Neutrinos and Cosmos. Hitoshi Murayama (Berkeley) Texas Conference at Stanford Dec 17, 2004

Size: px

Start display at page:

Download "Neutrinos and Cosmos. Hitoshi Murayama (Berkeley) Texas Conference at Stanford Dec 17, 2004"

Elaine May
5 years ago
Views:

1 Neutrinos and Cosmos Hitoshi Murayama (Berkeley) Texas Conference at Stanford Dec 17, 2004

2 Outline A Little Historical Perspective Interpretation of Data & Seven Questions Matter Anti-Matter Asymmetry Conclusions

3 A Little Historical Perspective

4 Rare Effects from High-Energies L = L SM + 1! L 5 + 1! 2L 6 + Effects of physics beyond the SM as effective operators L 5 = (LH)(LH) 1! (L H )(L H ) = m """ Can be classified systematically (Weinberg) L 6 =QQQL, L! µ" W µ" He, W µ " W " # B# µ,(h D µ H)(H D µ H),

5 Unique Role of Neutrino Mass Lowest order effect of physics at short distances Tiny effect (m ν /E ν )2 ~(ev/gev) 2 =10-18! Interferometry (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 high scales

6 Solar Neutrino Spectrum pp 7Be 8B

7 We don t get enough Can we get three numbers correctly with only two parameters? (Δm 2, θ)

8 Year of Neutrino: 2002 March 2002 April 2002 with SNO Dec 2002 with KamLAND June 2004 with KamLAND

9 Solar Neutrino Problem Finally Solved After 35 Years!

10 What we learned Atmospheric ν μ s are lost. P= (SK) converted most likely to ν τ (>99%CL) Solar ν e is converted to either ν μ or ν τ (>5σ) (SNO) Reactor anti-ν e disappear and reappear (99.6%CL) (KamLAND) Only LMA solution left for solar neutrinos Tiny neutrino mass: the first evidence for incompleteness of Minimal Standard Model

11 Grand Unification electromagnetic, weak, and strong forces have very different strengths But their strengths become the same at GeV if supersymmetry A natural candidate energy scale Λ~10 16 GeV m ~0.003eV m ~(Δm 2 atm )1/2 ~0.05eV m ~(Δm 2 sol )1/2 ~0.009eV Neutrino mass may be probing unification! L 5 = (LH)(LH) 1! (L H )(L H ) = m """

12 Typical Theorists View ca Solar neutrino solution must be small angle MSW solution because it s cute Wrong! Natural scale for Δm2 23 ~ ev2 because it is cosmologically interesting Angle θ 23 must be ~ V cb =0.04 Atmospheric neutrino anomaly must go away because it needs a large angle Wrong! Wrong! Wrong!

13 Surprises Prejudice from quarks, charged leptons: Mixing angles are small Masses are hierarchical All mixing except U large e3 big big small? (eµ!) big big big " e!m 2 solar big big big!m atm Two mass splittings not very different " µ "! Atmospheric mixing near maximal Any new symmetry or structure behind it? many models

14 Interpretation of Data & Seven Questions

15 Three-generation Framework Standard parameterization of MNS matrix for 3 generations: 3 angles, one phase M MNS = U e1u e2 U e3 U µ1 U µ2 U µ3 U!1 U!2 U!3??? solar c 12 s 12 s 12 c 12 c 13 s 13 e i" 1 1 c 23 s 23 1 s 13 e i" c 13 s 23 c 23 atmospheric Three mass eigenvalues m 1, m 2, m 3 Two mass-squared differences Δm 2 12, Δm2 23

16 Three-generation Solar, reactor, atmospheric and K2K data easily accommodated within three generations sin2 2θ 23 near maximal Δm 2 atm ~ ev 2 sin2 2θ 12 large Δm 2 solar ~ ev 2 sin2 2θ 13 = U e3 2 < 0.05 from CHOOZ, Palo Verde Because of small sin2 2θ 13, solar (reactor) & atmospheric ν oscillations almost decouple Maltoni et al, hep-ph/ Unknowns: θ 13, δ

17 Six Seven Questions Dirac or Majorana? How small is θ 13? CP Violation? Mass hierarchy? Verify Oscillation? LSND? Sterile neutrino(s)? CPT violation? Absolute mass scale?

18 Neutrinos have mass They have mass. Can t go at speed of light. What is this right-handed particle? New particle: right-handed neutrino (Dirac) Old anti-particle: right-handed anti-neutrino (Majorana)

19 Seesaw Mechanism Why is neutrino mass so small? Need right-handed neutrinos to generate neutrino mass, but ν SM neutral R ν L ν R ( ) m D m D M ν L ν R m ν = m D 2 M << m D To obtain m 3 ~(Δm 2 atm )1/2, m D ~m t, M 3 ~10 15 GeV (GUT!) Neutrinos are Majorana

20 Neutrinoless Double-beta Decay The only known practical approach to discriminate Majorana vs Dirac neutrinos 0νββ: nn ppe e with no neutrinos Matrix element <m ν e >= i m ν U ei 2 Current limit <m ν e > about 1eV

21 Three Types of Mass Spectra Degenerate All three around >0.1eV with small splittings Laboratory limit: m<2.3ev May be confirmed by KATRIN, cosmology <m νe > > 0.07m Inverted m 3 ~0, m 1 ~m 2 ~(Δm2 23 )1/2 0.05eV May be confirmed by long-baseline experiment with matter effect <m νe > >0.013eV (HM, Peña-Garay) Normal m 1 ~m 2 ~~0, m 3 ~(Δm2 23 )1/2 0.05eV <m νe > may be zero even if Majorana

22 Cosmological Limit CMB+LSS+Lyman α (Seljak et al, astro-ph/ ) : Σ m i ν i <0.42 ev, m <0.13 ev (95% CL) ν1 Puts upper limit on the effective neutrino mass in the neutrinoless double beta decay <m > <0.13eV (Pierce, HM) ν e Heidelberg-Moscow: <m > = ev νe Conflict?

23 Cosmology vs Laboratory Global fit to the World Data indeed, tension between the Heidelberg-Moscow claim and cosmology Still subject to the uncertainties in nuclear matrix element (Bahcall, HM, Peña-Garay) Better data and theory needed! Lisi et al, hep-ph/

24 Matter Anti-matter Asymmetry

25 Matter and Anti-Matter Early Universe 10,000,000,001 10,000,000,000 q q _

26 Matter and Anti-Matter Current Universe 1 us q q _ The Great Annihilation

27 Baryogenesis Gaussian scale-invariant fluctuation inflation Initial condition wiped out What created this tiny excess matter? Necessary conditions for baryogenesis (Sakharov): 1. Baryon number non-conservation 2. CP violation (subtle difference between matter and anti-matter) 3. Non-equilibrium ( B>0) > ( B<0) It looks like neutrinos have no role in this

28 Electroweak Anomaly Actually, SM converts L (ν) to B (quarks). In Early Universe (T > 200GeV), W is massless and fluctuate in W plasma Energy levels for lefthanded quarks/leptons fluctuate correspondingly ΔL=ΔQ=ΔQ=ΔQ=ΔB=1 (B L)=0

29 Leptogenesis You generate Lepton Asymmetry first. (Fukugita, Yanagida) Generate L from the direct CP violation in righthanded neutrino decay Γ(N 1 ν i H) Γ(N 1 ν i H) Im(h 1j h 1k h lk * hlj * ) 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 works! (e.g., Bari, Buchmüller, Plümacher)

30 Neutrino as inflaton Superpartner of a righthanded neutrino ~ V=m 2 ν 2 displaced from the minimum at the beginning rolls down slowly: inflation decays into both matter and anti-matter, but with a slight preference to matter decay products contain supersymmetry and hence Dark Matter H. Murayama et al, PRL 70, 1912 ~ V(ν) ~ ν log R ~ ν t t

31 Origin of the Universe Right-handed scalar neutrino: V=m 2 φ 2 n s =0.96 r=0.16 Verification/exclusion possible in the near future even if not inflaton, it may show up as a small isocurvature component

32 Conclusions Revolution in neutrino physics The solar neutrino problem solved! Small but finite neutrino mass: Interesting interplay between neutrinos and cosmos Neutrino mass may be responsible for our existence Neutrinos may even be the origin of the universe A lot more to learn in the next few years

Neutrino Basics. m 2 [ev 2 ] tan 2 θ. Reference: The Standard Model and Beyond, CRC Press. Paul Langacker (IAS) LSND 90/99% SuperK 90/99% MINOS K2K

Neutrino Basics. m 2 [ev 2 ] tan 2 θ. Reference: The Standard Model and Beyond, CRC Press. Paul Langacker (IAS) LSND 90/99% SuperK 90/99% MINOS K2K Neutrino Basics CDHSW m 2 [ev 2 ] 10 0 10 3 10 6 10 9 KARMEN2 Cl 95% NOMAD MiniBooNE Ga 95% Bugey CHOOZ ν X ν µ ν τ ν τ NOMAD all solar 95% SNO 95% CHORUS NOMAD CHORUS LSND 90/99% SuperK 90/99% MINOS K2K