Status of the OPERA experiment Yoshiaki Nonoyama(Nagoya univ) On behalf of the OPERA Collaboration

OPERA: first direct detection of neutrino oscillations in appearance mode through the nmnt channel  CERN　SPS 732km  Appearance INFN Gran Sasso < E > 　 17 GeV e /  　 　　　　 0.87 %  /  2.2 %  prompt negligible エネルギー Expected neutrino interactions in 1.25 kton target for 22.5x1019 pot: ~ 23600  CC + NC　 ~ 10  CC (m2 = 2.5 x 10-3 eV2)

nt identification -     No lepton except tau at 1ry vertex decay “kink”    ~1 mm oscillation , h- , e- plus 3-prong decay modes Requirements: 1) long baseline, 2) high neutrino energy, 3) high beam intensity, 4) detect short lived ’s Kink t-　→　e- 17.8 ％ t- 　→　μ- 17.4 ％ t- 　→　h- (t- 　→　r-) 49.5 ％ (25 ％) Trident t- 　→　h- h- h+ 15.2 ％ No lepton except tau at 1ry vertex Detect kink topology 3 3

The OPERA ECC （Emulsion Cloud Chamber ） 125mm 100mm 75.4mm 8.3kg 10X0 Neutrino Beam OPERA Film (before development) Lead plate : 1mm Sandwich structure OPERA film : 57plates 1mm thick lead : 56plates Changeable Sheet 0.3mm OPERA Film lead 1mm First observation of a tau neutrino in DONuT experiment

The OPERA detector 150,000 ECC SM1 SM2 Target area Muon spectrometer 数

8219 events collected until 30 August 2010 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 2010: 3rd physics run since 2008 CNGS program nominal goal: 4.5x1019 pot x 5 years 8219 events collected until 30 August 2010 ~9800 events will be collected until end of 2010. pot 2010 2009 2008 Days

Typical nmCharge Current nmNeutral Current like events The measured ratio of NC-like/CC-like events after muon ID and event location is ~20%, as expected from simulations 20 m 7

ECC extraction

Changeable Sheets (CS)  Found Track　→　Develop ECC Not found Track　→　Extract another ECC

4 hour to scan full area Of one film 10cmx10cm SutsでCSすきゃん CS scanning

Read out 100 micron tanθ = 0.5 10.0cm 12.5cm 1. E 08 tracks / Film Zoom in microscope view 10.0cm 12.5cm

CS track selection 10.0cm 12.5cm

n Scan back location 1 Connect CS to ECC 2 Follow up track in ECC 3 Confirm the stop plate 4 Scan around stop plate ECC CS STOP 5 mm n Found CS tracks 10cm 12.5cm The Plate changer for scan back in Japan

Located neutrino interaction 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. 1 cm 14 14

Located neutrino interaction 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. 1 cm 15 15

Located neutrino interaction 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. 1 cm 16 16

A nt candidate event was found. 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 Dm223 = 2.5 x10-3 eV2 and full mixing, OPERA expects: ~ 0.5 nt events A nt 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 topology Expected BG: ~2 events Expected NC/CC=0,31 -> 0,20 due to vertex location and muID bias/ BF x VTXloca=0,6 -> CC=0,64 NC=0,4 BF: NC=0,70 and CC = 0,80/ VTXloca: CC=0,80 NC=0,57 Scaling Proposal we expect 0,83 evts. Now we get 0,53. The discrepancy comes from a lower vtxloca for NC events: 0,64 -> 0,4 17 17

nt candidate event 9234119599, taken on 22 August 2009, 19:27 (UTC) (as seen by the electronic detectors)

Event topological features (Side view) 7 3 5 g2 1  g1 kink point primary vertex 2 8 (daughter) 4 ( cand) 6 1 radiation length 0.033 interaction length 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 The invariant mass of g1 g2 is consistent with p0. The invariant mass of g1 g2 and p-(8) is consistent with r(770). 12 (8)12 120 ± 20 ± 35 MeV 640 +125-80 +100-90 MeV

Decay Pt Decay length 20 Pt at decay vertex cut GeV/c mm Decay length red bands: values for this event with uncertainties Lead 1mm Decay Pt >300MeV/c Kink angle >20mrad Daughter momentum >2GeV/c Decay length Kink angle IP n  Decay point Primary vertex

p- cut f =180o t-decay x t- Azimuthal angle between Signal : f =180o t-decay t- nt p- X (hadron shower) ntN t-X nm kink nmN nmp-X f x BG: small f Azimuthal angle between the resulting hadron momentum direction and the parent track direction 21 Blue: MC - NC Black: MC - t rad cut

Back ground Charmed particle : 0.007+-0.004(syst) Charmed particle is similar topology of nt 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  - e- h-  ,e -, e- + e+ h+ D+ Miss identification of lepton charm in e for the 1-prong hadronic channel 0.007±0.004 (syst) background events are expected for the analyzed statistics BG expectation for our tau candidate 1-prong hadronic mode 1.8% (2.36s) all decay mode(1,3-prong h+1-prong m+1-prong e) 4.5% (2.01s)

Neutrino location Status at 2010/08/30 events Track found on CS Reach ~3000 events up to end of 2010 Located (total 2251) Decay search done date

Summary It is the first nt candidate event in OPERA. Goal of OPERA experiment is first direct detection of nt from neutrino oscillation of nm  nt channel. A t  1-prong hadron decay topology has been detected. It is the first nt 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.