3 <title>Higgs Processes</title>
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9 <h2>Higgs Processes</h2>
11 This page documents Higgs production within and beyond the Standard Model
12 (SM and BSM for short). This includes several different processes and,
13 for the BSM scenarios, a large set of parameters that would only be fixed
14 within a more specific framework such as MSSM. Two choices can be made
15 irrespective of the particular model:
17 <p/><code>flag </code><strong> Higgs:cubicWidth </strong>
18 (<code>default = <strong>off</strong></code>)<br/>
19 The partial width of a Higgs particle to a pair of gauge bosons,
20 <i>W^+ W^-</i> or <i>Z^0 Z^0</i>, depends cubically on the
21 Higgs mass. When selecting the Higgs according to a Breit-Wigner,
22 so that the actual mass <i>mHat</i> does not agree with the
23 nominal <i>m_Higgs</i> one, an ambiguity arises which of the
24 two to use [<a href="Bibliography.html" target="page">Sey95</a>]. The default is to use a linear
25 dependence on <i>mHat</i>, i.e. a width proportional to
26 <i>m_Higgs^2 * mHat</i>, while <code>on</code> gives a
27 <i>mHat^3</i> dependence. This does not affect the widths to
28 fermions, which only depend linearly on <i>mHat</i>.
29 This flag is used both for SM and BSM Higgses.
32 <p/><code>flag </code><strong> Higgs:runningLoopMass </strong>
33 (<code>default = <strong>on</strong></code>)<br/>
34 The partial width of a Higgs particle to a pair of gluons or photons,
35 or a <i>gamma Z^0</i> pair, proceeds in part through quark loops,
36 mainly <i>b</i> and <i>t</i>. There is some ambiguity what kind
37 of masses to use. Default is running MSbar ones, but alternatively
38 fixed pole masses are allowed (as was standard in PYTHIA 6), which
39 typically gives a noticeably higher cross section for these channels.
40 (For a decay to a pair of fermions, such as top, the running mass is
41 used for couplings and the fixed one for phase space.)
44 <h3>Standard-Model Higgs, basic processes</h3>
46 This section provides the standard set of processes that can be
47 run together to provide a reasonably complete overview of possible
48 production channels for a single SM Higgs.
49 The main parameter is the choice of Higgs mass, which can be set in the
50 normal <code>ParticleData</code> database; thereafter the properties
51 within the SM are essentially fixed.
53 <p/><code>flag </code><strong> HiggsSM:all </strong>
54 (<code>default = <strong>off</strong></code>)<br/>
55 Common switch for the group of Higgs production within the Standard Model.
58 <p/><code>flag </code><strong> HiggsSM:ffbar2H </strong>
59 (<code>default = <strong>off</strong></code>)<br/>
60 Scattering <i>f fbar -> H^0</i>, where <i>f</i> sums over available
61 flavours except top. Related to the mass-dependent Higgs point coupling
62 to fermions, so at hadron colliders the bottom contribution will
67 <p/><code>flag </code><strong> HiggsSM:gg2H </strong>
68 (<code>default = <strong>off</strong></code>)<br/>
69 Scattering <i>g g -> H^0</i> via loop contributions primarily from
74 <p/><code>flag </code><strong> HiggsSM:gmgm2H </strong>
75 (<code>default = <strong>off</strong></code>)<br/>
76 Scattering <i>gamma gamma -> H^0</i> via loop contributions primarily
77 from top and <i>W</i>.
81 <p/><code>flag </code><strong> HiggsSM:ffbar2HZ </strong>
82 (<code>default = <strong>off</strong></code>)<br/>
83 Scattering <i>f fbar -> H^0 Z^0</i> via <i>s</i>-channel <i>Z^0</i>
88 <p/><code>flag </code><strong> HiggsSM:ffbar2HW </strong>
89 (<code>default = <strong>off</strong></code>)<br/>
90 Scattering <i>f fbar -> H^0 W^+-</i> via <i>s</i>-channel <i>W^+-</i>
95 <p/><code>flag </code><strong> HiggsSM:ff2Hff(t:ZZ) </strong>
96 (<code>default = <strong>off</strong></code>)<br/>
97 Scattering <i>f f' -> H^0 f f'</i> via <i>Z^0 Z^0</i> fusion.
101 <p/><code>flag </code><strong> HiggsSM:ff2Hff(t:WW) </strong>
102 (<code>default = <strong>off</strong></code>)<br/>
103 Scattering <i>f_1 f_2 -> H^0 f_3 f_4</i> via <i>W^+ W^-</i> fusion.
107 <p/><code>flag </code><strong> HiggsSM:gg2Httbar </strong>
108 (<code>default = <strong>off</strong></code>)<br/>
109 Scattering <i>g g -> H^0 t tbar</i> via <i>t tbar</i> fusion
110 (or, alternatively put, Higgs radiation off a top line).
