Engineering topics

Yonamine, Ryo

Publications and source records attributed to Yonamine, Ryo.

143 records · Page 8

DOE OSTI2017

Measurement of the production cross section of a W boson in association with two b jets in pp collisions at $\sqrt{s} = 8{\,\mathrm{{TeV}}} $

The production cross section of a W boson in association with two b jets is measured using a sample of proton–proton collisions at $\sqrt{s} = 8{\,\mathrm{{TeV}}} $ collected by the CMS experiment at the CERN LHC. The data sample corresponds to an integrated luminosity of 19.8 $\,\text {fb}^\text {-1}$ . The W bosons are reconstructed via their leptonic decays, $\mathrm {W}\rightarrow \ell \nu $ , where $\ell =\mu $ or $\mathrm {e}$ . The fiducial region studied contains exactly one lepton with transverse momentum $p_{\mathrm {T}} ^{\ell }>30\,\mathrm{{GeV}} $ and pseudorapidity $|\eta ^{\ell } |<2.1$ , with exactly two b jets with $p_{\mathrm {T}} >25\,\mathrm{{GeV}} $ and $|\eta |<2.4$ and no other jets with $p_{\mathrm {T}} >25\,\mathrm{{GeV}} $ and $|\eta |<4.7$ . The cross section is measured to be $\sigma ( {{\mathrm {p}\mathrm {p}}} \rightarrow {\mathrm {W}} (\ell \nu )$ + ${\mathrm{{b}}\mathrm{{\overline{b}}}})= 0.64 \pm 0.03{\,\mathrm{{(stat)}}} \pm 0.10{\,\mathrm{{(syst)}}} \pm 0.06{\,\mathrm{{(theo)}}} \pm 0.02{\,\mathrm{{(lumi)}}}\,{\text {pb}}$ , in agreement with standard model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Search for heavy resonances decaying to tau lepton pairs in proton-proton collisions at $ \sqrt{s}=13 $ TeV

A search for heavy resonances that decay to tau lepton pairs is performed using proton-proton collisions at $\sqrt{s} = 13$ TeV. The data were collected with the CMS detector at the CERN LHC and correspond to an integrated luminosity of 2.2 inverse femtobarns. The observations are in agreement with standard model predictions. An upper limit at 95% confidence level on the product of the production cross section and branching fraction into tau lepton pairs is calculated as a function of the resonance mass. For the sequential standard model, the presence of Z' bosons decaying into tau lepton pairs is excluded for Z' masses below 2.1 TeV, extending previous limits for this final state. For the topcolor-assisted technicolor model, which predicts Z bosons that preferentially couple to third-generation fermions, Z' masses below 1.7 TeV are excluded, representing the most stringent limit to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Search for anomalous Wtb couplings and flavour-changing neutral currents in t-channel single top quark production in pp collisions at $\sqrt{s} =$ 7 and 8 TeV

Single top quark events produced in the t channel are used to set limits on anomalous Wtb couplings and to search for top quark flavour-changing neutral current (FCNC) interactions. The data taken with the CMS detector at the LHC in proton-proton collisions at $ \sqrt{s}=7 $ and 8 TeV correspond to integrated luminosities of 5.0 and 19.7 fb$^{−1}$, respectively. The analysis is performed using events with one muon and two or three jets. A Bayesian neural network technique is used to discriminate between the signal and backgrounds, which are observed to be consistent with the standard model prediction. The 95% confidence level (CL) exclusion limits on anomalous right-handed vector, and left- and right-handed tensor Wtb couplings are measured to be |f$_{V}^{R}$ | < 0.16, |f$_{T}^{L}$ | < 0.057, and − 0.049 < f$_{T}^{R}$ < 0.048, respectively. For the FCNC couplings κ$_{tug}$ and κ$_{tcg}$, the 95% CL upper limits on coupling strengths are |κ$_{tug}$|/Λ < 4.1 × 10$^{− 3}$ TeV$^{−1}$ and |κ$_{tcg}$|/Λ < 1.8 × 10$^{− 2}$ TeV$^{−1}$, where Λ is the scale for new physics, and correspond to upper limits on the branching fractions of 2.0 × 10$^{−5}$ and 4.1 × 10$^{−4}$ for the decays t → ug and t → cg, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

