What is the case for nufact Hitoshi Murayama

What is the case for nufact? Hitoshi Murayama (UC Berkeley) Intl Scoping Study Meeting of Nufact and Superbeam Boston University, March 8, 2006 ISS Physics WS Boston

The Question • • • Neutrino physics has been full of surprises We’ve learned a lot in the last ~8 years We want to learn more New projects are more and more expensive Is it really worth it? Especially worth ~B$, B€, 100 B¥? ISS Physics WS Boston 2

Elevator Pitch • If you happen to be on an elevator with a powerful senator, can you explain why you want to spend ~B$ on your project in 30 seconds? ISS Physics WS Boston 3

What will NOT work • • • For politicians and taxpayers, these arguments wouldn’t be convincing and/or interesting enough Measurements as precisely as we can Push limits on 13 as much as we can Verify the three-generation framework of neutrino oscillation Distinguish different flavor modles Field needs another machine to sustain itself ISS Physics WS Boston 4

Quantum Universe Report What are neutrinos telling us? • Of all the known particles, neutrinos are the most mysterious. They played an essential role in the evolution of the universe, and their tiny nonzero mass may signal new physics at very high energies. ISS Physics WS Boston 5

Quantum Universe Report • Einstein’s Dream of Unified Forces – Are there undiscovered principles of nature: new symmetries, new physical laws? – How can we solve the mystery of dark energy? – Are there extra dimensions of space – Do all the forces become one? • The Particle World – Why are there so many kinds of particles? – What is dark matter? How can we make it in the laboratory? – What are neutrinos telling us? • The Birth of the Universe – How did the universe come to be? – What happened to the antimatter? ISS Physics WS Boston 6

Outline • Why Neutrinos? • A few scenarios – – sin 2 2 13 ≪ 0. 01 sin 2 2 13 > 0. 01 Mini-Boo. NE confirms LSND LHC discovers new physics < Te. V • The Big Questions – Scenario to “establish” seesaw/leptogenesis • Conclusion ISS Physics WS Boston 7

Why Neutrinos? ISS Physics WS Boston

Interest in Neutrino Mass • So much activity on neutrino mass already. Why are we doing this? Window to (way) high energy scales beyond the Standard Model! ISS Physics WS Boston 9

Why Beyond the Standard Model • Standard Model is sooooo successful. But none of us are satisfied with the SM. Why? • Because it leaves so many great questions unanswered Drive to go beyond the Standard Model • Two ways: – Go to high energies – Study rare, tiny effects ISS Physics WS Boston 10

Rare Effects from High-Energies • Effects of physics beyond the SM as effective operators • Can be classified systematically (Weinberg) ISS Physics WS Boston 11

Unique Role of Neutrino Mass • Lowest order effect of physics at short distances • Tiny effect (m /E )2~(0. 1 e. V/Ge. V)2=10– 20! • Inteferometry (i. e. , Michaelson-Morley) – Need coherent source – Need interference (i. e. , large mixing angles) – Need long baseline Nature was kind to provide all of them! • “neutrino interferometry” (a. k. a. neutrino oscillation) a unique tool to study physics at very ISS Physics WS Boston 12 high scales

Ubiquitous Neutrinos They must have played some important role in the universe! ISS Physics WS Boston 13

The Data de Gouvêa’s classification: • “Indisputable” – Atmospheric – Solar – Reactor • “strong” – Accelerator (K 2 K) And we shouldn’t forget: • “unconfirmed” – Accelerator (LSND) ISS Physics WS Boston 14

Historic Era in Neutrino Physics We learned: • Atmospheric s are lost. P=4. 2 10– 26 (SK) (1998) • converted most likely to (2000) • Solar e is converted to either or (SNO) (2002) • Only the LMA solution left for solar neutrinos (Homestake+Gallium+SK+SNO) (2002) • Reactor anti- e disappear (2002) and reappear (Kam. LAND) (2004) ISS Physics WS Boston 15

