Eightfold Way (in Particle physics) | Why Quarks?

in the ancient philosophy of buddhism there is what is called the noble eight-fold pathway which simply consists of eight practices that can lead to enlightenment or freedom from samsara they consist of the right view the right speech wait this was supposed to be a video on particle physics right okay i got confused again i'll talk about this in some other video let's do the video of particle physics [Applause] [Music] okay so the eight-fold way in particle physics as opposed to the eightfold path in buddhism is a classification of subatomic particles now if you have followed my earlier videos on particle physics then in one of my earlier videos i have talked about the class of particles called hadrons so hadrons are a class of particles that experience the strong force and as it turns out there are a large number of hadron particles out there you have the usual neutron proton you have the pyme zones these sigma particles design particles omega particles scan particles and on and on and on one very simple question that you may ask is that are these particles fundamental are these particles elementary that is are they made up of more elementary particles or are they elementary on their own and to answer that question we need to uh look at this eight-fold way in particle physics so one of the earliest ideas of combining these kind of particles into fundamental entities consisted of organizing particles into multiplets so for example if you look at the neutron and the proton they seem to have similar mass but different charge neutron is neutral proton is positively charged so it was thought that maybe maybe they are the result of a fundamental entity but having different charge states you can see other groups also for example if you look at the sigma group if you look at the sigma particles sigma plus sigma zero and sigma minus the superscript simply represents the charge the plus zero and minus represents plus one electronic charge zero electronic charge and minus one electronic charge respectively they also have similar masses and it was thought that even maybe they are the result of a fundamental entity having different charge states as well as these uh zy particles so these are groups of particles which were organized as multiplets the idea is that maybe these particles are the result of some fundamental entity having different charge states now in the eight-fold way all of these groups of particles were combined in one chart that looks something like this which is a what you can call a super multiplet all right now before i talk about this chart in detail let me first mention that the idea of eight-fold whey is uh kind of similar to the idea of the periodic table now what is the periodic table when scientists were studying the chemical elements the huge diversity of atoms out there then they try to organize all the atoms in a particular manner in this particular table with certain rules and organizing all the chemical elements in this kind of a chart basically helped us create a certain kind of order in the chaos and the diversity of chemical elements it helped us in studying the similarities and dissimilarities between different atoms and also alluded to the fact that all of them are in fact made up of the very same particles but in different combinations electrons neutrons and protons so the idea of eight-fold whey is similar to that of the periodic table but for subatomic particles so the eightfold way is in a sense an organizational scheme or classification of the hadron particles in groups or charts or geometric patterns based on same spin but different charge and different strangeness it was independently proposed by two scientists murray gelman and yuwal neeman they propose this idea of eight fold way of organizing all these hadron particles into certain charts or grids or geometric patterns one of them is this the baryon octate so you see here this chart basically consists of eight particles you see eight the name eight fold so the idea of the naming of the eight-fold way the eight comes from these eight particles as it turns out that many of these charts or grouping of particles consists of eight particles not all the time and also murray gelman was inspired by the eight-fold pathway in buddhism okay so there is a relation there somewhere so he was inspired by the idea of eightfold pathway in buddhism and he used that word of eight-fold way in describing the organization of these particles so let us understand what they actually mean here we have the lightest baryon particles now what are baryons when i talked about hadron particles i said that hadrons can be divided into further two categories one is the baryon particle and other are the nison particles baryons are fermion particles they follow their poly's exclusion principle but mesons are boson particles that do not follow the poly's exclusion principle so the lightest baryons can be organized in this kind of a manner where you have these eight particles the neutron the proton the sigma plus sigma zero lambda sigma minus and the z and the psi zero now these are all spin half particles all of these have a spin half okay now they are not organized in some kind of a random fashion there is a logic to this kind of an organization you can understand this logic by imagining that this geometric pattern is being created by these lines you have these horizontal lines okay and you have these diagonal lines okay so there is a particular you can imagine a grid which ends up creating this kind of a hexagonal pattern so the top horizontal line represents strangeness quantum number of zero the middle horizontal line represents the strangest quantum number of minus 1 and the bottom horizontal line represents strangest number of minus 2. now what is the strangeness quantum number again in one of my previous videos uh i talked about strangeness quantum number you see uh in the last 50 to 100 years when scientists were experimentally discovering newer and newer hadron particles there is a time at which they found lots of particles which were being created in high energetic particle reactions which seem to behave in a strange manner and by strange manner i mean that particles were being created by either the strong interaction or the electromagnetic interaction but they were decaying via the weak interaction so scientists at that point in time thought they are behaving in a strange manner so just because they were behaving in a strange manner they name those