The CMS trigger system

This paper describes the CMS trigger system and its performance during Run 1 of the LHC. The trigger system consists of two levels designed to select events of potential physics interest from a GHz (MHz) interaction rate of proton-proton (heavy ion) collisions. The first level of the trigger is implemented in hardware, and selects events containing detector signals consistent with an electron, photon, muon, τ lepton, jet, or missing transverse energy. A programmable menu of up to 128 object-based algorithms is used to select events for subsequent processing. The trigger thresholds are adjusted to the LHC instantaneous luminosity during data taking in order to restrict the output rate to 100 kHz, the upper limit imposed by the CMS readout electronics. The second level, implemented in software, further refines the purity of the output stream, selecting an average rate of 400 Hz for offline event storage. The objectives, strategy and performance of the trigger system during the LHC Run 1 are described.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2017

Search for high-mass Z$\gamma$ resonances in $\mathrm{ e }^{+}\mathrm{ e }^{-}\gamma $ and $ \mu^{+}\mu^{-}\gamma$ final states in proton-proton collisions at $\sqrt{s} =$ 8 and 13 TeV

This paper describes the search for a high-mass narrow-width scalar particle decaying into a Z boson and a photon. The analysis is performed using proton-proton collision data recorded with the CMS detector at the LHC at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 2.7 fb$^{−1}$, respectively. The Z bosons are reconstructed from opposite-sign electron or muon pairs. No statistically significant deviation from the standard model predictions has been found in the 200-2000 GeV mass range. Upper limits at 95% confidence level have been derived on the product of the scalar particle production cross section and the branching fraction of the Z decaying into electrons or muons, which range from 280 to 20 fb for resonance masses between 200 and 2000 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Search for Dark Matter and Supersymmetry with a Compressed Mass Spectrum in the Vector Boson Fusion Topology in Proton-Proton Collisions at $\sqrt{s} =$ 8 TeV

A first search for pair production of dark matter candidates through vector boson fusion in proton-proton collisions at s=8 TeV is performed with the CMS detector. The vector boson fusion topology enhances missing transverse momentum, providing a way to probe supersymmetry, even in the case of a compressed mass spectrum. The data sample corresponds to an integrated luminosity of 18.5 fb−1, recorded by the CMS experiment. The observed dijet mass spectrum is consistent with the standard model expectation. In an effective field theory, dark matter masses are explored as a function of contact interaction strength. The most stringent limit on bottom squark production with mass below 315 GeV is also reported, assuming a 5 GeV mass difference with respect to the lightest neutralino.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Measurement of the mass of the top quark in decays with a $J/\psi$ meson in pp collisions at 8 TeV

A first measurement of the top quark mass in the decay channel t → (W → ℓν) (b → J/ψ + X → μ$^{+}$ μ$^{−}$ + X) is presented. The analysis uses events selected from the proton-proton collisions recorded by the CMS detector at the LHC at a center-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of 19.7 fb$^{−1}$, with 666 $ \mathrm{t}\overline{\mathrm{t}} $ and single top quark candidate events containing a reconstructed J/ψ candidate decaying into an oppositely-charged muon pair. The mass of the (J/ψ + ℓ) system, where ℓ is an electron or a muon from W boson decay, is used to extract a top quark mass of 173.5 ± 3.0 (stat) ± 0.9 (syst) GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Search for dark matter in proton-proton collisions at 8 TeV with missing transverse momentum and vector boson tagged jets

