9 Nuclear Emulsions
407
Table 9.1 Overall number of located neutrino interactions with the decay search procedure
applied
2008
2009
2010
2011
2012
Total
p.o.t. (10 19 )
1.7
3.5
4.1
4.8
3.9
18.0
0μ events
150
255
278
291
223
1197
1μ events (p μ <15 GeV/c)
543
1024
1001
1031
807
4406
Total events
693
1279
1279
1322
1030
5603
0
1 0
2 0
3 0
4 0
5 0
6 0
Visible energy (GeV)
0
1
2
3
4
5
6
events/5 GeV
τ
ν
bkg
data
Fig. 9.13 Visible energy distribution of the 10 tau neutrino candidates found in the final
sample [114]
candidate was reported in 2014 [109] while the discovery of ν τ appearance was
achieved in 2015 with the observation of a fifth tau neutrino candidate over an
expected background of 0.25 events [110]. The OPERA discovery of tau neutrino
appearance was explicitly mentioned in the Scientific Background of the 2015 Nobel
Prize in Physics.
The emulsion handling was completed in 2015 while the emulsion film scanning
was completed in 2016 when the detector was decommissioned. The final number of
events passing all the analysis chain up to the decay search are shown in Table 9.1.
Events are divided in two categories according to the presence (1μ) or absence (0μ)
of a muon in the final state and undergo different selections: a momentum cut of
15 GeV/c is applied to the muons in order to reduce the background.
Given the data-driven validation of the simulation in all corners of the parameter
space [103, 111, 112], the OPERA Collaboration decided to release the cuts and
exploit the kinematical features of the events with a likelihood approach: this
approach enlarges the selected sample, thus reducing the statistical uncertainty
for the estimate of the oscillation parameters. Ten tau neutrino candidates were
found with the new analysis strategy in the final sample. The distribution of the
visible energy for the 10 candidates is shown in Fig. 9.13 together with the expected
spectrum.
The number of expected tau neutrino events with looser cuts applied is reported
in Table 9.2, together with the number of observed ν τ candidates in each tau
407
Table 9.1 Overall number of located neutrino interactions with the decay search procedure
applied
2008
2009
2010
2011
2012
Total
p.o.t. (10 19 )
1.7
3.5
4.1
4.8
3.9
18.0
0μ events
150
255
278
291
223
1197
1μ events (p μ <15 GeV/c)
543
1024
1001
1031
807
4406
Total events
693
1279
1279
1322
1030
5603
0
1 0
2 0
3 0
4 0
5 0
6 0
Visible energy (GeV)
0
1
2
3
4
5
6
events/5 GeV
τ
ν
bkg
data
Fig. 9.13 Visible energy distribution of the 10 tau neutrino candidates found in the final
sample [114]
candidate was reported in 2014 [109] while the discovery of ν τ appearance was
achieved in 2015 with the observation of a fifth tau neutrino candidate over an
expected background of 0.25 events [110]. The OPERA discovery of tau neutrino
appearance was explicitly mentioned in the Scientific Background of the 2015 Nobel
Prize in Physics.
The emulsion handling was completed in 2015 while the emulsion film scanning
was completed in 2016 when the detector was decommissioned. The final number of
events passing all the analysis chain up to the decay search are shown in Table 9.1.
Events are divided in two categories according to the presence (1μ) or absence (0μ)
of a muon in the final state and undergo different selections: a momentum cut of
15 GeV/c is applied to the muons in order to reduce the background.
Given the data-driven validation of the simulation in all corners of the parameter
space [103, 111, 112], the OPERA Collaboration decided to release the cuts and
exploit the kinematical features of the events with a likelihood approach: this
approach enlarges the selected sample, thus reducing the statistical uncertainty
for the estimate of the oscillation parameters. Ten tau neutrino candidates were
found with the new analysis strategy in the final sample. The distribution of the
visible energy for the 10 candidates is shown in Fig. 9.13 together with the expected
spectrum.
The number of expected tau neutrino events with looser cuts applied is reported
in Table 9.2, together with the number of observed ν τ candidates in each tau