Higgs at 120Gev !

[CraigS]

Rumours are flying thick and fast following CERN's officially released Nov 18th combined ATLAS and CMS searches …

LHC Combination of Higgs Limits: MH<141 Gev (http://www.science20.com/quantum_diaries_survivor/lhc_combination_higgs_limits_mh141_ gev-84800)

The scoop seems to be that they'll be announcing a likely candidate for the Higgs Boson to a three sigma level, at around 120GeV. It seems we'll have to wait until Dec 13th for the official announcement … and at only 3 sigma, they'll probably be calling for more data to confirm it … so, maybe, add another six months to that date for the confirmation announcement.

Cheers

[spacezebra]

Craig

Is it possible to simplify the document attached, Im interested to know a little more about the Higgs Limits.

Cheers Petra d.

[CraigS]

Hi Petra;

Pretty convoluted graphs, eh ?

As I understand it, from the first graph, the intersection of black line and the red line indicates that if there were a Standard Model Higgs, (HB), boson at 140GeV, then the probability of getting a stronger signal than the one seen, would be 0.95.

Also, at the 140GeV point, there is almost a 3 sigma excess. What this means is that if there were not an HB at this point, then the probability of getting a weaker signal than the one observed, would be about 0.99. So, the signal indicating a Higgs boson at 140GeV is five times stronger than the one tending to exclude it.

The bottom plot of the second graph ('Best fit sigma/sigma SM' etc), takes into account past observations, (Bayesian analysis), and theoretical predictions, and assigns a higher probability that the HB will most likely be found at the lighter end of the mass scale. The presently found results are then re-plotted against the 'expected' range, in order to narrow down the mass search region. It shows the region from 110 to about 180 GeV, has the most chance of where theory and past observations would predict/expect finding the notorious HB.

The plot on top of this one has left me for dead .. I haven't got the time today to work out exactly what its saying … (sorry).

Hope that helps.

Cheers

[sjastro]

Petra and Craig,

Even though there is one LHC there are two experiments going on here, the Atlas and CMS searches. Both have the objective of locating the Higgs boson.

For the top plot in the second graph, each test produces it's own sample data. The data from Atlas and CMS has been combined.
While both tests separately should show the Higgs boson having the same mean energy value, sampling data from both experiments may indicate that the mean Higgs boson energy has deviated by some particular amount.
The P-value is the probability that this deviation is due to sampling errors in the tests.

The theoretical values are based on Monte Carlo experiments. (http://en.wikipedia.org/wiki/Monte_Carlo_method)

These are in effect mathematically generated virtual particle accelerator experiments.

Regards

Steven

[spacezebra]

Thank you both for taking the time to reply.

Okay, I think that I have a handle on this. I do have another question - but need to think it through. You may have already answered it.

Thank you again - this is really getting interesting.

Cheers Petra d.

[Robh]

Interesting final comment from this short article ...
http://www.wired.com/wiredscience/2011/12/higgs-lhc-anticipated/

"A 125 GeV Higgs is lighter than predicted under the simplest models and would likely require more complex theories, such as supersymmetry, which posits the existence of a heavier partner to all known particles."

Then add this from wikipedia (on the Higgs boson) ...

"The Standard Model does not predict the mass of the Higgs boson. If that mass is between 115 and 180 GeV/c2, then the Standard Model can be valid at energy scales all the way up to the Planck scale (1016 TeV). Many theorists expect new physics beyond the Standard Model to emerge at the TeV-scale, based on unsatisfactory properties of the Standard Model."

I don't understand. If the standard model doesn't predict the mass of the Higgs boson, then why is a mass of 125 GeV a problem?

Regards, Rob

[CraigS]

Been thinking about your question here, Rob .. my pure guess would be that one (or both) the two pieces of information you presented may not be founded in accurate assumptions (??)

I'm not sure I understand the overall problem posed by the Standard Model (SM) not making an accurate prediction of the HB mass, either (??).

It looks to me as though it is expected (by the author) that the SM should be capable of being extrapolated both up and down the energy scale (ad infinitum ?). I'd question the rationale behind this expectation. The SM theory seems to have been constructed after the discovery of particles (from particle accelerator experiments) … who is to say that it is accurate beyond the range over which we know it to be useful ?

