How Particle Accelerators Like The LHC Work.

The above video shows the best "layman" explanation for how particle accelerators, like the Large Hadron Collider (LHC), work that I have ever seen. I highly encourage you to watch it as it is very clear and straight forward.

Just remember, and this may be the most confusing part of the whole video, words like GeV and TeV refer to how much energy the particles have. Lets just say for particles to have that much energy is extraordinarily!

Webpage To Reassure You The LHC Hasn't Destroyed The World.

If many of you are like me you sometimes need some re-assurance that the Large Hadron Collider in Switzerland has not destroyed the world, especially after watching this video below that gives the LHC a clear 50-50 chance it may destroy the world.  (The video can be semi-crude in parts so sorry about that)

The Daily Show With Jon Stewart	Mon - Thurs 11p / 10c
Large Hadron Collider
www.thedailyshow.com
Daily Show Full Episodes Political Humor Rally to Restore Sanity

However, for people like me they've created a website called hasthelargehadroncolliderdestroyedtheworldyet.com.  It gives you up-to-date analysis of whether the world has been destroyed by the LHC or not using a user friendly info-graphic:

The comment section of the site's html source code offers this disclameir:

If the lhc actually destroys the earth & this page isn't yet updated please email mike@frantic.org to receive a full refund.

Thanks to bijanweb for this tip.

Could The Higgs Boson Be A Composite? (Composed of Many Particles)

As most you you know, the Higgs Boson is probably the most sought after un-discovered particle.  Currently, the Large Hadron Collider and the Tevetron ar busy trying to find this particle.   This particle is thought to hold the whole standard model of particle physics together.  (Take the Higgs out of the standard model and all kinds of problems arise like: how do particles have mass?)

Interestingly, the Higgs is best described mathematically as what is known as a scalar field.  We've never found a scalar field that actually exists fundamentally!  Will the Higgs be the first or will the Higgs turn out to be like the Pion?

The Pion is a particle that "at low energies" is well described by a scalar field.  However, fundamentally we have discovered the Pion is actually composed of more fundamental particles called quarks.  This composition is pictured above.  These quarks themselves are not scalar fields but are fermions best described mathematically by spinor fields. (Not scalar fields)

Reasons like these (plus the fact that the best fit mass for the scalar Higgs, assuming only the standard model, has been ruled out by nearly 2 sigma) have caused many physicists to come up with models where the Higgs is more like the pion: best described as a scalar at low energies but fundamentally a composite particle made up of more fundamental non-scalar particles.   Only time will tell.

LHC Still On Track. (Possible Z Boson Events?)

As mentioned here, the LHC should begin "re-discovering" the W and Z bosons if all goes well in the near future.  This is yet another step toward discovering the theoretical Higgs. (The W and Z masses are around 80-90 GeV and the Higgs should be somewhere between 115-150 GeV.)

Today I had a fellow grad student email me pictures of events they think may be the Z boson.  If so, the machine is right on track.  Pictured above are the events.

However, though things are on track, several people have told me it will still be a few years before we can definitively say the Higgs has been discovered.

Re-Discovering J/Psi Shows LHC On Right Track.

ATLAS, a detector at the largest particle accelerator in the world, the LHC, has "rediscovered" the particle J/Ψ.  From ATLAS news site:

In 1974 the J/Ψ meson was first discovered, heralding a new era of understanding in particle physics. Now again, in 2010, it's ‘rediscovery’ in ATLAS and the other LHC experiments’data signals an important stage towards what will hopefully also become an historic milestone in high energy physics.

In the plot above we see a particle is detected in just the right spot to be J/Ψ.  Its nice to see that withen a few months of collisions the LHC is already able to rediscover particles that took years to discover a few decades ago.  So, it appears things are moving forward nicely.

On to the Higgs?

Probably No Higgs Discovery Before 2013.

I said earlier on this blog it will take years before the LHC can actually discover big things.  To echo my claims I point you to a much more knowledgeable person on this subject Tommaso Dorigo.

