1 TOP2006 Workshop Coimbra, Portugal Jan,2006 Top quark reconstruction in ATLAS V. Kostyukhin INFN Genova on behalf of ATLAS collaboration.

Slides:



Advertisements
Similar presentations
03/31/2006 DOSAR Workshop at UTA Pat Skubic (OCHEP) OCHEP Physics Interests Pat Skubic, for the Oklahoma Center for High Energy Physics Introduction Physics.
Advertisements

Current limits (95% C.L.): LEP direct searches m H > GeV Global fit to precision EW data (excludes direct search results) m H < 157 GeV Latest Tevatron.
Electroweak b physics at LEP V. Ciulli INFN Firenze.
14 Sept 2004 D.Dedovich Tau041 Measurement of Tau hadronic branching ratios in DELPHI experiment at LEP Dima Dedovich (Dubna) DELPHI Collaboration E.Phys.J.
Summary of Results and Projected Sensitivity The Lonesome Top Quark Aran Garcia-Bellido, University of Washington Single Top Quark Production By observing.
September 27, 2005FAKT 2005, ViennaSlide 1 B-Tagging and ttH, H → bb Analysis on Fully Simulated Events in the ATLAS Experiment A.H. Wildauer Universität.
Summary of Results and Projected Precision Rediscovering the Top Quark Marc-André Pleier, Universität Bonn Top Quark Pair Production and Decay According.
Top Turns Ten March 2 nd, Measurement of the Top Quark Mass The Low Bias Template Method using Lepton + jets events Kevin Black, Meenakshi Narain.
Kevin Black Meenakshi Narain Boston University
Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 High Level Trigger for the ttH channel in fully hadronic decay at LHC with the CMS detector.
Sept 30 th 2004Iacopo Vivarelli – INFN Pisa FTK meeting Z  bb measurement in ATLAS Iacopo Vivarelli, Alberto Annovi Scuola Normale Superiore,University.
Introduction to Single-Top Single-Top Cross Section Measurements at ATLAS Patrick Ryan (Michigan State University) The measurement.
On the Trail of the Higgs Boson Meenakshi Narain.
S. Martí i García Liverpool December 02 1 Selection of events in the all-hadronic channel S. Martí i García CDF End Of Year Review Liverpool / December.
1 Hadronic In-Situ Calibration of the ATLAS Detector N. Davidson The University of Melbourne.
ADR for Massimiliano Chiorboli Universita’ and INFN Catania
1 Top Quark Pair Production at Tevatron and LHC Andrea Bangert, Young Scientist Workshop, , Ringberg Castle.
Measurement of B (D + →μ + ν μ ) and the Pseudoscalar Decay Constant f D at CLEO István Dankó Rensselaer Polytechnic Institute representing the CLEO Collaboration.
Tau Jet Identification in Charged Higgs Search Monoranjan Guchait TIFR, Mumbai India-CMS collaboration meeting th March,2009 University of Delhi.
W properties AT CDF J. E. Garcia INFN Pisa. Outline Corfu Summer Institute Corfu Summer Institute September 10 th 2 1.CDF detector 2.W cross section measurements.
Irakli Chakaberia Final Examination April 28, 2014.
Jet Studies at CMS and ATLAS 1 Konstantinos Kousouris Fermilab Moriond QCD and High Energy Interactions Wednesday, 18 March 2009 (on behalf of the CMS.
Simulation Calor 2002, March. 27, 2002M. Wielers, TRIUMF1 Performance of Jets and missing ET in ATLAS Monika Wielers TRIUMF, Vancouver on behalf.
1 A Preliminary Model Independent Study of the Reaction pp  qqWW  qq ℓ qq at CMS  Gianluca CERMINARA (SUMMER STUDENT)  MUON group.
Associated top Higgs search: with ttH (H  bb) Chris Collins-Tooth, 17 June 2008.
2004 Xmas MeetingSarah Allwood WW Scattering at ATLAS.
1 Realistic top Quark Reconstruction for Vertex Detector Optimisation Talini Pinto Jayawardena (RAL) Kristian Harder (RAL) LCFI Collaboration Meeting 23/09/08.
W+jets and Z+jets studies at CMS Christopher S. Rogan, California Institute of Technology - HCP Evian-les-Bains Analysis Strategy Analysis Overview:
1 Top Quark Pair Production at Tevatron and LHC Andrea Bangert, Herbstschule fuer Hochenergiephysik, Maria Laach, September 2007.
August 30, 2006 CAT physics meeting Calibration of b-tagging at Tevatron 1. A Secondary Vertex Tagger 2. Primary and secondary vertex reconstruction 3.
Commissioning Studies Top Physics Group M. Cobal – University of Udine ATLAS Week, Prague, Sep 2003.
HERA-LHC, CERN Oct Preliminary study of Z+b in ATLAS /1 A preliminary study of Z+b production in ATLAS The D0 measurement of  (Z+b)/  (Z+jet)
C. K. MackayEPS 2003 Electroweak Physics and the Top Quark Mass at the LHC Kate Mackay University of Bristol On behalf of the Atlas & CMS Collaborations.
