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 ...

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10
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1answer
461 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 ...
8
votes
2answers
726 views

Neutrino oscillations versus CMK quark mixing

I wish to describe in simple but correct terms the analogy between the Cabibbo–Kobayashi–Maskawa (CMK) and Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrices. The CMK matrix describes the rotation ...
6
votes
4answers
882 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 ...
5
votes
3answers
3k views

How does Higgs field relate to Aether theories?

I am an amateur learning about the Higgs because I was interested in what the LHC's purpose is. I read that as a particle passes through space, it is actually passing through a Higgs field and there ...
4
votes
2answers
641 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 ...
3
votes
1answer
314 views

Higgs boson in LHC

Recently,the higgs bosons are discovered in LHC. My question is How did they come to know that the particle that are created are actually Higgs boson? On the basis of which properties,they ...
1
vote
2answers
110 views

What is the reason for the $ i \tau_2 $ - factor in the higgs coupling with up-type quarks?

The quark mass term in the Standard Model Lagrangian looks like this: $$ L = - \lambda_d \bar{Q}\phi d_R - \lambda_u \bar{Q} i \tau_2 \phi^* u_R $$ What is the reason for the $ i \tau_2 $ - ...
-5
votes
2answers
305 views

Why did Standard Model never sense a requirement to include gravitational quantum? [closed]

Standard Model is advanced (lorentz invariant) 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 ...
-6
votes
2answers
486 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 $$a_1d+b_1u=c_1$$ $$a_2d+b_2u=c_2$$ ...
15
votes
2answers
2k 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, ...
10
votes
1answer
79 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
2answers
511 views

How does Annihilation work?

How does annihilation work? I'm wondering why matter and antimatter actually annihilates if they come into contact. What exactly happens? Is that a known process? Is it just because of their different ...
9
votes
3answers
469 views

What's with the very slightly larger mass of the neutron compared to the proton?

Neutron mass: 1.008664 u Proton mass: 1.007276 u Why the discrepancy? On a related note, how does one go about measuring the mass of a neutron or proton, anyway?
2
votes
3answers
343 views

Neutron decay and electron anti neutrino $n\to p + e + \bar{\nu}_e$

Why do we need neutrino to explain neutron decay? Is there any evidence regarding existence neutrinos in the context of $n\to p + e + \bar{\nu}_e$?
1
vote
1answer
139 views

Do massive particles exchange Higgs bosons?

Do massive particles exchange virtual Higgs bosons between themselves? If they do does the resulting Higgs force decay exponentially with distance?
1
vote
1answer
405 views

Why has the Higgs potential the form it has?

The potential for the Higgs field is a quartic one (Mexican hat). Is this done for simplicity or are there fundamental reasons for this choice? I can imagine further contributions to this potential ...
34
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 ...
21
votes
3answers
4k views

Why is gravity so hard to unify with the other 3 fundamental forces?

Electricity and magnetism was unified in the 19th century, and unification of electromagnetism with the weak force followed suit, bringing into play the electroweak force. I've been told that ...
21
votes
0answers
821 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 ...
8
votes
2answers
786 views

Was the Higgs mass correctly predicted by asymptotic safety of gravity?

This paper was published in Phys Lett B in 2009, and predicted the Higgs mass to be 126 GeV based on the asymptotic safety of gravity. Is this prediction taken seriously by the theory community, or is ...
7
votes
1answer
471 views

Why mass terms are forbidden?

I would like to clarify my understanding on why mass terms in Lagrangians of gauge theories are forbidden. It's often repeated that particle masses are forbidden by electroweak symmetry because it is ...
14
votes
1answer
1k views

Why is Standard Model + Loop Quantum Gravity usually not listed as a theory of everything

I have often seeen statements on physics.SE such as, The only consistent theory of everything which we know of to date (2013) is string theory. Why exactly is this so? Adding the Loop Quantum ...
17
votes
5answers
1k views

String Theory and Standard Model in CERN

I don't know how to say it, but in the TV dominatrices and the popular science books we see the string theory as "the best theory to explain everything", and as "the only game in town"... etc. And ...
5
votes
1answer
211 views

Weak isospin confinement?

