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32 views

Why can't we have a massive photon in the Standard Model of Particle Physics

I've heard that in the Standard Model of Particle Physics you can´t have a massive photon whatever you do but I'm having a few problems showing that. I understand that the trick to make this work is ...
1
vote
3answers
55 views

Why does the reconstructed mass of a particle have a fairly wide distribution?

In HEP experiments, a particle of interest (e.g. Higgs) is reconstructed using information about decay products, momentum, energy deposits, angle of those particles, etc. The invariant mass of the ...
0
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1answer
86 views

Mass of the mesons in a universe with massless quarks

As I propose in this post, About the mass of the particles, imagine a universe with massless quarks due to Higgs' VEV is exactly zero. In our universe, where quarks are massive, we have consider ...
3
votes
1answer
60 views

Why Aren't Hadron Masses More Useful In Determining Standard Model Constant Values?

Some of the most exquisitely precise experimental measurements in all of physics are the masses of the various hadrons. Consider these examples: the proton mass is known to eleven significant digits. ...
2
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1answer
95 views

Decay width of the tau lepton

The total decay width of a particle, $\Gamma$, is proportional to the fifth power of its mass, $m$, $$ \Gamma \propto m^5$$ We also know that the dominant decays of the tau lepton are $$\tau^- \to \...
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3answers
97 views

Why is the proton (uud) lighter than the $Δ^0$ (uud) baryon?

Neutron has quark composition udd with spin $\frac 12$. $\Delta^0$ baryon has quark composition udd with spin $3 \over 2$. On Wikipedia it says that $\Delta$ baryons have mass of approximately $1232 ...
2
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1answer
36 views

Interpretation of a CLs exclusion plot

I have some trouble with the interpretation of this plot. The plot on the right shows the CLs values for the SM Higgs boson hypothesis as a function of the Higgs boson mass in the range 110–145 GeV. I ...
3
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2answers
548 views

Why is neutron slightly heavier than the proton? [duplicate]

With latest knowledge of QCD, is there any explanation for why the neutron is slightly heavier than the proton? Can it be boiled down to a simple formula?
2
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1answer
179 views

Why the photon doesn't acquire mass with the Higgs mechanism?

I did the computation that from $$(0,v)^{T}(\partial_\mu+igA_\mu^a\tau^a+i\frac{g'}{2}B_\mu)(\partial_\mu-igA_\mu^b\tau^b-i\frac{g'}{2}B_\mu)(0,v)$$ with $(0,v)$ being the expectation value of the ...
5
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1answer
154 views

Is the electroweak $SU(2)$ gauge symmetry an exact symmetry in Standard Model before spontaneous symmetry breaking?

In Standard model, components of a $SU(2)$ doublet (for example $u$ and $d$) have different masses. This means there is no $SU(2)$ symmetry, but I think it is okay because the $SU(2)$ symmetry is ...
2
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1answer
114 views

What are significant applications of the Higgs Boson itself in the standard model?

I understand that the Higgs Field grants mass to all the matter in the universe, and is equally distributed in all parts of it, but it was the Higgs Boson that was discovered at the LHC, and ...
2
votes
1answer
166 views

How did the three quarks ($u, d, s$) acquire different masses?

If the three quarks $u, d, s$ had the same mass, they would have an $SU(3)$ flavor symmetry ($u, d, s$). This symmetry is broken because these three quarks have acquired different masses through ...
1
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1answer
39 views

Is a quark‘s constituent mass affected by the chiral limit?

The up- and down quark’s constituent mass is usually taken to be around $300\,\text{MeV}\approx \tfrac{1}{3} m_\text{proton}$. Is this quantity affected by the chiral limit, where we let the quarks’ ...
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2answers
160 views

Are elementary particles with inertial mass actually composite particles?

In the standard model, electrons, muons and taus are elementary particles i.e. they aren't composed of more fundamental particles. But after watching this YouTube video animated by an actual scientist,...
-1
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2answers
82 views

Can we tell something about rest mass from this plot of differential cross-section? [closed]

What we can interpret from the plots below? My aim is to find any resonance peak for di-leptons considering the the produced gamma from quarks and antiquarks can annihilate to lepton and anti ...
0
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0answers
15 views

Does an accessible experiment exist that would distinguish QED vs. EW/Higgs originated masses as having different properties for them?

