Search for W ’ WZ  evjj Blessing

1. Search for W’WZ  evjjBlessing David Toback & Chris Battle Texas A&M Henry Frisch University of Chicago

2. Outline Summary of: • Theory and Signature • Cuts and Data reduction • What signal would look like; Acceptance • Backgrounds; What signal would look like on top of backgrounds • Comparison of Data and Backgrounds • Fitting and Systematics • Limits • Conclusions

3. Feynman Diagram

4. Branching Ratio for W’WZ • Reference Model • W’ is the same as the SM W only heavier • Large width large branching ratio • Extended Gauge Model • Mixing angle between W and W’

5. Event Selection & Summary • 1 electron • Missing ET • 2 Jets • 110 pb-1 of data from Run 1A and 1B

6. Overview of Analysis • Constrain PZn using W mass • Reconstruct dijet and W+dijet masses • Look for bumps in dijet vs. W+dijet mass plane using a fit Reconstruction procedure does a good job of reproducing W’

7. Acceptance vs. W’ Mass • Good Acceptance for W’ • Reference Model • Large width at large mass • Lots of low mass events • Lower acceptance

8. Summary of Backgrounds Estimated from data { PYTHIA and cross sectionnormalization Combination of VECBOS and PYTHIA. Norm to measured Z0ee data Use VECBOS for shape. Large k factor uncertainty. Take normalization from fit to data. Agrees with Duke Group results

9. Dijet Mass Distributions • No evidence of Z0 produced in association with W • W+jets normalized to data and non-W+jets

10. W+dijet Mass Distributions • No evidence of W’ or other new particle production • W+jets normalized to the data and non-W+jets

11. W+dijet in 3 Mass Regions • Data outside Z0 mass region is well modeled telling us that the data inside the Z0 mass region is well modeled. • No evidence for WZ0 production. ( *Figure 1 in PRL)

12. Turning the Crank • Searching the data for W’ • Look for excess in dijet vs. W+dijet mass plane • Fit the data to signal, W+jets and non-W+jets • Fix non-W+jets background • Allow W+jets and signal to float • Fit in the 2-dim dijet vs. W+Dijet mass plane • Normalization mostly comes from outside signal region • Same technique as Dijet Mass bump search (R. Harris) • No evidence for signal (as seen in previous plots and in the fit results) • Get 95% C.L. cross section upper limit from the fit • Incorporate systematic errors

13. Example Signal Fits I Data vs. background with no signal.

14. Example Signal Fits II • Data vs. background with best fit signal.

15. Example: Signal Fits III Data vs. background with 95% C.L. signal.

16. Example: Signal Fits IV Data vs. background with reference model theoretical cross section signal. Excluded!

17. Systematic Errors Use same (conservative) methods as dijet mass bump search and bbbar mass bump search • Find the no-systematic 95% C.L. upper limit • Vary background or signal (depending on effect) by 1 sigma and –1sigma and refit • Recalculate new limit • Take absolute value of % change in limit (even if the cross section limit goes down!) • Take the larger % of the two variations (+1sigma and –1sigma) as the % smearing • Take all variations and add them in quadrature • Use this as a Gaussian smearing to the likelihood

18. Systematic errors Vary both signal and background separately to overestimate the magnitude of the effect • Amount of non-W+jets (vary background) • Absolute Jet energy scale (vary signal) • Energy resolution (vary signal) • Radiation (vary signal) • Q2 scale of W+Jets (vary background) • Structure functions (vary background) • Acceptance (add in quadrature) • Luminosity (add in quadrature)

19. Systematic Errors • Absolute energy scale dominates the error • Shifts signal into region with lots more background • Checked with Pseudo-Expts

20. Errors Cont.:Extended Gauge Model • Narrower width = less systematic uncertainty • Absolute energy scale again dominates the error

21. Pseudo-Experiments: Check Re-run entire analysis on fake data generated from backgrounds only • Generate fake data set • Allow number of events to float • Re-estimate the effect of all systematic errors for the fake data set • Add in quadrature as for data • Re-estimate the limit from the fake data set • Repeat many times • Repeat for different masses and mixing angles

22. Pseudo-Exper: Jet Energy Scale • The effect on the limit (in %) of the jet energy scale uncertainty for a set of pseudo-experiments with W’ mass of 200, 300, 400, 500, & 600 GeV respectively. This is for the reference model.

23. Pseudo-Experiments: Total Error • The total effect on the limit (in %) due to all systematic uncertainties for a set of pseudo-experiments with W’ mass of 200, 300, 400, 500, & 600 GeV respectively. This is for the reference model.

24. Pseudo-Exp: Jet Energy Error • The effect on the limit (in %) of the jet energy scale uncertainty for a set of pseudo-experiments with W’ mass of 200, 300, 400, 500, & 600 GeV respectively. This is for the reference model.

25. Pseudo-Experiments: Total Error • The total effect on the limit (in %) due to all systematic uncertainties for a set of pseudo-experiments with W’ mass of 200, 300, 400, 500, & 600 GeV respectively. This is for the reference model.

26. Systematic Errors • Systematic errors for lots of effects • Conservative estimation methods • We are not pulled unreasonably by an unexpected fluctuation in the data • Data is well modeled • Set limits

27. 95% C.L. Limits: Reference Model • We exclude the reference model of W’ from 200 to 480 GeV. • Taken in conjunction with exclusions from the W’ev limits, we exclude the entire model * Plot for Blessing

28. Pseudo-Experiments: Limit • 95% cross section upper limit from a set of pseudo-experiments with W’ mass of 200, 300, 400, 500, & 600 GeV respectively. This is for the reference model.

29. 95% C.L. Limits: Ext. Gauge Model • 95% C.L. upper limits on cross section vs. W’ mass for the extended gauge model • No mass limits for very small angles (Branching Ratio is tiny) • Cross section limits applicable for any new particle production with narrow width XWZ0 * Plot for Blessing

30. Pseudo-Experiments: Limit • 95% cross section upper limit from pseudo-experiments with W’ mass of 200, 300, 400, 500, & 600 GeV respectively. This is for the extended gauge model.

31. Cross Section vs. Mixing Angle 95% C.L. upper limits on cross section vs. W – W’ mixing angle * Plot for Blessing

32. Cross Section vs. W’ Width • 95% C.L. upper limits on the cross section vs. W’ width • These limits are good for any new particle production with XWZ0;narrow or wide width * Plot for Blessing, PRL Figure 2

33. Limits on Mixing Angle vs. W’ Mass 95% C.L. exclusion region for W-W’ mixing angle vs. W’ mass * Plot for Blessing, PRL Figure 3

34. Conclusions • No evidence forXWZ0in the enjjdecay channel • Narrow and width width approximations • First limits on direct W’ WZ0 • Reference model completely excluded • Large exclusions in an extended gauge model • Web page at -hepr8.physics.tamu.edu/hep/wprime/wpprl.html • All plots, documentation, correspondence with GPS and others, and PRL draft • CDFNote 5610 on web page • PRL draft with GPS and available on web page