1
<chapter name="Higgs Processes">
3
<h2>Higgs Processes</h2>
5
This page documents Higgs production within and beyond the Standard Model
6
(SM and BSM for short). This includes several different processes and,
7
for the BSM scenarios, a large set of parameters that would only be fixed
8
within a more specific framework such as MSSM. Three choices can be made
9
irrespective of the particular model:
11
<flag name="Higgs:cubicWidth" default="off">
12
The partial width of a Higgs particle to a pair of gauge bosons,
13
<ei>W^+ W^-</ei> or <ei>Z^0 Z^0</ei>, depends cubically on the
14
Higgs mass. When selecting the Higgs according to a Breit-Wigner,
15
so that the actual mass <ei>mHat</ei> does not agree with the
16
nominal <ei>m_Higgs</ei> one, an ambiguity arises which of the
17
two to use <ref>Sey95</ref>. The default is to use a linear
18
dependence on <ei>mHat</ei>, i.e. a width proportional to
19
<ei>m_Higgs^2 * mHat</ei>, while <code>on</code> gives a
20
<ei>mHat^3</ei> dependence. This does not affect the widths to
21
fermions, which only depend linearly on <ei>mHat</ei>.
22
This flag is used both for SM and BSM Higgses.
25
<flag name="Higgs:runningLoopMass" default="on">
26
The partial width of a Higgs particle to a pair of gluons or photons,
27
or a <ei>gamma Z^0</ei> pair, proceeds in part through quark loops,
28
mainly <ei>b</ei> and <ei>t</ei>. There is some ambiguity what kind
29
of masses to use. Default is running MSbar ones, but alternatively
30
fixed pole masses are allowed (as was standard in PYTHIA 6), which
31
typically gives a noticeably higher cross section for these channels.
32
(For a decay to a pair of fermions, such as top, the running mass is
33
used for couplings and the fixed one for phase space.)
36
<flag name="Higgs:clipWings" default="on">
37
The Breit-Wigner shape of a Higgs is nontrivial, owing to the rapid
38
width variation with the mass of a Higgs. This imples that a Higgs
39
of low nominal mass may still acquire a non-negligible high-end tail.
40
The validity of the calculation may be questioned in these wings.
41
With this option on, the <code>Higgs:wingsFac</code> value is used to
45
<parm name="Higgs:wingsFac" default="50." min="0.">
46
With <code>Higgs:clipWings</code> on, all Higgs masses which deviate
47
from the nominal one by more than <code>Higgs:wingsFac</code>
48
times the nominal width are forbidden. This is achieved by setting
49
the <code>mMin</code> and <code>mMax</code> values of the Higgs states
50
at initialization (but never so as to allow a wider range than already
51
set by the user, alternatively by the default values).
54
<h3>Standard-Model Higgs, basic processes</h3>
56
This section provides the standard set of processes that can be
57
run together to provide a reasonably complete overview of possible
58
production channels for a single SM Higgs.
59
The main parameter is the choice of Higgs mass, which can be set in the
60
normal <code>ParticleData</code> database; thereafter the properties
61
within the SM are essentially fixed.
63
<flag name="HiggsSM:all" default="off">
64
Common switch for the group of Higgs production within the Standard Model.
67
<flag name="HiggsSM:ffbar2H" default="off">
68
Scattering <ei>f fbar -> H^0</ei>, where <ei>f</ei> sums over available
69
flavours except top. Related to the mass-dependent Higgs point coupling
70
to fermions, so at hadron colliders the bottom contribution will
75
<flag name="HiggsSM:gg2H" default="off">
76
Scattering <ei>g g -> H^0</ei> via loop contributions primarily from
81
<flag name="HiggsSM:gmgm2H" default="off">
82
Scattering <ei>gamma gamma -> H^0</ei> via loop contributions primarily
83
from top and <ei>W</ei>.
87
<flag name="HiggsSM:ffbar2HZ" default="off">
88
Scattering <ei>f fbar -> H^0 Z^0</ei> via <ei>s</ei>-channel <ei>Z^0</ei>
93
<flag name="HiggsSM:ffbar2HW" default="off">
94
Scattering <ei>f fbar -> H^0 W^+-</ei> via <ei>s</ei>-channel <ei>W^+-</ei>
99
<flag name="HiggsSM:ff2Hff(t:ZZ)" default="off">
100
Scattering <ei>f f' -> H^0 f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
104
<flag name="HiggsSM:ff2Hff(t:WW)" default="off">
105
Scattering <ei>f_1 f_2 -> H^0 f_3 f_4</ei> via <ei>W^+ W^-</ei> fusion.
109
<flag name="HiggsSM:gg2Httbar" default="off">
110
Scattering <ei>g g -> H^0 t tbar</ei> via <ei>t tbar</ei> fusion
111
(or, alternatively put, Higgs radiation off a top line).
112
Warning: unfortunately this process is rather slow, owing to a
113
lengthy cross-section expression and inefficient phase-space selection.
117
<flag name="HiggsSM:qqbar2Httbar" default="off">
118
Scattering <ei>q qbar -> H^0 t tbar</ei> via <ei>t tbar</ei> fusion
119
(or, alternatively put, Higgs radiation off a top line).
