New Bounds On the Higgs Boson Mass

As the LHC continues to run at half power for the next year+, the US-based Tevatron continues to crank out results. Reader hweimer writes "Three new papers in Physical Review Letters present the latest results for the Higgs boson mass coming from Fermilab's Tevatron. The new data mandates that the Higgs boson mass within the standard model lies between 115 and 150 GeV." A year back we discussed the Tevatron's previous shrinking of the search space for the Higgs "God particle."

Comments

Re:I'm lost.

[zmooc]

particle physics for dummies

ALL (anti)matter, ALL forces, fields and waves and everything you can think of consists of particles. I'm not talking about neutrons and protons and the such, but even smaller particles known as subatomic particles or elementary particles. Most of us know the group of particles called quarks, but there are more groups of particle with cool names like leptons (an electron is a lepton) and bosons (a photon is a boson).

We know that a LOT of nature shows some kind of symmetry; this is the same in elementary particle physics. From this, it has been deduced that several particles not yet detected must exist in order to fill in the gaps in the symmetry. It is those particles we are looking for and they are predicted by the Standard Model, which is an enourmous collection of theories that together attempt to describe our entire universe (with the exception of gravity) (and to unify the newtonian and einsteinian physics).

Such particles have many hard-to-understand properties like spin, charge, mass etc. What we are looking for, however, is their specific energy. We do this by accelerating matter (protons typically) to incredible speed and then colliding it. In such a collision, enormous energies occur that cause elementary particles to cease to exist and create new elementary particles. All kinds of particles can sort of randomly be created during such a collision, but obviously the collision itself has to be powerful enough to reach at least the energy the particle we're looking for has. So we keep building more and more powerful particle accelerators in order to find these things. What we call the energy of such a particle is a bit complex; it sort of comparable to mass*speed, but that's not all there is to say about this; for example many particles have a fixed speed, namely the speed of light. Therefore, their mass is equivalent to their energy. That's the GeV number we're talking about here. Note that this is incredibly simplified; for example we don't really know the mass of the photon (except that it is 0 in rest, but photons don't exist in rest) but we DO know its' energy since we can measure that. Also, the charge is not factored into this equation. But, in general, elementary particle physicists think in "energy", not in "mass" or "speed".

Anyway, around the point of collision, enormous detectors have been built that attempt to trap the particles created in the collision. These detectors generate a small electric current comparable to the energy of the particle that collided, which is measured. Think about them as antenna's. After millions and millions of such collisions, patterns start to emerge and we can deduce a specific particle has been created in our collisions. For example, you see a lot of collisions with this energy and a lot with that energy, but none with energy such and so. The result is sort of like a spectrogram (but again, it's way more complex than that).

So in the case of the Higgs Boson, in this "spectrogram", we're looking for a peak somewhere between 115 and 150 GeV. This is obviously an incredibly simplified explanation, but I think this should make you understand just a bit more.