Possibility of tan  measurement with in CMS Majid Hashemi CERN, CMS IPM,Tehran,Iran QCD and Hadronic Interactions, March 2005, La Thuile, Italy.
Measurement of b-tagging Fake rates in Atlas Data M. Saleem * In collaboration with Alexandre Khanov** F. Raztidinova**, P.Skubic * *University of Oklahoma,
B-Tagging Algorithms for CMS Physics
FIMCMS, 26 May, 2008 S. Lehti HIP Charged Higgs Project Preparative Analysis for Background Measurements with Data R.Kinnunen, M. Kortelainen, S. Lehti,
Measurements of Top Quark Properties at Run II of the Tevatron Erich W.Varnes University of Arizona for the CDF and DØ Collaborations International Workshop.
Physics at LHC Prague, 6-12 July, 2003 R. Kinnunen Helsinki Institute of Physics A/H ->  and H + ->  in CMS R. Kinnunen Physics at LHC Prague July 6.
INCLUSIVE STANDARD MODEL HIGGS SEARCHES HIGGS SEARCHES WITH ATLAS Francesco Polci LAL Orsay On behalf of the ATLAS collaboration. SUSY08 – Seoul (Korea)
Study of pair-produced doubly charged Higgs bosons with a four muon final state at the CMS detector (CMS NOTE 2006/081, Authors : T.Rommerskirchen and.
B. Resende Top WG 28/10/05 Polarization studies in ttbar events 1 Polarization studies in tt events with full simulation 1.Physics motivations 2.Full simulation.
Susan Burke DØ/University of Arizona DPF 2006 Measurement of the top pair production cross section at DØ using dilepton and lepton + track events Susan.
October 2011 David Toback, Texas A&M University Research Topics Seminar1 David Toback Texas A&M University For the CDF Collaboration CIPANP, June 2012.
1 Measurement of the Mass of the Top Quark in Dilepton Channels at DØ Jeff Temple University of Arizona for the DØ collaboration DPF 2006.
06/2006I.Larin PrimEx Collaboration meeting  0 analysis.
Top quarks at the LHC: the early days Detector commissioning and first results T. Wengler Standard Model workshop UCL, London, 31 March 09.
Summary of Commissioning Studies Top Physics Group M. Cobal, University of Udine Top Working Group, CERN October 29 th, 2003.
Régis Lefèvre (LPC Clermont-Ferrand - France)ATLAS Physics Workshop - Lund - September 2001 In situ jet energy calibration General considerations The different.
Jessica Levêque Rencontres de Moriond QCD 2006 Page 1 Measurement of Top Quark Properties at the TeVatron Jessica Levêque University of Arizona on behalf.
La Thuile, March, 15 th, 2003 f Makoto Tomoto ( FNAL ) Prospects for Higgs Searches at DØ Makoto Tomoto Fermi National Accelerator Laboratory (For the.
Background Shape Study for the ttH, H  bb Channel Catrin Bernius First year talk 15th June 2007 Background Shape Study for the ttH 0, H 0  bb Channel.
1 UCSD Meeting Calibration of High Pt Hadronic W Haifeng Pi 10/16/2007 Outline Introduction High Pt Hadronic W in TTbar and Higgs events Reconstruction.
Search for the Higgs in ttH (H  bb) Chris Collins-Tooth.
V. Pozdnyakov Direct photon and photon-jet measurement capability of the ATLAS experiment at the LHC Valery Pozdnyakov (JINR, Dubna) on behalf of the HI.
I'm concerned that the OS requirement for the signal is inefficient as the charge of the TeV scale leptons can be easily mis-assigned. As a result we do.
Viktor Veszpremi Purdue University, CDF Collaboration Tev4LHC Workshop, Oct , Fermilab ZH->vvbb results from CDF.
Marcello Barisonzi First results of AOD analysis on t-channel Single Top DAD 30/05/2005 Page 1 AOD on Single Top Marcello Barisonzi.
Search for Standard Model Higgs in ZH  l + l  bb channel at DØ Shaohua Fu Fermilab For the DØ Collaboration DPF 2006, Oct. 29 – Nov. 3 Honolulu, Hawaii.
Royal Holloway Department of Physics Top quark pair cross section measurements in ATLAS Michele Faucci Giannelli On behalf of the ATLAS collaboration.
Eric COGNERAS LPC Clermont-Ferrand Prospects for Top pair resonance searches in ATLAS Workshop on Top Physics october 2007, Grenoble.
American Physical Society Meeting St. Louis, MO April th, 2008 Measuring the top mass at DØ using the Ideogram Method Amnon Harel
B Tagging Efficiency and Mistag Rate Measurement in ATLAS
Higgs → t+t- in Vector Boson Fusion
Prospects for sparticle reconstruction at new SUSY benchmark points
Susan Burke, University of Arizona
Northern Illinois University / NICADD
Study of Top properties at LHC
Measurement of b-jet Shapes at CDF
Presentation transcript:

1 TOP2006 Workshop Coimbra, Portugal Jan,2006 Top quark reconstruction in ATLAS V. Kostyukhin INFN Genova on behalf of ATLAS collaboration

V. Kostyukhin - INFN / Genova 2 TOP2006 Workshop Coimbra, Portugal Jan,2006 General remarks   Large production cross section for ~830pb  8.3 millions top pairs for one year of low luminosity. ~300pb for single top production.   Statistical error of top mass measurement is <100 MeV after one year of ATLAS running. Systematic is  1 GeV!!!   For many top studies statistics is not an issue. Systematic is the main problem. Later I will give a description of ATLAS efforts on top quark reconstruction with emphasis on decreasing the systematical errors and keeping them under control.

V. Kostyukhin - INFN / Genova 3 TOP2006 Workshop Coimbra, Portugal Jan,2006 Full simulation study of  jjbbl Jet reconstruction Three methods have been tested for top reconstruction: 1. 1.Cone R= Cone R= K  (d=1) Scale factor for K  d=1 makes it similar to cone with R=0.7. Key issue for any top studies is jet reconstruction

V. Kostyukhin - INFN / Genova 4 TOP2006 Workshop Coimbra, Portugal Jan,2006 Bquark-jet distance K  (d=1) Bquark-jet distance ConeR=0.7 Bquark-jet distance ConeR=0.4 Cone R=0.4 provides significantly better angular resolution with respect to b-quark direction!!! Bquark-jet distance   B-tagging performance is affected.   Impact on precision of kinematical reconstruction is not clear ( t-quark decays to partons) For the moment cone R=0.4 algorithm looks the best choice for top-quark reconstruction (in dense jet environment) K  algorithm with d=0.5 might be studied as another option.

