Result

The Standard Model forbids direct production of a strange quark from the decay of a bottom. Indirect decay of the kind illustrated here is possible and is the focus of this analysis. Since observation of direct production of strange quarks from bottom quarks would indicate a discovery, we need to understand very well the indirect production described here. Subatomic particles called quarks are some of the building blocks of our universe. The heaviest of the six types of quarks are…

This plot shows one of the new ways for B0s mesons to decay. The decay appears on this mass plot as the red bump (J/ψ K-Star). Particles can be rather particular about how they choose to decay. Though some particles may have hundreds of choices available to them, these particles typically have just a few ways that they prefer over all others. Despite having such strong preferences, particles do occasionally decay in one of their less preferred ways. CDF scientists…

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…

The Earth is a sphere with a diameter of approximately 8,000 miles. However, if you measure precisely enough, you find that the Earth is slightly pear shaped. The exaggerated figure conveys the basic idea, although the real variation is only about 0.1 percent, which is why the Earth looks spherical to the naked eye. This week’s article describes a similar concept in a DZero measurement. Suppose you needed to know the exact distance between Fermilab and CERN. To first approximation,…

A previous Result of the Week studied the difference between the masses of the top quark and antiquark. This week, DZero returns to the question, this time with a more precise scale. In July of 2009, DZero reported on a measurement of the difference between the mass of top quarks and antitop quarks. This is a very interesting topic. One of the most fundamental tenets of the Standard Model is that the laws of physics apply equally well to matter…

One of the first lead-ion collisions in the LHC as recorded by the CMS experiment on November 8, 2010. Image: Courtesy of CERN In 2006, the popular television show Mythbusters tried to test a legend, which was that two Civil War-era bullets, if fired at one another, would fuse into a single bullet. The team was unable to confirm the myth, simply because it was too hard to get the bullets to collide. They eventually did a simpler test and…

The di-jet invariant mass distribution for candidate events selected in an analysis of W+2 jet events. The black points represent the data. The red line plots the expected Standard Model background shape based on Monte Carlo modeling. The red shading shows the systematic and statistical uncertainty on this background shape. The blue histogram is the Gaussian fit to the unexpected peak centered at 144 GeV/c2 CDF Collaborator Viviana Cavaliere, University of Illinois at Urbana-Champaign, presents the new CDF result in…

The plot is proportional to the probability (invariant differential cross section) of observing lambda, cascade and omega particles as a function of their transverse momentum. The solid lines are fitted curves to the power law function (A(pT+1.3)-n) and n~8.5 for all three particles. The insert shows the ratios of cascades to lambdas and omega to lambdas. While physicists have learned a lot of about our world on a fundamental scale, there are still things that remain a mystery. One of…

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…

Because it is well known that protons and antiprotons contain quarks, we can precisely study subtle interplays of how quarks interact to form Z bosons and photons. Today’s result involves a study of photons and Z bosons. Photons carry the electromagnetic force. Z bosons carry the weak force. For photons, the laws of physics are symmetric. This just means that if you see an electromagnetic physics process going to the right, you could just as easily see it going to…