Status of the OPERA experiment

Yoshiaki Nonoyama(Nagoya univ)

On behalf of the OPERA Collaboration

732km

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

Appearance

%7.1~27.1sin2sin~ 2322

232

E

LmP 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 (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 ％

• No lepton except tau at 1ry vertex• Detect kink topology

identification

The OPERA ECC （ Emulsion Cloud Chamber ）

125mm

100mm

75.4mm

8.3kg10X0

Neutrino Beam

OPERA Film (before development)

1mmlead

0.3mm OPERA Film

Lead plate : 1mm

Sandwich structureOPERA film : 57plates1mm thick lead : 56plates

First observation of a tau neutrinoin DONuT experiment

Changeable Sheet

Target area Muon spectrometer

SM1 SM2SM1 SM2

The OPERA detector

150,000 ECC

OPERA running (CNGS) Year Beam days

Protons on target

Events in the bricks

2008 123 1.78x1019 1698

2009 155 3.52x1019 3693

2010 187 2.67x1019 (30 August)

2828(30 August)

8219 events collected 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

Typical Charge CurrentNeutral Current like events

The measured ratio of NC-like/CC-like events after muon ID and event location is ~20%, as expected from simulations

7

20 m

ECC extraction

Found Track　→　 Develop ECC

Not found Track　→　 Extract another ECC

Changeable Sheets (CS)

Suts で CS すきゃん

4 hour to scan full area Of one film 10cmx10cm

CS scanning

100 micron tanθ = 0.5

Zoom　in　microscope　view

1. E 08 tracks / Film

12.5cm

10.0

cmRead out

10.0

cm

12.5cm

CS track selection

Scan back location

5 mm

CSECC

STOP

1 Connect CS to ECC2 Follow up track in ECC3 Confirm the stop plate4 Scan around stop plate

The Plate changer for scan back in Japan

Found CS tracks

12.5cm

10cm

1 cm

Emulsions give 3D vector data, with micrometric precision of the vertexing accuracy.

The frames correspond to the scanning area. Yellow short lines measured tracks. Other colored lines interpolation or extrapolation.

Located neutrino interaction

14

1 cm

Emulsions give 3D vector data, with micrometric precision of the vertexing accuracy.

The frames correspond to the scanning area. Yellow short lines measured tracks. Other colored lines interpolation or extrapolation.

Located neutrino interaction

15

1 cm

Emulsions give 3D vector data, with micrometric precision of the vertexing accuracy.

The frames correspond to the scanning area. Yellow short lines measured tracks. Other colored lines interpolation or extrapolation.

Located neutrino interaction

16

17

Event statistics

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

20 charm candidate events selected by the kinematical cuts, 3 of them with 1-prong kink topology.

Expected: 16.0 ± 2.9 out of which 0.80 ± 0.22 with kink topologyExpected BG: ~2 events

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

(as seen by the electronic detectors)

2

1

3

2

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

20

Pt at decay vertex

cut

GeV/c

Decay Pt

mm

Decay length

red bands: values for this event with uncertainties

Lead 1mm

Primaryvertex

Decay pointIP Kink angle

Decay Pt >300MeV/c

Kink angle >20mrad

Daughter momentum >2GeV/c

Decay length

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

Signal :=180o

-decay -

-

X (hadron shower)

N -X

-

kink

N -X

-

x

BG:

small

21

Blue: MC - NC

Black: MC -

rad

cut

Back ground• 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(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.