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ATLAS TTBAR TO TAU ANALYSIS

William P. Edson, Teeba RashidAdviser: Mohammad Sajjad Alam

State University of New York at AlbanyAnirvan Sircar

Adviser: Dick GreenwoodLoisianna TechApril 14, 2013

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ttbar to tau Interaction Overview

t

W+

b

tbarW-

bbarντ

τ -

q’

q

Top Pair Branching Fractions for ttbar decays[5]

Cutflow C0: GRL C1: Trigger C2: Primary vertex with ntracks > 4 C3: Electron/muon overlap, larVeto C4: Jet cleaning C5: Lepton Veto C6: njets >= 4 with eta < 2.3 and |jvf| > 0.75 C7: MET > 60GeV C8: ptmiss significance > 8 C9: MT < 70GeV C10: Sum ET < 500GeV C11: >= 1 bjet (MV1 > 0.601713) C12: Tau n ≥ 1, BDTScore > 0.7 C13: Trigger matched tau n ≥ 1 and pT >= 40GeV C14: MC tau object match

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Backgrounds QCD multi-jet

estimated contribution determined via data driven techniques

W + jets Z + jets Diboson ttbar decay (muons and electrons)

ABCD Regions Signal Region (A):

BDTScore > 0.7 and Closest Top Mass < 230GeV

Background Regions (B, C and D): B: BDTScore < 0.7 and Closest Top Mass <

230GeV C: BDTScore > 0.7 and Closest Top Mass

>230GeV D: BDTScore < 0.7 and Closest Top Mass >

230GeV

BDTScore per Region

Closest Top Mass per Region

Top Mass with Highest pT b-jet per Region

Top Mass with Second Highest pT b-jet per Region

Mjj per Region

MC Subtraction Histograms

BDTScore per Region

Closest Top Mass per Region

Top Mass with Highest pT b-jet per Region

Top Mass with Second Highest pT b-jet per Region

Mjj per Region

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Cutflow -> Teeba Rashid’s Analysis

No cut C0:Event Cleaning: GRL && larError!=2 C1:Trigger C2: Primary vertex, ntr >4 C3 :LAr FEB C4: Event Cleaning: Jets C5: Jets: > = 4 jets C6: ==1 Tau C7: lepton veto C8: MET > 60 C9: sumPt > 0 C10: Pt miss significance > 13 C11: >=1 b C12: mt 120 - 240

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Sources of Uncertainty % Uncertainty Jet Energy Resolution +/-1.33 Jet Energy Scale +-/11 Jet Reconstruction Efficiency +/-0.39 B-JES +0.23 -0.30 Pdf In Progress QCD In Progress MC generator +/- 4.91 ISR/FSR Obtained Numbers/ some doubts to obtain the final Value Pile up In Progress JVF In Progress MET In Progress Parton Shower Obtained Numbers /some doubts to obtain final value

Tau ID efficiency In Progress Tau Energy Scale In Progress Etmiss uncertainty In Progress

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Cross-Section Measurement

σtt = 147.06 ± 13 (stat) pb

SM Prediction σtt = 166.8 +17.3 – 18.4 pb (Eur. Phys. J.C63:189-285, 2009)

Nikhef (τ + jets) σtt = 194 ± 18 (stat) pb (arXiv:1211.7205v1)

μ+ τ σtt = 186 ± 13 (stat) ± 20 (syst) pb (Phys. Lett. B 717 (2012) 89-108)

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Conclusions

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Thanks Dr. Sajjad Alam Dr. Pat Skupic Dr. Dick Greenwood Catrin Bernius ttbar to tau group

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References https://twiki.cern.ch/twiki/bin/viewauth/Atlas/WorkBook http://atlas.web.cern.ch/Atlas/SUB_DETECTORS/TILE/ [1] Marion Lambacher, Study of fully hadronic ttbar decays and their separation from QCD multijet background events in the first year of the ATLAS

experiment. July 2007. http://edoc.ub.uni-muenchen.de/7603/1/Lambacher_Marion.pdf. [2]CTEQ. http://www.phys.psu.edu/~cteq/. [3] V. Chekelian, Standard model physics at HERA. 2001. hep-ex/0107053. [4]http://pdg.lbl.gov/ [5]Neil Collins, TopCross Section (Current Status and Early LHC Prospects). 10 March 2010.

http://www.ep.ph.bham.ac.uk/general/seminars/slides/neil-collins-100310.pdf [6]Zofia Czyczula, Search for New Physics in Tau-pair Events in ATLAS at the LHC. June 2009.

http://cdsweb.cern.ch/record/1204789/files/CERN-THESIS-2009-078.pdf [7]Noel Dawe, Tau Identification with Boosted Decision Trees. 18 March 2010. [8]Bjorn Gosdzik, Tau Reconstruction at the ATLAS experiment. 22 January 2009.

http://wwwiexp.desy.de/studium/seminare/studsem/ws2008/talks/vortrag09-gosdzik.pdf [9] http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/ [10] http://public.web.cern.ch/public/en/lhc/lhc-en.html [11] http://www.uslhc.us/ [12] http://atlas.web.cern.ch/Atlas/Collaboration/ [13] https://twiki.cern.ch/twiki/bin/viewauth/Atlas/InnerDetector [14] The ATLAS Liquid Argon Calorimeter at the LHC: Overview and Performance – Mathieu Aurousseau,

http://cdsweb.cern.ch/record/1270159/files/ATL-LARG-SLIDE-2010-119.pdf [15] http://atlas.ch/ [16] ATLAS Tile calorimeter commissioning status and performance – Ana Henriques, http://cdsweb.cern.ch/record/1213918 [17] Muon Spectrometer Technical Design Report, http://atlas.web.cern.ch/Atlas/GROUPS/MUON/TDR/Web/TDR_chapters.html [18] http://atlas-magnet.web.cern.ch/atlas-magnet/ [19] The ATLAS Experiment at the CERN Large Hadron Collider. 2008. http://iopscience.iop.org/1748-0221/3/08/508003 [20] CERN faq LHC the guide. http://multimedia-gallery.web.cern.ch/multimedia-gallery/Brochures.aspx [21] Jane T. Bromley.,Investigation of the Operation of Resistive Plate Chambers. September 1994. www.hep.man.ac.uk/theses/jane.pdf [22] Joel Feltesse, Introduction to Parton Distribution Functions. Scholarpedia. 6 November 2010.

http://www.scholarpedia.org/article/Introduction_to_Parton_Distribution_Functions [24] CMS collaboration, First Measurement of the top quark pair production in the dilepton channel with tau leptons in the final state in pp collisions at √s =

7 TeV. CMS-PAS-TOP-11-06 [25] Interactions.org, Particle Physics Glossary. 2009. www.interactions.org/cms/?pid=1002289 [26] David Griffiths, Introduction to Elementary Particles. 2004. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim [27] Noel Dawe, Dugan O’Neil, Tau Identification with Boosted Decision Trees. 15 July 2010.

https://indico.cern.ch/getFile.py/access?contribId=18&resId=0&materialId=slides&confId=95501 [28] Michael Wright, Exclusive Jet Study with Kt, AntiKt and Cambridge Aachen Jet Finders. 10 June 2010.

https://ppes8.physics.gla.ac.uk/twiki/bin/view/ATLAS/ExclusiveJetStudy#AntiKt_Jet_Finder [29] Mark R. Leach, The INTERNET Database of Periodic Tables. 1999-2001.

http://www.meta-synthesis.com/webbook/35_pt/pt_database.php?Button=Misc+PTs [30] Arghir, S; Behar, S; Cavaliere, V; Coadou,Y ; Czodrowski, P; Flechl, M; Kopp, A; McCarn, A; zur Nedden, M ;Neubauer, M; Randle-Conde, A; Rozen, Y;

Sekula, S; Takahashi, Y; Tomoto, M; Vickey, T; Xella, S, Data-driven estimation of the background to H+ searches with hadronic-tau final states. 31 March 2011. https://cdsweb.cern.ch/record/1312955?

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