PrimEx p 0 radiative width extraction

1. PrimEx p0 radiative width extraction Eric Clinton University of Massachusetts Amherst July 19, 2007

2. Outline • Data Source and cuts • Event selection • Hybrid Mass Signal enhancement • Yields • Yields over entire HyCal acceptance presented for information on Incoherent photo-pion production only • Systematic effects from yield extraction • Simulation • Results • Sytematic Error Analysis

3. mysql -h primexdb -u primex_user book_keeping -b --execute="select run from run_list where radiator='A' and target='carbon' and type='pi0' and production='good';" > run_list.example mysql -h primexdb -u primex_user book_keeping -b --execute="select run from run_list where radiator='B' and target='carbon' and type='pi0' and production='good';" > run_list.example 1.) Two or more clusters/event. 2.) Minimum three (3) (PbWO4 or lead glass) detectors to define a “cluster”. 3.) 50 MeV or greater central (PbWO4 or lead glass) crystal detector energy in cluster. 4.) 10 MeV or greater minimum deposited energy in (PbWO4 or lead glass) detector. 5.) Max cluster energy 8 GeV. 6.) gg invariant mass greater than 0.085 GeV in at least one of the cluster pairs. 7.) Elasticity (cluster pair energy sum/tagger energy) greater than 0.70. 8.) Cluster energy greater than 0.5 GeV. 9.) Cluster X or Y position must be greater than 4.1 cm. 10.) Cluster pair energy sum between 3.5 and 6.5 GeV -- additional software cut not imposed on the skim, but imposed later: 11.) Timing cut of -15 ns to +5ns. “pi0gains” used as calibration Data Source and Cuts

4. Likelihood Event entries have invariant mass, elasticity, and timing Which entry to choose in a mutli-entry event? Which is "most likely"? Fit invariant mass, elasticity, timing signal and background Fitted signal lineshape as probability density function (PDF) Evaluate the PDF for each parameter for each entry. Three individual likelihoods. PDFInvariant mass, PDFElasticity, PDFTiming Total likelihood = PDFInvariant mass × PDFElasticity ×PDFTiming Entry with highest total likelihood "wins". Event selectionEliminate Tagger and HyCal combinatorics

5. Misidentification – any systematics?No. MisID is random, and event selection tends to pick smaller production angle pions.

6. Original 2-D data Elasticity vs.Invariant Mass New 1-D signal AKA “Hybrid Mass” Rotation of 2-D data onto 1-DTry to enhance signal to noise

7. Additional “Diagonal” Data CutWarning—departure from analysis note

8. Apply Additional Cut and VetoWarning—departure from analysis note • Result • Greatly improved signal to noise • Removes 3rd order curvature from background • Requires well understood veto • Veto systematic error small in comparison to fit error and other systematic effect improvements

9. Plateau Elastic Pion YieldsAdditional minimization of signal to noise • Timing • Elastic p0 as a function of the timing cut • Integration Range (left, below) • Elastic p0 as a function of the integration range • Fitting Range (right, below) • Elastic p0 as a function of the fitting range

10. Original timing cut/data source Timing cut vs. pion yield plateau Timing cut set to ±5 ns

11. Integration range plateau

12. Fitting range plateau

13. Selected Hybrid Mass Fits

14. p0 yields as a function of production angle. These yields are extracted from a data set where the “diagonal” and veto cuts are applied. Final radiative width MUST correct for veto Photon Misidentification.

