Status of the OPERA experiment

Yoshiaki Nonoyama(Nagoya univ)On behalf of the OPERA Collaborati

on

732km

OPERA: first direct detection of neutrino oscillations in appearance mode through the channel

Appearance

%7.1~27.1sin2sin~ 2322

232

ELmP τμ　

< E > 　 17 GeV e / 　 　　　　　　 0.87 % / 2.2 % prompt negligible

CERN 　 SPS

INFN Gran Sasso

Expected neutrino interactions in 1.25 kton target for 22.5x1019 pot:

~ 23600 CC + NC ~ 10 CC identified (m2 = 2.5 x 10-3 eV2)

3

Requirements:

1) long baseline, 2) high neutrino energy, 3) high beam intensity, 4) detect short lived ’s

-

decay “kink”

~1 mm

oscillation

- , h- , e-

plus 3-prong decay modes

Kink 　→　 e- 17.8 ％ 　→　 μ- 17.4 ％ 　→　 h-

　→　 -)49.5 ％(25 ％ )

Trident 　→　 h- h- h+

15.2 ％

• makes tau particle and tau decays with kink topology.• identification is detected kink and no lepton except tau at 1ry vertex.

identification

Branching of

The OPERA ECC （ Emulsion Cloud Chamber ）125mm

100mm

75.4mm

8.3kg10X0

Neutrino Beam

OPERA Film (before development)

Lead plate : 1mm

Sandwich structureOPERA emulsion film : 57plates1mm thick lead : 56plates

Changeable Sheet

Life time(c) of is ~87m

1 mm

Pb

Emulsion layers

Target area Muon spectrometer

SM1 SM2SM1 SM2

The OPERA detector

Total ECC 150,000Total mass 1.25 kton

Beam performance Year Beam days

Protons on target

Events in the bricks

2008 123 1.78x1019 16982009 155 3.52x1019 36932010 187 2.67x1019

(30 August)2828(30 August)

8219 events collected in target until 30 August 2010

~9800 events will be collected until end of 2010.

2010

2009

2008 Days

2010: 3rd physics run since 2008

CNGS program nominal goal:4.5x1019 pot x 5 years

pot

7

20 m

target Muon spectrometerCharge Current

Neutral Current

ECC extraction

Zoom in electronic detectors view

Judgment of interaction by CS (Changeable Sheets)

ECC

CS

• Judgment of interacted in ECC by found track from interaction. • Doublet of low BG emulsion films.• Attached downstream of ECC.

Developed CS

Found track → Develop ECCNot found track → Extract another ECC

Suts で CS すきゃん

High speed read out microscope4 hour to scan full area Of one film 10cmx10cm

CS scanning

Location of neutrino interaction in ECC

5 mm

CSECC

STOPHow to locate ?? 1. Connect track CS to ECC. 2. Follow up track in ECC. 3. Confirm the stop plate. 4. Scan around stop plate.

The Plate changer in Japan

Put emulsion like the seat. for changing plates easily.

1 cm

Scan about 10 plates around stop plate by follow up from down stream.

Located neutrino interaction in ECC

12

1 cm

Reject passing trough track and few plates connect track.

Located neutrino interaction in ECC

13

1 cm

Search tracks making vertex by neutrino interaction .

Located neutrino interaction in ECC

14

15

search result at June

• Total found neutrino vertices: 1921 (This is ~60% of the total 2008-2009 run statistics.)

• Events for which “ search” was completed: 1088 (187 NC) This is ~35% of the total 2008-2009 run statistics, corresponding to 1.85 x 1019 pot With the above statistics, and for m2

23 = 2.5 x10-3 eV2 and full mixing, OPERA expects: ~ 0.5 events

A candidate event was found.

candidate event 9234119599, taken on 22 August 2009, 19:27 (UTC)

(as seen by the electronic detectors)

2

1

32

75

1

6

8 (daughter)4 (cand)

track # tan x tan y p [GeV/c]

1 0.176 0.363 0.78 +0.13-0.10

2 -0.650 0.000 0.32 +0.31-0.11

3 0.108 0.113 1.97 +0.33-0.25

4（ parent） -0.027 0.022

5 0.157 0.267 1.30 +0.22-0.16

6 0.334 -0.584 0.36 +0.18-0.09

7(from neutral track) 0.438 0.419 0.49 +0.29

--0.13

8（ daughter） -0.007 -0.014 12 +6-3

1 radiation length0.033 interaction length

primary vertex

kink point

120 ± 20 ± 35 MeV 640 +125-80

+100-90 MeV

The invariant mass of 1 2 is consistent with 0.The invariant mass of 1 2 and (8) is consistent with

Event topological features (Side view)

Decay length

18

Pt at decay vertex

cut

GeV/c

Decay Pt

mm

Decay length

red bands: values for this event with uncertainties

Decay Pt >300MeV/c

Kink angle >20mrad

Daughter momentum >2GeV/c

Lead 1mm

Primaryvertex

Decay pointIP Kink angle

Decay length

Azimuthal angle between the resulting hadron momentum direction and the parent() track direction

19

Blue: MC – NC

Black: MC -

rad

cut

Data

Signal :

-

-

X (hadron shower)

N → -X

-

NC N → -X

-

x

BG : small

Back ground (in analyzed statistics)

• Charmed particle : 0.007+-0.004(syst)– Charmed particle is similar topology of decay– Muon ID ~95% in electronic detector.

• Hadronic reinteraction : 0.011– Searched reinteraction in 8 times of tau search length, but there was no signal in tau

signal region.

BG expectation for our tau candidate 1-prong hadronic mode

1.8% (2.36

all decay mode(1,3-prong h+1-prong +1-prong e)

4.5% (2.01

-

e-

h-

,e

-, e-

+

e+

h+D+

Miss identification of lepton

charm in e

Neutrino location Status at 2010/08/30

Track found on CS

Located in ECC(total 2251)

Decay search done

date

events

Reach ~3000 events up to end of 2010

Summary

Goal of OPERA experiment is first direct detection of from neutrino oscillation of channel.

A 1-prong hadron decay topology has been detected.

It is the first candidate event in OPERA.

Up to now, we located neutrino interaction in ECC is 2251 events.

Until end of 2010, We will locate 3000 event and expected tau neutrino interaction is 1.5.It is 3 times statistics of this analysis.