Left ChamberRight Chamber

The CNGS project

Pasquale Migliozzi

INFN - Napoli

The proof: “appearance” of ν

in a ν

beam ν

………..…. ν

High

High energy, energy, long long baseline baseline ν ν beam beam

( E( E_CMCM >> >> mm_{τ τ} L ~ 1000 km )L ~ 1000 km )

Detection of

Detection of τ τ leptons leptons

Sensitivity to ∆m² = 1.6−4.0 x 10^-3 eV² High background rejection

High background rejection andand MM_targettarget= O(1 kton= O(1 kton))

Discover the source of the atmospheric ν µ “ deficit”

ν

ν

oscillations?

?

The CNGS neutrino beam

ICARUS

The be am will

sta rt i n m ay 2 006

CNGS beam layout at CERN site.

Progress in the civil engineering work:

excavation completed concreting started

CNGS commissioning:

May 2006

Nominal ν beam (Nov. 2000) Shared SPS operation

200 days/year 4.5x10¹⁹ pot / year Average ν_µ energy 17 GeV

5 year run

Expected interactions in 1kton detector

~ 18000 ν

NC+CC

~ 80 ν

CC

at ∆m² = 2.5x10^-3 eV² and full mixing

The CNGS and the expected number of events

Limiting factor for θ₁₃ search:

ν_e+ anti-ν_e beam contamination ~0.87%

An updated CNGS with a flux 1.5 more intense than the one

approved in 2000 is now considered as the baseline option

d d

p p

Ionization electrons paths

Drift

ionizing track

Ionization electrons drift (msec) over large distances (meters) in a volume of highly purified liquid Argon (0.1 ppb of O₂) 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”.

The ICARUS working principle

Experience and results: 600 ton detector

„ Full scale technical run of the T300 detector in Pavia (2001)

ƒ Cryogenics

ƒ Wire chamber mechanics

ƒ Argon purification

ƒ Electronic noise

ƒ High voltage for the drift

ƒ PMTs for scintillation light collection

ƒ Readout & DAQ

ƒ Slow control

„ Event reconstruction SW with real events and data analysis (ongoing effort)

ƒ Event reconstruction

ƒ 3 plane readout

ƒ Calibration

ƒ Resolution

Industrial module made of two independent LAr containers

½ module equipped and filled with LAr (300 ton) Total volume : 350 m³

Readout planes: 2 x 3 (–60°,60°,0°), about 54000 wires Maximum drift distance: 150 cm

≈300‘000 = T300 kg LAr

ICARUS T600

(1 half-module out of 2)

ICARUS T600

(1 half-module out of 2)

Cryostat (half-module)

20 m 4 m

4 m

View of the inner detector

ICARUS T300 detector

Readout electronics

18 m

1.5 m1.5 m Left ChamberRight ChamberCathode

Long longitudinal muon track crossing the cathode plane

Track Length = 18.2 m

3D View Top View

dE/dx = 2.1 MeV/cm

3-D reconstruction of the long track 3-D reconstruction of the long track

dE/dx distribution along the track dE/dx distribution along the track

75 100

30 20 50 40

60 0 10 20 30 40 50 60 70 80 90

z (cm)

x (cm)

75 100

20 30

40 50

60 0

10 20 30 40 50 60 70 80 90

y (cm)

x (cm)

Run 939 Event 95 Right chamber Run 939 Event 95 Right chamber

T_e=36.2 MeV Range=15.4 cm T_e=36.2 MeV Range=15.4 cm

Stopping muon reconstruction example

Collection view

Induction 2 view

A

A B

B C

C

µ

µ+

e+

µ+

e+

Induction 1 view

ICARUS in Hall B

≈ 35 m

First Unit T600 + Auxiliary Equipment

First Unit T600 +

Auxiliary Equipment T1200 Unit (two T600 superimposed) T1200 Unit (two T600

superimposed) T1200 Unit (two T600 superimposed) T1200 Unit (two T600

superimposed)

≈ 60 m

ν _µ →ν _τ oscillations

„

Analysis of the electron sample

9

Exploit the small intrinsic ν

contamination of the beam (0.8% of ν

CC)

9

Exploit the unique e/π

separation

Statistical excess visible before cuts ⇒ this is the main reason for performing this experiment at long baseline !

