icarus-t600 collaboration carlo rubbia univ. of pavia, italy and infn, sezione pavia (oct. 3,2006)

1

Icarus-T600 Collaboration

Carlo Rubbia

Univ. of Pavia, Italyand INFN, Sezione Pavia

(Oct. 3,2006)

Progress Report to the SPS-C

SPS-C Oct 3, 2006 Slide# : 2

Which is the future of neutrino physics ? The experimental results of the recent years have profoundly changed the

pattern of neutrino physics.And, very likely, this is only a beginning.

Neutrinos have been shown to strongly oscillate between available

flavours while they propagate through space, whenever a sufficient

distance is provided from the source (solar, cosmic, accelerator or

reactor) and the detector.

All produced and observed neutrinos and antineutrino have left-handed or

right-handed helicities. These are the only chiralities included in the

Standard Model. But since they have mass, the presence of other

chiralities is not without problems.

Maybe their counterparts (right-handed neutrinos and left-handed

antineutrinos) simply do not exist and neutrino and antineutrino are in

fact the same particle. The key experiment for the search of Majorana

neutrinos is the neutrino-less double beta decay, actively investigated

at the Gran Sasso.

If their counterparts instead do exist, it may be that their properties

are substantially different from the ones of observable neutrinos and

antineutrinos.


How many neutrinos are present in nature ? According to the LEP result, three different

neutrinos are coupled with Z-bosons.

Consequently there are only 2 independent m2.

But the possibility of one or more additional, “sterile” kinds of neutrino — namely of neutrinos which do not participate in the weak interactions — is unaffected by these Z-boson-based measurements.

The existence for such additional neutrino particles has been claimed by a Los Alamos experiment called LSND, in which they have been created through oscillations from ordinary neutrinos. ,

It is possible that neutrinos are something very different than just a neutral counterpart of charged leptons and may couple to another segment of the Universe, the one of sterile neutrinos, which do not see fully ordinary electro-weak interactions but still introduce mixing oscillations with ordinary neutrinos.


LSND: Evidence for ( e)

Beam relatedbackgrounds

Excess of events: 87.9 22.4 6.0

Expectation for

oscillations

Data points afterbackground subtraction

The experimental evidence is very strong, namely 3.8 s.d.The experimental result so far has not been challenged experimentally


Present experimental status with many possible explanations

allowed regions left 1. CPT violation, with LSND related to

anti-neutrino and no need of more neutrinos ??

2. CPT conservation and one or more sterile neutrinos, weakly coupled to ordinary neutrinos. They do interact weakly via W or Z, but standard might oscillate to them ?

3. Which connections to Cosmology ??

Needs experimental confirmations: MiniBoone at FermiLab ICARUS-T600 at CNGS

Explanations ??


BooNE: Booster Neutrino ExperimentY. Liu, I. Stancu AlabamaS. Koutsoliotas BucknellE. Hawker, R.A. Johnson, J.L. Raaf CincinnatiT. Hart, E.D. Zimmerman ColoradoAguilar-Azevedo, L. Bugel, J.M. Conrad, J. Formaggio, J. Link, J. Monroe, D. Schmitz,M.H. Shaevitz, M. Sorel, G.P. Zeller ColumbiaD. Smith Embry RiddleL. Bartozek, C. Bhat, S.J. Brice, B.C. Brown,D.A. Finley, B.T. Fleming, R. Ford, F.G. Garcia,P. Kasper, T. Kobilarcik, I. Kourbanis,A. Malensek, W. Marsh, P. Martin, F. Mills,C. Moore, P.J. Nienaber, E. Prebys, A.D. Russell,P. Spentzouris, R. Stefanski, T. Williams FermilabD.C. Cox, A. Green, H.O. Meyer, R. Tayloe IndianaG.T. Garvey, C. Green, W.C. Louis, G. McGregor,S. McKenney, G.B. Mills, V. Sandberg, B. Sapp,R. Schirato, R. Van de Water, D.H. White Los AlamosR. Imlay, W. Metcalf, M. Sung, M.O. Wascko Louisiana StateJ. Cao, Y. Liu, B.P. Roe MichiganA.O. Bazarko, P.D. Meyers, R.B. Patterson,F.C. Shoemaker, H.A. Tanaka Princeton

protons mesons neutrinos

● 12 meters spherical steel tank

● 250,000 gallons of mineral oil (800 tons)

● 1280 PMT's in the main region (5.75 meters)

● 240 PMT in veto region

● Neutrino interactions in oil produce light (Cherenkov and scintillation)

● We measure time and charge for each tube

horn and target decay region absorber dirt (~450m) detector


MiniBoone proposal:signal and backgrounds (Montecarlo)

Cross sections estimates for nuclear target, especially at low energies, have been widely underestimated in the original proposal

Cross sections estimates for nuclear target, especially at low energies, have been widely underestimated in the original proposal


MiniBoone method for searching for oscillations

? ? ?


