ÿþ<html> <head> <title>Albert van der Sel - A few simple notes on the Higgs field</title> </head> <body> <h1>A few simple notes on the Higgs field and boson.</h1> Version : 0.8 (Ready)<br> Date : 10/03/2012<br> By : Albert van der Sel<br> For who : For anyone who likes a very simple explanation of Higgs.<br> <hr/> <br> <br> <font face="arial" size=2 color="blue"> Contents:<br> <br> 1. Introduction<br> 2. A few highlights in the standard model, and elementary particles<br> 3. Why Higgs? A few notes on symmetry breaking, and the Higgs field<br> <br> <br> <font face="arial" size=2 color="black"> <h3>1. Introduction:</h3> The Higgs field is believed to be an all permeating field in space, responsible for "attaching" mass to elementary<br> particles like the electron and quark.<br> You probably know, that mass is that perculiar property of an object to resist changes in motion. This rather Newtonian<br> interpretation, equates to "inertia": the unwillingness to accelerate.<br> The more "massive" a particle is, the more energy it will cost to set it into motion.<br> <br> As an analogy: It is "as if" the vacuum (the space all around us, everywhere) acts as if it's really <B>an ocean.</B><br> Suppose you are an elementary particle. Then all of the water is the <I>field</I>, and as you travel through the water<br> you will experience the <B>"drag"</B>, that is, you interact with Higgs bosons.<br> The more "drag" exists, the more massive the particle is.<br> <br> Or, in other words: <B>the coupling to the Higgs boson is proportional to the mass.</B><br> <br> Fig 1: a simple analogy of the Higgs field and bosons.<br> <br> <img src="higgs_1.jpg" align="centre"/> <br> <br> In the figure above: the gray space surrounding the particle is the "Higgs field", while the exponents of Higgs,<br> are the Higgs bosons (red dots) interacting with the partice, through which the partice aquires "mass".<br> <br> Often, the existence of the Higgs scalar field is discussed, in studies of the "symmetry breaking(s)"<br> that occurred moments after the Big Bang. At those moments, the state of the Universe<br> is regarded to changed into a "new state", where elementary particles, and various force carriers, emerged.<br> <br> The Higgs field then, came into existence when the spontaneous breaking of <B>electroweak symmetry</B> occurred.<br> <br> When you look at it the "reverse" way, <B>unification</B> of the <B>electromagnetic</B> and <B>weak nuclear force</B><br> into a single <B>electroweak</B> force, is believed to happen, when the energy (or Temperature) is high enough.<br> This is one important research area of high-energy physics, using large particle accelerators.<br> <br> <font face="arial" size=2 color="brown"> Note: Many physicists don't think that "one (type of) Higgs" found, will solve the "problem".<br> Since all forces should probably unite in a "supersymmetric" model, maybe several "Higgs" are needed.<br> More on this later on.<br> <br> <font face="arial" size=2 color="black"> As an interesting side-step, even much closer to home (in smaller Labs), at least one of the paradigms<br> of the Higgs mechanism might already have been observed !<br> Undoubtly, you have heard of "superconducting" materials, usually cooled to very low temperatures.<br> In such experiments, the Magnetic field has been completely removed from the centre regions of this material.<br> This "Meissner" effect has indeed several explanations. One explanation is, that the usual electromagnetic field<br> (with the photon as its force carrier), cannot penetrate the material as usual.<br> To explain it, the theory used, is in effect an "abelian" example for the Higgs mechanism.<br> If the theory passes, it <B>does not</B> mean the Higgs boson is proved, but it means that the theory<br> behind the "Higgs condensate" gets a boost.<br> <br> After this short introduction, let's first mention a couple of highlights of the "standard model" and<br> elementary particles (fermions, bosons). Those subjects will then form section 2.<br> Section 3 will spend a few words on symmetry breaking and why Higgs (or multiple Higgs) is "likely" to exist.<br> Then, to conclude this small note, I will present some highlights from "supersymmetry" and SUZY models.<br> <br> <br> <br> <h3>2. A few highlights in the standard model, and elementary particles:</h3> <br> The standard model is a framework describing all known fundamental particles, together with the forces and their carriers,<br> and how it all originate and evolve since the beginning of the Universe.<br> It tries "to tie together" all facts around those particles and forces.