After a very enlighting post he concludes like this:

The LHC experiments will be unable, in my opinion, to make up in two years of data taking, and with the 3.5 times larger energy, for the 8-year advantage in running time of the Tevatron. The Higgs boson will be unlikely to be discovered before 2013, and it will probably be a sole LHC business; however, until then the Tevatron will retain the better results as far as the mass exclusion range is concerned.

I've said it before and I will say it again: new discoveries from the LHC realistically are years away.

But at least there are lots of other experiments to be excited about in the meantime.  We'll keep our readers up to date with this information s well.

Primer On WIMP Dark Matter.

First, let's state that dark matter could be all sorts of things, but there is a lot of motivation to believe they are weakly interacting massive particles. (WIMPS)  It turns out our own Jonathan Feng at UC Irvine is considered one of the world's greatest experts on WIMPS and has some accessible review articles on dark matter collider physics here and here.  (The first especially should be assessable all physicists. I took images from them.)

I Think Therefore I Am

The fact that a particle exists should tell you it must somehow interact with other particles.  All particles are created and destroyed in interactions with other particles.  It turns out, using arguments from cosmology taking the expansion on the universe into account, how abundant a particle is is directly related to it's typical cross section, or likelihood that it interacts with other particles.  (See equation above.)


The graph on the right demonstrates this.  The higher the cross-section, the lower its abundance in the universe.  If it interacts too much, it won't be abundant enough.  It it interacts too little, it will be too abundant enough.

However, if a non-relativistic particle interacts with typical weak scale cross sections, its relative abundance to rest of the matter is just right to be dark matter.  This is called the "WIMP Miracle".

How Can We Detect it?

We know the the particle has to be non-relativistic because dark matter must be cold.  The typical non-relativistic weak scale cross section is given in the equation above.  Alpha is the hyperfine structure constant, m is the mass and k is a parameterizing allowed small deviations from from the weak scale to still work.  The graph on the right shows masses that work.

In some sense that's it!  If we can find any non-relativistic particle dominated by weak interactions with the right mass, 100 GeV - 1TeV, supersymmetric or not, we can feel fairly confident we have discovered dark matter.

At this point you may ask: "Wait, we know of particles whose dominate interaction is at the weak scale, like say neutrinos.  Why aren't they the dark matter?".  Well, the relativistic nature of these particles changes enough so that they don't work anymore.  (For example they have a different cross section.)

But How Do We Know If It Is Supersymmetric?


(I think) Most non-collider surveys will have a hard time answering this question.  They can answer the more important question: "Is this a non-relativistic particle dominated by weak interactions with a mass on the order of 100 GeV -1TeV?".  If yes, we have our dark matter.

Every different dark matter candidate, such as the supersymmetric ones, have specific ways they interact with other particles.  These ways are described by Feynman Diagrams.  The plot to the right shows the interactions specifically for the neutralino.  Colliders can test these diagrams better than anything else.

So here is the oversimplified formula:

1. Find a particle dominated by weak interactions.  (Like a neutrino except non-relativistic.)
2. Ensure the mass is on the order 100 GeV -1TeV. (You've discovered dark matter!!!)
3. Run an experiment at the LHC for a particle of just that mass interacting mostly through weak interactions. 
4. Compare the findings with the proposed models of such particles.
5. If one lines up perfectly you know what particle you are dealing with. (Ie... some like a supersymmetric neutralino)

Smarter people than me may be able to pinpoint the exact particle without a collider, but as far as I know it may take the LHC to do this.  It's initial discovery however should be able to be accomplished without the LHC however.

The Future Preventing The LHC From Working?

Two authors, Holger Nielse and Masao Ninomiya, have been cooking up a crazy theory which can be read in detail from their articles here, here and here.

Basically, they put forward the idea that perhaps the reason we keep failing to find the Higgs boson is that something from the future is stopping us from doing it.  From their latest article:

This previous work was concerned with looking for backward causation [noting] bad luck for large Higgs producing machines, such as LHC and the never finished SSC (Super- conducting Super Collider) stopped by Congress because of such bad luck, so as not to allow them to work.

So, in other words, perhaps the "bad luck" of the SSC being stopped by congress and the more recent bad luck in getting the LHC working comes from causing originating from the future.

