Changes between Version 6 and Version 7 of Octet_tcgg


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Timestamp:
11/03/15 23:22:06 (19 months ago)
Author:
druekeel
Comment:

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  • Octet_tcgg

    v6 v7  
    1 = A Coloron Model = 
     1= A Coloron Model with a Decay to a Single Top Quark = 
     2 
     3This 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. 
    24 
    35== Corresponding Authors == 
     
    1719== Description of the Model == 
    1820 
    19 The  
    20 {{{ 
    21 #!latex 
    22 $SU(3)_1 \times SU(3)_2 \to SU(3)_C$ 
    23 }}} 
    24 breaking induced by the expectation value of the  
    25 {{{ 
    26 #!latex 
    27 ({$\bf 3,\bar{ 3}$}) 
    28 }}} 
    29 scalar field Phi generates color-octet and color-singlet scalars. The most general renormalizable potential for Phi is: 
    30 {{{ 
    31 #!latex 
    32 $V(\Phi)=-m^2_{\Phi}\text{Tr}(\Phi\Phi^\dagger) -\mu (\text{det }\Phi+\text{H.c.})+\frac{\xi}{2}\left[ \text{Tr}(\Phi\Phi^\dagger) \right]^2+\frac{k}{2}\text{Tr}(\Phi\Phi^\dagger\Phi\Phi^\dagger) \ ,$ 
    33 }}} 
    34 where  
    35 {{{ 
    36 #!latex 
    37 $\text{det } \Phi = \frac{1}{6}\epsilon^{ijk}\epsilon^{i'j'k'}\Phi_{ii'}\Phi_{jj'}\Phi_{kk'} \ ,$ 
    38 }}} 
    39 and where, without loss of generality, one can choose mu > 0. Assuming  
    40 {{{ 
    41 #!latex 
    42 $m^2_\Phi >0$, 
    43 }}} 
    44 Phi acquires a (positive) diagonal expectation value: 
    45 {{{ 
    46 #!latex 
    47 $\langle \Phi \rangle = u \cdot \mathcal{I} \,.$ 
    48 }}} 
    49 The Phi expansion around the vacuum gives: 
    50 {{{ 
    51 #!latex 
    52 $\Phi=u+\frac{1}{\sqrt{6}}\left(\phi_R+i\phi_I\right)+\left(G^a_H+iG^a_G\right)T^a \ ,$ 
    53 }}} 
    54 where  
    55 {{{ 
    56 #!latex 
    57 $\phi_R$, $\phi_I$ 
    58 }}} 
    59 are singlets under SU(3)_C Additionally,  
    60 {{{ 
    61 #!latex 
    62 $G^a_G$, $a=1,\dots,8$,  
    63 }}} 
    64 are the Nambu-Goldstone bosons associated with the color-symmetry breaking, and 
    65 {{{ 
    66 #!latex 
    67 $G^a_H$ 
    68 }}} 
    69 are color octets.  
    70  
    71 GH can be produced in pairs through its interactions with gluons: 
    72 {{{ 
    73 #!latex 
    74 $\frac{g^2_s}{2}f^{abc}f^{ade}G^b_{\mu}G^{\mu d}G^c_H G^e_H +g_s f^{abc} G^a_{\mu} G^b_H \partial^{\mu} G^c_H \ ,$ 
    75 }}} 
    76 or it can be produced singly via gluon-gluon fusion. This occurs at one-loop order through the cubic interaction 
    77 {{{ 
    78 #!latex 
    79 $\frac{\mu}{6} d_{abc} G^a_H G^b_H G^c_H   \,,$ 
    80 }}} 
    81 which arises from the  
    82 {{{ 
    83 #!latex 
    84 $\mu(\det\Phi+\text{H.c.})$ 
    85 }}} 
    86 term in the potential; where  
    87 {{{ 
    88 #!latex 
    89 $d_{abc}$ 
    90 }}} 
    91 is the SU(3) totally symmetric tensor. The single production of GH can be described by the effective coupling 
     21The 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. 
     22[[Image(Coloron.png)]] 
     23The single production of GH can be described by the effective coupling 
    9224{{{ 
    9325#!latex 
     
    11850values 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.  
    11951 
    120 Various Feynman Diagrams for GH processes discussed in [http://arxiv.org/abs/1409.7607v2 1409.7607v2] are shown below: 
    121  
    122 [[Image(Coloron.png)]] 
    123  
    124 [[Image(Colorong.png)]] [[Image(Colorong2.png)]] 
    125  
    126 [[Image(ColoronDouble1.png)]] [[Image(ColoronDouble2.png)]] 
    127   
    12852See more details in 
    12953 
     
    14468p p > GH, GH > b~ c l- vl~ @2 GHT=1 QED=2 
    14569}}} 
    146 To generate the settings for a specific coloron mass, use the appropriate model directory contained in the Octet-tcgg zip file. 
     70To 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]. 
     71 
     72 
     73 
     74== Related Models == 
     75 
     76* [wiki:kkg_FV kkg_FV] 
     77* [wiki:modcolorS_trip modcolorS_trip] 
     78* [wiki:Wprime W-prime]