τ detection and ν oscillation
Gaston WILQUET
Symposium in honorem Prof. Jean SACTON Brussels, 7 - 8 September 2000 Contents
• The neutrino identity (brief) • Limits on neutrino masses • Neutrino oscillation phenomenology (brief) • Status of search for neutrino oscillation
• OPERA : search for νµ⇔ντ oscillation in LBL accelerator experiment (refer to K.Niwa’s talk) • The neutrino mass and the mass budget of the Universe (if time allows) The Standard Model neutrino
• The electron-neutrino νe is the massless, chargeless, colourless, spin 1/2, partner of the electron in the left handed SU(2) × U(1) lepton doublet
• Neutrinos also exist in 3 families like the other fermions (measured at LEP from the width of the Z0; why? why 3?)
νννe µτ −−− e LLL µτ • The lepton numbers Le , Lµ , Lτ are conserved independently B.R.(µγ− →<× e−− ) 51011 • Only ννLR and have CC and NC weak interactions (P conservation is fully violated)
• If they exist, RL and are sterile νν
Massless ν and ν are distinct by their observable helicity ≡ invariant chirality
Massless neutrinos may not be overtaken and their spin cannot be flipped What if neutrinos have (even tiny) mass Dirac or Majorana neutrinos?
− • νβ+ emitted in decay has vν may be overtaken and undergo spin flip → − + • Is it different from the − emitted in decay? They only differ by L If yes: Dirac neutrinos, like other fermions, distinguished by L =±1 eigenvalues νβ If no : Majorana neutrinos, νν≡ apparent distinction is artefact of - their V-A interactions - the difficulty to "flip spin" ν Limits on the neutrino masses: 1/ Direct measurements from decay kinematics ν • @%C.L.95 m..eVe < 22− 2 3 33 − from end of E − spectrum in HHee→++ ν e e (Troitsk and Mainz experiments, 2000) • mkeV<170 @%C.90L νµ µ ++ from E + in πµν→ µ (Assagam et al, PSI, 1996) • @%C.L90 m.MeVντ <18 2 ±± from phase space in → 35() ττ()ν (LEP -ALEPH 2000) τπν Limits on the neutrino masses: 2/ Big Bang cosmology 10 2 •≈×≈ At T210K2MeVm ν (t1kT0.25s) =() ≈ νγ γνν and / decouple ννγγ : +↔+ νγ nn≈ TT≈ • Taking account of - the thermodynamics of fermions/bosons - the adiabatic expension of the univers +− + − - γγγ and e/e decouple: e+↔+ e at T ≈ me ≈ 0.5eV 3 n03==n(03 412cm− ) = 113 cm− at present epoch ν 11 γ 4 1 T21o ===≈( )3 T0 ( 2.73 K ) 1.9 K × 0eV−4 ν 11 γ νν ν -4 • Yet undetected primeval neutrinos are non-relativistic if mν >10 eV 2 003H0 − 3 m×≈ n = ρρ meV≤ 60 ∑ νi i Limits on the neutrino masses: 3/ Supernovae SN1987A • February 23, 1987, 7h33 UT, 23 neutrino interactions in 3 underground experiments (Kamiokande, Japan; IMB, Ohio; Baksan, Caucase) in 12.3 s time gate • SN1987A: death of Sanduleak in LMC at 150 000 ly 46 58 SN-II models: 99% of ~2. 10 J released → ~10 ν with after 150 000 y : 10s flash of ~4. 1043 ν cross the Earth • From measured and model energy spectrum model emission time dispersion measured arrival time dispersion Confirmation of the SN-II models meV≤∼ 25 ν e • Identical fluxes of all ν and ν species expected νν− Events expected to be ee (much larger +→+nep cross-section) Limit on the neutrino masses: 4/ 0νββ decay experiments • The nuclear ν 0νββ decay experiment is THE spin-flip experiment (A,Z)→++ (A,Z 2 ) 2 e− L = 2 Process possible if the − - emitted right-handed e together with e - _ e e − ν ν absorbed as left-haν nded to produce e e e ∆ e ν W- Massive