Engineering topics

Yonamine, Ryo

Publications and source records attributed to Yonamine, Ryo.

At least 127 records · Page 7

DOE OSTI2017

Search for electroweak production of a vector-like quark decaying to a top quark and a Higgs boson using boosted topologies in fully hadronic final states

A search is performed for electroweak production of a vector-like top quark partner T of charge 2/3 in association with a standard model top or bottom quark, using 2.3 fb$^{−1}$ of proton-proton collision data at $ \sqrt{s}=13 $ TeV collected by the CMS experiment at the CERN LHC. The search targets T quarks decaying to a top quark and a Higgs boson in fully hadronic final states. For a T quark with mass above 1 TeV the daughter top quark and Higgs boson are highly Lorentz-boosted and can each appear as a single hadronic jet. Jet substructure and b tagging techniques are used to identify the top quark and Higgs boson jets, and to suppress the standard model backgrounds. An excess of events is searched for in the T quark candidate mass distribution in the data, which is found to be consistent with the expected backgrounds. Upper limits at 95% confidence level are set on the product of the single T quark production cross sections and the branching fraction $ \mathrm{\mathcal{B}}\left(\mathrm{T}\to \mathrm{t}\mathrm{H}\right) $ , and these vary between 0.31 and 0.93 pb for T quark masses in the range 1000-1800 GeV. This is the first search for single electroweak production of a vector-like T quark in fully hadronic final states.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Mechanical stability of the CMS strip tracker measured with a laser alignment system

The CMS tracker consists of 206 m(2) of silicon strip sensors assembled on carbon fibre composite structures and is designed for operation in the temperature range from −25 to +25°C. The mechanical stability of tracker components during physics operation was monitored with a few μm resolution using a dedicated laser alignment system as well as particle tracks from cosmic rays and hadron-hadron collisions. During the LHC operational period of 2011–2013 at stable temperatures, the components of the tracker were observed to experience relative movements of less than 30μm. In addition, temperature variations were found to cause displacements of tracker structures of about 2μm°C, which largely revert to their initial positions when the temperature is restored to its original value.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2017

Suppression and azimuthal anisotropy of prompt and nonprompt ${\mathrm{J}}/\psi $ production in PbPb collisions at $\sqrt{{s_{_{\text {NN}}}}} =2.76$ $\,\mathrm{TeV}$

The nuclear modification factor $R_{\mathrm{AA}}$ and the azimuthal anisotropy coefficient $v_{2}$ of prompt and nonprompt (i.e. those from decays of b hadrons) ${\mathrm{J}}/\psi $ mesons, measured from PbPb and pp collisions at $\sqrt{{s_{_{\text {NN}}}}} =2.76$ $\,\mathrm{TeV}$ at the LHC, are reported. The results are presented in several event centrality intervals and several kinematic regions, for transverse momenta $p_{\mathrm{T}} >6.5$ $\,{\mathrm{GeV}}/{\mathrm{c}}$ and rapidity $|{y}|<2.4$ , extending down to $p_{\mathrm{T}} =3$ $\,{\mathrm{GeV}}/{\mathrm{c}}$ in the $1.6<|{y}|<2.4$ range. The $v_{2}$ of prompt ${\mathrm{J}}/\psi $ is found to be nonzero, but with no strong dependence on centrality, rapidity, or $p_{\mathrm{T}}$ over the full kinematic range studied. The measured $v_{2}$ of nonprompt ${\mathrm{J}}/\psi $ is consistent with zero. The $R_{\mathrm{AA}}$ of prompt ${\mathrm{J}}/\psi $ exhibits a suppression that increases from peripheral to central collisions but does not vary strongly as a function of either y or $p_{\mathrm{T}}$ in the fiducial range. The nonprompt ${\mathrm{J}}/\psi $ $R_{\mathrm{AA}}$ shows a suppression which becomes stronger as rapidity or $p_{\mathrm{T}}$ increases. The $v_{2}$ and $R_{\mathrm{AA}}$ of open and hidden charm, and of open charm and beauty, are compared.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Measurement of the WZ production cross section in pp collisions at $\sqrt{s} = 7$ and 8 $\,\text{TeV}$ and search for anomalous triple gauge couplings at $\sqrt{s} = 8\,\text{TeV} $

