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  1. Determination of the spin and parity of all-charm tetraquarks

    Hayrapetyan, Aram ; Makarenko, V. ; Tumasyan, A. ; ... - Nature (London)
    The traditional quark model accounts for the existence of baryons, such as protons and neutrons, which consist of three quarks, as well as mesons, composed of a quark–antiquark pair. Only recently has substantial evidence started to accumulate for exotic states composed of four or five quarks and antiquarks. The exact nature of their internal structure remains uncertain. Here we report the first measurement of quantum numbers of the recently discovered family of three all-charm tetraquarks, using data collected by the CMS experiment at the Large Hadron Collider from 2016 to 2018 . The angular analysis techniques developed for the discoverymore » and characterization of the Higgs boson have been applied to the new exotic states. Here we show that the quantum numbers for parity P and charge conjugation C symmetries are found to be +1. The spin J of these exotic states is determined to be consistent with 2ħ, while 0ħ and 1ħ are excluded at 95% and 99% confidence levels, respectively. The JPC = 2++ assignment implies particular configurations of constituent spins and orbital angular momenta, which constrain the possible internal structure of these tetraquarks.« less

  2. Search for pair production of heavy particles decaying to a top quark and a gluon in the lepton+jets final state in proton–proton collisions at $$\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V}$$

    Hayrapetyan, A. ; Tumasyan, A. ; Adam, W. ; ... - European Physical Journal. C, Particles and Fields (Online)
    A search is presented for the pair production of new heavy resonances, each decaying into a top quark (t) or antiquark and a gluon (g). The analysis uses data recorded with the CMS detector from proton–proton collisions at a center-of-mass energy of 13 TeV at the LHC, corresponding to an integrated luminosity of 138 fb-1. Events with one muon or electron, multiple jets, and missing transverse momentum are selected. After using a deep neural network to enrich the data sample with signal-like events, distributions in the scalar sum of the transverse momenta of all reconstructed objects are analyzed in themore » search for a signal. No significant deviations from the standard model prediction are found. Upper limits at 95% confidence level are set on the product of cross section and branching fraction squared for the pair production of excited top quarks in the t* → tg decay channel. The upper limits range from 120 to 0.8 fb for a t* with spin-1/2 and from 15 to 1.0 fb for a t* with spin-3/2. These correspond to mass exclusion limits up to 1050 and 1700 GeV for spin-1/2 and spin-3/2 t* particles, respectively. These are the most stringent limits to date on the existence of t* → tg resonances.« less

  3. Measurement of multidifferential cross sections for dijet production in proton–proton collisions at $$\sqrt{s}$$ = 13 TeV

    Hayrapetyan, A. ; Tumasyan, A. ; Adam, W. ; ... - European Physical Journal. C, Particles and Fields (Online)
    A measurement of the dijet production cross section is reported based on proton–proton collision data collected in 2016 at $$\sqrt{s}$$ = 13 TeV by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of up to 36.3 fb–1. Jets are reconstructed with the anti-$$k$$T algorithm for distance parameters of R = 0.4 and 0.8. Cross sections are measured double-differentially (2D) as a function of the largest absolute rapidity |y|max of the two jets with the highest transverse momenta $$p$$T and their invariant mass $$m$$1,2, and triple-differentially (3D) as a function of the rapidity separation $$y$$*, the totalmore » boost $$y$$b, and either $$m$$1,2 or the average $$p$$T of the two jets. The cross sections are unfolded to correct for detector effects and are compared with fixed-order calculations derived at next-to-next-to-leading order in perturbative quantum chromodynamics. The impact of the measurements on the parton distribution functions and the strong coupling constant at the mass of the Z boson is investigated, yielding a value of $$α$$S($$m$$Z) = 0.1179 ± 0.0019.« less

  4. Reconstruction of decays to merged photons using end-to-end deep learning with domain continuation in the CMS detector

    Tumasyan, A. ; Adam, W. ; Andrejkovic, J.  W. ; ... - Physical Review. D.
    A novel technique based on machine learning is introduced to reconstruct the decays of highly Lorentz-boosted particles. Using an end-to-end deep learning strategy, the technique bypasses existing rule-based particle reconstruction methods typically used in high energy physics analyses. It uses minimally processed detector data as input and directly outputs particle properties of interest. The new technique is demonstrated for the reconstruction of the invariant mass of particles decaying in the CMS detector. The decay of a hypothetical scalar particle A into two photons, A→γγ , is chosen as a benchmark decay. Lorentz boosts more » γ L =60–600 are considered, ranging from regimes where both photons are resolved to those where the photons are closely merged as one object. A training method using domain continuation is introduced, enabling the invariant mass reconstruction of unresolved photon pairs in a novel way. The new technique is validated using π0→γγ decays in LHC collision data.« less

