Analysis Techniques

1
Analysis Techniques Status of the DONUT
experiment
Niki Saoulidou, Fermilab
2
-Outline-

• Introduction
• Physics Motivation
• DONUT Experiment (Brief Review)
• Spectrometer Analysis
• Neutrino Event Selection (Artificial Neural
  Networks)
• Neutrino event Characterization (ANN)
• Emulsion Analysis
• Neutrino Event Location
• Decay Search
• Signal from Background Separation (ANN)
• Conclusions

3
-Direct Observation of the vt-

• Weak Isospin Lepton Doublets
• The vt was not directly observed, the way the
  other two neutrinos have, through its CC
  interactions although there was plenty of
  indirect evidence that the tau lepton has a
  neutral, spin 1/2 weak isospin partner.
• E872 Experiment Direct Observation of the
  NUTau

4
-The DONUT Collaboration -

• Aichi Univ. Of Education
• K. Kodama, N. Ushida
• Athens University
• C. Andreopoulos, N. Saoulidou. G. Tzanakos
• California/Davis University
• P. Yager
• Fermilab
• B. Baller, D. Boehnlein, W. Freeman,
• B. Lundberg, J. Morfin, R. Rameika
• Gyeongsang University
• J. S. Song, I. G. Park, S. H. Chung
• Kansas State University
• P. Berghaus, M. Kubanstev, N. W. Reay,
• R. Sidwell, N. Stanton, S. Yoshida

Kobe University
S. Aoki, T. Hara
Kon-kuk University
J.T. Rhee
Minnesota
University D. Ciampa, C. Erickson,
K. Heller, R. Rusack R. Schwienhorst, J.
Sielaff, J. Trammell, J. Wilcox
Nagoya University N. Hashizume, K.
Hoshino, H. Iinuma, K. Ito, M. Kobayashi, M.
Miyanishi, M. Komatsu, M. Nakamura, K. Nakajima,
T. Nakano, K.Niwa, N. Nonaka, K. Okada, T.
Yamamori Pittsburgh University T. Akdogan, V.
Paolone Tufts University T. Kafka,
W. Oliver, J. Schneps, T. Patzak
5
-How the experiment is done -
KINK
6
-Analysis Flow-
4.0 x 104
1000
4.0 x 106
Software filter for interesting events
ANN visual scanning for neutrino
interactions
Reconstruct raw data
Vertex prediction from FT
Scan 5x5x15mm3 volume
Calibrate plates
Event Characterization with Spectrometer info.
Scan again 2.5x2.5x10mm3 for decay search
Look for kinks tridents in 1ry tracks
Special scans (momentum, electron ID)
Vertex found from digital info
t Sample
Analysis for t, charm
charm Sample
7
-Goals of the ANN analysis involving spectrometer
information

• Use Artificial Neural Network techniques to
  identify and classify Neutrino Interactions into
  
• CC ?µ ?e ?t
• NC
• Requirement MC should be capable of describing
  very well the neutrino data.

8
-Output of ANN2 (NC - ve CC )-
cut
NC
ve CC

• This network shows a quite good behavior and by
  choosing a cut _at_ 0.5 we select signal (NC ) and
  at the same time background events (ve CC) with
  
• NC
  efficiency 68 - purity 80
• ve CC efficiency 86 -
  purity 76

9
-Expected number of neutrino interactions per
run period per emulsion module-
Good agreement (within 1 s)
Expected number 964 235 Observed number
909 Difference 55 235
Ratios () ?µ CC ?e CC
?t CC NC expected 32.32.4
36.33.9 ------ 31.42.0 observed
34.31.6 36.01.6 ------
29.71.5 Difference 2.0 2.9 0.3
4.0 1.7 2.5 Numbers
?µ CC ?e CC ?t CC NC
expected 312 92 350 79 ------
303 75 observed 312 15 327
15 ------ 270 15 Difference
0 93 23 80
33 76
10
-Decay Search-

• 1. Long Decays
• parent measured
• kink resolved
• t ? no 1ry lepton
• 75

• 2. Short Decays
• IP wrt 1ry vertex
• only daughter meas.
• daughter seen in spect.
• 25

11
- Signal Background -

• Charm background
• Interactions (scattering)
• Tau signal

D
Lepton missed
12
-ANN vt CC - hadron scattering results on the 37
recognized kinks-
MC
Data
?p/p30

• EVENTS THAT EXCEED THE 0.5 CUT IN THE ANN OUTPUT
  FUNCTION
• RUN EVENT Pd ?d PT Ld
  ?p ?f Probabilities
• 3263 25102 1.900 0.1300 0.247 1890.1 0.1772
  0.176 0.136
• 3024 30175 2.900 0.0936 0.271 4504.8 0.0279
  1.027 0.971
• 3039 1910 4.600 0.0895 0.412 276.5 0.0653
  2.684 1.000
• 3333 17665 21.400 0.0130 0.278 564.6 0.0154
  2.806 1.000

13
-DONUT Status-
PHASE 1
PRESENT Neutrino Interactions 698
(898) 909 (1026) Emulsion Digitized Info
499 650 Located
262
432 Decay Search 203
432 Tau Events
4 6

14
-Tau neutrino CC and Charm interactions- backup

• ?t CC 1-prong observed Ns3.00 individual
  event probabilities
• (?t CC 1-prong observed Ns 4.00 Bkg 0.34
  PT cut)
• 
  K. Kodama et al., Phys.Lett.B504218-224,2001
• R. Schwienhorst et al.,
  Phys.Lett.B51323-29,2001
• Poisson Probability of the Background fluctuating
  to the Signal Level
• 2.6 x 10-8 ( 4 x 10-4 )
• ?t CC 1-prong expected 5.3 1.6
• ?t CC candidates observed 6
• ?t CC expected 6.3 1.8
• Total Charm events observed 8
• Charm events expected 6.9 1.8
• Charged Charm events observed 4
• Charged Charm events expected 3.0 1.2
• Charged Charm 1-prong events observed 3
• Charged Charm 1-prong events expected 1.3
  0.5

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16
-Conclusions-

• ANN techniques have been successfully used in
• the following parts of the analysis
• - Neutrino event selection
• - Neutrino event characterization
• - Signal selection and Background estimation
• The ANN analysis is consistent with expectations.
• The second Phase of the analysis is continued
  and expected to finish soon.

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18
-Example of a neutrino event- ?
19
- Characteristics of Selected ANN events- backup
PT of MC kinks for hadron scattering events (red)
and tau decays (black)
PT of experimental kinks
20
- Characteristics of Selected ANN events cont.-
backup
Parent angle
Daughter PT
Daughter momentum
MC, Hadron scattering Black MC, Tau decays
Yellow Data, Selected candidates Red
?f
Daughter angle
Decay Length