1. Calorimeter Transition Region Richard Jones & Paul Eugenio GlueX Collaboration Meeting January 11, 2008

2. Calorimeter Transition Region

3. CD3 geometry improved, but gap still apparent

4. Gap Access via Cerenkov voids Redesigned Cerenkov housing gap access

5. Add Conic Gap Calorimeter

6. Gap Calorimeter 0 17 + 6565 407 48 segment conical unit 9o9o 11 o GCAL 435460 cm

7. GCAL module concept Use BCAL module to construct GCAL modules  machine 16 GCAL per BCAL module  requires 3 additional BCAL modules (48→51, +6%)‏ 25 cm 8 cm 14 cm 10 cm 13 cm GCAL cone

8. Example: 1 GeV photon at 9.3º Provides a clean definition of the forward calorimeter acceptance

9. Noticethe early conversion in the cables is 99% recovered in the GCal Notice: the early conversion in the cables is 99% recovered in the GCal Example: 1 GeV photon at 10º

10. This is clearly the most difficult case. E bcal +E gcal = 88% E0 Notice:in addition to capturing most of the escape energy, the Gcal also shadows the Fcal from the forward splash Notice: in addition to capturing most of the escape energy, the Gcal also shadows the Fcal from the forward splash Example: 1 GeV photon at 11º

11. By 12º the BCal captures the entire shower Example: 1 GeV photon at 12º

12. No clustering, just summing energy but proximity to source means that the energy is highly localized – see event image at 10º These photons are substantially lost in the simulation without the GCal Energy Spectrum: 1 GeV photons at 10.5º