““L3”L3”

Jeff LandgrafJeff Landgraf

In July, Hank sent me a message asking In July, Hank sent me a message asking if I had any talks for this meeting.if I had any talks for this meeting.

““No, but I have some issues that could No, but I have some issues that could be discussed.” and followed up with a be discussed.” and followed up with a few paragraphs of rather obvious, few paragraphs of rather obvious, unconsidered, unprioritized, unconsidered, unprioritized, inconclusive, rambling opinions.inconclusive, rambling opinions.

Here they are.Here they are.

Point #1 – TPC is not going to be a slow detector. Point #1 – TPC is not going to be a slow detector. – TPC as fast, if not faster than EMC’sTPC as fast, if not faster than EMC’s

L0L0FEE’sFEE’s

RDO’sRDO’sRBRB

SB’sSB’sEVBEVB

Linux FarmLinux Farm

RCFRCFDSTDST

L2L2

L0L0FEE’sFEE’s

RDO’sRDO’sLinux FarmLinux Farm

RCFRCF DSTDSTLinux FarmLinux Farm

RB/SB/EVB/L2RB/SB/EVB/L2

700hz700hz 100hz100hz 100hz100hz 500hz500hz ??????

500hz500hz

The Old System:The Old System:

The New System:The New System:

700hz700hz 1-5khz1-5khz500hz500hz

??????

So what is the role of L2 / So what is the role of L2 / L3?L3?

It won’t be to abort TPC.It won’t be to abort TPC. Why not?Why not?

– L2 detectors would have to be faster L2 detectors would have to be faster than TPC (at least 10x faster to be than TPC (at least 10x faster to be worthwhile)worthwhile)

– Gated Grid would have to be faster than Gated Grid would have to be faster than TPC readout (10x for to be worthwhile)TPC readout (10x for to be worthwhile)

Reduce Data Volume?Reduce Data Volume? Write out tracks?Write out tracks?

– 8 helix parameters (including dedx & track 8 helix parameters (including dedx & track length), all floats. Need ~8 words per track not length), all floats. Need ~8 words per track not including niceties like chisquare, number of hits. including niceties like chisquare, number of hits. Current L3 structure has 13 words.Current L3 structure has 13 words.

– Need multiple origins for each track to Need multiple origins for each track to extrapolate to origin and to outer detectors?extrapolate to origin and to outer detectors?

– Between 16-26 words needed to define track.Between 16-26 words needed to define track.– Clusters only are 2 words / hit, so a 20 hit track Clusters only are 2 words / hit, so a 20 hit track

needs only ~40 words.needs only ~40 words.– Perhaps there is a 50% data volume savings… Perhaps there is a 50% data volume savings…

butbut– Calibrations need to be final before run starts.Calibrations need to be final before run starts.– Tracking algorithm would need to be trusted.Tracking algorithm would need to be trusted.

Reduce Data Volume? Reduce Data Volume? (continued)(continued)

Pileup rejection…Pileup rejection…– Do trackingDo tracking– Tag hits from tracksTag hits from tracks– Remove hits from datafile if they come Remove hits from datafile if they come

from pileup eventsfrom pileup events– Idea suffers from same calibration / Idea suffers from same calibration /

verification issues as writing out tracks.verification issues as writing out tracks.

MonitoringMonitoring Monitoring has been Monitoring has been

one of the biggest one of the biggest bonuses from both bonuses from both L2 and L3L2 and L3

Its important to keep Its important to keep this functionality up this functionality up (and to keep (and to keep expanding it), even expanding it), even if in the end there is if in the end there is no room for higher no room for higher level triggers.level triggers.

AnalysisAnalysis

CalibrationsCalibrations– It would be very nice to see more detector It would be very nice to see more detector

calibration procedures get automated and calibration procedures get automated and move into the counting house – ideally in an move into the counting house – ideally in an L2/L3 like entity, could save weeks L2/L3 like entity, could save weeks commissioning each year.commissioning each year.

L4 trigger, used only to reject events from L4 trigger, used only to reject events from going to RCF is a very possible idea… But going to RCF is a very possible idea… But the purpose would be to lighten the load the purpose would be to lighten the load on the reconstruction rather than increase on the reconstruction rather than increase bandwith.bandwith.

Express StreamsExpress Streams Express streams are always associated Express streams are always associated

with L2/L3 triggers, but are not! It is the with L2/L3 triggers, but are not! It is the event builders that determine data files.event builders that determine data files.

I would like to expand express streams I would like to expand express streams dramatically.dramatically.– 2005 ppProduction: if we separate EVERY 2005 ppProduction: if we separate EVERY

trigger into separate stream, then only suffer trigger into separate stream, then only suffer ~9% data overhead. ~9% data overhead.

– Analysis chains could be specifically tailored to Analysis chains could be specifically tailored to each trigger – in many cases (I believe) this each trigger – in many cases (I believe) this would lead to much more efficient analysis.would lead to much more efficient analysis.

– Reconstruction could be better prioritized.Reconstruction could be better prioritized.

SummarySummary

I’m pessimistic about high level triggers I’m pessimistic about high level triggers used to abort the TPC in the daq1000 era.used to abort the TPC in the daq1000 era.

We need to put real effort into maintaining We need to put real effort into maintaining and improving some analysis capability in and improving some analysis capability in the control room for monitoring & the control room for monitoring & calibrations.calibrations.

The function of L2/L3 like entities in the The function of L2/L3 like entities in the new system will be to support efficient new system will be to support efficient offline analysis, not to trigger.offline analysis, not to trigger.

New L0 trigger ideas, detectors are the New L0 trigger ideas, detectors are the path for improving STAR’s trigger.path for improving STAR’s trigger.