July 23: Tanmay Vachaspati

Title: Search for CP Violation in the Gamma Ray Sky
Time: 2pm
Place: 4N9
 
Abstract: Motivated by the possible existence of a cosmological magnetic field with non-trivial
helicity, we evaluate a CP odd statistic, $Q$, using gamma ray data obtained from
Fermi satellite observations at high galactic latitudes. Observed values of $Q$ arefound to be non-zero at the $2\sigma$ level ($3\sigma$ in the northern hemisphere)and also deviate at the same level from values obtained from simulated data. Contaminationfrom the Milky Way does not seem to be responsible for the excess since the signal ispresent even for data at very high galactic latitudes. Assuming that the excess is indeeddue to a helical cosmological magnetic field, our results indicate left-handed magnetic helicityand field strength $\sim 10^{-14}~{\rm G}$ on $\sim 10~{\rm Mpc}$ scales.