Questions tagged [baryons]
Baryons are hadrons (particles composed of quarks) with an odd number, at least 3, of valence quarks. The term is also often used in astrophysics, e.g. "baryonic matter", with a much looser definition understood to mean any matter composed mostly of baryons, but which may also include leptons and other particles, often in opposition to "dark matter".
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What is the connection between matter in the universe and the baryon number not being conserved?
Towards the end of "Quarks, the Stuff of Matter", the author discusses the implications of the proton is not stable and ultimately decays. He states, that if the proton decays, then the ...
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Why can't $uus$ and $uds$ quark content have $I = 1$ Isospin?
Well, I know the isospin singlet with $I=0$ and isospin triplet with $I = 1$. But for $I = 0$, why it must be $uds$ quark content rather than other assembly like $uus$ or $dds$? $ud$ can have $I = 0$ ...
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Which hadrons were present after the phase transition from the post-Big Bang QGP?
This question relates to the "hadron epoch" (after the initial quark-gluon plasma, but before the end of baryogenesis).
My understanding is that the phase transition that ends the quark-...
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Confusion about baryon number violation in the standard model
I'm reading Gauge Theory by David Tong and not understanding the concept of baryon number violation. I understand that the massless Dirac field has two symmetries, an $e^{i\theta}$ $U(1)$ symmetry and ...
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ELi5- How do pions hold nuclei together if they are so short-lived?
I need help understanding how particles do what they do and maintain the structures they maintain if so many of them exist for such a short time?
In the case of the nucleus and pions, pions only exist ...
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Octet and decuplet baryon wavefunction
I read the octet and decuplet baryons symmetric and anti-symmetric wavefunction from 'Riazzudin and Fiazzudin's book. But I am little confused about the wavefunction of neutral sigma and Lambda baryon....
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Baryon wavefunctions
The textbook I am currently using states that when all quarks have the same flavor, there are no $J=1/2$ baryon wavefunctions for the ground state $l=0$.
Is this an experimental result or is there a ...
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$J=1/2$ and $J=3/2$ Baryons with $uds$ quarks
Why are there two different $J = \frac{1}{2}$ baryons with quark content $uds$ (the $\Lambda_{0}$ and $\Sigma_{0}$) but only one $J = \frac{3}{2}$ baryon (the $Σ_{*,0}$) with the same quark content?
I ...
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Derivative of a "particle" field
Working with Lagrangian we often encounter derivatives of particles fields, for example let's consider the first term of the LO chiral Lagrangian
$$ \mathcal{L}_{B\phi}^{LO}=\text{Tr}[\overline{B}(i\...
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Quark structure of Baryons
I was studying Particle Physics then suddenly I came up with a question that why only Baryons are made up of three quarks, at first I thought to to conserve Baryon number which is $\frac{1}{3}$ for ...
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Baryon Number Conservation
To my understanding, every conservation law is associated with some continuous symmetry in the relevant theory. Then what is the symmetry associated with the conservation of Baryon number?
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Is there any way to think of Quarks in a baryon with Clebsch-Gordan coefficients?
I'm wondering if this idea is as un-natural as it feels in my head. My understanding of CGC's is that I have various fractional spin states like:
$$
\text{particle 1:} \ |j_1=\frac12, m_2=\frac12,-\...
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Method of Neutral Particle Mass Calculations from Bubble Chamber Images
I am looking into events within bubble chamber images and have come across a stumbling block. It relates to finding masses of neutral particles within bubble chamber images, specifically the mass of ...
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Total number of particles in the universe (according to Planck Surveyor measures, 2018)
Recently, Marco Ajello et al. (2018) has estimated the total number of photons in the whole observable universe as:
$$N_\gamma \approx 4\cdot 10^{84}$$
on the other hand, the ratio of baryons to ...
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On the quark composition of baryons
Baryons are made of three quarks, in the form $\vert qqq \rangle$. If we consider just the isospin doublet $u$ and $d$, there are 8 total possibilities:
Now, the first 4 are respectively $\Delta^{++}...
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What is the modern status on the Skyrmion theory of baryons?
It was noticed in the 1960s that chiral perturbation theory, describing the goldstone-bosons (pions) of the breaking $SU(N_f)_L \times SU(N_f)_R \to SU(N_f)_V$ of the chiral symmetry, has solitonic ...
