theoretical neutrino physics hitoshi murayama (berkeley) eps 2003 @ aachen july 22, 2003
TRANSCRIPT
Theoretical Neutrino Physics
Hitoshi Murayama (Berkeley)
EPS 2003 @ Aachen
July 22, 2003
EPS2003 Hitoshi Murayama 2
Milind Diwan
• “Neutrino physics is so simple. There are no hadronic corrections. We don’t need theorists.”
Why You Need Theoristsin Neutrino Physics
Hitoshi Murayama (Berkeley)
EPS 2003 @ Aachen
July 22, 2003
EPS2003 Hitoshi Murayama 4
Outline
• A Little Historical Perspective• Interpretation of Data & Seven Questions
– Solar Neutrino– Interpretation without LSND– Interpretation with LSND– Nature of neutrino mass
• Models of Flavor• Conclusions
A Little Historical Perspective
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Rare Effects from High-Energies
• Effects of physics beyond the SM as effective operators
• Can be classified systematically (Weinberg)
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Unique Role of Neutrino Mass
• Lowest order effect of physics at short distances
• Tiny effect (m/E)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
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Grand Unification
• electromagnetic, weak, and strong forces have very different strengths
• But their strengths become the same at 1016 GeV if supersymmetry
• A natural candidate energy scale ~1016GeV
m~0.003eV• m~(m2
atm)1/2~0.03eV• m~(m2
LMA)1/2~0.007eV
Neutrino mass may be probing unification!
Interpretation of DataSeven Questions
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What we learned since Budapest
• Atmospheric s are lost. P=4.2 10–26 (SK, Hayato)
• converted most likely to (>99%CL)• Solar e is converted to either or (>5) (SNO,
Poon)
• Reactor anti-e are lost (99.95%CL) (KamLAND, Lesko)
• Only the LMA solution left for solar neutrinos• Tiny neutrino mass: the first evidence for
incompleteness of Minimal Standard Model
Solar Neutrino Problem Finally Solved After 35 Years!
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SNO Result
• Only e produced in the Sun• Wrong Neutrinos are
coming from the Sun!• Somehow some of e were
converted to on their way from the Sun’s core to the detector neutrino flavor conversion!
€
ΦCC =1.76 ± 0.05 ± 0.09 ⋅106 cm−2 sec−1
€
ΦNC = 5.09 −0.43+0.44 −0.43
+0.46 ⋅106 cm−2 sec−1
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KamLAND result
• First terrestrial expt relevant to solar neutrino problem
Dec 2002Expected #events: 86.8±5.6
Background #events: 0.95±0.99Observed #events: 54
No oscillation hypothesisExcluded at 99.95%
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No other solution than oscillation
• Neutrino decay– Wrong energy dependence
• Spin-resonant flip– Relies on a large solar magnetic field
• New flavor-changing neutral current– Relies on a high solar matter density
• Violation of the equivalence principle– Relies on the strong solar gravitational potential
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March 2002
April 2002 with SNO
Dec 2002with KamLAND
Progress in 2002 on the Solar Neutrino Problem
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Solar Neutrino Spectrum
pp7Be
8B
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We don’t get enough
We need survival probabilities of
8B: ~1/3
7Be: <1/3
pp: ~2/3
Can we get three numbers correctly with two parameters?
