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2 Decay of 150 Nd, Preliminary Results (PhaseI data)

2 Decay of 150 Nd, Preliminary Results (PhaseI data). Nasim Fatemi-Ghomi. Introduction. Background study of 150 Nd 2 A study of the 207 Bi and 214 Bi background in the e -channel. A study of the 210 Bi, 207 Tl+ 211 Pb and 234m Pa background in the e-channel.

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2 Decay of 150 Nd, Preliminary Results (PhaseI data)

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  1. 2 Decay of 150Nd, Preliminary Results (PhaseI data) Nasim Fatemi-Ghomi

  2. Introduction • Background study of 150Nd2 • A study of the 207Bi and 214Bi background in the e-channel. • A study of the 210Bi, 207Tl+211Pb and 234mPa background in the • e-channel. • Cross check external background with Cu foil. • Extraction of half-life of 150Nd2 Data Selection • Good betbeta runs between 2019-3395 (phase I). • Data taking time =2.8836 x 107s = 0.91 yrs. • Events should come from Nd2O3. The foil has 57g mass (37gr pure 150Nd).

  3. External Background & Background on the Surface of the Wires and Foils. Internal Background Found by V.Vasilev checked with Cu foil Slide 9

  4. 207Bi and 214Bi Background Studies • Pre-Selection Cuts for e-channel: • One negatively charged track associated with an isolated PMT (E(e)> 0.2MeV). • Only one  cluster with E()> 0.2MeV. No other  with E()> 0.15MeV. • Internal TOF hypothesis for e events > 5% & external hypothesis < 1%. • Tracks must have one hit in one of the two first layers of GG. Cos(e) < 0.9

  5. Activity of 207Bi In addtion to the pre-selection criteria described there should not be any single or group delayed hit(s) in the tracker. Fit 207Bi with the data minus background

  6. Look at the energy region 0.7 MeV< Ee <1.1 MeV and 0.25 MeV< E <0.6 MeV where 207Bi dominated over all other backgrounds. A207Bi=13.4 ± 0.3 mBq ~ 235 ± 5 mBq/kg

  7. Activity of 214Bi Events should accompany with an alpha particle (delayed or single hits.) A214Bi = 0.87  0.17 mBq ~ 15.26  2.98 mBq/kg

  8. 1e Channel • Selection cuts: • One track with negative charge associated with isolated PMT. • Track has to have a reconstructed vertex. • E(e) > 0.5 MeV. • Track has to have a hit in one of the first two layers of GG.

  9. External background The external background activity found by V.Vasiliev is checked with looking at the energy distribution of the energy of e-  events coming from the Cu foil. Data = 35524±188, Total Background=34251± 382 Data-Background= 1273 ± 425 -> has to be added to the systematic uncertainty.

  10. 150Nd Half-life Pre-selection for 150Nd to 2 events: • Two negatively charged tracks associated with isolated PMTs and • E1 ,E2 > 0.2 MeV. • Both electrons originate from a common vertex • with |∆r| < 2 cm & |∆z| < 4 cm. • Internal TOF hypothesis > 4% & external TOF hypothesis < 1%. • Track starts from layers 1 & 2 of GG. • No delayed alpha decay with refiring time > 70 s. • No single or group delayed hit(s).

  11. Results Number of data events: 1011 Number of total background: 315 Efficiency =133643/2000000 6.68% T12= (9.04 -0.57+0.63(stat) +- 0.40 (Act)+- 0.78 (syst)) x 1018 y

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