Systematic uncertainties for the inelastic J/ y PHP analysis A. Bertolin (INFN- Padova )

1. 18/5/2012 Systematic uncertainties for the inelastic J/y PHP analysis A. Bertolin (INFN-Padova) R. Brugnera (Padova Uni.)

2. s vs z for different pt ranges: diffractive background • diffractive component quantified by comparing the z(rec.) distribution measured in data with an HERWIG (signal) + EPSOFT (background) MC mixture • increase / decrease the EPSOFT fraction while keeping a reasonable agreement between data and MC mixture • redo all calculations • only one bin, at low pt and high z, with cross section variations > ± 5 %

3. s vs z for different pt ranges: hadronic energy resolution • z = f (E-Pz(J/y),E-Pz(ZUFO)) • using the true J/y kinematic work out the true E-Pz • decrease or increase the difference E-Pz(ZUFO) - E-Pz by 20 % event by event • redo all calculations • variations < ± 5 % • may be 20 % seems “large” but even with this “large” value the results are stable … 20 % is also the value we used in the previous papers (no jets, visible hadronic system is soft …)

4. s vs z for different pt ranges: BMUI chambers efficiency • efficiency in data computed from two tracks J/y events, known within some statistical uncertainties (due to the finite number of two tracks J/y events) • data efficiency plugged into the MC at the analysis level (eaze) • decrease or increase the efficiency for the barrel section, rear section unchanged • redo all calculations • variations in the range ± 5 %, the size of the stat. uncertainties on the efficiencies

5. s vs z for different pt ranges: RMUI chamber efficiency • efficiency in data computed from two tracks J/y events, known within some statistical uncertainties (due to the finite number of two tracks J/y events) • data efficiency plugged into the MC at the analysis level (eaze) • decrease or increase the efficiency for the rear section, barrel section unchanged • redo all calculations • variations in the range ± 5 %, the size of the stat. uncertainties on the efficiencies, for z > 0.75 • variations much smaller for z < 0.75

6. s vs z for different pt ranges: l helicity parameter • l related to the polar distribution of the m in the J/y rest frame • l = 0: isotropic • l is weekly dependent on z and pt • from the ZEUS measurements (HERA I+II) we know that | l | < 0.5 “everywhere” • l = ± 0.5 at the event level • redo all calculations • largest sys. error of the analysis • unavoidable (even if you go to p p instead of PHP)

7. s vs z for different pt ranges: n helicity parameter • n related to the azimuthal distribution of the m in the J/y rest frame • n = 0: isotropic • n is weekly dependent on z and pt • from the ZEUS measurements (HERA I+II) we know that | n | < 0.5 “everywhere” • n = ± 0.5 at the event level • redo all calculations • largest sys. error of the analysis • unavoidable (even if you go to p p instead of PHP)

8. s vs z for different pt ranges: HERWIG MC pt spectrum • theHERWIGMCJ/y pt spectrum is reweighted to the data • can make the MC spectrum harder or softer while keeping a reasonable agreement between data and MC • additional weight given by exp(a pt2) at the event level • redo all calculations • small effect • as expected based on the experience with the past papers

9. s vs z for different pt ranges: EPSOFT MC Mx spectrum • theEPSOFTMCMx spectrum can be fitted with the function 1/Mx • E(FCAL) is the observable mostly sensitive to the Mx spectrum • can make the MC spectrum harder or softer while keeping a reasonable agreement between data and MC • additional weight given by 1/Mxa at the event level • redo all calculations • small effect • Mx has a small impact on z(rec) i.e. E-Pz in FCAL is small

10. s vs z for different pt ranges: EPSOFT MC W spectrum • theEPSOFTMCWgp spectrum is flat … unphysical … • reweight to a linear dependence: observe good agreement between data and MC for 2 tracks events at high z (diffractive background rich region we cut out in the analysis) • can make the MC spectrum harder or softer while keeping a reasonable agreement between data and MC • additional weight given by Wa at the event level • redo all calculations • small effect • W has a small impact on z(rec) with the kinematic of diffractive events

11. s vs z for different pt ranges: EPSOFT MC pt2 spectrum • theEPSOFTMCpt2 spectrum was set to -1 and -0.5 at the generation level and the two samples added • observe good agreement between data and MC for 2 tracks events at high z (diffractive background rich region we cut out in the analysis) • can make the MC spectrum harder or softer while keeping a reasonable agreement between data and MC • additional weight given by exp(a pt2) at the event level • redo all calculations • small effect • sizable only for z > 0.75 at low pt

12. s vs z for different pt ranges: invariant mass fit • invariant mass procedure is fitting the non resonant background away from the mass peak with a smooth function • an invariant mass window is defined for the signal: [2.85,3.3] • count the events in the window and subtract the integral of the non resonant background function over the signal window • change the window by ± 50 MeV (both in data and MC) • redo all calculations • at most a10 % effect in the low z bins, there the S/B ratio is decreasing with respect to the bins with z > 0.45

13. s vs z for different pt ranges: H1 track multiplicity cut • H1 analysis: ask for at least 5 vertex track, with pt > 125 MeV and | h | < 1.75 and DO NOT consider any diffractive background after this • redo the analysis “à la H1” • two bins with 20 % variations, one at high z and one at low z • this is testing the diffractive background procedure but also how well the track multiplicity cut is corrected for via MC

14. s vs pt2 for different z ranges: diffractive background • same steps shown previously • same steps done for DIS11

