1. MuID Efficiency Study RIKEN/RBRC Itaru Nakagawa This analysis has been done by Sarah Caussin (ENSICAEN) 1

2. MuID’s efficiency 2 -MuID’s Efficiency has been calculated by so called ‘data driven method’. 1.Data driven (DD): Efficiency is determined using the tracks registered in the previous and in the next gap. ? This approach is OK if tracks are not miss-reconstructed by accidental hits. ? ? Need a careful check to be used in high luminosity circumstances

3. MUID Efficiency MUID Efficiencies @ 500 GeV Operation 0.5 BBC Rate 5MHz Efficiency drops down to < 60%. This is a significant correction! 3

4. Alternative : HV Method …. x20 tubes V eff V=4400[V] VsVs R=400M  Efficiency by HV method can be calculated by the empirical formula determined in 2004 Continuously monitored 4 Each data points were measured by lowered operation voltage using cosmic. Efficiency was calculated by data driven formula.

5. 5 HV 法 V eff VsVs V0V0 R I 検出器 モニ ター 印加電圧

6. Back in Run5, the agreement between Data Driven and HV methods were good. Can we still make them agree under high rate circumstances? 6

7. 7 Drawing Currents / HV Chain [uA] Run Number Run13 Currents per HV Chain Stable baseline Unstable baseline

8. MUID’s geometry -MuID’s gaps are divided into two planes : one containing vertically-oriented tubes and the other containing horizontally-oriented tubes -The planes are then further divided into six panels (0 – 5) 8 -MuID’s High voltage supplies are separated in different groups, each serving about twenty tubes Vertical planeHorizontal plane Front view

9. 9 Drawing Currents per HV Group Horizontal axis : Luminosity Average Current per Tube [uA] I0I0 I1I1 I2I2

10. Current -> Efficiency 10

11. Resulting efficiencies X axis : Luminosity (kHz) Y axis : Efficiency A graph = A HV Group 11 Discrepancy between the two methods gets higher with luminosity Tendency of HV method to be higher than DD method ?

12. Discrepancy Between Data Driven and HV method 12 In general, HV method predicts higher efficiency than DD. The empirical formula determined in 2004 may not be relevant any longer?

13. 2014 HV scan 13 -Attempted to repeat 2004 HV scan measurement to update the efficiency formula with respect to the effective voltage. -Executed in early July right after Run14 by Itaru, SeYoung Young(Ewha Women’s University) and Junsang Kim (Seoul National Laboratory). -Analysis is done by Sarah Caussin (CAEN) -Our aim was to get a new Efficiency vs. HV plot in order to update the HV method formula.

14. Solid blue line : 2004 formula Dotted lines : 2014 fits 14

15. 2014 2004 Some cases need more careful study

16. Updating Average Deviation Using the formulas from the new fits, we re- evaluated the Average Deviation: Even with the odd cases, the distribution is now evenly distributed around 0. 16

17. Radial Dependent Efficiency -We saw strong rate dependence in MUID efficiencies. -Even within the same BBC rate, the rate is different depending on the distance from the beam pipe. -Thus MUID efficiency could be depending on this radius. 17

18. Dividing into zones To get a better idea of the dependency, we divided gaps into 4 zones and compared their efficiencies calculated with DD method: A radial dependency is indeed present, and we are currently investigating its nature. 18 20%

19. Efficiency Correction Scheme 19 Vertical planeHorizontal plane Present correction based on HV Groups. Proposed Scheme may be radially segmented zones. Present

20. Impact on Data Analysis 20 Hadronic Backgrounds (from real data) W (from MonteCalro) Heavy Quark (from MonteCalro) Hadronic Background shape reflects actual radial dependent efficiency. However, the predictions by Monte Calro don’t. Thus rapidity spectra may be incompatible with experimental spectra.

21. Conclusion Attempt to Cross check MUID efficiency based on conventional data driven approach. Data driven approach needs careful check to be used in high rate circumstances. Updated HV response seem to bring both methods in better agreement. Further cross checks and careful analysis is underway. The efficiency dependence on the radius is significant. May want to reconsider the present correction sckeme to be radius dependence. 21