Changes between Initial Version and Version 1 of MUED

02/16/10 10:25:08 (11 years ago)



  • MUED

    v1 v1  
     3== Minimal Universal Extra Dimensions (MUED) ==
     4=== Author ===
     6Priscila de Aquino
     7   * Katholieke Universiteit Leuven & Universite Catholique de Louvain - CP3
     8   *
     9=== Description of the model & references ===
     11One popular aproach to solve the Hierarchy Problem of the Standard Model is to extend space-time to higher dimensions. In this framework, the usual four-dimensional space-time is contained in a four-dimensional brane embedded in a large structure with N additional dimensions, the bulk.
     13Here, we shall focus on the Universal Extra Dimensional theory, in which the usual Standard Model particles are free to propagate in the bulk. As a consequence, these particles will be seem on the effective theory as a tower of N 4-dimensional particles with the same quantum numbers, but with increasing masses. This is called the Kaluza-Klein tower. Momentum conservation in the 5-dimensional space-time generates a conserved Kaluza-Klein number, which implies that different Kaluza-Klein modes can not mix with eachother.
     15In this implementation, a theory with five dimensions is considered, in which the fifth dimension is spatial and compactified on a S1/Z2 orbifold of radius R. We start from the most general five-dimensional Lagrangian. FeynRules derives the four-dimensional lagrangian automatically by imposing dimensional reduction and integratig out the extra-coordinate y.
     17The minimal Universal extra dimensional model is given in:
     19   * [ Physical Review D 66 (2002) 056006]: H-C. Cheng, K.T. Matchev, M. Schmaltz, ''Bosonic Supersymmetry? Getting fooled at the LHC.''
     21This implementation was based in another existing implementation in ''CalcHEP'':
     23   * []: A. Datta, K. Kong, K. T. Matchev, ''Minimal Universal Extra Dimensions in'' CalcHEP ''/CompHEP.''
     25The masses of Kaluza-Klein particles are computed via 1 loop:
     27   * [ Physical Review D 66 (2002) 036005]: H.-C. Cheng, K. T. Matchev, M. Schmaltz, ''Radiative Corrections to Kaluza-Klein Masses.''
     29=== Model files & extensions ===
     31'''The MUED implementation:'''
     32   * Main FeynRules files (as a tar-ball): [attachment:MUED.tar.gz MUED.tar.gz].
     33   * Run This is the main file. All the other files are called by this main file.
     34   * Example of a Mathematica® notebook loading the model and the parameters: [attachment:MUED.nb MUED.nb].
     35=== Instructions ===
     37The MUED is implemented in '''unitary gauge'''.
     38   * The switch <font color="saddlebrown" class="WYSIWYG_COLOR">FeynmanGauge</font> (future devlopments) must thus be set to <font color="saddlebrown" class="WYSIWYG_COLOR">False</font>,
     39   * To run it in !CalcHEP the switch <font color="saddlebrown" class="WYSIWYG_COLOR">FeynmanGauge</font> must be set to <font color="saddlebrown" class="WYSIWYG_COLOR">True</font> when asking the !CalcHEP output, and then to <font color="saddlebrown" class="WYSIWYG_COLOR">False</font> before any run.
     40   * In !MadGraph, the maximal number of particles must be increased to run the model:
     41      * Increase the value of {{{max_particles}}} in {{{}}} in the {{{MadGraphII}}} directory from =2*'''7-1= to =2'''*8-1=
     42      * Remove all excecutables in the {{{MadGraphII}}} directory ( =rm -rf *.o=).
     43      * recompile !MadGraph by typing {{{make}}} in the !MadGraph main directory.
     45=== Validation ===
     47In order to validate our implementation, we have checked 118 processes using a center-of-mass energy of 1400 GeV. It was done the following way:
     48   * '''Comparison of the built-in Madgraph Standard-Model and FeynRules generated''' '''Madgraph''' '''MUED for Standard Model''' '''processes.''' This comparison was done using squared matrix element at given phase-space points.
     49   * '''Comparison of the existing''' '''CalcHEP''' '''MUED (CH-ST) with the FeynRules generated ones in''' '''CalcHEP''' *,* '''Madgraph''' '''and Sherpa: CH-FR, MG-FR and SH-FR,''' through the calculation of several '''2 &rarr; 2''' cross-sections. All the checks performed were conclusive.
     51   * Validation Table - SM + Fermions (Cross sections given in pb):
     53   * <img width="824" alt="ValidationMUED.jpg" src="%ATTACHURLPATH%/ValidationMUED.jpg" height="2209" />
     55   * Validation Table - Gauge (Cross sections given in pb):
     57   * <img width="814" alt="ValidationGauge.jpg" src="%ATTACHURLPATH%/ValidationGauge.jpg" height="315" />
     59-- Main.PriscilaAquino - 15 Jun 2009