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 ...

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34 views

C-parity violation evidence

I know about the CP-violation experiments from the 60's and the P-violation from the 50's. But, is there a similar experiment which displays (perhaps historically in the same way as the experiements ...
3
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1answer
35 views

Is CP problem the problem?

I've heard an argument that the question of smallness of QCD $\theta$ parameter is called the problem (namely, strong CP problem), since the other dimensionless couplings (like $\alpha_{s}$), are of ...
3
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0answers
18 views

CP violation in B meson system through mixing

Mathematically, $\left|\Gamma_{12}\right|<<\left|M_{12}\right|$ implies $\left|q/p\right|=1$,i.e there is no CP violation due to mixing. Please explain why it happens beyond this mathematical ...
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119 views

axion couplings

As I understand it, the axion $a$ originates from the spontaenous symmetry breaking of $U(1)_{PQ}$. This symmetry being anomalous, and because of the QCD vacuum structure, a non vanishing term like $\...
4
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38 views

CP-Symmetry of the axion field and decay constant

In the $U(1)$-Peccei-Quinn-Symmetry an axion field $a$ is introduced in order to solve the strong CP-Problem. It is said, that below a certain scale $f_{a}$ this symmetry is broken and you are able to ...
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28 views

Assume that one of the generation of quarks is massless then cp violation is still there in quark sector?

If one of the generation of quarks(say up and down) is massless then cp-violation is still there in quark sector?
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48 views

Baryon / lepton number violation equivalence in Sakharov conditions

In the Sakharov conditions for matter-antimatter asymmetry the requirement for the baryon number violation is often interchanged with lepton number violation. In the context of the Sakharov conditions,...
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16 views

Assuming that one of the quark is massless,can we still observe CP violation in the quark sector?

If the mass of the one of the quarks (say the up quark) is taken to be zero, can we still observe CP violation in the quark sector?
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21 views

B meson mixing and CP violation

From my understanding of CP violation in the weak interation only the $V_{ub}$ and $V_{td}$ terms in the CKM matrix contain the complex phase terms which introduce CP violation. In B meson mixing, ...
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1answer
12 views

Conservation of $C$-Parity and $P$-parity

Under what situations are $C$-Parity $C=(-1)^{L+S}$ and/or $P$-parity $P=-(-1)^L$ conserved? ( $L$ here is the relative angular momentum and S is the total intrinsic spin). It would make sense that ...
3
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49 views

How to determine if interaction is allowed?

I'm trying to determine if the reaction $$n\rightarrow p\pi^-$$ is allowed. First of, this doesn't list this as one of the decay modes of the neutron, so I suspect that it should not be allowed. ...
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1answer
128 views

Mirror/Parity symmetry in spin

We just saw parity symmetry and we were told about the experiments to see the non parity symmetry of disintegration, in particular one involving the reaction: $$^{60}Co\longrightarrow^{60}Ni+ e + \...
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7 views

Reactor experiments are independent of CP phase

In several papers and also in books I got that the reactor neutrino experiment to measure the value of $\theta_{13}$ is independent of CP violating phases. But what is the reason of it? Why the ...
3
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1answer
52 views

Does the Peccei-Quinn (PQ) mechanism require fine-tuning?

The strong CP problem: the QCD theta parameter can not be arbitrarily small due to 't Hooft's doctrine of naturalness (a parameter can be arbitrarily small only when putting it to zero provides an ...
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1answer
41 views

Direct vs. indirect CP violation: theoretical foundations

I know very little about the difference between direct and indirect CP violation. I've been studying QFT from Peskin and Schroeder's "An Introduction to QFT", and they don't seem to address this issue....
5
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1answer
75 views

Importance of CP violation

To explain the matter-antimatter assymmetry, CP should be violated according to Sakharov conditions. Charge conjugation is required as matter and antimatter have opposite charges but why Parity ...
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48 views

Would CP Violation happen in a universe with four spatial dimensions?

