When translating research papers from Arabic to English, should I translate the Arabic sources (book titles, etc.) to English, or should I leave them in Arabic?
I will argue that, for maximum usefulness to your readers, you should do both. In other words, put both the original and the translation in the entry, e.g. either:
English citation (original: Arabic citation)
Arabic citation (translation: English citation)
I don't see either of these are being particularly dominant over the other. Both, however, allow one to both trace the original and know what it is without speaking Arabic.
Note that I would believe this answer should apply to any translation between languages. It is most critical, however, when the writing systems are incompatible, e.g., Arabic, Roman-character languages, South Asian languages, Chinese, etc.