120
Warning: unfortunately this process is rather slow, owing to a
121
lengthy cross-section expression and inefficient phase-space selection.
125
<h3>Standard-Model Higgs, further processes</h3>
127
A number of further production processes has been implemented, that
128
are specializations of some of the above ones to the high-<ei>pT</ei>
129
region. The sets therefore could not be used simultaneously
130
without unphysical doublecounting, as further explained below.
131
They are not switched on by the <code>HiggsSM:all</code> flag, but
132
have to be switched on for each separate process after due consideration.
135
The first three processes in this section are related to the Higgs
136
point coupling to fermions, and so primarily are of interest for
137
<ei>b</ei> quarks. It is here useful to begin by reminding that
138
a process like <ei>b bbar -> H^0</ei> implies that a <ei>b/bbar</ei>
139
is taken from each incoming hadron, leaving behind its respective
140
antiparticle. The initial-state showers will then add one
141
<ei>g -> b bbar</ei> branching on either side, so that effectively
142
the process becomes <ei>g g -> H0 b bbar</ei>. This would be the
143
same basic process as the <ei>g g -> H^0 t tbar</ei> one used for top.
144
The difference is that (a) no PDF's are defined for top and
145
(b) the shower approach would not be good enough to provide sensible
146
kinematics for the <ei>H^0 t tbar</ei> subsystem. By contrast, owing
147
to the <ei>b</ei> being much lighter than the Higgs, multiple
148
gluon emissions must be resummed for <ei>b</ei>, as is done by PDF's
149
and showers, in order to obtain a sensible description of the total
150
production rate, when the <ei>b</ei> quarks predominantly are produced
151
at small <ei>pT</ei> values.
153
<flag name="HiggsSM:qg2Hq" default="off">
154
Scattering <ei>q g -> H^0 q</ei>. This process gives first-order
155
corrections to the <ei>f fbar -> H^0</ei> one above, and should only be
156
used to study the high-<ei>pT</ei> tail, while <ei>f fbar -> H^0</ei>
157
should be used for inclusive production. Only the dominant <ei>c</ei>
158
and <ei>b</ei> contributions are included, and generated separately
159
for technical reasons. Note that another first-order process would be
160
<ei>q qbar -> H^0 g</ei>, which is not explicitly implemented here,
161
but is obtained from showering off the lowest-order process. It does not
162
contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
163
interesting for many applications.
167
<flag name="HiggsSM:gg2Hbbbar" default="off">
168
Scattering <ei>g g -> H^0 b bbar</ei>. This process is yet one order
169
higher of the <ei>b bbar -> H^0</ei> and <ei>b g -> H^0 b</ei> chain,
170
where now two quarks should be required above some large <ei>pT</ei>
172
Warning: unfortunately this process is rather slow, owing to a
173
lengthy cross-section expression and inefficient phase-space selection.
177
<flag name="HiggsSM:qqbar2Hbbbar" default="off">
178
Scattering <ei>q qbar -> H^0 b bbar</ei> via an <ei>s</ei>-channel
179
gluon, so closely related to the previous one, but typically less
180
important owing to the smaller rate of (anti)quarks relative to
182
Warning: unfortunately this process is rather slow, owing to a
183
lengthy cross-section expression and inefficient phase-space selection.
188
The second set of processes are predominantly first-order corrections
189
to the <ei>g g -> H^0</ei> process, again dominated by the top loop.
190
We here only provide the kinematical expressions obtained in the
191
limit that the top quark goes to infinity, but scaled to the
192
finite-top-mass coupling in <ei>g g -> H^0</ei>. (Complete loop
193
expressions are available e.g. in PYTHIA 6.4 but are very lengthy.)
194
This provides a reasonably accurate description for "intermediate"
195
<ei>pT</ei> values, but fails when the <ei>pT</ei> scale approaches
198
<flag name="HiggsSM:gg2Hg(l:t)" default="off">
199
Scattering <ei>g g -> H^0 g</ei> via loop contributions primarily
204
<flag name="HiggsSM:qg2Hq(l:t)" default="off">
205
Scattering <ei>q g -> H^0 q</ei> via loop contributions primarily
206
from top. Not to be confused with the <code>HiggsSM:qg2Hq</code>
207
process above, with its direct fermion-to-Higgs coupling.
211
<flag name="HiggsSM:qqbar2Hg(l:t)" default="off">
212
Scattering <ei>q qbar -> H^0 g</ei> via an <ei>s</ei>-channel gluon
213
and loop contributions primarily from top. Is strictly speaking a
214
"new" process, not directly derived from <ei>g g -> H^0</ei>, and
215
could therefore be included in the standard mix without doublecounting,
216
but is numerically negligible.
220
<h3>Beyond-the-Standard-Model Higgs, introduction</h3>
222
Further Higgs multiplets arise in a number of scenarios. We here
223
concentrate on the MSSM scenario with two Higgs doublets, but with
224
flexibility enough that also other two-Higgs-doublet scenarios could
225
be represented by a suitable choice of parameters. Conventionally the
226
Higgs states are labelled <ei>h^0, H^0, A^0</ei> and <ei>H^+-</ei>.
