K. Zuber, University of Dortmund

Latest

XXVII Rec. de Moriond, ElectroWeak Interactions and Unified Theories, Les Arcs, 9-16 Feb. 2002

Results

• νµ - ντ oscillations

• νµ - νe oscillations with NOMAD

• KARMEN anomaly search

• Charm production in νN-scattering

Contents

Accurate knowledge of beam crucial

λ Beamline described by GEANT, secondary interactions

simulated by latest FLUKA version

λ Cross sections and particle production in p Be

simulated by latest FLUKA versionmodified with NA56-SPY and

Atherton et al. data

CHORUS detector

Active target

Calorimeter

Spectrometer

Air-core magnet

Veto

ν

§ Active target§ nuclear emulsion target§ scintillating fiber tracker

§ Calorimeter§ ∆E/E = 32 %/√ E (hadrons)

= 14 %/√ E (electrons)§ ∆θhadrons = 60 mrad @ 10 GeV

§ Muon spectrometer§ ∆p/p = 10 – 15% (p < 70 GeV/c)

§ Air-core magnet§ ∆p/p = 0.035 p (GeV/c) ⊕ 0.22§ 1996-97 upgrade : ET, HC

(Data taking 1994 - 1997)

0 µm0 µm

CHORUS emulsion

-21 µm-21 µm

-36 µm-36 µm

-54 µm-54 µm

~ 800 kg active target~ 800 kg active targetMIP : 30 MIP : 30 ∼∼ 40 grains / 100 40 grains / 100 µµmmtransverse resolution ~ 0.5 transverse resolution ~ 0.5 µµmmdepth of focus : 1 to 3 depth of focus : 1 to 3 µµmm

350 µµm

90 µµm

Nucl. Instr. Meth. A 447 (2000) 361-376

Momentum resolution ~3.5 %(p<10 GeV)

Position resolution < 200 µm(small angle tracks)

Efficiency ≈97% (pµ > 5 GeV)

σ(E)/E = (1.04 ±0.01)% +(3.22±0.07)%/√E(GeV)

π rejection ~ 103

for electron efficiency >90%

Nucl. Instr. Meth. A 404 (1998) 96

NOMAD events

νµCC

νeCC

CHORUS - ντ Detection principle

Kink search in emulsion target

Emulsion target (BULK)

Interface emulsion sheets (CS and SS)

Fiber target tracker (TT)

NOMAD - ντ Detection principleSearch by kinematical

criteria

Basically isolationand imbalance

Likelihood Analysis

‘‘Blind Analysis‘‘

Procedure of analysis1) Event reconstruction by electronic detectors

2) Vertex location

3) Decay search

4) Post-scanning analysis

Pre-selection of events Momentum cuts Pµ- < 30 GeV/c, 1 < Ph- < 20 GeV/cAngle cut θ < 0.4 rad

Computer assisted eye-check

Kinematic study

Automatic scanning and offline selection for decay topology search

Automatic emulsion scanning : follow-up the selected tracks until interaction vertex

ντ

µ-,h-

νµ, (πo’s)ντ

τ path

vertex

kink

à reduce scanning load

à confirm presence of decay

(Only for τ search)

à Important to measure momenta

to identify the sign of charge (for τ candidate)

Emulsion triggers : 2,305K

2,282Selected for eye-scan11,398Selected for eye-scan

Vertex located

Events scanned

Initial sample

20,081143,742Vertex located

85,211355,395Events scanned

122,400477,600Momentum and angle selection

335,000713,000Initial sample

0µ sample1µ sample

CHORUS (Phase I)

0 0

1µ sample : events with one negative charged muon

0µ sample : events without muon

τ candidates τ candidates

Momentum and angle selection

channels: τ→µ-ντνµ, τ→h-(nπ0)ντ-

Osc. Prob.: Pµτ ≤ 3.4 x 10-4

NOMAD (Final)

eνeντ DIS 5 5.3 +0.7 –0.5h-(nπ0)ντ DIS 21 19.5 ± 3.53h-(nπ0)ντ DIS 3 4.9 ± 1.5eνe ντ LM 6 5.4 ± 0.9h-(nπ0)ντ LM 12 11.9 ± 2.93h-(nπ0)ντ LM 5 3.5 ± 1.2

Osc. Prob.: Pµτ ≤ 1.63 x 10-4

channel Obs. Tot. Backgnd

total 52 50.5 ± 10.6

NOMAD (final): Nucl. Phys. B 611,3 (2001)

Results of ντ search

CHORUS: Phys. Lett. B 497, 8 (2001)

NOMAD

sin2 2θ <6.8 x 10-4 large ∆m2CHORUS

Blind analysis in Reµ and νe CC

• Robust flux

prediction

•Detailed estimation of systematic errors and background

Alternative: Empirical parametrisation - more accurate flux

νµ → K- νe→KL, K-

analysed predictedNeutrino flux

- -also analysed:

Bin-to-bin systematicerrors: 5-8 %

Overall (normalization)uncertainty: 2%

10 energy bins and 3 radial bins

χ2: 19.7/29 d.o.f. (no osc.)

