Quark Content of these resonances

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Discussion Overview

The discussion revolves around the quark content of the K1(1270) resonance in particle physics, particularly in comparison to other mesons like K*(892). Participants explore how to determine the quark content based on available data and properties, while also questioning the implications of different resonances and their characteristics.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Conceptual clarification

Main Points Raised

  • Some participants inquire about the quark content of K1(1270) and whether it has neutral and charged varieties similar to K*(892).
  • Others suggest that the quark content can be inferred from the properties listed in the data sheet, but express uncertainty about how to apply this to K1(1270).
  • There are discussions about the relationship between different resonances, such as K1(1270) and K2, and whether their quark content remains the same despite differences in mass.
  • Some participants mention that resonances are excited states and question if this affects their quark content.
  • One participant points out that the quark content of mesons is determined by their charge and strangeness, emphasizing the need for this information to ascertain the quark content.
  • A later reply challenges the framing of questions about the quark content, suggesting a need for foundational knowledge in particle physics.

Areas of Agreement / Disagreement

Participants express uncertainty and differing views on how to determine the quark content of K1(1270) and whether it has varieties like K*(892). The discussion remains unresolved with multiple competing perspectives on the topic.

Contextual Notes

Participants acknowledge limitations in their understanding of the subject, and there are references to the need for foundational knowledge in particle physics to clarify concepts related to resonances and quark content.

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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