Questions tagged [cp-violation]

is a property of a system or theory where the combined charge conjugation (replacing particles with their anti-particles) and parity (reversing the sign of every vector, equivalent to reflecting the system through the origin) operations yield non-equivalent results. Only the weak interaction is know to produce CP-violation.

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Does $CP$-violation mean $CP$-odd?

This might be a very simple question but I'm doing some reading into the Higgs boson and $CP$-symmetry breaking. I've seen the terms $CP$-even and $CP$-odd terms in the Hamiltonian floated around and ...
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If the universe was dominated by antimatter instead of matter, would we physically notice?

I read that antimatter and matter are identical aside from their opposite charge and quantum number. Of course, the mystery of why matter dominates in our universe is an active field of research. But ...
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Working through the solution of the Ozma problem

I’m trying to work through the Ozma problem and the Wu experiment to get a better handle on parity and I’m being tripped up by something which is almost certainly trivial. I can explain negative ...
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Does the CPT theorem imply $CP=T$?

Does the CPT theorem imply $CP=T$? That is, does it imply that the action of Charge Conjugation and Parity inversion on some representation of the Lorentz group, is the same as doing a time reversal? ...
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Why is the neutron electric dipole term CP violating?

I have heard that a term of the form $\bar{q}\sigma^{\mu\nu}q F_{\mu\nu}$ is CP violating but looking at any Textbook (e.g. Peskin Schröder) one can see that the CP transformations are the following: $...
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Spark chamber spectrometer in Cronin and Fitch experiment

I'm currently studying Cronin and Fitch experiment that showed the indirect CP-violation. I understand the physics behind it and how the experiment was done, but while trying to go deeper into the ...
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Why do we care about chirality?

I'm trying to figure out what's the importance of chirality in QFT. To me it seems just something mathematical (the eigenvalue of the $\gamma^{5}$ operator ) without any physical insight in it. So my ...
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About the recent bounds on the baryon asymmetry

While I'm studying the baryon asymmetry, the ratio of baryons number to the photons number in the universe - some times is called baryon density - $: \eta= n_b/n_\gamma$ I have found many experimental ...
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What were the main results of the BaBar Experiment?

I have been trying to find a review of the BaBar experiment results for quite some time now. Can anyone link a few papers which illustrate what has been achieved so far?
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How can a quantum theory (eg. particle physics QFT) governed by Schroedinger eqn. break the $T$ symmetry (or $CP$) microscopically at all?

Why and how can a quantum system (like the quantum vacuum of our universe) governed by the Schroedinger equation break the time-reversal $T$ symmetry (or $CP$ symmetry) microscopically at all? p.s. ...
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What is the CKMFITTER plot?

I am struggling to understand the CKMFITTER plot which is attached here. Please, someone, try to explain to me what are all these color bands. What are their meanings? Why one band is circular in ...
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What are the implications of violation of the unitarity of CKM matrix?

What are the physical implications of such observation? In other words, why is everybody concentrating on the violation of the unitarity of the CKM matrix?
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Amount CP violation needed

It is widely known that the CP violation provided by the Standard Model ( SM )is insufficient to explain the baryon asymmetry that we observe. However, I never came across any quantitative ...
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CP violation phases counting in neutrino flavor mixing sector with $N$ sterile neutrinos

In the quark sector, the CKM matrix is obtained from (see p.723 of Peskin QFT) $$ V_{CKM} =U_u^\dagger U_d = \begin{bmatrix} V_{ud} & V_{us} & V_{ub} \\V_{cd} & V_{cs} & V_{cb} \\ V_{...
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PMNS matrix versus CKM matrix -- how precise is the analogy?

PMNS matrix is said to be the matrix for the neutrinos as the CKM matrix for the quarks. See https://en.wikipedia.org/wiki/Pontecorvo–Maki–Nakagawa–Sakata_matrix#The_PMNS_matrix However, I am ...
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Electric dipole moment (EDM) and magnetic dipole moment (MDM): CP violation in neutron

The neutron magnetic dipole moment (MDM) is the intrinsic magnetic dipole moment of the neutron. Under parity P, the MDM does not change direction. Under time reversal T which is equivalent to CP, ...
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Theta terms observable effects for $SU(3)$, $SU(2)$ and $U(1)$ in the standard model [duplicate]

In p.726 of Peskin QFT, it says: The theta terms are total derivative, that terms involving $SU(2)$ and $U(1)$ have no observable effects. However for the strong $SU(3)$, it costs a strong CP ...
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Parity and time reversal symmetries in QFT and the Standard Model

The parity transformation $\mathcal{P}$ and the time-reversal transformations $\mathcal{T}$ are defined as follows : \begin{equation} \mathcal{P}= \begin{bmatrix} 1 & & & \\ & -1 &...
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In this example, how can we have CP conservation with C violation?

