5,801 research outputs found

    Coherent and Non-Coherent Double Diffractive Production of QQˉ Q \bar {Q} - pairs in Collisions of Heavy Ions at High Energies

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    The double coherent and non-coherent diffractive production of heavy quark - antiquark pairs (QQˉQ \bar{Q}) in heavy ion scattering at high energies (LHC) is considered. The total and differential cross sections of these processes with the formation of ccˉc \bar{c} and bbˉb \bar{b} pairs in pppp, CaCaCaCa and PbPbPbPb collisions are evaluated. The contribution of the considered mechanisms is a few per cent of the number of heavy quark - antiquark pairs obtained in the processes of hard (QCD) scattering, and it will be taken into account in the registration of cc, bb quarks or, for instance, in the study of the heavy quarkonia suppression effects in Quark - Gluon Plasma, in the search for intermediate mass Higgs bosons and so on. It is shown that the cross section of the coherent scattering process is great enough. This makes it suitable for studying collective effects in nuclear interactions at high energies. An example of such effects is given: large values of the invariant mass of a QQˉQ \bar{Q}pair, M_{Q \bar{Q}} \gsim 100 GeV, in association with a large rapidity gap between diffractive jets Δη>5\Delta \eta > 5.Comment: 22 pages, 5(.eps) figures, 3 tables, LaTe

    Frustrations on decorated triangular lattice in Ising model

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    We study the frustration properties of the Ising model on a decorated triangular lattice with an arbitrary number of decorating spins on all lattice bonds in the framework of an exact analytical approach based on the Kramers--Wannier transfer matrix method. Expressions for the entropy, heat capacity, and spontaneous magnetization of the lattice are obtained, including the residual (zero-temperature) entropy and residual (zero-temperature) spontaneous magnetization of the system. The existence of magnetic frustrations in such a model and their influence on the behavior of the thermodynamic functions of the system are shown. The new and most important result of our study is related to the description of the possible coexistence of frustrations and long-range magnetic order in partially ordered spin systems