Underground Physics A. Bettini Universit di Padova, Dipartimento di - - PowerPoint PPT Presentation

July 15, 10

• A. Bettini. INFN

1

Underground Physics

• A. Bettini

Università di Padova, Dipartimento di Fisica G. Galilei; INFN - Sezione di Padova Laboratorio Subterráneo de Canfranc (Huesca) Spain

In Inte tern rnatio tional S l School o l on A Astro troPartic rticle le P Physic ics Euro ropean D Docto tora rate te S School

Multi-Messenger Approach to Astroparticle Physics

Univ iversid idad d de Z Zaragoza 1 13-22 J July ly 2 2010

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Tiny signals. Go underground

Discovery in underground laboratories with natural sources (sun, cosmic rays), and long base-lines Confirmation and improvement in precision with reactor and accelerator experiments, on unprecedented baselines

Physics beyond the Standard Model

Neutrinos are massive Lepton numbers are violated Neutrino change flavour

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The Models

The Standard Model is the most precise and comprehensive theory ever built Tested with high accuracy in experiments @ accelerators Does not include gravitation

• Gravitation. Macroscopic theory only

GR - differently from other interactions 2 basic constants: Coupling & Cosmological constant Rµ 1 2 Rgµ = 8GN c4 Tµ gµ Cosmology is now exact Tested by consistency by

• bservations @ different epochs

ΛCDM Normal matter 4% Cosmological constant 73% Dark matter 23% Neutrinos 0.15-1%

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Lepton mixing

Neutrinos change flavour in two different ways

• (vacuum) oscillation
• in the kinetic part of the Hamiltonian (∆m2/2Eν)
• Disappearance atmospheric νµ
• does not depend on θij⇔π/2–θij [but 2ndoscill. interference]
• does not depend on sign(Δm2) [but 2ndoscill. interference]
• flavour conversion in matter MSW (Sun, Supernova, Earth)
• dynamical phenomenon, due to the νee interaction (2GFne)
• Disappearance (& indirectly appearance) solar νe
• depends on θij⇔π/2–θij
• depends on sign(Δm2)

π/4 π/2

Δm2

θij π/4 π/2

Δm2

θij

• A. Bettini Introduction to Elementary Particle Physics. Cambridge University Press 2008

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Mass eigenstates - Flavour eigenstates

e µ

• =

1 c23 s23 –s23 c23

• c13

s13ei 1 –s13ei c13

• c12

–s12 s12 c12 1

• 1

ei1 ei2

• 1

2 3

• 9 independent real parameters

3 masses m1, m2, m3 3 mixing angles θ12, θ13, θ23

θij ∈ [0,π/2]

1 phase (δ ⇒CP violation if not δ ≠0, , δ ≠ π ) +2 phases (φ2,φ3), if neutrinos are Majorana ⇒irrelevant for oscillations What we know @ 2σ level (95% c.l.)

• G. Fogli et al. hep-ph/0805.2517

m2 m2

2 m1 2 = 76.6 ± 3.5 meV2

m2 m3

2 m2 2 + m1 2

( ) / 2 = 2380 ± 270 meV2

sin2 12 = 0.3260.04

+0.05

sin2 23 = 0.450.09

+0.16

sin2 13 < 0.032

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What we know

We do not know

• The absolute scale
• The sign of Δm2

m3 > m2 50 meV m2 > m2 8.5 meV m1,m2 > 50 meV m3 > 8.5 meV ν1, , ν2, , ν3 defined in decreasing νe fraction ν1 ⇒ ≈ 70% νe, ν2 ⇒ ≈ 30% νe, ν3 ⇒ ≈ 0% νe solar squared mass difference ⇒ δm2 ( >0 from solar neutrinos) atmospheric squared mass difference ⇒ Δm2 m2

( ) 2.5%

m2

( ) 5%

sin212

( ) 6%

sin223

( ) 11%

sin213

( ) 0.01

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Oscillation probabilities

A µ x

( ) = sin2 223

( )cos2 13 ( ) 1sin223 cos213

( ) 1

2 A e x

( ) = sin2 213 ( ) 413

2

P x y,L

( ) = A x y ( )sin2 1.27m2 eV2

( )

