cosmic and rare underground signals…

GSSC, A. Rubbia, Sept 2001

Cosmic and Rare Underground Signals…

ICARUS is…

… a solar + SN neutrino experiment… an atmospheric neutrino experiment… a long-baseline tau and electron appearance experiment… a background-free nucleon decay search experiment… etc…

The physics potentialities of ICARUS have been discussed

in many occasions ⇒⇒⇒⇒ see next slide…

We concentrate on recent updates not necessarily described

in existing documents…


1. The ICARUS Collaboration:ICARUS: a proposal for the Gran Sasso Laboratory Experiment proposal, INFN/AE-85/7,Frascati (Italy, 1985).

2. M.˚Baldo-Ceolin et al. (32 authors):ICARUS I: an optimized, real-time detector of solar neutrinos, Experiment proposal,LNF-89/005 (R), 10 Feb. 1989.

3. P. C̊ennini et al. (53 authors), ICARUS II: second generation proton decay experiment and neutrino observatory at the GranSasso laboratory (Volume I), Experiment proposal, LNGS-94/99-I, Sept. 1993.

4. P. C̊ennini et al. (57 authors), ICARUS II: second generation proton decay experiment and neutrino observatory at the GranSasso laboratory (Volume II), Experiment proposal, LNGS-94/99-II, May 1994.

5. P. C̊ennini et al. (59 authors):, A first 600 ton ICARUS detector installed at the Gran Sasso laboratory, Addendum toproposal, LNGS-95/10, May 1995.

6. P. C̊ennini et al. (70 authors):, A search programme for explicit neutrino oscillations at long and medium baselines with theICARUS detector, Experiment proposal, CERN/SPSLC/96-58, SPSLC/P304, Dec. 1996.

7. P. C̊ennini et al. (70 authors):, ICARUS-Like technology for long baseline neutrino oscillations, Experiment proposal,CERN/SPSC 98-33, Oct. 1998.

8. F.˚Arneodo et al. (112 authors), ICANOE: a proposal for a CERN-GS long baseline and atmospheric neutrino oscillationexperiment, Experiment proposal, INFN/AE-99-17, CERN/SPSC 99-25, SPSC/P314, Sep. 1999.

9. F.˚Arneodo et al. (109 authors), ICANOE: preliminary techincal design & cost estimate, Addendum to proposal, LNGS-P21/99-ADD1, CERN/SPSC 99-39, SPSC/P314 Add.1, Nov. 1999.

10. F.˚Arneodo et al. (123 authors), ICANOE: answers to questions and remarks concerning the ICANOE project, Addendum toproposal, LNGS-P21/99-ADD2, CERN/SPSC 99-40, SPSC/P314 Add.2, Nov. 1999.

11. F.˚Arneodo et al., THE ICARUS EXPERIMENT: A Second-Generation Proton Decay Experiment and Neutrino Observatoryat the Gran Sasso Laboratory., INITIAL PHYSICS PROGRAM, ICARUS-TM/2001-03 LNGS P28/01 LNGS-EXP 13/89add.1/01

ICARUS bibliography


Solar neutrino experiment

• Real-time detection of neutrinos through two independentreactions

• Signature: primary electron track• CC/NC separation: (secondary ionization from 40K* de-excitation)• Primary electron detection threshold (determined by background

considerations): Ethres = 5 MeV• Sensitive to 8B and hep components of the solar neutrino

spectrum

ν νx xe e+ → +− − νe Ar K e+ → + −40 40 *

Elastic scattering on atomicelectron

νννν absorption on Argonnuclei


Solar νννν and background event rates

Event rates foran exposure of1 kton×year

Tthresh = 5 MeV

No oscillation hypothesis

BP98 νννν Flux (8B) n flux measured @ LNGS


1 m

0.5 m

• e-like track~6.5 MeV

• 2 e-like spotsfrom Compton conversion

T600 test @ Pv: Run 785 - Evt 4 (July 22nd, 2001)

2 4 6 12 18

Drift Coord. (m)

Zoom view

~800KeV

~800KeV

Cosmic ray event containing a “Solar neutrino”-like signature “inverse ββββ reaction” type with:

Wire Coord. (m)

Preliminary analysis


Solar neutrino analysis• Elastic scattering

— σ precisely known <1%

– Directional (Sun correlation

possible), ε ≈ 50%

• Fermi (F) transition to 4.38 MeV IAS40K

— σ precisely known <1%

Bahcall, J.N. Rev. Mod. Phys., 50, 881 (1978)

• Gamov-Teller (GT) to various 40K

levels

— σ less precisely known ≈10%

Ormand et.al, PLB 345 (1995) 343.

