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Post Info TOPIC: Xi baryon


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Xi baryon

Compact Muon Solenoid (CMS) has observed the xi baryon by looking for events containing both lambda baryons and pi mesons. If these two particles are observed and came from a single parent particle, we expect to see a narrow peak in our data. This measurement used data taken in December, including the data taken during the period when the LHC ran at record-breaking energy, 20 percent higher than the Tevatron.
Some things are far stranger than others, and this week I'm reporting on the strangest thing CMS has seen so far. "Strange" in this context doesn't mean "weird" but rather describes something about the quarks inside the newly rediscovered particle.
There are many particles that are produced at the LHC. One particular type is called the baryon. Baryons are a class of particles that contain exactly three quarks. The most familiar baryons are the proton and neutron, which are made of up and down quarks. Indeed, the up and down quarks are all that is necessary to make up our universe. However, we know that four other kinds of quarks exist: strange, charm, bottom and top. Finding particles with these additional quarks is an important way-station in the CMS collaboration's journey to fully understanding our detector.
One interesting particle is the xi baryon. Discovered in 1964, this type of particle is also called the cascade particle because of its distinctive decay pattern. All baryons contain three quarks, but in order to be a xi baryon, two of those quarks must be strange quarks. Scientists observe these particles by their decay into a pi meson and a (lambda)  baryon. The lambda baryon contains a single strange quark and CMS collaborators observed the lambda baryon in December.

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