shower & rf theory david seckel, anita collab. mtg. nov. 24-25, /2002 theory notes on shower and...
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David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
Theory Notes on Shower and Radio Pulse
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
Outline
• Basic mechanism for Radio Cherenkov
• Coherence issues and pulse characteristics
• Types of showers
• EM shower characteristics (low E)
• EM showers at high energy
• Hadronic showers
• Codes
• Some Results
• Assessment
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
Basic mechanism
5 m
c = 56o +/- 3o
Details depend on
a) length of showerb) charge excessc) radial profile
Askaryan: Qs = Ne- - Ne+ ~ (Es/GeV)
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
Coherence issues
Consider five cases – all with the same “projected track length”
~/d Z = 1, d = 10, r = 0 P = 10
Z = 1, d = 10, r = 0 P = 10
Z = 10, d = 1, r = r0 P = 10( – 100(inf) ~0
~0 Z = 10, d = 1, r = 0 P = 100
Z = 10, d = 1, r = r0 ~0P ~ 10
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
Longitudinal and radial profiles
0 50 100 150 200
0
25
50
75
100
125
150 Avg. shower profiles from 100 GeV e’s in iceFLUKA (Clem).
red: e-
blue: e+
black: sumgreen: excess
-7.5 -5 -2.5 0 2.5 5 7.5 10
1
5
10
50
100
500
Radial Profiles.
Determined by multiple scattering, Moliere radius.
Energy dependence.
r(E) ~ 1/E (m.s. dominated by end of track)
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
Frequency/angle correlation
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
Shower Types
• Charged current events– lepton + recoil shower
– electron, mu, tau
• Neutral current events– hadronic shower
• Recoil fraction
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
1. 2. 3. 4. 5. 6.Log@EsDHPeVL- 3.
- 2.
- 1.
0.
1.
2.
goL@V ffeDHmk3 L
• LPM effect – lengthens shower, by say f, then
• Hadronic showers interactions compete with decay
High energy showers, above a few PeV
Z = 10, d = 1, r = r0 ~0/f P ~ 10/f
With LPMWithout LPM
“Hadronic”Es = 20% E
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
Codes
• Zas, Halzen, Stanev
• “Santiago” group, Zas, Alvarez-Muniz,… (LPM, Hadronic), high energy sampling techniques.
• GEANT 3.2.1 (under estimates track length, unless special care is taken)
• GEANT 4
• FLUKA
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
Simulation issues
• Normalization (ok, now (10%), at low energies)
• Spectrum – some disagreement between ZHS analytic form and preliminary GEANT results
• Fluctuations – dominated by first few interactions (or LPM effects)
• Do we really understand LPM?
• Summing hadronic and EM showers?
• Magnetic fields ?
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
SpectrumS. Seunerine: preliminary
by eye.
ZHS
ZHS
by eye.
f 11ff02 f 1
1ff0
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
Spectrum II
From Francis From Zed
David Seckel, ANITA Collab. Mtg. Nov. 24-25, /2002
Shower & RF theory
Fluctuations
Also: interference between hadronic and electromagnetic