PrimEx p0 radiative width extraction Eric Clinton Duke University April 5, 2008

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 Systematic effects. No Misidentification Any Systematic effects? 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

Apply Diagonal Cut and Veto 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

What does the “diffuse/diagonal” cut remove?

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 ±3 ns

Radiative width vs. the Integration (Background Subtraction) range Incoherent = Sergey Integration Range = 0.030 HMU’s Fitting Range = 0.030 HMU’s

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, Incoherent (Tulio’s latest and Sergey’s next to latest) 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 Closely match simulation mass and elasticity to data Vet the Simulation Push 4 vectors from experiment thru sim See how p0 candidate spectrum look, look for losses

Energy “loss” and correction in simulation Reasons: Energy lost out back of HyCal, Finite cluster size, airgap. Energy leaking out of cluster mask but remain in HyCal. Simulation Before any correction Before and after Energy leaking out of cluster mask but remaining in HyCal. Experimental data

Tuning experimental and simulation resolutions

Putting physics events thru the Simulation Around 99.2% fidelity

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 – 7.674 ± 0.119 eV (± 1.57 %), fit to 2.5o** Extracted width – 7.768 ± 0.118 eV (± 1.64 %), fit to 2.0o** Both radiators A and B Fit out to 2.5o Fit out to 2.0o **Plots reports slightly incorrect width

Fit to Data, and Extracted Width HyCal Tungstate Acceptance Radiator B only Extracted width – 7.600 ± 0.144 eV (± 1.89 %), fit to 2.5o Extracted width – 7.788 ± 0.147 eV (± 1.88 %), fit to 2.0o Radiator A only Extracted width – 7.732 ± 0.223 eV (± 2.89 %), fit to 2.5o Extracted width – 7.721 ± 0.212 eV (± 2.75 %), fit to 2.0o

Rad. Width vs. fit and point Incoherent = Sergey

Interference angle vs. fit end point Incoherent = Sergey

Acceptance Corrected Cross Sections

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: 7.442 -2.72 Method 1: 7.608 -0.47 * (+) Method 2: 7.680 +0.47 Method 4: 7.594 -0.66 * (-) Lineshape (degrees of freedom)*** DG3Po: 7.666 +0.28 * (-) TG2Po: 7.700 +0.66 * (+) Incoherent theory model Tulio 7.672 +0.4% * (+) ***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—Both radiators, fit to 2 Error Accounting HyCal Tungstate acceptance—Both radiators, fit to 2.5o Source % Error Error from Fit +1.57 %, -1.57 % Photon flux +1.10 %, -1.10 % Cluster Position Reconstruction +0.47 %, -0.66 % Signal Lineshape +0.66 %, -0.00 % Background Model +0.28 %, -0.00 % Dalitz Decay +0.03 %, -0.03 % Target Thickness +0.04 %, -0.04 % Veto Counter Inefficiency +0.06 %, -0.06 % Incoherent theory model +0.40 %, -0.00 % Total + 2.14 %, -2.03 %

Result HyCal Tungstate Acceptance Gp0→gg = 7.644 ± 0.119 eV +0.111 eV – 0.099 eV Gp0→gg = 7.644 ± 1.57 % % +1.45% - 1.29%

Extra slides

Scaled response functions Fit parameters at 2.5o Process Value Error Primakoff 0.00106511 1.66767e-05 Coherent 0.012388 0.000158472 Interference 0.00226527 6.63293e-05 Incoherent 0.00657753 0.00121239

The Veto—how it changes the angular spectrums