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