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    Firm Evidence Of A Higgs Boson At Last!
    By Tommaso Dorigo | December 13th 2011 07:18 AM | 103 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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    Updates:

    - Philip Gibbs does a great job, as always, at combining -albeit approximately- the results of different experiments in the Higgs search. He now has even a full combination of LEP II + Tevatron + CMS + ATLAS, where the signal strength, in SM units, fits absolutely bang on for a Higgs mass of about 125 GeV. Please see his article at the link above; but I cannot resist from stealing his most intriguing picture (sorry Phil!):


    If Phil did his homework correctly, the combination fits well the signal hypothesis and is over three sigma away from the no-Higgs hypothesis at that mass.... This reinforces my belief that what we saw today does constitute "firm evidence". My opinion, sure.

    - Information on the Higgs analyses is now publically accessible at this link.

    - Slides by Guido Tonelli are available here.
    - And the material shown by Fabiola Gianotti is now available here.

    - Also, on an afterthought I decided I will not update the plots in this article -they are nice in that they reflect the "draft" nature of this piece as I wrote it in real time. I will pick better pictures for the next posts commenting the result, of course.

    - Finally, Matt Strassler in his article about the Higgs today stresses that I am badly wrong on calling this a "firm evidence". Oh well - that's my opinion, and I believe I am entitled to it. He has a point (in a later comment in the thread) when he says that my prior beliefs are somewhat intermingled with my conclusions, but I think that is sincerely unavoidable if you ask people for their real opinion on something, rather than a dull scientific "uninformative" answer.

    ---



    (above, Heuer with Gianotti and Tonelli during the presentation)

    The news is all in the title of this post. I know some of my colleagues will disagree, and the message is by no means the one that officially CERN wants to deliver nor publicized by the press. But "Firm Evidence" is what I personally would call the now public results of the ATLAS and CMS experiments in their multi-pronged searches of a Standard Model Higgs boson.

    I will explain why below, using some of the most important graphs shown by Fabiola Gianotti and Guido Tonelli today; but before I continue, let me tell you why I have stressed "Standard Model" above. A particle which behaves like the Standard Model Higgs, both in the way it is produced and in the way it decays, cannot in my opinion be considered a hint of Supersymmetry just because some of the SUSY theories do predict that the lightest of the 5 or more Higgs particles will behave like a Standard Model Higgs boson!

    So, SUSY enthusiasts should remain quiet for the time being, especially since large swaths of parameter space are being directly canceled by the CMS and ATLAS searches -for instance, a 500 GeV gluino is by now almost totally excluded (it remains possible in very specialized and ad-hoc scenarios) and Gordy Kane no later than one year ago was willing to put his money on it.

    But let's not divagate. The Higgs. The Higgs (SM) was predicted to be light from the observation of many observable quantities connected to it - dozens of them, to be sure. Most of the precise results of the LEP experiments allowed to fit for the Higgs mass, once supplemented with information on the W and top quark masses. And the answer was unequivocal: the Higgs must be light, most probably below 161 GeV or so (the LEP electroweak working group indicates this in their web page, although it is probably not updated with the most recent information).

    So let me now answer the question I posed at the beginning to myself: why do I believe this is firm evidence of the existence of a SM Higgs at 124-126 GeV.

    First of all, we expected it to be around there, given the indirect information from electroweak fits.

    Second, three-point-six standard deviations above background expectations from one experiment would not be enough if the other one did not have a confirming evidence, albeit weaker, in the same place of the wide mass search region. But the two experiments are providing a very coherent picture.

    Third, the evidence is coming from different search channels, and they all appear to be coherent with the Standard Model expected cross section.

    Fourth, I do not believe we need to worry anymore too much about the look-elsewhere effect (aka trials factor), which is a derating of the local significance due to the many places you look. If (big if, but follow the argument) the Higgs boson exists, it is virtually certain to be where ATLAS and CMS have first found an indication. On the other hand, if you believed the Higgs did not exist, you would have to reckon with the fact that two experiments exclude it in a wide mass range, where a fluctuation might produce a signal with a cross section much different from SM predictions, while they find a significant excess with about the right production rate in the same place. In other words, no other place in the mass spectrum yields excesses which are compatible with the SM prediction, and we can revert the look-elsewhere effect argument: how likely is it that both experiments find an excess just at the same location in this wide range ?

    So let us examine the two "money plots" of ATLAS and CMS, which combine information from many different channels. ATLAS only updates results in the most sensitive channels, namely the diphoton, di-Z-boson, and di-W-boson final states (but the latter only with half the total statistics), using "solid" cut-based analyses. CMS instead did a better homework, and can boast results with the full statistics with all the available search channels, which include also b-quark pairs, tau lepton pairs, and uses also multivariate techniques in some cases.


    The one above is from ATLAS. The one below is from CMS:



    In these figures the y axis has the Higgs boson cross section, in Standard Model rate units. What is plot is the 95% confidence level limit obtained by the two experiments upon combining their search results in all the considered channels. The black curve shows the obtained limit, the band shows the 1- and 2-sigma range of expected limits. The fact that both experiments have upper limits departing from the expectation, for masses around 125 GeV (a bit below that for CMS, a bit above for ATLAS), is the result of both having excesses of events there.

    Next let us look at the p-value plots. These are tightly connected with the figures above, but give a different picture: they describe what is the agreement of backgrounds and data more directly. There are also expected p-values which would be obtained if the Higgs boson did exist: the compatibility of the observed p-values with the latter curve indicate that the fluctuated data are in agreement with expectations for the signal.