111 Warning: unfortunately this process is rather slow, owing to a
112 lengthy cross-section expression and inefficient phase-space selection.
116 <p/><code>flag </code><strong> HiggsSM:qqbar2Httbar </strong>
117 (<code>default = <strong>off</strong></code>)<br/>
118 Scattering <i>q qbar -> H^0 t tbar</i> via <i>t tbar</i> 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-<i>pT</i>
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 <i>b</i> quarks. It is here useful to begin by reminding that
138 a process like <i>b bbar -> H^0</i> implies that a <i>b/bbar</i>
139 is taken from each incoming hadron, leaving behind its respective
140 antiparticle. The initial-state showers will then add one
141 <i>g -> b bbar</i> branching on either side, so that effectively
142 the process becomes <i>g g -> H0 b bbar</i>. This would be the
143 same basic process as the <i>g g -> H^0 t tbar</i> 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 <i>H^0 t tbar</i> subsystem. By contrast, owing
147 to the <i>b</i> being much lighter than the Higgs, multiple
148 gluon emissions must be resummed for <i>b</i>, as is done by PDF's
149 and showers, in order to obtain a sensible description of the total
150 production rate, when the <i>b</i> quarks predominantly are produced
151 at small <i>pT</i> values.
153 <p/><code>flag </code><strong> HiggsSM:qg2Hq </strong>
154 (<code>default = <strong>off</strong></code>)<br/>
155 Scattering <i>q g -> H^0 q</i>. This process gives first-order
156 corrections to the <i>f fbar -> H^0</i> one above, and should only be
157 used to study the high-<i>pT</i> tail, while <i>f fbar -> H^0</i>
158 should be used for inclusive production. Only the dominant <i>c</i>
159 and <i>b</i> contributions are included, and generated separately
160 for technical reasons. Note that another first-order process would be
161 <i>q qbar -> H^0 g</i>, which is not explicitly implemented here,
162 but is obtained from showering off the lowest-order process. It does not
163 contain any <i>b</i> at large <i>pT</i>, however, so is less
164 interesting for many applications.
168 <p/><code>flag </code><strong> HiggsSM:gg2Hbbbar </strong>
169 (<code>default = <strong>off</strong></code>)<br/>
170 Scattering <i>g g -> H^0 b bbar</i>. This process is yet one order
171 higher of the <i>b bbar -> H^0</i> and <i>b g -> H^0 b</i> chain,
172 where now two quarks should be required above some large <i>pT</i>
174 Warning: unfortunately this process is rather slow, owing to a
175 lengthy cross-section expression and inefficient phase-space selection.
179 <p/><code>flag </code><strong> HiggsSM:qqbar2Hbbbar </strong>
180 (<code>default = <strong>off</strong></code>)<br/>
181 Scattering <i>q qbar -> H^0 b bbar</i> via an <i>s</i>-channel
182 gluon, so closely related to the previous one, but typically less
183 important owing to the smaller rate of (anti)quarks relative to
185 Warning: unfortunately this process is rather slow, owing to a
186 lengthy cross-section expression and inefficient phase-space selection.
191 The second set of processes are predominantly first-order corrections
192 to the <i>g g -> H^0</i> process, again dominated by the top loop.
193 We here only provide the kinematical expressions obtained in the
194 limit that the top quark goes to infinity, but scaled to the
195 finite-top-mass coupling in <i>g g -> H^0</i>. (Complete loop
196 expressions are available e.g. in PYTHIA 6.4 but are very lengthy.)
