STT simulations (Horst Wahl, 25 February 2000)

1. STT simulations(Horst Wahl, 25 February 2000) • trigger simulation • (Silvia Tentindo-Repond, Sailesh Chopra, John Hobbs, with help from Brian Connolly, Harrison Prosper, + Dave Toback) • queueing studies • (Stephan Linn) Outline:

2. STT trigger simulation(Silvia Tentindo-Repond, Sailesh Chopra,…...) • STT trigger simulator: • integral component of D0 RunII Trigger Simulator; • tasks: • simulate all components of the STT: • hit clustering (STC) • CTT road information handling (FRC) • hit filtering (STC) • tracking (TFC) • provide tool for optimization of • trigger parameters and algorithms • monitoring parameters • provide tool for determination of efficiencies • L2STT Simulator code split into three packages: • tsim_l2stt (main package) • l2stt_util • l2stt_fitting (for detailed studies of track fitting algorithms)

3. STT simulation status • presently available functionality • SMT hit clustering: • cluster algorithm: • so far, only one algorithm implemented: neighbor clustering without cap on clustersize, (same alg. as used in L3, but different from algorithm being studied for firmware implementation) • other algorithms foreseen • hit filter: • CTT roads now integrated into main package; • temporarily, use analytic expression for translation from CFT to SMT coordinates • first version of LUT (translation map) available (but based on nominal position -- will need possibility to use real positions) • tracking (with John Hobbs, Wendy Taylor): • l2stt_fitting contains all possible tracking algorithms (for testing); • main package will only have final choice of algorithm • still being debugged • test output: • create a text file that contains SMT hits in cable-format, to be used as an input for debugging and testing of VHDL code for clustering. (RCP switch) • CTT roads: to be done • most of the code committed to CVS t70

4. Clusters from t tbar events • only from barrels

5. Clusters from Zb bbar + 2 min.bias events • barrel only

6. Clusters vs SMT layer from Zb bbar + 2 min.bias events

7. Clusters from one t tbar event • Clusters from 100 t tbar events

8. one t tbar event • road centers in SMT • SMT clusters in CTT roads

9. CTT tracks from Zb bbar + 2 min.bias events • Clusters in roads • nb. of CTT tracks

10. Queueing Studies(Stephan Linn) • Questions to be answered by queueing studies: • how much processing (e.g. track fitting) time can we afford before deadtime becomes unacceptably high? • where are the potential bottlenecks in the data flow through the trigger? • additional buffering needed? • Queueing simulation software • previously, used RESQ (IBM product) • not supported anymore, only runs on IBM platforms  look for alternative • Ptolemy: • simulation package developed by EE and comp.science dept. at UC-Berkeley • can simulate complex systems at different levels of detail and with different time scales • elements of system represented by “queue and serve galaxies” • specified by service time and queue depth • event defined by starting time and data value (event number)

11. STT Model in Ptolemy • use available specifications(note by U.Heintz at http://physics.bu.edu/~heintz/STT_q.pdf) • parameterize (from MC data) • Nt = number of tracks per sextant • Nh = number of hits per detector • H = clusters per hit • T = clusters per track • transmission speeds • data sizes • model: • STT modeled as 6 independent sectors • random numbers Nt, (hyperexponential) Nh (double gaussian), track fitting time (double exponential, from JH+WT studies) • correlations between module delay times (depend on Nt, Nh) • PCI bus “arbitration” (priority to road transfer over filtered clusters) • STC filter waits for roads from FRC • (see draft of note by Stephan Linn at http://www-d0.fnal.gov/~linn/d0_private/queue.ps)

12. STT Queueing model

13. PCI bus model

14. distributions used • cluster multiplicity • track multiplicity • track fitting time

15. Queuing simulation results • latency • for one STT sextant: • latency for one sextant reproduces track fit delay • full system latency: worst-of-N convolution with five other sextants • total deadtime: < 1% (for nominal values) (not counting deadtime due to min. time between L1 accept) • 16 event buffer before track fitting takes care of 50s track fitting time -- never filled to capacity. • no additional buffer necessary

