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QCD and Electroweak Results from the Tevatron Nikos Varelas University of Illinois at Chicago

QCD and Electroweak Results from the Tevatron Nikos Varelas University of Illinois at Chicago http://www.uic.edu/~varelas for the DØ and CDF Collaborations Physics at LHC DESY June 10, 2010. 21. QCD EWK. Outline. Tevatron Run II and CDF&DØ Detectors High-P T Jets W/Z/ g + Jets

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QCD and Electroweak Results from the Tevatron Nikos Varelas University of Illinois at Chicago

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  1. QCD and Electroweak Results from the Tevatron Nikos Varelas University of Illinois at Chicago http://www.uic.edu/~varelas for the DØ and CDF Collaborations Physics at LHC DESY June 10, 2010 21 QCD EWK

  2. Outline • Tevatron Run II and CDF&DØ Detectors • High-PTJets • W/Z/g + Jets • Multiple Parton Interactions • Minimum Bias/Underlying Event Studies • Electroweak Results • Summary http://www-cdf.fnal.gov/physics/new/qcd/QCD.html http://www-cdf.fnal.gov/physics/ewk/ http://www-d0.fnal.gov/Run2Physics/WWW/results/qcd.htm http://www-d0.fnal.gov/Run2Physics/WWW/results/ew.htm

  3. Proton Anti-Proton Collisions

  4. Tevatron Complex Chicago  p p 1.96 TeV Booster p CDF DØ Tevatron p p source Main Injector & Recycler Run I 1992-1996 ECM = 1.8 TeV ~120 pb-1 (0.63 TeV ~600 nb-1) Run IIA 2002-2005 ECM = 1.96 TeV ~ 1.5 fb-1 Run IIB 2006- ECM = 1.96 TeV ~ 7.5 fb-1

  5. DØ Detector • Multipurpose Detector • Silicon Microstrip and Scintillating Fiber Tracker • 2-T Superconducting Solenoid • Preshower Detectors • EM and HadronicCalorimeters • Uranium – LiquidArgon • Coverage: |h|<4.2 (q~20) • Finely segmented • Compensating e/p~1 • Muon Detectors

  6. CDF Detector • Multipurpose Detector • Silicon Vertex Detector • Central Outer Tracker (Drift Chambers) • TOF • 1.4-T Superconducting Solenoid • EM (Pb/Scint) and Had (Fe/Scint) Calorimeters • Coverage: |h|<3.6 • MuonDetectors • Gas Cherenkov • 3.7<|h|<4.7

  7. Tevatron Luminosity Delivered ~9 fb-1 Recorded ~8 fb-1

  8. High-pT Jets • CDF Results (since PLHC2008) • Search for Quark Substructure in the Angular Distribution of Dijets: Preliminary • Inclusive Jet Production: PRD 78, 052006 (2008) • Dijet Production: PRD 79, 112002 (2008) • DØ Results (since PLHC2008) • Three-Jet Mass Cross Section: Preliminary • Ratio of Multi-Jet Cross Sections: Preliminary • Dijet Invariant Mass Cross Section: submitted to PLB • Determination of as: PRD 80, 111107 (2009) • Dijet Angular Distributions and Searches for Quark Compositeness and Extra Spatial Dimensions: PRL 103, 191803 (2009)

  9. High-pTJet Production (x,Q2) reach xT • Confront pQCD calculations • NLO predictions reliable @ ±10% level • Sensitive to dynamics, PDFs, as • Reach to high-x gluons Large kinematic reach • Sensitivity to new physics (e.g., quark substructure, new particles decaying into jet final states, extra dimensions, ...)