Dennis Overbye has this puts it like this:

[Perhaps] the troubled collider is being sabotaged by its own future. A pair of otherwise distinguished physicists have suggested that the hypothesized Higgs boson, which physicists hope to produce with the collider, might be so abhorrent to nature that its creation would ripple backward through time and stop the collider before it could make one, like a time traveler who goes back in time to kill his grandfather...“It must be our prediction that all Higgs producing machines shall have bad luck,”

Now, I know of scientists that think this is such crack-pottery that they are furious such papers have been successfully posted on arXix.org.  This is really crazy stuff.

But, if it is forever the case that potential Higgs producing machines have such bizarre bad luck at least we will have one theory why. :)

Fwd: Update on the LHC start-up plans and schedule

I got this email today. I thought someone out there might enjoy it:

Dear Colleagues,

The CERN Director-General has released a follow-up note on
the Chamonix LHC workshop (see mail distributed last Friday).
The note is copied below in full. Its basic message is that
a plan has been adopted which implies a schedule with first
collisions end of October 2009, followed by a long physics run
until autumn next year. Please read the DG's message below which
gives more details about this plan. The impact of this new LHC
schedule on our own ATLAS plans will be a central topic for the
forthcoming ATLAS Week.

These good news emphasize the first LHC physics to which we
are all looking forward!

Kind regards,

Peter Jenni




Subject: Message from the Director-General on the LHC schedule

The CERN Management today confirmed the restart schedule for the Large
Hadron Collider resulting from the recommendations from the Chamonix
workshop. The new schedule foresees first beams in the LHC at the end
of September this year, with collisions following in late October. A
short technical stop has also been foreseen over the Christmas period.
The LHC will then run through to autumn next year, ensuring that the
experiments have adequate data to carry out their first new physics
analyses and have results to announce in 2010. The new schedule also
permits the possible collisions of lead ions in 2010.

This new schedule represents a delay of 6 weeks with respect to the
previous schedule which foresaw LHC "cold at the beginning of July".
The cause of this delay is due to several factors such as implementation
of a new enhanced protection system for the busbar and magnet splices,
installation of new pressure relief valves to reduce the collateral
damage in case of a repeat incident, application of more stringent
safety constraints, and scheduling constraints associated with helium
transfer and storage.

In Chamonix there was consensus among all the technical specialists
that the new schedule is tight but realistic.

The enhanced protection system measures the electrical resistance in
the cable joints (splices) and is much more sensitive than the system
existing on 19 September.

The new pressure relief system has been designed in two phases. The
first phase involves installation of relief valves on existing vacuum
ports in the whole ring. Calculations have shown that in an incident
similar to that of 19 September, the collateral damage (to the
interconnects and super-insulation) would be minor with this first
phase.

The second phase involves adding additional relief valves on all the
dipole magnets and would guarantee minor collateral damage (to the
interconnects and super-insulation) in all worst cases over the life
of the LHC. One of the questions discussed in Chamonix was whether to
warm up the whole LHC machine in 2009 so as to complete the installation
of these new pressure relief valves or to perform these modifications
on sectors that were warmed up for other reasons. The Management has
decided for 2009 to install relief valves on the four sectors that were
already foreseen to be warmed up. The dipoles in the remaining four
sectors will be equipped in 2010.

The LHC turns on. We're Still Alive!

Though I am late, you know I had to post about the start up of the LHC.

The LHC should become a very exciting experiment. We have never, as humans, gone up a magnitude in energy scale without seeing new physics. The only question is what will the new physics be. (If this becomes the first time we went up a magnitude in energy and see nothing that would really be depressing.)

As you might have guessed, I really am pulling for some verification of supersymmetry. That alone will clear up volumes of theoretical problems. Sure I welcome any new physics, but something as elegant as supersymmetry with incredible explanation power is something I am really pulling for.

One exciting thing, which few people outside of particle physics talk about, is the LHC will have nearly 100 times the luminosity of the Tevetron at Fermilab. To first order this means, in a perfect world, that the LHC will see as much in one year as the Tevetron would see in a century! There is hope for a upgrade in the future that will boost the LHC's luminosity even another order of magnitude.