15. s vs pt2 for different z ranges: hadronic energy resolution

16. s vs pt2 for different z ranges: BMUI RMUI chamber efficiency

17. s vs pt2 for different z ranges: l n helicity parameters

18. s vs pt2 for different z ranges: HERWIG MC pt spectrum

19. s vs pt2 for different z ranges: EPSOFT MC Mxand W spectrum

20. s vs pt2 for different z ranges: EPSOFT MC pt2 spectrum

21. s vs pt2 for different z ranges: invariant mass fit

22. s vs pt2 for different z ranges: H1 track multiplicity cut

23. 2S to 1S cross sections ratios stat. uncertainty of about 15 % due to the small number of 2S events, unavoidable … sys. sources: diffractive background: cancel in the ratio hadronic energy resolution: expect cancellations in the ratio, see next slide BMUI chambers efficiency: cancel in the ratio, same hardware for 1S and 2S RMUI chambers efficiency: cancel in the ratio, same hardware for 1S and 2S helicity parameter l: cancel in the ratio helicity parameter n: cancel in the ratio HERWIG MC pt spectrum: tiny for 1S, furthermore will cancel in the ratio EPSOFT MC Mx spectrum: tiny for the 1S, furthermore will cancel in the ratio EPSOFT MC W spectrum: tiny for the 1S, furthermore will cancel in the ratio EPSOFT MC pt2 spectrum: tiny for the 1S, furthermore will cancel in the ratio invariant mass fit: see next to next slide

24. 2S to 1S cross sections ratio vs pt: hadronic energy resolution red: statistical uncertainty black: sys. uncertainty on E-Pz negligible due to cancellations …

25. 2S to 1S cross sections ratio vs pt: invariant mass fit • red: statistical uncertainty • black: sys. uncertainty on the 2S fitting range (± 50 MeV for both data and MC) • smaller than the stat. • red: statistical uncertainty • black: sys. uncertainty on the 1S fitting range (± 50 MeV for both data and MC) • insignificant • due to large S/B in the phase space selected for the 2S to 1S ratio

26. 2S to 1S cross sections ratio vs W: hadronic energy resolution red: statistical uncertainty black: sys. uncertainty on E-Pz negligible due to cancellations …

27. 2S to 1S cross sections ratio vs W: invariant mass fit • red: statistical uncertainty • black: sys. uncertainty on the 2S fitting range (± 50 MeV for both data and MC) • smaller than the stat. • red: statistical uncertainty • black: sys. uncertainty on the 1S fitting range (± 50 MeV for both data and MC) • insignificant • due to large S/B in the phase space selected for the 2S to 1S ratio

28. 2S to 1S cross sections ratio vs z: hadronic energy resolution red: statistical uncertainty black: sys. uncertainty on E-Pz negligible due to cancellations …

29. 2S to 1S cross sections ratio vs z: invariant mass fit • red: statistical uncertainty • black: sys. uncertainty on the 2S fitting range (± 50 MeV for both data and MC) • smaller than the stat. • red: statistical uncertainty • black: sys. uncertainty on the 1S fitting range (± 50 MeV for both data and MC) • insignificant • due to large S/B in the phase space selected for the 2S to 1S ratio

30. p flow along and against the J/y direction stat. uncertainty: most unfavorable case, small (< 5%) for small values of p flow and very large (> 20 %) for large values of p flow … the bin widths are already increasing as the p flow increases … can not optimize more … shape measurement: both data and MC predictions normalized to 1 sys. sources: diffractive background: evaluated hadronic energy resolution: evaluated BMUI chambers efficiency: cancel after normalizing to 1 RMUI chambers efficiency: cancel after normalizing to 1 helicity parameter l: evaluated helicity parameter n: evaluated HERWIG MC pt spectrum: evaluated EPSOFT MC Mx spectrum: evaluated EPSOFT MC W spectrum: evaluated EPSOFT MC pt2 spectrum: evaluated all uncertainties of the MC model

31. p flow along and against the J/y direction: diffractive background • red: statistical uncertainty • black: sys. uncertainty due to the diffractive background

32. p flow along and against the J/ydirection: hadronic energy resolution • red: statistical uncertainty • black: sys. uncertainty due to E-Pz(ZUFO) resolution

33. p flow along and against the J/ydirection: lhelicity parameter • red: statistical uncertainty • black: sys. uncertainty due to the l helicity parameter

34. p flow along and against the J/ydirection: nhelicity parameter • red: statistical uncertainty • black: sys. uncertainty due to the n helicity parameter

35. p flow along and against the J/ydirection: HERWIG MC pt spectrum • red: statistical uncertainty • black: sys. uncertainty due to the HERWIG MC pt spectrum

36. p flow along and against the J/ydirection: EPSOFT MC Mxspectrum • red: statistical uncertainty • black: sys. uncertainty due to the EPSOFT MC Mx spectrum

37. p flow along and against the J/ydirection: EPSOFT MC W spectrum • red: statistical uncertainty • black: sys. uncertainty due to the EPSOFT MC W spectrum

38. p flow along and against the J/ydirection: EPSOFT MC pt2 spectrum • red: statistical uncertainty • black: sys. uncertainty due to the EPSOFT MC pt2 spectrum

39. sys. errors are not visible in some bins stat. are dominant

40. errors are mostly sys. at low pt2 and mostly stat. at high pt2

41. errors are mostly sys. at high z and mostly stat. at low z

42. uncertainties of the MC model: boxes

43. Conclusions the systematic uncertainty evaluation for the inelastic J/y PHP analysis have been presented in detail