Mike Cooke

A sidereal day is the time it takes the Earth to rotate back to the same alignment with respect to distant stars. A premise of Einstein’s theory of Special Relativity, and a fundamental part of the Standard Model, is that the laws of physics are the same for everyone regardless of where they are and which way they are facing. If this were not true, the results of an experiment would depend on how the apparatus is oriented with respect…

Does the bottom quark behave differently depending on which other quarks it teams up with to form a composite particle? A bottom quark doesn’t last long before it decays into a charm quark or an up quark. Does its company during that brief moment affect the length of its life? Quarks are never seen on their own. Only their groupings, by twos into mesons or by threes into baryons, are observable. If the bottom quark were just a spectator in…

A magician’s feats are not meant to be repeatable, but the reproducibility of results, such as this confirmation of a newly observed particle, is key to the scientific process. When a magician produces a rabbit out of an empty hat during a performance, you don’t expect to go home and repeat the feat yourself. When a scientist claims to see something new, the expectation is that the observation can be repeated. Reproducibility is a key aspect of scientific inquiry and…

Improving the precision of the W boson mass measurement allows physicists to tighten the indirect constraints on the mass of the Higgs boson. As the race to discover or exclude the Higgs boson nears the finish line, a new precision measurement of the W boson’s mass tightens the constraints on where the Higgs boson could be found. The Standard Model does not predict the mass of the W boson or the Higgs boson, but it does predict a specific relationship…

Neutrinos are inferred by a momentum imbalance after adding up all visible detector activity. This conservative estimator helps reject background events where that momentum imbalance is measured poorly. The simultaneous production of two weak force carriers is a major background to the Higgs boson search. It also gives physicists an opportunity to study the weak sector of the Standard Model and probe for signs of new physics. A new DZero analysis focuses on the rarest of these processes, when a…

DZero physicists precisely determined the width of the top quark, something that cannot be measured with a ruler. In the Standard Model, the top quark is considered a point particle and lacks any spatial size or volume, yet DZero physicists have recently performed the most precise determination of the width of the top quark to date. This statement seems to contradict itself when considering the kind of width you might measure with a ruler, but is perfectly sensible when discussing…

To improve the precision of the top quark mass measurement, physicists must contend with both statistical and systematic sources of uncertainty. Two major factors contribute to the ultimate precision of a measurement of the top quark mass: the amount of data used to make that measurement and the understanding of the uncertainty introduced by the detector. The amount of data used affects the size of the statistical uncertainty of the measurement, while accounting for the bias of the detector effects…

A man on a high wire can only move in one dimension, but an ant on the same wire can move either along or around the wire. Does such a compact extra dimension exist as a fourth dimension of space? A man on a high wire can only choose to move along the wire towards either end. For all his acrobatic prowess, he could not imagine moving along the wire in more than that single dimension. On a smaller scale,…

DZero physicists looked for evidence of the Z boson directly emitting light, a process that is not part of the Standard Model. According to the Standard Model, the Z boson lives its life in the dark. Lacking an electric charge, this weak force carrier is ignored by photons. Their only interactions are indirect, with their communication mediated by charged particles. They can only be produced at the same time if light is emitted by a charged particle that either helped…

DZero physicists search for signs of top quarks teaming up to form new particles that would indicate exciting new physics. Top quarks live a short and lonely life in the Standard Model, where they are expected to survive such a brief amount of time that they never become part of something larger. While all other quarks team up in twos and threes to make mesons and baryons, respectively, the top quark keeps to itself. But some models of new physics…