Short Baseline neutrino experiments

Jaap Panman, CERN

Neutrino 2004, Paris, 15 June 2004

Outline

Status of oscillation experiments

Charm production

Summary

Oscillation searches In this talk concentrate on CERN programme, other

experiments are covered by other speakers.

MOTIVATION of the CERN - programme:

At proposal time:

•Cosmologically relevant region (few eV scale)

•Seesaw mechanism could accommodate eV scale masses and relatively small mixing

After SuperK:

•Smaller mass-differences more likely

•But, LSND …

Neutrino

beam

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

– <E> ~ 27 GeV

– <L> ~ 0.6 km

– Prompt : negligible

West Area Neutrino Facility at CERN SPS

CHORUS, NOMAD

450 GeV

<L>/<E> ~ 2 10-2 km/GeV m2 > 1

eV2

NOMAD

detection by kinematicalselection

CHORUS

Active target

•Nuclear emulsion

•Sci-Fi tracker

Calorimeter

Spectrometer

Air-core magnet

Veto

-,h-

, (o’s)

path

vertex

kink

-54 m-54 m

-36 m-36 m-21 m-21 m

0 m0 mRed frame: Red frame:

~30x40 ~30x40 mm22

beam

detection by decay KINK recognition

Status of oscillation into – e –

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

Search for –e oscillation in NOMAD

• Motivated by LSND result• Final results available• Due to electron neutrino component in beam (1%) – careful simulation of

beam line needed• Exploit powerful electron identification• Study energy spectra (enhanced at low energy) and radial distributions

(enhanced in the center)

Final results

Define ratio of electron and muon neutrino CC events

Events are compatible with known sourcesNo evidence for oscillations

NOMAD result rules out the LSND allowed region with m2 above 10 eV2

Charm production

Additional results of NOMAD and CHORUS:• Charm physics• (for other results see Camilleri’s talk)

NOMAD charm physics• D* production and fragmentation study• Exploiting mass resolution

CHORUS charm physics• Neutral and charmed particle production• Decay properties, fragmentation studies• Exploiting topological decay recognition• Charm studies only possible with PHASE-II NetScan technology

Automatic emulsion data

acquisition (phase-II)1

2

3

Angular acceptance : 400

mrad

Track segments from 8 plates overlapped

At least 2-segment connected tracks

Eliminate passing through tracks

Reconstruct full vertex topology

Volume : 1.5 x 1.5 mm2 x 6.3 mm

1

2Location of interaction vertex

guided by electronic detector.

Full data taking around interaction vertex called Netscan

Offline tracking and vertex

reconstruction

~ 11 minutes / event

Measurement of D0 production Phys. Lett. B 527 (2002) 173, based on ~25% of statistics

NOW: full sample: 95450 CC events

Candidate selection

Detector muon

I.P.

Primary track matched to detector muon

Daughter track matched to detector track

3 ~ 13 μm < I.P. wrt. 1ry vtx < 400 μm

2 prong (V2) 841 (background: 35)

4 prong (V4) 227 (no background)

Confirmed D0sample

Selection efficiencies

V4 : 74.2 ± 0.9 x 10-2

V2 : 56.3 ± 0.5 x 10-2

BG subtracted, efficiency corrected

V2 1426 ± 52

V4 305 ± 21

(D0 V4 ) / ( D0 V2)

= 21.4 ± 1.6 x 10-2

Preliminary

σ(D0)/σ(CC) = 2280/95450/0.88 =

= 2.71 ± 0.22 x 10-2

Fully neutral D0 decay modes:

BR4/BR2 – measuredBR4/BR2 – measured

BR4 = 0.1338 BR4 = 0.1338 ± 0.0058 PDG

BR(D0 neutrals) = 1-BR4 x(1+ BR2/BR4 ) = BR2/BR4 ) = 24.1 24.1 ± 4.5% 4.5% (6 prong negligible) (6 prong negligible)

Total production cross

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

Relative detection efficiency D0/CC = 0.88

Preliminary

Study of fragmentation

Different strategies to study fragmentation Properties of charm production:

NOMAD isolates D* using invariant mass reconstruction

For these events, kinematic quantities are well measured, but statistics is low

CHORUS uses a high statistics and pure sample of D0 events obtained by isolating neutral particle decays.

However, distributions have to be obtained by an unfolding method.

