NOSTOS Neutrino studies with a tritium source

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NOSTOSNeutrino studies with a tritium source

• Neutrino Oscillations with triton neutrinos
• The concept of a spherical TPC
• Measurement of the angle q13 ,Neutrino magnetic
  moment, Neutrino decay, Weinberg angle
  measurement at low energy, Supernova sensitivity
• The first prototype
• Conclusions

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The idea Study neutrino-electron elastic
scattering with very-low energy neutrinos
from a strong tritium source (En 14 keV)
Detect low energy electron recoils (Tmax 1.27
keV) by a spherical gaseous TPC surrounding the
tritium source The oscillation length is
shorter than the length of the detector The
modulation will be contained and seen in the
TPC Reconstruction of the relevant oscillation
parameters by a single experiment
I. Giomataris, J. Vergados, hep-ex/0303045 J.
Bouchez, I Giomataris DAPNIA-01-07
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The new strategy (I. Giomataris, J. Vergados,
hep-ex/0303045 ) L32 4pEn/dm232
dm232 2.510-3, En14 keV L13 L12/50 13
m fully contained in the TPC (radius10m)
New challenge q13 measurement The
sensitivity depends on statistics, backgrounds
and systematics gt104 neutrino-electron
interactions must be detected and localized
Tritium source activity can be measured on-line
at lt1 Background level can be measured and
subtracted (source on-off) Fitting the
oscillation will suppress systematics
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• 200 Mcurie T2 source
• 3000 m3 spherical TPC volume
• 5x1030 e- with Xe at p1 bar

NOSTOS Neutrino OScillation Tritium Outgoing
Source
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• The advantages of the spherical TPC
• Natural focusing system reasonable size
  detector
• Provides a full 4p coverage enhancement of the
  detected signal
• Allows a good determination of the depth of the
  interaction point by measuring the time
  dispersion of the signal
• The electric field is V0 the applied high
  voltage,
• R1 the internal radius,
• R2 the external radius
• st sL/vd, sL Dvr
• At low fields vd E and D 1/v E st
  1/E3/2 r3
• The time dispersion is highly enhanced in
  the spherical case
• Estimation of the depth of the interaction
  lt 10 cm

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Two Micromegas signals at 3 mm distance in depth
3 mm drift
Precise determination of the depth
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Low energy spectrum from Micromegas in CAST
Cu
Fe
Cu escape
Ar
Fe escape
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Energy distribution of detected neutrinos, Eth
200 eV 14 keV
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Detected neutrinos-versus distance, sin22q13.17,
Eth200 eV The effect of the unknown neutrino
energy distribution is small
Fitting the curve we extract the oscillation
parameters with a single experiment
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Neutrino-electron elastic scattering cross
section
G.t Hooft, Phys. Lett. B37,195(1971)
ne
ne
ne
ne
w-
z0
e-
e-
e-
e-
For Tltlt1 keV ds/dT a(2sin4qwsin2qw 1/4) High
accuracy measurement of the Weinberg angle at
very-low energy!! Test the weak interaction at
long distances
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Neutrino magnetic moment sensitivity ds/dT
(mn)2(1-T/En)/T
ltlt 10-12 mB


Actual limit 10-10 mB
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Target properties with 5.1030 electrons, 1000
events/year
Reasonable goal operate with Ar or Ne at
pressures gt10 bars gt104 events/year to tackle a
total number of events of 105 Good news The
HELLAZ prototype provide gains of about 106 with
He at 20 bar
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Supernova sensitivity Detect recoils from
coherent neutrino-nucleus interaction High cross
section s N2E 2 2.5x10-39 cm2, Xe and E10
MeV and 1.5x10-38 cm2 at 25 MeV For a a typical
supernova explosion and the spherical TPC
deterctor 15,000 detected with Xe at 1 bar for
a distance of 10kpc 15,000 at 10 bar pressure
!!! 30 at 700 kpc (Extragalactic detection !!!)
The challenge is again at the low-energy
threshold detection Tmax 1500 eV for E 10
MeV Detection efficiency independent of the
neutrino flavor
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• Plans
• 1.3 m prototype is under construction
• - Laboratory study of the radial spatial accuracy
• - Laboratory study of the electron attenuation
  length
• First investigations on the availability of the
  tritium source
• High gain operation of the detector at high
  pressure operation must be investigated with
  various gas candidates

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NOSTOS 1rst prototype

• Schedule
• 2003-2004
• Laboratory tests
• From 2004
• Operation in underground laboratory

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• Tests and studies with the 1.3 m prototype
• Laboratory tests with various gas mixtures up to
  5 bar
• Total mass 1 - 25 Kgr (He, Ne, Ar, Xe, CF4)
• First underground investigations
• Measure the background level in the sub-keV
  range
• Optimize the detector parameters, pitch, pulse
  shaping, gas mixture etc..
• If the background level is satisfactory
• Search for low mass dark matter candidates
• Search for WIMPs trapped in the solar system
• WIMP search in spin dependant interactions (CF4
  target)
• Possible investigations with reactor neutrinos
  coherent neutrino-nucleon scattering (gt100/day
  detected neutrinos)

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• Summary and Outlook
• The purpose of the new experiment is to
  establish the phenomenon of neutrino oscillations
  with a different experimental technique and
  measure the angle q13
• High sensitivity measurement of the neutrino
  magnetic moment
• Measurement of the Weinberg angle at very-low
  energy
• High sensitivity for supernova neutrinos
• Increase as much as possible the gas pressure
  will provide very-high statistics