CNGS physics potentials of ICARUS T600 The SPS schedule of CNGS foresees nominally 4.5 x1019 pot/y for the next five

years (2007-2012). This corresponds to a beam related rate ≈ 2500 ev/kton/year with 90 %

efficiency of collection. The T600 raw fiducial volume ≈ 480 t is equivalent nominally 1200 ev/y for

5 years, corresponding to ≈6000 beam related neutrino events. The T600 is also collecting simultaneously “self triggered” events. This in

particular represents:≈ 100 ev/year of individually recorded atmospheric CC cosmic rays.Solar neutrino electron rates >5 MeV.A zero background proton decay with 3 x 1032 nucleons for”exotic” channels.

T600 is a necessary intermediate technical step towards a much more massive LAr detector (3.3 kT LAr are equivalent to 20 kt NOVA scintillator), now being actively studied by INFN and US(Fermilab), but it offers also some interesting physics in itself. In the presentation I shall limit myself to two main topics:Searching for sterile neutrinos in T600 with deep e-like inelastic CC

events, complementary to MiniBooneThe proof of existence of decay with T600, the actual value of m2 being

already measured elsewhere by Soudan and S-K and in the future by OPERA.


Search for sterile neutrinos at LNGS Both LSND and MiniBoone experiments are characterised by

<< 1 GeV quasi-elastic events in C with elaborate selection criteria

a relatively short oscillation path from the source to the detector The addition of substantial competing backgrounds due to

misinterpreted events.Therefore the signal should appear as an event excess peaking at low

values of the visible energy. In contrast, the CNGS beam and the ICARUS “bubble chamber”

identification is based on:Deep inelastic -e CC events recorded in the minimum bias mode.Extremely good background discrimination, limited only to the

intrinsic beam e contamination: ≤0.5% in the chosen E interval of 10 ÷ 30 GeV.

Excellent electron discrimination against converted ’s because of the differences in ionization losses in the earliest part of the track (No NC backgrounds).

Very long path-length which ensures several oscillations from source to detector in the foreseen LSND window, but still wide enough in order to identify maxima and minima related to m2, which can also be measured.


Reconstructed CC events in T600

e-, 15 GeV, pT=1.16

GeV/c

Vertex: 10,2p,3n,2 ,1e-

CNGS e interaction, E=16.6 GeV120 cm

290 cm

CNGS interaction, E=21.3 GeV

Vertex: 3,5p,9n,3,1

80 c

m

300 cm


Events with leading electron signature. The basic spectrum of LNGS is made of

with a most probable energy in the order of 25 GeV.

The spectrum has also been calculated and found to to be accurate to about 5%.

Electron shower events are extremely well identified experimentally, because of the ionization behaviour in the first cells after the vertex.

€

e−

€

o

electron (right) and pion (left) in T600


Single wire

performance

10 MeV3.2 MeV1.8 MeV

Two consecutive

wires Noise

Threshold above noise ≈ 200 keV


E:10 ÷ 30 GeVN():4635N(e,beam): 18.8N(e,oscill): 45.5

E:10 ÷ 30 GeVN():4635N(e,beam): 18.8N(e,oscill): 94.9

Indicative energy spectra for LSND signals

Hypothetical sterile neutrino oscillations (LSDN) m2 = 0.4 eV2




E resolution for contained events ≤ 0.17sqrt(E)


Limits at T600 with 6000 events. Sensitivity region, in

terms of Standard Deviations , for 6000 raw CNGS neutrino events. The potential signal is above the background generated by the intrinsic e beam contamination, in the deep inelastic interval 10-30 GeV.

The m2 distribution extends widely beyond the LNSD and MiniBoone regions.

