De LHC deeltje 2

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Op donderdag 15 oktober 2009 12:23 schreef Haushofer het volgende:
Onze conclusie was eigenlijk dat er kennelijk bar weinig goede wetenschapsjournalisten zijn.

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Op donderdag 15 oktober 2009 13:28 schreef Haushofer het volgende:

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Ja, daar heb ik serieus wel over nagedacht. Ook omtrent de berichtgeving over de LHC; ik kan me best ergeren aan al die flauwekul wat in populaire bladen en zelfs kranten staan.

Tot dan vervul ik mijn roeping hier op Fok!

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LHC gets colder than deep space

The Large Hadron Collider (LHC) experiment has once again become one of the coldest places in the Universe.

All eight sectors of the LHC have now been cooled to their operating temperature of 1.9 kelvin (-271C; -456F) - colder than deep space.

The large magnets that bend particle beams around the LHC are kept at this frigid temperature using liquid helium.

The magnets are arranged end-to-end in a 27km-long circular tunnel straddling the Franco-Swiss border.

The cool-down is an important milestone ahead of the collider's scheduled re-start in the latter half of November.

The LHC has been shut down since 19 September 2008, when a magnet problem called a "quench" caused a tonne of liquid helium to leak into the LHC tunnel.

After the accident, the particle accelerator had to be warmed up so that repairs could take place.

The most powerful physics experiment ever built, the Large Hadron Collider will recreate the conditions just after the Big Bang. It is operated by the European Organization for Nuclear Research (Cern), based in Geneva.

Two beams of protons will be fired down pipes running through the magnets. These beams will travel in opposite directions around the main "ring" at close to the speed of light.

At allotted points around the tunnel, the proton beams cross paths, smashing into one another with cataclysmic energy. Scientists hope to see new particles in the debris of these collisions, revealing fundamental new insights into the nature of the cosmos.

Awesome energy

The operating temperature of the LHC is just a shade above "absolute zero" (-273.15C) - the coldest temperature possible. By comparison, the temperature in remote regions of outer space is about 2.7 kelvin (-270C; -454F).

The LHC's magnets are designed to be "superconducting", which means they channel electric current with zero resistance and very little power loss. But to become superconducting, the magnets must be cooled to very low temperatures.

For this reason, the LHC is innervated by a complex system of cryogenic lines using liquid helium as the refrigerant of choice.

No particle physics facility on this scale has ever operated in such frigid conditions.

But before a beam can be circulated around the 27km-long LHC ring, engineers will have to thoroughly test the machine's new quench protection system and continue with magnet powering tests.

Particle beams have already been brought "to the door" of the Large Hadron Collider. A low-intensity beam could be injected into the LHC in as little as a week.

This beam test would involve only parts of the collider, rather than the whole "ring".

Officials now plan to circulate a beam around the LHC in the second half of November. Engineers will then aim to smash low-intensity beams together, giving scientists their first data.

The beams' energy will then be increased so that the first high-energy collisions can take place. These will mark the real beginning of the LHC's research programme.

Collisions at high energy have been scheduled to occur in December, but now look more likely to happen in January, according to Cern's director of communications James Gillies.

Feeling the squeeze

Mr Gillies said this would involve delicate operation of the accelerator.

"Whilst you're accelerating [the beams], you don't have to worry too much about how wide the beams are. But when you want to collide them, you want the protons as closely squeezed together as possible.

He added: "If you get it wrong you can lose beam particles - so it can take a while to perfect. Then you line up the beams to collide.

"In terms of the distances between the last control elements of the LHC and the collision point, it's a bit like firing knitting needles from across the Atlantic and getting them to collide half way."

Officials plan a brief hiatus over the Christmas and New Year break, when the lab will have to shut down.

Although managers had discussed working through this period, Mr Gillies said this would have been "too logistically complicated".

The main determinant in the decision to close over winter were workers' contracts, which would have needed to be re-negotiated, he said.

An upgraded early warning system, or quench protection system, should prevent incidents of the kind which shut the collider last year, officials say.

This has involved installing hundreds of new detectors around the machine.

Cern has spent about 40m Swiss Francs (£24m) on repairs following the accident, including upgrades to the quench protection system.

