Top Quark Production at the LHC Masato Aoki (Nagoya University, Japan) For the ATLAS, CMS Collaborations
Phys. Rev. D 83 (2011) 091503, Phys. Rev. D 82 (2010) 054018, Phys. Rev. D 81 (2010) 054028, Comput. Phys. Commun. 182 (2011) 1034 LHC: top quark factory with pp collisions s [pb] @LHC 7 TeV 8 TeV Top pair Single top: t-ch. +13 164 10 +2.7 64. 6 2.0 +22 238 24 +3.4 87. 8 1.9 Single top: s-ch. 4. 6 ± 0. 2 5. 6 ± 0. 2 Single top: Wt 15. 7 ± 1. 1 22. 4 ± 1. 5 5 fb -1 @7 TeV + 20 fb -1 @8 TeV per experiment 5,600,000 top pairs, 2,700,000 single top events Top Quark Production at the LHC 2
Measurement of top quark Precise tests of perturbative QCD Precise understanding of background in new physics and Higgs searches New physics may be associated with top quark production Top Quark Production at the LHC 3 t H H t t c,g t c,g t t W W t t
Inclusive σ tt measurements @LHC σ tt @ 7 TeV pp collisions ATLAS and CMS combination Total uncertainty : 5.8% ATLAS-CONF-2012-134 CMS PAS TOP-12-003 First LHC combination First step in the discussion towards the harmonization of systematic treatment For the moment there were still important differences: e.g. treatment of generator systematics This could be a very good motivation for top modeling studies Top Quark Production at the LHC 4
New results on inclusive σ tt Improved analysis technique CMS: dilepton with 2.3 fb -1 161. 9 ± 2. 5 stat +5.1 5.0 syst ± 3. 6 lumi pb More refined event selections and analysis techniques, better estimate of systematics Eur. Phys. J. C72 (2012) 2202 σ tt New tool ATLAS: l+jets with 2.8 fb -1 165 ± 2 stat ± 17 syst ± 3 lumi pb Soft Muon b-tagger ATLAS-CONF-2012-131 BSM-sensitive channel ATLAS: t+jets with 1.7 fb -1 Use hadronic tau 194 ± 18 stat ± 46 syst pb Eur. Phys. J. C, 73 3 (2013) 2328 CMS: t+jets with 3.9 fb -1 Use hadronic tau 152 ± 12 stat ± 32 syst ± 3 lumi pb arxiv:1301.5755 Energy: 8 TeV ATLAS: l+jets with 5.8 fb -1 241 ± 2 stat ± 31 syst ± 9 lumi pb CMS: l+jets with 2.8 fb -1 228 ± 9 stat +29 26 syst ± 10 lumi pb CMS: dilepton with 2.4 fb -1 227 ± 3 stat ± 11 syst ± 10 lumi pb ATLAS-CONF-2012-149, CMS PAS TOP-12-006, CMS PAS TOP-12-007 Top Quark Production at the LHC 5
Eur. Phys. J. C (2013) 73: 2261 tt differential cross section @ATLAS 7 TeV, 2.05 fb -1, l+jets, at least one b-tag tt reconstruction by likelihood-based kinematic fitter Robust unregularized unfolding of m tt, y tt, p T tt compared with MCFM, ALPGEN, MC@NLO (and approx. NNLO for m tt ) Mostly systematics dominated (Jet/E T miss reco.): 10~20% Full covariance matrix provided All the measurements are in agreement with the standard model Top Quark Production at the LHC 6
arxiv:1211.2220, CMS PAS TOP-12-027, CMS PAS TOP-12-028 tt differential cross section @CMS 7 TeV 5 fb -1, and 8 TeV 12 fb -1 l+jets channel (at least 4 jets, at least 2 b-tagged jets) tt reconstruction: Constrained kinematic fitting algorithm Typical systematic uncertainty: 5.4% 3.9% from experimental uncertainty 3.8% from modeling uncertainty Dilepton channel (at least 2 jets, at least 1 b-tagged jets) tt reconstruction: Alternative kinematic reconstruction method Wider top-mass assumption (100GeV - 300GeV ) Typical systematics uncertainty: 3.9% 2.8% from experimental uncertainty 2.7% from modeling uncertainty Top Quark Production at the LHC 7