A search is presented for an excess of events with large missing transverse momentum in association with at least one highly energetic jet, in a data sample of proton-proton collisions at a centre-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of 19.7 fb$^{−1}$ collected by the CMS experiment at the LHC. The results are interpreted using a set of simplified models for the production of dark matter via a scalar, pseudoscalar, vector, or axial vector mediator. Additional sensitivity is achieved by tagging events consistent with the jets originating from a hadronically decaying vector boson. This search uses jet substructure techniques to identify hadronically decaying vector bosons in both Lorentz-boosted and resolved scenarios. This analysis yields improvements of 80% in terms of excluded signal cross sections with respect to the previous CMS analysis using the same data set. No significant excess with respect to the standard model expectation is observed and limits are placed on the parameter space of the simplified models. Mediator masses between 80 and 400 GeV in the scalar and pseudoscalar models, and up to 1.5 TeV in the vector and axial vector models, are excluded.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Search for lepton flavour violating decays of the Higgs boson to $e \tau$ and $e \mu$ in proton–proton collisions at $\sqrt s=$ 8 TeV

A direct search for lepton flavour violating decays of the Higgs boson (H) in the H→eτ and H→eμ channels is described. The data sample used in the search was collected in proton–proton collisions at s=8 TeV with the CMS detector at the LHC and corresponds to an integrated luminosity of 19.7 fb −1 . No evidence is found for lepton flavour violating decays in either final state. Upper limits on the branching fractions, B(H→eτ)<0.69% and B(H→eμ)<0.035% , are set at the 95% confidence level. The constraint set on B(H→eτ) is an order of magnitude more stringent than the existing indirect limits. The limits are used to constrain the corresponding flavour violating Yukawa couplings, absent in the standard model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Search for new physics in final states with two opposite-sign, same-flavor leptons, jets, and missing transverse momentum in pp collisions at sqrt(s) = 13 TeV

A search is presented for physics beyond the standard model in final states with two opposite-sign, same-flavor leptons, jets, and missing transverse momentum. The data sample corresponds to an integrated luminosity of 2.3 fb$^{−1}$ of proton-proton collisions at $ \sqrt{s}=13 $ TeV collected with the CMS detector at the LHC in 2015. The analysis uses the invariant mass of the lepton pair, searching for a kinematic edge or a resonant-like excess compatible with the Z boson mass. Both search modes use several event categories in order to increase the sensitivity to new physics. These categories are based on the rapidity of the leptons, the multiplicity of jets and b jets, the scalar sum of jet transverse momenta, and missing transverse momentum. The observations in all signal regions are consistent with the expectations from the standard model, and the results are interpreted in the context of simplified models of supersymmetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Measurement of electroweak production of a W boson and two forward jets in proton-proton collisions at $ \sqrt{s}=8 $ TeV

A measurement is presented of the cross section for the electroweak production of a W boson in association with two jets in proton-proton collisions at a center-of-mass energy of 8 TeV. The data set was collected with the CMS detector and corresponds to an integrated luminosity of 19.3 fb$^{−1}$. The measured fiducial cross section for W bosons decaying to electrons or muons and for p$_{T}^{j1}$ > 60 GeV, p$_{T}^{j2}$ > 50 GeV, |η$^{j}$| < 4.7, and m$_{jj}$ > 1000 GeV is 0.42 ± 0.04 (stat) ± 0.09 (syst) ± 0.01 (lumi) pb. This result is consistent with the standard model leading-order prediction of 0.50 ± 0.02 (scale) ± 0.02 (PDF) pb obtained with MadGraph5_amc@nlo 2.1 interfaced to pythia 6.4. This is the first cross section measurement for this process.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Decomposing transverse momentum balance contributions for quenched jets in PbPb collisions at $ \sqrt{s_{\mathrm{N}\;\mathrm{N}}}=2.76 $ TeV

