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    2012: The Higgs Is Found, Or Ruled Out
    By Tommaso Dorigo | April 10th 2010 07:41 AM | 47 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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    In two years the Higgs boson will be close to discovery, and its mass already known, or the particle will be already in the trash bin. That is the single line which best summarizes the scenarios I depicted yesterday, in the concluding slides of a seminar I gave at IFIC, in beautiful Valencia (below, placa de la Virgen on a pleasant evening, taken with my iphone).

    Those of you who follow closely this blog may remember that I gave a seminar on Higgs boson searches at the Tevatron two months ago in Louvain, Belgium. After the visit to Louvain, I noted here that it takes one a substantial amount of work to prepare a well-constructed seminar, regardless of how well one knows the topic. And I ventured to hypothesize that among my readers there could be somebody willing to invite me, to give an updated version of the same seminar at some other university or institute, preferably located in some interesting place to visit.

    My wish materialized overnight when Martin Alonso, a PhD student at IFIC Valencia, took contact with me to organize a presentation there. As I write these notes, I am in the Valencia airport, homebound after two very pleasant days. The people I met at IFIC were very kind and interesting, the city is quite beautiful to visit, and the food I ate there was spectacular. But the most fulfilling part of the trip was, indeed, the seminar.

    I hope my colleague Andrea Giammanco, who first invited me to Louvain, will not resent the fact that I am claiming my presentation in Valencia was appreciably better. Of course, unless you are really dumb you learn from your mistakes: and although my talk in Louvain was reasonably good, after giving it I realized I might cut some material, reshape some other, cite a few more papers, and include the latest results of searches that had not been published before February. The reshaped seminar received a very positive feedback at IFIC, where I got the attention of about thirty among staff physicists and graduate students, despite the absence of many for Easter vacations.

    I would be happy to advertise the package further, in the hope to collect other invitations; but I am traveling way too much these days, so for a while I will stop willfully overburdening my schedule -unless invitations come from really appealing places! Instead, let me reproduce here, amended and simplified, the part of the seminar where I discussed the future of the Higgs boson searches, and the scenarios that are taking shape in front of us.

    2013: The Higgs is found, or excluded, or ...

    One needs several ingredients in order to put together a meaningful prediction for when, how, and by whose hands this now over thirty-year-long saga of the Higgs boson will get to an end. But it so happens that those ingredients are available today, and for the first time we have a rather credible way of extrapolating both Tevatron reach and LHC reach at least three years in the future. There are, in fact, some factors making this particular moment of time a good pick to play the "seer".

    First of all, the Tevatron: Higgs searches there have become stable in their output, in the sense that the technology is quite refined, and it is not foreseen to improve significantly in the future (at least by yours truly). It might, but taking what now exists as a basis for extrapolation is a conservative, sound approach, and the one I will follow.

    Second, the LHC has finally started running at 7 TeV energy in the center-of-mass. The first W bosons are timidly popping up already! This means that the ball is rolling, and I do not think there are significant caveats in trusting the integrated luminosity profile versus time that the LHC machinists have predicted for the next two years, helium blowups allowing. And it also means that we can reliably take it for granted that CMS and ATLAS will be looking at roughly one inverse femtobarns of data by the end of 2011.

    And third, much of the hard work has been already done by CDF some time ago. Basically the CDF predictions are provided in the form of two pairs of plots, which are shown below. The first pair describes the 95% confidence-level limits on the ratio R between excluded Higgs cross section and standard model expectation, for two significant values (115 and 160 GeV) of the Higgs mass: if R=1 is excluded, then the Higgs is disfavored to exist at the corresponding mass.



    Above, expected 95% confidence-level limits on the ratio between production cross-section of a 115-GeV Higgs boson and its standard model prediction (on the vertical axis) are shown as a function of available integrated luminosity (on the horizontal axis), in the hypothesis of (1) a combination CDF and DZERO searches, in the further hypothesis (2) that DZERO analyses at low mass become as strong as the ones by CDF (they are significantly less stringent presently), and in the final hypothesis that (3) the data follow the expectation of the background (as opposed to producing a unlikely fluctuation upward or downward, which may change the picture quite sizably).

