Pomeron physics and QCD

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Levin's course Chapter 2, "The Great Theorems" is a "must" summary.

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It is alive and well, but out of focus, and nothing else in QCD, or elsewhere, can supplant its utility. In case you never noticed, in , the year Gell-Mann wrote his 2-page quark paper item 12 , the bulk of his research and publications was on vacuum trajectories and Regge theory. This was hardly a symptom of a collective community delusion or wrong-mindedness! It's just that soft physics is hard to do. The community moved away and only the old-guard creative Russian physicists stayed in.

What actually happened is that, in the 70s and early 80s, discovering new particles and confirming short distance QCD hard scattering, the confirmation of the tri-linear gluon coupling, quarkonia, But I don't know of any contributions of it to diffractive physics. So the answer to your questions "why? The QCD vacuum is the classic hic sunt dracones area, real and important as it might be But, hey! Reggeon Pomeron -hadron and reggeon-reggeon Pomeron-Pomeron scattering can be considered as a scattering of all possible real mesons lying on the Regge trajectory on hadrons for the Pomeron possible state is so called "glueball".

Conceptually it is similar to Hydrogen-hadron or Hydrogen-Hydrogen scattering Hydrogen is also "reggeon" in this sense , since Hydrogen has the spectrum of states, and each of them has its own probability to scatter on a hadron or another hydrogen atom. We can of course consider Pomeron as a mathematical object, but I prefer to have clear physical interpretation.

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The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. What exactly is a pomeron? Ask Question. Asked 1 year, 8 months ago. Active today. Viewed 1k times.

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Old theoretical sources such as this throw up a wall of math and seem to say that a pomeron is a purely mathematical object, whose meaning is not clear to me: The formal definition of Reggeon is the pole in the partial wave in t-channel of the scattering process. That mismatch confuses me, but Wikipedia goes even further and says the pomeron has been found: By the s, the existence of the pomeron as well as some of its properties were experimentally well established, notably at Fermilab and DESY.

Does this mean that the 'pomeron' is a group of mesons? If so, do you happen to know which group it is? Are they listed in the PDG or something? I tried to find links, not very successfully. I thought e. If you want a conventional "particle" like any other, you'd be as frustrated as trying to lasso a renormalon, an instanton, a sphaleron or a meron.

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It is the central tool in diffractive theory snobs call it "phenomenology" and the article details its role. It is not obsolete, and has not been superseded by anything else! But it is there. Cosmas Zachos Cosmas Zachos Roman Riutin Roman Riutin 1. New contributor. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.

Pomeron Physics and QCD

Post as a guest Name. Email Required, but never shown. This new object was named after the Russian physicist Isaac Pomeranchuk. It was originally called the pomeranchukon, but this was later abbreviated to pomeron. During the s it was found that, with the inclusion of the pomeron, Regge theory provides a very successful description of a huge quantity of experimental data.

This was summarised by Collins in a classic book, which was published in However, the phenomenology appeared to be complicated. It was not until the s that it became apparent that the reason for this was that the early data were at comparatively low energies. When higher-energy data became available, the phenomenology became much simpler Donnachie et al. Meanwhile, quantum chromodynamics QCD had been discovered in the early s.

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We discuss the Regge Ansatz for the pomeron and the two pomeron model. Then we present the results obtained from nonperturbative QCD. HD-THEP Pomeron Physics and QCD. O. Nachtmann1. Institut für Theoretische Physik. Universität Heidelberg. Philosophenweg 16, D Heidelberg.

It was natural to try to explain the pomeron in terms of QCD, and first attempts to do so were made by Low and by Nussinov These attempts were refined over the years, notably by Cheng and Wu and by Lipatov and his collaborators However, most of the recent work is based on what is known as perturbative QCD, which calculates physical quantities in powers of the strength of the force. But total cross sections are so large that the force must be too strong for such an expansion to be valid.

So Landshoff and Nachtmann began, in the late s the very difficult task of modelling it through nonperturbative QCD. Even now, we still cannot claim that we have more than a rough description of the pomeron in terms of QCD. See Figure 2. Two features of the pomeron may be seen in these fits.

That is, the latter exchanges are responsible for the difference between the cross sections shown in each of the two plots in Figure 2.

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Dispatch time is working days from our warehouse. This book describes the underlying ideas and modern developments of Regge theory, covering phenomenology, theory and experiment. Let us wish you a happy birthday! The formal definition of Reggeon is the pole in the partial wave in t-channel of the scattering process. I'm trying to explain

According to QCD, the basic mechanism for generating the force between quarks is the exchange of a gluon. As pomeron exchange does not correspond to the exchange of any of the particles listed in the data tables, a natural guess is that it is somehow related to gluon exchange. The simplest viable model for pomeron exchange is that it corresponds to the exchange of 2 gluons. As has been explained above, this exchange cannot be calculated from perturbative QCD. To explain the additive-quark rule, one needs both of the two gluons that are exchanged to prefer to couple to the same quark in each proton, rather than to two different ones: see Figure 1.

Calculation shows that this is achieved if.

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To understand this in fairly intuitive terms, work in a relativistic frame where the two initial colliding protons are moving in opposite directions. Calculating such effects is extremely difficult see Forshaw and Ross, As a final remark, note the discrepancy Amos et al.

As is seen in Figure 2 , the simple fit described above favours the lower ones. If the upper data point should turn out to be correct, this indicates the onset of an additional rapidly-rising contribution to the total cross section.