Measurement Of The C Jet Mistagging Efficiency In Ttover Bar Events Using Pp Collision Data At Square Roots
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| Author | : [Study Group] ATLAS Collaboration CERN |
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| Total Pages | : 0 |
| Release | : 2022 |
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Abstract: A technique is presented to measure the efficiency with which c-jets are mistagged as b-jets (mistagging efficiency) using tt ̄ events, where one of the W bosons decays into an electron or muon and a neutrino and the other decays into a quark-antiquark pair. The measurement utilises the relatively large and known W→cs branching ratio, which allows a measurement to be made in an inclusive c-jet sample. The data sample used was collected by the ATLAS detector at s√=13 TeV and corresponds to an integrated luminosity of 139 fb−1. Events are reconstructed using a kinematic likelihood technique which selects the mapping between jets and tt ̄ decay products that yields the highest likelihood value. The distribution of the b-tagging discriminant for jets from the hadronic W decays in data is compared with that in simulation to extract the mistagging efficiency as a function of jet transverse momentum. The total uncertainties are in the range 3-17%. The measurements generally agree with those in simulation but there are some differences in the region corresponding to the most stringent b-jet tagging requirement
| Author | : ATLAS Collaboration CERN |
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| Total Pages | : 0 |
| Release | : 2019 |
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Abstract: The algorithms used by the ATLAS Collaboration during Run 2 of the Large Hadron Collider to identify jets containing b-hadrons are presented. The performance of the algorithms is evaluated in the simulation and the efficiency with which these algorithms identify jets containing b-hadrons is measured in collision data. The measurement uses a likelihood-based method in a sample highly enriched in tt ̄ events. The topology of the t→Wb decays is exploited to simultaneously measure both the jet flavour composition of the sample and the efficiency in a transverse momentum range from 20 to 600 GeV. The efficiency measurement is subsequently compared with that predicted by the simulation. The data used in this measurement, corresponding to a total integrated luminosity of 80.5 fb−1, were collected in proton-proton collisions during the years 2015-2017 at a centre-of-mass energy s√= 13 TeV. By simultaneously extracting both the efficiency and jet flavour composition, this measurement significantly improves the precision compared to previous results, with uncertainties ranging from 1 to 8% depending on the jet transverse momentum
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| Total Pages | : 39 |
| Release | : 2011 |
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A new measurement of the inclusive production cross section for pp to t t-bar is performed at a center-of-mass energy of 7 TeV using data collected by the CMS experiment at the LHC. The analysis uses a data sample corresponding to an integrated luminosity of 36 inverse picobarns, and is based on the final state with one isolated, high transverse momentum muon or electron, missing transverse energy, and hadronic jets. The ttbar content of the selected events is enhanced by requiring the presence of at least one jet consistent with b-quark hadronization. The measured cross section is 150 +/- 9 (stat.) +/- 17 syst.) +/- 6 (lumi.) pb and is in agreement with higher-order QCD calculations. The combination of this measurement with a previous CMS result based on dileptons gives 154 +/- 17 (stat.+syst.) +/- 6 (lumi.) pb.
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| Release | : 2017 |
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The first measurement of the jet mass m[jet] of top quark jets produced in t t-bar events from pp collisions at sqrt(s) = 8 TeV is reported for the jet with the largest transverse momentum pt in highly boosted hadronic top quark decays. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 19.7 inverse femtobarns. The measurement is performed in the lepton+jets channel in which the products of the semileptonic decay t to bW with W to l nu where l is an electron or muon, are used to select t t-bar events with large Lorentz boosts. The products of the fully hadronic decay t to bW with W to q q'-bar are reconstructed using a single Cambridge-Aachen jet with distance parameter R=1.2, and pt>400 GeV. The t t-bar cross section as a function of m[jet] is unfolded at the particle level and is used to test the modelling of highly boosted top quark production. The peak position of the m[jet] distribution is sensitive to the top quark mass m[t], and the data are used to extract a value of m[t] to assess this sensitivity.
| Author | : Jacquelyn Kay Brosamer |
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| Total Pages | : 198 |
| Release | : 2016 |
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The transverse momentum and multiplicity of jets produced in top quark events are measured using 20.3 inverse fb of pp collision data at a center-of-mass energy of 8 tev. Jets are selected from top events requiring an opposite-charge $e\mu$ pair and two b-tagged jets in the final state. The data are corrected to obtain the particle-level fiducial cross section for additional jets with rank 1-4, where rank=1 is the leading additional jet. These distributions are used to obtain the extra jet multiplicity as a function of minimum jet pt threshold. The results are compared with several next to leading order Monte Carlo generators. The resulting measurements can be used to tune Monte Carlo QCD modelling and may also reduce associated modelling uncertainties for LHC top quark physics measurements.
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| Total Pages | : 68 |
| Release | : 1967 |
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| Author | : Heather L. Ray |
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| Total Pages | : 354 |
| Release | : 2004 |
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| Author | : Bradley Hubbard |
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| Total Pages | : 246 |
| Release | : 1989 |
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| Author | : Liaoyuan Huo |
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| Release | : 2012 |
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As one of the major mid-rapidity tracking devices of the STAR detector at the Relativistic Heavy-Ion Collider (RHIC), the Time Projection Chamber (TPC) plays an important role in measuring trajectory and energy of high energy charged particles in polarized proton-proton collision experiments. TPC's in-jet tracking efficiency represents the largest systematic uncertainty on jet energy scale at high transverse momentum, whose measurement contributes to the understanding of the spin structure of protons. The objective of this analysis is to get a better estimation of this systematic uncertainty, through methods of pure Monte-Carlo simulation and real- data embedding, in which simulated tracks are embedded into real-data events. Be- sides, simulated tracks are also embedded into Monte-Carlo events, to make a strict comparison for the uncertainty estimation. The result indicates that the unexplained part of the systematic uncertainty is reduced to 3.3%, from a previous quoted value of 5%. This analysis also suggests that future analysis, such as embedding jets into zero-bias real data and analysis with much higher event statistics, will benefit the understanding of the systematic uncertainty of the in-jet TPC tracking efficiency.
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| Total Pages | : 62 |
| Release | : 2016 |
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