icarus (cern-cngs2)

LNGS Scientific Committee – April 8, ,2005 1G.Battistoni for the ICARUS Coll.

ICARUS

(CERN-CNGS2)

A Second-Generation Proton Decay Experiment and Neutrino Observatory at the Gran Sasso

Laboratory


The ICARUS Collaboration

25 INSTITUTIONS, 150 PHYSICISTS

CIEMATGranada

UCLA

ETHZ

INR

IHEP

Katowice KrakowWarsaw, Wroclaw

L’Aquila, LNGS, Milano, Napoli, Padova, Pavia,

Pisa, LNF


The T600 modules are now at LNGS


The milestones for T600 installation and operation at LNGS

we are here


We are on schedule

On Monday 11th April the Air Liquid work begins (T600 yard)

T600 Mechanical frame construction completed


ICARUS status

o The ICARUS collaboration has built and run the T300 module on time and within budget

o The T3000 design was approvedo After that there were long delays not due to ICARUS responsibilityo The project of the muon spectrometer has been indefinitely

postponed by proponent groupso The two modules composing the T600 have been delivered to LNGSo INFN has provided essentially all the money for the T600, for the basic

infrastructures and for the first T1200 module. o INFN correctly argues that the second T1200 module should be

substantially funded by non italian collaborators. This is not yet the case.

o At this time, a T1800 configuration (T600+T1200) running for a significant time interval has to be considered as a necessary firm (i.e. possible and financed) step in the ICARUS project towards the completion of the final mass design.


T1200

o INFN has formally authorized the necessary calls for tender o However these steps are frozen waiting for the MoU document

We need to have a green light as soon as possible


The T1800 configuration


Physics with T1800

o In view of the previous considerations, the physics goals achievable with the T1800 are being reviewed by the collaboration.

o INFN also recommended this analysis, asking for an update of the previous documents on the physics goals, in the light of the recent progresses in the topics which are within the ICARUS interest.


An update of The Physics Program with T1800

• proton and neutron decay searches

• atmospheric neutrinos

• Long Baseline Neutrino Experiment

• solar neutrinos

• Cosmic neutrinos: SN, -ray bursts,

neutron star collapse uud

e

dd

p0


Basic features of T1800

Instrumented volume of T600: 340.35 m3 476.5 t LAr

Instrumented volume of T1200: 710.51 m3 994.5 t LAr

Energy resolution: /E = 11%/E(MeV) E<50 MeV checked with decay/E = 3%/ E(GeV) 1% e.m. showers checked with mass

drift length: 3m

drift length: 1.5m


1) Nucleon Decay

•This remains the original and most important physics item addressed by ICARUS

•The work exposed in the previous proposal documents remains valid

•full event simulation (FLUKA) with all relevant effects in Argon nuclei (including absorption or decay inside parent nucleus)

•background evaluated on a statistical sample of 100 kton yr exposure

•Topological and kinematical cuts as described in previous proposals

essential ingredients:


Comments on nucleon decay

Despite the reduction in mass, T1800 has still the capability to improve the current limits for several channels even with an exposure of few years.

In less than one year it is possible to improve SuperKamiokande limits on the following channels:p n e- K+

In all cases where exclusive channels are considered, the background is found to be much below 1 ev/kton yr, thus allowing a discovery capability even with the observation of a single event


2) Atmospheric Neutrinos

•From the analysis of the Super-Kamiokande significative systematic

uncertainties remain on the e sector, and in particular in the SubGeV region

•These appear in the comparison of absolute normalization between data

and predictions (see Super-Kamiokande results)

•These SubGeV e events might be important for the progress of the

understanding of neutrino oscillations

•ICARUS can study e events with an unprecedented level of experimental

systematics in addition to a very low threshold in lepton momentum


Why SubGeV e are important

•There is no evidence for atmospheric e oscillation: sin2 13 is consistent with 0 in the present 3 flavor analysis (m2

23, sin2 23, sin2 13)

•After solar and KamLAND results, we can say that oscillation of low energy e should appear at some level even if sin2 13 = 0

•sub-leading oscillations driven by m212

Fosce = F0

e P(e e) + F0 P( e)F0

e ,F0flux w/o osc.

