1. 16 May 20011 BTeV Level 1 Muon Trigger Algorithm Michael J. Haney 16 May 2001 www.hep.uiuc.edu/engin/btev/reports/16may01.ppt (and.pdf)

2. 16 May 20012 Numbers 2 arms, 8 octants –each octant-arm treated independently –16-fold (geographic) symmetry 3 stations (1,2,3), 4 views each (R,U,V,R) 13 (12?) planks, 32 tubes each –double-layer (16+16, offset)

3. 16 May 20013 Assumptions complete octant-arm data delivered to board –implies 16 “boards” –can be fewer if density permits (1/N) may be necessary… (see last slide) complete crossing data –no mixing –must finish current before beginning next

4. 16 May 20014 (soft) Assumptions complete view data –must finish current before beginning next data delivered radially inward –outer to inner These assumptions are not critical, but if they are easy for the Muon front end, they will reduce/eliminate sorting...

5. 16 May 20015 Algorithm (FPGA) compress adjacent tube hits –can be done serially (on-the-fly) if the soft assumptions are met… –need to understand how to handle many-adjacent hits...

6. 16 May 20016 Algorithm (FPGA/DSP) AND/OR (selectable) R,R views –reduce to single RR “view” working radially inward, form valid RR 2 -U 2 pairs (fixed table size => outer bias) look-up V 2 ‘s from RRU 2 ‘s; form RRUV 2 ’s –and RRV 2 ’s and UV 2 ’s, etc. as space/time permits... 6 8 10 4 2 3 4 2 3 R U V

7. 16 May 20017 Algorithm (DSP) window-search RR 3 ’s based on RRUV 2 ’s look-up U 3 ’s and V 3 ’s from RRUV 2 RR 3 ’s look-up RR 1 ’s, U 1 ’s, V 1 ’s from RRUV 2 RRUV 3 ’s declare RRUV 1 RRUV 2 RRUV 3 ’s (and various lessers) as “tracks” calculate  2 ’s (?)

8. 16 May 20018 Algorithm Notes radially-inward processing –biased in favor of higher P T –implications on front end readout (order) fixed table sizes –accommodates “wall of fire” near beam pipe octant-arm specific –16-fold symmetry in hardware –no inter-octant communications

9. 16 May 20019 Algorithm Notes (continued) combinatoric explosion - suppressed –RRU 2 ’s require O(N 2 ) –“look-up” steps require O(M) –window search? O(M) to O(M 2 ) could be fully implemented in the Pixel Trigger DSP Farm –but compression/table-building may be done in (Pixel Trigger?) FPGAs

10. 16 May 200110 Loose Ends pure 16-fold geographic symmetry produces 16 “opinions” per crossing for the Global L1 to consider –may need to collapse 16:1 at FPGA-DSP boundary –same as Pixel Trigger 31:1 Even if we can use the same FPGAs, will Muon front end look like Pixel front end (number of spigots)?

11. 16 May 200111 Highways The Muon Trigger has 16-fold geographic symmetry –(8-fold per arm) 8-fold highways imply 128-fold symmetry –may need need several “folds” per FPGA board just to keep the system size reasonable