5,265 research outputs found

    Resonances, and mechanisms of Theta-production

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    After explaining necessity of exotic hadrons, we discuss mechanisms which could determine production of the exotic Theta-baryon. A possible important role of resonances (producing the Theta in real or virtual decays) is emphasized for various processes. Several experimental directions for studies of such resonances, and the Theta itself, are suggested. We briefly discuss also recent negative results on the Theta-baryon.Comment: 6 page

    Extracting W Boson Couplings from the e+ee^{+}e^{-} Production of Four Leptons

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    We consider the processes e+e+ννˉe^{+}e^{-}\rightarrow \ell^{+} \ell^{\prime -}\nu \bar{\nu}^{\prime}, including all possible charged lepton combinations, with regard to measuring parameters characterizing the WW boson. We calculate at what level these processes can be used to measure anamolous triple-boson vertice coupling parameters for the cases of e+ee^{+}e^{-} colliders at 500 GeVGeV and 1 TeVTeV center of mass energies.Comment: 13 pages,OCIP/C-93-

    The A Dependence of Open Charm and Bottom Production

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    We study inclusive heavy quark and exclusive heavy quark pair production in pp, pA and AA interactions. Intrinsic transverse momentum is introduced in pp interactions. Nuclear effects, limited to kTk_T broadening and nuclear shadowing, are introduced in pA and AA interactions. The nuclear dependence is studied over a range of energies, both in fixed target and collider setups.Comment: 69 pages, 42 .eps figures, to appear in the Proceedings of the Hard Probe Collaboratio

    Measuring hadron properties at finite temperature

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    We estimate the numbers and mass spectra of observed lepton and kaon pairs produced from ϕ\phi meson decays in the central rapidity region of an Au+Au collision at lab energy 11.6 GeV/nucleon. The following effects are considered: possible mass shifts, thermal broadening due to collisions with hadronic resonances, and superheating of the resonance gas. Changes in the dilepton mass spectrum may be seen, but changes in the dikaon spectrum are too small to be detectable.Comment: 9 pages (revtex), 3 figures (uuencoded postscript

    K*(892)0 Production in Relativistic Heavy Ion Collisions at sqrt(s_NN) = 130 GeV

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    Preliminary results on the K*(892)0 -> pi + K production using the mixed-event technique are presented. The measurements are performed at mid-rapidity by the STAR detector in sqrt(s_NN) = 130 GeV Au-Au collisions at RHIC. The K*0 to negative hadron, kaon and phi ratios are obtained and compared to the measurements in e+e-, pp and pbarp at various energies.Comment: 8 pages, 3 figures, proceedings of Strange Quarks in Matter (SQM2001), Frankfurt am Main, Germany, to be published in J. Phys.

    On photoexcitation of baryon antidecuplet

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    We show that the photoexcitation of the baryon antidecuplet, suggested by the soliton classification of low-lying baryons, is strongly suppressed on the proton target. The process occurs mostly on the neutron target. This qualitative prediction can be useful in identifying the non-exotic members of the antidecuplet in the known baryon spectrum. We also analyze the interrelation between photocouplings of various baryon multiplets in the soliton picture and in the nonrelativistic quark model.Comment: 9 pages, one Latex figur

    Lifetimes of Heavy-Flavour Hadrons -- Whence and Whither?

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    A theoretical treatment for the weak decays of heavy-flavour hadrons has been developed that is genuinely based on QCD. Its methodology as it applies to total lifetimes and the underlying theoretical issues are sketched. Predictions are compared with present data. One discrepancy emerges: the beauty baryon lifetime appears to be significantly shorter than expected. The ramifications of those findings are analyzed in detail.Comment: 15 pages, no figures, LATEX, two references added and new information concerning a lower charm content in B decays incorporate

    Open and hidden charm in proton-nucleus and heavy-ion collisions

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    We review the collectivity and the suppression pattern of charmed mesons - produced in proton-nucleus and nucleus-nucleus collisions at SPS (158 AGeV) and RHIC energies (21 ATeV) - in comparison to dynamical and thermal models. In particular, we examine the charmonium `melting' and the `comover dissociation' scenarios - implemented in a microscopic transport approach - in comparison to the available data from the SPS and RHIC. The analysis shows that the dynamics of c, c-bar quarks at RHIC are dominated by partonic or `pre-hadronic' interactions in the strongly coupled plasma stage. Both the `charmonium melting' and the hadronic `comover absorption and recreation model' are found, however, to be compatible with the experimental observation at SPS energies; the experimental ratio of Psi'/J/Psi versus centrality clearly favors the `hadronic comover' scenario. We find that the collective flow of charm in the purely hadronic Hadron-String Dynamics (HSD) transport appears compatible with the data at SPS energies, but substantially underestimates the data at top RHIC energies. Thus, the large elliptic flow v2 of D-mesons and the low R_AA(p_T) of J/Psi seen experimentally have to be attributed to early interactions of non-hadronic degrees of freedom. Simultaneously, we observe that non-hadronic interactions are mandatory in order to describe the narrowing of the J/Psi rapidity distribution from pp to central Au+Au collisions at the top RHIC energy. We demonstrate additionally that the strong quenching of low-pT J/Psi's in central Au+Au collisions indicates that a large fraction of final J/Psi mesons is created by a coalescence mechanism close to the phase boundary. Throughout this review we, furthermore, provide predictions for charm observables from Au+Au collisions at FAIR energies of 25-35 AGeV.Comment: review for Int. J. Mod. Phys. E, 75 pages, 50 figure

    A possible explanation why the Theta+ is seen in some experiments and not in others

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    To understand the whole set of positive and null data on the Theta+(1530)-production, we suggest the hypothesis that multiquark hadrons are mainly generated from many-quark states, which emerge either as short-term hadron fluctuations, or as hadron remnants in hard processes. This approach allows us to describe both non-observation of the Theta+ in current null experiments and peculiar features of its production in positive experiments. Further, we are able to propose new experiments that might be decisive for the problem of the Theta+ existence. Distributions of the Theta+ in such experiments can give important information both on higher Fock components of conventional hadrons and about structure and hadronization properties of hadron remnants produced in hard processes. We also explain that description of multiquark hadrons may require a modified form of the constituent quark model, with quark masses and couplings being intermediate between their values for the familiar constituent quarks and the current ones.Comment: 18 pages. Some changes in the text; experimental suggestions collected in a special subsection, references added and refreshe
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