Majorana neutrino : d u W- ννee≡ and spin flipped d u T21090(Ge76→+> 76 See)− 25 y @ %C.L. d u 1 2 32 34 d u m.eV≤ 046 ν e B.Pontecorvo Massive neutrinos: 1957 Mixing & Neutrino oscillations B.Pontecorvo, V.N. Grimov 1967 ννl le,,= µτ family eigenstates k k,= 1 3 mass eigenstates νν 3 e 1 llkk= ∑U k,=1 ν ==U νµτννle,, ννµ 2 3 2 U = 1 τ 3 ∑ k k,=1 4 (6) parameters 3 Uα lk Dirac (Majorana) 1 (3) phases Straightforward extension to more than 3 neutrinos families, e.g. sterile neutrinos Oscillation cannot distinguish Dirac from Majorana neutrinos Propagation phase -i( E t - p L ) − i( m2 /( 2E ))L E ≈>>⇒p m e kk ≈e k + 3 u µ τ − + π + W ντ :Uτk νµµ:U k ν k ∑ + W k1= d d u n ddp u u Coherent propagation of different mass eigenstates over long L Oscillation probability (in practical units) P ((ν llllL0= )→=−νδ'' ()) L 13, meVLkm22[][] 4UUUU127Re(** sin2 . kk ' ∑ lk'' lk ' lk ' lk EGeV[] kk,'> k Mixingsdefine Maximum L/ E Oscillation term probability Sum on ∆ pairs of mass eigenstates 222 222 ∆∆∆∆mmmkk'' = k − k mmm0 12 + 23 + 31 = Neutrinos oscillate if massive and masses are non degenerate and if mixing between mass and weak eigenstates One mixing negligible : effective 2-family approximation cosθθeeµµ sin e.g. ν ≈ν U ≈ 1 mixing angle, no phase τ 3 − sin cos θθeeµµ νν θ mL2 P2127()sinsin(.)→=22 12 eeµµ E All mixings small : effective 2-family approximation ∆ 1 θθeeµτ θθ U1≈− µµτ all νl ≈νk e θθτµτ −−e 1 νν θ mL2 P2127()()sin(.)→= 2 kk ' lllll''≠ E ∆ Strong mass hierarchy : effective 2-family approximation ∆ δ if mm,m312 like quarks and charged leptons ν3 22222 ∆δmmmmm=−≈−31 32 222 2 mmm=−21 ∆m mm22 ν δm2 2 ⇓ ν1 L/ E δregion where ∆ m2 L/ E causes oscillation 2 mν and mL/E2 ≈ 0 ⇓ 22eff 2 P(ννl→≈ l' θ≠ l )∆ sin2127 ll' sin ( . m E / L) 2 sin2 24eff = U U ll'θ l33 l' Physics governed by: • ∆m2 • family composition of ν3 only Example of 2-family approximation: large mixing and strong mass hierarchy oscillation in phase (2-family like) from source composition from first process E = 1GeV strong mass hierarchy ∆λmeVkm232=×310− → = 825 δΛmeVkm272=×110− → = 2.5 ×10 7 large mixing -0.567 0.820 -0.0782 U = 0.515 0.279 -0.811 0.643 0.500 0.580 oscillation damping for large ∆m2 ∆ 1 mL 2 1.27 sin dispersion and resolution in⇒ L/E 2 2 E Matter effect on neutrino oscillations • Propagation phase in matter for weakly interacting particles ipx−−iEt in px iEt ee⇒ e e nfE=+12πρ (0)/ Z EMeV=<−= 1 : 0 | n 1 | 6.10−−19 [ gcm 3 ] 1 ν A • ννννes , , , have different interact ions thus nes,,, : νν+ µτeq−− ,→+ eq , (NC) ee,,µ ττ ,, ρ −− ννee+→ee (CC) µ s ν no interaction • Mass eigenstates have different family eigenstatesµ τ composition ⇒ Coherence of mass eigenstates propagation is affected by matter Matter effect on neutrino oscillations Oscillation enhancement Oscillation can be enhanced by matter and is maximum for 2 given electron density ρ∆θR (Em | , ) where mixing is full even if mixing in vacuum is extremely small MSW effect If neutrinos travel through medium where ρρeR varies and crosses slowly (e.g. through the Sun): e created in the Sun core may disappear totally into ν µ by reaching the Sun surface. ν Energy spectrum distortion ρ = ()E R ρ R Solar neutrino oscillation experiments Firsts experimental hints of neutrinos oscillation dates back from 1968 The solar neutrino deficit problem Radiochemical Experiments − ν e +→(Z,A)e +(Z + 1,A) τ (Z,A+≈ 1) 10 days Water Cerenkov −− Counting experiment νν+→+ee ν + ee−−→+ν Low E threshold ee High E threshold Ga Cl nuclear fusion pp cycle Measure E, θ,t 1 4 + 4 H→ He + 2 e + 2 νe + 25 MeV 38− 1 Φν(Sun)=× 1.s 8 10 e 10-- 2 1 ν νBe Φν(Earth)= 6. 