Context : Rich clusters offer a unique laboratory for studying the effects of local environment on the morphological transformation of galaxies moving from the blue star-forming cloud to the red passive sequence .
Due to the high-density , any environmental process should be more pronounced there compared to the field population .

Aims : Ideally , we would like to reconstruct the evolution of a single , hypothetical representative galaxy as it enters the cluster .
For that purpose wide-field imaging is crucial to probe a wide range of densities and environments ( from the core to the outskirts ) and isolate this way , the different physical processes which are responsible of the migration from the blue-cloud to the red-sequence .

Methods : We analyze a sample of 9 massive clusters at 0.4 < z < 0.6 observed with MegaCam in 4 photometric bands ( g , r , i , z ) from the core to a radius of 5 Mpc ( \sim 4000 galaxies ) .
Galaxy cluster candidates are selected using photometric redshifts computed with HyperZ .
Morphologies are estimated with galSVM in two broad morphological types ( early-type and late-type ) .
We examine the morphological composition of the red-sequence and the blue-cloud and study the relations between galaxies and their environment through the morphology-density relations ( T - \Sigma ) and the morphology-radius relation ( T - R ) in a mass limited sample ( log ( M / M _ { \odot } ) > 9.5 ) .

Results : We find that the red sequence is already in place at z \sim 0.5 and it is mainly composed of very massive ( log ( M / M _ { \odot } ) > 11.3 ) early-type galaxies .
These massive galaxies seem to be already formed when they enter the cluster , probably in infalling groups , since the fraction remains constant with the cluster radius .
Their presence in the cluster center could be explained by a segregation effect reflecting an early assembly history .
Any evolution that takes place in the galaxy cluster population occurs therefore at lower masses ( 10.3 < log ( M / M _ { \odot } ) < 11.3 ) .
For these galaxies , the evolution , is mainly driven by galaxy-galaxy interactions in the outskirts as revealed by the T - \Sigma relation .
Finally , the majority of less massive galaxies ( 9.5 < log ( M / M _ { \odot } ) < 10.3 ) are late-type galaxies at all locations , suggesting that they have not started the morphological transformation yet even if this low mass bin might be affected by incompleteness .

Conclusions :