[u/mrichter/AliRoot.git] / PYTHIA8 / pythia8130 / xmldoc / ProcessSelection.xml

<chapter name="Process Selection">

<h2>Process Selection</h2>

There is no way PYTHIA could contain all processes of interest, 
neither in terms of potential physics topics nor in terms of
high-multiplicity final states. What exists is a reasonably
complete setup of all <ei>2 -> 1</ei> and <ei>2 -> 2</ei>
processes within the Standard Model, plus some examples of
processes beyond that, again for low multiplicities. Combined with 
the PYTHIA parton showers, this should be enough to get a flying 
start in the study of many physics scenarios. 
Other processes could be fed in via the 
<aloc href="LesHouchesAccord">Les Houches Accord</aloc> 
or be implemented as a 
<aloc href="SemiInternalProcesses">Semi-Internal Process</aloc>. 
In the latter case the existing processes would act as obvious 
templates. 

<p/>
By default all processes are switched off. You should switch on 
those you want to simulate. This may be done at two (occasionally 
three) levels, either for each individual process or for a group of 
processes. That is, a process is going to be generated either if its 
own flag or its group flag is on. There is no built-in construction 
to switch on a group and then switch off a few of its members.

<p/>
Each process is assigned an integer code. This code is not used in
the internal administration of events (so having the same code for
two completely different processes would not be a problem), but only 
intended to allow a simpler user separation of different processes. 
Also the process name is available, as a string.

<p/>
To ease navigation, the list of processes has been split into several
separate pages, by main topic. The classification is hopefully
intuitive, but by no means unambiguous. For instance, essentially 
all processes involve QCD, so the "QCD processes" are the ones that
only involve QCD. (And also that is not completely true, once one 
includes all that may happen in multiple interactions.) On these 
separate pages also appear the settings that are completely local
to that particular process class, but not the ones that have a 
broader usage.

<h3><aloc href="QCDProcesses">QCD Processes</aloc></h3>

QCD processes fall in two main categories: soft and hard. The soft ones
contain elastic, diffractive and "minimum-bias" events, together
covering the total cross section. Hard processea are the normal
<ei>2 -> 2</ei> ones, including charm and bottom production. 
<br/>Reserved code range: 101 - 199. 

<h3><aloc href="ElectroweakProcesses">Electroweak Processes</aloc></h3>

Prompt-photon, <ei>gamma^*/Z^0</ei> and <ei>W^+-</ei> production, 
plus a few processes with <ei>t</ei>-channel boson exchange.
<br/>Reserved code range: 201 - 299. 

<h3><aloc href="OniaProcesses">Onia Processes</aloc></h3>

Colour singlet and octet production of charmonium and bottomonium.
<br/>Reserved code range: 401 - 499 for charmonium and 
501 - 599 for bottomonium. 

<h3><aloc href="TopProcesses">Top Processes</aloc></h3>

Top production, singly or doubly.
<br/>Reserved code range: 601 - 699. 

<h3><aloc href="FourthGenerationProcesses">Fourth-Generation 
Processes</aloc></h3>

Production of hypothetical fourth-generation fermions.
<br/>Reserved code range: 801 - 899. 

<h3><aloc href="HiggsProcesses">Higgs Processes</aloc></h3>

Higgs production, within or beyond the Standard Model.
See section on Left-Right-Symmetry processes for doubly charged Higgses.
<br/>Reserved code range: 901 - 999 for a Standard Model Higgs 
and 1001 - 1199 for MSSM Higgses. 

<h3><aloc href="SUSYProcesses">SUSY Processes</aloc></h3>

Production of supersymmetric particles, currently barely begun.
<br/>Reserved code range: 1001 - 2999. (Whereof 1001 - 1199
for Higgses; see above.) 

<h3><aloc href="NewGaugeBosonProcesses">New-Gauge-Boson 
Processes</aloc></h3>

Production of new gauge bosons such as <ei>Z'</ei> and <ei>W'</ei>.
<br/>Reserved code range: 3001 - 3099. 

<h3><aloc href="LeftRightSymmetryProcesses">Left-Right-Symmetry 
Processes</aloc></h3>

Production of righthanded <ei>Z_R</ei> and <ei>W_R</ei> bosons and of
doubly charged Higgses.
<br/>Reserved code range: 3101 - 3199. 

<h3><aloc href="LeptoquarkProcesses">Leptoquark Processes</aloc></h3>

Production of a simple scalar leptoquark state.
<br/>Reserved code range: 3201 - 3299. 

<h3><aloc href="CompositenessProcesses">Compositeness Processes</aloc></h3>

Production of excited fermion states and contact-interaction modification
to interactions between fermions (excluding technicolor; see below). 
<br/>Reserved code range: 4001 - 4099. 

<h3>Technicolor Processes</h3>

Production of technicolor particles and modifications of QCD processes
by technicolor interactions. Does not exist yet. 
<br/>Reserved code range: 4101 - 4199. 

<h3><aloc href="ExtraDimensionalProcesses">Extra-Dimensional 
Processes</aloc></h3>

A vast area, here represented by the production of a Randall-Sundrum
excited graviton state.
<br/>Reserved code range: 5001 - 5099. 

