Neutrino Experiments with Liquid Scintillator Detectors an Overview

Neutrinos Detection principles Experiments Summary

Neutrino Experiments with Liquid Scintillator Detectors An Overview

Daniel Bick

Institut fur¨ Experimentalphysik Hamburg University

Hamburg Student Seminar, October 29th 2007

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 1 Neutrinos Detection principles Experiments Summary

1 Neutrinos General facts Neutrino Mixing Neutrinos

2 Detection principles Neutrino detection Liquid Scintillators What can be investigated

3 Experiments KamLAND Borexino Propects

4 Summary

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 2 Neutrinos Detection principles Experiments Summary

1 Neutrinos General facts Neutrino Mixing Neutrinos

2 Detection principles Neutrino detection Liquid Scintillators What can be investigated

3 Experiments KamLAND Borexino Propects

4 Summary

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 2 Neutrinos Detection principles Experiments Summary

1 Neutrinos General facts Neutrino Mixing Neutrinos

2 Detection principles Neutrino detection Liquid Scintillators What can be investigated

3 Experiments KamLAND Borexino Propects

4 Summary

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 2 Neutrinos Detection principles Experiments Summary

1 Neutrinos General facts Neutrino Mixing Neutrinos

2 Detection principles Neutrino detection Liquid Scintillators What can be investigated

3 Experiments KamLAND Borexino Propects

4 Summary

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 2 Neutrinos Detection principles General facts Experiments Neutrino Mixing Summary

1 Neutrinos General facts Neutrino Mixing Neutrinos

2 Detection principles Neutrino detection Liquid Scintillators What can be investigated

3 Experiments KamLAND Borexino Propects

4 Summary

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 3 Neutrinos Detection principles General facts Experiments Neutrino Mixing Summary Some general aspects on the neutrino

The (electron-)neutrino was predicted by Wolfgang Pauli in 1930. It was experimentally discovered in 1956 by Reines and Cowan. There is one corresponding neutrino for each charged lepton.

νe νµ ντ e− µ− τ −

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 4 Neutrinos Detection principles General facts Experiments Neutrino Mixing Summary Neutrinos Sources

Many neutrino sources - both natural and man made - exist: β-decays (up to some MeV)

Atmospheric neutrinos νµ, ν¯µ, νe , ν¯e from π-decays (100 MeV - 10 TeV)

Solar neutrinos: νe (< 2 MeV)

Reactor neutrinos: ν¯e (up to 10 MeV)

Neutrino beams: mainly νµ (some 10 GeV)

Geoneutrinos: ν¯e (< 3.3 MeV) Supernovae: all ﬂavors (some 10 MeV) Supernova bursts Relic neutrinos

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 5 Neutrinos Detection principles General facts Experiments Neutrino Mixing Summary Neutrino Mixing

Neutrino ﬂavor eigenstates |ναi diﬀer from their mass eigenstates |νi i.

There are three mass eigenstates ν1, ν2, ν3 corresponding to the charged-lepton mass eigenstates e, µ and τ.

Eigenstates are connected by the mixing matrix UPMNS . ∗ |νi i = Uiα|ναi |ναi = Uiα|νi i. Xα Xi

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 6 Neutrinos Detection principles General facts Experiments Neutrino Mixing Summary Neutrino propagation

The propagation of the mass eigenstates is described by: 2 mi Ei t−p L −i L |νi (t)i = e i |νi (0)i = e 2E |νi (0)i

2 m2 −i i L P → e 2E να νβ = να νβ Xi

Neutrino mixing leads to oscillations.

∗ ∗ 2 2 L P → = δ − 4 Re(U U U j U ) sin ∆m να νβ αβ αi βi α βj ij 4E Xi>j

∗ ∗ 2 L + 2 Im(U U i U j U ) sin ∆m αi β α βj ij 2E Xi>j 2 2 2 With ∆mij = mi − mj

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 7 Neutrinos Detection principles General facts Experiments Neutrino Mixing Summary The mixing matrix

atmospheric cross-mixing −iδ 1 0 0 cos θ13 0 sin θ13e U = z0 cos θ23}| sin θ23 { × z 0 }|1 0 { 0 − sin θ cos θ − sin θ eiδ 0 cos θ  23 23  13 13  iα /2 cos θ12 sin θ12 0 e 1 0 0 iα /2 × − sin θ12 cos θ12 0 ×  0 e 2 0 0 0 1 0 0 1     solar majorana phases | {z } | {z }

−iδ c12c13 s12c13 s13e iδ iδ U = −s12c23 − c12s23s13e c12c23 − s12s23s13e s23c13  s s − c c s eiδ −c s − s c s eiδ c c  12 23 12 23 13 12 23 12 23 13 23 13 

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 8 Neutrinos Detection principles General facts Experiments Neutrino Mixing Summary The mixing matrix

atmospheric cross-mixing −iδ 1 0 0 cos θ13 0 sin θ13e U = z0 cos θ23}| sin θ23 { × z 0 }|1 0 { 0 − sin θ cos θ − sin θ eiδ 0 cos θ  23 23  13 13  cos θ12 sin θ12 0 × − sin θ12 cos θ12 0 0 0 1   solar | {z }

−iδ c12c13 s12c13 s13e iδ iδ U = −s12c23 − c12s23s13e c12c23 − s12s23s13e s23c13  s s − c c s eiδ −c s − s c s eiδ c c  12 23 12 23 13 12 23 12 23 13 23 13 

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 8 Neutrinos Detection principles General facts Experiments Neutrino Mixing Summary The mixing matrix

−iδ c12c13 s12c13 s13e iδ iδ U = −s12c23 − c12s23s13e c12c23 − s12s23s13e s23c13  s s − c c s eiδ −c s − s c s eiδ c c  12 23 12 23 13 12 23 12 23 13 23 13 

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 8 Neutrinos Detection principles General facts Experiments Neutrino Mixing Summary Matter Eﬀects (simpliﬁed)

Oscilliation in matter differs from vacuum oscillatons: Coherent forward scattering of neutrinos from particles along their way can have an effect. Coherent forward scattering via W exchange occurs for electron type neutrinos. Scattering via Z exchange for all neutrino types → effect cancels out. This means that neutrinos in matter have a different effective mass than neutrinos in vacuum! Matter effects depend on the neutrino energy. Larger effect for more energetic neutrinos.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 9 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary

1 Neutrinos General facts Neutrino Mixing Neutrinos

2 Detection principles Neutrino detection Liquid Scintillators What can be investigated

3 Experiments KamLAND Borexino Propects

4 Summary

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 10 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Detection methods

Three major methods of detecting neutrinos: Cerenkˇ ov Detectors (Ethr ' 5 MeV). Radiochemical Detectors (e.g. C2Cl4: Ethr = 814 keV, Ga: Ethr = 233 keV). No energy measurement possible. Liquid Scintillation Detectors (Ethr ' 200 keV for ν and Ethr ' 1.8 MeV for ν¯)

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 11 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Liquid Scintillators

Organic liquid scintillators are aromatic hydrocarbon compunds containing benzene-ring structures. Passing particles deposit ionizing energy in the scintillator, exciting the free valence electrons of the benzene-rings. Scintillation light is emitted due to transitions from excited states to the ground state.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 12 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary

ν¯e-detection via the inverse β-decay Inverse β decay on protons: + p + ν¯e → e + n CC reaction of a proton and an antineutrino. (cross section in the order of 10−42 cm2). The positron anihilates with some electron imediately emitting ¯ two γ’s. Visible energy: Eprompt = Eν¯e − En − 0.8 MeV The neutron will be captured after a short delay (typically around 200 µs), releasing 2.2 MeV. Coincidence signal between the prompt positron and the gammas from the delayed neutron-capture. Reaction threshold: 2 2 (Mn + Me ) − Mp Eν,min = = 1.806 MeV. 2Mp

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 13 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 13 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary ν-detection via elastic scattering

The process

− − νx + e → νx + e

is sensitive to all neutrino ﬂavors. Cross section 6 times higher for electron type neutrinos. Scattered electrons are detected by means of the scintillation light produced in the liquid scintillator. Recoil electron proﬁle is similar to that of Compton scattering of γ-rays. Sensitive to low energies

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 14 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary ν-detection via elastic scattering

The process

− − νx + e → νx + e

The process

− − νx + e → νx + e

The process

− − νx + e → νx + e

The process

− − νx + e → νx + e

A typical scintillator us usually made of: A solvent serving as a target and as a source of scintillation light. One or more ﬂuors (a few g per l). The solvent is in general not transparent for its own scintillation light. Therefore wavelength shifters (also denoted as ﬂuors) are added. For the delayed neutron capture when detecting antineutrinos, it’s of advantage to add a target element such as Gd to the LS.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 15 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Properties of LS

The light yield describes the number of photons emitted by the scintillator per amount of deposited energy by an incoming ionizing particle. Sometimes also expresses in the corresponding number of pe. In modern LS, about 400 photoelectrons per MeV are feasible. The attenuation length combines scattering and absorbtion eﬀects reducing the average distance scintillation light is able to propagate. Typical values vary around 10 m

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 16 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Properties of LS

The energy can be obtained from the number of observed photoelectrons (p.e.) in PMTs. Corrections to take into account: density of PMTs shadows from the geometry (eg. suspension ropes) transparencies of LS and other liquids involved.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 17 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Project Poltergeist

First experimental evidence of neutrinos was given in the Project Poltergeist experiment in 1956.

A solvent of Water and CdCl2 was used as a target. Two liquid scintillation counters were placed next to it Organic LS have been THE detection medium of choice for antineutrinos since the early discovery experiment of Reines and Cowan.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 18 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Observations done with LS

Liquid scintillators already oﬀer a large and intresting spectrum of possible obervations: Solar neutrinos (test SSM, look for oscillations)

Reactor neutrinos (Eν¯e > 1.8 MeV) Neutrinos from inside the Earth (Geoneutrinos)

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 19 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Neutrinos from the Sun: pp-chain

Energy production in the Sun through fusion: + − p + p → d + e + νe (pp) p + e + p → d + νe (pep) d + p → 3He + γ pp I: pp III:

3He + 3He → 4He + p + p 3He + 4He → 7Be + γ 7Be + 1H → 8B + γ 8 8 e+ pp II: B → Be + + νe 8Be ↔ 4He + 4He 3He + 4He → 7Be + γ 7 − 7 pp IV / HEP: Be + e → Li + νe 7 4 4 3 1 4 + Li + p → He + He He + H → He + νe + e

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 20 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Neutrinos from the Sun: pp-chain

Energy production in the Sun through fusion: + − p + p → d + e + νe (pp) p + e + p → d + νe (pep) d + p → 3He + γ pp I: pp III:

CNO:

12C + 1H → 13N + γ 13 13 + N → C + e + νe 13C + 1H → 14N + γ 14N + 1H → 15O + γ 15 15 + O → N + e + νe 15N + 1H → 12C + 4He

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 21 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary CNO cycle / neutrino spectrum

CNO:

12C + 1H → 13N + γ 13 13 + N → C + e + νe 13C + 1H → 14N + γ 14N + 1H → 15O + γ 15 15 + O → N + e + νe 15N + 1H → 12C + 4He

CNO: 862 keV 12C + 1H → 13N + γ 13 13 + 1.442 MeV N → C + e + νe 13C + 1H → 14N + γ 14N + 1H → 15O + γ 15 15 + O → N + e + νe 15N + 1H → 12C + 4He

Fluxes and energies are predicted by the SSM:

Neutrinos can be detected in a LS through elastic scattering:

− − νx + e → νx + e

Clear Compton edge from recoil electron is expected.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 22 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Reactor neutrinos

ν¯e are produced in nuclear reactors by beta decays of daughter nuclei from 4 ﬁssile nuclei: mainly 235U,239Pu and also 238U and 241Pu. Neutrino sprectra from these components are well modeled by β-spectrum measurements for 235U,239Pu,238U and theoretical calculations for 241Pu.