16. Parameters in queueing simulation • Parameters used in simulation: • number of hits per detector Nh double gaussian with mean = 36, max. = 90 (corresponds to 8 overlapped jet-brew events, with L1 trigger pt > 7 GeV, plus 2% add’l occupancy for noise) • number of L1CTT tracks per sextant Nt hyper-exponential with mean= 2 , rms = 4, max = 32 (corresponds to 6 overlapped jet-brew events, with L1 trigger pt > 7 GeV) • number of hits per cluster H: gaussian with mean 3.6, rms 2.8 (from t tbar events) • timing for tracking: double exponential, with “old” values, i.e. 15s • notes: • changing Nt to 4.8 with rms 8, other parametes unchanged: deadtime < 2% • Z  b bbar + 2 MB events: • Nt = 1.5 (9 per event with rms 5), • Nh = 9, H = 3.9 • for 8 overlapped jet-brew events, Nt = 3.7, rms 6.0 • time for track fitting now much shorter than that used • for 396ns bunch spacing: • for L = 0.8 x 1032cm2 s-1 : mean nb. of int. = 2.3 prob. of 7 int. = 1% • for L = 2.0 x 1032cm2 s-1 : mean nb. of int. = 5.4 prob. of 7 int. = 12%, of 8 8%

17. Probability of N(interactions)/crossing • For L = 0.8 x 1032cm2 s-1 N(int) 36 bunch 99 bunch 0 0.11219921 0.45137941 1 0.24543345 0.35904841 2 0.2684403 0.142802 3 0.19573587 0.03786381 4 0.10704204 0.00752966 5 0.04683045 0.00119789 6 0.01707344 0.00015881 7 0.0053354 1.8046E-05 8 0.00145888 1.7944E-06 1 or more 0.88780079 0.54862059 2 or more 0.64236734 0.18957218 4 or more 0.17819117 0.00890638 8 or more 0.00190983 1.9666E-06 <N> 2.18747933 0.79544703

18. Probability of N(interactions)/crossing • For L = 2.0 x 1032cm2 s-1 N(int) 36 bunch 99 bunch 0 0.00421672 0.13688453 1 0.02305996 0.27221098 2 0.06305397 0.27066177 3 0.11494105 0.17941425 4 0.15714448 0.08919658 5 0.17187515 0.03547558 6 0.15665555 0.01175789 7 0.122386 0.00334028 8 0.08366151 0.00083032 1 or more 0.99578328 0.86311547 2 or more 0.97272333 0.5909045 4 or more 0.79472831 0.14082848 8 or more 0.18666714 0.00105815 <N> 5.46869832 1.98861757

19. TFC timing • From “minimum bias jet-brew” with L1 pt > 7GeV, get mean number and standard deviation for CTT tracks; • parameterize Nt distribution by double exponential with  = 2 ; • integration of this function allows estimate of P(Nt <16) for given number of overlapping interactions • for L = 2.0 x 1032cm2 s-1 , and 396ns bunch crossing time, prob. of > 7 interactions is 18%; for 8 interactions, prob. of more than 16 tracks = 4%;  negligible effect on deadtime. Nint(Nt)(Nt) P(Nt < 16) 1 0.8 1.5  1 2 1.0 1.9  1 4 1.1 2.1 0.997 6 2.0 4.3 0.981 8 3.7 6.0 0.957

20. Simulation summary • STT trigger simulation tools close to being ready and useful; • tracking part operational; • alternative clustering schemes to be implemented; • LUT for hitfilter to be done • work on providing test output in progress; • caveat: need to ensure that algorithms in trig. simulation correspond to firmware implemented in hardware. • queueing simulation package operational • have STT queueing model which is quite realistic • studies so far show no major bottleneck in design; even for high luminosities and occupancies; • can easily adapt to new specifications as design progresses; • more detailed TFC simulation in progress