L km

( )

E GeV

( )

• A µ e

( ) = sin2 23

( )sin2 213 ( ) 213

2

A µ

( ) = sin2 223

( )cos4 13 ( ) 1

A e

( ) = cos2 23 ( )sin2 213 ( ) 213

2

Appearance Observed by OPERA @ CNGS Rare, not yet observed Disappearance - atmosphere/acceler. Reactor experiments

• The oscillation probabilities are combinations of functions oscillating in time, hence in

the distance between source and detector, better of L/E

• Frequency proportional to mass square difference
• Amplitude different for different processes

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The first appearance OPERA

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OPERA

Target mass = 1.25 kt Exposure2008-9 ≈ 5 1019 p.o.t. (≈ 1/5 of total) ≈ 35% completely analysed Exopected≈ 0.5 events after selection criteria

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The first candidate

Expected background 0.045±0.020

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MSW

Sun Transition @ Δm12 @ Eν>> MeV Sun produces ν2 kinetic term matter term = m2 / 2E

( )

2GFne

Relevant interaction (Earth, Sun, SN) = CC νee Mass eigenstate in high density matter ≈ νe.

Vacuum/MSW Supernova Transitions @ Δm12 and Δm23 High neutrino density ⇒ νν νν interactions important

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BOREXINO Vacuum-Matter transition

Before BOREXINO BOREXINO

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Helicity and Chirality

L = 1 2 15

( ), 5L = L

R = 1 2 1+5

( ), 5R = +R

Chirality is a property of the 4-component bispinor Only negative chirality fields have CC weak interactions The states of definite chirality are the eigenstates of γ5 Chirality is not an observable, we measure helicity instead x

( ) =

1 2 3 4

• =
• Helicity is a property of a 2-component spinor,

representing a particle with v≠0 It is the spin projection on the direction of velocity h =

• p

p

= 1 2 E pz m

• L

+1/2 + 1

2 E + pz m

• L

1/2 m

E L

+1/2 + 1

2 E + pz m

• L

1/2

If the particle is ultrarelativistic, its negative chirality state contains a m/E “wrong” helicity component, very small if E>>m Helicity content of the (Left) spinor χ (z axis along the motion)

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Majorana bispinor

M

C = i2M = M

Majorana neutrinos are their own antiparticles Particle and antiparticle have all the “charges” with opposite values ⇒ different particles Neutrinos and antineutrinos are possibly distinguished by a unique charge, the lepton number If lepton number is not conserved nothing distinguishes neutrino from antineutrino Neutrino may be its own antiparticle The charge conjugate of a Majorana bi-spinor is the bi-spinor itself (up to a phase factor) If m<<E ⇒ approximate distinction between Majorana “neutrinos” and “antineutrinos” possible CC weak current lL µl creates Dirac: Majorana: (h = +1) + m / E

( ) (h = 1)

• CC weak current l µlL creates

Dirac: Majorana: (h = 1) + m / E

( ) (h = +1)

• Majorana neutrino ≡ negative helicity (if m/E<<1 interacts almost as a Dirac neutrino)

Majorana antineutrino≡ positive helicity (if m/E<<1 interacts as almost a Dirac anti-ν)

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ββ ββ2ν and ββ ββ0ν Decay

2nd order weak interaction In nuclides stable against β decay A,Z

( ) A,Z +2 ( )+2e +2

e

@ nuclear level Lifetime measured for several isotopes T2ν

1/2=1019−1021yr

Forbidden in the Standard Model If observed

• Lepton number is violated ∆L=2
• Neutrinos are Majorana

A Majorana νe with E≈+pz>>m hitting a nucleus produces e– and a fraction (m/E)2 of e+ [10–20 for E=1 GeV, m=100 meV] ⇒ Leff=+1. Observation hopeless. Go to decays

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Nuclear matrix elements

Continuous progress in the nuclear matrix elements calculations in the last years Three methods

• Quasi Random Phase Approximation (QRPA)
• Shell Model (SM)
• Interacting Boson Model 2 (IBM2)