    Above, the ATLAS result. The expected p-value above is the dashed black curve extending toward low values at high mass. (I apologize for the poor quality of this picture, I will add a better one once it becomes available).
    And below see the CMS one:


    CMS has compatibility with SM expectations for the p-value in a wider mass region than ATLAS: both a 119 GeV Higgs and a 124 GeV one would be roughly in agreement with observations.

    Summary:

    So the summary is that ATLAS has a 3.6-sigma significance at 126 GeV, by combining their three most sensitive channels; CMS has a 2.4-sigma significance at 124 GeV, by combining all the meaningful search channels -even less sensitive ones. CMS also has a tantalizing fluctuation at 119 GeV due to three H->ZZ candidates at that mass, but I am willing to believe that those do constitute a fluctuation. The above numbers are, I remind you,


    The significance in ATLAS is driven by two signals: three ZZ candidates, and a inspiring bump in their gamma-gamma distribution (which is however more pronounced than what should be expected by the SM signal). See the mass distribution on the left: the small three-bin bump at 126 GeV is the source of the significance that ATLAS quotes at that mass. The signal is more prominent when examined in the lower band, which is a background-subtracted distribution.



    On the right I also attach the CMS gamma-gamma mass distribution. The signal is smaller than the one seen by ATLAS, but there is some sort of compatibility between the two.












    Now some additional random notes I took from the seminars. First of all, from ATLAS:




    • ATLAS has a 2.8-standard deviation fluctuation from backgrounds in the gamma-gamma mode alone. This is lucky for a signal, admittedly. Including the LEE this goes down to 1.5 standard deviations. The figure on the right shows that the p-value they would expect to have, for a signal at 126 GeV, would be much less significant. Maybe a slight inconsistency, but one cannot expect everything to be exactly bang on.
    • The three ZZ events from ATLAS are at 123.6, 124.3, and 124.8 GeV (the last one could be wrong, I did not read it correctly maybe. But 
    • 2.1 standard deviations come from these three events. 1.5 would be expected from a SM Higgs: again, ATLAS is apparently lucky!
    • Higgs masses below 115.5 GeV and above 131 GeV are excluded by ATLAS
    • In total, ATLAS has a signal amounting to 3.6 standard deviations (expected 2.4 from SM) at 126 GeV or so. This effect becomes a 2.3-2.5-sigma one if LEE is accounted for.
    • "It's too early to draw solid conclusions", "more studies are needed". This is the bottomline of Gianotti's talk.

    And now from CMS:

    • CMS has a 2.6-sigma deviation, which becomes a 1.9-sigma one once LEE effect is considered.
    • CMS excludes a Higgs boson with mass above 127 GeV, at 95% confidence level.
    • Both the above are compatible with the rate of Higgs bosons that are expected from Standard Model production.
    • The 124 GeV signal receives contributions from all final states: besides ZZ and diphotons, the WW as well as bb also provide mild positive confirmations.
    • Perhaps the most interesting plot by CMS is the following one, showing the best-fit signal cross section from each individual channel, compared with the one expected for a Higgs boson of 124 GeV (blue line): there is full compatibility with the Higgs!

    And I conclude with a very nice Higgs to gamma gamma candidate by CMS:

    Comments

    vongehr
    A few days back you reprimanded me for talking about an announcement of discovery of the Higgs on Dec. 13th ("Light Higgs Discovered And About To Destroy The Universe"), now you announce it yourself on Dec. 13th???
    Thank you! ;-)
    dorigo
    English must not be your native language... Discovery and firm evidence are quite a different thing; further, firm evidence is my words, and there is nothing official in them (you said that a discovery "will be officially announced")...
    vongehr
    O-tone Dorigo:
    There will be no discovery announced whatsoever, of this you can bet whatever is dear to you.
    So I am supposed to go along with PC wordings that you are forced to stick to because certain people fund you and all that and thus make a difference between "firm evidence" and "discovered", and this is then "English" (which is now apparently not due to the dictionary but also defined by the CERN collaboration)? Sorry, but if I discover firm evidence, you know, just saying ... ;-)
    Hank
    I don't think it's just wording in this case; understanding the difference between what constitutes evidence versus a discovery is vital. Part of the reason that God Particle stuff got so wound around the axle culturally was journalists not clarifying what terms mean properly so using correct language and distinctions lets people know how excited they can get.

    Along with Tommaso's glossary, the blogger at Cosmic Log also did a good layman introduction to this.
    vongehr
    I know well the sigmas that HEP people insist on (arbitrary convention!) in order to use "discovery". Can you give me the official reference for the number of sigmas that "firm evidence" (as opposed to "evidence") requires? If you have "firm evidence" for something, what does it mean to you, Hank, honestly? (I am tired of letting HEP people tell all of science and society how to talk and what sigmas mean this week (six not enough for FTL neutrinos?!?) so they can hype and spin everything however they please. Sigmas were here long before HEP!)
    this title will probably backfire.

    Thanks for making some of the plots available. The video broadcast was unfortunately very difficult to follow.

    I'd say things are still fairly inconclusive. From the 'looks' of things, we'll need 10fb-1 of data to be comfortable with any yes/no evidence. I'm disappointed in your uncharacteristic optimism :)

    Atlas has a Higgs signal at 100GeV in gamma-gamma that looks equally strong than that at 126. strange...

    Put me in the remains to be convinced camp. When either Atlas or CMS gets well over 4 sigma i'll be persuaded. I believe there have been numerous 3 and even 4 sigma bumps over the decades which end up being background and I'm uncomfortable with the combining of the two datasets.

    Mr. T I know you will be busy but when you do your final write up, could you also include D0/CDF for comparitive purposes (ie, this is where FNAL left things off...)

