Large Hadron Collider (LHC) News

[korjik]

I've read that the LHC's first task, once the champagne has stopped flowing, is to 're-discover the Standard Model'.

What does this mean, exactly?

Just a WAG, but I would imagine that it is going to duplicate several older experiments to see if the LHC gives the same results. That way you can make sure you are working right

[Tensor]

Just a WAG, but I would imagine that it is going to duplicate several older experiments to see if the LHC gives the same results. That way you can make sure you are working right

That's exactly it. Think of it as calibrating the collider. It should be able to match the discovery of all the currently known particles. If it can't do that, then there may be a problem.

[Jean Tate]

That's exactly it. Think of it as calibrating the collider. It should be able to match the discovery of all the currently known particles. If it can't do that, then there may be a problem.

Thanks.

Do you know if the timeline is published somewhere?

And is it all the thousands of particles, or just the quarks and leptons?

My guess would be that the program would involve not just the particles, but also their properties, with the rider that only those ATLAS etc can measure.

I wonder if there are projects to search for unexpected results, serendipitous discoveries, etc.

[Tensor]

Thanks.

Do you know if the timeline is published somewhere?

I'm not, but I can look around and let you know.

And is it all the thousands of particles, or just the quarks and leptons?

I would guess that it would be the quarks and leptons. After all, those are the building blocks of the other particles (well, the leptons don't build into other particles, but you know what i mean).

My guess would be that the program would involve not just the particles, but also their properties, with the rider that only those ATLAS etc can measure.

Not just ATLAS. You have the Compact muon solenoid (CMS), which I believe has already detected muons. Plus all the other detectors.

I wonder if there are projects to search for unexpected results, serendipitous discoveries, etc.

I'm quite sure there are, the problem will be going through all that data. With the reported rate of 100 collisions a second, think of all the data there will be, after a run of 18 months. Although I'm sure there will be data analysis ongoing throughout the run.

Wikipedia here lists the different experiments and detectors. I would recommend going to the different websites listed to find out exactly what is going on in the particular experiments you're interested in. I kinda like the sound of MOEDAL (and it fits in with your unexpected result question). The Monopole and exotic particle detector at the LHC. I need to look into that one.

[01101001]

I wonder if there are projects to search for unexpected results, serendipitous discoveries, etc.

From an old article, Device Daily: CERN Launches The Biggest Computing Grid In The World:

When the LHC starts running at full speed, it will produce enough data to fill about six CDs per second. As the first point of contact for LHC data in the United States, the computing centers at Brookhaven and Fermilab are responsible for storing and distributing a great amount of this data for use by scientists around the country. We’ve spent years ramping up to this point, and now, we’re excited to help uncover some of the numerous secrets nature is still hiding from us,” says Michael Ernst, director of the Tier-1 computing center from the Brookhaven National Laboratory.

All the data coming from the LHC will be examined by worldwide physicists including the United States, and they will be looking for “something” that could lead to important discoveries about the Universe.

Wikipedia: LHC Computing Grid

The data stream from the detectors provides approximately 300 GB/s, which is filtered for "interesting events", resulting in a "raw data" stream of about 300 MB/s. The CERN computer center, considered "Tier 0" of the LHC Computing Grid, has a dedicated 10 Gb/s connection to the counting room.
The project is expected to generate 27 TB of raw data per day, plus 10 TB of “event summary data”, which represents the output of calculations done by the CPU farm at the CERN data center.

[sarongsong]

From an old article...

October 3, 2008

[slang]

Wow, all the way down to page 3 to revive it. Science and Technology moves fast.

BBC News: LHC particle search 'nearing', says physicist

If commissioning work goes well, the LHC could become sensitive enough to probe a hitherto unexplored domain in particle physics by the end of summer.

Among the first candidates for discovery are two boson particles that have been predicted to exist.
[...]
One of the first prospects for new discoveries at this mass scale are particles known as W prime and Z prime bosons. These are heavier versions of the W and Z bosons, which are responsible for weak interactions.

[Swift]

From R&D Magazine on-line

CERN announced that the Large Hadron Collider (LHC) will run with a beam energy of 4 TeV this year, 0.5 TeV higher than in 2010 and 2011. This decision was taken by CERN management following the annual performance workshop held in Chamonix and a report delivered today by the external CERN Machine Advisory Committee (CMAC). It is accompanied by a strategy to optimize LHC running to deliver the maximum possible amount of data in 2012 before the LHC goes into a long shutdown to prepare for higher energy running. The data target for 2012 is 15 inverse femtobarns for ATLAS and CMS, three times higher than in 2011. Bunch spacing in the LHC will remain at 50 nanoseconds.

"When we started operating the LHC for physics in 2010, we chose the lowest safe beam energy consistent with the physics we wanted to do," said CERN's Director for Accelerators and Technology, Steve Myers. "Two good years of operational experience with beam and many additional measurements made during 2011 give us the confidence to safely move up a notch, and thereby extend the physics reach of the experiments before we go into the LHC's first long shutdown."

...

The schedule announced foresees beams back in the LHC next month, and running through to November. There will then be a long technical stop of around 20 months, with the LHC restarting close to its full design energy late in 2014 and operating for physics at the new high energy in early 2015.

[lpetrich]

Due diligence | Jon Butterworth | Life & Physics | Science | guardian.co.uk
The ATLAS and CMS teams have made more careful analyses, and their results do not differ much from the preliminary ones that they had announced earlier.
ATLAS Experiment -- Update: Higgs search papers submitted for publication
CMS Higgs boson search results from 2010-2011 data samples | CMS Experiment

Here are my estimates of the stdevs of the putatively-observed Higgs particle, extrapolated to 3 times the events.
Detector | Peak | Local sig. | Global sig. | Extrap L | Extrap G
ATLAS | 126 GeV | 3.6 sigma | 2.3 sigma | 6.2 sigma | 4.0 sigma
CMS | 124 GeV | 2.6 sigma | 1.9 sigma | 4.5 sigma | 3.3 sigma
Combined | 125 GeV | 4.4 sigma | 3.2 sigma | 7.6 sigma | 5.5 sigma
The "local" one is for a peak in isolation, while the "global" one takes into account the possibility that it could be elsewhere: the "look-elsewhere effect".

From this extrapolation, the LHC teams could have enough data to test a hypothesis about the Higgs particle: its spin. If it has nonzero spin, then its creation will produce an imprint: its spin polarization. That, in turn, will produce an imprint on the decay particles' direction. This combined imprint, along with knowledge of the creation and decay processes, will permit an estimate of its spin. But since it is expected to have zero spin, it will thus have zero imprint.

The obvious source of an imprint for the LHC is the beam directions. So one should compare decay directions to the beam directions to see if there is a difference between parallel to the beam and perpendicular to it.

Using the local stdevs for the peaks, one can divide the data into parallel and perpendicular directional subsets, making the expected heights drop by sqrt(2) (statistical significance ~ sqrt(number)). The combined height should be about 5.4 stdevs, which should be enough to establish the particle's spin, except for possible cancellations at higher spins. Dividing into three directional subsets yields 4.4 stdevs, strong, but not superstrong.

The LHC teams may also be able to compare branching fractions for different decay modes, which will provide tests of hypotheses about the interactions of this particle with other particles.

[lpetrich]

Someone has explored the implications of this putative discovery of the Higgs particle. [1112.3017] Implications of a 125 GeV Higgs scalar for LHC SUSY and neutralino dark matter searches
Howard Baer, Vernon Barger, Azar Mustafayev
(Submitted on 13 Dec 2011)

They analyzed it in two subsets of the Minimal Supersymmetric Standard Model:

mSUGRA: free parameters m₀, m_1/2, A₀, tan(beta), sign(mu)
and
NUHM2: free parameters m₀, m_1/2, A₀, tan(beta), mu, m_A

m₀ = mass scale of the spin-0 superpartners of the elementary fermions
m_1/2 = mass scale of the spin-1/2 superpartners of the gauge particles
m_A = mass scale of the heavy Higgs particles predicted by the MSSM

For both mSUGRA and NUHM2, m₀ >~ 0.8 TeV, pushing the squark and slepton masses into the multi-TeV range. Those particles may thus be difficult to make with the LHC.

However, m_1/2 is less constrained, meaning that the LHC may be able to make gluinos, neutralinos, and charginos more easily.

Both mSUGRA and NUHM2 tend to produce too much neutralino dark matter, except if the lightest neutralino is higgsino-like, with a mass around 0.8 TeV. However, that would bump the bino, wino, and gluino masses into the TeV range. Especially the gluinos, which are otherwise the easiest for the LHC to make.

Neutralinos = mixtures of the bino, neutral wino, and neutral Higgsinos
Charginos = mixtures of the charged wino and charged Higgsino
The lightest supersymmetric particle is usually expected to be a neutralino.

So this putative discovery may mean that it'll be awfully hard for the LHC to detect supersymmetric particles.

[schlaugh]

But apparently they still lack enough evidence to declare that it's "found".

http://phys.org/news/2012-07-cern-sc...ggs-boson.html

Scientists working at the world's biggest atom smasher plan to announce Wednesday that they have gathered enough evidence to show that the long-sought Higgs boson answering fundamental questions about the universe almost certainly does exist.

But after decades of work and billions of dollars spent, researchers at the European Organization for Nuclear Research, or CERN, aren't quite ready to say they've "discovered" the particle.

Instead, experts familiar with the research at CERN's vast complex on the Swiss-French border say that the massive data they have obtained will essentially show the footprint of the key particle known as the Higgs boson — all but proving it exists — but doesn't allow them to say it has actually been glimpsed.

"I agree that any reasonable outside observer would say, 'It looks like a discovery,'" British theoretical physicist John Ellis, a professor at King's College London who has worked at CERN since the 1970s, told The Associated Press. "We've discovered something which is consistent with being a Higgs."

[Tensor]

But apparently they still lack enough evidence to declare that it's "found".

http://phys.org/news/2012-07-cern-sc...ggs-boson.html

Interesting comments and speculations from Nature

CERN's head of communications, James Gillies, confirmed that four of the theorists who dreamt up the Higgs mechanism in the 1960s — François Englert, Carl Hagen, Peter Higgs and Gerald Guralnik — will be present at Wednesday's seminar, but he declined to be drawn on what will be announced. "Things are still evolving here," he says.

As the Los Angels Times points out, "It would be perhaps mean to drag them all that way and then announce, "Nothing yet, folks."

The article continues:

ATLAS's chief rival, the CMS experiment, also sees significant Higgs evidence in its 2012 data, according to a physicist there, who asked not to be named because both ATLAS and CMS have strict embargoes in place. “In practice you would have to be monstrously sceptical not to be convinced by what we have now,” the source says. "But the final decisions on what to say on Wednesday are still being made."

Physicists have maintained that they will not announce the discovery of the Higgs until the signal surpasses 5 sigma, meaning that it has just a 0.00006% chance of being wrong. The ATLAS and CMS experiments are each seeing signals between 4.5 and 5 sigma, just a whisker away from a solid discovery claim.

If they are seeing signals between 4.5 and 5 sigma, then I can see someone saying "...you would have to be monstrously sceptical not to be convinced."

[tnjrp]

Early comments on today's announcement:
http://cosmiclog.msnbc.msn.com/_news...d-new-particle
http://phys.org/news/2012-07-cern-ph...-particle.html
http://www.theverge.com/2012/7/4/313...n-announcement

The final word from the CERN spokesperson looks to be that they've set the combined confidence level at 4.9 sigma.

The Guardian's science blog treats the choicest morsels (in a reverse order of course), including a message from doctor Higgs himself:
http://www.guardian.co.uk/science/bl...-coverage-cern

[EDG]

The impression I got from watching the CERN webcast just now was that CMS was at 4.9 sigma, and Atlas was at 5 to 5.1 sigma. That makes it a real "discovery" of a new particle at 125 GeV (and everyone there seemed pretty convinced that they'd found something ). Whether it's the Standard Model Higgs or something else remains to be determined, but it's looking Higgs-like!

[Ivan Viehoff]

Although everyone is excited today, in reality this is the emerging confirmation that the LHC will be HEP's Apollo 17.

Peter Woit, I think it was, said that the most tedious possible outcome for the LHC would be if they found the Higgs and nothing else (well they did find a few little things but nothing that the SM didn't already talk about). Finding nothing at all, ie, excluding any possibility of the SM Higgs, would be a more exciting outcome than that.

Of course they are still only running LHC at below full power, and will do the mods to be able to turn it up later, and will be trying to find out more about it, and something may still be found at that higher power. The reason it would be tedious is that following such a "we found what we expected to find and nothing more" result, that no one would have the faintest chance of getting funding for a bigger collider.