</chapter>

<!-- Copyright (C) 2008 Torbjorn Sjostrand -->
Commit	Line	Data
5ad4eb21	1	<chapter name="Process Selection">
	2
	3	<h2>Process Selection</h2>
	4
	5	There is no way PYTHIA could contain all processes of interest,
	6	neither in terms of potential physics topics nor in terms of
	7	high-multiplicity final states. What exists is a reasonably
	8	complete setup of all <ei>2 -> 1</ei> and <ei>2 -> 2</ei>
	9	processes within the Standard Model, plus some examples of
	10	processes beyond that, again for low multiplicities. Combined with
	11	the PYTHIA parton showers, this should be enough to get a flying
	12	start in the study of many physics scenarios.
	13	Other processes could be fed in via the
	14	<aloc href="LesHouchesAccord">Les Houches Accord</aloc>
	15	or be implemented as a
	16	<aloc href="SemiInternalProcesses">Semi-Internal Process</aloc>.
	17	In the latter case the existing processes would act as obvious
	18	templates.
	19
	20	<p/>
	21	By default all processes are switched off. You should switch on
	22	those you want to simulate. This may be done at two (occasionally
	23	three) levels, either for each individual process or for a group of
	24	processes. That is, a process is going to be generated either if its
	25	own flag or its group flag is on. There is no built-in construction
	26	to switch on a group and then switch off a few of its members.
	27
	28	<p/>
	29	Each process is assigned an integer code. This code is not used in
	30	the internal administration of events (so having the same code for
	31	two completely different processes would not be a problem), but only
	32	intended to allow a simpler user separation of different processes.
	33	Also the process name is available, as a string.
	34
	35	<p/>
	36	To ease navigation, the list of processes has been split into several
	37	separate pages, by main topic. The classification is hopefully
	38	intuitive, but by no means unambiguous. For instance, essentially
	39	all processes involve QCD, so the "QCD processes" are the ones that
	40	only involve QCD. (And also that is not completely true, once one
	41	includes all that may happen in multiple interactions.) On these
	42	separate pages also appear the settings that are completely local
	43	to that particular process class, but not the ones that have a
	44	broader usage.
	45
	46	<h3><aloc href="QCDProcesses">QCD Processes</aloc></h3>
	47
	48	QCD processes fall in two main categories: soft and hard. The soft ones
	49	contain elastic, diffractive and "minimum-bias" events, together
	50	covering the total cross section. Hard processea are the normal
	51	<ei>2 -> 2</ei> ones, including charm and bottom production.
	52	<br/>Reserved code range: 101 - 199.
	53
	54	<h3><aloc href="ElectroweakProcesses">Electroweak Processes</aloc></h3>
	55
	56	Prompt-photon, <ei>gamma^*/Z^0</ei> and <ei>W^+-</ei> production,
	57	plus a few processes with <ei>t</ei>-channel boson exchange.
	58	<br/>Reserved code range: 201 - 299.
	59
	60	<h3><aloc href="OniaProcesses">Onia Processes</aloc></h3>
	61
	62	Colour singlet and octet production of charmonium and bottomonium.
	63	<br/>Reserved code range: 401 - 499 for charmonium and
	64	501 - 599 for bottomonium.
65
66	<h3><aloc href="TopProcesses">Top Processes</aloc></h3>
67
68	Top production, singly or doubly.
69	<br/>Reserved code range: 601 - 699.
70
71	<h3><aloc href="FourthGenerationProcesses">Fourth-Generation
72	Processes</aloc></h3>
73
74	Production of hypothetical fourth-generation fermions.
75	<br/>Reserved code range: 801 - 899.
76
77	<h3><aloc href="HiggsProcesses">Higgs Processes</aloc></h3>
78
79	Higgs production, within or beyond the Standard Model.
80	See section on Left-Right-Symmetry processes for doubly charged Higgses.
81	<br/>Reserved code range: 901 - 999 for a Standard Model Higgs
82	and 1001 - 1199 for MSSM Higgses.
83
84	<h3><aloc href="SUSYProcesses">SUSY Processes</aloc></h3>
85
86	Production of supersymmetric particles, currently barely begun.
87	<br/>Reserved code range: 1001 - 2999. (Whereof 1001 - 1199
88	for Higgses; see above.)
89
90	<h3><aloc href="NewGaugeBosonProcesses">New-Gauge-Boson
91	Processes</aloc></h3>
92
93	Production of new gauge bosons such as <ei>Z'</ei> and <ei>W'</ei>.
94	<br/>Reserved code range: 3001 - 3099.
95
96	<h3><aloc href="LeftRightSymmetryProcesses">Left-Right-Symmetry
97	Processes</aloc></h3>
98
99	Production of righthanded <ei>Z_R</ei> and <ei>W_R</ei> bosons and of
100	doubly charged Higgses.
101	<br/>Reserved code range: 3101 - 3199.
102
103	<h3><aloc href="LeptoquarkProcesses">Leptoquark Processes</aloc></h3>
104
105	Production of a simple scalar leptoquark state.
106	<br/>Reserved code range: 3201 - 3299.
107
108	<h3><aloc href="CompositenessProcesses">Compositeness Processes</aloc></h3>
109
110	Production of excited fermion states and contact-interaction modification
111	to interactions between fermions (excluding technicolor; see below).
112	<br/>Reserved code range: 4001 - 4099.
113
114	<h3>Technicolor Processes</h3>
115
116	Production of technicolor particles and modifications of QCD processes
117	by technicolor interactions. Does not exist yet.
118	<br/>Reserved code range: 4101 - 4199.
119
120	<h3><aloc href="ExtraDimensionalProcesses">Extra-Dimensional
121	Processes</aloc></h3>
122
123	A vast area, here represented by the production of a Randall-Sundrum
124	excited graviton state.
125	<br/>Reserved code range: 5001 - 5099.
126
127	</chapter>
128
129	<!-- Copyright (C) 2008 Torbjorn Sjostrand -->
130