    Cheers

    This looks very interesting, I agree, but it also has some problems: all of the result basically rests on the diphoton signal, and the peaks seen by ATLAS and CMS are NOT sueprimposed... In fact, CMS seems to have a valley exactly where ATLAS sees most of the excess events; how likely is it that a miscalibration of the detector could shift the energies of the gamma-gamma events linearly?

    Golden ZZ channel seems way too weak and noisy for it to be of any significance, up to now: CMS has events in a quite broad band, compared to ATLAS.

    I don't know if this is a blogging faux-pas, but I'll link the analysis by prof.Strassler, which seems very good and well reasoned to me: http://profmattstrassler.com/2011/12/13/higgs-update-today/

    Hfarmer
    First of all this entry is a masterful example of just what makes science blogging in general, and this website in particular so very good.  Who better to not only tell us what was said, but to interpret it in a user friendly way?  Reuters?  I don't think so.  
    Second. IF what you are saying proves out with further study then for those who theorize about canonical quantum gravity (Loop Quantum Gravity, Casual Dynamical Triangulations, Group Field Theory etc) will get a boost.  For the longest time the line was that a heavy susy higgs would be found, then that would rule those theories out at a stroke.  So much for that. ( I have written my own blog entry for anyone who is interested in the theoretical aspect of this. )

    Science advances as much by mistakes as by plans.
    Err, I hope you realize that what they have excluded are standard model Higgs in that mass range. What they have decidedly NOT excluded are non SM Higgs. The latter have different cross sections and decay paths, and are not excluded at all. In particular the 4 other MssM Higgs. This result also says identically zero about quantum gravity.

    1. Wait until they include Z->bb simulations for the background.
    2. Probably they have a quite large statistical significance, but they deliberately overestimated the systematics for now. Just to be "conservative".
    3. Your argument is only valid if you assume there is a Higgs.

    Agree with the author...
    We don't need to wait for 5 sigmas to convince ourselves about the SM Higgs existence.

    Knowing barely anything about the topic, I (being a visual person) paid attention at some sort of "echo waves" after the proposed excess of events in the ATLAS graph, that are apparently missing in the CMS graph... Wondering if that bears any significance, or is just due to the data processing differences between the two projects?

    Hi Tommaso,

    I am not so convinced. You should read this http://profmattstrassler.com/2011/12/13/higgs-update-today/.

    Best,

    Marco

    Atlas' peak is less convincing than the Higgs found in 1984 (and then not verified):
    http://slac.stanford.edu/pubs/slacpubs/3250/slac-pub-3380.pdf

    The look-elsewhere effect is quite important, as is the possible tuning of cuts to
    enhance a signal... that 1984 excursion was most likely unfair cut tuning.

    Great article Tomaso.

    One question, ignoring for a minute the last nice CMS plot which seems to indicate that what we are seeing is consistent with a SM Higgs, couldn't the ATLAS inconsistency between expected and measured p-values indicate that what they see is perhaps something different from a SM Higgs (but still some sort of) ? For example, one could perhaps fit a better hypothesis for the expected value and get better agreement with observation.

    Hi Tommaso,

    I think you did not answer my question the first time because I misspelled your name :-) . What I meant is, if we extrapolate what ATLAS is seeing now for the data to come and imagine the same pattern of more events than expected would remain, don´t you think this will shift the hypothesis of a SM Higgs to another type of Higgs and that alternative hypotheses to the fit would be worth checking? I mean, I know this is a SM Higgs search and the exclusions plots etc make sense only in the light of such an hypotheses but a well pronounced resonance in principle can be interpreted differently so just wanted to know what your opinion is. I am convinced the effect is almost surely real but I am much less convinced on what this is.

    dorigo
    Sorry Bernhard, I have been in Madrid and running around - the iphone is not ideal for answering comments. I think there is certainly a chance that this signal is not a SM Higgs, but all I see is consistency with it for now. The excess by Atlas is more pronounced than it should be, but not so much to constitute a hint of something gong on for the time being IMO. Add to that my bias against SUSY and you'll see why I am not too warm on these alternatives. Cheers, T.
    Hi Tommaso,

    thanks a lot for the answer. I agree with you the picture for now is very consistent with a SM Higgs, I was more like wide-guessing and speculating a bit given the excess observed by ATLAS. But then again I was not particularly with SUSY in mind just wondering (dreaming) could be something else.

    Vladimir Kalitvianski
    New data just reduced the region of Higgs masses, leaving a more narrow window to it due to still poor statistics. Can this be called a "firm evidence"?
    CMS speaker said several times "data can't exclude 120-127 GeV region". It is an important message. 2012 will give us the answer...

    Dear Tommaso,
    could you explain this claim?
    "First of all, we expected it to be around there, given the indirect information from electroweak fits."

    I'm kinda confused by it.

    dorigo
    Only that the indirect fits of EW information using knowledge of radiative corrections linking the Higgs mass to other observables points to a light higgs, but most of the resulting parameter space is already excluded by LEP II - leaving as the only likely window of 115 to 150 GeV the place where the Higgs is.  This is indirect information completely uncorrelated from the direct searches.

