Higgs excluded at 170 GeV (press release 4 August)

[marcus]

Monday 4 August press release
http://www.fnal.gov/pub/presspass/press_releases/Higgs-constraints-August2008.html

===sample excerpt===
Tevatron Experiments Double-Team Higgs Boson

Joint CDF, DZero effort lands Fermilab in Higgs territory

Batavia, Ill.--Scientists from the CDF and DZero collaborations at the U.S. Department of Energy's Fermilab have combined Tevatron data from the two experiments to advance the quest for the long-sought Higgs boson. Their results indicate that Fermilab researchers have for the first time excluded, with 95 percent probability, a mass for the Higgs of 170 GeV. This value lies near the middle of the possible mass range for the particle established by earlier experiments. This result not only restricts the possible masses where the Higgs might lie, but it also demonstrates that the Tevatron experiments are sensitive to potential Higgs signals.

"These results mean that the Tevatron experiments are very much in the game for finding the Higgs," said Pier Oddone, director of Fermilab.
==endquote==

the result was announced yesterday 3 August at this conference:
http://ichep08.com/
by Matthew Herndon (U Wisc. Madison)

 

[marcus]

from what I hear, this result means that the Higgs is not in the range where the LHC would have been especially at an advantage,

it means that if the Higgs exists at all, it should be at a mass considerably higher or lower than 170 GeV-----and for some reason, considerably higher is not considered likely.

so the conclusion is that if the range around 170 GeV is ruled out (apparently with 95% confidence) then, if there is a Higgs it is likely at a LOWER energy where Fermilab has a good chance of scooping LHC and finding it.

So the Fermilab people are happy about this result.

Comment? Anything to add?

 

[Gokul43201]

Wow! That was unexpected (to an outsider, I guess).

 

[malawi_glenn]

As far as I know, the 95% confidence interval is 120-160GeV for the Higgs Mass. I think this is stated somewhere here in these lecture notes on hadron colliders (CERN summer lectures)

Many cross section comparisons are made between Tevatron and LHC for the Higgs boson.


http://indico.cern.ch/materialDisplay.py?materialId=slides&confId=34707

http://indico.cern.ch/materialDisplay.py?materialId=slides&confId=34708

http://indico.cern.ch/materialDisplay.py?materialId=slides&confId=34709

http://indico.cern.ch/materialDisplay.py?materialId=slides&confId=34710

So it's good that Tevatron is sensible to Higgs signal, but LHC has many times higher luminosity and better detectors. Also, hadron colliders are just for finding particles, we can not (at least not to a very high probabilty) determine spin, couplings etc, to make sure that a particle found at say 145GeV IS the Higgs boson stated in the Standard Model. In order to do that, one needs lepton colliders.

 

[Haelfix]

CERN will require ~ 3 years or so before they have the inverse barns to get a 5 sigma response to a Higgs in that range, which gives Fermilab a chance (especially if the Higgs is ~120-125 or so).

Amusingly, CERN very well might pick up a Higgs doublet signal earlier (say from an MSSM Higgs) and then Tevatron would get the other one.

 

[vanesch]

In order to do that, one needs lepton colliders.

[ monty python mode on]
And NOW you say so ! You couldn't have said that at bit earlier, hey ! No, that was too much of an effort, right ? But letting people go on building the LHC for 15 years, that's not too much of an effort I suppose ! You... Twit !

 

[Count Iblis]

Hmmm, aren't there any other reactions possible at higher energies which will give a clean signal? If the Higgs is too light to decay into two Z particles, then isn't it possible to get some process at higher energies involving a virtual Higgs which then decays into two Z bosons?

 

[vanesch]

Hmmm, aren't there any other reactions possible at higher energies which will give a clean signal? If the Higgs is too light to decay into two Z particles, then isn't it possible to get some process at higher energies involving a virtual Higgs which then decays into two Z bosons?

Of course, but then it will not contribute a peak, but some smooth contribution to the ZZ production ; in other words, undistinguishable from all other virtual processes that make up ZZ end states.

 

[malawi_glenn]

[ monty python mode on]
And NOW you say so ! You couldn't have said that at bit earlier, hey ! No, that was too much of an effort, right ? But letting people go on building the LHC for 15 years, that's not too much of an effort I suppose ! You... Twit !

hehe yes - I am the evil himself

I'll chear for CMS @ LHC, just so you know (because I work there now hehe)

 

[humanino]

I've read here and there that Connes' NCG is dead. That is not the way I see it at all : what is dead is the hypothesis of "big desert" within his model, which is hardly a surprise honestly ! Any opinion ?

 

[Norman]

As far as I know, the 95% confidence interval is 120-160GeV for the Higgs Mass. I think this is stated somewhere here in these lecture notes on hadron colliders (CERN summer lectures)

Many cross section comparisons are made between Tevatron and LHC for the Higgs boson.


http://indico.cern.ch/materialDisplay.py?materialId=slides&confId=34707

http://indico.cern.ch/materialDisplay.py?materialId=slides&confId=34708

http://indico.cern.ch/materialDisplay.py?materialId=slides&confId=34709

http://indico.cern.ch/materialDisplay.py?materialId=slides&confId=34710

So it's good that Tevatron is sensible to Higgs signal, but LHC has many times higher luminosity and better detectors. Also, hadron colliders are just for finding particles, we can not (at least not to a very high probabilty) determine spin, couplings etc, to make sure that a particle found at say 145GeV IS the Higgs boson stated in the Standard Model. In order to do that, one needs lepton colliders.

Here is the .gif picture of the:
http://www.fnal.gov/pub/presspass/images/tevComboCLS_highmass_sheer.gif"

From what I can tell it looks to be 170 GeV +/- 1 GeV or so.

