Requested Beam time for Physics Runs A Gasparian
Requested Beam time for Physics Runs A. Gasparian JLab, November 30, 2007
Suggested Targets for 0 Ø Suggested targets: two targets, 12 C and 208 Pb the same as we had (3%R. L. ) Ø Justification: q there is a big competition for 6 Ge. V experiments at Hall B (we request less time to be competitive); q. 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; q We already reached less than percent uncertainty for them; q we have well developed package of theoretical models for them. A. Gasparian JLab, November 30, 2007 2
Requested Beam time for 0 Ø 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 = 8 x 106 x 9. 2 x 1020 x 2. 1610 -2 x 10 -27 x 0. 7 = 9, 600 events/day Ø Therefore we need: q 6 days for 208 Pb target (PAC days) q 7 days for 12 C target A. Gasparian JLab, November 30, 2007 3
Requested Beam time for Calibrations and setup checkout Ø For HYCAL calibration and checkout we need: q First “snake pass” for: ü Dynode signal equalizing (required for trigger efficiency); ü Propagation of the dynode signal up to “total sum” trigger; ü Check timing between channels (equalize if needed) q Second “snake pass” for Calibration (this can not be done in first pass since the HVs will be changed there) ü moving the tagged beem through the HYCAL continuously. q Calibration of VETO counters: the same time or separate time if needed (Rory) q Efficiency of HYCAL: same time or separate if needed Estimated beam time for the HYCAL is 5 days A. Gasparian JLab, November 30, 2007 4
Requested Beam time for Calibrations and setup checkout Ø 7 days (PAC days) for 12 C target (for 0. 4% stat error) Ø 6 days for 208 Pb Ø 3 days for Compton and e+e- run Ø 2 days for empty target run (both 0 and Compton configurations) Ø 1 day for TAC runs Ø 5 days for setup calibration and checkout. . . . . Ø 24 days in total A. Gasparian JLab, November 30, 2007 5
0 Event selection Three groups analyzed the data independently A. Gasparian JLab, November 30, 2007 6
0 Differential Cross section 12 C→ 0 12 C Experimental Yield per A. Gasparian GEANT: Ø acceptances; Ø efficiencies Ø… JLab, November 30, 2007 Preliminary Diff. cross section 7
Fit to Extract 0 Decay Width q Theoretical angular distributions smeared with experimental resolutions are fit to the data Primakoff Coherent Incoherent Interference q Combined average from three groups: Γ( 0 ) 7. 93 e. V 2. 10%(stat. ) A. Gasparian JLab, November 30, 2007 8
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% Hy. Cal Response function 0. 5% Beam energy (+parameters) 0. 4% 11/30/20070 Acceptance 0. 3% Total 2. 03% A. Gasparian JLab, November 30, 2007 9
0 Decay width (e. V) Prim. Ex Preliminary Result A. Gasparian ( ) = 7. 93 e. V 2. 1% 2. 0% ± 1. % JLab, November 30, 2007 10
Summary q Prim. Ex collaboration has developed an experimental program to perform precision test of chiral symmetry and anomaly effects in the light pseudoscalar meson sector. q A state-of-the-art high resolution experimental setup has been designed, developed and constructed in less than 5 years. q The first experiment, the 0 lifetime measurement has been successfully performed in fall of 2004. q Our preliminary result: Γ( 0 ) 7. 93 e. V 2. 10%(stat. ) 2. 0%(syst. ) improves the uncertainty in PDG average by 2. 5 times A. Gasparian JLab, November 30, 2007 11
Summary (cont. ) q The proposed 1. 4% accuracy in Γ( 0 ) can be reached with more stable data. q Reach experimental program in η, η’ widths and transition form factors at 12 Ge. V with upgraded setup is being developed. A. Gasparian JLab, November 30, 2007 12
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