The CNGS project Pasquale Migliozzi INFN - Napoli
Discover the source of the atmospheric ν µ deficit ν µ ν τ oscillations? The proof: appearance of ν τ in a ν µ beam? ν µ... ν τ High energy, long baseline ν beam ( E CM >> m τ L ~ 1000 km ) Detection of τ leptons Sensitivity to m 2 = 1.6 4.0 x 10-3 ev 2 High background rejection and M target = O(1 kton)
The CNGS neutrino beam The beam will start in may 2006 ICARUS
CNGS beam layout at CERN site. Progress in the civil engineering work: excavation completed concreting started CNGS commissioning: May 2006
The CNGS and the expected number of events Nominal ν beam (Nov. 2000) Shared SPS operation 200 days/year 4.5x10 19 pot / year Average ν µ energy 17 GeV 5 year run Expected interactions in 1kton detector ~ 18000 ν µ NC+CC ~ 80 ν τ CC at m 2 = 2.5x10-3 ev 2 and full mixing An updated CNGS with a flux 1.5 more intense than the one approved in 2000 is now considered as the baseline option Limiting factor for θ 13 search: ν e + anti-ν e beam contamination ~0.87%
The ICARUS working principle d Ionization electrons paths Drift p ionizing track Ionization electrons drift (msec) over large distances (meters) in a volume of highly purified liquid Argon (0.1 ppb of O 2 ) under the action of an E field. With a set of wire grids (traversed by the electrons in ~ 2-3 µs) one can realize a massive, continuously sensitive electronic bubble chamber. d p
Experience and results: 600 ton detector Industrial module made of two independent LAr containers ½ module equipped and filled with LAr (300 ton) Total volume : 350 m 3 Readout planes: 2 x 3 ( 60,60,0 ), about 54000 wires Maximum drift distance: 150 cm Full scale technical run of the T300 detector in Pavia (2001) Cryogenics Wire chamber mechanics Argon purification Electronic noise High voltage for the drift PMTs for scintillation light collection Readout & DAQ Slow control Event reconstruction SW with real events and data analysis (ongoing effort) Event reconstruction 3 plane readout Calibration Resolution
ICARUS T600 (1 half-module out of 2) 300 000 kg LAr = T300
Cryostat (half-module) 4 m ICARUS T300 detector View of the inner detector 4 m 20 m Readout electronics
Long longitudinal muon track crossing the cathode plane 1.5 m 1.5 m18 m Cathode Left Chamber Right Chamber Track Length = 18.2 m de/dx = 2.1 MeV/cm Top View 3-D 3-D reconstruction reconstruction of of the the long long track track 3D View de/dx de/dx distribution distribution along along the the track track
Stopping muon reconstruction example µ + [AB] e + [BC] Run Run 939 939 Event Event 95 95 Right Right chamber chamber Induction 1 view B e+ C µ+ Induction 2 view A x (cm) 90 80 70 60 50 x (cm) 90 80 70 60 50 A 40 30 40 30 µ+ Collection view B C e+ 20 10 0 60 50 z (cm) 40 30 20 20 10 100 0 75 75 T e =36.2 e =36.2 MeV MeV Range=15.4 cm cm y (cm) 100 60 50 40 30 20
ICARUS in Hall B First First Unit Unit T600 T600 + Auxiliary Auxiliary Equipment Equipment T1200 T1200 Unit Unit (two (two T600 T600 superimposed) superimposed) T1200 T1200 Unit Unit (two (two T600 T600 superimposed) superimposed) 35 m 60 m
ν µ ν τ oscillations Analysis of the electron sample Exploit the small intrinsic ν e contamination of the beam (0.8% of ν µ CC) Exploit the unique e/π 0 separation At m 2 =3.5x10-3 ev 2 165 τ e events are expected Main background from charged current interactions of ν e in the beam 700 events are expected Statistical excess visible before cuts this is the main reason for performing this experiment at long baseline!
