All Questions
Tagged with quantum-field-theory particle-physics
1,059
questions
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What are the differences of Scalar and Pseudoscalar Yukawa Theory?
I know that some polarized interactions are forbidden.
But for unpolarized (summed over incoming and outgoing spins), are the amplitudes and decay rates of a Yukawa scalar and pseudoscalar coupled to ...
- 81
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1
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52
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Square of the Feynman amplitude for $a +b\to c+d$ and its reverse
In quantum field theory, if a process $a +b\to c+d$ is allowed by a certain interaction Lagrangian (hermitian), the reverse process, $c+d\to a+b$, must also be allowed (as far as I understand) by the ...
- 11.8k
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73
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Mandelstam variables sign
I am self-studying the book "Quantum Field Theory and the Standard Model" by Schwartz, on page 99 (paragraph "Mandelstam variables"), the context is the $2\rightarrow 2$ scattering ...
- 613
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83
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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
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31
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QCD parton shower hard scale
Currently I'm studying parton showers from QCD and I'm having trouble with understanding how the hard scale $Q$ is related to the virtuality and energy of the parent parton. The Sudakov factor $\Delta(...
- 291
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36
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Difference between jets and inclusive hadron production
I know both jets and inclusive hadron production are measured in high energy collisions. Is the difference just the way you measure it, or are there differences in the process behind them? If you ...
- 13
2
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1
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88
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Why does the mass term not violate particle number conservation in a free theory?
The Lagrangian of a free real scalar field theory is
$$ \mathcal{L} = \frac{1}{2} \partial_{\mu} \phi\; \partial^{\mu} \phi \; - \frac{1}{2} m^2 \phi^2. $$
If we decompose $\phi$ in terms of the ...
- 61
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70
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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
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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 ...
2
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1
answer
65
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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
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90
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In the path integral formulation of QFT, how do we get quantized particles out of a field?
Every QFT textbook starts by basically postulating that we have discrete states connected by creation and annihilation operators. In Quantum Mechanics, we started from a differential equation and ...
- 1,262
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3
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501
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Is spin a fundamental property of QFT?
I am not a physicist, but my understanding is that the Standard Model of particle physics is not the foundational model but rather is emergent from Quantum Field Theory (QFT), and that QFT is within ...
- 1,772
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1
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112
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Yukawa Interaction with Chiral Fermions
I understand that an interaction like
$$g\overline\psi_L\psi_R\phi$$
is allowed in the SM (for the sake of this discussion lets ignore gauge charges and focus only on Lorentz invariance).
I want to ...
1
vote
0
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53
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Why can't other bosons fluctuate up the potential curve and gain mass?
If a Higgs boson is able to gain mass by fluctuating up the Mexican hat potential, what stops other bosons from doing the same thing and gaining mass without the need of the Higgs mechanism?
1
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2
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122
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Confusion about Higgs mechanism
I am trying to understand the mass acquisition of particles in the Standard Model based on the book 'Fundamentals of Neutrino Physics and Astrophysics' by C. Giunti, and several doubts have arisen ...
- 161