[u/mrichter/AliRoot.git] / PYTHIA8 / pythia8145 / xmldoc / LeftRightSymmetryProcesses.xml

<chapter name="Left-Right-Symmetry Processes">

<h2>Left-Right-Symmetry Processes</h2>

At current energies, the world is left-handed, i.e. the Standard Model 
contains an <ei>SU(2)_L</ei> group. Left-right symmetry at some larger 
scale implies the need for an <ei>SU(2)_R</ei> group. Thus the particle 
content is expanded by right-handed <ei>Z_R^0</ei> and <ei>W_R^+-</ei>
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 <ei>SU(2)</ei> 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. 

<p/>
PYTHIA implements the scenario of <ref>Hui97</ref>.

<p/>
The <ei>W_R^+-</ei> has been implemented as a simple copy of the 
ordinary <ei>W^+-</ei>, 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 <ei>Z_R^0</ei> implementation (without interference 
with the photon or the ordinary <ei>Z^0</ei>) allows decays both to 
left- and right-handed neutrinos, as well as other fermions, according 
to one specific model ansatz. Obviously both the <ei>W_R^+-</ei>
and the <ei>Z_R^0</ei> descriptions are  likely to be simplifications,
but provide a starting point.

<p/>
For the doubly-charged Higgses, the main decay modes implemented are
<ei>H_L^++ -> W_L^+ W_L^+, l_i^+ l_j^+ </ei> (<ei>i, j</ei> generation 
indices) and <ei>H_R^++ -> W_R^+ W_R^+, l_i^+ l_j^+</ei>.

<p/>
The right-handed neutrinos can be allowed to decay further. Assuming them 
to have a mass below that of <ei>W_R^+-</ei>, they decay to three-body 
states via a virtual <ei>W_R^+-</ei>, <ei>nu_Rl -> l+- f fbar'</ei>, 
where both lepton charges are allowed owing to the Majorana character 
of the neutrinos. If there is a significant mass splitting, also 
sequential decays <ei>nu_Rl -> l+- l'-+  nu'_Rl</ei> are allowed. 
Currently the decays are isotropic in phase space. If the neutrino 
masses are close to or above the <ei>W_R^</ei> ones, this description 
has to be substituted by a sequential decay via a real <ei>W_R^</ei> 
(not implemented, but actually simpler to do than the one here). 


<h3>Production processes</h3>

A few different production processes have been implemented, which normally 
would not overlap and therefore could be run together.

<flag name="LeftRightSymmmetry:all" default="off">
Common switch for the group of implemented processes within a 
left-right-symmetric scenario.
</flag>

<flag name="LeftRightSymmmetry:ffbar2ZR" default="off">
Scatterings <ei>f fbar -> Z_R^0</ei>. 
Code 3101.
</flag>

<flag name="LeftRightSymmmetry:ffbar2WR" default="off">
Scatterings <ei><f fbar' -> W_R^+</ei>. 
Code 3102.
</flag>

<flag name="LeftRightSymmmetry:ll2HL" default="off">
Scatterings <ei>l_i l_j -> H_L^--</ei>. 
Code 3121.
</flag>

<flag name="LeftRightSymmmetry:lgm2HLe" default="off">
Scatterings <ei>l_i gamma -> H_L^-- e^+</ei>. 
Code 3122.
</flag>

<flag name="LeftRightSymmmetry:lgm2HLmu" default="off">
Scatterings <ei>l_i gamma -> H_L^-- mu^+</ei>. 
Code 3123.
</flag>

<flag name="LeftRightSymmmetry:lgm2HLtau" default="off">
Scatterings <ei>l_i gamma -> H_L^-- tau^+</ei>. 
Code 3124.
</flag>

<flag name="LeftRightSymmmetry:ff2HLff" default="off">
Scatterings <ei>f_1 f_2 -> H_L^-- f_3 f_4</ei> via <ei>WW</ei> fusion. 
Code 3125.
</flag>

<flag name="LeftRightSymmmetry:ffbar2HLHL" default="off">
Scatterings <ei>f fbar ->  H_L^++ H_L^--</ei>. 
Code 3126.
</flag>

