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Boson Production at Hadron Colliders

Boson Production at Hadron Colliders. Beate Heinemann, University of Liverpool/UK. The Standard Model and Beyond Hadron-Colliders: TeVatron and LHC Di-Boson Production Exclusive Higgs Production Conclusions. Di-Boson Production: What’s that?.

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Boson Production at Hadron Colliders

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  1. Boson Production at Hadron Colliders Beate Heinemann, University of Liverpool/UK • The Standard Model and Beyond • Hadron-Colliders: TeVatron and LHC • Di-Boson Production • Exclusive Higgs Production • Conclusions Beate Heinemann - MIT seminar

  2. Di-Boson Production: What’s that? Associated production of ≥ 2 gauge bosons of electroweak interaction pp->gg, Wg, Zg, WW, WZ, ZZ + X ? Something happens Beate Heinemann - MIT seminar

  3. The Standard Model of Particle Physics • 3 generations of quarks and leptons interact via exchange of gauge bosons: • Electroweak SU(2)xU(1): W, Z, g • Strong SU(3): g • Symmetry breaking caused by Higgs field • Generates Goldstone bosons • Longitudinal degrees of freedom for W and Z • 3 massive and one massless gauge bosons -Standard Model survived all experimental challenges in past 30 years Gauge Bosons Higgs Boson • Vacuum quantum numbers (0++) • Couples to mass Beate Heinemann - MIT seminar

  4. TeVatron The Higgs Boson: the missing piece? • Precision measurements of • MW =80.450 +- 0.034 GeV/c2 • Mtop=174.3 +- 5.1 GeV/c2 • Prediction of higgs boson mass within SM due to loop corrections MW (GeV) Mtop (GeV) If higgs boson is found at predicted values the Standard Model will have succeeded again  193 GeV Beate Heinemann - MIT seminar

  5. What if there is no Higgs? • WW cross section would violate unitarity since amplitude perturbative expansion in s: σ~s2/v2 + s4/v4… • Need either a SM Higgs with M<1 TeV or some other new physics (e.g. SUSY, Technicolor) • TeVatron and LHC probe relevant scale of 1 TeV! => We will find something (higgs or more extraodinary) in the next 10 years! Beate Heinemann - MIT seminar

  6. What could be Beyond the SM? • Supersymmetry (SUSY): • Each SM particle has a “super”-partner with same quantum numbers apart from spin (top <-> stop, photon <-> photino, etc.) • Masses are O(1 TeV) • Unification of forces at GUT scale (1016 GeV) • Extra Dimensions • String theory: links gravity to other forces • Could be large (0.1mm): probed at TeV scale • The unexpected… Beate Heinemann - MIT seminar

  7. Booster p source Main Injector and Recycler The TeVatron: Run II CDF D0 525 people 13 countries 580 people 17 countries - p-p collisions at sqrt(s) = 2.0 TeV bunch crossing rate 396 ns Beate Heinemann - MIT seminar

  8. Run II at the Tevatron • Run I: 100 pb-1 until 1996 • Run II: • Started March 2001 • 2 fb-1 by 2004->2006 • 6.5 fb-1 by 2008 • Disappointing startup but have about run I luminosity now! • Performance continuously improving: • Peak luminosities: • Run I best: 2.8x1031 cm-2s-1 • Run II best: 3.5x1031 cm-2s-1 • Run II goal: 20 x1031 cm-2s-1 Run I CDF Trigger fully working Factor 20-65 increased statistics compared to Run I Beate Heinemann - MIT seminar

  9. The Upgraded CDF Detector Central calorimeters Solenoid Central muon New Old Partially new Front end Trigger DAQ Offline TOF Endplug calorimeter Silicon and drift chamber trackers Forward muon Beate Heinemann - MIT seminar

  10. Beate Heinemann - MIT seminar

  11. m END WALL 2.0 HADRON = 1.0 n CAL. 0 30 SOLENOID 1.5 1.0 = 2.0 n END PLUG HADRON CALORIMETER COT END PLUG EM CALORIMETER .5 = 3.0 n 0 3 0 2.5 0 .5 1.0 1.5 2.0 3.0 m Intermediate silicon Inner silicon 1 or 2 layers 6 layers All detectors inside the solenoid are new • wire drift chamber (96 layers)TOF System • A new 3d tracking • system and vertex detector • covering |h|out to 2.0. • A new scintillating tile plug • calorimeter covering • |h| out to 3.6.

