Quark Content of these resonances

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SUMMARY

The discussion centers on determining the quark content of the K1(1270) meson using data from the Particle Data Group (PDG) reference. Participants clarify that all mesons, including K1(1270), share the same quark structure despite differing masses, as they are excited states of kaons. The quark content is primarily influenced by the meson's charge and strangeness, with the K1(1270) being an excited state of a kaon. Understanding the flavor group SU(3) is essential for analyzing these resonances.

PREREQUISITES
  • Basic knowledge of particle physics concepts, including mesons and baryons.
  • Familiarity with the flavor group SU(3) and its implications in particle classification.
  • Understanding of quark content and how charge and strangeness determine it.
  • Experience with reading and interpreting scientific data tables, such as those from the PDG.
NEXT STEPS
  • Study the flavor group SU(3) and its role in particle physics.
  • Learn about meson classifications and their quark content, focusing on K mesons.
  • Investigate the properties of excited states in particle physics and their implications.
  • Review introductory textbooks on particle physics to solidify foundational knowledge.
USEFUL FOR

This discussion is beneficial for students and enthusiasts in high-energy physics (HEP), particularly those interested in meson properties and quark content analysis.

kuchenvater
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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?
 
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kuchenvater said:
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?
Why do you think resonances have different quark content?
 
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:
kuchenvater said:
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.

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)
 
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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.
 
kuchenvater said:
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.
Resonances are EXCITED STATES, they have different mass (energy) but the SAME structure. Does the ecited Hydrogen Atom has different structure (electronic content)?
 
Ah. Right. Thanks. This is embarrassing.
So, K1 is an excited state of...K? K+/-? Or K0? Or K*?
 
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
 
kuchenvater said:
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

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.
 

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