  5. Azimuthal Correlations within Exclusive Dijets with Large Momentum Transfer in Photon-Lead Collisions

    Tumasyan, A. ; Adam, W. ; Bergauer, T. ; ... - Physical Review Letters
    The structure of nucleons is multidimensional and depends on the transverse momenta, spatial geometry, and polarization of the constituent partons. Such a structure can be studied using high-energy photons produced in ultraperipheral heavy-ion collisions. The first measurement of the azimuthal angular correlations of exclusively produced events with two jets in photon-lead interactions at large momentum transfer is presented, a process that is considered to be sensitive to the underlying nuclear gluon polarization. This study uses a data sample of ultraperipheral lead-lead collisions at s NN = 5.02 more » TeV , corresponding to an integrated luminosity of 0.38 nb - 1 , collected with the CMS experiment at the LHC. The measured second harmonic of the correlation between the sum and difference of the two jet transverse momentum vectors is found to be positive, and rising, as the dijet transverse momentum increases. A well-tuned model that has been successful at describing a wide range of proton scattering data from the HERA experiments fails to describe the observed correlations, suggesting the presence of gluon polarization effects.« less

  6. Search for Higgs Boson and Observation of $$Z$$ Boson through Their Decay into a Charm Quark-Antiquark Pair in Boosted Topologies in Proton-Proton Collisions at $$\sqrt{s}$$ = 13 TeV

    Tumasyan, A. ; Adam, W. ; Andrejkovic, J.  W. ; ... - Physical Review Letters
    A search for the standard model (SM) Higgs boson ($$H$$) produced with transverse momentum ($$p_T$$) greater than 450 GeV and decaying to a charm quark-antiquark ($$c\bar{c}$$) pair is presented. The search is performed using proton-proton collision data collected at $$\sqrt{s} = 13$$ TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 138 fb$$^{-1}$$. Boosted $$H \to c\overline{c}$$ decay products are reconstructed as a single large-radius jet and identified using a deep neural network charm tagging technique. The method is validated by measuring the $$Z \to c\bar{c}$$ decay process, which is observed in association with jetsmore » at high $$p_T$$ for the first time with a signal strength of $$1.00^{+0.17}_{-0.14}$$ (syst)$$\pm 0.08$$ (theo) $$\pm 0.06$$ (stat), defined as the ratio of the observed process rate to the SM expectation. The observed (expected) upper limit on $$\sigma (H){\cal B}(H \to c\overline{c})$$ is set at 47 (39) times the SM prediction at 95\%confidence level.« less

  7. Search for narrow resonances in the b -tagged dijet mass spectrum in proton-proton collisions at s = 13 TeV

    Tumasyan, A. ; Adam, W. ; Andrejkovic, J.  W. ; ... - Physical Review. D.
    A search is performed for narrow resonances decaying to final states of two jets, with at least one jet originating from a b quark, in proton-proton collisions at s =13 TeV . The data set corresponds to an integrated luminosity of 138 fb - 1 collected with the CMS detector at the LHC. Jets originating from energetic b hadrons are identified through a b -tagging algorithm that utilizes a deep neural network or the presence of a muon inside a jet. The invariant mass spectrum of jet pairsmore » is well described by a smooth parametrization and no evidence for the production of new particles is observed. Upper limits on the production cross section are set for excited b quarks and other resonances decaying to dijet final states containing b quarks. These limits exclude at 95% confidence level models of Z ' bosons with masses from 1.8 TeV to 2.4 TeV and of excited b quarks with masses from 1.8 TeV to 4.0 TeV. This is the most stringent exclusion of excited b quarks to date.« less

  8. Measurements of Higgs boson production in the decay channel with a pair of τ leptons in proton–proton collisions at $$\sqrt{s}=13$$ TeV

    Tumasyan, A. ; Adam, W. ; Andrejkovic, J. W. ; ... - European Physical Journal. C, Particles and Fields (Online)
    Measurements of Higgs boson production, where the Higgs boson decays into a pair of τ leptons, are presented, using a sample of proton-proton collisions collected with the CMS experiment at a center-of-mass energy of , corresponding to an integrated luminosity of 138 fb–1. Three analyses are presented. Two are targeting Higgs boson production via gluon fusion and vector boson fusion: a neural network based analysis and an analysis based on an event categorization optimized on the ratio of signal over background events. These are complemented by an analysis targeting vector boson associated Higgs boson production. Results are presented in themore » form of signal strengths relative to the standard model predictions and products of cross sections and branching fraction to τ leptons, in up to 16 different kinematic regions. For the simultaneous measurements of the neural network based analysis and the analysis targeting vector boson associated Higgs boson production signal strengths are found to be 0.82 ± 0.11 for inclusive Higgs boson production, 0.67 ± 0.19 (0.81 ± 0.17) for the production mainly via gluon fusion (vector boson fusion), and 1.79 ± 0.45 for vector boson associated Higgs boson production.« less

  9. Search for Higgs Boson Pair Production in the Four b Quark Final State in Proton-Proton Collisions at s = 13     TeV

    Tumasyan, A. ; Adam, W. ; Andrejkovic, J. W. ; ... - Physical Review Letters

  10. Search for resonances decaying to three W bosons in the hadronic final state in proton-proton collisions at s = 13     TeV

    Tumasyan, A. ; Adam, W. ; Andrejkovic, J. W. ; ... - Physical Review. D.
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