High energy physics from 10 billion years' worth of data: Learning new physics from the Big Bang, stars and cosmic rays

Details High energy physics from 10 billion years' worth of data: Learning new physics from the Big Bang, stars and cosmic rays High energy physics from 10 billion years' worth of data: Learning new physics from the Big Bang, stars and cosmic rays

Sep 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002phdt........22p&link_type=abstract

Thesis (PhD). UNIVERSITY OF CALIFORNIA, LOS ANGELES, Source DAI-B 63/03, p. 1408, Sep 2002, 80 pages.

Physics

Scientific paper

Improving astroparticle data present an opportunity to learn new physics from a variety of processes that took place in the early universe and those that continue at present. My thesis will cover several lines of research in this rapidly developing field. Sources of ultrahigh energy photons operating at high red shift produce a diffuse background of neutrinos. At high red shift, when the cosmic microwave background radiation has a higher temperature, an electromagnetic cascade originated by an energetic photon can generate neutrinos via muon and pion production and decay. In chapter 2 we describe this process in detail. We present the results of a numerical calculation of the spectrum of cascade neutrinos produced by various photon sources. A distinctive feature of the produced flux is a “bump” in the spectrum at neutrino energies E ˜ 1017 1018 eV. The produced flux is largest for m = 3 sources (e.g. necklaces), with E2J(E) ˜ 1 eV cm-2 s-1 sr-1 at these energies. The neutrino flux is probably too small to be detected in the near future. Neutrino production by matter with a time-dependent density or velocity is the subject of chapter 3. Both ordinary matter and nuclear matter found in neutron stars carry a net SU(2) charge. Neutrinos couple to this charge through the electroweak interactions. In a time-dependent background this leads to neutrino pair-production, analogous to particle production by a time-varying gravitational field. Due to the smallness of all scales involved, the effect is small in all physical situations. Nevertheless, the results are quite interesting, as neutrino production is a fully non- perturbative process: production can occur even if it is perturbatively forbidden for kinematical reasons. In chapter 4 we study Q-ball formation in the early universe, concentrating on potentials with a cubic or quartic attractive interaction. Large Q-balls can form via solitosynthesis, a process of gradual charge accretion, provided some primordial charge asymmetry and initial “seed” Q-balls exist. We find that such seeds are possible in theories in which the attractive interaction is of the form AHχ*χ, with a light “Higgs” mass. Q-ball formation through fragmentation of a Bose-Einstein condensate is only possible for masses mψ in the sub-keV range. For both production mechanisms the parameter space for successful Q-ball formation is rather constraint. Q-balls that survive until present can be the, possibly self- interacting, dark matter in the universe.

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