The WZ production cross section is measured by the CMS experiment at the CERN LHC in proton–proton collision data samples corresponding to integrated luminosities of 4.9 $\,\text{fb}^{-1}$ collected at $\sqrt{s} = 7\,\text{TeV} $ , and 19.6 $\,\text{fb}^{-1}$ at $\sqrt{s} = 8\,\text{TeV} $ . The measurements are performed using the fully-leptonic WZ decay modes with electrons and muons in the final state. The measured cross sections for $71< m_{\mathrm{Z}} < 111\,\text{GeV} $ are $\sigma ({\mathrm{p}\mathrm{p}}\rightarrow {\mathrm{W}\mathrm{Z}},~\sqrt{s} = 7\,\text{TeV}) = 20.14 \pm 1.32\,\text{(stat)} \pm 0.38\,\text{(theo)} \pm 1.06\,\text{(exp)} \pm 0.44\,\text{(lumi)} $ $\,\text{pb}$ and $\sigma ({\mathrm{p}\mathrm{p}}\rightarrow {\mathrm{W}\mathrm{Z}},~\sqrt{s} = 8\,\text{TeV}) = 24.09 \pm 0.87\,\text{(stat)} \pm 0.80\,\text{(theo)} \pm 1.40\,\text{(exp)} \pm 0.63\,\text{(lumi)} $ $\,\text{pb}$ . Differential cross sections with respect to the $\mathrm{Z}$ boson $p_{\mathrm{T}}$ , the leading jet $p_{\mathrm{T}}$ , and the number of jets are obtained using the $\sqrt{s} = 8\,\text{TeV} $ data. The results are consistent with standard model predictions and constraints on anomalous triple gauge couplings are obtained.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Charged-particle nuclear modification factors in PbPb and pPb collisions at $ \sqrt{s_{\mathrm{N}\;\mathrm{N}}}=5.02 $ TeV

The spectra of charged particles produced within the pseudorapidity window |η| < 1 at $ \sqrt{s_{\mathrm{N}\,\mathrm{N}}}=5.02 $ TeV are measured using 404 μb$^{−1}$ of PbPb and 27.4 pb$^{−1}$ of pp data collected by the CMS detector at the LHC in 2015. The spectra are presented over the transverse momentum ranges spanning 0.5 < p$_{T}$ < 400 GeV in pp and 0.7 < p$_{T}$ < 400 GeV in PbPb collisions. The corresponding nuclear modification factor, R$_{AA}$, is measured in bins of collision centrality. The R$_{AA}$ in the 5% most central collisions shows a maximal suppression by a factor of 7-8 in the p$_{T}$ region of 6-9 GeV. This dip is followed by an increase, which continues up to the highest p$_{T}$ measured, and approaches unity in the vicinity of p$_{T}$ = 200 GeV. The R$_{AA}$ is compared to theoretical predictions and earlier experimental results at lower collision energies. The newly measured pp spectrum is combined with the pPb spectrum previously published by the CMS collaboration to construct the pPb nuclear modification factor, R$_{pA}$, up to 120 GeV. For p$_{T}$ > 20 GeV, R$_{pA}$ exhibits weak momentum dependence and shows a moderate enhancement above unity.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2017

Measurements of differential production cross sections for a Z boson in association with jets in pp collisions at $ \sqrt{s}=8 $ TeV

Cross sections for the production of a Z boson in association with jets in proton-proton collisions at a centre-of-mass energy of $ \sqrt{s}=8 $ TeV are measured using a data sample collected by the CMS experiment at the LHC corresponding to 19.6 fb$^{−1}$. Differential cross sections are presented as functions of up to three observables that describe the jet kinematics and the jet activity. Correlations between the azimuthal directions and the rapidities of the jets and the Z boson are studied in detail. The predictions of a number of multileg generators with leading or next-to-leading order accuracy are compared with the measurements. The comparison shows the importance of including multi-parton contributions in the matrix elements and the improvement in the predictions when next-to-leading order terms are included.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Search for electroweak production of charginos in final states with two τ leptons in pp collisions at $ \sqrt{s}=8 $ TeV

