LENA

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LENA a liquid scintillator detector for Low
Energy Neutrino Astronomy and proton decay

• Detector outline
• Physics potential
• solar neutrinos
• Supernova neutrinos
• diffuse Supernova neutrino background
• proton decay
• geoneutrinos
• RD on liquid scintillators
• Outlook

• Marianne Göger-Neff NNN07
• TU München Hamamatsu

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LENA detector outline
100 m

• detector size 100 m length
• 30 m Ø
• 50 kt liquid scintillator
• PXE as default option
• 13500 PMTs
• 30 coverage
• light yield 120 pe
• for events in center
• water Cerenkov muon veto
• 2m of active shielding
• located at gt 4000 mwe
• Pyhäsalmi mine, Finland
• Nestor site, Mediterranean Sea

30 m
alternative vertical tanks 25 kt each
L. Oberauer et al.,NPB 138 (2005) 108
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Why liquid scintillator for n detection?

• Neutrinos interact only weakly...
• gt low count rate experiments
• gt detectors must have large mass, good
  shielding,
• good background discrimination
• Liquid scintillators offer...
• high light yield (50 times more than water
  Cerenkov)
• gt low energy threshold
• quenching of heavy particles (a, n) LY(a)
  1/10 LY(b,g)
• gt background suppression
• liquid at ambient temperatures
• gt advantageous for detector construction and
  handling
• gt several purification methods applicable
  (distillation,
• water extraction, nitrogen sparging,
  column chromatography)
• easily available in large amounts, reasonable
  price ( 1/l)

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Neutrino Astronomy
neutrinos are ideal probes for astronomy neutral
no deflection by B-fields almost
no absorption in matter direct information about
their origin BUT hard to detect
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LENA - solar neutrinos

• high statistics solar neutrino spectroscopy
  (fiducial volume 18 kt)
• 7Be 5400 events per day
• test of small flux variations on short time
  scales, e.g. due to density profile fluctuations,
  look for coincidences with helioseismological
  data !
• test of day/night asymmetry (MSW effect in the
  earth)
• pep 150 events per day
• solar luminosity in neutrinos
• CNO 200 events per day
• important for heavy stars
• 8B-ne 360 events per year
• from CC reaction on 13C ( 1 ab.)
• distortion of 8B-n spectrum
• precise determination of solar fusion reactions
  and n oscillation parameters
• experience gained with Borexino

ne 13C -gt 13N e- Qthr 2.2 MeV back decay
(t863 s) 13N -gt 13C e ne Ianni et al.
Phys.Lett. B627 (2005) 38-48
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Detection of pep and CNO neutrinos

• transition region important
• to discriminate MSW from NSI
• need low 11C background
• to detect pep and CNO
• neutrinos
• at least 4000 mwe.
• discriminate 11C by
• 3fold coincidence
• ( µ n 11C)
• Borexino coll. PhysRevC 74, 045805(2006)
• about 90 reduction can
• be reached by local cuts around

Friedland, Lunardini, Peña-Garay hep-ph/0402266
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Supernova Neutrinos

• Core collapse Supernova Mprog 8 MSun, ?E
  1059 MeV
• 99 of the energy is carried away by neutrinos
• 1058 Neutrinos with ltEgt 10 MeV within few s
• Neutrinos provide information on
• 1. Supernova physics
• Gravitational collapse mechanism
• Supernova evolution in time
• Cooling of the proto-neutron star
• Shock wave propagation
• 2. Neutrino properties
• Neutrino mass (time of flight)
• Oscillation parameters (matter effects)
• 3. Early alert for astronomers
• (n burst several hours before optical burst)

T. Janka
ne
ne
nx
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LENA Supernova Neutrinos

• Possible reactions Event rate for a 8M?
  Supernova
• in liquid scintillator in 10 kpc distance
  (KRJ, no osc.)
• ne p ? n e (Q1.8 MeV)
  8700 ne spectroscopy
• ne 12C ? 12B e (Q13.4 MeV) 200
• ne 12C ? 12N e- (Q17.3 MeV) 130
  ne spectroscopy
• nx 12C ? 12C nx ? 12C g(15.1 MeV)
  950 total n flux
• nx e- ? nx e- (Ethr 0.2 MeV)
  700
• (mainly ne, ne)
• nx p ? nx p (Ethr 0.2 MeV)
  2200 total energy spectrum
• (mainly nm, nt)

Beacom et al. Phys.Rev.D 66(2002)033001
for different models (TBP, LL, KRJ) and different
oscillation scenarios the total rate changes
from 10000 to 24000 events
Diploma thesis by J. Winter, TUM 2007, to be
published
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LENA - Diffuse Supernova Neutrino Background

• DSN give information about star formation rate
• Super-Kamiokande limit (lt 1.2 cm-2 s-1 for E gt
  19.3 MeV) close to
• theoretical expectations (KamLAND 3.7 102
  cm-2 s-1 for 8.3 MeVltElt14.8MeV)
• use delayed coincidence ne p -gt e n
• advantage of LENA
• - low reactor neutrino background
• ? threshold 9 MeV (SK 19 MeV)
• - distinction btw. ne/ ne possible
• predicted SRN rate in LENA
• 6 - 10 counts per year
• limit after 10 years
• lt 0.3 cm-2 s-1 for 10 MeV lt E lt 19 MeV
• lt 0.13 cm-2 s-1 for 19 MeV lt E lt 25 MeV