<br> <br> <br> <h4>2.1 A few remarks on elementary particles:</h4> <font face="arial" size=2 color="blue"> <B>2.1.1 Fermions: Ordinary matter (quarks and leptons):</B><br> <font face="arial" size=2 color="black"> <br> What we nowadays consider as "ordinary matter" (like atoms), is made from two basic "types" called<br> <B>quarks</B> and <B>leptons</B>.<br> <br> <ul> <li>The quarks form the constituents of the well known protons and neutrons. So, the latter two, are not elementary particles.</li> <br> <li>The leptons are the familiar electrons and neutrino's.</li> </ul> <br> <font face="arial" size=2 color="blue"> <B>2.1.2 Bosons: Force carriers</B><br> <font face="arial" size=2 color="black"> <br> Physicists have found that there are four fundamental forces at work in the Universe:<br> the strong (nuclear) force, the weak force, the electromagnetic force, and the gravitational force.<br> They quite differently with respect to "range" and "strenght".<br> <br> - Bosons are said to be the particles that transmit interactions (force carriers).<br> One well-know example of a boson, is the "photon" which is the interacting mechanism for the electromagnetic force.<br> <br> Actually, there should be 6 (true) bosons of which 4 (or 5) are confirmed bosons (photon, gluon, Z, W+-),<br> and 2 more (hypothetical) bosons are expected to exist (namely the Graviton, and the Higgs boson).<br> <br> If you want, you may say: W+-? So we have a W+ (with positive electrical charge) and a W- (negative charge)?<br> That is true. But since most articles talk about 4 confirmed bosons (taken W+- together), I will do the same.<br> <br> To summarize the basic matter particles (fermions), and force carriers (bosons), take a look a figure 2 below.<br> <br> <font face="arial" size=2 color="brown"> Notes:<br> <br> (1) We haven't talked about the "anti-" particles yet.<br> (2) Actually, when considering the property "colour" charge too, we have 18 quark variants instead of 6.<br> <br> <font face="arial" size=2 color="black"> <br> Fig.2: Elementary particles (anti-particles, and "colour charge" of quarks left out)<br> <br> <img src="higgs_2.jpg" align="centre"/> <br> <br> There are many dozens of particles found! But they are not "elementary": you can decompose them into the true<br> elementary entities. So, figure 2 illustrates what we think is the collection of true elementary particles.<br> For example, the mesons consists of some quark, and some anti-quark. Again and again, it turns out that<br> quarks and leptons (and anti-quarks and anti-leptons) are the true building blocks of matter.<br> <br> The fundamental quarks "up" and "down", "charm" and "strange" and "top" and "bottom", are indeed shown<br> in figure 2. However, quark theory and chromodynamics, require a "colour charge" (red, green, blue) too<br> which has been left out. This is not really fundamental to our discussion.<br> <br> <br> <br> <font face="arial" size=2 color="blue"> <B>2.1.3 What about the "Anti-particles"?</B><br> <font face="arial" size=2 color="black"> <br> Section 2.1.1 was not completely "complete". Actually, for every matter particle (quarks, leptons) there exists<br> an anti-matter particle. Such an Anti-matter particle is the "opposite" in properties, where for example "electrical charge",<br> and "colour charge", are prominent examples.<br> <br> So, for example, an electron has an anti-particle partner, which is the "positron", with a positive charge,<br> completely opposite to the electron.<br> The same is true for the other leptons: they all have their anti-particle partner.<br> Again, the same is true for quarks: they all have their anti-particle partner.<br> <br> But what about a particle like the "anti-proton"? As we know, this particle exists, but just like the "regular" proton,<br> it's not elementary. It's build from the "anti-quarks", just like the proton is build from quarks.<br> So, yes, we have an "anti-proton", but it's really the anti-quarks the makes the pudding.<br> <br> <font face="arial" size=2 color="brown"> Note: although fermions and bosons are fundamental particles, many articles will once in a while refer to "hadrons",<br> "baryons", and "mesons". Don't worry: these are all composite particles. <br> <br> Hadrons is a generic term to denote matter that's build from quarks, so hadrons are composite particles,<br> and it is a general term. The following hadrons are real composite particles:<br> <br> &#8658; Baryons, for example, are our well-know protons and neutrons, which are "three quark combinations".