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 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). BSC, BPTX and triggering

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

5 Beam Halo trigger logic (NIM)

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

7 Beam splash triggers (2) +z beam gas (at least 2 hits) –z beam gas (at least 2 hits) 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

8 Minimum bias and beam splash trigger logic

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

10 BSC triggers - details Logic based on NIM, converted to LVDS, width = 25 ns Width of coincidences: = 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 "BSCMBI1" : BSC Min Bias Inner >=1 "BSCMBI2" : BSC Min Bias Inner >=2 "BSCOR" : BSC Min Bias Single Sided OR "BSCHIGHM" High Multiplicity Technical bits External Condition bits

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

16 BSC rack S1F08 at point 5 NIM logic and VME readout NIM  LVDS converter Trigger boards

17 BSC trigger rates Channel noise rates: < 1Hz (about 0.1 Hz) Trigger rates without beam are very small: min. bias ‘OR’: few Hz other m.b. triggers: < Hz beam halo: < 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] Channel noise rates with very low threshold [Hz]

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 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)