M. Wurm et al. Phys.Rev. D75 (2007) 023007
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LENA proton decay

• proton decay predicted by GUT, SUSY theories
• SUSY predicts dominant decay mode tp (p-gtKn)
  1034 years
• K is invisible in water Cerenkov detectors
• event structure

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LENA proton decay
Event structure 3-fold coincidence, use
energies, time and position correlation, pulse
shape analysis
m
Cutting at a rise time of 9 ns Acceptance
60 Background suppression (atmospheric nm -gt m)
5 x 10-5
K
T. Marrodan et al., Phys. Rev. D 72, 075014
(2005)
Expected background lt 0.1 ev/year (K production
by atmospheric n) Limit after 10 years 4 x
1034 years (90 CL) Current SK limit 2.3 x
1033 years (90 CL) gt 40 events in 10 years
in LENA (lt1 backgr. ev.)
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Geo-Neutrinos
Detection via p ne ? n e

• Neutrino flux and spectrum depend on the
• distribution of radioactive elements in the
  Earths crust and mantle (mainly U, Th)
• gt input data for Earth models
• neutrino geophysics
• First geo-neutrinos detected by KamLAND

gt in LENA 400 4000 ev/year
scaled from KamLAND
Hochmuth et al. Astrop.Phys 27, 21 (2007)
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Studies of liquid scintillator properties

• Light Yield
• Choice of right solvent
• Optimization of fluor concentration
• Transparency
• Measurement of attenuation and
• scattering length
• Influence of scintillator purification
• Fluorescence Decay Time
• Optimizing scintillator response time
• gt time and position resolution
• Alpha quenching
• gt alpha-beta discrimination

Investigated scintillators Phenyl-xylyl-ethane
(PXE) Linear Alkylbenzene (LAB)
r 0.99
r 0.86

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Light yield and decay time

• measure number of photoelectrons per MeV
• and exponential decay time constants
• for different solvent/fluor mixtures
• under study PXE/LAB/dodecane
• PPO/PMP/bisMSB

PXE 2g/l PPO
T. Marrodan, PhD thesis,, TUM, in preparation
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Scintillator emission spectrum

• excitation by UV light with deuterium lamp
• excitation by 10 keV electrons

T. Marrodan, PhD thesis,, TUM, in preparation
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Light propagation

• Measurement of attenuation length
• separate scattering and absorption
• measure angular dependence
• with polarized/unpolarized light
• attenuation length gt 10 m _at_ 430 nm
• scattering and absorption lengths gt 20 m

M. Wurm, diploma thesis, TUM, 2005
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Radiopurity
UGL in Garching, 15 mwe shielding 150 HPGe
detector with NaJ anti-Compton µ-veto
panels radiopurity screening of various
materials extension of the UGL planned 2008
passive shielding only
muon veto anti-Compton
Diploma thesis, M. Hofmann, TUM, 2007
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LAGUNALarge Apparatus for Grand Unificationand
Neutrino Astrophysics
LENALiquid-Scintillator Detector13,500 PMs, 50
kt target
100m
coordinated RD design studyin European
collaborationon-going application for EU
funding 20 participating institutes scientific
paper 0705.0116 (hep-ph)
30m
MEMPHYSWater Cerenkov Detector500 kt target in
3 shafts,3x 81,000 PMs
GLACIERLiquid-Argon Detector100 kt target, 20m
drift length, LEM-foil readout28,000 PMs for
Cerenkov- and scintillation light
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Summary and Outlook

• LENA multi-purpose detector for low energy
  neutrino astronomy and
• proton decay
• evaluation of physics potential solar
  neutrinos ?
• Supernova neutrinos ?
• diffuse SN background ?
• geoneutrinos ?
• proton decay ?
• atmospheric neutrinos ?
• reactor neutrinos ?
• beta beams / nu factory ?
• detector design under study scintillator
  development
• photosensors electronics
• optimum tank size and shape
  optimum location
• RD is funded in SFB/TR 27 Neutrinos and beyond
• and in excellence cluster Origin and structure
  of the universe

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LENA - geoneutrinos
Detection via p ne ? n e

• source of the terrestrial heat flow
• contribution of natural radioactivity
• distribution of U, Th, K in crust, mantle and
  core
• hypothetical natural reactor at the Earths
  center?

maximum
core enhanced
ref
minimal
Q (rad)
hep-ph0509136
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Supernova Neutrinos

• earth matter effect if SN neutrinos pass through
  the Earth before being the
• detector, see wiggles in spectrum

Dighe, Keil Raffelt hep-ph/0304150
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Requirements of the liquid scintillator
n detectors should feature

• high light yield
• high transparency

• low energy threshold
• good energy resolution
• precise position reconstruction
• correlated events with short delay
• good background separation ? different pulse
  shapes
• for alphas/betas
• low background from radioactivity ? high
  radiopurity
• long measuring time (5-10 years)
• safety in underground laboratories ? high flash
  point

• fast decay time
• high transparency

? long-term stability ? material compatibility
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Shock propagation neutrinos