Saturday, December 24, 2011

Discovery of the chib(3p) particle

The Large Hadron Collide (LHC) has proved its value once again.  This time by confirming the existence of an up till now hypothetical particle.  Known as the Chib(3p) particle, it is a boson, the same class of particle the Higgs is in.  Bosons are any particle with an integral spin (0, 1, 2, etc).  The existence of Chib had been expected for quite a while, but the energies required to detect it had yet to be attained.  However thanks to the LHC, teams of physicists working with the ATLAS (A Toroidal LHC ApparatuS ) detector were able to do just this.

Unlike the Higgs Boson, the chip particle is not an Elementary Boson, but composed out of other particles, namely a pairing of a Bottom and an antiBottom quark.  Sometimes still refereed to as the Beauty quark (it all depends on where the team you are working with hails from), interactions between this kind of pairing had been beyond the abilities of particle accelerators until now.

For a little more explanation into what this means, let me first explain what a meson is.  A meson is a pairing of a quark and an anti-quark.  While quarks are technically fermions (particles that have fractional spins, such as 1/2, 2/3, etc) and have a mass, when a quark and its anti-quark join up, their spins combine to form an integral spin (1/2 + 1/2 = 1), making them actually a Boson.  As I said, this puts them in a different class from elementery Bosons such as the photon, W and Z Bosons, gluon, and potentially the Higgs and Graviton.  Instead, they are called Composite Bosons, due to their being constructed of multiple parts.  This allows them to have mass and, because of this, does not allow them to have a trait shared by Elementary Bosons such as the ability for multiple to be in the same place at the same time.  Known as the Pauli Exclusion Principle, particles with mass cannot exist in the same place at the same time.  But Bosons do have an effect on the Pauli Exclusion principle, being that, for a short range, particles are attracted to one another if they are of the right type.

To elucidate this, think of a simple atom, say Helium.  A neutral atom of Helium is made of two protons, two neutrons (though this varies in isotopes) and two electrons.  Each Proton is composed of a series of Quarks, namely two Down and an Up Quark (while a Neutron is made up of one Down and two Up Quarks).  These are held together by the exchange of the Elementary Bosons called Gluons, which mediate the Strong Nuclear Force.  At very close distances, the interaction of these Quarks through their Gluons emit short lived Mesons, which, as we said, are Composite Bosons, usually made of an Up and an antiDown Quark (or vice versa) that radiates away and quickly decays.  But before it can decay, it extends the Strong Nuclear Force (mediated by the Gluons) to the nucleaus and holds the protons and neutrons together despite being of the same charge and wanting to be apart (remeber how like charges such as with a magnet repel?).  This is what I was meaning as the short range of the Pauli Exclusion principle where Fermions (in this case, the protons) can be held together.  The Composite Bosons (if you wish to know, the up and antidown pair is known as a Pion) keep them together, elaborating upon the Strong Nuclear Force.

Now that this is in place, we can understand what the Chib particle really is.  It is a Composite Meson that is made up of, and in turn, holds together a Bottom and and antiBottom pair.  Through this process, many ordinary bits of matter get much of their mass.  Their mass is an effect of the Strong Nuclear Force emiting these Mesons and holding things together.  The Higgs field is still needed to determin what that mass will be, but it cannot do it without the Strong Force. 

While this new particle is very short lived, it shows that the underlying physics that we have developed is still displayed in nature which is good news for researchers looking for this Higgs Boson.  It doesn't mean the Higgs does exist, it just means that there is a bit more evidence to suggests that it does based on what we have observed.
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