1 / 32

ATLAS physics studies

ATLAS physics studies. Lian-You SHAN On behalf of AtlasClusterChina TeV 4 @ Tango Aug 25, 2009 . Outline. Introduction Published studies Studies on going Possible Studies later Summary. Introduction. A brief report of past works For your review

willis
Download Presentation

ATLAS physics studies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ATLAS physics studies Lian-You SHAN On behalf of AtlasClusterChina TeV 4 @ Tango Aug 25, 2009

  2. Outline • Introduction • Published studies • Studies on going • Possible Studies later • Summary TeV 3 @ Tango, Aug 25, 2009

  3. Introduction • A brief report of past works • For your review • Thanks to ACC colleagues for the contributions • An presentation of works ongoing • For your suggestions, corrections • A short list of future possible works • For your ideas, collaborations TeV 3 @ Tango, Aug 25, 2009

  4. Published studies • Three works to ATL-COM-PHYS-2008/CERN-OPEN-2008-20 • ttH/WH production ( ACP-2008-199, IHEP ) • W pola & top S-corr ( ACP-2008-073, SDU ) • WZ x-sec ( ACP-2008-064, USTC ) • Other works unfortunately late (single top, RPVemu) • CSC-BOOK : the official/biggest publication • At least till 2008 before real data • Many test-beam exps, mature reconstruction, analysis-SW • A balance among many factors • Physics impact, luminosity, experimental feasibility • Experiences, International competition/collaboration TeV 3 @ Tango, Aug 25, 2009

  5. ttH/WH study • Physics motivation • Event selection • Preliminary results • Systematics TeV 3 @ Tango, Aug 25, 2009

  6. Ndata - Nbkg Measure Yt via ttH(HWW*) Yt Systematic errors • Nnl(n=2,3): observed events in ttH-WW* n-lepton final states • L: LHC integrated luminosity • εnl: total efficiency of n-lepton final states • I(MH): the integral over the parton momentum in initial states, propagator of gluon or quark in middle states and lepton/jet phase space in the final states • Cnl: the combination factor of branching of W decays Directly measures only: (ttH)*Br(HWW)=Nnl/(LnlCnl) TeV 3 @ Tango, Aug 25, 2009

  7. ttH Signatures • ttH2b4j2l2Vl 6jets + 2samecharge lep. + MissEt • Possible BGs: tt(1l), tt(2l), ttZ, ttW, tttt, ttWnq, ttbb... • ttH2b2j3l3Vl 4jets + 3leptons + MissEt • Possible BGs: tt(2l),ttZ,ttW,tttt,ttWnq,ttbb • Backgrounds come from: • Non-isolated leptons from jets • Gluon-jets are similar to quark-jets ( Worse in NLO ) • Electron-jet overlapping • Lepton Isolation is crucial 9 Mhiggs piontsfrom 120 to 200 GeV Default CSC results of MHiggs=160GeV • Try a survival from huge backgrounds: • Jet inefficiency/multiplicity • Faked electron • NonIsolated muon from semileptonic heavy flavor b P 2 leptons 4 light jets P b b P 3 leptons 2 light jets P b TeV 3 @ Tango, Aug 25, 2009

  8. Baseline selection • Basic selection e, mu, C4-jet: |η|<2.5; Pt>15 GeV/c e(Egamma):isEM=0x3FF,author=1,3 mu(StacoMu):IscombinedMuon=1 • Calo Isolation:etcone20<10 GeV • Track Isolation:trkPtmax20<2.0 GeV/c • Cone Isolation:muon:R(mu,jet)>0.25 electron:R(e,jet) > 0.2 or R(e,jet)<0.1 and Eele/Ejet>0.65 ( Remove related jet ) Isolation: Nlepton>=2/3, Njets>=6/4 • Nlep=2/3,Same charge (for 2L) • Zveto:(75,100) (lep Pt> 6GeV/c) • Muon_Pt> 20GeV/c Elec: eff=70.5% Muon: eff=92.7% TeV 3 @ Tango, Aug 25, 2009

  9. ttH(HWW) Cut flow 2L 3L TeV 3 @ Tango, Aug 25, 2009

  10. Preliminary results 2L : S/B ~ 1.87/11.1 3L : S/B ~ 0.82/3.7 precision(160GeV): 2L : 69% 3L : 66% Combined: 47% Result uncertainties dominated by Background systematic uncertainty to estimate and correct it by real data driven method is essential ! Can not sleep for backgrounds Can not awake without errors TeV 3 @ Tango, Aug 25, 2009

  11. Combined systematic uncertainties +0.0% -4.4% +4.9% -1.8% Take 10% Take 10% A work competed/collaborated among France, German, and finally Chinese dominate CSC TeV 3 @ Tango, Aug 25, 2009

  12. WH similarly A necessary supplementary/conformation of higgs production Needs a high luminosity >= 100 fb-1 , needs more efforts TeV 3 @ Tango, Aug 25, 2009

  13. spin=1/2 1/2 1 W polarization & top-pair spin correlation • Huge σtt@LHC ~ 850pb, BrtWb~1 • W polarization : • Top pair spin correlation : • Precise Measurement of F & A parameters • Please refer to Zong-Guo’s talk this morning for theory interests TeV 3 @ Tango, Aug 25, 2009

  14. Preliminary top results 0.304 0.695 0.001 0.422 -0.29 SM prediction TeV 3 @ Tango, Aug 25, 2009

  15. Preliminary top results(Ctd) A very good/precise measurement on hadronic colliders ! TeV 3 @ Tango, Aug 25, 2009

  16. WZ cross section • Common backgrounds/base in ATLAS • Early data measurement • Precise test of SM • Possible detection of anomalous TGC • Focus on l±νl+ l –channel • ZZ & Zjet dominate the backgrounds • 3 isolated high pTleptons, large MET, BDT tried TeV 3 @ Tango, Aug 25, 2009

