# Quark Content of these resonances

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1. Jan 16, 2015

### kuchenvater

Hi. I was reading an introductory book about particle physics and I visited the PDG for an exercise.
I found this....
http://pdg.lbl.gov/2014/tables/rpp2014-tab-mesons-strange.pdf
On page 9, the data of K1(1270) is given. How do I figure out it's quark content? If I look at the data for K*(892), it's easy to compare the data with the legend/key given right at the top of the pdf and figure out the quark content because the it mentions neutral and +/- resonances of K*(892) distinctly. But no such data is given for K1? Does it also have neutral and +/- varieties? Can I use some other property of this resonance to figure out its quark content? Am I missing something obvious here?

2. Jan 16, 2015

### samalkhaiat

Why do you think resonances have different quark content?

3. Jan 16, 2015

### kuchenvater

I thought since there are neutral and charged varieties of K*892, K1(1270) must have something similar going on... And as soon as their charges differ, their quark content would vary according to what's given in that box right at the top of the first page.
What is it's quark content then? There are multiple resonances in that data sheet with different I and JPC values. How do I figure out the quark content of each of those?
The s quark/antiquark is a given, how do I figure out whether the other quark is u or d?
Sorry, I'm a beginner in HEP.

Last edited: Jan 16, 2015
4. Jan 16, 2015

### samalkhaiat

All mesons (ordinary $0^{ - }$ and resonances $1^{ - }$) have the same quark content $q \bar{ q }$, the so-called Meson Octets. For example $K^{ 0 } \sim K^{ * 0 } = \bar{ s } d$, $K^{ + } \sim K^{ * + } = \bar{ s } u$ and $K^{ - } \sim K^{ * - } = \bar{ u } s$. You need to study the representation of the flavour group $SU(3)$

5. Jan 16, 2015

### kuchenvater

What about K1 (1270) though? It's straightforward if you are dealing with a direct analogue like K0 and K*0.
What if it's K2 K2*, with completely different masses(1420 vs 1770)? Or K1 (1270) K1(1400)? Is their quark content identical despite the mass difference? If so why?
Maybe I'm having trouble phrasing this or maybe my knowledge isn't enough but I can't find anything about this in my books either.

6. Jan 16, 2015

### samalkhaiat

Resonances are EXCITED STATES, they have different mass (energy) but the SAME structure. Does the ecited Hydrogen Atom has different structure (electronic content)?

7. Jan 16, 2015

### kuchenvater

Ah. Right. Thanks. This is embarrassing.
So, K1 is an excited state of...K? K+/-? Or K0? Or K*?

8. Jan 20, 2015

### kuchenvater

In case of the Delta baryon, it exists in four resonance states: two are excited analogues of the neutron and the proton and the other two are totally different. All four have different quark content. What I'm asking is in case of K1(1270) : is it an excited version of a certain kaon(and if so which one?) Is there a way to determine its quark content or wavefunction? Or are there differently charged varieties of K1(like there are of K*892) with all different quark contents?
http://pdg.lbl.gov/2014/tables/rpp2014-tab-mesons-strange.pdf

9. Jan 20, 2015

### samalkhaiat

You are asking incorrect questions about subject you don’t understand yet. So, I would suggest that you get an elementary textbook about particle physics. Only then you will understand that resonances are excitations which appear in hadronic scattering processes and therefore differ only in orbital angular momentum.
As for the lowest $(3/2)^{ + }$ baryons decuplet, it actually is ground state.
The quark content of any meson is determined by the charge and the strangeness of that meson. So, whether it is $K_{1}$ or $K_{ x }$ (whatever they might be), you need to know the charge and the strangeness of your meson.