The search for the Higgs boson is like a jigsaw puzzle. Just as no single piece reveals the whole picture, no single analysis will find the Higgs boson. Without all pieces, the picture is incomplete. In the 1960s, a bevy of physicists pieced together our current understanding of the electromagnetic and weak forces. The first task was to show how those forces were two facets of an underlying single force, called the electroweak force. The second task they accomplished showed…
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…
One theoretical speculation about why gravity is so much weaker than the other known forces postulates the existence of additional dimensions beyond the familiar three. If this idea is true, then the LHC might be able to create microscopic black holes. If observed, they would have a major impact on our understanding of the laws of physics. According to the laws of physics as we currently understand them, it is impossible to make microscopic black holes at the LHC. There…
The W’ boson is a hypothetical, much more massive, cousin of the W boson. This article describes a new search for it. In the late 1960s, theorists were able to mathematically show that the electromagnetic and weak nuclear forces were actually two facets of a single common force, now called the electroweak force. This new theory postulated two new particles called the W and Z bosons. The theory was vindicated in 1983 with the discovery of both of them by…
The figures show the number of top events as a function of delta rapidity. The blue shape is that of the background, the green is the Standard Model prediction for top, and the points are our data. The plot on the left contains events in which the ttbar mass is less than 450 GeV/c2 and is very symmetric. The plot on the right is for a ttbar mass of greater than 450 GeV/c2 and illustrates the discrepancy between expected and…
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…