Subject to SM being found inadequate,iIt's well known that some particles gain mass from the Higgs field/mechanism (EW bosons being classic examples) while others gain mass from gluon energy and QED (...
4
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4answers
147 views

Do electrons also gain mass by interacting with the EM field or all of its mass comes from the interaction with the Higgs field?

I'm confused. I thought that the only reason why electrons had mass was that they interacted with the Higgs field, but I've been told that the EM field also contributes to its mass. However, if this ...
2
votes
2answers
133 views

Where is the proton mass coming from?

I always thought that the mass of a proton would simply be the mass of the three separated quarks plus their binding energies. Nevertheless, I was once discussing with one of the developers of RICH ...
0
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1answer
40 views

Decay of composite particles

I know that a particle must decay to decay products that have less than or equal mass to the original particle. However, I am confused how this works for composite particles. Is it any different? Eg. ...
0
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0answers
43 views

Higgs coupling to particles

Plain question: Is it already solved why the Higgs couples different to various particles (causing distinct mass scales)? Or is it still an ongoing topic? Can't find an information about the current ...
-3
votes
1answer
108 views

Is this an acceptable formula for charged lepton masses?

Looking for a formula which gives good values for the charged lepton masses and which satisfy the Koide relationship, I derived this formula (note the square): $$\{m_e, m_\mu, m_\tau\} \propto ...
4
votes
1answer
265 views

Calculating $W$ - $Z$ bosons mass difference

Naively one might expect the W weak vector bosons to have slightly higher mass than the Z due to EM self-energy, while the opposite is true (80 vs. 91 Gev). Presumably due to the strong interactions ...
0
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0answers
62 views

Specific coupling constants, fermions and string theory

Can string theory answer why the Yukawa couplings or the v.e.v.s.have the values they have in our Universe? I mean, why can string theory answer( and EXPLAIN) the question of why the top coupling to ...
1
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0answers
66 views

What percent of the mass the proton comes from its electric field energy density?

How much heavier would the proton be with respect to the neutron if the up quark and the down quark had the same mass? How much does the electric field energy density of the proton contribute to its ...
4
votes
1answer
453 views

Neutrino flavor and mass eigenstates

Neutrions are produced and detected as flavor eigenstates $\nu_{\alpha}$ with $\alpha=e, \mu, \tau$. These states have no fixed mass, but are the combinations of three mass eigenstates $\nu_{k}$ with $...
0
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2answers
408 views

Why doesn't the Higgs give mass to neutrino? [duplicate]

We learn that elementary particles acquire mass through the weak interactions with the Higgs field. The photon and gluons do not interact weakly, do not coupe with the Higgs field and for this reason ...
1
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1answer
258 views

Does the existence of Higgs boson forbid the possibility of negative mass?

Since negative mass seems not to be impossible according to relativity, does the existence of a fixed particle responsible of mass contradicts with it?
19
votes
3answers
4k views

Why are gluons believed to be massless?

Earlier questions under a similar title referred to the short range of the strong force. My question is completely different. I'd like to know why gluons are considered massless in the Standard Model (...
7
votes
4answers
1k views

How does the Higgs field enable masses to attract each other?

Please refrain from quoting general relativity. I'd like to know whether the exchange of virtual Higgs bosons, which are responsible for giving particles their masses, can produce an attractive force ...
1
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2answers
82 views

Other than the Higgs field, what affects the mass of a particle? [closed]

Other than the Higgs field, what affects the mass of any particle?
1
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2answers
264 views

Why does the mass of a proton not equal the mass of its corresponding quarks? [duplicate]

The mass of a proton is around 900 mega electron volts/c2. The mass of two up quarks and a down quark is about 10 mega electron volts/c2.
2
votes
2answers
831 views

How does the Higgs boson give mass to other elementary particles like electrons? [duplicate]

So, the nucleus of an atom can be broken to protons and neutrons, and those can be broken down to quarks. Electrons however are a different story, they can't be broken down since they are elementary ...
0
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1answer
243 views

Electron mass from “Higgs-like” interaction with $Z$-boson?

