This plot shows CDF data at 1.96, 0.9 and 0.3 TeV on the charged-particle density in the transMIN region as defined by the leading charged particle as a function of the transverse momentum of the leading charge particle, PTmax. Almost all scientific publications on research at the Tevatron or the LHC focus on the physics of what happens when a postcollision particle, in particular a quark or gluon, shoots well away from the path of the incoming colliding beams. However,…
This artistic view of a Feynman diagram shows the process of proton colliding with an antiproton, producing a W’, which then decays into a top quark and an antibottom quark. We understand nature in terms of elementary particles interacting through a set of well-known forces, which are mediated by other particles. These are the graviton (mediator of gravity), the photon (mediator of electromagnetism), the gluon (mediator of the strong force), the W and Z bosons (mediators of the weak force)…
This plot shows mass spectra of π+π– pairs at center-of-mass energies (√s) of 0.9 and 1.96 TeV and their ratio. The main peak is a spin-2 f meson; there is evidence for spin-0 f mesons at 980 MeV/c2 (not shown here) and 1,370 MeV/c2 and some structures at higher mass. Among all the elementary and composite particles we know, there are a few that have the odd property of being much like the vacuum: They have no electric charge and…
The plot shows the fit to the dilepton data sample. The data are the points with error bars. The background (purple) and the signal plus the background (cyan) for the reconstructed top quark mass are normalized to the numbers returned by the fit. Nearly 30 years ago, the first pair of protons and antiprotons collided in the Tevatron. Ten years later the CDF and DZero experiments announced the discovery of the top quark, the heaviest known member of the Standard…
The black dots plot the distribution of the reconstructed top mass for events containing one or more b-tags. The distribution is compared to the expected yield for background and signal events, normalized to the best fit. Even after the discovery of the Higgs boson, the top quark is still a focus of attention because of its peculiar position of being the heaviest quark in the Standard Model and for its possible role in physics beyond the Standard Model. If the…
These plots show the effective lifetime asymmetries as function of decay time for D →K+K– (top) and D → π+π– (bottom) samples. Results of the fits not allowing for (dotted red line) and allowing for (solid blue line) CP violation are overlaid. Physicists gave funny names to the heavy quark cousins of those that make up ordinary matter: charm, strange, bottom, top. The Standard Model predicts that the laws governing the decays of strange, charm and bottom quarks differ if…
This event display of the observed ΥZ candidate shows the muon candidates identified from the Upsilon (μ3 and μ4) and Z (μ1 and μ2) decays. In 1977, Fermilab scientists discovered the bottom quark — one of six quarks in the Standard Model — through the production of upsilon mesons. An upsilon meson (Υ) is a bound state of a bottom quark and an antibottom quark. In a new analysis using the full CDF data set, scientists conducted a search for…
Inclusive jet pT differential cross sections for Z + one or more jet events. The measured differential cross section (black dots) is compared to the LOOPSIM + MCFM prediction (open circle). On the right many other theoretical predictions are shown. Our understanding of the strong force, called QCD (quantum chromodynamics) is very advanced. This theory describes the interactions between some of nature’s fundamental building blocks, quarks and gluons. The highly energetic quarks and gluons released in the Tevatron proton-antiproton collisions…
Best-fit signal strengths μ for two cases. Left: the Standard Model versus graviton-like boson (spin 2, positive parity) versus the Standard Model Higgs boson (spin 0, positive parity). Right: the pseudoscalar boson (spin 0, negative parity) versus the Standard Model Higgs boson. Since the discovery of the Higgs boson at CERN and the three-standard-deviation excess seen by the CDF and DZero experiments here at Fermilab, the experimental community has been focusing on measuring the properties of this new particle. It’s…
Results of the two-dimensional fit for σ(s) and σ(t+Wt). The black circle shows the best-fit value, and the 68.3 percent, 95.5 percent and 99.7 percent credibility regions are shown as shaded areas. The Standard Model (SM) predictions are also included with their theoretical uncertainties. CDF and DZero discovered the top quark in 1995 from proton-antiproton collisions that produced the top quark together with its antimatter partner, the antitop quark. It took 14 more years for the same collaborations to announce…