11 Mar 2004Nemo Collaboration Meeting1 Preliminary Study of 214 Bi Background in Mo foils Preliminary Study of 214 Bi Background in Mo foils Leo Jenner, UCL

11 Mar 2004Nemo Collaboration Meeting2 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…

11 Mar 2004Nemo Collaboration Meeting3  Principle decay: e - with delayed   Nemo 5.5: 150,000 MC foil events generated  Compare to 1,400,000 data events ( Apr 2003, Runs = 107 hours )

11 Mar 2004Nemo Collaboration Meeting4 MC :1 track, >1 delayed hits High energy tail…(reconstruction?)

11 Mar 2004Nemo Collaboration Meeting5 Monte Carlo

11 Mar 2004Nemo Collaboration Meeting6 Monte Carlo

11 Mar 2004Nemo Collaboration Meeting7 List of Cuts 1 track only 1 scintillator hit only (associated to track) 1 st 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 Q track <  sec < fast hits < 3.9  sec

11 Mar 2004Nemo Collaboration Meeting8 MC: Most fast hits appear in 2.08 – 3.9  sec window

11 Mar 2004Nemo Collaboration Meeting9 300  secs 140  secs Data: humpy?

11 Mar 2004Nemo Collaboration Meeting10 All cuts MC: 498/150,000 remain Efficiency : 0.332% Data: 2106 events

11 Mar 2004Nemo Collaboration Meeting11 All cuts MC: 498/150,000 remain Efficiency : 0.332% Data: 2106 events 34,364  Bq/kg !!!

11 Mar 2004Nemo Collaboration Meeting12 p2 offset in data corresponds to constant noise level? (20%) After noise removal…

11 Mar 2004Nemo Collaboration Meeting13 Summary… Far too many events remain after cuts… Noise (geigers?),  sources in detector? High Energy tail of MC distribution?  2 int /  2 ext Larger MC sample, gas, wires Nemos 6.0