I was watching a Leonard Susskind video, "Demystifying the Higgs.." https://www.youtube.com/watch?v=JqNg819PiZY At some point he is discussing the Z-boson and what he terms the Zilch field. (weak iso-...
0
votes
3answers
337 views

Can we theoretically “derive” the mass of a particle?

I read a pop sci book on the Higgs which said that particles get their mass due to interacting with the Higgs field. If that is true, could we use first principles to derive the mass of, say, an ...
67
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7answers
15k views

Why are protons heavier than electrons?

Our teacher told us that protons are nearly 1800 times heavier than electrons. Is there any known reason as to why this is so? Or is this just an empirical value, one we do not know the reason to?
4
votes
1answer
220 views

What is the problem with a Lagrangian that isn't gauge invariant?

In every textbook I've read the only argument why gauge bosons can't have mass is "because a mass term would break gauge invariance". Even fermions can't have mass because it would break the $SU(2)_L$ ...
2
votes
0answers
42 views

Why are the Weak force states different to the mass eigenstates?

On one hand we have the electro-weak interaction doublets $(u,d)$, $(c,s)$, $(e,\nu_e)$, etc. On the other hand, on the Yukawa interaction term that gives mass to fermions we have those same doublets. ...
0
votes
3answers
206 views

Why lepton, quarks and bosons acquire mass by a different method?

As we know that all particle acquire massed by interacting with the higgs field so why the leptons, quarks and bosons acquire mass by difference method?
1
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1answer
91 views

What quark mass to use in energy conservation?

I am looking into energy conservation within decay processes and am getting confused about which mass I need to use for quarks. For example to determine if the reaction: $$\mu^{-}\rightarrow \nu_\mu+q ...
3
votes
1answer
733 views

How does gauge invariance prevent the photon from acquiring a mass?

I have read that the photon is protected from acquiring a mass due to gauge invariance. However, I was under the impression that gauge invariance is not a true physical symmetry, but rather a ...
6
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1answer
434 views

Which Standard Model Constants have beta functions?

Background The Standard Model of Particle Physics has 26 experimentally measured parameters specific to the model (excluding physical constants like the speed of light that have applications outside ...
2
votes
3answers
1k views

How does the gluon field and the Higgs field interact with one another? [duplicate]

Assuming the theories that the Gluon field and the Higgs field are both responsible for particles gaining mass, how would both exist simultaneously in the same world? How would they interact with each ...
1
vote
2answers
226 views

Where is the mass of a proton coming from? From empty space or gluonfields?

Protons are made quarks and bosons. I think most physicists would agree that the mass of a proton is not coming from the quarks itself. About 90% is coming from something else, but what is that. I ...
6
votes
3answers
231 views

How can we experimentally tell the difference between particles with and without rest mass?

We only observe their decay products and that is what the rest-mass is reconstructed from. Also, there is a whole issue of running coupling which means that rest mass per se actually doesn't make ...
10
votes
5answers
952 views

If particles get mass from the Higgs field, why do we not see Brownian motion?

If an electron would otherwise be moving at the speed of light if it weren't constantly interacting with the Higgs Field, how is conservation of momentum preserved if it's constantly bouncing off of ...
1
vote
2answers
91 views

The Standard Model (SM) predicts mass ratios from book excerpt

I read a book excerpt in which the author states: "The SM predicts that the ratio of the muon mass/electron mass should be equal to the strange quark/down quark. This is known to be ...
0
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1answer
135 views

Does the Higgs Boson have a superposition?

Do particles with mass have a Higgs boson in their make up? and if so, when the particle is as an electron and is a wave going unobserved through both slits, is it carrying a Higgs in the same state?
2
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2answers
829 views

If it's impossible to create matter then how can a Higgs Boson field give objects mass?

mat·ter ˈmadər/ noun 1. physical substance in general, as distinct from mind and spirit; (in physics) that which occupies space and possesses rest mass, especially as distinct from energy. "the ...
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1answer
270 views

Geometric interpretation of mass [closed]

I have a question about the definition of mass. In general relativity mass is closely related the curvature of spacetime, which indicates that mass might be interpreted as a geometric concept (maybe ...
6
votes
1answer
867 views

Why neutrino is always left handed

Why all neutrinos are always left handed while all anti-neutrinos are right handed.