[tnjrp]

ATLAS has 5 sigma for a boson at 126.5 GeV but the other results don't seem to be quite that good (in fact one test looks to have failed to detect altogether).

[Don Alexander]

That notwithstanding...

WOOOOOOOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!!!!!!!!!! !!!

The ATLAS presentation, though, will be laughed at for weeks.

[tnjrp]

And here's doctor Plait:
http://blogs.discovermagazine.com/ba...2/07/04/higgs/

[EDG]

And here's doctor Plait:
http://blogs.discovermagazine.com/ba...2/07/04/higgs/

Glad to see that someone is excited about it... Skepticism is great and all, but seriously guys? This is big. It's OK to cheer about it!

[Perikles]

Glad to see that someone is excited about it... Skepticism is great and all, but seriously guys? This is big. It's OK to cheer about it!

The response does seem a little muted here, but yes, it is really big, and Hooray!

[Van Rijn]

The response does seem a little muted here, but yes, it is really big, and Hooray!

Well, it's a big holiday in the U.S., lots of people aren't going to be checking their computers today, or won't have much time for it. And it was pretty much a given they were going to announce this. Not a real surprise.

Now, if they announced something suggesting seriously new physics, or something that pointed towards direct detection of dark matter, I think you'd see more response.

[Swift]

The response does seem a little muted here, but yes, it is really big, and Hooray!

I guess I should be all excited, but I'm not. Maybe because it is the expected result; not finding it - that would have been exciting.

I'm not sure why, but I'm not feeling it.

Maybe someone needs to explain what this changes. What new science is coming out of this? Or does this just confirm what we already knew (or thought we knew)? Does the fact that it was found at the particular energy it was found at mean or change something?

[quotation]

I guess I should be all excited, but I'm not. Maybe because it is the expected result; not finding it - that would have been exciting.

I'm not sure why, but I'm not feeling it.

Maybe someone needs to explain what this changes. What new science is coming out of this? Or does this just confirm what we already knew (or thought we knew)? Does the fact that it was found at the particular energy it was found at mean or change something?

Apparently, it's both exciting and a little disappointing that the standard model is working so well:
What it would mean if we found the Higgs boson
http://dvice.com/archives/2012/07/what-it-would-m.php

[Jens]

I'm sure Peter Higgs is excited, as he may get a trip to Sweden next year!

[DancesWithFruitBats]

Newbie question:

So the Higgs Field slows some elementary particles giving them mass and this mass then bends spacetime leading to gravity. Is that a fair description? Also, where do gravitons fit in?

[Tensor]

The impression I got from watching the CERN webcast just now was that CMS was at 4.9 sigma, and Atlas was at 5 to 5.1 sigma. That makes it a real "discovery" of a new particle at 125 GeV (and everyone there seemed pretty convinced that they'd found something ). Whether it's the Standard Model Higgs or something else remains to be determined, but it's looking Higgs-like!

I didn't get to watch the webcast and I hadn't found the sigmas anywhere else, so thanks for listing the sigmas. Once they get to the point of combining the two results it should go over 5 sigma rather easily.

[Jens]

I have to say also that I didn't totally like Heuer's famous line about, "as a layman..." versus "as a scientist." It seems to me that if they found it, they found it both as laymen and scientists. There may be a more strict requirement in physics, but I don't really understand why there needs to be a higher requirement. If 5 sigma is required in physics, then it seems logical to me that 5 sigma should be required in general to say that it has been discovered.

[Ara Pacis]

The impression I'm getting is that it's not a discovery of what they want you to think it is. It's a "something, maybe, could be something else, we're not sure". It's hard to get worked up about that. Replace Higg's Boson with "Osama bin Laden" and you may see the point.

We think we've found something that we think is evidence that we know where Osama bin Laden is. It's definitely a person in the right place that may be Al Qaeda. We need to look a bit harder to make sure it's him.

Or in the words of Chris Rock, "Of course, he's your baby. He looks just like you. He's got your hat."

[tnjrp]

The most famous (that's not a lot) Finnish alternate physicist Matti Pitkänen agrees, it's all just smoke and mirrors:
http://matpitka.blogspot.fi/2012/07/...discovery.html
http://matpitka.blogspot.fi/2012/07/...discovery.html

[Perikles]

Well, it's a big holiday in the U.S., lots of people aren't going to be checking their computers today.. .

Wow - does this mean lots of BAUT members only check BAUT when they are at work? Hmmm