1. Level 0 Topology Trigger Falk Meissner LBNL CTB Readout Topology CTB-DSM Tree Trigger Algorithm UPC Trigger Other Examples Motivation : Level 3 requires full readout of TPC; it’s a filter not a trigger. Need to identify potentially interesting events in Level 0 to reduce background events where is TPC readout. Why in parrallel, better use of bandwidht /avail;able events, Calibration, Disadvantage: Need to separate events for analysis.

2. CTB Readout Topology 240 CTB Slats 16 ‘pixels’ of 15 slats read out by one DSM board phi*eta = 1.5 * 0.5 per pixel Basic Topology given by readout: Four rings in eta divided into quadrants. Top, Bottom, South, North symmetry after change of CTB cable map.

3. CTB-DSM Tree 3 Layers of DSM boards 104 ns per board 16/32 bits between layers Algorithms are limited by time constrain and number of available bits between layers.

4. Trigger Algorithm for UPC 0nly two oppositely charged tracks at low total p T Back- to-back in transverse plane Multiplicity per pixel: 1 or 2 mips in 1 or 2 slats Good Topology: SE-NE; SW-NW; SE-NW; SW-NE; Veto if: any hit in top or bottom any overflow out of time hit

5. Level-0 CTB Algorithm 2000 Central Trigger: sum ADC counts of all 240 CTB slats; require minimum count for central trigger 2001 Multiplicity/Topology Trigger: in parallel to central trigger –Convert ADC counts to # of Mips –Sum #of Mips for all slats –Sum #of hit slats –Multiplicity criteria on minimum and maximum # Mips and # hit slats in each of the 16 CTB pixels –Combine 16 pixels to topology decision –Possible veto if any overflow in pixel multiplicities –Veto out of time hits: leading edge within 20 ns (ADC integration time ~60ns) Possible parallel trigger decisions: –Central trigger: MipMin <  Mips –Topology trigger: Pixel topology * No out of time hits * No Pixel overflows

6. Other Possible Applications SVT Cosmic Trigger Trigger on low multiplicity coincidence in top and bottom Inner pixels only Possible to require crossing of inner membrane Jet Trigger for pp ? high multiplicity in a limited number of slats in one pixel

7. Summary/Status Code for all 3 layers of DSM’s implemented and tested on mock-up in Berkeley No cosmic test with STAR yet; a.s.a.p. Change of topology requirements simple Create your own burrito; two criteria: – Mip and Slat multiplicity per pixel – Good topology combinations Long write-up with more technical details available

8. ‘Re-Cabling’ of the CTB Reorder cable assignments in the front of the patch-panel – Internal change of cable map 5 slats (30 degrees) in West and 10 slats (60degrees) the East half of the CTB. Get symmetry Top, Bottom, South, North Ultra Peripheral Collisions: Use Top and Bottom quadrants as veto for cosmic rays. Spin: left-right symmetric trigger for single-spin asymmetry measurement with transverse beam polarization

9. No Impact to Central Trigger Caution: hard-coded indexing of slat numbers in software will cause problems – But, should not be there Proposed Change