  10. Inclusive Jets – The Old Days UA1 1986 Inclusive Jet CS UA2 1991 Inclusive Jet CS Uncertainties ~ 70% on CS: ±50% accept./jet corr (smearing) ±40% calib ±10% aging ±15% Lum LC > 400 GeV“Exp and theo. Uncerts. taken in to account” • √s = 0.5 – 0.6 TeV • Cone jet clustering • PT range: 20 – 200 GeV • Comparison to LO QCD • Compositeness LC > 0.8 TeV Uncertainties ~ 32% on CS: ±25% model dep. (fragmentation) ±15% jet alg/analysis params ±11% calib ±5% Lum LC > 825 GeV“...include sys. effects which could distort the CS shape” State of art: 3-jet production @ NLO (Next-to-Leading Order ~O(as4))

  11. Inclusive Jet Cross Section CTEQ6.5M PDFs pT (GeV) steeply falling pT spectrum: 1% error in jet energy calibration  5—10% (10—25%) central (forward) x-section Provide Input to PDF: MSTW2008 uses CDF and DØ results Data prefer lower gluon PDF at high-x DØ: PRL 101, 062001 (2008) CDF: PRD 78, 052006 (2008)

  12. The Strong Coupling Constant • Inclusive jet cross section is sensitive to as • asis determined from 22 inclusive cross section data points at the range 50<pT<145 GeV • MSTW2008NNLO PDFs • Most precise determination of as from a hadron collider jet jet PRL 101, 062001 (2008)

  13. Dijet Mass Distribution • Select jets with |y|<1.0 • Sensitive to new particles decaying to dijets Data described by NLO pQCD No indications for resonances Exclusions mass ranges: excited quarks 260 - 870 GeV Axigluon, flavor-universal coloron 260 - 1250 GeV E6Diquark 290 - 630 GeV Color-octet techni-r 260 - 1100 GeV W’ : 280 - 840 GeV Z’ : 320 - 740 GeV PRD 79, 112002 (2009)

  14. Dijet Mass Cross Sections Unfolded Cross Sections • Measurement in six |y|max regions • Jet Energy Scale is the leading source of data systematic uncertainty • CTEQ6.6 prediction too high • MSTW2008 consistent w/ data • 5-15% uncertainty • 10-15% mR,F variation arXiv: 1002.4594 (2010)

  15. Dijet Angular Distributions ds ~ [ QCD + Interference + Compositeness ] q q q q ds ~ 1/(1-cosq*)2 angular distribution ds ~ (1+cosq*)2 angular distribution From cosq* variable to c Rutherford with contact term LO QCD Mjj ~ Λ c cosq* dN/dcsensitive to contact interactions

  16. Dijet Angular: Results DØ: PRL 103, 191803 (2009) • Compositeness (L): ~2.8 – 3 TeV • ADD LED (GRW, Ms): ~1.6 – 1.7 TeV • TeV-1 Extra Dim (MC): ~1.6 – 1.7 TeV 1.1/fb, Mjj=550-950 GeV CDF Preliminary • CDF: L > 2.4 TeV for l = -1

  17. 3-Jet Mass Cross Section • First measurement of 3-jet cross section at Tevatron • Require at least 3 jets in the event • Jet1 pT> 150 GeV • Jet 2,3 pT> 40 GeV • Jets separated by DR > 1.4 = 2*Rcone • Measurement performed in: • rapidity intervals |y| < 0.8, 1.6, 2.4 • pT ranges of the 3rd jet: pTJet3 > 40, 70, 100 GeV • Compared data to NLO pQCD pTJet3 Dependence Rapidity Dependence

  18. R3/2: 3-Jet/2-Jet Cross Section Ratio S R3/2 = s3-jet / s2-jet = +... S + +... • R3/2 : probability to find a third jet in an inclusive dijet event • Sensitive to high order radiation and as • Almost independent of PDFs • Use inclusive n-jet (n=2,3) sample with n (or more) jets above pTmin • |yjet| < 2.4, DRjet-jet > 1.4 • Measurement of R3/2(pTmax, pTmin) vs. pTmax (i.e. leading jet pT)

  19. R3/2= s3-jet / s2-jet • Data can discriminate against PYTHIA tunes • Reasonable agreement with tune BW • Disagreement with tunes A & DW • SHERPA describes the data well

  20. Direct Photons • CDF Results (since PLHC2008) • Prompt Diphoton Production: Preliminary • Photons and b-quark Jet Production: PRD 81, 052006 (2010) • Inclusive Photon Production: PRD 80, 11106 (2009) • DØ Results (since PLHC2008) • Direct Photon Pair Production: Accepted by PLB • Photon + Heavy Flavor Production: PRL 102, 192002 (2009)

