Neutrino phenomenology Lecture 3: Aspects of neutrino astrophysics
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Transcript of Neutrino phenomenology Lecture 3: Aspects of neutrino astrophysics
Neutrino phenomenologyLecture 3: Aspects of neutrino astrophysics
Winter school Schladming 2010“Masses and constants”02.03.2010
Walter WinterUniversität Würzburg
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Contents (overall)
Lecture 1:Testing neutrino mass and flavor mixing
Lecture 2:Precision physics with neutrinos
Lecture 3:Aspects of neutrino astrophysics
3
Contents (lecture 3)
Introduction/repetition Solar oscillations (varying matter density) Neutrinos from cosmic accelerators … and the
determination of „other“ neutrino properties: The sources The fluxes Flavor composition and propagation Detection Flavor ratios Compementarity to Long baseline searches? Test of „other“ new physics properties
Example: Neutrino lifetime Summary
4
Nobel prize 2002
"for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos“
Raymond Davis Jr detected over 30 years 2.000 neutrinos from the Sun Evidence for nuclear fusion in the Sun‘s interior!
Masatoshi Koshiba detectedon 23.02.1987 twelve of the 10.000.000.000.000.000 (1016) neutrinos, which passed his detector, from an extragalactic supernovaexplosion. Birth of neutrino astronomy
Repetition
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Standard Solar Model
Neutrinos are produced as electron neutrinos at the source, in the deep interior of the Sun
Neutrinos propagate to the surface of the Sun and leave it
The neutrinos loose coherence on the way to the Earth, i.e., propagate as mass eigenstates
pp-fusion chain Neutrino spectra
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Matter effects (MSW) Ordinary matter:
electrons, but no , Coherent forward
scattering in matter: Net effect on electron flavor
Matter effects proportional to electron density ne and baseline
Hamiltonian in matter (matrix form, two flavors):
Y: electron fraction ~ 0.5
(electrons per nucleon)
(Wolfenstein, 1978; Mikheyev, Smirnov, 1985)
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Parameter mapping In vacuum:
In matter:
Neutrino oscillations in the Sun
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Constant vs. varying matter density
For constant matter density:
H is the Hamiltonian in constant density
For varying matter density: time-dep. Schrödinger equation (H explicitely time-dependent!)
Transition amplitudes; x: mixture and
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Adiabatic limit
Use transformation:
… and insert into time-dep. SE […]
Adiabatic limit:
Matter density varies slowly enough such that differential equation system decouples!
Amplitudes of mass eigenstates in matter
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Propagation in the Sun Neutrino production as e (fusion) at high ne
Neutrino propagates as mass eigenstate in matter (DE decoupled); : phase factor from propagation
In the Sun: ne(r) ~ ne(0) exp(-r/r0) (r0 ~ Rsun/10); therefore density drops to zero!
Detection as electron flavor:Disappearance
of solarneutrinos!
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Solar oscillations In practice: A >> 1 only for E >> 1 MeV For E << 1 MeV: vacuum oscillations
Galbiati, Neutrino 2008
Averaged vacuumoscillations:
Pee=1-0.5 sin22
AdiabaticMSW limit:
Pee=sin2~ 0.3Standardprediction
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Some additional comments… on stellar environments
How do we know that the solarneutrino flux is correct?SNO neutral current measurement
Why are supernova neutrinos so different?Neutrino densities so high that neutrino-self
interactionsLeads to funny „collective“ effects, as gyroscope
B. Dasgupta
Neutrinos from cosmic accelerators
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galactic extragalactic
Neutrino fluxes
Cosmic rays of high energies:Extragalactic origin!?
If protons accelerated, the same sources should produce neutrinos
(Source: F. Halzen, Venice 2009)
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Different messengers
Shock accelerated protons lead to p, , fluxes p: Cosmic rays:
affected by magnetic fields
(Te
resa
Mo
nta
ruli, N
OW
2008)
: Photons: easily absorbed/scattered : Neutrinos: direct path
18
Different source types
Model-independent constraint:Emax < Z e B R(Lamor-Radius < size of source)Particles confined to
within accelerator!
Interesting source candiates: GRBs AGNs …
(Hillas, 1984; version from M. Boratav)
(?)
The sources
Generic cosmic accelerator
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From Fermi shock acceleration to production
Example: Active galaxy(Halzen, Venice 2009)
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Synchroton radiation
Where do the photons come from?Typically two possibilities: Thermal photon field (temperature!) Synchroton radiation from
electrons/positrons (also accelerated)
?