  12. First Physics with CDF in Run II Z->μμ: 1st search for new high mass particles W->ev: cross-section measurement B-Physics: 1st lifetimes and masses ct=458±10 stat. ±11 syst. mm (PDG: 469±4 mm) A lot more in upcoming Spring Conferences (LaThuile, Moriond) Beate Heinemann - MIT seminar

  13. Beyond the TeVatron: LHC • pp-collider at CERN • Center-of-mass energy: 14 TeV • Starts operation in 2008 • 3 years “low” luminosity: 10 fb-1 /yr • High luminosity: 100 fb-1 /yr Beate Heinemann - MIT seminar

  14. Di-Boson Production: Why? • SM precision tests • SUSY • Large Extra Dimensions • Higgs • Run I anomalies ? Something happens Beate Heinemann - MIT seminar

  15. Di-Photon Production at the Tevatron • SM couplings small (αem) • New Physics Scenarios: • Large Extra Dimensions: • Graviton exchange contributes • Present sensitivity about 900 GeV • Run II: sensitivity about 2 TeV • Generic “bump” search • Extraodinary events with 2 photons and transverse momentum imbalance(?) Beate Heinemann - MIT seminar

  16. Di-Bosons: W/Z + Photon • Sensitive to coupling of gauge boson to each other: WWg vertex • Gauge structure of SU(2)xU(1) gives precise prediction • Construct effective Lagrangian: introduce “anomalous couplings” kand l • vanish in SM • E.g. sizeable if W not point-like • Z+γ don’t couple to another (diagram C non existent): • Test this experimentally! • Signatures: • Wg : charged lepton, photon and Et (neutrino) • Zg : 2 charged leptons, photon • Typical cuts: lepton and neutrino Et >20 GeV, photon Et>7 GeV Beate Heinemann - MIT seminar

  17. W/Z + Photon as Standard Model test CDF II • Limits on Δκ and λ: • Test SM at level of about 10(30)% in Run II • Similar precision achieved in measurements at LEP • “Radiation Zero” unique to TeVatron: • suppressed w.g. for W- cosΘ*=-(1+2Qi)=-1/3 • Observable in angular separation of lepton and photon: ηγ-ηlepton Beate Heinemann - MIT seminar

  18. W + Photon as Search Run I: Et>25 GeV, lepton Et>25 GeV, photon Et>25 GeV • Run II: • Repeat run I analysis (20 x more data) • Extend to forward region (silicon tracker, new Plug calorimeter, new forward muon system) Phys. Rev. Lett. 89, 041802 (2002) Beate Heinemann - MIT seminar

  19. W/Z+gamma+X: more exclusive channels • Run I: • found 1 event with 2 photons, 2 electrons and large imbalance in transverse momentum • SM expectation 10-6 (!!!) • Run II: • Any such new event would be exciting! • Key problem: misidentification of jets as photons (hard pi0’s) • Other exclusive channels: lepton+photon+Met+X (high Pt) SUSY? Beate Heinemann - MIT seminar

  20. WZ Production: leptonic channel • -Leptonic channel (Z->ll, W->lv) background rather low (S/B=3) but • cross section also low (s=2.5 pb) • Anomalous couplings: WWZ may be different to WWγ • Experimental signature similar to SUSY “trilepton” channel: • Associated production of chargino and neutralino: disentangle on basis • of imbalance in transverse momentum, angular distributions SUSY SM Beate Heinemann - MIT seminar

  21. Di-Boson Production: Run I vs Run II “Leptonic” channels -3.2 * All cross sections in pb • - Run I cross section measurements slightly higher than SM prediction • Run II: huge increase due to luminosity and higher acceptance in • forward region (new calorimeter, Si tracking) Beate Heinemann - MIT seminar

  22. WW,WZ: hadronic channels • Large backgrounds from QCD processes: W+jets, Z+jets • Use bbbar channel (QCD BG suppressed) • WW & WZ have to be seen in hadronic channel before seeing the higgs=> excellent calibration channel • Exercises mass resolution: combining calorimeter and tracking => 30% improvement in energy resolution (B.H. et al.) RunI:0.5-1% Beate Heinemann - MIT seminar

  23. Di-Boson Production via Higgs-decay Dominant Production: gg-> H Decay: Di-bosons (γγ, WW or ZZ) one year Main Higgs discovery channels at LHC: two bosons in final state Beate Heinemann - MIT seminar

  24. Di-Boson Production - Di-Photon Production: discovery channel at LHC for mh<130 GeV • WW and ZZ Production: • discovery channels at LHC for 500>mh>130 GeV Beate Heinemann - MIT seminar

  25. Exclusive Higgs A recent development: search for exclusive Higgs production pp p H p -jet exclusive gap gap H p p beam -jet p’ Cross sections somewhat uncertain ~ 2 fb at LHC dipole roman pots dipole p’ Beate Heinemann - MIT seminar roman pots

  26. Exclusive Higgs Production Measure ξ in Roman Pots Reconstruct mass from protons only: =>Mass resolution of O(1 GeV/c2) independent of decay mode Access all Higgs decay modes: =>verify coupling to mass Beate Heinemann - MIT seminar