V. Kostyukhin - INFN / Genova 5 TOP2006 Workshop Coimbra, Portugal Jan,2006 Jet calibration A problem to measure the QCD object (quarks, gluons) properties based on detector response can be divided into 2 parts: 1) 1)Detector corrections ( give energy of stable particles hitting detector at given region based on detector signal ): Calorimeter cracks, noncompensation, nonuniformity,  -dependence, dead material, noise, longitudinal energy leakage, etc… 2) 2)Physics corrections (give properties of parton which produces the jet): Energy leak outside jet cone, semyleptonic decays, jet masses, pileup, etc. Step (1) is well understood/developed Cell weighting method, testbeam data, cosmics and Cs calibration, detector weighing for amount of material estimations, data based single particle calibrations, etc… (a lot of information but outside the scope of current presentation) Step (2) is still obscure not clear which corrections must be applied to obtain parton properties from jet properties.

V. Kostyukhin - INFN / Genova 6 TOP2006 Workshop Coimbra, Portugal Jan,2006 P  b-jet >100 gev fast simulation Jets with detected muon Leptonic decays of B(D) in jets produce a strong shift of jet energy with a long tail. Jets without muon All jets   Worsening of b-jet energy resolution (additional to calorimeter performance)   Nongaussian shapes of all kinematical distributions with b-jets   Strong influence on reconstructed top kinematical parameters (  2 dependence…)  B-jet calibration: lepton in jet

V. Kostyukhin - INFN / Genova 7 TOP2006 Workshop Coimbra, Portugal Jan,2006 B-jet calibration: lepton in jet E b-jet – E initial b-quark for 100<E b-quark <105, |  | < 0.6 full simulation All b jets (b  µ) jets Taking into account a huge produced number of t-quark it seems that the best solution for precise top physics is to remove from analysis any jet with detected lepton inside! Up to 50% of the statistics might be lost depending on lepton in jet detection efficiency (30% for single top) but systematics will be greatly reduced For the processes where statistics is important (e.g. “single top”, FCNC) some other solutions can be used if needed (separate calibration, energy correction, etc…)

V. Kostyukhin - INFN / Genova 8 TOP2006 Workshop Coimbra, Portugal Jan,2006 Jet-parton difference Jet is a collection of particles. Lorentz boost gives different results for the collection of particles and single massless particle with the same total 3-momentum. M M m0m0 m=0 11 22  1  2 difference ~2% for m=8 GeV and M=80 GeV (W mass) A simplest way to take into account a fact that jet is a collection of particles is to introduce jet mass.   Jet direction and parton direction never coincide (except for specially chosen reference systems).   P  based jet calibration (Z+jets,…) doesn’t coincide with mass based (W mass). First one calibrates 3-momentum and second calibrates jet energy.   Jet-parton differences are at percent level but to get rid of this systematics in kinematical calculations (masses, angles) in a natural way one has to use jet mass. Simple example Consequences

V. Kostyukhin - INFN / Genova 9 TOP2006 Workshop Coimbra, Portugal Jan,2006 Light jet calibration A natural way to calibrate light jet energy for top physics is W peak in events. Jet energy (not direction!!!) is scaled based on W mass shift E Part / E E part before after MwMw E jet / E parton E parton E jet Due to changing jet energy resolution and non-flat jet energy spectrum one can make flat either E jet or E parton dependency BUT NOT BOTH TOGETHER!!! E parton calibration produce a P  dependent top mass estimation. Better way is to flatten E jet dependance.

V. Kostyukhin - INFN / Genova 10 TOP2006 Workshop Coimbra, Portugal Jan,2006 Jet calibration summary Seems important for precise top physics: 1. 1.Special treatment for b-jets with lepton inside (removal or special correction???) Using jet mass for any kinematical reconstruction Difference between P  -based and mass-based (W,Z peaks) jet calibrations. It seems that P  -based jet calibration always gives a shifted estimation of mass Decoupling of jet energy correction from jet energy resolution Correction for density of jet environments (leaks between jets) ATLAS has a clear strategy for detector based jet energy corrections Still not clear how to reconstruct parton energy/direction based on jet properties (physics corrections). Not a problem for QCD jet properties themselves, but a big problem if one needs to measure properties of parton system (e.g. top quark mass) with a precision <1%.

