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