Northern Illinois University / NICADD

Slides:



Advertisements
Similar presentations
Recent Results on the Possibility of Observing a Standard Model Higgs Boson Decaying to WW (*) Majid Hashemi University of Antwerp, Belgium.
Advertisements

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.
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
Top Physics at the Tevatron Mike Arov (Louisiana Tech University) for D0 and CDF Collaborations 1.
Introduction to Single-Top Single-Top Cross Section Measurements at ATLAS Patrick Ryan (Michigan State University) The measurement.
Single-Top Cross Section Measurements at ATLAS Patrick Ryan (Michigan State University) Introduction to Single-Top The measurement.
Top Results at CDF Yen-Chu Chen/ 陳彥竹 中央研究院物理所 Institute of Physics, Academia Sinica Taiwan, ROC For the CDF collaboration ICFP /10/03-08.
Michele Faucci Giannelli, Mike Green, Veronique Boisvert, Fabrizio Salvatore, Tao Wu LCWS 08, Chicago, 18 November 2008 Sensitivity to the Higgs self-coupling.
Jake Anderson, on behalf of CMS Fermilab Semi-leptonic VW production at CMS.
Tau Jet Identification in Charged Higgs Search Monoranjan Guchait TIFR, Mumbai India-CMS collaboration meeting th March,2009 University of Delhi.
Heavy charged gauge boson, W’, search at Hadron Colliders YuChul Yang (Kyungpook National University) (PPP9, NCU, Taiwan, June 04, 2011) June04, 2011,
H → ZZ →  A promising new channel for high Higgs mass Sara Bolognesi – Torino INFN and University Higgs meeting 23 Sept – CMS Week.
Associated top Higgs search: with ttH (H  bb) Chris Collins-Tooth, 17 June 2008.
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:
KIRTI RANJANDIS, Madison, Wisconsin, April 28, Top Quark Production Cross- Section at the Tevatron Collider On behalf of DØ & CDF Collaboration KIRTI.
Possibility of tan  measurement with in CMS Majid Hashemi CERN, CMS IPM,Tehran,Iran QCD and Hadronic Interactions, March 2005, La Thuile, Italy.
1 ttbar Cross-Section Studies D. Jana*, M. Saleem*, F. Rizatdinova**, P. Gutierrez*, P. Skubic* *University of Oklahoma, **Oklahoma State University.
Measurement of the branching ratios for Standard Model Higgs decays into muon pairs and into Z boson pairs at 1.4 TeV CLIC Gordana Milutinovic-Dumbelovic,
Study of Standard Model Backgrounds for SUSY search with ATLAS detector Takayuki Sasaki, University of Tokyo.
Simone Gennai SNS, INFN-Pisa1 Radion searches in CMS A first look to  hh G. Dewhirst, L. Fano, S. Gennai, S. Nikitenko.
Searches for the Standard Model Higgs at the Tevatron presented by Per Jonsson Imperial College London On behalf of the CDF and DØ Collaborations Moriond.
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.
1 Single top in e+jets channel Outline : - Data and MC samples - Overview of the analysis - Loose and topological cuts - MC efficiencies and expected number.
1 TOP MASS MEASUREMENT WITH ATLAS A.-I. Etienvre, for the ATLAS Collaboration.
Lake Louise (February 2002) Ivo van Vulpen 1 Z boson pair production Ivo van Vulpen Outline: LEP and its operation between ZZ production & final.
Abstract Several models of elementary particle physics beyond the Standard Model, predict the existence of neutral particles that can decay in jets of.
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.
A search for the ZZ signal in the 3 lepton channel Azeddine Kasmi Robert Kehoe Southern Methodist University Thanks to: H. Ma, M. Aharrouche.
29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 1 Search for Charged Higgs at the LHC Ashfaq Ahmad (Stony Brook)
Search for the Standard Model Higgs in  and  lepton final states P. Grannis, ICHEP 2012 for the DØ Collaboration Tevatron, pp √s = 1.96 TeV -
Mark OwenManchester Christmas Meeting Jan Search for h ->  with Muons at D  Mark Owen Manchester HEP Group Meeting January 2006 Outline: –Introduction.
EPS Manchester Daniela Bortoletto Associated Production for the Standard Model Higgs at CDF D. Bortoletto Purdue University Outline: Higgs at the.
Aug _5071 Top stop by charm channel analysis using D0 runI data OUTLINE physics process of top to stop Monte Carlo simulation for signal data.
1 Reinhard Schwienhorst, MSU Top Group Meeting W' Search in the single top quark channel Reinhard Schwienhorst Michigan State University Top Group Meeting,
 reconstruction and identification in CMS A.Nikitenko, Imperial College. LHC Days in Split 1.
Viktor Veszpremi Purdue University, CDF Collaboration Tev4LHC Workshop, Oct , Fermilab ZH->vvbb results from CDF.
DPF Conf., Oct. 29, 2006, HawaiiViktor Veszpremi, Purdue U.1 Search for the SM Higgs Boson in the Missing E T + b-jets Final State at CDF V. Veszpremi.
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.
Suyong Choi (SKKU) SUSY Standard Model Higgs Searches at DØ Suyong Choi SKKU, Korea for DØ Collaboration.
A Search for Higgs Decaying to WW (*) at DØ presented by Amber Jenkins Imperial College London on behalf of the D  Collaboration Meeting of the Division.
Low Mass Standard Model Higgs Boson Searches at the Tevatron Andrew Mehta Physics at LHC, Split, Croatia, September 29th 2008 On behalf of the CDF and.
Jieun Kim ( CMS Collaboration ) APCTP 2012 LHC Physics Workshop at Korea (Aug. 7-9, 2012) 1.
American Physical Society Meeting St. Louis, MO April th, 2008 Measuring the top mass at DØ using the Ideogram Method Amnon Harel
Top quark pair cross-section D0 (1 fb -1 results) Viatcheslav Sharyy for D0 collaborations CEA-Saclay / IRFU/ SPP ● Introduction ● Dilepton.
Satish Desai - 20 July Resonant Higgs Searches at DØ Satish Desai -- Fermilab on behalf of the DØ Collaboration 20 July 2007 European Physical Society.
The Hunt For Single Top Production
ATLAS results on inclusive top quark pair
Determining the CP Properties of a Light Higgs Boson
ttH (Hγγ) search and CP measurement
3rd Grenoble Top Workshop – October 25, 2008
Stop->4 bodies signal samples with 2 leptons in final state
Venkat Kaushik, Jae Yu University of Texas at Arlington
Search for WHlnbb at the Tevatron DPF 2009
Higgs → t+t- in Vector Boson Fusion
NIKHEF / Universiteit van Amsterdam
An Important thing to know.
W boson helicity measurement
Jessica Leonard Oct. 23, 2006 Physics 835
Tevatron Searches for Beyond-SM Higgs
Status of the H4l CSC Note (HG2)
Top mass measurements at the Tevatron and the standard model fits
Tim Scanlon Imperial College, London on behalf of the DØ Collaboration
Top quark production cross section Top quark mass measurement
The Hunt For Single Top Production
Measurement of the Single Top Production Cross Section at CDF
Susan Burke, University of Arizona
Presentation transcript:

Northern Illinois University / NICADD Measurement of the tt production cross section at DØ using t + jets events Mikhail Arov, Northern Illinois University / NICADD For DØ Collaboration

Slices of the “top quark pie” By ignoring this channel we lose up to 15 % of our top events! There are as many as the and But are there really? t+jets e+jets m + jets

tgH+b SM is flavor blind, however even the simplest extension of the SM Higgs sector requires two Higgs doublets (H+ and H-) The H+ is not flavor blind. It has Yukawa coupling to leptons, preferring the heaviest – t ! In fact BR(H+gtn) >> BR(W+gln) So if charged Higgs is lighter than top, then BR(ttgt+jets) becomes enhanced due to presence of tgH+b

Importance of t channels Addition of new tt modes orthogonal to explored ones. It decreases the measurement uncertainty on s Crucial test of the SM prediction of lepton universality. The results can signal new physics! If not we can use it to constrain the parameter space Charged Higgs search is the next logical extension of this analysis

Signal characteristics q 4 jets 2 b jets Hadronic t Missing ET b W+ q t p p t nt W- Hadrons b t- nt

t decay modes Type 1 Type 2 Type 3

t ID at DØ At DØ t are identified in their hadronic modes as narrow (0.3 DR cone) jets, isolated and matched to a charged track. Hence, the 3 t candidate types are defined (roughly corresponding to the decay channels: Type 1 contains only one charged track Type 2 has one charged track and an one or more electromagnetic clusters Type 3 has more than one track (multi-prong decays) Neural Net is trained to select the “good” candidates

Dataset and preselection Since a t candidate at DØ is essentially a narrow jet, our event signature is very similar to the tt g all hadrons channel. Therefore we used the dataset collected with multijet trigger. Preselection cuts were: No isolated electrons or muons Missing ET significance > 3 Njets > 3

MET significance significance combines the probability densities of reconstructed physical objects (jets, electrons and unclustered scalar energy) to give the total likelihood of physical Probability densities of these objects are assumed to form Normal distributions, defined by the energy resolution of this object: The probability distribution is obtained as their linear combination and is also parameterized by a Gaussian: Thus the significance is defined as

Results of the preselection Wgtn ALPGEN MC samples were normalized to the published W+4j cross section of 4.5±2.2 pb. The ALPGEN value of 5.54 pb was used for tt (just as a cross check, we are measuring this value after all!) We were able to reject the bulk of the QCD background, but S:B of 1:6500 is way too low! Next we apply the b-tagging and t ID.

b-tagging and t ID results Secondary Vertex b-tagging algorithm was used Instrumental background (multijet QCD) is responsible for most of the candidate events in both types of t candidates. We need a reasonably reliable method of estimating it 9.32<<269 a S:B is very low at this stage and additional selection is needed. Topological NN (using MLPfit) was used for that On the following slide we will describe the strategy we employed to address both issues

Analysis flow Preselected dataset b - veto tagged dataset Signal tagged dataset b - veto tagged dataset t - veto tagged dataset Used for measurement Used for QCD Used for NN training

t fake rate Type 2 Type 3 We assume that all t candidates in the b-veto sample are really jets faking t Therefore, we divide the PT and h distributions for t by the ones for the jets and fit, to obtain the t fake rate! Type 1 was discarded (low signal, high fake rate) Type 2 and 3 taus are treated as separate analysis channels from now on

QCD multijet prediction The “QCD background” in this case is composed of the events with no real t lepton in them, but with one or more 0.95 NN t candidate (fakes) We assume that the probability for a jet to fake a t is . Then the probability that at least one of the jets in the event fakes t can be computed as following: Summing up such probabilities over the tagged data we obtain the QCD background prediction

And the resulting NN distributions Control plots of selected input variables and the resulting NN distributions Type 2 Type 2 And the resulting NN distributions Type 2 Type 3

Finally – the measurement ! The cross section is defined as For type 2: And for type 3:

Systematic uncertainties

b-tagging systematics

Combined cross section

Conclusions & Outlook DØ performed the first measurement of s(t + jets) on the 350 pb-1. The dominant uncertainty is statistical one, so a huge improvement is expected at 1 fb-1 and we are working. H+ search is in the works. The final answer for this analysis is

Backup Slides

t decay modes (details) The t lepton has several decay channels, classified by the number of charged particles (tracks) associated with it: electron + muon (tgenent or tgmnmnt), BR=35% charged hadron (tgp-nt), BR=12% charged hadron + ≥1 neutral particle (i.e. tgrntgnp0+p-nt), BR=38% 3 charged hadrons + ≥1 neutral hadrons, BR=15% (so called “3-prong” decays)

Dataset breakdown by trigger version The trigger (4JT10) underwent several modifications throughout Run II, reflected on the next slide In 4JT12 jet threshold was raised to 12 GeV In a HT cut of 120 GeV JT2_4JT12L_HT added

Tagged sample per type

Fit function The fitting function was the chosen to be: The PT fitting function has been picked so that it would describe the data well and at the same time would be saturated at high PT (that is we require that ):

NN variables HT – the scalar sum of all jet PTs (and t candidates) Sphericity and Aplanarity – these variables are formed from the eigenvalues of the normalized Momentum Tensor. These are expected to be higher in the top pair events then in a typical QCD event Centrality, defined as where HE is the sum of energies of the jets (and t candidates) Top and W mass likelihoods – c2-like variable. where Mt , MW, st, sW are the top and W masses (175 GeV and 80 GeV respectively) and resolution values (45 GeV and 10 GeV respectively). M3j and M2j are invariant masses of the 3 and 2 jets respectively, picked so to minimize L PT and Secondary Vertex Lifetime Significance of the leading tagged jet

NN Cut optimization Type 3 Type 2 The signal significance is defined as Type 2 Type 3

NN application results Type 2 Type 3 Same plots, “zoomed” at high NN values:

Combined cross section We combined both channels by minimizing the negative log-likelihood function defined by the following formula: where Then the combined cross section is