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Jet reconstruction and spectroscopy at hadron colliders
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Europe/Rome
131 (INFN Pisa)
131
INFN Pisa
Polo Fibonacci
Largo B. Pontecorvo, 3
56127 Pisa
Paolo Azzurri
(Scuola Normale & INFN Pisa),
Fabrizio Scuri,
Giorgio Bellettini
(Dipartimento di Fisica),
Michele Cascella
(INFN, Sezione di Pisa)
Description
The workshop is intented to stimulate an open discussion on all technologies and methods used at hadron collider experiments to reconstruct jets, to set the energy scale and to make jet spectorscopy measurements.
Support
Participants
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- 1
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Overview PresentationsConvener: Vincenzo Cavasinni (University and INFN, Pisa)
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2
Effects of calorimeter peculiarities on the Jet Energy ScaleIt is well known that non-compensating calorimeters, such as the ones used in the general purpose experiments at the Tevatron and the LHC, offer particular problems for correctly reconstructing the energy deposited by single hadrons and jets. In this talk, I will review these problems, discuss the remedies usually employed, and offer possible alternatives.Speaker: Richard Wigmans (Texas Tech University)
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3
Jets in their habitatIn the talk I will cover recent aspects of jet reconstruction at the LHC. As an introduction I will start by addressing the need for a robust set of jet definitions and the progress that has been achieved in that direction over the last years. Then I will discuss various techniques, built on that robust set of jet definitions, that have been developed to improve jet reconstruction. In particular, I will show that jet areas can be used as a way to handle pile-up contamination and motivate the use of jet substructure to tag boosted particles.Speaker: Gregory Soyez (CEA Saclay)
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2
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10:40
Coffee break
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ATLAS & CMS OverviewConvener: Franco Bedeschi (University and INFN, Pisa)
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4
Jet measurements in ATLASThe ATLAS experiment at the Large Hadron Collider (LHC) features a multi-purpose detector system with nearly complete coverage of the solid angle around the proton-proton or heavy ion collisions. It collected nearly 40/pb of proton data in 2010, and resumed data taking in early Spring 2011. In this talk all aspects of jet physics, starting from jet reconstruction and calibration from the detector signals and the evaluation of the jet reconstruction performance with collision data, to the measurement of Standard Model (SM) physics and first access to exclusions of physics beyond the SM with jet final states, are presented. Among those are recently published results for the jet and di-jet cross-sections, the azimuthal correlation between jets in di-jet production, and results from other SM final state analysis involving jets. In addition, first results for new phase space limits for exclusions of new physics using jet final states are shown. Last but not least, the first results from jets in heavy ion collisions are briefly presented.Speaker: Peter Loch (University of Arizona)
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5
Overview of CMS performances and results with JetsThe performance of the Compact Muon Solenoid detector during the operation of the Large Hadron Collider with pp and HI collisions in 2010 will be reviewed. Selected results with emphasis on physics with jets will be presented, with an outlook to the 2011 data taking.Speaker: Roberto Tenchini (University of Pisa)
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4
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12:40
Lunch Break
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Jet Energy Scale and ResolutionConvener: Konstantinos Kousouris (Fermilab)
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7
Jet reconstruction and measurements in CMSWe present a summary of jet reconstruction and measurements of jet performance at CMS from the 2010 run. Examples of jet commissioning, and measurements of jet energy corrections and jet resolution along with their systematic uncertainty are shown. We also present studies of tagging boosted top quarks and W bosons using specialized jet algorithms.Speaker: Hartmut Stadie (Universität Hamburg)
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8
In-situ measurements of the Jet Energy Scale in ATLASHadron jets are the most commonly observed objects in p-p collisions at the Large Hadron Collider at CERN. Because of this, they are part of the final state of almost any process, and are an important probe in searches for extensions of the Standard Model. A precise knowledge of the energy calibration for jets is difficult to ascertain for a number of reasons, and is a necessary ingredient in the ATLAS experimental program. We will present in-situ techniques and results for the jet energy scale at ATLAS using recent collision data. We have demonstrated an understanding of the necessary jet energy corrections to within ~ 4% in the central region of the calorimeter.Speaker: Doug Schouten (Simon Fraser University (SFU))
- 9
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15:45
Coffee break
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QCD ResultsConvener: Roberto Carosi (University and INFN, Pisa)
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10