136Xe 150Nd 154Sm 76Ge 82Se 116Cd 100Mo 128Te 130Te

IBM-2 Barea & Iachello 2009 QRPA Simkoich et al. 2008 ShM Courier et al. 2008

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Upper limits on the masses

• 1. β-decay. Electron spectrum near to its end point is affected by mi≠0 . Observable:

< me

2 >=|Ue1 |2 m1 2+ |Ue2 |2 m2 2+ |Ue3 |2 m3 2 = c13 2 c12 2 m1 2 + c13 2 s12 2 m2 2 + s13 2 m3 2

0.7m1

2 + 0.3m2 2

Present limits <mνe> < 2.2 eV from Mainz and Troitsk experiments KATRIN (starts measurements in 2010) <mνe> < 200 meV

• 2. 0ν2β-decay. If neutrinos are Majorana particles. Observable:

M ee =| Uei

2 i

• mi |=| c13

2 c12 2 m1 + c13 2 s12 2 m2e i2 + s13 2 m3e i3 |

• 3. Cosmology. Large Scale Structures spectrum is sensitive to neutrino mass, because

neutrinos can escape from the structures during their formation, reducing the number of structures smaller than a scale depending on

mi

i

• Limits are model dependent

Conservative limit (CMB, BAO, LSS) Σ<600 meV ⇒mi<200 meV Expected to improve

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Characteristics of Underground Labs

Underground experiments give an indirect reach to energy scales beyond any conceivable

• collider. Example mν=50 meV⇒MM≈1016 GeV (seesaw)

Pushing forward the high-energy frontier = fight against background Facilities range from simple underground sites to full laboratories and observatories and underground cavity is not a laboratory Important differences

• Depth (µ flux, spallation n flux)
• Important, but “the deeper the better” is a false statement. Optimum depth depends on

physics

• Determines only a fraction of the background sources
• Maximum cavity size decreases with increasing depth, costs increase
• Diameter & height of the halls
• May limit the thickness of the shields
• Depends on rock quality and depth

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Characteristics of Underground Labs

• Distance from accelerator (>1000 km for sign∆m2)
• Horizontal vs. vertical access
• Support infrastructures, personnel (quantity and quality)
• Underground area allocation policy, turnover of experiments
• Laboratory vs. observatory
• Scientific Committee: international vs. local (or national)
• Degree of internationality of the community
• Safety and security policy
• Environment
• Other science (geology, biology, engineering, etc.) [not covered]

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Horizontal access

No interference with mine works Interference with traffic safety to be managed Drive in Large pieces of apparatus can be taken in (300 t ICARUS @ LNGS) Reduced construction costs if close to a just to be opened free way Cost about 50 M€ for a dedicated access LNGS LSC

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• SNOLAB. 2000 m deep

Area available for experiments 3055 m2 (tot. 7200) Laboratories in mines tend to have large fraction of volume used for “drifts” In a working mine need to coordinate access with mine operation, but can profit of the safety structures of the mine

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Future DUSEL. 4850’ and 7400’ Levels

≈4200 mwe Other similar structures @ 7100 mwe In an abandoned mine > 300 km abandoned tunnels Difficult access; old shaft not designed for a laboratory Large water inflow (1.2 Mt/yr) About 1.5 M$ / yr for H2O extraction and cleaning No insoluble problem, but costs

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Muons

Experimental sites must be characterized

• angular dependence of the µ flux
• (see e.g. LVD and MACRO)
• seasonal variations of the µ flux
• (see e.g. MACRO)
• energy dependence of n flux
• seasonal variations of the n flux
• γ flux
• Rn activity continuous monitoring
• ……………..

