A Universal picture of hadron interactions?

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Discussion Overview

The discussion revolves around the total cross-sections of various hadron interactions and their description through Reggeon and Pomeron trajectories. Participants explore the implications of these models, particularly in the context of photon-proton interactions, and question the underlying mechanisms that lead to the observed accuracy of these theoretical predictions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that the total cross-sections for hadron interactions can be described by a single Reggeon trajectory and a single soft Pomeron trajectory, providing specific mathematical expressions for various interactions.
  • There is confusion regarding the photon-proton interaction, with one participant questioning why the photon and proton exchange a Reggeon and Pomeron trajectory instead of behaving according to Compton scattering principles.
  • Another participant suggests that virtual quark loops in the photon propagator could explain the behavior of the photon in these interactions, seeking references to support this idea.
  • A later reply references historical literature on photon-rho mixing and discusses the complexities of QED in the context of strong interactions, noting that the scattering is dominated by strong interactions rather than electromagnetic effects.
  • One participant emphasizes that the vacuum in QCD is perturbed by protons, leading to a cloud of vacuum deformation that facilitates the exchange of bound states, although they acknowledge the lack of a quantitative theory to fully explain this phenomenon.
  • Another participant expresses gratitude for the references provided and indicates a willingness to explore the suggested literature further.
  • There is a side discussion regarding the relevance of the thread to the banning of a participant, with one individual seeking clarification on whether their questions are aligned with mainstream physics.

Areas of Agreement / Disagreement

Participants express varying degrees of understanding and interpretation regarding the mechanisms of hadron interactions, particularly concerning the role of the photon. There is no clear consensus on the explanations provided, and multiple competing views remain regarding the underlying physics.

Contextual Notes

Participants note the limitations of current theories in quantitatively addressing the observed phenomena, particularly in relation to the complexities introduced by massless photons and the nature of vacuum perturbations in QCD.

Anashim
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As far as I know, the total cross-sections of the following hadron interactions are well described
by a single Reggeon trajectory and a single Pomeron (soft Pomeron) trajectory.
  1. ##K^-p: (11.93s^{0.0808}+25.33s^{-0.4525})mb##
  2. ##K^+p:(11.93s^{0.0808}+7.58s^{-0.4525})mb##
  3. ##\bar pn:(21.70s^{0.0808}+92.71s^{-0.4525})mb##
  4. ##pn:(21.70s^{0.0808}+92.71s^{-0.4525})mb##
  5. ##p\bar p:(21.70s^{0.0808}+98.39s^{-0.4524})mb##
  6. ##pp:(21.70s^{0.0808}+56.08.39s^{-0.4524})mb##
  7. ##\pi^-p:(11.63s^{0.0808}+36.02s^{-0.4525})mb##
  8. ##\pi^+p:(11.63s^{0.0808}+7.58s^{-0.4525})mb##
  9. ##\gamma p:(0.0677s^{0.0808}+0.129s^{-0.4525})mb##
The last expression is hard for me to understand: in the ##1## to ##20 GeV## range the photon and the proton seem to exchange a Reggeon trajectory and a Pomeron trajectory, although I would tend to think that it should be some kind of Compton scattering. I just don't get it, the only charge a photon sees is the EM charge! Could anyone, please, offer a reasonable explanation?Why are these results so unexpectedly accurate? This is a theory I do not particularly like but its results are very precise, specially if you add multiple Pomerons and the Odderon. No other phenomenological model is able to match its results.

These plots can be see in slides number 35 and 36 of the following presentation (from a physicist working at the "KEK Theory Center"):

https://indico2.riken.jp/event/2729/attachments/7480/8729/PomeronRIKEN.pdf
 
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Anashim said:
The last expression is hard for me to understand
Virtual quark loops in the photon propagator?
 
mitchell porter said:
Virtual quark loops in the photon propagator?

Do you mean that renormalization via virtual quark loops makes a real photon behave like a neutral meson? Could you, please, provide some references?
 
Anashim said:
Do you mean that renormalization via virtual quark loops makes a real photon behave like a neutral meson? Could you, please, provide some references?

1970s picture of photon-rho mixing, there is a review by Kurt Gottfried in an early 1970s QED conference hosted at Cornell. It's referenced in Feynman's "Photon Hadron Interactions".
 