    Cheers,
    T.
    Tommaso, why should the look elsewhere effect be abandoned _now_? And, what would be the correct way of including it in the two experiments' combination? (whose presentation btw seems to have been cancelled at the last minute today; I agree with that decision if it amounts to ~3 sigma, since I find underenthusiasm will be better than overenthusiasm in the long run)

    (I'm told that the combination was never announced _officially_ for today, so the second part of what I've written might be meaningless; still, I'm interested in the first two questions!)

    dorigo
    Not abandoned, but the LEE depends on your beliefs to some extent. There is IMO no point in discussing significances to death in this situation. The experiments give a strong and coherent indication that the Higgs is there; it may be a fluke, and this goes regardless of how many sigmas we count. Look at the Wjj excess by CDF: four, five sigmas, but it will never materialize in a real signal; one simply does not believe it. Yes, this is Bayesian reasoning in some way. The expectations that we would find a Higgs boson in the low-mass region were sizable, at least for some of us. For us, three sigmas are enough to be called a "firm evidence" of a new particle. Contrast this with a uncalled-for new resonance in the W+jets final state at the Tevatron... Then, of course, we must stick to a well-established recipe in this case too; so we will announce a discovery only when we exceed five sigma, LEE included.

    Ciao
    T.
    As to the gamma-gamma channel,
    as you say "... there is some sort of compatibility between ..." CMS and ATLAS in the region from about 125 GeV to about 132 GeV
    (which is maybe not coincidentally that of the CDF bump)
    but
    if you look closely at each bin,
    you see that the highest ATLAS data point corresponds to a low CMS data point, so
    maybe the high ATLAS data point is a fluctuation
    and
    that might explain why the ATLAS bump "is however more pronounced than what should be expected by the SM signal".

    The fact that the interesting structure from 125 to 132 looks like a peak dropping to a valley and then back up does not to me look like a simple single SM Higgs,
    but rather something interestingly complicated.

    Tony

    PS - As to ATLAS supporting a single SM Higgs interpretation by 3 events in the Higgs to ZZ to 4l channel,
    those 3 events are all in one bin, with nothing in either of the two adjacent bins. If the 3 were spread out into the 3 bins, it would not look like much statistically, so my guess is that is a fluctuation that should not support any evidence/observation/etc.

    fundamentally
    The Higgs seems to be difficult to detect. Does this mean that it is very scarce? According to its assumed task in the SM it must be abundant, or is that a false conclusion?
    If you think, think twice
    dorigo
    Well Hans, there is a difference between playing a role and being produced in a particle collision :) The problem is that the Higgs couples strongly to heavy stuff, while we have only light projectiles to produce it with. If we could put together a bottom-antibottom collider, you'd see fireworks.

    Cheers,
    T.
    fundamentally
    Thanks. This sounds a good answer. Its role is to bind to those particles that exist in three generations. What you said means that the binding to the Higgs does not occur at the least weight generation. Is that correct? Why are two ways left for the resulting binding?
    If you think, think twice
    See http://en.wikipedia.org/wiki/Yukawa_interaction#Spontaneous_symmetry_bre...

    In the standard model, the mass e.g. of an up quark equals the product of two quantities, the Higgs field "vacuum expectation value", and the "Yukawa coupling" for the up quark. The amount of Higgs that is there for particles to interact with (the VEV), is the same for all particles. What differs e.g. between an up quark and a down quark is how strongly they interact with the Higgs field - the Yukawa. What Tommaso is saying is that the bottom quark is heavy and that is because its interaction with the Higgs field is strong. The light quarks also interact with the Higgs field, but not as strongly.

    This is one of the dissatisfying features of the standard model - the masses of leptons and quarks depend on their interactions with the Higgs field, each particle has a different interaction strength, and there's no explanation for any of those numbers. Such an explanation is something you would hope to get from a deeper theory.

    fundamentally
    Mitchell,
    I discovered a scheme in which massive elementary particles can be identified by a coupled pair of sign flavours of a quaternionic probabitity amplitude distribution (QPAD). At the same time the corresponding equation of motion (in quaternionic format) reads:
      ∇ψˣ = m ψʸ
    Here ∇ is the quaternionic nabla, m is a coupling factor and {ψˣ, ψʸ} forms the pair of sign flavours of a QPAD ψ.
    Multiplying both sides of the equation with ψʸ* and then integrate over the full parameter space, leads to an equation for the coupling factor m.

      ∫˯ψʸ*∇ψˣ  dV =m ∫˯ψʸ*ψʸ dV= m∫˯|ψ|²  dV=mg

    Here g is a real and positive constant.
    It means that m, which usually plays the role of mass in equation of motion, must be seen as a coupling constant.
    The scheme does not explain the existence of generations, but it explains the different categories of elementary particle types: electron (positron), neutrino, down quark, up quark, W bosons and Z boson.
    The Kerr-Newmann metric relates local curvature with some local properties, such as mass (or instead coupling factor m?), electric charge and angular momentum including spin. If the coupling factor plays the actual role, then this would mean that gravitation and inertia are determined by the above properties of the particles and not by an external Higgs. However, I can imagine that the Higgs plays a role in creating the higher generations.
    See: http://www.crypts-of-physics.eu/Quaternionic_continuity_equation_for_charges.pdf for the relation between the sign flavors in {ψˣ, ψʸ} and particle properties.
    If you think, think twice
    I'm glad I didn't take that bet with you T. It's a pretty good day for CERN and particle physicists everywhere, with all the usual caveats of course. I would be amazed if this didn't turn out to be the real thing.

    My main takeaway from the seminar was that with 95% confidence I can say all LHC physicists are Italian.

    If they are at 3.6 sigma and 2.4 sigma now (excluding the look-elsewhere effect), combined they are at sqrt(3.6^2+2.4^2)=4.3 combined. With (5/4.3)^2=1.33 times the data, they would be at 5 sigma (excluding the look-elsewhere effect). Seems like they might be there soon...

    dorigo
    Well, sigmas cannot be combined so easily, plus the 3.6 and the 2.4 are not laying at the same mass point. But I think one can certainly take away that the 3.6 sigma of ATLAS are confirmed by the CMS result, so this indeed is firm evidence. Add to that the fact that the cross section fits to the SM prediction for the Higgs (this is independent information working toward the signal hypothesis, while the "sigma" are just against the background-only hypothesis without any reference to a Higgs particle) and you understand why I call this a firm evidence. My opinion, of course. But my opinion is respected by my colleagues, so I do not understand people like Matt Strasler who seem to not respect it. Or rather (as I wrote in another comment) I do understand, unfortunately.