197 This provides a reasonably accurate description for "intermediate"
198 <i>pT</i> values, but fails when the <i>pT</i> scale approaches
201 <p/><code>flag </code><strong> HiggsSM:gg2Hg(l:t) </strong>
202 (<code>default = <strong>off</strong></code>)<br/>
203 Scattering <i>g g -> H^0 g</i> via loop contributions primarily
208 <p/><code>flag </code><strong> HiggsSM:qg2Hq(l:t) </strong>
209 (<code>default = <strong>off</strong></code>)<br/>
210 Scattering <i>q g -> H^0 q</i> via loop contributions primarily
211 from top. Not to be confused with the <code>HiggsSM:qg2Hq</code>
212 process above, with its direct fermion-to-Higgs coupling.
216 <p/><code>flag </code><strong> HiggsSM:qqbar2Hg(l:t) </strong>
217 (<code>default = <strong>off</strong></code>)<br/>
218 Scattering <i>q qbar -> H^0 g</i> via an <i>s</i>-channel gluon
219 and loop contributions primarily from top. Is strictly speaking a
220 "new" process, not directly derived from <i>g g -> H^0</i>, and
221 could therefore be included in the standard mix without doublecounting,
222 but is numerically negligible.
226 <h3>Beyond-the-Standard-Model Higgs, introduction</h3>
228 Further Higgs multiplets arise in a number of scenarios. We here
229 concentrate on the MSSM scenario with two Higgs doublets, but with
230 flexibility enough that also other two-Higgs-doublet scenarios could
231 be represented by a suitable choice of parameters. Conventionally the
232 Higgs states are labelled <i>h^0, H^0, A^0</i> and <i>H^+-</i>.
233 If the scalar and pseudocalar states mix the resulting states are
234 labelled <i>H_1^0, H_2^0, H_3^0</i>. In process names and parameter
235 explanations both notations will be used, but for settings labels
236 we have adapted the shorthand hybrid notation <code>H1</code> for
237 <i>h^0(H_1^0)</i>, <code>H2</code> for <i>H^0(H_2^0)</i> and
238 <code>A3</code> for <i>A^0(H_3^0)</i>. (Recall that the
239 <code>Settings</code> database does not distinguish upper- and lowercase
240 characters, so that the user has one thing less to worry about, but here
241 it causes probles with <i>h^0</i> vs. <i>H^0</i>.) We leave the issue
242 of mass ordering between <i>H^0</i> and <i>A^0</i> open, and thereby
243 also that of <i>H_2^0</i> and <i>H_3^0</i>.
245 <p/><code>flag </code><strong> Higgs:useBSM </strong>
246 (<code>default = <strong>off</strong></code>)<br/>
247 Master switch to initialize and use the two-Higgs-doublet states.
248 If off, only the above SM Higgs processes can be used, with couplings
249 as predicted in the SM. If on, only the below BSM Higgs processes can
250 be used, with couplings that can be set freely, also found further down
254 <h3>Beyond-the-Standard-Model Higgs, basic processes</h3>
256 This section provides the standard set of processes that can be
257 run together to provide a reasonably complete overview of possible
258 production channels for a single neutral Higgs state in a two-doublet
259 scenarios such as MSSM. The list of processes for neutral states closely
260 mimics the one found for the SM Higgs. Some of the processes
261 vanish for a pure pseudoscalar <i>A^0</i>, but are kept for flexiblity
262 in cases of mixing with the scalar <i>h^0</i> and <i>H^0</i> states,
263 or for use in the context of non-MSSM models. This should work well to
264 represent e.g. that a small admixture of the "wrong" parity would allow
265 a process such as <i>q qbar -> A^0 Z^0</i>, which otherwise is forbidden.
266 However, note that the loop integrals e.g. for <i>g g -> h^0/H^0/A^0</i>
267 are hardcoded to be for scalars for the former two particles and for a
268 pseudoscalar for the latter one, so absolute rates would not be
269 correctly represented in the case of large scalar/pseudoscalar mixing.
