Top Quark Physics at the LHC

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1 Top Quark Physics at the LHC Ayana Arce HEP 0 Lectures #7 March 4, 203

2 Outline Introduction 2 Why are top quarks interesting? 3 Creating Top Quarks 4 Identifying Top Quarks 5 Some LHC results 6 Beyond the top 7 Conclusions

3 Quarks (and other particles) You ve heard a lot about particles and interactions this semester: quarks are especially interesting They have all the interactions: SU(2) L U() SU(3) For us, they are hidden by confinement:

4 Quarks (and other particles) You ve heard a lot about particles and interactions this semester: quarks are especially interesting They have all the interactions: SU(2) L U() SU(3) For us, they are hidden by confinement:

5 Quarks (and other particles) You ve heard a lot about particles and interactions this semester: quarks are especially interesting They have all the interactions: SU(2) L U() SU(3) For us, they are hidden by confinement:

6 Quarks (and other particles) You ve heard a lot about particles and interactions this semester: quarks are especially interesting They have all the interactions: SU(2) L U() SU(3) For us, they are hidden by confinement:

7 Quarks (and other particles) You ve heard a lot about particles and interactions this semester: quarks are especially interesting They have all the interactions: SU(2) L U() SU(3) For us, they are hidden by confinement:

8 Quarks (and other particles) You ve heard a lot about particles and interactions this semester: quarks are especially interesting They have all the interactions: SU(2) L U() SU(3) For us, they are hidden by confinement:

9 The heaviest quark Top is important because it s such a heavy quark!

10 The heaviest quark Top is important because it s such a heavy quark! but why does the mass make it interesting?

11 The heaviest quark Theoretical importance in the Standard Model d Its weak interactions aren t weak! m t > m W t b Interaction strength GF 2M2 g 4 E 2? MW 4 u

12 The heaviest quark Theoretical importance in the Standard Model d Its weak interactions aren t weak! m t > m W t phew! b u

13 The heaviest quark Theoretical importance in the Standard Model m top [GeV] 90 G fitter SM May 2 68%, 95%, 99% CL fit contours excl. m top WA Its weak interactions aren t weak! m t > m W Its Higgs interactions are very important for SM consistency: LEP 95% CL LHC 95% CL Tevatron 95% CL σ band for m top M H [GeV] WA 68%, 95%, 99% CL fit contours incl. m top WA m Higgs includes virtual corrections: top top Heavy particles modify Higgs self-energy!

14 The heaviest quark Practical importance? Entries / 50 GeV ATLAS Preliminary L dt = 3.0 fb SRbC Data 202 ( s = 8 TeV) Standard model Multijets (data estimate) tt V+jets, VV tt+v, single top m ± t =200 GeV, mχ =50 GeV m ± t =350 GeV, mχ =300 GeV e+µ channels More reasons to care: It s the dominant background for many searches. 0 Data/SM miss ET [GeV]

15 The heaviest quark Practical importance? More reasons to care: It s the dominant background for many searches. dominant background good training samples!

16 The heaviest quark Practical importance? More reasons to care: It s the dominant background for many searches. dominant background good training samples! my personal reason: It s a mystery: (why is it so massive?)

17 Top quark production How are top quarks produced? Strong: σ = pb Electroweak: σ = 5.74 pb t t t t

18 Top quark production How are top quarks produced? Strong: σ = pb Electroweak: σ = 5.74 pb q q t t t t

19 Top quark production How are top quarks produced? Strong: σ = pb Electroweak: σ = 5.74 pb u d q t q t q d W + t t t g q t t W + d q W + t b

20 Top quark production How are top quarks produced? Strong: σ = pb Electroweak: σ = 5.74 pb u d q t q t q d W + t t t g q t t W + d q W + t b Study strong interactions, properties Test weak interactions

21 Top quark reconstruction How do top quarks decay? W coupling to q mass eigenstates: V CKM The top quark decay width: V ud V us.2 V ub V cd.2 V cs V cb V td V ts V tb Almost always W + b! Γ t Wb = V tb 2 8π.5GeV p b mt 2 What s the lifetime? M 2

22 Top Pair Decay Channels e µ τ ud cs electron+jets muon+jets eτ µτ eµ ee µµ tau+jets ττ µτ eµ eτ dileptons all-hadronic tau+jets muon+jets electron+jets t t W + bw b but W decays many ways. Signal and background depend on W decay! W decay e + µ + τ + ud cs

