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Testing the standard Model in the forward region at the LHC

Testing the standard Model in the forward region at the LHC. Ronan McNulty (UCD Dublin) Irish Quantum Foundations, Castletown House, 3,4 th May 2013. Outline. Theory : The Standard Model Experiment : LHCb detector Electroweak tests using W, Z; probing the proton structure

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Testing the standard Model in the forward region at the LHC

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  1. Testing the standard Model in the forward region at the LHC Ronan McNulty (UCD Dublin) Irish Quantum Foundations, Castletown House, 3,4th May 2013

  2. Ronan McNulty, Irish Quantum Foundations Outline • Theory: The Standard Model • Experiment: LHCb detector • Electroweak tests using W, Z; probing the proton structure • Electroweak tests using Z; sensitivity to Higgs • Test EM & QCD with exclusive production of dimuons, J/ and χc. .

  3. Ronan McNulty, Irish Quantum Foundations This is what we want to test....

  4. Ronan McNulty, Irish Quantum Foundations fermion mass Higgs mass W mass Z mass

  5. Ronan McNulty, Irish Quantum Foundations fermion propagator fermion mass W propagator photon prop. Z propagator Higgs mass W mass Higgs prop. Z mass gluon propagator

  6. Ronan McNulty, Irish Quantum Foundations fermion propagator fermion mass QED vertex W,Z vertex W propagator photon prop. W,Z,photon interactions Z propagator Higgs mass W mass Higgs interactions with fermions and bosons Higgs prop. Z mass gluon propagator QCD vertex

  7. Ronan McNulty, Irish Quantum Foundations fermion propagator fermion mass QED vertex W,Z vertex W propagator photon prop. W,Z,photon interactions Z propagator Higgs mass W mass Higgs interactions with fermions and bosons Higgs prop. Z mass gluon propagator QCD vertex

  8. Ronan McNulty, Irish Quantum Foundations The LHC ALICE ATLAS CMS LHCb Nominal Energy: 7TeV (10-15m)

  9. Ronan McNulty, Irish Quantum Foundations ATLAS and CMS surround the interaction region Fully instrumented in region: -2 <  < 2 Partial instrumentation: -5 <  < 5

  10. Ronan McNulty, Irish Quantum Foundations The LHCb detector 0.4

  11. Ronan McNulty, Irish Quantum Foundations Complementarity of LHC detectors

  12. Ronan McNulty, Irish Quantum Foundations 1. Electroweak tests using W, Z; probing the proton structure u u d u u d

  13. Ronan McNulty, Irish Quantum Foundations fq(x,Q2) • Parton Density Function (PDF): • Probability that the proton contains this parton with this momentum fraction • Q = Invariant mass of parton interaction • x = Qe±y/s [y is rapidity, s c.o.m] u u d u u d

  14. Ronan McNulty, Irish Quantum Foundations Theory v Experiment at the LHC Hadronic Cross-section PDFs Partonic Cross-section • Test the Standard Model at the highest energies. W/Z theory known to 1% • Constrain parton distribution functions. • Test QCD – of particular interest in regions with very soft gluons

  15. Ronan McNulty, Irish Quantum Foundations 9 8 7 6 5 log10(Q2) [GeV2] 4 3 2 1 0 -1 -6 -5 -4 -3 -2 -1 0 log10(x)

  16. Ronan McNulty, Irish Quantum Foundations 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)

  17. Ronan McNulty, Irish Quantum Foundations 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)

  18. Ronan McNulty, Irish Quantum Foundations 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)

  19. Ronan McNulty, Irish Quantum Foundations 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)

  20. Ronan McNulty, Irish Quantum Foundations 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)

  21. W,Z g* Ronan McNulty, Irish Quantum Foundations 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)

  22. W,Z g* Ronan McNulty, Irish Quantum Foundations 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)

  23. Ronan McNulty, Irish Quantum Foundations Pre-LHC precision on W,Z cross-sections e.g. very roughly

  24. Ronan McNulty, Irish Quantum Foundations W and Z production in the forward region Experimentally: =N/L Count number of events: Z, W Master formula:

  25. Ronan McNulty, Irish Quantum Foundations The LHCb detector 0.4

  26. Ronan McNulty, Irish Quantum Foundations First Z candidate

  27. Ronan McNulty, Irish Quantum Foundations Z cross-section measurement

  28. Ronan McNulty, Irish Quantum Foundations Efficiencies for W and Z analysis found from tag-and-probe

  29. Ronan McNulty, Irish Quantum Foundations First W candidate

  30. Ronan McNulty, Irish Quantum Foundations Purity of W selection 2<<2.5 2.5<<3 3<<3.5 + - 3.5<<4 4<<4.5

  31. Ronan McNulty, Irish Quantum Foundations W charge asymmetry

  32. Ronan McNulty, Irish Quantum Foundations Comparison to CMS

  33. Ronan McNulty, Irish Quantum Foundations Testing the theory

  34. Ronan McNulty, Irish Quantum Foundations Z differential cross-section as fn of rapidity and transverse momentumcompared to various PDF sets and different generators

  35. Ronan McNulty, Irish Quantum Foundations 1. Summary • Electroweak data from LHC is in good agreement with Standard Model Predictions. • PDFs constrained and thus predict other processes (e.g. Higgs) with greater precision.

  36. Ronan McNulty, Irish Quantum Foundations 2. Electroweak tests using Z; sensitivity to Higgs   e Are these couplings the same? Could something else produce ?

  37. Ronan McNulty, Irish Quantum Foundations Z->ττ signal and background

  38. Ronan McNulty, Irish Quantum Foundations Trigger and selection

  39. Ronan McNulty, Irish Quantum Foundations Estimated signal contributions μe μμ μμ eμ μh eh

  40. Ronan McNulty, Irish Quantum Foundations Comparison of Z->μμ and Z->ττ results

  41. Ronan McNulty, Irish Quantum Foundations Reinterpretation in terms of Higgs

  42. Ronan McNulty, Irish Quantum Foundations Higgs boson in the forward region Model independent limits SUSY limits (mhmax scenarios)

  43. Ronan McNulty, Irish Quantum Foundations 2. Summary • Lepton universality holds • SUSY parameter space severely constrained. • With more statistics we are sensitive to Higgs production in the forward region.

  44. Ronan McNulty, Irish Quantum Foundations 3. Exclusive J/ψ and ψ(2S), χc and μμ Results based on 37pb-1 of data taken in 2010

  45. Ronan McNulty, Irish Quantum Foundations Physics of the Vacuum Elastic p p It’s QCD – but not as we normally see it. It’s colour-free σelastic≈ 40mb σdiffractive ≈ 10mb σinelastic ≈ 60mb

  46. Ronan McNulty, Irish Quantum Foundations Physics of the Vacuum Pomeron (soft) Elastic p 0+ p It’s QCD – but not as we normally see it. It’s colour-free σelastic≈ 40mb σdiffractive ≈ 10mb σinelastic ≈ 60mb

  47. Ronan McNulty, Irish Quantum Foundations Physics of the Vacuum Pomeron (soft) p 0+ p It’s QCD – but not as we normally see it. It’s colour-free σelastic≈ 40mb σdiffractive ≈ 10mb σinelastic ≈ 60mb

  48. Ronan McNulty, Irish Quantum Foundations Physics of the Vacuum Pomeron (hard and soft) Diffractive No activity “rapidity gap” 0+ p p It’s QCD – but not as we normally see it. It’s colour-free σelastic≈ 40mb σdiffractive ≈ 10mb σinelastic ≈ 60mb

  49. Ronan McNulty, Irish Quantum Foundations Physics of the Vacuum “particle” Pomeron (hard) Central Exclusive “rapidity gap” 0+ p “rapidity gap” p Elastic diffractive: clean environment to study vacuum, and in particular, transition between soft and hard pomeron. σelastic≈ 40mb σdiffractive ≈ 10mb σinelastic ≈ 60mb

  50. Ronan McNulty, Irish Quantum Foundations Physics of the Vacuum “particle” Pomeron (hard) Central Exclusive “rapidity gap” 0+ p Photon “rapidity gap” p Elastic diffractive: clean environment to study vacuum, and in particular, transition between soft and hard pomeron. σelastic≈ 40mb σdiffractive ≈ 10mb σinelastic ≈ 60mb

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