    Cheers,
    T.
    If they data amount increases by x, will the error bars go down by sqrt(x), as usual, or are there other systematic uncertainties?

    What is the expected lifetime of the Higgs particle. A nanosecond, a picosecond, a femtosecond?

    I think it is about 10^-22 seconds in this mass range.

    The width is 0.003 GeV or so
    http://physics.stackexchange.com/questions/18242/whats-the-standard-mode...

    That's 4.8 x 10^{-13} Joule. Divide the Planck reduced constant 1 x 10^{-34} Js by this constant and you will get 2x 10^{-22} seconds or so. The distance traveled is still 10^{-14} meters or so, not far from the size of a nucleus.

    A shameful title. How do you know this "evidence" will not go away with more data? And how can you be sure this is "evidence of a Higgs", as opposed to any other color singlets?

    dorigo
    Leave me alone Orbifold. That is not a shameful title in the least, it is just my personal conviction. And firm evidence does, at times, go away, so what ?

    As for the other (more meaningful) question, we obviously cannot be sure, but the light Higgs hypothesis fits the data extremely well, considering that the signal shows up with the predicted strength in all the channels it should -of course within the large uncertainties. But other color singlets would not couple necessarily to the final state bodies that way. For instance, a gamma-gamma decay would not work for a particle not heavily coupled to W and top quarks.

    Cheers,
    T.
    Strassler on Dorigo('s blog post):

    "Oh boy. I cannot imagine how much hot water he is now in."

    [...]

    "I agree the word “firm” is the serious error. If he had said “some preliminary evidence” he would have gotten away with it. As it is, it seems to me that he has crossed a line, and created a media storm all on his own".

    dorigo
    You should also quote my reply, in his comments thread (but I do not know if he approved it yet):
    "You are mistaken about the hot water - I am enjoying my time in Madrid."

    And why does professor Matt Strasler (mind the single s in the surname - it will only be fixed when he spells my name correctly ;-) cast stones in my direction ? I have expressed an opinion, as clearly stated in the beginning of my post above. I even said "I know many of my colleagues will disagree". So if I say "firm evidence to me" it cannot be a serious error. It just reflects my degree of belief of the result.

    Alas, I know the answer, unfortunately. He is still angry at me for a blog post I wrote on a rather insulting paper against the CDF collaboration he published three years ago. In the post, I made it clear that he had calculated a cross section wrong by a factor of three, using CDF data. He probably did not like that.

    Cheers,
    T.

    Hadn't seen your reply, Tommaso (still don't), and was posting just as an FYI, in case you didn't know about it yet. Seems Peter Woit had stepped in to defend you. Personally I don't see anything wrong/improper in what you posted... Strassler says you went to far, Sascha says you're too politically correct. *shrug* Seems you just can't win. Keep up the good work.

    Kind regards.

    Hank
    Strassler says you went to far, Sascha says you're too politically correct. 
    That means he is probably right where he should be.
    I don't believe it for a second -- at least not with this amount of data. I'm impressed with the CMS analysis; it's quite amazing that you guys did all channels, and Tonelli really did a great job convincing us all that you really thought about things. I also liked the fact that he -- unlike others -- were not keen to claim possible HIggs signals, but rather stated the much calmer 'we can exclude down to 127 GeV'.
    As Atlas is where I'm involved myself, it perhaps makes some sense, that I've had some time to digest the Atlas results. You can refer to the plots here: https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011... they should be official by now.

    The moneyshot in 1a -- that's a bump, right? No it most certainly is not. You cannot just select out the bins you like to make a bump. Choose a different binning so the slight deficit in the two neighboring bins is included, the bump becomes a single outlier.

    Why is H->tau tau not included? It certainly should be at a mH ~ 125 GeV, considering the branching fractions. The analysis have been made -- just look at the plots 2a and 2b. Could it be that these plots does not show the desired result? Would this channel have been included if we've seen the same indication of a Higgs? Is it allowed to be selective in your analysis like that? It most certainly is not!

    But hey, only time will tell, right? I hope you CMS guys are going to continue to be as thorough as I saw today, because then the combined effort of our experiments will sure tell us by next Christmas. And crack open a good bottle of wine tonight anyway. The fact that our analysis is so far in such short time, is surely worth celebrating!

    Regards, John the Non-Believer

    dorigo
    Thanks - I am adding the link at the top of the page now.

    About the rest: as I explain in the post above, I believe this is a signal for several reasons. The strongest is that the CMS and ATLAS results are coherent in several aspects. But there is something more than just counting sigmas above background: there is the fact that these sigmas are exactly in the right ballpark of what you would expect for a Higgs boson. If we were discussing a unnamed resonance with a unspecified production model, I would of course be very unconvinced. But this is different. It also weighs in the fact that the prior belief pointed in the direction of a light higgs being there, of course...

    Cheers,
    T.
    Vladimir Kalitvianski
    "If we were discussing a unnamed resonance with a unspecified production model, I would of course be very unconvinced."

