Top Quark Physics at the LHC Ayana Arce HEP 0 Lectures #7 March 4, 203
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
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:
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:
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:
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:
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:
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:
The heaviest quark Top is important because it s such a heavy quark!
The heaviest quark Top is important because it s such a heavy quark! but why does the mass make it interesting?
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
The heaviest quark Theoretical importance in the Standard Model d Its weak interactions aren t weak! m t > m W t phew! b u
The heaviest quark Theoretical importance in the Standard Model m top [GeV] 90 G fitter SM 85 80 75 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: 70 65 60 55 50 LEP 95% CL LHC 95% CL Tevatron 95% CL σ band for m top 50 00 50 200 250 300 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!
The heaviest quark Practical importance? Entries / 50 GeV 6 0 5 0 4 0 3 0 2 0 0 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.5 0.5 00 200 300 400 500 600 miss ET [GeV]
The heaviest quark Practical importance? More reasons to care: It s the dominant background for many searches. dominant background good training samples!
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?)
Top quark production How are top quarks produced? Strong: σ = 238.06 pb Electroweak: σ = 5.74 pb t t t t
Top quark production How are top quarks produced? Strong: σ = 238.06 pb Electroweak: σ = 5.74 pb q q t t t t
Top quark production How are top quarks produced? Strong: σ = 238.06 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
Top quark production How are top quarks produced? Strong: σ = 238.06 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
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
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
A top event reconstructed at ATLAS
Selecting top rejecting backgrounds 0 9 proton - (anti)proton cross sections 0 9 Find one or two b-jets 0 8 0 8 σ tot 0 7 Tevatron LHC 0 7 0 6 0 6 σ (nb) 0 5 0 4 0 3 0 2 0 0 0 0 0-2 0-3 0-4 0-5 0-6 0-7 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) 0 5 0 4 0 3 0 2 0 0 0 0 0-2 0-3 0-4 0-5 0-6 0-7 events / sec for L = 0 33 cm -2 s
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 0 9 0 8 0 8 0 7 Tevatron LHC 0 7 0 6 σ tot 0 6 σ (nb) 0 5 0 4 0 3 0 2 0 0 0 0-2 σ b σ jet (E jet T > s/20) σ W σ Z σ jet (E jet T > 00 GeV) 0 5 0 4 0 3 0 2 0 0 0 0-2 ts / sec for L = 0 33 cm -2 s
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.
Top reconstruction techniques finding B-jets b quarks are special, too: often decays to leptons Long-lived! (.6 0 2 s)
Top reconstruction techniques finding B-jets b quarks are special, too: often decays to leptons Long-lived! (.6 0 2 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 jets -3 0-4 0 B hadron -0.8-0.6-0.4-0.2-0 0.2 0.4 0.6 0.8 Signed transverse impact parameter (mm) beamspot Decay Vertex track Impact Parameter
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 0 8 6 4 2 0.4.2 0.8 tt W+Jets Multijet Z+Jets Single Top Dibosons 0 40 80 20 60 200 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 + 4 + 8 0.70 fb 73 ± 6-7 pb - 50 00 50 200 250 300 350 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 0 250 68 ± 2 32 pb 2 pb + 60-57 ± 6 pb 0 200 50 ATLAS Preliminary 7 8 2 3 4 5 6 7 8
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 0 8 6 4 2 0.4.2 0.8 tt W+Jets Multijet Z+Jets Single Top Dibosons 0 40 80 20 60 200 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 + 4 + 8 0.70 fb 73 ± 6-7 pb - 50 00 50 200 250 300 350 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 + 60-57 ± 6 pb Consistent with QCD calculations at high mass! 250 0 200 50 ATLAS Preliminary 7 8 2 3 4 5 6 7 8
Top production cross section σ [pb] 2 0 ATLAS Preliminary Single top production L dt = (0.70 2.05) fb t channel Wt channel 0 Theory (approx. NNLO) stat. uncertainty s channel t channel, arxiv:205.330 Wt channel, arxiv:205.5764 s channel, ATLAS CONF 20 8 95% CL limit 5 6 7 8 9 0 2 3 4 CM energy [TeV] Consistency with electroweak calculations (so far)!
