26/7/01 A. Bettini 2001 1

Summary• The LNGS• Neutrino mixing (basic)• Status of the (new) neutrino physics• How LNGS contributed• How LNGS can contribute in the future?

Neutrinos from artificial sourcesNeutrinos from the atmosphereNeutrinos from the Sun

• Neutrinos from Supernovae• Neutrino mass• Conclusions

(New) Neutrino Physics at Gran SassoNational Laboratory

A. Bettini

INFN. Laboratori Nazionali del Gran Sasso

Università di Padova

Dipartimento di Fisica Galileo Galilei

INFN. Sezione di Padova

Will not have time forcold dark matter searchmonopoles searchcosmic raysgeology exptsbiology expts

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The mission

The energy region beyond the reach of present end futureaccelerators can be explored searching for naturallyhappening phenomena. But they are extremely rare

Extreme energy frontier = the frontier of background anddisturbance reduction

Two independent pieces of evidence from undergroundexperiments on

1. electron-neutrinos form the Sun2. muon - neutrinos from the atmosphere

have shown two oscillation phenomena @ two separate squaremass differences (oscillation periods)

∆m2 (“atmospheric” )δm2 ( “solar”)

Implications• e, and are not the mass-eigenstates ( 1, 2, 3)

but quantum superpositions of the mass-eigenstates (mixing)• 1, 2 and 3 have masses m1, m2 and m3 ≠ 0• flavour lepton numbers are not conserved

"Some people are so crazy that they actually venture into deepmines to observe the stars in the sky"Plino. -Naturalis Historia, 44 d.c

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The Gran Sasso Laboratory

•1400 m rock overburden•Flat cross-section•Low n fluence from rock (CaCO3)•Cosmic µ flux attenuation = 10–6 (1 /m2 h)•Underground area 18 000 m2

•Accelerator laboratory standard facilitieson the surface§ Operational budget 25 Glit/yr

Gran Sasso Labs TeramoL’Aquila

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Preparing the next phase

HALL AHALL B

Space has been made available for the next phase.Many new ideas and experimental proposals from the community

HALL C

The field is presently limited by availability of resources(human and financial) not by space

The completion of LNGS has been includedwith “emergency” priority in the publicworks program by the new Government

Funding = 100 Glit allocated

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Mixing. Two states

Neutrinos are produced (and observed) in states (νe e ν ) that are not themass eigenstates (ν1 e ν2)

The eigenstates have masses = m1 e m2

=

U1

U2

U1

U2

1

2

=

cos sin

–sin cos

1

2

=

12

12

–12

12

1

2

=

12

1 1

–1 1

1

2

Mixing matrixit is normal1 parameter onlythe mixing “angle”

Case of quarks Cabibbo small

the states coupled to WI are “almost” eigenstates

Case of leptons. Mixing probably close to maximum = π/4

0 ≤ ≤ / 4

Case of max mix

+

=

cos 2t( )

cos 1t( )

2cos 2 – 1

2t

cos 2 + 1

2t

+

=

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Oscillations. Two statesInitial state: pure , monochromatic, energy = EProbability of appearance at distance L (at proper time L/E)

P → = sin2 2 sin2 1.27∆m2 eV2( ) L km( )E GeV( )

For a non monochromatic beam and finite resolution in L/E,probability goes from 100% to 50% for maximum mixing

SBL LBL (baseline not too long!)

maximummixing

Non maximummixing

Medium resolution High resolutionLarge statistics

Period inv. prop. to absolute value of squared mass differenceOscillation amplitude is sin22 (only if two states!!)

