/sci/ - Science & Math

>be me an undergrad doing research in extremal combinatorics.
>going into my senior year so I started emailing some professors to see if I could do research with them for my capstone (graduation requirement)
>no responses after a month
>Middle of a pandemic so I shouldn't be surprised
>current research is taking longer than expected so I ask my current mentor (professor A) if I can do this project for my capstone
>he agrees
>like a week later
>actually get a response from one of the profs I emailed (professor B)
>He says he's willing to meet next week
I agreed to meet to discuss research opportunities. Should I tell my current research mentor about this?
My current research isn't done and it feels like progress is at a standstill at the moment.
I really want to do research with Professor B if only so I can get an extra letter of recommendation though.
I don't know what the social convention here is though and don't want to lose a letter from Professor A
What do?