271 <p/><code>flag </code><strong> HiggsBSM:all </strong>
272 (<code>default = <strong>off</strong></code>)<br/>
273 Common switch for the group of Higgs production beyond the Standard Model,
277 <h4>1) <i>h^0(H_1^0)</i> processes</h4>
279 <p/><code>flag </code><strong> HiggsBSM:allH1 </strong>
280 (<code>default = <strong>off</strong></code>)<br/>
281 Common switch for the group of <i>h^0(H_1^0)</i> production processes.
284 <p/><code>flag </code><strong> HiggsBSM:ffbar2H1 </strong>
285 (<code>default = <strong>off</strong></code>)<br/>
286 Scattering <i>f fbar -> h^0(H_1^0)</i>, where <i>f</i> sums over available
291 <p/><code>flag </code><strong> HiggsBSM:gg2H1 </strong>
292 (<code>default = <strong>off</strong></code>)<br/>
293 Scattering <i>g g -> h^0(H_1^0)</i> via loop contributions primarily from
298 <p/><code>flag </code><strong> HiggsBSM:gmgm2H1 </strong>
299 (<code>default = <strong>off</strong></code>)<br/>
300 Scattering <i>gamma gamma -> h^0(H_1^0)</i> via loop contributions primarily
301 from top and <i>W</i>.
305 <p/><code>flag </code><strong> HiggsBSM:ffbar2H1Z </strong>
306 (<code>default = <strong>off</strong></code>)<br/>
307 Scattering <i>f fbar -> h^0(H_1^0) Z^0</i> via <i>s</i>-channel <i>Z^0</i>
312 <p/><code>flag </code><strong> HiggsBSM:ffbar2H1W </strong>
313 (<code>default = <strong>off</strong></code>)<br/>
314 Scattering <i>f fbar -> h^0(H_1^0) W^+-</i> via <i>s</i>-channel <i>W^+-</i>
319 <p/><code>flag </code><strong> HiggsBSM:ff2H1ff(t:ZZ) </strong>
320 (<code>default = <strong>off</strong></code>)<br/>
321 Scattering <i>f f' -> h^0(H_1^0) f f'</i> via <i>Z^0 Z^0</i> fusion.
325 <p/><code>flag </code><strong> HiggsBSM:ff2H1ff(t:WW) </strong>
326 (<code>default = <strong>off</strong></code>)<br/>
327 Scattering <i>f_1 f_2 -> h^0(H_1^0) f_3 f_4</i> via <i>W^+ W^-</i> fusion.
331 <p/><code>flag </code><strong> HiggsBSM:gg2H1ttbar </strong>
332 (<code>default = <strong>off</strong></code>)<br/>
333 Scattering <i>g g -> h^0(H_1^0) t tbar</i> via <i>t tbar</i> fusion
334 (or, alternatively put, Higgs radiation off a top line).
335 Warning: unfortunately this process is rather slow, owing to a
336 lengthy cross-section expression and inefficient phase-space selection.
340 <p/><code>flag </code><strong> HiggsBSM:qqbar2H1ttbar </strong>
341 (<code>default = <strong>off</strong></code>)<br/>
342 Scattering <i>q qbar -> h^0(H_1^0) t tbar</i> via <i>t tbar</i> fusion
343 (or, alternatively put, Higgs radiation off a top line).
344 Warning: unfortunately this process is rather slow, owing to a
345 lengthy cross-section expression and inefficient phase-space selection.
349 <h4>2) <i>H^0(H_2^0)</i> processes</h4>
351 <p/><code>flag </code><strong> HiggsBSM:allH2 </strong>
352 (<code>default = <strong>off</strong></code>)<br/>
353 Common switch for the group of <i>H^0(H_2^0)</i> production processes.
356 <p/><code>flag </code><strong> HiggsBSM:ffbar2H2 </strong>
357 (<code>default = <strong>off</strong></code>)<br/>
358 Scattering <i>f fbar -> H^0(H_2^0)</i>, where <i>f</i> sums over available
363 <p/><code>flag </code><strong> HiggsBSM:gg2H2 </strong>
364 (<code>default = <strong>off</strong></code>)<br/>
365 Scattering <i>g g -> H^0(H_2^0)</i> via loop contributions primarily from
370 <p/><code>flag </code><strong> HiggsBSM:gmgm2H2 </strong>
371 (<code>default = <strong>off</strong></code>)<br/>
372 Scattering <i>gamma gamma -> H^0(H_2^0)</i> via loop contributions primarily
373 from top and <i>W</i>.
