LHC Science down to earth..

Rod
Rod
Joined: 3 Jan 06
Posts: 4,396
Credit: 811,266
RAC: 0
Topic 194434

Greetings:
Just listened to CBC Radio 1 Quirks and Quarks Radio Broadcast
Bob Mac Donald seems to put together a program that brings LHC Physics down to earth
For those who are interested here is a Podcast

Quirks and Quarks

There are some who can live without wild things and some who cannot. - Aldo Leopold

MAGIC Quantum Mechanic
MAGIC Quantum M...
Joined: 18 Jan 05
Posts: 1,246
Credit: 369,887,764
RAC: 80,027

LHC Science down to earth..

Thanks Rod

Always nice to hear about our projects,now if we can just get the LHC up and running so we can get started on these future discoveries!

 

tullio
tullio
Joined: 22 Jan 05
Posts: 1,994
Credit: 31,051,328
RAC: 4,173

Wandering around the LHC@home

Wandering around the LHC@home message boards, which are quite silent, I came across this link to an article on the LHC computing grid:
LHC Grid
Tullio

Mike Hewson
Mike Hewson
Moderator
Joined: 1 Dec 05
Posts: 6,013
Credit: 86,235,165
RAC: 236,666

I've had a long read through

I've had a long read through a couple of particle physics books, in an attempt to fathom all this interest in the Higgs. Some thoughts, if you'll suffer it :

- it's actually the Higgs mechanism being sought, as up to a point the Higgs particle(s) are virtual.

- the expectation is of a single type of Higgs particle, with a particular rest mass below the energy equivalent of 1 Tera electronvolt.

- from special relativity any detected particle must have a specific relationship between it's momentum and energy ( assuming a given rest mass ). Because of the way this relationship appears when plotted in a certain way this is called the 'mass shell'.

- by colliding the beams of protons one can create energy 'bubbles' at the centre of the collision. Then analysing the products emerging one can hopefully deduce/refine a consistent set of points on a mass shell curve, and thus derive a rest mass estimate. However quantum mechanics adds a couple of curly bits ....

- firstly, there is an 'anarchic principle'. If one has given initial and final states ( particles going in and out from some region ), then any and all possible/legal ways to transition between must be included. These ways interfere with each other. That is, they can act together ( with the same sign ) or against each other ( with opposite sign ). The summation of these various transition modes yields numbers, that when squared give the probabilities of outcomes ie. fractions of observed events. These transitions may be infinite in number, are characterised by Feynman diagrams, and thus require some fancy maths to yield an answer.

- secondly, these transitions may involve 'virtual' particles. By definition these are never detected. A virtual particle is 'off mass shell' and thus can have any combination of momentum and energy. However all particles meeting at a vertex ( where lines intersect on a Feynman diagram ) still must collectively satisfy a host of conservation rules - mass/energy, momenta, charge and numerous quantum numbers. Via Heisenberg uncertainty ( as applied to energy ) there is an inverse quality to energy and time. Greater departures from the mass shell curve can only exist for shorter times, smaller departures for longer. So if I am an electron relatively far away from a proton, say, I can only be affected by low energy/momentum virtual photons : those that can exist for long enough to reach me, and not violate Heisenberg or be detected. If I am rather closer then I can be influenced by virtual photons with higher energy/momenta. This roughly explains why the electromagnetic force is greater as you get closer, and lesser with distance. Don't try this at home with quarks though. The strong force is more or less constant with separation, and the gluons have energy of self interactions and stuff .... see QCD lattice .... let's not go there. :-)

- thirdly, while not directly observable these virtual particles affect results. Or at least the assumption of their presence gives stunning concordance between theory and measurements. See the 'radiative corrections' to the magnetic moment of the electron. Or that some quarks and their properties were accurately predicted from such considerations - and then detected later! This is the equivalent of predicting an unknown planet by examining perturbations in the orbits of existing ones.

- fourthly, as one is summing transitions over a potentially infinite range of values then it is important that a finite answer is reached. One solution for the difficult sums ( those that become infinite ) has been a bit of a cheat, in my view. Two parts are defined to some finite measurable quantity. The first part is negatively infinite and the second is positively infinite. Neither are separately measurable. But when you add them together a finite number is reached which equals the observed quantity. This effectively comes down usually to matching the Feynman diagrams in particular groups. Personally I think this is trickery but it is a well recognised manouevre under the label of 'renormalisation'.

