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Comment Anecdote from ICHEP 2014 (Score 1) 364

Last year I attended the ICHEP conference in Valencia, Spain, the largest and probably most important conference in the field of high-energy physics.

The keynote speaker, Francois Englert, noble prize physics 2013, couldn't come, and rather last minute Alan Guth from MIT was upgraded to that main talk. He's one of the fathers of ithe theory of inflation, and with the BICEP results around a fitting match for a keynote talk.

He gave an excellent first half of his talk. After that, he wandered into the multiverse, unfortunately. To me, and to many others, we had left physics, and entered philosophy. After the talk the question, which I have no doubt many had in mind, was readily asked: what about the experimental testability of it all. The answer was quite unsatisfactory, unfortunately.

Comment Re:Yes to Brexit (Score 0) 396

> The Eurozone nations have opted for a degree of financial integration that the UK doesn't want or need.
> Obviously that hasn't worked out very well recently, at least for the economically stronger EU nations.

You mean, it hasn't worked out well at all for the economically weaker, right? They are trapped in a system of expensive debt in hands of the richer out of which they can't devaluate themselves, since they share the same currency.

Comment "One cross each" (Score 1) 198

Coordinator: Crucifixion?
Mr. Cheeky: Er, no, freedom actually.
Coordinator: What?
Mr. Cheeky: Yeah, they said I hadn't done anything and I could go and live on an island somewhere.
Coordinator: Oh I say, that's very nice. Well, off you go then.
Mr. Cheeky: No, I'm just pulling your leg, it's crucifixion really.
Coordinator: [laughing] Oh yes, very good. Well...
Mr. Cheeky: Yes I know, out of the door, one cross each, line on the left.

Comment Re:I got a butt chewing for giving my daughter hon (Score 1) 243

This has nothing to do with allergies. You don't feed babies honey to avoid the very rare cases where it actually causes immediate problems. After a year it is perfectly fine.
It's like some of the things that are excluded while being pregnant (cats, game meat,...), just a precaution for the possible rare, but severe consequences of an unwanted contamination.

Comment Re:Actually 13/8 times the energy (Score 1) 89

The gluino plays a similar naturalness role as the stop, at 2-loop level. Now you are aware, though I made that point in my previous post too.

Just beyond the limits is not an arbitrary choice. Given our current limits already, naturalness points to these masses being as low as possible.

Comment Re:Actually 13/8 times the energy (Score 1) 89

For the same reasons the stop is expected light (naturalness, i.e. SUSY as a solution to the hierarchy problem), also the gluino is expected light. What is light? Some put it at 400GeV for the stop, and 1.5 TeV for the gluino. But it's a bit of a subjective point. So if you like natural SUSY, you expect the gluino to be around the corner, and the stop to be within reach, but probably decaying softly and therefore having escaped detection so far. How likely is such a scenario? There is no good metrci for the likelihood of models. Therefore I prefer to look at it experimentally, i.e. wrt our current limits. If the gluino and stop are just beyond our current limits, then, according to my previous posts (which apparenntly completely missed the point...) the gluino will jump in our face, while the stop will take more time.

Comment Re:Actually 13/8 times the energy (Score 1) 89

I referred to the current limits (~1.2TeV for gluino versus 700GeV for stop), which is more or less corresponding to a couple of events on a small background - for both gluino and stop searches at their high-mass extremes.
Production probability (cross section) plot for 8TeV can be seen here:
http://inspirehep.net/record/1...
Couldn't find a 13TeV version quickly; but the trends are the same: much higher probability for gluino paris (~g~g in red) than for stop pairs (blue curve).
Now, when we move from 8TeV to 13TeV, for a gluino just at the limit, the production probability goes up much more than for a stop at its own somewhat lower limit.
So I'm not assuming same mass, I'm assuming a heavier gluino actually.
Of course, for a 5TeV gluino, no chance; but the same goes for a 2TeV stop - production rate too low.

Comment Re:Actually 13/8 times the energy (Score 1) 89

Yes, the stop (and sbottom) squark is a prime target too.
But it will come again a little later than the gluino. The reason is that we have excluded the gluino in most scenarios already wel beyond 1.2TeV, while the stop squark is unlimited above ~700GeV (and that's assuming ideal decays).
Now, with the increase in energy, the heavier is the particle, the higher the increase in production probability. This is visualised in the following (M_X being the "mass" of the produced system, in this case twice the gluino or stop mass, since they come in paris; and the solid line being the most relevant here for strong production):
http://www.hep.ph.ic.ac.uk/~ws...
For a gluino at the limit of what we could exclude until now, a ~ fifteenfold increase in production probability is expected, while for stops it will be more a factor 6 or 7.
A final argument why stops take a little longer is that the main backgrounds (top quark pairs, mainly) are looking quite similar even in the easier decay modes, while many of the possible gluino decays lead to signals that have a tiny background (like four-top final states).

Comment Re:Actually 13/8 times the energy (Score 2) 89

True.
But, if we are going to discover a SUSY particle in the first months after turning on, it is indeed very likely to be the gluino. Just because the probability of creating it, if it is within kinematical reach, will be large, compared to many other SUSY particles. All weakly produced particles will take more data to get hold of because they are rarer. In addition, in most models, the gluino decays give rise to spectacular collisions, that are relatively easy to distinnguish from known backgrounds.

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