3,869 research outputs found

    Dependence of nucleotide physical properties on their placement in codons and determinative degree

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    Various physical properties such as dipole moment, heat of formation and energy of the most stable formation of nucleotides and bases were calculated by PM3 (modified neglect of diatomic overlap, parametric method number 3) and AM1 (Austin model 1) methods. As distinct from previous calculations, for nucleotides the interaction with neighbours is taken into account up to gradient of convergence equaling 1. The dependences of these variables from the place in the codon and the determinative degree were obtained. The difference of these variables for codons and anticodons is shown.Comment: 13 pages, 8 figures, PD

    Factorization Approach for Inclusive Production of Doubly Heavy Baryon

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    We study inclusive production of doubly heavy baryon at a e+e−e^+e^- collider and at hadron colliders through fragmentation. We study the production by factorizing nonpertubative- and perturbative effects. In our approach the production can be thought as a two-step process: A pair of heavy quarks can be produced perturbatively and then the pair is transformed into the baryon. The transformation is nonperturbative. Since a heavy quark moves with a small velocity in the baryon in its rest frame, we can use NRQCD to describe the transformation and perform a systematic expansion in the small velocity. At the leading order we find that the baryon can be formed from two states of the heavy-quark pair, one state is with the pair in 3S1^3S_1 state and in color 3ˉ{\bf \bar 3}, another is with the pair in 1S0^1S_0 state and in color 6{\bf 6}. Two matrix elements are defined for the transformation from the two states, their perturbative coefficients in the contribution to the cross-section at a e+e−e^+e^- collider and to the function of heavy quark fragmentation are calculated. Our approach is different than previous approaches where only the pair in 3S1^3S_1 state and in color 3ˉ{\bf \bar 3} is taken into account. Numerical results for e+e−e^+e^- colliders at the two BB-factories and for hadronic colliders LHC and Tevatron are given.Comment: Add results for large p_t, minor change

    Exlusive charmed meson pair production

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    The experimental data of BELLE Collaboration on the exclusive charmed meson pair production in the process of monophotonic e+e−e^+e^--annihilation (e+e−→γ∗→DDˉe^+e^-\to \gamma^* \to D\bar D) has been studied. It has been shown that these data is described satisfactorily in the frame work of constituent quark model. Our studies have demonstrated that the central production process e+e−→e+e−γγ→e+e−DDˉ+Xe^+e^-\to e^+e^-\gamma\gamma \to e^+e^-D\bar D +X and the process of monophotonic e+e−e^+e^--annihilation yield comparable numbers of the charmed meson pairs.Comment: 15 pages, 7 figures, RevTeX

    BCVEGPY2.0: A upgrade version of the generator BCVEGPY with an addendum about hadroproduction of the PP-wave BcB_c states

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    The generator BCVEGPY is upgraded by adding the hadroproduction of the PP-wave excited BcB_c states (denoted by BcJ,L=1∗B_{cJ,L=1}^* or by hBch_{B_c} and χBc\chi_{B_c}) and by improving some features of the original one as well. We denote it as BCVEGPY2.0. The PP-wave production is also calculated by taking only the dominant gluon-gluon fusion mechanism (with the subprocess gg→BcJ,L=1∗+cˉ+bgg\to B_{cJ,L=1}^*+\bar{c}+b being dominated) into account as that for SS-wave. In order to make the addendum piece of the upgraded generator as compact as possible so as to increase its efficiency, we manipulate the amplitude as compact as possible with FDC (a software for generating Feynman diagrams and the algebra amplitudes, and for manipulating algebra formulae analytically etc) and certain simplification techniques. The correctness of the program is tested by checking the gauge invariance of the amplitude and by comparing the numerical results with the existent ones in the literature carefully.Comment: 21 page, 4 figure
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