= F0e [ P(e e) + r P( e) ] r = F0

/ F0e : /e flux ratio

= F0e [ 1 – P2 + r cos2 23 P2 ] P2 = |Ae|2 : 2 transition

probability e in matter

driven by m212

(Fosce / F0

e) – 1 = P2 (r cos2 23 – 1)

screening factor for low energy (r ~ 2)

~ 0 if cos2 23 = 0.5 (sin2 23 = 0.5)

< 0 if cos2 23 < 0.5 (sin2 23 > 0.5)

> 0 if cos2 23 > 0.5 (sin2 23 < 0.5)


Consequences

The knowledge of the absolute level of SubGeV e can provide the best possible measurement of 23 and of its octant.

Of course, from the point of view of statistical significance, this requires a very high exposure

This can be achieved in a next detector generation in the ICARUS programme, but the unique features of T1800 can provide a first important indication and comprehension of the experimental systematics of SubGeV e.

T1800 can explore for the first time the region with Pe<100 MeV/c


New improved detector simulation

•a first study of containment using full simulation

•FLUKA + NUX with 3-f oscillations with matter effects (with F.Vissani, LNGS)•Atmospheric neutrino Fluxes (2002).

Baseline exposure: 1 yr 600 Tons + 4 yr 1800 Tons: 6.36 kton yr

Choice of oscillation parameters (SK and solar exp. results)

m223 = (1.5) - 2.1 – (3.4) x10-3eV2 (positive)

m212 = 8.3x10-5eV2

sin2212 = 0.825

sin2223 = 1.

CP = 0o

13 = Chooz limit

11o

merging with K2K:m223= 2.5 x10-3eV2

Generated Statistics: 20 times larger


Event selection and definition

Follow SK denomination but with different limits:Sub-GeV Evis < 1.0 GeV (SK: <1.33 GeV) Multi-GeV Evis > 1.0 GeV (SK: >1.33 GeV)

Super-Kamiokande Icarus

e (single prong) 100 MeV 10 MeV

muon (single prong) 200 MeV 10 MeV

Multi.prong muon 600 MeV 10 MeV

CC Interaction rates: evt/kton yrm23

2


1 statistical uncertainty level on e normalization achievable with T1800 for the baseline exposure

{

15% excess level as seen bySuper-Kamiokande

Main results

Possibility to separate charges(~75% probability capture for )

With containment requirement

255

200

we can measure -/+ with ~ 25% error or lessT.Suzuki et al., Phys. Rev. C35 (1987) 2212


We can use charge id by -decay to test the nuclear model:important for many future neutrino experiments

Our model prediction:in SubGeV -like events (~all q.e.) there is a recoiling proton with E>50 MeV in:

~42% of interactions~14% of interactions

examples of “anomalies”:

p

decaydecay

p


ICARUS T600+T1200 ντ appearance

To be combined with expected OPERA resultsIncrease the overall sensitivity

Δm2 = 2.5 x 10-3 eV2

5 years exposure of T600(5y) +T1200 (4y)

Expected rate Nominal CNGS beam:

6.5 ντ with 0.3 bg events

CNGS x 1.5 beam intensity

9.8 ντ with 0.5 bg events

3) Neutrino oscillations with the CNGS beam


ICARUS T600+T1200 νe appearance

New beam simulations with latest optics3 Flavour oscillations with matter effectsFull simulation in LArFiducial volume 90%Cut on Evis < 20 GeV

optimized forbackground reduction

All backgrounds included

ντ CC τ→e 12.6 ev

νe + νe intrinsic CC 47 ev Neutral currents suppressed by e/π0 discrimination:

0.1% π0 misidentification with 90% e efficiency


ICARUS T600+T1200 νe appearance

Evis spectra Δm223

=2.5 10 -3 eV2

Sin2(2θ13)= 0.14 (CHOOZ limit) 25 oscillated events

90% confidence levelFull = CNGS std. 1y t600 +4y t1800Dashed = CNGS x 1.5 5% systematic error on background


CNGS low energy

5 y CNGS low energy focalization , 400 GeV p on 1m long target 4.5 10 19 pot/yAverage νμ energy 1.8 GeV, 0.9% νe/ νμ CC

Evis <2.5 GeV Δm223 =2.5 10 -3 eV2 Sin2(2θ13)= 0.14 (CHOOZ limit)

13.5 oscillated events over 2.9 background events

90% CL sensitivity . Factor 4 over CHOOZFull: CNGS Low-e Dashed: CNGS τ


Muons from ν interactions in GS rock

All details of μ transport includedExpected: 43.6 μ /m2/1019 pot 0.98 μ/m2/day 196 μ/m2/year

In T600 : 3700 μ/year, of which

870 μ/year with P μ >20GeV

( mostly from νμ with Eν>40GeV)

Importance:a) beam monitoringb) measurement of the high energy sector of neutrino flux: they mostly come K which also contribute to e contamination


4) Solar neutrinos

• Solar neutrino event rates rescaled to T1800 volume.• Fluxes taken from BP04 SSM (8B flux larger by 14% with respect to BP2000) • Calculation of the absorption cross-section in the neutrino energy range 1.5 – 15 MeV from new measurements from 40Ti + decay

A full simulation based on FLUKA package was performed, using a detailed description of the different layers and materials of the T600 detector, to studythe topology and the rates of the solar neutrino and neutron capture background

• Detailed analysis of background neutron sources:

a) External sources (natural radioactivity of the rocks): 2 106 capt/year b) Internal sources (Al, stainless steel, etc…): 3 106 (optimistic) capt/year 13 106 (pessimistic) capt/year


We must increase the threshold of 5 MeV previously quoted in the original proposal

due to the Q-value of the neutron capture processes on 36Ar, no background is expected above 9 MeV. ICARUS T1800 can therefore provide accurate information on the high energy region of the solar neutrino spectrum, between 9 and 15 MeV.

Background free events per year (oscillated)


5) Cosmic neutrinos

ICARUS T1800 is a unique instrument, with high sensitive mass, able to detect neutrinos in a wide energy region of interest (from one to thousands MeV) from:

• Supernovae (SN) • Neutron star collapse into black hole• Active Galactic Nuclei and GRB (according to some non standard models)

The time correlation with other neutrino detectors (LVD, Borexino, SK, SNO) and X-gamma detectors (SWIFT, AGILE) or with international networks (SNEWS, GCN) can reduce the background effects and give reliability to the observations of such phenomena.

Number of expected SN events in ICARUS T1800 for inverted (normal) hierarchy


Sensitivity for SN search


Conclusions 1

• T600 is now at LNGS

• the work to install T600 has started and schedule is being respected

• We ask for the green light to continue the approved program: building the first T1200 module

• T600+1st T1200 = T1800 is an important intermediate step in the path of the complete ICARUS project towards the final mass design and has already the possibility to start a real physics investigation.

• T600 alone would remain just a demonstrative tool


Conclusions• T1800 has already important physics discovery capabilities in nucleon decay searches.

•T1800 already allows to have a new initial investigation with negligible or null experimental systematics of the SubGeV range of atmospheric neutrinos.

• T1800 has already discovery capability for appearance, and, as far as - e transitions are concerned, a factor of 2 of improvement with respect to Chooz limit is already possible

• We reinforce our convincement that resources must be allocated to obtain an improved neutrino beam: a) increasing intensity, b) a different beam (like CNGS-LE) in a second period .

• In general it must be put in evidence that T1800 is a fundamental step in the ICARUS programme: beyond the topic of nucleon decay the Liquid Argon technology emerges as a fundamental tool to investigate low energy neutrino physics. The validity of the project has to be evaluated in the long periodThe validity of the project has to be evaluated in the long period..

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