1. S1,N1 Counters RIKEN/RBRC Itaru Nakagawa

2. 4/15 ~ 4/29 S1,N1 Counters in MuID square hole. Lay down on the bottom of garage shielding.

3. S1,N1 Ratio to S4,N4 S1 N1 S4 N4 S4/S1N4/N1 Ratio102

4. 1 week sample (South) S4/S1 ~ 10, Consistently

5. 1 week sample (North) N4/N1 ~ 2, Consistently

6. 4/29 ~ S1,N1 Counters are vertically standing right next to the beam pipe N1

7. S1,N1 Ratio to S4, N4 After blue noise problem resolved South North S4/S1N4/N1 Ratio75

8. After Access (South) Post Blue Noise Problem Resolved

9. After Access (North) Post Blue Noise Problem Resolved

10. Before/After Access (South) Before Access After Access Don’t see drastic change in S1 counter rate

11. Before/After Access (North) Before Access After Access Obvious rate change in N1 counter rate

12. So what we learn form it? N1 counter rate trends is comprehensive in terms of the distance from the beam pipe S1 counter cannot be understood by the radial dependence of backgrounds. –Somehow locally hot? –Parallel flux traveling outside beam pipe happen to have weak radial dependence? –Background components with transverse momemtum? –…

13. Correlation with MuID (Before Access) S1 N1 S4 N4

14. Correlation with MuID (After Access) South North

15. Summary MuID background condition is stable before/after access. (simply scales with lumi) North & South MuID currents show different behavior –South background: Gap0>>Gap1, Gap4> Gap3, Gap2 –North background: Gap4, Gap0>>Gap1,Gap2,Gap3 -> suffered from BG from upstream beam line –Gap0 (South) > Gap0 (North) –Gap4 (North) > Gap4 (South) Is the high current in South gap-0 correlated with high rates S1 observed below beam pipe? –Not sure. At least z-position is around gap4.

16. Outlook Compare with Run08, 500 GeV. Investigate further about South backgrounds. Gap0 and high rates away from beam pipe in MuID square hole. The interesting candidate of next S1 counter condition is –Move as close as possible to Gap-0 in z. –Rotate paddle by 90 degrees to face beam pipe. (Presently facing DX magnet) to measure transverse component of backgrounds.