Abstract The double differential cross sections of the Drell–Yan lepton pair ( $$\ell ^+\ell ^-$$ ℓ + ℓ - , dielectron or dimuon) production are measured as functions of the invariant mass $$m_{\ell ...\ell }$$ m ℓ ℓ , transverse momentum $$p_{\textrm{T}} (\ell \ell )$$ p T ( ℓ ℓ ) , and $$\varphi ^{*}_{\eta }$$ φ η ∗ . The $$\varphi ^{*}_{\eta }$$ φ η ∗ observable, derived from angular measurements of the leptons and highly correlated with $$p_{\textrm{T}} (\ell \ell )$$ p T ( ℓ ℓ ) , is used to probe the low- $$p_{\textrm{T}} (\ell \ell )$$ p T ( ℓ ℓ ) region in a complementary way. Dilepton masses up to 1 $$\,\text {Te\hspace{-.08em}V}$$ Te V are investigated. Additionally, a measurement is performed requiring at least one jet in the final state. To benefit from partial cancellation of the systematic uncertainty, the ratios of the differential cross sections for various $$m_{\ell \ell }$$ m ℓ ℓ ranges to those in the Z mass peak interval are presented. The collected data correspond to an integrated luminosity of 36.3 $$\,\text {fb}^{-1}$$ fb - 1 of proton–proton collisions recorded with the CMS detector at the LHC at a centre-of-mass energy of 13 $$\,\text {Te\hspace{-.08em}V}$$ Te V . Measurements are compared with predictions based on perturbative quantum chromodynamics, including soft-gluon resummation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract A search for pair production of the supersymmetric partner of the top quark, the top squark, in proton-proton collisions at s $$ \sqrt{s} $$ = 13 TeV is presented in final states containing ...at least one hadronically decaying tau lepton and large missing transverse momentum. This final state is highly sensitive to scenarios of supersymmetry in which the decay of the top squark to tau leptons is enhanced. The search uses a data sample corresponding to an integrated luminosity of 138 fb −1, which was recorded with the CMS detector during 2016–2018. No significant excess is observed with respect to the standard model predictions. Exclusion limits at 95% confidence level on the masses of the top squark and the lightest neutralino are presented under the assumptions of simplified models. The results probe top squark masses up to 1150 GeV for a nearly massless neutralino. This search covers a relatively less explored parameter space in the context of supersymmetry, and the exclusion limit is the most stringent to date for the model considered here.
Abstract Measurements of Higgs boson production, where the Higgs boson decays into a pair of $$\uptau $$ 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 $$\,\text {fb}^{-1}$$ 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 the form of signal strengths relative to the standard model predictions and products of cross sections and branching fraction to $$\uptau $$ 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 $$0.82\pm 0.11$$ 0.82 ± 0.11 for inclusive Higgs boson production, $$0.67\pm 0.19$$ 0.67 ± 0.19 ( $$0.81\pm 0.17$$ 0.81 ± 0.17 ) for the production mainly via gluon fusion (vector boson fusion), and $$1.79\pm 0.45$$ 1.79 ± 0.45 for vector boson associated Higgs boson production.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract A search for long-lived particles decaying in the outer regions of the CMS silicon tracker or in the calorimeters is presented. The search is based on a data sample of proton-proton ...collisions at s $$ \sqrt{s} $$ = 13 TeV recorded with the CMS detector at the LHC in 2016–2018, corresponding to an integrated luminosity of 138 fb −1. A novel technique, using nearly trackless and out-of-time jet information combined in a deep neural network discriminator, is employed to identify decays of long-lived particles. The results are interpreted in a simplified model of chargino-neutralino production, where the neutralino is the next-to-lightest supersymmetric particle, is long-lived, and decays to a gravitino and either a Higgs or Z boson. This search is most sensitive to neutralino proper decay lengths of approximately 0.5 m, for which masses up to 1.18 TeV are excluded at 95% confidence level. The current search is the best result to date in the mass range from the kinematic limit imposed by the Higgs boson mass up to 1.8 TeV.