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Anashim said:
As far as I know, the total cross-sections of the following hadron interactions are well described
by a single Reggeon trajectory and a single Pomeron (soft Pomeron) trajectory.
  1. ##K^-p: (11.93s^{0.0808}+25.33s^{-0.4525})mb##
  2. ##K^+p:(11.93s^{0.0808}+7.58s^{-0.4525})mb##
  3. ##\bar pn:(21.70s^{0.0808}+92.71s^{-0.4525})mb##
  4. ##pn:(21.70s^{0.0808}+92.71s^{-0.4525})mb##
  5. ##p\bar p:(21.70s^{0.0808}+98.39s^{-0.4524})mb##
  6. ##pp:(21.70s^{0.0808}+56.08.39s^{-0.4524})mb##
  7. ##\pi^-p:(11.63s^{0.0808}+36.02s^{-0.4525})mb##
  8. ##\pi^+p:(11.63s^{0.0808}+7.58s^{-0.4525})mb##
  9. ##\gamma p:(0.0677s^{0.0808}+0.129s^{-0.4525})mb##
The last expression is hard for me to understand: in the ##1## to ##20 GeV## range the photon and the proton seem to exchange a Reggeon trajectory and a Pomeron trajectory, although I would tend to think that it should be some kind of Compton scattering. I just don't get it, the only charge a photon sees is the EM charge! Could anyone, please, offer a reasonable explanation?Why are these results so unexpectedly accurate? This is a theory I do not particularly like but its results are very precise, specially if you add multiple Pomerons and the Odderon. No other phenomenological model is able to match its results.

These plots can be see in slides number 35 and 36 of the following presentation (from a physicist working at the "KEK Theory Center"):

https://indico2.riken.jp/event/2729/attachments/7480/8729/PomeronRIKEN.pdf

The question is "why does Regge exchange work". Forget about the photon, the scattering is strong-interaction dominated, and would be the same for two neutrons. The QED part is annoying because it doesn't really have a well-defined cross section, because of log-annoyances due to massless photons, people just ignore the charge effects in these cross sections. There is no quantitative theory which can answer this. The best way to understand it qualitatively is that the vacuum in QCD is perturbed by a proton so that there is a cloud of deformation of the vacuum glue and quark condensates, and the protons exchange bound states which define the vacuum deformation. The best reference is Gribov's book "Theory of Complex Angular Momentum", but you should look at all the Regge literature of the late 60s, because this is not covered well anywhere, including later string books.
 
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Ron Maimon said:
1970s picture of photon-rho mixing, there is a review by Kurt Gottfried in an early 1970s QED conference hosted at Cornell. It's referenced in Feynman's "Photon Hadron Interactions".
Ron Maimon said:
The question is "why does Regge exchange work". Forget about the photon, the scattering is strong-interaction dominated, and would be the same for two neutrons. The QED part is annoying because it doesn't really have a well-defined cross section, because of log-annoyances due to massless photons, people just ignore the charge effects in these cross sections. There is no quantitative theory which can answer this. The best way to understand it qualitatively is that the vacuum in QCD is perturbed by a proton so that there is a cloud of deformation of the vacuum glue and quark condensates, and the protons exchange bound states which define the vacuum deformation. The best reference is Gribov's book "Theory of Complex Angular Momentum", but you should look at all the Regge literature of the late 60s, because this is not covered well anywhere, including later string books.

Ok thank you very much for the info. I will read both books, although I suspect that it's going to take me awhile.
 
Me asking about the ##\gamma p## elastic scattering has anything to do with Ron Maimon being banned? I am not aware of having asked anything unrelated to mainstream physics, but if I have, I would be grateful if anybody could tell me what it is, so that, in the future, I can avoid the topic. Moreover, if I have, I guess it's only fair to ban me, not him.
 
Last edited:
Anashim said:
Me asking about the ##\gamma p## elastic scattering has anything to do with Ron Maimon being banned? I am not aware of having asked anything unrelated to mainstream physics, but if I have, I would be grateful if anybody could tell me what it is, so that, in the future, I can avoid the topic. Moreover, if I have, I guess it's only fair to ban me, not him.
We do not discuss bans, but I can say that this thread has nothing to do with it.
 

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