JEF meeting Jan 26, 2015

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Meeting time and location= 13:30 EST (JLab time) CC F326-327

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  1. Task list updates?
  2. Update on pi+pi- studies (Dave M.)


Attendees: Liping Gan, Dave Mack, Sascha Somov, Justin Stevens, Simon Taylor

  • Dave Mack presented comparisons between a toy MC for the reaction γ p → p ρ, ρ→π+π-; (and continuum π+π- events) and histograms created by Justin Stevens from the Fall Commissioning Run data
    • The recoil proton was not reconstructed. A proton band is seen in missing mass: Dave's toy MC mimics the behaviour of the data well for signal events where the correct photon in the tagger is measured.
    • Inclusion of continuum π+π- accounts for the grass above and below the rho peak for missing mass consistent with a proton.
    • The data is dominated by a large bump at low two-pi mass and high missing mass
      • ρ events from photons below the range of the tagger can only account for some of this enhancement
      • Dave can account for most of the enhancement by adding continuum 2-pion events; JS pointed out that multi-prong events (5 pions, etc) could account for some of this as well.
    • Cutting on the energy of the 2-pion pair cleans up the data considerably.