Andrew Beretvas

The transverse mass distribution of electron + missing transverse energy for data and standard model expectation. The red region shows our expectations for a W-prime of mass equal to 800 GeV/c2. In the Standard Model the quarks and leptons communicate with each via the exchange of particles known as bosons. The bosons of the Standard Model are the photon, the gluon and the W and Z particles. It is natural to wonder if there are additional bosons present in nature;…

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…

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…

The top (CDF) and bottom (DZero) images show the expected and observed 95 percent confidence level upper limits on the production rate of a Higgs boson as a multiple of the Standard Model prediction, assuming standard model decay branching ratios. The solid, horizontal line shows the prediction for the Higgs boson according to the Standard Model. We determine our measurement by how our data relates to this solid line. The figures have two squiggly lines: one dotted and one solid….

The plot shows the rapidity difference between the reconstructed top and anti-top quarks in data, and the predicted signal and background simulations. The observed forward backward asymmetry in the data is Afb = 14 ± 5 percent. The corresponding reconstructed forward-backward asymmetry, after correcting for experimental effects, is Afb = 42 ± 16 percent, which can be compared to the Standard Model prediction of Afb = 6 ± 1 percent Symmetries have long been an important part of characterizing physical…

In the insert figure, the measured top quark mass is shown at the bottom of the curve. In the larger image, the blue points show the data from the most recent measurement and the red lines show how well the data fit with a prediction of the signal and background combined. The black line shows the predicted background only. The top quark is the heaviest currently known elementary particle, with a mass nearly equal to that of a gold atom….

Some of the Feynman diagrams that contribute to the decay of a D0 (a meson composed of a charm quark and up anti-quark) to a pair of muons. The loops (square or triangle) in the diagrams are an indication that the processes they represent are suppressed. This decay has no processes without loops in the Standard Model. But new physics can have processes without loops and these can dominate over the Standard Model contribution, so this decay becomes an interesting…

The plot shows four different measured cross sections (points) compared to the hashed lines, which are the theoretical expectation. The top three are control samples that are in excellent agreement with theory. The lower most point is the presented measurement that is also in excellent agreement with Standard Model expectation. Physicists test the Standard Model to see if the pieces in place, or those they think might be missing, can tell them anything new. One important test is to measure…

The above image shows the expected and observed 95 percent confidence level upper limits on cross section multiplied by a branching ratio of a supersymmetric neutrino produced in quark-antiquark annihilation and decaying via lepton-flavor-violating interactions into (electron and muon) or (muon and tau) or (electron and tau) final states. Supersymmetry is a theoretical idea that states that for every fermion observed, there is another, yet-undiscovered, boson (and vice versa.) This theory effectively doubles the number of types of particles that…