Grand Unified Theories & Proton Decay. Ed Kearns Boston University NEPPSR 2009

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1 Grand Unified Theories & Proton Decay Ed Kearns Boston University NEPPSR 2009

2 Planetary Mo<on Falling Bodies What is unification? Fast Par<cles Electric Current Magne<sm Atoms Nuclei Quarks Gravity Special Rela<vity Electromagne<sm Quantum Mechanics Weak Force Strong Force General Rela<vity Quantum Field Theory QED: Quantum Electrodynamics The Standard Model Electroweak Theory QCD: Quantum Chromodynamics Dark MaMer Dark Energy??? BeMer Electroweak Theory (String?) Theory of Everything GUTS: Grand Unified Theories

3 8/13/09 Ed Kearns - NEPPSR

4 100 EeV Cosmic Ray Enrico Fermi s Globatron E cm = 2 E m E ~ ev x 1 GeV E ~ 10 6 GeV p = 0.3 B[T] r[m] p ~ 100 T x 10 6 m E ~ 10 8 GeV

5 only way to probe the grand unification scale is by virtual particle exchange A α X α B propagator ~ 1/M 2 C Proton (nucleon) decay turns out to be one of the most useful systems.

6 In the Standard Model, proton decay is forbidden by Conservation of Baryon Number Origins: baryon number conservation formulated by: Weyl (1929), Stueckelberg (1938), Wigner (1949), Lee & Yang (1950) to explain stability of matter. Phenomenological limits (1950 s): M. Goldhaber observes that life requires τ > years. Isotope abundance requires τ > years. Sakharov Conditions (1966): Matter-Antimatter asymmetry requires baryon number non-conservation.

7 Other work of this era:! Pati and Salam: Is Baryon Number Conserved? PRL 31, 661 (1973) Georgi, Quinn, and Weinberg: PRL 33, 451 (1974) proton lifetime ~ years.

8 Grand Unified Theories Assume SU(3) SU(2) U(1) is part of a larger symmetry group E.g. SU(5) Consequences: generators Single (unified) coupling Charge quantization: Q d =Q e /3, Q u =-2Q d Q p = -Q e New gauge interactions (X, Y bosons) proton decay Other predictions of SU(5): magnetic monopoles, value of weak mixing angle (3/8 not so good), massless neutrinos (oops!)

9 or SO(10) or E 6 or Flipped SU(5) or G224 or... and would you like SUSY with that?

10 Gauge Coupling Unification α α α α Log 10 (Q/1 GeV)

11 How can we find proton decay if protons live for years? watch 1 proton for years or watch protons (~kton) for a month or something in between

12 IMB Experiment Morton Salt Mine, Ohio 610 meters deep 1570 mwe 3.3 kton (fiducial volume) 2000 PMTs, 4% coverage 935 events in 851 live days no proton decay found τ(e + π 0 ) > years (1990) similar results from Kamiokande (1 kton) both saw SN 1987a, both uncovered atmospheric neutrino anomaly Kamiokande measured solar neutrinos

13 Problems solved by SUSY α 1 1 α α α Log 10 (Q/1 GeV) Unification scale pushed up! τ(e + π 0 ) years

14 Problems introduced by SUSY... d u u s e + Dimension = 5 operators e.g. QQQL proton life<me years something new to look for! u u Rapid proton decay: Dimension = 4 operators e.g. U c D c D c and QLD c M squark 1 TeV proton life<me 1 second that s OK saved by R parity d u u τ t H ν τ τ M s 4 m p 5 s u dimension counting: powers of (mass) D for each field! fermion D = 3/2, boson D = 1, Lagrangian terms must be D=4!

15 Many Other GUTs Beyond This Simple Story Uncertainties in the predictions: Nuclear matrix elements updated w. lqcd, still: x10 uncertainty in lifetime SUSY masses: ~ x100 uncertainty in lifetime A. Bueno et al. hep-ph/

16 Modes beyond e + π 0, K + ν and other antilepton + meson decays p µ π + K + n n B + L ΔB = 2, TeV < scale < GUT pp K + K + '' λ uds <10 8 p e π + π + ν ν n ν ν ν p e + γ 6 dimensions invisible radiative there is plenty to keep us busy...!

17 Tracking calorimeters Soudan 2 Proportional to fiducial mass Water Cherenkov detectors

18 Antilepton + meson Soudan Frejus Kamiokande IMB Super-K p e + π0 n e + π- p µ + π0 n µ + π- p ν π+ n ν π0 p e + η p µ + η n ν η p e + ρ0 n e + ρ- p µ + ρ0 n µ + ρ- p ν ρ+ n ν ρ0 p e + ω p µ + ω n ν ω p e + K 0 n e + K - p µ + K 0 n µ + K - p ν K + n ν K 0 p e + K*(892) 0 p ν K*(892) + n ν K*(892) 0 7/ τ/b (years)

Super-Kamiokande 22.5 kton fiducial volume 7.

Oct 2005 Recovery from accident 5182 50-cm inner PMTs Acrylic + FRP protective Outer detector fully restored SK-III:

19 Super-Kamiokande 22.5 kton fiducial volume p n SK-I: cm inner PMTs, 40% coverage cm outer PMTs SK-II: Jan Oct 2005 Recovery from accident cm inner PMTs Acrylic + FRP protective Outer detector fully restored SK-III: May August 2008 Restored 40% coverage Outer detector segmented (top barrel bottom) SK-IV: September SK-IV Replace all electronics 2008 T2K beam late 2009 Add gadolinium - 201?

