In today’s world of constant connectivity, rumors abound, even in science. Over the last few days, you may have seen in your social media feeds that scientists might have discovered a new particle that might be a sibling of the Higgs boson. The Higgs boson was supposed to be an only child. If another one is found, this will force us to rewrite our theories and give us a better idea of the rules that govern our universe. But note that I said “if.” Perhaps it’s time to pause for a moment and take a hard look at what the scientists involved in the measurement did and didn’t say.
A 13 TeV proton collision recorded by CMS. The two green lines show two photons generated by the collision. (Image: CERN/CMS)
The Large Hadron Collider (LHC) is the scientific wonder of our times. Seventeen miles around, over twenty years in the making and costing around ten billion dollars, the LHC accelerates beams of protons to almost the speed of light and collides them. These collisions generate temperatures that last prevailed when the universe was only a tenth of a trillionth of a second old and probe distances as tiny as 5×10-20 meters: that’s as small compared to you as you are compared to the thickness of the entire Milky Way galaxy.
So, it is not surprising that the scientific world was waiting with barely concealed excitement for the seminar at CERN, the LHC’s host laboratory, announcing measurements generated during the accelerator’s 2015 run. The announcements this year were especially anticipated. After running from 2010 to 2012 at a collision energy of seven or eight trillion electron volts, the LHC shut down for a couple of years for retrofits, refurbishments and upgrades. In 2015, the accelerator resumed operations at a much higher energy: thirteen trillion electron volts, over 60% higher than when it generated the data that revealed the Higgs boson. And, because in particle physics more energy means more discovery potential, this year’s data might have held something unexpected.
On December 15, 2015, the new LHC physics results were unveiled to the scientific community. Keep in mind that the LHC is simply the accelerator and that the measurements are made by detectors. While there are four detectors arrayed around the LHC, two of them are large, multi-purpose, detectors, designed to be able to study anything nature throws at us. These two detectors are called ATLAS (A Toroidal LHC ApparatuS) and CMS (Compact Muon Solenoid). The two detectors were built to study the same phenomena and so therefore have similar capabilities. However, the designs were different, and this is a good thing, as the measurements made by the two detectors can cross-check one another.
The data presented in the seminar represent a dazzling success. Between the two experiments, approximately sixty new physics results were announced. Most of the results were in good agreement with theoretical predictions, but those weren’t the ones that scientists were interested in. What the world wanted to know…