501 research outputs found

    Constituent quark and diquark properties from small angle proton-proton elastic scattering at high energies

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    Small momentum transfer elastic proton-proton cross-section at high energies is calculated assuming the nucleon composed of two constituents - a quark and a diquark. A comparison to data (described very well up to -t = 2 GeV^2/c) allows to determine some properties of the constituents. While quark turns out fairly small, the diquark appears to be rather large, comparable to the size of the proton.Comment: 10 pages, 5 figure

    An attempt to construct pion distribution amplitude from the PCAC relation in the nonlocal chiral quark model

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    Using the PCAC relation, we derive a compact formula for the pion decay constant FπF_{\pi} in the nonlocal chiral quark model. For practical calculations this formula may be used both in the Minkowski and in the Euclidean space. For the pion momentum Pμ0P_{\mu}\to0 it reduces to the well known expression derived earlier by other authors. Using a generalized dipole Ansatz for the momentum dependence of the constituent quark mass in the Minkowski space, we express Fπ2F_{\pi}^{2} in terms of a single integral over the quark momentum fraction uu. We interpret the integrand as a pion distribution amplitude ϕ(u)\phi(u). We discuss its properties and compare with the π\piDA's obtained in other models.Comment: To appear in the special issue of Acta Physica Polonica to celebrate the 65th Birthday of Professor Jan Kwiecinski. 14 pages, 4 figure

    Wounded quarks and diquarks in high energy collisions

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    Particle production in Au-Au, Cu-Cu, d-Au and p-p collisions at 200 GeV c.m. energy are analyzed in the wounded quark-diquark model. Existing data are well reproduced. Emission functions of wounded and unwounded constituents are determined. Implications for the collective evolution of the system are discussed.Comment: version to be published in Phys. Rev. C, minor changes, discussion extende

    Hidden asymmetry and forward-backward correlations

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    A model-independent method of studying the forward-backward correlations in symmetric high energy processes is developed. The method allows a systematic study of properties of various particle sources and to uncover asymmetric structures hidden in symmetric hadron-hadron and nucleus-nucleus inelastic reactions.Comment: 11 pages, no figure

    Forward-backward multiplicity correlations in the wounded nucleon model

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    The forward-backward multiplicity correlation strength is calculated for arbitrary nucleus-nucleus collision in the framework of the wounded nucleon model. Discussion of our results in the context of the recent STAR data in Au+Au collisions at sqrt{s}=200 GeV is presented. It is suggested that the observed (i) growth of the correlation coefficient with centrality and (ii) approximately flat pseudorapidity dependence of the correlation strength for central collisions are due to the fluctuations of the number of wounded nucleons at a given centrality bin.Comment: 15 pages, 4 figures, accepted for publication in Phys. Rev. C. Changed content: STAR data included, extended discussion, added reference

    Symmetric correlations as seen at RHIC

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    We analyze the forward-backward multiplicity correlation coefficient as measured by STAR. We show that in the most central Au+Au collisions bins located symmetrically around \eta = 0 with large separation in pseudorapidity are more strongly correlated than bins located asymmetrically with smaller separation. In proton-proton collisions the opposite effect is observed. It suggests a qualitatively different behavior of the two-particle correlation as a function of pseudorapidity sum in p+p and Au+Au collisions.Comment: 7 pages; argument with the STAR ZDC added, more accurate calculation performed, conclusions unchanged; new section 4 with comments, to appear in Phys. Rev. C Rapid Com

    Baryon number conservation and the cumulants of the net proton distribution

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    We discuss the modification of the cumulants of the net baryon and net proton distributions due to the global conservation of baryon number in heavy-ion collisions. Corresponding probability distributions and their cumulants are derived analytically. We show that the conservation of baryon number results in a substantial decrease of higher order cumulants. Based on our studies, we propose an observable that is insensitive to the modifications due to baryon number conservation.Comment: 6 pages, 4 figures, to be published in Phys. Rev.

    Uncertainties on exclusive diffractive Higgs and jets production at the LHC

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    Two theoretical descriptions of exclusive diffractive jets and Higgs production at the LHC were implemented into the FPMC generator: the Khoze, Martin, Ryskin model and the Cudell, Hern\'andez, Ivanov, Dechambre exclusive model. We then study the uncertainties. We compare their predictions to the CDF measurement and discuss the possibility of constraining the exclusive Higgs production at the LHC with early measurements of exclusive jets. We show that the present theoretical uncertainties can be reduced with such data by a factor of 5

    The QCD phase diagram and statistics friendly distributions

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    The preliminary STAR data for proton cumulants for central collisions at s=7.7GeV component proton multiplicity distribution. We show that this two-component distribution is statistics friendly in that factorial cumulants of surprisingly high orders may be extracted with a relatively small number of events. As a consequence the two-component model can be tested and verified right now with the presently available STAR data from the first phase of the RHIC beam energy scan