  The task of Cross-document Coreference Resolution has been traditionally
formulated as requiring to identify all coreference links across a given set of
documents. We propose an appealing, and often more applicable, complementary
set up for the task - Cross-document Coreference Search, focusing in this paper
on event coreference. Concretely, given a mention in context of an event of
interest, considered as a query, the task is to find all coreferring mentions
for the query event in a large document collection. To support research on this
task, we create a corresponding dataset, which is derived from Wikipedia while
leveraging annotations in the available Wikipedia Event Coreference dataset
(WEC-Eng). Observing that the coreference search setup is largely analogous to
the setting of Open Domain Question Answering, we adapt the prominent Deep
Passage Retrieval (DPR) model to our setting, as an appealing baseline.
Finally, we present a novel model that integrates a powerful coreference
scoring scheme into the DPR architecture, yielding improved performance.
