Questions tagged [quarks]

The quark model postulates that the hadrons such as protons and neutrons have an inner structure; quarks.

792 questions
Filter by
Sorted by
Tagged with
27 views

I have encountered myself with the following definition for $\pi$-fields as quark bilinears: $$\pi^a = i\bar{q}\tau^a \gamma_5 q \ ,\quad\text{with }\ q = \left(\begin{array}{c}u\\d\end{array}\right) ... • 591 3 votes 1 answer 78 views Why can't we insist that the strong interactions must preserve CP? I'm having some trouble wrapping my head around the strong CP problem. I know that the non-trivial vacuum structure of QCD induces the topological theta term in the strong sector of the SM, which is ... 12 votes 3 answers 4k views Why so much kinetic energy inside a proton? I'm reading 'Waves in an impossible sea' by Matt Strassler - a very good, popular science book, by the way - and he explains that the rest mass of a proton mostly comes from the kinetic energy of the ... • 699 1 vote 1 answer 81 views Quark condensate and VEV of \pi^0 In David Tong's lectures on the Standard Model I saw that there is a quark condensate, which is just a Vacuum Expectation Value (VEV) of the \bar{q}_{Li}\, q_{Ri} operator,$$ \left< \bar{q}_{Li}...
1 vote
71 views

I am trying to understand the different combinations of quarks in a hadron. I have seen that the positive pion is written as $\pi^{+}=u\bar{d}$, but I have not seen it written in the opposite order. ...
65 views

• 175
172 views

Is there something special about the $b$ quark?

I have seen many papers about measurements related to $b$ quarks, for example the forward-backward asymmetry of the $b$ quark or the decay width of $Z$ to $b \bar b$ pairs, but not so many for the ...
• 313
328 views

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 ...
• 99
58 views

'Elementary' particles (electrons) vs non-elementary particles (protons) regarding relativistic mass

Is there a possible slight difference between protons and electrons behaviour while they are accelerated at speeds that cause relativistic changes to their mass. Why am I asking that? Because for a ...
• 2,219
134 views

$J=1/2$ 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 ...
• 57
45 views

Matter-antimatter conversion in quarks

If in beta plus decay, regular matter such as the up quark can decay into a positron, I have to wonder under high pressure, could it be possible for a quark to decay into the antiquark of its opposite?...
1 vote
210 views

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 ...