Top Quark Properties and Physics at LHC V

Top Quark Properties and Physics at LHC V Šimák CTU-FJFI, ASCR-FZU Prague (on behalf of ATLAS collaboration) Weak Interactions and Neutrinos (WIN'05) 6 -11 June 2005, Delphi, Greece • Electroweak gauge bosons • Top quark mass • Physics with top quark WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague

p-p collisions at √s = 14 Te. V bunch crossing every 25 ns (40 MHz) Ø low-luminosity: L ≈ 2 x 1033 cm-2 s-1 (L ≈ 20 fb-1/year) Atlas Ø high-luminosity: L ≈ 1034 cm-2 s-1 (L ≈ 100 fb-1/year) WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 2

Magnetic Field 2 T solenoid plus air core toroid Inner Detector s/p. T ~ 0. 05% p. T(Ge. V) (+) 0. 1% Tracking in range |h| < 2. 5 EM Calorimetry s/E ~ 10% / √E(Ge. V) (+) 1% Fine granularity up to |h| < 2. 5 Hadronic Calorimetry s/E ~ 50% / √E(Ge. V) (+) 3% Muon Spectrometer s/p. T ~ 2 -7 % Covers |h| < 2. 7 WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 3

pp → W+X with W→ l and l = e, m W - mass • isolated charged lepton with • p. T > 25 Ge. V inside |h| < 2. 4 • missing transverse energy • ETmiss > 25 Ge. V • rejection of large p. T W’s and plot the transverse mass, m. T, given by where f is the azimuthal angle between the l and the recoil X sensitivity is reduced by detector smearing LHC cross section is 30 nb: after selection acceptance, reconstruction and identification expect 60 M Ws per low luminosity year => precision on m. W is systematics limited… WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 4

Process Z→e+e. W→ev t anti-t Rate [Hz] Event s/Year Events (total) 1. 5 ~107 LEP 15 800 ~108 ~107 ~104 LEP 104 Tevatron Source Statistics 2 E-p scale 15 Energy resolution 5 Recoil model 5 Lepton identification 5 p TW 5 Parton distribution functions At low luminosity Combining channels this reduces to 20 Me. V (15 Me. V combined with CMS) MW (Me) 10 W width 7 Radiative decays 10 Background 5 Total WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 25 5

WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 6

stt(th)=825± 150 pb NNLO-NNNLL: Kidonakis, Vogt, PRD 68 (03) 114014 8 millions tt pairs/year (1 pair/second) at low luminosity! qq->tt: 13% gg->tt: 87% Top decays classification: di-lepton, lepton+jets, all jets WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 7

Cross sections 1. 96 Te. V 14 Te. V ttbar pairs 6. 70+0. 71 -0. 88 pb 825± 150 pb Single top (s-channel) 0. 75± 0. 12 pb 10± 1 pb Single top (t-channel) 1. 47± 0. 22 pb 245± 17 pb Single top (Wt channel) 0. 15± 0. 04 pb 60± 10 pb Wjj ~1200 pb ~7500 pb bb+other jets ~2. 4 x 105 pb ~5 x 105 pb hep-ph/9806332] WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 8

gg->tt: 87% % e qq e 1. 2 2. 5 14. 8 1. 2 14. 8 qq 44. 4 Top decays classification: di-lepton, lepton+jets, all jets Top quark properteis: charge, mass, spin, decay, dynamics of production WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 9

t coupling to photon can be probed via t tbar events can also be used to confirm Q=2/3 SM: Qt = +2/3 Qt = -4/3 Br(t Wb) 99. 9% Br(t Ws) 0. 1%, Br(t Wd) 0. 01% Many Beyond SM models involve anomalous top couplings Atlas Several possible rare decay modes (eg. FCNC) have clear experiment signatures and, if observed at the LHC, would be evidence for new physics p. T( ) [Ge. V] WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 10

• Semileptonic channel: 0. 2% efficiency • Total background 5% (-> large error from jet scale uncertainty) • Stat. error: ± 0. 25 Ge. V • Error from Pt(t) spectrum: ± 0. 4 Ge. V Atlas • Mass extracted from jjb system • Jet scale: DEj/Ej~1% -> DM~± 0. 3 Ge. V Require: • Isolated lepton with p. T(l) > 20 Ge. V • Exactly 4 jets ( R=0. 4), each with p. T(j) > 40 Ge. V • No b-tagging used • Plot m(jjj) of combo with max p. T mt 1 -2 Ge. V WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 11

Dilepton channel WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 12

• Unfeasible at low luminosity • Independent from jet scale • Promising at high luminosity • Among main systematics: b fragmentation mt 1 Ge. V WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 13

WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 14

W Polarization in Top Decays f 0 t WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague t t b 15

V-A weak interaction determines the top quark decay in SM WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 16

Polarization of Top WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 17

« Spin studies in tt pairs » WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 18

κ= 0 κ= -0. 34 SM LO WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 19

WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 20

Atlas κ= 0 WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague κ= -0. 34 SM LO 21

Neutral Higgs boson φ with unspecified CP parity W. Bernreuther, M. Flesch, P. Haberl – Phys. Rev. D 58 (1998) a, ã – reduced scalar and pseudoscalar couplings (SM Higgs boson: a=1, ã=0) WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 22

top quark Yukawa coupling can be measured from t tbar H production for m(H) < 130 Ge. V, H bb is dominant decay Þ tt. H final state is WWbbbb) Þ look for events with one W l , Þ the other W jj • p. T(lep) > 20 Ge. V • Njet 6 with p. T(jet) > 15 Ge. V • Nbjet = 4 WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 23

Single Top Production 3, 000 events/yr WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 24

• • there are large bkgnds (eg. tt [830 pb], Wbb [>300 pb]) with similar final states ability to extract signal depends critically on detector performance, including look at lepton, jet, bjet multiplicities, as well as kinematic distributions, to separate single top processes from ttbar, Wjj, Wbb, as well as from each other Atlas • Jet eta WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 25

Each process is sensitive to possible new physics in different ways Some examples: heavy W’ enhancement in schannel W* FCNC gu t enhancement in “Wg fusion” It is important to measure each process separately Also want to measure W, top helicities Eg. sensitivity to V+A, anomalous couplings WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 26

Phys. Rev. D 70, p 15015, 2004 e-Print Archive: hep-ph/0409273 Helicity angle correlations in model with graviton (MD = 0. 5 Te. V, λ = 1) A = +0. 97 The influence of extra-dimensions on the spin correlations of topantitop quarks could be visible at the LHC in the case the effective scale MD is lower than ~1. 5 -2 Te. V WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague

W helicity Top Mass l+ Top Width Production cross-section Resonance production Top Spin W+ Anomalous Couplings CP violation Top Charge n t Production kinematics Top Spin Polarization b _ Y t Rare/non SM Decays X Branching Ratios |Vtb| WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 28

One of the most urgent problems in HEP to identify the mechanism of EWSB and mass generation, in which the top quark may play a special role. The LHC has a large potential for discovery of New Physics effects: e. g. heavy tt resonances, FCNC decays, etc… Test some models beyond SM : New type of interactions (resonant Higgs, extra-dimensions, …) Modifications of SM couplings : anomalous gtt couplings anomalous Wtb coupling u WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague d s c b t 29

I would like to thank to my collegues from ATLAS and CMS for most of pictures in this talk Directly from Apollo: “If you switch on LHC you will see what you have never seen” Pythia (Delphi. June 7, 2005) WIN 05 Delphi 6 -11 June 2005 V. Šimák, CTU Prague 30

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