Title: Impact of virtual REU experiences on students' psychosocial gains during the COVID-19 pandemic

Abstract: In the Summer of 2020, due to COVID-19, institutions either canceled or remotely hosted their Research Experience for Undergraduates (REU) programs. We carried out a 16-week longitudinal study examining the impact of these fully remote research experiences on mentees' psychosocial gains (e.g., identity). We studied the phenomenon of a remote research experience from the standpoint of the mentees ($N$=10) and their mentors ($N$=8), who were each interviewed seven and three times, respectively (94 total interviews). All mentees reported that this experience was highly beneficial through different factors and that they developed a sense of belonging, self-efficacy, and identity despite working remotely. Then, we synthesize these results with prior literature and develop a framework showing how different experiences and constructs affect the development of the physics and researcher identity. Gaining greater understanding regarding factors leading to the growth of psychosocial gains may help REU coordinators and REU mentors to re-design their undergraduate research program and provide the support that their mentees' needed to have a positive undergraduate research experience.