Results are presented from a search for the electroweak production of supersymmetric particles in pp collisions in final states with two τ leptons. The data sample corresponds to an integrated luminosity between 18.1 fb$^{−1}$ and 19.6 fb$^{−1}$ depending on the final state of τ lepton decays, at $ \sqrt{s}=8 $ TeV, collected by the CMS experiment at the LHC. The observed event yields in the signal regions are consistent with the expected standard model backgrounds. The results are interpreted using simplified models describing the pair production and decays of charginos or τ sleptons. For models describing the pair production of the lightest chargino, exclusion regions are obtained in the plane of chargino mass vs. neutralino mass under the following assumptions: the chargino decays into third-generation sleptons, which are taken to be the lightest sleptons, and the sleptons masses lie midway between those of the chargino and the neutralino. Chargino masses below 420 GeV are excluded at a 95% confidence level in the limit of a massless neutralino, and for neutralino masses up to 100 GeV, chargino masses up to 325 GeV are excluded at 95% confidence level. Constraints are also placed on the cross section for pair production of τ sleptons as a function of mass, assuming a massless neutralino.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Search for massive resonances decaying into WW, WZ or ZZ bosons in proton-proton collisions at $\sqrt{s} = $ 13 TeV

A search is presented for new massive resonances decaying to WW, WZ or ZZ bosons in $ \ell \nu q\overline{q} $ and $ q\overline{q}q\overline{q} $ final states. Results are based on data corresponding to an integrated luminosity of 2.3-2.7 fb$^{−1}$ recorded in proton-proton collisions at $ \sqrt{s}=13 $ TeV with the CMS detector at the LHC. Decays of spin-1 and spin-2 resonances into two vector bosons are sought in the mass range 0.6-4.0 TeV. No significant excess over the standard model background is observed. Combining the results of the $ \ell \nu q\overline{q} $ and $ q\overline{q}q\overline{q} $ final states, cross section and mass exclusion limits are set for models that predict heavy spin-1 and spin-2 resonances. This is the first search for a narrow-width spin-2 resonance at $ \sqrt{s}=13 $ TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Measurement and QCD analysis of double-differential inclusive jet cross sections in pp collisions at $ \sqrt{s}=8 $ TeV and cross section ratios to 2.76 and 7 TeV

A measurement of the double-differential inclusive jet cross section as a function of the jet transverse momentum p$_{T}$ and the absolute jet rapidity |y| is presented. Data from LHC proton-proton collisions at $ \sqrt{s}=8 $ TeV, corresponding to an integrated luminosity of 19.7 fb$^{−1}$, have been collected with the CMS detector. Jets are reconstructed using the anti-k$_{T}$ clustering algorithm with a size parameter of 0.7 in a phase space region covering jet p$_{T}$ from 74 GeV up to 2.5 TeV and jet absolute rapidity up to |y| = 3.0. The low-p$_{T}$ jet range between 21 and 74 GeV is also studied up to |y| = 4.7, using a dedicated data sample corresponding to an integrated luminosity of 5.6 pb$^{−1}$. The measured jet cross section is corrected for detector effects and compared with the predictions from perturbative QCD at next-to-leading order (NLO) using various sets of parton distribution functions (PDF). Cross section ratios to the corresponding measurements performed at 2.76 and 7 TeV are presented. From the measured double-differential jet cross section, the value of the strong coupling constant evaluated at the Z mass is α$_{S}$(M$_{Z}$) = 0.1164$_{− 0.0043}^{+ 0.0060}$ , where the errors include the PDF, scale, nonperturbative effects and experimental uncertainties, using the CT10 NLO PDFs. Improved constraints on PDFs based on the inclusive jet cross section measurement are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Search for CP violation in $ t\overline{t} $ production and decay in proton-proton collisions at $ \sqrt{s}=8 $ TeV

The results of a first search for CP violation in the production and decay of top quark-antiquark ( $ t\overline{t} $ ) pairs are presented. The search is based on asymmetries in T-odd, triple-product correlation observables, where T is the time-reversal operator. The analysis uses a sample of proton-proton collisions at $ \sqrt{s}=8 $ TeV collected by the CMS experiment, corresponding to an integrated luminosity of 19.7 fb$^{−1}$. Events are selected having one electron or muon and at least four jets. The T-odd observables are measured using four-momentum vectors associated with $ t\overline{t} $ production and decay. The measured asymmetries exhibit no evidence for CP-violating effects, consistent with the expectation from the standard model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Measurement of the $t\bar{t}$ production cross section using events in the e$\mu$ final state in pp collisions at $\sqrt{s} =$ 13 TeV

