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Abstract:
This talk gives a status report on our work on explaining the baryon stopping phenomenon, or the puzzle of nuclear stopping power, by a new model of pure color octet (soft gluon) exchange in pp and pA reactions. Our results indicate that spectra of baryons are governed by color configurations of constituents, that is valence and sea quarks. They also point at the presence of a qualitative difference between single and multiple proton-nucleon collisions, that is, between pp and pA reactions. In pp collisions, inelastic baryon spectra including
"diffractive'' protons can be fully described by the exchange of one soft gluon coupling either to valence quarks or to the sea quark-antiquark pair. In pA reactions the exchange of two or more color octets brings new color configurations, revealing the purely effective character of the diquark which can be either disintegrated or recombined from available valence and sea quarks. This leads to stronger baryon stopping as a function of nucleus size and centrality. The encoding of knowledge on the number of nucleons which the proton collides with proceeds through the partonic structure of the proton, account taken of a properly complete ensemble of Fock states. The increase of the nuclear stopping power in pA reactions is driven by the appearance of new color configurations with disintegration of the valence diquark and possible appearance of effective diquarks including sea quarks.
Important: This seminar is held in building D-11 room 104.
Please, be advised that due to the pandemic sanitary rules, we can absorbe 1 unvaccinated person per 10m^2, which means 4 people. As most of us are vaccinated, this should not be a problem. There will be a list of participants, stating that they were (or were not) vaccinated / are immune / with a valid covid test, where we will ask you to sign in upon arrival. Also, people with ANY symptoms of cold (either of running nose, cough, temperature, ...), not necessarily covid, are not allowed to participate according to the rules. We hope you understand. The situation is dynamic and we will of course keep you posted. At the moment we plan to proceed “live”, similary to teaching at AGH.