D. Seckel, Univ. of Delaware Mar 9, 2005 GZK Neutrinos Theory and Observation
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D. Seckel, Univ. of Delaware
Mar 9, 2005
GZK NeutrinosTheory and Observation
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Topics
• “Theory”– UHECR - overview– GZK neutrinos (Engel, Seckel, Stanev)– Model choices and parameters– GZK neutrinos and UHECR spectrum (with TS)
• Detection issues– Radio detection
• Rates– Scaling of Askaryan pulses– HE interactions
• Event Topology (old picture)• New considerations (Scales, LPM, dE/dX)
– Scaling dE/dX– Photonuclear– Pair Production– LPM issues– Line radiation
• Expectaions for e, at PeV, EeV, ZeV
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Start with cosmic rays
• Composition• Spectrum• Source• Propagation• History
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UHECR
• AGASA - • HiRes -
• + Propagation
UHECR Models:
Quantity Behaviour Cutoffbreak qm 1 zm zmax
d N
d pp1 cut
d d p
Aqmp1
qtq H0q52 1 13
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Propagation
• UHECR with E > 5 1019 are young (<0.01 t0)
• + Magnetic fields: Could be diffusive, Old and Local?
Interactions with CMBR
Reaction Threshold EE ee few Mpc me
2
T1
p pee 100kpc?memp
T
memp
p n, p0, BX 5Mpcmmp
T
mmp
n p, n0, BX 5Mpcmmp
T
mmp
n pee E
1020 Mpc memp
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UHECR puzzles
• Sources young, but no candidates. (AGASA: clustering?)
• Solutions– Bad data (my personal favorite)– Stable penetrating particle– Diffuse source (particle decay?)– Local source + magnetic fields
• More Data– Build Pierre Auger Obs.– But degeneracy of models
a) Flat spectrum, evolution, galactic contribution
b) Steep spectrum, no evolution, no galaxy
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GZK Neutrino production I
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GZK neutrino production II
Production kinematics and scaling:a) Go to center of mass frame sp pp2 p2 pp2 2pp p mp
2 2p1 cos b) Boost by Epmp back to the lab framec) For a given value of s, the boost is s
mpT
d) For a power law spectrum, the neutrino yield scales with redshift
Ed y
dEE, p, t Ed y0
dEq2E, qp
Now, just do the integral over epoch...
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Simple scaling of GZK
• Spectrum: (Ep)-(1+)
• Evolution (1+z)m
• Matter dominated cosmology (1+z)-5/2
• Spacing q = 1 dB
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Neutrinos break degeneracy
a) Flat spectrum, evolution, galactic contribution
b) Steep spectrum, no evolution, no galaxy
c) Cutoffs, Lambda…
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Neutrino Detection
Atmospheric 1-100 GeV
Astro-Sources0.1 TeV - 10 PeV
GZK +0.1-10 EeV
50 m
500 km
1 km
5 km
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-p cross-section
Interaction Rel. Strength Hadronic? yH Lepton yLCC 1 yes 0.2 yes 0.8NC 12 yes 0.2 no
5% in 3 km salt
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Shower Rate per km3
5 6 7 8 9 10 11 12log Esh
0
0.002
0.004
0.006
0.008
ENdEdmk
3ry1
Shower rate : ESS GZK , isoflavor , 1lepton CC black , NCCC hadronic red5 6 7 8 9 10 11 12log Esh
0
0.002
0.004
0.006
0.008
ENdEdmk
3ry1
Shower rate : ESS GZK , pure e, 1lepton CC black , NCCC hadronic red
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Radio Detection of Showers
Askaryan: Coherent radiation
• S ~ Q ~ 0.25 Es/GeV• ~ RM ~ 10 cm• /l ~ 3 deg• Confirmed by
– SLAC T444, Saltzberg et al. PRL 2001
– SLAC T460, Gorham et al. 2002
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Scaling behavior
fractional excess
Single particle & shower signals
Includes LPM effect
z
y
c
to observer
ivt
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RF spectrum
Field calculation is integral over shower profile