  21. Direct Photon Production (all quark/anti-quark subprocesses)‏ Diphotons • Photon processes: • Annihilation • Compton • Also fragmentation contributes • But suppressed with isolation • Directly sensitive to hard scatter • Important for QCD studies, detector calibration, gluon PDFs, background to new physics • Challenging measurement • Large QCD jet background • Observable: isolated photons

  22. Inclusive Photon Cross Section Similar effect observed: PLB 639, 151 (2006) • Data/theory: shape discrepancies at low-pT • Experimental and theory uncertainties ~ PDF uncertainty  No PDF sensitivity yet PRD 80, 11106 (2009)

  23. Photon + HF Jet Production g+b • Sensitive to HF-content of photon • Photon pT : 30 – 150 GeV • Rapidities: |yg|<1.0, |yjet|<0.8 • 0.01<x<0.3  b,c, gluon PDF • Photon+b: • Agreement over full pT range • Photon+c: • Agree only at pT<50 GeV • Using PDF w/ intrinsic charm (IC) improves the theory behavior vs pT g+c pTg (GeV) DØ: PRL 102, 192002 (2009) CDF: PRD 81, 052006 (2010)

  24. Di-Photon Production • 2 photons with pT > 21(20) GeV • |yg|<0.9, DR(g,g)>0.4, pT(gg)<M(gg) • Data are compared to RESBOS, DIPHOX, PYTHIA Accepted by PLB asXiv:1002.4917 (2010)

  25. Di-Photon Results Discrepancies between data and theoretical predictions

  26. Di-Photon Results Diphoton results w/ 5.4 fb-1 show discrepancies with predictions

  27. W/Z + Jets • CDF Results (since PLHC2008) • Z(mm) + Jets: Preliminary • pT Balance in Z+Jet Events: Submitted to NIM • W + Charm: Preliminary • W + b-Jet: PRL 104, 131801 (2010) • Z + b-Jet: PRD 79, 052008 (2009) • DØ Results (since PLHC2008) • Measurement of the s(Z+b jet)/s(Z+jet): Preliminary • Z/g+jet Angular Distributions: PLB 682, 370 (2010) • Differential Cross Sections of Z/g+jets : PLB 678, 45 (2009) • Differential Z/g+jet Cross Sections: PLB 669, 278 (2008)

  28. Z + Jets Jet multiplicity 1st and 2nd leading jet pT Good agreement with NLO MCFM PRL 100, 102001 & update

  29. Z(ee) + (1, 2, 3) Jets: pT Spectra Normalize to inclusive Z production  compare to MC Event Generators 1st jet 3rd jet 2nd jet Parton-shower MCs disagree in shape & normalization ME + Parton-shower generators describe shape better PLB 669, 278 (2008) PLB 678, 45 (2009)

  30. Z + b jet • Z+b probes the b-quark PDF and provides an important test of pQCD • Background for many channels: ZH, top, SUSY, … • Analysis combines Zee and mm channels • At least one jet with pT>20 GeV, |h|<1 • 2 electrons (muons) • pT>15 GeV (10 GeV), |h|<2.5 (2.0) Measurement: s(Z+b)/s(Z+j) = 0.01760.0024(stat)0.0023(sys) Good agreement with NLO QCD: 0.0180.004 Previous measurements: DØ: PRL 94, 161810 (2005) CDF: PRD 79, 052008 (2009)

  31. W + b jet • Important process from many searches at Tevatron and LHC • Invariant mass of charged particles associated with the secondary vertex is used to discriminate between the possible jet flavors to yield the b-jet fraction pTe,m> 20 GeV/c, |hem| < 1.1, pTn> 25 GeV/c pTbjet> 20 GeV, |hbjet| < 2.0‏ σ b-jets (W+b-jets) ⋅ BR(W → l v) = 2.74 ± 0.27 (stat) ± 0.42(syst) pb All predictions are lower than the measurement: Pythia: 1.10 pb, ALPGEN: 0.78 pb, NLO: 1.22±0.14 pb CDF: PRL 104, 131801 (2010)