227
If the scalar and pseudocalar states mix the resulting states are
228
labelled <ei>H_1^0, H_2^0, H_3^0</ei>. In process names and parameter
229
explanations both notations will be used, but for settings labels
230
we have adapted the shorthand hybrid notation <code>H1</code> for
231
<ei>h^0(H_1^0)</ei>, <code>H2</code> for <ei>H^0(H_2^0)</ei> and
232
<code>A3</code> for <ei>A^0(H_3^0)</ei>. (Recall that the
233
<code>Settings</code> database does not distinguish upper- and lowercase
234
characters, so that the user has one thing less to worry about, but here
235
it causes probles with <ei>h^0</ei> vs. <ei>H^0</ei>.) We leave the issue
236
of mass ordering between <ei>H^0</ei> and <ei>A^0</ei> open, and thereby
237
also that of <ei>H_2^0</ei> and <ei>H_3^0</ei>.
239
<flag name="Higgs:useBSM" default="off">
240
Master switch to initialize and use the two-Higgs-doublet states.
241
If off, only the above SM Higgs processes can be used, with couplings
242
as predicted in the SM. If on, only the below BSM Higgs processes can
243
be used, with couplings that can be set freely, also found further down
247
<h3>Beyond-the-Standard-Model Higgs, basic processes</h3>
249
This section provides the standard set of processes that can be
250
run together to provide a reasonably complete overview of possible
251
production channels for a single neutral Higgs state in a two-doublet
252
scenarios such as MSSM. The list of processes for neutral states closely
253
mimics the one found for the SM Higgs. Some of the processes
254
vanish for a pure pseudoscalar <ei>A^0</ei>, but are kept for flexiblity
255
in cases of mixing with the scalar <ei>h^0</ei> and <ei>H^0</ei> states,
256
or for use in the context of non-MSSM models. This should work well to
257
represent e.g. that a small admixture of the "wrong" parity would allow
258
a process such as <ei>q qbar -> A^0 Z^0</ei>, which otherwise is forbidden.
259
However, note that the loop integrals e.g. for <ei>g g -> h^0/H^0/A^0</ei>
260
are hardcoded to be for scalars for the former two particles and for a
261
pseudoscalar for the latter one, so absolute rates would not be
262
correctly represented in the case of large scalar/pseudoscalar mixing.
264
<flag name="HiggsBSM:all" default="off">
265
Common switch for the group of Higgs production beyond the Standard Model,
269
<h4>1) <ei>h^0(H_1^0)</ei> processes</h4>
271
<flag name="HiggsBSM:allH1" default="off">
272
Common switch for the group of <ei>h^0(H_1^0)</ei> production processes.
275
<flag name="HiggsBSM:ffbar2H1" default="off">
276
Scattering <ei>f fbar -> h^0(H_1^0)</ei>, where <ei>f</ei> sums over available
281
<flag name="HiggsBSM:gg2H1" default="off">
282
Scattering <ei>g g -> h^0(H_1^0)</ei> via loop contributions primarily from
287
<flag name="HiggsBSM:gmgm2H1" default="off">
288
Scattering <ei>gamma gamma -> h^0(H_1^0)</ei> via loop contributions
289
primarily from top and <ei>W</ei>.
293
<flag name="HiggsBSM:ffbar2H1Z" default="off">
294
Scattering <ei>f fbar -> h^0(H_1^0) Z^0</ei> via <ei>s</ei>-channel
295
<ei>Z^0</ei> exchange.
299
<flag name="HiggsBSM:ffbar2H1W" default="off">
300
Scattering <ei>f fbar -> h^0(H_1^0) W^+-</ei> via <ei>s</ei>-channel
301
<ei>W^+-</ei> exchange.
305
<flag name="HiggsBSM:ff2H1ff(t:ZZ)" default="off">
306
Scattering <ei>f f' -> h^0(H_1^0) f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
310
<flag name="HiggsBSM:ff2H1ff(t:WW)" default="off">
311
Scattering <ei>f_1 f_2 -> h^0(H_1^0) f_3 f_4</ei> via <ei>W^+ W^-</ei>
316
<flag name="HiggsBSM:gg2H1ttbar" default="off">
317
Scattering <ei>g g -> h^0(H_1^0) t tbar</ei> via <ei>t tbar</ei> fusion
318
(or, alternatively put, Higgs radiation off a top line).
319
Warning: unfortunately this process is rather slow, owing to a
320
lengthy cross-section expression and inefficient phase-space selection.
324
<flag name="HiggsBSM:qqbar2H1ttbar" default="off">
325
Scattering <ei>q qbar -> h^0(H_1^0) t tbar</ei> via <ei>t tbar</ei> fusion
326
(or, alternatively put, Higgs radiation off a top line).
327
Warning: unfortunately this process is rather slow, owing to a
328
lengthy cross-section expression and inefficient phase-space selection.
332
<h4>2) <ei>H^0(H_2^0)</ei> processes</h4>
334
<flag name="HiggsBSM:allH2" default="off">
335
Common switch for the group of <ei>H^0(H_2^0)</ei> production processes.
