• Question: What happens to unstable hadrons?

    Asked by anon-201909 to Meirin on 5 Mar 2019.
    • Photo: Meirin Oan Evans

      Meirin Oan Evans answered on 5 Mar 2019:

      Great question! Unstable hadrons decay into (change into) particles of smaller mass. These decays would continue until the smaller mass daughter particles (that’s actually what we call them!) are stable. An unstable beauty hadron (another real name!) might only last for 0.000000000001s

Comments

  • Photo: Andy

    Andy commented on :

    What Meirin says is spot on. The exact way that the decays work depends on the hadron in question: not everything is possible since some properties like charge and momentum need to be preserved in the decay. Sometimes it can be hard to satisfy all those conditions and so the hadron has difficulty decaying, even though it’s technically unstable: such particles are long-lived, and sometimes enough that we can see their flight path before the decay in our detectors. These are a bit unusual: typically unstable hadrons decay within the size of an atomic nucleus!

    A particularly cool example is hadrons that contain bottom quarks: the bottom quark *really* wants to decay to a top quark to get rid of its “bottomness”. But the top quark mass is about 35 times larger than the bottom, so that decay isn’t going to happen! I think of it as the bottom hadron flying along, thinking, “Think I’ll decay now, to….. top! Oh, still not working. Let’s try again….. top! Hmm….” As a result, by the time it tries a decay mode that does actually work, it’s flown quite a long way and we can see the b-hadron production and decay happening at different places in our detectors. This is very handy, and we call it “b-tagging”.