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Matter Effect
• CC interaction in the presence of non-relativistic electron
€
L = −GF
2e γμ (1−γ5 )ν eν eγ
μ (1−γ5 )e
= −GF
2e γμ (1−γ5 )eν eγ
μ (1−γ5 )ν e
= − 2GFneν eγ0ν e
• Neutrino Hamiltonian
€
H = common
+Δm2
4E
−cos2θ sin 2θ
sin 2θ cos2θ
⎛
⎝ ⎜
⎞
⎠ ⎟
+ 2GFne1 0
0 0
⎛
⎝ ⎜
⎞
⎠ ⎟
Electron neutrino higher energy in the Sun
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Adiabatic
• Use “instantaneous” eigenstates + and –
• For the LMA region, the dynamics is adiabatic: there is no hopping between states
20
Solar Neutrino Astrophysics
• Davis and Bahcall started solar neutrino work because they wanted to probe physics of the sun
• Finally one can fit all solar neutrino data together with KamLAND to measure all major components: pp, 7Be, 8B (Bahcall, Peña-Garay)
Solar luminosity confirmed
• Possible concern: density perturbation (Reggiani)
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Loose Ends
• Energy dependence in the solar neutrino survival probability not fully demonstrated– pp, 7Be solar neutrino experiments
• Nobody has seen “oscillation,” i.e., the survival probability dips and comes back up– Atmospheric: MINOS– Solar/reactor: continued KamLAND
• Evidence for “appearance” in atmos still not strong enough (99%CL)– OPERA, ICARUS
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Low-Energy Solar Neutrinos
• Solar neutrino data suggest energy-dependent survival probability tests MSW effect
12
Helps interpretation of CP violation, double beta decay data
7%1%
20%
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Verify Oscillation
• Even atmospheric neutrino data do not show “oscillation” yet MINOS, J-PARC
m223, 23, mass
hierarchy and 13
• KamLAND data is consistent with overall suppression continued running
m212
Interpretation Without LSND
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Three-generation Framework
• Standard parameterization of MNS matrix for 3 generations
€
UMNS =
Ue1 Ue2 Ue3
Uμ 1 Uμ 2 Uμ 3
Uτ 1 Uτ 2 Uτ 3
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
=
c12 s12
−s12 c12
1
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
c13 s13e−iδ
1
−s13eiδ c13
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
1
c23 s23
−s23 c23
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
atmospheric???solar
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Three-generation
• Solar, reactor, atmospheric and K2K data easily accommodated within three generations
• sin2223 near maximal m2
atm ~ 310–3eV2
• sin2212 large m2
solar ~ 710–5eV2
• sin2213=|Ue3|2< 0.05 from CHOOZ, Palo Verde
• Because of small sin2213, solar (reactor) & atmospheric oscillations almost decouple Gonzalez-Garcia, Peña-Garay
2/dof=136/173
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Seven Questions
• Dirac or Majorana? • Absolute mass scale?
• How small is 13?
• CP Violation?• Mass hierarchy?• Verify Oscillation?• LSND? Sterile neutrino(s)? CPT violation?
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Seven Questions
• Dirac or Majorana? • Absolute mass scale?
• How small is 13?
• CP Violation?• Mass hierarchy?• Verify Oscillation?• LSND? Sterile neutrino(s)? CPT violation?
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Now that LMA is confirmed...
• Dream case for neutrino oscillation physics!• m2
solar within reach of long-baseline expts• Even CP violation may be probable
– neutrino superbeam– muon-storage ring neutrino factory
• Possible only if:– m12
2, s12 large enough (LMA)– 13 large enough
€
P(ν μ → ν e ) − P(ν μ → ν e ) = −16s12c12s13c132 s23c23
sinδ sinΔm12
2
4EL
⎛
⎝ ⎜
⎞
⎠ ⎟sin
Δm132
4EL
⎛
⎝ ⎜
⎞
⎠ ⎟sin
Δm232
4EL
⎛
⎝ ⎜
⎞
⎠ ⎟
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13 decides the future
• The value of 13 crucial for the future of neutrino oscillation physics
• Determines the required facility/parameters/baseline/energy
• Two paths to determine 13
– Long-baseline accelerator neutrino oscillation– Reactor neutrino experiment with two detectors
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Shootout (Lindner)
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Seven Questions
• Dirac or Majorana? • Absolute mass scale?
• How small is 13?
• CP Violation?• Mass hierarchy?• Verify Oscillation?• LSND? Sterile neutrino(s)? CPT violation?
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Intepretation With LSND
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ν μ
ν e?
ν ep→ e+n
μ+→ e+νeν μ
p→ π +
π+→ μ+νμ
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3.3 Signal
• Excess positron events over calculated BG
P(ν μ → ν e)
=(0.264±0.067±0.045)%
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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 neutrino
New type of neutrino with no weak interaction
• 3+1 or 2+2 spectrum?
