From: James Wells Subject: susy and LC Date: January 30, 2012 11:48:46 AM GMT+01:00 To: Steinar Stapnes , Lucie Linssen , Mark Thomson Hi, Steinar pointed out to me the paper by Csaki, Randall and Terning hep-ph/1201.1293 that shows a particular susy scenario that gives light superpartners that simultaneiously are very difficult to find at LHC and also might be the explanation for the 125 GeV Higgs mass. Lisa Randall was here and I talked about this with her briefly. I was gone last week, but she also gave a talk in the theory group about it. I will see what people thought of it. My first reaction is that although they are perhaps overselling the superiority of this approach to susy over others, it is an interesting and natural susy framework to accomodate LHC results and Higgs "discovery". Furthermore, it gives a really nice benchmark reason to consider 500 GeV collider, over slightly lower mass colliders. The ties in to a bigger question: I think that one of the key reasons why it is better for us to start with a 500 GeV over say 2*mtop collider (or even more restrictive, ~230 GeV collider), is that a 500 GeV does all the SM things as well as we would probably want them done (i.e., Higgs and top physics), while at the same time making a nontrivial leap into the energy frontier. There is no guarantee of find truly new things at 500 GeV of course, and perhaps even it might be slightly unexpected to find new things, but still: it gives much more hope than a low-energy Higgs machine. The Csaki, Randall Turning paper gives another illustration of this. One caveat: Csaki, Randall and Terning are not experts on LHC pheno, and so it is possible that their idea is more constrained than they may realize on the surface. They are professionals, so they know to check with people before putting out such a paper, but it would still be important to think about more deeply. Also, I don't have a sense yet of how well the full parameter space of this idea could be discovered and studied at LHC before a LC turns on many years later. Best regards, James -- James Wells, CERN, +41 22 767 2449