n m t n OPERA Maximiliano Sioli Bologna

n m→ t n OPERA Maximiliano Sioli (Bologna University and INFN) for the OPERA Collaboration NOW 2006, Conca Specchiulla, Sep 9 -16, 2006 Maximiliano Sioli, NOW 2006

The OPERA Collaboration (37 groups, ~160 physicists) Belgium IIHE (ULB-VUB) Brussels Bulgaria Sofia China IHEP Beijing, Shandong Croatia IRB Zagreb France LAPP Annecy, IPNL Lyon, IRES Strasbourg Germany Hamburg, Münster, Rostock Israel Technion Haifa Italy Bari, Bologna, LNF Frascati, L’Aquila, LNGS, Naples, Padova, Rome La Sapienza, Salerno Japan Aichi, Kobe, Nagoya, Toho, Utsunomiya Russia INR Moscow, ITEP Moscow, JINR Dubna, Obninsk Switzerland Bern, Neuchâtel, Zurich Turkey METU Ankara Maximiliano Sioli, NOW 2006 2

Outline Physics goal of OPERA The OPERA detector Physics performances: – nm nt oscillation channel – nm ne oscillation channel Low intensity run Conclusions Maximiliano Sioli, NOW 2006 3

Physics motivation Atmospheric neutrino anomaly interpretable as nμ→nt oscillation CHOOZ: no nμ→ne oscillation provide an unambiguous evidence for n μ → n t oscillation in t h e region of atmospheric neutrinos by looking for ν τ appearance in a pure ν μ b e a m CNGS beam (1999) CNGS 1 (2000) Maximiliano Sioli, NOW 2006 4

The CNGS beam: overview Beam main features L 732 km <E > 17 Ge. V L/ <E > 43 km/Ge. V “Off peak” ( e+ e)/ 0. 87% Limiting for / 2. 1% prompt negligible nm ↔ ne searches Radial distribution at LNGS Event rate for OPERA (at 4. 5 x 1019 pot/year, 200 days/year): ~6200 (CC+NC)/year, ~25 t CC/year @ 2. 4 x 10 -3 e. V 2 Maximiliano Sioli, NOW 2006 5

OPERA ≡ Oscillation Project with Emulsion t. Racking Apparatus Primary goal of OPERA: direct observation of t leptons produced in nt. CC interactions t decay “kink” t t ~ Detector resolution must be O(1 mm) m m 0. 6 Target mass must be O(1 kton) for Dm 2 =O(10 -3 e. V 2) ECC concept adopted Maximiliano Sioli, NOW 2006 6

The Emulsion Cloud Chamber technique ECC ≡ sequence of emulsion-lead layers: 1 mm Lead: target mass t Emulsion: tracking device Pb 3 m 12. 9 c It allows high spatial resolution capability and the possibility to have large masses in a modular way . 10 cm In OPERA, the basic ECC unit is the “BRICK” 7. 8 cm 8. 3 kg Sequence of 56 lead sheets + 56 emulsion layers (10 X 0 for p measurements and e. ID) Maximiliano Sioli, NOW 2006 7

Target Tracker: trigger and localize the n interaction Spectrometer: measure m ID, charge and momentum Target superm Spectrometer odule ECC: measure kink, p. ID, momentum (via MCS), d. E/d. X, e/g separation, general event kinematics “changeable sheets” Pb/Em. brick Vertex Location 8 m ECC cell Extract selected brick 8 cm Maximiliano Sioli, NOW 2006 Pb Emulsion 1 mm 8

The Gran Sasso Laboratory (Central Italy, 900 m a. s. l. ) CNGS External Lab Underground Lab: 1400 m of rock shielding: Cosmic Ray flux reduced by a factor 106 wrt surface; very reduced enviromental radioactivity. Maximiliano Sioli, NOW 2006 9

OPERA general structure Hybrid detector (electronic + emulsions) with a modular structure: 2 supermodules = 2*(31 walls + 1 spectrometer) ↳ 31 walls = 31*(56*64 bricks + 1 scintillator tracker plane) Total mass = 1766 tons, # of bricks = 206336 SM 1 SM 2 n Target sections Magnetic spectrometers Maximiliano Sioli, NOW 2006 10

dipolar magnets (1. 55 T) Spectrometers RPC+XPC ( ID + shower energy) drift tubes (muon momentum) 12 Fe slabs per magnet side coil e 8. 2 m coil 12 1 - charge ≅ (0. 1 -0. 3)% Dp/p ≃ (20 -25)% m. ID ≳ 95% (with TT) 12 Fe (5 cm) B= 1. 55 T RPC 22 gaps filled with RPC Precision Trackers (drift tubes) event recorded in the first magnet Iron slabs coil Total Fe weight ~ 1. 2 kton Maximiliano Sioli, NOW 2006 11

Target section: TT + Walls TT ≡ plastic scintillators Ø Trigger neutrino interactions Ø Find the brick to be extracted Ø Muon tracking and ID Suspension from the top Height ~ 6. 7 m Ø XY planes (7000 m 2 in total) readout by WLS fibers Ø 1000 PMT Hamamatsu (64 channels) Maximiliano Sioli, NOW 2006 Tensioning from the bottom 12

OPERA in pictures Details of the first spectrometer BAM at LNGS: ~1000 bricks/day at regime Maximiliano Sioli, NOW 2006 BMS ready to fill the target 13

Automatic emulsion scanning Based on the tomographic acquisition of emulsion layers The experiment size requires a scanning speed of ~20 cm 2/h. (tens of n interaction/day → thousend of cm 2/day) Dedicated hardware Hard coded algorithms Commercial products Software algorithms European station S-UTS in Japan (Nagoya) - Ultra High Speed CCD Camera for S-UTS (3 k frames/sec) - 15 m/brick for 15 predictions - 1 h 35 m/brick for 100 predictions - Running at ~20 cm 2/h - High efficiency (>90%) and high purity - resolution ~2 mrad Maximiliano Sioli, NOW 2006 14