    The black like, which passes through the most recent CDF result (doubled in sensitivity to incorporate hypothesis 1) corresponds to a simple scaling of the R limit with the square root of the integrated luminosity on which the analyses are based. The colored points and curves refer to earlier instantiations of the same analysis, which were less powerful and thus exploited less well the available data.



    Above you may instead see the twin plot corresponding to a 160 GeV Higgs boson search. As before, you may note how the limit has become more and more stringent with increases in luminosity, scaling way more steeply than what the data increase predicted. The reason is that the time between the various results was used successfully by the experiments to improve the precision and care of their results. But let us concentrate on the future, not on the past.

    Instead, before I start discussing the power of Tevatron searches to actually see a signal if one is there, let me stress one point about these plots. What is shown is the power of the data and its analysis; even if future data should withstand a statistical fluctuation, the results shown would still stand -because they are not actual results but averages, or rather medians. A wild fluke might make the exclusion significantly stronger, or weaker. For instance, a 115-GeV Higgs boson might have already been excluded with 5 inverse femtobarns of CDF and D0 data, if backgrounds had fluctuated down by about 2.5 standard deviations!

    Once that is clear, let us examine the second pair of graphs: these are a different kind of sensitivity reach plots, again produced over a year ago. They still constitute our best predictions for the chance of a Higgs boson sight; actually, the recent developments -Tevatron performance and added improvements in the analyses- make the predictions more trustable. These plots show, as a function of the Higgs boson mass (on the horizontal axis), the probability (on the vertical axis) that CDF and DZERO, by combining their 5- (in red) or 10- (in blue) inverse femtobarns datasets, may obtain a 2-standard-deviation excess due to Higgs bosons, if that particle exists at that mass. Please ignore the dashed lines, which represent the case of further improvements in the analysis techniques which I doubt will ever be possible. Still, you can observe that the probability of a 2-sigma excess is quite sizable, and even a 3-sigma evidence is possible if the Tevatron gets lucky.



    Above, the probabilities for a 2-sigma excess as a function of Higgs mass, with 5- and 10-inverse-femtobarns.



    And above, the probability of a 3-sigma evidence as a function of Higgs mass.


    Including Luminosity estimates and LHC predictions in three scenarios

    None of what I showed above is new to you, if you have followed this blog in the course of the past year. Yet we can build something more interesting with that information. We need some more input to make more precise predictions on what will happen in the next few years, on the west side of the Atlantic. We need to know what is the total integrated luminosity that CDF and DZERO will be able to analyze, and when.

    Please have a look at the graph below: it shows the integrated luminosity that the Tevatron collider delivered to the experiments as a function of time. The curve has followed an almost exponential trend: it has fulfilled our wildest dreams of five years ago, delivering data in perfect accordance to a "design plan". Including the now customary yearly shutdowns of two months, the machine now produces over 2 inverse femtobarns per year.



    With that trend in mind, we can extrapolate to the end of 2011, which is the probable date when the Tevatron will stop running for good. It does not make much sense, in fact, for the US Department of Energy to spend over 200 million dollars a year running a machine that is now outdated by the LHC startup: every additional year of running would add only 10% more reach for discoveries and measurements (2 femtobarns over 10 is 20% luminosity, or 10% statistical power).

    So by the end of 2011 it is a safe bet to claim that the Tevatron will have delivered about 11 inverse femtobarns of data to the experiments. This translates in a bit less than 10 inverse femtobarns of collected collisions (the efficiency is never 100%, for several reasons which would get this post wildly off-topic).

    In Europe, in the meantime, the LHC will deliver one inverse femtobarns of data to ATLAS and CMS. There exist predictions for the reach of these experiments in the search for the Higgs boson, but they were computed assuming 10 or 14 TeV collisions. At 7 TeV, the Higgs boson has a cross section which is twice smaller; backgrounds are also smaller, but the net result is a significant hit in sensitivity. It is however possible to make some extrapolations and compute the sensitivity that a combination of ATLAS and CMS data will have on the Higgs boson. I did the exercise, and have my own results.

    Putting everything together, I can now post here a slide of the seminar, showing three different scenarios for what will happen by 2012.

    Three Scenarios



    As usual, my slides are quite descriptive, so there is little to comment on. It is important, however, to note that the existence of the "standard-model-like" Higgs boson is what makes a difference: if the Higgs exists, it will most likely be found by the LHC experiments. If it does not exist, however, it will be the Tevatron to rule it out first.

