The DONUT Experiment: Fermilab E872

The DONUT Experiment: Fermilab E872 DONUT Collaboration E.Maher

 - nt  nt + ne + e q´  nt + nm + m q  nt + ho+ h Observation ofnt CC interactions E872 has analyzed 203 neutrino interactions recorded in nuclear emulsion targets. Four events are due to nt interactions. The expected background is .3 events. The probability that all 4 events are from background sources is  410 -4

t t nt nt Ds nt Production and detection of nt BEAM DUMP SHIELDING EMULSION STACK SPECTROMETER 800GeV protons Ct=.87mm nt + N  t + X   nt + 1 charge • ~1017 protons/ ntint. • flux: ~107 @ 35cm • ~1012 @ 2m

Spectrometer Muon ID Calorimeter 5.5m Drift Chambers 3.25m Magnet (225Mev) Veto Wall (Double scintillator) • trigger • muon ID • electron ID • momentum calibration • vertex location Emulsion and Sci-Fi Planes n

Fe Fe Emulsion Target BULK ECC800 ECC200 • AgBr suspended in a gel • 100m coated on plastic base • Fuji ET7C • 29±2 grains per 100mm for m.i. Track • Total target mass 260kg Resolution of segments Spatial: .3 mm Angular: 3mrad/100mm Segment detection efficiency : > 98% 95% emulsion ~ 5% emulsion

Emulsion Data Analysis

901 predicted vertices from spectrometer (consistent w/ 3.6x1017 POT) 699 within fiducial volume 511 digitized emulsion data exists 264 vertex found Data set 6.6106 triggers + 28 Phase 2 as of Feb 2001 + 95 203systematic decay search Phase 1 data set of 203 n interactions: ExpectFind nm ~ne 71 nm cc 61 ne cc nm(m-)/nm(m+) = 1.847 / 26 = 1.7

nt interaction selection  track Single charge decay accounts for 86%of all t decay modes. These result in a kink in the reconstructed emulsion track Only events with no m or e identified from n interaction vertex t Cuts: Parent track  1 visible segment Q kink > 10 mrad(110 mr) Decay length < 5 mm (2.3 mm) Transverse Momentum > 250 MeV IP of daughter to interaction vertex <.5 mm Total acceptance = .50 Expected number of nt (data set of 203) 41

NC, e or mlost h NC, e or m lost Background sources I Random: association of background track with a primary track 7.9 m of primary tracks scanned Using LEPTO/GEANT simulation passing nt cuts.10 kinks /203evts. • Density of background tracks rstarting • Stopping primary tracks N primary • Probability of match with SFT PSFTmatch • N rndn = rstarting. p r2match N primary. PSFT match • rmatch = 5 m (5s) • passing nt cut .017kinks/203evts. Hadronic interactions

e orm: not recognized charm nm ,e cc Background sources II : charm Totalnm & ne 155 ±18 cc in sample 0.077±0.007 12.1±1.8 Charm production 0.47±0.05 5.72±1.0 Charged 6.46 ±1.1 Neutral 0.38±0.02 2.2 ±.4 single charge decay .18 ± .03 e ormnot recognized & pass cuts Displaced vtx: example of neutral charm

Event 3024_30175 •  nt+ e + ne Decay occurs in plastic base • Event 3263_ •  nt + h Decay occurs in steel plate

Event 3039_01910 •  nt + h Decay occurs in plastic base • Event 3333_17665 •  nt + e + ne Decay occurs in plastic base

 prim prim  PT Ld n   n  Individual event parameters Parameters used to characterize event: Distributions of event parameters: nt interactions prim production angle of  Lddecay length PT transverse momentum of the decay  event angular symmetry

probability density function nt vs. background hypotheses The probability of an event with measured parameters belonging to a given hypothesis is determined using multi-dimensional PDF. The PDF’s are generated with simulated events of each hypothesis. Ai prior probability of hypothesis i = nt, hadron interaction or charm Probability all events are background = 8.0  10-5

Status Results of “Long” decay search : (Physics Letters B ) Measurement of nt magnetic moment : (Physics Letters B ) Upper limitnt4.27 10-7B PHASE 2 of analysis (in progress) Data set of located n interactions increasing +95 Feb. 2001 Goal of 400 total by summer 2001 “Short” decay search to be completed : expect ~ 1 nt interaction Relax cuts for decay search

The DONUT Experiment: Fermilab E872