Proton decay studies in Liquid Argon TPC Dorota Stefan Epiphany Conference on Neutrinos and Dark Matter January 2006, Cracow, Poland

References L. E. Ibanez, CERN-TH.5237/88 Hitoshi Murayama and Aaron Pierce, Phys. Rev. D (2002) Mario E. Gómez Yukawa coupling and proton decay in SUSY models K. Kobayashi, hep-ex/ Y. Hayato, hep-ex/ Kenneth S. Ganezer, the SuperKamiokande Collaboration, The Search for Proton Decay at SuperKamiokande W.W.M. Allison, hep-ex/ D. Wall, hep-ex/ 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 E 6

SU(5) SO(10) E 6 GUT SU(5) unification scale ~ GeV 24 gauge bosons no place for more quarks or leptons extra particles E 6 plenty of possibilities for breaking the symmetry down to the standard modelSO(10)

SUSY GUTs 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 -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 Result from SK has been reached ~ Result from SK has been reached ~ 10 32

Search for p  e +   in SuperKamiokande Limit from PDG July 2004  p  e     x years (79.3 ktyr exposure) Signature for p  e +   in the SK detector in the SK detector

Search for p  K + in SuperKamiokande K +      K +      For a bound proton -prompt gamma-ray For a free proton -mono-energetic muon Limits from PDG July 2004  p  K   x years The newest result:  p  K   x years p  K  p  K 

Search for p  K + in experiment Soudan 2 K+K+    MeV/c  e+e+  K+K+  Simulated events K +      K +     

Proton decay in ICARUS detector

ChannelEfficiency (%) Background (5 kTonxyear)  B x years (5 kTonxyear) PDG limit x10 30 years Needed Exposure to reach PDG (kTon x year) p  K + p  K +     p  e +     p    p      Different channels for proton decay in LAr high efficiency low bakground relevant results in relatively short time

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 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 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

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