N. Saoulidou, Fermilab

Analysis Techniques & Status of the DONUT experiment

Niki Saoulidou, Fermilab

N. Saoulidou, Fermilab

-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

N. Saoulidou, Fermilab

-Direct Observation of the vτ-

• Weak Isospin Lepton Doublets:

• The vτ 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 :

e

ve

v

v

XNv

N. Saoulidou, Fermilab

-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

N. Saoulidou, Fermilab

-How the experiment is done -

KINK

N. Saoulidou, Fermilab

-Analysis Flow-

Calibrate plates

Vertex prediction from

FT

Scan 5x5x15mm3

volume

Vertex found from digital

info

Scan again 2.5x2.5x10mm3

for decay search

Look for kinks & tridents

in 1ry tracks

Special scans

(momentum, electron

ID)

Analysis for Analysis for ττ, charm, charm

τ Sample

charm

Sample

Reconstruct raw data

Software filter for

“interesting events”

ANN & visual scanning for “neutrino interactions”

Event Characterization

with Spectrometer info.

4.0 x 106 4.0 x 104 1000

N. Saoulidou, Fermilab

-Goals of the ANN analysis involving spectrometer information –

• Use Artificial Neural Network techniques to identify and classify Neutrino Interactions into:

• CC νμ νe ντ

• NC

• Requirement: MC should be capable of describing very well the neutrino data.

N. Saoulidou, Fermilab

-Output of ANN2 (NC - ve CC )-

NCve

CC

cut

• This network shows a quite good behavior and by choosing a cut @ 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 %

N. Saoulidou, Fermilab

-Expected number of neutrino interactions per run period & per emulsion module-

int.v

exp. PPOTPOTN

N

Expected number 964 ± 235

Observed number 909

Difference 55 ± 235

Ratios (%) νμ CC νe CC ντ CC NC

expected 32.3±2.4 36.3±3.9 ------ 31.4±2.0

observed 34.3±1.6 36.0±1.6 ------ 29.7±1.5

Difference 2.0 ±2.9 0.3 ±4.0 1.7 ±2.5

Numbers νμ CC νe CC ντ CC NC

expected 312 ± 92 350 ±79 ------ 303 ± 75

observed 312 ± 15 327 ±15 ------ 270 ± 15

Difference 0 ± 93 23 ± 80 33 ± 76

Good agreement (within ~ 1 σ)

N. Saoulidou, Fermilab

-Decay Search-

1. Long Decays• parent measured• kink resolved• τ no 1ry lepton• ~75%

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

N. Saoulidou, Fermilab

- Signal & Background -

• Charm background

• Interactions (scattering)

• Tau signal

D+

Lepton missed

N. Saoulidou, Fermilab

-ANN vτ CC - hadron scattering results

on the 37 recognized kinks-

EVENTS THAT EXCEED THE 0.5 CUT IN THE ANN OUTPUT FUNCTION

RUN EVENT Pd θd PT Ld θp Δφ 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 1.0003333 17665 21.400 0.0130 0.278 564.6 0.0154 2.806 1.000

Data

MCΔp/p=30%

N. Saoulidou, Fermilab

-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*

N. Saoulidou, Fermilab

ντ CC 1-prong observed : Ns=3.00 individual event probabilities

(ντ CC 1-prong observed : Ns= 4.00 Bkg= 0.34 PT cut) K. Kodama et al., Phys.Lett.B504:218-224,2001

R. Schwienhorst et al., Phys.Lett.B513:23-29,2001

Poisson Probability of the Background fluctuating to the Signal Level :

2.6 x 10-8 ( 4 x 10-4 )

ντ CC 1-prong expected : 5.3 ± 1.6

ντ CC candidates observed : 6

ντ 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

-Tau neutrino CC and Charm interactions- backup

N. Saoulidou, Fermilab

N. Saoulidou, Fermilab

-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.

N. Saoulidou, Fermilab

N. Saoulidou, Fermilab

-Example of a neutrino event- ?

N. Saoulidou, Fermilab

- Characteristics of Selected ANN events- backup

PT of experimental kinks

PT of MC kinks for hadron scattering events (red) and tau decays (black)

N. Saoulidou, Fermilab

- Characteristics of Selected ANN events cont.- backup

MC, Hadron scattering: Black MC, Tau decays: Yellow Data, Selected candidates : Red

Decay Length

Daughter momentum

Daughter PT

Parent angle

Daughter angle

Δφ