# Changes between Version 6 and Version 7 of Octet_tcgg

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Timestamp:
11/03/15 23:22:06 (4 years ago)
Comment:

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Unmodified
 v6 = A Coloron Model = = A Coloron Model with a Decay to a Single Top Quark = This model introduces a heavy scalar color octet, the coloron. It is produced through gluon fusion and decays to a top quark and a charm quark. == Corresponding Authors == == Description of the Model == The {{{ #!latex $SU(3)_1 \times SU(3)_2 \to SU(3)_C$ }}} breaking induced by the expectation value of the {{{ #!latex ({$\bf 3,\bar{ 3}$}) }}} scalar field Phi generates color-octet and color-singlet scalars. The most general renormalizable potential for Phi is: {{{ #!latex $V(\Phi)=-m^2_{\Phi}\text{Tr}(\Phi\Phi^\dagger) -\mu (\text{det }\Phi+\text{H.c.})+\frac{\xi}{2}\left[ \text{Tr}(\Phi\Phi^\dagger) \right]^2+\frac{k}{2}\text{Tr}(\Phi\Phi^\dagger\Phi\Phi^\dagger) \ ,$ }}} where {{{ #!latex $\text{det } \Phi = \frac{1}{6}\epsilon^{ijk}\epsilon^{i'j'k'}\Phi_{ii'}\Phi_{jj'}\Phi_{kk'} \ ,$ }}} and where, without loss of generality, one can choose mu > 0. Assuming {{{ #!latex $m^2_\Phi >0$, }}} Phi acquires a (positive) diagonal expectation value: {{{ #!latex $\langle \Phi \rangle = u \cdot \mathcal{I} \,.$ }}} The Phi expansion around the vacuum gives: {{{ #!latex $\Phi=u+\frac{1}{\sqrt{6}}\left(\phi_R+i\phi_I\right)+\left(G^a_H+iG^a_G\right)T^a \ ,$ }}} where {{{ #!latex $\phi_R$, $\phi_I$ }}} are singlets under SU(3)_C Additionally, {{{ #!latex $G^a_G$, $a=1,\dots,8$, }}} are the Nambu-Goldstone bosons associated with the color-symmetry breaking, and {{{ #!latex $G^a_H$ }}} are color octets. GH can be produced in pairs through its interactions with gluons: {{{ #!latex $\frac{g^2_s}{2}f^{abc}f^{ade}G^b_{\mu}G^{\mu d}G^c_H G^e_H +g_s f^{abc} G^a_{\mu} G^b_H \partial^{\mu} G^c_H \ ,$ }}} or it can be produced singly via gluon-gluon fusion. This occurs at one-loop order through the cubic interaction {{{ #!latex $\frac{\mu}{6} d_{abc} G^a_H G^b_H G^c_H \,,$ }}} which arises from the {{{ #!latex $\mu(\det\Phi+\text{H.c.})$ }}} term in the potential; where {{{ #!latex $d_{abc}$ }}} is the SU(3) totally symmetric tensor. The single production of GH can be described by the effective coupling The color octet (GH) is a neutral heavy hadronic resonance. The Feynman diagram for the production of GH and its decay to a single top quark and a charm quark is shown below. [[Image(Coloron.png)]] The single production of GH can be described by the effective coupling {{{ #!latex values that give a 50% GH decay into tc and 50% into gg. GH is a very narrow resonance, with a width of the order of 10^-4 GeV. Various Feynman Diagrams for GH processes discussed in [http://arxiv.org/abs/1409.7607v2 1409.7607v2] are shown below: [[Image(Coloron.png)]] [[Image(Colorong.png)]] [[Image(Colorong2.png)]] [[Image(ColoronDouble1.png)]] [[Image(ColoronDouble2.png)]] See more details in p p > GH, GH > b~ c l- vl~ @2 GHT=1 QED=2 }}} To generate the settings for a specific coloron mass, use the appropriate model directory contained in the Octet-tcgg zip file. To generate the settings for a specific coloron mass, use the appropriate model directory contained in the Octet-tcgg zip file. Parameter card files are included for the combination of settings that gives a branching ratio of 0.5 to tc. For other BR values, please see [http://arxiv.org/abs/1409.7607v2 1409.7607v2]. == Related Models == * [wiki:kkg_FV kkg_FV] * [wiki:modcolorS_trip modcolorS_trip] * [wiki:Wprime W-prime]