    Maybe one more thing to note remains to be made. The title of this post suggests that by 2012 the Higgs might be found and its mass known: this, for particle physicists, usually implies a 5-sigma excess of signal events. But it needs not be so: in 1994, for instance, the top quark was found by CDF, and its mass was measured (with excellent accuracy, as demonstrated later). That was not a discovery, since the effect amounted to only three standard deviations; the discovery came one year later, by both CDF and DZERO together. Nevertheless, by 1994 everybody was convinced that the top quark was there. And those who doubted were later proven wrong... So if you are not a blind sceptic, 2012 may be the year for the Higgs as well!

    And one final remark: however it goes, the next two years will be quite exciting!








    Comments

    Tommaso,

    Thanks for this excellent report.

    My humble prediction is that debates on how to interpret the data will last far longer than 2012. Too much hangs in balance when it comes to Higgs physics / EWSB mechanism/ unitarity and contending camps are not going to easily give up.

    Cheers,

    Ervin

    Hi,

    it might be interesting to note that right now the Tevatron is seeing exactly as many Higgs-like events as to be expected for a Higgs mass at or above 115 GeV. Only the statistical power is not very strong yet.
    The same holds for LEP: also here exactly the "right" number of Higgs-like evens were observed for MH = 116 GeV
    (resulting in the final 1.7 sigma fluctuation).
    There is hope. :-)

    Cheers, Sven

    hi, great post! Could you include a link to your slides? Thanks, A.

    MarshallBarnes
    Tommaso:
    You almost had me going there  - I saw the beginning of the article title and thought that I had finally won my bet with Stephen Hawking. Ah, but the suspense builds...
    Aw, shucks, Tommaso, you called it a Fairy Field! Made my day. But Ervin is right ... the way things are now in theory, it will take many deaths for progress to be made.

    Hi,
    while it is worth to look for a SM Higgs, I think it's far more crucial to find (or exclude) SUSY. How heavy have gluino and stops to be in order to evade discovery by 2012?
    Best, B.

    I'll be sure to check back in 2012! : )
    Hi,

    > I hope my colleague Andrea Giammanco, who first invited me to Louvain, will not resent the fact that I am claiming my presentation in Valencia was appreciably better.

    Don't worry, I know very well by experience that the N-th seminar on a subject is always much better than the (N-1)-th, whatever the value of N :)

    (I have discovered a truly marvelous proof that this series does not converge, but this margin is too narrow to contain it.)

    L O L!

    What does 2x in the 2xCDF stand for? The current combined CDF+D0 sensitivity (expected 95% limit) with 4.8-5.4 fb^-1 data is R~3 at mH=115 GeV http://tevnphwg.fnal.gov/results/SMHPubWinter2010/fig3.gif,
    while your plot gives R<2 expected with even smaller luminosity. Any comment?

    dorigo
    Hi Slava,

    2xCDF means what CDF and DZERO would get, with their expected limits, if they had sensitivity equal to CDF. D0 has currently a smaller sensitivity at low mass than CDF, but this should not be attributed to a worse detector but rather analyses less refined. This means that, investing enough manpower, they will eventually reach down in sensitivity as much as CDF is doing now.

    The current 95% cl limits at 115 GeV for single-experiment combinations are:

    CDF R<3.10 observed, R<2.38 expected
    DZERO R<4.05 observed, R<2.80 expected.

    When extrapolating, expected limits are used to avoid giving weight to statistical fluctuations.

    Cheers,
    T.
    Hank
    If the Higgs is not found, I am buying the prediction that it will be because the Higgs is so dangerous to mankind that we are not ready for it, so it will travel back in time and destroy itself and maybe a few continental plates, just to be certain.   

