Requested Beam time for Physics Runs

A. Gasparian

A. Gasparian JLab, November 30, 2007 2

Suggested Targets for 0

Suggested targets: two targets, 12C and 208Pbthe same as we had (3%R.L.)

Justification: there is a big competition for 6 GeV experiments at Hall B (we request less time to be competitive);This set includes one low Z and one high Z target. Past experiment Shows that these two targets are enough for precision extractionAnd control of theory model errors; We already reached less than percent uncertainty for them; we have well developed package of theoretical models for them.

A. Gasparian JLab, November 30, 2007 3

Requested Beam time for 0 To reach 0.4% statistical errors for each target

(taken from original proposal) we need ~ 60,000 0 Primakoff events:

(for E = (0.85-0.95)Eo energies the expected rate for Pb target:

Nev = N x Nnucl x Δσ x έeff

= 8x106x9.2x1020x2.1610-2x10-27x0.7 = 9,600 events/day

Therefore we need:

6 days for 208Pb target (PAC days) 7 days for 12C target

A. Gasparian JLab, November 30, 2007 4

Requested Beam time for Calibrations and setup checkout

For HYCAL calibration and checkout we need: First “snake pass” for: Dynode signal equalizing (required for trigger efficiency); Propagation of the dynode signal up to “total sum” trigger; Check timing between channels (equalize if needed)

Second “snake pass” for Calibration (this can not be done in first pass since the HVs will be changed there) moving the tagged beem through the HYCAL continuously. Calibration of VETO counters: the same time or separate time if needed (Rory) Efficiency of HYCAL: same time or separate if needed

Estimated beam time for the HYCAL is 5 days

A. Gasparian JLab, November 30, 2007 5

Requested Beam time for Calibrations and setup checkout

7 days (PAC days) for 12C target (for 0.4% stat error)

6 days for 208Pb

3 days for Compton and e+e- run

2 days for empty target run (both 0 and Compton configurations) 1 day for TAC runs 5 days for setup calibration and checkout

...................................... 24 days in total

A. Gasparian JLab, November 30, 2007 6

0 Event selection

Three groups analyzed the data independently

A. Gasparian JLab, November 30, 2007 7

0 Differential Cross section

Experimental Yield per

GEANT: acceptances; efficiencies …

Diff. cross section

12C→012C Preliminary

A. Gasparian JLab, November 30, 2007 8

Fit to Extract 0 Decay Width

Combined average from three groups:

Γ(0) 7.93 eV 2.10%(stat.)

Interference

Incoherent

Coherent

Primakoff

Theoretical angular

distributions smeared with

experimental resolutions

are fit to the data

A. Gasparian JLab, November 30, 2007 9

Estimated Systematic Errors (preliminary)

Photon flux 1.0%

Target thickness (+impurity) 0.4%

Background subtraction 1.0%

Theoretical model error ‹1.0%

Event selection 0.5%

HyCal Response function 0.5%

Beam energy (+parameters) 0.4%

11/30/20079Acceptance 0.3%

Total 2.03%

A. Gasparian JLab, November 30, 2007 10

PrimEx Preliminary Result

() = 7.93eV2.1%2.0%

0

D

eca

y w

idth

(eV

)

±1.%

A. Gasparian JLab, November 30, 2007 11

Summary

A state-of-the-art high resolution experimental setup has been designed, developed and constructed in less than 5 years.

Our preliminary result:

Γ(0) 7.93 eV 2.10%(stat.) 2.0%(syst.)

improves the uncertainty in PDG average by 2.5 times

PrimEx collaboration has developed an experimental program to perform precision test of chiral symmetry and anomaly effects in the light pseudoscalar meson sector.

The first experiment, the 0 lifetime measurement has been successfully performed in fall of 2004.

A. Gasparian JLab, November 30, 2007 12

Summary (cont.)

The proposed 1.4% accuracy in Γ(0) can be reached with more stable data.

Reach experimental program in η, η’ widths and transition form factors at 12 GeV with upgraded setup is being developed.