<br> &#8658; Mesons (like the pion) are intermediate mass particles which are made up of a quark-antiquark pair.<br> <font face="arial" size=2 color="black"> <br> Fig.3: a proton and antiproton<br> <br> <img src="higgs_3.jpg" align="centre"/> <br> <br> When a particle and an anti-particle "meet", they destroy each other, giving pure energy and<br> energetic force-carrier particles (bosons), such as gluons, photons or Z-bosons.<br> So, if for example a electron and positron annihilate, a powerfull gamma-ray will result.<br> This phenomena is remarkable: a particle and antiparticle give rise to bosons, while in other cases, a boson like a photon<br> can (in some circumstances) result in an electron and positron pair (pair-forming).<br> <br> In high-energy physics, using for example particle accelerators which let particles collide, anti-matter may be produced.<br> Ofcourse, these sorts of events occur everywhere in the universe (stars, supernova, near black-holes etc..); it's just natural.<br> However, it's still somewhat of an unsolved mystery why the universe is dominated by matter, and why the abundance of<br> anti-matter is so low.<br> There is an asymmetry between matter and anti-matter. Why, ultimately, is the world made of matter and not antimatter?<br> It might be due to "electroweak baryogenesis", which fits the standard model quite well. More about this later.<br> <br> <br> <font face="arial" size=2 color="blue"> <B>2.1.4 Fermions: half integer spin, Bosons: integer spin:</B><br> <font face="arial" size=2 color="black"> <br> There is another difference between fermions and bosons. It's their possible "spin" values,<br> and the consequences thereoff. The notion of "spin" will be explained in a minute.<br> <br> A fermion is (defined as) any particle that has an odd half-integer spin (like 1/2, 3/2, and so forth)<br> So, our Quarks and leptons have an half-integer spin. We already know these are Fermions.<br> Quarks and leptons are the fundamental (elementary) particles, which we cannot (as the standard model says up to now),<br> decompose in even more fundamental particles.<br> <br> However, even non-elementary particles may have an half-integer spin, so they are fermions as well, like<br> for example the proton. But remember, these are not elementary particles (the quarks and leptons <I>are</I>).<br> <br> Likewise, a lot of other composite particles may have an integer spin (like 0,1), and then they classify<br> as being a "boson". As an extreme example: in a metallic lattice, two electrons (leptons) may "pair" up,<br> in a certain extraordinary case, by which they collectively have spin 0, and that pair then acts as a boson.<br> As another example: a composite particle, like a 4He atom, always has spin 0, so it's a boson.<br> <br> But remember, we have 6 "true" bosons (as listed in fig.2) which are the force carriers.<br> <br> Now, the following is very remarkable (and fundamental):<br> <br> <ul> <li> Fermions obey the Pauli Exclusion Principle and therefore cannot co-exist in the same state<br> at same location at the same time. Only one fermion can occupy a particular quantum state at any given time.</li> <li> Bosons can occupy the same quantum state. They can occupy the same place in space, with the same<br> quantum properties. The wave functions are symmetric under particle interchange, and they are allowed<br> to be in the same state.</li> </ul> In some extreme cases, (composite atomic))bosons can condensate, as if it's one super-sized atom.<br> <br> <font face="arial" size=2 color="brown"> <B>Note: What is spin?</B><br> <br> That's not a simple question. If we can imaging a fundamental particle as "spinning", we can visualize<br> that a certain "angular momentum" is associated with that paticle. But this propery is "quantized", or, in other words<br> it can only take certain discrete values. Now, in the framework of Quantum Mechanics, "discrete values"<br> of other observables are not uncommon. Many observables, like quantum spin, has no classical counterpart.<br> Sometimes, it just makes it quite hard to understand such an observable.<br> We will not spend too much words on "spin", but there exists some deeper relation of "spin" with spacetime,<br> because it relates to how "algebra of rotations" acts on this property.<br> It's still not understood completely. It has "to do" with the metrics of spacetime, since Galilean or<br> relativistic transformations/algebra are today common means to deal/describe this property.