<flag name="LeftRightSymmmetry:ll2HR" default="off">
Scatterings <ei>l_i l_j -> H_R^--</ei>. 
Code 3141.
</flag>

<flag name="LeftRightSymmmetry:lgm2HRe" default="off">
Scatterings <ei>l_i gamma -> H_R^-- e^+</ei>. 
Code 3142.
</flag>

<flag name="LeftRightSymmmetry:lgm2HRmu" default="off">
Scatterings <ei>l_i gamma -> H_R^-- mu^+</ei>. 
Code 3143.
</flag>

<flag name="LeftRightSymmmetry:lgm2HRtau" default="off">
Scatterings <ei>l_i gamma -> H_R^-- tau^+</ei>. 
Code 3144.
</flag>

<flag name="LeftRightSymmmetry:ff2HRff" default="off">
Scatterings <ei>f_1 f_2 -> H_R^-- f_3 f_4</ei> via <ei>WW</ei> fusion. 
Code 3145.
</flag>

<flag name="LeftRightSymmmetry:ffbar2HRHR" default="off">
Scatterings <ei>f fbar ->  H_R^++ H_L^--</ei>. 
Code 3146.
</flag>

<h3>Parameters</h3>

The basic couplings of the model are

<parm name="LeftRightSymmmetry:gL" default="0.64" min="0.0">
lefthanded coupling <ei>g_L = e / sin(theta)</ei>.
</parm>

<parm name="LeftRightSymmmetry:gR" default="0.64" min="0.0">
righthanded coupling <ei>g_R</ei>, assumed the same as <ei>g_L</ei>.
</parm>

<parm name="LeftRightSymmmetry:vL" default="5." min="0.0">
vacuum expectation value <ei>v_L</ei> (in GeV) for the left-triplet. 
</parm>

<p/>
The corresponding vacuum expectation value <ei>v_R</ei> is assumed 
given by <ei>v_R = sqrt(2) M_WR / g_R</ei> and is not stored explicitly.

<p/>
The Yukawa couplings of a lepton pair to a <ei>H^--</ei>, assumed the 
same for <ei>H_L^--</ei> and <ei>H_R^--</ei>, is described by a symmetric
3-by-3 matrix. The default matrix is dominated by the diagonal elements 
and especially by the <ei>tau tau</ei> one.

<parm name="LeftRightSymmmetry:coupHee" default="0.1" min="0.0">
Yukawa coupling for <ei>H^-- -> e- e-</ei>.
</parm>

<parm name="LeftRightSymmmetry:coupHmue" default="0.01" min="0.0">
Yukawa coupling for <ei>H^-- -> mu- e-</ei>.
</parm>

<parm name="LeftRightSymmmetry:coupHmumu" default="0.1" min="0.0">
Yukawa coupling for <ei>H^-- -> mu- mu-</ei>.
</parm>

<parm name="LeftRightSymmmetry:coupHtaue" default="0.01" min="0.0">
Yukawa coupling for <ei>H^-- -> tau- e-</ei>.
</parm>

<parm name="LeftRightSymmmetry:coupHtaumu" default="0.01" min="0.0">
Yukawa coupling for <ei>H^-- -> tau- mu-</ei>.
</parm>

<parm name="LeftRightSymmmetry:coupHtautau" default="0.3" min="0.0">
Yukawa coupling for <ei>H^-- -> tau- tau-</ei>.
</parm>