The cross section of top quark-antiquark pair production in proton-proton collisions at $\sqrt{s} = 13$ TeV is measured by the CMS experiment at the LHC, using data corresponding to an integrated luminosity of 2.2 inverse femtobarns. The measurement is performed by analyzing events in which the final state includes one electron, one muon, and two or more jets, at least one of which is identified as originating from hadronization of a b quark. The measured cross section is 792 $\pm$ 8 (stat) $\pm$ 37 (syst) $\pm$ 21 (lumi) pb, in agreement with the expectation from the standard model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Search for heavy neutrinos or third-generation leptoquarks in final states with two hadronically decaying $\tau$ leptons and two jets in proton-proton collisions at $ \sqrt{s}=13 $ TeV

A search for new particles has been conducted using events with two high transverse momentum (p$_{T}$) τ leptons that decay hadronically, at least two high-p$_{T}$ jets, and missing transverse energy from the τ lepton decays. The analysis is performed using data from proton-proton collisions, collected by the CMS experiment in 2015 at $ \sqrt{s}=13 $ TeV, corresponding to an integrated luminosity of 2.1 fb$^{−1}$. The results are interpreted in two physics models. The first model involves heavy right-handed neutrinos, N$_{ℓ}$ (ℓ = e, μ, τ), and right-handed charged bosons, W$_{R}$, arising in a left-right symmetric extension of the standard model. Masses of the W$_{R}$ boson below 2.35 (1.63) TeV are excluded at 95% confidence level, assuming the N$_{τ}$ mass is 0.8 (0.2) times the mass of the W$_{R}$ boson and that only the N$_{τ}$ flavor contributes to the W$_{R}$ decay width. In the second model, pair production of third-generation scalar leptoquarks that decay into ττbb is considered. Third-generation scalar leptoquarks with masses below 740 GeV are excluded, assuming a 100% branching fraction for the leptoquark decay to a τ lepton and a bottom quark. This is the first search at hadron colliders for the third-generation Majorana neutrino, as well as the first search for third-generation leptoquarks in the final state with a pair of hadronically decaying τ leptons and jets.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Search for dark matter and unparticles in events with a Z boson and missing transverse momentum in proton-proton collisions at $ \sqrt{s}=13 $ TeV

A search for dark matter and unparticle production at the LHC has been performed using events containing two charged leptons (electrons or muons), consistent with the decay of a Z boson, and large missing transverse momentum. This study is based on data collected with the CMS detector in 2015, corresponding to an integrated luminosity of 2.3 fb$^{−1}$ of proton-proton collisions at the LHC, at a center-of-mass energy of 13 TeV. No excess over the standard model expectation is observed. Compared to previous searches in this topology, which exclusively relied on effective field theories, the results are interpreted in terms of a simplified model of dark matter production for both vector and axial vector couplings between a mediator and dark matter particles. The first study of this class of models using CMS data at $ \sqrt{s}=13 $ TeV is presented. Additionally, effective field theories of dark matter and unparticle production are used to interpret the data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Measurement of the transverse momentum spectrum of the Higgs boson produced in pp collisions at $ \sqrt{s}=8 $ TeV using $H \to WW$ decays

The cross section for Higgs boson production in pp collisions is studied using the H → W$^{+}$W$^{−}$ decay mode, followed by leptonic decays of the W bosons to an oppositely charged electron-muon pair in the final state. The measurements are performed using data collected by the CMS experiment at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.4 fb$^{−1}$. The Higgs boson transverse momentum (p$_{T}$) is reconstructed using the lepton pair p$_{T}$ and missing p$_{T}$. The differential cross section times branching fraction is measured as a function of the Higgs boson p$_{T}$ in a fiducial phase space defined to match the experimental acceptance in terms of the lepton kinematics and event topology. The production cross section times branching fraction in the fiducial phase space is measured to be 39 ± 8 (stat) ± 9 (syst) fb. The measurements are found to agree, within experimental uncertainties, with theoretical calculations based on the standard model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Searches for invisible decays of the Higgs boson in pp collisions at $\sqrt{s}$ = 7, 8, and 13 TeV