<br> <font face="arial" size=2 color="black"> <br> <br> <h3>2.2 A few remarks on fundamental forces:</h3> Say, up to 1850, physicist believed that forces worked <I>instantaneous</I>, so, for example, an electrically charged<br> object, influenced another electrically charged object directly, without delay.<br> Ofcourse, in later periods this assumption was disproved at countless experiments.<br> <br> It was not for long that the notion of a "field" entered the arena. This field, is some sort of "a change" in the space<br> around the object. Especially, the work of Maxwell (electrodynamics) contributed to that view.<br> <br> The concept of a "field" remained important, and is good way to explain how objects interact and how forces works.<br> Still, it is realized that it cannot be a complete picture. Like so many things in physics, often a dualistic view<br> is needed. One famous example ofcourse is the "wave-partice duality" which is demonstrated in Quantum Mechanics.<br> <br> Equivalent to a "modern view of the field", is describing the interactions between the matter particles, using "gauge"<br> bosons, which are the "force carriers".<br> <br> So, forces are transmitted by "force carriers" which are our gauge bosons. For example, the photon<br> transmits electromagnetism, while W and Z bosons transmit weak interactions.<br> <br> The two views, that is "field", and "force carrier (boson)", are both unavoidable.<br> As a simple example: high energetic radiation behaves as a field in many experiments. In other occasions,<br> like the Compton effect, the field gets synonym to a boson (the photon), a particle even capable in transferring momentum<br> to an electron. Actually, the best description of a photon then is: it's the boson that emerges when a field interacts<br> with a matter particle (like the electron).<br> <br> High Energy physics experiments, have revealed some of the other bosons too, like the W and Z bosons.<br> This was an incredable succes for the Standard model, which predicted those bosons. The prediction followed from a rather<br> succesfull attempt to <B>unify</B> the "electromagnetic interaction", with the "weak interaction" into<br> the "electro-weak" (unified) force.<br> This unification happens at sufficienly high energies (temperatures) which can be realized in highenergy particle accelerators.<br> <br> Both the electromagnetic and gravitational force, are long-ranged (likely to be "infinite"). The gravity between<br> elementary particles is extremely low, but the electromagnetic force is very relevant.<br> The strong interaction, acts between quarks, using gluons as the force carrier. It's very short ranged (about 10<sup>-15</sup>m)<br> I think, whatever your background is, you probably have a reasonable idea about those three fundamental forces, especially<br> gravitation and the electromagnetic force.<br> <br> Since the "weak interaction" might be not so familiar, and since it will play a role in chapter 3, we will<br> spend a few words on this specific force.<br> The weak interaction is very short-ranged too. It plays a very important role in the decay of particles, like<br> for example in the decay of a neutron (the socalled &#914; decay)<br> Also, it's several orders of magnitude less "in power" compared to both electromagnetism and the strong interaction.<br> <br> As we will see in chapter 3, the W<sup>+ -</sup> bosons, and the Z boson, are involved, which all three <br> are very "massive". Later on, we will see how this "high mass" is coupled to the "short range" of this force.<br> Here is where Higgs will come in, as we will see later on.<br> <br> <font face="arial" size=2 color="brown"> Note:<br> <br> Even without any unification considerations, you might suspect there is some relation between the weak interaction,<br> and the electrodynamic interaction. The <B>force carriers</B> of the weak interaction, W+-, are electrically charged<br> and experience an effect in an Electromagnetic field.<br> <font face="arial" size=2 color="black"> <br> As said before, the Standard Model says that the <B>electromagnetic interaction</B> and the <B>weak interaction</B>,<br> are two different aspects of a single <B>electro-weak interaction</B>. The unification will occur at very high Energy.<br> In the process of symmetry breaking, where the single <B>electro-weak interaction</B> "breaks" into<br> <B>electromagnetic interaction</B> and the <B>weak interaction</B>, the Higgs field plays an important role.<br> Some people regard the finding of Higgs, to be a test for the validity of the Standard Model.