particular strange particles these are behaving as strange particles so let's name them as strange particles do you understand the logic of the name well that's how particle physicists name particles and so they uh therefore came up with a quantum number called the strangeness quantum number based on how these particles are created and how they decay which i've talked about in detail in one of my earlier videos and this is what the s represents here it represents the strangeness quantum number of 0 minus 1 and minus 2. also the diagonal lines here represent the charge you have qe is equal to plus one electronic charge zero electronic charge and minus electronic charge okay and as you can see when these three lines of charges plus one zero and minus 1 intersect with strangeness of 0 minus 1 and minus 2 at each point you end up getting a hadron particle so you have the neutron and the proton which have zero strangeness but they have charges of zero and plus one all right you have the sigma plus which has strangeness of minus one but the charge of plus one similarly you have the zei particles which has a unions of minus two so all these hadron particles the eight particles which are baryons of spin half can be organized in this kind of a hexagonal geometric pattern so essentially they all have same spin of half but they are different in terms of their charge in terms of their strangeness this is therefore known as the baryon octate now this is not the only organization of particles there are other organizations so for example you have the meson octate which is another hexagonal organization of nison particles so as i said nisons are hedrons which are basically bosons they do not follow the police exclusion principle so you have eight nissan particles here which are organized in a similar fashion but in this case the horizontal lines represent strangeness of plus one zero and minus 1 while the diagonal lines represent again the same and you end up getting these eight particles which are a combination of pi mesons eta particles k on particles and on and on these are meson particles that can be placed and at the intersection of these individual lines now because they are boson particles they have spin of integer they all have spin zero so all these eight particles have zero spin but differ in terms of their strangeness and electronic charge now initially this kind of a classification consisted of eight meson particles but later on another particle the eta prime particle was added to it and now most of the time this kind of a chart is referred to as a mesonate because it consists of nine particles now there are other organizations of other particles for example you have the baryon decouplet which is not a hexagonal pattern but rather a triangular pattern now but instead of eight particles it consists of ten particles so you have the strangeness number represented by the horizontal lines so you have s is equal to zero minus one minus two and minus three and the diagonal lines represent the charge you have minus one zero plus 1 and plus 2. so this is a triangle a sort of a pattern consisting of 10 particles now originally when murray gilman was organizing these particles in these charts or geometrical patterns only nine out of these ten intersection points were experimentally discovered nine of these particles were known at that point in time so what he suggested was that he said that there must be a tenth particle you see the particle at the very bottom that has a strangeness number of minus three and charge of minus one that was a particle which is not discovered at that point in time so murray gilman he proposed that there must be a tenth particle having strangeness of -3 and charge of -1 and he said that this kind of a particle can be discovered and he suggested the experimental physicists at that time how this kind of a particle can be created and in fact in 1964 this very famous omega minus particle was experimentally discovered thereby giving a certain kind of credibility to this kind of an organization of these hetero particles now why are we talking about organizing headroom particles in these weird geometrical shapes ah this is because the eight-fold way actually was responsible in initiating uh you can say a modern era in particle physics because it led to the idea of the core model it predicted the existence of quarks now you see i talked initially about the whether or not these particles are fundamental or are they made up of more fundamental particles this this is a very important question right now if you look at these charts if you look at the hexagonal form of the eight baryon particles if you look at the hexagonal shape of the nine meson particles if you look at the triangular shape of these ten baron particles of spin 3x2 then you might feel as if that they all have separate spins all of them belong to the same spin and they are differentiated by charge and strangeness so maybe maybe they might be the result of something more fundamental okay here i'm going to talk about let's suppose a periodic table so if you look at the periodic table all the atoms having different chemical properties okay you have gases you have solids you have liquids you have metals you have semiconductors you have insulators all these vast majority or vast diversity of chemical properties are fundamentally the result of water they are the result of a few particles combining in different numbers you have the electron you have the proton you have the neutron these are the particles that combine in different numbers to create these chemical elements and this diversity of properties right so in the same way that the entire period table is in a sense created by these three fundamental particles organized in different combinations to create this diversity we can think of it in the same way in the eight-fold way of classification that maybe these classification of particles there are other further more classifications of other particles also will not discuss too much into it maybe they are the result of something more fundamental or maybe there is one fundamental entity or maybe there is more than one fundamental entity which when they combine or recombine in different proportions ends up creating this vast diversity of properties and vast diversity of particles so in a sense this uh uh eight-fold way led to the proposition of what is known as the quark model so murray gelman and zweig they proposed what is called the quark model what does it mean so what they propose is that all