23 A top event reconstructed at ATLAS

24 Selecting top rejecting backgrounds 0 9 proton - (anti)proton cross sections 0 9 Find one or two b-jets σ tot 0 7 Tevatron LHC σ (nb) σ jet (E T jet > s/20) σ jet (E T jet > 00 GeV) σ jet (E jet T > s/4) σ Higgs (M H =20 GeV) 200 GeV WJS2009 σ b σ W σ Z σ t 500 GeV 0. 0 s (TeV) events / sec for L = 0 33 cm -2 s

25 Selecting top rejecting backgrounds Find one or two b-jets 2 Find one or leptons (or W q q ) If you take the lepton, you must use E miss T! 0 9 proton - (anti)proton cross sections Tevatron LHC σ tot 0 6 σ (nb) σ b σ jet (E jet T > s/20) σ W σ Z σ jet (E jet T > 00 GeV) ts / sec for L = 0 33 cm -2 s

26 Selecting top rejecting backgrounds Find one or two b-jets 2 Find one or leptons (or W q q ) If you take the lepton, you must use E miss T! 3 Reconstruct m T from Wb pairs.

27 Top reconstruction techniques finding B-jets b quarks are special, too: often decays to leptons Long-lived! ( s)

28 Top reconstruction techniques finding B-jets b quarks are special, too: often decays to leptons Long-lived! ( s) B hadron beamspot Decay Vertex track Impact Parameter

Top reconstruction techniques finding B-jets Arbitrary units 0-2 0 ATLAS (MC simulation) Tracks in b-jets Tracks in c-jets Tracks in light

29 Top reconstruction techniques finding B-jets Arbitrary units ATLAS (MC simulation) Tracks in b-jets Tracks in c-jets Tracks in light jets B hadron Signed transverse impact parameter (mm) beamspot Decay Vertex track Impact Parameter

30 Top production cross section Golden channel: l+jets+ν Events / 0 GeV Data / Expectation 3 0 ATLAS Preliminary Ldt = 5.8 fb 2 µ+ 3 jets Data s = 8 TeV tt W+Jets Multijet Z+Jets Single Top Dibosons miss E T [GeV] [pb] tt σ ATLAS Preliminary Data 20, s Channel & Lumi. Single lepton Dilepton All hadronic.02 fb = 7 TeV 20 Dec 202 Theory (approx. NNLO) for m t = 72.5 GeV stat. uncertainty total uncertainty ±(stat) ±(syst) ±(lumi) 0.70 fb 79 ± 4 ± 9 ± 7 pb fb 73 ± 6-7 pb σ [pb] tt σ tt 67 ± 8 ± 78 ± + 8 Combination 77 ± 3-7 ± 7 pb Single lepton, b Xµν 4.66 fb τ had τ had + jets + lepton All hadronic 4.7 fb 2 0 NLO QCD (pp) 65 ± 2 ± 7 ±.67 fb 94 ± 8 ± 46 pb 6 pb 3 pb 2.05 fb 86 ± 3 ± 20 ± 7 pb Approx. NNLO (pp) NLO QCD (pp) Approx. NNLO (pp) CDF D0 Single Lepton (8 TeV) 24 ± Single Lepton (7 TeV) 79 ± +7 Dilepton 73 pb 4 All hadronic 67 ± 8 pb Combined 77 + pb ± 2 32 pb 2 pb ± 6 pb ATLAS Preliminary

31 Top production cross section Golden channel: l+jets+ν Events / 0 GeV Data / Expectation 3 0 ATLAS Preliminary Ldt = 5.8 fb 2 µ+ 3 jets Data s = 8 TeV tt W+Jets Multijet Z+Jets Single Top Dibosons miss E T [GeV] [pb] tt σ ATLAS Preliminary Data 20, s Channel & Lumi. Single lepton Dilepton All hadronic.02 fb = 7 TeV 20 Dec 202 Theory (approx. NNLO) for m t = 72.5 GeV stat. uncertainty total uncertainty ±(stat) ±(syst) ±(lumi) 0.70 fb 79 ± 4 ± 9 ± 7 pb fb 73 ± 6-7 pb σ [pb] tt σ tt 67 ± 8 ± 78 ± + 8 Combination 77 ± 3-7 ± 7 pb Single lepton, b Xµν 4.66 fb τ had τ had + jets + lepton All hadronic 4.7 fb 2 0 NLO QCD (pp) 65 ± 2 ± 7 ±.67 fb 94 ± 8 ± 46 pb 6 pb 3 pb 2.05 fb 86 ± 3 ± 20 ± 7 pb Approx. NNLO (pp) NLO QCD (pp) Approx. NNLO (pp) CDF D0 Single Lepton (8 TeV) 24 ± Single Lepton (7 TeV) 79 ± +7 Dilepton 73 pb 4 All hadronic 67 ± 8 pb Combined 77 + pb 0 68 ± 2 32 pb 2 pb ± 6 pb Consistent with QCD calculations at high mass! ATLAS Preliminary

32 Top production cross section σ [pb] 2 0 ATLAS Preliminary Single top production L dt = ( ) fb t channel Wt channel 0 Theory (approx. NNLO) stat. uncertainty s channel t channel, arxiv: Wt channel, arxiv: s channel, ATLAS CONF % CL limit CM energy [TeV] Consistency with electroweak calculations (so far)!

