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A 'Fifth Force' Discovered By Scientists
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TV news. No link. Looks interesting.
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To be fair, that last was me talking to myself almost.
To try and elaborate, as best I can:
The problem with trying to find anything "new" is that we obviously don't know what it is yet (although we have some ideas). So that leads to two general techniques for trying to find the "new":
1. "Direct detection". Here, the claim is that we've managed to produce new stuff directly, and either it just about manages to show up in a detector, or, more likely, it escapes altogether and we don't see it. But if it escaped then it was travelling, and so it must have energy. Key law of physics: total energy before anything happens = total energy after it happens. So if there's energy missing then you can tell it's gone missing, and so you "see" the new stuff by noting that the energy afterwards is less than the energy before! Second key law: momentum (mass times speed) is also always constant, so you can also tell what direction the stuff went and potentially how massive it was.
I hope that makes sense: it's not unlike coming across a hit-and-run car crash: you don't need to have seen the car that drove off to know that it, or something like it, was involved.
2. "Indirect detection": this is the really weird one. The "new" stuff doesn't escape the detector at all, but instead is created and then disappears inside it, turning into particles we already know about. But, to cut a long story short, if that happens then it will change the behaviour of the "stuff we already know about" just enough to be noticeable, telling us again that something new must have happened, and allowing us to deduce that there was a new particle. Amazingly, that can be enough to tell you almost everything about the properties of the new particle without ever observing it (or even its absence!).
I hope *that* makes sense, too, although I can't think of any reasonable analogy just now. Quantum mechanics is just weird.
To try and elaborate, as best I can:
The problem with trying to find anything "new" is that we obviously don't know what it is yet (although we have some ideas). So that leads to two general techniques for trying to find the "new":
1. "Direct detection". Here, the claim is that we've managed to produce new stuff directly, and either it just about manages to show up in a detector, or, more likely, it escapes altogether and we don't see it. But if it escaped then it was travelling, and so it must have energy. Key law of physics: total energy before anything happens = total energy after it happens. So if there's energy missing then you can tell it's gone missing, and so you "see" the new stuff by noting that the energy afterwards is less than the energy before! Second key law: momentum (mass times speed) is also always constant, so you can also tell what direction the stuff went and potentially how massive it was.
I hope that makes sense: it's not unlike coming across a hit-and-run car crash: you don't need to have seen the car that drove off to know that it, or something like it, was involved.
2. "Indirect detection": this is the really weird one. The "new" stuff doesn't escape the detector at all, but instead is created and then disappears inside it, turning into particles we already know about. But, to cut a long story short, if that happens then it will change the behaviour of the "stuff we already know about" just enough to be noticeable, telling us again that something new must have happened, and allowing us to deduce that there was a new particle. Amazingly, that can be enough to tell you almost everything about the properties of the new particle without ever observing it (or even its absence!).
I hope *that* makes sense, too, although I can't think of any reasonable analogy just now. Quantum mechanics is just weird.
LHC discoveries to date (a short list compiled from the top of my head, so by no means complete):
1. Higgs boson;
2. Several new particles that fit into the "particle zoo";
3. Tetraquarks and pentaquarks (exotic matter made from either four quarks or five quarks, as opposed to "normal" particles like protons which are made from just three quarks).
That's basically it for discoveries -- (1) alone is huge, as it was the missing piece of the Standard Model for around 50 years, while (2) and (3) cover around 60 new particles so far. Apart from that, the LHC has made lots and lots of improvements to previous measurements, and has seen some tantalising hints of new stuff, but nothing compelling as yet.
1. Higgs boson;
2. Several new particles that fit into the "particle zoo";
3. Tetraquarks and pentaquarks (exotic matter made from either four quarks or five quarks, as opposed to "normal" particles like protons which are made from just three quarks).
That's basically it for discoveries -- (1) alone is huge, as it was the missing piece of the Standard Model for around 50 years, while (2) and (3) cover around 60 new particles so far. Apart from that, the LHC has made lots and lots of improvements to previous measurements, and has seen some tantalising hints of new stuff, but nothing compelling as yet.
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