    I will be having a party December 21st, 2012 to celebrate being right.  Though it will be something of a Pyhhric victory.
    can you please give links to plots produced by the experiments showing the expected exclusion limits that you cite?
    do I read correctly that this plot
    http://www-cdf.fnal.gov/physics/new/hdg//Results_files/results/hwwmenn_0...
    gives R~10 (expected) for mH~115 (CDF)?
    thanks a lot,
    Slava

    Trying to find the theoretical higgs boson and string theory in an under ground super magnet is like trying to catch a butter fly with a atom bomb. Take a little time off and go outside when there is some cloud cover and study the patterns in the clouds you see when you look up. Earth's cloud cover and upwards to about 90 kms gives you all the understanding that you are seeking. You are looking at the negative image of the strings of space in earth's cloud cover. Strings of negative dark energy that pull in positive moisture particles and we call them clouds. Your missing dark matter isnt missing and isnt dark either, the stuff is every where in the universe and its clear it doesnt reflect light. It is part of light as we see it, on our tiny little planet with our tiny little eyes that are restrictive to only white light. NASA is hidding a very spectial picture of something called (Kite-lightning). The picture was taken many years ago and they have been investigating it every since. They for some reason showed a picture of it on TV in the houston area right after the Columbia STS 107 crashed in 2003. The picture actualy shows the strings of space you are looking for and the study of it also shows that gravity is a local force, not energy acting from a distance.
    You people are looking at the micro when you should have been looking at the macro. I saw that NASA press release and marvaled at the pattern in the picture of Kite-lightning. The pattern is made up of cells of positive and negative material that matter doesnt easily act with, planes fly right through and just build up static electrical charges. I have a book out called Thor's Anvil Revealed, its on Amazon.com books. There is a picture of Kite-lightning on the books cover. Just look at it on Amazon books and see for yourself. Just positive and negative matter seperated with some insulator material.
    When a lightning strike occurs the Kite-lightning sets off and shoots the red sprite high into the atmosphere pulling along with it many miles of the structure of space's solid clear matter. The plasma ball created by the Kite-lightning ignites the material as it glows for a few milli seconds. Most of the structure comes back down and is woven into the rest of this special matter and again awaits another lightning strike. Some of the material is burnt to ash and returns to earth as helium 3 isotope space dust. The same material is being burnt and comsumed by our sun. Its the same type of helium 3 isotope space dust thae fills our solar system. This is how helium 3 isotope space dust is generated in earth's own atmosphere. Thor's Anvil Revealed by Charles E. Schirmer

    I don't think I've ever seen an internet kook post this level of crazy-crazy in such well formed sentences before. Hats off to you Dr. Kookinstein! Seriously though you should talk to your doctor about a refill on your Clozapine.

    Come, come, Mr. Schirmer, back to the room and don't forget to take your medicine.

    Hi Tommaso,

    I'd like to add my thanks for this clear and comprehensive post. I'd also like to add comments in the role of 'blind skeptic' :-) or if not blind at least ignorant, but definitely skeptic. The LHC has gotten off to a great start. Truly amazing technology, not to mention several thousand of the world's smartest people on hand to make it run. But I think there are still reasons for cautious skepticism.

    1) Murphy's Law - After several postponements and unexpected setbacks, what chance is there that the LHC's current three-year plan will come off without a hitch? With 27 km worth of equipment that must not fail, I am reminded of that early Univac computer that had 10,000 vacuum tubes ready to burn out. I'm just saying that the LHC depends on many critical pieces working together, and a 99 percent success rate for each may combine unfavorably. I'll feel better after a month or two, after we've had time to see if the glitches are tending to mount up or taper off.

    2) You say it's not worth running the Tevatron for an extra year for a mere 2/fb additional data. Yet the LHC's plans call for only 1/fb to be gathered in the next two years. True it is at a higher energy, but barring a spectacular surprise in that energy range how is this a greater value? I see we will gain experience in running the new machine, calorimeter calibration and so forth, but two years from now we will not be any closer to finding the Higgs. More likely the best results during that time will come from LHCb and ALICE.

    3) I'm surprised at the low target of 1/fb in the next two years compared to the LHC's design which calls for 10/fb/year. Currently they are populating two buckets per beam out of 2808 and calling it 'probe beam', not even up to 'pilot beam' level. The reason of course is that a fully populated beam can cause damage if it goes astray, and they are right to start small. Most analyses for Higgs discovery that I've read assume 20 to 30/fb, i.e. two to three years at full power. In an ideal scenario (assuming everything stays on schedule!) such a run could begin in 2013, not before.

