Friday, February 03, 2012 ... Deutsch/Español/Related posts from blogosphere

LHC: rumor about stop squark signal

Update: Note that on February 14th, there's been a CERN/ATLAS seminar (webcast was on air) that could have been relevant for the rumor but it wasn't: it only presented results that had already been released which contain no BSM signals

Another update: one of my Massachusetts sources told me that the rumor talked about the results at CMS and the source that was deeper by one step were theoretical physicists at CERN.

Originally posted on February 3rd

A commenter from an unnamed Ivy League University in Cambridge, Massachusetts, West of the Central Square, has pointed out that he or she has also heard the same rumors about the signal hinting at the existence of the stop squarks – the supersymmetric partners of the third-generation top quarks – at the LHC collider.

This 2011 image from Resonaances could become obsolete soon. The traffic sign above is really "do not enter" and not "stop" but relatively to the accuracy expected from a phenomenologist who has betrayed SUSY, it is OK enough. ;-)

I am not able to give you the accurate data now. However, ...

However, I find it rather likely (40% is the conditional probability, assuming that the rumor is true at all) that the rumor does refer to some results that should be unmasked during this seminar at CERN:

Ximo Poveda Torres (University of Wisconsin):

Search for supersymmetry in events involving third generation squarks and sleptons with ATLAS

Tuesday, February 14th, 2012
The seminar will be webcast between 11:00 am and 12:00 pm Pilsen Winter Time (subtract 6 or 9 hours for Boston or San Francisco, respectively).

The abstract has a somewhat interesting format:
Supersymmetry with large mixing between left and right scalar fermions predicts that the lightest partners of the SM fermions belong to the third generation. Moreover, naturalness arguments favour stop masses not too far from that of the top quark. The seminar presents results from searches for gluino mediated sbottom and stop production, direct sbottom production, and gluino and squark mediated stau production using 2/fb of data recorded with the ATLAS detector.
That's a lot of otherwise speculative theory/phenomenology about the optimized supersymmetry scenarios for an experimental talk, at least for a world that has no data that would clearly favor some superpartner mass hierarchies over others. ;-)

Superpartners at the LHC, by Don Garbutt

Let me mention that a stop squark that would be close to the top quark would make SUSY much more accessible than many famous phenomenologists have argued on TRF and elsewhere – heavy scalars by Gordon Kane, Nima Arkani-Hamed, etc. I don't have to explain to you that if the signal turned out to be real, it would arguably be the most striking discovery of particle physics in decades or ever, quite easily humiliating God particles and similar routine tasks.

So stay tuned, dear readers, and save [$10,000], Jester, save [$10,000]. :-)

BTW Jester's Twitter says that he's been hearing the rumor from "theorists" in the last 2 days. At this level of the propagation cycle of the rumor, his testimony is therefore "mostly independent" from mine even though, our sources are ultimately likely to share a common ancestor.

Murray Gell-Mann revealed that he is familiar with the squark rumor on January 23rd, in his CERN interview (click his name to see it).

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snail feedback (5) :

reader Unknown said...

Ok, I have to ask Why is the stop mass different from the top?

reader Luboš Motl said...

It's because supersymmetry is spontaneously broken. It's the same reason why photons have a different mass than W and Z bosons although some of them are also related by symmetries: the electroweak symmetry is also spontaneously broken. The laws are symmetric but the vacuum and its excitations are not.

Quite generally, spontaneous symmetry breaking only breaks the symmetry at long distances of low energies. At high energies, it still holds and guarantees various nice cancellations.

At the same moment, I must say that the stop may be heavier than the top but if the most straightforward ways to explain the lightness of the Higgs relatively to the Planck scale (the hierarchy problem) works, then stop and top should be close. The stop (and top) has the biggest impact on the mass of the Higgs (via the quantum loops).

reader Rudolf Zelsacher said...

In the picture that is no STOP it is a oneway.

reader alberto said...

Bad news, the presentation at CERN today "Search for supersymmetry in events involving third generation squarks and sleptons with ATLAS" shows no hint of supersymmetric particles.

So the "rumor" was just a false hope or it referred to another result, different than the CERN release of today?

There is any remaining hope that any SUSY evidence will show up in the coming months?

reader Luboš Motl said...

Dear Alberto, it was purely my speculation - that I estimated to have 40% odds, see the article above - that the Valentine Tuesday seminar could shed light on the rumor: I had no other reason to think so, besides 3rd generation squarks being in the abstract.

So the rumor is as alive as it was today, just my more specific hypothesis has been ruled out.

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