MACRO Rough n. of µ About one ord of magn for 500 m overburden

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Neutrons

• From (α,n) and fission (mainly U/Th) in the rocks at lower energies (typical < 8 MeV)
• not difficult to shield
• dependent on geology. However, in practice fluxes are pretty similar (few 10–2m–2s–1)
• independent of depth @> 200 m’s
• Interactions of µs in the rocks
• higher neutron energies (several GeV)
• thicker shields needed
• flux depends on geology and depth
• flux 3-4 orders of magnitude smaller than thermal
• Interactions of µs in the shields & in the detector
• cannot be shielded
• decreases with increasing depth
• induced fast background can be reduced by anticoincidence
• 4 orders of magnitude in BOREXINO
• metastable nuclides more difficult, can be reduced by depth
• experiment dependent, more severe for high-Z materials

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Depth Requirements

Only R&D, measurements and simulations can define the level of acceptable depth-dependent background for a frontier experiment However, some general statements can be made (see for ex. Mai & Hime astro-ph/0512125; W. Haxton et al.

Nucl-ex/0604004/)

Example: GERDA: DBD with enriched Ge, 100 kg exposure, b=10–3/ (kg keV y) Location: LNGS Neutrons produced by µ in the rock Φn≈10–5 m–2s–1 ⇒ bkg in detector after shields (3m H2O, 2 m LAr) b=4×10–5 ev/(kg keV y) After anti-coincidence between segments b<10–5 ev/(kg keV y) µ-induced bkg from long-lived (>5 ms) isotopes in detectors (MC) (LAr shield) b=10–4 ev/(kg keV y) in detectors (MC) (LN2 shield) b=10–5 ev/(kg keV y)

• Physics with Mt-size detectors (p-decay, long-baseline ν

beam from accelerators, SN) do

not require large depth

• CC solar neutrino, geo-neutrino, accelerator nuclear astrophysics: 3000-4500 m.w.e.

generally enough

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The most powerful neutrino source near to us

• B. Pontecorvo 1968: “From the observational point of view the ideal object is the sun. If the
• scillation length is smaller than the radius of the sun region effectively producing

neutrinos….. The only effect on the earth's surface would be that the flux of observable sun neutrinos must be two times smaller than the total (active and sterile) neutrino flux”

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BOREXINO

Calaprice

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• BOREXINO. The spectrum

7Be region 100-400 keV b≈0.25 x 10–5 ct keV–1 kg–1 yr–1

Cosmogenic C isotopes

14C T1/2=5700 yr 11C T1/2=20’ 10C T1/2=19”

≈1000m deeper No depth problem @ LNGS depth µ+12C−−>11C+n+µ n capture γ (2.2 (2.2 MeV) 20’ 300 µs

11Β+e++νe

Off-line discrimination

• f 11C (@92%)

Look for e+ annihlation near µ track in 100’ and subsequent γ

Borex Coll. Phys.Rev. C74,2006

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Antineutrinos from the Earth

Earth produces energy, at a rate of 30-40 TW. What are the mechanisms? Can neutrinos teach us something?

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BOREXINO Geoneutrinos

Future Multi kt hyperpure (BOREXINO grade) liquid scintillator detectors array in strategic locations on Earth Very low background due to Extreme radiopurity Distance from nuclear power reactors

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Dirac or Majorana?

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Measuring the 2 electrons energy spectrum

• The most powerful technique: Source=detector
• Surfaces (sources of bkgnd) can be taken far away
• Good energy resolution
• High purity materials
• Ge diodes, Te bolometers, Xe gas TPC, Xe liquid TPC, Isotope

dissolved in liquid scintillator

• Tracking may provide additional discrimination power

+ “continuous” fluctuating background + lines background

• NEXT. 10 bar

gas Xe TPC

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“Majorana mass”

The fraction of ββ2ν events in ΔE near end point is F 7 E

( )

6

meQ

5

0ν2β signal/ 2ν2β background S B meQ

5

7 E

( )

6

T1/2

2

T1/2 Background free condition and and energy resolution are the key features sensitivity to 1 M ee

M F M =

MT bE

• 1/4

F

M

MT

2

Sensitivity of an experiment with background index b, sensitive mass M, live time T and energy resolution ΔE If b=0 during T, in an energy window of about ΔE (a few keV for Ge and bolometers) sensitivity to Mee∝ 2nd root of the exposure