τ e search: 3D likelihood A simple analysis approach: a likelihood method based on 3 variables 3 variables E visible, P T miss, ρ l P T lep /(P T lep +P T had +P T miss ) Exploit correlation between them L S ([E visible,p miss T, ρ l ]) (signal) L B ([E visible,p miss T, ρ l ]) (ν e CC back) Events/12 kton x year 5 T600 modules, 5 years CNGS (4.5 x 10 19 p.o.t./year) 40 35 30 25 20 15 10 ν e CC + ν τ CC ν e CC ν τ CC, τ e Discrimination given by lnλ L([E visible, P T miss, ρ l ]) = L s /L B 5 0 Overflow -2 0 2 4 6 8 10 lnλ lnλ
ν µ ν τ appearance search summary T3000 detector (2.35 kton active, 1.5 kton fiducial) Integrated pots = 2.25 x10 20 Super-Kamiokande: 1.6 < m 2 < 4.0 at 90% C.L. (these numbers have to be multiplied by a factor 1.5) Several decay channels are exploited (golden channel = electron) (Low) backgrounds measured in situ (control samples) High sensitivity to signal, and oscillation parameters determination
To identify τ leptons, see their decay topology ν τ τ decay kink τ ~ 0.6 mm τ ν oscillation massive target The challenge AND decay topology micron resolution Lead nuclear emulsion sandwich Emulsion Cloud Chamber, in brief ECC
The Emulsion Cloud Chamber (ECC) Emulsions for tracking, passive material astarget 1 mm < µm space res. mass Established technique ν τ charmed X-particle first observed in cosmic rays (1971) Pb DONUT/FNAL beam-dump experiment: 7ν τ observed (2000) m 2 = O (10-3 ev 2 ) M target ~ 2 kton modular structure ( bricks ): basic performance is preserved large detector sensitivity, complexity required: industrial emulsions, fast automatic scanning Emulsion layers track segments Experience with emulsions and/or ν τ searches : E531, CHORUS, NOMAD and DONUT
Target Trackers µ spectrometer ν Pb/Em. target Pb/Em. brick A hybrid experiment at work 8 m Basic cell ν τ (DONUT) Extract selected brick 8 cm Pb Emulsion 1 mm Electronic detectors select ν interaction brick µ ID, charge and p Emulsion analysis vertex search decay search e/γ ID, kinematics
OPERA performance has been evaluated by using not only Monte Carlo, but it is based on test results with real data
Event reconstruction with an ECC High precision tracking (δx < 1µm ; δθ < 1mrad) Kink decay topology Electron and γ/π 0 identification Energy measurement Multiple Coulomb Scattering Track counting (calorimetric measurement) Ionization (de/dx meas.) π/µ separation e/π 0 separation Topological and kinematical analysis event by event mm 4 0 3 0 2 0 1 0 0-2 ECC exposure at CERN-PS π 0-1 0 1 mm 5 cm 1 mm 5X 0 ( ~ ½ brick)
Cell structure; exploited τ decay channels and topologies Long decays Long decays kink angle θ kink > 20 mrad kink θ kink τ e Progr. Rep. 1999 τ µ Progr. Rep. 1999 τ h (nπ 0 ) Proposal 2000 + ρ search Status Rep. 2001 Short decays impact parameter I.P. > 5 to 20 µm Pb (1 mm) I.P. emulsion layers Pb (1 mm) τ e Proposal 2000 τ µ Status Rep. 2001 An optimized channel by channel analysis is in progress. Ready by summer Short decays plastic base
Global kinematics for τ h (for events with a τ decay candidate) P ν µ NC τ ν Φ τ-h τ π/2 Φ τ-h H P t miss τ ν µ NC 1 P t miss (GeV( GeV/c) In these plots the improvements from γ detection are not taken into account
Backgrounds for the ν µ ν τ search Charm production Cross-section and charmed fractions based on neutrino data Large angle µ scattering Scattering off lead of µ (p= 6-10 GeV/c) experimentally studied by the Collaboration. Results in agreement with expectations Hadron reinteractions with kink topology the present estimate is based on a FLUKA simulation consistent with preliminary results from dedicated experiments