V. Kostyukhin - INFN / Genova 11 TOP2006 Workshop Coimbra, Portugal Jan,2006 B-tagging Several algorithms based on track impact parameters and secondary vertex in jet presence are available in ATLAS LogL 2. 2.ALEPH style 3. 3.Simple counting (under development…) Primary vertex Secondary vertex in jet Currently most powerful ATLAS algorithm is based on LogL approach and is a combination of different taggers : 2D impact + Z impact +SV+… (leptons in jet, jet shape, etc… in future)

V. Kostyukhin - INFN / Genova 12 TOP2006 Workshop Coimbra, Portugal Jan,2006 B-tagging For top reconstruction b-tagging is needed to remove physical (W+jets, Z+jets) and combinatorial background. Also it’s needed to distinguish between top pair and single top production. B-tagging performance is usually characterized by 2 numbers: b-jet tagging efficiency Light jet rejection, These numbers are unambiguous only when there is a single jet in event, either b-jet or light one!!! definitions For multijet events like top pair production these numbers strongly depends on definitions: - what is a maximal allowed distance between jet direction and b-quark for “b-jet”, - what is a minimal allowed distance between jet direction and b-quark for “light quark jet”. R u (ε b =50%) (raw) R u (ε b =60%) (raw) R u (ε b =50%) (purified) R u (ε b =60%) (purified) SV1+IP3D505 ± ± 3773 ± ± 5 Example of rejections for fully simulated tt events “Raw” – minimal distance between light jet and b/c quark is 0.3 “Purified” – minimal distance between light jet and b/c quark is 0.8

V. Kostyukhin - INFN / Genova 13 TOP2006 Workshop Coimbra, Portugal Jan,2006 B-tagging - another example ttjj-system, final state l 4j2b (6 jets) ATLFAST(truth) jets, 3 layers pixel detector, no pileup,  R(jet-jet)=0.7  b =50% R u =320  b =60% R u =160 + no b-quark in a cone  R=0.6 around light quark jet  b =50% R u =2500  b =60% R u =680 B-tagging performance is strongly dependent on jet density and cuts used for definition of “b” jet and “light” jets. For multijet event there is a big probability that near a “light quark jet” there is a b-quark. This decreases the “light jet rejection” of b-tagging in comparison with “single jet” event. B-tagging efficiency is also affected because the angular accuracy of jet reconstruction depends on jet amount due to jet overlap. It seems that b-tagging performance must be compared with data (calibrated) on well separated jets only (preferably in “single jet” events). Then one should rely on MonteCarlo to propagate this performance to multijet events to be able to estimate the “event selection efficiency” with b-tagging. !!! Great sensitivity to gluon splitting and occasional coincidence between light jet direction and b-quark nearby Not a problem for MC but what about data???

V. Kostyukhin - INFN / Genova 14 TOP2006 Workshop Coimbra, Portugal Jan,2006 B-tagging SV1+IP3D IP3D IP2D Lifetime2D lhSig Light jet rejection vs b-tag efficiency for ttH, ttjj events (no purification of light jet) R u (ε b =50%) R u (ε b =60%) R u (ε b =70%) 610 ± ± 353 SV1+IP3D IP2D SV1+IP3D

V. Kostyukhin - INFN / Genova 15 TOP2006 Workshop Coimbra, Portugal Jan,2006 B-tagging It’s very difficult to predict a process (not jet!!!) selection efficiency with b-tagging because it depends on: 1. 1.Jet density 2. 2.Jet P  and , which are process selection cuts dependent 3. 3.Jet algorithm 4. 4.Time dependent detector and luminosity conditions For the moment ATLAS doesn’t have a well established strategy for b-tagging performance calibration on real data and its monitoring with time. Work just started… ATLAS b-tagging is very effective but… 99.5% 99% 98.5% 98% Expected events for 10 fb -1 b-jet sample purity First attempt of b-jet selection from tt  bbjjl events for b-tagging calibration