    4) What happens in 2012? The solder connections will be time consuming to fix, but at least there it's well understood what the problems are. How about the magnets? How we can get those other magnets up to 8T? I think that may be the real motivation for the present three-year plan - that sometime between now and then, maybe someone will think of a solution!

    dorigo
    Hi Bill,

    I share your concerns for point number 1, but there is little to comment. The LHC is a daring concept, and we will have to be lucky.

    As for the value of the first 1/fb at LHC compared to the 11th and 12th 1/fb at the Tevatron, it is just incommensurably higher. With the latter you cannot discover anything -what you have in the data after 10/fb, is there after 12. With the former, you may discover supersymmetry, Z' bosons, large extra dimensions in a space so much wider than that accessed so far at the Tevatron and elsewhere, that I should not spend time on this answer.

    As for luminosity, there are several factors. Beam stability at 7 TeV, safety, finding the right tune of the machine... I however believe that the LHC machinists will surprise us.

    Cheers,
    T.
    You should be very cautious with titles like that, specially when you know you have journalists checking out your blog.
    What you say is simply not true but it sure sounds catchy. Don't complain afterward when journals (even as serious as The Economist) write carelessly about the LHC.

    dorigo
    Armonyous,

    maybe you fail to realize it, but this is already a form of journalism... And as such, sometimes it uses catchy titles. I prefer my articles to those of new scientist or other magazines, which have catchy titles _and_ incorrect content.

    Cheers,
    T.
    Whether it is a form of journalism or not, the fact is that the most likely situation in 2012 is that neither Tevatron nor LHC will have sufficient indication of a Higgs signal to do more than setting a bound on its mass. This is in blatant contradiction with your title and to that extent, your article is misleading.

    I completely agree with the above comment and think you are being extremely careless here Tommaso. We have a 5 sigma discovery rule in particle physics for a very good reason and there is absolutely no way we'll get anywhere near that by 2012.

    I simply don't understand the need to hype and essentially tell lies about what is already very interesting physics. Be cautious and if the Higgs is discovered early everyone can then take credit for doing an even better job than expected. By giving the most ridiculously optimistic scenario you are only setting all particle physicists up for a fall.

    Just for the record I would predict no confirmed Higgs before 2016!

    Are you the Jack of all trades and master too?

    dorigo
    And what does "I" mean, anonymous commenter ? You are nobody until you have a name here.

    In any case,  you do not understand that the public needs to feel the excitement for a competition and a search, rather than sterilized comments only when the "certified discovery" is confirmed. We need to create expectations, without the fear of "setting all particle physicists up for a fail". Fail, fail. A taboo word especially for americans (from where I guess you come). Nobody is failing if there is no higgs, nor if the higgs is discovered in 20 years. We can predict something with the data we have, and by that I can stand: by the end of 2012 there are 50% chances that we will have a significant hint of where the Higgs is, or have excluded it. This I presented in Louvain and Valencia, in front of a total of about 60 particle physicists, none of whom unnamed and faceless like you, and none objecting meaninglessly like you.

    Cheers,
    T.
    I'm sorry that I am anonymous but I prefer to stay that way, if you wish I will send an email explaining why.

    You now say: "by the end of 2012 there are 50% chances that we will have a significant hint of where the Higgs is, or have excluded it".

    Compare this to: "2012: The Higgs Is Found, Or Ruled Out, In two years the Higgs boson will be close to discovery, and its mass already known, or the particle will be already in the trash bin."

    First of all, you have now significantly weakened your original statement (never mind that I still think it is extremely optimistic).

    Secondly do you honestly think that the Higgs Boson will be anywhere near the trash bin in 2012 even if we haven't seen any excess at all above background? My worry is that this site is read by journalists who will take the initial statement as gospel. When 2012 comes around and surprise, surprise, in all probability we have very little evidence for the Higgs the conclusion in the popular press could be that either the LHC has failed or there is no Higgs. Neither of these things will be anywhere near the truth!

    Sorry, to add a little extra:

    Of course I realise the need for competition and excitement and this blog definitely helps to enthuse the public. I would just be a little more careful with the predictions. There can still be a competition, just have the finishing line a little further in the distance!

