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Physicists from four experiments – two at Fermi lab near Geneva, Illinois; and two at the LHC near Geneva, Switzerland – announced discovering a new particle that could be the long-sought Higgs Boson.
These experiments cannot yet determine what the new particle is; they have only determined its mass. This could be the Higgs or could be something else, which actually might be even more interesting.
What all these groups observed is an excess of apparent particles with a mass of about 125 GeV (130 times heavier than a proton). Here “excess” means more than expected based on the Standard Model of particle physics. I say “apparent” because none of the newly discovered particles were directly observed—they don’t live long enough to leave a detectable signal.
What the experimenters actually observed were other well-known particles that do live long enough to be detected, emanating from high-energy collisions. From the energies and trajectories of the detected particles, experimenters found some combinations that are consistent with the decay of a new particle of mass 125 GeV. Since each of these high-energy collisions can produce hundreds of particles, there are a myriad of possible combinations and possible “new particle” masses. The key to claiming a discovery is to establish an excess—more than expected—at a specific mass. The discovery presumes that the Standard Model correctly predicts what would be observed if the Higgs Boson did not exist.
The process sounds complex, and it is, but fundamentally it is similar to examining a coin to find if it has a hidden property. Flipping a normal coin would give heads 50% of the time. If a certain coin comes up heads 75% of the time, the coin might be special in some way. Statistics tells us how many times we have to flip a coin to convincingly establish that it’s special.
The excess in the two American experiments have a 1-in-500 chance of being an accidental fluke.
The excess in the two European experiments have a 1-in-1 million chance of being an accidental fluke.
It is interesting that Fermi lab collected data from collisions between protons and antiprotons, whereas LHC collected data from proton-proton collisions. The experiments are thus finding the new particle in significantly different environments, adding to the credibility of its existence.
While the Europeans have more convincing data, we should acknowledge the contribution made by an American high-energy particle accelerator. Since American accelerators have been shut down, this may be the last important contribution made by American fundamental physics labs for at least the next several decades.
Below is the latest American data, with the solid black line showing the measured particle masses and the dotted line showing the expected masses without a Higgs Boson. The excess is circled in red.
Below is the latest LHC-ATLAS data, with the solid red line showing the measured particle masses and the dotted line showing the expected masses without a Higgs Boson. The excess is the bump at about 125 GeV.
Physicists have been searching for the Higgs Boson for over 40 years. They convinced governments to spend over $10 billion building the LHC to find the Higgs. So they are praying they have found the ‘God’ particle, and are eager to celebrate. But confirming that will take a lot more work.
Author- Dr. Robert Piccioni.
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