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Preliminary Study of 214 Bi Background in Mo foils. Leo Jenner, UCL. In Brief…. Analysis developed to identify 214 Bi events from foils Apply to MC, extract efficiency, apply to data Look for 214 Po decay T 1/2 spectrum as cross-check Rather higher rate than expected…. - PowerPoint PPT Presentation
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11 Mar 2004 Nemo Collaboration Meeting 1
Preliminary Study of Preliminary Study of 214214Bi Bi Background in Mo foilsBackground in Mo foils
Leo Jenner, UCL
11 Mar 2004 Nemo Collaboration Meeting 2
In Brief…
• Analysis developed to identify 214Bi events from foils
• Apply to MC, extract efficiency, apply to data
• Look for 214Po decay T1/2 spectrum as cross-check
• Rather higher rate than expected…
11 Mar 2004 Nemo Collaboration Meeting 3
Principle decay: e- with delayed Nemo 5.5: 150,000 MC foil events generated Compare to 1,400,000 data events ( Apr 2003, Runs 2010-2019 = 107 hours )
11 Mar 2004 Nemo Collaboration Meeting 4
MC :1 track , >1 delayed hits
High energy tail…(reconstruction?)
11 Mar 2004 Nemo Collaboration Meeting 5
Monte Carlo
11 Mar 2004 Nemo Collaboration Meeting 6
Monte Carlo
11 Mar 2004 Nemo Collaboration Meeting 7
List of Cuts
• 1 track only• 1 scintillator hit only (associated to track)• 1st layer of geigers hit (fast)• 4+ delayed geiger hits, >60 sec• Mo foil sectors• Track and delayed geiger start in same sector
and IO• Prob circle, line fit > 0.1
• Qtrack < 0
• 2.08 sec < fast hits < 3.9 sec
11 Mar 2004 Nemo Collaboration Meeting 8
MC: Most fast hits appear in 2.08 – 3.9 sec window
11 Mar 2004 Nemo Collaboration Meeting 9
300 secs
140 secs
Data: humpy?
11 Mar 2004 Nemo Collaboration Meeting 10
All cuts
MC: 498/150,000 remain
Efficiency : 0.332%
Data: 2106 events
11 Mar 2004 Nemo Collaboration Meeting 11
All cuts
MC: 498/150,000 remain
Efficiency : 0.332%
Data: 2106 events
34,364 Bq/kg !!!
11 Mar 2004 Nemo Collaboration Meeting 12
p2 offset in data corresponds to constant noise level? (20%)
After noise removal…
11 Mar 2004 Nemo Collaboration Meeting 13
Summary…
• Far too many events remain after cuts…
• Noise (geigers?), sources in detector?
• High Energy tail of MC distribution?
• 2int / 2
ext
• Larger MC sample, gas, wires• Nemos 6.0