Trigger Peter Jacobs, LBNL

21
An EMC for ALICE 1 ICE Collaboration Meeting NL, Oct 15-16, 2005 Trigger Peter Jacobs, LBNL 0 : 10 Hz p T ~20 GeV/c Inclusive jets: 10 Hz E T ~50 GeV/c 10 Hz Pb interaction rate ~ 4-8 kHz d process trigger ~ 10 Hz ed rejection factor 400-800

description

10 Hz. Trigger Peter Jacobs, LBNL. Pb+Pb interaction rate ~ 4-8 kHz Hard process trigger ~ 10 Hz  need rejection factor 400-800. p 0 : 10 Hz  p T ~20 GeV/c Inclusive jets: 10 Hz  E T ~50 GeV/c. EMCal trigger: enhancement factor relative to minbias trigger + TPC. s=0: p 0 vs p ±. - PowerPoint PPT Presentation

Transcript of Trigger Peter Jacobs, LBNL

Page 1: Trigger Peter Jacobs, LBNL

An EMC for ALICE 1ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

TriggerPeter Jacobs, LBNL

0: 10 Hz pT~20 GeV/c

Inclusive jets:10 Hz ET~50 GeV/c

10 Hz

Pb+Pb interaction rate ~ 4-8 kHzHard process trigger ~ 10 Hzneed rejection factor 400-800

Page 2: Trigger Peter Jacobs, LBNL

An EMC for ALICE 2ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

EMCal trigger: enhancement factor relative tominbias trigger + TPC

Live time: • DAQ dynamic scaledown of common triggers (“central”, “minbias”)• Pierre v.d.Vyvre: reasonable to expect 90% livetime

sacc

saccefffLE

TPC

EMCtrigmbmbAA

Trig

tapetorateevtmax

s=0: 0 vs p±

Page 3: Trigger Peter Jacobs, LBNL

An EMC for ALICE 3ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

Why bother with jets in p+p?

Is ALICE irrelevant for jet studies in p+p? Maybe not.

• p+p at top luminosity: 1034/cm2/s x 100 mb ~ 109 Hz

20 ns bunch spacing 20 minbias interactions per bunch crossing

• ALICE runs at L~1031 much cleaner environment in low to intermediate pT 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

Page 4: Trigger Peter Jacobs, LBNL

An EMC for ALICE 4ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

PHOS L1 Trigger

L1 (6 s): 2x2 tower analog sum TRU 4x4 tower peak finderEMCal: 12 FEE/GTL bus 12*32=384 towers/TRU

(x ~0.24 x 0.36)

Page 5: Trigger Peter Jacobs, LBNL

An EMC for ALICE 5ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

Charged jets (HLT study)

ETcharged>m

Charged jets: poor energy resolution, slow turn-on above trigger threshold, highly biased

C. Loizides, FfM

Page 6: Trigger Peter Jacobs, LBNL

An EMC for ALICE 6ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

Conjecture: better solution is Level 1 EMCal + HLT TPC+EMCal

Some rough numbers:

Minbias data rate ~ 20 MB/evt*4 KHz ~ 80 GB/sHLT input bandwidth ~ 15 GB/s

Least-biased efficient trigger algorithm:

• EMCAL@L1: 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

Page 7: Trigger Peter Jacobs, LBNL

An EMC for ALICE 7ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

Jet patch trigger in p+p

0.21x0.21

Strong biases for ETmax>10 GeV

PYTHIA

Page 8: Trigger Peter Jacobs, LBNL

An EMC for ALICE 8ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

Jet Patch Trigger SimulationsAndre Mischke (Utrecht)

• Pythia jet (ET~50 GeV) + HIJING background• square candidate jet patches x s x s • sweep patch quasi-continuously over detector, find maximum ET

max

Page 9: Trigger Peter Jacobs, LBNL

An EMC for ALICE 9ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

Why a large-ish trigger patch in A+A?Leading particle (0) trigger strongly biased

• Fragmentation bias (prefer low ET 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

Page 10: Trigger Peter Jacobs, LBNL

An EMC for ALICE 10ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

Jet patch trigger in Pb+Pb

bkgd

jet (ET~50 GeV)

• Centrality dependent pedestal (no surprise)• Background and fragmentation fluctuations of similar magnitude

Weighted by Nch data volume

PYTHIA+HIJING

0.21x0.21

ET cut for 80% trigger efficiency @ 50 GeV

Page 11: Trigger Peter Jacobs, LBNL

An EMC for ALICE 11ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

L1 output data rate for 80% jet efficiency @ 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

Page 12: Trigger Peter Jacobs, LBNL

An EMC for ALICE 12ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

Trigger efficiency I

PYTHIA+HIJING

Good efficiency at 100 GeVBackground dependencies at 50 GeV

Page 13: Trigger Peter Jacobs, LBNL

An EMC for ALICE 13ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

Trigger efficiency II: patch size dependence

0.3 x 0.3 apparently larger than optimal

Page 14: Trigger Peter Jacobs, LBNL

An EMC for ALICE 14ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

Trigger efficiency III: quenching models

Strong model dependencies

But models are only first guesses prudent experimental design requires flexible patch trigger

Page 15: Trigger Peter Jacobs, LBNL

An EMC for ALICE 15ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

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

Page 16: Trigger Peter Jacobs, LBNL

An EMC for ALICE 16ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

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

SummaryTRU

Low-latency serial pass-through

Low-latency serial pass-through Low-latency serial

pass-through

Max aggregate input bandwidth= 3 Gbit/s

Jet patch trigger

late

ncy

1-2

s

< 10

0 M

bit/s ~100 bits/evt

Page 17: Trigger Peter Jacobs, LBNL

An EMC for ALICE 17ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

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

Page 18: Trigger Peter Jacobs, LBNL

An EMC for ALICE 18ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

V0 response to Pb+Pb

Large generation of secondaries in beampipe but response is nicely linear

Forward detector TRD fig 3.6

Page 19: Trigger Peter Jacobs, LBNL

An EMC for ALICE 19ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

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

……………

SummaryTRU

Low-latency serial pass-through

Low-latency serial pass-through Low-latency serial

pass-throughlate

ncy

1-2

s

< 10

0 M

bit/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 bitsSignificant problem: no L1 cross-correlation in Central Trigger Processor (Orlando V-B)

technically feasible (H. Muller, F. Fomenti, Y. Zoccarato)

Centrality-dependent threshold?

Page 20: Trigger Peter Jacobs, LBNL

An EMC for ALICE 20ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

To CTP

L0

in

65LVDM31

Q+

Q-

from FPGACYCLONE EP1C12

(ALTERA) Trigger 1 - 5

To LTUin

65LVDM31

Q+

Q-

from FPGACYCLONE EP1C12

(ALTERA) busy

in+

in-Q

65LVDS32B

from LTUto FPGA

CYCLONE EP1C12(ALTERA)

16

HDMP-1032

clk

data

from FPGACYCLONE EP1C12

(ALTERA)

Q+

Q-

+3.3V num

130

+3.3V num

To EMCal100nF

100nF

130

V0 Interface between CTP, LTU, EMCal and FEE

Page 21: Trigger Peter Jacobs, LBNL

An EMC for ALICE 21ALICE Collaboration MeetingLBNL, Oct 15-16, 2005

General trigger issues

Interface with ALICE CTP for issuing and receiving L0/L1Decisions being made now, we need to be involved …