From Quantum Diaries and CERN: “LHCb is trying to crack the Standard Model”

LHCb, one of the Large Hadron Collider (LHC) experiments, was designed specifically to study charge-parity (or CP) violation. In simple words, its goal is to explain why more matter than anti-matter was produced when the Universe slowly cooled down after the Big Bang, leading to a world predominantly composed of matter. This is quite puzzling since in laboratory experiments, we do not measure a preference for the creation of matter over antimatter. Hence the CP-conservation law in physics that states that Nature should not have a preference for matter over antimatter. So why did the Universe evolve this way?

One of the best ways to study this phenomenon is with b quarks. Since they are heavy, they can decay (i.e break down in smaller parts) in many different ways, but are light enough for us to produce in copious amounts (unlike the heaviest quark, the top quark). In addition, theorists can make very precise predictions on their decay rates using the Standard Model, the theoretical framework we have to describe most phenomena observed to this day. Once we have predictions on how often b quarks should decay into one or another decay mode, we can compare this with what is measured with the LHCb detector, and see if there are any deviations from the Standard Model predictions. Such deviations would indicate that this model is incomplete, as every physicist suspects, even though we have not been able to define the nature of the more complex theoretical layer that must be hidden or measure anything in contradiction with the Standard Model.

Here is how LHCb wants to do it: by studying rare decays with a precision never achieved before.

When electrons or protons collide in large accelerators, b quarks are produced, but they do not come alone. They are typically accompanied by one other quark (mostly u, d or s) to form composite particles called B mesons. Such mesons have been produced at several colliders, most abundantly in b-factories in the US and Japan, but also at the Tevatron, an accelerator similar to the LHC and located near Chicago in the US.”

This is exciting stuff. Read the full article here.

Participants in Quantum Diaries:

Fermilab

Triumf

US/LHC Blog

CERN

Brookhaven Lab

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