Study of the performance of a solar neutrino Time Projection Chamber T' P' C'

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Study of the performance of a solar neutrino Time
Projection Chamber (T. P. C.)

• Juliana Amariutei-Grigorescu
• Wayne State University

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Outline

• Neutrinos
• Standard solar model and neutrino species
• Neutrinos as elementary particles
• Neutrino oscillations
• Solar neutrino experiments
• Neutrino-electron scattering and experimental
  setup
• Analysis Results
• Performances of the T.P.C.
• Analyzing data
• Conclusions

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Neutrinos
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Neutrinos and the Standard Solar Model

• SSM based on the following assumptions
• hydrostatic and thermal equilibrium
• transfer of energy via radiation, convection,
  neutrino emission
• thermonuclear reactions are the only source of
  energy production inside the Sun
• the Sun was initially of a homogeneous
  composition and convective as its main sequence
  turned on

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Radial profiles of physical parameters of the Sun
dT/dr-??L / (16?acr2 T3)
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Neutrino species
The pp chain (pp), (pep), 7Be, and 8B
neutrinos
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The (pp1), (pp2) and (pp3) chains
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The CNO chain (C ) and (O ) neutrinos
The CNO cycle produces about 1.6 of the total
energy output of the Sun.
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Neutrino energy spectrum
uncertainties in the flux
(pp) neutrinos 2 (pep) neutrinos 5 7Be
neutrinos 15 8B neutrinos 37 (CNO)
neutrinos 50

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Neutrinos as elementary particles
Pauli postulated the existence of neutrinos in
1930, to describe the continuous spectrum of the
?-decay
ZAX? Z1AX e- ?e
In 1956 Cowan and Reines first detected neutrinos
through the inverse ?-decay.

• 3 flavor types of neutrinos

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Charged and neutral currents interactions

• The Standard Model of Particle Physics
• The model for the electroweak interaction, known
  as the Glashow-Weinberg-Salam (GWS) model

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Neutrino oscillations

• Vacuum oscillations (2 neutrinos)

Pee1-(sin2 2?) sin2 (?R/ LV) LV2 E h/ ?m2 c3
R distance traveled LV vacuum oscillation
length
E?0.8 MeV, ?m2 6.x 10-5 eV2 ? LV 10 Km
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Matter oscillations
ne electron density GF Fermi constant
Feynman diagram contributing to (e - ?e)
scattering, but not to neutrinos of other
flavors.
Mixing angle in matter
tan 2 ? M tan 2 ? / 1( LV/ Le) sec 2 ?

Le electron neutrino interaction length
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MSW Effect
Maximum mixing at resonance
(?m2 / 2E) cos 2? 2 1/2 GF ne
MSW Effect Large flavor conversion for slowly
varying ne
Transformation of electron neutrinos, created at
high electron densities, to neutrinos with flavor
? at low densities, for the case that the
electron density changes adiabatically
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Neutrino experiments
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The Chlorine experiment

• Raymond Davis Jr. started the experiment in 1968
• 100,000-gallon tank of perchloroethylene
• 4,800 feet underground in the Homestake Gold
  Mine (South Dakota)
• Ar observed through its ?-decay and counted

37Cl ?e ? 37Ar e-
Eth0.814 MeV
Initial capture rate2.050.3 SNU Predicted
capture rate7.92.6 SNU
Solar neutrino problem
1SNU 10-36 events/target atom x s-1
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Kamiokande II

• the detector was a tank which contained 3,000
  tons of pure water
• 1,000 photomultiplier tubes (PMTs) attached to
  the inner surface
• 1,000 m underground of Mozumi Mine, Japan
• record the Cherenkov light from relativistic
  charged particles

e- ?e ? e-' ?e '
Eth8 MeV
?observed / ?predicted 0.465 0.05
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main characteristic - directionality
Signal angular peak on top of a broad
background
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Gallium experiments

• GALLEX
• SAGE
• GNO

71Ga ?e ? 71Ge e-
Eth0.250 MeV
Initial capture rate - pp neutrinos 77.58
SNU Predicted capture rate - pp neutrinos 129
SNU
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SNO Experiment

• The detector is a 1,000 tons heavy water
  detector, salt added to it
• 2,070 m underground in the Creighton Mine,
  CANADA
• Detects electron and non-electron neutrinos

Initial capture rate ? Predicted capture rate.
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Main reactions - SNO
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KamLAND Experiment

• 1,000 tons of light emitting liquid target,
  Mozumi Mine, Japan
• 1,879 photomultiplier tubes
• reactor antineutrino experiment
• defines the parameter space region allowed as
  LMA (Large
• Mixing Angle).