Interactions between jets and the quark-gluon plasma produced in heavy ion collisions are studied via the angular distributions of summed charged-particle transverse momenta (p$_{T}$) with respect to both the leading and subleading jet axes in high-p$_{T}$ dijet events. The contributions of charged particles in different momentum ranges to the overall event p$_{T}$ balance are decomposed into short-range jet peaks and a long-range azimuthal asymmetry in charged-particle p$_{T}$. The results for PbPb collisions are compared to those in pp collisions using data collected in 2011 and 2013, at collision energy $ \sqrt{s_{\mathrm{N}\,\mathrm{N}}}=2.76 $ TeV with integrated luminosities of 166 μb$^{−1}$ and 5.3 pb$^{−1}$, respectively, by the CMS experiment at the LHC. Measurements are presented as functions of PbPb collision centrality, charged-particle p$_{T}$, relative azimuth, and radial distance from the jet axis for balanced and unbalanced dijets.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Phenomenological MSSM interpretation of CMS searches in pp collisions at sqrt(s) = 7 and 8 TeV

Searches for new physics by the CMS collaboration are interpreted in the framework of the phenomenological minimal supersymmetric standard model (pMSSM). The data samples used in this study were collected at $ \sqrt{s}=7 $ and 8 TeV and have integrated luminosities of 5.0 fb$^{−1}$ and 19.5 fb$^{−1}$, respectively. A global Bayesian analysis is performed, incorporating results from a broad range of CMS supersymmetry searches, as well as constraints from other experiments. Because the pMSSM incorporates several well-motivated assumptions that reduce the 120 parameters of the MSSM to just 19 parameters defined at the electroweak scale, it is possible to assess the results of the study in a relatively straightforward way. Approximately half of the model points in a potentially accessible subspace of the pMSSM are excluded, including all pMSSM model points with a gluino mass below 500 GeV, as well as models with a squark mass less than 300 GeV. Models with chargino and neutralino masses below 200 GeV are disfavored, but no mass range of model points can be ruled out based on the analyses considered. The nonexcluded regions in the pMSSM parameter space are characterized in terms of physical processes and key observables, and implications for future searches are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Search for supersymmetry in pp collisions at $ \sqrt{s}=13 $ TeV in the single-lepton final state using the sum of masses of large-radius jets

Results are reported from a search for supersymmetric particles in proton-proton collisions in the final state with a single, high transverse momentum lepton, multiple jets, including at least one b-tagged jet, and large missing transverse momentum. The data sample corresponds to an integrated luminosity of 2.3 fb$^{−1}$ at $ \sqrt{s}=13 $ TeV, recorded by the CMS experiment at the LHC. The search focuses on processes leading to high jet multiplicities, such as gluino pair production with $ \tilde{\mathrm{g}}\to \mathrm{t}\overline{\mathrm{t}}{\tilde{\chi}}_1^0 $ . The quantity M$_{J}$ , defined as the sum of the masses of the large-radius jets in the event, is used in conjunction with other kinematic variables to provide discrimination between signal and background and as a key part of the background estimation method. The observed event yields in the signal regions in data are consistent with those expected for standard model backgrounds, estimated from control regions in data. Exclusion limits are obtained for a simplified model corresponding to gluino pair production with three-body decays into top quarks and neutralinos. Gluinos with a mass below 1600 GeV are excluded at a 95% confidence level for scenarios with low $ {\tilde{\chi}}_1^0 $ mass, and neutralinos with a mass below 800 GeV are excluded for a gluino mass of about 1300 GeV. For models with two-body gluino decays producing on-shell top squarks, the excluded region is only weakly sensitive to the top squark mass.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Measurement of the double-differential inclusive jet cross section in proton–proton collisions at $\sqrt{s} = 13\,\text {TeV} $

