Oscillation Project with Emulsion tRacking Apparatus F. Juget Institut de Physique Université de Neuchâtel Neutrino-CH meeting, Neuchâtel June

Physics motivation The OPERA detector Physics performance Conclusion

Motivation Appareance search of    oscillations in the parameter region indicated by S-K for the atmospheric neutrino deficit. P(    ) = cos 4 (   ) sin 4 (  23 ) sin 2 (2  23 ) sin 2 (1.27  m 2 L/E) P(   e ) = sin 2 (   ) sin 2 (  13 ) sin 2 (1.27  m 2 L/E)  m 2 =  m 2 23 ≈  m 2 13 Search for   e : put new constraints on    Actual result: (CHOOZ): sin 2  13 < 0.1 => Search for  appearance in the CNGS  beam Recent results Super-Kamiokande (NOON 2004) best fit:  m 2 = eV 2 sin  23 = eV 2 <  m 2 < eV 2 sin  23 > 0.9 } at 90% CL P(    ) = cos 4 (   ) sin 4 (  23 ) sin 2 (2  23 ) sin 2 (1.27  m 2 L/E)

OPERA/CNGS: long base-line project Seach for   appearance at the Gran Sasso laboratory 732 km from CERN Beam optimized for   appearance For  m 2 = and maximal mixing (sin 2 2  expect 23  CC/kton/year at Gran sasso pot/year at CERN (shared mode)

Principle: direct observation of  decay topologies in  cc events The basic unit: The BRICK sandwich of 56 Pb sheets 1mm + 57 emulsion layers bricks are needed → target mass: 1.8 ktons requires high resolution detector (  m): use photographic emulsions Needs large target mass: alternate emulsion films with lead layer

8 m Target Trackers Pb/Em. target Electronic detectors  select  interaction brick Emulsion scanning  vertex search Extract selected brick Pb/Em. brick 8 cm Pb 1 mm Basic “cell” Emulsion  decay search  spectrometer  e/  ID, kinematics   ID, charge and p  (DONUT) OPERA an hybrid detector What the brick cannot do:  trigger for a neutrino interaction  muon identification, charge measurement => need for an hybrid detector

Spectrometer 1 May 17

Last slab placing 19/5 (2.5 weeks in advance)

May 25: Main structure start (drilling the floor for fixing)

Detector installation schedule Brick walls and Target Tracker walls for SM1 Aug. 04 – Jun 05 Brick walls and Target Tracker walls for SM2 Jul. 05 – Mar 06 Installation of Brick Manipulator System (BMS) Beginning 2005 Start filling walls with bricks July 2005 Ready to take data for 2006

  CC interaction identified looking at the  decay => search for a kink in consecutive emulsions  decay channels:      (17%)   e e    (18%)     h + neutrals +  (49%)  3h + neutrals +  (15%)

Basic Ideas of Volume Scanning 3D reconstruction of microtracks Track linking through emulsion base Track linking through different emulsion sheets Vertex/Decay Reconstruction Track processing takes further steps to reach physics goals

Automatic Scanning:Nagoya and Europe R&D efforts Bari, Bern, Bologna, Lyon, Münster, Napoli, Neuchâtel, Roma, Salerno Routine  10cm 2 /hr Near future  20cm 2 /hr S-UTS prototype at Nagoya Dedicated hardware Hard coded algorithms Europe prototype (Neuchâtel exemple) Commercial products Software algorithms   ~ 2mrad  x ~ 0.5  m

 Track M Track D 1 Manual Check Track M was not found in sheet 29; Track D 1 was not found in sheet 30; Track D 2, pointing to interaction vertex, was found only in upstream layer of sheet 29 (electron?); Sheet 30 Sheet 29 Track M Track D 1 Track D  m Reconstruction Track M having beam slopes (0.056; ) and track D 1 having slopes intersect in a kink topology; Brick exposed to  beam at 7 GeV/c Detected  interaction vertex