  32. W + Charm • Probes s-content on proton • g+s ~ 90%, g+d ~ 10% • At TevatronW+c is ~5% of the inclusive W+1 jet cross section with pTjet>10 GeV • Charge correlation of leptons used in event selection • Use soft lepton tagger +NN for c-jet Preliminary Measurement (4.3 fb-1) s(Wc)BR(W lv) = 33.7 ± 11.4 (stat) ± 7.3 (syst) pb Theory prediction @NLO (MCFM): 16.5 ± 4.7 pb Previous CDF: PRL 100, 091803 (2008) • Measure of the ratio of s(W+c jet)/s(W+jets) cancels many systematic uncertainties • pTjet>20 GeV, |hjet|<2.5 DØ: PLB 666, 23 (2008)

  33. Soft QCD • CDF Results (since PLHC2008) • Hyperons in Min. Bias Events: Preliminary • Diffractive W and Z Production: Preliminary • KTDistributios of Particles in Jets: PRL 102, 232002 (2009) • Underlying Event in Drell-Yan Production: Submitted to PRD • Exclusive Charmonium Production and ggm+m-: PRL 102, 242001 (2009) • Search for Exclusive Z-Boson Production and Observation of High Mass pp̅ →pγγp̅ →pl+l-p̅ : PRL 102, 222001 (2009) • DØ Results (since PLHC2008) • Study of Phi and Eta Correlations in MB Events: Preliminary • Measurement of the Differential Cross Section ds/dt in Elastic ppbar Scattering: Preliminary • High Mass Exclusive Dijet Production: Preliminary • Double Parton Interactions in g+3 Jet Events: PRD 81, 052012 (2010)

  34. Double Parton in g + 3 Jets • Scattering of two parton pairs in a collision • seff: a measure of effective size of interaction region • Contains information on the spatial distribution of partons • Uniform  Large seff small sDP • Clumpy  Small seff  large sDP • Double parton scattering can be background to many rare processes

  35. Double Parton: Results In agreement with previous CDF measurements: PRD 47, 4857 (1993); PRL 79, 584 (1997) DØ: PRD 81, 052012 (2010) Average seff = 16.4 ± 0.3(stat) ± 2.3 (syst) mb

  36. The Underlying Event “Hard Scattering” Component • The “underlying event” consists of the “beam-beam remnants” and of particles arising from soft or semi-soft multiple parton interactions (MPI) • Underlying event is not the same as a minimum bias event • Define three regions: • “toward” • “away” • “transverse” • Sensitive to UE • Study • charged particle multiplicity • pT and ET sum density • Average charge particle pT • Tevatron measurements are used to tune MC event generators “Underlying Event”

  37. UE in Drell-Yan and Jet Production • Use the direction of the lepton pair per event to define the three regions • Correct observables to particle level • Comparison of distributions between jets and DY CDF: Submitted to PRD arXiv: 1002.3146

  38. Charged Particle Correlations in MB Events • Selection of MB Sample: • Trigger on dimuon events • Then require one or more Minimum Bias primary vertex • At least 0.5 cm away from triggered PV • Within 20 cm from z=0 • With at least 5 tracks Observable: (background subtracted, normalized) Df distribution of tracks from leading pT track Regions: |h|< 1, |h|<2, same/opposite sides Compare data to Pythia predictions

  39. Charged Particle Correlations: Results Sensitivity to Pythia tunes  Further studies are under way

  40. Hyperon Production in Min. Bias • pT differential cross section of hyperons with |h|<1 • Λ0pπ, Ξ±Λ0π±, Ω±Λ0K± • Use Minimum Bias sample Cross section drops by 7 for each s quark

  41. Electroweak • CDF Results (since PLHC2008) • ZZ Production: Preliminary • Z+g Production: Preliminary • Anomalous Triple Gauge-Boson Coupling Limits: Preliminary • Search for W  pg : Preliminary • Measurement of Z Forward-Backward Asymmetry: Preliminary • ds/dy Distribution of Drell-Yan Dielectron Pairs: Submitted for publication • W Charge Asymmetry and Comparison between CDF and DØ Results: Preliminary • Update on WW/WZ Production (hadronic): Preliminary • First Observation of Vector Boson Pairs in a Hadronic Final State at the Tevatron Collider: PRL 103, 091803 (2009) • Measurement of the WW+WZ Production Cross Section using Lepton+Jets Final State: PRL 104, 101801 (2010)

