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W, Z and exclusive mm at LHCb

W, Z and exclusive mm at LHCb. Ronan McNulty University College Dublin. Workshop on Heavy Particles at the LHC Pauli Centre, ETH, Zurich 05.01.2011. Outline. Overview W,Z production (x~10 -4 ) Sensitivity to PDFs Sensitivity to sin 2 q W g * production (x~10 -6 ) Exclusive processes.

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W, Z and exclusive mm at LHCb

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  1. W, Z and exclusive mm at LHCb Ronan McNulty University College Dublin Workshop on Heavy Particles at the LHC Pauli Centre, ETH, Zurich 05.01.2011 Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  2. Outline • Overview • W,Z production (x~10-4) • Sensitivity to PDFs • Sensitivity to sin2qW • g* production (x~10-6) • Exclusive processes Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  3. EW physics motivation Partonic Cross-section FEWZ NNLO(1%) Hadronic Cross-section PDFs (3-5%) Test the SM at highest energies Check out that DGLAP evolution works (test QCD) Push theory into interesting regions with very soft gluons Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  4. 9 8 7 6 5 log10(Q2) [GeV2] 4 3 2 1 0 -1 -6 -5 -4 -3 -2 -1 0 log10(x) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  5. 9 8 7 6 5 log10(Q2) [GeV2] 4 3 2 1 0 -1 LHC kinematic region -6 -5 -4 -3 -2 -1 0 log10(x) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  6. 9 8 7 6 5 log10(Q2) [GeV2] 4 3 2 1 0 -1 LHC kinematic region DGLAP evolution -6 -5 -4 -3 -2 -1 0 log10(x) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  7. 9 8 7 6 5 log10(Q2) [GeV2] 4 3 2 1 0 -1 y: 6 4 2 0 2 4 6 LHC kinematic region Production of object of mass Q at rapidity DGLAP evolution -6 -5 -4 -3 -2 -1 0 log10(x) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  8. 9 8 7 6 5 log10(Q2) [GeV2] 4 3 2 1 0 -1 y: 6 4 2 0 2 4 6 LHC kinematic region ATLAS & CMS ATLAS & CMS: Collision between two partons having similar momentum fractions. PDFs either already measured by HERA or Tevatron, or requiring modest extrapolation through DGLAP. -6 -5 -4 -3 -2 -1 0 log10(x) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  9. LHCb: a forward spectrometer y Tracking Stations Muon Chambers Interaction Point 250mrad 10mrad Vertex detector l 20m z Magnet RICH detectors ECAL HCAL Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  10. 9 8 7 6 5 log10(Q2) [GeV2] 4 3 2 1 0 -1 y: 6 4 2 0 2 4 6 LHC kinematic region LHCb: Collision between one well understood parton and one unknown or large DGLAP evolved parton. LHCb LHCb -6 -5 -4 -3 -2 -1 0 log10(x) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  11. hep-ph/9927031 Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  12. ~LHCb Effect of PDF uncertainties on cross-sections • Region where the most precise EW tests can be made. • At highest rapidities, PDFs can be constrained. • Experimental statistical error <<1%. • Systematic error likely to be ~1% Z W+ W- Percentage uncertainty on cross-sections due to PDF Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  13. But you can do better ! So ratio of Ws is sensitive to d to u ratio. (For LHCb dv/uv) W asymmetry is sensitive to difference in u and d. (For LHCb uv-dv) Ratio of Z to W is almost insensitive to PDFs! Gold plated test of SM at the highest energies Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  14. Effect of PDF uncertainties on cross-sections • RWZ precise test of SM everywhere. • Difference in u and d quarks can be significantly improved by all experiments at the LHC. • Going forward, you increasingly constrain the u-valence to d-valence ratio. • Even nicer, most experimental systematics (especially luminosity) cancel in the ratio. (W+-W-)/(W+W-) W+/W- Percentage uncertainty on cross-section ratios due to PDF W/Z Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  15. Z Cross-section Measurement at LHCb Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  16. 8% of Z within LHCb acceptance 17% (16%) of W+ (W-) within LHCb acceptance Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  17. Z: Characteristic signature of two high transverse momentum muons with invariant mass mZ Require two muons: pt>20GeV, 2<η<4.5. 81<M<101 GeV Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  18. =1 =1 Z: Characteristic signature of two high transverse momentum muons with invariant mass mZ Require two muons: pt>20GeV, 2<η<4.5. 81<M<101 GeV 16.5 pb-1 To turn into cross-section: Insomuch as possible, take everything from data. Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  19. Muon identification efficiency • W=98.2  0.5% • Z=96.5 0.7% Efficiency flat in pT,h,f No evidence for charge bias data simulation truth level Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  20. Track Efficiency from Tag and Probe • W+=73  3% • W-= 78  3% • Z = 83  3% (W+/W- differ due to lepton h distribution) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011 (flat in pT and f)