338
<flag name="HiggsBSM:ffbar2H2" default="off">
339
Scattering <ei>f fbar -> H^0(H_2^0)</ei>, where <ei>f</ei> sums over available
344
<flag name="HiggsBSM:gg2H2" default="off">
345
Scattering <ei>g g -> H^0(H_2^0)</ei> via loop contributions primarily from
350
<flag name="HiggsBSM:gmgm2H2" default="off">
351
Scattering <ei>gamma gamma -> H^0(H_2^0)</ei> via loop contributions primarily
352
from top and <ei>W</ei>.
356
<flag name="HiggsBSM:ffbar2H2Z" default="off">
357
Scattering <ei>f fbar -> H^0(H_2^0) Z^0</ei> via <ei>s</ei>-channel
358
<ei>Z^0</ei> exchange.
362
<flag name="HiggsBSM:ffbar2H2W" default="off">
363
Scattering <ei>f fbar -> H^0(H_2^0) W^+-</ei> via <ei>s</ei>-channel
364
<ei>W^+-</ei> exchange.
368
<flag name="HiggsBSM:ff2H2ff(t:ZZ)" default="off">
369
Scattering <ei>f f' -> H^0(H_2^0) f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
373
<flag name="HiggsBSM:ff2H2ff(t:WW)" default="off">
374
Scattering <ei>f_1 f_2 -> H^0(H_2^0) f_3 f_4</ei> via <ei>W^+ W^-</ei> fusion.
378
<flag name="HiggsBSM:gg2H2ttbar" default="off">
379
Scattering <ei>g g -> H^0(H_2^0) t tbar</ei> via <ei>t tbar</ei> fusion
380
(or, alternatively put, Higgs radiation off a top line).
381
Warning: unfortunately this process is rather slow, owing to a
382
lengthy cross-section expression and inefficient phase-space selection.
386
<flag name="HiggsBSM:qqbar2H2ttbar" default="off">
387
Scattering <ei>q qbar -> H^0(H_2^0) t tbar</ei> via <ei>t tbar</ei> fusion
388
(or, alternatively put, Higgs radiation off a top line).
389
Warning: unfortunately this process is rather slow, owing to a
390
lengthy cross-section expression and inefficient phase-space selection.
393
<h4>3) <ei>A^0(H_3^0)</ei> processes</h4>
395
<flag name="HiggsBSM:allA3" default="off">
396
Common switch for the group of <ei>A^0(H_3^0)</ei> production processes.
399
<flag name="HiggsBSM:ffbar2A3" default="off">
400
Scattering <ei>f fbar -> A^0(H_3^0)</ei>, where <ei>f</ei> sums over available
405
<flag name="HiggsBSM:gg2A3" default="off">
406
Scattering <ei>g g -> A^0(A_3^0)</ei> via loop contributions primarily from
411
<flag name="HiggsBSM:gmgm2A3" default="off">
412
Scattering <ei>gamma gamma -> A^0(A_3^0)</ei> via loop contributions primarily
413
from top and <ei>W</ei>.
417
<flag name="HiggsBSM:ffbar2A3Z" default="off">
418
Scattering <ei>f fbar -> A^0(A_3^0) Z^0</ei> via <ei>s</ei>-channel
419
<ei>Z^0</ei> exchange.
423
<flag name="HiggsBSM:ffbar2A3W" default="off">
424
Scattering <ei>f fbar -> A^0(A_3^0) W^+-</ei> via <ei>s</ei>-channel
425
<ei>W^+-</ei> exchange.
429
<flag name="HiggsBSM:ff2A3ff(t:ZZ)" default="off">
430
Scattering <ei>f f' -> A^0(A_3^0) f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
434
<flag name="HiggsBSM:ff2A3ff(t:WW)" default="off">
435
Scattering <ei>f_1 f_2 -> A^0(A_3^0) f_3 f_4</ei> via <ei>W^+ W^-</ei> fusion.
439
<flag name="HiggsBSM:gg2A3ttbar" default="off">
440
Scattering <ei>g g -> A^0(A_3^0) t tbar</ei> via <ei>t tbar</ei> fusion
441
(or, alternatively put, Higgs radiation off a top line).
442
Warning: unfortunately this process is rather slow, owing to a
443
lengthy cross-section expression and inefficient phase-space selection.
447
<flag name="HiggsBSM:qqbar2A3ttbar" default="off">
448
Scattering <ei>q qbar -> A^0(A_3^0) t tbar</ei> via <ei>t tbar</ei> fusion
449
(or, alternatively put, Higgs radiation off a top line).
450
Warning: unfortunately this process is rather slow, owing to a
451
lengthy cross-section expression and inefficient phase-space selection.
454
<h4>4) <ei>H+-</ei> processes</h4>
456
<flag name="HiggsBSM:allH+-" default="off">
457
Common switch for the group of <ei>H^+-</ei> production processes.
460
<flag name="HiggsBSM:ffbar2H+-" default="off">
461
Scattering <ei>f fbar' -> H^+-</ei>, where <ei>f, fbar'</ei> sums over
462
available incoming flavours. Since couplings are assumed
463
generation-diagonal, in practice this means <ei>c sbar -> H^+</ei>
464
and <ei>s cbar -> H^-</ei>.
468
<flag name="HiggsBSM:bg2H+-t" default="off">
469
Scattering <ei>b g -> H^+ tbar</ei>. At hadron colliders this is the
470
dominant process for single-charged-Higgs production.