The weak force is the force that violates CP symmetry as the way it effects a particle depends on that particles handedness. Particles have a property known as spin although it is different from ...
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2answers
267 views

Topological susceptibility

In QCD we have strong CP violation (and hence a $\theta$-dependence of the theory) only if the topological susceptibility of the vacuum is nonzero: $<F\tilde{F},F\tilde{F}>_{q \rightarrow 0} =...
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15 views

T invariance in flavored meson system

Consider Kaon CP conjugate states $\left|K^{0}\right>$ and $\left|\bar{K^{0}}\right>$. The physical states i.e, eigenstates of effective hamitonian can be written as \begin{equation} \left|M_{a}...
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1answer
46 views

Wu experiment beta decay

maybe it's a stupid question. But in Wu experiment she showed that parity in not conserved in beta decay. So how to say on general that this is true for any weak force interaction?
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1answer
56 views

How was there an extra particle in the early universe?

According to theories.. In the early universe.. There were particles and anti-particles in equal number.. But there seems to be one extra particle against the number of anti-particles.. As the ...
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1answer
235 views

Understanding Kaon Mixing

While studying Neutral-Kaon mixing, I learnt that the way we observe them is through their decays to Pions. But the states that decay are not the particles/antiparticles themselves but their mixture. $...
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1answer
95 views

What is a dual field?

Can you give me an intuitive, physical understanding of a "dual field"? For example, the Hodge dual of the gluon field strength matrix $F$ is $\tilde{F}_{\mu \nu}=\epsilon_{\mu \nu \alpha \beta} F^{\...
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0answers
52 views

Condition for CP violation

I am studying how weak and strong phases lead to CP violation. I am following CP Violation by Branco. There is some algebra that I can not follow. Consider the process : $ a + \bar{a} \rightarrow b ...
2
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1answer
133 views

CP-violation in weak and strong sectors

There is a possible CP-violating term in the strong sector of the standard model proportional to $\theta_\text{QCD}$. In the absence of this term, the strong interactions are CP-invariant. In the ...
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2answers
85 views
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CP violation and arrow of time

Does CP (and thus T) violation imply a definite arrow of time? How does it relate to the thermodynamic one? Does the microscopic irreversibility reflect itself to macroscopic level? If not why?
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1answer
117 views

Direct and indirect CP violation

Experimentally, what is the difference between direct and indirect CP violation? An example of indirect CP violation is: $$ \Gamma(\overline{B}^0 \rightarrow B^0) \neq \Gamma(B^0 \rightarrow \...
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1answer
70 views

Why does the pion not undergo netural particle oscillation?

$K$, $B$ and now $D$ mesons exhibit neutral particle oscillation, where we see the spontaneous interchange between a particle and its antiparticle, i.e. $K^0 \Leftrightarrow \overline{K}^0$, $B^0 \...
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1answer
527 views

What is the status of Witten's and Vafa's argument that the QCD vacuum energy is a minimum for zero $\theta$ angle?

The argument, which I reproduce here from Ramond's `Journies BSM', is originally by Witten and Vafa in ($\it{Phys}$. $\it{Rev}$. $\it{Lett}$. 53, 535(1984)). The argument is that for $\theta = 0 $ (...
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1answer
68 views

How to separate different CP eigenstates?

Someone can tell me how to separate different CP eigenstates(even and odd) using angular distribution of B meson decay?
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1answer
91 views

What CP violating processes do we know of?

So, after going over my particle physics notes and some introducing literature, it seems the currently known processes we experimentally confirmed to be CP violating are Kaon mixing (an indirect ...
3
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1answer
340 views

anomalous chiral symmetry and the $\bar\theta$ parameter

I am studying anomalous $U(1)$'s, related to the strong CP problem, and I have some trouble with the origin of the parameter $\bar{\theta}$. We start with the QCD Lagrangian with the topological ...
4
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0answers
175 views

Strong CP Problem

So, as far as I know, the Strong CP Problem in QCD results from the theta angle term in the action: $i\theta\int_X F_\nabla\wedge F_\nabla$ where $\nabla$ is the gauge connection and $X$ is a manifold ...
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101 views

Origin of CP violation in CKM matrix?

