Trigger Accounting for 2002

Jeff LandgrafJeff LandgrafSTAR Trigger Workshop: Oct 21, STAR Trigger Workshop: Oct 21, 20022002

Trigger Accounting for Trigger Accounting for 20022002


Issues to be addressedIssues to be addressed

Multiple triggers at the same timeMultiple triggers at the same time– Mutually exclusive L0 TriggersMutually exclusive L0 Triggers– Interaction between L0/L1/L2/L3Interaction between L0/L1/L2/L3

Offline interfaceOffline interface– Scalers and countersScalers and counters– Evolution of trigger definitionsEvolution of trigger definitions


2001 STAR Trigger model2001 STAR Trigger model

Each event gets Each event gets analyzed separately analyzed separately at each trigger levelat each trigger level

Events labeled by Events labeled by trgWord, noL3Bias()trgWord, noL3Bias()

Only worked because:Only worked because:– No L0 overlap No L0 overlap

attemptedattempted– No L1/L2 usedNo L1/L2 used

Event

L0 -- 1,2,3...

L1 -- 1,2,3...

L2 -- 1,2,3...

L3 -- 1,2,3...

Tape


L0 Overlap IssueL0 Overlap IssueExample:Example:

Mixed Central (ps=1) & Min-bias (ps=100)Mixed Central (ps=1) & Min-bias (ps=100)

L0 TriggerL0 Trigger Trigger word, PSTrigger word, PS

not Central && not Min-biasnot Central && not Min-bias N/AN/A

not Central && Min-biasnot Central && Min-bias 1, 1001, 100

Central && not Min-biasCentral && not Min-bias 2, 12, 1

Central && Min-biasCentral && Min-bias 3, 1 (conflict: MB 3, 1 (conflict: MB 100, Central 100, Central 1) 1)

Using the trigger word alone gives a biased Min-biasUsing the trigger word alone gives a biased Min-bias Reconstructing an unbiased trigger is simple:Reconstructing an unbiased trigger is simple:

– Min-bias Min-bias every TW=1 and 1 of every 100 TW=3 every TW=1 and 1 of every 100 TW=3– Central Central every TW=2 and every TW=3 every TW=2 and every TW=3

L1 marks each event according to this rule L1 marks each event according to this rule “L1 rescaling.” “L1 rescaling.” The Configuration/L1 rescale algorithm works with arbitrary The Configuration/L1 rescale algorithm works with arbitrary

triggerstriggers


Interaction between Interaction between L0/L1/L2/L3L0/L1/L2/L3

Correlated triggers (analyzed naively) introduce Correlated triggers (analyzed naively) introduce biasbias

To untangle these interactions we would need: To untangle these interactions we would need: – NNL0L0 * 2^N * 2^NL1L1 * 2^N * 2^NL2L2 * 2^N * 2^NL3 L3 counterscounters– Additional PS logic (Accept untriggered)Additional PS logic (Accept untriggered)– Very complicated analysis logicVery complicated analysis logic

Instead, I will show how to avoid the problem Instead, I will show how to avoid the problem entirely by some simple constraints on how L1/L2 entirely by some simple constraints on how L1/L2 & L3 algorithms are defined.& L3 algorithms are defined.

L2: High Pt L2: High Pt L3: High L3: High multiplicitymultiplicity

High Pt, High High Pt, High Multiplicity Multiplicity eventsevents

example:


2002 STAR Trigger Model2002 STAR Trigger Model

L0 – 1

L1 -- 1

L2 -- 1

L3 -- 1

L0 – 2

L1 -- 2

L2 -- 2

L3 -- 2

L0 – 3

L1 -- 3

L2 -- 3

L3 -- 3

Event

Tape

Pretend that we have N Pretend that we have N independent trigger systems. independent trigger systems.

Each system has its own L0, Each system has its own L0, L1, L2 and L3 components. L1, L2 and L3 components.

Configure one trigger on Configure one trigger on each system. each system.

If any one of the trigger If any one of the trigger systems accepts the trigger, systems accepts the trigger, the event is saved to tape. the event is saved to tape.

The event gets marked The event gets marked according to which trigger according to which trigger systems accepted it.systems accepted it.

No accounting biases.No accounting biases.

2002 we simulate this 2002 we simulate this situationsituation


Implementation of the 2002 Implementation of the 2002 Trigger ModelTrigger Model

Configure N Triggers in run control. The Configure N Triggers in run control. The configuration for each trigger is roughly equivalent configuration for each trigger is roughly equivalent to setting last years TRG_SETUP parameters. to setting last years TRG_SETUP parameters.

