## Universal extra dimensions (P. Aquino)

This page contains the model file and the Mathematica file for "Minimal Universal Extra Dimensions Theory - (MUED)". This model file is still under development and it is not ready to be used in interfaces yet.

UED (Universal Extra Dimensions theory) is a theory that uses extra dimensions to explain physics at high energies scales. In particular we will focus on the Mininal UED theory (MUED) based on **Datta, <a href="http://home.fnal.gov/~kckong/mued/" title="Kong">Kong</a>** and **Matchev's** work: " *Minimal Universal Extra Dimensions in CalcHEP/CompHEP* ".

Using FeynRules we wanted to calculate the Feynman Rules from MUED directly from its effective lagrangian. In order to do it we first wrote the model file declaring all MUED particles and parameters. This model file defines the theory in which the feynman rules are calculated. Subsequently, we wrote the effective lagrangian as it is on the above reference, and ran the code. We used the feynman rules obtained by **Datta, Kong** and **Matchev** to compare with our results. Finally we were able to use it to perform calculations in interfaces as Madgraph/Madevent? and CalcHEP/CompHEP.

It is important to notice that in this model file we only consider the zero and first KK modes of the MUED particles. ---

Summary of what has been done:

- We wrote the model file for MUED (considering only the zero mode and the first mode for KK particles). We used the same parameters as it is used in the above reference.

- We wrote the lagrangians and obtained all Feynman rules. We compared both feynman rules: the ones we obtained, with the ones in the above reference; they check.

- We obtained the MUED model file output to implement it both in MadGraph? and CalcHEP.

- We chose some SM and MUED processes and we computed its cross-sections using MadGraph? and CalcHEP. We compared both FR implementations with Matche's MUED model, which it was already implemented in CacHEP.

Most of the processes they check, we only found 3 processes with discrepancies. The two first discrepancies arise from uu~>ZZ and uu~>W+W-. These processes have an instability in MG due to the fact they have a massless particle within the propagator of one of its diagram. However we checked that the matrix elements for these processes agree with the SM stock version of MadGraph?. The last discrepancy it seems to be a bug in Matchev's model, as it blows up when it should be around 8pb. The full results you can find on MUEDResults.jpg file attached below.

-- Main.PriscilaAquino? - 23 Feb 2009