1. W and Z Boson Physics with the CMS Experiment QCD@LHC 2012 Jeffrey Berryhill, Fermilab On behalf of the CMS Collaboration August 20, 2012

2. 2 Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 Outline W and Z inclusive cross sections at 8 TeV W lepton charge asymmetry at 7 TeV Drell-Yan differential cross sections at 7 TeV Drell-Yan differential forward-backward asymmetry at 7 TeV

3. 3 W and Z Cross Sections@8 TeV pQCD predicts a 15-20% cross section increase as the proton beam energy increases from 7 TeV to 8 TeV W/Z and W+/W- cross section ratios (and 7/8 double ratios) are (sub-)percent predictions of pQCD Important initial experimental benchmarks for precision physics with leptons at 8TeV Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 1% experimental (non-lumi, non-theory) precision achieved at 7 TeV with just 36 /pb ( J. High Energy Phys. 10 (2011) 132 ) J. High Energy Phys. 10 (2011) 132

4. 4 W and Z Cross Sections@8 TeV To swiftly reproduce the 2010 7 TeV W cross section precision at 8 TeV, 2010-like pileup and triggers were required During the 2012 intensity ramp-up, while opportunity costs were still low, CMS requested for a couple of fills that the LHC transversely offset the beams from one another in CMS by a few transverse sigma. This reduced mean pileup to ~5 interactions @L=3-6E32 A special trigger menu with 2010-like, low-threshold, loose single lepton triggers (22 GeV e, 15 GeV mu) was deployed for these runs 19 /pb were accumulated in this configuration. We do not expect more such runs in 2012. Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 CMS-PAS-SMP-12-011

5. 5 Z Cross Sections@8 TeV Z to mumu analysis: Opp sign mu pairs with PT > 25 GeV and |eta| < 2.1 Pair mass 60-120 GeV 6000 candidates, ~0 background, 1.3% stat. Z reconstruction, ID, trigger efficiency known to 1.1% syst. from tag and probe methods Excellent lineshape description from POWHEG+PYTHIA Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012

6. 6 Z to ee analysis: Opp sign e pairs with PT > 25 GeV and |eta| < 2.5 Pair mass 60-120 GeV 5000 candidates, ~0 background, 1.4% stat. Z reconstruction, ID, trigger efficiency known to 2.8% syst. from tag and probe methods Excellent lineshape description from POWHEG+PYTHIA Z Cross Sections@8 TeV

7. 7 Z cross section dominated by lumi (4.4%) and acceptance theory error (2- 3%). Agreement with FEWZ + MSTW08 total NNLO cross section Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 Z Cross Sections@8 TeV

8. 8 W muv analysis: =1 muon PT > 25GeV, |eta| < 2.1, 81k W’s No MET cut, signal extracted via binned MLH simultaneous fit of MET to isolated and non-isolated muons. Signal,QCD yields + 2 QCD shape parameters floating. W signal MET model corrected with Z recoil data Lepton efficiency dominant exp. error (1%) Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 W Cross Sections@8 TeV

9. 9 W ev analysis: =1 electron PT > 25GeV, |eta| < 2.5, 75k W’s No MET cut, signal extracted via binned MLH fit of MET. Signal,QCD yields + 2 QCD shape parameters floating. W signal MET model corrected with Z recoil data (0.9% syst) Lepton efficiency dominant exp. error (2.5%) Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 W Cross Sections@8 TeV

10. 10 W cross section dominated by lumi (4.4%) and acceptance theory error (2- 3%). Agreement with FEWZ + MSTW08 total NNLO cross section Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 W Cross Sections@8 TeV

11. 11 W/Z ratio: acc. ratio theory error 2% (2.5%) for e (mu) Exp. error 3.9% (1.7%) for e (mu) 1.5 sigma agreement with FEWZ + MSTW08 NNLO total cross section Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 W and Z Cross-Section Ratios@8 TeV

12. 12 W/Z ratio: acc. ratio theory error 2% (2.5%) for e (mu) Exp. error 3.9% (1.7%) for e (mu) 1.5 sigma agreement with FEWZ + MSTW08 NNLO total cross section Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 W and Z Cross-Section Ratios@8 TeV

13. 13 Not likely to add more data. Finish estimation of total (and fiducial) cross sections, ratios, and 8/7 double ratios, in context of each PDF family. 8/7 ratios: – Cross sections: Lumi error does *not* cancel, ~8 % precision for 8/7 ratio – Cross section ratios: if everything but stat cancels, 1% precision possible for 8/7 double ratio – (W/Z) 8 /(W/Z) 7 : 1.01 +/- 0.01 (stat), expect 1.03 from FEWZ+MSTW – (W+/W-) 8 /(W+/W-) 7 : 0.98 +/- 0.01 (stat), expect 0.99 from FEWZ+MSTW – PDF families disagree in double ratio prediction at ~1% level Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 W and Z Cross-Section Prospects

14. 14 W Electron Asymmetry @ 7 TeV In pp, charge asymmetric CMS-fiducial W production at 10-20%, increasing with lepton |eta| Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 Sensitive to u/d valence and sea at x = 0.001 to 0.1 36/pb measurement with 2010 data already had constraining power

15. 15 W Electron Asymmetry @ 7 TeV For the first 840 /pb of 2011, could trigger electrons inclusively down to 35 GeV Repeat technique of W+/- cross section in 11 bins of 0.2 in |eta|, range 0 to 2.2 Rel. stat. error/bin of better than 3% Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 CERN-PH-EP-2012-151

16. 16 Dominant error is statistics for e+/e- efficiency ratio measurement in Z’s(~0.5% abs. error) Agreement with CT/HERA/NNPDF Disagreement with MSTW2008NLO at low |eta| (subsequently improved) Full covariance presented Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 W Electron Asymmetry @ 7 TeV