Two indicated points are reference values of MiniBoone proposal and of previous slide T600 at the CNGS offers an

unique possibility of searching for sterile neutrinos, largely complementary and comparable to

the Fermilab programme.

T600 at the CNGS offers an unique possibility of searching for sterile neutrinos, largely complementary and comparable to

the Fermilab programme.


Searching for the signature.

e-, 9.5 GeV, pT=0.47 GeV/c

- e- + e + _

CNGS interaction, E=18.7 GeV280 cm

105 cm

The original international proposal for T1800, recently cancelled by lack of funding, would have ensured a number of events adequate to cover the signature with a sensitivity comparable to the one OPERA. The electron decay channel is however quite significant goal also for the presently reduced T600 mass, uniquely characterized by a large transverse momentum unbalance due to the emission of the two neutrinos.


How many are necessary for a “signature” At the effective neutrino energy of 20 GeV and m2 = 2.5E-3

eV2, the expected => is 1.4%. Therefore for 6000 CNGS events in the T600 we expect 84 raw events.

The branching ratio for => eis 16%; hence we expect 13.4 electron deep inelastic events, in addition to the ≈ 14 intrinsic beam associated e with energy <20 GeV. This is already “per-se” a significant effect, namely with 27.4 electron events observed vs. 14 ± 3.7 expected (3.6 s.d.).

Events are absolutely clean and they are characterised by a momentum unbalance because of neutrino emission and a relatively low electron momentum. Selection criteria suggest a sufficiently clean separation from intrinsic beam associated e with kinematic cuts and an efficiency of 50%.

Therefore one should expect about 7 ± 2.6 => e events, some of which, hopefully, gold plated.

This should be sufficient for a proof of existence, the actual value of m2 being already measured elsewhere in Soudan and S-K.


+ LSND like sterile neutrinos

-> e decays

Likelihood weight

e balanced events or tau decays ?

Likelihood distributions may separate an

hypothetical LSND excess from the expected presence of

decays

Likelihood distributions may separate an

hypothetical LSND excess from the expected presence of

decays


General T600 layout

Dewar LN2 (30 m3)

Dewar LAr (30 m3)

Passive heaters


SITE T600

Modules T600 parking site

Control RoomsICARUS & OPERA

OPERA building BAM

OPERA Service Area

Hall B logistics


Leaving from SeregnoLeaving from Seregno

September 18th.The base insulation at SeregnoThe base insulation at Seregno

Transport to LNGS


Sept. 20Sept. 20thth @ HALL B!Incoming…

Flying over OPERAFlying over OPERA.

IncomingIncoming

… … in the Hall in the Hall to the working area.to the working area.


Sept. 22Sept. 22thth,, @ Seregno

The lateral panels on the road.The lateral panels on the road.


New anti seismic and safety structures underground

• The steel structure has an anti seismic function. It also contributes to hold a maximum over-pressure of 100 mbar.

• The insulation will be a closed box, in order to contain hypothetical cryogenic leaks.


JAN FEB MAR MAY JUN JUL2006

Top insulation assembled

Instrumentation

Cryo roof pass-through

2nd cryostat in place

Projected T600 planning of cryogenics


ICARUS Cool-down Filling the T600 requires 2 x 275’000 litres (786.5 tons) of L Ar to

be transported by trucks from the outside into Hall B. The initial start-up procedure will be as follows:

1.Vacuum phase and cryostat fill with GasAr: 1 LAr truck to be kept in Hall B

2.N2 “pre-cooling”: 7 days duration 1 LN2 truck/2-3 days

3.N2 cooling: 7 days duration 1-2 LN2 trucks/ day

4.LAr filling: 10-20 days duration 1-2 LN2 trucks/ day

2-4 LAr trucks/ day

The normal running procedure will be as follows: Permanent general LNGS N2 facility: Stierling liquefiers inside the

laboratory, presumably ready only by the end of the 2007 Intermediate start up phase with additional N2 trucks from outside

(to be authorized) for the duration period before STIERLING/tank delivery

1 LN2 trucks/ 1-3 days


SPS 2007 Accelerator Schedule (draft)


Conclusion

In all likelihood, the T600 detector may be able to run for a major fraction of the

2007 schedule !

icarus-t600 collaboration carlo rubbia univ. of pavia, italy and infn, sezione pavia (oct. 3,2006)

Documents