I think this aspect is why they're excited about 'new physics' emerging.

I can't see why 125 GeV would be seen as being outside the range of usefulness of the SM. If the HB is discovered at this mass range, to me, it would seem to be well within the applicability range of the SM ? Perhaps they're saying that the HB can only exist at this range if SUSY is found to be valid … (I'm not sure this rationale is logical, however).

Sorry I can't be of more help on this one.

Cheers

[sjastro]

Rob and Craig,

The problem with a low Higgs boson mass is that it can create fine tuning problems. (http://en.wikipedia.org/wiki/Fine-tuning)

It's difficult to explain without going into some very deep theory but one of the principles of Quantum field theory (QFT) is to define and sum all the momentum changes as a particle goes from an initial quantum state to a final quantum state. This can lead to divergences (the UV catastrophe) where the summed momentums become infinite.
To avoid such infinities the theory needs to be renormalizable (http://en.wikipedia.org/wiki/Renormalization).
Quantum electrodynamics and Quantum chromodynamics are examples of renormalizable theories.
Quantum gravity is not renormalizable which is why no one has been able to unify gravity to the other forces.

A problem with a low Higgs mass is that renormalization can add mass to the Higgs boson. To avoid this the theory needs to be very finely tuned.
If SUSY exists then the problem goes away as the infinite terms are cancelled out.

Unfortunately technical papers describing this issue are very complicated and require a knowledge of the mathematical aspects of QFT.
This is one of the "simpler" explanations (warning high maths content).:(
http://www.weizmann.ac.il/particle/nir/uploads/file/chapter1.pdf

Regards

Steven

[Robh]

Steven, thanks for the info.

I actually get some of that. Renormalization is used to remove infinities and make the theory conform to reality. A low Higgs mass is more sensitive to renormalization. I don't pretend to know how they derived those equations but I understand how the function can diverge to infinity.

So, are you saying with SUSY that renormalisation isn't needed?

Regards, Rob

[sjastro]

Hi Rob,

SUSY doesn't eliminate the need for renormalization.
There are two types of divergences, logarithmic and quadratic divergences.
Renormalization handles logarithmic divergences quite well, quadratic divergences are a different story.

SUSY eliminates the quadratic divergences.

http://en.wikipedia.org/wiki/Hierarchy_problem

Regards

Steven

[Robh]

Nice clarification! Thanks, Steven.

Regards, Rob

[CraigS]

Thanks Steven ... very interesting.
I'm starting to see why the 120 GeV mass range might represent a kind of interesting prospect for particle physicists.

I read somewhere, (can't remember who said it), words to the effect that: 'possibly the most boring result which could come from the LHC, would be if the Higgs is found ... and nothing else'.

If the Higgs is found at 125 GeV however ... and nothing else ... then the fine tuning issue may drive some particle physicists to drink !

Cheers

[sjastro]

Hi Craig,

That remark came from none other then Steven Weinberg, the winner of the 1974 Nobel Prize for the development of Electroweak theory.

I find the remark a trifle strange as Electroweak theory as developed by Weinberg assumes the existence of the Higgs boson.:shrug:

Regards

Steven

[CraigS]

Well, from what you've pointed out, perhaps he knows that more than a mere particle 'discovery' will be needed to answer the truly nagging issues iconified by the Higgs ?
Cheers

[sjastro]

Not sure about this, but 5.0 sigma is the trigger for announcing the discovery.

http://physicsworld.com/blog/2011/12/higgs_rumours_fly_as_meeting_a.html

Regards

Steven

[CraigS]

Whaaaa ????
Talk about cookin' the numbers !??!

At the very best, this has to be the worst kept announcement of all time !
The way its going, there's no need for the official annoucement ... everyone already knows it all !
:lol:
cheers

[sjastro]

I think we need the input of a statistician on this.

Incidentally I hear the announcement will be webcast.
https://indico.cern.ch/conferenceDisplay.py?confId=164890

Steven

[Robh]

Craig, I agree with you.