474
<h4>5) Higgs-pair processes</h4>
476
<flag name="HiggsBSM:allHpair" default="off">
477
Common switch for the group of Higgs pair-production processes.
480
<flag name="HiggsBSM:ffbar2A3H1" default="off">
481
Scattering <ei>f fbar -> A^0(H_3) h^0(H_1)</ei>.
485
<flag name="HiggsBSM:ffbar2A3H2" default="off">
486
Scattering <ei>f fbar -> A^0(H_3) H^0(H_2)</ei>.
490
<flag name="HiggsBSM:ffbar2H+-H1" default="off">
491
Scattering <ei>f fbar -> H^+- h^0(H_1)</ei>.
495
<flag name="HiggsBSM:ffbar2H+-H2" default="off">
496
Scattering <ei>f fbar -> H^+- H^0(H_2)</ei>.
500
<flag name="HiggsBSM:ffbar2H+H-" default="off">
501
Scattering <ei>f fbar -> H+ H-</ei>.
505
<h3>Beyond-the-Standard-Model Higgs, further processes</h3>
507
This section mimics the above section on "Standard-Model Higgs,
508
further processes", i.e. it contains higher-order corrections
509
to the processes already listed. The two sets therefore could not
510
be used simultaneously without unphysical doublecounting.
511
They are not controlled by any group flag, but have to be switched
512
on for each separate process after due consideration. We refer to
513
the standard-model description for a set of further comments on
516
<h4>1) <ei>h^0(H_1^0)</ei> processes</h4>
518
<flag name="HiggsBSM:qg2H1q" default="off">
519
Scattering <ei>q g -> h^0 q</ei>. This process gives first-order
520
corrections to the <ei>f fbar -> h^0</ei> one above, and should only be
521
used to study the high-<ei>pT</ei> tail, while <ei>f fbar -> h^0</ei>
522
should be used for inclusive production. Only the dominant <ei>c</ei>
523
and <ei>b</ei> contributions are included, and generated separately
524
for technical reasons. Note that another first-order process would be
525
<ei>q qbar -> h^0 g</ei>, which is not explicitly implemented here,
526
but is obtained from showering off the lowest-order process. It does not
527
contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
528
interesting for many applications.
532
<flag name="HiggsBSM:gg2H1bbbar" default="off">
533
Scattering <ei>g g -> h^0 b bbar</ei>. This process is yet one order
534
higher of the <ei>b bbar -> h^0</ei> and <ei>b g -> h^0 b</ei> chain,
535
where now two quarks should be required above some large <ei>pT</ei>
537
Warning: unfortunately this process is rather slow, owing to a
538
lengthy cross-section expression and inefficient phase-space selection.
542
<flag name="HiggsBSM:qqbar2H1bbbar" default="off">
543
Scattering <ei>q qbar -> h^0 b bbar</ei> via an <ei>s</ei>-channel
544
gluon, so closely related to the previous one, but typically less
545
important owing to the smaller rate of (anti)quarks relative to
547
Warning: unfortunately this process is rather slow, owing to a
548
lengthy cross-section expression and inefficient phase-space selection.
552
<flag name="HiggsBSM:gg2H1g(l:t)" default="off">
553
Scattering <ei>g g -> h^0 g</ei> via loop contributions primarily
558
<flag name="HiggsBSM:qg2H1q(l:t)" default="off">
559
Scattering <ei>q g -> h^0 q</ei> via loop contributions primarily
560
from top. Not to be confused with the <code>HiggsBSM:qg2H1q</code>
561
process above, with its direct fermion-to-Higgs coupling.
565
<flag name="HiggsBSM:qqbar2H1g(l:t)" default="off">
566
Scattering <ei>q qbar -> h^0 g</ei> via an <ei>s</ei>-channel gluon
567
and loop contributions primarily from top. Is strictly speaking a
568
"new" process, not directly derived from <ei>g g -> h^0</ei>, and
569
could therefore be included in the standard mix without doublecounting,
570
but is numerically negligible.
574
<h4>2) <ei>H^0(H_2^0)</ei> processes</h4>
576
<flag name="HiggsBSM:qg2H2q" default="off">
577
Scattering <ei>q g -> H^0 q</ei>. This process gives first-order
578
corrections to the <ei>f fbar -> H^0</ei> one above, and should only be
579
used to study the high-<ei>pT</ei> tail, while <ei>f fbar -> H^0</ei>
580
should be used for inclusive production. Only the dominant <ei>c</ei>
581
and <ei>b</ei> contributions are included, and generated separately
582
for technical reasons. Note that another first-order process would be
583
<ei>q qbar -> H^0 g</ei>, which is not explicitly implemented here,
584
but is obtained from showering off the lowest-order process. It does not
585
contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
586
interesting for many applications.
590
<flag name="HiggsBSM:gg2H2bbbar" default="off">
591
Scattering <ei>g g -> H^0 b bbar</ei>. This process is yet one order
592
higher of the <ei>b bbar -> H^0</ei> and <ei>b g -> H^0 b</ei> chain,
593
where now two quarks should be required above some large <ei>pT</ei>
595
Warning: unfortunately this process is rather slow, owing to a
596
lengthy cross-section expression and inefficient phase-space selection.