Top mass LHC vs. the Tevatron 7 ATLAS m top summary - July 202, L = 35 pb - 4.7 fb int ATLAS 200, l+jets* CONF-20-033, L int = 35 pb (*Preliminary) 69.3 ± 4.0 ± 4.9 Events / 5 GeV 600 500 400 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 ± 2.3 300 200 ATLAS 20, all jets* CONF-202-030, L int ATLAS 20, dilepton* CONF-202-082, L int = 2.05 fb = 4.7 fb 74.9 ± 2. ± 3.8 75.2 ±.6 ± 3.0 ± (stat.) ± (syst.) 00 0 00 50 200 250 300 350 400 reco m top [GeV] Tevatron Average July 20 73.2 ± 0.6 ± 0.8 ATLAS Preliminary 50 60 70 80 90 m top [GeV] Entries / 0 GeV 800 700 600 500 ATLAS Preliminary Ldt =.02 fb s = 7 TeV 20 Data Background signal LHC has more top quarks, but large systematic uncertainties! 400 300 200 00 0 0 00 200 300 400 500 600 m(jjj) [GeV]
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 ± 4.9 74.5 ± 0.6 ± 2.3 74.9 ± 2. ± 3.9 75.5 ± 4.6 ± 4.6 73. ± 2. ± 2.7 73.3 ±.2 ± 2.7 72.6 ± 0.4 ±.5 LHC June 202 73.3 ± 0.5 ±.3 Tevatron July 20 73.2 ± 0.6 ± 0.8 ± (stat.) ± (syst.) 50 60 70 80 90 m top [GeV] LHC has more top quarks, but large systematic uncertainties! Events / 5 GeV Entries / 0 GeV 600 500 400 300 200 00 = 7 TeV 20 Data 0 00 50 200 250 300 350 400 800 700 600 500 400 300 200 00 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 0 0 00 200 300 400 500 600 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. 2000 000 Data / MC 0.5 0.5 0 200 400 600 800 000 200 had H T [GeV] Understanding the top-higgs coupling is important! Events / 20 GeV 4 2 0 8 6 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 0.5 0.5 0 50 00 50 200 250 300 350 400 m bb [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. 2000 000 Data / MC 0.5 0.5 0 200 400 600 800 000 200 had H T [GeV] Understanding the top-higgs coupling is important! Events / 20 GeV 4 2 0 8 6 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 0.5 0.5 0 50 00 50 200 250 300 350 400 m bb [GeV]
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 +- + 0 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 - + 0 0 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 [208.4688] L=4.7 fb, 7 TeV [208.4688] L=4.7 fb, 7 TeV [20.34] L=4.8 fb, 7 TeV [209.0753] 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 [208.4305, 209.202] 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 [208.447,208.2590,209.486] L=2. fb, 7 TeV [204.6736] L=4.7 fb, 7 TeV [208.2884] L=4.7 fb, 7 TeV [208.2884] L=3.0 fb, 8 TeV [ATLAS-CONF-20254] L=3.0 fb, 8 TeV [ATLAS-CONF-20254] L=4.7 fb, 7 TeV [20.2852] 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 [20.4826] 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 0 900 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 0 900 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) 0 850 GeV g mass (m( χ ) < 300 GeV) 0 860 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) 0 620 GeV b mass (m( χ ) < 20 GeV) ± 0 405 GeV b mass (m( χ ) = 2 m( χ )) 0 t mass (m( χ ) = 55 GeV) 0 ± 60-350 GeV t mass (m( χ ) = 0 GeV, m( χ ) = 50 GeV) 0 ± 60-440 GeV t mass (m( χ ) = 0 GeV, m( t)-m( χ ) = 0 GeV) 0 230-560 GeV t mass (m( χ ) = 0) 0 230-465 GeV t mass (m( χ ) = 0) 0 30 GeV t mass (5 < m( χ ) < 230 GeV) 0 8595 GeV l mass (m( χ ) = 0) ± χ 0 ± 0 0-340 GeV mass (m( χ ) < 0 GeV, m( l, ν) = (m( χ ) + m( χ ))) ± ± 0 2 0 580 GeV χ mass (m( χ ) = m( χ ), m( χ ) = 0, m( l, ν) as above) ± ± 0 0 2 40-295 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, -5 700 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) 0 700 GeV mass (m( χ ) > 300 GeV, λ or λ 0 > 0) 2 22 430 GeV l mass (m( χ ) > 00 GeV, m( l e)=m( l µ)=m( l τ), λ or λ > 0) 2 22 666 GeV g mass 00-287 GeV sgluon mass (incl. limit from 0.2693) 704 GeV M* scale (m χ < 80 GeV, limit of < 687 GeV for D8) Ldt = (2. - 3.0) fb < m, g decoupled) ATLAS Preliminary s = 7, 8 TeV 8 TeV results 7 TeV results 0 0 Mass scale [TeV]
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!