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EW @ LHCb: Future Look

EW @ LHCb: Future Look. Ronan McNulty (UCD) EW meeting 29 th November 2011. Working Group on Electroweak precision measurements at the LHC Tuesday, Nov 29 th , 2011. Channels. Z W W/Z W+/W- (W asymmetry) A fb Low mass DY Z + jets W + charm. General Comments 2010->2011.

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EW @ LHCb: Future Look

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  1. EW @ LHCb: Future Look Ronan McNulty (UCD) EW meeting 29th November 2011 Working Group on Electroweak precision measurements at the LHC Tuesday, Nov 29th, 2011

  2. Channels • Z • W • W/Z • W+/W- (W asymmetry) • Afb • Low mass DY • Z + jets • W + charm Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  3. General Comments 2010->2011 • Luminosity for 2011 is 1.1 fb-1 (factor 30) • Average number of interactions is 1.7 • Due to luminosity levelling, same running conditions throughout fills and throughout year • Triggers unchanged • *Very stable* for analysis • Since almost everything is data-driven, most systematics are statistical in nature • Factor 5.5 improvement Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  4. Z 2010 measurement dominated by statistics (sys. are statistical in nature) 2011 dominated by luminosity. How well can we know this? Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  5. W 2010 measurement dominated by statistics (sys. are statistical in nature) 2011 dominated by luminosity. How well can we know this? Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  6. How can we improve luminosity? • Well known process studied by all LHC • experiments. • A.G.Shamov and V.I.Telnov, NIM A 494 (2002) 5156, 2002. • J. Vermaseren, Nucl. Phys. B229, 347,1983. • CMS PAS DIF-07-001 • Bryan Caron, CERN-THESIS-2006-024 • CERN-LHCb-CONF-2011-022 • Difficulty is in selecting a pure enough signal. QED process Uncertainty <1% Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  7. Exclusive J/psi (not background subtracted) Candidates for di-photon produced dimuons Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  8. Fit elastic and inelastic components Shape for inelastic events Note: this time we have simulation that predicts the shape for the three contributions. Fit to signal events Background shape from data Signal shape from simulation. Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  9. Luminosity through pp->pmmp Note: Better than N improvement in 2011 due to lower average number of proton-proton interactions Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  10. W/Z (Remove luminosity) 2010 measurement dominated by statistics (sys. are statistical in nature) 2011 dominated by statistics & W bkg: 1% measurement looks possible Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  11. W+/W- 2010 measurement dominated by statistics (sys. are statistical in nature) 2011 dominated by statistics: Most sensitive experimental test of SM (<0.5%) Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  12. W asymmetry 2010 measurement dominated by statistics (sys. are statistical in nature) 2011 dominated by statistics Most sensitive experimental test of SM Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  13. Indicative uncertainties with 2011 data Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  14. Z boson: AFB (see WG meeting 5th April) 60,000 Z with 2011 data Precision of 0.004 on Afb. Precision of ~0.001 on sin2W (Similar to precision from Afb0l from one LEP experiment) Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  15. *-> below Z • Backgrounds appear controllable down to 10 GeV (x~2.10-5) • Statistical uncertainty ~ as for Z • Systematics under study: background description likely to be dominant. Purity ~ 25%. • Results hopefully for early 2012. • Excellent method for constraining gluon pdf at low x. Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  16. Z+jets • Z sample for 2011 being analysed using anti-kt, cone 0.5. • Requires jet energy calibration • difficult at LHCb • EM calorimeter saturation • Can’t use jet balancing techniques Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  17. W+charm • Possible once jet energy calibration understood …. • Require evidence for secondary vertices • generic HF tagging • IP of high pt tracks (as in Z->) • D meson reconstruction Working Group on Electroweak precision measurements at the LHC. 29.11.2011

  18. Summary • W,Z limited by luminosity uncertainty which can improve using pp • Ratios become systematic limited at ~ 1% • New measurements: Afb, low mass DY, Z+jets, W+charm Working Group on Electroweak precision measurements at the LHC. 29.11.2011

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