33 Top mass LHC vs. the Tevatron 7 ATLAS m top summary - July 202, L = 35 pb fb int ATLAS 200, l+jets* CONF , L int = 35 pb (*Preliminary) 69.3 ± 4.0 ± 4.9 Events / 5 GeV ATLAS µ + jets L dt =.04 fb s = 7 TeV 20 Data tt, m = 72.5 GeV top single top, m = 72.5 GeV top Z + jets WW, WZ, ZZ W + jets QCD multijets Uncertainty ATLAS 20, l+jets Eur. Phys. J. C72 (202) 2046, L int =.04 fb 74.5 ± 0.6 ± ATLAS 20, all jets* CONF , L int ATLAS 20, dilepton* CONF , L int = 2.05 fb = 4.7 fb 74.9 ± 2. ± ±.6 ± 3.0 ± (stat.) ± (syst.) reco m top [GeV] Tevatron Average July ± 0.6 ± 0.8 ATLAS Preliminary m top [GeV] Entries / 0 GeV ATLAS Preliminary Ldt =.02 fb s = 7 TeV 20 Data Background signal LHC has more top quarks, but large systematic uncertainties! m(jjj) [GeV]

34 Top mass LHC vs. the Tevatron 2 ATLAS 200, l+jets L int = 35 pb, ( CR, UE syst.) ATLAS 20, l+jets L int = fb ATLAS 20, all jets L int = 2 fb, ( CR, UE syst.) CMS 200, di lepton L int = 36 pb, ( CR syst.) CMS 200, l+jets L int = 36 pb, ( CR syst.) CMS 20, di lepton L int = 2.3 fb, ( CR, UE syst.) CMS 20, µ+jets L int = 4.9 fb, ( CR, UE syst.) LHC m top combination June 202, L = 35 pb 4.9 fb int ATLAS + CMS Preliminary, s = 7 TeV 69.3 ± 4.0 ± ± 0.6 ± ± 2. ± ± 4.6 ± ± 2. ± ±.2 ± ± 0.4 ±.5 LHC June ± 0.5 ±.3 Tevatron July ± 0.6 ± 0.8 ± (stat.) ± (syst.) m top [GeV] LHC has more top quarks, but large systematic uncertainties! Events / 5 GeV Entries / 0 GeV = 7 TeV 20 Data ATLAS µ + jets L dt =.04 fb ATLAS Preliminary Ldt =.02 fb s tt, m = 72.5 GeV top single top, m = 72.5 GeV top Z + jets WW, WZ, ZZ W + jets QCD multijets Uncertainty s reco m top [GeV] = 7 TeV 20 Data Background signal m(jjj) [GeV]

Top quarks and the Higgs Events / 60 GeV 5000 4000 3000 ATLAS Preliminary L dt = 4.7 fb e+µ 4 jets, 2 b tags Data ( s = 7 TeV) tth (25) tt ttv W+jets Z+jets Diboson Single top Multijet Tot bkg unc.

35 Top quarks and the Higgs Events / 60 GeV ATLAS Preliminary L dt = 4.7 fb e+µ 4 jets, 2 b tags Data ( s = 7 TeV) tth (25) tt ttv W+jets Z+jets Diboson Single top Multijet Tot bkg unc Data / MC had H T [GeV] Understanding the top-higgs coupling is important! Events / 20 GeV ATLAS Preliminary L dt = 4.7 fb e+µ 6 jets, 4 b tags Data ( s = 7 TeV) tth (25) tt ttv W+jets Z+jets Diboson Single top Multijet Tot bkg unc. 4 2 Data / MC m bb [GeV]

36 Top quarks and the Higgs Events / 60 GeV ATLAS Preliminary L dt = 4.7 fb e+µ 4 jets, 2 b tags Data ( s = 7 TeV) tth (25) tt ttv W+jets Z+jets Diboson Single top Multijet Tot bkg unc Data / MC had H T [GeV] Understanding the top-higgs coupling is important! Events / 20 GeV ATLAS Preliminary L dt = 4.7 fb e+µ 6 jets, 4 b tags Data ( s = 7 TeV) tth (25) tt ttv W+jets Z+jets Diboson Single top Multijet Tot bkg unc. 4 2 Data / MC m bb [GeV]

