All Questions
Tagged with standard-model quantum-field-theory
484
questions
5
votes
1
answer
74
views
$ \pi^0\to \gamma\gamma$ parity conservation
Let's consider the decay process $\pi^0\to \gamma \gamma$. After we spontaneously broke the chiral symmetry of QCD coupled to an abelian gauge field $A^\mu$, we end up with the Goldstone boson ...
- 357
1
vote
2
answers
108
views
Checks of anomaly cancellation
In a textbook I read that if $G$ is a global symmetry of the classical Lagrangian, then one has to check $G\times H^2$ anomalies, where $H$ is one of the SM gauge groups.
For example, when $G$ refers ...
- 51
1
vote
1
answer
60
views
Does electroweak theory have mass gap (not just Higgs mechanism)?
I am extremely confused by seemingly contradictory statements.
In this PE answer, the electroweak sector in the Standard Model does NOT have a mass gap (or at least not observed). In fact, the gauge ...
- 1,669
1
vote
0
answers
83
views
Doubt in $e^{+}e^{-}\rightarrow W^{+}W^{-}$ scattering
I am trying to understand how to compute the scattering amplitude for the process $e^{+}e^{-}\rightarrow W^{+}W^{-}$, as a reference one could look at Peskin chapter 21.
What I do not understand is ...
- 475
0
votes
1
answer
70
views
Where is antineutrino in standard model Lagrangian?
I'm somewhat confused by the content I studied in Srednicki's work, where the neutrino is described as a Majorana field. In this framework, there shouldn't technically be antineutrinos, given the ...
- 619
1
vote
0
answers
44
views
One-Loop beta function for gauge couplings
I am currently doing my homework on Standard Model one-loop correction. When I am reading Quantum Field Theory by Mark Srednicki and Journeys Beyond the Standard Model by Pierre Ramond, I notice some ...
- 81
1
vote
0
answers
73
views
Is there a Higgs-pole like the $Z$-pole?
Why isn’t there studies of direct Higgs production like for the $Z$ boson?
Looking for future colliders, they all aim for
$$e-e+ -> HZ $$
which for me makes sense for measuring a physical Higgs but ...
1
vote
0
answers
40
views
Regarding vanishing of a triangle diagram
Furry's theorem ($C$ symmetry) is very important in calculations in QCD, Electroweak theory. Primarily it says everything about QED (three photon triangle diagram), but can be extended to QCD, and ($Z$...
- 534
2
votes
1
answer
65
views
Field redefinitions in the Higgs mechanism
Consider the Higg's mechanism for a simple $U(1)$ theory. Leaving aside the lagrangian which consists of a kinetic term for the gauge field, a covariant derivative term and the potential term for the ...
- 1,791
1
vote
1
answer
42
views
Matrix element including weak currents
If a $\overline{B^0}$ meson decays into $D^+$, $e^-$ and $\overline{\nu}_e$ we have a matrix element $$\langle{D^+ \, e^- \, \overline{\nu}_e |\, (\overline{c_L} \gamma^{\mu} b_L) \, (\overline{e_L} \...
- 53
1
vote
0
answers
56
views
Is the Higgs sector in the Standard Model also asymptotically free?
I have always thought that the Higgs sector, which is $\phi^4$ theory in essence, is not asymptotically free.
However, I ran into the following statement from this paper:
The standard model is, in ...
- 1,669
0
votes
1
answer
58
views
$W$ and $B$ bosons when choosing a different minimum of the Higgs doublet
When comparing the experimental phenomenology with the standard model, one usually takes a combination of the $W^a_\mu$ and $B_\mu$ gauge bosons to obtain the physically observable ones ${W^+}_\mu$, ${...
- 601
3
votes
1
answer
104
views
Why can't we insist that the strong interactions must preserve $CP$?
I'm having some trouble wrapping my head around the strong $CP$ problem. I know that the non-trivial vacuum structure of QCD induces the topological theta term in the strong sector of the SM, which is ...
0
votes
1
answer
56
views
Why don't we include diagrams with fermion and gauge boson external lines while calculating the effective potential of Standard model?
While calculating the effective potential of Higgs boson, we aim at $V_{eff}(h)$ instead of $V_{eff}(h, W^{+}, W^{-}, Z, quarks, leptons)$. I think the true vacuum should be the minimum of this ...
- 619
3
votes
1
answer
426
views
Is there really a strong CP problem?
The strong CP problem is considered one of the major unsolved physics problems. A non-vanishing value of $\theta$ in QCD $\theta$-term violates CP-symmetry. A primary strong CP violating observable is ...
- 4,452