Cosmic neutrinos and new physics beyond the electroweak scale

Abstract

New physics beyond the electroweak scale may increase weak interaction cross sections beyond the Standard Model predictions. Such cross sections can be expected within theories that solve the hierarchy problem of known interactions with a unification scale in the TeV range. We derive constraints on these cross sections from the flux of neutrinos expected from cosmic ray interactions with the microwave background and the non-observation of horizontal air showers. We also discuss how this limit can be improved by upcoming cosmic ray and neutrino experiments, and how the energy dependence of the new interactions can be probed by these experiments.PACS numbers: 12.60. 95.30.Cq, 98.70.Sa

Neutrino bounds on astrophysical sources and new physics

“…Bounds on anomalous νN cross sections which are near-hadronic strength can be obtained through considerations of their feedback to low energy physics via dispersion relations [41]. The bounds shown in Table II strengthen previous bounds [7] by roughly one order of magnitude. This enhancement results from a number of factors.…”

“…Second, the cosmogenic flux used in Ref. [7] assumes a source cutoff energy of 10 11.5 GeV, and is smaller by roughly a factor of 4 than the one used here. We find it unnatural to assume that the the source cutoff coincides with the maximum observed cosmic ray energy, and so have used the flux corresponding to the larger cutoff energy.…”

“…First, the exposure used in Ref. [7] was limited to the first 6 × 10 6 s of Fly's Eye operation. The updated exposure used here is roughly 9 times larger.…”

“…IV we derive model-independent bounds on high energy neutrino cross sections, assuming a conservative cosmogenic flux. These significantly improve existing limits [7]. We then derive model-dependent bounds on cross sections, focusing on the example of TeV-scale gravity scenarios in Sec.…”

Status of particle physics solutions to the UHECR puzzle

“…Nevertheless, both cases offer future experiments exciting possibilities: the discovery of the relic neutrino background and, perhaps, a measurement of the absolute neutrino masses via the Z burst mechanism, or the discovery of new contributions to the neutrino-nucleon interaction in horizontal EAS [32,36].…”