χ2min: 18.6/27 d.o.f. (with osc.)

No evidence for oscillations

Preliminary results

Exclusion Plot (Preliminary)

Large ∆m2: sin22θ < 1.2 x 10-3

(90 % CL)

NOMAD excludes high ∆m2

(∆m2 > 10 eV2) region of

allowed LSND parameters

(Feldman-Cousins method)

Neutral 33.9 MeV particles in π+-decay?

P.Astier et al., Phys. Lett. B 527, 23 (2002)

BR(π+ →µ++X) BR(X →visible)X → νe+e- favoured

Motivated by KARMEN Anomaly

NOMAD search forexcess in isolated

e+e- -pairs

No excess found

Neutrino charm production

d,sd,s cc

EEhadhad

µµ--

νννν

µµ

hh

θθµµBeam knowledge

|Vcd|2,|Vcs|2

Quark density functions,strange sea (κ)

Charm fragmentationD0 : D+ : Ds

+ : Λc+

z = pc/pD

B(c→µ)

+ NLO effects

ν

g

µ

s

ccc

ν

sg

µ

s+ radiative gluonand self energydiagrams

Opposite sign dimuons in ν N scattering

Using FCAL data of NOMAD (~15 % oftotal FCAL data)

2714 µ- µ+ events (νµ)115 µ- µ+ events (νµ)

P.Astier et al., Phys. Lett. B 486, 35 (2000)

νµN →µ- + c + X s + µ+ +νµ

-

mc, κ and Bc consistent with other experiments

8 plates

1.5 mm

1.5 mm

••Sample of 25,693 Sample of 25,693 ννµµ CC interactions, ~15% of final statisticsCC interactions, ~15% of final statistics

•• selection selection efficiency : efficiency : V2 V2 →→ 58.658.6±±0.7% , 0.7% , V4 V4 →→ 70.170.1±±1.7% 1.7%

•• 851 (3.3%) selected events851 (3.3%) selected events

D0 production

CHORUS net scan

V2 226 V4 57

Neutral ~ 33 %Neutral ~ 33 %

•• ss(D(D00) / ) / ss (CC) = 1.99 (CC) = 1.99 ±± 0.13 (stat.) 0.13 (stat.) ±± 0.17 (0.17 (systsyst.) %.) %

•• <E<Eνν>=27GeV, P>=27GeV, Pµµ < 30GeV/c< 30GeV/c

ss(D0)/ss(CC)

Eν (GeV)

To appear in Phys.Lett.B (Measurement of D0 production in …, A.Kayis-Topaksu et al.)

ss (D(D00) / ) / ss (charm) (charm) = 53 = 53 ±± 11 %11 %

Slow rescaling modelSlow rescaling modelmmcc = 1.3= 1.3 GeVGeV/c/c22

CHORUSCHORUS

E531E531DD00 →→ V4 / V4 / DD00 →→ V2V2= 23.1 = 23.1 ±± 4.0 %4.0 %

NOMAD (NOMAD (rescalrescal.).)

D0 Production rate

Study of D*+ - production

D*+→D0 + π+K- + π+

NOMAD searchAnalysis is

using neutral net

(<10 % BG sample)

D*+ yield in νµCC: T = 0.79 ± 0.17 (stat.) ± 0.10 (syst.) %P.Astier et al., Phys. Lett. B 526, 278 (2002)

35 ± 7.2 events

Summary

No oscillations in νµ - ντ channel observed

NOMAD excludes large ∆m2 region of LSND

Improved limits in νe - ντ channel

No hint for a 33.9 MeV neutral found in NOMAD

First new results on Charm physics(OSDM, D0, D*+ )

A lot of interesting results from CHORUS and NOMAD still to come

90 µm plastic base

350 µ m (175 µ m)emulsion sheet

CCDcamera

CCDcamera

mic

rosc

ope

stro

ke

tomographic image

350 µ m (175 µ m)emulsion sheetem

ulsi

on p

late

Automatic emulsion scanning

Hardware tracking

Software tracking

developed by Nagoya group

CERN group

• Flexible and adaptable

• Profit from Moore’s law