arxiv:1211.2220, CMS PAS TOP-12-027, CMS PAS TOP-12-028 tt differential cross section @CMS 7 TeV data 8 TeV data Good agreement between data and theoretical predictions The approximate NNLO provides the best description of the data Top Quark Production at the LHC 8
ATLAS-CONF-2012-155 Jet multiplicity in tt event ATLAS: 7 TeV, 4.7fb -1, l+jets channel, at least one b-tagged jet Number of jets (n jets ) measurement varying jet p T threshold Unfolded n jets distributions compared with several MC predictions Systematics dominated by Jet/E T miss reco. Discrepancy at large n jets for MC@NLO+HERWIG Reasonable agreement with ALPGEN+PYTHIA(or HERWIG) and POWHEG+PYTHIA p T >25GeV p T >40GeV p T >60GeV Top Quark Production at the LHC 9
CMS PAS TOP-12-018 Additional jets in l+jets CMS: 7 TeV, 5 fb -1, l+jets channel Additional jets in tt events extracted by fitting to likelihood discriminant Comparing with MadGraph, MC@NLO, POWHEG A slight discrepancy with MC@NLO Top Quark Production at the LHC 10
Eur.Phys.J. C72 (2012) 2043, CMS PAS TOP-12-023 Additional jets in dilepton Look at tt (ll + 2 b-jets) + additional jets ATLAS: 2 fb -1 @ 7TeV CMS: 5 fb -1 @7 TeV Gap fraction: Fraction of events produced in the absence of an additional jet above a p T (Q 0 ) threshold Full rapidity interval: All those generators give a reasonable description of the data Central: MC@NLO is too large Forward: None of the predictions agrees with data Central y 2.4 y 2.1 Forward Top Quark Production at the LHC 11
CMS PAS TOP-12-024 CMS: bb associated with tt 7 TeV, 5 fb -1 Dilepton + 4 jets Measure σ(tt bb)/σ(tt jj) Large cancellation of uncertainties b ID by Combined Secondary Vertex tagger (CSV) Combining SV and Track-based lifetime info Signal extraction by fitting to b-jet multiplicity σ(tt bb)/σ tt jj = 3. 6 ± 1. 1 stat ± 0. 9(syst) MADGRAPH: 1.2% POWHEG: 1.3% Δ = 39% 31%: Data stat. 23%: mistag rate 6.7%: Signal modeling 6.0%: b-tag eff. Top Quark Production at the LHC 12
Single top at LHC Alternative top quark production via the weak interaction Sensitive to many models of new physics Allow for a measure of V tb without assumptions about the number of quark generations Can be used to measure the b-quark parton distribution function t-channel s-channel Wt-channel Top Quark Production at the LHC 13
Phys. Lett. B 716 (2012) 142-159, Phys. Rev. Lett. 110 (2013) 022003 Wt associated production @7 TeV Final state: two leptons + E miss T + one b-jet Simultaneous fit of BDT outputs in different jet-bin regions (1-jet bin: signal region, 2>=jet bin: background control region) First evidence from ATLAS using 2fb -1, and confirmation by CMS with more stats. Δσ/σ=34% 16%: JES 15%: PS 10%: Gen. 10% Pile-up Δσ/σ=31% 20%: Stat. 15%: JES 10%: PS 22 variables 4 variables L [fb -1 ] Wt cross section [pb] Significance V tb +0.16 ATLAS 2.05 16. 8 ± 2. 9(stat.) ± 4. 9(syst.) 3.3σ 1. 03 0.19 +5 CMS 4.9 16 4 4.0 σ 1. 01 +0.16 0.13 exp. 0.04 +0.03 (th.) Top Quark Production at the LHC 14
