Proton decay studies in

Liquid Argon TPC

Dorota StefanEpiphany Conference on Neutrinos and Dark Matter

5 - 8 January 2006, Cracow, Poland

ReferencesReferences

• 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 presentationThe outline of the presentation

• Grand Unification Theory

• Results from SuperKamiokande and Soudan 2

• Simulation studies of proton decay in LAr TPC

The Grand Unification IdeaThe 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) ESU(5) SO(10) E66 GUT GUT

SU(5)SU(5)• unification scale ~ 1015

GeV• 24 gauge bosons

• no place for more quarks or leptons

• extra particles

EE66

• plenty of possibilities for breaking the symmetry down to the standard model

SO(10)SO(10)

SUSY GUTsSUSY GUTs

SUSYSUSYeach SM particle has its super-partner

• SM bosons super-fermions• SM fermions super-bosons

Search for proton decaySearch for proton decay

• Experiment SuperKamiokande with water Cherenkov detector -Minimal SU(5) was ruled out by SK

-Minimal SU(5) SUSY:

• SUSY GUT models have been tested in SuperKamiokande and Soudan 2 experiments

predicted by SU(5):year

p K+) 2.9 x 1030

Result from SK has been reached ~ 1033

Result from SK has been reached ~ 1032

Search forSearch for p pee++in SuperKamiokandein SuperKamiokande

Limit from PDG July 2004Limit from PDG July 2004

p p e ex 10x 1033 33 years (79.3 ktyr exposure)years (79.3 ktyr exposure)

Signature for p Signature for p ee++ in the SK detectorin the SK detector

Search forSearch for p pKK++in SuperKamiokandein SuperKamiokande

K+

K+

For a bound protonFor a bound proton -prompt gamma-ray

For a free protonFor a free proton -mono-energetic muon

Limits from PDG July 2004Limits from PDG July 2004

p Kx 1033 years

The newest result:

p Kx 1033 years

p p K K

Search forSearch for p pKK++in experiment Soudan 2in experiment Soudan 2

K+

MeV/c

e+

K+

Simulated eventsSimulated events

K+

K+

Proton decay in ICARUS detectorProton decay in ICARUS detector

Channel

Efficiency (%)

Background (5 kTonxyear)

B x 1030years (5 kTonxyear)

PDG limit x1030

years

Needed Exposure to reach PDG (kTon x year)

p K+ p K+

p e+

p p

96.75

97.55

18.60

41.85

44.80

0.005

0.005

0.125

3.91

0.04

565

570

109

117

262

2300

245

82

25

473

20.36

2.15

3.78

0.52

9.04

Different channels for proton decay in LArDifferent channels for proton decay in LAr

high efficiency low bakground relevant results in relatively short time

Analysis of the particle which stops in LAr Analysis of the particle which stops in LAr

Kaon

Pion

Energy Loss of the detected particle from the last wire to the last minus last wire

Particle Identification by using Neural NetworkParticle Identification by using Neural Network

Kaon

Pion

Signal and background distribution

The geometry of the Neural Network used for particle recognition:

9 : 3 : 3

Purity - Efficiency for kaon and pionPurity - Efficiency for kaon and pion

purity = 100% Nsig (OutputSet)/ ( Nbkg(OutputSet) + Nsig(OutputSet) )

efficiency = 100% Nsig (OutputSet) / Nsig(InputSet)

Kaon

Pion

- Electronics noise is not taken into account

- particles are very well recognized by the neural network with very high efficiency and purity

SummarySummary

• 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 decay

...if SUSY GUTs are correct, nucleon decay must be seen soonPDG