Yasunori Nomura UC Berkeley; LBNL Particle physics Try to - PowerPoint PPT Presentation

Yasunori Nomura UC Berkeley; LBNL

Particle physics Try to understand ―fundamental laws‖ in nature Conventional view / focus … energy frontier E … Quantum gravity / string theory? Fundamental physics … Grand unification? … New TeV physics? (supersymmetry, technicolor, …) Standard Model

Revolution is happening String compactification Our low-energy 4D world … result of compactification on manifold with complex geometry Image by Colonna Dark Energy (Cosmological Constant) Our universe is accelerating r L ~ (10 -3 eV) 4

Our universe is one of many universes (multiverse) … Eternal inflation realizes these ―different universes‖ in spacetime Observed small cosmological constant is natural • r L 0 No observer No observer Weinberg (‗87)

Low energy theory may naturally be ―complicated‖ … ―minimality‖ may not be a good guiding prin ciple E Unification (?) Standard Model Dark / hidden sectors … other low energy sectors weakly interacting with the SM (light) dark matter, string axiverse, Goldstini, …

It is impossible to cover progress in all these fronts → focus on physics probed by (large) neutrino detectors Proton (nucleon) decay … extremely sensitive probe of high energy physics — prohibited in the SM Lagrangian — occurs (only) through higher dimension operators Light hidden sectors … long -lived, weakly-interacting light states → Neutrino experiments have sensitivities

Proton decay and unification Proton does decay The baryon ( B ) and lepton ( L ) numbers in the SM → accidental symmetries at low energies (write down the most general renormalizable Lagrangian → B and L ) B and L are not the ―fundamental‘‘ symmetries Consider p Hawking Black hole radiation No net B → Baryon number is violated In quantum gravity, this process is occurring virtually (unless killed by an additional Proton does decay at some level symmetry ―by hand‘‘)

Importance of ―models‖ The proton is expected to decay anyway → Who cares models? (Just go out and look for p decay … it is already well motivated) What is the rate? In the SM, The scale M ~ (reduced) Planck scale M Pl = 2 x 10 18 GeV The lifetime is → Yes, the proton decays, but at a rate outside the expected reach

Proton decay and grand unification Proton decay will be out of reach unless there is new physics below M Pl Is there a well-motivated candidate? Grand Unification Predictions: • 3 forces of the SM unified at a high energy scale M GUT • Proton decay caused by exchange of GUT bosons: M ~ M GUT → For M GUT < M Pl , p decay may be within reach

Grand unification works with supersymmetry Non-SUSY g 3 g 2 g 1 Supersymmetry (SUSY) SUSY Superparticle at ~ TeV g 3 • stabilizes the weak scale • change the RGEs for g 1,2,3 R parity • the existence of dark matter g 2 M GUT ~ 2 x 10 16 GeV g 1

Proton decay in SUSY GUTs Dimension five ( d =5): color triplet Higgsino exchange ~ ~ dominantly p → K + n Dimension six ( d =6): GUT gauge boson exchange dominantly p → e + p 0

Dilemma after Super-K The minimal SUSY SU(5) GUT is ―excluded‘‘ Limits on proton decay [years] p → e + p 0 p → K + n 10 40 10 40 10 38 10 38 10 36 10 36 10 34 10 34 10 32 10 32 10 30 10 30 Is there any reason to expect p decay in the (near) future?

Dilemma after Super-K The minimal SUSY SU(5) GUT is ―excluded‘‘ Limits on proton decay [years] p → e + p 0 p → K + n GUT in d =5 from M Pl d =5 from M Pl higher-dim. 10 40 10 40 10 38 10 38 10 36 10 36 10 34 10 34 10 32 10 32 10 30 10 30 Is there any reason to expect p decay in the (near) future? Yes, it is reasonable to expect p decay within the reach (in a variety of final states)

Proton Decay from Physics at M Pl Supersymmetry allows faster proton decay 1 ~ ~ 1 L ~ 𝑁 𝑟 𝑟 𝑟 𝑚 ( ← W ~ 𝑁 𝑅𝑅𝑅𝑀 ) For M ~ M Pl , t p ~ 10 17 years! We expect Q ‘s and L ‘s to carry suppression factors L ~ y 𝑟 𝑟 ℎ ( y « 1 ) 𝑧 2 ~ ~ L ~ 𝑁 Pl 𝑟 𝑟 𝑟 𝑚 Proton decay probes flavor physics at M Pl — a wide variety of final states with t partial ~ O (10 28 – 10 39 ) years

