Recently, S. Clinchant and E. Gaussier from Xerox/Grenoble University, have developed a new information-based model for ad hoc information retrieval, from the DFR family. See below:
Stephane Clinchant and Eric Gaussier. Bridging Language Modeling and Divergence From Randomness Approaches: A Log-logistic Model for IR. ICTIR 2009, London, UK.
More details about the model can also be found in the forthcoming SIGIR 2010 paper:
Stephane Clinchant and Eric Gaussier. Information-Based Models for Ad Hoc Information Retrieval. SIGIR 2010, Geneva, Switzerland.
Gianni Amati has kindly provided an implementation of the LGD model for testing.