– σGT ≈ 2σF

IAS

3.79

8 M

eV3.11

0 M

eV2.

730

MeV

νe Ar K e+ → + −40 40 *

K deexcitation

E (MeV) BR (%)

2.290 0.19

2.730 28.94

3.110 18.16

3.146 1.90

3.739 0.45

3.798 13.69

4.384 32.76

4.789 0.48

5.282 0.93

5.642 0.09

5.922 0.83

6.151 0.04

6.428 0.92

6.480 0.42

6.683 0.05

6.876 0.01

40K

exc

ited

ener

gy s

tate

s

IAS


Real Event recorded with 50lt ICARUS Prototype

5.6 MeV e-Track

End-point

(Gamma source)


Compton activitylimited to volume ofabout 50 cm radius

aroundthe primary vertex

(mean free path γγγγ(1MeV) ¯ 20 cm)


γγγγ’s energy reconstruction� Energy depositions

collected andregrouped intoclusters.

� The most energeticcluster is assigned tothe primary electron.

� The other clusters(the associatedCompton energy)correspond to thedeexcitation photons.

� Assume threshold onsingle wire at 50, 100or 150 KeV.

mult = 4Evis = 9.35 MeVElep = 5.65 MeV

IAS

e−−−−

γγγγγγγγ

γγγγ

γγγγ

γγγγ

γγγγ

e−−−−

X-Y projection

Y-Z projection


Precise measurement of the CC rate

IAS

3.798 MeV line

A precise measurement of thesolar flux can be obtained by

distinguishing thesuperallowed Fermi transition

among the other excitedstates

Reconstructed photon spectrum

An accurate calibration ofthe detector energy

response is fundamental

Ethreshold = 50 KeV

(Ongoing study)(no background included)


IAS discrimination vs energy threshold

Line resolution depends on energy detection threshold

Plots normalized to 2 years running of 5 T600 modules

Ethreshold = 50 KeV Ethreshold = 150 KeV

IASIAS

3.798 MeVline

3.798 MeVline


IAS discrimination

1.036

0.968

1.052

0.948

αααα ⇐ IAS normalization

ββββ ⇐ GT (3.798 MeV) normalization

At 70% C.L., αααα could be determined with 5% precision(Ethreshold = 150 KeV) in 2 years with 5 T600 modules

Ethreshold = 50 KeV Ethreshold = 150 KeV

5 T600 modules 2 years running 5 T600 modules 2 years running

αααα αααα

ββββ ββββ

(no background included)


Solar neutrino event analysis

� Rather thanrelying on theaccuratereconstruction ofthe associatedCompton energy,one can classifyevents�Multiplicity of

Comptonelectrons

� Discrete cut onassociatedenergy, e.g. >1MeV or < 1 MeV

ES

GT

F

Backgrounds


Background estimates

• Natural radioactivity: 40K, U, Th, Ra present in the rockand atmosphere ⇒⇒⇒⇒ photons and neutrons (SF, (αααα,n)reaction)

• Radioactive Ar isotopes: 39Ar, 42Ar• Radioactivity of the chamber and detector walls structure• Nuclear photo-dissociation: high energy C.R. muons

All these various contributions have been evaluated.Neutrons are the only radiation able to generate high

energy electrons in the region Ee> 5 MeV.


Backgrounds from γγγγ and n• Direct photons

– Natural radioactivity limited to Eγ < 2.4 MeV– Detector resolution studied with Am-Be 4.13 MeV γ source– Source considered to be negligible above 5 MeV

• Neutrons– Neutron flux measured in situ (Nuov. Cim. A8 (1999) 819)– Reduced by about factor 100 by neutron shield– Remaining neutron produce background by capture on

various elements Stableisotope

Abundance(%) Process

σσσσ(barns)

Q-value(MeV)

40Ar 99.6 n + 40Ar → 41Ar* → 41Ar + γ‘s 0.66 6.09936Ar 0.337 n + 36Ar → 37Ar* → 37Ar + γ‘s 5.2 8.78838Ar 0.063 n + 38Ar → 39Ar* → 39Ar + γ‘s 0.8 6.598