This experiment should run for decades to come. (It fact, the upgrade is probably about a decade away.) Between the extra order of magnitude in energy, and the extra 2-3 orders of magnitude in luminosity, we should expect great things.

*Note*: The experimentalists I talk to here think the experiments won't really be going full steam for another 6 months. Sure the beam is circulating now, but the detector is still not 100% completed, software is still being written and there is a good chance as they observe the current data they will find things are misaligned etc... Plus, the machine itself is not yet running at full capacity. So, hopefully, some time in the next year or two the discoveries will begin.

CERN Rap

As you(should) know, the LHC at CERN is scheduled to turn on on September 10. Slashdot has reported on a rap song a few have put together.

At first I wasn't going to post it but then I thought: "Everyone needs to know about the LHC, and maybe this form of the message will reach out to some people better."

The LHC is Declared Safe

The LHC Safety Assessment Group (LSAG), (seriously that's what 's called) has released their report that is an update of an earlier report released in 2003. A summary by the European Organization for Nuclear Research can be found here. The report addresses concerns ranging from the creation of mini-black holes that could "gobble up the earth" to the creation of strangelets.

Their basic argument comes down to this: "Over the past billions of years, Nature has already generated on Earth as many collisions as about a million LHC experiments – and the planet still exists. Astronomers observe an enormous number of larger astronomical bodies throughout the Universe, all of which are also struck by cosmic rays. The Universe as a whole conducts more than 10 million million LHC-like experiments per second. The possibility of any dangerous consequences contradicts what astronomers see - stars and galaxies still exist."

In other words: The universe has not ceased to exist, therefore it will continue to exist. Hmmm, novel thought.

The release of this report has given the Department of Energy some ammunition to respond to a lawsuit filed in Hawaii back in March to force the Federal Government to cease operations at CERN. A news article about the lawsuit can be read here. Basically their response is that the federal government does not have jurisdiction in this case and cannot force CERN to not turn on the LHC, and also there has been no credible objection to conducting the experiment as "the claims of potential injury are 'overly speculative and not credible'".

So the LHC can go ahead and do its stuff and we can rest easy knowing that if the earth is destroyed because of the LHC someone somewhere will get some pleasure thinking "I told them so!" milliseconds before they are sucked into a black hole, or converted into a strangelet.

ATLAS@CERN

ATLAS is a project at CERN that will preforms several experiments, including searching for the Higgs Boson and other new particles.

ATLAS is detector at the LHC.

There are several people here at UC Irvine working on the ATLAS project. Here is a youtube video giving more details of ATLAS itself:


Part two can't be embedded for some reason. Here is the link for Episode 2 Part One. Here is the link for Episode 2 part two.

Does Higgs Have Insider Information?

Okay, before I go into it, I have to say it drives me crazy that the "popular" media continues to refer to the Higgs Boson as the "God particle." I know why they do it but it is a pet peeve of mine. I just don't like it.

With that said, I have been interested in the recent reporting that Dr. Peter Higgs, whom the particle was named after, is claiming he think it will be discovered within the next year. Furthermore, he says that his recent trip to CERN convinced him of this and also suspects evidence of the Higgs may exist in data at Fermilab but the data is to difficult to bring it out as of now.

I have no evidence of this, but all these statemements make me wonder if he has some insider information on what people are seeing. It could be the media is playing his comments up too much, but a part of me wonders if some groups have some interesting data where the details just need to be worked out. If he is correct we should find out in the next year or so.

One reason I question if he has insider information is there are several people at Irvine with ties to many experimental groups and they don't seem to claim anything special is being seen. So, I don't know.

From the USA Today:

GENEVA — The father of a theoretical subatomic particle dubbed "the God particle" says he's almost sure it will be confirmed in the next year in a race between powerful research equipment in the United States and Europe.

British physicist Peter Higgs, who more than 40 years ago postulated the existence of the particle in the makeup of the atom, said his visit to a new accelerator in Geneva last weekend encouraged him that the Higgs boson will soon be seen...

Higgs said Monday the particle may already have been created at the rival Fermi National Accelerator Laboratory outside Chicago, where the Tevatron is currently the world's most powerful particle accelerator.

