1. NS=1 event Satoru Takahashi DONuT collaboration meeting @ Nagano 2006/10/11

2. Review of NETSCAN back Basic study for NETSCAN back by Nonaka For 76 predictions, 718 tracks have been followed up in ECC 76 predictions no stop track : 6 single stop track : 70 multi stop tracks : 0

3. Miss detection probability of BG track by NSB ε : detection efficiency of signal track / prediction n BG : number of miss detection BG tracks / prediction η : mean of n BG P(n BG ) : probability in the “n BG ” case / prediction n : stop track numbers / prediction N (n) : prediction numbers in the “n” stop tracks case P (0) =e -η, P (1) =ηe -η, P (>=2) =1-{P(0)+P(1)} N (0) = (1-ε)P (0) ×76 = 6 N (1) = {εP (0) +(1-ε)P (1) }×76 = 70 N (>=2) = (εP (1) +P (>=2) )×76 = 0 ① ② ③ from eq. ①, ②, ③ ε=0.92, η= 0 η < 0.03 (=2.3/76) (90%CL) Even if stop is judged as location, miss detection probability of BG track is low.

4. NS=1 event We have located 68 NS=1 events I checked the quality of location for NS=1 events.

5. emulsion BG tracks high momentum BG tracks low momentum BG tracks ν station4 ν x checked correlation with emulsion BG tracks

6. high momentum BG region 1916 10 11 NS=1 : 68events, 68tracks θ<0.1 : 56tracks typical BG tracks θu[rad] 0.10-0.1 θu[rad] 0.10-0.1 θv[rad] 0.1 0 -0.1 θv[rad] 0.1 0 -0.1 29+-5.4 27+-5.2 no significant difference

7. low momentum BG region 26 2 2 NS=1 : 68events, 68tracks θ>0.1 : 12tracks typical BG tracks θu[rad] 0.40-0.4 θv[rad] 0.4 0 -0.4 θu[rad] 0.40-0.4 θv[rad] 0.4 0 -0.4 2+-0.8 6+-2.4 a little a lot, but not so significant difference ( =4+-2.5, 6% of NS=1 events)

8. short summary At high momentum BG region (θ<0.1), no significant difference At low momentum BG region (θ>0.1), a little a lot, but not so significant difference –( =4+-2.5, 6% of NS=1 events) NS=1 events are not correlated with emulsion BG tracks.

9. Momentum match between spec. and MCS 2157 / 42868 / 68 all [track#] / [event#] 21930 P spec. < 80GeV/c & P MCS < P MCS limit [track#] 31741 having spec.momentum & MCS momentum [track#] 202559 not electron (electron identified by emulsion and counter) [track#] >=31 NS Is “located event” “triggered event”? checked by momentum match analysis

10. momentum match 70+-20% (21/30)52+-6.0% (114/219) NS=1 NS>=3 Spec. [GeV/c] MCS [GeV/c] Spec. [GeV/c] MCS [GeV/c] random combination case : 22.8+-3.6% For NS>=3 events, there are some tracks with significant difference between spec. and MCS. Park is analyzing the quality of momentum for such tracks. However match ratio of NS=1 event is significantly high for match ratio of random combination case and same as NS>=3. Definition of match : consistent within error bar (coverage of error bar : 80%)

11. summary of NS=1 event NS=1 events are not miss detection of emulsion BG tracks. –Miss detection probability of BG tracks is low. –not correlated emulsion BG tracks Triggered event are located. –Match ratio is significantly high for random combination case. –Match ratio is same as NS>=3. We may add NS=1 events to DONUT located events.