27Al 100 n + 27Al → 28Al* → 28Al + γ‘s 0.23 7.725

56Fe 91.72 n + 56Fe → 57Fe* → 57Fe + γ‘s 2.59 7.64654Fe 5.8 n + 54Fe → 55Fe* → 55Fe + γ‘s 2.25 9.29857Fe 2.2 n + 57Fe → 58Fe* → 58Fe + γ‘s 2.48 10.04558Fe 0.28 n + 58Fe → 59Fe* → 59Fe + γ‘s 1.28 6.581

Dewar

Inner chamberstructure

Natural Ar


Energy resolution at a few MeV

600

500

400

300

200

100

0

Cou

nts

per

bin

(200

0 el

ectr

ons)

18016014012010080Deposited charge (electrons)

• 103

Com

pton

spe

ctru

m

(ba

ckgr

ound

sub

trac

ted) σσσσE/E=7% for electrons

around 4 MeV

∆∆∆∆E ≈≈≈≈ 3 MeV

Consistent with zero

Am-Be 4.13 MeV γγγγ source in 3 ton prototype


Detailed T600 geometry simulation

� Detailed description ofthe detector geometry:dimensions, layers andmaterials used.

� Implemented inFLUKA standalone.

HALL B

T600

�

ROCK

Y (cm)

X (c

m)

X coordinate Height direction

Y coordinate Drift direction

Z coordinate Along the beam


T600 detailed geometry

a

b

cd

e

f

gh

i

j

kk

�

ICARUS T600

�

Y (cm)

X (c

m)

a) rockb) hallBc) neutron shieldd) cables-electronicse) platformsf) insulationg) gaph) containeri) gas phase Arj) inactive LArk) active LAr


Neutron capture background (I)ICARUS T600 REGIONS

Neutron capturesper sec in region

Rock 1.97Hall B 0.10Neutron shield 0.77Cables-electronics 1.04 × 10-5

Platforms 7.43 × 10-5

3rd insulation layer 6.92 × 10-5

2nd insulation layer 2.70 × 10-4

1st insulation layer 8.70 × 10-5

Insulation between half-modules 5.54 × 10-6

1st half-module gap 1.45 × 10-5

2nd half-module gap 1.47 × 10-5

Al container wall: 1st half-module 3.08 × 10-5

Al container wall: 2nd half-module 3.06 × 10-5

Stainless Steel layer: 1st half-module 2.00 × 10-4

Stainless Steel layer: 2nd half-module 2.01 × 10-4

Gas phase Ar layer: 1st half-module 5.10 × 10-8

Gas phase Ar layer:2nd half-module 5.98 × 10-8

LAr inactive volume: 1st half-module 1.61 × 10-4

LAr inactive volume: 2nd half-module 1.61 × 10-4

LAr active volume: 1st half-module 1.02 × 10-4

LAr active volume: 2nd half-module 1.06 × 10-4

� FLUKA standalonesimulation

� Full propagation ofneutron withindetailed T600geometry in LNGShall.

� Input :

� Neutron fluxspectrum measured@ LNGS.


Neutron capture background (II)

Naturalradioactivity

Spontaneous fission orSpontaneous fission or((αα ,n) reactions,n) reactions

Captures in the detectorCaptures in the detector((4040Ar, Ar, 2727Al, Al, 5656Fe,Fe,……))

n flux γγγγ-rays e-

energies inenergies inthe the 88BBrangerange

Y(cm)�

X(c

m)�

n/cm2/s capt./cm3/s

Y(cm)

X(c

m)

Neutronshield

(Full FLUKAsimulation)

≈7400 captures/year in 500 ton fiducial

≈150 /year with Ee>5 MeV


Neutron capture backgrounds (III)• Neutron capture in fiducial volume

– n capture in natural Argon ≈7400 /year in T600– Dangerous component: 36Ar (0.3% abundance) Q=8.8 MeV– Not localized

• Neutron capture in other parts of detector, producing photonswhich enter the liquid argon fiducial volume– Aluminum dewar ≈2500 /year in T600– Stainless-steel inner chamber structure ≈15000 /year in T600– Very localized ⇒ fiducial volume cut, well defined distribution of

distance from detector walls

Beware:¥mean free path γγγγ(1MeV) ≈≈≈≈ 20 cm

¥mean free path n(1MeV) ≈≈≈≈ 200 cm


Neutron capture photon lines (I)