5 10 e cm s pp KAMIOKANDE CHLORINE SuperK • ν pp 99.75% of flux: bound by Sun luminosity ν very low energy B very difficult to detect extremely low rate GALLEX SAGE GNO •− Strong correlation Be B fluxes Eν(MeV) νν Measured event rates v.z. SSM predictions GNO +10. 8 65. 8−10. 2 Overall flux deficit 03./.≤≤ΦΦmeas pred 06 +78. 75. 4−74. +0. 015 0.. 465± 0 005−0. 013 A Crude solution meas pred ΦΦννpp≈ pp bound by Luminosity meas≈ 0.5 pred not well known ΦΦBBνν meas Be ≈ 0 not well known Φν pred pred Contradiction with strong ΦΦννBe− B correlation No astrophysical explanation νe→νx (νµ,ντ, νs) Oscillation Signals? Inside the Sun? Between Sun-Earth? χ2/NDF = 13.7/17 - Total flux too low by factor 0.3-0.5 in all 6 experiments - E spectrum distortion: Eν SuperK and SSM spectra agree (En >6.5 MeV): - Seasonal effects: Effect of Sun-Earth distance variation (besides 1/L2): SuperK flux time dependence agrees with 1/L 2(t) - Day/Night effect: matter effect inside Earth ? SuperK flux time dependence compatible with no effect D-N =−0.. 034 ± 0 022+0. 013 (D+N)/2 −0. 012 Flux deficit is the only smoking gun Y.Suzuki Neutrino 2000 Y.Susuki Vietnam 2000 Global fit for ν eactive→ ννν (µ or τ ) Allowed by SK All measurements Excluded by SK Day/Night spectrum only Allowed by Ga+Cl+SK Flux measurements only Oscillation in Sun matter @ 95% C.L. Oscillation in vacuum 2 Y.Suzuki Neutrino 2000 tan θ Y.Susuki Vietnam 2000 Note Global fit for ν eactive→ ννν (µ or τ ) ∆ 2 solutions at sin2 2θ ≈ 1 ∆ meV2452≈−10−− 10 meV272≈ 10− @ 95% C.L. νe→νs disfavoured at 95% C.L. 2 Y.Suzuki Neutrino 2000 tan θ Y.Susuki Vietnam 2000 Note Solar neutrino oscillation: Summary and Future The solar neutrino deficit can be explained by νe oscillation to active neutrinos θ @ 95% C.L. 2 sets of parameters are favoured by combining all data ∆meV252≈ 10− sin2 2≈ 1 (maximum mixing) 272− ∆meV≈ 10 @ 95% C.L. oscillation to sterile neutrinos is disfavoured SNO: measures independently the CC and NC solar event rates (NC rate unaffected by oscillation between active neutrinos) KAMLAND, BOREXINO: Very LBL reactors experiments (L>100 km) (from 2001) reach ∆m10eV252≥ − Neutrino Oscillation Experiments at Accelerators Motivation Search for neutrinos with masses of cosmological relevance: “Hot dark matter” candidates with mν > 1 eV -3 -4 with sensitivity to Posc > 10 -10 (given previous results) 2 mν > S∆m > 1 eV High sensitivity = low intrinsic background = well know source Large ∆m2 = high energy High sensitivity + Large ∆m2 = accelerator experiment Neutrino Oscillation Experiments at High Energy Accelerators CHORUS and NOMAD short baseline experiments Search for νµ−ντ oscillation -6 ντ appearance in ντ free (~10 ) νµ beam at the CERN SPS Wide Band Neutrino Beam -4 Sensitivity Posc(νµ−ντ) > 10 Same beam, Complementary concepts NOMAD: ντ signal extraction technique: excess of events in kinematics box No µ in final state CHORUS: Observation of the τ-lepton track produced in CC ντ interactions in 770 kg nuclear emulsion target : “kink” topology −13 ττ= 2.9 10 σ < βγcττ > ≈ 1.5 mm See talk by K.Niwa “Kink” NOMAD: Results •± expects 55.2 5.2 background events • observes 58 M. Mezzetto Neutrino 2000 ν P.Astier at al. CERN-EP-2000-049) • would have seenµ 14937 ντ , would all have oscillated −4 CHORUS Posc ().