Consider a simple two-body decay process $X\to Y+Z$ where $X$ is a boson, and $Y,Z$ are fermions. If $C$ is violated, $$\Gamma(X\to Y+Z)\neq \bar{\Gamma}(\bar{X}\to\bar{Y}+\bar{Z}).\tag{1}$$ However, ...
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What happens to $\theta_{CP}$ for ${\rm U}(1)$ in the Standard Model?

I'm trying to understand how we can get rid of the ${\rm U}(1)$ theta term (whose $\theta$ I call $\theta_1$) in the SM. In Schwartz's QFT textbook he writes Before discussing the strong CP phase ...
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Regarding matter-antimatter asymmetry

We all know that the asymmetry between matter and antimatter is a big puzzle in physics. But I don't know why one expects matter-antimatter symmetry in the first place? As in, is there a fundamental ...
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Electric dipole moment (EDM) and dilogarithm with complex argument

In the paper https://arxiv.org/abs/1310.1385 it's calculated the electron electric dipole moment (eEDM) in terms of a function $f_1(x)$ defined as $$ f_1(x) = \frac{2x}{\sqrt{1 - 4x}}\left[Li_2\left(...
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A pair-universe solution to CP-violation problem [closed]

Disclamer Before I continue, I'd like to state clearly that I'm by no means an expert in this field. What I regularly do is read popular literature on this topic (if such a thing could be considered '...
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Electric dipole moment (EDM) and CP violation

It's well known that a non-zero value for the electric dipole moment (EDM) would imply CP violation. If we consider the interaction Hamiltonian of an EDM $d$ with an electric field $\vec{E}$, $$ H = -...
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Are antileptons and antibaryons linked?

The recent news about the T2K experiment got me thinking: is there any linkage in the Standard Model between the matter and antimatter categories across the families of Standard Model particles? Are ...
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Neutrino Oscillation Transition Probability With CP Violation

The transition probability for neutrino vacuum oscillation is $P_{\nu_{\alpha}\rightarrow\nu_{\beta}}=\delta_{\alpha\beta}-4\sum_{k>j}\text{Re}\left[U^{*}_{\alpha k}U_{\beta k}U_{\alpha j}U^{*}_{\...
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What do you mean by in the mirror world?

I was trying an attempt to replicate Wu experiment mentally when I heard the term mirror world kept popping ups, why should we care what happens inside the mirror world? Is it a math thing?
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What is the antiparticle corresponding to the left neutrino $\nu_L$?

What is the antiparticle corresponding to $\nu_L$ ? -According to this thread : What distinguishes the behaviour of particle from its antiparticle: C violation or CP violation? "The operation that ...
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How is a T-violation inherited in a QFT?

CP violation In quantum field theory (QFT), ${\rm CP}$ symmetry or ${\rm CP}$ violation is a property of the Lagrangian. For a ${\rm CP}$ violating QFT, in general, the absolute square of the Feynman ...
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Does it mean time reverses if all particles were antiparticles and vice versa?

First of all, I'm not major in physics and the question might seems stupid, as I'm layman studying for my self-interest and I really don't know much about it. I only think it might open some ...
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CP violation and matter- anti-matter asymmetry

It is clear that C violation is a must for matter-antimatter asymmetry. But why CP violation also necessary for the same?
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7 votes
1 answer
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$CP$ Invariance of Yang-Mills Vacua in Electroweak Theory

It is well know that quantum Yang-Mills theory has a periodic vacuum structure. Consider electroweak theory. For a single generation of fermions, the theory is CP invariant. I would like to know if ...
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8 votes
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Why does the axion solve the CP problem?