Inclusive jet cross section measurement in ATLASThe inclusive jet cross section has been measured in proton-proton collisions at a centre-of-mass energy of 7 TeV using the ATLAS detector at the LHC. The full 2010 dataset has been used, consisting of a total integrated luminosity of 37 pb-1 . The anti-kt algorithm is used to identify jets with two jet radius parameters, R = 0.4 and R = 0.6. Jet shapes measurements are performed to validate the models for parton shower, fragmentation into hadrons, and the underlying event contributions contained in the event generators. The inclusive jet cross section measurement is presented as a function of jet transverse momentum and rapidity, for jets with transverse momentum from 20 GeV to 1.5 TeV in a rapidity range |y| < 4.4. The data are compared to expectations based on next-to-leading order QCD corrected for non-perturbative effects. In addition to a validation of the theory in a new kinematic regime, the data also provide sensitivity to parton distribution functions in a region where they are currently poorly constrained.Speaker: Francesc Vives Vaque (Inst. de Fisica de Altas Energias (IFAE))
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11
Measurement of multi-jet cross-sections in proton-proton collisons at 7 TeV center-of-mass energyInclusive multi-jet production is studied using the ATLAS detector for pp collisions with a center-of-mass of 7 TeV. The data sample corresponds to an integrated luminosity of 2.43 pb-1, using the first pp data collected by the ATLAS detector in 2010. Results on multi-jet cross sections and angular distributions are presented and compared to both LO plus parton-shower Monte Carlo predictions and NLO QCD predictions.Speaker: Zinonas Zinonos ((University and INFN, Pisa))
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12
Jet and multijet results from CMSVarious jet measurements based on the 2010 data collected by the CMS experiment at a center-of-mass energy of 7 TeV are presented. Results from inclusive jet cross-sections, dijet mass spectra, dijet angular distributions, hadronic event shapes and the ratio of the 3 jet to 2 jet production cross-sections will be illustrated.Speaker: Konstantinos Kousouris (Fermilab)
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10
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Searches and New Physics with JetsConvener: Chiara Roda (University and INFN, Pisa)
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13
CMS new physics searches with jetsWe discuss the results of searches for various new physics phenomena with jets from the pp collisions at 7 TeV delivered by LHC and collected with the CMS detector in 2010. Final states with di-jets, multi-jets, jets+MET and jets+leptons are explored. In in many cases the searches set the most stringent limits on possible new physics phenomena.Speaker: Daniel Duggan (Rutgers University)
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14
Searches for new physics with jets in ATLASWe present the latest results of searches for new physics beyond the Standard Model with jets in the final state using the ATLAS detector. These analysis are performed with the full LHC 2010 data from proton-proton collisions at center-of-mass energy of 7TeV. The results are based on the integrated luminosity between 33 to 37 pb-1 depending on the analysis. No significant discrepancy is found with the expected Standard Model predictions. However, new limits on various models are set beyond the reach of previous experiments.Speaker: Belen Salvachua (ANL)
- 15
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13
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Top Quark Physics with JetsConvener: Sandra Leone (INFN Pisa)
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16
Top quark physics at CDFTop quark physics is one of the most important successes of the concluding Tevatron program. In this talk, a summary of the most recent measurements of top quark properties, including the mass and its Winter 2011 average, will be presented. Some common techniques and discussion of major systematic uncertainties for top measurements will also be presented. Furthermore, the possibility to use top samples for future improvement of the jet calibration and resolution for b and light jets will be discussed as well.Speaker: George Velev (FNAL)
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17
Top mass reconstruction in ATLASThe top-quark mass is a fundamental parameter of the Standard Model. After the discovery of the top quark, the measurements of its properties were of substantial interest. Within the framework of the SM, the top-quark mass can be used in combination with other electroweak precision measurements to constrain the mass of the yet unobserved Higgs boson. In the new era of the Large Hadron Collider (LHC), the first top quarks have been produced in Europe in proton-proton collisions at a center-of-mass energy of 7 TeV. The top-quark mass measurement of ATLAS in the so called lepton+jets channel with 35 pb−1 integrated luminosity will be presented. In this early data-taking period the largest uncertainty on this measurement comes from the knowledge of the jet energy scale. It will be shown how this uncertainty is determined and which methods are used for measuring the top-quark mass.Speaker: Andrea Neusiedl (University of Mainz)
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18
Top quark and ttbar mass measurements at CMSWe present measurements of the top quark mass and of the ttbar invariant mass using the 2010 data collected by the CMS detector in pp collisions at a center-of-mass energy of 7TeV, amounting to a total integrated luminosity of 36 pb-1.Speaker: Roberto Chierici (CNRS/IPNL)
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16