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Sterile Neutrino disfavored
• 2+2 spectrum: past fits preferred– Atmospheric mostly
– Solar mostly ea (or vice versa)
– Now solar sterile getting tight due to SNO
Disfavored 1.6 10–6 (Maltoni et al)
• 3+1 spectrum: sin22LSND=4|U4e|2|U4|2
– |U4|2 can’t be big because of CDHS, SK U/D
– |U4e|2 can’t be big because of Bugey
Disfavored 5.6 10–3 (Maltoni et al)
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PLSND<0.10% PLSND< 0.20%
P(ν μ → ν e)
=(0.264±0.067±0.045)%
More Sterile Neutrinos?
• Who said there is only one sterile neutrino?
• There could well be one for each generation
• Do more sterile neutrinos help?
• Maybe 3+2 better (Sorel, Conrad, Shaevitz)
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WMAP+2dF+Lyman Maltoni, Schwetz, Tortola, Vallehep-ph/0209368
Pierce, HMHannestad
Spergel et al
∑m<0.7eV (95%)
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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)
Best fit to data before KamLAND (Strumia)
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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.
• New CPT violation:
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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.
• However fit not good (Gonzalez-Garcia, Maltoni, Schwetz)
• MINOS atmospheric data will settle this
• New CPT violation:
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LSND not as oscillation
• Maybe LSND detected anomalous decay of muon (Babu, Pakvasa)
• Lepton-number violation• KARMEN disfavors it
– BR<0.009 (90%) while LSND wants BR=0.019–0.040
• No signal at Mini-BooNE• Predicts Michel parameter =0.74850.75• Current accuracy: =0.7518±0.0026• TWIST experiment at TRIUMF measures Michel
parameter down to a few times 10–4
€
+ → e+ν μ ν e
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Seven Questions
• Dirac or Majorana? • Absolute mass scale?
• How small is 13?
• CP Violation?• Mass hierarchy?• Verify Oscillation?• LSND? Sterile neutrino(s)? CPT violation?
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Extended Standard Model
• Massive Neutrinos Minimal SM incomplete• How exactly do we extend it?• Abandon either
– Minimality: introduce new unobserved light degrees of freedom (right-handed neutrinos)
– Lepton number: abandon distinction between neutrinos and anti-neutrinos and hence matter and anti-matter
• Dirac or Majorana neutrino• Without knowing which, we don’t know how to
extend the Standard Model
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Seesaw Mechanism
• Why is neutrino mass so small?
• Need right-handed neutrinos to generate neutrino mass
νL νR( )mD
mD
⎛
⎝ ⎜
⎞
⎠ ⎟
νL
νR
⎛
⎝ ⎜
⎞
⎠ ⎟ νL νR( )
mD
mD M
⎛
⎝ ⎜
⎞
⎠ ⎟
νL
νR
⎛
⎝ ⎜
⎞
⎠ ⎟ mν =
mD2
M<<mD
To obtain m3~(m2atm)1/2, mD~mt, M3~1015GeV (GUT!)
Neutrinos are Majorana
, but R SM neutral
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Neutrinoless Double-beta Decay
• The only known practical approach to discriminate Majorana vs Dirac neutrinos
0: nn ppe–e– with no neutrinos• Matrix element <me>=imiUei
2
• Current limit |<me>| ≤ about 1eV• m3Ue3
2<<m3 and we can typically ignore m3 • <me>=m1cos212+eim2sin212
– possible cancellation due to unknown Majorana phase
• Fortunately, they cannot cancel exactly because the maximal angle 12 excluded by SNO: cos212–sin212=cos2212>0.07 (1)
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Three Types of Mass Spectrum
• Degenerate– All three around >0.1eV with small splittings– Possible even after WMAP+2dF: m<0.23eV– May be confirmed by KATRIN, cosmology– |<me>|=|imiUei
2|>m cos2212>0.07m
• Inverted– m3~0, m1~m2~(m2
23)1/2≈0.05eV– May be confirmed by long-baseline experiment with matter effect– |<me>|=|imiUei
2|>(m223)1/2 cos2212>0.0035eV
• Normal– m1~m2~0, m3~(m2
23)1/2≈0.05eV– |<me>|=|imiUei
2| may be zero even if Majorana
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WMAP again
• WMAP constraint:– m<0.23eV each (95%CL)
• Puts upper limit on the effective neutrino mass in the neutrinoless double beta decay (Pierce, HM)
– |<me>|=|imiUei2|<imi |Uei
2|<0.23eV
– Heidelberg-Moscow: |<me>|=0.11–0.56 eV
– Reanalysis by Vogel: |<me>|=0.4–1.3 eV
Models of Flavor
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Typical Theorists’ View ca. 1990
• Solar neutrino solution must be small angle MSW solution because it’s cute
• Natural scale for m223 ~ 10–100 eV2
because it is cosmologically interesting• Angle 23 must be of the order of Vcb
• Atmospheric neutrino anomaly must go away because it needs a large angle
Wrong!