"The Tevatron has plenty of energy to do it," Higgs said. "It's just the difficulty of analyzing the data which prevents you from knowing quickly what's hiding in the data."

Why Give Money To Particle Physicists?

We had a post a while back musing over different reasons to give for demanding our research is funded.

Here you go: If you give money to particle physicists they will do something like create the internet. Why do I say that? Well: Particle Physicists at CERN created the internet!

*One reason you know it was scientists and not some free market company is the world wide web was released for free to the public. (See below.) Would we better off if some company patented it and controlled it? I think not. Go open source!*

Back in the 80s particle physicists wanted to create something that would send their data to people all over the world. They created the world wide web. Recently, CERN has created a "new version of the internet" that is 10,000 times faster.

From the new Times story:

"THE internet could soon be made obsolete. The scientists who
pioneered it have now built a lightning-fast replacement capable of
downloading entire feature films within seconds.

At speeds about 10,000 times faster than a typical broadband
connection, "the grid" will be able to send the entire Rolling Stones
back catalogue from Britain to Japan in less than two seconds.

The latest spin-off from Cern, the particle physics centre that
created the web, the grid could also provide the kind of power needed
to transmit holographic images; allow instant online gaming with
hundreds of thousands of players; and offer high-definition video
telephony for the price of a local call."

From the Wikipedia:

The World Wide Web began as a CERN project called ENQUIRE, initiated by Tim Berners-Lee and Robert Cailliau in 1989. Berners-Lee and Cailliau were jointly honored by the ACM in 1995 for their contributions to the development of the World Wide Web.

Based on the concept of hypertext, the project was aimed at facilitating sharing information among researchers. The first website went on-line in 1991. On 30 April 1993, CERN announced that the World Wide Web would be free to anyone. A copy of the original first webpage, created by Berners-Lee, is kept here

Prior to the Web's development, CERN had been a pioneer in the introduction of Internet technology in Europe, beginning in the early 1980s. A short history of this period can be found here.

So, again, if you give money to particle physicists they will do something like create the internet.

Doomsday Created at CERN

I've read a few articles on this, but after I saw it became the number one blogged about story for a time today according to blogrunner.com, I decided to join the bandwagon.

Two men in Hawaii are going to court to stop CERN from turning on. They maintain physicits there will do something like create a black hole that will grow as it eats up the whole earth or something just as bad or worse.

I guess their claims are drawing enough attention that CERN is actually investigating the issues. They are trying to make sure all their claims are highly unlikely. For instance, they are making sure that any black holes created will evaporate fast enough that they would do no harm. But, then again, what if they don't evaporate? We don't know for sure Hawking is right about that. (Though if we detect it he might be scooting in his chair to Stockholm.)

This has happened before. Before the first nuclear weapon was detonated there was fear that it might start a chain reaction that would destroy humanity. They checked that it was unlikely, and lucky for us, they were right.

I think Dr. Arkani-Hamed, a string theorist, put it best: (Alluding to how improbable these doomsday senarios are):

Dr. Arkani-Hamed said concerning worries about the death of the Earth or universe, “Neither has any merit.” He pointed out that because of the dice-throwing nature of quantum physics, there was some probability of almost anything happening. There is some minuscule probability, he said, “the Large Hadron Collider might make dragons that might eat us up.”

What, dragons! Oh man! We better make sure the court considers that posibility too.

Major Article In New York Times On CERN

The New York Times is running an article called "A Giant Takes On Physics’ Biggest Questions" which takes up 3 whole pages starting on D1 and 6 internet pages here. They have a lot of nice pictures, diagrams and explanations of what will be going on at CERN. It is really a great article. (There are more pictures/diagrams in the paper version. Really good ones too.) I'm glad we get the New York Times here at BYU for free. (BYU foots the bill)

CERN Blows Up

You probably heard about this by now, it's kind of old news, but I found a rather humerus article about it. Actually the article was uninteresting, but the comments were rather funny. Oh, the things people don't know. Also I find it interesting how the article is blaming Fermilab for the whole mess (are they implying a kind of cloak and dagger secret sabotage?).

W Boson, and Higgs Just Around the Corner?

