Analysis Techniques & Status of the DONUT experiment

1. Analysis Techniques & Status of the DONUT experiment Niki Saoulidou, Fermilab N. 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 N. Saoulidou, Fermilab

3. -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 : N. Saoulidou, Fermilab

4. -The DONUT Collaboration - 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 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 N. Saoulidou, Fermilab

5. -How the experiment is done - KINK N. Saoulidou, Fermilab

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 Scan 5x5x15mm3volume Vertex prediction from FT Event Characterization with Spectrometer info. Calibrate plates Scan again 2.5x2.5x10mm3for decay search Look for kinks & tridents in 1ry tracks Special scans (momentum, electron ID) Vertex found from digital info τSample Analysis for τ, charm charmSample N. Saoulidou, Fermilab

7. -Goals of the ANN analysis involving spectrometer information – • Use Artificial Neural Network techniques to identify and classify Neutrino Interactions into: • CC νμνeντ • NC • Requirement: MC should be capable of describing very well the neutrino data. N. Saoulidou, Fermilab

8. -Output of ANN2 (NC - ve CC )- cut NC ve CC • 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 efficiency68 % -purity 80 % ve CC efficiency 86 % -purity 76 % N. Saoulidou, Fermilab

9. -Expected number of neutrino interactions per run period & per emulsion module- Good agreement (within ~ 1 σ) Expected number 964 ± 235 Observed number 909 Difference 55 ± 235 Ratios (%) νμCC νeCC ντCC 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 νμCC νeCC ντCC NC expected 312 ± 92 350 ±79 ------ 303 ± 75 observed 312 ± 15 327 ±15 ------ 270 ± 15 Difference 0 ± 93 23 ± 80 33 ± 76 N. Saoulidou, Fermilab

10. -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

11. - Signal & Background - • Charm background • Interactions (scattering) • Tau signal D+ Lepton missed N. Saoulidou, Fermilab

12. -ANN vτCC - hadron scattering results on the 37 recognized kinks- MC Data Δp/p=30% EVENTS THAT EXCEED THE 0.5 CUT IN THE ANN OUTPUT FUNCTION RUN EVENT PdθdPT LdθpΔφ 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 N. Saoulidou, Fermilab

13. -DONUT Status- PHASE 1 PRESENT Neutrino Interactions 698 (898) 909 (1026) Emulsion Digitized Info 499 650 Located 262432 Decay Search 203432 Tau Events 4 6* N. Saoulidou, Fermilab

14. -Tau neutrino CC and Charm interactions- backup ντCC 1-prong observed : Ns=3.00 individual event probabilities (ντCC 1-prong observed : Ns= 4.00 Bkg= 0.34PT 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 ) ντCC 1-prong expected : 5.3 ± 1.6 ντCCcandidates observed : 6 ντCC 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 N. Saoulidou, Fermilab

15. N. Saoulidou, Fermilab

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. N. Saoulidou, Fermilab

17. N. Saoulidou, Fermilab

18. -Example of a neutrino event- ? N. Saoulidou, Fermilab

19. - Characteristics of Selected ANN events- backup PT of MC kinks for hadron scattering events (red) and tau decays (black) PT of experimental kinks N. Saoulidou, Fermilab

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 Δφ Daughter angle Decay Length N. Saoulidou, Fermilab