Bron: BBC.

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Op maandag 19 oktober 2009 08:32 schreef RRGJL het volgende:
http://www.nu.nl/wetensch(...)zende-deeltjes-.html
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Op maandag 19 oktober 2009 08:32 schreef RRGJL het volgende:
http://www.nu.nl/wetensch(...)zende-deeltjes-.html
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LHC Physicist Steven Nahn on the Elusive Higgs Boson

the detector in the 12,500-ton Compact Muon Solenoid experiment
A view of the detector in the 12,500-ton Compact Muon Solenoid experiment (CMS). Courtesy of CERN
In September 2008, scientists at CERN sent the first beams of protons running through the Large Hadron Collider (LHC), the world's most powerful particle accelerator. CERN scientists hope to produce the elusive Higgs boson and other novel particles. But the project has seen numerous setbacks. An explosion caused by a failed connection between two magnets last autumn led to a yearlong delay in all operations. And, earlier this month, French police arrested a French-Algerian postdoc working at the LHC on charges of terrorism.

Two physicists recently put forth a new theory on why the accelerator has encountered so many delays. Holger Bech Nielsen, of the Niels Bohr Institute in Copenhagen, and Masao Ninomiya of the Yukawa Institute for Theoretical Physics in Kyoto, Japan, suggest that the hypothesized Higgs boson would have such harmful effects that the particle is essentially traveling back through time to stop its own creation.

In this interview, MIT particle physicist Steven Nahn, a leader of the team working on the collider's CMS (compact muon solenoid) detector, says that, while there is a long history in physics of "crazy" theories becoming widely accepted, he's not convinced by this one.

Q. Should we take seriously the idea that the Higgs boson is trying to sabotage its own production?
A. The premise is fairly crazy, but many things in physics are constructed that way: Make up a universe where the laws of physics are a bit changed compared to our current understanding, and see where that takes you. That's a common practice amongst the theory crowd. You'd have to check with a historian to be sure, but I can imagine a similar reception to quantum mechanic — but then it explained all sorts of things, like why atoms don't collapse, the Balmer series of quantized radiation from electron transitions, the structure of the periodic table, etc. QM explained certain mysteries already exposed by experiments, and made predictions that could be tested (and were). Similar descriptions apply to both special and general relativity, both of which were probably "crazy" at the time. In special relativity, there is the famous "twin paradox," a prediction that if you take a set of twins, leave one on Earth and send one traveling through space at nearly the speed of light, when the second one returns he will be younger than the one left behind. Sounds "crazy," meaning outside of our normal experience. But, in 1972, they put some atomic clocks on planes, flew them around the world, and indeed found that the moving ones were behind relative to ones left on the ground. Experiments like these are essential to have a theory accepted into the canon of physics.

The difference here is that these previous "crazy" ideas gave consequences that were clearly testable and attestable to the new nature of the theory, in an objective manner, and involved the behavior of inanimate objects (i.e., not humans). However, in this case, the consequences seem quite contrived — specifically, setting up the theory such that the Higgs particle thwarts its own discovery at the LHC seems to be creating the means to fit the desired end. Exactly in line with their argument, I could say that Nature abhors the Chicago Cubs, such that the theory which describes the evolution of our universe prescribed Steve Bartman to interfere on October 14, 2003 (http://en.wikipedia.org/wiki/Steve_Bartman_incident), extending the "bad luck" of the Cubbies. Rather hard to show that this incident is directly attributable to the modification these guys are proposing. On the other hand, if you buy this, we now have a new scapegoat to blame all our misfortunes on: the "imaginary action"!

Then the question, "Why Higgs?" Admittedly, I haven't read the whole series of papers, which means my comments should be taken with a grain of salt, but I did skim, and the authors do make an argument for why a new unknown particle (they use Higgs as their poster boy for unknown theoretical particle) can do this and not the ones we know about, based on the experimental evidence we have on the known particles and the existence of yet another theoretically possible but experimentally undetected (not without trying) phenomenon, a magnetic monopole. But, I think the same argument could have been made in the past regarding any yet-to-be-discovered particle — we don't know its properties, so it could be that it thwarts its own discovery. But (a posteriori) we know that they didn't. Seems a little circular.

