-1 -0.5 0 0.5 1
efficiency
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
FGD1 FGD2
signal in FGD1
fractional reconstructed
Figure 5.5: Efficiency as a function of the true muon direction, in terms of theθ angle respect to the neutrino direction, for both selections, in FGD1 (red) and in FGD2 (blue).
Statistical error bars are shown, but small. The fractional distribution of the reconstructed events in FGD1 is shown as well.
Fig. 5.6 shows the true muon (pµ,cosθ) phase space predicted by NEUT forνµ-CC
1809
interactions in FGD1 and in FGD2 fiducial volumes. High energy muons are more
1810
likely to be in the forward direction, where the detector efficiency is high. On the
1811
contrary, muons scattered at high and negative angles, where the detector efficiency
1812
is low, always have a relatively low momentum. This explain why the efficiency as
1813
a function of the true muon momentum decreases below 1 GeV, as it can be seen in
1814
Fig. 5.7. Considerations on the phase space are discussed in Section 7.3.
1815
The purity is defined as:
1816
purity = Nselected−Nbackground
(5.6)
true muon cosθ
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
true muon momentum [GeV/c]
0
Integral 4.052e+04 Integral 4.052e+04
0
Integral 4.052e+04
FGD1
true muon cosθ
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
true muon momentum [GeV/c]
0
Integral 3.868e+04
0
Integral 3.868e+04
FGD2
Figure 5.6: (pµ,cosθ) phase space of the true muons from νµ-CC interactions predicted by NEUT in FGD1 (left) and FGD2 (right)fiducial volumes.
true muon momentum [GeV/c]
0 0.5 1 1.5 2 2.5 3 3.5 4
Figure 5.7: Efficiency as a function of the true muon momentum, for both selections, in FGD1 (red) and FGD2 (blue). Statistical error bars are shown, but small. The fractional
whereNselected−Nbackground is the number of signal events among the selected ones.
1817
The purity predicted by NEUT after the last cut is 90.31 % for the selection in FGD1
1818
and 88.65 % for the selection in FGD2. The reconstructed momentum and direction
1819
distributions of the muon candidates are shown in Fig. 5.8 for both the FGD1 and
1820
the FGD2 selections, broken down by the predicted NEUT reactions. The sources of
1821
background are:
1822
1. out offiducial volume (main background): νµ-CC interactions happening outside
1823
thefiducial volume of FGD1 or FGD2 respectively;
1824
2. non νµ-CC interactions: these are neutral-current (NC), ¯νµ and νe interactions,
1825
where a π− (in most cases) is mis-identified as theµ− candidate (cf. Fig. 5.9).
1826
candidate muon reconstructed momentum [GeV]
0 0.2 0.4 0.6 0.8 1 1.2
16000 Integral 349475
CC 88.11 %
candidate muon reconstructed momentum [GeV]
0 0.2 0.4 0.6 0.8 1 1.2
16000 Integral 344814
CC 85.98 %
candidate muon reconstructed cosθ
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
candidate muon reconstructed cosθ
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Figure 5.8: Reconstructed momentum (top) and direction (bottom) distributions of the muon candidates for both the FGD1 (left) and the FGD2 (right) selections, broken down by the predicted NEUT reactions. “out FV” are the events occurred out of the fiducial volume. The percentages on the legend are the fractions of each component in the whole plotted distribution.
Fig. 5.9 shows again the reconstructed momentum and direction distributions but
1827
broken down by the true particles associated to track chosen as muon candidate. In a
1828
non-negligible fraction of events the chosen track is not associated to the true muons,
1829
but most of them are background events: this can be seen in Fig. 5.10 where it is shown
1830
the same distributions after removing the background events. The remaining∼2% of
1831
non-true muons in CC signal events is not considered background, nor in the T2K
1832
oscillation analyses neither in this analysis, hence it is considered as a reconstruction
1833
inefficiency (which might cause events being reconstructed in a wrong bin). Note that
1834
events where a pion is selected as muon candidate affect the secondary interaction pion
1835
systematics (cf. Section 6.2.3.1).