A measurement of the double-differential inclusive jet cross section as a function of jet transverse momentum $p_{\mathrm {T}} $ and absolute jet rapidity $|y |$ is presented. The analysis is based on proton–proton collisions collected by the CMS experiment at the LHC at a centre-of-mass energy of 13 $\,\text {TeV}$ . The data samples correspond to integrated luminosities of 71 and 44 $\,\text {pb}^\text {-1}$ for $|y |<3$ and $3.2<|y |<4.7$ , respectively. Jets are reconstructed with the anti- $k_{\mathrm {t}} $ clustering algorithm for two jet sizes, R, of 0.7 and 0.4, in a phase space region covering jet $p_{\mathrm {T}} $ up to 2 $\,\text {TeV}$ and jet rapidity up to $|y |$ = 4.7. Predictions of perturbative quantum chromodynamics at next-to-leading order precision, complemented with electroweak and nonperturbative corrections, are used to compute the absolute scale and the shape of the inclusive jet cross section. The cross section difference in R, when going to a smaller jet size of 0.4, is best described by Monte Carlo event generators with next-to-leading order predictions matched to parton showering, hadronisation, and multiparton interactions. In the phase space accessible with the new data, this measurement provides a first indication that jet physics is as well understood at $\sqrt{s}=13\,\text {TeV} $ as at smaller centre-of-mass energies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Search for massive WH resonances decaying into the $\ell \nu \mathrm{b} \overline{\mathrm{b}} $ final state at $\sqrt{s}=8$ $~\text {TeV}$

A search for a massive resonance ${\mathrm{W}^{\prime }}$ decaying into a W and a Higgs boson in the $\ell \nu \mathrm{b} \overline{\mathrm{b}} $ ( $\ell = \mathrm {e}$ , $\mu $ ) final state is presented. Results are based on data corresponding to an integrated luminosity of 19.7 $\,\text {fb}^{{-1}}$ of proton–proton collisions at $\sqrt{s}=8$ $~\text {TeV}$ , collected using the CMS detector at the LHC. For a high-mass ( $\gtrsim $ 1 $~\text {TeV}$ ) resonance, the two bottom quarks coming from the Higgs boson decay are reconstructed as a single jet, which can be tagged by placing requirements on its substructure and flavour. Exclusion limits at 95 % confidence level are set on the production cross section of a narrow resonance decaying into WH, as a function of its mass. In the context of a little Higgs model, a lower limit on the ${\mathrm{W}^{\prime }}$ mass of 1.4 $~\text {TeV}$ is set. In a heavy vector triplet model that mimics the properties of composite Higgs models, a lower limit on the ${\mathrm{W}^{\prime }}$ mass of 1.5 $~\text {TeV}$ is set. In the context of this model, the results are combined with related searches to obtain a lower limit on the ${\mathrm{W}^{\prime }}$ mass of 1.8 $~\text {TeV}$ , the most restrictive to date for decays to a pair of standard model bosons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Search for Excited Leptons in Proton-Proton Collisions at $\sqrt{s}$ = 8 TeV

A search for compositeness of electrons and muons is presented using a data sample of proton-proton collisions at a center-of-mass energy of $ \sqrt{s} = 8 $ TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb$^{−1}$. Excited leptons (ℓ$^{*}$) produced via contact interactions in conjunction with a standard model lepton are considered, and a search is made for their gauge decay modes. The decays considered are ℓ$^{*}$ → ℓγ and ℓ$^{*}$ → ℓZ, which give final states of two leptons and a photon or, depending on the Z-boson decay mode, four leptons or two leptons and two jets. The number of events observed in data is consistent with the standard model prediction. Exclusion limits are set on the excited lepton mass, and the compositeness scale Λ. For the case M$_{ℓ*}$ = Λ the existence of excited electrons (muons) is excluded up to masses of 2.45 (2.47) TeV at 95% confidence level. Neutral current decays of excited leptons are considered for the first time, and limits are extended to include the possibility that the weight factors f and f′, which determine the couplings between standard model leptons and excited leptons via gauge mediated interactions, have opposite sign.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