I need to connect bow copper as on the picture with a copper pipe, and I'd like to avoid soldering. Is there a special tool for this?
There is a system for connecting copper tubing and copper fittings that does not use solder. Just google "Propress" for an example. Some places rent the tool or you can purchase one. Before I retired the company I worked for used this tool for a lot of copper fittings from 1/2" thru 4". It works very well, is quick and does a lasting job.
Depending on what you're planning on using the pipes for, you could use an epoxy that was designed for metal to metal bonds.
I wouldn't use epoxy for a constant pressure in-wall application, but I did use it to extend a short nipple for a tub spout on an acrylic tub. I wrapped it in a heating pad to post cure for extra insurance.