Separation of shower profile
Separation of form factors
With scaled frequencies• Adapted from Alvarez, Vazquez, Zas• “Full sim” is approx a
• Blue – Gaussian for f(z), AVZ approx c for Gy
• Red – Griessen for f(z)
Separation of phase factors
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Phases I
• ZHS phase?• gaussian profile symmetric – no phase in g(z)• Realistic shower profiles should have phases• Proposal: use phases based on RSBMRS
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Phases II
-20 -10 0 10 20z
0
0.2
0.4
0.6
0.8
1
z
Greissenredvs Gaussianshower profile
0 50 100 150 200freq
0
0.2
0.4
0.6
G z
GreissenGaussian ProfilesSpectral composition
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Radio Event Topology: Old Picture
Particle PeV EeVe Shower LPMnarrows C cone not visible not visible 50mdecay 50 km decay Non intracting Non interacting
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New Considerations (dE/dX)
Scenario XlepkmweXRF Aperaturekm3H XEdEdXRICE 1 10 10att 100 5, 60 0.1 1
ANITA 10 2geom103 105 5, 5 1
SALSA 10 10geom103 104 5, 90 1
X RICE 1 10 10att103 104 5, 90 0.1 1
Particle Concern Change in thoughte LPM N, e, pp
dEdX few 106 pergmcm2 3km salt
dEdX 0.1
2nd interaction P2EeV102
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Scaling of dE/dX
Brem Pair PhotoNuclear y
e 1 1 1
mem2me
m2 1
mem2me
m2 1
y 1
memme
m?
memme
m?
y Ns Ns 1
Nsm Ns
m1
Nsm Ns
m
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Photonuclear review I
2 3 4 5 6 7 8 9LogEGeV
0.1
0.2
0.5
1
2
5
10
016 mc
2 g
Standard Rock , vs
2 3 4 5 6 7 8 9LogEGeV
0.2
0.5
1
2
5
10
0172
mc2
Standard Rock , vs
Comments
• From DRSS• 10-6 = 3km salt•
– y-distribution important
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Photonuclear review II
Contributions to pn for ml.01 to 1000 , 103108
-6 -5 -4 -3 -2 -1 0logy0
0.0250.050.0750.1
0.1250.15
-6 -5 -4 -3 -2 -1 0logy0
0.00250.005
0.00750.01
0.01250.015
0.0175
-6 -5 -4 -3 -2 -1 0logy0
0.000250.00050.000750.001
0.001250.00150.00175
-6 -5 -4 -3 -2 -1 0logy0
0.51
1.52
2.53
-6 -5 -4 -3 -2 -1 0logy0
0.5
1
1.5
2
-6 -5 -4 -3 -2 -1 0logy0
0.2
0.4
0.6
0.8
• ~ /(+mlep)
• <y> ~ /(+mlep)
• Growth with due to growth in photon cross-section (QCD) with E
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Pair Production
• From LKV
• ~ 1/mlep
• <y> ~ me/mlep ?
• Quasi-continuous 2 3 4 5 6 7 8 9LogEGeV
0.010.02
0.050.10.2
0.512
016
mgmc2
pair for ,
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LPM issues
• Is reduction in eN-eN N-Nee the whole story ?
• N (see S. Klein)
– Convert energy to hadronic shower
• eN-eNX ,(1019 eV?), eN-eNee (1020 eV (lpm?))
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Line radiation (just like SLAC salt stack !?)
• Showers vs radiation from a moving “charge”
• Coherence region along track
• Lumpy?
Ld 103cm
Eeff L dE
d X 103E
Lpair few 103cm ?
L
d
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Expectations
PeV: Threshold dominated, e initiated showers, CC events dominateEeV: LPMreduces signal from e. CC NC Hadronic comparableZeV: CC produced e may convert to hadronic via N or eN
PeV: Threshold dominated, initiated showers difficult, NC CC hadronic events dominateEeV: CC NC hadronic recoil showers. B, pn at 0.1E possible
ZeV: B, pn at 0.1E important. CC NC hadronic recoil showers present. pair
may allow reconstruction of the track withEeff EeV, a` la optical cerenkov
PeV: Threshold dominated. NC CC hadronic events barely visible.decay complicates50msignal. initiated showers unikely.
EeV: CC NC hadronic recoil showers. decay at 50 km is second source.
B unlikely, pn at 0.02E possible
ZeV: CC NC hadronic recoil showers present. decay is second source.
B unlikely. pn possible, tracks unlikely.
e
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