An Exotic Particle at LHCb
April 9, 2014
There is interesting news for the particle physics community today, courtesy of the LHCb (Large Hadron Collider beauty) experiment. They are now claiming that the hint of a new particle that they saw a few years ago has now been confirmed as existing, and the interesting part of the story is that it is not a traditional quark-based particle. This is the first piece of matter to be produced in the lab that is neither a meson nor a baryon, but something completely different. (The original announcement can be viewed here)
Since the 1960s, the accepted model of particle physics has held that all matter (except dark matter of course) is composed of smaller particles called quarks and their antimatter partners, antiquarks. These quarks are so tightly bound to one another that they can only appear in bound states with other quarks or antiquarks. Because of the nature of the strong nuclear force that binds quarks together, this force is very strong between three quarks (called a baryon) or between a single quark and a single anti-quark (called a meson), but once one of these combinations forms the force is too weak to bind any more quarks or anti-quarks to the system.
However the LHCb has published an observation of a new particle, known as the Z(4430) that does not appear to be either a baryon or a meson. This particle has been seen before, in the BELLE experiment in 2008, but at the time they didn't have enough data on it to conclude exactly what its properties were or even if it truly was a particle. Now the LHCb has collected far more information and confirmed the original results and demonstrated many of its properties. This new result is based on analyzing 180 trillion reactions, finding 25,000 decays of a heavy particle called a B-meson, and sifted through those for a handful of these exotic hadrons.
The LHCb team also claim that the minimal quark content of this new particle is two quarks (a charm and an down-type quark) and two antiquarks (an anticharm and an anti-up type), which makes it the first particle to be composed of four fundamental constituents.
Unless an error is found in their analysis, which is unlikely, this is truly an exotic particle!
Since the 1960s, the accepted model of particle physics has held that all matter (except dark matter of course) is composed of smaller particles called quarks and their antimatter partners, antiquarks. These quarks are so tightly bound to one another that they can only appear in bound states with other quarks or antiquarks. Because of the nature of the strong nuclear force that binds quarks together, this force is very strong between three quarks (called a baryon) or between a single quark and a single anti-quark (called a meson), but once one of these combinations forms the force is too weak to bind any more quarks or anti-quarks to the system.
However the LHCb has published an observation of a new particle, known as the Z(4430) that does not appear to be either a baryon or a meson. This particle has been seen before, in the BELLE experiment in 2008, but at the time they didn't have enough data on it to conclude exactly what its properties were or even if it truly was a particle. Now the LHCb has collected far more information and confirmed the original results and demonstrated many of its properties. This new result is based on analyzing 180 trillion reactions, finding 25,000 decays of a heavy particle called a B-meson, and sifted through those for a handful of these exotic hadrons.
The LHCb team also claim that the minimal quark content of this new particle is two quarks (a charm and an down-type quark) and two antiquarks (an anticharm and an anti-up type), which makes it the first particle to be composed of four fundamental constituents.
Unless an error is found in their analysis, which is unlikely, this is truly an exotic particle!
Posted In : Particle Physics
I am a theoretical physicist & mathematician, with training in electronics, programming, robotics, and a number of other related fields.