377 <p/><code>flag </code><strong> HiggsBSM:ffbar2H2Z </strong>
378 (<code>default = <strong>off</strong></code>)<br/>
379 Scattering <i>f fbar -> H^0(H_2^0) Z^0</i> via <i>s</i>-channel <i>Z^0</i>
384 <p/><code>flag </code><strong> HiggsBSM:ffbar2H2W </strong>
385 (<code>default = <strong>off</strong></code>)<br/>
386 Scattering <i>f fbar -> H^0(H_2^0) W^+-</i> via <i>s</i>-channel <i>W^+-</i>
391 <p/><code>flag </code><strong> HiggsBSM:ff2H2ff(t:ZZ) </strong>
392 (<code>default = <strong>off</strong></code>)<br/>
393 Scattering <i>f f' -> H^0(H_2^0) f f'</i> via <i>Z^0 Z^0</i> fusion.
397 <p/><code>flag </code><strong> HiggsBSM:ff2H2ff(t:WW) </strong>
398 (<code>default = <strong>off</strong></code>)<br/>
399 Scattering <i>f_1 f_2 -> H^0(H_2^0) f_3 f_4</i> via <i>W^+ W^-</i> fusion.
403 <p/><code>flag </code><strong> HiggsBSM:gg2H2ttbar </strong>
404 (<code>default = <strong>off</strong></code>)<br/>
405 Scattering <i>g g -> H^0(H_2^0) t tbar</i> via <i>t tbar</i> fusion
406 (or, alternatively put, Higgs radiation off a top line).
407 Warning: unfortunately this process is rather slow, owing to a
408 lengthy cross-section expression and inefficient phase-space selection.
412 <p/><code>flag </code><strong> HiggsBSM:qqbar2H2ttbar </strong>
413 (<code>default = <strong>off</strong></code>)<br/>
414 Scattering <i>q qbar -> H^0(H_2^0) t tbar</i> via <i>t tbar</i> fusion
415 (or, alternatively put, Higgs radiation off a top line).
416 Warning: unfortunately this process is rather slow, owing to a
417 lengthy cross-section expression and inefficient phase-space selection.
420 <h4>3) <i>A^0(H_3^0)</i> processes</h4>
422 <p/><code>flag </code><strong> HiggsBSM:allA3 </strong>
423 (<code>default = <strong>off</strong></code>)<br/>
424 Common switch for the group of <i>A^0(H_3^0)</i> production processes.
427 <p/><code>flag </code><strong> HiggsBSM:ffbar2A3 </strong>
428 (<code>default = <strong>off</strong></code>)<br/>
429 Scattering <i>f fbar -> A^0(H_3^0)</i>, where <i>f</i> sums over available
434 <p/><code>flag </code><strong> HiggsBSM:gg2A3 </strong>
435 (<code>default = <strong>off</strong></code>)<br/>
436 Scattering <i>g g -> A^0(A_3^0)</i> via loop contributions primarily from
441 <p/><code>flag </code><strong> HiggsBSM:gmgm2A3 </strong>
442 (<code>default = <strong>off</strong></code>)<br/>
443 Scattering <i>gamma gamma -> A^0(A_3^0)</i> via loop contributions primarily
444 from top and <i>W</i>.
448 <p/><code>flag </code><strong> HiggsBSM:ffbar2A3Z </strong>
449 (<code>default = <strong>off</strong></code>)<br/>
450 Scattering <i>f fbar -> A^0(A_3^0) Z^0</i> via <i>s</i>-channel <i>Z^0</i>
455 <p/><code>flag </code><strong> HiggsBSM:ffbar2A3W </strong>
456 (<code>default = <strong>off</strong></code>)<br/>
457 Scattering <i>f fbar -> A^0(A_3^0) W^+-</i> via <i>s</i>-channel <i>W^+-</i>
462 <p/><code>flag </code><strong> HiggsBSM:ff2A3ff(t:ZZ) </strong>
463 (<code>default = <strong>off</strong></code>)<br/>
464 Scattering <i>f f' -> A^0(A_3^0) f f'</i> via <i>Z^0 Z^0</i> fusion.
468 <p/><code>flag </code><strong> HiggsBSM:ff2A3ff(t:WW) </strong>
469 (<code>default = <strong>off</strong></code>)<br/>
470 Scattering <i>f_1 f_2 -> A^0(A_3^0) f_3 f_4</i> via <i>W^+ W^-</i> fusion.
474 <p/><code>flag </code><strong> HiggsBSM:gg2A3ttbar </strong>
475 (<code>default = <strong>off</strong></code>)<br/>
476 Scattering <i>g g -> A^0(A_3^0) t tbar</i> via <i>t tbar</i> fusion
477 (or, alternatively put, Higgs radiation off a top line).
