1. A method of performing cross-lingual information retrieval, the method comprising: translating a query q s ={w s1 ,. .. , w sl } in a source natural language represented as a starting query language model P(w s |q s ) in the source natural language into a target natural language different from the source natural language to generate a starting query in the target natural language, wherein P(w s |q s )=0 for words w s that are not in the query q s ={w s1 ,. .. , w sl }; performing a first information retrieval operation on a corpus of documents in the target natural language by inputting the starting query in the target natural language to a monolingual information retrieval system configured to operate in the target natural language in order to retrieve a set of pseudo-feedback documents in the target natural language; generating an updated query in the target natural language represented as an updated query language model p(w t |q s ) in the target natural language computed as: p ⁡ ( w t | q s ) = ∑ w s ⁢ θ st adapted ⁢ P ⁡ ( w s | q s ) where θ st adapted represents a translation model generated by maximizing a likelihood of the set of pseudo-feedback documents in the target natural language given the starting query language model P(w s |q s ) in the source natural language using an expectation maximization (EM) algorithm with the starting query in the target natural language as the starting translation model; and performing a second information retrieval operation on the corpus of documents in the target natural language by inputting the updated query in the target natural language to the monolingual information retrieval system in order to retrieve an updated set of documents in the target natural language; wherein the method of performing cross-lingual information retrieval is performed by a computer.