Probing Planck scale physics with IceCube

Neutrino oscillations can be affected by decoherence induced e.g. by Planck scale suppressed interactions with the space-time foam predicted in some approaches to quantum gravity. We study the prospects for observing such effects at IceCube, using the likely flux of TeV antineutrinos from the Cygnus spiral arm. We formulate the statistical analysis for evaluating the sensitivity to quantum decoherence in the presence of the background from atmospheric neutrinos, as well as from plausible cosmic neutrino sources. We demonstrate that IceCube will improve the sensitivity to decoherence effects of $\mathcal{O}(E^2/M_{\mathrm{Pl}})$ by 17 orders of magnitude over present limits and, moreover, that it can probe decoherence effects of $\mathcal{O}(E^3/M_{\mathrm{Pl}}^2)$ which are well beyond the reach of other experiments.

Figure 1

Skymap of correlated event excess significance ($\sigma$) from all HEGRA IACT-System data ($3°\times 3°\mathrm{FoV}$) centered on the TeV source $\mathrm{J}2032\text{}+\text{}4130$. Nearby objects are also shown: 95% contours for 3 EGRET sources (indicated by the ovals), their possible x ray associated counterparts (as given in Ref. 53), and Cygnus X-3. The center of gravity with statistical errors and intrinsic size (standard deviation of a 2-dim Gaussian, ${\sigma }_{\mathrm{src}}$) are indicated by the white cross and white circle, respectively. The TeV source, $\mathrm{J}2032\text{}+\text{}4130$, is positioned at the edge of the error circle of the EGRET source 3EG $\mathrm{J}2033\text{}+\text{}4118$, and within the core circle of the extremely dense OB stellar association Cygnus OB2 [16].

Figure 2

The integrated neutron flux expected from Cygnus OB2 (dash-dotted line) is superimposed over the integrated fluxes observed from the Cygnus region by the Fly’s Eye [9] and AGASA [10, 23] experiments. Also shown is the $\gamma$-ray flux reported by the HEGRA experiment [16] and the upper limits on neutral particles derived from the CASA-MIA [11] and KASCADE [12] experiments. The solid line is a fit to the HEGRA data and the dashed line is the extrapolation to unobserved energies.

Figure 3

Integrated flux of ${\overline{\nu }}_{\mu }+{\overline{\nu }}_e+{\overline{\nu }}_{\tau }$ (solid line) predicted to arrive at Earth from the direction of the Cygnus region. Also shown are the integrated ${\nu }_{\mu }+{\overline{\nu }}_{\mu }$ and ${\nu }_e+{\overline{\nu }}_e$ atmospheric fluxes for an angular bins of $1°\times 1°$ and $10°\times 10°$, respectively. The shaded band indicates the region excluded by the AMANDA experiment [54]. The fluxes of neutrinos inferred from HEGRA measurements of the $\gamma$-ray flux are also shown: the lower line is based on the assumption of $p\gamma$ interactions, whereas the upper line is based on $pp$ interactions (the charged/neutral pion-production ratio depends on the interaction). In each case the solid portion of the line indicates the region where HEGRA data is available and the dashed part is an extrapolation to unobserved energies.

Figure 4

IceCube’s sensitivity to quantum decoherence assuming ${\mathcal{N}}_{\mathrm{obs}}^{\mathrm{tr}}=62$ tracking events and ${\mathcal{N}}_{\mathrm{obs}}^{\mathrm{sh}}=72$ showering events from Cygnus. The regions above and to the right of the solid, dashed and dotted lines can potentially be excluded at 90%, 95%, and 99% confidence level, respectively.