Left-Right-Symmetry Processes
 
  - Production processes
- Parameters
At current energies, the world is left-handed, i.e. the Standard Model 
contains an SU(2)_L group. Left-right symmetry at some larger 
scale implies the need for an SU(2)_R group. Thus the particle 
content is expanded by right-handed Z_R^0 and W_R^+- 
and right-handed neutrinos. The Higgs fields have to be in a triplet 
representation, leading to doubly-charged Higgs particles, one set for 
each of the two SU(2) groups. Also the number of neutral and 
singly-charged Higgs states is increased relative to the Standard Model, 
but a search for the lowest-lying states of this kind is no different 
from e.g. the freedom already accorded by the MSSM Higgs scenarios. 
 
 
PYTHIA implements the scenario of [Hui97]. 
 
 
The W_R^+- has been implemented as a simple copy of the 
ordinary W^+-, with the exception that it couples to 
right-handed neutrinos instead of the ordinary left-handed ones. 
Thus the standard CKM matrix is used in the quark sector, and the 
same vector and axial coupling strengths, leaving only the mass as 
free parameter. The Z_R^0 implementation (without interference 
with the photon or the ordinary Z^0) allows decays both to 
left- and right-handed neutrinos, as well as other fermions, according 
to one specific model ansatz. Obviously both the W_R^+- 
and the Z_R^0 descriptions are  likely to be simplifications, 
but provide a starting point. 
 
 
For the doubly-charged Higgs bosons, the main decay modes implemented are 
H_L^++ → W_L^+ W_L^+, l_i^+ l_j^+  (i, j generation 
indices) and H_R^++ → W_R^+ W_R^+, l_i^+ l_j^+. 
 
 
The right-handed neutrinos can be allowed to decay further. Assuming them 
to have a mass below that of W_R^+-, they decay to three-body 
states via a virtual W_R^+-, nu_Rl → l+- f fbar', 
where both lepton charges are allowed owing to the Majorana character 
of the neutrinos. If there is a significant mass splitting, also 
sequential decays nu_Rl → l+- l'-+  nu'_Rl are allowed. 
Currently the decays are isotropic in phase space. If the neutrino 
masses are close to or above the W_R^ ones, this description 
has to be substituted by a sequential decay via a real W_R^ 
(not implemented, but actually simpler to do than the one here).Production processes
 
 
A few different production processes have been implemented, which normally 
would not overlap and therefore could be run together. 
 
flag   LeftRightSymmmetry:all   
 (default = off)
Common switch for the group of implemented processes within a 
left-right-symmetric scenario. 
   
 
flag   LeftRightSymmmetry:ffbar2ZR   
 (default = off)
Scatterings f fbar → Z_R^0. 
Code 3101. 
   
 
flag   LeftRightSymmmetry:ffbar2WR   
 (default = off)
Scatterings f fbar' → W_R^+. 
Code 3102. 
   
 
flag   LeftRightSymmmetry:ll2HL   
 (default = off)
Scatterings l_i l_j → H_L^--. 
Code 3121. 
   
 
flag   LeftRightSymmmetry:lgm2HLe   
 (default = off)
Scatterings l_i gamma → H_L^-- e^+. 
Code 3122. 
   
 
flag   LeftRightSymmmetry:lgm2HLmu   
 (default = off)
Scatterings l_i gamma → H_L^-- mu^+. 
Code 3123. 
   
 
flag   LeftRightSymmmetry:lgm2HLtau   
 (default = off)
Scatterings l_i gamma → H_L^-- tau^+. 
Code 3124. 
   
 
flag   LeftRightSymmmetry:ff2HLff   
 (default = off)
Scatterings f_1 f_2 → H_L^-- f_3 f_4 via WW fusion. 
Code 3125. 
   
 
flag   LeftRightSymmmetry:ffbar2HLHL   
 (default = off)
Scatterings f fbar →  H_L^++ H_L^--. 
Code 3126. 
   
 
flag   LeftRightSymmmetry:ll2HR   
 (default = off)
Scatterings l_i l_j → H_R^--. 
Code 3141. 
   
 
flag   LeftRightSymmmetry:lgm2HRe   
 (default = off)
Scatterings l_i gamma → H_R^-- e^+. 
Code 3142. 
   
 
flag   LeftRightSymmmetry:lgm2HRmu   
 (default = off)
Scatterings l_i gamma → H_R^-- mu^+. 
Code 3143. 
   
 
flag   LeftRightSymmmetry:lgm2HRtau   
 (default = off)
Scatterings l_i gamma → H_R^-- tau^+. 
Code 3144. 
   
 
flag   LeftRightSymmmetry:ff2HRff   
 (default = off)
Scatterings f_1 f_2 → H_R^-- f_3 f_4 via WW fusion. 
Code 3145. 
   
 
flag   LeftRightSymmmetry:ffbar2HRHR   
 (default = off)
Scatterings f fbar →  H_R^++ H_R^--. 
Code 3146. 
   
 
 
Parameters
 
 
The basic couplings of the model are 
 
parm   LeftRightSymmmetry:gL   
 (default = 0.64; minimum = 0.0)
lefthanded coupling g_L = e / sin(theta). 
   
 
parm   LeftRightSymmmetry:gR   
 (default = 0.64; minimum = 0.0)
righthanded coupling g_R, assumed the same as g_L. 
   
 
parm   LeftRightSymmmetry:vL   
 (default = 5.; minimum = 0.0)
vacuum expectation value v_L (in GeV) for the left-triplet. 
   
 
 
The corresponding vacuum expectation value v_R is assumed 
given by v_R = sqrt(2) M_WR / g_R and is not stored explicitly. 
 
 
The Yukawa couplings of a lepton pair to a H^--, assumed the 
same for H_L^-- and H_R^--, is described by a symmetric 
3-by-3 matrix. The default matrix is dominated by the diagonal elements 
and especially by the tau tau one. 
 
parm   LeftRightSymmmetry:coupHee   
 (default = 0.1; minimum = 0.0)
Yukawa coupling for H^-- → e- e-. 
   
 
parm   LeftRightSymmmetry:coupHmue   
 (default = 0.01; minimum = 0.0)
Yukawa coupling for H^-- → mu- e-. 
   
 
parm   LeftRightSymmmetry:coupHmumu   
 (default = 0.1; minimum = 0.0)
Yukawa coupling for H^-- → mu- mu-. 
   
 
parm   LeftRightSymmmetry:coupHtaue   
 (default = 0.01; minimum = 0.0)
Yukawa coupling for H^-- → tau- e-. 
   
 
parm   LeftRightSymmmetry:coupHtaumu   
 (default = 0.01; minimum = 0.0)
Yukawa coupling for H^-- → tau- mu-. 
   
 
parm   LeftRightSymmmetry:coupHtautau   
 (default = 0.3; minimum = 0.0)
Yukawa coupling for H^-- → tau- tau-.