At ∆m

=3.5x10

eV

165 τ → e events are expected Main background from charged current interactions

of ν

in the beam 700 events are expected

τ→ e search: 3D likelihood

„

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_T^miss, ρ_l]) (signal)

L_B ([E_visible, P_T^miss, ρ_l]) (ν_e CC back)

Discrimination given by

5 T600 modules, 5 years CNGS (4.5 x 10¹⁹ p.o.t./year)

0 5 10 15 20 25 30 35 40

-2 0 2 4 6 8 10

lnλ

Events/12 kton x year

ν_e CC + ν_τ CC ν_e CC

ν_τ CC, τ→ e

Overflow→

lnλ ≡L([E

, P

, ρ

]) = L

/L

lnλ

A simple analysis approach: a likelihood method based on 3 variables

ν _µ → ν _τ appearance search summary

Super-Kamiokande: 1.6 < ∆m² < 4.0 at 90% C.L.

„ T3000 detector (2.35 kton active, 1.5 kton fiducial)

„ Integrated pots = 2.25 x10²⁰

„ Several decay channels are exploited (golden channel = electron)

„ (Low) backgrounds measured in situ (control samples)

„ High sensitivity to signal, and oscillation parameters determination

(these numbers have to be multiplied by a factor 1.5)

ν

τ

τ decay “kink”

~ 0.6 mm

AND decay topology → micron resolution

ν oscillation → massive target

The challenge

To identify τ leptons, “see”

their decay topology

Lead – nuclear emulsion sandwich

“Emulsion Cloud Chamber”, in brief “ECC”

The Emulsion Cloud Chamber (ECC)

„ Emulsions for tracking, passive material astarget

„

Established technique

„ charmed “X-particle” first observed in cosmic rays (1971)

„ DONUT/FNAL beam-dump experiment: 7

ν

observed (2000)

< µm space res. mass

Pb

ν τ

1 mm

Emulsion layers track segments

Experience with emulsions and/or ν

searches : E531, CHORUS, NOMAD and DONUT

∆m² = O (10^-3 eV² ) → M_target ~ 2 kton

modular structure (“bricks”): basic performance is preserved large detector → sensitivity, complexity

required: “industrial” emulsions, fast automatic scanning

ν

8 m

Target Trackers

Pb/Em.

target

Electronic detectors

→ select ν interaction brick

A “hybrid”

experiment at work

Emulsion analysis

→ vertex search Extract selected

brick

Pb/Em. brick

8 cm Pb 1 mm

Basic “cell”

Emulsion

→ decay search

µ spectrometer

→ e/γ ID, kinematics

→ µ ID, charge and p

ν

(DONUT)

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/π⁰ identification

„

Energy measurement

„ Multiple Coulomb Scattering

„ Track counting (calorimetric measurement)

„

Ionization (dE/dx meas.)

„ π/µ separation

„ e/π⁰ separation

Topological and kinematical analysis event by event

5X 0( ~ ½brick)

1 mm

5 cm

ECC exposure at CERN-PS

0 1

-1 mm

mm

0 1 0 3 02 0 4 0

-2

π⁰

Cell structure; exploited τ decay channels and topologies

¾ “Long” decays

kink angle θ_kink> 20 mrad

τ → e Progr. Rep. 1999 τ → µ Progr. Rep. 1999 τ → h (nπ⁰) Proposal 2000 + ρ search Status Rep. 2001

¾ “Short” decays

impact parameter I.P. > 5 to 20 µm τ → e Proposal 2000 τ → µ Status Rep. 2001

kink

θ_kink Long decays

Pb

(1 mm)

plastic base

I.P.

