A model of the basic particles and forces featuring six quarks, three charged leptons, three massless neutral leptons and four fundamental force carrying bosons. The twelve fermions are arranged into three generations, while the bosons serve to explain the electromagnetic interaction plus the strong ...
11
votes
5answers
2k views
Are W & Z bosons virtual or not?
W and Z bosons are observed/discovered. But as force carrying bosons they should be virtual particles, unobservable? And also they require to have mass, but if they are virtual they may be off-shell, ...
32
votes
5answers
2k views
Why do we think there are only three generations of fundamental particles?
In the standard model of particle physics, there are three generations of quarks (up/down, strange/charm, and top/bottom), along with three generations of leptons (electron, muon, and tau). All of ...
8
votes
4answers
409 views
strange modulation of radiactive decay rates with solar activity
Recently i found out this uber strange article about nuclear decay rates being somehow showing seasonal variations with a high correlation with sun activity. Two very precise questions:
1) has this ...
5
votes
1answer
350 views
Is there a concise-but-thorough statement of the Standard Model?
I’m a grad student in high-energy physics. I’m familiar enough with the Standard Model, but I’ve always wondered whether there existed a canonical statement of, effectively, “what we talk about when ...
-7
votes
2answers
428 views
Could the fractional model of Quarks electric charge turn out to be false? [closed]
The delta baryons (also called delta resonances) are a family of subatomic hadron particles which have the symbols $\Delta^{++}$, $\Delta^{+}$, $\Delta^{0}$, and $\Delta^{−}$ and electric charges +2, ...
4
votes
3answers
132 views
How quark electric charge directly have been measured?
How quarks electric charge directly have been measured when quarks never directly observed in isolation? (Due to a phenomenon known as color confinement.)
10
votes
4answers
2k views
Why do electron and proton have the same but opposite electric charge?
What is the explanation between equality of proton and electron charges (up to a sign)? This is connected to the gauge invariance and renormalization of charge is connected to the renormalization of ...
10
votes
2answers
2k views
Shape of the Higgs branching ratio to ZZ
I've been looking at the, now very popular, graph of the SM Higgs decay branching ratios:
You see that the ZZ branching ratio has a funny dip around the $170\, GeV$, very different from the WW ...
19
votes
5answers
1k views
Could gravity be an emergent property of nature?
Sorry if this question is naive. It is just a curiosity that I have.
Are there theoretical or experimental reasons why gravity should not be an emergent property of nature?
Assume a standard model ...
15
votes
2answers
1k views
If the LHC doesn't find the Higgs Boson, what would be the implications for the Standard Model?
What would be the implications to the Standard Model if the Higgs Boson hadn't been found with the LHC?
Also, if the Higgs Boson had not been found with the LHC, would it have been successfully ...
10
votes
1answer
806 views
115 GeV, 170 GeV, and the noncommutative standard model
Several years ago, noncommutative geometry was used to describe the standard model, somehow yielding a prediction of 170 GeV for the mass of the Higgs boson, a prediction which was falsified a few ...
8
votes
2answers
305 views
Do current models of particle physics explain the chemical properties of elements/compounds?
I have a particle system of seven protons and seven (or sometimes eight) neutrons (each formed by their appropriate quarks, etc.) bound together in a state that can be macroscopically described as a ...
4
votes
2answers
222 views
About free quarks and confinement
I simply know that a single free quark does not exist. What is the reason that we can not get a free quark?
If we can't get a free quark then what is single-top-quark?
10
votes
1answer
287 views
What does the latest $B_s^0\rightarrow \mu^+\mu^-$ results mean for SUSY?
A paper from the LHCb collaboration just came out last week, stating basically that the $B_s^0\rightarrow\mu^+\mu^-$ decay matches standard model predictions, and people are already shouting that SUSY ...
5
votes
2answers
486 views
Other possible theories (other than string theory) which are generalizations of the standard model with incorporation of gravity
The only finite mathematical framework that incorporates both the standard model of particle physics and gravity under one umbrella that I am aware of is string theory. I would like to know whether ...
4
votes
2answers
406 views
Predicting Decay Rates via the Standard Model
Question 7584 illustrated a procedure to forecast the decay rates of isotopes with known long average lifetimes. Lifetimes of the many U isotopes vary from micoseconds to gigayears. F has only one ...