Nomad D*+ measurement

Step 1: exploit invariant mass combinationsStep 2: kinematical cutsStep 3: neural network to reduce combinatorial background

Cleanest sample: Neural Net estimator cut at K=0.8735

35+-7.2 events (12 background)

Larger statistics: K>0.6

Use decay chain:

Study larger statistics sample:Background is combinatorial MC: S+B Data

D* mass in clean sample

D* yield in CC events (T):

Compatible with BEBC

pT2 distribution of charmed particles

The transverse momentum of charmed particles wrt thedirection of the hadronic system is usually parametrized as

2

2Tbp

T

edp

dN

Phys. Lett. B 206 (1988) 380-384• NOMAD 47-12 eventsPhys. Lett. B 526 (2002) 278-286

NOMAD

Measurement of D0 momentum

Use correlation between

opening angle

of decay daughters and

charm

momentum to obtain

momentum distribution

D Momentum

Inverse of

geometrical

mean of

opening angle

of daughters

Momentum distribution of D0

can be measured by

unfolding opening angle

distribution

(curve is the model in the

CHORUS MC)

Prelim

inary

NOMAD

Z-distribution

NOMADFits to Collins-Spiller and Peterson:

Also an E531 measurement Indirect measurements from dimuon

data: CDHS, CCFR, CHARMII, NuTeV,

CHORUS

CHORUSCHORUS

Prelim

inary

CHORUS:

Fit to Peterson formula

(dotted curve is MC model)

Feynman x distribution

Prelim

inary

NOMAD

Most charmed particles are produced in the forward region

CHORUS

Charm fragmentation

results

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

• Dimuon experiments: weighted by muonic decay mode

Measurement of Λc production

A statistical approach using flight length

distribution

Short flight decay :

Λc enriched

sample

Long flight decay :

D+, Ds dominant

Two different set of

criteria

have been adopted.

Strategy

Flight length in

μm

MC

Λc

D+

Ds

Phys.Lett.B 555 (2003) 156 based on 50414 Phys.Lett.B 555 (2003) 156 based on 50414 CCCC

Measurement of Λc production

Short flight decay (A)Daughter track : Distance to the muon 5 µm to 30

µm

Long flight

decay (B)

Candidate selection

Parent track : distance to the muon < 5 µm

Distance between daughter and parent 5µm to 30

µm

1614 events from 50,414 CC events were

selected for visual inspection

Detector muon

Detector muon

586 events from 56,761 CC events were

selected for visual inspection

(A)

(B)

Samples after flight length

cut1

prong

3 prong

(A) 40 mm < FL < 400 mm

(B) 400 mm < FL < 2400 mm

62 66133 195

• Combining short (A) and long (B) decay search,and taking Combining short (A) and long (B) decay search,and taking

into account efficiency and background:into account efficiency and background:

• c c = 861 = 861 198 (stat.) 198 (stat.) 98 (syst.) 98 (syst.)+140 +140 (QE)(QE)

• Br(Br(cc 3prong) = (24 3prong) = (24 7 (stat.) 7 (stat.) 4 (syst.)) 4 (syst.)) 10 10-2-2

σσ((c) /σ(CC)= (1.54 c) /σ(CC)= (1.54 0.35(stat) 0.35(stat) 0.18 (syst)) 0.18 (syst)) 10 10-2-2

-54-54

σσ((c)/σ(CC)c)/σ(CC)Br(Br(cc 3prong)=(0.37 3prong)=(0.37 0.10(stat) 0.10(stat)

0.02(syst))X100.02(syst))X10-2-2

Λc

a) n - c+ b) n - c

+ (c*+) c) p - c

++(c*++)

Quasi-elastic charm production

•Require 2 or 3 tracks at primary vertex• 165° (angle between muon and charm in the transverse plane)•Flight length < 200 m (enriched c sample)

•Calorimeter energy < 10 GeV and electromagnetic energy < 2 GeV

Topological and kinematical selection criteria:

13 events with a background of 1.70.60.6 (mainly from DIS c)

QE production is about

15% of c production

Phys.Lett.B 575 (2003) 198 based on 46105 Phys.Lett.B 575 (2003) 198 based on 46105 CCCC

Energy measured in calorimeter

Azimuthal angle

Kinematical selection of QE candidates

Events in first bin

Associated charm production

Charged-current

Gluon bremsstrahlung

c

–c

W

g

D+D+X–

One event has been observed and published.

Phys. Lett B 539 (2002) 188, CHORUS Coll.Phys. Lett B 539 (2002) 188, CHORUS Coll.