Approx. 6 ν¯e result from each ﬁssion event leading to 20 2 × 10 ν¯e per GWth per second. Average energy of 3.7 MeV.

ν¯e spectra known with an uncertainty of 2%. ⇒ Nuclear reactors are an excellent source for neutrinos.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 23 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Reactor neutrinos

Approx. 6 ν¯e result from each ﬁssion event leading to 20 2 × 10 ν¯e per GWth per second. Average energy of 3.7 MeV.

ν¯e spectra known with an uncertainty of 2%. ⇒ Nuclear reactors are an excellent source for neutrinos.

Neutrino fluxes from main fuel components

1 235U 239Pu 10-1 241Pu 238U 10-2 Nb neutrino/fission

10-3

10-4

10-5

10-6 2 4 6 8 10 12 Energy (MeV)

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 24 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Geoneutrinos

Heat ﬂow from Earth measured to be approx 44 TW. Almost half the power from radioactivity of material inside Earth (16 TW) Geological studies: 84% produced by 238U and 232Th decays.

rent 10 238U series pa 232Th series

er 40

p K

V e M 0 er 10 p

-1 nti-neutrino 10 a

f er o mb u N -2 10 0.5 1 1.5 2 2.5 3 3.5 Anti-neutrino energy, Eν (MeV) Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 25 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Geoneutrino detection

Detectable via inverse beta decay. No direct angular information form liquid scintillator. Indirect directional determination because the ﬁnal neutron is displaced in the forward direction. Oﬀset between e+ and neutron capture location can be determined Can be done by analyzing the arrival times and the number of photons for each PMT. Hard to distinguish from reactor antineutrinos.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 26 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary Geoneutrino detection - what can be found out?

Get geophysical information: Get the distribution of radioactive elements in Earth Radioactive elements in core? Nuclear reactor in core? Interpretation of geomagnetism.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 27 Neutrinos Neutrino detection Detection principles Liquid Scintillators Experiments What can be investigated Summary It would be too simple... without Background

Background mainly a problem for νx detection. Cosmic: 11C cosmogenic events from the reaction µ +12 C + secondaries → µ +11 C + n + secondaries Radioactive: 14C: β− end point energy: 156 keV 210 222 Po (daughter of Rn), T1/2 ≈ 138 d, deposits ≈ 350 keV 85Kr: β− end point energy: 687.4 keV

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 28 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary

1 Neutrinos General facts Neutrino Mixing Neutrinos

2 Detection principles Neutrino detection Liquid Scintillators What can be investigated

3 Experiments KamLAND Borexino Propects

4 Summary

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 29 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary KamLAND

KamLAND - Kamioka Liquid Scintillator Anti-Neutrino Detector.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 30 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary KamLAND

53 commercial nuclear reactors in Japan Located at the former Kamiokande site. 70 GW of power is generated by nuclear reactors at distances between 130 and 220 km (7% of world total). This contributes to 80% of the total neutrino ﬂux at the site. Inside Mt. Ikenoyama → 2700 m.w.e. rock shielding.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 31 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary KamLAND

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 31 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Physics perspective

Neutrino ﬂux is approx. 6 × 106/cm2/sec at site.

Opportunity to investigate ν¯e oscillations.

2 2 2 ∆m12L P → ≈ 1 − sin 2θ sin ν¯e ν¯e 12 4E

1 ton of ultrapure LS used to meausre ν¯e disappearance.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 32 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Physics perspective

Neutrino ﬂux is approx. 6 × 106/cm2/sec at site.

Opportunity to investigate ν¯e oscillations.