If you have two random variables x and y with mean1 and mean2, and then you add the variables x + y, the new mean = mean1 + mean2.
The standard deviations add in quadrature i.e. new sd = sqr(sd1^2+sd2^2).
In the article, given 2.5 sigma and 3.5 sigma,
then he proposes that the new sd = sqr(2.5^2+3.5^2) = 4.3 or 4.3 sigma.

However, this is different to just combining two lots of data together.
Here the mean will be (m*mean1+n*mean2)/(m+n) where m and n are the size of each population.
Similar calculations for the new sd will involve sd1 and sd2 with elements that reflect the population size in each experiment,
new sd = sqr((m*sd1^2+n*sd2^2)/(m+n)).

The author is mistakingly using the sum of two variables x + y.

Regards, Rob.

[CraigS]

Cool explanation, Rob.

Thanks for confirming what I must admit is now, was just a remnant recollection from a past life which required some involved data analysis.
There are many other treatments which may end up being applied to the datasets before combining them also (eg: normalisations, weighting factors, skewing corrections ... and stuff I have no idea about). These treatments can easily rule out seemingly 'obvious' handling of derived distribution statistics. (As an aside, I've lost track of how many times I've seen people attempting to average averages, arithmetically).

Still, it all depends on which process step of the two datasets they attempt to combine. Until they present it all, we should view it with a 'steely eye', eh ?
I'm sure the folk dealing with the information know exactly what they're doing ... perhaps it was just the journo at work this time eh ?

Cheers

[sjastro]

There is a conspiracy theory going around that since the Dec 13th announcement is being presented by the ATLAS and CMS project leaders instead of the usual subordinates, this is a sign of a major discovery.:shrug:

Some interesting comments, some very strange, from physicists speculating on the 13th December announcement.



Regards

Steven

[CraigS]

All this just goes to demonstrate the desperate need for the LHC.

Without it, these disparate views seem unlikely to congeal, and allow theory to move forward.

Some very big names on that list, also.

Sheldon Glashow's poem is very perplexing ….
I suppose the key line is: "Whether Cern finds it this year" … I gather this might mean he thinks it might be heavier than the impending 125 GeV/c^2 announcement (??)

Gerard 't Hooft's comment is a nicely balanced one. This guy is a progenitor of, and Grand-father of, String Theory. (A very cluey guy).

Cheers

[Robh]

Interesting assessments from some highly talented people in the field.

Even with my limited knowledge, I can't help but get excited as to where this research will lead us. For this reason, I like David Curtin's comment. Not that my viewpoint can add any more credibility to his remarks.

David Curtin, Stony Brook University

"It could be the Standard Model Higgs, but I sincerely hope not. Only data will reveal what nature chose, but two of my favourite alternatives are extra dimensions and supersymmetry – their discovery would tell us incredibly exciting things about several fundamental questions, including (but not limited to) the nature of space-time itself."


Regards, Rob

[CraigS]

Yep Rob;

Curtin's simplicity (in his comment) also caught my eye ! Good one !

The last I heard though, there seemed to be less chance (or signs) of SUSY than the HB ! (Has anyone heard anything which changes this ?)
Fingers crossed though .. I agree with him !

Cheers

[sjastro]

You learn something new everyday.



Didn't know a pony was a fundamental particle.:P

Seriously what is impressive with these comments, it should forever dispel the idea that science is a dogma. Clearly no one is towing a standard line.

Regards

Steven

[CraigS]

Ya reckon Steven ?

Guess we should wait and see what happens after the announcement … personally, I think I can hear the knives being sharpened under the table ! That 3 sigma, (or better), figure will be the first bit to be torn to shreds .. (IMO).

Very entertaining stuff ! .. I'm with Rob .. very exciting !

Cheers

[Suzy]

I second that.
Thanks so much Craig, for explaining it better!

Last week I was watching a recorded episode of Morgan Freeman's "Through the Wormhole" documentary, entitled "Does Time Exist?" Full episode here (http://www.youtube.com/watch?v=q2Gy2xwD5LI). If you f/fwd to 39 mins (watch the whole doco tho, very interesting), one of the theorists (Lee Smoulden) is suggesting that time is older than the universe and goes on to explain that the laws of physics 13 billion years ago are different to the laws we know today. A cartoon demonstrates to photons travelling at the speed of light at different rates.
Quote (quoting both Freeman & Smoulden here): "Did space come first or did time come first. Physicists agree that the big bang created space, they don't agree on whether it also created time. There's a lot of people in physics and philosophy who think that time is an illusion, that's really true with the deepest, deepest level is timeless is outside of time and I don't believe that, I used to believe that but I've come to believe that time is really really real. Lee Smoulden believes that time is older than the universe, it was here before the big bang, and it will be here after the universe ends and he thinks he can prove it by looking at closely at how particles of light behave over long distances. One of the core laws of physics takes that light travels at 186,282 miles per second. If time is an illusion, then this will be true everywhere in the universe no matter where we look. But if time is real, it's possible that the laws of physics changed as the universe has aged. If a basic law of physics such as the speed of light doesn't hold true out in the oldest part of the universe, we'll know that physics has evolved since the universe was born. So time can't be an illusion."
Then goes on to explain the tests that Fermi is doing on gamma ray bursts giving us the chance to check out what the laws of physics as they were 13 billion years ago. Then goes on to show a little animation (at 42mins) of two photons travelling at different speeds after a gamma ray burst.
I watched that doco it seems in good timing with release of this news. Hmmm... so it appears we have to change the laws of physics for today.

Another great episode, "The Equation of Everything" actually shows an example of how two photons of light travelling at the same speed can behave differently when they are "watched". Have a look at 17 mins. :eyepop:Doh, there is no YouTube Video for that one, it was a good too!.:mad2:

:confuse3:Heavy stuff... As you guys know, I have a limited understanding of physics, but I do enjoy reading about it, learning about it and asking questions here.

[CraigS]

Hi Suzy;

Sounds like you're really getting into it all there !

Humans have probably been pondering time for as long as they've been around. Whether or not it exists without humans being around, is kind of a moot philosophical point, as there wouldn't be much conversation about it, if there were no brains to contemplate it, or mouths, (or fingers in our case), to talk about it. Nonetheless, it is a fundamental to theoretical physics for self-consistency, and for us to interpret its outputs.

A little word of warning … Lee Smolin has some pretty innovative ideas which may yield some interesting insights, and his work may ultimately take physics to new levels of descriptiveness. At the moment, I wouldn't say his ideas have been adopted by the broader scientific community. Some time spent baking in the light of plain ol' Special Relativity, described by authors like Brian Greene, might be of assistance in gaining more understanding of why Smolin's ideas are kind of neat.

This discussion is probably more relevant to the recently suspected faster-than-light measurements of neutrinos, by the OPERA research team at CERN in Italy. I think most folk suspect something has been overlooked in the measurements themselves, whilst at the same time, most would also love for them to be verified by another team elsewhere.

The discovery of the Higgs Boson on the other hand, would confirm that particle physics is on the right track and .. yes .. even Cox might present those big white pearlies in a big grin, if they formailse the rumours.

Cheers .. & good to see you posting your progress updates in the Science Forum .. always interested to hear how your seeing things.

[Suzy]

Craig, thank you for explaining all of that, and a special thank you for the lovely comment at the bottom of the post.:)

Brian Greene is a favourite of mine and he does explains things so incredibly well. In fact, this afternoon I have just downloaded his latest NOVA series, "Fabric of the Cosmos". Here are the episodes if anyone is interested...
Quantum Leap (http://www.youtube.com/user/ZZZFROMHELLZZZ#p/u/30/zNin-lzX-Jk)

The Illusion of Time (http://www.youtube.com/watch?v=Rp3_cPRQSh0)

What is Space (http://www.youtube.com/watch?v=wy9gXKwRpXc&feature=related)

Apologies if I have deviated from thread a wee bit, but in order to help understand what's going on today in physics, these documentaries are helpful.

[CraigS]

Suzy;

Thanks for those links. I downloaded them last night and watched 'The Illusion of Time' .. I highly recommend it. It skims some of the details in Greene's book, but it is a pretty reasonable attempt at getting to the heart of the essence of relativity and spacetime, in a doco. (The best I've seen so far). If you can absorb some of the concepts he presents, you'll be well over several 'humps' in the learning curve ! Good material for discussion here, as well.

It also provides some answers to your questions about how time can be perceived as an illusion and it addresses the concepts behind 'Time's Arrow', Entropy, the Big Bang and how each is connected into a logical cohesive theory. An incredible achievement based on real physics (for a TV documentary)!

Feel free to query anything in it .. there's good hard science behind what he's presenting .. (not just whimsical sci-fi dressed up to gain ratings).

Cheers

[CraigS]

Meanwhile .. back to business ..

Some rumour-quenching back-peddling in the news this morning ..?…

LHC to narrow search for Higgs boson (http://www.physorg.com/news/2011-12-lhc-narrow-higgs-boson.html)


Seems like that 3 sigma issue may be driving the release of any announcements (??) After all, a double whammy of bloopers for CERN at the moment, may not bode well for future credibility (??) ;) .. (Chuckle, chuckle).

Cheers

[avandonk]

I will wait for a time where my superbly developed sense of hindsight will proclaim I knew all along!

Science is all about groping in the dark. Once the lights have been turned on and the phenomena is 'self evident' with hindsight, after the pioneers showed the way. The rest of us then sit smugly and say I told you so.

I remember arguing many years ago about the existence of quarks!

Bert

[CraigS]

Hi Bert;

It seems that in this particle physics business, boldness in the face of risk is only admirable if there exists the capability of independently verifiable results. Risking large resource when there is clearly no verifiability from the outset is a 'con'.

There seem to be many desperate scientists out there at the moment .. courtesy of business realities.

Now where's my CEO's payout cheque ?

Cheers

[avandonk]

The probability of a CEO's payout exceeding 125Gev is about 10M sigma!

Bert

[CraigS]

… and that's easily independently verifiable !
:)
Cheers

[sjastro]

http://www.scientificamerican.com/article.cfm?id=higgs-lhc&WT.mc_id=SA_CAT_SPC_20111208

Regards

Steven

[CraigS]

Now how accurate is that ?

Its also the first time I've ever heard the term 'postdiction' !
:lol: :)
.. Yet another first ...!… coming direct to you from the mighty Theory of Strings!
:P :)
Cheers

[sjastro]

Postdiction is a term borrowed from the electric universe.:P

Steven

[CraigS]

… resting upon the shoulders of giants, I tell ya !
:P :)

[renormalised]

But they always do things "after the fact" (or should that be fantasy):):P

[renormalised]

Bright sparks, you mean :):P:P

[sjastro]

CERN status on Higgs boson tonight.

Webcast can be seen here.
http://webcast.web.cern.ch/webcast/

The status update will commence at 14.00 CET (Central European time) or 23.00 AEDT. (11.00 pm)

Regards

Steven

[sjastro]

As any astroimager knows more data is the key to increasing the signal/noise ratio, the Atlas and CMS experiments are in the same boat.

The fact that 2 separate experiments are revealing the same effect is significant, unless each experiment afflicted with the same systematic errors.

http://www.youtube.com/watch?v=0KOoumH4dYA
(There is a stupid ad at the start)

Regards

Steven

[CraigS]

Good on 'em for being honest about it !!!

The pressure to tell everyone what they want to hear must be immense, but the way they've handled the announcement shows respect for the teams involved … and those eagerly awaiting.

Great stuff !
:)

Cheers

[Suzy]

Brian Greene & Lawrence Krauss answering some questions regarding Higgs.
See it here (http://wsftv-videos.s3.amazonaws.com/BG_Krauss_Higgs_Boson_121311-WSF_TV.mov) at the World Science Festival.

And here (http://richarddawkins.net/articles/644207-the-hunting-of-the-higgs-what-is-it-and-why-does-it-matter) by Lawrence Krauss, "Hunting the Higgs: what is it and why does it matter?"
Nicely explained for learner physicists wannabes like me.:D

[Suzy]

Does anyone know why this is referred to as the "champagne particle" by scientists (more popularly known as the God particle that the media have coined)?

[Robh]

Hi Suzy,

I'm not sure that it is referred to this way by scientists. Apparently the British Guardian held a competition for an alternative name and chose "the champagne bottle boson" as the winner. The Higgs potential is in the shape of the bottom central part of a wine bottle (also Mexican Hat shaped).

The experimental physicist Leon Lederman initially wanted to call the Higgs Boson "the goddamn particle" because no-one could find it. However his editor wouldn't pass this one and his book was titled "The God Particle: If the Universe is the Answer, What is the Question?". The media were quick to adopt the God particle.

Regards, Rob

[strongmanmike]

I was thinking about the Higgs Boson last night and when I stopped, it was a massive weight off my mind :D

[Suzy]

:lol::lol::lol:

Rob,
Thanks so much for all that info. We were talking about it on facebook so now I can go and tell them. We were all guessing how they derived "champagne" out of it.:screwy: It now makes sense.:thumbsup:

[skies2clear]

Perhaps they should have called it the Chocolate boson. Proximity gains you a lot of mass.

Sorry for the corny joke!

Clear skies

[xelasnave]

Can anyone suggest a good movie of how it works?

I am confused really...I get the impression the Universe is awash with HB,s and yet they are also bound to matter.

I took a long time reading Stevens link to Princetons work but it did not give that mental picture I crave...no odubt there is a good utube that reduces years of study on the matter to 2 or 3 minutes:D

alex:):):)

[sjastro]

Alex,

The key is to understand what a boson is. In simple terms a boson is the product of an interaction.

Here is a Brian Cox video describing various bosons, such as the photon, gluon, W and Z bosons and the Higgs boson.

http://www.guardian.co.uk/science/video/2010/oct/05/brian-cox-quantum-mechanics-higgs?INTCMP=ILCNETTXT3487

Hope it helps.

Steven

[Robh]

Alex,

Here is a short video. Don't know whether it explains enough for you but worth a look.
http://www.youtube.com/watch?v=RIg1Vh7uPyw

Regards, Rob

[xelasnave]

Thank you Steven thank you Rob:thumbsup::thanx:.

alex:):):)

[Robh]

Hi All,

Rather than start another thread on the Higgs boson, I thought it might be appropriate here.
This is a great little read. It is an interesting appraisal of the relevance of the Higgs boson to physics and whether we are any closer to the "theory of everything".

Some excerpts ...
<Lederman himself confessed that “the Goddamn Particle” might have been a better name for the Higgs, given how hard it had been to detect “and the expense it is causing.” >

<But the Higgs doesn’t take us any closer to a unified theory than climbing a tree would take me to the Moon.>

<... The quest for a unified theory will come to be seen not as a branch of science, which tells us about the real world, but as a kind of mathematical theology.>

Some of the philosophical points here are also relevant to discussions going on in other threads.


http://blogs.scientificamerican.com/cross-check/2011/12/17/does-the-goddamn-higgs-particle-portend-the-end-of-physics/

Regards, Rob

[renormalised]

The moniker, "The God Particle", was probably the most unfortunate one ever pinned on a particle, of any sort. The moment it became public....well, you know what happened.

A ToE has to encompass all that is known about physics and how everything is interconnected, then wrap it up into a simple, elegant explanation that anyone could see the beauty and elegance of. They're far, far away from achieving that and the Higgs isn't the answer. It is just another (possible) particle and maybe one more rung in the ladder. Even if they discover all the particles there are and all the physical interactions that are possible and how everything is interconnected through all the possible pathways etc etc, they may still not find a ToE. It mightn't even exist or it could be right under our noses and we just don't even realise it.

Someone (thanks Rob) wrote this...



Who's to say what is real and what is reality. Despite it's pronouncements to the contrary, science deals as much in "theology" as mathematics does. Whilst it tends to confine itself to only what it can observe and therefore verify, science knows no more about what is present "reality" than what a soothsayer can know of the future. It deals with the past, exclusively, especially in fields such as astronomy, cosmology and such. All it can do is extrapolate on what it finds of the past and then project that extrapolation into the present and future. What's even more interesting is that all of this is time dependent and yet we have no clue as to what "time" actually is. For all we know it maybe an illusion of our own consciousness and how that consciousness interacts with its environment (or creates it in the first place)...the physicality it resides in. Illusions can be just as concrete and solid as anything deemed physical, if one is willing to "believe" in them honestly enough.