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Analysis of Compton Event Yields and Background Efficiency: PrimEx Collaboration Insights

This document outlines recent findings from the PrimEx Collaboration meeting held on June 23, 2006, regarding Compton event analysis. It covers changes in pair-contamination, the most recent yield figures, and significant data decisions. Key areas of focus include geometric cuts, trigger bit multiplicity, and photon selection methods. The analysis highlights that current yields are approximately 10% below expectations, emphasizing the need for a deeper understanding of background effects and data selection efficiencies. The group calls for further Monte Carlo simulations to elucidate these issues.

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Analysis of Compton Event Yields and Background Efficiency: PrimEx Collaboration Insights

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  1. Status of Compton Analysis Yelena Prok PrimEx Collaboration Meeting June 23, 2006

  2. Outline • Recent changes • Pair-contamination • Most recent yields • What needs to be done

  3. (Trigger) Bit 9! Bit 2 makes more sense Multiplicity of bit 9 Multiplicity of bit 2

  4. (Trigger) Bit 9! Bit 2 Hycaltime(bit9)-TAGM.t Hycaltime(bit2)-TAGM.t Bit 2 Bit 9 No major changes in time distribution

  5. Event Selection • Run 5150 • To select a photon: choose the one closest in time to HYCAL (10 ns window) • To select a pair of clusters: choose the one with (E1+E2) closest to Ecompton where • Ecompton=[me*sin]/[2*sin2(/2)*tanel]-me

  6. Effect of geometric cuts 100K, No cuts 25.3K, emin cut 19.5K emin+hole cut 13.3K, emin, hole, vert cut

  7. Acceptance by TCountergeometry

  8. Counting Events Geom cut, +elasticity cut (20 %) Z Ebeam- Ecomp N N N  N GeV cm Be target, TCounter 2

  9. Normalized Yield per electron Acceptance corrected normalized yield NCNY: NCNY=N/L/A N=counts under the first gaussian function L=*th*NA* th=target thickness =target density NA=Avogadro’s Number =atomic mass A=geometric acceptance obtained from simulation Detection efficiency and reconstruction efficiency are not known and set to 1

  10. Yield vs Run TCounter 1 TCounter 2 Consistent except for run 4972

  11. Compare 2 regions 1 2

  12. Region 1 vs Region 2 both charged one charged ptx mix pty GeV GeV

  13. Region 1 vs Region 2 (cont) Z separation cm cm

  14. Region 1 vs Region 2 (cont) deg deg mostly pairs what are these? GeV GeV

  15. Summary • Current yields are on average ~10% below expectation • Need to understand the background, efficiency and effect of cuts on the data ! • Need full MC (trying to make sense out of “primsim”, not very successfully so far) Compton event in “primsim” J’ai besoin d’aide…

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