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Matter effects

The MSW effectIn the matter νe interact with the electrons via weak chargedcurrent, acquiring an “effective” mass(or a refraction index).For other neutrino types only NCLevel crossing possible @ critical value of density*energy

If matter effects, “effective mixing angle” range is 0 – /2,even for two neutrino flavours

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Mixing

U =1 0 0

0 c23 s23

0 –s23 c23

c13 0 s13

0 1 0

–s13 0 c13

c12 –s12 0

s12 c12 0

0 0 1

U is unitary4 independent real parameters

3 “mixing angles” 12, 13, 23 ( )1 phase (CP violation)

exp(i ) (very small effects. Forget for the moment)+2 more phases ( ), if neutrinos are Majorana

irrelevant for oscillations

ATMOSPHERIC SOLARCHOOZ

from CHOOZ

e

=Ue1 Ue2 Ue3

U 1 U 2 U 3

U 1 U 2 U 3

1

2

3

e from Sun from atmosphere

P → e = sin223( )sin2 2 13( )sin2 1.27∆m2 eV2( ) L km( )

E GeV( )

P → = sin2 2 23( )cos413( )sin2 1.27∆m2 eV2( ) L km( )

E GeV( )

A simple case. The oscillation probabilities between two states attimes short compared to the “slow” (solar) oscillation(L/E<<1/ m2), in vacuum. Approximate expressions (as examples)

Probab. of f →

Prob. of → e

Oscillation amplitude is not equal to sin22 Oscillation amplitude is different for different oscillations“Mixing angles” ranges are 0 – /2 not 0 – /4

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Use of improper variables

•2-state variable sin22used incorrectly fordifferent oscillationsamongst 3 states

wrong comparisonbetween e disappearance (CHOOZ) and appearance (MINOS)

•range of (effective)mixing angle0 /4 usedincorrectly for mattereffects

•different meanings ofexclusion and signalregions limits not shown

Review of Particle Physics. 2000Murayama. Massive Neutrinos and Lepton Mixing

CHORUS and NOMADincluded in the bookletand in the WEB,Borexino and CNGSprogram not included

EPJ 15 (2000) 1-878

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Neutrino massesMass spectrum. Two possibilities

“Mass” is a property of astationary stateνe, or ν , or ν “mass” isimproperWhat does it mean?

It depends on what and howone measures

“Direct” measurements(Tritium deacay)<m e> < 2-3 eV

< m e2 >=| Ue1 |2 m1

2 + | Ue2 |2 m22 + | Ue3 |2 m3

2

If different “steps” are not resolved

m1

m2

m3

∆m2 (atm.)

δm2 (Sun)

NORMAL∆m2 > 0

m1

m2

m3

∆m2 (atm.)

δm2 (Sun)

INVERTED∆m2 < 0

From cosmology (elaborating from Wang, Tegmark, Zaldarriaga 2001):

m , m , m < 1.5 eV (best limit!!!

Where is the zero??We don’t know

Hierarchic vs. degenerate

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The masses of Majorana e-neutrinos

If Majorana and massive, measure neutrino-less double beta decay lifetimes

MeeM =||Ue1 |2 m1 + |Ue2 |2 e2i m2+ |Ue3 |2 e2i m3 |

≈||Ue1 |2 m1 + |Ue2 |2 e2i m2 |

Z Z+1 Z+2

β

β β

Nuclear physics effects must be calculated to go from a limit on lifetimeto a limit on neutrino mass. Uncertainties: factors 2-3

Best limit: MMee < 350 meV (Heidelberg-Moscow)

SM neutrinos are massless.Are described by a 2-component (left) spinor

MeeM

2 L RC + h.c.( )

Pure Majorana neutrino L = 2eC = e

The mass term

Many other possibilities exist

Measure total energy oftwo electrons

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Status of neutrino oscillations

Solar electron-neutrino disappearance (a few MeV, 150 000 000 km)and active flavours appearance (SNO). Fit by the Bari group.

Muon-neutrinos from the atmosphere ( GeV, 10-13 000 km)Super-Kamiokande

Zenith angle distribution 1250 d (77 kt yrs)1.8 x 10–3 < m2 < 4 x 10–3 eV2 (90% c.l.), sin2 2 23> 0.88

CHOOZReactor anti electron-neutrino disappearance (a few MeV, 1km)

Combining with solar data 132 |Ue3|2 < 0.025

The Sun is not onlythe most powerful e

source nearby, butalso the mostefficient neutrinoflavour converter

PRE-SNO fit

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Status of neutrino oscillations. Post SNO

Muon-neutrinos from the atmosphere ( GeV, 10-13 000 km)Super-Kamiokande

Zenith angle distribution 1250 d (77 kt yrs)1.8 x 10–3 < m2 < 4 x 10–3 eV2 (90% c.l.), sin2 2 23> 0.88

