Some added info:
Old Geekster is spot on with his advice. They have to be the same. Of interest, Intel may create several versions of the same processor, and each has its own unique sSpec code. If that is the case you always want the most recent version, to get the things Intel has improved upon built in.
Ideally a HP workstation's two processors are matched even at the sSpec code level, but that is not always necessary according to HP. You have the added benefit that your primary processor only has 1 sSpec code, and in the Intel Ark site it is listed as SLBV6, with suggested retail price new of $1220.00. Never buy a processor that starts with a Q... it is a "qualification sample" and will not be in your BIOS microcode as an approved processor.
I never buy these processors new. I just checked under that sSpec code and you can get them used off eBay with free shipping for about $70-$80 USD each. It is a 95W max TDP processor, and I would recommend adding a second one to your workstation. I virtually never have gotten a bad used processor off eBay.... probably over 100 bought now.
A corresponding heatsink/fan should be simple... match what you have from its part number(s) on the fan's side label, also used off eBay. Your total will be about $100.00 USD for processor/heatsink & fan. Use Noctua thermal paste... it is excellent, and non-conductive. Screw down the heatsink screws to gentle hand tight... you will feel them bottom out.
Your workstation likely will want to do one restart after your first cold boot, and then you're off and running.