Movie from E. Barbuto Salerno University

Event reconstruction with emulsions Topological and kinematical analysis event by event High precision tracking (  x < 1  m ;  < 1mrad) –Kink decay topology –Electron and  /  0 identification Energy measurement –By Multiple Coulomb Scattering  P/P < 0.2 after 5X 0 up to 4 GeV

 “Long” decays (   ) kink angle  kink > 20 mrad kink  kink Long decays Pb (1 mm)  “Short” decays (   ) impact parameter I.P. > 5 to 20  m plastic base I.P. Short decays emulsion layers Pb (1 mm) Exploited  decay topologies

Expected number of background events (5 years run with  kton average target mass) Total per channel Hadronic background.174 Large angle μ scattering Charm background total τhτhτμτμτeτe 1. Charm background : Being revaluated using new CHORUS data: cross section increased by 40% πμ id by dE/dx would reduce this background by 40%  tested at PSI (pure beam of π or μ stop)  x 18 ! in the μ channel without a spectrometer 2.Large angle μ scattering : Upper limit from CERN Calculations including nuclear form factors give a factor 5 less  will be measured this autumn in X5 beam with Si detectors 3.Hadronic background : Estimates based on Fluka standalone : 50% uncertainty Extensive comparison of FLUKA with CHORUS data and GEANT4 would reduce this uncertainty to ~15% τ3hτ3h.44

Expected number of events Channel Signal (  m 2 (eV 2 ) )  BR  BR Background e % % 0.31  % % 0.33 h % % h % % 0.44 Total % ~ % 1.5 full mixing, 5 years 6.7 x10 19 pot / year

Probability of claiming a 4  discovery in 5 years SK 90% CL Opera, no beam upgrade but half background Opera with beam*2 Opera with beam*3 Opera with beam*4 Opera no beam upgrade Opera with foreseen beam upgrade (1.5)

Electron identification and Energy measurement Identification : Method based on shower identification and on Multiple Coulomb Scattering of the track before showering e/  ratio is measured with Cerenkov and ECC (test beam) ECC 1.42±0.17 Cerenkov 1.46±0.11 at 2GeV ECC 0.41±0.05 Cerenkov 0.32±0.03 at 4GeV 5X 0 ( ~ ½ brick) 1 mm 5 cm Energy : Measured by counting the number of track segments into a cone along the electron track Multiple Coulomb Scattering before a few GeV

Electron identification efficiency e.m. and hadronic shower simulated in OPERA brick. No background simulation. Analysis based on neural network. Note that in the range 2  15 GeV and for particle crossing at least 2.5 X 0, eID and pID is ~ 99%.  OK for both τ  e and ν μ  ν e searches efficiencies for showers followed for 36 ECC (6.4 ~X 0 ) To be tested in DESY with a pure electron beam at 1-6 GeV

Expected signal and background for the    e search º3º  e CC beam  NC  CC ee signal  º7º º9º Statistique sur le bdf…

OPERA sensitivity to  13 Only 15% increase scanning because the event location is already performed for  search. Preliminary 2.5x10 -3 eV  7° sin 2 2  13  m 2 23 (eV 2 ) pot/yr pot/yr syst. on the e contamination up to 10% By fitting simultaneously the E e, missing p T and E vis distributions we got the sensitivity at 90% NC   e e beam    Events Missing p T (GeV)

Activities of the swiss groups Bern and Neuchâtel are involved in OPERA  Electronics Frontend Chip for the target tracker (Bern) Test and calibration of PMT for the Target Tracker (Bern)  Scanning 1 microsope in each lab is already working A third one will be installed this year in Bern Development of an automatic emulsion changer (Bern)  Simulation Geant4 simulation (Neuchâtel)

Conclusions  Important Physics Program First evidence of  -  appearance in few years data taking In a five years run: 18 signal (SK best fit) and 1.5 background events Studies to improve efficiency and to reduce the background Significant measurement of  13  Detector construction and installation Installation of detector in progress Detector (and CNGS beam !) will be ready in 2006 Scanning strategy still to be optimised Very low background is the key issue