    The statement is not weaker, it is just more accurate. By blogging for years I have learned that to communicate effectively you need to trade accuracy for clarity. If a science reporter can only read titles is not my fault; the post explains things better but takes time to read.
    In any case you continue to avoid the real issue: there is nothing to lose ("cerdibility"?), but a lot to gain, namely the attention of laypersons. I will continue to work in that direction, even to the benefit of those like you, who do not realize that it is crucial for the survival of pure research that the public gets familiar with what we search and why. I explained it too many times why I believe a string of "failures" ending in a discovery is more valuable than a discovery alone. I am kind of tired...
    Cheers
    T.

    And sorry for having missed your last question, but yes, chances indeed are that cdf and dzero exclude 115-180 by end of 2012, and cms+atlas 150-200. This is pretty clear from the tevatron plots at least, and all the info and experience I can add to that does not change the pic.
    Cheers,
    T.

    ... And one last comment: we have to stop trying to babysit the science media. Leave them alone and rather start doing some outreach ourself! There is no other way.

    Hank
    ... And one last comment: we have to stop trying to babysit the science media. Leave them alone and rather start doing some outreach ourself! There is no other way.
    Preaching to the choir.  It's the whole reason this site was created!
    dorigo
    Hank you sound like you thought my comment was from the other guy :) I definitely was not clear. The "us" in my comment was particle physicists in general, not me or you (who already know what needs to be done and are doing it, as you point out)...

    Cheers,
    T.
    I think the definition 'exclude' is potentially misleading to the layperson.

    For example, it is my understanding (and I am not an expert) that with the latest 2010 Tevatron results if you reduce the standard model Higgs cross section by 1 sigma (or increase the background by 1 sigma) the 2-sigma tevatron 'exclusion' disappears. Hence, the definition of 'exclusion' is important!

    In addition, I don't know if you are aware of the following paper but please take a look: http://arxiv.org/abs/1003.4266

    The conclusion is that the errors used in the tevatron analysis (where in my opinion the 'exclusion' is rather weak) assumed a theoretical error on the production xsec~10%, but a more reasonable estimate is ~40%. If you are a pessimist, this reduces the number of Higgs by a factor of 2 and you can completely forget any exclusion. Of course an optimist can also say that the Tevatron is back in the game for discovery as the cross section may be much higher!

    dorigo
    Anon, of course a "95% cl exclusion" means very little. The meaning of "exclusion" in fact, is quite slippery. The LEP II exclusion at 114.4 GeV is really a brick wall -go to 112 and the probability has fallen to 10^-7. For the Tevatron it is indeed different. Again, the hope is that readers will little by little learn what we call "exclusion" and grow a critical thinking of their own. You seem to be learning well in fact ;-) (you are anonymous so I am entitled to putting you in whatever category I prefer).

    About the article. The uncertainty is claimed higher in the direct channel, which will not be useful at low mass, where the LHC cannot reach. So it does not change the picture of my predictions -the region where the gg channel dominates the searches will be beaten to death already by 1/fb of LHC data in two years.

    Cheers,
    T.
    Ok, I'll ask the question a little more directly, if in 2012 we have seen no sign of the Higgs, is it dead below 140 GeV or so? I would certainly say that we have to wait for the LHC to get something of the order of 30fb-1 before we can really start to make any firm conclusions. i.e 2016 at the earliest!

    The article was simply to illustrate my point that exclusion bounds mean very little at a hadron collider when you are pushing searches to the limit (as you seem to agree). I also agree that the LEP bound is something very different!

    dorigo
    Yes and no. At 160 GeV, with 10/fb/exp the Tevatron either sees the Higgs, or it is not there. Now it is fifty-fifty.

    By the end of 2012, if the Higgs does not exist, with 10/fb/exp, there is roughly a 50% chance that the exclusion probability surpasses 95%. This means little, but it makes my claim grounded. Please note: the exclusion probability might be ridiculously small -if backgrounds fluctuate up- or even above 3-sigma in the other case.

    Cheers,
    T.
    I honestly think you (and I say "you", not "one") can really transmit the enthusiasm and thrill of the Higgs search without making those not sufficiently cautious and uncalled predictions. Yes, it can be fun playing that game, but then say it's a bit of a game.
    And being careful on that count is not babysitting the media. You are the expert here: do you expect the journalists to start arguing with you about this like other readers of the blog do?
    By the way, do you have an opinion on that paper mentioned above, http://arxiv.org/abs/1003.4266 ?

    dorigo
    Yes armonyous, I do have an opinion. I think it is a honest work, and I believe it will be taken into account in some way in the future analyses. However, their approach of varying the scale such that the NLO result includes the NNLO band is a bit arbitrary and too conservative. Also, they are not the only theorists playing this game, and if they are the only ones quoting so large uncertainties (and they are), I would be a bit cautious.

