Transcript Document

ICARUS
(CERN-CNGS2)
A Second-Generation Proton
Decay Experiment and Neutrino
Observatory at the Gran Sasso
Laboratory
LNGS Scientific Committee – April 8, ,2005
G.Battistoni for the ICARUS Coll.
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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
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The T600 modules are now at LNGS
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The milestones for T600 installation and operation at LNGS
we are here
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We are on schedule
T600 Mechanical frame construction completed
On Monday 11th April the Air Liquid work begins (T600 yard)
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ICARUS status
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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.
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T1200
INFN has formally authorized the necessary calls for tender
o However these steps are frozen waiting for the MoU document
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We need to have a green light as soon as possible
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The T1800 configuration
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Physics with T1800
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In view of the previous considerations, the physics goals achievable
with the T1800 are being reviewed by the collaboration.
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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.
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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
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p
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u
u
d
e+
d
d
p0
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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
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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
essential ingredients:
•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
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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
In less than one year it is possible to improve
SuperKamiokande limits on the following channels:
p  p+ n
n  e- K+
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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
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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) ]
= F0e [
1 – P2
+ r cos2 q23 P2 ]
r = F0m / F0e : m/e flux ratio
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)
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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
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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.
merging with K2K:
<Dm223> = 2.5 x10-3eV2
 dCP = 0o
 q13 = Chooz limit
11o
Baseline exposure: 1 yr 600 Tons + 4 yr 1800 Tons: 6.36 kton yr
Generated Statistics: 20 times larger
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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 yr
Dm223
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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
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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
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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
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-
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decay
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3) Neutrino oscillations with the CNGS beam
ICARUS T600+T1200 ντ appearance
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
To be combined with
expected OPERA results
Increase the overall sensitivity
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ICARUS T600+T1200 νe appearance
New beam simulations with latest optics
3 Flavour oscillations with matter effects
Full simulation in LAr
Fiducial volume 90% optimized for
Cut on Evis < 20 GeV background 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
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ICARUS T600+T1200 νe appearance
Evis spectra Δm223 =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
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CNGS low energy
5 y CNGS low energy focalization , 400 GeV p on 1m long target 4.5 10 19 pot/y
Average 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 CHOOZ
Full: CNGS Low-e Dashed: CNGS τ
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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 P μ >20GeV
( mostly from νμ with Eν>40GeV)
Importance:
a) beam monitoring
b) measurement of the high energy sector of neutrino flux: they mostly come K which
also contribute to ne contamination
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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  106 capt/year
b) Internal sources (Al, stainless steel, etc…): 3  106 (optimistic) capt/year
13  106 (pessimistic) capt/year
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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)
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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 Xgamma detectors (SWIFT, AGILE) or with international networks (SNEWS, GCN) can
reduce the background effects and give reliability to the observations of such
phenomena.
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Sensitivity for SN search
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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
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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 CNGSLE) 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.
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