Showing papers by "Jie Zhang published in 2016"
TL;DR: In this article, the performance of the ATLAS muon identification and reconstruction using the first LHC dataset recorded at s√ = 13 TeV in 2015 was evaluated using the Monte Carlo simulations.
Abstract: This article documents the performance of the ATLAS muon identification and reconstruction using the first LHC dataset recorded at s√ = 13 TeV in 2015. Using a large sample of J/ψ→μμ and Z→μμ decays from 3.2 fb−1 of pp collision data, measurements of the reconstruction efficiency, as well as of the momentum scale and resolution, are presented and compared to Monte Carlo simulations. The reconstruction efficiency is measured to be close to 99% over most of the covered phase space (|η| 2.2, the pT resolution for muons from Z→μμ decays is 2.9% while the precision of the momentum scale for low-pT muons from J/ψ→μμ decays is about 0.2%.
440 citations
Queen's University1, Polytechnic University of Valencia2, Pacific Northwest National Laboratory3, Northwestern University4, Indiana University5, Saha Institute of Nuclear Physics6, Fermilab7, University of Toronto8, University of Chicago9, Université de Montréal10, Laurentian University11, Czech Technical University in Prague12, University of Alberta13, Virginia Tech14, Drexel University15, National Autonomous University of Mexico16
TL;DR: These data provide the most sensitive direct detection constraints on WIMP-proton spin-dependent scattering to date, with significant sensitivity at low W IMP masses for spin-independent WIMp-nucleon scattering.
Abstract: New results are reported from the operation of the PICO-60 dark matter detector, a bubble chamber filled with 52 kg of C_{3}F_{8} located in the SNOLAB underground laboratory. As in previous PICO bubble chambers, PICO-60 C_{3}F_{8} exhibits excellent electron recoil and alpha decay rejection, and the observed multiple-scattering neutron rate indicates a single-scatter neutron background of less than one event per month. A blind analysis of an efficiency-corrected 1167-kg day exposure at a 3.3-keV thermodynamic threshold reveals no single-scattering nuclear recoil candidates, consistent with the predicted background. These results set the most stringent direct-detection constraint to date on the weakly interacting massive particle (WIMP)-proton spin-dependent cross section at 3.4×10^{-41} cm^{2} for a 30-GeV c^{-2} WIMP, more than 1 order of magnitude improvement from previous PICO results.
429 citations
TL;DR: In this paper, an independent b-tagging algorithm based on the reconstruction of muons inside jets as well as the b tagging algorithm used in the online trigger are also presented.
Abstract: The identification of jets containing b hadrons is important for the physics programme of the ATLAS experiment at the Large Hadron Collider. Several algorithms to identify jets containing b hadrons are described, ranging from those based on the reconstruction of an inclusive secondary vertex or the presence of tracks with large impact parameters to combined tagging algorithms making use of multi-variate discriminants. An independent b-tagging algorithm based on the reconstruction of muons inside jets as well as the b-tagging algorithm used in the online trigger are also presented. The b-jet tagging efficiency, the c-jet tagging efficiency and the mistag rate for light flavour jets in data have been measured with a number of complementary methods. The calibration results are presented as scale factors defined as the ratio of the efficiency (or mistag rate) in data to that in simulation. In the case of b jets, where more than one calibration method exists, the results from the various analyses have been combined taking into account the statistical correlation as well as the correlation of the sources of systematic uncertainty.
362 citations
TL;DR: The methods employed in the ATLAS experiment to correct for the impact of pile-up on jet energy and jet shapes, and for the presence of spurious additional jets, are described, with a primary focus on the large 20.3 kg-1 data sample.
Abstract: The large rate of multiple simultaneous protonproton interactions, or pile-up, generated by the Large Hadron Collider in Run 1 required the development of many new techniques to mitigate the advers ...
316 citations
TL;DR: The luminosity determination for the ATLAS detector at the LHC during pp collisions at s√= 8 TeV in 2012 is presented in this article, where the evaluation of the luminosity scale is performed using several luminometers.
Abstract: The luminosity determination for the ATLAS detector at the LHC during pp collisions at s√= 8 TeV in 2012 is presented. The evaluation of the luminosity scale is performed using several luminometers ...
286 citations
TL;DR: The results suggest that the ridge in pp collisions arises from the same or similar underlying physics as observed in p+Pb collisions, and that the dynamics responsible for the ridge has no strong sqrt[s] dependence.