17. 17 W Muon Asymmetry @ 7 TeV For first 234 /pb of 2011, could trigger non- isolated muons down to 25 GeV and |eta| < 2.4 Precision comparable to electron result (better acc*eff for W’s and Z control samples), similar trends of PDF agreement Already systematics limited by equal parts momentum scale, eff. ratio, signal model Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 CMS-PAS-EWK-11-005

18. 18 W asymmetry prospects Impact on next-gen PDFs being assessed Another factor of 2 in precision is feasible, but alignment/energy scale is a limiting factor going forward. Full 2011 result for muons in progress W boson rapidity asymmetry being explored Asym. with/without jets or vs. PT: additional constraining power? Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 MSTW, PDF4LHC May 2012

19. 19 Drell-Yan Differential Cross Section With full 2011 data set, 1D differential Drell-Yan cross section vs. mass measured in electrons and muons for M=20- 1500 GeV. Mu pair analysis: Mu PT > 14,9 GeV, |eta(mu)| < 2.4 QCD background estimated from SS and non-isolated mu pairs, tt from emu data. NNLO corrections important at low mass (we select mostly boosted pairs here) FSR effects unfolded Good agreement of total Born level cross section with FEWZ+MSTW Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 CMS-PAS-EWK-11-007

20. 20 Drell-Yan Differential Cross Section e pair analysis: E PT > 20,10 GeV, |eta(e)| < 2.5 QCD background estimated from e+anti-select e convolved with fake rate Good agreement of total Born level cross section with FEWZ+MSTW Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012

21. 21 For mu pairs, double-differential (M, y) cross section obtained (detector fiducial cross section, normalized to NZ) Six bins in M and varying bins in y. Low-mass bins (20-30, 30-45): NNLO important here, preliminary disagreement with POWHEG, FEWZ and data observed (FEWZ theory value/errors being revisited) Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 Drell-Yan Differential Cross Section

22. 22 On-peak bins (45-60, 60-120): excellent agreement with POWHEG and FEWZ 60-120 (aka “Z rapidity”) systematics limited, consistent with 2010 result Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 Drell-Yan Differential Cross Section

23. 23 High mass bins (120-200, 200-1500): excellent agreement with FEWZ, statistics limited Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 Drell-Yan Differential Cross Section

24. 24 Drell-Yan Cross Section Prospects Final 2011 result nearing completion – Combine e and mu for 1D cross section – Add e for 2D cross section – Compute full covariance for 1D and 2D – Field testing PDF impact 8 TeV data will extend the mass reach and improve statistics at high mass Improving on on-peak or low-mass will require improved detector/FSR understanding (alignment/scale, FSR unfolding) Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012

25. 25 Drell-Yan Differential AFB @7 TeV Angular production asymmetries sensitive to weak mixing angle (on-peak) and gamma-Z (or Z-Z’ or Z-new physics) interference off-peak In pp, quark direction only weakly correlated with Z longitudinal boost, with stronger correlation at high rapidity. Observed angular distributions (cos theta*) have diluted asymmetries relative to “MC-parton-truth” level. Detector acceptance also dilutes observed AFB Measure AFB – in fiducial acceptance – Corrected for efficiency and FSR (unfolded to Born level) – As a function of mass, in four slices of y (0-1, 1-1.25, 1.25-1.5, 1.5-2.4) – Compared with Born-level POWHEG+CT10 Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 CERN-PH-EP-2012-187

26. 26 Drell-Yan Differential AFB @7 TeV Dilepton selection: PT > 20 GeV, |eta|< 2.4 10 mass bins from 40 to 2000 GeV Efficiency corrected Born-level unfolded Systematics limited below~150 GeV (alignment/scale/FSR unfolding) Stat-limited above Excellent agreement with POWHEG+CT10 Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012

27. 27 Drell-Yan AFB Prospects Other differential angular coefficients will be studied Off-peak precision will improve with 8 TeV data set (esp. above 200 GeV) and test electroweak interactions at highest masses. Electroweak corrections important at ~TeV? On-peak AFB and weak mixing angle already systematics limited by alignment/energy scale, pQCD, and PDF effects 50-100 /fb required for stat error of weak mixing angle to approach LEP+SLD precision -> need full 14 TeV run Not constraining for PDFs for foreseeable future Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012

28. 28 Conclusions LHC electroweak boson measurements have had a strong impact on understanding of PDFs and pQCD (required for any future LHC insight on MW or sin 2 theta W ) On-peak/low mass, detector systematics (esp. lepton momentum/energy) dominating total error and impeding progress At highest mass, DY will always be worth pursuing Topics pursued but not mentioned: – Z rapidity using forward electrons – Strange quark PDF fits – Z multiply-diff angular distributions – Z PT – W PT (@low lumi) Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012

29. 29 Detector-level distributions of Drell-Yan mass spectrum, vs. FEWZ-corrected POWHEG Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012

30. 30 FSR unfolding of the 1D Drell-Yan spectrum Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012

31. 31 Drell-Yan efficiency, acceptance and eff*acc vs. mass Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012

32. 32 Detector-level rapidity distribution of low-mass Drell-Yan dimuons, compared with FEWZ-corrected POWHEG Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012

33. 33 Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 Detector-level rapidity distribution of on-peak Drell-Yan dimuons, compared with FEWZ-corrected POWHEG

34. 34 Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012 Detector-level rapidity distribution of high-mass Drell-Yan dimuons, compared with FEWZ-corrected POWHEG

35. 35 Jeffrey Berryhill, Fermilab -- QCD@LHC Workshop August 20 2012