Q. Why do physicists want to find the Higgs boson?
A. "Finding the Higgs boson" is really code for understanding why fundamental particles have different masses. We have this wonderfully symmetric structure called the standard model — three "generations" of matter, each with a pair of leptons and a pair of quarks, with each generation looking like a carbon copy of the others. The current leading theory which explains all the interactions of these things does such a good job passing many stringent experimental tests that it is referred to as the "Standard Model." The Standard Model (without the Higgs) requires all these particles to have zero mass, or it fails to be a consistent theory, meaning it will predict outcomes with probability greater than 100 percent at sufficiently high energy — that can't be right! But, the big problem is all these symmetries are drastically broken by the mass of these particles. In units of electron volts, the lightest ones weigh less than 0.2, the heaviest 170,000,000,000. And in between there is no pattern. Not only are they not zero, but they are all over the map!

The "Higgs Mechanism" and its associated Higgs boson is just the most economical way of restoring the consistency of the Standard Model while allowing fundamental particles to have non-zero mass. There are other ways of doing it, but this one fits very neatly into the theory. So, finding the Higgs boson would allow us to further explore why the fundamental particles have the mass they do. The excitement about the LHC is that, in order for the theory to be consistent, the Higgs mass has to lie in a particular range — not too heavy, not too light — and the LHC is the first collider that will have access to the whole range, so we should be able to (eventually) answer this question once and for all.

Q. Barring any further setbacks, when do you expect the Large Hadron Collider to start producing useful data? How long might it take to find evidence of the Higgs boson?
A. From what I have heard just last week, the LHC is still on schedule for circulating beam in the middle of November. But that is just the beginning — then you have to tune the beam and make sure you have it under control, then establish counter-circulating beams, then make sure they collide at the right place, and then ramp up the energy as well. So, it can be a long process. Currently, they think it should take about six weeks until we get to "collisions," so maybe by Christmas we'll start getting "real physics" data.

And then, we need to understand our apparatus with this real physics data. We have a bunch of analyses based on simulated data, but it is very difficult to match simulation to actual collisions, so we'll need to use the first batch of data to make sure our strategies based on simulation are, in fact, optimal for the real deal. We do this by using known physics as benchmarks, the same way you would take an object of known weight to calibrate your bathroom scale.

And then, how long to the Higgs. First, that depends on the mass of the Higgs — in certain mass regions, there are more "false signatures" of the Higgs relative to others, so it takes longer to distinguish the real thing from background. Also, it depends on the machine: For a certain energy, you have a certain probability to make a Higgs — the higher the beam energy, the higher the probability. In addition, the rate at which the machine makes collisions also matters — for a fixed number of Higgses per collision (which is a very tiny number), the more collisions per second, the sooner you get a decent sample to work with.

OK, with all those caveats, we expect to start being able to rule out certain Higgs masses with the data set we will have collected by about one year from now. So, don't hold your breath, it will take a few years to have the answer for the whole mass range — this is a marathon, not a sprint, and the path is not perfectly smooth, as we have seen already. But, I don't believe physics itself is deliberately setting up roadblocks!

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Voor het eerst weer deeltjes in de LHC

AMSTERDAM - Afgelopen weekend hebben voor het eerst in meer dan een jaar weer protonen door de kolossale deeltjesversneller LHC in Geneve bewogen. In september 2008 raakte de 27 kilometer lange ondergrondse machine bij een heliumexplosie defect, een dikke week nadat hij onder toeziend oog van de wereldpers was opgestart.

Bron: Volkskrant, lees meer….

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Op donderdag 29 oktober 2009 22:35 schreef Iblis het volgende:
Volkskrant bericht er ook over:

[url=http://www.volkskrant.nl/wetenschap/article1308194.ece/Voor_het_eerst_weer_deeltjes_in_de_LHC?source=rss]
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Op vrijdag 30 oktober 2009 09:14 schreef Haushofer het volgende:

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Denk je niet dat het juist andersom is?

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Op vrijdag 30 oktober 2009 09:32 schreef eleusis het volgende:
Zitten meer mensen zich continu eraan te storen dat 't “het LHC-deeltje” zou moeten zijn?

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