Example models Harnik, Larson, Murayama, Thormeier

Grand unification in higher dimensions Hall, Y.N.; Kawamura (‘00 - ‘02) The basic framework Q 3 A m , H A m , H Q 1,2,3 Q 1,2 SU(3) C x SU(2) L x U(1) Y (3-2-1) on the ― brane ‘‘ ~ R ~ M GUT -1 unified? SU(5) non-unified? in the ―bulk‘‘ minimal case Review for a wide audience; Hall, Y.N., hep-ph/0212134

Consistent quantum theory ―boundary condition‘‘ 321 (+,+): A m X (+,-): A m (compactified on an S 1 / Z 2 orbifold) From 4 dimensional point of view, Gauge breaking & doublet-triplet splitting … automatic !

Gauge coupling unification preserved Minimal model Precision unification prediction M c ~ M X < M unif … generic feature

Suppressed d =5 proton decay • 4D • 5D 5D partners simply absent • U (1) R symmetry T (1), F (1), H (0), H (0), H’ (2), H’ (2), … … d =5 proton decay does not arise

Matter fields • Matter fields can be either on a brane or in the bulk bulk matter: touch to the defect • SU(5) prediction for m q / m l does not arise Q, L • No d =6 proton decay T, F Light (volume dilution) brane matter: locally SU(5) symmetric • SU(5) prediction for m q / m l holds … Successful correlation ! Heavy (no volume dilution)

Flavor physics: matter geography • T 1 in the bulk ( M X = 1/2 R ~ 10 15 GeV) • T 3 on the brane (top Yukawa coupling) T 3 T 2 F 1 F 2 F 3 T 1 b / t unification F 3 on the brane • s / m , d / e mass ratio either T 2 or F 2 in the bulk • Example) … realistic fermion masses T 3 , F 1,2,3 T 1,2 ( V, H, H ) SU(5)

Implications on proton decay • No d =4 or d =5 proton decay • No d =6 proton decay at leading order ( T 1 in the bulk) d =6 proton decay occurs through flavor mixing / brane op. Y.N.; Hebecker, March-Russell CKM / volume suppressed, but M X = 1/(2 R ) ~ 10 15 GeV < M GUT ~ 2 x 10 16 GeV → A variety of final states with the rates within reach Example) p → e + p 0 , m + p 0 , e + K 0 , m + K 0 , p + n , K + n T 3 , F 1,2,3 comparable rates T 1,2 calculable branching ratios t ~ 10 34 years Hall, Y.N. Proton decay as a probe of geometry at the unification scale!

Light Hidden Sectors The existence of light hidden sectors — especially natural in supersymmetric theories Kinetic mixings: scale transmission SUSY SM hidden sector • U(1) - gauge portal … e F mn F ‘ mn Holdom; Baumgart, Cheung, Ruderman, Wang, Yavin ; … • Singlet portal … e ∂ m s ∂ m s ‘ Cheung, Y.N. Pseudo Nambu-Goldstone bosons from physics at F ~ TeV • Next -to-Minimal SUSY Standard Model (NMSSM) Dermisek, Guinion ; … • Axion-portal models for dark matter Y.N., Thaler ; … Light neutral states with M hidden ~ O (MeV – 10 GeV)

Long-lived, weakly-interacting, light states PNGB Hidden photon Existing constraints Bjorken, Essig, Schuster, Toro; Essig, Harnik , Kaplan, Toro; …

Neutrino experiments can constrain / discover SM states ( e ± , m ± , …) f high intensity p Batell, Pospelov, Ritz; Essig, Harnik, Kaplan, Toro LSND LSND, MiniBooNE, MINOS/MINERvA

Summary Revolutionary changes of our view on nature – Energy frontier – Multiple universes – Multiple sectors (Large-scale) neutrino detectors are useful • proton decay … Wide class of well -motivated theories lead to it within the future reach Important to push limits on all possible modes: p → e + p 0 , m + p 0 , e + K 0 , m + K 0 , p + n , K + n, ... • light hidden sectors ... Long-lived, weakly-interacting, light states Neutrino experiments can constrain / discover