Wrong!
Wrong!
Wrong!
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Surprises
• Prejudice from quarks, charged leptons:– Mixing angles are small
– Masses are hierarchical
• In 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 medium?
big big big
big big big
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
ν e
ν μ
ν τ
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
Δmsolar2
Δmatm2 ~0.01– 0.2
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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
• Try to find underlying symmetries from data (bottom-up)– Repeat Heisenberg, Gell-Mann–Okubo
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Different Flavor Symmetries
Altarelli-Feruglio-Masina hep-ph/0210342
Hall, HM, Weiner
Sato, YanagidaVissani
Barbieri et al
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Lack of symmetry explains data
• Suppose there is no symmetry behind the neutrino masses and mixings (“anarchy”)
• Random 3 by 3 matrix• MNS matrix
distributed to the group invariant measure (Haba, HM)
3-D Kolmogorov–Smirnov test(de Gouvêa, HM)
P=68%
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Lower Bound on 13
• Anarchy predicts flat distribution in cos413
• 1D PKS= 2(1–cos413)~sin2213 for small 13
• Lower bounds:– sin2213>0.05 (95%CL)
– sin2213>0.01 (99%CL)
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Critical Measurements
• sin2 223=1.000.01?– Determines a need for a new symmetry to enforce the maximal
mixing
• sin2 213<0.01?– Determines if the flavor quantum number of electron is different
from , • Normal or inverted hierarchy?
– Most symmetries predict the normal hierarchy
• CP Violation?– Plausibility test of leptogenesis
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Dynamics behind flavor symmetry?
• Once flavor symmetry structure identified (e.g., Gell-Man–Okubo), what is dynamics? (e.g., QCD)
• Supersymmetry:–Anomalous U(1) gauge symmetry with Green-Schwarz mechanism
• Large Extra Dimensions:–Fat brane with physically separated left- and right-handed particles
• Technicolor:–New broken gauge symmetries at 100TeV scale
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Large 23 and quarks
• Large mixing between and
• Make it SU(5) GUT
• Then a large mixing between sR and bR
• Mixing among right-handed fields drop out from CKM matrix
• But mixing among superpartners physical
• O(1) effects on bs transition possible evading ebs constraints
(Chang, Masiero, HM)
• Expect CP violation in neutrino sector especially if leptogenesis (Rodejohann)
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Consequences in B physics
• Addt’l contrib to ms
• CP violation in Bs mixing (BsJ/ )
• Addt’l CP violation in penguin bs
(Bd Ks)
Very reasonable place for new physics to show up!
EPS2003 Hitoshi Murayama 63Harnik, Larson, HM, Pierce
also
Uli
Nie
rste
in H
eavy
Fla
vour
ses
sion
RR-dom case
EPS2003 Hitoshi Murayama 64
Conclusions
• Enormous progress in neutrino data– Solar neutrino problem solved!
• Still some loose ends– Many forthcoming experiments
• Three-generation oscillation very reasonable• LSND still unclear• Cosmological constraints beginning to be interesting• Next key: 13
– Long-baseline or reactor
• Neutrinos not stand alone– Need info from high-energy frontier, quark sector to address the origin
of masses and mixing
Do We Need Theorists?