Andy Beretvas

Comparison of expected and observed distributions of both Z invariant masses. The region CDF looked at contained only seven events (inside the blue lines). While the production of a single W or Z boson in particle collisions at the Tevatron happened quite often and has been a reference for precise electroweak measurements, a pair of such bosons was produced less frequently. Scientists predict that, in collisions between protons and antiprotons, a ZZ boson pair is produced only once for every…

The figure shows the decay of the D*+ into a D0 and a soft (low-momentum) pion. The D0 then decays into a negative kaon and a positive pion. This is called a right-sign decay. Another decay mode called a wrong-sign, which is very rare, can occur. In this mode, the D0 decays into a positive kaon and a negative pion. Since the discovery of the charm quark in 1974, physicists have postulated a rare process in which a charm particle…

Best-fit cross section for inclusive Higgs boson production, normalized to the Standard Model expectation, for the combination of all CDF search channels as a function of the Higgs boson mass. The solid line indicates the fitted cross section, and the associated shaded regions show the 68 percent and 95 percent credibility intervals, which include both statistical and systematic uncertainties. CDF’s physicists have been searching for the Higgs boson since the early days of Run I, publishing their first paper on…

Output of the neural network used to separate 125-GeV/c2 Higgs boson signals from the multi-jet background. The multi-jet background is very large, so the lower plot shows the output with the multi-jet contributions removed. The data tends to follow the background prediction, which implies no Higgs boson has been observed. Searching for gold is a hard game—you spend so much time digging through the dirt. But if you persist, you may find a huge bounty of treasures … much like…

Particles in love. The Higgs boson gives mass to fundamental particles, and so it likes to interact the most with the most massive particles. The top quark, discovered by CDF and DZero in 1995, is the most massive fundamental particle known, and its large mass could indicate that it has a special relationship with the Higgs boson. If so, learning about that relationship will be one of the most important tasks in understanding the Higgs boson and how it produces…

The x-axis, which goes from zero to one, shows that a Higgs signal has a peak at a value of 0.85. The backgrounds peak at a value of 0.2. The Higgs boson has been a very elusive particle: It has escaped observation for more than 48 years since theorists postulated its existence in 1964. The particle observed at the LHC with a mass of about 125 GeV/c2 is most likely the long-sought Standard Model Higgs boson. Scientists need to conduct…