Production cross section Measurement of tq Z using

Production cross section Measurement of tq. Z using CMS 2012 data

Outline q Motivations q Top Quark q Analysis Introduction q Analysis Cut Flow q Pileup q Basic Plots q Background Estimation q PAT vs AOD q Analysis Documentation q Summary and Conclusion 3/9/2021 NCP-ICTP LHC School 2014 2

Motivations q Plan to measure tq. Z cross-section using 8 Te. V, CMS data with 19. 6 fb-1 Integrated Luminosity. q tq. Z is rare standard model process and it is irreducible background for ttbar and ttbar +Z, FCNC. v Measuring will confirm a predicted feature of the standard model and allow other analyses to include tq. Z as a background. v. In LHC run-II, with more top statistic, we will also be able to study vector boson association with top. q Analysis techniques are similar to SUSY multi-lepton analysis 3/9/2021 NCP-ICTP LHC School 2014 3

What is top quark q The heaviest quark in the SM M ~ 172. 4 Ge. V q Mass near the electroweak symmetry breaking scale, has “natural” Yukawa coupling. q Discovered in 1995. q Charge of +2/3 and weak isospin of +1/2 q Lifetime 5× 10− 25 s: q ~20 times shorter then time scale of strong int. q decays before hadronization q the spin information is kept by its decay products q Gives opportunity to study “bare” quark 3/9/2021 NCP-ICTP LHC School 2014 4

Top quark Single top production: Life Time: 5 * 10 -25 sec Proceeds via weak interactions: - exchange of virtual W in s and t channel - associated production with real W 3/9/2021 NCP-ICTP LHC School 2014 5

Analysis Introduction The single top + Z cross section is about the same size as the t¯t. Z one Cross section for ttbar+Z is ~ 0. 2057 tb. Z Cross-section mentioned on single top page ~ 0. 0114 pb σ. L = N Total events with this cross section and 19600 pb-1 integrated luminosity ~ 223 tq. Z cross-section ~ 0. 02450 pb Total events with this cross section and 19600 pb-1 integrated luminosity ~ 480 3/9/2021 NCP-ICTP LHC School 2014 6

Analysis Framework q. Developed AOD based analysis framework ØRun under CMSSW_5_3_21 ØHave producers for all basic objects ØCut flow about Muons and Electron implemented ØPlus analyzers for various tasks like final cut flow, top reconstruction ØAdapted some existing tools such as Pz calculation for MET (using W constrain) q. Recommended MET filter incorporated. q. Jet Energy Corrections(JEC) Type-I applied. q. Now migrated to PAT formate 3/9/2021 NCP-ICTP LHC School 2014 7

Event Selection q. Tri-lepton final state. v eee v eeu v euu v uuu q. Two leptons should be same flavor and opposite charge. q. Third lepton should be from top decay with neutrino (MET). q. One b-tag. q Light Jets should be more than 1. 3/9/2021 NCP-ICTP LHC School 2014 8

Datasets q. Data used: Ø CMS 2012 (Re. Reco 8 Te. V) data: 19. 7 fb-1 Lumi v. Double Electron v. Double Mu v. Mu. EG Ø JSON file: v. Cert_190456 -208686_8 Te. V_22 Jan 2013 Re. Reco_Collisions 12_JSON. txt 3/9/2021 NCP-ICTP LHC School 2014 9