</chapter>

<!-- Copyright (C) 2010 Torbjorn Sjostrand -->
Commit	Line	Data
9419eeef	1	<chapter name="Left-Right-Symmetry Processes">
	2
	3	<h2>Left-Right-Symmetry Processes</h2>
	4
	5	At current energies, the world is left-handed, i.e. the Standard Model
	6	contains an <ei>SU(2)_L</ei> group. Left-right symmetry at some larger
	7	scale implies the need for an <ei>SU(2)_R</ei> group. Thus the particle
	8	content is expanded by right-handed <ei>Z_R^0</ei> and <ei>W_R^+-</ei>
	9	and right-handed neutrinos. The Higgs fields have to be in a triplet
	10	representation, leading to doubly-charged Higgs particles, one set for
	11	each of the two <ei>SU(2)</ei> groups. Also the number of neutral and
	12	singly-charged Higgs states is increased relative to the Standard Model,
	13	but a search for the lowest-lying states of this kind is no different
	14	from e.g. the freedom already accorded by the MSSM Higgs scenarios.
	15
	16	<p/>
	17	PYTHIA implements the scenario of <ref>Hui97</ref>.
	18
	19	<p/>
	20	The <ei>W_R^+-</ei> has been implemented as a simple copy of the
	21	ordinary <ei>W^+-</ei>, with the exception that it couples to
	22	right-handed neutrinos instead of the ordinary left-handed ones.
	23	Thus the standard CKM matrix is used in the quark sector, and the
	24	same vector and axial coupling strengths, leaving only the mass as
	25	free parameter. The <ei>Z_R^0</ei> implementation (without interference
	26	with the photon or the ordinary <ei>Z^0</ei>) allows decays both to
	27	left- and right-handed neutrinos, as well as other fermions, according
	28	to one specific model ansatz. Obviously both the <ei>W_R^+-</ei>
	29	and the <ei>Z_R^0</ei> descriptions are likely to be simplifications,
	30	but provide a starting point.
	31
	32	<p/>
	33	For the doubly-charged Higgses, the main decay modes implemented are
	34	<ei>H_L^++ -> W_L^+ W_L^+, l_i^+ l_j^+ </ei> (<ei>i, j</ei> generation
	35	indices) and <ei>H_R^++ -> W_R^+ W_R^+, l_i^+ l_j^+</ei>.
	36
	37	<p/>
	38	The right-handed neutrinos can be allowed to decay further. Assuming them
	39	to have a mass below that of <ei>W_R^+-</ei>, they decay to three-body
	40	states via a virtual <ei>W_R^+-</ei>, <ei>nu_Rl -> l+- f fbar'</ei>,
	41	where both lepton charges are allowed owing to the Majorana character
	42	of the neutrinos. If there is a significant mass splitting, also
	43	sequential decays <ei>nu_Rl -> l+- l'-+ nu'_Rl</ei> are allowed.
	44	Currently the decays are isotropic in phase space. If the neutrino
	45	masses are close to or above the <ei>W_R^</ei> ones, this description
	46	has to be substituted by a sequential decay via a real <ei>W_R^</ei>
	47	(not implemented, but actually simpler to do than the one here).
	48
	49
	50	<h3>Production processes</h3>
	51
	52	A few different production processes have been implemented, which normally
	53	would not overlap and therefore could be run together.
	54
	55	<flag name="LeftRightSymmmetry:all" default="off">
	56	Common switch for the group of implemented processes within a
	57	left-right-symmetric scenario.
	58	</flag>
	59
	60	<flag name="LeftRightSymmmetry:ffbar2ZR" default="off">
	61	Scatterings <ei>f fbar -> Z_R^0</ei>.
	62	Code 3101.
	63	</flag>
	64
65	<flag name="LeftRightSymmmetry:ffbar2WR" default="off">
66	Scatterings <ei><f fbar' -> W_R^+</ei>.
67	Code 3102.
68	</flag>
69
70	<flag name="LeftRightSymmmetry:ll2HL" default="off">
71	Scatterings <ei>l_i l_j -> H_L^--</ei>.
72	Code 3121.