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Finding $\Sigma$ wavefunctions from proton wavefunction. Any operator which can achieve this?
Knowing the isospin part of the wavefunction of the proton, it is possible to find that of the neutron by applying the isospin lowering operator $I_-$ which sits horizontally to the left of the proton ...
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Which force is responsible for $\Sigma$(1385) decay?
I was looking at the excited state of the $\Sigma^+$, the $\Sigma^{*+}(1385)$, on Wikipedia. I was wondering which forces are responsible for its two most dominant decays
$$ \Sigma^{*+}(1385) \to \...
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Spinor index contractions for baryons
For an $SU(N)$ QCD with $N_f$ flavours one writes baryons as
\begin{equation}
B^{{a_1}…a_{{N}_f}}=\epsilon^{i_1…i_N}\psi_{i_1}^{a_1}… \psi_{i_N}^{a_{Ν_f}}
\end{equation}
by contracting the colour ...
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Could exotic baryons be stable inside exotic stars?
Neutrons are stable inside a neutron star because beta decay doesn't release enough energy to send the proton and electron up to the Fermi energy. Could this principle apply to baryons that have charm,...
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What is the value of the baryon asymmetry? [duplicate]
Define the baryon asymmetry, which sometimes is called the baryon density, as the baryons to photons ratio $\eta = n_b/n_\gamma$.
I found in Ref. 1, published in 2018, that the value of $\eta$ is of ...
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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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Higgs decay into baryon-antibaryon pair
I have an exercise for "Introduction to high energy physics" and I'm baffled. The exercise states:
Problem: Higgs particle of mass 125.7 GeV decays in an exclusive channel of baryon-...
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Mass of baryons and their spin state. Is there any connection?
Baryons are made of three quarks which are spin-1/2 particles. According to the rule of addition of angular momentum, baryons can have either spin-1/2 or spin-3/2. It is intriguing to note that light ...
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Nucleon resonance
I tried to fit low baryon resonances to N(1440) in an SU(3) octet.
So I started with
$$\frac{N + \Xi}{2} = \frac{3 \Lambda + \Sigma}{4}$$
What should the respective $\Lambda (I=0), \Xi(I=\frac{1}{2})...
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Gell-Mann—Okubo formula
How was the Gell-Mann—Okubo formula
$$
M = a_0 + a_1 Y + a_2 \left[ I \left( I + 1 \right)-\frac{1}{4} Y^2 \right]
$$
rewritten using isospin and strangeness to this formula?
$$\frac{N + \Xi}{2} = \...
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Why can't $\Sigma$ baryons decay strongly?
First of all, I must say this is a homework question. The complete question includes particles like $p$, $e^-$, $\Lambda$ and $\Omega$.
It's pretty easy to understand why $\Omega$ and $\Lambda$ have ...
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Why are Delta baryons called "Delta isobars"?
A lot of people seem to call the $\Delta$ baryon "Delta isobar", however there is no mention of "isobar" on its Wikipedia page. Am I missing something? Why do people use the term &...
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Probabilities of $ \Omega^- $ baryon decay
The $ \Omega^- $-decay can occur in a few different ways. According to this document (page 3, $\Omega^−$ DECAY MODES), the three most probable decays are
\begin{align}
\Omega^- &\to \Lambda^0 + ...
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’t Hooft anomaly matching and massless baryons
In Lectures on Gauge Theory by David Tong there is statement (section 5.6.3 The Vafa-Witten-Weingarten Theorems), that:
To invoke the full power of ’t Hooft anomaly matching, we needed to assume that ...
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Is it possible that rescuing the Idea of a Baryo/lepto-dynamic Field had some Relevance in the FermiLab Result?
We know that Fermilab, Brookhaven, and other laboratories have found discrepancies with the SM.
One option that almost immediately comes to mind is that the so-far exact conservation law of baryon and ...
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Baryon to photon ratio
In Dodelson's "Modern Cosmology", the current baryon-to-photon ratio is defined as $$ \eta_b \equiv \dfrac{n_b}{n_\gamma} = 5.5 \times 10^{-10} \left(\dfrac{\Omega_b h^2}{0.020}\right). $$
I ...
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What fraction of the mass of all baryonic matter are black holes?
