For what my two cents might be worth on this topic, I insist that whether or not the resurrection actually happened, is not a question that needs to concern historians for several reasons.
1. Because of biology. Dead bodies remain dead. They are not physically brought back from the dead after three days, two days, one day, or otherwise. It is a theological argument to say otherwise, and it can never be made into anything other than a theological argument.
2. If a historian studying any other person than Jesus made the claim that such-and-such person came back from the dead, what would we think of that historian? Especially if the reason to believe such a claim was because many people say they witnessed it and were willing to die for it? How many people are willing to die for things they think have happened, are happening, or will happen? This doesn't mean they have happened, are happening, or will happen. It means that human beings believe all kinds of things that didn't or can't happen, even to the point of dying for that belief. This is a psychological issue, not a historical one. By the way, in case we should forget, there were a lot of Christians who were not willing to die for their beliefs and opposed those who did.
3. I think we are asking the wrong question, and getting bogged down (yet again) in theology. What matters for the historical study of early Christianity is that the early Christians thought/believed/promoted/remembered/taught that Jesus had risen, not whether it "really" happened. It is the belief that is foundational to understand the early Christian movement. It tells us that it was an apocalyptic movement with strong eschatological factors, including the belief that Jesus' resurrection had begun the events of the last days - he had inaugurated the general resurrection (i.e. Matthew's wonderful story of the holy men and women in Jerusalem, and Paul's comment that he was the "first" to rise).
In other words, if we grant that "something" happened, that some of the early Christians experienced something, they went on to interpret it according to their Jewish expectations and traditions at hand. If we don't grant this, then we have to say they made it up, which I am less likely to think given what I have studied about religious experiences and the hermeneutical processes that follow such experiences. I continue to make detailed studies of human memory - both individual and collective - as well as the processes by which stories are created and spread within an environment dominated by an oral consciousness. All of this scientific data - if studied without theological blinders - supports the fact that stories and memories about things does not mean that the thing as it is told or interpreted actually happened the way it was told or interpreted (or happened at all)!
4. If some early Christians experienced something (after-death dream? visions? or some other naturalistic possibility?), what it meant was NOT immediately the same for all of them. Not all of them thought it was a physical-material body that they encountered. Luke tells us that some thought it was a ghost, but not him - Luke has Jesus eat a piece of fish to prove Luke's own belief in the physicality of Jesus' resurrection and to polemicize against the ghost interpretation. John does not tell us that it was a physical body, at least not the same one Jesus had before his death. It may have had some corporeality (which spiritual bodies were thought to have - see Tertullian on this), but it was also a body that could walk through walls! Paul opts for a spiritual body, not a material one, as the resurrected body, a point that later Christian Gnostics like the Valentinians point out and develop. The fleshly interpretation is one that eventually came to dominate and win the day, but it took almost two centuries for that to happen.