First events from the OPERA experiment at Gran Sasso at Gran Sasso Gabriele Sirri Istituto Nazionale di Fisica Nucleare BOLOGNA, ITALY on behalf of the OPERA COLLABORATION
OPERA Collaboration L’Aquila LAPP Annecy Bern IHE Brussels Hamburg IRB Zagreb Sofia Bari IPNL Lyon Neuchâtel Münster Bologna IPHC Strasbourg ETH Zurich Rostock LNF Frascati LNGS Napoli OPERA is an international Padova Roma collaboration of ∼ ∼ 200 ∼ ∼ ∼ ∼ ∼ ∼ INR Moscow Salerno NPI Moscow physicists from 36 institutions physicists from 36 institutions ITEP Moscow SINP NSU Moscow SINP NSU Moscow JINR Dubna and 13 countries Obninsk Tunis Aichi Toho Kobe Nagoya METU Ankara Utsunomiya Technion Haifa Jinjiu 2008.08.25 COSMO08 G.Sirri , INFN Bologna 2
Outline � Physics motivations � CNGS Beam � OPERA Detector � Physics potential � First events in the CNGS 2007 run � First events in the CNGS 2007 run � CNGS 2008 run � Conclusions 2008.08.25 COSMO08 G.Sirri , INFN Bologna 3
OPERA Physics Motivation Road to OPERA OPERA 1998 Atmospheric neutrino anomaly: provide an unambiguous deficit of ν � with zenith angle evidence for dependence. � OSCILLATION ν 9 → ν τ oscillation in the region of atmospheric neutrinos by looking for ν τ appearance CHOOZ: final in a pure ν 9 beam flavour not ν e … ν ν 1999 CNGS beam design 2000 direct observation of ν τ in nuclear emulsions (DONUT) 2000 OPERA proposal 2008.08.25 COSMO08 G.Sirri , INFN Bologna 4
CNGS CERN Neutrino to Gran Sasso beam optimized to maximize ν ν ν ν τ τ CC ∫ CC = φ σ ε τ τ � � M ( E ) P ( E ) ( E ) ( E ) dE interaction rate at LNGS τ ν ν A D � ν → ν τ � τ CERN LNGS BEAM MAIN FEATURES <E ν ν � ν ν � > 17 GeV � � ( ν ν e + ν ν ν ν e ) / ν ν ν ν � ν ν 0.87% � � � ν ν � ν ν � / ν ν � ν ν 2.4% � � � � � ν ν τ ν ν τ prompt negligible τ τ • 4.5x10 19 p.o.t./year • 200 days/year 2008.08.25 COSMO08 G.Sirri , INFN Bologna 5
CNGS event rate (nominal beam) Nominal CNGS beam (running 200 days/year): 4.5 × 10 19 pot/year OPERA (1.35 kton), 5 years running �m 2 (eV 2 ) ν � �� 19572 80 (2.0×10 �3 ) ν � �� ν � �� 5880 5880 ν τ �� ν τ �� 125 125 (2.5×10 �3 ) ν � �� 411 180 (3.0×10 �3 ) ν �� �� 156 ν �� �� 13 Total: ~ 26000 interactions Additional 10000 events in the OPERA magnets ��������������������������������������������������� ���� 2008.08.25 COSMO08 G.Sirri , INFN Bologna 6
OPERA: Detection of the ν τ appearance ν � ν The challenge is to ν ν � � � identify ν ν τ ν ν τ interactions � � � � � τ τ from ν ν � ν ν � interactions ν ν � ν ν � � � � � τ decay modes τ τ τ − ν � � − � � ν ν τ ν τ ν ν ν ν � − − B. R. ~ 17% ν τ τ � � � Decay “kink” h % ν ν ν ν τ τ n( π π π π ο ο ο ) ο ) ) ) B. R. ~ 50% ν � ν ν ν ν ν � ν ν τ τ � � � � � � � � � � � � � � � � e % ν e % ν τ % τ % τ τ τ τ τ τ ν ν ν τ ν ν ν τ ν ν ν ν ν ν e ν ν B. R. ~ 18% B. R. ~ 18% τ τ ν ν τ ν ν π + π π % π π % ν oscillation τ τ τ π π π π π π π ν ν ν τ τ n( π π ο π π ο ο ) ο ) ) ) B. R. ~ 14% τ τ ~0 .6 mm conflicting requirements: OPERA solution: • Large mass Emulsion Cloud Chamber � low Xsection (ECC) tecnique • High granularity � signal selection � background rejection 2008.08.25 COSMO08 G.Sirri , INFN Bologna 7
The Emulsion Cloud Chamber technique 205 � m ECC ≡ sequence of emulsion,lead layers: Lead: target mass Emulsion: tracking device ���� τ Emulsion Resolution: δ x = 1 µm δθ = 2 mrad 99.8 mm 99.8 mm 125.1 mm Pb Pb Pb 44 � m High spatial resolution capability and large masses in a modular way. In OPERA, the basic ECC unit is the “BRICK”: 56 Pb sheets + 57 emulsion layers (10X 0 ) Total # of bricks ~ 155000 8.3 kg 2008.08.25 COSMO08 G.Sirri , INFN Bologna 8