Abstract: ATLAS has measured two-particle correlations as a function of relative azimuthal-angle, $\Delta \phi$, and pseudorapidity, $\Delta \eta$, in $\sqrt{s}$=13 and 2.76 TeV $pp$ collisions at the LHC using charged particles measured in the pseudorapidity interval $|\eta|$<2.5. The correlation functions evaluated in different intervals of measured charged-particle multiplicity show a multiplicity-dependent enhancement at $\Delta \phi \sim 0$ that extends over a wide range of $\Delta\eta$, which has been referred to as the "ridge". Per-trigger-particle yields, $Y(\Delta \phi)$, are measured over 2<$|\Delta\eta|$<5. For both collision energies, the $Y(\Delta \phi)$ distribution in all multiplicity intervals is found to be consistent with a linear combination of the per-trigger-particle yields measured in collisions with less than 20 reconstructed tracks, and a constant combinatoric contribution modulated by $\cos{(2\Delta \phi)}$. The fitted Fourier coefficient, $v_{2,2}$, exhibits factorization, suggesting that the ridge results from per-event $\cos{(2\phi)}$ modulation of the single-particle distribution with Fourier coefficients $v_2$. The $v_2$ values are presented as a function of multiplicity and transverse momentum. They are found to be approximately constant as a function of multiplicity and to have a $p_{\mathrm{T}}$ dependence similar to that measured in $p$+Pb and Pb+Pb collisions. The $v_2$ values in the 13 and 2.76 TeV data are consistent within uncertainties. These results suggest that the ridge in $pp$ collisions arises from the same or similar underlying physics as observed in $p$+Pb collisions, and that the dynamics responsible for the ridge has no strong $\sqrt{s}$ dependence.
246 citations
TL;DR: In this article, a search for a high-mass Higgs boson in the,,, and decay modes using the ATLAS detector at the CERN Large Hadron Collider is presented.
Abstract: A search is presented for a high-mass Higgs boson in the , , , and decay modes using the ATLAS detector at the CERN Large Hadron Collider. The search uses proton-proton collision data at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb. The results of the search are interpreted in the scenario of a heavy Higgs boson with a width that is small compared with the experimental mass resolution. The Higgs boson mass range considered extends up to for all four decay modes and down to as low as 140 , depending on the decay mode. No significant excess of events over the Standard Model prediction is found. A simultaneous fit to the four decay modes yields upper limits on the production cross-section of a heavy Higgs boson times the branching ratio to boson pairs. 95 % confidence level upper limits range from 0.53 pb at GeV to 0.008 pb at GeV for the gluon-fusion production mode and from 0.31 pb at GeV to 0.009 pb at GeV for the vector-boson-fusion production mode. The results are also interpreted in the context of Type-I and Type-II two-Higgs-doublet models.
241 citations
TL;DR: In this article, a search for new phenomena in final states with an energetic jet and large missing transverse momentum was performed using proton-proton collision data corresponding to an inte...
Abstract: Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an inte ...
203 citations
TL;DR: In this paper, a measurement of the inelastic proton-proton cross section using 60''μb^{-1} of pp collisions at a center-of-mass energy sqrt[s] of 13'TeV with the ATLAS detector at the LHC is presented.
Abstract: This Letter presents a measurement of the inelastic proton-proton cross section using 60 μb^{-1} of pp collisions at a center-of-mass energy sqrt[s] of 13 TeV with the ATLAS detector at the LHC. Inelastic interactions are selected using rings of plastic scintillators in the forward region (2.07 10^{-6}, where M_{X} is the larger invariant mass of the two hadronic systems separated by the largest rapidity gap in the event. In this ξ range the scintillators are highly efficient. For diffractive events this corresponds to cases where at least one proton dissociates to a system with M_{X}>13 GeV. The measured cross section is compared with a range of theoretical predictions. When extrapolated to the full phase space, a cross section of 78.1±2.9 mb is measured, consistent with the inelastic cross section increasing with center-of-mass energy.
191 citations
TL;DR: In this article, the authors describe a model-agnostic search for pairs of jets (dijets) produced by resonant and non-resonant phenomena beyond the Standard Model.
185 citations
DOI•
12 Aug 2016
TL;DR: The Compact Linear Collider (CLIC) is a multi-teV high-luminosity linear e+e-collider under development as discussed by the authors, which is foreseen to be built and operated in a staged approach with three center-of-mass energy stages ranging from a few hundred GeV up to 3 TeV.
