long baseline accelerator neutrino experiments: present and...

André Rubbia, ETH/Zürich, 10/1/00

Long Baseline Accelerator NeutrinoExperiments: Present and Future

André RubbiaETH Zürich

Cracow Epiphany Conference on Neutrinos inPhysics and Astrophysics

6-9 January 2000, Cracow, Poland


“Disappearing” muon neutrinos?

-1 -0.6 -0.2 0.2 0.6 10

50

100

150Super-Kamiokande 45 kt-yr Preliminary

cosΘ

multi-GeV e-like

Data

Monte Carlo (no osc.)

Best Fit νµ-ντ

cosΘ

multi-GeV µ-like + PC

-1 -0.6 -0.2 0.2 0.6 10

50

100

150

“Atmospheric neutrino anomaly”, first published by Kamiokande (1988),stands today as a clear and convincing evidence that muon neutrinos are“disappearing”

0

0.5

1

0

0.5

1

Neutrino Energy (GeV)10

-11 10 10

20

0.5

1

L= 25 km

L= 500 km

L= 10000 km

∆m2= .005 eV2

cos θ = .8, L= 10000 km

cos θ = .8,L= 25 km

cos θ = 0L= 500 km

θ

L

Earth

Detector

Pm L

Eν ν θµ µ→( ) = −1 2

1 272 22

sin sin (.

)∆

(∆m2 in eV2, L in km, E in GeV)

⇒

≈ ≈ ÷

max

–LE

mkm

GeV∆ 2 2 310

Ø Need “long” baselines...


Neutrino oscillation phenomenologyO To elucidate in a comprehensive way the pattern of neutrino masses and mixings,

following the atmospheric and solar neutrino results

O In general, the oscillation pattern may be complicated and involve a combination oftransitions to νe, νµ, ντ and by symmetry with quark sector it is natural to expect CPviolation at some level.

O The presence of “matter” should affect the transition probabilities (MSW mechanism).

O Moreover, this scheme cannot accommodate all experimental data (solar, atm and LSND);therefore, transitions to “sterile” states could be occurring as well.

3 angles, 1 CP phase, and 2 independent ∆m2

P P PCP CP( ) ( ) ( )ν ν ν ν ν να β α β α β→ = → + →/ /P P PCP CP( ) ν να β→ = − / /

(in vacuum)

P J P JCP jk jkj k

CP jk jk jkj k

= − =>

/ />

∑ ∑δαβ αβ αβ4 42Re sin Im sin cos ∆ ∆ ∆

J U U U Um L

Ejk k k j j jkjk

αβ α β α β= =* * ∆∆ 2

4


New challengesO The experimental solution to the neutrino phenomenology requires a

complementary and comprehensive study of atmospheric and acceleratorLBL neutrinos by various experiments with different systematics

O Accelerator experiments are facing new challenges:Ü In order to cope with the flux attenuation because of distance, detectors must have

multi-kton fiducial massÜ The study of the full mixing matrix requires to identify νe, νµ, ντ components

– Appearance and disappearance signatures needed !– To tag efficiently and measure the interactions from νe’s and ντ’s out of the bulk of νµ events

requires a detailed event reconstruction that can be achieved only by means of highgranularity detectors

O Likewise, the comprehensive investigation of atmospheric neutrinos withstatistics of about one thousand/year also requires detectors of several ktons. Thecapability to observe all separate processes (electron, muon and tau CC and NC)without detector biases and down to kinematical threshold is highly desirable

⇒ K2K, MINOS, ICANOE, OPERA, ...


Long baseline beams (scale ≈ country)Japan: K2K(250 km) USA: NUMI

(732 km)

Europe: NGS(732 km)


The long baseline beams

4004.8 x 1013

27.6

2450/kt544

2005


CERN-GranSasso neutrino beam

O CERN SPS p 400 GeV

O Optimized optics:<Eν> ≈ 17 GeV (WBB)

O Distance: L=732 km

O Experimental halls in GranSassoalready pointing towards CERN

O Already approved “stand-alone”program in GranSasso (ICARUS)

O Requires the construction of anew beam-line (opposite tocurrently existing WANF line)

O Approved (Dec 99), beam readyin Spring 2005.

SPS

LEP/LHC

West AreaCHORUS/NOMAD

To Jurabeam comes out from the groundat 17 km

WANFNNF

450 GeV

To GranSassoNear position(-135 m underground)

beam slope +42 mrad

beam slope –58 mrad

TI8

New transfer line built for LHC injection

CERN Gran Sasso

CERN Neutrino Beam in the Direction of Gran Sasso

earth

Distance = 732 Km

Ear

th r

adiu

s =

638

0 K

m

10.5 km below ground


The CERN NGS event rates

O High energy p: 400 GeV

O Pots per year:Ü4.5x1019 pots “shared”

Ü7.6x1019 pots “dedicated”

CERN 98-02 - INFN-AE/98-05

CERN-SL/99-034(DI) - INFN/AE-99/05


Goal 1: Is it “flavor” oscillation?

O Long baseline neutrino oscillation experimentsÜCombined results from various experiments fit toward same

oscillation parameters:– Best fit ⇒ sin22θ≈1, ∆m2 ≈ 3.5 x 10–3 eV2

ÜCHOOZ:– νe do not significantly disappear in the “atmospheric ν region”

ÜSuperKamiokande:– No evidence of νe appearance– Evidence for νµ disappearance

ÜK2K:– Check νµ disappearance and no large νe appearance

ÜThe key issue: Is signal from νµ → ντ oscillation ?Is there any νµ → νe oscillation ?

⇒ flavor appearance (direct!)


Detection of ντ from ντ CC interactions

O Tools for background rejectionÜ kinematics:

– Requires good particle identification and resolution inmomentum unbalance (unseen ν) (à la NOMAD)

Ü direct observation of decay topology “signature”– γcτ = 0.5-1 mm

– Requires emulsion : ~ 1mm granularity (à la CHORUS)

νµ → ντ → τ + Xoscillation CC

e

h nh

h h h nh

ννµνν

νν

−

− + −

0

0

18%18%50%14%


Optimization for tau appearance

NUMI

NGS

O Conflicting requirements:Ü Sensitivity at low ∆m2 è low energy since Posc ≈ 1/E2

Ü Tau production kinematical supression è high energy τ

ν τ C

C e

ven

t ra

tes


10-4

10-3

10-2

10-1

1

0 0.2 0.4 0.6 0.8 1sin22θ

∆m2 (

eV2 )

Super-Kamiokande Preliminary: 736 days FC + 685 day

νµ - ντ

90% C.L.KamiokandeSuper-Kamiokande (Dec. 98)Super-Kamiokande (Jun. 98)

Expected number of ντ CCevents (5 kton and 4 years“shared” CNGS)

Rate of ντ CC eventsO The rate of ντ CC events

is at the moment notknown, since ∆m2 is notyet precisely determinedby atm neutrinos.

O Within the currentlyallowed parameters ofSuperK, it can vary in therange:

(for 5kton and 4 years„shared“ mode @ CNGS)

≈ ≤ ≤ ≈50 4000Ntau

4300

61720552


The ICANOE detector

O “Merging of two technologies”ÜCommon effort of ICARUS & NOE collaborations towards a

design of a new enhanced “general-purpose” undergrounddetector to be installed at LNGS

ÜAppropriate combination of “low” & “high” density targets– Liquid target : ICARUS liquid argon imaging– Solid target : NOE fine grain calorimeter, upgraded for magnetic

analysis of the muon

ÜICANOE has unique capabilities to identify & measure finalstate electron, photons, muons and hadronic jets (a greatadvantage over previously existing or planned detectors)

ÜSupermodule layout: “classical” neutrino detector, with eventsreconstructed with the quality of a bubble-chamber (liquidtarget) complemented by an external identifier (solid target)


The ICARUS Collaboration

F. Arneodo, E. Bernardini, O. Palamara.Laboratori Nazionali di Gran Sasso, INFN, s.s. 17bis, km 18+910, Assergi (AQ), Italy

B. Babussinov, S. Centro, G. Meng, D. Pascoli, F. Pietropaolo, S. Ventura.Dipartimento di Fisica e INFN, Università di Padova, via Marzolo 8, Padova, Italy

A. Badertscher, A. Bueno, M. Campanelli, C. Carpanese, J. Rico, A. Rubbia, N. Sinanis.Institute for Particle Physics, ETH Honggerberg, Zurich, Switzerland\label

G. Battistoni, D. Cavalli, P. Sala, T. Rancati.Dipartimento di Fisica e INFN, Università di Milano, via Celoria 16, Milano, Italy

P. Benetti, R. Brunetti,E. Calligarich, R. Dolfini, A. Gigli Berzolari, F. Mauri, L. Mazzone,C. Montanari, A. Piazzoli, A. Rappoldi, G.L. Raselli, M. Rossella, C. Rubbia, D. Scannicchio,

P. Torre, C. Vignoli, Z. Xu.Dipartimento di Fisica e INFN, Università di Pavia, via Bassi 6, Pavia, Italy

A. Borio di Tigliole, A. Cesana, M. Terrani.Politecnico di Milano (CESENF), Università di Milano, via Ponzio 34/3, Milano, Italy

F. Cavanna, D. Mazza, G. Nurzia, S. Petrera, G. Piano Mortari, C. Rossi.Dipartimento d Fisica e INFN, Università dell’Aquila, via Vetoio, L'Aquila, Italy

P. Cennini, A. Ferrari1.CERN, CH 1211 Geneva 23, Switzerland

C. Chen, Y. Chen, K. He, X. Huang, Z. Li, F. Lu, J. Ma, G. Xu, C. Zhang, Q. Zhang, S. ZhenIHEP -- Academia Sinica, 19 Yuqnan Road, Beijing, People’s Republic of China

D. Cline, C. Matthey, S. Otwinowski, H. Wang, J. Woo.Department of Physics, UCLA, Los Angeles, CA 90024, USA

P. Picchi2

University of Torino, Torino, Italy

F. SergiampietriINFN Pisa, via Livornese 1291, San Piero a Grado (PI), Italy

1 Also at Dipartimento di Fisica e INFN, Università di Milano, via Celoria 16, Milano, Italy2 A lso at Laboratori Nazionali di Frascati, INFN, Frascati, Italy and Istituto di Cosmogeofisica, CNR,Torino, Italy

The NOE Collaboration

M.Ambrosio, C.Aramo, G.C.Barbarino, D.Campana, F.Guarino, A.Lauro, A.Ordine, G.Osteria,V.Palladino.

Dip.di Scienze Fisiche dell' Università di Napoli and INFN Sez.di Napoli-Italy

K.V.Alexandrov, V.A.Chechin, A.P. Chubenko, A.D.Erlykin, F.F.Kayumov, S.K.Kotel'nikov,E.P.Kuznetsov, B.N.Lomonosov, G.I.Merzon, V.A.Ryabov, V.O.Tikhomirov, V.A.Tsarev.

P.N.Lebedev Physical Institute, Moscow, Russia

A.M.Baranov, E.T.Gushchin, V.A.Kantserov, A.A.Semak, S.V.Somov.Moscow Engineering Physical Institute, Moscow, Russia

P.Bernardini, I.De Mitri, G.Mancarella, D.Martello, A.Surdo.Dip. di Fisica dell’Università di Lecce and INFN Sez. di Lecce – Italy

A.Di Credico, A.Grillo, S.Mikheyev, E.Scapparone.Laboratori Nazionali di Gran Sasso, INFN, s.s. 17bis, km 18+910, Assergi (AQ), Italy

C.Favuzzi, P.Fusco, N.Giglietto, F.Loparco, A.Rainò, M.N.Mazziotta, I.Panunzio, P.Spinelli.Dip. di Fisica dell’Università di Bari and INFN Sez. di Bari - Italy

R. Fiore, E.Lamanna, A. Papa, G.Russo.Università della Calabria and INFN Laboratori Nazionali di Frascati-Italy

G.V.Gavalian, R.L.Kavalov, M.P.Lorikian.Yerevan Physical Institute, Yerevan, Armenia

S.V.Golovkine, A.M.Gorine.Institute for High Energy Physics, Moscow, Russia

R.A.Mukhamedshin, G.T.Zatsepin.Institute of Nuclear Research, Moscow, Russia

V.A.Smotryaev, I.S.Trostin.Institute of Theoretical and Experimental Physics, Moscow, Russia

This is an open Collaboration and other Participants are being invitedto join

Institutes that have already expressed their interest

P. Assimakopoulos, I. Papadopoulos, P. Pavlopoulos, V. Vlachoudis.University of Ioannina, Greece

G. Fanourakis, S. Tzamarias.Institute of Nuclear Physics, “Democritos”, Greece

V.A. Matveev, E.N. Goloubeva, A.V. Kovzelev, O.V. Kazachenko, A.V. Polarush, V.E. Postoev,I.N. Semeniouk, A.N. Toropin.

Institute of Nuclear Research, Moscow, Russia}

P. Razis, A. Vorvolakos.

And

ré R

ubbi

a, E

TH

/Zür

ich,

10/

1/00


The 4 ICANOE supermodules

82.5 m long

5.7+3.2 ≈ 9 kton instrumented


The ICANOE supermodule

O Liquid target:Ü 1.4(1.9)kton active (total) mass

Üexternal dimensions 11.3x11.3x18.0 m3

O Solid target:ÜMagnetized calorimeter

module, 9x9x2.6 m3

(2 meter of Fe)

Ü0.8 kton mass

O Supermodule:ÜJoining 1 liquid + 1 solid

target, i.e. 2.6kton

Ü“Expandable”


The liquid target

Liquid Argon imaging


Liquid Argon TPC (ICARUS)

O Fully homogeneous, continious, precisetracking device with high resolution dE/dxmeasurement and full samplingelectromagnetic and hadroniccalorimetry (X0=14cm, λ int=84cm)

O Excellent imaging capabilities “bubble-chamber-like” device

O Excellent electron id and e-¹0 separation

O Calorimetry allows full kinematicsreconstruction of “contained” events

O dE/dx provides particle id (with range) andprecise momentum measurement for softparticles; rejection of conversions andDalitz decays

O Large detectors (kilotons) with highgranularity feasible (600 ton approved)

O LAr TPC is the outcome of many yearsof R&D by the ICARUS Collab.

CERN ν-beam

νµ + n → µ − + p12

8 re

adou

t w

ires

2.54

mm

wire

pitc

h

Real ν eventin the 50 liter LAr TPC in

CERN WANF beamtime (400 ns/sample)46 cm max. drift distance

ICARUS-CERN-Milano Collab.

(Chamber located in front of NOMAD detector)

collection view


Neutrino Event in the 50 lt Prototype

47 cm Drift

32 c

mW

ires


The ICARUS technique – challenges

O Liquid Argon environment in big volumes:Ü Cool and maintain the temperature of the detector at T=90K

with T uniformity of ±1K (uniform drift velocity)Ü Temperature gradient during cooling phase implies

mechanical stress ⇒ e.g. chamber wires contraction

O Long drift path ⇒ drift electron lifetime > 1 ms:Ü Ultra high vacuum (UHV) requirementsÜ “Clean” elements (chamber structure, cryogenic

instrumentation, …) and limited degassing (cables, …)Ü Reach a purity of LAr at the level of <0.1 ppm O2 equivalent

While these goals have been reached in laboratory environment,they have now to be reached at the industrial scale for the T600detector! ⇒ 15 ton prototype


The 15 ton ICARUS prototype

O The prototype was designed and built by the Air Liquide industryto reproduce as much as possible the working conditions of theT600 detector:

– the cryogenic layout basically same as foreseen for the T600 module

– the installed units (the cryostat itself, liquid nitrogen circulation pump and thecooling circuit, liquid argon purification and recirculation units, sensors, controlsystem, etc..) are like those intended to be installed on the T600;

O The cryostat dimensions are such as to reproduce with areasonable approximation the behaviour of the liquid argon (LAr)inside the T600; in particular, the cryostat height is exactly thesame as the one of the T600 so that any stratification effect ontemperatures distributions and LAr purity is correctly represented


The 15 ton ICARUS prototype

15 ton cryostat Chamber structure


Cryogenic circuit

GAr purifactioncircuit

LAr purif.circuit LN2 circuit

COOLING


15 ton prototype


Cooling 15 ton prototype March ‘996To avoid large thermalstresses, first part of thecooling, down to about -30 °Cmade using a dedicateddevice. Cooling is performedunder vacuum.

6Then filled the cryostat withpurified gas argon (GAr).

6After 2.5 days, when all thetemperatures were below–150°C started filling thecryostat with purified LAr.

6The position meter installedon one of the three tensioningdevices of the chambersmodule, measured a totalelongation of the spring ofabout 1.2 mm ⇒ confirms thefunctionality of the variablegeometry mechanics


Electron lifetime in 15 ton prototype

100

1000

-50 0 5 0 100 150 200 250

Lifetime evolution

Life

time

( µs

)

Elapsed Time (hours)

Pump OFF

Pump ON

6The free electrons lifetime (i.e. LAr purity), measured just after thefilling, was between 200 µs to 300 µs.

6After start of LAr recirculation/purification with the immersed pump, thefree electrons lifetime rapidly increased with a slope consistent with a onevolume recirculation time of about 40 hours. The final electrons lifetime,after about 4 days of recirculation, was between 2 ms to 3 ms.

Taking into accountthat the maximum drifttime in the T600 will beabout 1 ms, the goalfor purity is reached.