600
<flag name="HiggsBSM:qqbar2H2bbbar" default="off">
601
Scattering <ei>q qbar -> H^0 b bbar</ei> via an <ei>s</ei>-channel
602
gluon, so closely related to the previous one, but typically less
603
important owing to the smaller rate of (anti)quarks relative to
605
Warning: unfortunately this process is rather slow, owing to a
606
lengthy cross-section expression and inefficient phase-space selection.
610
<flag name="HiggsBSM:gg2H2g(l:t)" default="off">
611
Scattering <ei>g g -> H^0 g</ei> via loop contributions primarily
616
<flag name="HiggsBSM:qg2H2q(l:t)" default="off">
617
Scattering <ei>q g -> H^0 q</ei> via loop contributions primarily
618
from top. Not to be confused with the <code>HiggsBSM:qg2H1q</code>
619
process above, with its direct fermion-to-Higgs coupling.
623
<flag name="HiggsBSM:qqbar2H2g(l:t)" default="off">
624
Scattering <ei>q qbar -> H^0 g</ei> via an <ei>s</ei>-channel gluon
625
and loop contributions primarily from top. Is strictly speaking a
626
"new" process, not directly derived from <ei>g g -> H^0</ei>, and
627
could therefore be included in the standard mix without doublecounting,
628
but is numerically negligible.
632
<h4>3) <ei>A^0(H_3^0)</ei> processes</h4>
634
<flag name="HiggsBSM:qg2A3q" default="off">
635
Scattering <ei>q g -> A^0 q</ei>. This process gives first-order
636
corrections to the <ei>f fbar -> A^0</ei> one above, and should only be
637
used to study the high-<ei>pT</ei> tail, while <ei>f fbar -> A^0</ei>
638
should be used for inclusive production. Only the dominant <ei>c</ei>
639
and <ei>b</ei> contributions are included, and generated separately
640
for technical reasons. Note that another first-order process would be
641
<ei>q qbar -> A^0 g</ei>, which is not explicitly implemented here,
642
but is obtained from showering off the lowest-order process. It does not
643
contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
644
interesting for many applications.
648
<flag name="HiggsBSM:gg2A3bbbar" default="off">
649
Scattering <ei>g g -> A^0 b bbar</ei>. This process is yet one order
650
higher of the <ei>b bbar -> A^0</ei> and <ei>b g -> A^0 b</ei> chain,
651
where now two quarks should be required above some large <ei>pT</ei>
653
Warning: unfortunately this process is rather slow, owing to a
654
lengthy cross-section expression and inefficient phase-space selection.
658
<flag name="HiggsBSM:qqbar2A3bbbar" default="off">
659
Scattering <ei>q qbar -> A^0 b bbar</ei> via an <ei>s</ei>-channel
660
gluon, so closely related to the previous one, but typically less
661
important owing to the smaller rate of (anti)quarks relative to
663
Warning: unfortunately this process is rather slow, owing to a
664
lengthy cross-section expression and inefficient phase-space selection.
668
<flag name="HiggsBSM:gg2A3g(l:t)" default="off">
669
Scattering <ei>g g -> A^0 g</ei> via loop contributions primarily
674
<flag name="HiggsBSM:qg2A3q(l:t)" default="off">
675
Scattering <ei>q g -> A^0 q</ei> via loop contributions primarily
676
from top. Not to be confused with the <code>HiggsBSM:qg2H1q</code>
677
process above, with its direct fermion-to-Higgs coupling.
681
<flag name="HiggsBSM:qqbar2A3g(l:t)" default="off">
682
Scattering <ei>q qbar -> A^0 g</ei> via an <ei>s</ei>-channel gluon
683
and loop contributions primarily from top. Is strictly speaking a
684
"new" process, not directly derived from <ei>g g -> A^0</ei>, and
685
could therefore be included in the standard mix without doublecounting,
686
but is numerically negligible.
690
<h3>Parameters for Beyond-the-Standard-Model Higgs production and decay</h3>
692
This section offers a big flexibility to set couplings of the various
693
Higgs states to fermions and gauge bosons, and also to each other.
694
The intention is that, for scenarios like MSSM, you should use standard
695
input from the <aloc href="SUSYLesHouchesAccord">SUSY Les Houches
696
Accord</aloc>, rather than having to set it all yourself. In other cases,
697
however, the freedom is there for you to use. Kindly note that some
698
of the internal calculations of partial widths from the parameters provided
699
do not include mixing between the scalar and pseudoscalar states.
702
Masses would be set in the <code>ParticleData</code> database,
703
while couplings are set below. When possible, the couplings of the Higgs
704
states are normalized to the corresponding coupling within the SM.
705
When not, their values within the MSSM are indicated, from which
706
it should be straightforward to understand what to use instead.
707
The exception is some couplings that vanish also in the MSSM, where the
708
normalization has been defined in close analogy with nonvanishing ones.
709
Some parameter names are asymmetric but crossing can always be used,
710
i.e. the coupling for <ei>A^0 -> H^0 Z^0</ei> obviously is also valid
711
for <ei>H^0 -> A^0 Z^0</ei> and <ei>Z^0 -> H^0 A^0</ei>.