Strategy for the ν τ location On,line analysis of OPERA: an hybrid detector electronic data (Brick selection) Brick Extraction B spectrometer and scanning of 2 Target Tracker external films (CS) + Brick Walls (higher level trigger) Brick exposure to CR 10 m (fine alignment) and scanning backwards ν from CS predictions Vertex location and τ ID and τ ID ���� τ Pb Pb Pb Target Tracker: trigger ( ε > 99%) ECC: measure kink, pID, localize brick with ν interaction ( ε ≈ 70 ÷ 90%) momentum (via MCS), Spectrometer: � ID, charge and momentum dE/dX, e/ γ separation, general event kinematics Up to p ~ 25 GeV : Op/p < 25%; Wrong charge < 0.3% 2008.08.25 COSMO08 G.Sirri , INFN Bologna 9
The OPERA detector SuperModule 1 SuperModule 2 0.68 0.68 kton kton Veto plane Target and Target Tracker 6.7 × 6.7 � 2 (RPC) ● Target : 77500 bricks, 29 walls High precision tracker Instrumented dipole magnet ● Target tracker : 31 XY doublets of 256 ● 6 4Ffold layers of ● 1.53 � scintillator strips + WLS fibres + multiF drift tubes ● 22 XY planes of RPC in anodes PMT for both arms • Brick selection Muon spectrometer (8 × 10 � 2 ) • Calorimetry 2008.08.25 COSMO08 G.Sirri , INFN Bologna 10
Target Filling ��� �������������������������� �������������������� �������������������� ���������� ��������������������� ������������������������� ����������������� ��������������������������������� ��������������������������������� ������������������ ������"����� �������� ��������������!��������� �"��������"����#���� ������!�����������$ 2008.08.25 COSMO08 G.Sirri , INFN Bologna 11 now
Target Filling January 2007: start filling target July 2008 : end of filling target 146200 bricks today � 1.26 kton 6 m 6 m 2008.08.25 COSMO08 G.Sirri , INFN Bologna 12 now
Automatic emulsion scanning Based on the tomographic acquisition of emulsion layers. The experiment size requires a scanning speed of ~20 cm 2 /h. ~ 30 bricks will be daily extracted → thousands of cm 2 /day) S,UTS in Japan (Nagoya) European station 90% ÷ 95% track finding efficiency 90% ÷ 95% track finding efficiency 10 ÷ 10 4 fake tracks / cm 2 (slope < 0.5) Commercial products Dedicated hardware Software algorithms Hard coded algorithms High speed CCD Camera (3 kHz) Customized commercial optics and Synchronization of objective lens and stage mechanics + asynchronous DAQ software 1.5h/brick for 100 predictions Running at ~20 cm²/h 2008.08.25 COSMO08 G.Sirri , INFN Bologna 13
Tracks in Emulsion Camera 15 tomographic views Field of view Move the focal plane 44 � m Emulsion 44 µm 390 9m × 310 9m Track segment: aligned clusters Track segments found in Passing'through tracks Vertex reconstruction 8 consecutive plates rejection in the brick 2008.08.25 COSMO08 G.Sirri , INFN Bologna 14
Expected number of events full mixing, 5 years run, 4.5 x 10 19 pot/year, 1.35 kton τ identification Efficiency ε = ε trigger x ε brick x ε geom x ε primary_vertex NOT included 99% x 80% x 94% x 90 % ε(%) τ decay signal Backgroun BR(%) channel d Om 2 =2.5x10 ,3 eV 2 with τ identification τ→ 9 17.5 17.7 2.9 0.17 τ→ e τ→ e 20.8 20.8 17.8 17.8 3.5 3.5 0.17 0.17 τ→ h 5.8 49.5 3.1 0.24 τ→ 3h 6.3 15 0.9 0.17 ε x BR = 10.6 % 10.4 0.76 Total Main background sources: , large,angle muon scattering in lead If no primary muon identified: , charm production and decays , hadron re,interactions in lead 2008.08.25 COSMO08 G.Sirri , INFN Bologna 15
ν � ↔ ν τ discovery potential Discovery probability vs � � 2 90% CL exclusion plot 5 year of data taking 4' σ evidence ������������������ 3' σ evidence ������������ � m 2 (10 '2 eV 2 ) 2008.08.25 COSMO08 G.Sirri , INFN Bologna 16
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