Posts Tagged “quarks”

How about taking a “closer” look onto a microbe??? I’ll try to take you on a journey deep into the nature of the particles constituting it, deep to the extent of  subatomic levels, in a trial to learn more about the beginning of life and matter…

Since being a nuclear physicist has always been a dream for me, but obviously didn’t come true, I have been very interested lately in the news about the re-operation of the Large Hadrons Collider (LHC) at CERN  and the experiments being conducted there in their attempts to find out more about the composition of matter and the origins of our universe, and the effects these discoveries will have on all different fields of science.

My readings into this topic have brought me to know more about one of the fundamental building blocks of matter, the Quark. Being an elementary particle, quarks theoretically can’t be broken down into smaller units. Their existence was first proposed by physicists Murray Gell-Mann and George Zweig in 1964 as “the Quark model”. The model was introduced to give a better explanation and understanding of atomic Nucleii composition, but there was little evidence for their existence. This lasted till “deep inelastic scattering “experiments were conducted at SLAC National Accelerator Laboratory operated by Stanford University in 1968. since then, six types of quarks also known as “the six flavors” have been discovered, divided into three generations : 1st generation including ( up) and (down) quarks, 2nd including (charm) and (strange) quarks and the 3rd including (bottom) and ( top) quarks. The (top) quark, first observed at “Fermilab” in 1995, was the last to be discovered. There have been trials to prove the existence of a 4th generation of quarks, but till now, all have failed but in the future,  and thanks to the current  LHC experiments, who knows? After all, protons, neutrons and even atoms were once considered fundamental units of matter and that there was nothing more beyond them!!!

Higher generations of quarks  are heavier and less stable, so they undergo certain type of particle decay into the more stable types, those are the up and down quarks, the most abundant in our Universe. The higher generation quarks can’t be produced except at extreme conditions of heat and pressure and with the help of high energy collision, a state believed to exist just after “The big bang” that created our universe.

Unfortunately quarks can’t exist solely in space. They form composites known as Hadrons, the most stable of which are protons and neutrons (so quarks are the building units of the building units of the nucleus of an atom!). This is because of two very important physical phenomenons known as “color charge” and “strong interaction”. These very strong bonds are mediated by energy carriers known as “gluons” (actually derived the word glue, as to stick!) and therefore quarks can’t be isolated singularly, making their observation not an easy task for physicists through the years. Simulating the cosmic conditions present just after the big bang, at which quarks were supposed to exist singularly in what is known as “the quark-gluon plasma” is one of the major aims of the CERN experiments through the LHC.

So you might ask yourself, if they can’t be observed by themselves and can’t exist singularly under normal conditions, how can they prove their existence in the first place? The answer simply is that proposing their presence justifies a lot of physical phenomenons and fits into certain physical models and gives the right answers to lots of experiments, so science has to admit that they are there!

Quarks have lots of interesting characteristics. For example, they have fraction charges ( like -1/3, and +2/3). Each quark has an antiquark having the same magnitude, mean half life but opposite charges (+1/3, -2/3).Hadrons, consisting of quarks, will always have integer charges (for example, a neutron has a charge of 0 consisting of 1 up quark (+2/3) and 2 down quarks( 2*-1/3) that is a sum of zero). They are the only  elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as fundamental forces (electromagnetism, gravitation, strong interaction, and weak interaction) .

The quarks got their name when Gell-Mann named them after the sound made by ducks!!!! The “strange” quarks were termed so because they had exceptionally long half lives!!.As for the “charm” type, Glashow, who co proposed charm quark with Bjorken, is quoted as saying, “We called our construct the ‘charmed quark’, for we were fascinated and pleased by the symmetry it brought to the subnuclear world.”

References:

http://en.wikipedia.org/wiki/Elementary_particle

http://www2.slac.stanford.edu/vvc/theory/quarks.html

http://public.web.cern.ch/public/en/lhc/ALICE-en.html

http://en.wikipedia.org/wiki/Quark

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