Left allowed regions from KamLAND (shaded) and
solar neutrino experiments (lines). Right
combined two-neutrino oscillation analysis of
KamLAND and the observed 8B solar neutrino fluxes.
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Calculation of neutrino survival probabilities
The neutrino survival probability in the LMA
region, as a function of neutrino energy. We
use 4 points in the our lattice, to illustrate
the sensitivity of Pee to a change in the mixing
parameters. The program was written by V.
Paolone at Univ. of Pittsburgh.
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Neutrino-electron scattering and experimental
set-up
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Neutrino-electron scattering
e- ?e ? e-' ?e '
backward direction
measuring Te , ??
E?-m Te / (p cos?? Te)
m mass of the e- P momentum of the e-
forward direction
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The experimental set-up

• device - Time Projection Chamber (T.P.C.) a
  cylinder 40 m long and 28 m in diameter inside a
  completely enclosed Faraday cage, 2 equal
  compartments
• low depth (800 m)
• P10 Atm, m61 tons (He/CH4 97/3)
• Nt number of target electrons

Total drift length 10 m Maximum drift time
8.3 msec at 100 KeV Total diffusion/10 m 4.3 mm
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The T. P. C. as a detector
Mid plane - Hv grid V -100 ? -200 keV End
caps - detector planes (a set of wires and a set
of stripes).
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Wires - ( x,z) profile strong electric field
E2?k/r
Strips (y,z) profile
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100 KeV track electron cloud
(x, z) projection
projection along major axis
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Analysis Results
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Performances of the T. P. C.

• Angular resolution
• depends on
• multiple scattering
• aspect ratio of the track.
• Typical length track is 9 cm for
• Te ? 100 KeV and 10 Atm.

Angular resolution 15? at 100 KeV.
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Insensitivity to changes in the background

• Due to directionality of solar neutrinos
  background fluctuations source of uncertainty

• Efficient calibration
• ?-rays from cosmic rays 108 events/ year.
• double events - 106 events/ year.

• Resolution from Monte Carlo simulations
• ?T (Te) 0.016 / Te0.5 5 at 100 KeV (Te
  expressed in Mev)
• ??(Te) 4.7? / Te0.6 15? at 100 KeV

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Calibration
?-rays
Te 2 m / tan2 ?e
double Compton
p1 cos ?1/ T1 p2 cos ?2/ T2 2
Double-Compton events in the T.P.C. A gamma ray
enters the T.P.C. and scatters twice, producing
two usable electron tracks.
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Neutrino electron cross section
neutrino cross sections pp neutrinos
scattering, ??-e 1110-46 cm2
scattering cross section is known to better than
0.1
R Nt ? ?
R rate of events
Top Differential Te cross section . Bottom
Differential Te probability.
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Angular cuts
Signal neutrino energy spectra (no background)
with different cuts on the cosine of the angle
relative to the Sun.
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Backgrounds

• internal backgrounds (85Kr, Rn)
• no internal cosmogenic activity
• external backgrounds (238U, 232Th, 40K )
• 238U assumed to be dominant (overall
  contamination 24 ?g 800 tracks/day)
• 14C strongly suppressed in methane.

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Signal neutrino energy spectra
Signal neutrino energy spectra. The input values
?m26.62 x 10-5 eV2, tan2?0.337 and SSM
neutrino fluxes.
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The five parameters fit
?m2, tan2 ?, rBe, rCNO, rpep
rBe1-(?PP/ ?Be) (?Be/ ?pp) SSM rCNO1-(?PP/
?CNO) (?CNO/ ?PP) SSM rpep1-(?PP/ ?pep) (?PeP/
?pp) SSM
Fit results. Top row (?m2, tan2) plane. Bottom
row rBe. The input values ?m26.62 x 10-5 eV2,
tan2 ? 0.337 and SSM neutrino fluxes.
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Why no ?m2 sensitivity ?
The neutrino survival probability in the LMA
region, as a function of neutrino energy
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• Lower statistics for (CNO) and (pep) neutrinos

Fit results. Top row rCNO,. Bottom row rpep.
The input values ?m26.62 x 10--5 eV2,
tan2 ? 0.337 and SSM neutrino fluxes.
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Conclusions
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Well measured parameters
Simultaneous and precise measurement of

• mixing angle
• individual flux for (pp), 7Be, (pep) and (CNO)
  neutrinos

LMA region, various hypothesis . Blue latest SNO
KamLAND, Red Yellow our points. The
simulated background 800 events/day. Other input
values ?m26.62 x 10--5 eV2, tan2 ? 0.337,
rBe0, rCNO0.
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Acknowledgements

• Prof. Giovanni Bonvicini
• The PhD committee
• Prof. David A. Cinabro
• Prof. Alexey A. Pertov
• My Professors at Wayne State
• Prof. William B. Rolnick, Prof. Thomas M.
  Cormier,
• Prof. Paul H. Keyes, Prof. Jhy-Jiun
  Chang, Prof. Alvin M.
• Saperstein, Prof. Ratna Naik, Prof.
  Sergei Voloshin, Prof.
• Claude Pruneau and Dr. John Carlson
• My Colleagues at Wayne State. Special thanks to
• Dr. Mircea Pantea, Phd. Students Ying Guo
  and
• Mohhamed Abdel-Aziz
• My family
• My daughter and my husband.