<br> <br> But even if the Higgs field is found, is can only be part of the solution. Remember, we have four fundamental forces today,<br> and at "ultra-super-high" energies, it's suspected that today's manifestations of forces,<br> all merge into one force: also called "Grand Unification".<br> <br> <br> The figure below illustrates the known force carriers, together with the elementary- and composite particles.<br> <br> <br> Fig.4: Force Cariers and known forces, and know elementary particles.<br> <br> <img src="higgs_4.jpg" align="centre"/> <br> <br> This chapter was a bit factual in nature. It more or less gave a simple overview of known particles and forces.<br> It did indeed explained a couple of things, but many questions still remain, like:<br> <br> <ul> <li>Why and how should unification of forces occur?</li> <li>Where does "symmetry breaking" comes in?<br> <li>Why seems there to exist an asymmetry between particles and anti-particles?</li> <li>And, how exactly does the Higgs field comes in?</li> </ul> Anyway, without the facts as presented in this chapter, it was probably more difficult to proceed to the next one,<br> where we shift focus to symmetry breaking models and Higgs.<br> <br> Up to now, the Standard Model sounds "pretty good". It should be something as a theory that fits all<br> particles and forces, and how they originated. <B>But no</B>: there are still many difficulties. For example, to reconcile<br> Einsteins General Relativity with Quantum Mechanics, has turned out to be a true "brain crusher".<br> And there exists even many more "difficulties". So, it's not a theory that "fits all" right now.<br> A handfull of physicist don't even like the concept of a "Standard Model", due to several reasons.<br> <br> It's probably fair to say that most active physicist, view the Standard Model as a "working" principle,<br> a sort of set of "insights", which gets refined at every major discovery, and, up to now, was remarkably succesfull.<br> <br> But the Standard Model already has a sort of "follow-up", namely models which takes "super-symmetry" into account,<br> like the "(Minimal) Supersymmetric Standard Model".<br> <br> <br> <br> <h3>3. Why Higgs?: A few notes on symmetry breaking, and the Higgs field</h3> <br> <h4>3.1 A Pictorial Description:</h4> <br> Ever noticed that you can throw a little rock with high speed, and much further away then, say, a heavy brick?<br> Ofcourse you do! The mass of the brick limits how far you can throw it. And a <I>very heavy brick</I>,<br> might even fall just inches before your toes (if you're lucky).<br> <br> In nature, it might work quite "similar", although the analogy must not be pushed too far.<br> <br> The force carrier of the Electromagnetic field, the photon, has no rest-mass: It zips around with "c",<br> while it's range is unlimited.<br> <br> On the other hand, the carriers of the short-ranged "weak interaction", the W+, W- & Z bosons, are very heavy! <br> These bosons have been found at experiments in CERN, and have masses in the order of 80 GeV/c<sup>2</sup>,<br> which indeed is very heavy. A key point now is, that we note that the "range" at which the weak interaction operates,<br> (in other words:the bosons), is extremely short.<br> <br> Why, with the (rest) mass-less photon a long range, why with the W and Z bosons a short range?<br> Is the analogy with the light- and heavy stones applicable here too?<br> <br> The force carriers may be regarded as virtual particles. Anyway, it's very reasonable to assume that the<br> <B>Heisenberg uncertainty relations</B> are in effect here as well. Here, the relation &#916;E . &#916;t > h/2<br> is important. If a "heavy" particle emerge (from the vacuum), thus with high energy, the corresponding "time span"<br> must be short. This short time, relates to the "short range" of this carrier.<br> <br> Note that we are not "mis-using" Heisenberg, because the boson appears, borrowing energy from the vacuum so to speak,<br> possible only for a "certain duration", which justifies the appliance of the relations.<br> <br> Indeed, at some point in history, the theoreticians came to the idea the the mass of the "heavy" bosons is just a property<br> of the vacuum, how weird that may sound when you first hear of it.<br> Using this idea, it's quite "natural" to assume there is an "all-existing" field, responsible for associating mass<br> to particles. Since it's a field, a boson (as an exponent) needs to exists as well: that's the Higgs boson.<br> <br> The key point this "pictorial" description tries to tell, is that we know that the W+, W- & Z are very heavy.<br> And we also know that the associated "range" is very short ! So the vacuum is "dragging" those bosons dramatically.