Browsing by Author "Mehen, T"

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    Pair production of color-octet scalars at the LHC
    (Physical Review D - Particles, Fields, Gravitation and Cosmology, 2010-10-26) Idilbi, A; Kim, C; Mehen, T
    Heavy colored scalar particles, which exist in many models of new physics, can be pair produced at the LHC via gluon-gluon fusion and possibly form quarkoniumlike bound states. If the scalars are also charged under the electroweak gauge group, these bound states can then decay into electroweak bosons. This yields a resonant cross section for final states such as γγ that can exceed standard model backgrounds. This paper studies this process in the Manohar-Wise model of color-octet scalars (COS). Important threshold logarithms and final state Coulomb-like QCD interactions are resummed using effective field theory. We compute the resummed cross section for gluon-gluon fusion to COS pairs at the LHC as well as the resonant cross section for octetonium decaying to γγ. The latter cross section exceeds the standard model diphoton cross section when the COS mass is less than 500 (350) GeV for √s=14(7)TeV. Nonobservation of resonances below these energies can significantly improve existing bounds on COS masses. © 2010 The American Physical Society.
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    Scattering of an ultrasoft pion and the X(3872)
    (Physical Review D - Particles, Fields, Gravitation and Cosmology, 2010-08-16) Braaten, E; Hammer, HW; Mehen, T
    The identification of the X(3872) as a loosely-bound charm-meson molecule allows it to be described by an effective field theory, called XEFT, for the D*D̄, DD̄*, and DD̄π sector of QCD at energies small compared to the pion mass. We point out that this effective field theory can be extended to the sector that includes an additional pion and used to calculate cross sections for the scattering of a pion and the X(3872). If the collision energy is much smaller than the pion mass, the cross sections are completely calculable at leading order in terms of the masses and widths of the charm mesons, pion masses, and the binding energy of the X(3872). We carry out an explicit calculation of the cross section for the breakup of the X(3872) into D*+D̄*0 by the scattering of a very low energy π+. ©2010 The American Physical Society.