    But the Higgs mechanism in SM is a purely theoretical construction, it's not even an unnamed resonance observed experimentally. Strictly speaking, before its discovering in experiments, there is nothing to discuss. You guys see the experimental data via the SM pattern, unfortunately. OK, you have nothing better than SM, I admit, but stay moderate.
    Sure, can't argue against a believer (or a bayesian) :). Actually I may have sounded a bit more harsh than I intended to. English is not my first language either. What I really meant to say was, that I don't think this is conclusive at all, but of course if there is a Higgs at 124-6 GeV, this would be the way we would first see it. My personal bayesian prior does not favor a SM Higgs boson.

    I sure hope that Vladimirs point is the correct one. If Higgs is really there at this energy, HEP is going to be a boring field -- we don't have to see anymore exiting new physics up to 1000 TeV.

    So you bet on higgs at 124-126 with this data and not in LENR devices ?
    :-b

    dorigo
    What are LENR devices ?

    I bet on a SM Higgs in the 123-126 GeV range, yes. If we make it 122-127 I am willing to bet 300$ against 100$ with the first three takers who have a name in HEP or who find somebody with a name in HEP guaranteeing for them.

    Cheers,
    T.
    LENR is the "greatest" contribution of Italy to science since Galileo, and according to many sources, it is exceeding Gianotti, Tonelli, and Dorigo combined. Congratulations to Andrea Rossi. ;-) It stands for Low Energy Nuclear Reaction which is just another name for "cold fusion". A new name for this pseudoscience apparently allows many people to act as idiots repeatedly, without realizing that a repeatedly brainwashed idiot becomes an imbecile regardless of the change of the name.

    Incidentally, Rossi's blog called "Journal for Nuclear Physics" recently argued that a neutron is a bound state of a proton and selectron! :-) I am sure that no Higgses are needed in this new kind of science.

    Can you point to a single interaction which is proof of a "Higgs boson", even in principle? No.

    There is a statistical correlation of emissions of gamma rays in one detector and leptons in another that proves nothing, but is merely circumstantial evidence that there might be a spin-0 particle.

    You're then claiming that evidence of a spin-0 particle around 126 GeV is "firm evidence of a Higgs boson", when a Higgs boson is defined as the U(1) X SU(2) electroweak symmetry breaking boson.

    But we don't know that U(1) X SU(2) is the electroweak symmetry:

    “One of us (Wilczek) recalls that as a graduate student he considered the now standard SU(2) x U(l) model of electroweak interactions to be ‘obviously wrong’ just because it requires such ugly hypercharge assignments. … it still seems fair to call the model ‘obviously incomplete’ for this reason.”

    - Savas Dimopoulos, Stuart Raby and Frank Wilczek, “Unification of Couplings,” Physics Today, Oct. 1991.

    “Stephen Weinberg and Abdus Salam tried to combine quantum electrodynamics with what’s called the ‘weak interactions’ (interactions with W’s) into one quantum theory, and they did it. But if you just look at the results they get you can see the glue, so to speak. It’s very clear that the photon and the three W’s are interconnected somehow, but … you can still see the ‘seams’ in the theories; they have not yet been smoothed out so that the connection becomes … more correct.”

    - Richard P. Feynman, QED, 1985, p. 142 (Penguin edition, 1990).

    You are assuming that if there is a spin-0 126 GeV boson with electroweak interactions, it's the specific particle breaking the electroweak theory's symmetry. You don't have any null hypothesis to test that theory! The Chi-squared test for the "Higgs boson" has two "possibilities": either it doesn't exist, or it does exist and is the particle in the mainstream electroweak theory.

    This is fraud. It's precisely Joesph Priestley's error in his phlogiston experiment: either phlogiston exists, or it doesn't. There was a third possibility: oxygen exists. This was recognised by Lavoisier. Surely you're aware that the theory could be wrong? You need to take account of alternative theories to the Higgs mechanism and the standard elelectroweak theory, before you can claim that the spin-0 boson (if it exists) is the one you are looking for. Otherwise, it's like interpreting the "motion of the sun" across the sky as clear evidence that the sun orbits the earth daily. The failure in the search for the "Higgs boson" is that it's prejudiced in favour of only one theory. Whatever is found is then assumed to be the particle needed for the mainstream theory.

    Good. How do these new theories fit LHCb data? And how do they fit neutrino oscillations?

    A billion times better than string theory and the Standard Model, which failed to predict gravity quantitatively or the cosmological acceleration in 1996 two years before discovery, and fail to predict all the masses of the particles.

    Tommaso, as you know I like the idea of a Higgs signal around 240 GeV
    so
    can you tell me why for the Higgs to ZZ to 4l channel
    the CMS paper at HIG-11-025-pas.pdf shows 5 events at 240
    while
    the CMS slide shown at the 13 Dec 2011 webcast shows 4 events at 240 GeV ?

    Also in two adjacent bins around 320 the CMS paper shows 3 and 2 events
    while
    the CMS slide shows 2 and 3 events respectively.
    Maybe it is statistically inconsequential
    but
    the discrepancies do exist and there should be an explanation.

    Tony

    PS - Also in the Higgs to ZZ to 4l channel,
    around 230-240 GeV CMS shows background about 4 events
    while
    ATLAS shows background about 3 events.
    With similar luminosity, why should the backgrounds be so different ?

    dorigo
    Hi Tony,

    am very tired, need to sleep, will check tomorrow. For backcgrounds, the two experiment may well have different numbers -the detectors are not that similar after all.

    Cheers,
    T.
    Thanks for the post, Tommaso.
    Very interesting signal we have here, no matter how it will end up in 2012.

    A question: all the graphs from CMS I've seen today seem to refer to 4.6-4.8/fb of data in various channels. How could it be the "full dataset"as you said? Wasn't it close to 5.3/fb recorded, including that little 2010 contribution? Did some data get removed?
    Of course I understand that an extra 10-15% doesn't really change anything, just curious.