<br> This drag is what we know as mass. So that's why they are so heavy and short-ranged!<br> <br> <br> <h4>3.2 A few words on symmetry and invariance:</h4> True scientific papers are very hard to read. And even some popular articles can be quite an endavour too.<br> <br> The subject is very wide, and you can view it from different angles.<br> A potential problem are the different technical descriptions, which are indeed related,<br> but have different meanings, like "gauge invariance", "symmetry" and "supersymmetry".<br> <br> It's probably best to leave in-depth discussions of "symmetry" and the like, to philosophers and theoretical physicists,<br> but it's in order to spend a few words on some of those terms.<br> <br> <font face="arial" size=2 color="Purple"> <B>&#8658; Symmetry:</B><br> <font face="arial" size=2 color="Black"> <br> I hope that in all of the above in this note, you may have understood that one of the deepest principles<br> of nature seems to be that <B>the breaking of an inherent symmetry</B> accounts for the matter and forces<br> we see today.<br> So, it is suspected that early in the history of the Universe, a "supersymmetry" was in effect. For this reason,<br> most physicists in the frontlines of science, don't think that "one Higgs" found, will solve the problem.<br> <br> Indeed, in the context of the "famous" Higgs field/Boson, the discussion is limited to the process of <br> symmetry breaking where the single <B>electro-weak interaction</B> "breaks" into <B>electromagnetic interaction</B><br> and the <B>weak interaction</B>.<br> Thus, a more fundamental step would be to unite all forces into one description at superhigh energies, as was<br> probably present in the earliest phase in the Universe.<br> But, the smaller step is element of the large step (supersymmetry), so finding, or not finding, (a type of) Higgs<br> is very relevant for the foundations of physics (and other disciplines as well like Cosmology, Philosopy etc..).<br> <br> <font face="arial" size=2 color="Purple"> <B>&#8658; Invariance:</B><br> <font face="arial" size=2 color="Black"> <br> In physics "gauge invariance", actually is a form of symmetry.<br> Suppose you discovered (what you first think) is a fundamental physical "formula". But, some time later, you found out<br> that it only applies in your local neighbourhood, then surely it's not "fundamental"!.<br> <br> One essential verification of a universal law, is that it should be invariant from your frame of reference.<br> So, if you for example rotate coordinates, the laws should not change fundamentally. <br> Also, inherently, if a law stays invariant even if transformations are applied, it's actually a good test for that law.<br> <br> Not all things in physics are perfectly invariant, but when it comes to fundamental particles and forces,<br> something called "unitary symmetry" (charge, isospin, color) should be in effect.<br> I mean, something like electrical charge of an electron should be the same everywhere.<br> <br> The same should be true for fundamental theories. They should be the same in every frame of reference, everywhere.<br> Whether you replace coordinates, rotate, or inverse a physical system against some origin, the fundamental interactions<br> should not change.<br> <br> A long time ago, when the fundamental laws of Electrodynamics were studied under transformations, the essence did not<br> changed at all, and to express that fact, the term "gauge invariance" was used for the first time.<br> Nowadays, generally, whenever fields and force carriers are studied, the invariance is expressed by "gauge invariance".<br> <br> <font face="arial" size=2 color="Purple"> <B>&#8658; Asymmetries:</B><br> <font face="arial" size=2 color="Black"> <br> This is an important subsection.<br> As of the fifties from the former century, several asymmetries have been found, both due to theoretical work,<br> and experimental observations<br> <br> One remarkably asymmetry is, is that the "weak force" seems to have a sort of "preference",<br> as if the "dices" it uses, are biased. Another strange asymmetry is the abundance of matter over anti-matter.<br> <br> We already have spoken of theories which are invariant under transformations.<br> <br> One certain transformation is "mirorring" which creates the mirror image of a physical system,<br> comparable to what an ordinary mirror does.<br> It's referred to as "<B>Parity (P) symmetry</B>". You may also see this Parity (or space inversion) as the reflection in the origin<br> of the space coordinates of a particle or particle system. This inversion should not change the interactions between the<br> particles in a fundamental way.<br> With all physical events observed until the fifties of the former century, the symmetry really worked !<br> For example, electrodynamical events, or gravity, obey P symmetry.<br> <br> A second rather special operation is "<B>Charge conjugation</B>". Here, in a physical system, we would replace every particle<br> by it's anti-particle, and the net result should be, that the fundamental interactions do not change at all.<br> <br> For years it was assumed that charge conjugation and parity were symmetries in effect in elementary processes,<br> determined by the electromagnetic, strong, and weak interaction.<br> For example, if you mirror a nuclear process, the same effects are observed.<br> <br> Now, if an event violates Parity, or Charge conjugation, it's referred to as "P violation" and "C violation".<br> If <I>both</I> happens at the same event, we evendently will speak of "CP Violation".<br> <br> It's still not fully explained, but the "weak interaction" which as we know is involved in decay processes,<br> exhibits "CP Violation", which has been confirmed experimentally by observing meson decays.<br> This is more strange than you might think at first sight. It effectively means that the mirror of the event<br> shows a different decay (different numbers of different decay components) than the unmirrored version of the event.<br> It's still puzzling up to this day, for example, why don't we see CP violations at the strong interaction?<br> Anyway, different lines of thoughts emerged, like for example postulating a fifth fundamental force,<br> namely the "superweak" interaction.<br> <br> <font face="arial" size=2 color="Purple"> <B>&#8658; Sponteneous symmetry breaking:</B><br> <font face="arial" size=2 color="Black"> <br> When for example, the force carrier of the "Electromagnetic interaction" (the photon) interacts with an electron,<br> the electron (as a particle) stays the same.<br> <br> Also, with the "strong interaction", where the force carrier is the gluon, interactions between quarks will be in such<br> a way, that the underlying symmetry stays the same.<br> <br> <I>Now for the weak interaction:</I> It really <B>change</B> the particle (fermion) involved in emitting or absorbing a W- boson.<br> Suppose we take a look at the decay of a neutron. Here, the Neutron{up,down.down} transforms to a Proton{up,up,down}<br> by emitting a W- boson. Ofcourse, the W- "lasts" only for an extremely short time and it's corresponding range will be<br> extremely short too.<br> <br> Why isn't the same sort of symmetry present with the Weak interaction?<br> <br> Also, the photon has no mass (restmass). It's very likely that the gluon has no mass too.<br> But with the weak interaction, the W+- and Z bosons, are very heavy.<br> <br> Why is that asymmetry present if we compare the masses of the force carriers between the strong- en elctromagnetic<br> interactions on one side, and the weak interaction on the other side?<br> <br> The weak interaction has shown to have a "preference" (see the section above) which is shown by CP violation.<br> Why so?<br> <br> As a modern explanation: is is believed to be possible for a physical theory to have a symmetry that isn t reflected<br> in the <B>current state</B> of the system which this theory describes.<br> If this is the case, physicists often say the the <B>symmetry is spontaneously broken</B>. <br> As we already often have seen in this note: the symmetry is believed to be restored at high energies, where the<br> electromagnetic- and weak interactions, unify in the "electro-weak" interaction.<br> <br> <font face="arial" size=2 color="Brown"> <br> For our discussion, all what's mention above will do for our small note dealing on the Higgs field.<br> <br> Only one thing more, might be of interest! Remember I said it's actually strange that matter dominates<br> above anti-matter? Although far from proven, a certain "bias" (a sort of CP violation) in the early phase of the Universe,<br> could have been responsible for matter to be produced a little more often than antimatter.<br> So, when matter and anti-matter "cancelled out" at a later moment, a net result of matter still remained.<br> Development of these sort of theories, are currently still in progress. Actually, it's quite "hot" stuff.<br> <font face="arial" size=2 color="Black"> <br> <br> <I>Hope you have found this short, and very simple note, to be "informative"!</I> <br> <br> <br> <br> <br> </body> </html>