3 <title>Left-Right-Symmetry Processes</title>
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9 <h2>Left-Right-Symmetry Processes</h2>
11 At current energies, the world is left-handed, i.e. the Standard Model
12 contains an <i>SU(2)_L</i> group. Left-right symmetry at some larger
13 scale implies the need for an <i>SU(2)_R</i> group. Thus the particle
14 content is expanded by right-handed <i>Z_R^0</i> and <i>W_R^+-</i>
15 and right-handed neutrinos. The Higgs fields have to be in a triplet
16 representation, leading to doubly-charged Higgs particles, one set for
17 each of the two <i>SU(2)</i> groups. Also the number of neutral and
18 singly-charged Higgs states is increased relative to the Standard Model,
19 but a search for the lowest-lying states of this kind is no different
20 from e.g. the freedom already accorded by the MSSM Higgs scenarios.
23 PYTHIA implements the scenario of [<a href="Bibliography.html" target="page">Hui97</a>].
26 The <i>W_R^+-</i> has been implemented as a simple copy of the
27 ordinary <i>W^+-</i>, with the exception that it couples to
28 right-handed neutrinos instead of the ordinary left-handed ones.
29 Thus the standard CKM matrix is used in the quark sector, and the
30 same vector and axial coupling strengths, leaving only the mass as
31 free parameter. The <i>Z_R^0</i> implementation (without interference
32 with the photon or the ordinary <i>Z^0</i>) allows decays both to
33 left- and right-handed neutrinos, as well as other fermions, according
34 to one specific model ansatz. Obviously both the <i>W_R^+-</i>
35 and the <i>Z_R^0</i> descriptions are likely to be simplifications,
36 but provide a starting point.
39 For the doubly-charged Higgses, the main decay modes implemented are
40 <i>H_L^++ -> W_L^+ W_L^+, l_i^+ l_j^+ </i> (<i>i, j</i> generation
41 indices) and <i>H_R^++ -> W_R^+ W_R^+, l_i^+ l_j^+</i>.
44 The right-handed neutrinos can be allowed to decay further. Assuming them
45 to have a mass below that of <i>W_R^+-</i>, they decay to three-body
46 states via a virtual <i>W_R^+-</i>, <i>nu_Rl -> l+- f fbar'</i>,
47 where both lepton charges are allowed owing to the Majorana character
48 of the neutrinos. If there is a significant mass splitting, also
49 sequential decays <i>nu_Rl -> l+- l'-+ nu'_Rl</i> are allowed.
50 Currently the decays are isotropic in phase space. If the neutrino
51 masses are close to or above the <i>W_R^</i> ones, this description
52 has to be substituted by a sequential decay via a real <i>W_R^</i>
53 (not implemented, but actually simpler to do than the one here).
56 <h3>Production processes</h3>
58 A few different production processes have been implemented, which normally
59 would not overlap and therefore could be run together.
61 <p/><code>flag </code><strong> LeftRightSymmmetry:all </strong>
62 (<code>default = <strong>off</strong></code>)<br/>
63 Common switch for the group of implemented processes within a
64 left-right-symmetric scenario.