2 2 2 ∆m12L P → ≈ 1 − sin 2θ sin ν¯e ν¯e 12 4E

1 ton of ultrapure LS used to meausre ν¯e disappearance.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 32 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

1200 m3 liquid scintillator 20% 1,2,4-trimethylbenzene

80% dodecane (C12H26) Fluor: 1.52 g/l PPO (2,5-diphenyloxazole)

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 33 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

1200 m3 liquid scintillator target

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 33 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

1200 m3 liquid scintillator target 1800 m3 buﬀer oil 50% dodecane 50% isoparaﬃn

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 33 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

1200 m3 liquid scintillator target 1800 m3 buﬀer oil Schields target from external radiation, e.g. emitted by PMTs

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 33 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

1200 m3 liquid scintillator target 1800 m3 buﬀer oil Schields target from external radiation, e.g. emitted by PMTs Phototubes 1325 newly developed 17” tubes 554 old Kamiokande 20” tubes

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 33 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

1200 m3 liquid scintillator target 1800 m3 buﬀer oil Schields target from external radiation, e.g. emitted by PMTs Phototubes Photocoverage of 34%

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 33 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

1200 m3 liquid scintillator target 1800 m3 buﬀer oil Schields target from external radiation, e.g. emitted by PMTs Phototubes Photocoverage of 34% Water Cerenkˇ ov detector 3.2 kton pure water 225 old Kamiokande 20” tubes

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 33 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

1200 m3 liquid scintillator target 1800 m3 buﬀer oil Schields target from external radiation, e.g. emitted by PMTs Phototubes Photocoverage of 34% Water Cerenkˇ ov detector Absorbs γ-rays and neutrons from surrounding rock and acts as a tag for cosmic muons.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 33 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Performance

e+ and the delayed 2.2 MeV gamma from neutron capture on proton make a clear coincidence signal (mean neutron capture time 210 µs) Energy response calibrated with 68Ge, 65Zn, 60Co and Am-Be γ-ray sources Event locations can be reconstructed from the timing of PMT hits with a typical resolution of ≈ 25 cm

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 34 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Analysis

Trigger: 200 PMT hits corresponding to about 0.7 MeV. Cuts: ﬁducial volume: R < 5.5 m time correlation (0.5µs < ∆t < 660 µs)

delayed energy (1.8 MeV < Edelay < 2.6 MeV) ⇒ Fiducial Volume contains 4.61 × 1031 free protons ⇒ Spatial resolution of 25 cm (Reconstructed from the timing of PMT hits) Events with less than 10000 p.e. (approx. 30 MeV) and no prompt tag from the outer detector are candidates for reactor ν¯e , more energetic events are muon candidates.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 35 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Oscillation Results

1.4 ◦ θ12 ≈ 33 1.2 2 −5 2 m 1.4 ∆ 12 = 5.5 × 10 eV 2.6 MeV prompt KamLAND data analysis threshold 1.0 1.2 best-fit oscillation

exp 0.8 1 /N ILL 0.8 obs 0.6 Savannah River Bugey N Rovno Ratio 0.6 0.4 Goesgen Krasnoyarsk Palo Verde 0.4 0.2 Chooz KamLAND 0.2 0.0 0 20 30 40 50 60 70 80 101 102 103 104 105 L0/Eν (km/MeV) Distance to Reactor (m) e In 515.1 days of data taking smoking gun evidence for neutrino oscillation in the solar sector was found. 258 events were observed whereas 365.3 23.7 would have been expected:

2 +0.6 −5 2 ∆m12 = 7.9−0.5 × 10 eV

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 36 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary More Oscillation Results

1.2×10-4

-4 10 1×10-4 ) ) 2 2

-5 (eV (eV 8×10 2 2 m m ∆ ∆

-5 Solar KamLAND KamLAND+Solar fluxes 10 6×10-5 95% C.L. 95% C.L. 95% C.L. 99% C.L. 99% C.L. 99% C.L. 99.73% C.L. 99.73% C.L. 99.73% C.L. solar best fit KamLAND best fit global best fit 4×10-5 10-1 1 10 0.2 0.3 0.4 0.5 0.6 0.7 0.8 tan2 θ tan2 θ

Combined with solar neutrino results the mixing angle θ12 can also be obtained

2 +0.10 tan θ12 = 0.40−0.07

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 37 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Geoneutrino observation

749 days of data taking: ν¯e candidates: 20 30 a b 15 Observed: 152 10 25 5 Estimated bg:

Events / 0.17MeV 0 2 4 6 8 127 13 20 Anti-neutrino energy, Eν (MeV) bg sources: 15 Reactor ν¯e Events / 0.17MeV 13 16 10 C(α, n) O (α from 210Po) 5 Random coincidences 0 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 Anti-neutrino energy, Eν (MeV) Consistent with geophysical models.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 38 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Future prospects

Puriﬁcation of scintillator ongoing to get rid of 222Rn contmination and the corresponding daughters eg. 210Pb. 7Be solar neutrino detection feasible. Not deep enough for pep detection (11C bg)

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 39 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Borexino

Located at the Gran Sasso Laboratory in Italy Main goal: Detection of 7Be solar neutrinos.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 40 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Borexino

Borexino Detector External water tank Stainless Steel Sphere Water Nylon Outer Vessel Ropes Nylon Inner Vessel Fiducial volume Internal PMTs Buffer

Steel plates Scintillator for extra shielding Muon PMTs

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 41 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

Borexino Detector Inner Vessel: External water tank Stainless Steel Sphere Water Nylon Outer Vessel Ropes Nylon Inner Vessel 300-ton liquid scintillator Fiducial volume Internal contained in an 125 µm PMTs Buffer nylon inner vessel Steel plates Scintillator Radius: 4.25 m for extra shielding Muon PMTs LS: pseudocumene (PC, 1,2,4-trimethylbenzene) doped with PPO (2,5-diphenyloxazole) 1.5 g/l

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 42 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

Borexino Detector Outer Vessel: External water tank Stainless Steel Sphere Water Nylon Outer Vessel Ropes Nylon Inner Vessel 5.5 m radius Fiducial volume Internal pseudocumene PMTs Buffer 5.0g/l DMP Steel plates Scintillator (dimethylphthalate) to for extra shielding Muon PMTs quench scintillation. OV is barrier against radon and other background contaminations from outside.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 42 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

Borexino Detector Stainless Steel Sphere External water tank Stainless Steel Sphere Water Nylon Outer Vessel Ropes Nylon Inner Vessel Radius: 6.85 m Fiducial volume Internal Encloses PC-DMP buﬀer PMTs Buffer ﬂuid. Steel plates Scintillator Support structure for PMTs for extra shielding Muon PMTs

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 42 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

Borexino Detector Outer Tank External water tank Stainless Steel Sphere Water Nylon Outer Vessel Ropes Nylon Inner Vessel Radius of 9 m Fiducial volume Internal Height of 16.9 m PMTs Buffer Filled with ultra pure water Steel plates Scintillator for extra 208 PMTs acting as a shielding Muon PMTs Cenrenkˇ ov muon detector

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 42 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

Borexino Detector PMTs External water tank Stainless Steel Sphere Water Nylon Outer Vessel Ropes Nylon Inner Vessel 2212 8” PMTs (ETL 9351) Fiducial volume Internal uniformly distributed on the PMTs Buffer inner surface of the SSS Steel plates Scintillator Mostly equipped with for extra shielding Muon PMTs aluminum light concentrators

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 42 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary A view inside

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 43 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector properties

Covered by 1400 m of rock or 3800 m.w.e. No nuclear reactors nearby. Approx. 5.5 m.w.e. shielding of the central volume from the rock. → Predicted γ background in the ﬁducial volume is less than 0.5 counts/(day · 100 tons). Optical attenuation length in the scintillator is approx. 7 m. Approx. 500 p.e./MeV are seen. Electrons from β−-decay of 14C dominate the rate below 160 keV. Limits neutrino observation to energies above 200 keV.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 44 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector properties

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 44 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detection method

For detector monitoring and calibration all PMTs are illuminated every two seconds by a 394 nm laser pulse Similar system using LEDs used for outer detector. Monochromatic 862 keV neutrinos from 7Be oﬀer two signatures: 1 Recoil electron with a clear Compton edge at 665 keV. 2 3.5% annual variation of the ﬂux due to the Earth orbit eccentricity

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 45 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Radio-purity