37 Top quarks and dark matter? Inclusive searches 3rd gen. sq. gluino med. 3rd gen. squarks direct production EW direct RPV Long-lived particles MSUGRA/CMSSM : 0 lep + j's + E MSUGRA/CMSSM : lep + j's + E Pheno model : 0 lep + j's + E Pheno ± ± χ model χ : 0 lep + j's + E Gluino med. ( g qq ) : lep + j's + E GMSB GMSB (τ ( l NLSP) : 2 lep (OS) + j's + E NLSP) : -2 τ + 0 lep + j's + E GGM (bino NLSP) : γγ + E GGM (wino NLSP) : γ + lep + E GGM (higgsino-bino NLSP) : γ + b + E GGM (higgsino NLSP) : Z + jets + E Gravitino LSP : 'monojet' + E 0 g bbχ (virtual b) : 0 lep + 3 b-j's + E 0 g ttχ (virtual t) : 2 lep (SS) + j's + E 0 g ttχ (virtual t) : 3 lep + j's + E 0 g ttχ (virtual t) : 0 lep + multi-j's + E 0 g ttχ (virtual t) : 0 lep + 3 b-j's + E 0 χ bb, b b : 0 lep + 2-b-jets + E ± χ bb, b ± χ t : 3 lep + j's + E tt (light), t b : /2 lep (+ b-jet) + E ± χ tt (medium), t b : lep + b-jet + E ± χ tt (medium), t b : 2 lep + E 0 tt, t tχ : lep + b-jet + E 0 tt, t tχ : 0//2 lep (+ b-jets) + E tt (natural GMSB) : Z( ll) + b-jet + E 0 l l l lχ : 2 lep + E χ ± χ 0, χ L lν(lν) lν L, χ : 2 lep + E,miss χ χ l l νν), lν l νν) T : 3 lep + E ±0 ( )0 L l( ( )0 χ W * χ Z * χ : 3 lep + E ± ± Direct χ χ L ν L l( 2 2 pair prod. (AMSB) : long-lived χ Stable g R-hadrons : low β, βγ (full detector) Stable t R-hadrons : low β, βγ (full detector) GMSB : stable τ 0 χ qqµ (RPV) : µ + LFV : pp ν heavy ν displaced vertex LFV : pp ν τ +X, ν τ e+µ resonance τ +X, τ e(µ)+τ resonance Bilinear RPV CMSSM : lep + 7 j's + E + χ χ, χ + - Wχ, χ eeν : 4 lep + E 0 0 l l, l χ, χ µ,eµν T : 4 lep + E eeν,eµν e,miss L L L l µ e g qqq : 3-jet resonance pair Scalar gluon : 2-jet resonance pair WIMP interaction (D5, Dirac χ) : 'monojet' + E L=5.8 fb, 8 TeV [ATLAS-CONF-20209] L=5.8 fb, 8 TeV [ATLAS-CONF-20204] L=5.8 fb, 8 TeV [ATLAS-CONF-20209] L=5.8 fb, 8 TeV [ATLAS-CONF-20209] L=4.7 fb, 7 TeV [ ] L=4.7 fb, 7 TeV [ ] L=4.7 fb, 7 TeV [20.34] L=4.8 fb, 7 TeV [ ] L=4.8 fb, 7 TeV [ATLAS-CONF-20244] L=4.8 fb, 7 TeV [2.67] L=5.8 fb, 8 TeV [ATLAS-CONF-20252] L=0.5 fb, 8 TeV [ATLAS-CONF-20247] L=2.8 fb, 8 TeV [ATLAS-CONF-20245] L=5.8 fb, 8 TeV [ATLAS-CONF-20205] L=3.0 fb, 8 TeV [ATLAS-CONF-2025] L=5.8 fb, 8 TeV [ATLAS-CONF-20203] L=2.8 fb, 8 TeV [ATLAS-CONF-20245] L=2.8 fb, 8 TeV [ATLAS-CONF-20265] L=3.0 fb, 8 TeV [ATLAS-CONF-2025] L=4.7 fb, 7 TeV [ , ] 67 GeV L=3.0 fb, 8 TeV [ATLAS-CONF-20266] L=3.0 fb, 8 TeV [ATLAS-CONF-20267] L=3.0 fb, 8 TeV [ATLAS-CONF-20266] L=4.7 fb, 7 TeV [ , , ] L=2. fb, 7 TeV [ ] L=4.7 fb, 7 TeV [ ] L=4.7 fb, 7 TeV [ ] L=3.0 fb, 8 TeV [ATLAS-CONF-20254] L=3.0 fb, 8 TeV [ATLAS-CONF-20254] L=4.7 fb, 7 TeV [ ] L=4.7 fb, 7 TeV [2.597] L=4.7 fb, 7 TeV [2.597] L=4.7 fb, 7 TeV [2.597] L=4.4 fb, 7 TeV [20.745] L=4.6 fb, 7 TeV [Preliminary] L=4.6 fb, 7 TeV [Preliminary] L=4.7 fb, 7 TeV [ATLAS-CONF-20240] L=3.0 fb, 8 TeV [ATLAS-CONF-20253] L=3.0 fb, 8 TeV [ATLAS-CONF-20253] L=4.6 fb, 7 TeV [20.483] L=4.6 fb, 7 TeV [ ] L=0.5 fb, 8 TeV [ATLAS-CONF-20247] *Only a selection of the available mass limits on new states or phenomena shown. All limits quoted are observed minus σ theoretical signal cross section uncertainty. ATLAS SUSY Searches* - 95% CL Lower Limits (Status: Dec 202).50 TeV q = g mass.24 TeV q = g mass 0.8 TeV g mass (m( q) < 2 TeV, light χ ) 0.38 TeV q mass (m( g) < 2 TeV, light χ ) 0 ± g mass GeV (m( χ ) < 200 GeV, m( χ ) = (m( χ 2.24 TeV g mass (tanβ < 5).20 TeV g mass (tanβ > 20) 0.07 TeV g mass (m( χ ) > 50 GeV) 69 GeV g mass GeV g mass (m( χ ) > 220 GeV) 690 GeV g mass (m( H) > /2-4 F scale (m(g 200 GeV) 645 GeV ) > 0 ev) 0.24 TeV g mass (m( χ ) < 200 GeV) GeV g mass (m( χ ) < 300 GeV) GeV g mass (m( χ ) < 300 GeV) 0.00 TeV g mass (m( χ ) < 300 GeV) 0.5 TeV g mass (m( χ ) < 200 GeV) GeV b mass (m( χ ) < 20 GeV) ± GeV b mass (m( χ ) = 2 m( χ )) 0 t mass (m( χ ) = 55 GeV) 0 ± GeV t mass (m( χ ) = 0 GeV, m( χ ) = 50 GeV) 0 ± GeV t mass (m( χ ) = 0 GeV, m( t)-m( χ ) = 0 GeV) GeV t mass (m( χ ) = 0) GeV t mass (m( χ ) = 0) 0 30 GeV t mass (5 < m( χ ) < 230 GeV) GeV l mass (m( χ ) = 0) ± χ 0 ± GeV mass (m( χ ) < 0 GeV, m( l, ν) = (m( χ ) + m( χ ))) ± ± GeV χ mass (m( χ ) = m( χ ), m( χ ) = 0, m( l, ν) as above) ± ± GeV χ mass (m( χ ) = m( χ ), m( χ ) = 0, sleptons decoupled) ± 2 ± 220 GeV χ mass ( < τ( χ ) < 0 ns) 985 GeV g mass 683 GeV t mass 300 GeV τ mass (5 < tanβ < 20) -5, GeV q mass (0.3 0 < λ, mm < cτ 2 <.5 0 )+m( g)),.6 TeV ν τ mass (λ 3 =0.0, λ 32 =0.05),.0 TeV ν + χ τ mass (λ 3 =0.0, λ (2)33 =0.05).2 TeV q = g mass (cτ LSP < mm) GeV mass (m( χ ) > 300 GeV, λ or λ 0 > 0) GeV l mass (m( χ ) > 00 GeV, m( l e)=m( l µ)=m( l τ), λ or λ > 0) GeV g mass GeV sgluon mass (incl. limit from ) 704 GeV M* scale (m χ < 80 GeV, limit of < 687 GeV for D8) Ldt = ( ) fb < m, g decoupled) ATLAS Preliminary s = 7, 8 TeV 8 TeV results 7 TeV results 0 0 Mass scale [TeV]

38 Outlook At the LHC we have learned that: Perturbative QCD works for heavy quarks! Top quark properties are consistent with predictions! Top quarks look like ordinary Standard Model particles. Are we done with top? No! Top quarks will still play a large role in LHC-II physics: it s hard to search for new physics without selecting or excluding top quarks!

Status of Supersymmetric Models

Status of Supersymmetric Models Sudhir K Vempati CHEP, IISc Bangalore Institute of Physics, Bhubhaneswar Feb, 203 Outline Why Supersymmetry? Structure of MSSM Experimental Status New models of SUSY S/(S+B)