Trigger 3/9/2021 NCP-ICTP LHC School 2014 10

MC Samples Used Signal. MC /TZJets. To 3 LNu. B_8 Te. V_Tune. Z 2 Star_madgraph_tauola/ [1] ttbar. MC /TTJets_Massive. Bin. DECAY_Tune. Z 2 star_8 Te. V-madgraph-tauola/ [1] ttbar. W /TTWJets_8 Te. V-madgraph/ [1] ttbar. Z /TTZJets_8 Te. V-madgraph_v 2/ [1] WZ (3 l + Nu) /WZJets. To 3 LNu_Tune. Z 2_8 Te. V-madgraph-tauola/ [1] ZGamma /ZGTo. LLG_8 Te. V-madgraph/ [1] Z + Jets /DYJets. To. LL_M-10 To 50 filter_8 Te. V-madgraph/ [1] /DYJets. To. LL_M-50_Tune. Z 2 Star_8 Te. V-madgraph-tarball/ [1] /Zbb. To. LL_massive_M-50_Tune. Z 2 star_8 Te. V-madgraph-pythia 6_tauola/[1] WV /WW_Tune. Z 2 star_8 Te. V_pythia 6_tauola/ [1] /WGstar. To. LNu 2 E_Tune. Z 2 star_8 Te. V-madgraph-tauola/ [1] /WGstar. To. LNu 2 Mu_Tune. Z 2 star_7 Te. V-madgraph-tauola/ [1] ZZ /ZZTo 4 e_8 Te. V-powheg-pythia 6/ [1] /ZZTo 4 mu_8 Te. V-powheg-pythia 6/ [1] /ZZTo 2 e 2 mu_8 Te. V-powheg-pythia 6/ [1] 3/9/2021 [1]= Summer 12_DR 53 X-PU_S 10_START 53_V 19 -v 1/AODSIM NCP-ICTP LHC School 2014 11

Object Selection q Selection of objects (TOP-PAG recommendations): q Exactly three `tight' leptons, two of which must be oppositely charged, same flavour and invariant mass within the z mass window (78 -102 Ge. V). q Events with good vertex cuts: Ø Ndof>5, Z<24. 0, rho()<2. 0 q Muon selection q Electron Selection q Jet & MET Selection 3/9/2021 NCP-ICTP LHC School 2014 12

Muons Selection 3/9/2021 NCP-ICTP LHC School 2014 13

Electron Selection 3/9/2021 NCP-ICTP LHC School 2014 14

Jet and MET Selection q Jet selection: Official jet ID implemented Ø Ø Ø PFJets with Jet pt> 20 Ge. V, eta< 3. and CVS disc < 0. 679 neutral. Hadron. Energy. Fraction > 0. 99 charged. Hadron. Energy. Fraction > 0 neutral. Em. Energy. Fraction > 0. 99 charged. Em. Energy. Fraction > 0. 99 Jet. Iso (j, l) < 0. 3 q Tag jet: CSV (Combined Secondary Vertex ) disc > 0. 679 Ø Eta<2. 4, pt > 25 Ge. V, It’s a Medium working point q MET: p. FMET with 25 Ge. V MET Cut. 3/9/2021 NCP-ICTP LHC School 2014 15

Cut Flow Table Dmu DE Mu. EG t. Data t. MC Signal ttbar. W ttbar. Z WZ WW Zgamma ZZ (2 e 2 mu) ZZ (4 e) ZZ (4 mu) Z Jets (Less Z Jets (Grtr 50) Zbb WGstar. To. L Nu 2 Mu Nu 2 E All events 1. 00 E+08 9. 15 E+07 5. 64 E+07 2. 48 E+08 9. 33 E+07 485. 075 510876 4593. 37 3445. 03 20947. 3 1. 13 E+06 2. 63 E+06 3498. 48 1522. 74 1. 70 E+07 6. 99 E+07 1. 86 E+06 37895. 3 116280 Dilepton 5. 20 E+07 2. 14 E+07 3. 51 E+07 1. 08 E+08 9. 33 E+07 485. 075 510876 4593. 37 3445. 03 20947. 3 1. 13 E+06 2. 63 E+06 3498. 48 Trigger 1522. 74 1. 70 E+07 6. 99 E+07 1. 86 E+06 37895. 3 116280 6. 94 E+07 1. 86 E+06 37717. 2 115610 Primary 5. 20 E+07 2. 14 E+07 3. 51 E+07 1. 08 E+08 9. 26 E+07 484. 665 510642 4591. 82 3443. 9 20859. 6 1. 13 E+06 2. 61 E+06 3484. 95 vertx cut 1516 1517. 4 1. 69 E+07 tight 316 297 leptons 3 7 620 803 20 1 4 9 464 0 18 56 30 23 0 30 4 7 136 elec 3 +Z + 0 W(MET) 57 0 57 69 3 0 0 1 57 0 1 0 4 0 0 2 0 0 1 Muon 3 + Z 75 + W(MET) 0 0 75 79 3 0 0 1 70 0 0 5 0 0 0 1 0 muons 2 + elec 1 + Z + W(MET) 54 0 2 56 68 2 0 0 1 58 0 0 5 0 0 0 2 0 0 0 muons 1+ elec 2 + Z + W(MET) 1 54 0 55 68 2 0 0 1 60 0 0 4 0 0 0 0 Elec 3 + Z + MET + 1 b 0 2 4 1 0 0 1 1 0 0 0 0 0 Muon 3 + Z + MET +1 b 3 0 0 3 3 2 0 0 0 1 0 0 0 0 0 Muon 2 + elec 1 + Z + MET +1 b 3 0 0 3 3 1 0 0 0 0 Muon 1 + elec 2 +Z + MET +1 b 0 4 4 1 0 0 1 1 0 0 0 0 0