Is there a calculation of how much of the mass of baryonic matter is black holes, including supermassive black holes in the center of galaxies?
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Like quark baryons
Why aren't there particles like neutrons or protons but with 3 up or 3 down quarks, instead of 2 up/1 down or 2 down/1 up. Does there have to be 2 different types of quarks for the strong force to ...
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How does the process $\bar{K}^0+p \to \Lambda^0+\pi^+$ work?
I was asked to find an energy for the $\bar{K}^0+p \to \Lambda^0+\pi^+$ interaction for an exercise and I got curious about how the Feynman diagram for this process would look like.
In terms of quarks,...
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Is the process $\pi^{-}+p^+\to\bar{n}+n+n $ allowed?
Is the process $\pi^{-}+p^+\to\bar{n}+n+n $ allowed?
Is there any collision involving only the mesons and baryons that would produce antibaryons (along with other particles)?
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What happens to extra-galactic rays when they arrive at the solar system?
Quazars send baryons from other galaxies towards us which are deflected from by the local magnetosphere. The early solar system probably picked up many millions of extragalactic cosmic rays for every ...
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Is the baryon number consistent when it comes to annihilation?
I've previously asked a question on here about if it was possible to change the barion number by radioactive decay, for example positron emission, and the answer was of course no, as the baryon number ...
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Could a Λ or Σ baryon be stable inside a nucleus?
A common "cartoon model" of a nucleus is that there are a set of bound energy levels for the protons and a similar set of bound energy levels for the neutrons. The existence of these energy ...
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Can protons and neutrons be completely converted into Leptons?
In beta decay, a neutron releases an electron and turns into a proton. The inverse happens, though usually not naturally, in positron emission, where a proton emits a positron and becomes a neutron. ...
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Can indistinguishable particle wavefunctions be written as a product of total observable eigenstates?
Consider the wavefunction of say two electrons in an external potential, associated with two possible states $\phi_a$ and $\phi_b$. Furthermore, each electron can have two spin states $\chi_1$ and $\...
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Can a baryon consist of two quarks and an antiquark? Or a pentaquark be made of three quarks and two antiquarks? [duplicate]
I suspect these particles exist, but are extremely short-lived, even compared to other unstable, exotic particles...
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Baryon number vs electromagnetic charge, what is the difference?
What exactly is a Baryon number? I looked up definition from wikipedia and still struggle to understand this. And how does this differ than the
electromagnetic charge?
My textbook did the following ...
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Understanding Baryonic Acoustic Oscillations
I was reading the book of Barbara Ryden "Introduction to cosmology":
In the chapter number 9, in the page 203. She says:
"The photons, electrons, and protons together make a single ...
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Why is the density of atoms in space so much higher than the baryon density from BBN and CMB?
If you ask the question: "how many atoms per cubic meter in space", you can get a consensus of around $5$ atoms per cubic cm or about $5\times 10^6\space \text{atoms}\space m^{-3}$. If we ...
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What is the (model independent) density of baryons in the Universe?
I know that Planck has measured the baryon density, $\Omega_B$, as a fraction of the critical density, $\rho_{CRIT}$. Is there a measurement of baryon density that's independent of the critical mass ...
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Why are semileptonic decays of the $\Lambda$ baryon so suppressed?
Looking at the Particle Data Group tables of the $\Lambda$ baryon, I find that the rate of the hadronic decay $\Lambda \to p \pi^-$ is 64% while the semileptonic decay $\Lambda \to p e^-\nu_e$ has the ...
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Why are the lifetimes of the neutral and charged $\Xi$ hyperons so different?
According to the Particle Data Group, the lifetimes of the neutral and charged $\Xi$ baryons differ significantly: $\tau(\Xi^-) = (1.639 \pm 0.015) \times 10^{-10}$ s, while $\tau(\Xi^0) = (2.90 \pm 0....
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What is a "multicharge nuclei"?
When doing some reading on particle physics, I came across the concept of a "multicharge nuclei". A Google search of this phrase returns a number of research papers, but no definition for what a "...
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Fujikawa Jacobian for Baryon number anomaly
Reviewing the anomalies of the standard model, one knows that the Baryon number is not conserved because of an anomaly associated to the global $U(1)$ symmetry that quarks have. That is the current
$$...
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