  21. Tag muon fired trigger Does probe muon fire trigger ? Trigger Efficiency from Tag and Probe eW=0.9*(80.5  1.4)% eZ=0.9*(95.7  0.5)% (Globel cuts: Very large events rejected by trigger) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  22. Z analysis Phase space for measurement Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  23. Differential distribution (Z) LHCb preliminary (Requiring both muons have pt>20, 2<η<4.5.) 16.5 pb-1 FEWZ NLO with MSTW2008 PDF Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  24. Measuring AFB in pp->Z->mm ? A0FB=3/4 Am( u Au + d Ad + s As) LHC Problems: 1. PDF uncertainties 2. which is quark direction? HORACE (Born level) statistical uncertainty with 100fb-1 at 14TeV Δ(AFB) for Δsin2q=0.0001 Z rapidity Statistically, a forward detector at high luminosity could measure AFB with better precision than current WA. How confident are we of theory? of PDF uncertainties? of detector systematics? Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  25. W Cross-section Measurement at LHCb Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  26. n W W: One high transverse momentum muon with little else. Background much larger than for Z Require muon pt>20GeV + little activity in ‘rest of event’ Can be found using Z events in data Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  27. Selecting W events • pt of muon (>20GeV) • ip significance of muon (<2) • Mass of rest of event (<20 GeV) • Pt of rest of event (<10 GeV) • Charged transverse momentum in cone of 0.5 units of √(Δη)2+(ΔΦ)2 around muon. (<2 GeV) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  28. W analysis LHCb preliminary LHCb preliminary Z in simulation Z data W in simulation Bkg from data using anti-cuts • Z(sim) = W(sim) • Z(data) ~ Z(sim) • Bkg(data) != Z(data) • Data derived: • cuts; • efficiency; • purity. LHCb preliminary LHCb preliminary Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  29. W analysis LHCb preliminary 16.5 pb-1 Z (fixed with sim) t (fixed and scaled to W) QCD: fit fraction. (shape from data) W+/-: fit fraction (shape from data) W+ W- and all found from data. Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  30. W analysis Phase space for measurement (Measurement as function of lepton rapidity) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  31. W asymmetry 16.5pb-1 Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  32. W,Z Summary LHCb preliminary Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  33. How well can W,Z measurements constrain the PDFs? Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  34. Improvement to MSTW08 PDFs with 0.1fb-1 of high mass vector bosons at 7TeV Uncertainty on PDF with 0.1fb-1 of LHCb data Uncertainty on PDF without LHCb data 10-5 10-4 10-3 10-2 10-1 1 10-5 10-4 10-3 10-2 10-1 1 10-5 10-4 10-3 10-2 10-1 1 10-5 10-4 10-3 10-2 10-1 1 10-5 10-4 10-3 10-2 10-1 1 Modest improvement with small amount of data Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  35. Comparison with different PDFs using 0.1fb-1 of high mass vector bosons at 7TeV Uncertainty on PDF with 0.1fb-1 of LHCb data Uncertainty on PDF without LHCb data Similar sensitivity. Ability to distinguish models Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  36. Improvement to CTEQ66 PDFs with 1fb-1 of high mass vector bosons at 14 TeV Uncertainty on PDF with 1fb-1 of LHCb data Uncertainty on PDF without LHCb data More data and higher energy lead to larger improvements. Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  37. Using g* to go to very low-x. Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  38. W,Z g* 9 8 7 6 5 log10(Q2) [GeV2] 4 3 2 1 0 -1 y: 6 4 2 0 2 4 6 LHC kinematic region LHCb: Collision between one well understood parton and one unknown or large DGLAP evolved parton. Potential to go to very low x, where PDFs essentially unknown LHCb LHCb DGLAP evolution -6 -5 -4 -3 -2 -1 0 log10(x) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  39. 9 8 7 6 5 log10(Q2) [GeV2] 4 3 2 1 0 -1 Why this is interesting… LHC kinematic region Unexplored region Very little HERA data at this x More theoretical work required to make predictions Sensitivity to saturation? -6 -5 -4 -3 -2 -1 0 log10(x) Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  40. ~LHCb Effect of PDF uncertainties on cross-sections Percentage uncertainty on cross-sections due to PDF Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  41. PDF uncertainties at low-x, low-Q2 MSTW08. (Thanks to Graeme Watt) NLO LO NNLO Different behaviour and uncertainty with order of calculation. Gluon essentially unconstrained by data below 10-4 DGLAP evolution not trustworthy in this region. Gluon re-summation effects. Possibly entering saturation regime. Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  42. First analysis using just 37nb-1 of data. Challenge is in control of backgrounds Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  43. Improvement to MSTW08 PDFs with 0.1fb-1 of low mass vector bosons at 7TeV 10-5 10-4 10-3 10-2 10-1 1 10-5 10-4 10-3 10-2 10-1 1 10-5 10-4 10-3 10-2 10-1 1 10-5 10-4 10-3 10-2 10-1 1 10-5 10-4 10-3 10-2 10-1 1 Similar improvements to NNPDF, CTEQ and Alekhin PDFs. Sensitivity exists to distinguish between models. Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  44. Current uncertainty on MSTW08 PDFs and projections with 0.1fb-1, 1fb-1 of very low invariant mass muons at 7TeV 20% 20% 20% 10% 10% 10% 10-6 10-5 10-4 10-3 10-2 10-1 1 10-6 10-5 10-4 10-3 10-2 10-1 1 10-6 10-5 10-4 10-3 10-2 10-1 1 20% 20% 10% 10% 10-6 10-5 10-4 10-3 10-2 10-1 1 10-6 10-5 10-4 10-3 10-2 10-1 1 Significant improvements possible with modest amount of data Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  45. Exclusive dimuon final states Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  46. Exclusive particle production(2m and nothing else) 1 2 3 For LHC Luminosity Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  47. But is it exclusive ? Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  48. #J/Psi as Fn of #tracks Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  49. Exclusive J/Psi (compared to Starlight) 1 Require 2m consistent with Jpsi + no other charged or neutral activity Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

  50. Exclusive Chi_c (compared to SuperCHIC) 2 Require 2m consistent with Jpsi, 1 photon, and nothing else Ronan McNulty, Workshop on Heavy Particles at the LHC, Pauli Centre, ETH, Zurich, 05.01.2011

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