Well, I threatened to blog about this, and now I am. Before I do I want to say people should consider taking a look at Science Daily every once and a while since they stay on top of really cool recent physics being published.

With that said, according to the report by Science Daily:

Scientists of the CDF collaboration at the Department of Energy's Fermi National Accelerator Laboratory have announced the world's most precise measurement by a single experiment of the mass of the W boson, the carrier of the weak nuclear force and a key parameter of the Standard Model of particles and forces. The new W-mass value leads to an estimate for the mass of the yet-undiscovered Higgs boson that is lighter than previously predicted, in principle making observation of this elusive particle more likely by experiments at the Tevatron particle collider at Fermilab. Scientists working at the Collider Detector at Fermilab measured the mass of the W boson to be 80,413 +/- 48 MeV/c2, determining the particle's mass with a precision of 0.06 percent.

What is so interesting to me is this suggests the Higgs Boson may be light enough to be detected by FermiLab! This also means the needed energy level is likely to be in the crosshairs of CERN. Just any day now and we will be overturning cars in the streets over some monumental news.

What Would I Like to See in Graduate School?

As many of you may know I hope to be off to graduate school next year. If I am like the average graduate student I will be there 5-6 years meaning I may be there until 2012-2013.(Yikes!) I happen to be going at perhaps the best time in history. In the next 5-6 years we may come up with some of our most profound discoveries ever. Here is what I hope to see.

1. The Higgs field and Supersymmetry: We all have been thankful for the success of the Standard Model, but I believe we are ready to move on. One major particle that I am desperately hoping CERN finds is the Higgs Boson. Come 2007, the LHC, at CERN will be operating at energies higher then currently being achieved anywhere else; on the order of of 14 TeV. In addition to finding the Higgs, I am really crossing my fingers that we will find strong evindence for supersymmetry. Not only will supersymmetry give us a huge slew of new particles to explore, it will hopefully resolve some of our issues such as the vacuum energy problem and candidates for dark matter.

2. Gravitational Waves: Being able to detect light we cannot see visually, like infrared and microwaves, has greatly furthered our understanding of nature. I hope we will soon add to that gravitational waves. Gravitational waves will greatly enhance our ability to study the universe. We will better understand centers of Galaxies, neutron stars and black holes. In addition, many are very excited on what light gravitational waves will shed on the initial stages of the universe. That will help us further understand not only large stellar objects, but also the small particles which formed in the early stages of the universe. Hopefully LIGO and LISA will be successful which I am at graduate school.

3. Neutrino Background: Many are familiar with the CMB or cosmic microwave background radiation but not as many people are familiar with the theoretical neutrino background. It turns out, there should be a huge collection of neutrinos left over from the big bang era which haven't interacted with anything. We should be able to study this collection much as we can study the CMB to determine truths about the universe. Surely there will be much learned from the neutrino background, and this is yet another discovery I hope we make soon.

4. Pop III Objects: Stars and planets today have lots of elements heavier then hydrogen and helium. During the initial stages of the universe, it was practically all hydrogen and helium. Because of this the physics of the cosmos was very different then it is today. These differences make all the difference in the world if you are trying to understand the universes history. Understanding the universe's history is very important in uncovering how and why the universe is the way it is. Hopefully the Hubble, or more realistically the new James Webb Telescope which will launch in 2013, will detect these objects.

5. Dark Matter and Dark Energy: This may be asking a little much, but with some luck the above things will set straight what is dark matter and dark energy. Maybe supersymmetry is responsible, or maybe something else.

6. The Stage Set for the Theory of Everything: Okay, I have to realistically believe quantum gravity, etc... will not be solved in the next 5-6 years. However, if we can understand the basics of supersymmetry, information coming from gravitational waves, the neutrino background, early population III objects and the higgs field, we might be able to have enough cosmological data to really get somewhere. I've said it before, and I will keep saying it, string theorists are demanding particle accelerators the size of the solar system to test things that will result in understanding quantum gravity. We may never have such accelerators, but we do have an event about 13.7 Billion years ago with energies high enough that if we could examine it close enough we may be knocking on the door to understanding quantum gravity and more. These are the events I hope to see which I believe will lead up to that.