712
Note that couplings usually appear quadratically in matrix elements.
714
<parm name="HiggsH1:coup2d" default="1.">
715
The <ei>h^0(H_1^0)</ei> coupling to down-type quarks.
718
<parm name="HiggsH1:coup2u" default="1.">
719
The <ei>h^0(H_1^0)</ei> coupling to up-type quarks.
722
<parm name="HiggsH1:coup2l" default="1.">
723
The <ei>h^0(H_1^0)</ei> coupling to (charged) leptons.
726
<parm name="HiggsH1:coup2Z" default="1.">
727
The <ei>h^0(H_1^0)</ei> coupling to <ei>Z^0</ei>.
730
<parm name="HiggsH1:coup2W" default="1.">
731
The <ei>h^0(H_1^0)</ei> coupling to <ei>W^+-</ei>.
734
<parm name="HiggsH1:coup2Hchg" default="0.">
735
The <ei>h^0(H_1^0)</ei> coupling to <ei>H^+-</ei> (in loops).
736
Is <ei>sin(beta - alpha) + cos(2 beta) sin(beta + alpha) /
737
(2 cos^2theta_W)</ei> in the MSSM.
740
<parm name="HiggsH2:coup2d" default="1.">
741
The <ei>H^0(H_2^0)</ei> coupling to down-type quarks.
744
<parm name="HiggsH2:coup2u" default="1.">
745
The <ei>H^0(H_2^0)</ei> coupling to up-type quarks.
748
<parm name="HiggsH2:coup2l" default="1.">
749
The <ei>H^0(H_2^0)</ei> coupling to (charged) leptons.
752
<parm name="HiggsH2:coup2Z" default="1.">
753
The <ei>H^0(H_2^0)</ei> coupling to <ei>Z^0</ei>.
756
<parm name="HiggsH2:coup2W" default="1.">
757
The <ei>H^0(H_2^0)</ei> coupling to <ei>W^+-</ei>.
760
<parm name="HiggsH2:coup2Hchg" default="0.">
761
The <ei>H^0(H_2^0)</ei> coupling to <ei>H^+-</ei> (in loops).
762
Is <ei>cos(beta - alpha) + cos(2 beta) cos(beta + alpha) /
763
(2 cos^2theta_W)</ei> in the MSSM.
766
<parm name="HiggsH2:coup2H1H1" default="1.">
767
The <ei>H^0(H_2^0)</ei> coupling to a <ei>h^0(H_1^0)</ei> pair.
768
Is <ei>cos(2 alpha) cos(beta + alpha) - 2 sin(2 alpha)
769
sin(beta + alpha)</ei> in the MSSM.
772
<parm name="HiggsH2:coup2A3A3" default="1.">
773
The <ei>H^0(H_2^0)</ei> coupling to an <ei>A^0(H_3^0)</ei> pair.
774
Is <ei>cos(2 beta) cos(beta + alpha)</ei> in the MSSM.
777
<parm name="HiggsH2:coup2H1Z" default="0.">
778
The <ei>H^0(H_2^0)</ei> coupling to a <ei>h^0(H_1^0) Z^0</ei> pair.
779
Vanishes in the MSSM.
782
<parm name="HiggsH2:coup2A3H1" default="0.">
783
The <ei>H^0(H_2^0)</ei> coupling to an <ei>A^0(H_3^0) h^0(H_1^0)</ei> pair.
784
Vanishes in the MSSM.
787
<parm name="HiggsH2:coup2HchgW" default="0.">
788
The <ei>H^0(H_2^0)</ei> coupling to a <ei>H^+- W-+</ei> pair.
789
Is <ei>sin(beta - alpha)</ei> in the MSSM.
792
<parm name="HiggsA3:coup2d" default="1.">
793
The <ei>A^0(H_3^0)</ei> coupling to down-type quarks.
796
<parm name="HiggsA3:coup2u" default="1.">
797
The <ei>A^0(H_3^0)</ei> coupling to up-type quarks.
800
<parm name="HiggsA3:coup2l" default="1.">
801
The <ei>A^0(H_3^0)</ei> coupling to (charged) leptons.
804
<parm name="HiggsA3:coup2H1Z" default="1.">
805
The <ei>A^0(H_3^0)</ei> coupling to a <ei>h^0(H_1^0) Z^0</ei> pair.
806
Is <ei>cos(beta - alpha)</ei> in the MSSM.
809
<parm name="HiggsA3:coup2H2Z" default="1.">
810
The <ei>A^0(H_3^0)</ei> coupling to a <ei>H^0(H_2^0) Z^0</ei> pair.
811
Is <ei>sin(beta - alpha)</ei> in the MSSM.
814
<parm name="HiggsA3:coup2Z" default="0.">
815
The <ei>A^0(H_3^0)</ei> coupling to <ei>Z^0</ei>.
816
Vanishes in the MSSM.
819
<parm name="HiggsA3:coup2W" default="0.">
820
The <ei>A^0(H_3^0)</ei> coupling to <ei>W^+-</ei>.
821
Vanishes in the MSSM.