Neutrinos do oscillate! Proper time ISS Physics WS Boston 16

What we learned • Lepton Flavor is not conserved • Neutrinos have tiny mass, not very hierarchical • Neutrinos mix a lot the first evidence for incompleteness of Minimal Standard Model Very different from quarks ISS Physics WS Boston 17

Typical Theorists’ View ca. 1990 • Solar neutrino solution must be small angle Wrong! MSW solution because it’s cute • Natural scale for Dm 223 ~ 10– 100 e. V 2 Wrong! because it is cosmologically interesting Wrong! • Angle 23 must be ~ Vcb =0. 04 • Atmospheric neutrino anomaly must go Wrong! away because it needs a large angle ISS Physics WS Boston 18

The I visibles ISS Physics WS Boston 19

ISS Physics WS Boston 20

The Big Questions • • • What is the origin of neutrino mass? Did neutrinos play a role in our existence? Did neutrinos play a role in forming galaxies? Did neutrinos play a role in birth of the universe? Are neutrinos telling us something about unification of matter and/or forces? • Will neutrinos give us more surprises? Big questions tough questions to answer ISS Physics WS Boston 21

Immediate Questions • • Dirac or Majorana? Absolute mass scale? How small is 13? CP Violation? Mass hierarchy? Is 13 maximal? LSND? Sterile neutrino(s)? CPT violation? ISS Physics WS Boston 22

Tools • Available tools now: – Super. K, SNO, Kam. LAND, Borexino, Mini-Boo. NE, MINOS, Cuoricino, NEMO, SDSS, … • Available soon (? ): – Opera, Double-Chooz, T 2 K, MINER A, Sci. Boo. NE, NO A, reactor 13 expts, KATRIN, PLANCK, new photometric surveys, more 0 expts, … Do we really need more? What do we need? ISS Physics WS Boston 23

Do we really need more? What do we need? • The answer depends on what we will find in the near future • Talk about a few scenarios – sin 2 2 13 ≪ 0. 01 – sin 2 2 13 > 0. 01 – Mini-Boo. NE confirms LSND – LHC discovers new physics < Te. V ISS Physics WS Boston 24

sin 2 2 13≪ 0. 01 ISS Physics WS Boston

Obvious case? • Superbeams will not address 13, mass hierarchy, or CP violation • A clear case for neutrino factory and/or beam • de Gouvêa: Will we get the funds to get a neutrino factory even if all previous investments end up “unsuccessful”? ISS Physics WS Boston 26

sin 2 2 13>0. 01 ISS Physics WS Boston

sin 2 2 13>0. 01 • Reactor/T 2 K/NO A finds sin 2 2 13 This is my prejudice • Upgrades (4 MW J-PARC to Hyper. K, Proton Driver+NO A 2 nd detector, etc) – Measures sin 2 2 13 precisely – Determines mass hierarchy – Discovers CP violation What’s left then? ISS Physics WS Boston 28

The source of CP violation • Having seen does not tell us what is causing it (in particular in the presence of “matter effect background”) • Is it due to the Dirac phase in the MNS matrix? • Exactly the same question being addressed by Bfactories – i. e. , K can be explained by the KM phase, but is it? – Cross check in a different system, e. g. , B Yes! – Is there new interaction (e. g. SUSY loop)? future ISS Physics WS Boston 29

Testing MNS hypothesis • One way I know is to use tau modes • Consequence of CPT and three flavors • Can they be studied at neutrino factory? – I know it is tough even for a neutrino factory, but other facilities will clearly not do it ISS Physics WS Boston 30

Testing MNS hypothesis • A simulation like this will make the case with new neutrino interaction ( ) w/o new neutrino interaction (e ) ISS Physics WS Boston 31