Photon Energy (MeV)

Kinetic energy of the leading Compton electron (MeV)

Neutron capture on natural Argon

Cut

• ≈≈≈≈2% of captures onnatural Ar produce aCompton electronsabove 5 MeV

•However, we mustconsider correlatedphoton emission

•Example: for 36Ar

•Q=8.8 MeV

•Ee> 5 MeV →→→→ ΣΣΣΣ Eγγγγi< 3.8 MeV

•To be compared to IASphoton at 4.384 MeV

LOG

SC

ALE

!


Preliminary backgrounds inclusion

Fraction ES

F

GT

Contamination from (n,γ) capture on 40Ar+36Ar

• Fully correlated

photon emission

•Very little background

expected for IAS

photon at 4.384 MeV


Neutron capture photon lines (II)

Photon Energy (MeV)


Neutron capture on Aluminum

Photon Energy (MeV)


Neutron capture on natural Iron

Cut

27.2% ofcaptures on Alhave electronsabove 5 MeV

Cut

52.4% ofcaptures on Fehave electronsabove 5 MeV

LOG

SC

ALE

!

Reassessment of correlated photon emission under study!


Solar neutrino expected rates

Expected events/year(for a 600 ton detector

in case of no oscillations)

Elastic channel Background

2126

Absorption channels Background

759 26

all cuts imposed

Nucl Instr. And Methods A455 (2000) 376

Off-line event selection done in terms of energy of the primary electronplus

a) Elastic: Angle between electron and solar direction (ε=57%)

b) F+GT: correlation between multiplicity and energy of the associated Compton electrons

(εF=70%, εGT=82%)

Ee > 5 MeV


Solar neutrinos• Question #1: You use cross-sections on Argon-K40 which have to be

obtained from models or with the help of calibrations with mirror nuclei.You mention in the text a discrepancy between 2 expts, what is the size ofthis discrepancy? What is the error on the theoretical cross-section that youwill use? Can you reduce this error at the necessary 1-2%?

• Answer:– We use the calculations of Ormand et al. (PLB345 (1995) 343)

which are close to the results of Liu et.al.– They quote a theoretical error of 6%, but F transition is known to

<1%Tcutoff (MeV) Neutrino absorption cross sections (10-43 cm2)

Elastic Fermi Gamow-Teller0 0.608 10.4 10.5 20.7 28.61 0.509 10.2 10.3 20.3 28.12 0.415 9.44 9.56 18.8 26.03 0.327 8.06 8.16 16.0 22.24 0.248 6.07 6.15 12.1 16.75 0.180 3.85 3.90 7.65 10.66 0.123 1.87 1.89 3.72 5.15

W.Trinder et al., Phys. Lett.B415 (1997) 211

W.Liu et al., Z. Phys. Lett A359(1997) 1


Solar neutrinos• Question #2: In our discussion in Pavia there was a mention of separating GT and F

reactions: what is the physics advantage of doing so? If this is interesting, how is itexperimentally done? Again in case the physics justifies it, with what accuracy doyou separate the two reactions?

• Answer:

– The advantage of measuring GT and F separately is becausetheoretically the F transition is known with high precision (<1%),compared to the GT transitions (≈6%). Hence, measuring the tworates independently is important for comparison with expected rates.

– We are contemplating a preliminary analysis, in which, the separationis done considering the energy of the associated Compton electrons.The excited K* levels should be separately reconstructable.

– We are still working on the background estimates.– The statistical error depends on exposure… ignoring backgrounds, we

get a 5% statistical error for an exposure of 5 ktxyear.


Solar neutrinos• Question #3: We would like to come back to the background evaluation: in table 5

the only dominant background is neutron which is calculated from alpha-nreactions or fissions in the surrounding rock. The photon background is assumed tofall from 2e6 to zero by raising the threshold above 3 MeV! However it was pointedout orally that radioactive material inside the cryostat (or the neutron shield) docause a problem… does a semi quantitative estimate exist?

• Answer:– The photon background is assumed to fall from 2e6 to zero because the

resolution for few MeV tracks has been measured to be 7%. Hence, thisbackground is not expected to contribute above a threshold of 5 MeV.