15. Yield extraction for various signal and background models

16. Simulation Work • Thrown with E-Channel Photon flux weighting • Primakoff (with FSI), Coherent (Cornell with FSI), Incoherent (Glauber) • Energy correction added • Energy lost out back of HyCal, out of cluster mask • Added back about 10% of energy • Tracking threshold tuned • Proper shower development • Resolution and centroid tuned • Get invariant mass right to proper mock physics • Vet the Simulation • Push 4 vectors from experiment thru sim • See how p0 candidate spectrum look, look for losses • Turn off detectors, see how acceptance behaves

17. Putting physics events thru the Simulation Around 99.2% fidelity

18. Turning off glass detectorsHyCal Tungstate Acceptance Only

19. Efficienciesas a function of the photo-pion process, HyCal Tungstate acceptance

20. Geometric efficiency and reconstruction (cut) efficiency HyCal tungstate acceptance Turning off cluster energy and invariant mass cuts

21. Fit to Data, and Extracted WidthHyCal Tungstate AcceptanceExtracted width – 8.166 eV ± 0.133 eV (1.63%)

22. Acceptance Corrected Cross Sections PRELIMINARY HyCal Tungstate Acceptance

23. Extracted yields over the entire pion angle range must be stable as these parameters are varied. Systematic error sources?

24. Systematic Effects from Yield ExtractionHyCal Tungstate acceptance • Nominal 8.166 NA Cluster Position Finding Method • Method 0: 8.044 -1.50 • Method 1: 8.202 +0.43 * (+) • Method 2: 8.156 -0.13 * (-) • Method 4: 8.195 +0.35 • Lineshape (degrees of freedom)*** • DG3Po: 8.173 +0.09 * (-) • TG2Po: 8.188 +0.26 * (+) • Integration range (nom. = ±0.013 HMU’s) • ± 0.010 8.102 -0.79 % • ± 0.011 8.155 -0.13 % • ± 0.012 8.148 -0.21 % • ± 0.013 8.166 NA • ± 0.014 8.170 +0.04 % • ± 0.016 8.206 +0.48 % • ± 0.018 8.242 +0.923 % • No systemtatic effect will be claimed. Fit errors go up faster than any shifts above, and yield plateau for smaller pion angles is present. • Fit Range (nominal = ±0.029 HMU’s) • ± 0.026 8.105 -0.74 % • ± 0.027 8.123 -0.52 % * (-) • ± 0.028 8.152 -0.18 % • ± 0.029 8.166 NA • ± 0.030 8.192 +0.31% * (+) • ± 0.031 8.130 -0.44 % • ± 0.032 8.141 -0.31 % • ± 0.0338.120 -0.57 % • ± 0.0348.134 -0.39 % • Total Error will be “asymmetric” since many of “systematic effects” tend to go in only one direction. • All positive contribution will be added in quadrature for the total “positive systematic error” • Vice versa for the negative contributions ***Nominal = Double gaussians with 2nd order polynominal DG3Po = Double gaussians with 3rd order polynomial TG2Po = Triple gaussians with 2rd order polynominal

25. Error Accounting HyCal Tungstate acceptance

26. HyCal Tungstate Acceptance Gp0→gg= 8.166 eV ± 0.133 eV +0.102 eV – 0.100 eV Gp0→gg= 8.166 eV ± 1.63 % +1.25% - 1.23% Result

27. Future work • Work another nuclear incoherent generator • Latest from Tulio in hand • Evolve cross sections to the weighted mean photon energy • “Conjoined” analysis • Lead Target Data?

28. Extra slides

29. The Veto—how it changes the angular spectrums

30. Extracting a Photon Misidentification EfficiencyPME = 0.80 ± 0.057% (HYCALCLUSTER veto flag == 4) PME = 2.20 ± 0.16% (HYCALCLUSTER veto flag == 3) PME = 2.80 ± 0.21% (HYCALCLUSTER veto flag == 2) PME = 3.20 ± 0.23% (HYCALCLUSTER veto flag == 1) ** ongoing work

31. Photon flux

32. Poor Elasticity

33. Energy CorrectionAcross entire HyCal acceptance

34. Tracking Threshold, resolution, and centroid tuning

35. Turning off glass detectorsEntire HyCal Acceptance

36. Turning off tungstate detectorsEntire HyCal Acceptance

37. Efficienciesas a function of the photo-pion process, entire HyCal acceptance

38. Geometric efficiency and reconstruction (cut) efficiency.Entire HyCal Acceptance