Abstract: The Compact Linear Collider (CLIC) is a multi-TeV high-luminosity linear e+e- collider under development. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in a staged approach with three centre-of-mass energy stages ranging from a few hundred GeV up to 3 TeV. The first stage will focus on precision Standard Model physics, in particular Higgs and top-quark measurements. Subsequent stages will focus on measurements of rare Higgs processes, as well as searches for new physics processes and precision measurements of new states, e.g. states previously discovered at LHC or at CLIC itself. In the 2012 CLIC Conceptual Design Report, a fully optimised 3 TeV collider was presented, while the proposed lower energy stages were not studied to the same level of detail. This report presents an updated baseline staging scenario for CLIC. The scenario is the result of a comprehensive study addressing the performance, cost and power of the CLIC accelerator complex as a function of centre-of-mass energy and it targets optimal physics output based on the current physics landscape. The optimised staging scenario foresees three main centre-of-mass energy stages at 380 GeV, 1.5 TeV and 3 TeV for a full CLIC programme spanning 22 years. For the first stage, an alternative to the CLIC drive beam scheme is presented in which the main linac power is produced using X-band klystrons.
TL;DR: In this article, the authors measured the transverse momentum and the related angular variable of DrellΓCoYan lepton pairs with the ATLAS detector at the LHC and compared their results to predictions from perturbative and resummed QCD calculations.
Abstract: Distributions of transverse momentum [Formula: see text] and the related angular variable [Formula: see text] of DrellΓCoYan lepton pairs are measured in 20.3┬afb[Formula: see text] of protonΓCoproton collisions at [Formula: see text]┬aTeV with the ATLAS detector at the LHC. Measurements in electron-pair and muon-pair final states are corrected for detector effects and combined. Compared to previous measurements in protonΓCoproton collisions at [Formula: see text]┬aTeV, these new measurements benefit from a larger data sample and improved control of systematic uncertainties. Measurements are performed in bins of lepton-pair mass above, around and below the Z-boson mass peak. The data are compared to predictions from perturbative and resummed QCD calculations. For values of [Formula: see text] the predictions from the Monte Carlo generator ResBos are generally consistent with the data within the theoretical uncertainties. However, at larger values of [Formula: see text] this is not the case. Monte Carlo generators based on the parton-shower approach are unable to describe the data over the full range of [Formula: see text] while the fixed-order prediction of Dynnlo falls below the data at high values of [Formula: see text]. ResBos and the parton-shower Monte Carlo generators provide a much better description of the evolution of the [Formula: see text] and [Formula: see text] distributions as a function of lepton-pair mass and rapidity than the basic shape of the data.
TL;DR: In this article, a search for strongly produced supersymmetric particles is conducted using signatures involving multiple energetic jets and either two isolated leptons (e or μ) with the same electric charge or at the same location.
Abstract: A search for strongly produced supersymmetric particles is conducted using signatures involving multiple energetic jets and either two isolated leptons (e or μ) with the same electric charge or at ...
Queen's University1, Polytechnic University of Valencia2, Pacific Northwest National Laboratory3, Northwestern University4, Indiana University5, Saha Institute of Nuclear Physics6, Fermilab7, University of Toronto8, University of Chicago9, Université de Montréal10, University of Alberta11, Laurentian University12, Czech Technical University in Prague13, Virginia Tech14, Drexel University15, National Autonomous University of Mexico16
TL;DR: In this article, the PICO Collaboration thanks SNOLAB for their exceptional laboratory space and technical support, and also thanks Fermi National Accelerator Laboratory (Contract No. DE-AC02-07CH11359) and Pacific Northwest National Laboratory for their support.
Abstract: The PICO Collaboration thanks SNOLAB for their exceptional laboratory space and technical support. We also thank Fermi National Accelerator Laboratory (Contract No. DE-AC02-07CH11359) and Pacific Northwest National Laboratory for their support. This work is supported by the National Sciences and Engineering Research Council of Canada (NSERC), the Canada Foundation for Innovation (CFI), the National Science Foundation (NSF) under the Grants No. PHY-1242637, No. PHY-0919526, No. PHY-1205987, and No. PHY-1506377 and by the U.S. Department of Energy under Award No. DE-SC-0012161. We also acknowledge the support of Department of Atomic Energy (DAE), Government of India, under the Center of AstroParticle Physics II project (CAPP-II) at Saha Institute of Physics (SINP); the Czech Ministry of Education, Youth and Sports (Grant No. LM2011027); the Spanish Ministerio de Economia y Competitividad, Consolider MultiDark (Grant No. CSD2009-00064) and DGAPA-UNAM through grant PAPIIT No. IA100316.
