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