CMS PAS TOP-12-011, ATLAS-CONF-2012-132 t-channel single top @8 TeV miss Final state: one lepton + E T + one b-jet + one recoil jet Signal extracted by a fitting with ATLAS: NN discriminant CMS: η distribution of recoil jet * 11 input variables L[fb -1 ] t-channel cross section [pb] V tb +0.10 ATLAS 5.8 95. 1 ± 2. 4 stat. ± 18. 0(syst.) 1. 04 0.11 CMS 5.0 Δσ/σ=19% 9%: I/FSR 9%: b-tag 8%: JES 7%: Gen. 80. 1 ± 5. 7 stat. ± 11. 0 syst. ± 4. 0(lumi.) Δσ/σ=16% 8%: JES 6%: Gen. 5%: Muon 5%: b-tag 5%: PDF 0. 96 ± 0. 08 exp. ± 0. 02(th.) Top Quark Production at the LHC 15
ATLAS-CONF-2012-056, CMS PAS TOP-12-038 R t : ratio of top and anti-top in t-channel R t is sensitive to PDF x [0.02,0.5] can be probed W-charge asymmetry [10-3,10-1 ] at LHC [0.005,0.3] at Tevatron ATLAS@7 TeV: 1.81±0.10 stat. ATLAS: 7 TeV 4.7 fb -1 Fit to NN outputs for l + and l - CMS: 8 TeV 12 fb -1 Fit to h of recoil jets for l + and l - Both results agree with SM predictions +0.21 CMS@8 TeV: 0.20 (syst.) 1.76±0.14 stat ± 0. 21 (syst) Top Quark Production at the LHC 16
Summary Many top measurements from 7 TeV 5 fb -1 of data, and with further statistics of 8 TeV data First LHC σ tt combination Improved σ tt and σ t measurements Large statistics of the LHC sample allows to perform more detailed top measurements Differential cross section Jet multiplicity bb associated with tt R t measurement in t-channel single top Need to improve modeling of the top production in order to be able to probe kinematics regions where new physics may exist More detailed and interesting top results yet to come Top Quark Production at the LHC 17
BACKUP SLIDES Top Quark Production at the LHC 18
CMS PAS TOP-12-014 CMS: Vector boson associated with tt 7TeV, 5fb -1 Trilepton approach : tt +Z lvbjjb+ll Same-sign dilepton approach : tt +Z and tt +W σ tt V = 0. 51 +0.15 0.13 stat +0.05 0.04 (syst) pb 4.7σ significance! Top Quark Production at the LHC 19
Top Quark Production at the LHC 20
Eur. Phys. J. C72 (2012) 2202 7 TeV: Further improvement CMS: σ tt in dilepton with 2.3 fb -1 More refined event selections and analysis techniques, better understanding of systematics Signal extraction by a profile likelihood ratio method to N jets N b jets 161. 9 ± 2. 5 stat +5.1 5.0 (syst) ± 3. 6(lumi) pb Δσ/σ=4.2% Main systematics 2.2% Lumi. 1.9% JES 1.7% BR(W ln) * MADGRAPH used for tt MC Top Quark Production at the LHC 21
arxiv:1301.5755 tt with τ @7 TeV Final state with taus sensitive to charged Higgs CMS: τ+jets in 3.9 fb -1 of data Hadronic τ candidate BDT to separate τ from e/m 4jets ( 1 b-tagged) Largest background from multijet Control sample from untagged data Signal extraction by fitting to Neural Network discriminant 152 ± 12 stat ± 32 syst ± 3 lumi pb Δσ/σ=23% 11% from JES 9% from τ ID Top Quark Production at the LHC 22
ATLAS-CONF-2012-131 7 TeV: tt with semileptonic b-tag ATLAS: 4.7 fb -1 @7 TeV High p T and central lepton(=1) and jets( 3) Soft Muon Tagger (SMT) Uncertainty on σ tt measurement: 1.4% 1.3% from muon identification 0.6% from c 2 matching efficiency Uncorrelated with other b-taggers Cut & count analysis: σ tt = 165 ± 2(stat) ± 17(syst) ± 3(lumi) pb Total uncertainty : 10.5% 6.6% from signal modeling 3.1% from BR(b μx) 5.5% from W+jets estimate 4.4% from multijets estimate SMT b-tagged Signal region Top Quark Production at the LHC 23