TL;DR: Searches for new resonances decaying into two photons in the ATLAS experiment at the CERN Large Hadron Collider are described in this article, based on protonproton collision data corresponding to two photons.
Abstract: Searches for new resonances decaying into two photons in the ATLAS experiment at the CERN Large Hadron Collider are described. The analysis is based on protonproton collision data corresponding to ...
TL;DR: Plasmonic MoO3-x@MoO3 nanosheets obtained from surface oxidation of MoO 3-x were employed as a SERS substrate for methylene blue detection and exhibit extraordinary sensitivity comparable to noble metals, which is attributed to shell-isolated electromagnetic enhancing by the plasmono-x core and elimination of the photocatalytic degradation by the MoO2 shell.
TL;DR: In this paper, the results on two-particle angular correlations for charged particles produced in pp collisions at a center-of-mass energy of 13 TeV were presented, and the data were taken with the CMS detector at the LHC.
Abstract: Results on two-particle angular correlations for charged particles produced in pp collisions at a center-of-mass energy of 13 TeV are presented. The data were taken with the CMS detector at the LHC and correspond to an integrated luminosity of about 270 nb^(−1). The correlations are studied over a broad range of pseudorapidity (|η| 2.0), near-side (Δϕ≈0) structure emerges in the two-particle Δη–Δϕ correlation functions. The magnitude of the correlation exhibits a pronounced maximum in the range 1.0
TL;DR: In this article, a search for single top quark production in the s channel in proton-proton collisions with the CMS detector at the CERN LHC in decay modes of the top quarks containing a muon or an electron in the final state is presented.
Abstract: A search is presented for single top quark production in the s channel in proton-proton collisions with the CMS detector at the CERN LHC in decay modes of the top quark containing a muon or an electron in the final state. The signal is extracted through a maximum-likelihood fit to the distribution of a multivariate discriminant defined using boosted decision trees to separate the expected signal contribution from background processes. Data collected at centre-of-mass energies of 7 and 8 TeV yield cross sections of 7.1 +/- 8.1 pb and 13.4 +/- 7.3 pb, respectively, and a best fit value of 2.0 +/- 0.9 for the combined ratio of the measured and expected values. The signal significance is 2.5 standard deviations, and the upper limit on the rate relative to the standard model expectation is 4.7 at 95% confidence level.
TL;DR: In this article, an inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment, where first and second generation leptoquarks were sought in events with two electrons (muons) and two or more jets.
Abstract: An inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment. Scalar leptoquarks, pair-produced in pp collisions at √s = 13 TeV at the large hadron collider, have been considered. An integrated luminosity of 3.2 fb−1, corresponding to the full 2015 dataset was used. First (second) generation leptoquarks were sought in events with two electrons (muons) and two or more jets. The observed event yield in each channel is consistent with Standard Model background expectations. The observed (expected) lower limits on the leptoquark mass at 95% confidence level are 1100 and 1050 GeV (1160 and 1040 GeV) for first and second generation leptoquarks, respectively, assuming a branching ratio into a charged lepton and a quark of 100%. Upper limits on the aforementioned branching ratio are also given as a function of leptoquark mass. Compared with the results of earlier ATLAS searches, the sensitivity is increased for leptoquark masses above 860 GeV, and the observed exclusion limits confirm and extend the published results.
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam2 +2287 more•Institutions (178)
TL;DR: In this article, the angular distribution and the differential branching fraction of the decay B0 to K*0(892) mu mu are studied using data corresponding to an integrated luminosity of 20.5 inverse femtobarns collected with the CMS detector at the LHC in pp collisions at sqrt(s) = 8 TeV.
TL;DR: In this paper, a search for a Higgs boson produced via vector-boson fusion and decaying into invisible particles is presented, using 20.3 fb−1 of proton-proton collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the LHC.
Abstract: A search for a Higgs boson produced via vector-boson fusion and decaying into invisible particles is presented, using 20.3 fb−1 of proton-proton collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the LHC. For a Higgs boson with a mass of 125 GeV, assuming the Standard Model production cross section, an upper bound of 0.28 is set on the branching fraction of H → invisible at 95% confidence level, where the expected upper limit is 0.31. The results are interpreted in models of Higgs-portal dark matter where the branching fraction limit is converted into upper bounds on the dark-matter-nucleon scattering cross section as a function of the dark-matter particle mass, and compared to results from the direct dark-matter detection experiments.
