The photons measured by CMS differ from visible light only in energy: light that we see has 2-3 electron-volts per photon, while photons from the LHC have billions of electron-volts. When protons collide in the LHC, they sometimes emit a flash of light. Light is made of particles called photons, and the energy of the photons determines the color of the light. Red light is approximately 2 electron volts (eV) while blue light is about 3 eV, with all visible…
Since the bottom quarks (b and b) inside the Upsilon 1S (left) are held together more tightly than in the Upsilon 3S (right), the Upsilon 1S is less likely to fall apart when clobbered by quarks and gluons in a hot plasma. There have been some hot days this summer; not quite hot enough to cook an egg on the sidewalk, but hot enough to bake cookies in a car. But we don’t need a thermometer to quantify temperature. Besides…
What looks like a one-dimensional world to a large creature might actually be two-dimensional at smaller scales. One of the goals of the LHC is to search for evidence of extra dimensions— spatial directions such as length, breadth and height, but curled or curved in a way that hides their existence in everyday life. In a recent paper, CMS scientists presented new bounds on such a scenario. Extra dimensions could hide from our perception by curling into tiny loops. A…
The top quark is the most massive particle in the Standard Model, and might be pointing to what lies beyond. Regular readers of Fermilab Today may be familiar with the top quark. For 15 years after its discovery in 1995, top quarks could only be produced by the Fermilab Tevatron. This changed with last year’s start-up of the LHC, when scientists saw top quarks in the CMS detector. The top quark is, in a sense, at the extreme edge of…
A proton contains two up quarks, a down quark and a soup of quark-antiquark pairs, seething below the surface. It is often said that a proton is made of three quarks: two of the same type, called up quarks, and one of a different type called a down quark. But that’s not the whole story. In the space between these three stable quarks there is a boiling soup of quark–antiquark pairs. That is, a quark and an antimatter quark spontaneously…
A schematic of the sort of collision debris that would hint at supersymmetry: a muon and an electron accompanied by jets and missing energy (invisible particles inferred from the lopsidedness of the rest of the debris). The vast majority of proton collisions produce only jets. If you smash two protons together what would come out in the debris? In 99.9999 percent of the collisions, the result would be nothing but quarks and gluons, each of which then becomes a jet…
A photon, a particle of light, has no mass. A Z boson has most of the same properties as a photon, but it is very massive. Even heavier photon-like particles could exist, but a new result from CMS sets the lower limit of their mass to at least 12.5 times heavier than Z bosons. You may have heard that when matter and antimatter collide, they annihilate into pure energy. That is, when a negatively charged electron encounters its positively charged…
Collision events in the figure above are arranged according to degree of momentum imbalance: balanced events pile up on the left while unbalanced events are put on the right. One of the supersymmetric models that CMS ruled out is shown in yellow: if this model were true, the physicists would have observed twice as many unbalanced events (See figure 2 in the paper for details). Editor’s note: This is the first CMS Result written by Jim Pivarski, a CMS collaborator….