ννµτ→< 2 03 × 10 E531 NOMAD CCFR CHORUS: CHARM II • expects 1.2 background events • observes 0 ν • would have seenµ 10018 ντ , would all have oscillated ν µ ↔ ντ −4 P3410osc ().ννµτ→<× CDHS • CHORUS is able to detect events: relaxed selection cuts: 3.3 background expected 4 events observed E.Eskut at al. CERN-EP-2000-0??) Neutrino Oscillation Experiments at Low Energy Accelerators νν 22 Search for ν µ →ν e oscillation at rather large ∆m~.eV> 0 1 Sensitivity P( - ) > 10-3 πµosc µ e Concept: ννν • 800 MeV p beam dump • ++, stopped and decays at rest µµ • only ,,e produced (below 53 MeV) -3 •Almost no ν e (<10 ) • 800 MeV p beam dump Concept • 2ndry πµ , stopped in dump ν from Decays/Captures at Rest • mostly νννµµ , ,e produced ν ()π ++→ µν in ++πµ , decays at rest µ µ ν → ν below 53 MeV ++ µ e ν µ ()µ → e ννe µ oscillation • -3 Almost no ν e (<10 ) ++ ν e ()µ → e ννe µ ν → ν − µ e ν µ (X)µνN → µ −− oscillation search −− ()µ → e νν ν µ e µ ν e ()µ → e ννe µ EMeV< 53 ()π ++→ e ν ν ν e e Signal: Inverse β decay + νe + p→e n ν e 53MeV LSND expects 50.3 ν background events Results e observes 83 KARMEN-II excess 32.7± 9.2 expects 12.29± 0.69 ν background events e all measurememts well fitted by observes 11 ν µ →ν e oscillation LSND: G.Mills Neutrino 2000 KARMEN2: K.Eitel Final word by MiniBOONE at Fermilab in 2002(3) Preliminary joined KARMEN2-LSND analysis JoinedJoined likelihood likelihood 3 “sensible” common favoured regions Statistical analysis of small event numbers 90% is very touchy: Bayesian v.z. frequentist 99% variations LSND alone CERN 2000-005 Yellow report KARMEN2, NOMAD,BUGEY The result of two analysis is NOT the overlap K. Eitel hep-ex-990906 excluded of an exclusion contour on a signal contour and New J. Phys. 2 K. Eitel hep-ex-990906 and (2000)1 New J. Phys. 2(2000)1 Atmospheric Neutrinos Oscillation Experiments Beautiful atmospheric neutrinos beam line 15 km νµ µ− + 500 km π µ− µ+ νµ ε+ 13 000 km νµ νε νµ Wide L/E range ν E measured (Φ + Φν ) u u L measured from θ ν ≈ 2 (Φ + Φ ) How precise are the flux e ν e P,He,…Fe MC predictions? Rates ()ννµ e R = Data most model and experiment systematic cancels ()ννµ e MC SuperK (Water Cerenkov tank) H.Sobel Neutrino 2000 Y.Susuki Vietnam 2000 Sub-GeV events Multi-GeV events R =±±0. 652 0 . 019 0 . 051 0 . 668 ±± 0 . 034 0 . 079 Soudan-2 (tracking calorimeter) R =±±068... 011 006 T.Mann Neutrino 2000 Macro (tracking calorimeter) B.Barrish Neutrino 2000 R =±±0... 731 0 028 0 044 Is the νννµµ deficit due to → X oscillation? What is ? ? ? ? Xeνννν s Not just rates, but L andτ E dependence of rates needed to confirm oscillation SuperK L(θ) and E dependence of rates MC no oscillation data Deficit depends on L and E Up-going Down-going cos θ = -1 cos θ = 1 L=13000km L=15km ∆m2 SuperK (eV2) ν µ ↔ ν τ -2 Signal region 10 Best fit 5 10-3 -3 sin2 21θ = (full mixing) • 3.2 10 ∆ m.2 =×32 10−32 eV 1.5 10-3 Macro 10-3 sin2 21θ = ∆ 2 −32 68 % C.L. m.