-4
votes
1answer
153 views
Why did Standard Model never sense a requirement to include gravitational quantum?
Standard Model is advanced version of Quantum physics. It tried to include everything which came in the way while understanding quantum world. It even didn't bother to include even Higgs Boson which ...
13
votes
2answers
1k views
Did the researchers at Fermilab find a fifth force?
Please consider the publication
Invariant Mass Distribution of Jet Pairs Produced in Association with a W boson in $p\bar{p}$ Collisions at $\sqrt{s} = 1.96$ TeV
by the CDF-Collaboration, ...
6
votes
3answers
189 views
Origin of lepton/quark generations?
What theoretical explanations exist for the fact that there are three generations of leptons and quarks?
I'm not so much asking why there are exactly 3 generations, but rather what makes electron, ...
6
votes
2answers
208 views
Is there an explanation for the 3:2:1 ratio between the electron, up and down quark electric charges?
I understand that the NNG formula relates $Q$, $I_3$, and $Y$ and can be derived in QCD; does this unambiguously predict the electric charge ratios without making assumptions about the definitions of ...
3
votes
1answer
230 views
What's the deepest reason why QCD bound states have integer charge?
What's the deepest reason why QCD bound states have integer electric charge, i.e. equal to an integer times the electron charge?
Given that the quarks have the fractional electric charges they do, ...
-6
votes
2answers
243 views
Cramer's rule, Origin of Quarks Fractional electric charge? [closed]
In linear algebra, Cramer's rule is an explicit formula for the solution of a system of linear equations with as many equations as unknowns.
2u+1d=1
1u+2d=0
$$a_1d+b_1u=c_1$$ $$a_2d+b_2u=c_2$$ ...
28
votes
4answers
2k views
What is needed to claim the discovery of the Higgs boson?
As I understand the Higg's boson can be discovered by the LHC because the collisions are done at an energy that is high enough to produce it and because the luminosity will be high enough also.
But ...
15
votes
6answers
2k views
Why should the Standard Model be renormalizable?
Effective theories like Little Higgs models or Nambu-Jona-Lasinio model are non-renormalizable and there is no problem with it, since an effective theory does not need to be renormalizable. These ...
15
votes
2answers
1k views
How does string theory reduce to the standard model?
It is said that string theory is a unification of particle physics and gravitation.
Is there a reasonably simple explanation for how the standard model arises as a limit of string theory?
How does ...
14
votes
7answers
1k views
What Do We Get From Having Higher Generations of Particles?
Background: I have written a pop-science book explaining quantum mechanics through imaginary conversations with my dog-- the dog serves as a sort of reader surrogate, popping in occasionally to ask ...
10
votes
0answers
275 views
A dictionary of string - standard physics correspondences
Motivated by the (for me very useful) remark
''Standard model generations in string theory are the Euler number of
the Calabi Yau, and it is actually reasonably doable to get 4,6,8, or 3
...
16
votes
1answer
225 views
Why is there no theta-angle (topological term) for the weak interactions?
Why is there no analog for $\Theta_\text{QCD}$ for the weak interaction? Is this topological term generated? If not, why not? Is this related to the fact that $SU(2)_L$ is broken?
2
votes
5answers
245 views
Could Quark model turn out to be false?
Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei.
Due to a phenomenon known as color confinement, quarks ...
8
votes
4answers
2k views
Why don’t photons interact with the Higgs field?
Why don’t photons interact with the Higgs field and hence remain massless?
7
votes
2answers
1k views
Why is the Higgs boson spin 0?
Why is the Higgs boson spin 0? Detailed equation-form answers would be great, but if possible, some explanation of the original logic behind this feature of the Higgs mechanism (e.g., "to provide ...
5
votes
2answers
333 views
More questions on string theory and the standard model
This is a followup question to
How does string theory reduce to the standard model?
Ron Maimon's answer there clarified to some extent what can be expected from string theory, but left details open ...
3
votes
1answer
236 views
Relationship between hierarchy problem and higgs fine tuning?
I often hear of hierarchy problem being used synonymous with Higgs fine tuning (esp with regards with motivations for SUSY). What exactly is the relationship between the two problems? As I understand ...
