CHORUS Recent Results on Oscillation and Charm

Physics

For theFor the collaborationcollaboration

M. GulerM. Guler

Middle East Technical University, Middle East Technical University, AnkaraAnkara

Wide Band Beam • 5.06 1019 POTs (1994-1997)

• <E> ~ 27 GeV

• <L> ~ 0.6 km

• Prompt : negligible

West Area Neutrino Facility at CERN SPSCHORUS, NOMAD

450 GeV

<L>/<E> ~ 2 10-2 km/GeV

m2 > 1 eV2

Neutrino beam

CHORUSCHORUS detectordetectorCHORUSCHORUS detectordetector

770 kg emulsion target

and scintillating fibre tracker

Calorimeter

Air core spectrometer andemulsion tracker

Air core spectrometer andemulsion tracker Veto plane

Muon spectrometerMuon spectrometer

- -

h-h-

T=5°T=5°Nucl. Instr. Meth A 401 (1997) 7

1947, first nuclear emulsions. Lattes et al., Brown et al.:

Discovery of pionDiscovery of pion

Nuclear emulsion Nuclear emulsion yesterdayyesterday

•3-d spatial resolution better than 1 m

CCD and XYZ stage

CCD and XYZ stage

New Track SelectorNew Track Selector

Host CPUHost CPU

Network Network data data

storagestorage

CHORUS automatic CHORUS automatic microscopesmicroscopes

Found track

track shifting

summing

track

Automatic Scanning: The Track Selector (TS)

PRINCIPLES:

• Multi-track predictions (and Scanback) without kinematical cuts

• Full vertex emulsion data taking (on located vertices)

• Offline Emulsion Analysis

CHORUS Phase II

New EMULSION data-taking and analysis for

• Increased sensitivity oscillation search

• Charm physics

Oscillation Analysis

Decay mode considered

i)-ii)- h-(n0), iii)- 3h-(n0) Pre-selection (data from electronic detector)

-vertex predicted in the emulsion-At least one negative track

-1 sample-0 sample

Emulsion Scanning-Scan back of selected tracks CSSSbulkvertex plate-Vertex reconstruction & decay Search, NETSCAN-Event selection-Eye-Scan Check, visible recoil, blob or Auger electron

Final kinematical cuts-decay length, kink angle, Pt at vertex

scan-back track

Automatic vertex location

• Follow up the track, plate by plate to vertex• 100 m most upstream part of each target plate are

scanned• Vertex plate defined by the first plate out of two

consecutive plates where track segment is not found.

Offline Emulsion Analysis

1

2

3

Track segments from 8 plates overlapped

At least 2-segment connected tracks

Eliminate passing through tracks

Reconstruct full vertex topology

12

Location of interaction vertex

guided by electronic detector.

Full data taking around interaction vertex called

NETSCANOffline tracking and vertex

reconstruction

CHORUS Background

Definition: 1-prong nuclear interactions with no heavily ionizing tracks or other evidence for nuclear breakup in the hadronic decays.

Poor previous knowledge of WK(P, Pt). Difficult to extrapolate (sensitive to the operative definition of “whiteness”)

MC development to tune the cuts against the WK background

Fluka to model the hadron interactions in emulsion Cuts to reproduce the minimum observable activity

(the white-gray transition) in the Chorus emulsions

Triger 2,305K

1mu 0mu

Initial sample 713,000 335,000

Events scanned 335,395 85,211

Events located 143,742 24,184

Events selected 11,398 1082

Data flow

After cuts : 0 candidates

Status of oscillation into

– e –

NOMAD data: final - CHORUS phase-II is not yet finished

Measurement of D0 production

Detector muon

I.P. Candidate selection

•Primary track matched to detector muon

•Daughter track matched to detector track

•3 ~ 13 μm < I.P. wrt. 1ry vtx < 400 μm Confirmed D0sample • 2 prong (V2) 841 (background: 35)