≈×25 10 eV 90 % C.L. 99 % C.L. Soudan 2 sin2 209θ = . ∆ 10-4 m.2 ≈×79 10−32 eV sin2 2 θ SuperK checks of the oscillation hypothesis ν µ ↔ ντ Angular distribution Sub GeV Multi GeV MC best fit MC no oscillation data e-like µ-like SuperK checks of the oscillation hypothesis ν µ ↔ ντ MC best fit Angular distribution MC no oscillation data upward going νµ events MC best fit MC no oscillation L/E distribution data µ-like e-like higher lower energy energy ν µτ↔↔ννν or µ s oscillation? Discrimination based on L dependence of the matter effect in Earth ν µ ↔ ν s excluded at 99% C.L. ν µτ↔↔ννν or µ e oscillation? • Data is compatible with a some νµ−νe mixing •νµ−νe mixing must be small: - all νe data agree with model predictions without oscillation -large νµ→νe affect νe data significantly • Strong restriction from reactor experiments ν µτ↔↔ννν or µ s oscillation? Discrimination based on L (or θ) dependence of the matter effect in Earth Matter has no effect on ννµτ↔ σ oscillation: same NC Matter effects suppress ννs ↔ oscillation and suppression increases withµ E (not trivial!) Suppression increases with amount L of matter traversed (θ ) up-going µ from up-going νµ interacting in rock high energy events ν µ ↔ ν s ν µ ↔ ντ data ν µ ↔ ν s excluded at 99% C.L. -1 cos θ 0 L=13000km L=500km Absolute E spectrum at CHOOZ Nuclear Reactor Long e+ L=1km Base Line (1 km) experiment E+ spectrum measured R = e E+ spectrum expected if no oscillation Calculated and measured e ν flux and e energy spectra at L=0 agree to ~ 2% (Bugey 1995) Signal: Inverse n β decay + νe + p→e n E 3 MeV <>≈e+ Ee+ (MeV) LE/10≈ −3 R= 1.010±± 0.028 (stat) 0.027 (syst) No ν ex↔ ν oscillation signal Is ννµ ↔ e oscillation in atmospheric neutrinos fully excluded by CHOOZ/PaloVerde negative result? 3-family mass hierarchy model (Sun + Atmospheric signals) ∆m3510eV232≈×. − : atmospheric δm10eV252< − : solar SK 90% C.L. SK 99% C.L. CHOOZ excluded 90% C.L. Space for small ννµ ↔ e mixing 2eff 0 sin 2θeµ 1 Summary of oscillation signals ν e E.Lisi, 3-family mass hierarchy model G.Fogli, ... ∆ m155010eV2 ≈−..× −3 2 :atmospheric + negative ννex↔ : reactor 2 2 Uτ 3 Uµ 3 δ m1252<↔0eV−νν :slaro ν 3 e active ν ν full mixing µ 2 τ Ue3 νν 223− − LSND µ ↔ e at small mixing∆ sin21010θ ≈− ~ 2 2 large m≈−ν01 . 1eV ∆ requires 4 eigenstates and a s neutio r n m2 ∆m2 sun atm e.g. mm12<< mm 34 ∆ 2 mLSND How to probe/improve the atmospheric neutrino signal? Atmospheric neutrinos - project MONOLITH in Gran Sasso underground laboratory: More precision on E and θ, thus L being submitted, to start in2005 Long Base Line accelerator neutrinos - running K2K: KEK to Kamioka mine: L = 250 km νµ disappearance experiment νµ flux Near/Far (Super Kamiokande) detectors 1 year data taking : expects 29.3 ± 3.4 events sees 17 Compatible with atmospheric neutrino signal 2-sigma incompatibility with no oscillation Statistics still small Long Base Line accelerator neutrinos - approved, in preparation MINOS: Fermilab to Soudan mine: L = 730 km νµ disappearance experiment νµ flux Near/Far detectors νµ Energy spectrum distortion Near/Far detectors CC νµ / NC Data taking to start in fall 2003 Long Base Line accelerator neutrinos - submitted OPERA: CERN to Gran Sasso underground laboratory ICANOE: CERN to Gran Sasso underground laboratory ??? Belgium The OPERA IIHE(ULB-VUB) Brussels Long Base Line China IHEP Beijing, Shandong Neutrino CERN Oscillation COLLABORATION France Project IPLN Lyon, LAL Orsay, LAPP Annecy, Strasbourg Germany