Top-Down Models and UHECRs - rencontres de blois

Fragmentation of heavy particles
consider Bremsstrahlung, X → ¯f fV:
soft and collinear singularities generate terms ln 2 (m 2 V /m2 X ) for
m 2 X ≫ m2 V ⇒ compensate the small couplings g2 ,
g 2 ln 2 (m 2 X /m2 V ) ≈ 1
M X > ∼
10 6 GeV, ⇒ naive perturbation theory breaks down:
electroweak and SUSY sector have a QCD-like behavior
(“jets”)
[Berezinsky, MK ’98, Berezinsky, MK, Ostapchenko ’02 ]
Rencontres de Blois 2008 Michael Kachelrieß Top-Down Models