    Ah, and you didn't say how much you're ready to bet on this signal being the real deal :-)

    Oh sorry, I missed your answer about the bet you gave a couple posts above - kind of a busy thread to follow :-)

    Still curious about the "missing" data anyway.

    dorigo
    Hi Algernon (is that your real name ? I recall a Algernon in a story by Oscar Wilde).

    The data collected (>5/fb) needs to be validated, calibrated, etcetera. Some fraction is taken off because we want all detector components to be active for the events we study. So if different subdetectors have 99% efficiency, asking all of them being on reduces the dataset a bit.

    About the bet, the sum is always the same, $1000. This time I think I can offer to bet 3:1 that the Higgs is in 123:127 GeV for real, so I can take three 100$ bets at $300 payoff.

    Cheers,
    T.
    Vladimir Kalitvianski
    I did not follow the posts carefully, but does the angular momentum of those two photons equal 0? What do the experimental data say?
    dorigo
    Hi Vladimir,

    and how would we measure the angular momentum of the gammas ? If you tell me I'll fly over to Geneva overnight to do it!

    Cheers,
    T.
    Vladimir Kalitvianski
    What a hysteric "answer" to my idle question!
    Interesting first year (in principle) quantum mechanics problem, that. From a few back to back photon events, we can't say anything I would say, because we are not measuring an angular momentum eigenstate. If we had many many photon events that were all prepared (produced in the interaction the same way), we could measure the angular distribution and then look which orbital distribution function it corresponds to. Since they can't all be expected to be prepared in the same angular momentum state in the realistic LHC case, this doesn't work. Does that sound right?

    Vladimir Kalitvianski
    Yes, Alex, thanks, it looks much more relevant than Tommaso's answer. So, there is no way to make sure the data are from spin-0 boson decay? Can't believe it!

    Maybe with better statistics it can be done? Not the same conditions for the decaying Higgs are OK. Instead of "rotating" detectors (or placing them everywhere), one "rotates" the prepared Higgs state.
    I may have been to pessimistic. In principle the way one would see the spin from the decay products only as I outlined it is roughly correct I think, but I was probably much too pessimistic about the production mechanism, you can deduce the "orbital shape" of the decaying stuff with enough events, which manifests itself in an asymmetry in the detector.

    There is this recent paper: http://arxiv.org/pdf/1103.1973

    which basically looks at the angular distributions I have mentioned. They also give some references to previous analyses.

    I gave a reply which is apparently stuck in the queue because I included a link (I suppose). I think I have been too pessimistic. My remarks about the general methods are correct, but you can do what I describe given enough statistics. Search the arxiv for higgs and spin, and you will find a few recent papers to that effect.

    I think this is very exciting.

    Here is a possibly dumb question. I keep seeing all these "Brazil Graphs", with an excess jumping above two sigma. Where the line dips above the two-sigma yellow bar, we seem to claim to see evidence of a particle there. However-- in some of the Brazil graphs, it looks like the line drops or threatens to drop BELOW the LOWER yellow bar, so we have a deficit! What is one to interpret these deficits as meaning?

    dorigo
    Hi Coin,

    It is normal to get downward flukes as it is normal to get upward flukes. Their number in a way tells you how many different places you've searched in -it's the so-called trials factor, or Look-Elsewhere Effect.
    I don't think it's frequent to get those kinds of departures from expected green-and-yellow bands, anyway - I have looked at a hundred of them in the last few years and I don't recall a single one being off by 3.6 sigmas, either positive or negative. Which makes sense, sort of. If it goes negative by 3.6 sigma, people will not publish and start back working on their background estimates!!

    Cheers,
    T.
    There's that question again that I have had for a long time - how does hypothetically scaling the higgs production cross section take into account interference effects. And if interference effects are not taken into account, could downwards "flukes" simply be neighboring destructive interference with other (e.g.) diphoton production graphs in the wake of the higgs pole?

    Woah some of the comments on this blog really blow.

    The author expresses a personal opinion about the significance of an experiment and all the cranks' feathers get ruffled so he is suddenly responsible for everything from mainstream terminology, to funding, badly conducted experiments and particles that could spoof the Higgs signal. Also, faster-than-light neutrions.

    "Haters Gonna Hate"

    One word: Bubbly. ;)

    As a physicist (but not a HEP one), I am having a ball looking at the "evidence" as seen in each individual channel. Really? REALLY?

    The only conclusion I can make at the end of today is that nobody has any reason to conclude anything, either way.

    As far as I am concerned, it's settled. There's a 125 GeV Higgs and no other comparably major Higgs at least up to 500 GeV. Phil Gibbs' tricollider combination makes this point totally persuasive.

    An article about it, 125 GeV Higgs is a sure thing:

    http://motls.blogspot.com/2011/12/higgs-at-124-126-gev-is-sure-thing.html

    It would surely be a priori unexpected that I would agree with Tommaso Dorigo against Matt Strassler but there's a 4-sigma overall evidence that this is what has actually occurred.

    Thank you so much for this blog - as a regular reader I appreciate it very much, specially at this exciting time. A simple minded question: if the Higgs boson exists and the Higgs field is real, what is its density in kg per cubic m, and why does it not have gravity - or does it?

    Hi, that is an excellent question. Let me restate it slightly to be more accurate: I think you are interested in the energy density which the constant value of the higgs field contributes to the energy density of the vacuum.

    This energy density from the higgs is then a contribution to what is generally called Dark Energy because, as you rightly suspect, it gravitates.