Only a very small contribution of external background. The key requirement in the technology of Borexino is extremely low radioactive contamination. Intrinsic bg-sources: 210Po intrinsic to the scintillator. Peak at 350 keV. 85Kr one of major uncertainties. Spectrum is similar to that of 7Be recoil electron. The rate can be estimated from the decay to 85Rb which is followed by a γ of 514 keV. 11C is produced in reactions induced by cosmic muons. Signal between 1 and 2 MeV. 14C content ratio 14C/12C of the order 10−18. Dominate spectrum below 200 keV.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 46 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Radio-purity

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 46 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Event Selection

Trigger conditions: Reject events with Cerenkˇ ov light Fiducial volume of 100 tons of LS z < 1.8 m (removes bg from 222Rn daughters in the upper inner vessel) 30 PMTs each detect at least one p.e. within a time of 60 ns For each pe the arrival time and the charge are measured during a time gate of 7.2 µs Typical trigger rate 15 Hz. (dominated by 14C)

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 47 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Results

14C dominates the spectrum for low energies. 210Po peak at 200 pe is intrinsic to scintillator. Clear shoulder at 380 pe (approx 750 keV). Spectrum rises again mainly because of 11C cosmogenic events.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 48 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Results

7 Interaction rate of Be-neutrinos: 47 7stat 12sys counts/(day· 100 ton) 85Kr rate: 22 7 5 counts/(day· 100 ton) The expected rate from the SSM is 49 4 counts/(day· 100 ton) with and 75 4 counts/(day· 100 ton) without oscillations respectively.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 48 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Future prospects

Reduce bg from 11C Measurement of pep and CNO neutrinos becomes feasible. Measurement of geoneutrinos.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 49 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Future Perspectives for a Next Generation LS Detector

Detector for next galactic supernova Cosmic diﬀuse supernova neutrino background spectroscopy High statistics neutrino spectroscopy Geoneutrino measurement including directionality (Search for proton decay)

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 50 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary LENA

Preferred Location: Phyasalmi¨ (Finland) Other possible locations: Pylos (Greece) Boulby (UK) Canfranc (Spain) Fr´ejus (France) Sieroczewice (Poland) Henderson (USA) Homestake (USA) Kimballton (USA) Hawaii (USA)

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 51 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary LENA

Cylindrical shape. Length of approx. 100 m. Diameter of approx. 30 m. Approx 13000 photo-multipliers. 50 kt of liquid scintillator.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 52 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary LENA

Cylindrical shape. Length of approx. 100 m. Diameter of approx. 30 m. Approx 13000 photo-multipliers. 50 kt of liquid scintillator.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 52 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary LENA

Cylindrical shape. Length of approx. 100 m. Diameter of approx. 30 m. Approx 13000 photo-multipliers. 50 kt of liquid scintillator.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 52 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary LENA

Cylindrical shape. Length of approx. 100 m. Diameter of approx. 30 m. Approx 13000 photo-multipliers. 50 kt of liquid scintillator.

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 52 Neutrinos KamLAND Detection principles Borexino Experiments Propects Summary Detector Design

PXE as scintillator Admixture of dodecane increases number of protons (25%) and enhances optical properties Attenuation length of 12 m at 450 nm wavelength can be reached. Non hazardous, ﬂash-point at 145◦C. Borexino and KamLAND show that LS can be well handled!

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 53 Neutrinos Detection principles Experiments Summary

1 Neutrinos General facts Neutrino Mixing Neutrinos

2 Detection principles Neutrino detection Liquid Scintillators What can be investigated

3 Experiments KamLAND Borexino Propects

4 Summary

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 54 Neutrinos Detection principles Experiments Summary Summary and Outlook

Liquid Scintillators oﬀer an excellent detection method for low energy neutrinos.

ν¯e -oscillations have been conﬁrmed in KamLAND. Successful detection of geoneutrinos 7 Be-νe from the Sun have been observed in Borexino Plans for a 50 kton LS detector look promising

Daniel Bick Neutrino Experiments with Liquid Scintillator Detectors 55 Neutrinos Detection principles Experiments Summary Summary and Outlook