  17. Preliminary WZ results • Skipping many analisis details : • Skipping many systematics details : σS = 9.2%, σB = 18.3% Errors included At different Lumi : 0.1, 1, 10 and 30 fb−1 TeV 3 @ Tango, Aug 25, 2009

  18. Studies on going • All above published studies are still on going • Real data needs more efforts/works • Your supports for funds • Four progressive works in addition • RPV emu ( USTC ) • Single top ( NJU & SDU ) • Measurement of Z+g (USTC) • ZH->ZW*W observation ( IHEP ) • All results are preliminary, NOT official to show TeV 3 @ Tango, Aug 25, 2009

  19. R-parity violating sneutrio resonance to e Parity in SUSY can be partially violated in generic super-potential: -- Tri-linear on-spontaneous B- & L-number violation interactions  stable proton -- Bi-linear couplings  neutrino mass for oscillation -- Constraints from indirect low energy experiments • Signal ( Comphep/pythia) and relevant backgrounds samples simulated • PID and event selection defined and backgrounds fraction estimated • Uncertainties and suitable statistics investigated 10-20 folded improvement on RPV parameter sensitivity would be expected @ATLAS TeV 3 @ Tango, Aug 25, 2009

  20. Single top measurement • The only known way to directly measure CKM matrix element Vtb t-channel (~247pb) W+t channel (~66pb) s-channel (~11pb) • Try to distinguish s-channel from t-channel production mode to test SM • Suffer top pair backgrounds, Smaller S-channel even suffer T channel backgrounds • PID and event selection defined and backgrounds fraction estimated • In improving by echniques fromm MultiVariable Analysis TeV 3 @ Tango, Aug 25, 2009

  21. Measurement of Z+γ • Presice test of SM • detect possible ZZg/Zgg anomaly SM FSR SM ISR Anomalous Zgg Anomalous ZZg • Joint ATLAS Z+g group • proposed data driven analysis on Z+Jet • Determine EM-like jet fake to gamma from di-jet sample • Fit the PDF of “prompt”gamma from Monte Carlo samples TeV 3 @ Tango, Aug 25, 2009

  22. ZH->ZW*W observation • SM Higgs should be observed/confirmed here • More important if theory of fermion-forbic Higgs • Measurement of σZH/σWH ∝ g2z / g2w • Combined with WH->W*W channel • expecting some errors cancelled • Progress • Relevant signal/backgrounds samples produced • Basic cut flow established • Some variables seem useful especially in MVA TeV 3 @ Tango, Aug 25, 2009

  23. Possible Studies later • Fermion-forbic Higgs ? • W1 production in jWZj ( USTC & IHEP ) • H-J HE, Y-P KUANG, Y-H QI, B. ZHANG • Phys. Rev. D 78, 031701(R) (2008) • VBF Higgs production with semi-leptonic W • CSC-NOTE discussed, overwhelming backgrounds • W+W+ production via anomalous HVV • Expect helps on generator from Theory side • ξ++ to same-charged lepton pair • Seeming feasible, needing generator • SUSY study ? (e final state,USTC ) TeV 3 @ Tango, Aug 25, 2009

  24. Fermionforbic Higgs decays • bb, cc, tautau drop more steeply • Zγ, especially γγ, increase much. • WW starts dominance earlier • ZZ contributes more • Only below 200GeV bb WW ZZ tau gg cc Z γ γ γ TeV 3 @ Tango, Aug 25, 2009

  25. If no Yukawa qqH dominates • Larger γγ relatively • important ZZ eventhough small branch • WW significance in semileptonic mode ★★★ ★★★ ★★★ ★★★ ★★ ★★ ★?★ ★?★ TeV 3 @ Tango, Aug 25, 2009

  26. W1 production in jWZj • Seems possible in experiment • ttbar, WZjets, ZZ, Zjets… • 3 isolated high pTleptons • large MET, 2 Forward jet tag • Possible Z/W1 reconstruction • Models are not what we care • Only if observable at lower luminosity • Only if executable generator presented • Thanks to Prof.CHEN, J.G.BIAN Z.X.ZHANG in CMS • Also thanks to Prof. HAN, B.ZHANG TeV 3 @ Tango, Aug 25, 2009

  27. A possible update on WH q1 V W W* H W V q2 W Toooo many backgrounds ! • Forward jets as Handles to pick up signal from backgrounds • Reasonable signal production x-sec ~ hundred of fb • Your precise estimation/calculation on signal and backgrounds ? TeV 3 @ Tango, Aug 25, 2009

  28. Summary • Many works done • Computing facility established and improved • Work quality is in improving • Many subjects are in exploration • Dynamical Balance among real data, competition... • Progress with vitality • Expect &Thanks for your suggestions&helps • generators TeV 3 @ Tango, Aug 25, 2009

  29. Thanks ! you are welcome ! TeV 3 @ Tango, Aug 25, 2009

  30. Backup slides TeV 3 @ Tango, Aug 25, 2009

  31. Higgs without Yukawa • Not forbidden in theory • No gluon-gluon production • , nor decay to gluons • Decay to photons changed TeV 3 @ Tango, Aug 25, 2009

  32. Yukawa is to fermions From ZPC 53, (1992) 507 Take : Γhff = 0.15* Γ0hff for all TeV 3 @ Tango, Aug 25, 2009

More Related