TL;DR: In this paper, measurements of W(+/-)Z production in pp collisions at a center-of-mass energy of 8 TeV were presented, where the gauge bosons were reconstructed using their leptonic decay modes into electrons and m...
Abstract: This paper presents measurements of W(+/-)Z production in pp collisions at a center-of-mass energy of 8 TeV. The gauge bosons are reconstructed using their leptonic decay modes into electrons and m ...
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam2 +2239 more•Institutions (171)
TL;DR: In this paper, a search for the resonant production of high-mass photon pairs is presented based on samples of proton-proton collision data collected by the CMS experiment at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 3.3 fb(-1).
Abstract: A search for the resonant production of high-mass photon pairs is presented. The analysis is based on samples of proton-proton collision data collected by the CMS experiment at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 3.3 fb(-1), respectively. The interpretation of the search results focuses on spin-0 and spin-2 resonances with masses between 0.5 and 4 TeV and with widths, relative to the mass, between 1.4 x 10(-4) and 5.6 x 10(-2). Limits are set on scalar resonances produced through gluon-gluon fusion, and on Randall-Sundrum gravitons. A modest excess of events compatible with a narrow resonance with a mass of about 750 GeV is observed. The local significance of the excess is approximately 3.4 standard deviations. The significance is reduced to 1.6 standard deviations once the effect of searching under multiple signal hypotheses is considered. More data are required to determine the origin of this excess.
TL;DR: In this paper, the authors present a survey of NSF projects in the European Union and the United States of America, including the following countries: Austria, Australia, Germany, Austria, Belgium, Canada, Czech Republic, Denmark, Netherlands, Norway, Portugal, Slovenia, Spain, Sweden, Switzerland, Turkey, United Kingdom, United States, Netherlands and Switzerland.
Abstract: ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWF, Austria; FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq, Brazil; FAPESP, Brazil; NSERC, Canada; NRC, Canada; CFI, Canada; CERN; CONICYT, Chile; CAS, China; MOST, China; NSFC, China; COLCIEN-CIAS, Colombia; MSMT CR, Czech Republic; MPO CR, Czech Republic; VSC CR, Czech Republic; DNRF, Denmark; DNSRC, Denmark; Lundbeck Foundation, Denmark; EPLANET; ERC; NSRF; European Union; IN2P3-CNRS, France; CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, Germany; DFG, Germany; HGF, Germany; MPG, Germany; AvH Foundation, Germany; GSRT, Greece; NSRF, Greece; ISF, Israel; MINERVA, Israel; GIF, Israel; DIP, Israel; Benoziyo Center, Israel; INFN, Italy; MEXT, Japan; JSPS, Japan; CNRST, Morocco; FOM, Netherlands; NWO, Netherlands; BRF, Norway; RCN, Norway; MNiSW, Poland; GRICES, Portugal; FCT, Portugal; MERYS (MECTS), Romania; MES of Russia; ROSATOM, Russian Federation; JINR; MSTD, Serbia; MSSR, Slovakia; ARRS, Slovenia; MIZS, Slovenia; DST/NRF, South Africa; MICINN, Spain; SRC, Sweden; Wallenberg Foundation, Sweden; SER, Switzerland; SNSF, Switzerland; Canton of Bern, Switzerland; Canton of Geneva, Switzerland; NSC, Taiwan; TAEK, Turkey; STFC, United Kingdom; Royal Society, United Kingdom; Leverhulme Trust, United Kingdom; DOE, United States of America; NSF, United States of America
Vardan Khachatryan, Albert M. Sirunyan, Armen Tumasyan, Wolfgang Adam1 +2369 more•Institutions (184)
TL;DR: In this article, a search for fermionic top quark partners T of charge 2/3 was carried out in proton-proton collisions corresponding to an integrated luminosity of 19.7 inverse femtobarns collected at a center-of-mass energy of sqrt(s) = 8 TeV with the CMS detector at the LHC.