- this is where the Higgs seems to come in. If it exists then one can add it in to the diagrams and simplify the summations dramatically - this is the Higgs mechanism - and rely less on that renormalisation trickery. It ought to be involved with all particles with a non-zero rest mass. In fact the idea of 'rest mass' is a bit squirrely too. Given that Heisenberg says nothing can truly be at rest then perhaps one should say that rest mass refers to the energy axis intercept of the mass shell curve when you set momentum to zero.

- so I guess if they don't find evidence for the Higgs it will be disappointing on several levels. Obviously one can't then explain the mass values of known particles. But more deeply it embarrasses the whole program of using virtual particles in calculations, which has worked so well elsewhere, and I'd expect also prejudices an older problem - that of incorporating gravity too.

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

tullio
tullio
Joined: 22 Jan 05
Posts: 1,994
Credit: 31,051,328
RAC: 4,173

Many years ago a physicist

Many years ago a physicist whose name was Emilio Segre' wrote an article in a magazine long defunct called "Endeavour" which said that a new particle accelerator never solves the problem for which it was built but opens new problems. This was 1972. A couple of years after, two Italian physicists, Angelo Baracca and Silvio Bergia, wrote a book titled "La spirale delle alte energie" in which they repeated the same thesis from a marxist point of view. The spiral in the title refers to both a particle's trajectory in a cyclotron and to the spiraling costs of high energy physics. This is what will happen to the LHC when and if they will have solved their welding problems, I have both a degree in theoretical physics and a diploma as an aluminium welder and I know it is more difficult to weld two aluminium plates by the TIG or MIG methods than to solve a Lie algebra. But they told me there is a new welding method, my diploma goes back to the Eighties and my laurea to the Sixties. So good luck to LHC. If you go to the LIGO home page,scientific collaboration, Amaldi conference, Amaldi biography by Carlo Rubbia. you will find a fascinating story about great discoveries which were made by instruments costing far less than the LHC. Then the spiral mechanism took over. Cheers.
Tullio

tullio
tullio
Joined: 22 Jan 05
Posts: 1,994
Credit: 31,051,328
RAC: 4,173

An article on today's NYTimes

An article on today's NYTimes says "LHC fizzles". You can find a link to it in a LHC@home forum. The superconducting magnets are not working as expected. They were installed to give magnetic fields capable of curving the protons' trajectories into the 27 km tunnel which hosted the LEP collider, now shut, But protons are almost 2000 times heavier than electrons. CERN gambled on the superconducting technology in order to avoid to have to bore a new tunnel with a far larger radius. To gamble is to take risks,
Tullio

Donald A. Tevault
Donald A. Tevault
Joined: 17 Feb 06
Posts: 439
Credit: 73,516,529
RAC: 0

RE: Wandering around the

Message 93605 in response to message 93601

Quote:
Wandering around the LHC@home message boards, which are quite silent, I came across this link to an article on the LHC computing grid:
LHC Grid
Tullio

Well, they're still blocking my IP address, so I guess that they don't need my participation.

tullio
tullio
Joined: 22 Jan 05
Posts: 1,994
Credit: 31,051,328
RAC: 4,173

You are not missing much.

You are not missing much. They are not giving out any work and even the fora are quite silent,

Rod
Rod
Joined: 3 Jan 06
Posts: 4,396
Credit: 811,266
RAC: 0

I might be wrong but I get

I might be wrong but I get the impression its just students who are experimenting with Boinc when it comes to LHC... The big boys have their funding..

There are some who can live without wild things and some who cannot. - Aldo Leopold

MAGIC Quantum Mechanic
MAGIC Quantum M...
Joined: 18 Jan 05
Posts: 1,246
Credit: 369,887,764
RAC: 80,027

LHC News Aug. 6th 2009

tullio
tullio
Joined: 22 Jan 05
Posts: 1,994
Credit: 31,051,328
RAC: 4,173

There was an interesting

There was an interesting article,written by a physicist in the NYTimes, comparing LHC to a Maya temple in the Belize forest, abandoned by its builders for unknown reasons. The temple, like most Maya temples, had also an astronomical purpose and was used to foresee solstices, equinoxes and other astronomical events. The author asked himself what would happen if the LHC could not be made to work, even at a lower energy level, and the thousands of people who built it and prepared to use it had to go elsewhere. This reminded me of the Parkinson law, which states that empires build their biggest monuments when they are already in the declining phase. Let's hope this is not the case of LHC, after all it was built with our money.
Tullio

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.