Berlin, Hagen, Hamburg, Münster, Rostock Israel Technion Haifa Italy Bari, LNF Frascati, Naples, Padova, Rome, Salerno Japan Aichi, Toho, Kobe, Nagoya, Utsunomiya Russia ITEP Moscow Switzerland Bern ~ 120 physicists Turkey METU Ankara Physics Motivation Confirm unambiguously νµ →ντ oscillation explanation to atmospheric νµ deficit How? - Direct observation of CC ντ +N →τ + X interactions Identified τ- track through 1-prong decay topologies −− τνν→ e τ e B.R. 17.8% −−→ B.R. 17.4% τµνντµ −−→ h (n 0 ) B.R. 49.5% τνπτ Requirements High sensitivity in 90% C.L. parameter space of SuperK 15..×≤ 10−−32∆ m ≤× 50 10 32 eV at full mixing How? Long Base Line experiment CERN CNGS new νµ beam points to OPERA detector in LNGS underground laboratory @ 730 km from CERN under Gran Sasso 3800 w.e.m. (1400m) E17GeV= ν → access to small ∆m2 L730km= ν Prompt free beam τ cosmic muons fluence ~ 1 m-2 h-1 How? High resolution Emulsion chambers (ECC) massive target (2kt) Why High resolution? τ − decay length≈ 05mm . Why massive? expected νµ event rate : 30 / day / 2kt CHORUS @ CERN: 700 kg plain emulsion target sees charm decays 2 kt plain emulsion : ∞ cost prohibitive DONUT @ Fermilab: ECC (Fe-emulsion tracker sandwiches) ντ discovery “On-line” event analysis - Segmented ECC target (“bricks) + Electronics detector - Remove, process and analyse daily ~40 bricks identified to contain~30 events DONUT ντ event − *+ νµN → µ Ds N + →Ds γ + →τ ντ CHORUS + →µ νµντ Instrumented & segmented target OPERA detector Muon spectrometer 3 Super-Modules Target: 24 planar modules - 652 t Module: Wall segmented in ECC bricks H-V Target tracker Wall: 6.75 × 6.75 m2 × 7.5 cm Tracker : 2 planes: H & V 3264 bricks 256 7 m scintillator strips Brick: 5” × 4” × 7.5 cm Strip: 2.6 × 1 cm2 × 7 m 56 cells light collected by WLS fibres read-out at both ends 10 X0 - 8.3 kg Cell: 5” × 4” × 1.3 mm by 64-channel PMT 1 mm Pb layer 8 tubes / plane 0.3 mm emulsion tracker OPERA ECC brick 235 000 bricks - 1.96 kt Full automatization of Brick assembly, packing Wall construction Removal of bricks fired by events 6.7 m 16 strips PMT * 4 WLS fibers = 64 strips PMT OPERA Scintillator strip target trackers PMT # p.e. distance to PMT (m) Light read at both WLS fibre ends Prob (0 p.e.) = 0.05% cables Target structure design: Role 1 of target trackers: identify event brick Brick size large: easier to identify small: less dead target ⊗ High scanning power + Low cosmic/beam background allows coarse tracking ν ⊗ Tracker resolution identify bricks efficiently ⊗ Largest target transverse dimensions ⊗ Brick removing strategy Role 2 of target trackers + ECC : Hadron shower calorimetry ∆E065. Kinematics analysis of ντ candidates =+016. E EGeV[] OPERA muon spectrometers High precision -identify, measure p and charge of muons drift tubes trackers -tag ν CC event µ 0.5 1 m 0.5 m m -kinematics analysis of ντ candidates -reduce the C→µ+ background - + target calo: measure Eν spectrum 1.55 T Dipole magnet 8 x8.75m2 2 Fe walls : 12 Fe plates + 11 RPC instrumented with RPC chambers H-V 3.5 cm strips 3 external high resolution trackers 2-plane 3-layer 35 mm drift tubes overall σx = 0.5mm Alignment is not a small issue no beam! no cosmic! σ Target p <<25% for p 25GeVx / c p Magnets Fe plates + RPC Wrong charge < 0.5 % z Spectrometer More on the emulsion, ECC and automatic scanning see K.Niwa’s talk in addition to be a high resolution target, 10 X0 bricks of ECC allow to: - identify electron by multiple scattering and shower analysis - measure electron energy by counting track segments in shower - detect photons - measure hadron and muon momentum by multiple scattering - identify muon by comparing p from multiple scattering and E from range ∆ Φθ∆σεCNGS Beam νν 2L[]= 730km E( GeV )=≈<→ 2 GeV E (ντ production) 247.