CHOOZReactor anti electron-neutrino disappearance (a few MeV, 1km)

Combining with solar data 132 |Ue3|2 < 0.025

Inclusion of SNOresults, SMA (just)disappears @ 3 In the Valencia fit(same data) SMA isjust below 3

tan2θ12

θ13=0

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Bi-maximal mixing

Solar data favour maximum or nearly maximum mixing(LMA, LOW, quasi VO)

U =

12

− 12

0

1

2

1

2–

1

212

12

12

e = 12 1 – 2( )

= 1

2 1 + 1

2 2 –1

2 3

= 12 1 + 1

2 2 + 12 3

Atmospheric oscillation

Solar oscillation

⇔ full amplitude

e ⇔ full amplitude

with = 1

2+( )

3 is a maximum mixing of and

1 and 2 are orthogonal maximum mixings of e and

1 = 12 e +( )

2 = 1

2– e +( )

3 = 12

– +( )

u

deνe

csµνµ

t

bτντ

families

quark

leptons

eigenstates

states withflavour

The three “families” have beendefined assuming neutrinoswith definite flavour to bemass eigenstates

Inconsistent with quark sector

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LUNA & LUNA2Measure thermonuclear cross-sections in the energy range ofastrophysical interest (Gamow peak)LUNA. 50 kV accelerator. Research program completed in 2000LUNA2. Accelerator energy 400 kV. BGO detector

Installed and working. Physics in 2001

LUNA2. Programme14N (p, ) 15O7Be (p, ) 8B (most important)3He (4He, ) 7B (2nd import.)and more

Measuredby LUNA

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GNO

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GALLEX & GNO

Aim Detect low energy electron-neutrinos from pp fusion.Flux known @ ±2% from solar luminosity

Reaction 71Ga e e–) 71Ge (30 t natural Ga)Threshold 233 keVSSN prediction 129±7 SNUminimum from luminosity 80 SNUGALLEX final 76±8 SNU (1 σ systematic included)

First absolute calibration with an artificial e-neutrino source 51Cr 62 PBq1994 R=1.0±0.1 1995 R=0.83±0.1

STATUSCompleted in 1997

Present and future. GNOContinuously collect data for a long periodBetter low background (cryogenic) detectors (increase efficiency)Bring uncertainty below 5%GNO first run = 65.8+10.2/-9.6(stat) +3.4/-3.6 (syst [5.3%]) SNU

The Be neutrino puzzleBe = GALLEX – Luminosity – B (Super-K) < 0

But Be must be presentbecause B comes from Be

No astrophysical solutionNeutrino behaviour is not as expectedMust probably

neutrino oscillations

Previous evidence from Homestake and Kamiokande: strongdeficit of higher energy e-neutrinos (but expected flux modeldependence. The solar neutrino puzzle.

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77m

12.3m

10 m

Neutrinos from the atmosphere. MACRO

Upward-going µ’s from interactions in the rocksGood time resolution (up vs. down). Good angular resolutionBlind to electrons

Tracking:LST.0.2˚ angular resol.3 mm spatial resol.

Timing: scintillators0.5 ns resol

Select energy bins from multiple scatteringinformation, get L/E distributionIncompatible with no oscillationsOscillation parameters similar to SuperK

STATUSCompleted in 2000Decommiss. in 2001

Favours oscillation into vs. sterile @ 3

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Next steps. How can Gran Sasso contribute?

• Detect direct oscillation signals @ m2 (atmospheric)

• Prove if oscillation is between and or else

– detect appearance

• Improve knowledge of mixing parameters and m2

• CNGS project

– OPERA

– ICARUS

• Atmospheric neutrinos

– MONOLITH proposal

• Detect direct oscillation signals @ m2 ( “solar”)

• Improve knowledge of mixing parameters and m2

– Choose solar solution

• GNO

• BOREXINO

• LENS proposal

• Measure relevant cross-sections and screening effect

• LUNA2

• Nature of neutrinos: Majorana or Dirac• Measure sign of m2

• Measure absolute values of the masses

– Neutrino-less double beta decay

• HM, GENIUS-TF, GENINO, GENIUS

• MIBETA, CUORICINO, CUORE

• CP violation not at reach for a while.Doubly suppressed. m2 / m2 and |Ue3|2 are both small!