these particles they said are essentially made up of three fundamental particles which they called quarks so you see here this is the what you can say triangular eight-fold way organization of quarks okay so murray gilman said that there are three quarks you have the down quark the up quark and the strange quark that can be organized in this kind kind of a manner so the horizontal line above represents strangeness of zero the horizontal line below represents strangeness of minus one the diagonal line represents charges of minus one by three electronic charge and plus two by three electronic charge so he said that these are the fundamental entities called quarks the downward the up quark and the strange quark which when they combine in different manner ends up creating those hadron particles that we just now talked about now one peculiar thing about these quarks these supposed fundamental particles is the idea of fractional charges you see here the up quark has a fractional charge of plus two by three electronic charge while the down quark and the strange quark has a fractional charge of minus one by three electronic charge now at that point in time people had not yet discovered free particles that have fractional charges even today we have not yet found free particles having fractional charges so the idea of the quarks was uh met with a certain resistance because people didn't want to accept this idea of fractional charges however gelman suggested that maybe these particles they are always in a bound state inside these hadrons they are never free from these hadron particles they are always bound inside these hetron particles and also high energetic scattering experiments of protons suggested that maybe the proton is made up of three point mass objects and over time this kind of an idea got acceptance that quarks became a very much sensible idea of explaining this kind of an organization and by looking at these quirks their strangeness and their charges we can easily uh look at these previous charts or previous hexagonal diagrams and see how they are made up of a combination of these particles so the quark model suggests what it suggests two things first of all all baryon particles are made up of three quarks similarly all antibarion particles are made up of three antiquarks and second all meson particles are made up of a core anti quark pair based on this idea we can reorganize let's suppose the baryon octane so you see the barium oxide which consisted of eight hadron particles can all be thought of as consisting of three individual quarks inside them all reorganized in different manner so for example the neutron consists of two down quark one up quark the proton consists of two up quark one down quark similarly meson on it can also be thought of as being uh consisting of nine particles which are individually made up of a quark anti-quark pair and similarly we can also show that the baryon decouplet is also made up of 10 particles each made up of three quarks each now the interesting idea of this kind of a quark model is that we can explain the properties of these individual hadron particles based on the properties of the quarks that make them up so for example if you look at the neutron particle so the neutron consists of one up and two down quarks so the up quark has a charge of plus two by three and the down box has a charge of s one by three so if you add up the charges of the neutron particle plus two by three minus one by three minus one by three turns out to be zero so the neutron is electrically neutral similarly the quarks have spin half you can organize the spin half of these three quarks in such a manner that the neutron turns out to also have spin half also the up and the downwards have strangeness of zero so the neutron also has a strangeness of zero it is not a strange particle similarly you can also take a look at the proton particle which consists of two up and one down quark so basically its charge must be plus two by three plus two by three minus one by three which is plus one so the proton is plus one electronic charge it is also spin half particles because three quarks are coming together in this kind of a fashion and its region is also comes out to be zero if you look at the meson particles let's suppose a prime is on a pi plus which is made up of uh up and the anti downward then it seems to have a charge of plus two by three plus one by three which is equal to what one so a pi plus has a charge of plus one while it has a spin of zero and a strangeness of zero while the omega minus particle has three strange quarks inside them so it has a charge of minus one by three minus one by two minus one omega which is equal to minus one while a strangeness of minus three so in this kind of a fashion the quark model can be used to explain the individual properties of all the hydraulic particles out there so in a way the eight-fold way in particle physics led to the development of quark model which basically predicted the existence of these fundamental entities called quarks that make up all the hadron particles so you see how important this kind of a characterization or this kind of a classification was so this in a way opened up a completely new era in modern physics because we for the first time got an idea about what some of these fundamental entities that make up matter themselves are so these are none other than the quarks themselves which make up all the hedon particles now you remember i talked about three different kinds of quarks the up down and the strange work as it turns out there are more quarks out there and the quarks have some very interesting peculiar properties but i'm going to talk about quarks in detail maybe in some other video this is all for today as far as the discussion of the eight fold way is concerned in my next video i will talk about quirks that is all for today thank you very much [Music] [Applause] [Music] you

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Keywords: eightfold way, eightfold way in particle physics, eightfold way physics, eightfold way particle physics, meson nonet, meson octet based on quark model, baryon octet diagram, baryon octet, meson octet diagram, meson octet, baryon decuplet, baryon octet and decuplet, Eight fold, quark model in particle physics, particle physics, quark model, for the love of physics, physics, education, lectures, particle physics lecture, elementary particles, Elementary particle physics

Id: 9hsabeoi4U8

Length: 21min 21sec (1281 seconds)

Published: Tue May 19 2020