In CC interactions

c

–cg

Z

Z-gluon fusion

D+D+X–

Associated charm productionNEW

In NC interactions

ANDGluon bremsstrahlung

c

–c

Z

g

D+D+X–

In the past only one event• Observed in E531 emulsionIndirect search performed by NuTeV• Production rate (2.6x1.6)x10-3 of CCSystematic search for double decay topologies Events observed in NC and CC interactions with very low background (order 0.1 event)

TTT #6 PT #6 PPP>0.66 GeV/C @ 90 CL.>0.66 GeV/C @ 90 CL.

TTT #3 T #3 PPd4d4>2.72 GeV/c @ 90 CL.>2.72 GeV/c @ 90 CL.

TTT #8, T #8, PPd2d2>4.66 GeV/C @ 90 CL.>4.66 GeV/C @ 90 CL.

TTT #5, T #5, PPd1d1> 1.39 GeV/C @ 90CL.> 1.39 GeV/C @ 90CL.

ppl23l23 ppl22l22

example of NC eventexample of NC event

E=29.9GeVE=29.9GeV

PPd3d3>3.33 GeV/c @ 90 CL.>3.33 GeV/c @ 90 CL.

Both neutral decays Both neutral decays inconsistent with two-inconsistent with two-body decay body decay (acoplanarity)(acoplanarity)

E=36.9 GeVE=36.9 GeV P=-16.9 P=-16.9 GeV/cGeV/c

Pl31Pl31 pl30 pl30

example of CC example of CC eventevent

PPd1d1>4.70 GeV/c @ 90 CL.(>4.70 GeV/c @ 90 CL.(TTT #2)T #2)

PPd2d2>0.67 GeV/c @ 90 CL.>0.67 GeV/c @ 90 CL.

PPd3d3>2.32 GeV/c @90 CL.(>2.32 GeV/c @90 CL.(TTT T #7)#7)

PPd2d2>1.92 GeV/c @90 CL.(>1.92 GeV/c @90 CL.(TTT #5)T #5)

Evis= 53.8 GeVEvis= 53.8 GeV

Both neutral decays Both neutral decays inconsistent with two-inconsistent with two-body decay body decay (acoplanarity)(acoplanarity)

CCharm production in antineutrino

interactionsN+ = 2725

N- = 93890

Selected events = 82

found charm = 61

after reconstruction cut = 32

“1 spectrometer events”

kink> 50 mrad, F.L > 50 m

fC-

fCo= 2.9

+ 1.9

- 1.2 (stat)

(N +cX)(N +X) = 4.8 %+ 1.2

- 0.9

N= 4374 ± 135

Prelimina

ry

Energy dependence

CDHS and HPWF (1978): ~100 events - origin largely unknown

CHORUSCHORUS:: ~6x10~6x106 6 22 calorimeter triggers calorimeter triggers

observed: observed: 42 , 3 (P(P > 5 GeV/c) > 5 GeV/c) Detailed Monte-Carlo (LEPTO/JETSET/GEANT) Detailed Monte-Carlo (LEPTO/JETSET/GEANT)

4x104x106 6 events with full detector simulationevents with full detector simulation present knowledge of production rates andpresent knowledge of production rates and

-decays of -decays of ’

data-MC validation using 2data-MC validation using 2 events (known origin) events (known origin)

data-MC comparison for data-MC comparison for 3event sampleevent sample

Trimuon events in CC interactions

Angle between leading Angle between leading and sum of two othersand sum of two others

DATADATA

All MCAll MC

Charm->Charm-> + +

Int. bremsstrahlungInt. bremsstrahlung

TrimuonsTrimuons

nono int. bremsstrahlungint. bremsstrahlung

TrimuonsTrimuons

MC 2MC 2 validation validationPP and and well reproducedwell reproduced

Charm->Charm-> + + decaydecay 8.38.32.82.8Internal bremsstrahlungInternal bremsstrahlung (theoretical) (theoretical) 8.68.64.54.5 4040

main 3main 3 sources sources MC MC predictions predictions

Observed in experiment: 42 Observed in experiment: 42

Conclusions – MC predictions Conclusions – MC predictions on on 33 rate are in agreement rate are in agreement with measurementswith measurements

SUMMARY

• SBL oscillation programme at CERN:– NOMAD final data

– CHORUS, final statistics, but phase-II analysis ongoing

• Many additional measurements (in this talk concentrated on charm physics)– Production cross-sections

– Fragmentation functions

– Decay properties

• Other results will be shown by Camilleri