Melanie Day

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CLAS Data Analysis

• Melanie Day
• University of Rochester
• 3/25/08

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Introduction Goals

• CLAS is a nuclear target experiment
• Using eg2 data, C D2 targets
• Pion ID in two steps, RECSIS and Sieve
• Want to understand Pion production
• Monte Carlo calibration
• Angle, momentum, background, difference between
  heavier and lighter targets
• The Plan
• Look for missing pion events in missing mass
• Analyze information from current pion ID
• Do radiative corrections with simulation
• See if we can do pi0 as well as p/-

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Missing Pions?

• Missing mass is the magnitude of the four
  momentum that is unaccounted for by IDed
  particles
• Mm (elecinmom-elecoutmom)protmom-idedpartmom
• Missing mass could be additional particles, or
  poor ID on existing particles...
• First use data at elastic peak to check
• Find two pion threshold
• Find missing mass for one and two pion events

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W at Elastic Peak
Elastic Peak
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Elastic Peak Missing Mass
Mostly zero
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W threshold for Two Pion Events
Doesnt start until 1.4
Starts around 1.2
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One Pion Missing Mass With and Without Cut
Significantly less mm at high W with cut
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Missing Mass at High and Low Q2 Without Cut
Higher Avg. mm for low Q2
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Analyzing Pion Data With Existing Cuts
Much lower angle at higher mom.

• Little change with Q2 except no pi at high Q2
• These are pi particles.
• Pi- particles angle different because of magnet

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Conclusion

• Missing mass histograms seem to indicate some
  pions not being IDed
• Need to do radiative corrections
• Hyup Woo working on Tree structure to make
  histogramming easier

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The End
(Penguin Pie)