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CNGSCERN to Gran Sasso Neutrino Project

Beam energy p 400 GeVCC inter/kt*yr 2500

inter/kt*yr 25 @ full mixing and ∆m2 = 3.2 x 10–3 eV2

Further optimisation still possibleReady in May 2005

Detect – through itscharged decay products

18%h n

0 50%e e 18%

n0 14%

Tools for background reduction

observe decay (CHORUS, DONUT, OPERA)ct = O (1mm)

extreme spatial resolution. Only technique: emulsions

kinematics (NOMAD, ICARUS+spectrometer/calorimeter?)good particle id.good missing momentum resolution (“detect” neutrinos)

+ N → – + X

Produce ’s via CC interactions

Beam and experimentsoptimised for appearance

Complementary to K2Kand NUMI+MINOS

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The experiments at LNGS

OPERA (2 000 t). Approved

ICARUS 600t in testFirst 300 t semi-module operational

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ICARUSLiquid Ar TPCProposed (3.6 kt) in 1985

Future•present the final proposal•have adequate international collaboration•Fiducial/tot. volume, modularity, spectrometer?•Safety issues for large cryogenic volumes underground to beunderstood•Must be ready by spring 2005

∆m2 = 3.2 x 10–3 eV2

Exposure = 20 kt*yAfter kinematic cuts

29 eventsBackgr 5.1 eventsSystematics not included

Status:show feasibility at hundreds tons scale•a 600 t module under construction in Pavia•first 300 t half-module operational•long (18 m) tracks images obtained (June)•safety issues (600 t) being studied

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OPERA

ν

8 m

TargetTrackers

Pb/Em.target

Pb/Em. brick

8 cm

spectrometer

Extract selectedbrick

Electronic detectors→ select interaction brick→ ID, charge and p

basic cell

•Status. Approved•Must be ready in spring 2005

3 super-modules2000 t sensitive mass

Number of detected ’s per5 years runMaximal mixing4 ev. @1.5x10–3 eV2

18 ev. @3.2x10–3 eV2

44 ev. @5x10–3 eV2

backgr 0.6 ev.Further beam optimisation possible

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Ue3Ue3 is small. If =0 it would point to something relevant.ICARUS @ CNGS can observe the oscillation between and e

Two-state formalism (as used in ICANOE and MINOS proposals) ismisleading!Sensitivity to Ue3 = sin 13 is different in disappearance andappearance experiments.Remember: mixing and close to maximum

|Ue3 |2 ≈ 1

4"sin2 2 " in e diasppearance experiments

|Ue3 |2 ≈ 1

2"sin2 2 " in appearance experiments

A → e = sin223( ) sin2 2 13( ) ≈ 1

2sin2 2 13( )

A e→ x = sin2 2 13( )

A. Rubbia private comm.

Estimate improved w.r.t.Proposal including energydependence

sin2 2 13 = 4 |Ue3|2

Limit on |Ue3|2may be improved by a factor 4 with a 20 kt*year exposure(10% systematics, dominated by statistics)To proceed further

optimise beam energy ( than for appearance ) = 1-3 GeVbuild high intensity beambuild large mass (specialised?) detector |Ue3|2 O (10–3 )

Oscillationamplitudes

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MINOS. Ue3

Gain a factor 1.6 in exclusion

( from discovery)

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MONOLITH proposalAtmospheric neutrinos experiments are complementary to those onartificial beamsIf m2 < 1-2 x 10–3 eV2 we need cosmic rays

experiment easier if m2 lowerScopes of MONOLITH

Detect oscillation patternGood m2 measurement

NeedGood direction resolution (L)Good energy resolution (E)

good L/EVery large sensitive mass (> 30 kt)Rough calorimetry

2.0 cm

8 cm

STATUSProposal underconstructionCollaboration to bestrengthened

32 m

12.6 m

B B15 m

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BOREXINOReal time neutrino detector. Threshold E >0.4 MeVPhysics run in 2002

