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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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$CP$-transformation for fermionic bilinears

I am trying to derive the transformation of the fermionic bilinear $\bar{\psi}\psi$ under $CP$ transformation. I know that $P$ acts as: $$\psi(t, \vec{x}) \xrightarrow{P} \gamma^0 \psi(t, -\vec{x})$$ ...
Damiano Scevola's user avatar
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How can baryonic CP violation contribute to the explanation of the large matter-antimatter asymmetry in our universe?

I have been doing baryonic CPV experimental search in the past few years. However, I never really get a good clue on this fundamental question. The thing is that CPV has only been found in the meson ...
RedQuark's user avatar
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Equivalence of axion to fermion couplings

In order to solve the Strong CP problem through the axion, we introduce the axion-gluon coupling $$ \dfrac{a(x)}{f_a} \text{Tr}\, G\tilde{G}.\tag{1} $$ In a similar fashion, we may introduce the axion-...
Gabriel Ybarra Marcaida's user avatar
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CP Violation in Neutrinos Requied for Standard Model Baryogenesis

CP violation is required for baryogenesis in the standard model, but CP violation in the quark sector due to the CP violating phase in the CKM matrix is too small to account for it. Following that, ...
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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 ...
qavidfostertollace's user avatar
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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 ...
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Furry's theorem in Electroweak and strong interactions

We can think of Furry's theorem as the consequence of $CP$ invariance of $QED$. For parity, the vector bilinear changes sign, hence, under charge conjugation, it should. The vacuum is $C$-invariant, ...
Tanmoy Pati's user avatar
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Doubt in Kaon decay problem

Reading the CP symmetry section from Griffiths elementary particles book, 2nd revised edition, page 146. As mentioned in the above picture the neutral kaon and its antiparticle form linear ...
Sagar K. Biswal's user avatar
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2 answers
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How does parity conservation follow from the Wu experiment?

The Wu experiment shows how parity symmetry does not hold for the weak force. However, how does this proof that parity conservation also doesn't hold? If my understanding is correct, the absence of ...
QuantumQuasar's user avatar
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Noether's Theorem application [duplicate]

So I know that Noether's theorem has a symmetry that corresponds to a conservation law. I was wondering what quantity is conserved in charge conjugation symmetry.
averageenjoyer1234's user avatar
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Axion production from vacuum realignment and the strong CP problem

I am trying to understand axions as a possible candidate for dark matter. My understanding of one of the mechanisms by which energy could up in the axion field is by an initial misalignment between ...
Panopticon's user avatar
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Jarlskog Invariant

Jarlskog Invariant is directly proportional to CP violation. I want to know why it's called "an invariant". What is the nomenclature of the Jarlskog Invariant?
Anil Sharma 's user avatar
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Can we save Feynman's martian rendez-vous with $CP$ violation?

There's a short part in The Feynman Lectures where he explains the why you should never shake a martian's left hand. He introduces a "martian" who we can only communicate with in some ...
Shep's user avatar
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Does CP symmetry dictates that a particle and its antiparticle behave the same when moving in opposite directions and how can I observe CP asymmetry?

I have started reading in particle physics very recently. I have been reading a bit about tau particles, and I came across the idea of CP symmetry and how it’s violation may present an explanation for ...
Belal Bahaa's user avatar
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QFT symmetry breaking and CP violation

Since the weak interaction violates CP symmetry but electromagnetism doesnt,does it mean that the electroweak fields also violates CP symmetry?Can a field which violates some symmetry be the product ...
appliedSciences's user avatar
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Fixing $CP$ phases to cancel CKM phases

When we try to see if the weak sector is $CP$ invariant, we $CP$ transform all the fields in the charged interactions terms and we get a condition involving the elements of the CKM matrix and the ...
Siupa's user avatar
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Why the long lived Kaon can not decay into two pions?

The short-lived and long-lived states of kaon $|K_1>$ and $|K_2>$ respectively have the following compositions if they are the eigen states of CP parity: $|K_1> = \frac{|K^0>\:-\:|\bar{K^0}...
Igris's user avatar
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Experimental searches for magnetic quadrupole moment

My professor mentioned that a particle with an intrinsic magnetic quadrupole moment would be CP violating in an analogous manner to how a particle with an electric dipole would be evidence for new ...
klippo 's user avatar
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Strong $CP$ problem and fine tuning

I have worked my way up to and through Srednicki's Quantum Field Theory chapter 94 and was also doing some reading on the internet about the strong $CP$ problem. Wikipedia's entry on the strong $CP$ ...
Cory's user avatar
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If the protons in a nucleus were replaced by antiprotons and the electrons by positrons what fundamental change would be introduced into the universe?

Exactly what the question says; If all the protons and electrons in every single atom in the universe were swapped for their anti-particles, what would essentially change?
Safiul's user avatar
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how can the virtual fermionic lines be vertical in kaon mixing feynman diagram?

how can the virtual fermionic lines be vertical in kaon mixing Feynman box diagram (or in general)? Wuouldn't this mean that they travel a distance $\neq 0$ in 0 time?
charm_quark's user avatar
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On neutral Kaon mixing

Kaons are not eigenstates of $CP$: $$ CP|K\rangle =|\overline K\rangle\\ $$ Why do we need to mix them? One answer I read is "since they both decay into $2$ or $3$ pions". Couldn't they ...
ric.san's user avatar
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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 ...
Learningthemath's user avatar
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1 answer
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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? ...
Craig's user avatar
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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: $...
krabby patty's user avatar
25 votes
3 answers
3k views

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 ...
Mathew's user avatar
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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 ...
Dr. phy's user avatar
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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?
darzan's user avatar
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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. ...
ann marie cœur's user avatar
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1 answer
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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 ...
Twinklestar's user avatar
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88 views

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?
Bastam Tajik's user avatar
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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 ...
thephysics17's user avatar
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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_{...
ann marie cœur's user avatar
2 votes
1 answer
375 views

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 ...
ann marie cœur's user avatar
8 votes
1 answer
1k views

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, ...
ann marie cœur's user avatar
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0 answers
72 views

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 ...
ann marie cœur's user avatar
2 votes
1 answer
516 views

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 &...
xpsf's user avatar
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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, ...
SRS's user avatar
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1 vote
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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 ...
Kris's user avatar
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4 answers
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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 ...
Ayush Raj's user avatar
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1 answer
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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(...
Vicky's user avatar
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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 '...
ercegovac's user avatar
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2 votes
1 answer
478 views

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 = -...
Vicky's user avatar
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1 vote
5 answers
152 views

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 ...
taciteloquence's user avatar
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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^{*}_{\...
bulmust's user avatar
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3 answers
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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?
user6760's user avatar
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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 ...
Mathieu Krisztian's user avatar
2 votes
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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 ...
SRS's user avatar
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