• 4 prong (V4) 230 (no background)Selection efficiencies

• V2 : 56.3 ± 0.5 x 10-

2• V4 : 74.2 ± 0.9 x 10-

2

BG subtracted, efficiency corrected• V2 1426 ± 52

• V4 310 ± 20

(D0 V4 ) / ( D0 V2)

= 21.8 ± 1.6 x 10-2

Fully neutral D0 decay

modesBR4/BR2 – measuredBR4/BR2 – measured

BR4 = 0.1338 BR4 = 0.1338 ± 0.0058 PDG

BR(D0 neutrals)=1-BR4 x(1+ BR2/BR4)=24.1 BR2/BR4)=24.1 ± 4.5% 4.5%(V6 (V6

negligible)negligible)Total production cross

sectionAll All D0’s = NV4/BR4 = 2280 ± 151(stat.) ± 26(stat.eff.) ± 99(BR4 err.)

Relative detection efficiency D0/CC = 0.88

σ(D0)/σ(CC) = 2280/95450/0.88 =

= 2.71 ± 0.22 x 10-2

Prelim

inary

Associated charm production

In CC interaction In NC interaction Gluon bremsstrahlung Gluon

bremsstrahlung & Z-gluon fusion

One event has been observedOne event has been observed and publishedand published

Phys. Lett B 539 (2002) 188Phys. Lett B 539 (2002) 188

W

g

D+D+X– c

gZ

D+D+X–

c

c

c

–

In the past only one event• Observed in E531 emulsionIndirect search performed by NuTeV• Production rate (2.6±1.6)x10-3 of CC

CCbar candidate beam

-704 m, Pl 23-704 m, Pl 23

-700 m, Pl 23-700 m, Pl 23

-640 m, pl 23-640 m, pl 23

-600 m, Pl 23-600 m, Pl 23

-600 m, pl 22-600 m, pl 22

-588 m, pl 22-588 m, pl 22

int. V2 V2

(Event: 8132 12312)(Event: 8132 12312)

CCharm production in antineutrino interactions

N+ = 2725

N- = 93890

Selected events = 82

found charm = 61

after reconstruction cut = 32

N= 4374 ± 135

fC-

fCo=

2.9

+ 1.9

- 1.2(stat) (N +cX)

(N +X)= 4.8 %

+ 1.2

- 0.9

Energy dependence

Prelim

inary

Measurement of D0

momentum Use correlation between opening

angle

of decay daughters and charm

momentum to obtain momentum

distribution

D0

Momentum

Invers

e o

f g

eom

etr

ical

mean

of

op

en

ing

an

gle

of

dau

gh

ters

Momentum distribution of D0 can

be measured by unfolding

opening angle distribution

(curve is the model in the

CHORUS MC)

D0

Momentum

Z & X-Feynman

distributions

• Also an E531 measurement• Indirect measurements from dimuon

data:• CDHS, CCFR, CHARMII, NuTeV,

CHORUS

Peterson formulaPrelim

inary

Collins-Spiller

Charm fragmentation

results

Large spread in valuesMay be due to different mixtures of charm final states:• E531: all charm decays• Nomad: D*• CHORUS: D0

• Dimuon experiments: weighted by muonic decay mode

Prelim

inary

Emulsion scanning is completed.

Estimate the efficiencies & tune the cuts.

Final oscillation result is before the end of year.

Conclusion I

So far, we have measured:Trimuon events

Λc production

QE charm production

D0 production

CC associate charm production

BR

Diffractive Ds* production

Phys. Lett. B. 596 (2004) 44Phys. Lett. B. 555 (2003) 156Phys. Lett. B. 575 (2003) 198Phys. Lett. B. 527 (2002) 173Phys. Lett. B. 539 (2002) 188Phys. Lett. B. 549 (2002) 48Phys. Lett. B. 435 (1998) 458

We are studying :D0 decay in neutralsD* D0 + +

Associated charm production in CC and NCCharm fragmentation functionAnti-neutrino charm productionx distributionVcd

Conclusion II