cal cluster id (a.k.a. eflow) gary r. bower, slac santa cruz lcd workshop june 28, 2002

Cal Cluster ID(a.k.a. Eflow)

Gary R. Bower, SLACSanta Cruz LCD Workshop

June 28, 2002

June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop

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Acknowledgement

• Ron Cassell has made many essential contributions to this project.


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Outline• This is a work in progress.• (Very preliminary) results first!

– Describe test data sets and testing methods.– Efficiencies and fake rates.

• Details (as time permits)– Approach to problem– Discriminator tools– Discriminator capabilities

• Summary• Next Steps


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Test procedure

• Three datasets of 1000 single particle events.– piminus, gamma, and K0L– 1-50 Gev momentum– In barrel, within 45o of perpendicular to beam

• Make contiguous hit clusters– Ignore clusters with energy < 0.5 GeV– Treat most energetic cluster as primary deposition– Treat second most energetic cluster as fragment.

• Test both primary and secondary cluster– Is it a gamma, piminus, K0L, and/or fragment?


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ID result:gamma piminus K0L fragment Input:

gamma

piminus

KOL

fragment


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Multiple ID rates


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Philosophy of Technique

• The Eflow problem: a common approach:– solve it with a clever cluster builder but still

need to identify shower origin.– Assumes showers fragment badly.– Assumes showers overlap each other.

• We take a different approach: – work with (simple) clusters of contiguous hits.– distinguish origins based on cluster properties


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Fragmentation problem?input piminus


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“Secret” to solving fragmentation problem

• Combine EM and Had clusters using contiguous hits cluster builder by Ron Cassell.

• Caveat: For the occasional neutral hadron there will be significant fragments but we have a promising technique to find and associate them.


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Isolation of gammas


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Gamma shower characteristics

• Compact• Standard cigar shape• Shower initiates in first few EM layers• Shower contained in EM (if deep enough)• Many hits/much energy in first few layers• Accurately point back to IP


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Piminus shower characteristics

• Diffuse in shape and energy spread.• Some fragmentation.• Min-I track begins in first layer.• Few hits/little energy until first interaction.


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KOL shower characteristics

• Diffuse in shape and energy• Some fragmentation• First hit layer may be very deep• Generally points back at IP


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Fragment shower characteristics

• Diffuse in shape and energy• First hit layer may be very deep• Generally do not point back at IP


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Measure cluster properties

• Form energy tensor– Energy (shape) eigenvalues– Energy axes– Center of Energy

• First and last layers with hits• Energy/# of hits in first N layers


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Superb gamma location resolutionResolve gamma direction to ~1/6 cell size using

center of energy of hits


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Separating gammas


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Separating piminuses


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Separating K0Ls


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Summary

• Can find gammas with ~100% efficiency and ~few percent fakes.

• Can identify most pions without tracking• Can identify majority of K0Ls.• Have only sketched the power of the

method.


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Next steps (arbitrary order)• Many details to cross-check.• Reconstruct π0s (dE/E~5%, loc res ~same as π±.)• Associate neutral hadron fragments (improve dE/E).• Work out special cases, eg, charge exchange.• Combine clusters between barrel and endcap.• Use neural net to improve results.• Test on signal events.• Test on physics measurement.• Release tools.

cal cluster id (a.k.a. eflow) gary r. bower, slac santa cruz lcd workshop june 28, 2002

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