This article let you know who deleted Application in CA Dseries?
Release : All Supported Versions
Go to the repective trace log and filter with "deleteArtifact" which will promote as below(check the application if its the one which you are looking for)see the userId(It would be the user who has deleted the App).
20211210 09:01:22.743 [facade:request] [INFO] RMI TCP Connection(3514)-xx.xx.xxx.xxx: [2021-12-10_09:01:22.742] AmsFacade.deleteArtifact() request: userToken=[UserToken[userId=X014353,tokenId=1132152991835001856]], artifactType=[APPLICATION], identifier=XXX_R3_ALL_CLRM_LAB_PARALLEL_PROCESS