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Questions tagged [hadron-dynamics]

66 questions
46
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9 answers

What are the strings in string theory made of?

This is a follow-up to an intriguing question last year about tension in string theory. What are the strings in string theory composed of? I am serious. Strings made of matter are complex objects that require a highly specific form of long-chain…
Terry Bollinger
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5 answers

How do we know that the nucleus isn't a quark-gluon plasma?

The standard picture of the nucleus of atom is that is several distinct nucleons, which themselves are composed of quarks. However, it seems to me like a much simpler picture is that the nucleus is directly made out of quarks, without having…
Itai Bar-Natan
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14
votes
2 answers

Nuclear physics from perturbative QFT

Is there a renormalizable QFT that can produce a reasonably accurate description of nuclear physics in perturbation theory? Obviously the Standard Model cannot since QCD is strongly coupled at nuclear energies. Even the proton mass cannot be…
Squark
13
votes
2 answers

If massless objects ALWAYS travel at the speed of light and gluons are massless, how are they trapped within hadrons without a need for event horizon?

From what I heard, unless we have some kind of other influence, all things and light move at the straight lines in spacetime. If they have a mass, then they can never reach the speed of light, but all the massless ones are constantly traveling at…
Kusavil
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12
votes
1 answer

Chiral perturbation theory: what is the Quark Condensate? why expand in $U$ rather than Goldstone fields?

I'm studying Chiral Perturbation Theory ($\chi PT$) from Scherer's Introduction to Chiral Perturbation Theory. What I am currently having some trouble understanding are two things: The quark condensate. What is this and why is it a sufficient…
kloptok
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10
votes
2 answers

In less technical language, what exactly is a "gravitational form factor"?

The term "gravitational form factor" is a term I don't recall ever seeing before the year 2018 (about three decades after I started reading physics papers). I have read several recent papers about them, most recently, this one, claiming to have…
ohwilleke
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10
votes
2 answers

Why does the Walecka model not include pions?

The Walecka or $\sigma$/$\omega$-model is an effective theory describing nucleon-nucleon interaction by an exchange of $\sigma$/$\omega$-mesons. Why does it not include interactions by pions?
dan-ros
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8
votes
2 answers

Why do quarks and antiquarks tend to bond in groups in which the number of quarks minus the number of antiquarks is divisible by 3?

Why do quarks and antiquarks tend to bond in groups with quark number a multiple of 3? I understand why they might in bond in groups of three to create a net charge of zero (i.e. neutrons), but I don't understand why they form protons and not, for…
Mason
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7
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2 answers

Where do negative powers of $f_\pi$ in the hadronic amplitudes come from?

According to Peskin and Scrhroeder the pion decay constant $f_\pi$ is defined via the following matrix element $$\left\langle0|j^{\mu5a}(x)|\pi^b(q)\right\rangle=-if_\pi \delta^{ab} q^\mu e^{-iqx}$$ while $j^{\mu5a}=\bar{Q}\gamma^\mu\gamma^5\tau^a…
Weather Report
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6
votes
1 answer

At what stage is it necessary to introduce a field theory in the regeon-pomeron-odderon model of hadron interactions?

I've been reading some papers from G.F. Chew and S. C. Frautschi and they do not even bother to introduce the concept of "Field" when they describe hadron interactions. My impression is that they do not need to because interactions seem to be…
Carlos L. Janer
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5
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1 answer

Emergence of Dual Resonance model from QCD

This question is about getting to understand better what the Dual Resonance (DR) model actually managed to successfully predict or model from the nuclear interactions, in the context of understanding what aspects of the DR are expected to be…
lurscher
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5
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2 answers

How do we decide the proton wave function?

The fully symmetric spin-up proton spin-flavour wave function in the constituent quark model is usually presented as follows: $$\begin{align} \frac{1}{\sqrt{18}} ~ ( &2 |u\uparrow ~ u\uparrow ~ d\downarrow \rangle - |u\uparrow ~ u\downarrow ~…
Craig
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5
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2 answers

Yang-Mills theories, confinement and chiral symmetry breaking

I was thinking about hadrons in general Yang-Mills theories and I have some doubts that I'd like to discuss with you. Suppose that we have a Yang-Mills theory that, like QCD, tend to bind quarks into color singlet states. So far nothing strange,…
Cervantes
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5
votes
1 answer

Can the effective vertex for $\gamma\to3\pi$ be derived directly from the anomaly?

My question is whether the effective vertex for $\gamma\to3\pi$ can be derived directly from the anomaly (given in the first equation below), in analogy with the $\pi^0\to2\gamma$ vertex? As far as I understand, based on the anomaly one can derive…
Weather Report
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5
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1 answer

A pedagogical exposition of the hadron physics?

I am looking for a textbook/lecture notes/etc. on the basics of hadron physics. I wish to understand how to construct the effective Lagrangian for pions and nucleons starting from the QCD Lagrangian. In other words,…
Weather Report
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