André Rubbia, ETH/Zürich, 10/1/00ICARUS T600: semi-module at AirLiquide construction site

André Rubbia, ETH/Zürich, 10/1/00ICARUS T600: inner view of semi-module

holes

André Rubbia, ETH/Zürich, 10/1/00ICARUS T600: front door of semi-module


ICANOE physics goalsO “to elucidate in a comprehensive way the pattern of

neutrino masses and mixing” beyond what availableat the time from SuperK

O Observe directly the oscillation mechanism andmeasure the full mixing matrix and mass differencesÜSimultaneous study in a single experiment of atmospheric

and CERN-NGS neutrinos (⇐ fully isotropic detection techniqueand full event reconstruction)

ÜTest of large mixing angle MSW solution to solar neutrinodeficit; study of matter effects in Earth with atmosphericneutrinos down to kinematical threshold

O Stability of matter: search for nucleon decays


Addressed topics

O CERN-NGSl direct tau and electron appearancel muon disappearance

O Atmospheric neutrinos ⇐l Detection of all neutrino flavors , CC & NC modesl Study of L/E distributions for e,µ samples, clean NC/CC, direct

tau appearancel Upward going muonsl Low energy electrons

l Determination of the oscillation parameters ⇐l Combine all measurements (χ2 method)

l Nucleon decay


νe CC from CERN

σ ( ) / %/ %E E Eem em em= ⊕3 1

σ ( ) / %/ %E E Ehad had em≈ ⊕16 1

Class 1: Events in liquid targetO Fully homogeneous, continuous, precise tracking device with high resolution dE/dx

measurement and full sampling electromagnetic and hadronic calorimetry(X0=14cm, λ int=84cm)

O Excellent imaging capabilities “bubble-chamber-like” deviceO Excellent electron id and e-¹0 separationO Calorimetry allows full kinematics reconstruction of “contained” eventsO dE/dx provides particle id (with range) and precise momentum measurement for soft

particles; rejection of conversions and Dalitz decaysO Momentum measurement via multiple scattering

for pure Argon, correction for quenching & compensation


Beam neutrinos (CNGS) event rates

20 kt year = 4 years “shared”

LAr 1900 ton

LAr active 1400 ton (8x8x16m3)

LAr fiducial 1245 ton (7.45x7.45x16m3)

4 supermodules: 5000 ton fid. liquid targ2500 ton solid target

Solid ≈800 ton


Muon measurement

νµ CC from CERN

0.0

0.1

0.2

0.3

1 10 40

Mom

entu

m r

esol

utio

n, σ

Muon Momentum, p (GeV/c)

= 0.109 +0.043ln(p/1GeV)σ

Momentum resolution

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 5 10 15 20 25 30

Momentum (GeV/c)

∆p/p

B=0.5T

Momentum (GeV/c)

∆p/p

B=0.6T

Momentum (GeV/c)

∆p/p

B=0.8T

Momentum (GeV/c)

∆p/p

B=1.2T

Momentum (GeV/c)

∆p/p

B=1.6T

Momentum (GeV/c)

∆p/p

B=2T

Multiple scatteringMagnetic measurement

O Muon momentum can be estimated by two methods:

5 meter length


Contained events in the solid target

O The rate in the solid target will be about ≈7000 νµ CCevents/year with corresponding νe CC and NC samplesÜStraightforward measurement of the muon momentum and of

the hadronic jet with proven technology

O Measure spectrum and compositions of the CNGSbeam.

O Provide cross-check for the reconstruction andcalibration of the events fully contained in Argon andin the transition region.


Seach for muon disappearance

Sin22θ = 1

Sin22θ = 0.8

Sin22θ = 0.5

Sin22θ = 0.2

5 10 15 20 25 300

0.2

0.4

0.6

0.8

1.0

1.2Survival Probability

Rat

io

E (GeV)ν

∆m eV2 3 25 10= × − O Simplest analysis with

events in the solid target

O ≈7000 νµ CC events/year

O For a restricted range of∆m2, it is possible to lookfor muon neutrinodisappearance throughthe distortion of thepredicted νµ CCspectrum.


Detection of ντ from ντ CC interactions

O Tools for background rejectionÜ kinematics:

– Requires good particle identification and resolution inmomentum unbalance (unseen ν) (à la NOMAD)

Ü direct observation of decay topology “signature”– γcτ = 0.5-1 mm

– Requires emulsion : ~ 1mm granularity (à la CHORUS)

νµ → ντ → τ + Xoscillation CC

e

h nh

h h h nh

ννµνν

νν

−

− + −

0

0

18%18%50%14%


Tau appearance - Electron channelO Search for distortions in the visible energy spectrum of

leading electron sampleÜ Exploit the small intrinsic νe contamination of the beam (0.8% of νµ CC)

Ü Exploit the unique e/¹0 separation

Ü Excess at low energy

O Excess visible

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40

νe + ντ CCνe CCντ CC

Evisible (GeV)

Eve

nts

/20k

ton

x y

ear

Total visible energy

ν e CC

≈≈ + →

470

110

νν τ νντ

eCC

CC e

∆m eV2 3 23 5 10= × −.


Search for tau appearance

O Golden channel: electron decay mode of the tau leptonÜ Take advantage of the small intrinsic νe contamination of the beam (0.8%

of νµ CC)

O Analysis best performed in the liquid targetÜ Leading electron identification (hadrons misid) and excellent energy

measurement in ArÜ Jet reconstruction in Ar, used as homogeneous calorimeter, very good

kinematical reconstruction (in particular, transverse plane)

O Backgrounds in liquid target (20 kt x year):Ü νe CC events (470 events)

– “leading electrons” samples: Intrinsic beam contamination, hard energyspectrum, balanced events

Ü ν NC events (17800 events)– “non-prompt” electrons: Dalitz decays, misidentified hadrons

Ü νµ CC events (54300 events)– “non-prompt” electrons– Only when leading muon cannot be identified (very soft muon or escaping)


Tau appearance - kinematical selection

O Kinematical selection in order to enhance S/B ratioÜ Will be tuned “a posteriori” depending on the actual ∆m2

O Intrinsic beam νe CC componentÜ Event kinematics simulated with nuclear model (initial state fermion+final

state tracking of hadrons) à “tuned” to reproduce NOMAD dataÜ Kinematical reconstruction will be studied in situ with νµ CC events