73	</flag>
74
75	<flag name="LeftRightSymmmetry:lgm2HLe" default="off">
76	Scatterings <ei>l_i gamma -> H_L^-- e^+</ei>.
77	Code 3122.
78	</flag>
79
80	<flag name="LeftRightSymmmetry:lgm2HLmu" default="off">
81	Scatterings <ei>l_i gamma -> H_L^-- mu^+</ei>.
82	Code 3123.
83	</flag>
84
85	<flag name="LeftRightSymmmetry:lgm2HLtau" default="off">
86	Scatterings <ei>l_i gamma -> H_L^-- tau^+</ei>.
87	Code 3124.
88	</flag>
89
90	<flag name="LeftRightSymmmetry:ff2HLff" default="off">
91	Scatterings <ei>f_1 f_2 -> H_L^-- f_3 f_4</ei> via <ei>WW</ei> fusion.
92	Code 3125.
93	</flag>
94
95	<flag name="LeftRightSymmmetry:ffbar2HLHL" default="off">
96	Scatterings <ei>f fbar -> H_L^++ H_L^--</ei>.
97	Code 3126.
98	</flag>
99
100	<flag name="LeftRightSymmmetry:ll2HR" default="off">
101	Scatterings <ei>l_i l_j -> H_R^--</ei>.
102	Code 3141.
103	</flag>
104
105	<flag name="LeftRightSymmmetry:lgm2HRe" default="off">
106	Scatterings <ei>l_i gamma -> H_R^-- e^+</ei>.
107	Code 3142.
108	</flag>
109
110	<flag name="LeftRightSymmmetry:lgm2HRmu" default="off">
111	Scatterings <ei>l_i gamma -> H_R^-- mu^+</ei>.
112	Code 3143.
113	</flag>
114
115	<flag name="LeftRightSymmmetry:lgm2HRtau" default="off">
116	Scatterings <ei>l_i gamma -> H_R^-- tau^+</ei>.
117	Code 3144.
118	</flag>
119
120	<flag name="LeftRightSymmmetry:ff2HRff" default="off">
121	Scatterings <ei>f_1 f_2 -> H_R^-- f_3 f_4</ei> via <ei>WW</ei> fusion.
122	Code 3145.
123	</flag>
124
125	<flag name="LeftRightSymmmetry:ffbar2HRHR" default="off">
126	Scatterings <ei>f fbar -> H_R^++ H_L^--</ei>.
127	Code 3146.
128	</flag>
129
130	<h3>Parameters</h3>
131
132	The basic couplings of the model are
133
134	<parm name="LeftRightSymmmetry:gL" default="0.64" min="0.0">
135	lefthanded coupling <ei>g_L = e / sin(theta)</ei>.
136	</parm>
137
138	<parm name="LeftRightSymmmetry:gR" default="0.64" min="0.0">
139	righthanded coupling <ei>g_R</ei>, assumed the same as <ei>g_L</ei>.
140	</parm>
141
142	<parm name="LeftRightSymmmetry:vL" default="5." min="0.0">
143	vacuum expectation value <ei>v_L</ei> (in GeV) for the left-triplet.
144	</parm>
145
146	<p/>
147	The corresponding vacuum expectation value <ei>v_R</ei> is assumed
148	given by <ei>v_R = sqrt(2) M_WR / g_R</ei> and is not stored explicitly.
149
150	<p/>
151	The Yukawa couplings of a lepton pair to a <ei>H^--</ei>, assumed the
152	same for <ei>H_L^--</ei> and <ei>H_R^--</ei>, is described by a symmetric
153	3-by-3 matrix. The default matrix is dominated by the diagonal elements
154	and especially by the <ei>tau tau</ei> one.
155
156	<parm name="LeftRightSymmmetry:coupHee" default="0.1" min="0.0">
157	Yukawa coupling for <ei>H^-- -> e- e-</ei>.
158	</parm>
159
160	<parm name="LeftRightSymmmetry:coupHmue" default="0.01" min="0.0">
161	Yukawa coupling for <ei>H^-- -> mu- e-</ei>.
162	</parm>
163
164	<parm name="LeftRightSymmmetry:coupHmumu" default="0.1" min="0.0">
165	Yukawa coupling for <ei>H^-- -> mu- mu-</ei>.
166	</parm>
167
168	<parm name="LeftRightSymmmetry:coupHtaue" default="0.01" min="0.0">
169	Yukawa coupling for <ei>H^-- -> tau- e-</ei>.
170	</parm>
171
172	<parm name="LeftRightSymmmetry:coupHtaumu" default="0.01" min="0.0">
173	Yukawa coupling for <ei>H^-- -> tau- mu-</ei>.
174	</parm>
175
176	<parm name="LeftRightSymmmetry:coupHtautau" default="0.3" min="0.0">
177	Yukawa coupling for <ei>H^-- -> tau- tau-</ei>.
178	</parm>
179
180	</chapter>
181
182	<!-- Copyright (C) 2010 Torbjorn Sjostrand -->
183