By Joice Alves LONDON (Reuters) – Europe’s upcoming corporate earnings season is likely to show whether the renewed optimism about the economy that has buoyed equities in recent weeks is grounded in reality. The pan-European STOXX index is up 6% since the start of the year, hitting its highest since April after better-than-expected economic data and improved German investor sentiment. The STOXX 600 index is on course for its best January since 2019. In a sign analysts were unprepared for such optimism, Citi’s economic surprise indicator for the euro zone jumped last week to its highest since J…