and Turkish Atomic Energy Authorit

A search is presented for physics beyond the standard model (SM) using electron or muon pairs with high invariant mass. A data set of proton-proton collisions collected by the CMS experiment at the LHC at $$ \sqrt{s} $$ s = 13 TeV from 2016 to 2018 corresponding to a total integrated luminosity of up to 140 fb−1 is analyzed. No significant deviation is observed with respect to the SM background expectations. Upper limits are presented on the ratio of the product of the production cross section and the branching fraction to dileptons of a new narrow resonance to that of the Z boson. These provide the most stringent lower limits to date on the masses for various spin-1 particles, spin-2 gravitons in the Randall-Sundrum model, as well as spin-1 mediators between the SM and dark matter particles. Lower limits on the ultraviolet cutoff parameter are set both for four-fermion contact interactions and for the Arkani-Hamed, Dimopoulos, and Dvali model with large extra dimensions. Lepton flavor universality is tested at the TeV scale for the first time by comparing the dimuon and dielectron mass spectra. No significant deviation from the SM expectation of unity is observed.

A search for new physics using events containing an imbalance in transverse momentum and one or more energetic jets arising from initial-state radiation or the hadronic decay of W or Z bosons is presented. A data sample of proton-proton collisions at ffiffi ffi s p ¼ 13 TeV, collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 35.9 fb −1 , is used. The observed data are found to be in agreement with the expectation from standard model processes. The results are interpreted as limits on the dark matter production cross section in simplified models with vector, axial-vector, scalar, and pseudoscalar mediators. Interpretations in the context of fermion portal and nonthermal dark matter models are also provided. In addition, the results are interpreted in terms of invisible decays of the Higgs boson and set stringent limits on the fundamental Planck scale in the Arkani-Hamed, Dimopoulos, and Dvali model with large extra spatial dimensions.

The standard model (SM) production of four top quarks (tt tt) in proton-proton collisions is studied by the CMS Collaboration. The data sample, collected during the 2016-2018 data taking of the LHC, corresponds to an integrated luminosity of 137 fb −1 at a center-of-mass energy of 13 TeV. The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the tt tt signal are respectively 2.6 and 2.7 standard deviations, and the tt tt cross section is measured to be 12.6 +5.8 −5.2 fb. The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson, y t , yielding a limit of |y t /y SM t | < 1.7 at 95% confidence level, where y SM t is the SM value of y t. They are also used to constrain the oblique parameter of the Higgs boson in an effective field theory framework,Ĥ < 0.12. Limits are set on the production of a heavy scalar or pseudoscalar boson in Type-II two-Higgs-doublet and simplified dark matter models, with exclusion limits reaching 350-470 GeV and 350-550 GeV for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.

Abstract:In searches for new physics in the energy regime of the LHC, it is becoming increasingly important to distinguish single-jet objects that originate from the merging of the decay products of W bosons produced with high transverse momenta from jets initiated by single partons. Algorithms are defined to identify such W jets for different signals of interest, using techniques that are also applicable to other decays of bosons to hadrons that result in a single jet, such as those from highly boosted Z and Higgs bosons. The efficiency for tagging W jets is measured in data collected with the CMS detector at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb −1 . The performance of W tagging in data is compared with predictions from several Monte Carlo simulators. The CMS collaboration 29 IntroductionThe LHC at CERN probes a new energy regime in particle physics, where searches for physics beyond the standard model (SM) at high mass scale often involve objects with large transverse momenta (p T ). In final states that contain the W ± and Z gauge bosons or Higgs bosons (H), it is possible to achieve a high selection efficiency through the use of hadronic decay channels. At sufficiently large boost above order of p T > 200 GeV, the final state hadrons from the W→ qq decay merge into a single jet, and the traditional analysis techniques relying on resolved jets are no longer applicable. However, in such cases the analysis of jet substructure can be used to identify those jets arising from decays of W, Z or H bosons. Because the values of the mass of the W and Z bosons are rather close to each other, we do not distinguish the two, and refer to such jets collectively as V jets, while the Higgs boson mass is significantly higher and can be distinguished. The focus -1 - JHEP12(2014)017of this paper is solely on the identification of W jets, however, we note that many of the procedures described are equally applicable for handling highly boosted Z and H bosons. Measurements of jet substructure observables related to identification of W bosons have been previously reported by CMS [1,2] and ATLAS [3,4]. Several searches at CMS have employed jet substructure techniques for identifying ("tagging") W jets and Z jets. These include searches in all-jet tt final states [5,6], single and pair produced V bosons in inclusive dijet final states [7,8], and searches in the VV final states, where one of the vector bosons decays leptonically [9,10]. In these searches, a variety of different observables have been used to identify the V jets. This paper aims to compare and measure the performance in 8 TeV pp collisions of various jet substructure techniques that can be used to distinguish V jets from more ordinary quark-and gluon-initiated jets, which we refer to as QCD jets.This paper is organized as follows. The CMS detector is described in section 2. The procedures chosen for the reconstruction of events are described in section 3. The data and simulated events used in our studies as well as the e...