 

[malawi_glenn]

Yes I can see it. But according to the results our teacher told us, mass of 170 +/- 1 GeV is not even part of the game. So what Tevatron has done is to exclude a Higgs boson of mass 170GeV or higher with 95% conf. ? So what did you want to tell me Norman?

 

[marcus]

I've read here and there that Connes' NCG is dead. That is not the way I see it at all : what is dead is the hypothesis of "big desert" within his model, which is hardly a surprise honestly ! Any opinion ?

Connes allowed for this interpretation in what he wrote in the blog "Noncommutative Geometry". You may have seen it. He sounded a little sad---and he quoted some beautiful Latin verse by Lucretius.
http://noncommutativegeometry.blogspot.com/2008/08/irony.html

Arivero then showed himself to be a man of learning by giving the next two lines of Lucretius---and even scorning to translate the Latin (whereas Connes gave an English translation for the lines he quoted)
sed nil dulcius est bene quam munita tenere
edita doctrina sapientum templa serena,
[but nothing is sweeter than to possesses a serene precinct well fortified by the teachings of the wise]

Connes said it was ironical that the central figure 170 GeV, in what they had excluded, was exactly what he had predicted (based on the big desert assumption). (I agree with you Humanino---it also seems to me that what they excluded was as much the big desert as anything else including the NCG prediction). Connes too seems to suggests that we be hopeful of seeing some new physics at accessible energies.

 

[humanino]

Connes allowed for this interpretation in what he wrote in the blog "Noncommutative Geometry". You may have seen it. He sounded a little sad---and he quoted some beautiful Latin verse by Lucretius.

I've read several blogs (among which, my personal opinion of Motl as a human being keeps dropping). But I have not seen this interpretation. Connes reaction is "a profound discouragement, mixed with an enhanced curiosity about what new physics will be discovered at the LHC." : discouragement seems to mean, NCG has nothing to say about this new physics. And he goes on to quote Lucretius, which seems to me re-enforce the idea that he has been honestly seeking a "truth" but passes the mission to others.

Fortunately, Connes' NCG is beautiful enough that I will still feel happy about the time I spent trying to understand it.

So Connes too suggests that we be hopeful of seeing some new physics at accessible energies.

I just hope that the NCG interpretation can be recovered, that's just an aesthetic wish.

Arivero mentions "first shot", so maybe he also shares these hopes.

 

[arivero]

Arivero then showed himself to be a man of learning by giving the next two lines of Lucretius---and even scorning to translate the Latin (whereas Connes gave an English translation for the lines he quoted)
sed nil dulcius est bene quam munita tenere
edita doctrina sapientum templa serena,
[but nothing is sweeter than to possesses a serene precinct well fortified by the teachings of the wise]

Could I try/dare to translate the latin to english? For sure not; so I kept myself just following the threading.

For Spanish speakers, I dare to recommend the bilingual translation, to Castillian verse, done by Agustin Garcia Calvo:

Lucrecio
DE RERVM NATVRA / De la Realidad
Edicion critica y version ritmica de Agustin Garcia Calvo
Editorial Lucina, Zamora 1997
​

 

[Count Iblis]

Of course, but then it will not contribute a peak, but some smooth contribution to the ZZ production ; in other words, undistinguishable from all other virtual processes that make up ZZ end states.

What amazes me (I'm an outsider) is that despite the huge increase in computer power we still can't take the data of experiments as input and then compute the best fit values for the parameters of the Standard Model (or extentions of it) in the case that the data do not show some clear smoking gun.

From an information theoretical point of view, the ratio between the amount of data that will be generated by the LHC and the amount of data contained in the model parameters that one wants to extract from the data is huge.

 

[humanino]

What amazes me (I'm an outsider) is that despite the huge increase in computer power we still can't take the data of experiments as input and then compute the best fit values for the parameters of the Standard Model (or extentions of it) in the case that the data do not show some clear smoking gun.

That's exactly what we do. The amount of data you have merely fixes statistical fluctuations. The more you gather data, the clearer you can see the patterns.

 

[Barmecides]

Hello,

it is much easier to exclude an Higgs at 170 GeV than at 120 GeV for both Tevatron and LHC.
Just because around that energy H -> WW* which is much easier to check than low energy signatures.
High energy higgs (> 170 GeV) are also quite easy to discover/exclude due to H -> ZZ -> llll
The most difficult part is above LEP limit where you need to combine different decay channels (H -> gamma-gamma, ttbarH, H->tautau + forward jet,...)
Discovering a light higgs will be very difficult for Tevatron and challenging for LHC.

 

[BenTheMan]

Discovering a light higgs will be very difficult for Tevatron and challenging for LHC.

"Light" means 120-125 Gev? I was under the impression that Tevatron had a better shot at this range?

 

[DaveC426913]

Does larger mass/energy mean larger size? And how massive is massive?

I keep imagining they'll see this baseball-sized particle drifting lazily through their cloud chamber...

 

[Norman]

Does larger mass/energy mean larger size? And how massive is massive?

I keep imagining they'll see this baseball-sized particle drifting lazily through their cloud chamber...

Define size...

 

[DaveC426913]

Define size...

Yeah, I know.

 

[Barmecides]

"Light" means 120-125 Gev? I was under the impression that Tevatron had a better shot at this range?

Hello,

if you look at the bottom figure from this web page :
http://tevnphwg.fnal.gov/results/SM_Higgs_Winter_08hepex/
you will see a plot drawing 95% exclusion limit/SM. As long as this number is > 1, you cannot exclude the point.
To summarize this plot, the higher is this number, the more difficult it is to exclude an higgs with such a mass.
As you can see, the easiest part to exclude is around 160 GeV, which explains why this summer they did it.