imatfaal Posted November 13, 2012 Posted November 13, 2012 It seems the LHC is consistently narrowing the range in which SUSY particles might exist (apart from some frantic goal-post maneuvering) - and failing to find any of the decay pathways that the theory predicts. http://www.bbc.co.uk...onment-20300100 Researchers at the Large Hadron Collider have detected one of the rarest particle decays seen in nature. The finding deals a significant blow to the theory of physics known as supersymmetry. Many researchers had hoped the LHC would have confirmed this by now. Supersymmetry, or Susy, has gained popularity as a way to explain some of the inconsistencies in the traditional theory of subatomic physics known as the Standard Model. The new observation, reported at the Hadron Collider Physics conference in Kyoto and outlined in an as-yet unpublished paper, is not consistent with many of the most likely models of Susy. Prof Chris Parkes, who is the spokesperson for the UK participation in the LHCb experiment, told BBC News: "Supersymmetry may not be dead but these latest results have certainly put it into hospital." http://www.math.colu...woit/wordpress/ The bad news for SUSY out of Kyoto however does not end there. ATLAS and CMS are both coming out with new analyses using this year's 8 TeV data which significantly expand previous limits on SUSY, getting close to ruling out popular last-ditch efforts to save the theory. For the latest, look at this HCP2012 page, this ongoing Chicago workshop, and CMS results announced here (like this), ATLAS results announced here. 1
Dekan Posted November 14, 2012 Posted November 14, 2012 It seems the LHC is consistently narrowing the range in which SUSY particles might exist (apart from some frantic goal-post maneuvering) - and failing to find any of the decay pathways that the theory predicts. http://www.bbc.co.uk...onment-20300100 http://www.math.colu...woit/wordpress/ If the LHC has insufficient magnification to resolve the SUSY particles, then a bigger instrument is needed. Or perhaps there aren't any SUSY particles. They might be the equivalent of Martian Canals?
Ben Banana Posted November 15, 2012 Posted November 15, 2012 then a bigger instrument is needed. I hope we stick with this philosophy... Only joking.
imatfaal Posted November 16, 2012 Author Posted November 16, 2012 A few more of the sci-bloggers comment on the rate of bottom-charmed and bottom-strange decay into muon antimuon pairs http://scienceblogs.com/startswithabang/2012/11/14/is-there-any-particle-physics-beyond-the-standard-model/ http://profmattstrassler.com/2012/11/13/supersymmetry-dealt-a-blow/ Ethan is writing obituaries yet Matt is writing defences. You gotta love it!
juanrga Posted November 18, 2012 Posted November 18, 2012 It seems the LHC is consistently narrowing the range in which SUSY particles might exist (apart from some frantic goal-post maneuvering) - and failing to find any of the decay pathways that the theory predicts. http://www.bbc.co.uk...onment-20300100 http://www.math.colu...woit/wordpress/ Not a surprise for me. SUSY is very difficult to accept for me. I also said time ago that LHC would not detect extra-dimensions or strings.
imatfaal Posted November 19, 2012 Author Posted November 19, 2012 Juan - am I right in thinking that without susy many of the string/brane theories are in trouble too?
juanrga Posted November 19, 2012 Posted November 19, 2012 (edited) Juan - am I right in thinking that without susy many of the string/brane theories are in trouble too? Yes/no Yes because many predictions made by string theorists about what we would observe at LHC have been now falsified. We did not see any gluino with mass below the TeV. No because string/brane theory is maintained in a safe state by changing its parameters. E.g. Kane 'predicted' a gluino mass of about 600 eV, when this was ruled out, he changed his 'prediction' to 1 TeV. Now that gluinos have been ruled out up to 1.24 TeVe, he is going to change his 'prediction' again... Edited November 19, 2012 by juanrga 2
DarkStar8 Posted February 3, 2013 Posted February 3, 2013 Does the supersymetry partners have to be a particle... Can't the partner be the associated field of a particle? I'm guessing the properties of the supersymetry partner is spread out everywhere and contributes to the dark energy observed.
ajb Posted February 4, 2013 Posted February 4, 2013 Does the supersymetry partners have to be a particle... Can't the partner be the associated field of a particle? I'm guessing the properties of the supersymetry partner is spread out everywhere and contributes to the dark energy observed. There is a strong link between particle states and fields. With no details, every particle has a field associated with it and vice versa. So, the distinction between particle and field in this context is moot. In supersymmetry every bosonic field/ fundamental particle has a partner fermionic field/ fundamental particle and vice versa.
SamBridge Posted February 7, 2013 Posted February 7, 2013 (edited) There is a strong link between particle states and fields. With no details, every particle has a field associated with it and vice versa. So, the distinction between particle and field in this context is moot. In supersymmetry every bosonic field/ fundamental particle has a partner fermionic field/ fundamental particle and vice versa. In that theory what exactly makes something a super-partner of a given particle? What are some examples right now? Edited February 7, 2013 by SamBridge
ajb Posted February 7, 2013 Posted February 7, 2013 In that theory what exactly makes something a super-partner of a given particle? What are some examples right now?What it means is that there is a mathematical transformation that interchanges the two particles, one bosonic and one fermionic (for the simplest kind of SUSY). If supersymmetry is an exact symmetry, then there will be situations where the two particles are treated equally. The pair of particles must have the same mass. However, we know that SUSY cannot be an exact symmetry at low energy scales, we would have seen it by now. Thus, if SUSY is used by nature then it is broken. This separates the masses of the pairs. Presumably the "sparticles" have such a large mass they are not produced in any significant quantities at low energies. Hopefully, the LHC is starting to probe SUSY, or maybe the SUSY scale is much higher than first expected. There are no examples of particle-sparticle pairs like that found so far. Supersymmetric ideas also come up in quantum mechanics and nuclear physics, but that is not quite what we are talking about here.
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