– The flux of neutron has to be carefully monitored. Their flux in the LNGS hallhas been measured (Nuov. Cim. A8 (1999) 819). Radioactive material inside thedetector can produce neutrons (SF or (α,n)) which could increase the totalflux of neutrons.

– The contamination of the elements used inside the detector have beenmeasured.

– The resulting rates are being reassessed with a FLUKA standalonesimulation. We are working on the “correlated photon emission” spectra byneutron capture on stainless-steel and aluminum.


Solar neutrinos• Question #4: Comparing table 9 and fig 11 with the exclusion of table 8, how

do you define your exclusion ? We do not understand the first statement..Most of the zone for SMA to be for R between 0.99 and 1.08 where after2kt-year you would not reach a 2 sigma exclusion…

• Answer:– The zones indicated in the Figure and the exclusion level in the table

are indicative. They do not represent a “combined” statisticalanalysis, hence do not represent an actual correct statisticaltreatment, but do qualitatively indicate the sensitivity of ICARUS.


Solar neutrino sensitivity

RN N

N N

EStheoryES

ABStheoryABS≡

/

/

ν νx xe e+ → +− − νe Ar K e+ → + −40 40 *

∆R R kt yr kt yr kt yr/ %( ), %( ), %( )≈ × × ×7 1 5 2 4 4

10 10 10 10 10-4 -3 -2 -1 0

10

10

10

10

10

10

10

10

10

10

10

-11

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0.950.98

0.98

0.990.99

0.99

0.99

0.99

1

1.08

1.08

1.08

1.08

1.2

1.3

1.51.92.2

510

20

57

MS

W -

LOW

JustSo

MSW - SMA

MS

W -

LMA

sin2 2 θ

∆ m

2 (eV

)2

(a)

ES=elastic scattering ABS=absorption events

Independent of the 8Btotal ν flux predicted bysolar models.

90%C.L.95%C.L.


Understanding atmospheric neutrinos• ICARUS thanks to its unprecedented imaging properties

will provide– An observation of atmospheric neutrino events with very

high quality.– An unbiased, mostly systematic free, observation of

atmospheric neutrino events⇒ CC/NC separation, clean e/µ discrimination, all final

states accessible, excellent e/π0 separation, particleidentification (p/K/π) for slow particles

– An excellent reconstruction of incoming neutrinoproperties (energy and direction)

A new tool to understand completely atmosphericneutrinos, in terms of their basic properties (flux,flavor) & of the physics of neutrinos (oscillations)


Atmospheric νννν events

Eνννν = 370 MeV

Pµµµµ = 250 MeV Tp = 90 MeV

ννννµ quasi-elastic interaction

Eνννν = 450 MeV

Pe = 200 MeV Tp = 240 MeV

ννννe quasielastic interaction

90 cm

90 c

m

µp e

(simulated νµ event)

100 cm

90 c

m

pe

(simulated νe event)


Cosmic ray event containing a hadronic interaction vertex

providing an “Atmospheric neutrino”-like topology

10 m3 test @ LNGS: Run 641 - Evt 14 (Apr. 14th, 2000)

15

3

24

4

3

5

2

1

vertex

vertex

• Trk. 1 - m.i.p. Edep= 31 MeVLtrk~ 18 cm

• Trk. 2 – heavily i.p.Edep= 191 MeVLtrk~ 53 cm


• Trk. 4 - heavily i.p.Edep= 42 MeVLtrk~ 16 cm


2D view 2D view Preliminary analysis


Atmospheric neutrino rates


Rates for upward/downward eventsFor a 2 kton x year exposure, we expect to measure a

significant deficit of upward-going muon-like events


Atmospheric up-down asymmetryAll particles�

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∆ m�2� = 3.0 x 10�-3� eV�2�

+– 1�σ (2 kton x year exposure)�+– 1�σ (5 kton x year exposure)�

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kton x year

U DU D

kton x year

−+

= − ±

−+

= − ±

0 228 0 100 2

0 228 0 060 5

. . ( )

. . ( )

U DU D

kton x year

U DU D

kton x year

−+

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0 057 0 100 2

0 057 0 060 5

. . ( )

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All particles Lepton only

2σσσσ effect for 2 kton x year

4σσσσ effect for 5 kton x year

No discrimination


10-1

1

10

10 2

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2

νµ + νµbarνe + νebar

Log10(Eν/GeV)

Arb

. Uni

ts

Comparison of atmospheric event rates

ICARUS Coll. prediction(FLUKA+NUX)

Standard BARTOL prediction(Lipari cross-sections)

Note: BARTOL group does not have a prediction Eν<100 MeV


FLUKA capability of reproducing AMS data

Measured proton fluxBelow cutoff (loopers)

ICRC01, Hamburg


Neutrino flux from new BARTOL and FLUKA(same primary spectrum)

Bartol group, Proc. ICRC 2001, HE3.02.1

Current discrepancies at low energy depend primarily frominteraction model at low energy ⇒ HARP results can help!

KAM(less affected)

SOUDAN(more affected)


Muon flux measured in CAPRICE94 and predicted by FLUKA

G. Battistoni et.al., hep-ph/0107241

Ground-level comparison


Angular resolution• Question #1: You stress the unique angular resolution for the

reconstruction of the neutrino direction. For whichmeasurement do you have enough statistics to profit from thisfeature?

• Answer:– The excellent angular resolution comes from the bubble-

chamber-like ability of ICARUS to measure all final stateparticles. This feature is of utmost importance to understandcompletely the features of an event, including its nature(CC,NC), its flavor (e,muon, tau), the incoming neutrino energyand direction.

– We hence stress the unique reconstruction capabilities ofICARUS as a whole.

– A specific quantitative example where angular resolution isimportant was shown: in the up/down asymmetry measurement,a 2σ effect is reached thanks to the excellent resolution.


Low energy atm events• Question #2: Of the atmospheric events, 50% will be below the SuperK threshold of

400 MeV. Can you be more quantitative on how these events can contribute to thephysics result? Especially important are here the consideration of systematicuncertainties in the prediction of the fluxes. In table 1 you show that half yourstatistics in mu/e ratio comes from this region. Can you describe in a quantitativeway whether these events contribute to other analyses (e.g. angular distributions?)

• Answer:– The SuperK cut at 400 MeV is imposed by their detection considerations,

which are irrelevant in the case of ICARUS. ICARUS can detect events below400 MeV as well as above.

– Flux systematic uncertainties in atmospheric neutrinos have always beenimportant and should be dealt with care (also in SuperK!).

– The Collaboration has developed a great expertise in atmospheric fluxprediction based on FLUKA. It was for ex. the first to use a 3D calculation.

– Work is ongoing and various comparisons with experimental data show thatthe model is correct and is gradually becoming a standard for other groups.See slides.

– We are confident that we will reach the adequate systematic uncertainty alsoin the region below 400 MeV that will allow us to perform new physics withthese events.


Tau appearance experiment

• Detector configuration– 5 T600 modules– Active LAr: 2.35 ktons

• 5 years of CNGS running– Shared mode– 4.5 x 1019 p.o.t./year

• 280 ννννττττ CC expected for ∆∆∆∆m223=3

x 10-3 eV2 and maximal mixing


CNGS beam full event reconstruction

• Free electrons recombination(quenching) effects could affectkinematics reconstruction ofbeam neutrino events

• Two scenarios have beenconsidered– Pure Liquid Argon– TMG-doped Liquid Argon

• Full simulation of ννννe CC usingFLUKA MC package anddetailed description of T600geometry

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• A and B are free parameters• Assume every “cell” (3 x 3 x 3

mm3) is traverse by a single track• Collected charge corrected on

average ⇒⇒⇒⇒ detector linearityresponse recovered

• Effective recovering of charge lostdue to quenching, since depositedenergy for most of the cellscompatible with m.i.p. hypothesis(2 MeV/cm)

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16.68� 6.529�


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No quenching�

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Evisible Missing PT

Quenching effects do not degrade appreciably event kinematics

TMG doping does not seem mandatory for CNGS event reconstructionQuenching effects do not degrade appreciably event kinematics

TMG doping does not seem mandatory for CNGS event reconstruction


Reconstruction algorithm

• “Tracking” approach– Identify through imaging all

primary tracks (direction)and their secondaries;energy found by summingdE/dx

• “Calorimetric” approach– Total energy computed as

energy-weighted center ofgravity of elementary “cells”

– Compensation isintroduced

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Missing PT

“Tracking” algorithm better suited for tau analysis based onkinematics criteria

“Tracking” algorithm better suited for tau analysis based onkinematics criteria


Missing PT resolution ICANOE module8 x 8 x 16 m3, 1.4 kton LAr

without vertex fiducial cuts�

full simulation NGS �νe CC events�

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T600 module3.2 x 6 x 18 m3, 0.47 kton LAr

Optimized missing PT reconstruction requiresvertex fiducial cuts


ICANOE vs T600 configurations

• ICANOE– Vertex cut efficiency: 86%– <Missing PT> ≈ 400 MeV

• T600 module– Vertex cut efficiency: 64%– <Missing PT> ≈ 410 MeV

Full simulation CNGS �νe� CC events (vertex cuts imposed)�

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4 x T600 modules�

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ICANOE 1 module x 1.4 kton x 0.86 = 1.2 ktonseffective

T600 4 module x 0.47 kton x 0.64 = 1.2 ktonseffective

Four T600 modules equivalent to

one ICANOE module


eννBr ≈ 18%

ττττ→→→→ννννµµµµ→→→→ ννννττττCharged current (CC)

ννννττττ++++N→→→→ττττ+jet;

Charged current (CC)ννννe++++N→→→→e+jetBackground:

• Analysis of the electron sample

– Exploit the small intrinsic νe contamination of the beam(0.8% of νµ CC)

– Exploit the unique e/π0 separation

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

Tau appearance experiment


ττττ→→→→e analysis: sequential cuts

• Exploit small natural contamination of ννννe

• Expected excess at low energy

5 x T600 modules, 5 years CNGS running�

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All previous cutsapplied

Vertex cutsapplied

Total visible energy Missing PT

262

49

νν ττ

e CC

CC e, →∆m eV2 3 23 10= × −

Before cuts:


ττττ→→→→e search for ICANOE and T600

Sequential cut search summary:

5 year CNGS running


ττττ→→→→e search: 3D likelihood

• Analysis based on 3 dimensionallikelihood– Evisible, PT

miss, ρρρρl≡≡≡≡PTlep/(PT

lep+

PThad+PT

miss)– Exploit correlation between

variables– Two functions built:

κ LS ([Evisible, PTmiss, ρρρρl]) (signal)

κ LB ([Evisible, PTmiss, ρρρρl]) (νe

CC background)– Discrimination given by

5 T600 modules, 5 years CNGS (4.5 x 10�19� p.o.t./year)�

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νe� CC�

ντ CC, �τ→ e�

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Vertex cutsapplied


ττττ→→→→e search: 3D likelihood summary

Likelihood approach enhances signal detectionefficiency by 20%, decreases background

contamination by factor 3

Maximum sensitivity

5 year CNGS running

5 T600 modules


3D likelihood selected signal

• Sequential cut approach selectsevents with PT

miss>0.6 GeV• Signal events selected by 3D

likelihood have missingtransverse momentum as lowas PT

miss≈≈≈≈0.2 GeV

Selected �ντ CC, �τ→e events�

0�

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Recover signal inlow PT

miss region


Hadronic channels: ττττ→→→→ρρρρ search

• Search exploits:− π/π0 candidate

system compatiblewith ρ hypothesis

− Isolation of ρcandidate w.r.t.hadronic jet

• Analysis performed forboth DIS and QE events

• Largest backgroundcomes from νννν NC events

ττττ→→→→ρρρρ DIS search

ττττ→→→→ρρρρ QE search

10638

139

νν τ ρτ

NC

CC, →∆m eV2 3 23 10= × −

Before cuts:


ννννµµµµ→→→→ ννννττττ appearance search summary

5 T600 modules(2.35 kton active LAr)

5 year CNGS running(2.25 x 1020 p.o.t.)

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


Conclusion• After the successful completion of the series of technical tests

performed at the assembly hall in Pavia, the T600 detector will beready to be transported into the LNGS tunnel.

• The operation of the T600 at the LNGS will allow– To develop the local infrastructure needed to operate the large

detector– To start the handling of the underground liquid argon

technology– Check backgrounds in actual final detector configuration– To start the data taking with an initial liquid argon mass that will

eventually reach the multi-kton goal.

The operation of the T600 in the LNGS tunnel is the only way todemonstrate in situ the expected performance of the liquid Artechnique

cosmic and rare underground signals…

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