21 (1) proton decay MC (2) atmospheric neutrino MC Δt i 1e6 evts/ day vertex Δt i Reduc<on no OD ac<vity remove flashing PMTs etc. Reconstruc<on energy, vertex, ring coun<ng, par<cle iden<fica<on, muon decay etc. Final analysis Good event criteria

22 Good event criteria: Fully contained Fiducial volume 2 or 3 rings All rings are EM showers π 0 mass MeV/c 2 No µ-decay electrons Mass range MeV/c 2 Net momentum < 250 MeV/c

23 Example event: (p µ + π 0 )

24 Sit at reconstructed vertex and adjust Δt. Look forward/backward in two hemispheres

25 Proton Decay Signal Prediction (Monte Carlo) free protons (hydrogen) Effective mass in 16 O Correlation with other nucleons Fermi motion by shell Initial position (Woods-Saxon) Nuclear de-excitation γ pion-nuclear interactions - Elastic Scattering - Charge Exchange - Absorption efficiency 44% main source of inefficiency: π 0 absorption in 16 O nucleus

26 Background: Atmospheric Neutrinos ν e e + π 0 p n

27 Atmospheric Neutrino Background (Monte Carlo) Flux (E, flavor) Cross sections: - quasielastic - 1-π, multi-π - DIS Pauli blocking Intranuclear scattering ν oscillations

28 Direct measurement of proton decay background using K2K neutrino beam (1KT near detector) 15.9 Mt yr CC, 4.5 Mt yr NC NEUT NUANCE

29 p e + π 0 Search Results: Super-K DATA Total Momentum (MeV/c) SK I SK II SK-I SK-II Detection efficiency 44.6%±19% 43.6±19% Background estimate 0.30±0.04± ±0.05±0.12 Exposure d (91.6 kt yr) Data d (49.1 kt yr)

30 Setting a limit a simple calcula<on of the rate if we measured something: τ B = λε n b n = number of observed events b = expected number of background events λ = exposure = N proton Δt ε = efficiency τ B = λε S 90 S 90 = S P poiss. (n, x + b)dx P poiss. (n, x + b)dx a simple calcula<on of a 90% CL limit, but... does not take into account n=0 properly (see F&C) and does not take into account systema<c uncertainty τ /B > years treatment of limit using Bayes theorem to incorporate systema<c uncertainty: P(Γ n) = e Γλε +b (Γλε + b) n P(Γ) P(λ) P(ε) P(b) dγ dλ dε db n! τ /B(e + π 0 ) > years

31 p K + ν Nuclear interac<on is negligible Kaon momentum s 340 MeV/c: is below Cherenkov threshold essen<ally a search for kaon decay at rest

32 Some cleverness Gamma Tag Single Muon Search: BR ε = 8.6±20 sys % Background = 0.7 events (±59%)

34 Limits in context with theory Soudan Frejus Kamiokande IMB Super-K I+II p e + π0 p e + π0 predictions minimal SU(5) 1 2 minimal SUSY SU(5) flipped SU(5), SO(10), 5D SUSY SU(5) p e + K 0 p µ + K 0 n ν K 0 p ν K + p ν K + predictions minimal SUSY SU(5) SUGRA SU(5) SUSY SU(5) with additional U(1) flavor symmetry various SUSY SO(10) SUSY SO(10) with G(224) τ/b (years) 10 35

35 Thinking Big(ger)

36 The Next Generation? Icarus T kt WC 100 kt LAr 5 kt LAr ε Fiducial Mass Hyper K A Hyper K B 300 kt WC 200 kt WC Frejus IMB Soudan 2 Kamiokande Super K 100 kt WC

37 Liquid Argon Time Projection Chamber pixel size ~ mm de/dx no Cherenkov threshold

p e + π 0 Lifetime Sensitivity (90% CL) 10 35 10 34 10 33 SK1 SK2 SK3/4 +100 kton LAr 300 kton 200 kton 100

39 p e + π 0 Lifetime Sensitivity (90% CL) SK1 SK2 SK3/ kton LAr 300 kton 200 kton 100 kton Year Efficiency = 0.45 BG = 0.2 evts/100 kty Nobs = Nbg

p K + ν 10 35 +100 kton LAr Lifetime Sensitivity (90% CL) 10 34 10 33 SK1 SK 3/4 LAr 5kt Icarus T600 300 kton WC 200 kton WC 100 kton WC 10 32 1995 2000

40 p K + ν kton LAr Lifetime Sensitivity (90% CL) SK1 SK 3/4 LAr 5kt Icarus T kton WC 200 kton WC 100 kton WC Year WC efficiency = 0.14 BG = 1.2 evts/100 kty Nobs = Nbg LAr efficiency = 0.98 BG = 0.1 evts/100 kty Nobs = Nbg

41 Many people think proton decay is important EPP2010 (2005) Action Item 5: A Staged Neutrino and Proton Decay Research Program HEP Future Facili<es Roadmap (2003) Scientific potential: absolutely central. Specific Facility: Don t know enough yet. NRC CommiMee on the Physics of the Universe Eleven Science Ques<ons for the New Century (2003) #8 Are protons unstable? D. Gross et al. Ten Ques<ons for the New Millenium (NYT August 15, 2000) #3. What is the lifetime of the proton and how do we understand it? D. Mermin rebumal Ten Ques<ons (Phys. Today, Feb. 2001) #9. What indeed is the lifetime of the nucleus of the neutral hydrogen atom?

42 What does it take to get a new megaton-class detector started? firm theore<cal predic<ons are unlikely discovery of SUSY at the LHC would help perhaps a candidate or two from Super K? real progress in reducing costs (PMTs = $$$$) demonstrated feasibility of mul< kt LAr TPC a funded next genera<on neutrino beam

Recent Nucleon Decay Results from Super-Kamiokande

Recent Nucleon Decay Results from Super-Kamiokande Jennifer L. Raaf Boston University April 14, 28 Motivation Super-Kamiokande n ν π decay search Results Motivation Interesting candidate for grand unification: