The Known (Apparently-) Elementary Particles | Of Particular Significance

Of Particular SignificanceConversations About Science with Theoretical Physicist Matt Strassler

The Known (Apparently-) Elementary Particles

ast 115 years, physicists have discovered that pretty much everything material, including rocks

un and sunshine, ocean waves and radio waves, can be described in terms of particles (and

.) Experiments have uncovered a large handful of types of particles that appear

, not made from yet more elementary things.) The full complexity of our

is constructed from just a few of these. The rest of the particles are evanescent, decaying

that we don’t encounter them in normal circumstances. But they may hold the keys to

he universe that continue to elude us at the moment.

cle you will find a brief overview of our present state of knowledge, as of August 2011, showing

rticles we know about and how they can be organized usefully into a few classes… a sort of

ble of the particles, with a few twists. Along the way you’ll learn what the Higgs field does to

, and the crucial role it plays in our universe.

t knowledge, along with our simplest conjecture for the workings of the Higgs particle and

mmarized in a set of equations called “The Standard Model of Particle Physics”, or just

Model” for short. The elementary particles of the Standard Model have somewhat wacky

historical reasons) and a very wide range of masses. In Figure 1 below, notice that

rawn heavier particles at the top, the lighter particles at the bottom. (I do this because

is as low as a particle can go, but particles can have an arbitrarily high mass; in

t, there’s a hard floor below, but above, the sky’s the limit.)

ad of masses I’ve given the equivalent mass-energies (E = m c-squared) which is what particle

(Keeping track of energy, which is never lost or gained, is easier than

ing track of mass, which can change in some processes, such as decays.) The unit of a GeV is

t the mass-energy of the lightest atom, hydrogen.

ndicated three classes of particles — charged leptons (blue disks), the neutrinos (black disks),

(red disks). (The quarks are typically sub-divided into two classes, up-type and

, which differ only in their electric charge.) The importance of this classification will

e indicated three forces in boxes, along with their force carrier particles (see below).

sicists call the forces “interactions”, and the force carriers “mediators”; I am using more

I have not indicated a fourth force, that of gravity, to avoid clutter on the

(or something playing its role) is known to be on average non-zero in nature. I’ve

sented this with a great green sea. (You can learn more about fields and particles, and the

video clips from my public talk at the Secret Science Club.)

The Known (Apparently-) Elementary Particles | Of Particular Si... http://profmattstrassler.com/articles-and-posts/particle-physics-ba...

1 of 24 10/21/15 10:31 AM

Fig, 1:The names and masses of the known elementary particles, along withthe Higgs particle. The universe's non-zero Higgs field is evoked by the green

sea. Particle masses (actually their mass-energies E = m c-squared) areshown, in units of a GeV, which is a few percent bigger than the mass-energy

of the lightest atom (hydrogen). Neutrino masses haven't yet been naileddown. To avoid clutter, the gravitational force (and its carrier the presumed

graviton) is not shown.

[All of these particles have anti-particles, but to keep things short I won’t

em, except to point you to this page on anti-particles if you are interested.] Let me quickly

structure of matter, pulling it apart until we get down to the right levels.

s, about a billion times smaller in radius than your head, are made from electrons and

s can absorb and emit particles of light, called photons. This occurs through

lectromagnetic force, for which the photon is the carrier (which means that photons are

ys in action when the electromagnetic force is operating).

ic nuclei are made from protons and neutrons, 100,000 times smaller in radius than an atom,

up and down quarks (and anti-quarks) and gluons.

rotons and neutrons are kept intact, and also kept within an atomic nucleus, by the strong

, carried by the 8 types of gluons.

un shines, and some atomic nuclei decay, because of processes that convert quarks of one

to quarks of another type, while emitting electrons and neutrinos, particles that stream

ght out of the center of the sun.

e quark-conversion and neutrino-emitting processes are caused by the weak nuclear force,

, W and Z particles.

ast force we know about is gravity, carried presumably by the graviton. Because of

ity’s astonishing weakness, this is not an easy particle to discover.

ry aspect of our daily world is determined by these particles. But there are a few more. The

– 0


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he neutrino-1, the up quark and the down quark are called a single “generation” of particles —

being used here loosely in the sense in which it applies to a family tree [though the particles

ry any familial relationship that the word might imply.] There are two heavier generations,

ing a heavier copy of these four types of particles.

econd generation consists of the muon, the neutrino-2, the charm quark and the

hird generation consists of the tau, the neutrino-3, the top quark and the bottom

tional structure divides these particles into horizontal strata. One can also divide them

nto those classes I mentioned: people often speak of “the electron-type particles” or the

eptons” to refer to the electron, muon and tau, speak of “the neutrinos” in general, and divide

into the “up-type quarks” (up, charm, top) and the “down-type quarks” (down, strange,

onder why the neutrinos have boring names compared to the rest of the particles. We used

something else, but we learned a lot of new things about neutrinos in the past 15 years,

still in the middle of that learning process. Maybe when things settle down we’ll get them

now much about the Higgs particle yet (though we will soon) and in the meantime you can

it (or them, or whatever is the true story) here.

a closer look at the various masses. Not only is the range of masses huge, there isn’t an easily

pattern. Here are some comments about the particle masses, starting with the lightest ones:

hoton and graviton are probably massless — they must be astonishingly lightweight in order

ow the observed intergalactic magnetic field and the immense structures found in the

luon is as massless as you can meaningfully define it to be — gluons spend their lives trapped

hadrons such as protons, and you can’t easily measure how light they are.

rists long debated whether neutrinos were massless or not. Experiments of the last decade or

(though the evidence is still indirect so small loopholes remain). Neutrino

es are very tiny, with the heaviest at least a billion times lighter than the lightest atom

rogen), and the lightest one possibly much lighter indeed.

asses of the other elementary particles are known. The electron is roughly 1800 times lighter

hydrogen, while the top quark has a mass almost 400,000 times heavier than the electron,

a few percent less than a single atom of gold. And the W particle and Z particles are about half

f the known elementary particles that have substantial masses get them directly from their

action with the Higgs field. (The neutrinos may get their masses in a more indirect way, but

iggs field is essential for their masses too.) I have indicated this with green borders of

ng thickness on the particle disks.

o not know the mass of the Higgs particle (or particles). The Large Hadron Collider should

there are already hints).

ched out the particles and forces in a different way in Fig. 2.


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Fig. 2: The particles again, with the interactions between types of particlesshown. The non-zero Higgs field makes the known particles massive, and the

Higgs field and Higgs particle have stronger interactions with the heavierparticles.

shows which particles directly affect one another. In the figure I’ve drawn lines between all

f particles that interact directly with one another. Here’s something interesting. Notice:

of what are often called the matter particles — charged leptons, neutrinos, or quarks —

tly interact with one another.

atter particles only interact directly with the force carrier particles!

force carrier particles are so-named. When an electron in an atom

with an up quark inside the atomic nucleus, it does so indirectly. The electron interacts

ith photons, the quark interacts directly with photons, and the net (and rather

ted and initially counter-intuitive) indirect result is that the electron is pulled toward the

d vice versa. Similarly, the force between two quarks is indirect, and stems from the direct

n of quarks with gluons. All known forces between matter particles are indirect, and

he mediation of force particles. When you push a door open, photons are at work.

e also captures a few other important features of the forces and the particle classes.

he particles of a given class are affected by the same forces; this is what defines them

lass, in fact. Neutrinos feel only the weak nuclear force; only quarks and gluons feel the

ed lines indicate that some of the force carriers interact directly with themselves or other force


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ers. Note gluons interact with themselves, but the photon does not interact with itself (at

e is a sense in which the Higgs particle is a force carrier too. But it’s a very special case. The

ger is the effect of the Higgs force on a particle, the larger is that particle’s mass when the

(Note: The previous sentence is true for the known particles, but it may

be false for other as-yet-undiscovered particles.) I’ve indicated this tendency by showing the

sea as darker at the top of the page, indicating that it has a bigger effect on the heavier

n particles. Similarly, the Higgs particle interacts with the heavyweight particles more

gly than with the lightweight ones.

awfully strange-looking world, but like it or leave it: it’s ours. Although you can see some

erns, it is not exactly crisply organized. A lot of the disorganization turns out, in one way or

be associated with the Higgs field (or fields). You can read more about this association, and

t the world would be like if the Higgs field were on average zero, in this article.

Google

THE KNOWN (APPARENTLY-) ELEMENTARY PARTICLES”

ow for the science bit… « Slugger O'Toole

upernovas and Neutrinos « physics4me

October 18, 2011 at 9:14 AM | Reply

he matter particles don’t ever interact with each other, and I can see that when you

a door it must be photons working to mediate the interaction between your

nd the door’s, since it isn’t the strong or weak nuclear forces. Can you explain how

otons work to move the door, or how they carry the force from you to the door?

October 20, 2011 at 7:25 AM | Reply

read my article on “virtual particles” yet? It’s not photons (the particles of the

agnetic field) that do the job, but more general disturbances in the

agnetic field (typically called “virtual photons” even though they are really not

s at all.) To explain why a disturbance can do this requires simple equations, but

equations. For instance, nothing I say in words can explain to you why the


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ance between two electrons leads to a repulsion, while the disturbance between an

and a proton leads to an attraction.. To understand that you must do a calculation

s fail at precisely this point.

tandard Model Tutorials for the Masses (…er, sorry about the pun…) « Whiskey…Tango…Foxtrot?

November 30, 2011 at 9:31 PM | Reply

This is a very interesting site. My training was in plasma physics, but I’ve

an interest in particle physics since the announcement of (apparently)

nal neutrinos from the OPERA experiment. My question has to do with your

that neutrinos have mass. Hasn’t the results of SN1987A shown that to a very small

y neutrinos (at least the ones observed in1987) travel exactly at the speed of light?

oesn’t that mean they are massless?


fact that supernova neutrinos travel very close to the speed of light to a very

only means that neutrinos are massless to a very small

. And now we have to work out how big that very small uncertainty is.

trinos from the supernova had energies around 10 MeV or so (that’s 10,000,000

ey arrived within a few seconds of one another. As scientists calculated almost

iately, that indeed put a limit on the supernova neutrino’s masses: they could not

. See http://adsabs.harvard.edu/abs/1988neph.work..306M

er, we have better limits from cosmology today: the limit is closer to 1 eV/c^2. And

evidence from neutrino oscillations (http://profmattstrassler.com/articles-

sts/particle-physics-basics/neutrinos/neutrino-types-and-neutrino-oscillations/)

utrinos do have mass; at least one has mass around or above .1 eV/c^2.

In physics, you must be quantitative about what you do

ow, if you are to come to correct quantitative conclusions about what

2


tt – after posting the above, I found your article on SN1987A. I realize that the

rtainty in arrival time leaves a small possible mass. I have a few other questions, if

n’t mind looking at them. The SN1987A neutrinos velocity discrepancy was about

0^-12, I remember, depending if you looked at arrival time or energy width. In the

ohn & Schalow, they remark that the existence of TEV neutrinos indicate that the

lung effect limits their velocity discrepancy to about that of the SN1987A

Very close to C at low energies and at high energies. Doesn’t Occam’s Razor

at the velocity is pretty much the same or identical for all energies?

question I had (maybe it is also addressed somewhere on your site) is the relation

chyons and superluminal neutrinos. I guess I thought that all FTL particles were

but isn’t a tachyon supposed to go faster as it looses energy? Due to Bremstrahlung


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s, all particles would accelerate and thus lose energy faster and etc. Maybe this is

g the eqns of special relativity, and we’re not supposed to apply them to the

uest Post: Matt Strassler on Hunting for the Higgs | Cosmic Variance | Theoretical Physics

December 7, 2011 at 6:48 PM | Reply

to add gravity and gravitons to this diagram, would they interact with everything?

less photons can be bent by gravity, right?

it said that the electromagnetic force is “long-ranged” because photons do not

th themselves, whereas gluons and W/Zs do. Would it be right to generalize and

avitons must not interact with themselves either because gravity is also “long-

ravitons interact with everything except themselves?


uess but not so. Gravitons do interact with everything *including* themselves. In

t’s a key reason why Einstein’s theory differs from Newton’s (though Einstein

hrase it that way initially.)

t true that “the electromagnetic force is `long-ranged’ because photons do not

t with themselves, whereas gluons and W/Zs do.” I’m not sure who told you that;

ply false. The question of whether a force is long range is quite separate from

r the corresponding particles have self-interactions. You can have self-interacting

s that generate long-range forces; there’s a whole subject of study called

mal field theory” which is all about that. Or you can have short-range forces from

-like particles that do not self-interact; in fact, inside a superconductor a photon

nerate a short-range force, through a Higgs-like phenomenon first understood by

on, a year or so before Higgs (and some other particle physicists too, who should

orgotten) considered the question. (However, Anderson did not predict a

ike particle as a consequence, I believe.)

December 8, 2011 at 9:52 AM | Reply

anks for the great website. I stumbled upon your guest-post on Cosmic Variance

een fascinated by your posts ever since.

estion that may sound extremely silly (then again, I’m a molecular biologist and

my field around here). The way I understood it from your posts, the set of

that form the “Standard Model” describe the physical world in particles, by

eaning the smallest manifestation of a field allowed by quantum mechanics. How

dard Model unified with the so-called wave-particle dualism? Does this present a

uspect my problem with thinking clearly about this issue is that I’m overly

by the “common sense” meaning of the words particle and wave, both probably a


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for irreplaceable but overly complicated equations)


e, Davide. You are right that common-sense notions make things complicated, but

rse than that, there are two different particle-wave things going on here. It makes

xtremely confusing for everyone, even graduate students as they’re learning the

t me answer the easy question: “How is the Standard Model unified with the

d wave-particle dualism? Does this present a problem at all?” No problem at all;

article dualism (which has to do with the wave-function of quantum mechanics) is

rate into the very structure of quantum field theory (in which particles are viewed

tized ripples, or “quanta”, as Einstein dubbed them when he first invented the

t of a photon.) Since the Standard Model is an example of a quantum field theory,

extremely messy is that quantum mechanics (which is what most people learn

read about) gives intuition about particles and waves and the relationship between

at is quite different from the intuition that one learns from quantum field theory.

is reading about what Bohr and Einstein were saying back in the 20s and 30s has

oblem: in some ways, it is out of date, at least linguistically. I’m struggling with

deal with this problem on the website; I think it is going to need a long article, but

sure what it is going to say.

a (probably incomprehensible) preview:

cept of particle in quantum mechanics, before you do quantum field theory, is

bit more like the Newtonian concept of a particle; and the wave that shows up in

m mechanics is the wave function, which is not a function in ordinary space at all,

nction in the space of possibilities. (A wave function for one particle in quantum

ics is a function of 3 dimensions, but a wave function for two particles is a function

ensions — because the space of possible positions of two particles is specified by

,x2,y2,z2) Wave-particle duality arises from having a wave function evolve

ly and describe probabilistically what a particle might be doing.

s, in quantum field theory, there’s still a wave function (of an infinite dimensional

f possibilities now — eeeek!!) but that’s not the type of wave I’m talking about in

classical field theory, before quantum mechanics, there are waves

r waves, waves on a violin string, sound waves, electromagnetic waves — and these

, three-dimensional waves, ripples on a field. Now when we go

field theory, quantum mechanics demands these ripples have a quantized

they can have a minimal size, or twice that size, or three times that size, but not

es that size. Einstein called such things “quanta”. They’re really not what our

n imagines for “particle”. But in many ways they do behave like “particles” — they

finite energy and momentum, they bounce off of things, they can be emitted or

d — and so we retain the word “particle” for them. Maybe it would have been

o stick with “quanta” and avoid linguistic confusion, but then again, particle

n is often useful for them. Anyway, what’s going on here isn’t really the


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article relationship of quantum mechanics; it’s ordinary waves, not a wave

n, and an unfamiliar (but appropriate for nature!) notion of particle, not the one

r granted in one’s first quantum mechanics class.

rst of all — the wave-particle duality concept that Bohr developed partially draws

of these wave-particle relations! Ugh! Very hard to tease this apart. I guess

y I’ll have to do it very carefully; then I’ll try to explain it clearly to you.


s for your answer! To understand that there are two different particle-wave duality

s a great start…I liked the bit about notions that are unfamiliar…but appropriate

This is the very thing that makes it hard for folks like me to follow (and for you to

ut without that I somehow doubt I would be that interested in knowing (if it’s


be one step clearer — there aren’t two particle-wave *duality* problems, but rather

erent precise contexts in which both waves and particles appear. There are

ns to go by. Wave-particle duality, by contrast, is a conceptual approach to

g about nature and the corresponding equations, not itself backed by any specific

ns, arguing that to understand nature properly you have to understand that an

has wave-like properties as well as particle-like properties, and the same is true

tons, Higgs particles, etc.

probably say that better too. Sigh…

July 11, 2012 at 2:01 PM | Reply

I thought I was beginning to understand… Which view is “right” as far as

erstanding the fundamental nature of the universe, quantum mechanichs or

tum field theory? I can see that both can be “right” simoultaneously as far as their

ations to go by” make accurate predictions in their respective areas of application,

that’s not fully satisfactory… Let me rephrase the question. When we talk about the

entary particles, the elementary constituents of the world, including the Higgs

on, are we mainly talking about those “quanta” of QFT? Or is there an alternative

based on quantum mechanics? And if there is, are both interchangeable? Or is

of the theories subsumed by the other? It seems like there is no wave-particle

ity “problem” in quantum field theory, just “quantized waves/fields”, with no need

articles, except maybe as a metaphor. But then how should one interpret things

the quantum double slit experiments, the idea that measuring some magnitude

lapses” a probability (the interpretation of the wave function in quantum

hanics) into a “real” value for that magnitude, the uncertainty principle, the

erposition” of states in e.g. quantum computers, etc. i.e things that suggest that

probably mixing things up badly, sorry about that. I thought I understood the

e-particle duality as explained in e.g. http://physics.about.com/od/lightoptics

, but not any longer after reading your (very clear) description of


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ifferences between quantum mechanics and quantum field theory.

July 12, 2012 at 9:53 AM | Reply

here’s a risk of semantic confusion, so let’s first eliminate that.

he term “quantum mechanics” has two uses. One is as the general category of

uantum techniques, of which quantum field theory is one application. String

heory would be another application. The second use is in its specific application to

iscrete objects that we think of as point-particles; this is what we learn first in

chool, for example for describing electrons in atomic physics. Let’s call that

1920s quantum mechanics” to avoid confusion.

n other words, 1920s-quantum-mechanics and quantum-field-theory are both

xamples of the general class of things that operate according to the general

rinciples of quantum mechanics.

ow: 1920s quantum mechanics is inconsistent with relativity, both special and

eneral. The only way to bring them special relativity into quantum mechanics is to

se quantum field theory. So yes, 1920s quantum mechanics has to be supplanted

y something more general. Doing so has many benefits, including explaining many

uzzles of 1920s quantum mechanics, predicting the positron [the electron’s

nti-particle], and allowing (for example) for a full quantum theory of both light

nd electrons, which isn’t possible in 1920s quantum mechanics. And many aspects

f the world cannot be calculated successfully, or at all, using 1920s quantum

echanics, while quantum field theory does very well.

ndeed, 1920s quantum mechanics was obsolete by the mid-to-late 1930s. However,

should note that it wasn’t clear that quantum field theory was entirely the right

ramework for all of the non-gravitational forces until the 1970s; indeed most

eople in the 1960s didn’t think it was.

he question of how the physics of particles in quantum field theory reduces down,

ay in atomic physics, to what you know about the behavior of particles in 1920s

uantum mechanics is not a trivial one at all. (It’s also not trivial to see how

ewton’s law of gravity emerges from general relativity — it takes some real work.) I

on’t think I can give you a non-technical explanation of this. For instance, in 1920s

uantum mechanics one speaks of position and momentum for particles; in

uantum field theory one does not, and the language of 1920s quantum mechanics

herefore has to emerge in a complicated way. And in quantum field theory the wave

unction is not a function of particle positions but of the field values across all of

pace… it’s such a messy object that no one ever uses it.

think the best thing for me to say right now is that I don’t feel that I myself can

xplain this clearly enough to answer your question right now. Thinking of a good

ay to do so is on my list of things for the future. A technical discussion of bound

tates (i.e. something like an atom) appears in some quantum field theory books,


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uch as Peskin and Schroeder… but I assume you want a non-technical discussion.

cember 10, 2011 at 2:54 PM | Reply

Variance article that links here you actually mention the “equations of standard

t this article is about the particles not about the equations. I am trying to

d how much of what is done in LHC is done by computer programming and

nd how much of it is actually “standard model equations.”


that’s a very complicated story. I don’t think I could put up a page about the

ns of the Standard Model on a public website — learning how to use the equations

tum field theory was the single most complicated intellectual leap that I ever made

dent. I am still learning new things every time I try to teach a course on it. We’re

about taking limits in applied infinite dimensional calculus… and other nasty

: there is some modeling of the proton that has to be done, but most everything

n attempt to carry out bona fide equations, not modeling. That said, the

tions are very complicated, often involving integrals over many variables, and they

performed analytically. And certain approximation schemes are always being

. But the calculations are all based on analytic equations (except for the structure

roton, which has to be modeled using past experiments.)


can see the mysterious parameters of the particle’s rest masses are now replaced

esponding mysterious parameters of their interaction strength with the Higgs

ere some way in which the Higgs field is making anything more clear and less


estion is on target, and your impression is absolutely right. The Higgs field is

ry so that the masses of W and Z particles, quarks and leptons can be non-zero,

th the exception of the W and Z particles themselves, whose masses are related to a

ation of the value of the Higgs field and the strength of the electromagnetic and

uclear forces) it provides no explanation for the actual values of the masses of the

and leptons… no reason why the top quark should be 400,000 times heavier than

tron. That is one of the key problems in particle physics today, for which perhaps

C will give us some guidance.

ther point which is a little harder to explain is that the Higgs field doesn’t just give

to things — it rearranges the forces. (See http://profmattstrassler.com/articles-

sts/particle-physics-basics/the-known-particles-if-the-higgs-field-were-zero/ )

oes so in a very precise way, one that has been carefully verified over the years,

lly at the SLC and LEP colliders (at Stanford and CERN, respectively.)

t get the impression that the only thing the Higgs field is good for is giving masses


11 of 24 10/21/15 10:31 AM

ch of particles. There’s much more going on.

uest Post: Matt Strassler on Hunting for the Higgs | Cosmic Variance « Science Technology

his Site’s Background Articles on the Higgs | Of Particular Significance

| Reply

ription – I’m 17 and trying to understand some of this… when I was alright until

hen you push a door open, photons are at work”. So why exactly don’t we see

omly emanating from doors across the country?

July 12, 2012 at 9:33 AM | Reply

od catch. I shouldn’t have said that in quite that way.

have said: virtual photons (disturbances in the electric and magnetic fields) are at

’ve spent all this time elsewhere on the website emphasizing that virtual photons

http://profmattstrassler.com/articles-and-posts/particle-physics-

virtual-particles-what-are-they/

caught an inconsistency in my explanations; a consequence of the order in which

cles were written. Thanks, I’ll fix that.

HC Program Evolving: From Broad Searches To Precision Tests | Of Particular Significance

July 17, 2012 at 11:26 PM | Reply

push a door open, (virtual photons are at work=disturbances in the

netic field), do atomically bound electrons and nucleus bound quarks feel force?

pushing a door open) change the kinetic and potential (interaction) energy of these

hy the Higgs and Gravity are Unrelated | Of Particular Significance

oes the Higgs Field Give the Higgs Particle Its Mass, or Not? | Of Particular Significance

irst News from Kyoto Conference | Of Particular Significance

vember 18, 2012 at 9:11 PM | Reply

14… But im interested in partical and nuclear physics.


12 of 24 10/21/15 10:31 AM

estions regarding matter and anti matter. It is said that when a particle meets its

al they annihilate each other, transforming into energy. However, when our

as created, matter somehwhat ‘overtook’ antimatter. For example a proton+ a

hydrogen atom, so does that mean that an anti proton+ a positron= anti hydrogen

t I am trying to say is that if a hydrogen atom can have its anti particle, just like

r has antimatter, does that mean that our universe may also have its own ‘anti-

n other words a parallel universe?


ee it, parallel universe (or extra dimensions hypotheses in general) has nothing to

timatter, at least directly. Antimatter can, and does, exist in observable universe, it

ed a separate one. For instance, the very common process of neutron

s-decay creates, among its other products, a particle called electron antineutrino.

u’re totally correct about the antihydrogen atom consisting of 1 antiproton and 1

this is the most interesting part, is how it came to be that there is much more

n antimatter in observable universe. I just checked Wikipedia

.wikipedia.org/wiki/Baryogenesis) where it says that this problem is not yet solved.

e current Standard Model has no facility to explain this phenomenon.


problem is not yet solved, do you think that I should continue researching? Would


estion of why there is more ordinary matter than ordinary anti-matter in the

e (or at least in the part that we can observe — it may be much larger than that) is

an open problem, and you are welcome to work on it. However, you must also

that hundreds of very smart people have tried already, and there are a number of

asonable suggestions that have already been made, one of which may be correct.

e precisely, it is not known to have been solved, but it **might** have been solved

. It’s not as though no one has any ideas.

iginal question asked “could the universe have its own anti-universe.” I presume

ea here is that there could be a second parallel universe with more anti-matter than

so that the two universes added together have equal amounts of matter and


13 of 24 10/21/15 10:31 AM

tter. Well, there have certainly be suggestions that are similar to this. See for

http://arxiv.org/abs/hep-ph/9904221 ; although this will be far too technical

to read, just look at the last two sentences in the abstract describing this paper,

’ll see the idea here is that there are two “branes” (like membranes, but with three

dimensions) that are literally parallel — like parallel lines — and are separated by a

istance in a fourth spatial dimension that we don’t yet know about. It’s almost (not

ike two independent universes that are literally parallel. (The reason they are not

dent is that objects on one brane attract objects on the other brane via ordinary

) And the excess of matter (or “baryon number”) on the brane we inhabit is

d by the deficit on the other brane.

afraid that smart people have been here ahead of you… it is *really* hard to have a

iginal idea, especially when you are just starting out. But you should not be

aged. What you need to do is learn enough about the technical side of the science

le to make proposals which go beyond words and ideas, and are grounded in the

atics that we use to describe quantum theory and general relativity, and even

mplex theories that have been proposed over time. That is probably (for the

t) the best use of your time, rather than actually trying to solve this problem now

ou can really read technical papers about what other people have already tried. A

rs from now, once you have that math and physics background, you will be able to

to all of these great problems, and a young mind that has few preconceptions is

e best one for making breakthroughs. So — good luck!


reciate your feedback and insight:)

he Constancy of the Heavens — Verified Anew | Of Particular Significance

’s (not) The End of the World | Of Particular Significance

elcome, 2013! | Of Particular Significance

lectrons and Their Properties | Of Particular Significance

January 28, 2013 at 8:43 PM | Reply

the diagram, mass ordered, sometimes I wonder if the neutrinos should really be

ls of top, bottom, and down quarks… given that the other three leptons are near of


ys what it says; neutrinos are lightweight. There’s no evidence to relate the

os in any way with those three quarks. Also there’s no known reason why charm,

and up should be combined into a family of three. You may be reading a pattern

one exists… as we humans are wont to do! :-)


14 of 24 10/21/15 10:31 AM

January 30, 2013 at 7:31 AM | Reply

t I could also be reading a pattern where nobody has considered, because it sounds

. Or any pattern looking for some application…

============= the (almost) complete pattern ====vel | fermions | u-type bosons | d-type | e-type | n-type 4.1 |n1, top | | | |64 |n2, bottom | bb bs bd + anti | bu bc + anti | B- Bc- B+ Bc+ | eta_b B0 /698 |tau, charm | | sc dc + anti | D- Ds- D+ Ds+ | eta_c D0 /1219|mu, strange | ss sd dd + anti | su du + anti | K- pi- K+ pi+ | pi0, eta_8 |e, up | |n3, down |


u accounted for the fact that quark masses are renormalized as a function of

e scale? This is something that non-experts often leave out.


I was not worried about it here in the pattern, because it includes QCD quantities,

ither it is something to be exploited at low energy, or it can not be exploited at all.

basic point in the table (by the way, good that the comments do support CODE and

tags!) is that the list of bosons is exhaustive and it matches the number of degrees

eedom of the fermion side, which is also exhaustive, so it could be used in some

superstring stunt trick or similar. To my regret, all the susy breaking stuff has

developed for the practical case of very massive scalar partners, so the literature

not have mechanisms with such mild breaking, nor even as exersice

ing that people usually leaves out is that for equations involving mass quotients the

ing mass correction can be small, sometimes smaller that other second order

ts equally unaccounted. For instance, in the above table I have choosen levels so

3-4-5 and 5-6-7 fit Koide equation, and 4-5-6 is Koide using -sqrt(s) instead.

http://prd.aps.org/abstract/PRD/v77/i11/e113016 , one can see that

ifference between evaluating this last equation for [tex]\overline MS[/tex]

]m_q(m_q)[/tex] masses and masses al electroweak scale [tex]M_Z[[tex] is only a

percent; and the difference between the electroweak scale and the same quotient at

:-(

rom Moriond, Higgs Evidence Piles Up | Of Particular Significance

MS sees no excess in Higgs decays to photons | Of Particular Significance

nd the New Rich and Famous Man Is: Sasha Polyakov | Of Particular Significance

MS Presents Some First Results | Of Particular Significance

iggs Workshop in Princeton | Of Particular Significance

MS Presents Some First Results on Cosmic Rays and Dark Matter | Cientificos.pe


15 of 24 10/21/15 10:31 AM

Second Higgs Particle? | Of Particular Significance

age not found | Of Particular Significance

Short Break | Of Particular Significance

Couple of Rare Events | Of Particular Significance

First Stab at Explaining “Naturalness” | Of Particular Significance

Discrepancy to Keep an Eye On | Of Particular Significance

ight-Hearted Higgs Questions From a High School Teacher | Of Particular Significance

August 29, 2013 at 9:34 PM | Reply

icles are the low-energy effective particles, right? Do the “real” elementary

the standard model, i.e., before electroweak mixing, have names?


profmattstrassler.com/articles-and-posts/particle-physics-basics/the-known-

tly-elementary-particles/the-known-particles-if-the-higgs-field-were-zero/


e it there’s no electroweak mixing without the Higgs? :-)


our question isn’t clear.

harryjohnston | August 30, 2013 at 1:23 AM |

Sorry; carelessly stated, and besides which, if I’d read the article first the answer

would have been obvious.

dding to the Naturalness Article | Of Particular Significance

n)Naturalness, Explained | Of Particular Significance

n-Naturalness or A Miracle? | The Way

uantum Field Theory, String Theory, and Predictions | Of Particular Significance

uantum Field Theory, String Theory, and Predictions (Part 2) | Of Particular Significance

uantum Field Theory, String Theory and Predictions (Part 3) | Of Particular Significance


16 of 24 10/21/15 10:31 AM

uantum Field Theory, String Theory and Predictions (Part 4) | Of Particular Significance

October 7, 2013 at 4:11 PM | Reply

……….ontosofiax memorialx eventux memorialx proust-heidegger…p

he Twists and Turns of Hi(gg)story | Of Particular Significance

isiting the Host Lab of the Large Hadron Collider | Of Particular Significance

Busy Week at CERN | Of Particular Significance

t a CMS/Theory Workshop in Princeton | Of Particular Significance

November 28, 2013 at 2:18 AM | Reply

http://profmattstrassler.com/articles-and-posts/particle-physics-basics

n-apparently-elementary-particles/ appears to be

to a completely different webpage when I click the home page button.

ant to have this looked at.

hat’s the Status of the LHC Search for Supersymmetry? | Of Particular Significance


aluable info you provide in your articles.

mark your weblog and check again here regularly.

certain I’ll learn many new stuff right here!


rb blog! Does running a blog similar to this require a massive amount work?

nderstanding of computer programming but I had been hoping to start

og in the near future. Anyways, should you

ecommendations or techniques for new blog owners please share.

s is off subject nevertheless I simply needed to


physicist but I run a Science and Technology group. I would like to pose a question

thering me. How does a photon manage to be so stable, with no loss of energy,

ns of years when it is travelling through space that is not entirely empty? If there

loss or energy then would that be manifested as a reduction in frequency? If then a

velling through space produces a ‘red shift’ it would no longer be necessary for red

ply movement away from the observer which would change our view of cosmology.


17 of 24 10/21/15 10:31 AM


ividual photons don’t lose energy (and hence frequency) when traveling through

te-empty space. You can think of it this way: a particular photon either hits

ing en route to us or it doesn’t. If it does, it is scattered or absorbed and we never

f it doesn’t, it isn’t affected. (By way of analogy, a baseball doesn’t slow down if the


nd the conventional wisdom and in the short term I have no difficulty accepting it.

m is the assumption that no energy is lost to a photon over the vast distances of

ere no interaction with all the gravitational fields and background radiations out

would result in some loss of energy in millions of years? Just imagine if ‘red shift’

sed of two parts one due to doppler and one due to distance travelled, it would

mology, we would not need a ‘big bang’ we would have a steady state universe with


m mechanics prohibits interactions of the sort you’re describing.


ou mentioned quantum mechanics. That teaches us that light is a particle

with a wavelength and not a wave. The doppler effect is concerned with waves

in a medium where the source is moving relative to that medium and in my view

lt to marry that with photons. Photons of light are emmited from a body at the

ght with an associated frequency, assuming no change they will reach an observer

ill have the same frequency. If there is a red shift what is the conclusion, either they

ing below the speed of light or they have lost energy. Conversly a blue shift implies

nergy or they are travelling faster than the speed of light. So I have a problem

way I try to look at the origins of red shift. I should say that this line of enquiry

h our group wanting to understand Dark Energy and I started at looking at the

ptions of cosmology.


say what you want, but you should try to make contact with data. Gravitational

t (which is what you are disputing) has been observed.


e Doppler effect and gravitational redshift can be observed in the lab, so there’s

ery little room for doubt about the physics involved.

kes particles behave like waves and also makes waves behave like particles, so

n based on the macroscopic world is typically of little use, but in this case there’s a

mple explanation: time dilation. Because a moving object measures time

tly than a stationary one, it also measures frequency differently. The frequency of

ton as measured by the moving object is different than the frequency of the same


18 of 24 10/21/15 10:31 AM

as measured by the stationary one, and that’s the Doppler effect.

ly, General Relativity tells us that gravitational fields also affect the measurement

. An observer on the ground measures time differently than an observer in orbit

(again) they measure the frequency of the same photon differently. And that’s


your help. I will now be able to sleep a bit better. I regret that I had not looked for

confirmation of the doppler effect in light. I was hung up on how the doppler

d be applied to particles. I had tried to get an answer from my neice who is a

n astronomy but just got a pat on the head.

on-Standard-Model Higgs Particle Decays: What We Found | Of Particular Significance

February 14, 2014 at 3:08 AM | Reply

wrote “Gravitons do interact with everything”… That caught my attention. I

at the graviton has not yet been “found,” and that we “know” nothing about its

(other than a load of conjectures (fancy word for guesses)): When was the graviton

nd by whom? Where can I read more about this?

February 14, 2014 at 8:25 PM | Reply

viton is still hypothetical. However, if it exists, then by definition it interacts with

ing. A particle that does not interact with everything would not be called a


; the graviton is to gravitational waves and gravitational forces as the photon is to

agnetic waves and electric forces. Now, by the very nature of electrical forces, we

utomatically that electromagnetic waves and the photons from which they are

teract with anything that has electric charge. Similarly, by the very nature of

tional forces (Einstein’s version thereof) we know that gravitational waves (which

indirectly observed, but have still not directly observed) and the gravitons that we

e* they are made from [since all waves in a quantum world are made from

] will interact with anything that has energy and momentum. This universality of

at the level of forces is automatically transferred to the gravitons — if the gravitons

they don’t exist, then there is something very fundamental about quantum theory

rong, and no one has ever made a consistent suggestion as to how our

tanding of it could be *that* messed up.

ould the Higgs Decay to New Z-like Particles? | Of Particular Significance


19 of 24 10/21/15 10:31 AM


ryone adamant about determining the nature of light; wavy or particulate? Why

vert the idea; something like ,fundamental particles are made up of light.


uld be a good question , but I think light is the stream of photons, so what does it

Does it mean everything is made up of photons? Then how is it possible to find the

state of photons? I think it would be impossible , because what would be the

ors for photons, which are also force carriers.

f you have more questions or suggestions.

