[u/mrichter/AliRoot.git] / PYTHIA8 / pythia8175 / phpdoc / LeptoquarkProcesses.php

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<h2>Leptoquark Processes</h2>

Leptoquarks arise in many scenarios, and can have widely different
characteristics, with respect to spin, isospin am d flavour.
The current implementation in no sense attempts to exhaust these 
possibilities, but only to encode one of the simplest possibilities,
with a single scalar leptoquark, denoted <i>LQ</i> and assigned PDG
code 42. The leptoquark is assumed to carry specific quark 
and lepton quantum numbers, by default <i>u</i> quark plus electron. 
These flavour numbers are conserved, i.e. a process such as 
<i>u e^- -> LQ -> d nu_e</i> is not allowed.
  
<p/>
Although only one leptoquark is implemented, its flavours may be 
changed arbitrarily to study the different possibilities. The 
flavours of the leptoquark are defined by the quark and lepton 
flavours in the decay mode list. Therefore, to change from the 
current <i>u e^-</i> to <i>c mu^+</i>, say, you only need 
a line
<br/><code>pythia.readString("42:0:products = 4 -13");</code>
<br/>in your main program, or the equivalent in a command file.
The former must always be a quark, while the latter could be a lepton 
or an antilepton; a charge-conjugate partner is automatically defined 
by the program. At initialization, the charge is recalculated as a 
function of the flavours defined; also the leptoquark name is redefined 
to be of the type <code>LQ_q,l</code>, where actual quark and lepton 
flavours are displayed. 
  
<p/>
The leptoquark is likely to be fairly long-lived, in which case it 
could have time to fragment into a mesonic- or baryonic-type state, which 
would decay later on. Currently this possibility is not handled; therefore 
the leptoquark is always assumed to decay before fragmentation. 
For that reason the leptoquark can also not be put stable.

<h3>Production processes</h3>

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

<br/><br/><strong>LeptoQuark:all</strong>  <input type="radio" name="1" value="on"><strong>On</strong>
<input type="radio" name="1" value="off" checked="checked"><strong>Off</strong>
 &nbsp;&nbsp;(<code>default = <strong>off</strong></code>)<br/>
Common switch for the group of lowest-order <i>LQ</i> production
processes, i.e. the four ones below.
  

<br/><br/><strong>LeptoQuark:ql2LQ</strong>  <input type="radio" name="2" value="on"><strong>On</strong>
<input type="radio" name="2" value="off" checked="checked"><strong>Off</strong>
 &nbsp;&nbsp;(<code>default = <strong>off</strong></code>)<br/>
Scatterings <i>q l -> LQ</i>. 
Code 3201.
  

<br/><br/><strong>LeptoQuark:qg2LQl</strong>  <input type="radio" name="3" value="on"><strong>On</strong>
<input type="radio" name="3" value="off" checked="checked"><strong>Off</strong>
 &nbsp;&nbsp;(<code>default = <strong>off</strong></code>)<br/>
Scatterings <i>q g -> LQ l</i>. 
Code 3202.
  

<br/><br/><strong>LeptoQuark:gg2LQLQbar</strong>  <input type="radio" name="4" value="on"><strong>On</strong>
<input type="radio" name="4" value="off" checked="checked"><strong>Off</strong>
 &nbsp;&nbsp;(<code>default = <strong>off</strong></code>)<br/>
Scatterings <i>g g -> LQ LQbar</i>. 
Code 3203.
  

<br/><br/><strong>LeptoQuark:qqbar2LQLQbar</strong>  <input type="radio" name="5" value="on"><strong>On</strong>
<input type="radio" name="5" value="off" checked="checked"><strong>Off</strong>
 &nbsp;&nbsp;(<code>default = <strong>off</strong></code>)<br/>
Scatterings <i>q qbar -> LQ LQbar</i>. 
Code 3204.
  

<h3>Parameters</h3>

In the above scenario the main free parameters are the leptoquark flavour
content, set as already described, and the <i>LQ</i> mass, set as usual. 
In addition there is one further parameter.

<br/><br/><table><tr><td><strong>LeptoQuark:kCoup </td><td></td><td> <input type="text" name="6" value="1.0" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>1.0</strong></code>; <code>minimum = 0.0</code>)</td></tr></table>
multiplicative factor in the <i>LQ -> q l</i> squared Yukawa coupling, 
and thereby in the <i>LQ</i> width and the <i>q l -> LQ</i> and 
other cross sections. Specifically, <i>lambda^2/(4 pi) = k alpha_em</i>, 
i.e. it corresponds to the $k$ factor of [<a href="Bibliography.php" target="page">Hew88</a>].
  

