Download Proton decay studies in Liquid Argon TPC

Proton decay studies
in
Liquid Argon TPC
Dorota Stefan
Epiphany Conference on Neutrinos and Dark Matter
5 - 8 January 2006, Cracow, Poland
References
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•
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L. E. Ibanez, CERN-TH.5237/88
Hitoshi Murayama and Aaron Pierce, Phys. Rev. D.65.055009(2002)
Mario E. Gómez Yukawa coupling and proton decay in SUSY models
K. Kobayashi, hep-ex/0502026
Y. Hayato, hep-ex/9904020
Kenneth S. Ganezer, the SuperKamiokande Collaboration, The Search
for Proton Decay at SuperKamiokande
• W.W.M. Allison, hep-ex/9803030
• D. Wall, hep-ex/9910026
• The ICARUS Collaboration, ICARUS TM 05-XX(2005)
The outline of the presentation
• Grand Unification Theory
• Results from SuperKamiokande and Soudan 2
• Simulation studies of proton decay in LAr TPC
The Grand Unification Idea
• Three U(1)SU(2)SU(3) interactions into a single one
• There are different candidates of the unification group
such as SU(6) ... SU(N+1) or SO(10) ... SO(2N+4)
• The most attractive groups are SO(10) and E6
SU(5) SO(10) E6 GUT
SU(5)
• unification scale ~ 1015 GeV
• 24 gauge bosons
• no place for more quarks or leptons
SO(10)
• extra particles
E6
• plenty of possibilities for breaking
the symmetry down to the standard
model
SUSY GUTs
SUSY
each SM particle has its super-partner
• SM bosons  super-fermions
• SM fermions  super-bosons
Search for proton decay
• Experiment SuperKamiokande with water Cherenkov detector
-Minimal SU(5) was ruled out by SK
predicted by SU(5):
t/B ~ 1031+1 year
-Minimal SU(5) SUSY:
t/B(p  nK+)  2.9 x 1030
Result from SK
has been reached
~ 1033
Result from SK
has been reached
~ 1032
• SUSY GUT models have been tested
in SuperKamiokande and Soudan 2 experiments
Search for pe+p0 in SuperKamiokande
Signature for p  e+p0
in the SK detector
Limit from PDG July 2004
t (p  e+p0) > 5.0 x 1033 years (79.3 ktyr exposure)
Search for pK+n in SuperKamiokande
K+  p+ p0
K+  m+ nm
For a bound proton
-prompt gamma-ray
For a free proton
-mono-energetic muon
p  K+ n
Limits from PDG July 2004
t (p  K+n) > 1.6 x 1033 years
The newest result:
t (p  K+n) > 2.3 x 1033 years
Search for pK+n in experiment Soudan 2
Simulated events
K+  p+ p0
K+
p0
p+
K+  m+ nm
K+
m+ (236MeV/c)
e+
Proton decay in ICARUS detector
Different channels for proton decay in LAr
Channel
Efficiency
(%)
p  K+ n
p  K+ m-p+
p  e+ p+ pp  p+ n
p  m+ p0
96.75
97.55
18.60
41.85
44.80
Background
(5 kTonxyear)
0.005
0.005
0.125
3.91
0.04
high efficiency
low bakground
relevant results
in relatively short time
t/B x 1030years
(5 kTonxyear)
565
570
109
117
262
Needed
PDG limit Exposure
to reach PDG
x1030
years
(kTon x year)
2300
245
82
25
473
20.36
2.15
3.78
0.52
9.04
Analysis of the particle which stops in LAr
Kaon
Energy Loss of the
detected particle
from the last wire
to the last minus
last wire
Pion
Particle Identification by using Neural Network
Signal and background distribution
The geometry of the Neural Network
used for particle recognition:
Kaon
Pion
9:3:3
Purity - Efficiency for kaon and pion
Kaon
- Electronics noise
is not taken into
account
- particles are very
well recognized by
the neural network
with very high
efficiency and purity
Pion
purity = 100% Nsig (OutputSet)/ ( Nbkg(OutputSet) + Nsig(OutputSet) )
efficiency = 100% Nsig (OutputSet) / Nsig(InputSet)
Summary
• Variety of GUT models to be tested experimentally
proton decay essential in model verification
–
• SuperKamiokande has given impressive limits and
excluded minimal SU(5)
• Sufficiently large Liquid Argon detector ideal for
background-free studies of the p  K n decay
...if SUSY GUTs are correct, nucleon decay must be seen soon
PDG