1 Timing in HCAL Digitization Rick Wilkinson

2 Timing We should try to maximize charge in time bin 5, for high energy (no time slew) We should try to maximize charge in time bin 5, for high energy (no time slew) Reconstruction uses time bins 5,6,7 & 8 Reconstruction uses time bins 5,6,7 & 8 Any energy in time bin 4 is lost! Any energy in time bin 4 is lost!

3 The Pulse Shape Peaks at 13.9 ns Integrated over bunch crossing Peaks at 5 ns That’s where we want time bin 5 to start

4 Jitter SimHit time minus time of flight to face of cell SimHit time minus time of flight to face of cell

5 Time Slew Smaller signals get delayed Smaller signals get delayed

6 Time Slew Implementation In current releases: In current releases: Each hit gets delayed based on its charge Each hit gets delayed based on its charge Future releases: Future releases: Hits are summed by cell and by estimated BX Hits are summed by cell and by estimated BX Will give smaller effect than current releases Will give smaller effect than current releases

7 Conclusion CMSSW has a “time phase” parameter CMSSW has a “time phase” parameter Should be 5 ns in ideal case Should be 5 ns in ideal case To maximize time bin 5 To maximize time bin 5 If we start too early, we lose the energy in bin 4 If we start too early, we lose the energy in bin 4 Jitter causes ~5-10 ns delay Jitter causes ~5-10 ns delay Time slew causes ~5-10 ns delay Time slew causes ~5-10 ns delay How to tune the number to use? How to tune the number to use? Optimize for infinite-energy limit? 100 GeV pions? Optimize for infinite-energy limit? 100 GeV pions?