Abstract: A search for fermionic top quark partners T of charge 2/3 is presented. The search is carried out in proton-proton collisions corresponding to an integrated luminosity of 19.7 inverse femtobarns collected at a center-of-mass energy of sqrt(s) = 8 TeV with the CMS detector at the LHC. The T quarks are assumed to be produced strongly in pairs and can decay into tH, tZ, and bW. The search is performed in five exclusive channels: a single-lepton channel, a multilepton channel, two all-hadronic channels optimized either for the bW or the tH decay, and one channel in which the Higgs boson decays into two photons. The results are found to be compatible with the standard model expectations in all the investigated final states. A statistical combination of these results is performed and lower limits on the T quark mass are set. Depending on the branching fractions, lower mass limits between 720 and 920 GeV at 95% confidence level are found. These are among the strongest limits on vector-like T quarks obtained to date.
TL;DR: The Compact Linear Collider (CLIC) is a multi-teV high-luminosity linear e+e-collider under development as mentioned in this paper, which is foreseen to be built and operated in a staged approach with three center-of-mass energy stages ranging from a few hundred GeV up to 3 TeV.
Abstract: The Compact Linear Collider (CLIC) is a multi-TeV high-luminosity linear e+e- collider under development. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in a staged approach with three centre-of-mass energy stages ranging from a few hundred GeV up to 3 TeV. The first stage will focus on precision Standard Model physics, in particular Higgs and top-quark measurements. Subsequent stages will focus on measurements of rare Higgs processes, as well as searches for new physics processes and precision measurements of new states, e.g. states previously discovered at LHC or at CLIC itself. In the 2012 CLIC Conceptual Design Report, a fully optimised 3 TeV collider was presented, while the proposed lower energy stages were not studied to the same level of detail. This report presents an updated baseline staging scenario for CLIC. The scenario is the result of a comprehensive study addressing the performance, cost and power of the CLIC accelerator complex as a function of centre-of-mass energy and it targets optimal physics output based on the current physics landscape. The optimised staging scenario foresees three main centre-of-mass energy stages at 380 GeV, 1.5 TeV and 3 TeV for a full CLIC programme spanning 22 years. For the first stage, an alternative to the CLIC drive beam scheme is presented in which the main linac power is produced using X-band klystrons.
Vardan Khachatryan1, Robin Erbacher2, C. A. Carrillo Montoya3, Wagner Carvalho4 +2303 more•Institutions (174)
TL;DR: In this paper, the authors describe the algorithms used by the CMS experiment to reconstruct and identify tau to hadrons + tau neutrino decays during Run 1 of the LHC.
Abstract: This paper describes the algorithms used by the CMS experiment to reconstruct and identify tau to hadrons + tau neutrino decays during Run 1 of the LHC. The performance of the algorithms is studied in proton-proton collisions recorded at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 inverse femtobarns. The algorithms achieve an identification efficiency of 50-60%, with misidentification rates for quark and gluon jets, electrons, and muons between per mille and per cent levels.
TL;DR: In this article, a search for a high-mass Higgs boson H is performed in the H -> WW -> l nu l nu and H-> WW-> l nu qq decay channels using pp collision data corresponding to an integrated luminosity.
Abstract: A search for a high-mass Higgs boson H is performed in the H -> WW -> l nu l nu and H -> WW -> l nu qq decay channels using pp collision data corresponding to an integrated luminosity o ...
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2242 more•Institutions (139)
TL;DR: A search for narrow resonances decaying into dijet final states is performed on data from proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 18.8 fb^{-1}.
Abstract: A search for narrow resonances decaying into dijet final states is performed on data from proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 18.8 fb(-1). The data were collected with the CMS detector using a novel technique called data scouting, in which the information associated with these selected events is much reduced, permitting collection of larger data samples. This technique enables CMS to record events containing jets at a rate of 1 kHz, by collecting the data from the high-level-trigger system. In this way, the sensitivity to low-mass resonances is increased significantly, allowing previously inaccessible couplings of new resonances to quarks and gluons to be probed. The resulting dijet mass distribution yields no evidence of narrow resonances. Upper limits are presented on the resonance cross sections as a function of mass, and compared with a variety of models predicting narrow resonances. The limits are translated into upper limits on the coupling of a leptophobic resonance Z'(B) to quarks, improving on the results obtained by previous experiments for the mass range from 500 to 800 GeV.
TL;DR: Results of a search for new phenomena in events with at least three photons are reported, with limits at the 95 % confidence level on new phenomena presented based on the rate of events in an inclusive signal region and a restricted signal region targeting the rare decay of the Higgs boson.
Abstract: Results of a search for new phenomena in events with at least three photons are reported. Data from proton-proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated lumi ...