Room for improvements? Changeable Sheet : increase efficiency by 10-15 % CS reduce scanning load by a factor 2 More trials in brick finding Higher brick finding efficiency -> higher τ yield de/dx : background reduction by about 40% Charm background events have low momentum muons not identified a large fraction stops in the target region and is identified through the de/dx Better use of spectrometer: reduce the background in µ channel by about a factor 30%
Expected number of events full mixing; 5 years run @ 6.75x10 19 pot/year signal ( m 2 = 1.8 x 10-3 ev 2 ) signal ( m 2 = 2.5 x 10-3 ev 2 ) signal ( m 2 = 4.0 x 10-3 ev 2 ) Back Final Design CNGSx1.5 *) 9.0 17.2 43.8 1.06 With possible improvements 10.3 19.8 50.4 0.67 Aim at the evidence of ν τ appearance after a few years of data taking
Probability of nσ significance for different m 2 m 2 (ev 2 ) 3 years (20.3x 10 19 pot) P 3σ (%) P 4σ 5 years (33.8x 10 19 pot) P 3σ (%) P 4σ 1.8x 10-3 77.2(91.1) 46.8(68.2) 97.2(99.5) 87.4(96.2) 2.2x 10-3 94.9(98.9) 80.5(93.0) 99.9(100) 99.0(99.9) 2.5x 10-3 98.9(99.9) 93.9(98.6) 199(100) 99.9(100) 3.0x 10-3 100(100) 99.6(100) 100(100) 100(100) 4.0x 10-3 100(100) 100(100) 100(100) 100(100) Best fit of SK + K2K is m 2 = (2.6±0.4) ev 2 Fogli et al. hep-ph/0303064 The number in parenthesis are obtained assuming possible improvements
also competitive to search for ν e appearance Limits at 90% C.L. on sin 2 2θ 13 and θ 13 ( m 2 23 =2.5x10-3 ev 2 ; sin 2 θ 23 =1) Experiment CHOOZ MINOS 2 yr ICARUS 5 yr OPERA 5 yr CNGS 5 yr JHF 5 yr sin 2 2θ 13 < 0.14 < 0.06 < 0.03 < 0.05 < 0.025 < 0.006 θ 13 < 11º < 7.1º < 5.8º < 7.1º < 4.5º < 2.5º For details on the sensitivity dependence on δ CP see P. Migliozzi, F. Terranova hep-ph/0302274 (in press on PLB)
Accelerator expts. sensitivity vs δ CP (1) There are δ CP values for which the sensitivity on θ 13 is even better than the one compute in the 2-flavor approximation (δ CP =0). Notice the different behaviour on m 2 of the CNGS sensitivity Possible measurement of the sign of m 2 31?
Status of the construction The first holes for the detector installation in the Hall C have been drilled. The full detector is foreseen to be ready by mid 2006
The support structure for the brick walls" Tests of full scale prototypes Suspension from the top Bricks inserted from the side wall Height ~ 6.7 m Tensioning from the bottom Brick loading test
The Brick Manipulator System (BMS) prototype: a lot of fun for children and adults! The robotised Ferrari for insertion/extraction of bricks with vacuum grip by Venturi valve Tests with the prototype wall Carousel brick dispensing and storage system
Target Tracker: plastic scintillators 64 strips of 6.7 m length, 2.6 cm width, 1 cm thickness Readout by wavelength shifting optical fibres in co-extruded grooves Co-extruded TiO 2 coating N pe 10 9 Coextruded strip Kharkov (2m) 8 7 6 5 4 3 2 Well above 5 p.e. / readout end (in the middle: worst case for two-end readout) 1 Full scale prototype module 0 300 350 400 450 500 550 Length (cm) N pe versus Length (cm)
Dipolar magnet RPCs inside gaps: muon identification, shower energy Drift Tubes: muon momentum Total Fe weight ~ 1 kton coil Full scale prototype of magnet section constructed and tested 12 Fe slabs in total Fe (5 cm) RPC B= 1.55 T 8.2 m slabs base Iron in tendering-ordering phase Magnet during construction