  27. Exclusive Higgs: Competitive channel at LHC 30 fb-1 at LHC DeRoeck, Khoze, Martin, Orava, Ryskin Eur.Phys.J.C25:391-403,2002 Beate Heinemann - MIT seminar

  28. Exclusive Higgs: Status of Theory • (fb) MH=120 GeV: Tevatron LHC Normalisation • Cudell, Hernandez (1994) - exclusive 30 200-400 elastic and soft pp • Cox, Forshaw, Heinemann: Phys.Lett.B540:263-268,2002 • inelastic 0.03-0.1 2-4 HERA x gap survival • Khoze, Martin, Ryskin: Eur.Phys.J. C23 (2002) 311-327 • inelastic ~0.05 ~3 • exclusive 0.02 3.0 “absolute” • Enberg et al. (2002) • inelastic 1.2-2.4.10-4 0.19 P(soft gluon exchange) • exclusive < 10-4 - Predictions difficult due to soft gluon contributions -Two predictions agree but need experimental testing! Beate Heinemann - MIT seminar

  29. Diffractive Higgs: Experimental Status All predictions tested by just one run I measurement of dijet-production: s(inel.)=44±20 nb s(excl.)<3.7 nb at 95% C.L. exclusive CDF Run I data - Higgs mass reconstruction only possible in exclusive channel but never observed experimentally - Prediction (KMR): σ≈1nb => Run II Beate Heinemann - MIT seminar

  30. Diffractive Higgs: Measurements at the Tevatron Should see bb, di-photon and Xb at TeVatron if predictions correct 1000 events/pb-1 100 events/fb-1 Excl. Xb->Yγ: σ≈120 pb • Should observe exclusive production: Xb and ggvery clean • Test theoretical predictions => build such detectors at LHC? Beate Heinemann - MIT seminar

  31. WW W/Zγ WZ SM precision tests ZZ Run I anomalies SUSY cb Conclusions Process Physics Inclusive Higgs γγ Exclusive Higgs Non-SM Higgs Large Extra Dimensions Mostly relevant for TeVatron and LHC Beate Heinemann - MIT seminar

  32. Why WW scattering? Without the Higgs, WL WL WL WL violates perturbative unitarity at 1.2 TeV (WT WT WT WT doesn’t) In the high energy limit, the WL ARE the 3 goldstone bosons associated with electroweak symmetry breaking Using all we know about electroweak symmetry breaking, (v = 246 GeV, 3 goldstone bosons, MW ~ MZ (residual global SU(2) symmetry)), can write quite generally, to 1 loop (from the EWChL): a4 anda5 parameterise our ignorance of the new physics (they come from the only dimension-4 terms we could add to the EWChL ) Beate Heinemann - MIT seminar

  33. Signatures for Diffraction Elastic protons Single Diffraction Double Diffraction DPE Non-Diffractive Beate Heinemann - MIT seminar

  34. Exclusive central diffraction is experimentally distinctive - inclusive has higher rate... • In exclusive process: pp  p + X + p: • only Jz = 0, P=+1 contribute1 • signature: forward-backward pair of protons separated • by two rapidity gaps from the central pair of jets • In inclusive process: pp  p X p extra particles emitted • in the central region. • (see:Ch. Royon) Khoze, Martin, Ryskin Boonekamp, Peschanski, Royon Cox, Lonnblad,... 1Amplitude averaged over the two transverse polarisations of the incoming gluons Beate Heinemann - MIT seminar

  35. Double Pomeron Exchange: exclusive channels with leading protons and rapidity gaps. The Pomeron has the internal quantum numbers of vacuum. • PP: C = +, I=0,... • P: JPC = 0++, 2++, 4++,... (not 1++ etc.) • gg vs. uu, dd, ss, cc, bb ? p1’ p1 - P - - - - P compare to: V-mesons, elastic scatt.... p2’ p2 Two types of signatures 2p  Gap Jet+Jet Gap diffractive system proton:p1’ proton:p2’ 0 hmin h hmax rapidity gap rapidity gap hmin hmax Rapidity Gap Survival Probability1 Tevatron LHC CD 5-14% 2-11% But there is a price to be paid for exclusivity! Beate Heinemann - MIT seminar 1 Khoze, Martin, Ryskin/Levin/Block et al

  36. Experimental Aspects: Photons • Backgrounds: • jet fragmenting into single hard pi0 • Use high granularity strip and wire chambers in central calorimeter to separate pi0 from photon • New strip and wire chambers in forward calorimeter • Electrons where track is not found • Difficult in forward region where only Silicon (no drift chamber) • Developing robust and efficient algorithms • Develop generic methods to estimate backgrounds (B. Heinemann et al.): • Jet fake rate about 0.1-0.01% for developed cuts P(jet->photon) Beate Heinemann - MIT seminar