Measure mono-energetic (0.86 MeV) 7Be neutrino fluxVery sensitive to parameters

m2 and mixing matrix elements40 ev/d if SSM, 0 for some solutionlarge day-night and seasonal effects for some solutions

300 t liquid scintillator (Pseudocumene + PPO) in a nylon bagInnermost 100 t: fiducial volumeS/S sphere, 13.7 m diam. Supports the PMs & optical concentratorsSpace inside the sphere contains purified PCSecond nylon bag (11 m diam.) to block radonPurified water outside the S/S sphere (18 m diam., 16.9 m height)PM coverage 30%Energy resolution (02-0.8 Mev) 8%Space resolution 10-15 cm

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BOREXINO

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BOREXINO. Mounting the PMs

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Rates

Strong seasonal variations expected if ∆m2 < 10-10 eV2

0.30.5

0.7

0.9

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LENS ProposalTo complete the solar neutrino program, we need

sensitivity to the low energy (pp) neutrinos in real time flavour sensitivitysource sensitivity (pp. 7Be,8B)

YbLS techniqueThreshold E = 301 keVpp 200 ev/20 t * yBe 280 ev/20 t * y

R&D is necessary onliquid scintillator stabilityradiopuritycalibration sources

70

60

50

40

30

20

10

0

MSW-SMA∆m2 = 5x10-6 eV2

MSW-LMA∆m2 =1.3x10-5eV2

sin2 2θ=0.63

70

60

50

40

30

20

10

0

Measured Energy (MeV)

∆m2 = 4.2x10-10 eV2

VO- “Just-so”

sin2 2θ=0.937Be line- Seasonal Var.pp bump ~constant

Measured Energy (MeV)

MSW-LOW∆m2 = 1.1x10-7 eV2

sin2 2θ=0.83

Night Day

0 0.4 0.8 1.2 1.6 2.0

0 0.4 0.8 1.2 1.6 2.00 0.4 0.8 1.2 1.6 2.0

0 0.4 0.8 1.2 1.6 2.0

Return to In may happen as aconsequence of the YbLStechniques development

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The nature of neutrinosNeutrinos have only one “charge”: lepton numberIf total lepton number is not conserved, then e-neutrino and anti e-neutrino (etc.) may be the same particle: Majorana neutrino

Look for 0 2 decayNeutrino “mass” (Mee) values orlimits are indirectly extracted fromdata

Need to measure on differentisotopes

Heidelberg-MoscowTechnique: Enriched 76Ge detect.Limit: Mee<340 meV (best)Exposure: 372.2 kg y

GENIUS-TFTest facility for GENIUSWith the present HM Ge andb = 6 x 10–3 ev/(kg keV y)Mee<100 meV in 6 yearsStatus. Approved

GENIUSNaked enriched Ge crystals in LN2b = 3x10–4 ev/(kg keV yr))Sensitive mass: 1000 kg 76GeMee< 20-30 meVStatus. Experimental testsrequested (GENIUS-TF)Collaboration should bestrengthened

MIBETA (Milano)Technique:natural TeO2bolometers (130Te = 34%)130Te mass = 2.3 kgb = 0.5 ev/(kg keV yr)Limit: Mee < 2 eV (2nd best)

CUORICINO (expected)Sensitive 130Te mass = 14.3 kgb = 0.02-0.05 ev/(kg keV yr)Limit: Mee < 200-400 meVStatus. Approved

CUORE (expected)Sensitive 130Te mass = 250 kgb = 2x10–3 ev/(kg keV yr)Limit: Mee > < 50 meVStatus. R&D = CUORICINO

@ sensitivity levels of a few 10 meV neutrino effective mass mayappear, sign of m2 may be determined in some scenarios

The struggle for background reduction

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Supernova neutrinos

In the SN explosionneutrinos of all flavours areproduced

Total duration: 20-50 s

From SN 1987A <m > < 10-20 eVLimited by uncertainties on the “light” curve. Difficult to improve

Neutrinos produced in the SN core, cross the SN and its ejectaMatter effects and vacuum oscillations take placeConversions change the composition in 1, 2 and 3 and their spectra

