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Preparation for Physics

Preparation for Physics. Masahiro Morii for the ATLAS Group Harvard University Laboratory for Particle Physics and Cosmology. LHC Schedule. 2008: 5 TeV x 5 TeV First circulating beam scheduled for 10 September 2008 First collision in October Luminosity 10 29 –10 31 cm -2 s -1

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Preparation for Physics

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  1. Preparation for Physics Masahiro Morii for the ATLAS Group Harvard University Laboratory for Particle Physics and Cosmology

  2. LHC Schedule • 2008: 5 TeV x 5 TeV • First circulating beam scheduled for 10 September 2008 • First collision in October • Luminosity 1029–1031 cm-2s-1 • Opportunity for early physics • 2009: 7 TeV x 7 TeV • Dipole training to 7 TeV during the winter shutdown • Luminosity increasing to 1033 cm-2s-1 • Integrate 6 fb-1 • Discovery potential for new physics beyond the SM ATLAS Physics

  3. Muon Spectrometer Deep knowledge in all aspects of the MDT system MDT chambers, electronics, DAQ, monitoring, and offline reconstruction Early physics with muon-based signatures Top Quarks Expertise in top-quark analyses from Tevatron Black, Brandenburg, Franklin, Guimarães da Costa, Huth, Kagan, Mills, Moed Attractive (and natural) place to search for BSM physics Building on Our Strengths ATLAS Physics

  4. Top Quark @ Tevatron ATLAS Physics

  5. Theory Colleagues • Particle Theory group at Harvard Howard Georgi • Pioneered GUTs (w/ Glashow), SUSY (w/ Dimopoulos) • Recent work: little Higgs, unparticles Lisa Randall • Warped extra dimension (w/ Sundrum) • Collider signatures of Kaluza-Klein gravitons, gluons Matthew Schwartz (new hire) • Effective field theory (SCET) applied to high-energy jets • QCD jets and high-PT top signatures at the LHC ATLAS Physics

  6. Muon Signatures • ATLAS muon spectrometer provides stand-alone tracking • Robustness suited for physics with early data • Kevin Black is the Muon Commissioning Software Manager • First things first: Find the SM resonances • Lashkar Kashif is working on the Z0PT spectrum with Z0 μμ • Heavy dilepton resonance (Z’  μμ) will be one of the earliest BSM physicsfrom the LHC • Black is leading the dilepton/diphoton analysis effort as the convener of the Lepton + XExotics working group • Black is also working on multi-lepton final states ATLAS simulation250 nb-1 ATLAS Physics

  7. Z0 Differential Cross Section • Z0 production cross section, PT spectrum, and ηdistribution serve many interesting physics • PT spectrum is a good test of QCD • η distribution is sensitive to the PDFs • Excess in high PT may come fromBSM physics • Understanding Z0 production iscrucial preparation for the next step • Calibration sample for jet energy scale, missing ET resolution • Control sample for Z0 νν • Major source of missing ET background CDF  distribution of Z0 e+e− ATLAS Physics

  8. Z0PT Spectrum • Kashif is preparing an early measurement of the PT spectrum • Analyzed simulated data for the Full-Dress Rehearsal (FDR) • Streaming test from Point 1 (ATLAS) through Tier-0  1  2 • Data are reconstructed, calibrated, and distributed to user analyses • Kashif was the first to successfully analyze muon data with triggeraccess in FDR1 and FDR2 • Demonstrated analysis w/ 250 nb-1 • Continue optimization in future exercises with increasingly more realistic data quality • Goal: Measurement with the first colliding-beam data ATLAS FDR1250 nb-1 ATLAS Physics

  9. Dilepton Resonances • Search for a bump in mμμ above the Drell-Yan background • Tevatron limits are 0.8–1 TeV depending on the models ATLAS will be able to reach ~2 TeV with 1 fb-1 CDF IIPreliminary2.3 fb-1 ATLAS prelim.5σ discovery curve cross-section limit ATLAS Physics

  10. Multi-lepton Final States • Black has studied new particles decaying into a WZ pair • Final state contains 3 leptons and a missing ET • Example: techni-ρ and techni-a in “walking” technicolor • ρT with mass up to 400 GeVcan be discovered with 5 fb-1 ATLAS prelim.50 fb-1 ρT,aT ATLAS Physics

  11. Top Quark • mt = 172.4 GeV Yukawa coupling ≈ 1 • Occupies a special place in BSM theories of EW symmetry breaking • Predicted new particles often couple strongly to top • Attractive probe for BSM physics • Large tt cross section at the LHC • 7 pb at Tevatron  900 pb (14 TeV) ≈ 1 event/s at 1033 cm-2s-1 • LHC is a top factory • Good: study top properties; use top for calibration • Bad: major background for New Physics ATLAS Physics

  12. Top Quark Reconstruction • Statistically most powerful tt samples are obtained in the semileptonic channel • 1 high-PT lepton, 4 jets, and missing ET • Optionally: tag b jets to enhance S/B • Need broad detector expertise in the group • Cross section helps • 100 x Tevatron  S/B better by x10 • Top quarks are boosted • Especially for BSM production mechanisms via heavy particles • Decay products (lepton, jets) are collimated See next talk by Ben Smith ATLAS Physics

  13. tt Resonances • Many BSM theories predict heavy spin-1 particles (e.g. leptophobic Z’ in topcolor) decaying preferentially into tt • CDF search for such a resonance [PRD 77, 051102 (2008)] set a limit at mZ’ > 720 GeV • Michael Kagan did this analysis as an undergrad ATLAS Physics

  14. Kaluza-Klein Gluon • Randall-Sundrum model predict KK excitation of gluons coupling strongly to right-handed top quarks • mKK > 1 TeV • Produced by qq • Signature: peak at large Mtt • Srivas Prasad and Ben Smithare studying reconstruction of such resonances Lillie, Randall, WangJHEP 0709:074 (2007) ATLAS Physics

  15. Statistical significanceagainst SM tt backgd. Heavy TQuark • Little Higgs models with T parity predicts pair creation of heavy top-like quarks (TT) • Each T decays into top + heavy photon • Signature: tt + missing ET • Verena Martinez Outschoorn has studied signal separation from SM tt using missing ET and • Working on W + jets backgrounds ATLAS Physics

  16. Outlook • We are organizing for analysis of early LHC data • Build on our strengths in muon spectrometer and top-quark analysis • Collaborate with the theory colleagues • Many challenges ahead, but we are getting ready for physics • Muon signature • Z0 xsection, PT spectrum • Z’  μμ, multi-lepton final states • Key: muon reconstruction and fast access to data Top quark signature • SM top production • tt resonances, heavy T quarks • Start from Tevatron experience and broaden skills • Key: high-PT top reconstruction ATLAS Physics

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