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Requested Beam time for Physics Runs. A. Gasparian. Suggested Targets for 0. Suggested targets: two targets, 12 C and 208 Pb the 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);
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Requested Beam time for Physics Runs A. Gasparian
Suggested Targets for 0 • Suggested targets: two targets, 12C and 208Pb the 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 extraction And control of theory model errors; • We already reached less than percent uncertainty for them; • we have well developed package of theoretical models for them. JLab, November 30, 2007
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 JLab, November 30, 2007
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 JLab, November 30, 2007
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 JLab, November 30, 2007
0 Event selection Three groups analyzed the data independently JLab, November 30, 2007
0 Differential Cross section 12C→012C Preliminary GEANT: • acceptances; • efficiencies • … Experimental Yield per Diff. cross section JLab, November 30, 2007
Fit to Extract 0 Decay Width • Theoretical angular distributions smeared with experimental resolutions are fit to the data Primakoff Coherent Incoherent Interference • Combined average from three groups: Γ(0) 7.93 eV 2.10%(stat.) JLab, November 30, 2007
Estimated Systematic Errors (preliminary) JLab, November 30, 2007
PrimEx Preliminary Result () = 7.93eV2.1%2.0% 0 Decay width (eV) ±1.% JLab, November 30, 2007
Summary • PrimEx collaboration has developed an experimental program to perform precision test of chiral symmetry and anomaly effects in the light pseudoscalar meson sector. • A state-of-the-art high resolution experimental setup has been designed, developed and constructed in less than 5 years. • The first experiment, the 0 lifetime measurement has been successfully performed in fall of 2004. • Our preliminary result: Γ(0) 7.93 eV 2.10%(stat.) 2.0%(syst.) improves the uncertainty in PDG average by 2.5 times JLab, November 30, 2007
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. JLab, November 30, 2007