Every Trigger has a L0 requirement and exactly Every Trigger has a L0 requirement and exactly one algorithm at each level, L1, L2 & L3.one algorithm at each level, L1, L2 & L3.

Then, as we run:Then, as we run:– Perform L1 rescaling before running any L1 algorithms.Perform L1 rescaling before running any L1 algorithms.

Result is that each event is labeled according to which Result is that each event is labeled according to which Triggers were satisfied at L0.Triggers were satisfied at L0.

– The L1, L2, & L3 algorithms for each Trigger check to The L1, L2, & L3 algorithms for each Trigger check to ensure that the Trigger was satisfied at the previous ensure that the Trigger was satisfied at the previous level. If not, the event is ignored by that algorithm.level. If not, the event is ignored by that algorithm.

These two steps are all that is needed to ensure These two steps are all that is needed to ensure that no bias is introduced by running multiple that no bias is introduced by running multiple triggers.triggers.


Scalers and CountersScalers and Counters Some scaler information will be stored to the database. Some scaler information will be stored to the database.

The information will be organized by Trigger. The following The information will be organized by Trigger. The following will be available for each Trigger:will be available for each Trigger:– The number of events satisfying the physics of the L0 The number of events satisfying the physics of the L0

component without regard to the detector busycomponent without regard to the detector busy– The number of events seen and rejected by the L1, L2 and L3 The number of events seen and rejected by the L1, L2 and L3

componentscomponents– The prescales for each trigger at each levelThe prescales for each trigger at each level

These counters will be written every 2 minutes or so during These counters will be written every 2 minutes or so during the run. The contributions from different trigger levels will the run. The contributions from different trigger levels will be synchronized to ~1 second.be synchronized to ~1 second.

This is enough information to obtain absolute cross sections This is enough information to obtain absolute cross sections in units of (bunch crossings) in units of (bunch crossings) -1-1

**note: This is a VERY small part of the information available **note: This is a VERY small part of the information available in the scaler boards (5 boards * 2^24 counters.)in the scaler boards (5 boards * 2^24 counters.)


Offline Event LabelingOffline Event Labeling

In the data file each trigger is represented In the data file each trigger is represented by a bit in a 32-bit mask, the TriggerID. by a bit in a 32-bit mask, the TriggerID. The value of this bit is arbitrary.The value of this bit is arbitrary.

The database contains the key to translate The database contains the key to translate the TriggerId into a meaningful identifier.the TriggerId into a meaningful identifier.

Jerome has made a request for service Jerome has made a request for service work for someone to provide the interface work for someone to provide the interface that reads the database to make the that reads the database to make the scalers and the trigger descriptions easily scalers and the trigger descriptions easily accessible offline.accessible offline.


Evolution of Trigger Evolution of Trigger DefinitionsDefinitions

The trigger word has many disadvantages for use as the offline event The trigger word has many disadvantages for use as the offline event selection criteria:selection criteria:– A given word has different meanings in different configurations (vertexMinBias, A given word has different meanings in different configurations (vertexMinBias,

MinBiasVertex, etc...)MinBiasVertex, etc...)– It can only specify one trigger, even though the event can satisfy more than one It can only specify one trigger, even though the event can satisfy more than one

triggertrigger– It is insensitive to threshold changesIt is insensitive to threshold changes– It is insensitive to TCU bit definition changesIt is insensitive to TCU bit definition changes– It is insensitive to PS changesIt is insensitive to PS changes

The offline trigger identifier will replace the trigger word for event The offline trigger identifier will replace the trigger word for event selection.selection.

It will have one field that describes the trigger. This field will be fixed for It will have one field that describes the trigger. This field will be fixed for all time to the same value.all time to the same value.

It will also have separate version fields for:It will also have separate version fields for:– Trigger Definition (TCU Lookup tables & Tier 1 files are the same)Trigger Definition (TCU Lookup tables & Tier 1 files are the same)– Threshold Values (All thresholds must be the same)Threshold Values (All thresholds must be the same)– P.S. (The full set of prescales must be the same)P.S. (The full set of prescales must be the same)

These versions can be obtained automatically from the configuration files These versions can be obtained automatically from the configuration files each run and stored to a database. We will provide a tool to browse this each run and stored to a database. We will provide a tool to browse this database and check the documentation for each version. database and check the documentation for each version.

Documents

Trigger Accounting for 2002