Kin

emat

ical

sele

ctio

n


Tau appearance - kinematic selection (II)

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40


Evisible (GeV)

Eve

nts

/20k

ton

x y

ear

0

5

10

15

20

25

30

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5


Electron PT (GeV)E

ven

ts/2

0kto

n x

yea

r

Total visible energy Transverse P electron

ν e CC ενeCC =17 5. %

εντCC = 93%

ενeCC = 48%

εντCC = 81%


Kinematical cuts are tuned a posteriori

0

2

4

6

8

10

12

14

16

18

20

0 0.5 1 1.5 2 2.5 3


Missing PT (GeV)

Eve

nts/

20kt

on x

yea

r

20 kton x year exposure

0

10

20

30

40

50

60

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Missing PT Cut (GeV)

Nu

mb

er

of

exp

ecte

d e

ven

ts

Transverse missing PT

ν e CC ενeCC =14%

εντCC = 65%P GeVT miss, . :> 0 6


O Golden electron channel in liquid target alreadyprovides large tau appearance signal

O Other decay modes (hadronic 1-prong & 3 prongs)and searches with all classes of events (solid and“transition” region) will complement the analysis andprovide powerful cross-checks.

Summary tau appearance

Fully identified

P GeVT miss, . :> 0 6


1

2

3

4

5

6

7

8

0 5 10 15 20 25 30 35 40

Exposure (kton x year)

Sta

tistic

al S

igni

fican

ce (σ

)

4 years CNGS (shared)←

1 year CNGS(dedicated)→

Statistical significance of golden channel

O The statisticalsignificance iscomputed usingPoisson distribution

O Over the fullSuperkamiokandefavored region(@99%C.L.), will anexcess appear at theCNGS in 4-5 years ofrunning.

O Dedicated runs(a.s.a.p.) should not beneglected!

P GeVT miss, . :> 0 6


Search for electron appearance

O Selection of leading electron

events

O Non-leading electron

(conversions, Dalitz) rejected

by imaging

O Simple event counting

Ü Evis < 20 GeV

Ü Can be improved by E-dependent

fitting procedure

O Assume overall 5-10% νe

beam fraction systematic error⇒ Cover LSND claim…

⇒ Look for small νe mixing at low ∆m2

10-4

10-3

10-2

10-1

1

10

10-5

10-4

10-3

10-2

10-1

sin2 2Θ

∆m2 (

eV2 )


Electron appearanceO Relevant for testing LSND signal and possible muon-electron mixing at low ∆m2

0

20

40

60

80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80Evisible (GeV)

Eve

nts

/20k

ton

x y

ear

νe CC + oscillated νµνe CCOscillated νµ

10-4

10-3

10-2

10-1

1

10

10-5

10-4

10-3

10-2

10-1

sin2 2Θ

∆m2 (

eV2 )∆m eV2 2 20 4 2 0 025= =. ; sin .θ

]


Electron appearance

O Sensitivity at low ∆m2

ÜLimited by knowledge ofthe beam

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20 25 30 35 40Evisible (GeV)

Eve

nts

/20k

ton

x y

ear

νe CC + oscillated νµνe CCOscillated νµ

∆m eV2 3 2 23 10 2 0 02= × =− ; sin .θ

10-4

10-3

10-2

10-1

1

10

10-5

10-4

10-3

10-2

10-1

sin2 2Θ

∆m2 (

eV2 )

]


Beam systematics: νµ component

O Influence of instrumental effectsinvestigated:ÜCNGS nominal setupÜCNGS1: misalignment beam-axis

detector of 400 mÜCNGS2 (unrealistic!):

– Beam impact point 1mm out from rod axis– Horn and reflector offset of 2cm w.r.t.

target axis– Simulation of non gaussian tails in beam

shape– Horn and reflector peak currents lowered

by 10%

O High energy part of νµ spectrumless sensitive to beam setup

10 2

10 3

10 4

0 20 40 60 80 100

CNGS-1 beam

CNGS-2 beam

CNGS beam

Eν

30% bin to bin systematics is a conservative estimate


Beam systematics: νe component

O Less sensitive to variationsin beam setup since νemostly come from kaondecays

O νe component accuratelydetermined in absolutenormalization and spectralshape from high energypart of νµ spectrum (alsocomes from kaon decay)

10-1

1

0 20 40 60 80 100

CNGS beam

CNGS-1 beam

CNGS-2 beam

(νe CC x 40)/νµ CC

Eν

10% systematic error is

conservative!


Comparison of sensitivities (CNGS)

νµ → ντ νµ → νe

(MINOS high energy beam (PH2high) configuration, NUMI-L228 & TDR)(OPERA, CERN/SPSC 99-20)(ICANOE, tau appearance, electron channel only, optimized for low ∆m2)

10-4

10-3

10-2

10-1

1

10

10-5

10-4

10-3

10-2

10-1

sin2 2Θ

∆m2 (

eV2 )

10-3

10-2

10-1

10-3

10-2

10-1

sin2 2θ

∆m2 (e

V2 )

10-3

10-2

10-1

e)

High ∆m2 furtherimproved by inclusion ofhadronic channels

4 years


Atmospheric (CR) neutrinos

O Innovative & improved experimental technique than SuperK orSoudan

O Similar statistics as SuperK but free of systematic biases!Ü Complete event reconstructionÜ Minimal sets of cutsÜ Measurement of all neutrino flavors in all modes (CC & NC)

O We have considered the following topics:C ν disappearance, for any flavor not only muon neutrinos:

C Detection of the oscillation pattern in L/EC Double ratio (µ/e)C Up/down asymmetry, zenith angle

C ντ appearance: clean comparison NC/CC with expectationC Direct ντ appearance: upward vs downward rates of „tau-like“ eventsC Upward going muonsC Low energy electrons


Atmospheric neutrino ratesO Flux: 3D calculation, Battistoni et.al., hep-ph/9907408

O Cross-sections: „NUX“, ICARUS Collab.