ATLAS-CONF-2012-149, CMS PAS TOP-12-006 8 TeV: tt in l+jets channel One high p T central lepton, and jets with at least one b-tagged jet Signal extracted by a fit to ATLAS: Likelihood discriminant CMS: M lb distribution 3 jets 4 jets NN-based b-tagger Jet prob. b-tagger Δσ/σ=13% Δσ/σ=13% 11%: signal modeling 8%: b-tag 6%: Jet/E miss T reco. 5%: Jet/E miss T reco. 3.7%: luminosity 4.4%: luminosity L [fb -1 ] σ tt [pb] @8TeV ATLAS 5.8 241 ± 2 stat ± 31 syst ± 9(lumi) CMS 2.8 228 ± 9 stat +29 26 syst ± 10(lumi) Top Quark Production at the LHC 24
CMS PAS TOP-12-007 CMS result in dilepton channel @8 TeV 2.4 fb -1 of data A simple and robust cut&count Analysis baseline is the same as 7 TeV analysis Channel ee mm em ll Cross section [pb] 231 ± 8 stat ± 15 syst ± 10(lumi) 220±6 stat ± 15 syst ± 10(lumi) 227 ± 4(stat) ± 11(syst) ± 10(lumi) 227 ± 3(stat) ± 11(syst) ± 10(lumi) Δσ/σ =6.7% 4.4% from luminosity 2.5% from JES Top Quark Production at the LHC 25
Jet multiplicity in dilepton @CMS 7 TeV, 5 fb -1, dilepton channels Unfolded jet multiplicities comparing with several QCD calculations MadGraph and POWHEG describe well the data MC@NLO generates lower multiplicities than observed Top Quark Production at the LHC 26
8 TeV: tt with b-tagging at ATLAS Use 5.8 fb -1 of data High p T and central lepton(=1) and jets( 3) At least one b-tagged jet Use neural network-based tagger Signal extraction by fitting to a likelihood discriminant (lepton rapidity, aplanarity) Δσ/σ=13% 1. 11% from signal modeling 2. 6% from Jet/E T miss reco. 3. 3.7% from luminosity ATLAS-CONF-2012-149 σ tt = 241 ± 2(stat. ) ± 31(syst.) ± 9(lumi.) pb Top Quark Production at the LHC 27
8 TeV: tt with b-tagging at CMS Up to 2.8 fb -1 of data High p T and central lepton(=1) and jets( 4) At least one b-tagged jet Signal extraction by fitting to M lb distribution Δσ/σ=13% 8% from b-tag 5% from Jet/E T miss reco. 4.4% from luminosity CMS PAS TOP-12-006 σ tt = 228. 4 ± 9. 0 stat. 26.0 +29.0 syst. ± 10. 0 lumi. pb Top Quark Production at the LHC 28
ATLAS-CONF-2012-056 R t : ratio of top and anti-top in t-channel R t is sensitive to PDF x [0.02,0.5] can be probed W-charge asymmetry [10-3,10-1 ] at LHC [0.005,0.3] at Tevatron ATLAS: 4.7 fb -1 of 7TeV data Signal extraction by fitting NN outputs top quark anti-top quark σ(t) σ(t ) 53.2±1.7 stat. ±10.6 syst. pb 29.5±1.5 stat. ±7.3 syst. pb R t 1.81±0.10 stat. +0.21 0.20 (syst.) Δσ(t)/σ(t)=20%, Δσ(t )/σ(t)=25% (JES is dominant: 16 20%) ΔR t /R t =13% (6% Stat., 4% for MC stat., Bkg, JES, ISR/FSR ) Top Quark Production at the LHC 29
CMS PAS TOP-12-038 R t measurement at 8 TeV CMS: 8 TeV, 12 fb -1 Signal extraction by a fit to η distributions of recoil jet for l + and l -, simultaneously σ(t) σ(t ) R t 49.6±2. 0 stat ±8. 8 syst pb 28.2±2. 2 stat ±4. 8 syst pb 1.76±0.14 stat ± 0. 21 (syst) Δσ(t)/σ(t)=18%, Δσ(t )/σ(t )=19% Signal modeling is dominant: 11 15% ΔR t /R t =15% 9% from data stat. 8% from PDF 7% from W+jets, tt extraction top quark anti-top quark Top Quark Production at the LHC 30
Top Quark Production at the LHC 31
Top Quark Production at the LHC 32
Top Quark Production at the LHC 33
Top Quark Production at the LHC 34
Top Quark Production at the LHC 35
Top Quark Production at the LHC 36
Top Quark Production at the LHC 37
Top Quark Production at the LHC 38
Top event in the detector 33% 67% tt analysis modes e/m + jets 34.3% All hadronic 59.2% ee/mm/em 6.4% *t is considered as either hadronic or e/m Top Quark Production at the LHC 39