Searches for invisible decays of the Higgs boson are presented. The data collected with the CMS detector at the LHC correspond to integrated luminosities of 5.1, 19.7, and 2.3 fb$^{−1}$ at centre-of-mass energies of 7, 8, and 13 TeV, respectively. The search channels target Higgs boson production via gluon fusion, vector boson fusion, and in association with a vector boson. Upper limits are placed on the branching fraction of the Higgs boson decay to invisible particles, as a function of the assumed production cross sections. The combination of all channels, assuming standard model production, yields an observed (expected) upper limit on the invisible branching fraction of 0.24 (0.23) at the 95% confidence level. The results are also interpreted in the context of Higgs-portal dark matter models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV

Improved jet energy scale corrections, based on a data sample corresponding to an integrated luminosity of 19.7 fb(-1) collected by the CMS experiment in proton-proton collisions at a center-of-mass energy of 8 TeV, are presented. The corrections as a function of pseudorapidity η and transverse momentum p(T) are extracted from data and simulated events combining several channels and methods. They account successively for the effects of pileup, uniformity of the detector response, and residual data-simulation jet energy scale differences. Further corrections, depending on the jet flavor and distance parameter (jet size) R, are also presented. The jet energy resolution is measured in data and simulated events and is studied as a function of pileup, jet size, and jet flavor. Typical jet energy resolutions at the central rapidities are 15–20% at 30 GeV, about 10% at 100 GeV, and 5% at 1 TeV. The studies exploit events with dijet topology, as well as photon+jet, Z+jet and multijet events. Several new techniques are used to account for the various sources of jet energy scale corrections, and a full set of uncertainties, and their correlations, are provided.The final uncertainties on the jet energy scale are below 3% across the phase space considered by most analyses (p(T),>30 GeV and 0| η| <5.). In the barrel region (| η| <1.3) an uncertainty below 1% for p(T)>30 GeV is reached, when excluding the jet flavor uncertainties, which are provided separately for different jet flavors. A new benchmark for jet energy scale determination at hadron colliders is achieved with 0.32% uncertainty for jets with \pt of the order of 165–330\GeV, and | η| <0.8.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Measurement of the transverse momentum spectra of weak vector bosons produced in proton-proton collisions at $ \sqrt{s}=8 $ TeV

The transverse momentum spectra of weak vector bosons are measured in the CMS experiment at the LHC. The measurement uses a sample of proton-proton collisions at $ \sqrt{s}=8 $ TeV, collected during a special low-luminosity running that corresponds to an integrated luminosity of 18.4 ± 0.5 pb$^{−1}$. The production of W bosons is studied in both electron and muon decay modes, while the production of Z bosons is studied using only the dimuon decay channel. The ratios of W$^{−}$ to W$^{+}$ and Z to W differential cross sections are also measured. The measured differential cross sections and ratios are compared with theoretical predictions up to next-to-next leading order in QCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Search for top quark decays via Higgs-boson-mediated flavor-changing neutral currents in pp collisions at $ \sqrt{s}=8 $ TeV

A search is performed for Higgs-boson-mediated flavor-changing neutral currents in the decays of top quarks. The search is based on proton-proton collision data corresponding to an integrated luminosity of 19.7 inverse-femtobarns at a center-of-mass energy of 8 TeV collected with the CMS detector at the LHC. Events in which a top quark pair is produced with one top quark decaying into a charm or up quark and a Higgs boson (H), and the other top quark decaying into a bottom quark and a W boson are selected. The Higgs boson in these events is assumed to subsequently decay into either dibosons or difermions. No significant excess is observed above the expected standard model background, and an upper limit at the 95% confidence level is set on the branching fraction B(t -> Hc) of 0.40% and B(t -> Hu) of 0.55%, where the expected upper limits are 0.43% and 0.40\%, respectively. These results correspond to upper limits on the square of the flavor-changing Higgs boson Yukawa couplings $|\lambda^{H}_{tu}|^2$ < 6.9E-3 and $|\lambda^{H}_{tu}|^2$ < 9.8 x 10$^{-3}$.

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