3
votes
3answers
236 views
If the electron is point like, then what is the significance of the classical radius of the electron?
What is the physical meaning/significance of the classical radius of the electron if we know from experiments that the electron is point like?
Is there similarly a classical radius of the photon? The ...
3
votes
1answer
411 views
Introduction to Physical Content from Adjoint Representations
In particle Physics it's usual to write the physical content of a Theory in adjoint representations of the Gauge group. For example:
$24\rightarrow (8,1)_0\oplus (1,3)_0\oplus (1,1)_0\oplus ...
0
votes
0answers
98 views
Weak isospin and types of weak charge
My understanding is that QCD has three color charges that are conserved as a result of global SU(3) invariance. What about SU(2) weak? Does it have two types of charges? What I'm getting at is:
U(1) ...
0
votes
2answers
393 views
Can photons and gluons be holes in an aether?
Consider photons and gluons have 0 mass and 0 charge. In many respects they're already understood as the absence of a particle by mathematical models. Couldn't this be interpreted to mean they ...
10
votes
1answer
57 views
N=2 SSM without a Higgs
In arXiv:1012.5099, section III, the authors describe a supersymmetric extension to the standard model in which there is no Higgs sector at all, in the conventional sense. The up-type Higgs is a ...
9
votes
0answers
87 views
infrared free QED and Higgsless standard model phenomenology
This is one of those "what if" fantasy world type questions. I like hard sci-fi so please no "well, you changed one thing about the world so now anything goes." :)
What if the Higgs had no vev?
That ...
8
votes
1answer
357 views
Do color-neutral gluons exist?
If I'm correct a quark can change color by emitting a gluon. For example a blue up quark $u_b$ can change into a red up quark by emitting a gluon:
$$u_b \longrightarrow u_r + g_{b\overline{r}}$$
...
7
votes
2answers
500 views
Why do leptons and quarks mix?
Is the fact that weak eigenstates are not mass eigenstates completely arbitrary? Or is there a deeper reason for the existence of the PMNS and CKM matrices?
6
votes
1answer
136 views
What is the origin of flavor? [duplicate]
Possible Duplicate:
Origin of lepton/quark generations?
In the standard model (and in nature), Fermions appear in different generations, or flavors. Besides up and down quarks and ...
5
votes
1answer
220 views
Why are WW gg ττ branching ratios so similar for a 115 GeV SM Higgs?
In a previous question on Higgs branching ratios, I find this image
(originally from page 15 here).
I am VERY intrigued by the fact that decays to WW, gg, and ττ are almost equally probable, for ...
4
votes
0answers
105 views
What is the rate of B violation expected in the standard model during high energy collisions?
In a recent question Can colliders detect B violation? I asked about detecting B violation in collisions. Here I am interested in the theory aspect. (I asked both questions originally in the same ...
4
votes
5answers
3k views
The Higgs field a new Luminiferous aether?
As of this writing it has been made clear to me that classical physics' Luminiferous aether was a terriblly poor discriptor of space. With the advent of Special Relativity and General Relativity, that ...
4
votes
4answers
544 views
Why are neutrino oscillations considered to be “beyond the Standard Model”?
Is this just a historical artifact - that the particle physics community decided at some point to call all of the pre-oscillation physics by the name the "Standard Model"? The reason I ask is because ...
3
votes
1answer
177 views
Lepton Number Conservation
What is the global symmetry of the electroweak Lagrangian that gives rise to lepton number conservation?
As I understand it, electric charge is some linear combination of the conserved quantities ...
2
votes
1answer
118 views
Fine Tuned Universe
Is the fine tuning that cosmologists talk about (that our Universe is fine tuned for intelligent life) is the same as the fine tuning of the squared mass parameter of the Higgs in the Standard Model? ...
2
votes
1answer
129 views
Similar masses and lifetimes of the $\Delta$ baryons
Why do the four spin 3/2 $\Delta$ baryons have nearly identical masses and lifetimes despite their very different $u$ and $d$ quark compositions?
0
votes
1answer
260 views
What is the relationship between the Higgs field and quarks?
I have some difficulty considering the relative size of each and the meaning behind the shape of Higgs boson. I ask relating to the structures of both the Higgs field and quarks. How is it that the ...