1, 2 e 3 (not e, µ e τ) propagate from SN to us

Measured <m >’s are weighted averages of m1, m2 and m3 with weightsdepending on

initial abundancesmixing matrix elementsdetected flavour and energy range

Detection of neutrinos of a flavour does not give a limit on the“mass” of that flavourfor ex.: νe arrival gives t = 0, delay in ντ [νµ] gives m(ντ) [m(νµ)].WRONG

SN neutrino detection with several different techniques can giveinformation on mixing matrixImportance of SNEWS, the global worning network (GWshould be included)

neutrinisation(r-process)

core collapse(ms)νe only

t (s) = 0.05 [m(eV)/E(MeV)]2 D (kpc)

If m 0, delay is

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LVD

DetectorLiquid scintillator 1000tHighly modular

up-time 99.3% in 2000

12C + e+ + νe

12C + γA few dozens of evts in case

of matter conversions oroscillations

On top of a “tower”A porta-tank (8 tanks)38 porta-tanks per tower114 in 3 towers)

e +12C → e – +12N 6 evts

followed (τ =185 µs) by ncapture (used as a tag)

detected with 60% efficiency

n + p → + d + 2.2 MeV

e ⇔ ,may render νe more energetic, increasing the rates of certain reactions

Astrophysics (e.g.). r-process requires n’se + n e– + p destroys n’s

higher energy e’s are more efficient at this

Expected yield for a collapse inthe centre of Galaxy (8.5 kpc)Mainly:

e + p → n + e+ 300- 600 evts

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GENINO

Dark matter search

Very interesting results, but still more work neededIncrease detector mass (250 kg), further reduce background, etc

Need a balanced set of different experiments (not only at LNGS)to check independently the resultto deeper explore the parameters space

CRESST 2Detect heat and lightSeparate signal from backgroundExpect 10–2 c/ (kg keV d)@ 15 keVExpected to run end 2001

GENIUS-TFif b = 10–1 ev /(kg keV d)GENINO, 100 kg natural Ge,if b = 3x10–3 ev /(kg keV d)GENIUS 1000 kg enriched Geif b =10–4 ev / (kg keV d)

DAMALook for annual ratemodulationStrong R&D program115 kg NaI (Tl) radiopurecrystals

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Conclusions• Neutrino oscillation phenomena may provide

– An important tool to discover physics beyond the SM– A way towards the extremely high energy

• Neutrino masses <<< quark masses. Different mechanism?• Neutrino mixing quark mixing. Different mechanism?• Majorana, see-saw, p-decay

• Underground experiments in the next decades may/should– Discover physics beyond the Standard Model– Progress in the knowledge of neutrino properties

• Measure the mass-eigenstate mixing in the lepton sector

• Experimental proposals in different stages of preparation for– Oscillations on an artificial beams (accelerators and reactors)– Atmospheric neutrinos oscillations– Solar neutrinos oscillations– Neutrinos from supernova– Search for Majorana mass

• Need larger detectors and collaborations• Any decision on neutrino factories requires better knowledge of

both |Ue3|2 and m2 (solar). But R&D must be done now• Search for non-baryonic dark matter

– Need different, complementary techniques• Need stronger collaborations to cope with larger

experiments• Proton decay may be close

– Next generation p-decay (1 Mt) experiment(HyperKAMIOKANDE) is a principal issue

• Requires large international co-ordination

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DAMASun moves in the Galaxy @ 230 km/sEarth moves around the Sun @ 30 km/s

DAMAStrong R&D program115 kg NaI (Tl) radiopure crystals

Very interesting results, but still more work neededIncrease detector mass (250 kg), further reduce background, etc

Modulated part= a few %

June

December

Signal expectedone year period maximum in Juneamplitude < 0.07

Need a balanced set of different experiments(at LNGS and world wide)

to check independently the resultto deeper explore the parameters space

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CRESSTPhase 1 (Completed)Background reduced below 1 c / (kg keV day)

Phase 2Detect heat and lightSeparate signal from background(mainly )Expect 10–2 c/ (kg keV day) @ 15 keVExpected to run end 2001