Abstract A measurement of the jet mass distribution in hadronic decays of Lorentz-boosted top quarks is presented. The measurement is performed in the lepton + jets channel of top quark pair ...production ( $$\hbox {t}\overline{\hbox {t}}$$ t t ¯ ) events, where the lepton is an electron or muon. The products of the hadronic top quark decay are reconstructed using a single large-radius jet with transverse momentum greater than 400 $$\,\text {Ge}\hspace{-.08em}\text {V}$$ Ge V . The data were collected with the CMS detector at the LHC in proton-proton collisions and correspond to an integrated luminosity of 138 $$\,\text {fb}^{-1}$$ fb - 1 . The differential $$\hbox {t}\overline{\hbox {t}}$$ t t ¯ production cross section as a function of the jet mass is unfolded to the particle level and is used to extract the top quark mass. The jet mass scale is calibrated using the hadronic W boson decay within the large-radius jet. The uncertainties in the modelling of the final state radiation are reduced by studying angular correlations in the jet substructure. These developments lead to a significant increase in precision, and a top quark mass of $$173.06 \pm 0.84\,\text {Ge}\hspace{-.08em}\text {V} $$ 173.06 ± 0.84 Ge V .
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract The path-length dependent parton energy loss within the dense partonic medium created in lead-lead collisions at a nucleon-nucleon center-of-mass energy of s NN $$ \sqrt{s_{\textrm{NN}}} $$ ...= 5.02 TeV is studied by determining the azimuthal anisotropies for dijets with high transverse momentum. The data were collected by the CMS experiment in 2018 and correspond to an integrated luminosity of 1.69 nb −1. For events containing back-to-back jets, correlations in relative azimuthal angle and pseudorapidity (η) between jets and hadrons, and between two hadrons, are constructed. The anisotropies are expressed as the Fourier expansion coefficients v n , n = 2–4 of these azimuthal distributions. The dijet v n values are extracted from long-range (1.5 < |∆η| < 2.5) components of these correlations, which suppresses the background contributions from jet fragmentation processes. Positive dijet v 2 values are observed which increase from central to more peripheral events, while the v 3 and v 4 values are consistent with zero within experimental uncertainties.
Abstract A search is reported for pairs of light Higgs bosons ( $${\textrm{H}} _1$$ H 1 ) produced in supersymmetric cascade decays in final states with small missing transverse momentum. A data set ...of LHC $$\hbox {pp}$$ pp collisions collected with the CMS detector at $$\sqrt{s}=13\,\text {TeV} $$ s = 13 TeV and corresponding to an integrated luminosity of 138 $$\,\text {fb}^{-1}$$ fb - 1 is used. The search targets events where both $${\textrm{H}} _1$$ H 1 bosons decay into pairs that are reconstructed as large-radius jets using substructure techniques. No evidence is found for an excess of events beyond the background expectations of the standard model (SM). Results from the search are interpreted in the next-to-minimal supersymmetric extension of the SM, where a “singlino” of small mass leads to squark and gluino cascade decays that can predominantly end in a highly Lorentz-boosted singlet-like $${\textrm{H}} _1$$ H 1 and a singlino-like neutralino of small transverse momentum. Upper limits are set on the product of the squark or gluino pair production cross section and the square of the branching fraction of the $${\textrm{H}} _1$$ H 1 in a benchmark model containing almost mass-degenerate gluinos and light-flavour squarks. Under the assumption of an SM-like branching fraction, $${\textrm{H}} _1$$ H 1 bosons with masses in the range 40–120 $$\,\text {GeV}$$ GeV arising from the decays of squarks or gluinos with a mass of 1200–2500 $$\,\text {GeV}$$ GeV are excluded at 95% confidence level.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract The results of a search for Higgs boson pair (HH) production in the WW*WW*, WW* ττ, and ττττ decay modes are presented. The search uses 138 fb −1 of proton-proton collision data recorded by ...the CMS experiment at the LHC at a center-of-mass energy of 13 TeV from 2016 to 2018. Analyzed events contain two, three, or four reconstructed leptons, including electrons, muons, and hadronically decaying tau leptons. No evidence for a signal is found in the data. Upper limits are set on the cross section for nonresonant HH production, as well as resonant production in which a new heavy particle decays to a pair of Higgs bosons. For nonresonant production, the observed (expected) upper limit on the cross section at 95% confidence level (CL) is 21.3 (19.4) times the standard model (SM) prediction. The observed (expected) ratio of the trilinear Higgs boson self-coupling to its value in the SM is constrained to be within the interval −6.9 to 11.1 (−6.9 to 11.7) at 95% CL, and limits are set on a variety of new-physics models using an effective field theory approach. The observed (expected) limits on the cross section for resonant HH production range from 0.18 to 0.90 (0.08 to 1.06) pb at 95% CL for new heavy-particle masses in the range 250–1000 GeV.