Rat

es p

er k

t/yea

ron

Arg

on

Energy (GeV)

CC

/GeV

Top

Bottom

νµ + νµ CC-

0 0.5 1 1.5 2 2.5 3

0

500

1000

1500

2000

2500

3000

3500

4000

1500060001500


Atmospheric νµ CC

90 cm

90 c

mEν = 370 MeV

Pµ = 250 MeV

Tp = 90 MeV

µ

p


Atmospheric νe CC

100 cm

90 c

m

Eν = 450 MeV

Pe = 200 MeV

Tp = 240 MeVp

e


Muon measurement

O Full muon containmentrequires an extraordinarydetector mass thickness

O However, in ICANOE,this is not mandatorysince we can exploitmultiple scattering inthe measurement of themuon momentum

O Resolution comparableto magnetized Femeasurement

0

10

20

30

40

50

60

70

80

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5Energy Threshold (GeV)

% C

on

tain

men

t

0

10

20

30

40

50

60

70

80

% R

esol

utio

n

µ containment


µ momentum by multiple scattering (III)

Theta Angle-10 0 10 20 30 40 50 60 70 80 90

Rel

ativ

e E

rro

r

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8Angular Dependence for Different Track Length

E = 10 GeV

L = 2.5 m

L = 3.0 m

L = 5.0 m

Θ (angle between track direction and wire plane in

degrees)

The precision on µmomentum measurementby means of multiplecoulomb scattering isentirely adequate tomatch the requirementsfor both atmospheric andbeam neutrino events andcomplements the goodcalorimetric energyresolution for the hadronicjet


Reconstructed L/E resolution

∆( / ) %L E RMS ≈ 30

O Smearing in L/E is introduced by finite resolutionÜFermi motion: we apply a cut on Evisible > 1 GeV (40% of all

events!)

ÜMeasurement resolution

Ful

l sim

ulat

ion

ν νµ µ+ CC

0

50

100

150

200

250

300

350

400

-1 -0.5 0 0.5 1

Mean

RMS

-0.3652E-01

0.3098

((L/E)MC-(L/E)meas)/(L/E)MC

Eve

nts

(arb

itrar

y un

its)

0

100

200

300

400

500

600

700

800

-1 -0.5 0 0.5 1

Mean

RMS

-0.4069E-01

0.2875

((L/E)MC-(L/E)meas)/(L/E)MC

Eve

nts

(arb

itrar

y un

its)


L/E distribution: electrons and muons

O Oscillation parameters:Ü∆m2

32 = 3.5 x 10-3 eV2

Üsin2 2Θ23 = 0.9

Üsin2 2Θ13 = 0.1

O Electron sample canbe used as areference for nooscillation case

0

10

20

30

40

50

60

0 0.5 1 1.5 2 2.5 3 3.5 4Log10(L/E)

Eve

nts

for

25 k

ton

x ye

ar

0

20

40

60

80

100

120

140

0 0.5 1 1.5 2 2.5 3 3.5 4Log10(L/E)

Eve

nts

for

25 k

ton

x ye

ar

Electrons

Muons

25 kt year


νµ disappearance – L/E distribution

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.5 1 1.5 2 2.5 3 3.5 4

log(L/E (km/GeV))

(νµ

+ ν µ- C

C)o

bs / (

ν µ +

ν µ- CC

)exp

O Compare expecteddistribution with observed

O Extremely simple selection:Ü Keep all events with

Evisible>1 GeV : ε ≈ 40% of allevents!

O The characteristicmodulation of a given ∆m2 isclearly visible.

O “DIP” visible

O Can precisely measure theoscillation parameter andresolution can be improved(items under study)

50 kt year


Alternative models — neutrino decayO „SuperK data does not

have sufficient resolutionto exclude exotic solutionto muon neutrinodisappearance“cf Barger et.al., PRL 82(1999) 2640 & hep-ph/9907421

O By resolving the „dip“characteristic of theflavor oscillation, wecan exclude exoticsolutions.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.5 1 1.5 2 2.5 3 3.5 4

log(E/L(km/GeV))

(νµ

+ ν µ- C

C)o

bs / (

ν µ +

ν µ- CC

)exp

50 kt year


Comparison of atmospheric ν rates

O SuperKamiokande vs ICANOE (data for µ/e)ÜSuperK: 22.5 kton sensitive mass

– Single ring, fully contained, Sub+Multi GeV 2100

ÜICANOE:– 5.6 kton LAr sensitive mass 1150– 3.2 kton calorimeter mass 500

O Monolith(30kt) vs ICANOE (data for L/E analysis)

νµ CC 420 380

νe CC V 160

ν NC V 400

Eµ > 1.5 GeV+quality cuts

Evisible > 1 GeVMonolith ICANOE liquidEvents/year ICANOE solid

260}

1650}

Events/year

Evisible > 1 GeV


Neutral currents

O „Indirect tau appearance“: Discriminate betweenνµ→ντ and νµ→νs oscillations

O Neutral current selection based on absence of leadingfinal state leptonÜVery clean, does not rely on unknown cross-sections (e.g.

SuperK, ¹0)

0

0.2

0.4

0.6

0.8

1

1.2

10-6

10-5

10-4

10-3

10-2

10-1

1∆m2 eV2

(NC

/νe

CC

) DA

TA/(

NC

/νe

CC

) MC

ντ

νs


Search for „Tau-like“ atm events

O „Direct tau appearance“: Discriminate between νµ→ντ andνµ→νs oscillations by looking for excess of „neutral-current-like“ events produced by upward neutrinos (large taubranching into hadronic channels)

O Search for ντ CC at high energy (tau threshold)

νµ → ντ → τ + Xoscillation

e

h nh

h h h nh

ννµνν

νν

−

− + −

0

0

18%18%50%14%

≈1 ντ CC/kt/year


Up/down asymmetry of NC events

O Compare NC(top) to NC(bottom) at high energyÜRequires good discrimination of NC event direction