  37. Going to High Energy 100 GeV 1000 GeV SLC LEP Tevatron: 1000 GeV protons LHC: 7000 GeV protons Beate Heinemann - MIT seminar

  38. The Success of the Standard Model Tevatron (CDF+D0) The Standard Model survived all experimental challenges of the last 30 years: D0 • Discovery of 2nd and 3rd family of leptons • Discovery of W- and Z-bosons • Precision measurements of various SM parameters (MW, Mtop, sin2θW, etc.): e.g. indirect prediction of top mass (LEP) agrees with direct measurements (TeVatron) CDF LEP lower limits Beate Heinemann - MIT seminar

  39. Di-Boson Production: What’s that? Associated production of ≥ 2 gauge bosons of electroweak interaction pp->γγ, Wγ, Zγ, WW, WZ, ZZ + X ? Something happens Beate Heinemann - MIT seminar

  40. The Standard Model of Particle Physics • - 6 quarks and 6 leptons interact via exchange of gauge bosons: • Electroweak: W, Z, γ • Strong: gluon (g) • All particles apart form gluon and photon are massive • All particles have been observed apart from Higgs boson • Particle mass is consequence of electroweak symmetry breaking due to Higgs field Mass (GeV/c2) Particle Beate Heinemann - MIT seminar

  41. The Success of the Standard Model TeVatron (CDF+D0) The Standard Model survived all experimental challenges of the last 30 years: D0 • E.g. LEP precision measurements (MW,MZ): • Predicted top quark mass agrees with direct measurement at TeVatron • No physics found beyond the Standard Model despite trying very hard… CDF LEP But most crucial higgs-boson Not seen yet! lower limits Beate Heinemann - MIT seminar

  42. Double Diffractive Dijets Appleby & Forshaw, Phys.Lett.B451:108-114,2002 Beate Heinemann - MIT seminar CDF Phys. Rev. Lett 85 4215 (2000)

  43. IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS 1 E+ -11101 0 0 4 5 0.00 0.00 980.0 980.0 0.00 2 E- 11 102 0 0 6 7 0.00 0.00 -980.0 980.0 0.00 3 CMF 0 103 4 6 0 0 0.01 -1.05 -31.1 163.0 160.02 4 GAMMA 22 3 1 0 0 0 0.07 -0.81 65.9 65.9 -0.84 5 E+ -11 1 1 0 0 0 -0.07 0.81 914.1 914.1 0.00 6 GAMMA 22 3 2 0 0 0 -0.06 -0.24 -97.1 97.1 -0.27 7 E- 11 1 2 0 0 0 0.06 0.24 -882.9 882.9 0.00 ---HARD SUBPROCESS--- IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS 8 GLUON 21 121 10 9 11 9 0.05 -0.62 50.8 50.9 0.75 9 GLUON 21 122 10 8 15 8 -0.04 -0.16 -65.0 65.0 0.75 10 HIGGS 25 120 8 9 67 67 14.85 -6.11 -14.4 117.0 115.01 ---H/W/Z BOSON DECAYS--- IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS 79 BQRK 5 123 67 80 81 80 25.96 -26.45 -57.1 68.2 4.95 80 BBAR -5 124 67 79 86 79 -11.11 20.34 42.6 48.8 4.95 Double Diffractive Higgs Beate Heinemann - MIT seminar

  44. Double Diffractive Dijets and Higgs Production POMWIG : “Central-inelastic” process p+p p + gap + H + X + gap + p • Is this really a contender for a light Higgs discovery channel ? • We won’t see DD Higgs at Tevatron, BUT we do see DD dijets • Question : Can we see the exclusive contributions in the DD dijets ? • Answer: Not yet, but we should (if it exists) in RunII. “exclusive” Khoze, Martin & Ryskin, hep-ph/0207313, Eur.Phys.J. C23 (2002) 311-327Cox, Forshaw & Heinemann, Phys.Lett.B540:263-268,2002 De Rouke, Khoze, Martin, Orava & Ryskin hep-ph/0207042 Albrow and Rostovtsev, hep-ph/0009336 … Beate Heinemann - MIT seminar

  45. QCD Hard scattering factorisation : conditional proton parton densities for particular xIP, t Regge factorisation : Beate Heinemann - MIT seminar

  46. WHAT IS POMWIG ? • No doubt that Ingelman – Schlein (Regge factorisation) works at HERA • Pomwig uses measured structure functions and flux from H1 OR user defined structure functions / flux Beate Heinemann - MIT seminar

  47. Why not the Standard Model? • Electroweak scale (100 GeV) much much lower than Planck Scale (1019 GeV)… (hierarchy problem) • No unification of forces • No explanation for matter/ anti-matter asymmetry in universe (CP-violation) • Many free parameters, e.g. masses of all particles => unsatisfactory Beate Heinemann - MIT seminar

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