1836
candidate muon reconstructed momentum [GeV]
0 0.2 0.4 0.6 0.8 1 1.2
16000 Integral 349475
88.22 %
candidate muon reconstructed momentum [GeV]
0 0.2 0.4 0.6 0.8 1 1.2
16000 Integral 344814
87.93 % candidate muon reconstructed cos
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 candidate muon reconstructed cos
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Figure 5.9: Reconstructed momentum (top) and direction (bottom) distributions of the muon candidates for both the FGD1 (left) and the FGD2 (right) selections, broken down by the true particles associated to the muon candidate (as predicted by NEUT). The percent-ages on the legend are the fractions of each component in the whole plotted distribution.
Fig. 5.11 shows again the reconstructed momentum and direction distributions but
1837
broken down by the target nucleus elements where the true neutrino interaction
oc-1838
Integral 307933
candidate muon reconstructed momentum [GeV]
0 0.2 0.4 0.6 0.8 1 1.2
Integral 307933 Integral 307933 97.42 %
Integral 296455
candidate muon reconstructed momentum [GeV]
0 0.2 0.4 0.6 0.8 1 1.2
Integral 296455 Integral 296455 97.43 %
Integral 478646
θ candidate muon reconstructed cos
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Integral 478646 Integral 478646 97.19 %
Integral 454059
θ candidate muon reconstructed cos
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Integral 454059 Integral 454059 97.13 %
Figure 5.10: Reconstructed momentum (top) and direction (bottom) distributions of the muon candidates for both the FGD1 (left) and the FGD2 (right) selections, without the background events, broken down by the true particles associated to the muon candidate (as predicted by NEUT). The percentages on the legend are the fractions of each component in the whole plotted distribution.
curred. There are non-negligible contributions from heavy targets, but they are
actu-1839
ally background events occurred out of the fiducial volume (“out FV”), as it can be
1840
seen in Fig. 5.12, where it is shown the same distributions after removing the “out FV”
1841
background events. This allows assuming that any interaction model uncertainties on
1842
heavy targets is covered by the out offiducial volume systematics (Section 6.2.4.1).
1843
candidate muon reconstructed momentum [GeV]
0 0.2 0.4 0.6 0.8 1 1.2
16000 Integral 349475
Carbon 85.91 %
candidate muon reconstructed momentum [GeV]
0 0.2 0.4 0.6 0.8 1 1.2
16000 Integral 344814
Carbon 46.93 %
candidate muon reconstructed cosθ
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
candidate muon reconstructed cosθ
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Figure 5.11: Reconstructed momentum (top) and direction (bottom) distributions of the muon candidates for both the FGD1 (left) and the FGD2 (right) selections, broken down by the target nucleus elements where the true neutrino interaction occurred (as predicted by NEUT). The percentages on the legend are the fractions of each component in the whole plotted distribution.
Integral 307933
candidate muon reconstructed momentum [GeV]
0 0.2 0.4 0.6 0.8 1 1.2
Integral 307933 Integral 307933 Carbon 89.58 % Oxygen 4.63 % Hydrogen 2.74 % other 3.05 % FGD1
Integral 296455
candidate muon reconstructed momentum [GeV]
0 0.2 0.4 0.6 0.8 1 1.2
Integral 296455 Integral 296455 Carbon 48.18 % Oxygen 47.04 % Hydrogen 3.45 % other 1.34 % FGD2
Integral 478646
candidate muon reconstructed cosθ
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Integral 478646 Integral 478646 Carbon 89.24 %
Oxygen 4.61 % Hydrogen 3.19 % other 2.96 %
FGD1
Integral 454059
candidate muon reconstructed cosθ
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Integral 454059 Integral 454059 Carbon 47.98 %
Oxygen 46.73 % Hydrogen 3.99 % other 1.30 %
FGD2
Figure 5.12: Reconstructed momentum (top) and direction (bottom) distributions of the muon candidates for both the FGD1 (left) and the FGD2 (right) selections without the
“out FV” background events, broken down by the target nucleus elements where the true neutrino interaction occurred (as predicted by NEUT). The percentages on the legend are the fractions of each component in the whole plotted distribution.