Short decays

emulsion layers

(1 mm)Pb

An optimized channel by channel

analysis is in progress. Ready by summer

P_t miss

ν τ

H Φ_τ-H

P

PP_{t t} miss (GeVmiss (GeV/c)/c) ΦΦ_{ττ--H H}

ν_µ NC τ

τ ν_µ NC

π/2

1

Global kinematics for τ → h

(for events with a τ decay candidate)

In these plots the improvements from γ detection

are not taken into account

„

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

Backgrounds for the ν _µ → ν _τ search

Room for improvements?

ƒ Changeable Sheet : increase efficiency by 10-15 %

ƒ CS reduce scanning load by a factor 2 Ö More trials in brick finding

Ö Higher brick finding efficiency -> higher τ yield

ƒ dE/dx : background reduction by about 40%

ƒ Charm background events have low momentum muons not identified

Ö a large fraction stops in the target region and is identified through the dE/dx

ƒ Better use of spectrometer: reduce the

background in µ channel by about a factor 30%

Aim at the evidence of ν

appearance after a few years of data taking

0.67 50.4

19.8 With possible 10.3

improvements

1.06 43.8

17.2 Final Design 9.0

CNGSx1.5 *)

signal Back

(∆m² = 4.0 x 10^-3 eV²)

signal

(∆m² = 2.5 x 10^-3 eV²)

signal

(∆m² = 1.8 x 10^-3 eV²)

Expected number of events

full mixing; 5 years run @ 6.75x10

pot/year

Probability of ≥ nσ significance for different ∆m ²

P

P

(%)

P

P

(%)

100(100) 100(100)

100(100) 100(100)

4.0x 10

100(100) 100(100)

99.6(100) 100(100)

3.0x 10

99.9(100) 199(100)

93.9(98.6) 98.9(99.9)

2.5x 10

99.0(99.9) 99.9(100)

80.5(93.0) 94.9(98.9)

2.2x 10

87.4(96.2) 97.2(99.5)

46.8(68.2) 77.2(91.1)

1.8x 10

5 years (33.8x 10

pot) 3 years

(20.3x 10

pot)

∆ m

(eV

)

Best fit of SK + K2K is ∆m² = (2.6±0.4) eV² 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 sin2 2θ 13and θ 13 (∆m^{2 2}3=2.5x10-3 eV2 ; sin2 θ 23=1)

< 4.5º

< 0.025 CNGS 5 yr

< 2.5º

< 0.006 JHF 5 yr

< 7.1º

< 0.05 OPERA 5 yr

< 5.8º

< 0.03 ICARUS 5 yr

< 7.1º

< 0.06 MINOS 2 yr

< 11º

< 0.14 CHOOZ

θ₁₃ sin² 2θ₁₃

Experiment

For details on the sensitivity dependence on δ

see

P. Migliozzi, F. Terranova hep-ph/0302274 (in press on PLB)

Accelerator expts.

sensitivity vs δ _CP (1)

There are

δ

which the sensitivity on

θ

is even better than the one compute in the 2-flavor

approximation (

δ

Notice the different behaviour on ∆m

of the CNGS sensitivity

⇒ Possible measurement

of the sign of ∆m

?

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

wall

Tensioning from the

bottom

Bricks inserted from the side Suspension

from the top

Brick loading test

Height ~ 6.7 m

The support structure for the “brick walls"

Tests of full scale prototypes

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

“Carousel” brick dispensing and storage system

Tests with the prototype wall

Full scale prototype module

• 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

coating

Coextruded strip Kharkov (2m)

N_pe versus Length (cm) Length (cm) Npe

0 1 2 3 4 5 6 7 8 9 10

300 350 400 450 500 550

Well above 5 p.e. / readout end

(in the middle: worst case for two-end readout)

Target Tracker: plastic

scintillators

Dipolar magnet

Full scale prototype of magnet section constructed and tested

Magnet during construction

RPCs inside gaps: muon identification , shower energy Drift Tubes: muon momentum

slabs base

coil

Fe

(5 cm)

