Post on 25-Jan-2016
description
Cal Cluster ID(a.k.a. Eflow)
Gary R. Bower, SLAC
Santa 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.
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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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
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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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?
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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ID result:gamma piminus K0L fragment
Input:
gamma
piminus
KOL
fragment
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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Multiple ID rates
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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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
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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Fragmentation problem?input piminus
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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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.
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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Isolation of gammas
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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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
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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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.
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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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
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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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
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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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
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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Superb gamma location resolution
Resolve gamma direction to ~1/6 cell size using center of energy of hits
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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Separating gammas
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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Separating piminuses
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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Separating K0Ls
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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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.
June 28, 2002 G.R.Bower - Santa Cruz LCD Workshop
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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.