Abstract A search is reported for heavy resonances and quantum black holes decaying into eμ, eτ, and μτ final states in proton-proton collision data recorded by the CMS experiment at the CERN LHC ...during 2016–2018 at s $$ \sqrt{s} $$ = 13 TeV, corresponding to an integrated luminosity of 138 fb −1. The eμ, eτ, and μτ invariant mass spectra are reconstructed, and no evidence is found for physics beyond the standard model. Upper limits are set at 95% confidence level on the product of the cross section and branching fraction for lepton flavor violating signals. Three benchmark signals are studied: resonant τ sneutrino production in R parity violating supersymmetric models, heavy Z′ gauge bosons with lepton flavor violating decays, and nonresonant quantum black hole production in models with extra spatial dimensions. Resonant τ sneutrinos are excluded for masses up to 4.2TeV in the eμ channel, 3.7TeV in the eτ channel, and 3.6TeV in the μτ channel. A Z′ boson with lepton flavor violating couplings is excluded up to a mass of 5.0TeV in the eμ channel, up to 4.3Te V in the eτ channel, and up to 4.1TeV in the μτ channel. Quantum black holes in the benchmark model are excluded up to the threshold mass of 5.6TeV in the eμ channel, 5.2TeV in the eτ channel, and 5.0TeV in the μτ channel. In addition, model-independent limits are extracted to allow comparisons with other models for the same final states and similar event selection requirements. The results of these searches provide the most stringent limits available from collider experiments for heavy particles that undergo lepton flavor violating decays.
Abstract Results are presented from a search for the Higgs boson decay H → Zγ, where Z → ℓ + ℓ − with ℓ = e or μ. The search is performed using a sample of proton-proton (pp) collision data at a ...center-of-mass energy of 13 TeV, recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 138 fb −1. Events are assigned to mutually exclusive categories, which exploit differences in both event topology and kinematics of distinct Higgs production mechanisms to enhance signal sensitivity. The signal strength μ, defined as the product of the cross section and the branching fraction σ pp → H B H → Zγ $$ \left\sigma \left(\textrm{pp}\to \textrm{H}\right)\mathcal{B}\left(\textrm{H}\to \textrm{Z}\upgamma \right)\right $$ relative to the standard model prediction, is extracted from a simultaneous fit to the ℓ + ℓ − γ invariant mass distributions in all categories and is measured to be μ = 2.4 ± 0.9 for a Higgs boson mass of 125.38 GeV. The statistical significance of the observed excess of events is 2.7 standard deviations. This measurement corresponds to σ pp → H B H → Zγ = 0.21 ± 0.08 $$ \left\sigma \left(\textrm{pp}\to \textrm{H}\right)\mathcal{B}\left(\textrm{H}\to \textrm{Z}\upgamma \right)\right=0.21\pm 0.08 $$ pb. The observed (expected) upper limit at 95% confidence level on μ is 4.1 (1.8), where the expected limit is calculated under the background-only hypothesis. The ratio of branching fractions B H → Zγ / B H → γγ $$ \mathcal{B}\left(\textrm{H}\to \textrm{Z}\upgamma \right)/\mathcal{B}\left(\textrm{H}\to \upgamma \upgamma \right) $$ is measured to be 1.5 − 0.6 + 0.7 $$ {1.5}_{-0.6}^{+0.7} $$ , which agrees with the standard model prediction of 0.69 ± 0.04 at the 1.5 standard deviation level.