I don't understand why the CP violating term in QCD vanishes when we introduce the axion. The term is $$\left(\frac{a}{f_a}+\theta\right)G\tilde{G}$$ It is claimed that $\left\langle a\right\rangle=-\...
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Is there violation of energy conservation when a particle transforms to its anti-particle, for example $B^0\to\bar{B}^0$, or $K^0\to\bar{K}^0$

additive information : $B^0$ and $\bar{B}^0$ don't have the same mass, $K^0$ and $\bar{K}^0$ don't have the same mass. is there energy violation? if yes, is the key explanation of this coming from the ...
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CP violation measurement

I have a question regarding the measurement of CP Violation in experiment. How is parity measured in an experiment? I know that in the direct measurement of CP violation we look at a particle process ...
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Detail on C vs. CP violation

In the answer given by knzhou to the post What distinguishes the behaviour of particle from its antiparticle: C violation or CP violation? it is said that "but the reaction $i \rightarrow f$ will ...
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6 votes
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How do we see that the axion is a pseudoscalar?

The axion is the pseudo-Goldstone boson associated to the breaking of the conjectured Peccei-Quinn Abelian symmetry. The axion couples to the SM gauge fields in a CP-invariant manner (e.g. $aF\tilde F ...
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2 votes
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Antiparticles, CPT and leptogenesis

When people are being careful they'll tell you that antiparticles are the CPT conjugates of particles. You can't say that they are C conjugates or CP because these, while they do reverse the charge, ...
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Is a constant electric field CP violating?

Consider, for instance, a fundamental massless three-form field $C_{\alpha\beta\gamma}$ in the Coulomb phase: $$ \mathcal L = E_{\mu\alpha\beta\gamma}E^{\mu\alpha\beta\gamma} + C_{\alpha\beta\gamma}J^...
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CP-symmetery conservation

How can one show that for a given decay, say $\pi^+ \rightarrow \nu_\mu + \mu^+$, CP-symmetry is conserved or violated? Is there a visual way of doing such?
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3 answers
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Can the CKM matrix supply the CP asymmetry as required by baryogenesis, in principle?

In the process of Baryogenesis through Leptogenesis from the decay of heavy Majorana neutrinos, the necessary CP violation is perhaps provided only by the CP phases in the PMNS matrix. But the Weak ...
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How does the global $G^2G'$ anomaly make all the $\theta$-vacua associated to the gauge group $G$ physically equivalent?

Consider a gauge group $G$ and suppose that there is a $\theta$-term associated to it. According to this answer, the existence of a global anomalous symmetry $G'$ which rotates the $\theta$-term, ...
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What does $B+L$ anomaly have to do with a phase redefinition of the left-handed quark field?

According to this answer, the reason why $SU(2)_L$ weak theory does not have a theta vacuum is because any theta term can be reabsorbed with a phase redefinition of the left-handed quark field. ...
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Does the weak force obey the CPT symmetry? How?

I have read that the weak force does not obey the charge symmetry, the parity symmetry, and the time reversal symmetry. Then how does it obey the CPT symmetry?
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How can spontaneous $P$ or $CP$ violation arise? Examples needed

In quantum field theory, there can be a spontaneous breakdown of discrete and continuous symmetries. Can there be a spontaneous breakdown of P and CP violation where P represents parity and C ...
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3 votes
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What distinguishes the behaviour of particle from its antiparticle: C violation or CP violation?

It is said that a CP violation would mean that the behaviour of the particle is different from the behaviour of antiparticle. Why is C violation not good/enough?
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What is unsolved in CP Violation?

I learnt about CP Violation in my Quantum Information Theory and Particle Physics courses. However I have not understood what exactly has not been solved yet about CP Violation. I thought that the ...
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About the asymmetry of baryons

I don't understand why CP violation is insufficient to explain the observed baryon asymmetry? And how do you solve it using the lepton sector? Key Words: CKM - Cabibbo-Kobayashi-Maskawa Matrix: in ...
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Parity violation

I've been reading on wikipedia about parity violation in the weak force and the conclusion is: This implies that parity is not a symmetry of our universe, unless a hidden mirror sector exists in ...
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CP Phases in the PMNS Matrix

I am interested in how to derive the correct number of CP violating phases in the neutrino mixing matrix (or PMNS matrix). My approach is the following. By hypothesis, the neutrino mixing is given by ...
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