    This question is tantamount to asking what the value of the higgs field potential would be at the field value that it has. The answer is simple in the absence of supersymmetry: there is no prediction in the standard model, i.e. it is a free parameter. This free parameter is physically identical to Einstein's cosmological constant. The generic it has to be fine tuned to devastating precision in order to make the observed Dark Energy small enough.

    In Supersymmetry, the contribution of the scalar potential to the vacuum energy can actually be calculated more reliably, but there it is still a function of the unknown mechanism of supersymmetry breaking. Either way, all modesl tend to require a terrible amount of fine tuning to get the resulting cosmological constant right.

    Hi anonymous,

    no, it cannot have a gravity, becouse it can exist in a flat Minkowski as an inevitable reality.

    Tomas

    I have no clue what you are talking about with your inevitable reality in minkowski space

    Hi Alex,

    if A bounded by B is a solution of the KGE in Minkowski and is observed, then a field of B is the inevitable reality in this space provided, that the KGE is mathematically correctly extended for the Minkowski.

    Tomas

    Sorry Tomas, you are not making any sense to me :(

    Ok Alex, imagine that A is a "field of lightings" and B is the "avoidance" of "ball lighting", then the "field of this avoidance" is an inevitable phenomenon as the ball lighting itself with respect to A. If analogically the A is a zero-spin field so B is the "avoidance" of non zero spins, then the "field of this avoidance" is "non zero spins" (not (single) non zero spin ) with respect to A. It exists as a "not non zero spin" field as an inevitable reality, as already defined.

    You are welcome to copy my graphs of course. Thanks for the vote of confidence.

    Your link to my post at the top is broken because I corrected the date having prepared the introduction in advance of the event.

    dorigo
    Sorry Phil! Going to fix asap
    T.
    Hi people,

    If one can read the Klein Gordon equation extended for Minkowski flat, then one inevitably agree that the Higgs can be a reality, so it is a reality. I congratulate the colleagues in CERN to the definitive demonstrating of Higgs phenomenon.
    Tomas

    Great, a new Boson! Can we make a Bose-Einstein condensate of it? Oh wait... But seriously, what would happen?

    Is it really theoretically impossible to Bose Einstein Condensate this new Boson?

    That's an amusing question. You know that the Higgs-field-value which produces the elementary particle masses, is indeed a condensate of the higgs field. However, I don't think this is the same as a bose-einstein condensate of Higgs bosons - the latter is difficult to achieve because the Standard Model Higgs boson decays in an incredibly short time scale. If they were stable, you could surely have a bose-einstein condensate of Higgs bosons. Still, it's interesting to think about it.

    gunn
    It is not Higgs ( http://arxiv.org/abs/physics/0302013v3 ) because every physics event is interpretted by particles which similar well-known elementary particles - leptons, quarks and gauge bozons. Therefore, if anybody will claim that he had found Higgs then not believe - this is not Higgs.
    There is no physics event inrerpretable by Higgs. Higgs field mediates physics events under very special symmetry. Examle: A_B → F(B) → AF(B) = F(B)A . - Some stable symmetry like AB=BA is absolute avoided and the given symmetry with Higgs field F is absolute unstable.

    Tomas
    '

    dorigo
    Once again, sorry to all for being a bit away from this thread - I have been traveling this week (to Spain, for a workshop on hypothesis testing in Madrid). Usually I am more careful with answering comments in the threads. Apologies to all.

    Best,
    T.
    Vladimir Kalitvianski
    "Philip Gibbs does a great job...", so I propose to call it a "Gibbs boson" if it is proven to be a boson. ;-)  Otherwise, a "Gibbs buzzon".
    Hi Tommaso,

    what do you think about this article:

    http://arxiv.org/abs/hep-ex/0504027

    in terms of relevance for the discussion of the potential Higgs signal? Do you think something similar could happen for the Higgs (or whatever) excess?
    Why not ? ;-)

    dorigo
    Hello Bernhard,

    sure, the pentaquark is just one example where many fake signals were published in the past. There, the problem was the prior expectation of the researchers that something should be there, IMO; but the signals arose only because of one crucial thing: the modeling of the background shape was usually insufficiently motivated, and a serious systematic assessment of the related systematic usually absent.

    In the Higgs our prior is strong, but the background systematics are better under control...

    Cheers,
    T.
    I offer an explanation of a Higgs @ 124.443 GeV (a public retrodiction) http://theoryofeverything.org/wordpress/?p=563

    As noted in equation 18 of http://theoryofeverything.org/TOE/JGM/ToE.pdf, I had one of several possible predictions for a Higgs sector mass. It turns out my aesthetic choice was in error.

    Also of interest in this paper (and recent experimental evidence) WRT an exponential (accelerating) Universe, it seems that the Opera FTL neutrinos may confirm my proposal for a variable speed of light type solution using a Doubly Special Relativity (DSR) kind of approach.

    Not sure what all the hubbub is about regarding the title of your post. If you want to define "Firm Evidence" as as what both ATLAS and CMS presented, you are clearly not in the wrong since you can define "Firm Evidence" to mean what ever you want. I suppose its the implication of what most people expect when they hear the term "Firm Evidence" that upsets them as your definition is likely different than most.

    One man's "hints" is another's "firm evidence" as is another's "discovery". (Assuming you don't define discovery to be 5 Sigma).

    dorigo
    Agreed. Further, if evidence == 3 sigma, and observation == 5 sigma, I think that the ATLAS + CMS result (certainly above 3 sigma together) is definitely above evidence level. So even in more quantitative terms, firm evidence is what I'd stand by.

    Cheers,
    T.
    Until Gravity is understood, matter will not be defined. Gravity is not a 'pull'; it is a 'push'. It is an electro-dynamic response influenced by electromagnetism. It is a by-product of matter's reality.