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The experimental challenge

430 Xe enrich. (85%) 250 400 TeO2 natural Ge enrich. (85%) Mee=500 meV 4.3 2.5 4 Mee=50 meV 0.4 0.2 0.4 Mee=15 meV Events per ton per year Within a factor ≈ 2 Student Workshop on Double Beta Decay LNGS 11-13 Novembre INFN & Ateneo Italo tedesco http://www.pit.physik.uni-tuebingen.de/grabmayr/workshop/

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CUORE=Cryogenic Underground Observatory of Rare Events

988 detectors in towers M(130Te) = 203 kg Pavan E FWHM

( ) = 4.6±1.2 keV @ 2615 keV

“Background free condition” <10—3 ct/(kg (Te130) keV yr) Present condition (measurements + simulations) Irreducible from cryostat 48±2(stat)±5(syst) 10—3 ct/(kg keV yr) From supports & detectors surfaces 48±7(stat)±5(syst) 10—3 ct/(kg keV yr) If not improved, sensitivity Mee>≈250 meV Foresees data taking in 2013

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Shielding may require large volumes. GERDA@LNGS

Water Tank bottom

3 m thick hyper pure H2O active shield 2 m thick hyper pure LAr shield Enriched Ge crystals

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GERDA

Phase 2: 100 kg y b = 10–3 ev/(kg keV yr)

• Sensit. T1/2=13 × 1025 y; Mee= 140 meV

Phase 1; 15 kg y b = 10–2 ev/(kg keV yr) Sensitivity T1/2=2 × 1025 y: Mee≈ 400 meV Technical run with 3 (2) detectors data taking Commissioning & background measurements.

5 F/E, cables, supports 25 (ph1) 5 (ph2 after 2 years) Cosmogenic in crystals

68Ge (t1/2= 270 d)

120 (ph1) 0.35 (ph2 after cuts) Cosmogenic in crystals

60Co (t1/2= 5.27 y)

2 µ induced 0.3 γ’s from external 208Tl Rate (10–4 kg–1 y–1 keV–1) Source

From measurements and simulations Inside the water tank

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GERDA Phase 2 Ge diodes

The control of the Cosmogenic activation of 68Ge during detector production

Purification Zone ref. & Crystal Pulling Detector Fabrication

Calculate the N(68Ge/kg) vs exposure on surface time Transportation to Europe for further processing in a specially designed container: reduce activation by factor 20 Storage underground Enrichment in Siberia

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The ultimate background: 2β2ν

Expos.=0.5 t y Mee=60 meV FWHM= 3.5% Expos.=0.5 t y Mee=60 meV FWHM= 1% Expos.=5 t y Mee=20 meV FWHM= 1% Expos.=5 t y Mee=20 meV FWHM= 3.5%

Example 136Xe assuming T1/2(2ν2β)≈1021 (exp lower limit)

EXO FWHM = 3.8% NEXT High pressure TPC with FWHM = 0.5-1% in principle feasible with no charge amplification S B meQ

5

7 E

( )

6

T1/2

2

T1/2

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The penultimate background. Daughters of Rn

A cartoon for the principal background lines in the RoI of 136Xe DBD FWHM = 1%, heights of the lies is arbitrary

New Qββ

ββ

measurement EXO

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KAMLAND ZEN

400 kg 136Xe FWHM = 10% 2% Xe dissolved in liquid scintillator

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SNO+ 56 kg of 150Nd in liquid scintillator

Mee= 100 meV 6.4% FWHM @ Q-value 3 years livetime U, Th at Borexino levels dominant background is

8B solar neutrinos! 214Bi (from radon) is

almost negligible

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Dark matter

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Principles of WIMPs Detection

Target = Detector Measure the energy deposited by the hit nucleus Part of this energy appears as charge, light or heat Main challenges

• Signal rate is small
• Energy deposit is tiny (few keV)
• Signal spectrum decreases exponentially
• 3 basic backgrounds
• electromagnetic (β & γ); dominant ⇒ electrons
• neutrons (and WIMPs) ⇒ nuclear recoil
• surface contamination (partial energy release)

