In this work we propose the Z → γγ decay as a process strictly forbidden in the standard model, suitable for the search of noncommutativity of coordinates at very short distances. We computed the Z → γγ partial width in the framework of the recently proposed one-loop renormalizable gauge sector of the noncommutative standard model. New experimental possibilities at LHC are analyzed and a firm bound to the scale of noncommutativity parameter is set around 1 TeV.

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In this paper we show that in the noncommutative chiral gauge theories the 4-fermion vertices are finite. The 4ψ-vertices appear in linear order in quantization of the θ-expanded noncommutative gauge theories; in all previously considered models, based on Dirac fermions, the 4ψ-vertices were divergent and nonrenormalizable.

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We analyze quantization of noncommutative chiral electrodynamics in the enveloping algebra formalism in linear order in noncommutativity parameter θ. Calculations show that divergences exist and cannot be removed by ordinary renormalization, however they can be removed by the Seiberg-Witten redefinition of fields. Performing redefinitions explicitly, we obtain renormalizable lagrangian and discuss the influence of noncommutativity on field propagation. Noncommutativity affects the propagation of chiral fermions only: half of the fermionic modes become massive and birefringent. * majab@ipb.ac.rs