O Count events as a function of visible energy

Zenith angle distribution of events, Fluka 3D

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1cos(zenith angle)

dN

/dco

sθ (

Evt

s/kt

/yea

r)

cos θ = .8, L= 10000 km

cos θ = .8,L= 25 km

cos θ = 0L= 500 km

θ

L

Earth

Detector

ντ

Zenith angle

Rates as a function of energy ∆m2 = 3.5 x 10–3 eV2


Kinematical selection „tau-like“ events

1

1.5

2

2.5

3

3.5

4

4.5

5

0 20 40 60 80 100Exposure (kton x year)

Sta

tist

ical

Sig

nif

ican

ce (

σ)

•Improved discrimination by a study ofthe event kinematical properties (bymeans of a likelihood function)

•Further detailed studies underprogress

50 kt year


Test of LMA MSW solutionO The currently preferred solution to the solar neutrino deficit

involves a “matter-enhanced” large-mixing angleνµ ↔ νe oscillations

O The parameters areÜ ∆m2

21 ≈ 10–(4÷5) eV2

Ü sin22θ ≈ 0.7

O SK D/N effectO Matter effect:

∆mP

Pe

e

2 0>↔ ↑↔ ↓

: ( )

( )

ν νν ν

µ

µ

∆mP

Pe

e

2 0<↔ ↓↔ ↑

: ( )

( )

ν νν ν

µ

µ

Can distinguish ν from ν ⇒ test sign!


Low energy electron events

O Study low energy region (below 1 GeV) of electron CCsample

O Assume electron-muonoscillation at ∆m2

relevant for solarneutrino deficit

O Test matter affectedoscillations inneutrinoscoming from below.

νµ ← → νe oscillations in matter

0

10

20

30

40

50

60

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Evisible (GeV)

Eve

nts

/20

kto

n x

yea

r

Oscillated νe + νµ CCUnoscillated νe CC


Excess in low energy electron sample

νµ ← → νe oscillations in matter

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Evisible (GeV)

Osc

illat

ed/U

no

scill

ated

(20

kto

n x

yea

r)

è Distortion of the visibleenergy spectrum at low energy

èFurther studies in progress


Oscillations in matter

0

0.2

0.4

0.6

0.8

1

0 2000 4000 6000 8000 10000 12000Distance (km)

P(ν

µ →

νe)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 2000 4000 6000 8000 10000 12000Distance (km)

P(ν

µ →

νe)

Eν = 700 MeV

Eν = 100 MeV

Red: ν, anti-ν osc vacuumBlack: ν osc matterBlue: anti-ν osc matter

_ _ _

_ _ _


Upward going muons

O Measurement of upward going muons produced ininteraction of neutrinos in surrounding rock.

O Rejection factor of at least 106 needed againstdownward going muonsÜObtained thanks to the fine spatial resolution which allows to

identify the δ-rays produced along the track (≈1 ray Eδ > 10MeV per meter of track)

O Event rates comparable to that of MACROÜabout 250 events/yearÜ≈30% reduction in case of oscillation with ∆m2≈3x10–3 eV2

O In addition, ICANOE can add new information sincemuon energy can be measured by MS or by thespectrometer.


Sorting out mixing

O If neutrino oscillations are indeed the cause of the effectseen in atmospheric neutrinos, then the next task willbe to measure oscillation parameters

O ICANOE can fully sort out mixing scenarios, sinceÜBoth beam and atmospheric neutrino can be measured with

unprecedented resolution

ÜUnambiguous flavor identification of all neutrino species

ÜFull kinematical reconstruction to distinguish electrons fromnue’s and taus from nutau’s ν e νµ

ντ

∆m122

∆m322


Three neutrino mixing

O Mixing determined by 3 angles and 2 ∆m2

O Assume that oscillations from solar and atmosphericdecouple ⇒ θ13∈ [0,¹/4], θ23 ∈ [0,¹/4], ∆m2

32

CKM-like

∆ ∆322 2

3221 27=

sin . m

LE

where


χ2-method

O Reference parametersÜsin22θ13= 0.1 sin22θ23 = 0.9 ∆m2

32=3.5x10–3 eV2

O Perform χ2 test combining observation fromÜAtmospheric neutrinosÜBeam CNGS electron and tau appearanceÜBeam CNGS muon disappearance

Binned histograms

•Visible energy, pTmiss, pTe•Visible energy•Zenith angle distributions


Combining complementary informationMuons

0

20

40

60

80

100

120

140

-1 -0.5 0 0.5 1

cosθ

Evis ‹ 0.4 GeV

0

20

40

60

80

100

120

140

-1 -0.5 0 0.5 1

cosθ

0.4 ‹ Evis ‹ 1.0 GeV

0

20

40

60

80

100

120

140

-1 -0.5 0 0.5 1

cosθ

1.0 ‹ Evis ‹ 2.5 GeV

0

20

40

60

80

100

120

140

-1 -0.5 0 0.5 1

2.5 ‹ Evis ‹ 50 GeV

cosθ

∆m2 = 3.5 x 10-3 eV2 sin2 2Θ23=0.9 sin2 2Θ13=0.1

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40 45 50

Allνe CCνµ→νe CCντ CC

Evisible (GeV)

Eve

nts/

20kt

on x

yea

r

Atmospheric neutrinosBeam CNGSelectron and tau

appearance

Beam CNGSmuon

disappearance

⇒ Very powerful constraints on mixing scenarios!


CNGS electron appearance

CNGS e-appearance data only

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01

0 0.2 0.4 0.6 0.8 1

sin2 2Θ23

∆ m

2 32 (

eV2 )

(68% C.L.)(90% C.L.)(99% C.L.)

