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

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

Data Source and Cuts 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

Event selection Eliminate Tagger and HyCal combinatorics 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".

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

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

Additional “Diagonal” Data Cut Warning—departure from analysis note

Apply Additional Cut and Veto Warning—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

Plateau Elastic Pion Yields Additional 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

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

Integration range plateau

Fitting range plateau

Selected Hybrid Mass Fits

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.

Yield extraction for various signal and background models

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

Putting physics events thru the Simulation Around 99.2% fidelity

Turning off glass detectors HyCal Tungstate Acceptance Only

Efficiencies as a function of the photo-pion process, HyCal Tungstate acceptance

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

Fit to Data, and Extracted Width HyCal Tungstate Acceptance Extracted width – 8.166 eV ± 0.133 eV (1.63%)

Acceptance Corrected Cross Sections PRELIMINARY HyCal Tungstate Acceptance

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

Systematic Effects from Yield Extraction HyCal 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 % ± 0.033 8.120 -0.57 % ± 0.034 8.134 -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

Error Accounting HyCal Tungstate acceptance Source % Error Error from Fit +1.63 %, -1.63 % Photon flux +1.10 %, -1.10 % Cluster Position Reconstruction +0.43 %, -0.13 % Fitting Range +0.31 %, -0.52 % Signal Lineshape +0.26 %, -0.00 % Background Model +0.08 %, -0.00 % Dalitz Decay +0.03 %, -0.03 % Target Thickness +0.04 %, -0.04 % Veto Counter Inefficiency (if used) +0.06 %, -0.06 % Total (w/ Veto, w/out Error from Fit) +1.25 %, - 1.23 % Total (with Veto) + 2.06 %, -2.04 %

Result 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%

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?

Extra slides

The Veto—how it changes the angular spectrums

Extracting a Photon Misidentification Efficiency PME = 0. 80 ± 0 Extracting a Photon Misidentification Efficiency PME = 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

Photon flux

Poor Elasticity

Energy Correction Across entire HyCal acceptance

Tracking Threshold, resolution, and centroid tuning

Turning off glass detectors Entire HyCal Acceptance

Turning off tungstate detectors Entire HyCal Acceptance

Efficiencies as a function of the photo-pion process, entire HyCal acceptance

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