neutrino physics iii
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Neutrino Physics III. Hitoshi Murayama University of Pisa February 26, 2003. Outline. Three Generations LSND Implications of Neutrino Mass Why do we exist? Models of flavor Conclusions. Three Generations. MNS matrix. - PowerPoint PPT PresentationTRANSCRIPT
Neutrino Physics III
Hitoshi MurayamaUniversity of PisaFebruary 26, 2003
2
Outline
• Three Generations• LSND• Implications of Neutrino Mass• Why do we exist?• Models of flavor• Conclusions
Three Generations
4
MNS matrix
• Standard parameterization of Maki-Nakagawa-Sakata matrix for 3 generations
UMNS =Ue1 Ue2 Ue3Uμ1 Uμ2 Uμ3Uτ1 Uτ2 Uτ3
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
=1
c23 s23−s23 c23
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
c13 s13e−iδ
1−s13e
iδ c13
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
c12 s12−s12 c12
1
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
atmospheric ??? solar
5
Three-generation
• Solar & atmospheric oscillations easily accommodated within three generations
• sin2223 near maximal, m2atm ~ 310–3eV2
• sin2212 large, m2solar ~ 510–5eV2
• sin2213 < 0.05 from CHOOZ, Palo Verde
• Because of small sin2213, solar & atmospheric oscillations almost decouple
• Need to know sin2213,
and mass hierarchy
6
Raised More Questions
• Why do neutrinos have mass at all?
• Why so small?• We have seen mass
differences. What are the masses?
~m/15eV• Do we need a fourth
neutrino?• Are neutrinos and anti-
neutrinos the same? • How do we extend the Standard Model to incorporate massive neutrinos?
7
3-flavor mixing
• If m1 and m2 not very different, it reduces to the 2-flavor problem
€
τ μ ,t =Uτ 1* Uμ1 e−im1
2t /2 p
+Uτ 2* Uμ 2 e−im2
2t /2 p +Uτ 3* Uμ 3 e−im3
2t /2 p
≅ Uτ 1* Uμ1 +Uτ 2
* Uμ 2( )e−im1
2t /2 p +Uτ 3* Uμ 3 e−im3
2t / 2 p
= −Uτ 3* Uμ 3e−im1
2t /2 p +Uτ 3* Uμ 3 e−im3
2t /2 p
= eiφ sinθ −e−im12t / 2 p + e−im3
2t /2 p ⎛ ⎝ ⎜
⎞ ⎠ ⎟
8
When is 3-flavor important?
€
τ μ ,t2
= Uτi*UμiUτjUμj
* e−i mi
2 − m j2
( )t / 2 p
i, j∑
= −2ℜe Uτi*UμiUτjUμj
*( ) sin2 mi
2 − m j2
4 pi, j∑ t
+ ℑm Uτi*UμiUτjUμj
*( ) sin
mi2 − m j
2
2 pi, j∑ t
When all masses significantly differentAnti-neutrinos: UU*, the last term flips signPossible CP violation
9
CP Violation
• Possible only if:– m12
2, s12 large enough (LMA)
– 13 large enough
P(νe → νμ)−P(νe → νμ) =16s12c12s13c132 s23c23
sinδsin Δm122
4EL
⎛ ⎝ ⎜
⎞ ⎠ ⎟ sin Δm13
2
4EL
⎛ ⎝ ⎜
⎞ ⎠ ⎟ sin Δm23
2
4EL
⎛ ⎝ ⎜
⎞ ⎠ ⎟
10
11
LSND
12
ν μν e?
ν ep→ e+n
μ+→ e+νeν μ
p→ π +
π+→ μ+νμ
13
3.3 Signal
• Excess positron events over calculated BG
P(ν μ → ν e)=(0.264±0.067±0.045)%
14
Mini-BooNE
• LSND unconfirmed• Neutrino beam from
Fermilab booster• Settles the issue of
LSND evidence• Started data taking the
summer 2002
15
LSND Affects SN1987A neutrino burst
HM, Yanagida
• Kamiokande’s 11 events:– 1st event is forward
may well be e from deleptonization burst(p e- n e to become neutron star)
– Later events most likely e
• LSND parameters cause complete MSW conversion ofeμ if light side (e lighter)eμ if dark side (e heavier)
• Either mass spectrum disfavored
_
_ _
16
LSND Affects SN1987A neutrino burst
HM, Yanagida
17
Sterile Neutrino
• LSND, atmospheric and solar neutrino oscillation signalsm2
LSND ~ eV2
m2atm ~ 310–3eV2
m2solar < 10–3eV2
Can’t be accommodated with 3 neutrinos
Need a sterile neutrinoNew type of neutrino with no
weak interaction
• 3+1 or 2+2 spectrum?
18
Sterile Neutrino getting tight
• 3+1 spectrum: sin22LSND=4|U4e|2|U4μ|2
– |U4μ|2 can’t be big because of CDHS, SK U/D
– |U4e|2 can’t be big because of Bugey– Marginally allowed
• 2+2 spectrum: past fits preferred– Atmospheric mostly μτ
– Solar mostly es (or vice versa)
– Now pretty much ruled out(Barger et al, Giunti et al, Gonzalez-Garcia et al, Strumia, Maltoni et al)
19
WMAPMaltoni, Schwetz, Tortola, Vallehep-ph/0209368
20
CPT Violation?“A desperate remedy…”
• LSND evidence:anti-neutrinos
• Solar evidence:neutrinos
• If neutrinos and anti-neutrinos have different mass spectra, atmospheric, solar, LSND accommodated without a sterile neutrino
(HM, Yanagida)(Barenboim, Lykken, et al)
Best fit to data before KamLAND (Strumia)
21
KamLAND impact
• However, now there is an evidence for “solar” oscillation in anti-neutrinos from KamLAND
• Barenboim, Borissov, Lykken: evidence for atmospheric neutrino oscillation is dominantly for neutrinos. Anti-neutrinos suppressed by a factor of 3.
• Not a great fit (Strumia)
• New CPT violation:
22
CPT Theorem
• Based on three assumptions:– Locality– Lorentz invariance– Hermiticity of Hamiltonian
• Violation of any one of them: big impact on fundamental physics
• Neutrino mass: tiny effect from high-scale physics– Non-local Hamiltonian? (HM, Yanagida)– Brane world? (Barenboim, Borissov, Lykken, Smirnov)– Dipole Field Theory? (Bergman, Dasgupta, Ganor, Karczmarek, Rajesh)
23
Implications on Experiments
• Mini-BooNE experiment will not see oscillation in neutrino mode, but will in anti-neutrino mode
• Because KamLAND is consistent with LMA, atmospheric neutrino oscillation relies on m2
LSND ~ eV2 (not a great fit)
• Katrin may see endpoint spectrum distortion in t3He+e–+e
We’ll see!
_
24
Maybe even more surprisesin neutrinos!
25
Mass Spectrum
What do we do now?
26
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 very weakly coupled
– Why?
27
Extra Dimension
• All charged particles are on a 3-brane• Right-handed neutrinos SM gauge singlet
Can propagate in the “bulk”• Makes neutrino mass small
(Arkani-Hamed, Dimopoulos, Dvali, March-Russell;Dienes, Dudas, Gherghetta)
• Barbieri-Strumia: SN1987A constraint“Warped” extra dimension (Grossman, Neubert)
• Or SUSY breaking(Arkani-Hamed, Hall, HM, Smith, Weiner;
Arkani-Hamed, Kaplan, HM, Nomura)
€
d 4θ S*
M (LHu N∫ )
28
Two ways to go
(2) Majorana Neutrinos:– There are no new light
particles– What if I pass a
neutrino and look back?
– Must be right-handed anti-neutrinos
– No fundamental distinction between neutrinos and anti-neutrinos!
29
Seesaw Mechanism
• Why is neutrino mass so small?• Need right-handed neutrinos to generate
neutrino mass
νL νR( )mD
mD
⎛ ⎝ ⎜
⎞ ⎠ ⎟
νLνR
⎛ ⎝ ⎜
⎞ ⎠ ⎟ νL νR( )
mDmD M
⎛ ⎝ ⎜
⎞ ⎠ ⎟
νLνR
⎛ ⎝ ⎜
⎞ ⎠ ⎟ mν =mD
2
M<<mD
To obtain m3~(m2atm)1/2, mD~mt, M3~1015GeV (GUT!)
, but R SM neutral
30
Grand Unification
• electromagnetic, weak, and strong forces have very different strengths
• But their strengths become the same at 1016 GeV if supersymmetry
• To obtain m3~(m2
atm)1/2, mD~mt
M3~1015GeV!Neutrino mass may be probing unification:
Einstein’s dream
M3
Why do we exist?Matter Anti-matter Asymmetry
32
Big-Bang NucleosynthesisCosmic Microwave Background
η =nBnγ
= 4.7−0.8+1.0( )×10−10
5.0±0.5( )×10−10
(Thuan, Izatov)
(Burles, Nollett, Turner)
WMAP
33
Matter and Anti-MatterEarly Universe
10,000,000,001 10,000,000,000
Matter Anti-matter
34
Matter and Anti-MatterCurrent Universe
The Great Annihilation
1
us
Matter Anti-matter
35
Sakharov’s Conditionsfor Baryogenesis
• Necessary requirements for baryogenesis:– Baryon number violation– CP violation– Non-equilibrium (B>0) > (B<0)
• Possible new consequences in– Proton decay– CP violation
36
Original GUT Baryogenesis
• GUT necessarily breaks B. • A GUT-scale particle X decays out-of-equilibrium
with direct CP violation
• Now direct CP violation observed: ’!
• But keeps B–L0 “anomaly washout”• Also monopole problem
B(X → q) ≠B(X → q)
B(K0 → π+π−) ≠B(K0 → π+π−)
37
Electroweak Anomaly
• Actually, SM converts L to B.– In Early Universe (T >
200GeV), W/Z are massless and fluctuate in W/Z plasma
– Energy levels for left-handed quarks/leptons fluctuate correspon-dingly
L=Q=Q=Q=B=1 B–L)=0
38
Two Main Directions
• BL0 gets washed out at T>TEW~174GeV• Electroweak Baryogenesis (Kuzmin, Rubakov, Shaposhnikov)
– Start with B=L=0– First-order phase transition non-equilibrium– Try to create BL0
• Leptogenesis (Fukugita, Yanagida)
– Create L0 somehow from L-violation– Anomaly partially converts L to B
39
Leptogenesis
• You generate Lepton Asymmetry first.• 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”
Γ(N1→ νiH)−Γ(N1 → νiH)∝ Im(h1jh1khlk* hlj
*)
40
Does Leptogenesis Work?
• Much more details worked out(Buchmüller, Plümacher; Pilaftsis)
• ~1010 GeV R OK• Some tension with supersymmetry because
of unwanted gravitino overproduction• Ways around: coherent oscillation of right-
handed sneutrino (HM, Yanagida+Hamaguchi)
41
Does Leptogenesis Work?
• Some tension with supersymmetry:– unwanted gravitino
overproduction– gravitino decay
dissociates light nuclei– destroys the success of
Big-Bang Nucleosynthesis
– Need TRH<109 GeV(Kawasaki, Kohri, Moroi)
42
Leptogenesis Works!
• Coherent oscillation of right-handed sneutrino (Bose-Einstein condensate) (HM, Yanagida+Hamaguchi)
– Inflation ends with a large sneutrino amplitude
– Starts oscillation – dominates the Universe– Its decay produces asymmetry– Consistent with observed
oscillation pattern– isocurvature perturbation at
WMAP? (Moroi, HM)nBs
~εTdecay
M1~ nB
s⎛ ⎝ ⎜ ⎞
⎠ ⎟ obs
Tdecay
106GeVargh132
h332
43
Can we prove it experimentally?
• We studied this question at Snowmass2001 (Ellis, Gavela, Kayser, HM, Chang)
– Unfortunately, no: it is difficult to reconstruct relevant CP-violating phases from neutrino data
• But: we will probably believe it if– 0 found– CP violation found in neutrino oscillation– EW baryogenesis ruled out
Archeological evidences
Models of Flavor
45
Question of Flavor
• What distinguishes different generations?– Same gauge quantum numbers, yet different
• Hierarchy with small mixings: Need some ordered structure
• Probably a hidden flavor quantum number Need flavor symmetry
– Flavor symmetry must allow top Yukawa– Other Yukawas forbidden– Small symmetry breaking generates small Yukawas
46
Fermion Mass Relationin SU(5)
• down- and lepton-Yukawa couplings come from the same SU(5) operator 10 5* H
• Fermion mass relationmb= mτ, ms = mμ, md = me @MGUT Reality:mb≈ mτ, 3ms ≈ mμ, md ≈ 3me @MGUT
• Not bad! (small correction compared to inter-generational splitting ~20–200)
47
Broken Flavor Symmetry
• Flavor symmetry broken by a VEV ~0.02• SU(5)-like:
– 10(Q, uR, eR) (+2, +1, 0)
– 5*(L, dR) (+1, +1, +1)
– mu:mc:mt ~ md2:ms
2:mb2
~ me2:mμ
2:mτ2 ~4: 2 :1
Mu ~ε4 ε3 ε2
ε3 ε2 εε2 ε 1
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟ ,Md~
ε3 ε3 ε3
ε2 ε2 ε2
ε ε ε
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟ ,Ml~
ε3 ε2 εε2 ε2 εε3 ε2 ε
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
48
Not bad!
• mb~ mτ, ms ~ mμ, md ~ me @MGUT
• mu:mc:mt ~ md2:ms
2:mb2
~ me2:mμ
2:mτ2
49
New Data from Neutrinos
• Neutrinos are already providing significant new information about flavor symmetries
• If LMA, all mixing except Ue3 large
– Two mass splittings not very different– Atmospheric mixing maximal– Any new symmetry or structure behind it?
e μ τ( )big big smallbig big bigbig big big
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
νeνμντ
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
Δmsolar2
Δmatm2 ~0.01– 0.2
50
Is There A StructureIn Neutrino Masses & Mixings?
• Monte Carlo random complex 33 matrices with seesaw mechanism
(Hall, HM, Weiner; Haba, HM)
51
Anarchy
• No particular structure in neutrino mass matrix– All three angles large– CP violation O(1)– Ratio of two mass splittings just right for LMA
• Three out of four distributions OK– Reasonable Underlying symmetries don’t distinguish 3 neutrinos.
52
13 in Anarchy
• 13 cannot be too small if anarchy
• How often can “large” angle fluctuate down to the CHOOZ limit?
• Kolmogorov–Smirnov test: 12%
• sin2 213>0.004 (3)• If so, CP violation
observable at long baseline experiment
53
Anarchy is Peaceful
• Anarchy (Miriam-Webster): “A utopian society of individuals who enjoy complete freedom without government”
• Peaceful ideology that neutrinos work together based on their good will
• Predicts large mixings, LMA, large CP violation• sin2213 just below the bound• Ideal for VLBL experiments• Wants globalization!
54
Program:More flavor parameters
• Squarks, sleptons also come with mass matrices• Off-diagonal elements violate flavor: suppressed by flavor symmetries
• Look for flavor violation due to SUSY loops• Then look for patterns to identify symmetries
Repeat Gell-Mann–Okubo!• Need to know SUSY masses
M ˜ Q 2 ~M ˜ L
2 ~1 ε ε2
ε 1 εε2 ε 1
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
55
To Figure It Out…
• Models differ in flavor quantum number assignments
• Need data on sin2213, solar neutrinos, CP violation, B-physics, LFV, EWSB, proton decay
• Archaeology• We will learn insight on origin of flavor by
studying as many fossils as possible– cf. CMBR in cosmology
56
More Fossils:Lepton Flavor Violation
• Neutrino oscillation lepton family number is not conserved!– Any tests using charged leptons?– Top quark unified with leptons– Slepton masses split in up- or neutrino-basis– Causes lepton-flavor violation (Barbieri, Hall)
– predict B(τμ), B(μe), μe at interesting (or too-large) levels
57
Barbieri, Hall, Strumia
58
More Fossils:Quark Flavor Violation
• Now also large mixing between τ and μ
– (τ, bR) and (μ , sR) unified in SU(5)
– Doesn’t show up in CKM matrix
– But can show up among squarks
– CP violation in Bs mixing (BsJ )
– Addt’l CP violation in penguin bs (Bd Ks)
(Chang, Masiero, HM)
Conclusions
60
Conclusions
• Historic era in neutrino physics• Oscillation in atmospheric neutrino: an unexpected
discovery, strong evidence for neutrino mass• Decades-long problem in solar neutrinos now being
resolved• A lot more to learn in the near future• Interesting connections to cosmology, astrophysics• We’d like to know how to build the new Standard
Model!