Why the LHC matters

Resident Joined: Aug 31, 2006 Posts: 315

This is a period of great excitement in the physics world as the LHC is about to get functional. Here’s why.

i) One of the theorems of the Standard Model (SM) is that the number of quark families is equal to the number of lepton families, which they are at the moment – each being equal to 3 families, each family containing two particles. So, presently the SM contains 6 leptons and six quarks.

But suppose that another, new lepton is found?!? It would mean a new family of leptons has been discovered. The consequence would then be to find its partner to complete the family AND the two quarks of the corresponding new family. Because of symmetry, these new particles (4 so far) would have their anti-particle partners, thus automatically doubling the number of new particles to 8. So finding one single new lepton would trigger the search of seven more.

ii) Supersymmetry (SUSY) is a theory crucial to String Theory (ST), Grand Unifying Theories (GUT’s) and in cosmology. Now all particles fall into two broad categories: fermions, with half-integral spins, constitute the building blocks of matter; bosons, with integral spins, mediate the force between particles of matter. SUSY postulates that for every boson there is a fermion, and vice-versa. For example, the electron, a fermion with ½ spin, would have a partner dubbed the selectron with spin 0. The photon, a boson with spin 1, would have as its partner, the photino with spin ½.

If any of these are discovered, we wouldn’t know what their use is for, perhaps they might make up Dark matter or Dark energy, but that’s just a guess.

iii) The Higgs boson is crucial to SM. Here’s why. Back in the 1930’s, when people were working on quantum field theory (QFT), they were faced with a theory riddled with infinities. Dirac was the first one to work around by introducing what is called a Lagrange multiplier – a fancy name but technically is very simple, it’s just a constant. The trick is, instead of performing an integration which gives the infinity, one plugs in a constant, does the integration, which now doesn’t go to infinity, then removes the constant. It turns out this made QFT a theory of the real world, but most physicists, including Dirac, were highly unsatisfied with this math trick. Feynman was able to do the same by using graphs and looking at the path integrals by considering all possibilities. When this was applied to the electromagnetic force, quantum electrodynamics (QED) became the most precise theory on this planet.

However, this trick only works because the photon, the particle that mediates the electromagnetic force, is massless. In the weak and strong nuclear forces, the bosons have masses. When that is taken into consideration, the infinities reappear.

Higgs was able to work around this by proposing that these bosons acquire their masses by a process called spontaneous symmetry breaking – a fancy name, but it is just another math trick. The analogy is the particle on a hill. It is at rest and every direction is equal (the symmetry) But once it’s nudged, it will roll down the hill. By choosing a direction, it has broken the symmetry. In the SM, the massless boson acquires mass – that is, breaks the symmetry – by traveling through a Higgs field.

By adopting this scheme, called the Higgs mechanism, Weinberg and Salam were able to get rid of the infinities that plagued SM. So the Higgs particle is a must for SM to be validated.

iv) If no discovery of new particles takes place, then this would be just as intriguing. No SUSY particles means String Theory is in trouble; no Higgs boson, and SM would be on very shaky ground.

And so, the bets are on. Will the LHC confirm SM, SUSY and ST, or throw a monkey wrench into any of these theories???

Newbie First Class Joined: Mar 29, 2008 Posts: 48

I won't even pretend that I understand any of this.

Thinker Joined: Mar 26, 2008 Posts: 429

One question: what the hell's a Higg's field?

Resident Joined: Aug 31, 2006 Posts: 315

Cygnus wrote:

One question: what the hell's a Higg's field?

Accoding to what I said in the OP, the Higgs field is that field that gives mass to the elementary particles. According to the Standard Model, the vacuum in which all particle interactions take place is not actually empty, but is instead filled with a condensate of Higgs particles. The quarks, leptons, and W and Z bosons continuously collide with these Higgs particles as they travel through the "vacuum". The Higgs condensate acts like molasses and slows down anything that interacts with it. The stronger the interactions between the particles and the Higgs condensate are, the heavier the particles become.

The Learned Joined: May 21, 2008 Posts: 128

Will the LHC create a large enough abyss to throw God into?

Thinker Joined: Mar 26, 2008 Posts: 429

Missionary wrote:

Will the LHC create a large enough abyss to throw God into?

WHAT DOES THAT HAVE TO DO WITH ANYTHING???

This thread is about a physics theory. Not abiogenesis or evolution. If discovering how particles work is somehow contrary to god, then I'm sorry, god is wrong. String theory is being used to explain expansion of the universe and dark matter yet you somehow manage to sneek God into this. Seriously, what the hell!?

Posted: Mon Jul 07, 2008 1:20 am

Missionary wrote:

Will the LHC create a large enough abyss to throw God into?

How quickly they forget...

Science closes gaps, Missionary. It's the theist's job to hold them open so their God can fit.

Posted: Wed Sep 17, 2008 6:02 am

First of all I'm going to say this: it took me around fifteen minutes to read through the OP. I'm not adept at physics. But I was wondering, how will the scientists actually be able to identify the presence of the Higgs boson? And why do they need the LHC to do it?

Posted: Wed Sep 17, 2008 6:53 am

The7thScribe wrote:

First of all I'm going to say this: it took me around fifteen minutes to read through the OP. I'm not adept at physics. But I was wondering, how will the scientists actually be able to identify the presence of the Higgs boson? And why do they need the LHC to do it?

I've watched a number of Science channel presentations about this and it's my take on it (by what they say) is the Higgs Boson no longer exists as a particle, it went extinct (probably not the right word to describe it)shortly after the expansion. The Large Hadron Collider has the potential to recreate the circumstance as they existed at the moment the Higgs boson existed and also reproduce the particle itself. It will be a fleeting existence however and will only exist for the briefest of time and they plan to detect that brief existence. The reason why this is important to them is not the particle itself, but they need to prove the particle to prove the Higgs field (any field must have an associated particle), which is necessary to explain mass under the current understanding of particle physics.

None of the shows I watched explained the method by which they'll identify the particle.


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