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1350A

Studies were carried out on the electromagnetic rates in the detector as a function of the solenoid current. The actual rates will come from measurements, but if they are too high, they will limit the primary photon beam rate.

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1350A

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  1. Studies were carried out on the electromagnetic rates in the detector as a function of the solenoid current. • The actual rates will come from measurements, but if they are too high, they will limit the primary photon beam rate. • All GlueX proposals have assumed a maximum photon rate of no more than ½ of the design photon current. • Three typical physics reactions were studied using the GlueX software. • Reconstruction efficiency improves as the solenoid current decreases. • Sample purity gets worse as the solenoid current decreases

  2. Normalized Electromagnetic Rates in the most-sensitive detectors (forward drift chamber---FDC and the start counter---ST. In a linear model, rates rise by 20% to 30% for a decrease in current of 100A. In a quadratic model, this is ultimately worse. Actual rates will not be known until we have beam. These can affect the lifetime of detectors and our ability to trigger events.

  3. Plot ``Signal Events’’ divided by the square root of ``Background Events’’ and normalize to the ratio found at 1350A Solenoid Current. 1350A What happens for currents above 1300A depends on the reaction, however below this Solenoid Current, there is a rapid degradation of S/B½.

  4. Plot ``Signal Events’’ divided by ``Background Events’’ and normalize to the ratio found at 1350A Solenoid Current. 1350A What happens for currents above 1300A depends on the reaction, however below this Solenoid Current, there is a rapid degradation of S/B.

  5. We do not believe that running the magnet at 1300 – 1350 A will negatively impact the physics program. In fact the optimal field may be closer to 1350A than 1500A. The Electromagnetic Backgrounds may ultimately limit the primary photon beam flux. The final answer can only come from data. However, all proposals assume a maximum photon flux that is ½ of the design flux (108g/s in coherent peak).

  6. Efficiency improves as solenoid current is lowered, a plateau is suggested. • Purity decreases as the solenoid current is lowered. • Signal over Background falls rapidly below 1300 A Backup Slide

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