  42. Electroweak • DØ Results (since PLHC2008) • W Charge Asymmetry (muon channel): Preliminary • Anomalous Charged Trilinear Gauge-Boson Couplings From Diboson Production: Preliminary • Measurement of the Normalized Z/g* mmpT Distribution: Submitted to PLB • Direct Measurement of the W Boson Width: PRL 103, 231802 (2009) • Evidence of WW+WZ Production with Lepton+Jets Final States: PRL 102, 161801 (2009) • Measurement of Trilinear Gauge Boson Couplings from WW + WZ → lνjj Events: PRD 80, 053012 (2009) • Measurement of the WW Production Cross Section with Dilepton Final States and Limits on Anomalous Trilinear Gauge Couplings: PRL 103, 191801 (2009) • Measurement of the WZ→lνll Cross Section and Limits on Anomalous Triple Gauge Boson Couplings: Submitted to PLB • Measurement of the σ(pp → Z + X)Br(Z → τ+τ−): PLB 670, 292 (2009) • Search for a Scalar or Vector Particle Decaying into Zγ: PLB 671, 349 (2009) • Measurement of the Zγ → ννγ Production Cross Section and Limits on Anomalous ZZγ and Zγγ Couplings: PRL 102, 201802 (2009) • Tevatron Results (since PLHC2008) • CDF and DØ Results on the W Width: Preliminary • CDF and DØ Results on the W Mass: Preliminary

  43. Electroweak Results

  44. Z Rapidity • Sensitive to PDFs • At LO • Large dilepton rapidity |y| probes PDFs of the two colliding partons at large and low x • Sample: Z ee, 2.1 fb-1 • ds/dy data compared to NLO/NNLO + variety of PDFs CDF: arXiv: 0908.3914 (2009) Previous measurement: DØ: PRD 76, 012003 (2007)

  45. W Charge Asymmetry • u quarks carry more momentum than d quarks • W+ preferentially boosted along the proton direction • Due to V-A interaction the charge lepton from W decay heads backwards in the W frame • Sensitive to PDFs • Precision of data can probe inconsistencies with latest PDFs

  46. W Charge Asymmetry  P (d) P (u)  • Probes the u(x)/d(x) PDF ratio • x1 and x2 are the momentum fractions in the proton and anti-proton • Traditionally the Lepton Asymmetry A(|hlepton|) is used • Experimentally very well defined W+

  47. W Charge Asymmetry: A(|hm|) • W mn, 4.9 fb-1 • 2.3M reconstructed W decays • pT(m) > 20 GeV, |h(m)|<2, MET>20 GeV • Backgrounds: multijets, Wtn, Zmm, Ztt • Measure A(|h(m)|) in 3 pT(m) bins • pT(m) > 20 GeV • 20 < pT(m) < 35 GeV • pT(m) > 35 GeV • Results compared to RESBOS+CTEQ6.6M • Reasonable agreement with predictions for the inclusive sample • Disagreement when data are divided into pT(m) bins

  48. Direct Measurement of A(|yW|) • Reconstruct yW distribution with MW constraint • Weight both yW solutions with probability given by production and decay • Iterate since weight depends on yW • Method documented in A.Bodek et al., PRD 77, 111301(R) (2009). • Results compared to CTEQ6.1M (NLO) and MRST2006 (NNLO) PDFs • Experimental precision is much better than the theoretical uncertainty CDF: PRL 102, 181801 (2009)

  49. Comparison of DØ and CDF Results • CDF has measured the electron asymmetry from the published W asym. data sample and compared the results with the DØ muon and electron data – with a higher pT cut of 25 GeV DØ and CDF lepton asymmetry results are consistent with each other, but disagree with theoretical predictions for binned lepton pT

  50. Z Forward-Backward Asymmetry • The presence of both vector and axial-vector couplings in the • gives rise to an asymmetry (AFB) in the polar angle (q *) of the negatively charged lepton momentum relative to the incoming quark momentum in the lepton pair rest frame • Sensitive to sin2qW and possible new physics (Z’)

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