Unmistakable Gluino Signal In ATLAS !!
    By Tommaso Dorigo | March 31st 2012 04:17 PM | 25 comments | Print | E-mail | Track Comments
    About Tommaso

    I am an experimental particle physicist working with the CMS experiment at CERN. In my spare time I play chess, abuse the piano, and aim my dobson...

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    And after all I said about Supersymmetry being an invention, I fear I now have to eat it all with my hat to boot ! The ATLAS Collaboration has just released results of a very striking search for gluinos, which increases the sensitivity over past analyses by employing a much improved and cleaned-up version of missing transverse energy along with a higher-resolution version of the effective mass variable used in the past, and has found a first strong evidence for Supersymmetric decays !!

    I am disrespectfully happy despite this might mean I have lost a $1000 bet -an "insurance bet", if you like- I placed six years ago with theorist Jacques Distler and experimentalist Gordon Watts (and the latter belongs to the ATLAS collaboration, by the way). The events unearthed by ATLAS in their 2011 data, which had been overlooked by previous versions of missing ET plus jet search signatures, have no possible explanation in the standard model, while they fit perfectly the hypothesis of a mass>1-TeV gluino. I have not had a chance to screen the material carefully yet - will update this post as I go along, but check this distribution below first. It shows the missing transverse energy distribution in events containing one electron after the refined selection strategy of the ATLAS analysis.

    Yes, the point at the far right in the figure above is what you should concentrate on. One event, in this search subchannel. Only one event. But ATLAS estimates that standard model backgrounds amount to basically zero events in their signal region, missing ET>500 GeV. It is in such situations that one event grants a clean observation of a new signal. But if this odd event were all ATLAS has, one could remain unconvinced, of course. Why, the CDF experiment once saw a striking event which had an even smaller probability of being due to backgrounds, and had all the features it was expected for a cascading SUSY decay... But later no other such events turned up, and it was archived as a fluctuation, mixed with a detector problem. Here, the story is different, though.

    See the following figure. A different search channel, the one including no charged leptons - and another event pops up at an abnormally high value of effective mass, 1500 GeV ! Please note that the dashed blue curve is what one expects to see for a 800-GeVgluino, while this signal must correspond to a gluino with mass well above a TeV. Also note how standard model backgrounds are practically non-existent above effective masses of 1200 GeV.

    Finally, maybe a little less striking, but actually not less significant, is the observation of three events in the tail of the effective mass distribution in an orthogonal signal box, see below. Again, the events are compatible with being produced by the chain decay of a >1-TeV gluino (the dashed blue line again indicates what is expected for a 800 GeV gluino). From the little I understand of the ATLAS analysis -which is approved, but as far as I know has not yet been made public- these events have been studied with great care and they are picture-perfect SUSY decays!

    Stay tuned as I try to gather more information from my ATLAS friends!

    UPDATE: Of course this was an April's Fool. But the plots above are real, as are the events in the tails... I will have a serious piece on this analysis out soon.


    Daniel de França MTd2
    Alright. You got me for a few seconds. Happy April Fool's day to you  too!
    Did you break the embargo? Aren't you 25 minutes early?

    April's fool?

    My sincere apologies if I'm spoiling your April Fools joke -- although, in that case, you have posted a bit early. In any case, the plots are from the ATLAS preprint here, from March 28:

    It is certainly worth noting that the ATLAS Collaboration does not interpret these plots in the way that you do. It also seems they do not have sufficient MC statistics for the very high bins, making it impossible to judge the probability of the events you arising due to statistical fluctuations of the null hypothesis.

    Ok, I suppose I wasn't so much spoiling it as (sort of) falling for it. But you'd better be at least an hour east of Geneva this weekend, or your posting time was a total cheat.

    Isn't it a little early for an April fools joke?

    Good one, it's not midnight here yet so it nearly worked.

    April's fool of course.

    And after all I said about Supersymmetry being an invention, I fear I now have to eat it all with my hat to boot ! 
    I read that first sentence and was about to write a comment and thought, "Wait a minute, what is the date?"
    Rick Ryals
    Not again, Dorigo... ;)
    And here I was hoping the universe was sufficiently perverse to issue true preprints at confusing times of the year.

    The only thing that gave me pause for a second (besides Greece being a few time zones ahead) is how much perverse joy Tommaso would get from releasing any such real news on this date. :]

    Ha ha exactly Cliff,

    now we can wait for a similar or even more perverse 1.April joke to appear at another (trolling) site (which I`ve completely stopped clicking about one and a half year ago because this guy is too ****, ******, and ****** without any ****** sense of *****, ****,****** ... !) with which Tommaso seems to be strongly correlated or entangled respectively, LOL :-D

    Happy 1.April ;-)

    Its a sad statement about the state of SUSY when everyone assumes a report of evidence for a super symmetric particle must be a joke,

    I can't really work out if this is going a april fools or not from reading it. We've actually been luckly the supersymmetry might give clear enough signals, that we haven't yet been inundated by suzy false alarms. No doubt that resignation of Antonio over the superluminal neutrino false alarm, is going to make every CERN physicists more conversative over releasing early "MAYBE" signals. And that might save theorists from lots of additional work over finding models for signals that turn out to be false. Still despite the heart brake come with a beautiful model being slain by an ugly fact, that is the job of the theorist or especially the phenomologist, and it takes practice and criticism to refine the modern ultra complex world of physics.
    BDOA Adams, Axitronics

    You caught more fish last year...:)
    Well, april's fool or not, ATLAS has shown two events . Look at the bottom of the page.

    The Stand-Up Physicist
    There is one event, and with the error bars, it forms a cross.  Surely this is a sign from God.
    This year's crop of April 1 jokes seems curiously lame. I wonder why. Perhaps the amount of disappointment in the air has something to do with it? Or is it just the incredible boredom of hearing about the same old tired theoretical ideas? I'm so old that I can remember when supersymmetry seemed like an interesting idea.

    Thor Russell
    Well feel free to join the site, you have a whole year until next 1 April to put us all to shame with your brilliantly hilarious and insightful article in 2013 then.
    Thor Russell
    Not even Lubos would fall for this.

    I am not sure, Tommaso, why you consider this a joke. I call it a "typo". Instead of "stop squark", you have written "gluino", and you written the analysis a month or two too early and included not the most important graphs, but otherwise the text is valid....

    This problem with the joke is similar to that of RealClimate.ORG. Most readers over there haven't figured out that their "wrong sign" article was a joke. The reason is simple. Those people who love to spin everything and write things that are upside down have a rather understandable property: the more they are trying to joke, the more serious and credible their written text looks (and is, by the way).

    If the April 1st and other dates were interchanged, i.e. if there were 364-365 Aprils first a year, the credibility of your texts might increase by the factor of 364.25.

     if there were 364-365 Aprils first a year, the credibility of your texts might increase by the factor of 364.25.
    Finally, you got in the spirit and say something funny!
    This problem with the joke is similar to that of RealClimate.ORG. Most readers over there haven't figured out that their "wrong sign" article was a joke.

    From checking RealClimate, by an amazing coincidence only the few who did figure it out decided to post comments.

    It's not true at all, JollyJoker. ...

    Capitalist Imperialist Pig is an alarmist whacko just like the Real Climate thugs but he did notice that the comments make it obvious that the readers didn't get it. See 

    Maybe they erased the comments that didn't get it?