[.] m232=× 32 10− eV thresh τ Spectrum optimized for ντ production and detection µ µτ→ 2232− ν ()Eνν⊗=PEL730km21m3210eVEosc ( | µτ,sin ==×⊗⊗ , . νννν ) () () E E17GeV= 45. × 1019 p.../ o t yr ν ⇒ 30ν µ interactions / day in a 2 kt detector (OPERA) 232−ττ ⇒=×50ν∆ τinteractions / yr for m 3 . 2 10 eV ⇒ 250 interactions in 5 years of run ντ 2 2 number ν∆τ interactions÷ ()m - - - - - Search for ντ candidates : τ→e ,µ ,h (π ,ρ ) “Long ” decays ( ~ 40 % of τ ) “Short ” decays ( ~ 60 % of τ ) E E E BaE Ba m m m se m Pb se Pb ul ul ul ul si si si si on on on on θ I.P kink ν ν . Not to scale Search for a “kink” Search for a large impact parameter At least 2nd high p track θkink > 20 mrad IP > 5-20 µm (depends of event depth) ε kink ≈ 90% ε 2t * ε IP ≈ 66% * 45% = 30% Total ε ≈ 54% very conservative Kinematics selection of ντ candidates in view of background reduction - - - ,µ ,h p e pT θ - τ- h ν Φ τ- ν mis sin g PT H H τ −−−−−→ eh,,(,)µπρ- τ − → h− High p, high pT reject Select isolated h- low E scatters outside H shower π-,K- decays h- scatters Monte-Carlo estimate of background ττµτ−−−−−−→→eh →Total νπ charm production 0.162 0.028 0.140 0.330 0 e CC andµ 0.006 0.006 large − scatter0.100 0.100 h− interaction0.1000.100 Total 0.168 0.128 0.240 0.530 4 The background is given in events for 2. 10 νµ DIS CC expected in 5 years data taking 2.25 1020 p.o.t. known to 50% test measurements in progress Events for maximal mixing and 5 years running τ decay ∆m2 (in 10-3 eV2 ) Bckgd Signal τ decay ∆m (in 10 eV ) Bckgd 1.5 3.2 5.0 5-year run e 1.7 7.7 18.5 0.19 µ 1.3 5.7 13.8 0.13 h 1.1 4.9 11.8 0.25 Total 4.1 18.3 44.1 0.57 2 2 number ν∆τ interactions÷ ()m expected number of events expected number 10-3 ∆m2 (eV2)10-2 Discovery potential 5-year run ) σ significance ( N observed events Probability - in equivalent # of σ - that background fakes signal > 54 events is a "DISCOVERY" at ≥ σ ∆m1810eV5232=×.− and years of run SuperK @ 90 % C . L .: 1 . 5×≤ 10−−32 m ≤× 5 . 0 10 32 eV ∆ Sensitivity 5-year run average 90 % CL upper limit for a large # exp.ts in the absence of a true signal ) 1 2 (eV 2 OPERA m ∆ @ sin2 (2θ) = 1 -1 10 ∆m2 (eV2 ) < 1.2 10-3 eV2 2 ye ars -2 10 SUPER-K 90%CL 5 ye ν ars 2000 νµ → ντ 90% C.L. -3 10 -2 -1 10 10 1 sin2 2θ Constraint on oscillation parameters 2 Number of events ÷× sin222mθ∆() ∆ for small m 2 ) 2 OPERA Example in case observed (eV 2 OPERA m number of events = expected ∆ -2 10 90 % CL in 5 years from SK best fit ∆m2 = 3.2 10-3 eV2 3.2 10-3 SUPER-K 90%CL ν 2000 -3 10 sin2 2θ Status - schedule CNGS beam - Construction approved December 1999 - Beam for physics May 2005 OPERA detector - Proposal July 2000 - Presentation to SPSC on September 5, 2000 Officious green light - Presentation to LNGSSC on September 11, 200 - Hope for approval end 2000 - Ready to take data in May 2005 Because of modular structure, need not be fully completed when beam arrives.