RPC 12 Fe

slabs in total

Iron in tendering-ordering phase

8.2 m

B= 1.55 T

Total Fe weight

~ 1 kton

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

beam

„

A measurement of ∆m

at 20-30%

„

Extend sensitivity for small ν

->ν

mixings (competitive with other experiments)

„

The construction of the detectors is in progress

and it is planned to be completed by mid 2006

Expected Performance

cf. “Addendum” of 1999:

- priority to LBL

ν

-> 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

CNGS Overview

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 data- taking 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

Maximum sensitivity

5 year “shared”CNGS running T3000 configuration

∆m

=3.5x10

eV

; sin

2θ

= 1

Search for θ ₁₃ ≠0 (I)

P( ν

→ ν

) = sin

2 θ

sin

θ

∆

P( ν

→ ν

) = cos

θ

sin

2 θ

∆

4 years @ CNGS

P(ν_µ → ν_e) = sin ² 2θ₁₃ sin ²θ₂₃ ∆²³²

P(ν_µ → ν_τ ) = cos⁴ θ₁₃ sin² 2θ₂₃∆²³²

∆m

=3.5x10

eV

; sin

2θ

= 1 ; sin

2θ

= 0.05

Transverse missing P_T Total visible energy

Search for θ ₁₃ ≠0 (II)

Sensitivity to θ ₁₃ in three family-mixing

„ Estimated sensitivity to ν_µ → ν_e oscillations in presence of ν_µ → ν_τ (three family mixing)

„ Factor 5 improvement on sin²2θ₁₃ at ∆m² = 3x10^–3 eV²

„ Almost two-orders of magnitude improvement over existing limit at high

∆m²

4 years @ CNGS

ν _µ → ν _e search with OPERA

(interesting by product)

Backgrounds for the ν _µ → ν _e

search

¾

π

identified as electrons produced in ν

NC and ν

CC with the µ not identified

¾

ν

beam contamination (main background)

¾

τ → e from ν

→ ν

oscillations (strongly reduced thanks to the capability in

detecting decay topologies)

In the following we assume a three family

mixing scenario with θ

= 45º

ν _µ →ν _e : selection efficiencies

ν_eCC ν_µNC beam

ν_µCC τ→e

signal θ₁₃

18 5.2

1.0 4.7

1.2 3º

18 5.2

1.0 4.6

3.0 5º

18 5.2

1.0 4.6

5.8 7º

18 5.2

1.0 4.5

7.4 8º

18 5.2

1.0 4.5

9.3 9º

Expected signal and background assuming 5 years data taking with the nominal CNGS beam and ∆m²₂₃=2.5x10^-3 eV², sin²2θ₂₃=1

ν_eCC ν_µNC beam

ν_µCC τ→e

signal

0.082 7.0x10^{- 4}

0.34x10^{- 4} 0.032

0.31 ε

0.53 0.48

0.52 0.053

0.53 ξ

Total eff.

Location eff.

OPERA sensitivity to θ ₁₃

By fitting simultaneously the

E_e, missing p_T and E_vis distributions we got the sensitivity at 90%

2.5x10^-3 eV²

0.05

M.Komatsu, P.Migliozzi and F.Terranova, J. Phys. G29 (2003) 443 5years data taking

Comparing experiments

Limits at 90% C.L. on sin2 2θ 13and θ 13 (∆m^{2 2}3=2.5x10-3 eV2 ; sin2 θ 23=1)

< 4.5º

< 0.025 CNGS 5 yr

< 2.5º

< 0.006 JHF 5 yr

< 7.1º

< 0.05 OPERA 5 yr

< 5.8º

< 0.03 ICARUS 5 yr

< 7.1º

< 0.06 MINOS 2 yr

< 11º

< 0.14 CHOOZ

θ₁₃ sin² 2θ₁₃

Experiment

Sensitivity reduction of accelerator expts.

0.020 0.025

~0.006 ~0.015

∆m

= 0.003 eV

Hence assuming complete ignorance on δ

and on the sign of ∆m

and using no other

information to lift the ambiguities, the actual excluded sin

2θ

is

and this is even worse for large values of

α=∆ m

/|∆m

|