100 TeV Proton-Proton Collider? | Of Particular Significance

hat if the Large Hadron Collider Finds Nothing Else? | Of Particular Significance

hilosophia Naturalis I | Patrice Ayme's Thoughts

s courses for psychologists | March 29, 2014 at 7:01 PM | Reply

sive share! I’ve just forwarded this onto a coworker who has been doing a little

fact ordered me lunch due to the fact that I discovered it

ol. So let me reword this…. Thank YOU for the meal!!

hanks for spending the time to talk about this subject here on your blog.

April 11, 2014 at 7:47 AM | Reply

hole article but I didnt get any thing about tachyons. Which I was hoping so could

l me please wats that ???

April 11, 2014 at 8:12 PM | Reply

ns are not in the Standard Model. So far as we know, there’s no such thing.

April 29, 2014 at 9:06 PM | Reply

ks very much for this information. I enjoyed reading it. As an interested person in

hysics but with only a high school diploma, I struggle to make sense of the subject

enjoy the information all the same. I will continue looking for your publications

s for putting it on the net.

May 8, 2014 at 6:33 PM | Reply

I learn something new and challenging on sites I stumbleupon every day.

helpful to read through articles from other authors and practice


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s online. Please let me know if you have any ideas or tips for brand new aspiring

August 29, 2014 at 3:45 AM | Reply

ment I am going to do my breakfast, once having my breakfast

ain to read more news.

September 2, 2014 at 5:39 PM | Reply

ething that has always puzzled me: how do we know the mass associated with a

at I am getting at is that the quark is always bound, and hence there is always

ergy, so what we measure is the sum of the energies of all quarks in a particle and

all binding energies in the particle. Is the separation really just what we need to

quations of the standard model work? Do we even know that the quark is a

rticle, as opposed to, say, some sort of energy wave? There are a range of particles

ge of masses that superficially make little sense, although on the other hand there

ns out there that appear to predict these masses reasonably and they are not part


21 of 24 10/21/15 10:31 AM

dard model. (I put that there because just because an equation gets certain

with observation, that does not necessarily make it a correct assessment of

rry if this is complicated.

hysics mind blower: Matt Strauss | MGB, or Some Odd Magpie

September 10, 2014 at 9:09 AM | Reply

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indly drop me a e-mail?

tober 18, 2014 at 11:58 PM | Reply

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November 14, 2014 at 1:30 AM | Reply

elf with a weapon designed for advanced combat and technology for hours of

e of Obligation Black Ops II Gaming Mouse.


ed to know about the particle carrier of sound waves…do sound travelswith a

yes then which particle?………As We all know Photon is particle carrier of light

hich is the particle carrier of sound wave


called “phonons”. See http://en.wikipedia.org/wiki/Phonon


I just want to know ,, you said earlier that quarks can convert from one type to

ould it mean that quarks can further be divided?

February 13, 2015 at 9:39 AM | Reply

esentation is great, illuminating and, of course intriguing. I thank you, Sir, very

March 21, 2015 at 7:22 AM | Reply

iv.org/abs/1503.03290v1

hat’s the Matter with Dark Matter, Matt? | 4 gravitons

ril 16, 2015 at 10:15 PM | Reply

tly read an article in “Scientific American” principally on gluons. The three

s said that the oft repeated statement that the Higgs mechanism is the origin of

e visible universe is incorrect. They said further that the mass of quarks accounts

% of the mass of protons and nenutrons and that the rest apparently comes from


23 of 24 10/21/15 10:31 AM

Blog at WordPress.com. The Coraline Theme.

physics doesn’t go beyond an upper level undergraduate course in modern

t if the remainder of the mass comes from gluons, why isn’t that stated more

he discussion of the Higgs mechanism? Is there some connection between the

o the Higgs mechanism and the mass due to gluons such that the Higgs

engenders the mass caused by gluons? Thanks so much. You have an immensely

ptember 5, 2015 at 1:39 AM | Reply

for this article. I really appreciate your explanation on why “Force Carrier

were so named. I was struggling to find something clear and concise. Thanks.


I liked this passage very much:

les we know about and how they can be organized usefully into a few classes… a

iodic table of the particles, with a few twists”.

d “at a lower layer”, since as an IT engineer I’m so used with “layers” to see them

e, and then ask: how many more layers to go down thru?


owing all of this, what is possible? Knowing what something is made of is great,

t I think is the interesting science we never hear about. Knowing each particle and

and cons what should be possible? Anti gravity? Free energy device perhaps?

we can manipulate them there must be something exciting we can do with them.


24 of 24 10/21/15 10:31 AM

The Known (Apparently-) Elementary Particles | Of Particular Significance

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