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10:30
Coffee break
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W/Z and HiggsConvener: Fabrizio Palla (University and INFN, Pisa)
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19
Use of the jet mass in the reconstruction of hadronic W and Z boson decays in the D0 experimentUse of the jet-mass variable can significantly improve the reach of searches for high-mass diboson resonances. Traditional searches for this process have focused on the purely leptonic final state to reduce contamination from the large QCD jet background. We show that the significance to diboson resonances can be enhanced when considering events with one or two leptons and at least one high transverse momentum jet, whose reconstructed mass is consistent with a W or Z boson decay. We will present the jet mass as a strong discriminating variable between QCD jets and W/Z boson initiated jets and the level to which this quantity is modeled by Monte Carlo simulations. We will illustrate this approach using the search for WW and WZ resonances with 5.4 fb-1 of DZero data.Speaker: Thomas Gadfort (BNL)
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20
W/Z + jets with the CMS detectorWe present a study of jet production in association with W and Z bosons in proton-proton collisions at ECM=7 TeV using the full 2010 data set collected by CMS corresponding to an integrated luminosity of 36+-4 pb-1. The production of vector bosons with jets provides a stringent and important test of perturbative QCD calculations, and is an important background in searches for new physics and for studies of the top quark. Jet reconstruction in this particular final state topology is also made more difficult by the presence of leptons from the vector boson decay in the final state. A precise measurement of the cross section and an understanding of lepton and jet kinematics is therefore essential. We report the normalized inclusive rates of jets produced as well as the ratios sigma(V+(n+1) jets)/sigma(V+n jets) and with a jet threshold of 30 GeV. We also present the first test of the Berends-Giele scaling at 7 TeV.Speaker: Massimo Nespolo (University and INFN, Padova)
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21
Methods and algorythms in CDF for diboson production in hadronic final statesA benchmark for Higgs discovery at the Tevatron is the diboson production in hadronic final states. Before every finding of the Higgs we have to show that we can re-discover this known Standard Model process. The same set of techniques used for Higgs can be tried on dibosons to see their effectiveness: jet reconstruction algorythms, b tagging methods, background reduction methods etc. I will review in this talk the latest set of methods and algorithms used to search for dibosons in hadronic final states.Speaker: Alexandru Rusu (Fermilab)
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22
Search for diboson production in the lepton + MET + bb channel in b-jet in final statesStudying diboson associated production in a final state with a lepton, neutrino, and bb-pair is important since the event topology of this process is the same as expected for associated production of a W and a Standard Model light-Higgs boson. Thus, we consider the search for Diboson production as a preliminary step towards the Higgs discovery. Here we present a search for WW/WZ in events with a lepton, missing transverse energy, and b-quark jets. A first attempt to improve the QCD and W+jets background modeling in this sample will be presented. In addition a new multivariate tagger to distinguish b-quark jets from light-quark jets is introduced. This study is an application of one of the diboson search methods discussed by V. Rusu. We expressly require events with a leptonically decayed W, and search for associated b-jets.Speaker: Marco Trovato (INFN, Pisa)
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19
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12:50
Lunch
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Inputs from TheoryConvener: Roberto Tenchini (Universita di Pisa)
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25
Experineces on QCD Monte Carlo simulations: a user point of view on the inclusive jet cross-section simulationsIn the last couple of years important progresses in the simulation of the QCD high pT processes have been carried out. In this talk, a review of the tools and techniques historically used to simulate QCD cross sections will be presented from a user point of view. The benchmark process selected for the discussion is the inclusive jet cross section. The talk will focus on the uncertainties of the Next to Leading Order (NLO) cross sections, on the strategies adopted to correct for the non perturbative effects such as the hadronization and the underlying event, and the new techniques derived during the last years to incorporate in a coherent way the NLO matrix elements in the Monte Carlo generators.Speaker: Paolo Francavilla (University and INFN, Pisa)
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26
LHC bounds on extra-large dimensionsWe will discuss the new dominant bounds that can be derived on the coefficient of the effective operator generated by tree-level graviton exchange in large extra dimensions from pp -> jj data at LHC: M_T > 2.1TeV (ATLAS after 3.1/pb of integrated luminosity), M_T > 3.4 TeV (CMS after 36/pb). We clarify the role of on-shell graviton exchange and compare the full graviton amplitude to data, setting bounds on the fundamental quantum-gravity scale.Speaker: Paolo Lodone (Scuola Normale Superiore, Pisa)
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16:15
Coffee brak
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