O Systematic errors: uncorrelated bin-to-bin:Ü±10% νeCC, ±10% ντ CC

CNGS e-appearance data only

0

2

4

6

8

10

12

0.002 0.004 0.006 0.008 0.01

1σ2σ

∆ m2 32 (eV2)

χ2

0

2

4

6

8

10

12

0 0.25 0.5 0.75 1

1σ2σ

sin2 2Θ23

χ2

0

2

4

6

8

10

12

0 0.25 0.5 0.75 1

1σ2σ

sin2 2Θ13

χ2


CNGS muon disappearance

O Systematic errors: uncorrelated bin-to-bin: ±30% νµ CC

CNGS disappearance data only

0

2

4

6

8

10

12

0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01

1σ2σ

∆ m2 32 (eV2)

χ2

0

2

4

6

8

10

12

0 0.2 0.4 0.6 0.8 1

1σ2σ

sin2 2Θ23

χ2

CNGS disappearance data only

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01

0 0.2 0.4 0.6 0.8 1

sin2 2Θ23

∆ m

2 32 (

eV2 )

(68% C.L.)(90% C.L.)(99% C.L.)


Atmospheric zenith angle

O Systematic errors: uncorrelated bin-to-bin: ±20%Atmospheric data only

0

2

4

6

8

10

12

0.002 0.004 0.006 0.008 0.01

1σ2σ

∆ m2 32 (eV2)

χ2

0

2

4

6

8

10

12

0 0.25 0.5 0.75 1

1σ2σ

sin2 2Θ23

χ2

0

2

4

6

8

10

12

0 0.25 0.5 0.75 1

1σ2σ

sin2 2Θ13

χ2

Muons

0

20

40

60

80

100

120

140

-1 -0.5 0 0.5 1

cosθ

Evis ‹ 0.4 GeV

0

20

40

60

80

100

120

140

-1 -0.5 0 0.5 1

cosθ

0.4 ‹ Evis ‹ 1.0 GeV

0

20

40

60

80

100

120

140

-1 -0.5 0 0.5 1

cosθ

1.0 ‹ Evis ‹ 2.5 GeV

0

20

40

60

80

100

120

140

-1 -0.5 0 0.5 1

2.5 ‹ Evis ‹ 50 GeV

cosθ

Electrons

0

20

40

60

80

100

-1 -0.5 0 0.5 1

cosθ

Evis ‹ 0.4 GeV

0

20

40

60

80

100

-1 -0.5 0 0.5 1

cosθ

0.4 ‹ Evis ‹ 1.0 GeV

0

20

40

60

80

100

-1 -0.5 0 0.5 1

cosθ

1.0 ‹ Evis ‹ 2.5 GeV

0

20

40

60

80

100

-1 -0.5 0 0.5 1

2.5 ‹ Evis ‹ 50 GeV

cosθ


All data combined

CNGS+atm data combined

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01

0 0.2 0.4 0.6 0.8 1

sin2 2Θ23

∆ m

2 32 (

eV2 )

(68% C.L.)(90% C.L.)(99% C.L.)


0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

sin2 2Θ13

sin

2 2Θ

23

(68% C.L.)(90% C.L.)(99% C.L.)


All data combined

O Accurate measurementpossible:

O Ongoing similar study formeasurement of ∆m2

12and sin22θ12


0

2

4

6

8

10

12

0.002 0.004 0.006 0.008 0.01

1σ2σ

∆ m2 32 (eV2)

χ2

0

2

4

6

8

10

12

0 0.25 0.5 0.75 1

1σ2σ

sin2 2Θ23

χ2

0

2

4

6

8

10

12

0 0.25 0.5 0.75 1

1σ2σ

sin2 2Θ13

χ2

sin22θ13= 0.10±0.04sin22θ23 = 0.90±0.12∆m2

32=(3.5±0.4)x10–3 eV2


Superkamiokande comparisonTwo family (νµ, ντ) mixing

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01

0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1

ICANOE Beam+atm events (68% C.L.)ICANOE Beam+atm events (90% C.L.)ICANOE Beam+atm events (99% C.L.)

Kamiokande (90% C.L.)SuperKamiokande (90% C.L.)

sin2 2Θ23

∆ m

2 32 (

eV2 )

Ref. parameters: sin22θ13= 0 sin22θ23 = 1 ∆m2

32=3.5x10–3 eV2


p→νK decay


p→e+ π0 decay


p→e+ π0 decay mode

00.10.20.30.40.50.60.70.80.9

1

0 0.2 0.4 0.6 0.8 1 1.2Invariant Mass (GeV/c2)

Tota

l Mom

entu

m (G

eV/c

)

00.10.20.30.40.50.60.70.80.9

1


Tota

l Mom

entu

m (G

eV/c

)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1


Tota

l Mom

entu

m (G

eV/c

)

pà e+ π0

ve CC

Argon


ICANOE Nucleon Decay Sensitivities

p fi˚e- k+ p+p fi m-k+p+p fi m+ k0Sp fi˚m+ k0Lp fi e-p+p+

p fi n p+p fi e+n n

p fi m+n nn fi e-e+n

n fi e-p+n fi m-p+

n fi m+e-nn fi e-k+n fi˚m-k+

n fi e-e+e-p+n fi e-e+e-k+

n fi m-e+e-p+n fi m-e+e-k+

10 10 10 10 10Lifetime Limit (years)

p → e− κ+ π+p → µ− κ+ π+p → µ+ κ0Sp → µ+ κ0Lp → e− π+ π+p → ν π+p → e+ ν νp → µ+ ν νn → e− e+ νn → e− π+n → µ− π+n → µ+ e− νn → e− κ+n → µ− κ+n → e− e+ e− π+n → e− e+ e− κ+n → µ− e+ e− π+n → µ− e+ e− κ+

PDG98

ICARUS 5 / 20 / 50 kton ¥ year

30 31 32 33 34


ICANOE physics goalsO “to elucidate in a comprehensive way the pattern of

neutrino masses and mixing” beyond what availableat the time from SuperK

O Observe directly the oscillation mechanism andmeasure the full mixing matrix and mass differencesÜSimultaneous study in a single experiment of atmospheric

and CERN-NGS neutrinos (⇐ fully isotropic detection techniqueand full event reconstruction)

ÜTest of large mixing angle MSW solution to solar neutrinodeficit; study of matter effects in Earth with atmosphericneutrinos down to kinematical threshold

O Stability of matter: search for nucleon decays

long baseline accelerator neutrino experiments: present and...

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