Search for characteristic signal: annual modulation (DAMA/LIBRA & ANAIS) Passive shielding. Against external backgrounds only Active discrimination. Against external and internal background Measure two quantities. Achieve event by event rejection (as opposed to statistical) Track images Tagging

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Neutralino SI cross sections

Lower limit from cosmology ≈ 6 GeV Lower limit from LEP is on chargino, indirectly on neutralino No firm theoretical upper limit on the χ mass (but reasonably < 1000 GeV)

• R. Gaitskell, V. Mandic, J. Filippini http://dendera.berkeley.edu/plotter/entryform.html

1 ev/(t d)

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ArDM (LSC) & XENON100 (LNGS)

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Noble Liquids self shielding

Noble liquids, Xe, Ar, and Ne look very promising for the WIMP detection, because

• can be easily assembled in large masses
• can be cleaned from radioactive traces at very high levels
• self-shielding structures can be built, with the central part

shielded by a large contiguous mass (in the same container)

• f the same liquid ⇒ no free surface, no surface

contamination

• Shield can be instrumented to act as a veto

PMTs Fiducial volume Shielding volume

γ γ γ W W

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Dual phase Xe/Ar. Light vs charge S1/S2

• Two-phase (Liquid & Gas)
• Localisation of the event via TPC ⇒ definition of fid. vol. without surfaces
• Discrimination between nuclear and electromagnetic recoils by
• Detection of primary scintillation light and ionisation via proportional scintillation

(Benetti et al. in 1993)

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Noble Liquids. Dual-phase Pulse shape

• Two-phase (Liquid & Gas)
• discrimination between nuclear and

electromagnetic recoils by

• difference in the time

dependence of luminescence for light (slow component from 3Σ states) and heavy recoils (fast component from 1Σ states) (A. Hitachi

et al. in 1983)

• Lifetimes
• Xe 3/27 ns
• Ar 10/1500 ns
• Couplings
• Xe SI and SD
• Ar SI only

Heavy recoil L i g h t r e c

• i

l

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XENON 100 Background

• E. Aprile WONDER 2010

LNGS depth (rock overburden) will be certainly enough for XENON 1000. Water tank. And for NEXT 10 000?

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Neutrino physics at accelerators Next to next generation

The physics programme after the present generation experiments will depend, in particular on the value of θ13 If it is not too small, we have access to CP violation in leptons sector Need high fiducial mass detectors (100 kt - 1 Mt) High luminosity beam (several MW on target) Physics measure CP phase δ precision measurements of the other oscillation parameters With the same detector proton decay supernova neutrinos

• NB. Such a large facility needs to be multi-purpose

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p→e+π0

Bob Svoboda

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p→K+ν

Bob Svoboda

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FNAL to DUSEL. H2O Cherenkov 300 kt

Normal hierarchy Inverse hierarchy Neutrino Antineutrino L=1300 km P=1.2 MW, 3 1021 p.o.t 3 years run θ13

2=0.01

Large background (2nd peak) NC π0 Uncertainties on bkgnd difficult to evaluate, even with good measurement at near detector 10% systematic assumed (??)

• NB. If the base line is

shorter, neutrino energy is smaller @ L/E. Much less NC π0 arXiv:0705.4369

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FNAL to DUSEL. LAr TPC 100 kt

Normal hierarchy Inverse hierarchy Neutrino Antineutrino L=1300 km P=1.2 MW , 3 1021 p.o.t 3 years run θ13

2=0.01

Background almost only νe beam contamination 10% systematic assumed arXiv:0705.4369

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LAGUNA

European initiative (1.7 M€ PM7) for next generation detectors for neutrino physics and proton decay Siete candidatos a albergarlo: 1.Laboratory IUS Boulby Mine, UK 2.Laboratory LSM, France 3.Laboratory LSC, Spain 4.Pyhäsalmi Mine, Finland 5.Unirea Mine, Rumania 6.Sieroszowice Mine, Poland 7.Non INFN site, Italy Feasibility study: geotechnique, economic, environmental, social, political, Three technologies:

• 1. Water-Cherenkov

~ 1 MT

• 2. Aliquid Ar

~ 0.1 MT

• 3. Liquid scintillator

~ 0.05 MT

http://www.lsc-canfranc.es/pagina-279/

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LAGUNA-LSC-GLACIER

75 m (h), >35 m (dia) Plastification study Romana Ruiz

July 15, 10

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LAGUNA-LSC-LENA

115 m (h), 34 m (dia) Plastification study Romana Ruiz

July 15, 10

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LAGUNA-LSC-MEMPHYIS

85 m (h), 65 m (dia) Plastification study

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Pre-design of one of the three cavities for MEMPHYS @ LSC

73 m 85 m

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General layout Environmental impact study Dispose of the excavation material ~1 millionn m3 red zones

LAGUNA-LSC

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Thank you

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Additional pages

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Core collapse Supernovae

July 15, 10

• A. Bettini. INFN

65

Net result adiabatic condition if |θ13

13|2<

< few 10–4 νe spectrum made harder if Δm2>0 antiνe spectrum made harder if Δm2<0 kt to multi-kt, complementary, detectors needed Existent (mainly sensitive to antiνe): LVD, SK, BOREXINO, ICECUBE Futuro: 1 Mt Water Cherenkov

Core collapse supernovae

• The evolution of isolated Fe core stars (SNII) terminates with the collapse of the nucleus
• The Gravitational energy is released in ν and antiν : Eb =3x1046 J

larger than the EM radiation of the host galaxy

• Neutrinos and antineutrinos with all flavours are produced in the core
• νe <E> ≈10 MeV, ≠νe <E> ≈12-15 MeV, νµ & ντ <E> ≈ 20-25 MeV, (uncertain values)
• Propagating states are the eigenstates in matter
• The eigen energies depend on
• Sign Δm2
• θ13
• Observable effects on
• total flux
• energy spectrum
• temporal evolution of spectr
• SN frequency
• 3-4 century in our Galaxy
• 0.3-0.4 /yr < 5 Mpc
• Good perspectives for 1Mt WC

July 15, 10

• A. Bettini. INFN

66

Super-K and LVD

1m 1m 1 . 5 m

8 7 6 5

4

3 1 2

22 kt water Cherenkov 1 kt Liquid scintillator LVD tags using delayed (τ =185 µs) n capture n + p + d + 2.2 MeV Both media are mainly sensitive to antiνe e + p n + e+

( )

e + e e + e

( )

10 E 10 MeV

July 15, 10

• A. Bettini. INFN

67

Example, antineutrinos

ν1 νe ∆m2>0 ∆m2<0, adiabatic νe ν3 ∆m2<0, non-adiabatic νe ν1 Pee= |Ue1|2 ≈ cos2θ12 ≈ 0.7 Spectrum is medium-soft e 0.7e

SN + 0.3µ SN

Spectrum is hard Pee= |Ue3|2

July 15, 10

• A. Bettini. INFN

68

Neutrino spectrum

Jegerlehner, Neubig, Raffelt PRD 54 (1996) 1194

Fit simply assumes equipartition energy between 3 neutrino and 3 antineutrino flavours νe do not look hotter than theory ⇒ Δm2>0 or θ13 small

We need a galactic SN explosion soon

July 15, 10

• A. Bettini. INFN

69

Diffuse supernovae neutrino flux

Even if a SN explosion is a rare event in our Galaxy, neutrinos of the past explosions are

• here. Can we detect them?

Best limit from SuperKamiokande Close to theoretical expectations Background limited

• M. Vagins + J. Beacom (HEP-Ph/0309300)

⇒ GADZOOKS!= SK Gd doped

e + p e– + n

• 0.2 % of GdCl3 ⇒90% tag efficiency
• SK+Gd can 5 ev./yr, almost bkgnd free
• Gd makes SK see low energy neutrons; background??
• tests with 1 kt WC near detector of K2K
• Systematic assay at LSC

M.Malek et al., Phys. Rev. Lett. 90 061101

Tag n to suppress background n capture cross section on 49 kbarn ⇒ γ cascade 8 MeV Low threshold possible

before spallation cut after spallation cut after sub-event cut after Cherenkov cut after solar direct. cut