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<!-- Copyright (C) 2013 Torbjorn Sjostrand -->
Commit	Line	Data
c6b60c38	1	<html>
	2	<head>
	3	<title>Leptoquark Processes</title>
	4	<link rel="stylesheet" type="text/css" href="pythia.css"/>
	5	<link rel="shortcut icon" href="pythia32.gif"/>
	6	</head>
	7	<body>
	8
	9	<script language=javascript type=text/javascript>
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	25	}
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	27
	28	<form method='post' action='LeptoquarkProcesses.php'>
	29
	30	<h2>Leptoquark Processes</h2>
	31
	32	Leptoquarks arise in many scenarios, and can have widely different
	33	characteristics, with respect to spin, isospin am d flavour.
	34	The current implementation in no sense attempts to exhaust these
	35	possibilities, but only to encode one of the simplest possibilities,
	36	with a single scalar leptoquark, denoted <i>LQ</i> and assigned PDG
	37	code 42. The leptoquark is assumed to carry specific quark
	38	and lepton quantum numbers, by default <i>u</i> quark plus electron.
	39	These flavour numbers are conserved, i.e. a process such as
	40	<i>u e^- -> LQ -> d nu_e</i> is not allowed.
	41
	42	<p/>
	43	Although only one leptoquark is implemented, its flavours may be
	44	changed arbitrarily to study the different possibilities. The
	45	flavours of the leptoquark are defined by the quark and lepton
	46	flavours in the decay mode list. Therefore, to change from the
	47	current <i>u e^-</i> to <i>c mu^+</i>, say, you only need
	48	a line
	49	<br/><code>pythia.readString("42:0:products = 4 -13");</code>
	50	<br/>in your main program, or the equivalent in a command file.
	51	The former must always be a quark, while the latter could be a lepton
	52	or an antilepton; a charge-conjugate partner is automatically defined
	53	by the program. At initialization, the charge is recalculated as a
	54	function of the flavours defined; also the leptoquark name is redefined
	55	to be of the type <code>LQ_q,l</code>, where actual quark and lepton
	56	flavours are displayed.
	57
	58	<p/>
	59	The leptoquark is likely to be fairly long-lived, in which case it
	60	could have time to fragment into a mesonic- or baryonic-type state, which
	61	would decay later on. Currently this possibility is not handled; therefore
	62	the leptoquark is always assumed to decay before fragmentation.
	63	For that reason the leptoquark can also not be put stable.
	64
65	<h3>Production processes</h3>
66
67	Four production processes have been implemented, which normally would
68	not overlap and therefore could be run together.
69
70	<br/><br/><strong>LeptoQuark:all</strong> <input type="radio" name="1" value="on"><strong>On</strong>
71	<input type="radio" name="1" value="off" checked="checked"><strong>Off</strong>
72	(<code>default = <strong>off</strong></code>)<br/>
73	Common switch for the group of lowest-order <i>LQ</i> production
74	processes, i.e. the four ones below.
75
76
77	<br/><br/><strong>LeptoQuark:ql2LQ</strong> <input type="radio" name="2" value="on"><strong>On</strong>
78	<input type="radio" name="2" value="off" checked="checked"><strong>Off</strong>
79	(<code>default = <strong>off</strong></code>)<br/>
80	Scatterings <i>q l -> LQ</i>.
81	Code 3201.
82
83
84	<br/><br/><strong>LeptoQuark:qg2LQl</strong> <input type="radio" name="3" value="on"><strong>On</strong>
85	<input type="radio" name="3" value="off" checked="checked"><strong>Off</strong>
86	(<code>default = <strong>off</strong></code>)<br/>
87	Scatterings <i>q g -> LQ l</i>.
88	Code 3202.
89
90
91	<br/><br/><strong>LeptoQuark:gg2LQLQbar</strong> <input type="radio" name="4" value="on"><strong>On</strong>
92	<input type="radio" name="4" value="off" checked="checked"><strong>Off</strong>
93	(<code>default = <strong>off</strong></code>)<br/>
94	Scatterings <i>g g -> LQ LQbar</i>.
95	Code 3203.
96
97
98	<br/><br/><strong>LeptoQuark:qqbar2LQLQbar</strong> <input type="radio" name="5" value="on"><strong>On</strong>
99	<input type="radio" name="5" value="off" checked="checked"><strong>Off</strong>
100	(<code>default = <strong>off</strong></code>)<br/>
101	Scatterings <i>q qbar -> LQ LQbar</i>.
102	Code 3204.
103
104
105	<h3>Parameters</h3>
106
107	In the above scenario the main free parameters are the leptoquark flavour
108	content, set as already described, and the <i>LQ</i> mass, set as usual.
109	In addition there is one further parameter.
110
111	<br/><br/><table><tr><td><strong>LeptoQuark:kCoup </td><td></td><td> <input type="text" name="6" value="1.0" size="20"/>   (<code>default = <strong>1.0</strong></code>; <code>minimum = 0.0</code>)</td></tr></table>
112	multiplicative factor in the <i>LQ -> q l</i> squared Yukawa coupling,
113	and thereby in the <i>LQ</i> width and the <i>q l -> LQ</i> and
114	other cross sections. Specifically, <i>lambda^2/(4 pi) = k alpha_em</i>,
115	i.e. it corresponds to the $k$ factor of [<a href="Bibliography.php" target="page">Hew88</a>].
116
117
118	<input type="hidden" name="saved" value="1"/>
119
120	<?php
121	echo "<input type='hidden' name='filepath' value='".$_GET["filepath"]."'/>"?>
122
123	<table width="100%"><tr><td align="right"><input type="submit" value="Save Settings" /></td></tr></table>
124	</form>
125
126	<?php
127
128	if($_POST["saved"] == 1)
129	{
130	$filepath = $_POST["filepath"];
131	$handle = fopen($filepath, 'a');
132
133	if($_POST["1"] != "off")
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135	$data = "LeptoQuark:all = ".$_POST["1"]."\n";
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161	fwrite($handle,$data);
162	}
163	fclose($handle);
164	}
165
166	?>
167	</body>
168	</html>
169
170	<!-- Copyright (C) 2013 Torbjorn Sjostrand -->
171