Plans for first beams - - triggers from the BRM group (BSC, BPTX)

1. Plans for first beams - - triggers from the BRM group (BSC, BPTX) Gábor Veres for the BRM group CMS Trigger Technical Coordination Meeting 8 October, 2009

2. BSC, BPTX and triggering • BSC and BPTX are primarily beam monitoring tools. • Their secondary functionality is triggering. • Triggers are implemented not to detract from the  primary functionality. • Operation/readout is independent of the other CMS subsystems. i.e. BRM readouts are independent of CMS DAQ (stand-alone).

3. “Customers” for the BRM triggers • BPTX zero bias; one or both beam bunches present • an essential trigger for CMS in general. QCD directly uses it. • BSC beam halo triggers: • tracker group (tracker end-cap alignment) • BSC beam splash triggers: • HF group (calibrations using one beam) • BSC minimum bias triggers: • QCD group (min. bias analyses, trigger x-section monitoring) • Heavy Ion group (min. bias trigger for Pb+Pb) • BSC high multiplicity trigger: • QCD and HI group (clean high-multiplicity events)

4. +z outer (beam 2) +z inner (beam 2) -z inner (beam 1) -z outer (beam 1) Beam halo triggers (4) Coincidence: at least 1 hit each side, in any segment, w/in 40 nstimed for muons moving with c +/- z refers to the direction of the muon

5. Beam Halo trigger logic (NIM)

6. Minimum bias triggers (5) Coincidences timed for collisions MB inner >=1 (at least 1 hit) MB all >=1 MB inner >=2 (at least 2 hits) MB all >=2 MB all OR “single sided” (any hit)

7. Beam splash triggers (2) Single-side coincidences At startup, it will be useful for triggering on beam-gas events occurring in the CMS volume, before collisions occur Not sensitive to single beam halo muons Also sensitive to cosmic muons and p+p collisions +z beam gas (at least 2 hits) –z beam gas (at least 2 hits)

8. Minimum bias and beam splash trigger logic

9. High Multiplicity trigger Selects events with very high multiplicity at the startup (when pileup<<1) 8 hits each side

10. BSC triggers - details • Logic based on NIM, converted to LVDS, width = 25 ns • Width of coincidences: 20+20 = 40 ns • LVDS signals connected to the general trigger • Connections to trigger boards tested • Standalone monitoring: • Trigger signals connected to VME scalers • Analog signals are connected to ADC Bits 36-39: beam halo triggers Bits 40-41: two minimum bias triggers based on all segments (>=1, >=2) Bits 42-43: beam splash triggers Technical bits "BSCMBI1" : BSC Min Bias Inner >=1 "BSCMBI2" : BSC Min Bias Inner >=2 "BSCOR" : BSC Min Bias Single Sided OR "BSCHIGHM" High Multiplicity ExternalCondition bits https://twiki.cern.ch/twiki/bin/view/CMS/L1TechnicalTriggerBits https://twiki.cern.ch/twiki/bin/view/CMS/L1ExternalConditions

11. BPTX triggers Sensors picking up the mirror charge of the passing beams. Trigger: 3 cables (with max. 4 signals) to trigger boards: Cable 1: BPTX +z .AND. BPTX –z‘zero bias’ (technical) BPTX +z BPTX –z BPTX +z .OR. BPTX –z Cable 2: (technical) BPTX +z .AND. BPTX –z‘zero bias’ BPTX +z .AND. (.NOT. BPTX –z) ‘empty target’, BPTX –z .AND. (.NOT. BPTX +z)for beam gas studies Cable 3: (external BPTX +z .AND. BPTX –z‘zero bias’conditions) (We prefer the notation ‘BPTX1’ = beam direction +z to –z). These triggers are important for timing trigger efficiencies dead-time measurements zero bias physics data taking } Responsible: Vladimir Ryjov

12. Plans for first beam • set/adjust HV values (~ few days) • study MIP signals with first halos/splashes (~ few days) • set discriminator levels accordingly (~ 1 day) • time in all segments w.r.t. each other (~ few days) (apply few ns cable delays if needed) • measure event-by-event jitters (~ 1 day) • test trigger signals/logic (~ few days) • rate checks and comparisons btw triggers with collisions (~ few days) Some of the above can be done in parallel Continuous beam/collisions are preferred

13. Conclusion • BSC and BPTX trigger hardware is available and tested • Full software implementation is needed/ongoing • commissioning planned with the first beam

14. BACKUPS

15. Geometry of the BSC At z = ± 10.91 m Distance: 73 ns·c BSC1 annular rings: inner radius: 21 cm outer radius: 45 cm 8 channels/side Paddles not -symmetric 8 channels/side BC408 scintillators (also BSC2: a few smaller segments further away in z)

16. BSC rack S1F08 at point 5 NIM  LVDS converter NIM logic and VME readout Triggerboards

17. BSC trigger rates Channel noise rates with very low threshold [Hz] • Channel noise rates: • < 1Hz (about 0.1 Hz) • Trigger rates without beam are very small: • min. bias ‘OR’: few Hz • other m.b. triggers: < 10-5 Hz • beam halo: < 10-3 Hz • beam gas: < 0.1 Hz • Pulse height stability: • good, less than 10% level • Scalars: • monitoring the rate of all channels and • all triggers Time [h]

18. Timing of the BSC signals • The analog signals from the 32 channels will be re-synchronized with the first beam (compensate few ns variations) • Trigger signals will be timed in after that • Approximate arrival time of the signals to the GT board • after the bunch crossing (status at the moment): • Beam 1 halo (+z -going muon): 550 ns • Beam 2 halo (-z -going muon): 490 ns • Minimum bias: 570 ns • Beam gas: 560 ns • High multiplicity: 570 ns

19. Simulation of BSC triggers • CMSSW 2_2_9 was used • PYTHIA 6.416 event generator was used with: - default CMS min-bias settings (D6T tune) • - ATLAS tune with higher dN/d • Trigger cross sections for inelastic p+p: • double sided (>=1 hits each side): • 51% (D6T tune), 56% (ATLAS tune) • single sided OR (any hit): 84% (D6T tune), 90% (ATLAS tune)