I have already seen this question but I am not very familiar with the group theoretical framework of the Standard Model and was hoping for a more diluted answer. So I have come across this slide: ...
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1answer
391 views

Origin of phases in amplitudes in QFT

Amplitudes in QFT are typically real. I'd like to understand the physical meaning of an amplitude having a phase. I know of three ways that amplitudes can get a phase: If the couplings have an ...
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2answers
65 views

Lepto-genesis and electroweak theory

Is there any term in standard electroweak theory that breaks CP-symmetry and thus explains lepto-genesis?
14
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2answers
924 views

Yang-Mills CP violation

Why does a term proportional to $\left(F,\,\tilde{F}\right)\propto Tr\left[ F_{\mu\nu}\tilde{F}^{\mu\nu}\right]$ in the Lagrangian of the pure Yang-Mills theory violate CP?
3
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1answer
236 views

Which interaction violates T symmetry?

While reading Peskin and Schroeder (page 64) I come across this Although any relativistic field theory must be invariant under the proper orthocronous Lorentz group, it need not be invariant under ...
5
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1answer
76 views

How could one measure the necessary CP violation needed to account in the SM?

The Standard Model contains at least three sources of CP violation. The first of these, involving the Cabibbo–Kobayashi–Maskawa matrix in the quark sector, has been observed experimentally and can ...
5
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1answer
431 views

CP violation from the Electroweak SU(2)$_{weak,flavor}$ by $\int \theta F \wedge F $

Question: Why there is NO Charge-Parity (CP) violation from a potential Theta term in the electroweak SU(2)$_{weak,flavor}$ sector by $\theta_{electroweak} \int F \wedge F$? (ps. an explicit ...
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0answers
86 views

Could CP violation be exploited to violate the second law?

I don't understand well CP-violation, but since it introduces a microscopic irreversible process, couldn't it be somehow exploited to decrease entropy? For instance, if we could somehow use it to bias ...
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5answers
691 views

Matter-Antimatter Asymmetry in Experiments?

As I hope is obvious to everyone reading this, the universe contains more matter than antimatter, presumably because of some slight asymmetry in the amounts of the two generated during the Big Bang. ...
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56 views

B physics and CP violation

So I am studying CP violation in SM. Experimentalists are trying to study B meson decays now a days. B meson systems involve quarks from the third generation and hence B physics gives more information ...
1
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2answers
270 views

Conservation of Energy and CP violation

In classical mechanics there is Noether's theorem: If a system has a certain symmetry there is a related conserved quantity. Energy conservation is a result of a system being time invariant. This is ...
9
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1answer
363 views

Baryogenesis only at the Planck scale, or none at all?

I can think of three general ways of explaining why the universe contains more matter than antimatter: (1) Near the Planck time, the universe had zero baryon asymmetry, but at some later time, ...
3
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1answer
132 views

How to determine predicted CP violation for a given SUSY point?

I'm currently studying at the spectra of some supersymmetric models, and would like to know whether the parameter points I'm looking at are ruled out due to excessive CP violation. I am using SPheno, ...
6
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1answer
1k views

Theta parameter of QCD: Very small, periodic in $2\pi$ or both?

I've been learning about the theta parameter of QCD and I'm confused about the fact that it's supposed to be very small but at the same time some sources say that the Yang-Mills theory should be ...
2
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0answers
87 views

CP-symmetry and Ward identities and finite temperature

I have a few questions about Ward-identities which I summarize here. For each I am very greateful for answers and references to literature. Wikipedia states about Ward-identities: The Ward-...
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2answers
209 views

Do any good theories exist on why the weak interaction is so profoundly chiral?

I find the profound asymmetry in the sensitivity of left and right chiral particles to be one of the most remarkable analytical observations captured in the Standard Model. Yet for some, I've not ...