824
<parm name="HiggsA3:coup2H1H1" default="0.">
825
The <ei>A^0(H_3^0)</ei> coupling to a <ei>h^0(H_1^0)</ei> pair.
826
Vanishes in the MSSM.
829
<parm name="HiggsA3:coup2Hchg" default="0.">
830
The <ei>A^0(H_3^0)</ei> coupling to <ei>H^+-</ei>.
831
Vanishes in the MSSM.
834
<parm name="HiggsA3:coup2HchgW" default="1.">
835
The <ei>A^0(H_3^0)</ei> coupling to a <ei>H^+- W-+</ei> pair.
839
<parm name="HiggsHchg:tanBeta" default="5.">
840
The <ei>tan(beta)</ei> value, which leads to an enhancement of the
841
<ei>H^+-</ei> coupling to down-type fermions and suppression to
842
up-type ones. The same angle also appears in many other places,
843
but this particular parameter is only used for the charged-Higgs case.
846
<parm name="HiggsHchg:coup2H1W" default="1.">
847
The <ei>H^+-</ei> coupling to a <ei>h^0(H_1^0) W^+-</ei> pair.
848
Is <ei>cos(beta - alpha)</ei> in the MSSM.
851
<parm name="HiggsHchg:coup2H2W" default="0.">
852
The <ei>H^+-</ei> coupling to a <ei>H^0(H_2^0) W^+-</ei> pair.
853
Is <ei>sin(beta - alpha)</ei> in the MSSM.
857
Another set of parameters are not used in the production stage but
858
exclusively for the description of angular distributions in decays.
860
<modepick name="HiggsH1:parity" default="1" min="0" max="3">
861
possibility to modify angular decay correlations in the decay of a
862
<ei>h^0(H_1)</ei> decay <ei>Z^0 Z^0</ei> or <ei>W^+ W^-</ei> to four
863
fermions. Currently it does not affect the partial width of the
864
channels, which is only based on the above parameters.
865
<option value="0">isotropic decays.</option>
866
<option value="1">assuming the <ei>h^0(H_1)</ei> is a pure scalar
867
(CP-even), as in the MSSM.</option>
868
<option value="2">assuming the <ei>h^0(H_1)</ei> is a pure pseudoscalar
870
<option value="3">assuming the <ei>h^0(H_1)</ei> is a mixture of the two,
871
including the CP-violating interference term. The parameter
872
<ei>eta</ei>, see below, sets the strength of the CP-odd admixture,
873
with the interference term being proportional to <ei>eta</ei>
874
and the CP-odd one to <ei>eta^2</ei>.</option>
877
<parm name="HiggsH1:etaParity" default="0.">
878
The <ei>eta</ei> value of CP-violation in the
879
<code>HiggsSM:parity = 3</code> option.
882
<modepick name="HiggsH2:parity" default="1" min="0" max="3">
883
possibility to modify angular decay correlations in the decay of a
884
<ei>H^0(H_2)</ei> decay <ei>Z^0 Z^0</ei> or <ei>W^+ W^-</ei> to four
885
fermions. Currently it does not affect the partial width of the
886
channels, which is only based on the above parameters.
887
<option value="0">isotropic decays.</option>
888
<option value="1">assuming the <ei>H^0(H_2)</ei> is a pure scalar
889
(CP-even), as in the MSSM.</option>
890
<option value="2">assuming the <ei>H^0(H_2)</ei> is a pure pseudoscalar
892
<option value="3">assuming the <ei>H^0(H_2)</ei> is a mixture of the two,
893
including the CP-violating interference term. The parameter
894
<ei>eta</ei>, see below, sets the strength of the CP-odd admixture,
895
with the interference term being proportional to <ei>eta</ei>
896
and the CP-odd one to <ei>eta^2</ei>.</option>
899
<parm name="HiggsH2:etaParity" default="0.">
900
The <ei>eta</ei> value of CP-violation in the
901
<code>HiggsSM:parity = 3</code> option.
904
<modepick name="HiggsA3:parity" default="2" min="0" max="3">
905
possibility to modify angular decay correlations in the decay of a
906
<ei>A^0(H_3)</ei> decay <ei>Z^0 Z^0</ei> or <ei>W^+ W^-</ei> to four
907
fermions. Currently it does not affect the partial width of the
908
channels, which is only based on the above parameters.
909
<option value="0">isotropic decays.</option>
910
<option value="1">assuming the <ei>A^0(H_3)</ei> is a pure scalar
912
<option value="2">assuming the <ei>A^0(H_3)</ei> is a pure pseudoscalar
913
(CP-odd), as in the MSSM.</option>
914
<option value="3">assuming the <ei>A^0(H_3)</ei> is a mixture of the two,
915
including the CP-violating interference term. The parameter
916
<ei>eta</ei>, see below, sets the strength of the CP-odd admixture,
917
with the interference term being proportional to <ei>eta</ei>
918
and the CP-odd one to <ei>eta^2</ei>.</option>
921
<parm name="HiggsA3:etaParity" default="0.">
922
The <ei>eta</ei> value of CP-violation in the
923
<code>HiggsSM:parity = 3</code> option.
928
<!-- Copyright (C) 2012 Torbjorn Sjostrand -->
added
removed
xmldoc/HiggsProcesses.xml
