The Neutral Kaons

<p><strong>The Field Guide to Particle Physics : Season 2<br></strong><a href="https://pasayten.org/the-field-guide-to-particle-physics">https://pasayten.org/the-field-guide-to-particle-physics</a><br>©2022 The Pasayten Institute <a href="https://creativecommons.org/licenses/by-sa/4.0/">cc by-sa-4.0</a><br>The definitive resource for all data in particle physics is the Particle Data Group: <a href="https://pdg.lbl.gov/">https://pdg.lbl.gov</a>.</p><p>The Pasayten Institute is on a mission to build and share physics knowledge, without barriers! <a href="http://pasayten.org/heysean">Get in touch</a>.</p><p><a href="https://pasayten.org/the-field-guide-to-particle-physics/neutral-kaons"><strong>The Neutral Kaons</strong></a></p><p><br>Before we can describe neutral kaons in the wild, we need to take a quick detour to the city.</p><p>South of Downtown Seattle resides the historic Pioneer Square. Bricks line the sidewalks and the ends of metal, reinforcement bars stick out of the old, stone buildings. Approaching the iconic Smith Tower, you cross Yesler Way, and something happens. The direction of the streets change.</p><p>South of Yesler, the streets all run north-south. The grid, in other words, matches the cardinal points of the compass: north south, east west. When you cross Yesler, confusingly, everything rotates by 45 degrees.</p><p>The streets of downtown Seattle - between Yesler Way and Denny Way - all point Northwest. The rotation of streets is made to match the contour of Elliot Bay. The waterfront goes NW to SE. Streets run parallel and perpendicular to it.</p><p>It’s often easier for us to think in terms of north south east west, but sometimes the geographic features of the terrain forces a change. There are still two directions, it’s just a shift in our frame of reference.</p><p>This idea of a 45-degree shift in our frame of reference, mixing North with West and South with East, is very similar to how the neutral kaons behave.</p><p><strong>Introducing the Neutral Kaons</strong></p><p>There are t