ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE1 Trigger Peter Jacobs, LBNL  0 : 10 Hz  p T ~20 GeV/c Inclusive jets: 10 Hz  E T ~50 GeV/c 10 Hz Pb+Pb interaction rate ~ 4-8 kHz Hard process trigger ~ 10 Hz  need rejection factor

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE2 EMCal trigger: enhancement factor relative to minbias trigger + TPC Live time: DAQ dynamic scaledown of common triggers (“central”, “minbias”) Pierre v.d.Vyvre: reasonable to expect 90% livetime s=0:  0 vs p ±

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE3 Why bother with jets in p+p? Is ALICE irrelevant for jet studies in p+p? Maybe not. p+p at top luminosity: /cm 2 /s x 100 mb ~ 10 9 Hz 20 ns bunch spacing  20 minbias interactions per bunch crossing ALICE runs at L~10 31  much cleaner environment in low to intermediate p T region ALICE may have a unique niche in p+p: detailed studies of jet fragmentation down to low z  important reference for A+A program

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE4 PHOS L1 Trigger L1 (6  s): 2x2 tower analog sum  TRU  4x4 tower peak finder EMCal: 12 FEE/GTL bus  12*32=384 towers/TRU (  x  ~0.24 x 0.36)

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE5 Charged jets (HLT study) E T charged >m Charged jets: poor energy resolution, slow turn-on above trigger threshold, highly biased C. Loizides, FfM

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE6 Conjecture: better solution is Level 1 EMCal + HLT TPC+EMCal Some rough numbers: Minbias data rate ~ 20 MB/evt*4 KHz ~ 80 GB/s HLT input bandwidth ~ 15 GB/s Least-biased efficient trigger algorithm: mildly biased jet patch trigger to cut minbias rate by factor 10 ~ 8 GB/s do the rest in HLT incorporating charged tracks, neutral energy from emcal, dijet topologies (?), etc

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE7 Jet patch trigger in p+p 0.21x0.21 Strong biases for E T max >10 GeV PYTHIA

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE8 Jet Patch Trigger Simulations Andre Mischke (Utrecht) Pythia jet (E T ~50 GeV) + HIJING background square candidate jet patches  x  s x s sweep patch quasi-continuously over detector, find maximum E T max

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE9 Why a large-ish trigger patch in A+A? Leading particle (  0 ) trigger strongly biased Fragmentation bias (prefer low E T jets fragmenting hard) Geometric bias (prefer lower than average energy loss surface emission) PYTHIA fragmentation requires relatively small patches (0.1 x 0.1) for efficient triggering (Bill, Chris)  fragmentation fluctuations primarily in distribution of few hardest (colinear) hadrons But the physics we are after is the modification of the fragmentation, including potentially large jet broadening effects (and correspondingly smaller background fluctuations?)  no really solid theory guidance  prudent experimental design requires flexible patch trigger  also for lighter systems than Pb+Pb

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE10 Jet patch trigger in Pb+Pb bkgd jet (E T ~50 GeV) Centrality dependent pedestal (no surprise) Background and fragmentation fluctuations of similar magnitude Weighted by N ch  data volume PYTHIA+HIJING 0.21x0.21 E T cut for 80% trigger 50 GeV

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE11 L1 output data rate for 80% jet 50 GeV Details strongly dependent on models of signal + background Qualitative conclusion nevertheless: required L1 rejection achievable with reasonable efficiency for ~50 GeV jets  requires centrality-dependent threshold input rate Output rate

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE12 Trigger efficiency I PYTHIA+HIJING Good efficiency at 100 GeV Background dependencies at 50 GeV

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE13 Trigger efficiency II: patch size dependence 0.3 x 0.3 apparently larger than optimal

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE14 Trigger efficiency III: quenching models Strong model dependencies But models are only first guesses  prudent experimental design requires flexible patch trigger

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE15 PHOS trigger: Trigger Regional Unit each TRU:  x  ~0.24x0.36 (depends on how we cable) no inter-TRU communication  large acceptance hit for jet patch, limited maximum patch size

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE16 Candidate implementation: TRU hierarchy TRU ~400 towers TRU ~400 towers TRU ~400 towers TRU ~400 towers TRU ~400 towers TRU ~400 towers …………… 13K towers ~ 30 TRUs Summary TRU Low-latency serial pass-through Max aggregate input bandwidth= 3 Gbit/s Jet patch trigger latency 1-2  s < 100 Mbit/s ~100 bits/evt

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE17 Centrality-dependent trigger threshold? V0 Uniform jet trigger efficiency across centralities: need to account for centrality- correlated pedestal fluctuations V0 is only fast (L1) detector with sufficient coverage

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE18 V0 response to Pb+Pb Large generation of secondaries in beampipe but response is nicely linear Forward detector TRD fig 3.6

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE19 V0 bits in jet patch summary TRU? TRU ~500 towers TRU ~500 towers TRU ~500 towers TRU ~500 towers TRU ~500 towers TRU ~500 towers …………… Summary TRU Low-latency serial pass-through latency 1-2  s < 100 Mbit/s V0 System design issues: non-locality of trigger logic (i.e. not in CTP), scalars,… PHOS TRU: Hans Muller has added 3 optical Gigabit ports for interconnectivity… few bits Significant problem: no L1 cross- correlation in Central Trigger Processor (Orlando V-B) technically feasible (H. Muller, F. Fomenti, Y. Zoccarato) Centrality-dependent threshold?

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE20 V0 Interface between CTP, LTU, EMCal and FEE

ALICE Collaboration Meeting LBNL, Oct 15-16, 2005 An EMC for ALICE21 General trigger issues Interface with ALICE CTP for issuing and receiving L0/L1 Decisions being made now, we need to be involved …