Search for ↔ t oscillations: expected number of events t decay channel signal (Dm 2 = 2. 4 x 10 -3 e. V 2) (Dm 2 = 3. 0 x 10 -3 e. V 2) τ e 4. 3 6. 7 0. 23 τ μ 3. 6 5. 6 0. 23 τ h 3. 8 5. 9 0. 32 τ 3 h 1. 1 1. 7 0. 22 Total 12. 8 19. 9 1. 0 background Full mixing, 5 years run, 4. 5ˣ 1019 pot/year, 1. 8 kton fiducial mass Maximiliano Sioli, NOW 2006 15

t discovery potential 90% CL exclusion plot (i. e. in absence of a signal) in 5 years of data taking Probability Dm 2 (e. V 2) Probability to observe, in 5 years, a signal far away 4 s from the bg sin 22 qmt Dm 2 (e. V 2) Uncertainties on background (33%) and on efficiencies (15%) are accounted for Maximiliano Sioli, NOW 2006 16

nm ne oscillation channel Ø Due to its good e. ID capability, OPERA is well suited for e searches Ø Main backgrounds are: Ø ne beam contamination (larger contribution) Ø p 0 identified as electrons produced in nm. NC or nm. CC with the muon not identified Ø t e from nm nt oscillations q 13 signal t e nm. CC nm. NC ne. CC beam 9º 9. 3 4. 5 1. 0 5. 2 18 8º 7. 4 4. 5 1. 0 5. 2 18 7º 5. 8 4. 6 1. 0 5. 2 18 5º 3. 0 4. 6 1. 0 5. 2 18 Efficiency 0. 31 0. 032 0. 34 x 10 -4 7. 0 x 10 -4 0. 082 5 years data taking, nominal CNGS, Dm 223=2. 5 x 10 -3 e. V 2, sin 22 q 23=1 Maximiliano Sioli, NOW 2006 17

nm ne sensitivity n S/B enhanced with simultaneous fit of Evisible, Eelectron and missing pt Sensitivity fully dominated by statistics 6. 4 o 2. 5 x 10 -3 e. V 2 7. 1 o sin 22 q 13 n pot (x 1019) Maximiliano Sioli, NOW 2006 18

Low intensity run (18 30 Aug 2006) 10. 5 ms 50 ms 10. 5 ms 1. 7 x 1013 pot/extraction TOTAL: 7. 6 E 17 pot Wed 30 Aug. 2006 05: 00 1 st 2 nd extraction Maximiliano Sioli, NOW 2006 Fri 18 Aug. 2006 13: 40 EXT 1: 3. 81 E 17 pot EXT 2: 3. 79 E 17 pot MD days Unix time 19

Event selection by electronic detectors using GPS timing information Ext 1 Ext 2 50 ms Zoom on the spill peaks 10 µs Δt first extraction (ns) N. of in-spill events in the whole run ~320 Δt closest extraction (ns) Maximiliano Sioli, NOW 2006 20

Beam events CC event originated upstream of the detector (rocks) CC event originated in the first magnet First TT CS connections successfully tested! Maximiliano Sioli, NOW 2006 21

Angular distribution of recorded events nary! elimi ry pr Ve y qy >0 qy <0 z MC (only cosmics) Zoom on beam events coming 3. 5° from below DATA Angle with respect to the horizontal direction (deg) Maximiliano Sioli, NOW 2006 22

Summary n n n The main aim of the OPERA experiment is to unambiguously confirm/disproof the t atmospheric oscillation channel The low intensity CNGS run operated smoothly with good quality and stability The electronic detectors of OPERA took data almost continuously and with the expected tracking performances More than 300 in-spill events have been recorded with a clear time distribution The detector is ready for the next phase: observing neutrino interactions inside ECC bricks Maximiliano Sioli, NOW 2006 23

Spares Maximiliano Sioli, NOW 2006 24

t- 17. 4% h- nt (np 0) 49. 5% t- kink angle qkink > 20 mrad m- n m n t t- “Long” decays 17. 8% t- t decay topologies e- ne nt 3 h- nt (np 0) 14. 5% “Short” decays impact parameter I. P. > 5 to 20 m emulsion layers Long decays kink qkink I. P. Pb (1 mm) t m t e t h (np 0) t 3 h (np 0) Short decays t m t e Maximiliano Sioli, NOW 2006 plastic base 25

Angular and position resolutions For q ≃ 0. 013 rad q 2. 1 mrad 0. 4 m Maximiliano Sioli, NOW 2006 26

Tracking resolution with emulsions 100 mm Ag grain after development M. I. P. Track dx m. i. p. Track intrinsic tracking accuracy Fog s = 0. 06 mm Compton Electron § Grain Density: ~30 grains / 100 m for m. i. p. § Grain Size: 0. 2 m (original crystal) 0. 8 m (after development) sx = 0. 2 m/ 12 = 0. 06 m § However, DAQ effects spoils the resolution (CCD pixel size, stage movements); routinely we have sx = 0. 3 m Maximiliano Sioli, NOW 2006 27

Fuji emulsions, from production to scanning Production at FUJI Refreshing Mass production started April 2003 (~150, 000 m 2) Refreshing in the Tono Mine in Japan: started Refreshing conditions: • Humidity : > 95% • Temperature : 30 ºC • Time : ~ 3 days Transportation from JAPAN to LNGS First batch to LNGS by June ’ 04 Brick assembly Experiment Cosmic Ray exposure Scanning Maximiliano Sioli, NOW 2006 Emulsion storage barrack ready in Hall B 28