Mini-Boo. NE confirms LSND ISS Physics WS Boston

The hell breaks loose • In this case, it is hard to understand what is going on, because there is currently no simple way to accommodate LSND result with other neutrino data – Multiple sterile neutrinos? – Sterile neutrino and CPT violation? – Mass varying neutrinos? – Something even more wild and wacky? ISS Physics WS Boston 33

What it takes • We will need neutrino “oscillation” experiments with multiple baselines, multiple modes – E~10 Ge. V, L~10 km, looking for appearance – Redo CDHSW ( disappearance experiment with L=130 & 885 m, E=19. 2 Ge. V) – E~1 Ge. V, L~1 km, looking for oscillatory behavior and CP violation in e , or better, e – Some in the air, some in the earth – Probably more – Muon source would help greatly ISS Physics WS Boston 34

LHC discovers new physics <Te. V ISS Physics WS Boston

Te. V new physics • Whatever it is, – SUSY, large extra dimensions, warped extra dimension, technicolor, Higgsless, little Higgs it is hard to avoid the Te. V-scale physics to contribute to flavor-changing effects in general • Renewed strong case for, e. g. , super-B • Very strong case for lepton flavor violation, g 2 – Hence, for a muon storage ring • Obvious competition with ILC and beyond ISS Physics WS Boston 36

For example, SUSY • High-energy data (LHC/ILC) will provide masses of superparticles – But most likely not their mixings • Low-energy LFV experiments (e. g. , e , A e. A) provide rates (T-odd asymmetry if lucky) – Combination of virtual particles in the loop and their mixing • Put them together – Resolve the mixing – Constrain models of flavor ISS Physics WS Boston 37

What about the Big Questions? • • • What is the origin of neutrino mass? Did neutrinos play a role in our existence? Did neutrinos play a role in forming galaxies? Did neutrinos play a role in birth of the universe? Are neutrinos telling us something about unification of matter and/or forces? • Will neutrinos give us more surprises? Big questions tough questions to answer ISS Physics WS Boston 38

Origin of Neutrino Mass, our existence, even our universe ISS Physics WS Boston

Neutrinos must be Massless • All neutrinos left-handed massless • If they have mass, can’t go at speed of light. • Now neutrino right-handed? ? contradiction can’t be massive ISS Physics WS Boston 40

Two ways to go (1) Dirac Neutrinos: – There are new particles, right-handed neutrinos, after all – Why haven’t we seen them? – Right-handed neutrino must be very weakly coupled – Why? ISS Physics WS Boston 41

Extra Dimensions • All charged particles are on a 3 -brane • Right-handed neutrinos SM gauge singlet Can propagate in the “bulk” • Makes neutrino mass small m ~ 1/R if one extra dim R~10 m • An infinite tower of sterile neutrinos • Or anomaly mediated SUSY breaking ISS Physics WS Boston 42

Two ways to go (2) Majorana Neutrinos: – There are no new light particles – Why if I pass a neutrino and look back? – Must be right-handed anti-neutrinos – No fundamental distinction between neutrinos and antineutrinos! ISS Physics WS Boston 43

Seesaw Mechanism • Why is neutrino mass so small? • Need right-handed neutrinos to generate neutrino mass , but R SM neutral To obtain m 3~(Dm 2 atm)1/2, m. D~mt, M 3~1015 Ge. V (GUT!) ISS Physics WS Boston 44

Grand Unification • electromagnetic, weak, and strong forces have very different strengths • But their strengths become the same at 1016 Ge. V if supersymmetry • To obtain m 3~(Dm 2 atm)1/2, m. D~mt M 3~1015 Ge. V! ISS Physics WS Boston M 3 Neutrino mass may be probing unification: Einstein’s dream 45

Leptogenesis • You generate Lepton Asymmetry first. (Fukugita, Yanagida) • Generate L from the direct CP violation in right-handed neutrino decay • L gets converted to B via EW anomaly More matter than anti-matter We have survived “The Great Annihilation” • Despite detailed information on neutrino masses, it still ISS Physics WSPlümacher) Boston works (e. g. , Bari, Buchmüller, 46

~R Origin of Universe – slowly rolls down the potential – oscillates around it minimum – decays to produce a thermal bath • The superpartner of right-handed neutrino fits the bill • When it decays, it produces the lepton asymmetry at the same time (HM, Suzuki, Yanagida, Yokoyama) • Decay products: supersymmetry and hence dark matter Neutrino is mother of the Universe? size of the universe amplitude • Maybe an even bigger role: inflation • Need a spinless field that ISS Physics WS Boston 47

Origin of the Universe • Right-handed scalar neutrino: V=m 2 f 2 • ns=0. 96 • r=0. 16 • Detection possible in the near future ISS Physics WS Boston 48

Can we prove it experimentally? • Unfortunately, no: it is difficult to reconstruct relevant CP-violating phases from neutrino data • But: we will probably believe it if the following scenario happens Archeological evidences ISS Physics WS Boston 49

A scenario to “establish” seesaw • We find CP violation in neutrino oscillation – At least proves that CP is violated in the lepton sector • Ue 3 is not too small – At least makes it plausible that CP asymmetry in right-handed neutrino decay is not unnaturally suppressed • But this is not all ISS Physics WS Boston 50

A scenario to “establish” seesaw • • LHC finds SUSY, LC establishes SUSY no more particles beyond the MSSM at Te. V scale Gaugino masses unify (two more coincidences) Scalar masses unify for 1 st, 2 nd generations (two for 10, one for 5*, times two) strong hint that there are no additional particles beyond the MSSM below MGUT except for gauge singlets. ISS Physics WS Boston 51

Gaugino and scalars • Gaugino masses test unification itself independent of intermediate scales and extra complete SU(5) multiplets • Scalar masses test beta functions at all scales, depend on the particle content ISS Physics WS Boston 52

A scenario to “establish” seesaw • Next generation experiments discover neutrinoless double beta decay • Say, m ee~0. 1 e. V (quasi-degenerate) • There must be new physics below ~1014 Ge. V that generates the Majorana neutrino mass ISS Physics WS Boston 53

A scenario to “establish” seesaw • It leaves the possibility for R-parity violation • Consistency between cosmology, dark matter detection, and LHC/ILC will remove the concern ISS Physics WS Boston 54

High precision even for ILC = 1014 Ge. V y r a seesaw Modified Type-I New particles 3 1 3 24 (m. Q 2 -m. U 2)/M 12 1 1. 283 i l e r P (m. Q 2 -m. E 2)/M 12 (m. D 2 -m. L 2)/M 12 n i m 1 1 1. 084 1. 040 Type-II seesaw 15+15* 1. 078 1. 026 1. 014 Matt Buckley ISS Physics WS Boston 55

A scenario to “establish” seesaw • B-mode fluctuation in CMB is detected, with a reasonable inflationary scale strong hint that the cosmology has been ‘normal’ since inflation (no extra D etc) ISS Physics WS Boston 56

A scenario to “establish” seesaw Possible additional archeological evidence, e. g. , : • lepton-flavor violation ( e conversion, ) seen at the “reasonable” level expected in SUSY seesaw (even though I don’t believe m. SUGRA) • Bd KS shows deviation from the SM consistent with large b. R-s. R mixing above MGUT • Isocurvature fluctuation seen suggestive of N 1 coherent oscillation, avoiding the gravitino problem ISS Physics WS Boston 57

Conclusions • • Revolutions in neutrino physics Neutrino mass probes rare/subtle/high-energy physics There is a very good chance for further big progress Most likely, we will need superbeam, and also neutrino factory and/or beta beam • Neutrino physics is within the context of particle physics, astrophysics and cosmology • Big questions can be answered only based on collection of experiments, not oscillation alone What’s the elevator pitch? ISS Physics WS Boston 58