(example from Reynoso, Romero, arXiv:0811.1383)
B
~ (1-s)/2+1determined by spectral index s of injection
Determined by particle‘s
minimum energy Emin=m c2
(~ (Emin)2 B )
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Pion photoproduction
(Photon energy in nucleon rest frame)
(Mücke, Rachen, Engel, Protheroe, Stanev, 2008; SOPHIA)
Resonant production,
direct production
Multi-pionproduction
Differentcharacteristics(energy lossof protons)
Powerlaw injection
spectrumfrom Fermishock acc.
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Pion photoproduction (2) Often used: (1232)-resonance approximation In practice: this
resonance hardly ever dominates for charged pions. Example: GRB
The neutrino fluxes from the -approximation are underestimated by a factor > 2.4 (if norm. to photons from 0)
(Hümmer, Rüger, Spanier, Winter,
2010)
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Neutrino production
Described by kinematics of weak decays(see e.g. Lipari, Lusignoli, Meloni, 2007)
Complication:Pions and muons loose energy through synchroton radiation for higher E before they decay – aka „muon damping“
(example from Reynoso, Romero,
arXiv:0811.1383)
Dashed:no lossesSolid:with losses
The fluxes
Single source versus diffuse flux versusstacking
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Neutrinos from a point source
Example: GRBs observed by BATSE
Applies to other sources in atmosphericBG-free regime as well …
Conclusion: Most likely (?) no significant statistics with only one source!
(Guetta et al, astro-ph/0302524)
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Diffuse flux (e.g. AGNs)
Advantage: optimal statistics (signal)
Disadvantage: Backgrounds(e.g. atmospheric,cosmogenic)
(Becker, arXiv:0710.1557)
Single sourcespectrum
Sourcedistributionin redshift,luminosity
Comovingvolume
Decreasewith
luminositydistance
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Stacking analysis Idea: Use multi-messenger approach
Good signal over background ratio, moderate statistics
Limitations: Redshift only measured for
a small sample (BATSE) Use empirical relationships
A few bursts dominate the rates Selection effects?
(Source: NASA)
GRB gamma ray observations(e.g. BATSE, Fermi-GLAST, …)
(Source: IceCube)
Neutrino observations
(e.g. AMANDA,IceCube, …)
Coincidence!
(Becker et al, astro-ph/0511785;from BATSE satellite data)
Extrapolateneutrino spectrum
event by event
Flavor composition and propagation
Neutrino flavor mixing
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Astrophysical neutrino sources producecertain flavor ratios of neutrinos (e::):
Pion beam source (1:2:0)Standard in generic models
Muon damped source (0:1:0)Muons loose energy before they decay
Neutron beam source (1:0:0)Neutrino production by photo-dissociationof heavy nulcei
NB: Do not distinguish between neutrinos and antineutrinos
Flavor composition at the source(Idealized)
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Pion beam source (more realistic)
(Hümmer, Rüger, Spanier, Winter, 2010;
see also Lipari, Lusignoli, Meloni, 2007)
Nominal line 1:2
Neutrondecays
Kinematics ofweak decays: muon helicity!
32
Flavor composition at the source(More realistic)
Flavor composition changes as a function of energy
Pion beam and muon damped sources are the same sources in different energy ranges!
Use energy cuts?
(from Kashti, Waxman, astro-ph/0507599;see also: Kachelriess, Tomas, 2006, 2007;
Lipari et al, 2007 for more refined calcs)
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Neutrino propagation
Key assumption: Incoherent propagation of neutrinos
Flavor mixing: Example: For 13 =0, 12=/6, 23=/4:
NB: No CPV in flavor mixing only!But: In principle, sensitive to Re exp(-i ) ~ cos
Take into account Earth attenuation!
(see Pakvasa review, arXiv:0803.1701,
and references therein)
The detection
Neutrino telescopes
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High-E cosmic neutrinos detected with neutrino telescopes
Example: IceCube at south poleDetector material: ~ 1 km3 antarctic ice (1 million m3)
Short before completion
IceCube
http://icecube.wisc.edu/
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Neutrino astronomy in the Mediterranean: Example ANTARES
http://antares.in2p3.fr/
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Different event types
Muon tracks from Effective area dominated!(interactions do not have do be within detector)Relatively low threshold
Electromagnetic showers(cascades) from eEffective volume dominated!
Effective volume dominated Low energies (< few PeV) typically
hadronic shower ( track not separable) Higher Energies:
track separable Double-bang events Lollipop events
Glashow resonace for electron antineutrinos at 6.3 PeV (Learned, Pakvasa, 1995; Beacom et
al, hep-ph/0307025; many others)
e
e
Flavor ratios
… and their limitations
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Definition
The idea: define observables which take into account the unknown flux normalization take into account the detector properties
Three observables with different technical issues: Muon tracks to showers
(neutrinos and antineutrinos added)Do not need to differentiate between electromagnetic and hadronic showers!
