ICARUS (CERN-CNGS2)

ICARUS (CERN-CNGS2) A Second-Generation Proton Decay Experiment and Neutrino Observatory at the Gran Sasso Laboratory

The ICARUS Collaboration L’Aquila, LNGS, Milano, Napoli, Padova, Pavia, Pisa, LNF ETHZ Katowice Krakow Warsaw, Wroclaw UCLA INR CIEMAT Granada IHEP 25 INSTITUTIONS, 150 PHYSICISTS

The T600 modules are now at LNGS

The milestones for T600 installation and operation at LNGS we are here

We are on schedule T600 Mechanical frame construction completed On Monday 11th April the Air Liquid work begins (T600 yard)

ICARUS status • The ICARUS collaboration has built and run the T300 module on time and within budget • The T3000 design was approved • After that there were long delays not due to ICARUS responsibility • The project of the muon spectrometer has been indefinitely postponed by proponent groups • The two modules composing the T600 have been delivered to LNGS • INFN has provided essentially all the money for the T600, for the basic infrastructures and for the first T1200 module. • INFN correctly argues that the second T1200 module should be substantially funded by non italian collaborators. This is not yet the case. • 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 • INFN has formally authorized the necessary calls for tender • 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 • In view of the previous considerations, the physics goals achievable with the T1800 are being reviewed by the collaboration. • 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.

e+ u u d p p0 d d An update of The Physics Program with T1800 • proton and neutron decay searches • atmospheric neutrinos • Long Baseline Neutrino Experiment • solar neutrinos • Cosmic neutrinos: • SN, g-ray bursts, neutron star collapse

Work in Progress!!

Basic features of T1800 Instrumented volume of T600: 340.35 m3 476.5 t LAr drift length: 1.5m Instrumented volume of T1200: 710.51 m3 994.5 t LAr drift length: 3m Energy resolution: s/E = 11%/E(MeV)E<50 MeV checked with m decay s/E = 3%/  E(GeV)  1%e.m. showers checked with p0 mass

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:

In less than one year it is possible to improve SuperKamiokande limits on the following channels: p  p+ n n  e- K+ 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 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 ne 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 ne events might be important for the progress of the understanding of neutrino oscillations • ICARUS can study ne events with an unprecedented level of experimental systematics in addition to a very low threshold in lepton momentum

Why SubGeV ne are important • There is no evidence for atmospheric ne oscillation: sin2 q13 is consistent with 0 in the present 3 flavor analysis (Dm223, sin2 q23, sin2 q13) • After solar n and KamLAND results, we can say that oscillation of low energy ne should appear at some level even if sin2 q13 = 0 • sub-leading oscillations driven by Dm212 Fosce = F0e P(ne  ne) + F0m P(nm  ne) F0e ,F0m : n flux w/o osc. = F0e [ P(ne  ne) + r P(nm  ne) ] r = F0m/ F0e : m/e flux ratio = F0e [ 1 – P2 + r cos2 q23 P2 ] P2 = |Aem|2 : 2n transition probability ne  nmt in matter driven by Dm212 (Fosce / F0e) – 1 = P2 (r cos2 q23 – 1) screening factor for low energy n (r ~ 2) ~ 0 if cos2 q23 = 0.5 (sin2 q23 = 0.5) < 0 if cos2 q23 < 0.5 (sin2 q23 > 0.5) > 0 if cos2 q23 > 0.5 (sin2 q23 < 0.5)

Consequences The knowledge of the absolute level of SubGeV ne can provide the best possible measurement of q23 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 ne. T1800 can explore for the first time the region with Pe<100 MeV/c

11o New improved detector simulation • FLUKA + NUX with 3-f oscillations with matter effects (with F.Vissani, LNGS) • Atmospheric neutrino Fluxes (2002). • a first study of containment using full simulation Choice of oscillation parameters (SK and solar exp. results) • Dm223 = (1.5) - 2.1 – (3.4) x10-3eV2 (positive) • Dm212 = 8.3x10-5eV2 • sin22q12= 0.825 • sin22q23= 1. • dCP = 0o • q13 = Chooz limit merging with K2K: <Dm223> = 2.5 x10-3eV2 Baseline exposure: 1 yr 600 Tons + 4 yr 1800 Tons: 6.36 kton yr Generated Statistics: 20 times larger

Dm23 2 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) CC Interaction rates: evt/kton yr

Main results 15% excess level as seen by Super-Kamiokande { 255 With containment requirement 1 s statistical uncertainty level on ne normalization achievable with T1800 for the baseline exposure 200 Possibility to separate charges (~75% probability capture for m-) we can measure m-/m+ with ~ 25% error or less T.Suzuki et al., Phys. Rev. C35 (1987) 2212

Our model prediction: in SubGeV m-like events (~all q.e.) there is a recoiling proton with E>50 MeV in: ~42% of nm interactions ~14% of nm interactions nm We can use charge id by m-decay to test the nuclear model: important for many future neutrino experiments examples of “anomalies”: p p nm m+ decay decay m-

Δm2 = 2.5 x 10-3 eV2 5 years exposure of T600(5y) +T1200 (4y) Expected rate Nominal CNGS beam: 6.5 ντwith 0.3 bg events CNGS x 1.5 beam intensity 9.8ντwith 0.5 bg events ICARUS T600+T1200ντappearance 3) Neutrino oscillations with the CNGS beam To be combined with expected OPERA results Increase the overall sensitivity

optimized for background reduction All backgrounds included ντCCτ→e 12.6 ev νe + νe intrinsicCC 47 ev Neutral currents suppressed by e/π0 discrimination: 0.1%π0 misidentification with90% eefficiency ICARUS T600+T1200νe appearance New beam simulations with latest optics 3 Flavour oscillations with matter effects Full simulation in LAr Fiducial volume 90% Cut on Evis < 20 GeV

ICARUS T600+T1200νe appearance Evis spectraΔm223=2.5 10 -3 eV2 Sin2(2θ13)= 0.14 (CHOOZ limit) 25 oscillated events 90% confidence level Full = CNGS std. 1y t600 +4y t1800 Dashed = 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/y Averageνμenergy 1.8 GeV, 0.9%νe/ νμCC Evis <2.5 GeVΔm223 =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 CHOOZ Full: CNGS Low-eDashed: CNGSτ

Muons from ν interactions in GS rock All details of μ transport included Expected: 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 Pμ>20GeV ( mostly fromνμwith Eν>40GeV) • Importance: • beam monitoring • measurement of the high energy sector of neutrino flux: they mostly come K which • also contribute to ne contamination

4) Solar neutrinos A full simulation based on FLUKA package was performed, using a detailed description of the different layers and materials of the T600 detector, to study the topology and the rates of the solar neutrino and neutron capture background • 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 b+ decay • Detailed analysis of background neutron sources: • a) External sources (natural radioactivity of the rocks): 2  106capt/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) Number of expected SN events in ICARUS T1800 for inverted (normal) hierarchy 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.

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 nt appearance, and, as far as nm - ne 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 period.

ICARUS (CERN-CNGS2)