V. Kostyukhin - INFN / Genova 16 TOP2006 Workshop Coimbra, Portugal Jan,2006 Kinematical constraint fit for tt J1J1 J2J2 Kinematical fit with constraints is able to restore a complete topology of  bbjjl decay.   Equal t-masses constraint:   W-masses constraints: W mass constraint determines angle between lepton and neutrino  ambiguous neutrino direction  Equal top masses constraint determines second angle between neutrino and b-quark  no ambiguity in neutrino direction 

V. Kostyukhin - INFN / Genova 17 TOP2006 Workshop Coimbra, Portugal Jan,2006 Kinematical constraint fit for tt   Reduce significantly a sensitivity to light jet calibration due to W mass constraint.   Fit  2 is a powerful tool to reject combinatorial and physical background.   Method is applicable both for “lepton+jets” and “6 jets” channels of decay. W mass term works well for ideal light jet calibration. W mass constraint is more robust and works even for nonprecise light jet calibration! Fit variables are jet energies (not directions!!! ) and z component of neutrino momentum. 3 jet mass with W mass constraint Top mass after complete constraint fit

V. Kostyukhin - INFN / Genova 18 TOP2006 Workshop Coimbra, Portugal Jan,2006 ATLAS commissioning   Can we see top signal during ATLAS startup?   If so – what can be done with it? “Initial” ATLAS 1) Tracking and muon systems are not well aligned. 2) Hadron calorimeter response is uniform up to 1% level (Cs source calibration and monitor system), but not correctly scaled. 3) LAr electromagnetic calorimeter response is known up to 1-2% precision. 4) Trigger thresholds are increased to reduce rate. Top quark reconstruction related issues: 1) Jets are reconstructed with good resolution but shifted energy. 2) Leptons (e and  ) are detectable but again with incorrect energy. 3) B-tagging efficiency is significantly reduced if present at all. Reference is 100 pb -1 (a few days of accelerator work depending on initial luminosity)

V. Kostyukhin - INFN / Genova 19 TOP2006 Workshop Coimbra, Portugal Jan,2006 “Initial” top-quark 1 lepton P T > 20 GeV Missing energy E T > 20 GeV 4 jets(R=0.4,|  | 40 GeV Selection efficiency = ~4.5% (~11pb) “Standard” ATLAS offline selection for this mode without b-tagging: A simplest accessible mode is  jjbbl (~250 pb production cross section) Trigger – isolated lepton (e,  ) 1100 ev for 100 pb -1 Top reconstruction efficiency ~70%. ~750 ev in the peak for 100 pb -1. Top reconstruction is extremely simple – one needs to select 3 jets with maximal One may select 2 jets out 3 top quark jets again with highest This selection gives W peak.

V. Kostyukhin - INFN / Genova 20 TOP2006 Workshop Coimbra, Portugal Jan,2006 “Initial” top-quark Main background for  jjbbl is W+jets process. Other background contributions are small. and W+jets for 150 pb -1 Further combinatorial and physical background reduction can be obtained with constraint fit for top pair:  2 tt signal  2 W+jets “Initial” top signal is clearly visible even with background after a few days of ATLAS running. tt only tt only  2 <6 tt only  2 >6 In a few weeks (trigger conditions dependent) after ATLAS startup a rather clean sample of several thousands top-quarks will be available for physics measurements and detector calibration

V. Kostyukhin - INFN / Genova 21 TOP2006 Workshop Coimbra, Portugal Jan,2006 Summary 1. 1.LHC is a real “top factory” and for many top related measurements the main issue is systematics Even with a limited ATLAS performance at startup it’s possible to see top quark signal for preliminary physics and calibration studies The needed level of systematical accuracy requires additional efforts in understanding of basic reconstruction algorithms performance Some ideas how to decrease the systematical errors in top reconstruction have been presented Let’s hope that very precise top physics measurements will be done at LHC.