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| <p class="lead">You discovered CP violation!</p> | ||
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| <section data-min-level="1"> | ||
| <h4>CP Symmetry</h4> | ||
| <h4>The Mystery of CP Violation</h4> | ||
| <p> | ||
| C (Charge) and P (Parity) are discrete transformations that can be applied to a physical system. | ||
| The study of CP violation is concerned with some very fundamental questions:<br> | ||
| <ul> | ||
| <li>Are the laws of physics different for matter and antimatter?</li> | ||
| <li>Why is there an abundance of matter in our universe, instead of equal amounts of matter and antimatter?</li> | ||
| </ul> | ||
| </p> | ||
| </section> | ||
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| <section data-min-level="5"> | ||
| <h4>What is CP?</h4> | ||
| <p> | ||
| CP is a possible <em>symmetry</em> of nature. | ||
| If the laws of nature were symmetric under CP, then matter and antimatter would be governed by the same rules. | ||
| This means that if we communicated with aliens from a distant galaxy, there would be no way to find out if they are made from matter or antimatter: | ||
| No experiment they could perform would allow us to deduce if they lived in a matter or antimatter world. | ||
| On the other hand, if there was a fundamental difference between matter and antimatter, such an experiment would be possible. | ||
| It turns out that this is the case in our universe! | ||
| </p> | ||
| </section> | ||
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| <section data-min-level="10"> | ||
| <h4>How was CP violation discovered?</h4> | ||
| <p> | ||
| In 1964, a team lead by Val Fitch and Jim Cronin performed experiments with <em>neutral Kaons</em>, particles formed by a strange and an anti-down quark. | ||
| These neutral Kaons have the amazing property that they can spontaneously transform into their own antiparticle. | ||
| Fitch and Cronin discovered that the rate at which these Kaons changed from matter to antimatter and vice versa was different, clear evidence for CP violation! | ||
| This discovery came as a total surprise to physicists (it was assumed that nature was symmetric under CP) and earned Cronin and Fitch the <a target="_blank" href="http://www.nobelprize.org/nobel_prizes/physics/laureates/1980/">Nobel price</a> in 1980. | ||
| </p> | ||
| </section> | ||
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| <section data-min-level="20"> | ||
| <h4>How is CP violation currently understood?</h4> | ||
| <p> | ||
| If a theory is symmetric under C, then it works the same if all particles are exchanged with their antiparticles. If it has P-symmetry, then it is invariant under inversion ("mirroring") of all spatial coordinates | ||
| In 1973, two Japanese physicists, <a target="_blank" href="http://en.wikipedia.org/wiki/Makoto_Kobayashi_(physicist)">Makoto Kobayashi</a> and <a target="_blank" href="http://en.wikipedia.org/wiki/Toshihide_Maskawa">Toshihide Maskawa</a>, found a very simple and elegant way to explain the occurence of CP violation in our universe. | ||
| The only problem: The explanation required a third generation of quarks (the <em>top</em> and <em>bottom</em> quarks) for which there was zero evidence at the time. | ||
| </p> | ||
| <p data-min-level="5"> | ||
| For a long time, physicists believed that all of physics is invariant under the combination CP of both symmetries. It turned out that this is wrong, as was discovered by Cronin, Fitch et al. in 1964 when they studied the decay of the neutral K meson. | ||
| <p> | ||
| This turned out to be an incredible prediction, when both of these quarks were discovered decades later. | ||
| So far, the idea of Kobayashi and Maskawa, called the <a target="_blank" href="http://en.wikipedia.org/wiki/Cabibbo–Kobayashi–Maskawa_matrix">CKM mechanism</a>, has been able to explain every single occurence of CP violation that physicists managed to detect in the lab. | ||
| They were awarded the Nobel price in 2008. | ||
| </p> | ||
| </section> | ||
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| <section class="container" data-min-level="10"> | ||
| <div class="row"> | ||
| <h5>CPV in the Kaon System</h5> | ||
| <div class="col-md-3"> | ||
| <img class="img-responsive" src="assets/info/cpv.png" alt="A plot from the original publication"> | ||
| </div> | ||
| <div class="col-md-3"> | ||
| <p>In 1964, Cronin, Fitch, et al. showed that CP symmetry is broken in the decay of the long-lived neutral K meson.</p> | ||
| <p>If all of physics was invariant under CP transformation, then this long-lived version of the K meson would never decay into two pions.</p> | ||
| <p>However, this kind of decay was discovered!</p> | ||
| <p>You can see their results on the left: In the middle plot (the one relevant for K-meson decays), a clear excess is recognizable.</p> | ||
| <p>For their discovery, Cronin and Fitch received the Nobel Prize in Physics in 1980.</p> | ||
| </div> | ||
| <section data-min-level="20"> | ||
| <h4>What's next for CP violation?</h4> | ||
| <p> | ||
| CP violation is one of the necessary ingredients for explaining the abundance of matter over antimatter in our universe. | ||
| But there is one problem: The CKM mechanism predicts too little of it. | ||
| The amount of matter in our universe suggests that a correction or even a complete revolution in our understanding of CP violation is necessary. | ||
| </p> | ||
| <p> | ||
| CP violation remains a hot topic in Physics research. | ||
| Specialized experiments like the <a href="http://lhcb-public.web.cern.ch/lhcb-public/Welcome.html">LHCb detector</a> at CERN in Switzerland are currently searching for hints of New Physics that could explain how our universe came to be the way it is. | ||
| </p> | ||
| </section> | ||
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| <hr> | ||
| <h5>Resources</h5> | ||
| <ul> | ||
| <li><a href="http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.13.138" target="_blank">The original publication by Cronin, Fitch et al.</a></li> | ||
| <li><a href="http://en.wikipedia.org/wiki/CP_violation" target="_blank">Wikipedia on CP violation</a></li> | ||
| <li><a href="http://en.wikipedia.org/wiki/Kaon#CP_violation_in_neutral_meson_oscillations" target="_blank">Neutral kaon mixing on Wikipedia</a></li> | ||
| </ul> | ||
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