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The latest issue of The Economist had a story about the Large Hadron Collider getting ready for its next run. Its last period of operation found the Higgs boson. Physicists hope that with greater power and improved instrumentation it can bring equally significant discoveries that perhaps resolve difficulties with the Standard Model of particle physics. Inconsistencies are piling up, especially with regards to the muon, and theoreticians don't know where to go from here. (Well, actually they have lots of theories with very pretty math, but no clue which are true.) The Standard Model also relies on mathematical hacks that seem arbitrary, but they make the numbers come out right. (Thinking of the famous cartoon where the theory on the blackboard includes the step, "And then a miracle happens.") Physicists hope that new data will suggest the reason behind the math jiggery-pokery. Some hint as to what dark matter is made of might be possible, too.


The prediction of the Higgs boson was the high point for theoretical physics. Now the experimenters are firmly in charge again. The Universe will not give up its secrets to the exercise of pure reason.


Dean Shomshak

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There are some pessimists grousing that they'll need to build the next-generation lepton (electron-electron and electron-positron) collider to get new physics rather than just colliding protons together (which what LHC is doing) or even protons and antiprotons.  The trouble is: to do that, you're going to need an entirely new bunch of hardware to do that.  You will probably have to build a new, gigantic linear accelerator ("linac").


The reason for that is physics.  When you accelerate a charged particle, that makes radiation (light, radio waves, x-rays); and making the particle turn *is* acceleration.  How much radiation depends on the kinetic energy of the particle, and the particle's rest mass, and the amount of acceleration.  It turns out that the fractional energy loss (that is, what fraction of the kinetic energy of the particle gets lost from the particle and turned into radiation) is proportional to the particle mass raised to the minus 4th power.  Electrons are about 1/2000 of the mass of a proton, so the radiation loss from making electrons run around a circular racetrack is MUCH larger than that suffered by making protons run around the same racetrack at comparable kinetic energy.  Now, the acceleration is inversely proportional to the radius of curvature, so a bigger curvature would diminish the lateral acceleration and the associated energy loss, but it also means a bigger machine.  The 8.5 km ring that's at CERN and now is the site of the LHC was the location of the LEP (which was an electron-positron collider), which ran from 1989 to 2000. 


With foreseeable magnet and accelerator technology, you're going to need a much larger ring, or settle for a "straight-line" accelerator where the radius of curvature approaches infinity.  And that's going to be expensive, and those who remember the SSC fiasco in the US in the 1990s know that there are limits to what you can raise money for.


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