According to the Wikipedia article on color confinement: The current theory is that confinement is due to the force-carrying gluons having color charge [...], i.e. because the gauge group is ...
14
votes
2answers
301 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 ...
2
votes
5answers
580 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 ...
1
vote
2answers
648 views

What is the expectation value of the number operator when the vacuum has a VEV?

The number operator N applied to a field whose vacuum has zero VEV gives $N|0>=0$. What if we apply it to the Higgs field? The background of this question is that in popular scientific accounts, ...
13
votes
4answers
691 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?
9
votes
1answer
118 views

Why more than one Higgs?

Since by introducing one Higgs Boson we can give a mass to the leptons and gauge bosons of the weak interaction: Why should we consider more than one Higgs (doublet) once we go beyond the standard ...
8
votes
1answer
184 views

Why $SU(3)$ and not $U(3)$?

Is there a good reason not to pick $U(3)$ as the colour group? Is there any experiment or intrinsic reason that would ruled out $U(3)$ as colour group instead?
7
votes
1answer
285 views

Spin of 125 GeV Higgs boson

Can someone please explain to me why (according to decay of Higgs boson into 2 photons) Higgs boson cannot have spin $S=1$?
3
votes
0answers
257 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) ...
2
votes
1answer
722 views

Fermion mass Higgs mechanism

How get fermion like a electron a mass through the higgs-mechanism? Can someone explain me this with formulas (Lagrangian)? I know that the Yukawa interaction has something to do with, is that right? ...
2
votes
1answer
474 views

Symmetry and conservation laws related to baryon number, lepton number and strangeness

According to Noether's theorem, Every continuous symmetry of the action leads to a conservation law. For example, conservation of linear momentum corresponds to translational symmetry, conservation ...
8
votes
1answer
598 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
493 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 ...
5
votes
1answer
335 views

Is color charge a quantum mechanical observable?

If I had 2 pions that were identical, except one was comprised of a red and anti-red, and the other was comprised of a green and anti-green, would I be able to perform an experiment that distinguishes ...
5
votes
1answer
965 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 ...
4
votes
3answers
464 views

Does the Standard Model require neutrinos to be massless?

I am an undergraduate student in Physics, I have a basic understanding of Particle Physics and Quantum Mechanics but none whatsoever of Quantum Field Theory. I know that Neutrino mixing requires ...
3
votes
1answer
90 views

About $SU(2)_L \times U(1)_L = U(2)_L $

In the many textbook of standard model, i encounter the relation \begin{align} SU(2)_L \times U(1)_L ~=~ U(2)_L. \end{align} Here $L$ means the left-handness. (It is a physical ...
3
votes
1answer
160 views

What is meant by Proton Structure Function?

I am going to embark on a project involving deep-inelastic scattering but first I am trying to do some really basic background reading to get me up to task. My only background in particle physics is ...
3
votes
0answers
98 views

Were fermions ever massless?

In a discussion of the Standard model and Higgs mechanism it was claimed that accordingly: "During an early phase of the cosmos all fermions were massless." I wonder whether this claim can be ...
3
votes
0answers
137 views

List of cross sections?

Sometimes I need to look up a certain cross section, say the inclusive Z production cross section at $\sqrt{s}$ = 7 TeV. Is there a place where 'all the' cross sections are tabulated ...
3
votes
2answers
163 views

Playground of Forces

Why is it that the gravitational force acts on large sized objects while the strong and weak nuclear forces act at subatomic levels only? What is that stops each other to enter each others domain?
0
votes
2answers
157 views

Reasons for choosing $SU(3)$ as the color group vs. $SO(4)$

What are the reasons that $SU(3)$ is used for QCD? Why wouldn't the simpler & smaller group $SO(4)$ make a better candidate?
-1
votes
1answer
600 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 ...
8
votes
3answers
2k views

Why do quarks have a fractional charge?

I am aware that evidence exists that strongly suggests the existence of quarks and do not doubt it. It is just simply really weird to me that they can have a fractional charge. While other ...
6
votes
1answer
237 views

Is color confinement detected?

I'm a graduate student studying QFT. I'm quite interested that is color confinement detected or proved? (both directly and indirectly) Or it is just an assumption?
6
votes
1answer
327 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 ...
6
votes
0answers
168 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 ...