35 research outputs found

    Effective Gluon Interactions from Superstring Disk Amplitudes

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    Maximally Helicity Violating Disk Amplitudes, Twistors and Transcendental Integrals

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    We obtain simple expressions for tree-level maximally helicity violating amplitudes of N gauge bosons from disk world-sheets of open superstrings. The amplitudes are written in terms of (N-3)! hypergeometric integrals depending on kinematic parameters, weighted by certain kinematic factors. The integrals are transcendental in a strict sense defined in this work. The respective kinematic factors can be succinctly written in terms of "dual" momentum twistors. The amplitudes are computed by using the prescription proposed by Berkovits and Maldacena.Comment: 7 page

    Disk level S-matrix elements at eikonal Regge limit

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    We examine the calculation of the color-ordered disk level S-matrix element of massless scalar vertex operators for the special case that some of the Mandelstam variables for which there are no open string channel in the amplitude, are set to zero. By explicit calculation we show that the string form factors in the 2n-point functions reduce to one at the eikonal Regge limit.Comment: 17 pages, Latex file, no figur

    Supersymmetry Relations and MHV Amplitudes in Superstring Theory

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    We discuss supersymmetric Ward identities relating various scattering amplitudes in type I open superstring theory. We show that at the disk level, the form of such relations remains exactly the same, to all orders in alpha', as in the low-energy effective field theory describing the alpha'-> 0 limit. This result holds in D=4 for all compactifications, even for those that break supersymmetry. We apply SUSY relations to the computations of N-gluon MHV superstring amplitudes, simplifying the existing results for N<7 and deriving a compact expression for N=7.Comment: 34 pages, harvmac; v2: 2 figs added; final version to appear in NP

    Higher Spin Scattering in Superstring Theory

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    We compute scattering amplitudes of leading Regge trajectory states in open superstring theories. Highest spin states at mass level n with spin s=n+1 for bosons and s=n+1/2 for fermions are generated by particularly simple vertex operators. Hence, the cubic couplings of bosons and fermions on the leading Regge trajectory are given for arbitrary n. The same can be achieved for higher point amplitudes, and this article focuses on four point level with one heavy maximum spin state and three massless states in any bose-fermi combination, putting particular emphasis on manifest cyclic symmetry. Except for the four fermion coupling, all our results remain valid in any D<10 dimensional compactification scenario, so they might become relevant at LHC in case of an experimentally accessible low string scale. But even if not directly observable, superstring amplitudes provide important clues on higher spin dynamics and their consistent interactions in field theory.Comment: 31 pages; v3: final version published in Nuclear Physics
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