The DONUT Experiment: Fermilab E872

Aichi Univ. of Education K. Kodama,N. Ushida

Kobe University S. Aoki,T. Hara

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

Univ. of California/Davis P. Yager

Fermilab B.Baller,D.Boehnlein,W.Freeman,B.Lundberg,J.Morfin,R. Rameika

Kansas State Univ. P. Berghaus,M. Kubanstev,N.W. Reay,

R. Sidwell,N. Stanton,S. Yoshida

Univ. of Minnesota D. Ciampa,C. Erickson,K. Heller,R. Rusack,R. Schwienhorst, J. Sielaff,J. Trammell,J. Wilcox

Univ. of Pittsburgh T. Akdogan,V. Paolone

Univ. of South Carolina A. Kulik,C. Rosenfeld

Tufts University T. Kafka,W. Oliver, J. Schneps,T. Patzak

Univ. of Athens C. Andreopoulos,G. Tzanakos,N. Saoulidou

Gyeongsang University J.S. Song,I.G. Park,S.H. Chung

Kon-kuk University J.T. Rhee

DONUT Collaboration

E.Maher

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

The probability that all 4 events are from background sources is 410 -4

e

e ho

h

-

q´q

E872 has analyzed 203 neutrino interactions recorded in nuclear emulsion targets.

Four events are due to interactions.

The expected background is .3 events.

Observation of CC interactions

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

Production and detection of

C=.87mm

800GeV protons

Ds

BEAM DUMP

SHIELDING EMULSIONSTACK

SPECTROMETER

~1017 protons/ int. flux: ~107 @ 35cm~1012 @ 2m

+ N + X + 1 charge

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

Spectrometer

Muon ID

Calorimeter

Drift Chambers

Magnet (225Mev)

Emulsion andSci-Fi Planes

• trigger• muon ID• electron ID• momentum calibration•vertex location

5.5m

3.25m

Veto Wall (Double scintillator)

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

Emulsion Target

• AgBr suspended in a gel • 100 coated on plastic

base • Fuji ET7C • 29±2 grains per 100m

for m.i. Track• Total target mass 260kg

95% emulsion ~ 5% emulsion

Resolution of segmentsSpatial: .3 mAngular: 3mrad/100m

Segment detection efficiency : > 98%

BULK ECC800 ECC200

Fe

Fe

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

Emulsion Data Analysis

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

203 systematic decay search

6.6106 triggers

Data set

Phase 1 data set of 203 interactions:

Expect Find

e 71 cc 61 e cc

901 predicted vertices from spectrometer (consistent w/ 3.6x1017 POT)

699 within fiducial volume

511 digitized emulsion data exists

264 vertex foundPhase 2 as of Feb 2001

+ 95

+ 28

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

interaction selection

Cuts: Parent track 1 visible segment kink > 10 mrad (mr)

Decay length < 5 mm (2.3 mm)Transverse Momentum > 250 MeV IP of daughter to interaction vertex < .5 mm Total

acceptance = .50

track

Expected number of (data set of 203) 41

Single charge decay accounts for 86% of all decay modes.These result in a kink in the reconstructed emulsion track

Only events with no or e identified from interaction vertex

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

Background sources I

7.9 m of primary tracks scanned

Using LEPTO/GEANT simulation

passing cuts .10 kinks /203evts.

NC, e or lost

Random: association of background track with a primary track

Hadronic interactions

NC, e or lost

h

Density of background tracks starting Stopping primary tracks N primary Probability of match with SFT PSFTmatch

N rndn = startingr2match N primary. PSFT match

rmatch = 5 (5) passing t cut .017kinks/203evts.

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

Background sources II : charm

Total & e 155 ±18

0.47±0.05 5.72±1.0 Charged 6.46 ±1.1 Neutral

0.38±0.02 2.2 ±.4 single chargedecay

cc in sample

0.077±0.007 12.1±1.8 Charm production

recognized

.18 ± .03 e or not

& pass cuts

e or : not recognized

e cccharm

Displaced vtx: example of neutral charm

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

Event 3024_30175

e +

Decay occurs in plastic base

Event 3263_

h

Decay occurs in steel plate

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

Event 3333_17665

e +

Decay occurs in plastic base

Event 3039_01910

h

Decay occurs in plastic base

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

Individual event parameters

prim production angle of L d decay lengthPT transverse

momentum of the decay

event angular symmetry

prim

L dPT

Parameters used to characterize event:

prim

Distributions of event parameters:

interactions

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

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.

)|(

)|(|

ipgA

pgApP

i

p

i = , hadron interaction or charm

Ai prior probability of hypothesis)|( ipg

probability density function

.88 .97 .13 .98

charm .12 .03 .01 .02

had. int. NC 0<.001

.51 0

had. int. e CC

0<.001

.15 0

had. int. m CC

0<.001

.02 0

30

24

-3

01

75

30

39

-0

19

10

32

63

-2

51

02

33

33

-1

76

65

Probability all events are background = 8.0 10-5

FermilabE872

Moriond 2001

Jason Sielaff U. of Minnesota

Status

Results of “Long” decay search : (Physics Letters B )

Measurement of magnetic moment : (Physics Letters B )

Upper limit 4.27 10-7 B

PHASE 2 of analysis (in progress)

Data set of located interactions increasing +95 Feb. 2001Goal of 400 total by summer 2001

“Short” decay search to be completed : expect ~ 1 interaction

Relax cuts for decay search