Directional correlations between UHECRs and neutrinos observed with IceCube

TL;DR

This study investigates directional correlations between ultra-high energy cosmic rays and neutrinos using IceCube data, finding a slight excess near UHECR directions that suggests potential common sources, with further analysis planned.

Contribution

First high-statistics analysis of UHECR-neutrino directional correlations using IceCube data, employing strict blind analysis and including external cosmic ray data.

Findings

Detected an excess of neutrino candidates near UHECR directions with 1% probability of being a random fluctuation.

Used data from IceCube 22-string configuration and external cosmic ray observatories.

Discussed extension to newer IceCube data with a likelihood approach.

Abstract

Ultra-high energy cosmic rays (UHECR) above an energy threshold of tens of EeV might undergo only small deflections due to interstellar magnetic fields. Their arrival directions would then point to regions of possible hadronic acceleration processes, which are likely to be also sources of high energy neutrinos. To search for such cosmic accelerators, we present here the first high statistics analysis of directional correlations between neutrino candidates from the IceCube Observatory and UHECR events. Data taken with IceCube in a configuration of 22 strings provided the basis for using published events from both the Pierre Auger Observatory and the HiRes experiment as reference directions in a search for coincidences with neutrinos. The analysis was optimized according to strict blindness criteria and showed an excess of neutrino candidates close to UHECR directions with a probability of 1% to occur as a random fluctuation, consistent with a background-only hypothesis. An extension of this analysis to include newer IceCube data, taken with 40 strings and using a likelihood approach, is discussed in the outlook.