Conclusion Construction of CNGS is well underway. The tunnel excavation is complete. The remaining construction work is on schedule (Beam starts by mid 2006) The ICARUS and OPERA experiments will permit An unambiguous direct evidence of τ appearance in a ν µ beam A measurement of m 2 at 20-30% Extend sensitivity for small ν µ ->ν e mixings (competitive with other experiments) The construction of the detectors is in progress and it is planned to be completed by mid 2006
CNGS Overview Expected Performance cf. Addendum of 1999: - priority to LBL ν τ appearance - - SBL experiment out -> result: lower energy beam - more compact layout of target / horn / reflector cf. Note of Dec. 2000: -> higher current in reflector -> space after target for monitor
T600 detector performance Technical run held in Pavia in Summer 2001: ascertain the maturity of large scale liquid Argon imaging TPC. Main phases: clean-up (vacuum) 10 days, cool-down 15 days, LAr filling 15 days, debug and datataking 68 days. In addition to the 18 m long track requested by the Scientific Committees, a large number of cosmic-ray events was collected: about 28000 triggers with different topologies 4.5 TB of data, 200 MB/event. Valuable data: check performance of a such large scale detector. Found that: results of the same quantitative quality as those obtained with small prototypes (e.g. 3 ton, 50 liter, ) are achieved with a 300 ton device. scaling up is successful
τ e search: 3D likelihood summary 5 year shared CNGS running T3000 configuration Maximum sensitivity
Search for θ 13 0 (I) m 2 32 =3.5x10 3 ev 2 ; sin 2 2θ 23 = 1 4 years @ CNGS P(ν µ ν τ ) = cos 4 θ 13 sin 2 2θ 23 2 32 P(ν µ ν e ) = sin 2 2θ 13 sin 2 θ 23 2 32
Search for θ 13 0 (II) m 2 32 =3.5x10 3 ev 2 ; sin 2 2θ 23 = 1 ; sin 2 2θ 13 = 0.05 Total visible energy Transverse missing P T P(ν µ ν τ ) = cos 4 θ 13 sin 2 2θ 23 2 32 P(ν µ ν e ) = sin 2 2θ 13 sin 2 θ 23 2 32
Sensitivity to θ 13 in three family-mixing 4 years @ CNGS Estimated sensitivity to ν µ ν e oscillations in presence of ν µ ν τ (three family mixing) Factor 5 improvement on sin 2 2θ 13 at m 2 = 3x10 3 ev 2 Almost two-orders of magnitude improvement over existing limit at high m 2
ν µ ν e search with OPERA (interesting by product)
Backgrounds for the ν µ ν e search π 0 identified as electrons produced in ν µ NC and ν µ CC with the µ not identified ν e beam contamination (main background) τ e from ν µ ν τ oscillations (strongly reduced thanks to the capability in detecting decay topologies) In the following we assume a three family mixing scenario with θ 23 = 45º
ν µ ν e : selection efficiencies Location eff. Total eff. ξ ε signal 0.53 0.31 τ e 0.053 0.032 ν µ CC 0.52 0.34x10-4 ν µ NC 0.48 7.0x10-4 ν e CC beam 0.53 0.082 Expected signal and background assuming 5 years data taking with the nominal CNGS beam and m 2 23 =2.5x10-3 ev 2, sin 2 2θ 23 =1 θ 13 9º signal 9.3 τ e 4.5 ν µ CC 1.0 ν µ NC 5.2 ν e CC beam 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 3º 1.2 4.7 1.0 5.2 18
OPERA sensitivity to θ 13 By fitting simultaneously the E e, missing p T and E vis distributions we got the sensitivity at 90% 5years data taking 2.5x10-3 ev 2 0.05 M.Komatsu, P.Migliozzi and F.Terranova, J. Phys. G29 (2003) 443
Comparing experiments Limits at 90% C.L. on sin 2 2θ 13 and θ 13 ( m 2 23=2.5x10-3 ev 2 ; sin 2 θ 23 =1) Experiment CHOOZ MINOS 2 yr ICARUS 5 yr OPERA 5 yr CNGS 5 yr JHF 5 yr sin 2 2θ 13 < 0.14 < 0.06 < 0.03 < 0.05 < 0.025 < 0.006 θ 13 < 11º < 7.1º < 5.8º < 7.1º < 4.5º < 2.5º
Sensitivity reduction of accelerator expts. m 132 = 0.003 ev 2 0.020 0.025 Hence assuming complete ignorance on δ CP and on the sign of m 2 31 and using no other information to lift the ambiguities, the actual excluded sin 2 2θ 13 is ~0.006 ~0.015 and this is even worse for large values of α= m 2 sol/ m 2 atmo