67 <p/><code>flag </code><strong> LeftRightSymmmetry:ffbar2ZR </strong>
68 (<code>default = <strong>off</strong></code>)<br/>
69 Scatterings <i>f fbar -> Z_R^0</i>.
73 <p/><code>flag </code><strong> LeftRightSymmmetry:ffbar2WR </strong>
74 (<code>default = <strong>off</strong></code>)<br/>
75 Scatterings <i><f fbar' -> W_R^+</i>.
79 <p/><code>flag </code><strong> LeftRightSymmmetry:ll2HL </strong>
80 (<code>default = <strong>off</strong></code>)<br/>
81 Scatterings <i>l_i l_j -> H_L^--</i>.
85 <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HLe </strong>
86 (<code>default = <strong>off</strong></code>)<br/>
87 Scatterings <i>l_i gamma -> H_L^-- e^+</i>.
91 <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HLmu </strong>
92 (<code>default = <strong>off</strong></code>)<br/>
93 Scatterings <i>l_i gamma -> H_L^-- mu^+</i>.
97 <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HLtau </strong>
98 (<code>default = <strong>off</strong></code>)<br/>
99 Scatterings <i>l_i gamma -> H_L^-- tau^+</i>.
103 <p/><code>flag </code><strong> LeftRightSymmmetry:ff2HLff </strong>
104 (<code>default = <strong>off</strong></code>)<br/>
105 Scatterings <i>f_1 f_2 -> H_L^-- f_3 f_4</i> via <i>WW</i> fusion.
109 <p/><code>flag </code><strong> LeftRightSymmmetry:ffbar2HLHL </strong>
110 (<code>default = <strong>off</strong></code>)<br/>
111 Scatterings <i>f fbar -> H_L^++ H_L^--</i>.
115 <p/><code>flag </code><strong> LeftRightSymmmetry:ll2HR </strong>
116 (<code>default = <strong>off</strong></code>)<br/>
117 Scatterings <i>l_i l_j -> H_R^--</i>.
121 <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HRe </strong>
122 (<code>default = <strong>off</strong></code>)<br/>
123 Scatterings <i>l_i gamma -> H_R^-- e^+</i>.
127 <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HRmu </strong>
128 (<code>default = <strong>off</strong></code>)<br/>
129 Scatterings <i>l_i gamma -> H_R^-- mu^+</i>.
133 <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HRtau </strong>
134 (<code>default = <strong>off</strong></code>)<br/>
135 Scatterings <i>l_i gamma -> H_R^-- tau^+</i>.
139 <p/><code>flag </code><strong> LeftRightSymmmetry:ff2HRff </strong>
140 (<code>default = <strong>off</strong></code>)<br/>
141 Scatterings <i>f_1 f_2 -> H_R^-- f_3 f_4</i> via <i>WW</i> fusion.
145 <p/><code>flag </code><strong> LeftRightSymmmetry:ffbar2HRHR </strong>
146 (<code>default = <strong>off</strong></code>)<br/>
147 Scatterings <i>f fbar -> H_R^++ H_L^--</i>.
153 The basic couplings of the model are
155 <p/><code>parm </code><strong> LeftRightSymmmetry:gL </strong>
156 (<code>default = <strong>0.64</strong></code>; <code>minimum = 0.0</code>)<br/>
157 lefthanded coupling <i>g_L = e / sin(theta)</i>.
160 <p/><code>parm </code><strong> LeftRightSymmmetry:gR </strong>
161 (<code>default = <strong>0.64</strong></code>; <code>minimum = 0.0</code>)<br/>
162 righthanded coupling <i>g_R</i>, assumed the same as <i>g_L</i>.
165 <p/><code>parm </code><strong> LeftRightSymmmetry:vL </strong>
166 (<code>default = <strong>5.</strong></code>; <code>minimum = 0.0</code>)<br/>
167 vacuum expectation value <i>v_L</i> (in GeV) for the left-triplet.
171 The corresponding vacuum expectation value <i>v_R</i> is assumed
172 given by <i>v_R = sqrt(2) M_WR / g_R</i> and is not stored explicitly.
175 The Yukawa couplings of a lepton pair to a <i>H^--</i>, assumed the
176 same for <i>H_L^--</i> and <i>H_R^--</i>, is described by a symmetric
177 3-by-3 matrix. The default matrix is dominated by the diagonal elements
178 and especially by the <i>tau tau</i> one.
180 <p/><code>parm </code><strong> LeftRightSymmmetry:coupHee </strong>
181 (<code>default = <strong>0.1</strong></code>; <code>minimum = 0.0</code>)<br/>
182 Yukawa coupling for <i>H^-- -> e- e-</i>.
185 <p/><code>parm </code><strong> LeftRightSymmmetry:coupHmue </strong>
186 (<code>default = <strong>0.01</strong></code>; <code>minimum = 0.0</code>)<br/>
187 Yukawa coupling for <i>H^-- -> mu- e-</i>.
190 <p/><code>parm </code><strong> LeftRightSymmmetry:coupHmumu </strong>
191 (<code>default = <strong>0.1</strong></code>; <code>minimum = 0.0</code>)<br/>
192 Yukawa coupling for <i>H^-- -> mu- mu-</i>.
195 <p/><code>parm </code><strong> LeftRightSymmmetry:coupHtaue </strong>
196 (<code>default = <strong>0.01</strong></code>; <code>minimum = 0.0</code>)<br/>
197 Yukawa coupling for <i>H^-- -> tau- e-</i>.
200 <p/><code>parm </code><strong> LeftRightSymmmetry:coupHtaumu </strong>
201 (<code>default = <strong>0.01</strong></code>; <code>minimum = 0.0</code>)<br/>
202 Yukawa coupling for <i>H^-- -> tau- mu-</i>.
205 <p/><code>parm </code><strong> LeftRightSymmmetry:coupHtautau </strong>
206 (<code>default = <strong>0.3</strong></code>; <code>minimum = 0.0</code>)<br/>
207 Yukawa coupling for <i>H^-- -> tau- tau-</i>.
213 <!-- Copyright (C) 2010 Torbjorn Sjostrand -->