    Also, they were a bit careless here and there in the paper. The Tevatron limit reference, for instance, has a typo.

    Cheers,
    T.

    First of all, varying the scale is always arbitrary and there is no 'correct' procedure. However, what is important is that the previous, less accurate prediction has a large enough uncertainty associated with it, so that any future more accurate prediction lies within it. Too often we have seen a calculation done to a higher order and the new prediction lies outside the previous uncertainty bounds. Whilst it may go against your instincts, caution is the better part of valour!

    Secondly, the scale choice contributes to less than half of the total error, the pdf and strong coupling uncertainties alone are more important!

    Finally, I have nothing to do with the authors of this particular paper (although I do know that they are extremely well respected). However, although they are the first to write a complete paper on all the uncertainties, it has been well known for a long time that the uncertainties were underestimated in the Tevatron analysis and the result presented in the paper comes as no surprise.

    dorigo
    Your third paragraph is a unsubstantiated allegation, and coming from an anonymous source is liable to be censored. I leave it there but you do sound a anonymous troll, while CDF and DZERO have 1200 prestigious scientists with a 20-year-long record of careful and conservative physics results.

    Cheers,
    T.
    Ok, so how do you explain the fact that uncertainties coming from the PDF's and coupling constants alone are greater than the total theoretical uncertanties used in the Tevatron analysis. (Note that this ignores the scale uncertainties which are the largest single contributor)

    Hmmm, maybe I should now shut up before I say something silly. At the end of the day, what we are interested in is if we can one day find the Higgs and that is the important task. I just feel that people should be aware that even if the Tevatron 'rules out' the Higgs in a particular mass window....... well lets just say that it isn't really ruled out at all.

    Let me repeat my concrete question. Can you please provide links to collaboration plots citing the exclusion limits that you cite. The plots on the Tevatron and CDF Higgs working group page give several times bigger R for m_H=115 GeV.

    dorigo
    Sure. The combined numbers are in arxiv:0911.3930  which has both numbers and plot.

    You find there, for 115 GeV, Rexp<1.78 , Robs<2.70 for the combination.

    For CDF, at 115 GeV it is Rexp<2.38, Robs<3.12, see here.

    For D0, at 115 GeV it is Rexp<2.80, Robs<4.05, see here.

    Still confused ?

    Cheers,
    T.
    Now it's clear, thanks.

    Jun 14, 2010

    I am not a member of the Physical Society of Japan.
    I live in the world of suffering. I am distressful fine.
    My english is not necessarily a good.

    My manuscript ( http://hwbb.gyao.ne.jp/k_aoki/zoetrope/index.html )
    was submitted to Annalen der Physik in 2009.
    Since 2008, I have been revised my paper to submit.

    You may already know it.
    Many researchers around the world already know.

    If it is not wrong, I do wish we should reconsider the modern physics.

    (Feynman Diagram, Dirac sea,
    Parity violation in weak interaction (-> Parity Conservation?),
    Early universe, Kobayashi-Maskawa Theory, ...)

    If the world were born to photons(particle-antiparticle pairs) in light,
    we will return to photons.

    Thanks for the bounds, we've had a long wait already, but looks like a couple of years of excitting physics ahead. A question does it make if difference if the Higg is not elementary but comes from some type of techicolour theory? Personally i'd feel god let us down, if adding ad hoc scalars whenever you need one, was a good way to explain reality. I.e. I've developed a prejudice against scalars boson, while reading arVix.

    dorigo
    Hi Barry,

    it of course does make a big difference for the structure of the theory. I think the true laws of nature may only look ugly to us because we do not understand them well, though. We'll see what happens in a couple of years!

    Cheers,
    T.
    At last, my paper is in Press.

    Open Journal of Microphysics
    http://www.scirp.org/journal/ojm/

    About OJM
    -> Articles In Press

    Volume 1, Number1(May)
    Hypothesis of Conservation of Particle Number
    Kozo Aoki
    PDF (Size:740KB), PP.1-12