Electromagnetic to hadronic showers(neutrinos and antineutrinos added)Need to distinguish types of showers by muon content or identify double bang/lollipop events!
Glashow resonance to muon tracks(neutrinos and antineutrinos added in denominator only). Only at particular energy!
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Applications of flavor ratios
Can be sensitiveto flavor mixing,neutrino properies
Example: Neutron beam
Many recent works inliterature
(e.g. for neutrino mixing and decay: Beacom et al 2002+2003; Farzan and Smirnov, 2002; Kachelriess, Serpico, 2005; Bhattacharjee, Gupta, 2005; Serpico, 2006; Winter, 2006; Majumar and Ghosal, 2006; Rodejohann, 2006; Xing, 2006; Meloni, Ohlsson, 2006; Blum, Nir, Waxman, 2007; Majumar, 2007; Awasthi, Choubey, 2007; Hwang, Siyeon,2007; Lipari, Lusignoli, Meloni, 2007; Pakvasa, Rodejohann, Weiler, 2007; Quigg, 2008; Maltoni, Winter, 2008; Donini, Yasuda, 2008; Choubey, Niro, Rodejohann, 2008; Xing, Zhou, 2008; Choubey, Rodejohann, 2009; Bustamante, Gago, Pena-Garay, 2010, …)
(Kachelriess, Serpico, 2005)
Complementarity to long-baseline experiments
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Oscillation probability of interest to measure 13, CP, mass hierachy (in A)
Appearance channels
(Cervera et al. 2000; Akhmedov et al., 2004)
Almost zerofor narrow band superbeams
43
Flavor ratios: Approximations
Astro sources for current best-fit values:
Superbeams:
(Source: hep-ph/0604191)
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SB-Reactor-Astrophysical
Complementary information for specific best-fit point:
Curves intersect in only one point!
(Winter, 2006)
Particle properties
… from flavor ratios (examples)
see Pakvasa, arXiv:0803.1701 for a review of other examples: mass varying neutrinos, quantum decoherence, Lorentz/CPT violation, …
46
Constraining CP
No CP in Reactor exps Astro sources
(alone)
Combination:May tell something on CP
Problem: Pion beam has little CP sensitivity!
(Winter, 2006)
47
Neutrino lifetime Neutrino flux (oscillations averaged):
i(E)=0 E/m: lab frame lifetime of mass eigenstate i
Strongest bound from SN1987A: /m > 105 s/eV on e
Lifetime refers to mass eigenstates, but flavor eigenstates are observed Unclear if bound on 1 or 2
Astrophysical neutrinos probably best direct test of neutrino lifetime
Distinguish: Complete decays: L >> i(E) Incomplete decays: L <~ i(E)
48
R
Complete decays
Using the observables R and S, some complete decay scenarios can be excluded!
99% CLallowed regions
(present data)
(Maltoni, Winter, 2008)
1
1
Unstable
Stable
R
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Incomplete decays
Decay into 1 with /m ~ 0.1:
Bhattacharya, Choubey, Gandhi, Watanabe, 2009
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Summary and conclusions
Matter effects in the Sun tests Neutrino oscillations in vacuum MSW effect Standard solar model
The observation of astrophysical neutrinos is important for Identification of cosmic ray accelerators Test of source properties Test of neutrino properties
Literature: e.g. Giunti, Kim: Fundamentals of neutrino physics and astrophysics, Oxford, 2007
51
Limitations of flavor ratios
Flavor ratios dependon energy if energylosses of muonsimportant
Distributionsof sources oruncertainties withinone source
Unbalanced statistics:More useful muontracks than showers
(Lipari, Lusignoli, Meloni, 2007; see also:
Kachelriess, Tomas, 2006, 2007)
52
Complementarity LBL-Astro
Superbeams have signal ~ sin CP
(CP-odd) Astro-FLR have
signal ~ cos CP (CP-even)
Complementarity for NBB
However: WBB, neutrino factory have cos-term!
(Winter, 2006)
Smallestsensitivity
53
Neutrino decays on cosmological distances?
23 possibilities for complete decays
Intermediate states integrated out
LMH: Lightest, Middle, Heaviest
I: Invisible state(sterile, unparticle, …)
123: Mass eigenstate number(LMH depends on hierarchy)
(Maltoni, Winter, 2008; see also Beacom et al 2002+2003; Lipari et al 2007; …)
H ?LM
#7a 1-a
1-b
b