Pileup q the additional interactions that occur in each beam crossing because the instantaneous bunch-by-bunch collision luminosity is very high. q “additional” implies that there is a hard-scatter interaction that has caused the event to fire the trigger. Ø end of 2011: ~15 interactions per crossing Ø End of 2012: as high as 40 interactions per crossing q “In-time pileup”: Ø the interactions that occur in the bunch crossing that fires the trigger 3/9/2021 NCP-ICTP LHC School 2014 17

Pileup q“Out-of-time pileup”: Øthe interactions that occur in bunch crossings earlier or later than the in-time interaction Ødepending on the integration time of the different CMS detector elements, these interactions can leave energy or tracks in the detector ØTracker: only sensitive to in-time pileup Ø– Calorimeters: sensitive to out-of-time pileup Ø– Muons: sensitive to out-of-time pileup 3/9/2021 NCP-ICTP LHC School 2014 18

Pileup Reweighting All used MC Samples produced using same scheme PU_S 10 Weight for Pileup reweighting calculated using WZ MC sample before after

Leptons Multi

Muons Pt after Pre-selection

Electrons Pt after Pre-selection

MET after pre-selection 3/9/2021 NCP-ICTP LHC School 2014 23

Z mass after pre-selection 3/9/2021 NCP-ICTP LHC School 2014 24

Z Pt after pre-selection 3/9/2021 NCP-ICTP LHC School 2014 25

W transverse Mass in combinations 3/9/2021 NCP-ICTP LHC School 2014 26

Di-Lepton Mass in Final Combinations 3/9/2021 NCP-ICTP LHC School 2014 27

Background SF q Main backgrounds: WZ, ttbar, ttar. W, Z+Jets q Plot Z mass for events with 0 bjets q calculate ratio of data and MC in Z mass window [78, 101] q Apply these scale factors to reweight dominant WZ MC in final plots/cutflow q Can do the above bin-by-bin but that would over correct MC uue SF = 0. 788539 eeu SF = 0. 736197 ee e SF = 0. 780372 uuu SF = 0. 92914 3/9/2021 NCP-ICTP LHC School 2014 28

Without SF 3/9/2021 NCP-ICTP LHC School 2014 29

With Background Scale (WZ) 3/9/2021 NCP-ICTP LHC School 2014 30

Background Scale Factors (Plotting Z mass with 0 bjets) 3/9/2021 NCP-ICTP LHC School 2014 31

Applying Scale Factors to WZ MC in background enriched mass plots 3/9/2021 NCP-ICTP LHC School 2014 32

Applying Scale Factors to WZ MC in preselected mass plots 3/9/2021 NCP-ICTP LHC School 2014 33

Basic Plots with PAT q. Pat Tuple Produced usingle top file ØAt least one tight lepton ØLight jet quarks >= 2 3/9/2021 NCP-ICTP LHC School 2014 34

Basic Plots with PAT 3/9/2021 NCP-ICTP LHC School 2014 35

Analysis Documentaion q Twiki page: all analysis strategy and updates https: //twiki. cern. ch/twiki/bin/view/Sandbox/Single. Topin. Associationof. Zboson q. CMS Analysis Note: Ø AN 2014_182 3/9/2021 NCP-ICTP LHC School 2014 36

Summary and Plan q Validation plots after pre-selection shows reasonable agreement between data and MC q pileup reweighting applied q Background SF have been calculated and Applied q Pat tuple produced with single top file and basic plots with signal MC. q Future plans q AN 2014 -182 completion up to end of year q Work on systematic q Fake Rate Estimation 3/9/2021 NCP-ICTP LHC School 2014 37

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