478 Warning: unfortunately this process is rather slow, owing to a
479 lengthy cross-section expression and inefficient phase-space selection.
483 <p/><code>flag </code><strong> HiggsBSM:qqbar2A3ttbar </strong>
484 (<code>default = <strong>off</strong></code>)<br/>
485 Scattering <i>q qbar -> A^0(A_3^0) t tbar</i> via <i>t tbar</i> fusion
486 (or, alternatively put, Higgs radiation off a top line).
487 Warning: unfortunately this process is rather slow, owing to a
488 lengthy cross-section expression and inefficient phase-space selection.
491 <h4>4) <i>H+-</i> processes</h4>
493 <p/><code>flag </code><strong> HiggsBSM:allH+- </strong>
494 (<code>default = <strong>off</strong></code>)<br/>
495 Common switch for the group of <i>H^+-</i> production processes.
498 <p/><code>flag </code><strong> HiggsBSM:ffbar2H+- </strong>
499 (<code>default = <strong>off</strong></code>)<br/>
500 Scattering <i>f fbar' -> H^+-</i>, where <i>f, fbar'</i> sums over
501 available incoming flavours. Since couplings are assumed
502 generation-diagonal, in practice this means <i>c sbar -> H^+</i>
503 and <i>s cbar -> H^-</i>.
507 <p/><code>flag </code><strong> HiggsBSM:bg2H+-t </strong>
508 (<code>default = <strong>off</strong></code>)<br/>
509 Scattering <i>b g -> H^+ tbar</i>. At hadron colliders this is the
510 dominant process for single-charged-Higgs production.
514 <h4>5) Higgs-pair processes</h4>
516 <p/><code>flag </code><strong> HiggsBSM:allHpair </strong>
517 (<code>default = <strong>off</strong></code>)<br/>
518 Common switch for the group of Higgs pair-production processes.
521 <p/><code>flag </code><strong> HiggsBSM:ffbar2A3H1 </strong>
522 (<code>default = <strong>off</strong></code>)<br/>
523 Scattering <i>f fbar -> A^0(H_3) h^0(H_1)</i>.
527 <p/><code>flag </code><strong> HiggsBSM:ffbar2A3H2 </strong>
528 (<code>default = <strong>off</strong></code>)<br/>
529 Scattering <i>f fbar -> A^0(H_3) H^0(H_2)</i>.
533 <p/><code>flag </code><strong> HiggsBSM:ffbar2H+-H1 </strong>
534 (<code>default = <strong>off</strong></code>)<br/>
535 Scattering <i>f fbar -> H^+- h^0(H_1)</i>.
539 <p/><code>flag </code><strong> HiggsBSM:ffbar2H+-H2 </strong>
540 (<code>default = <strong>off</strong></code>)<br/>
541 Scattering <i>f fbar -> H^+- H^0(H_2)</i>.
545 <p/><code>flag </code><strong> HiggsBSM:ffbar2H+H- </strong>
546 (<code>default = <strong>off</strong></code>)<br/>
547 Scattering <i>f fbar -> H+ H-</i>.
551 <h3>Beyond-the-Standard-Model Higgs, further processes</h3>
553 This section mimics the above section on "Standard-Model Higgs,
554 further processes", i.e. it contains higher-order corrections
555 to the processes already listed. The two sets therefore could not
556 be used simultaneously without unphysical doublecounting.
557 They are not controlled by any group flag, but have to be switched
558 on for each separate process after due consideration. We refer to
559 the standard-model description for a set of further comments on
562 <h4>1) <i>h^0(H_1^0)</i> processes</h4>
564 <p/><code>flag </code><strong> HiggsBSM:qg2H1q </strong>
565 (<code>default = <strong>off</strong></code>)<br/>
566 Scattering <i>q g -> h^0 q</i>. This process gives first-order
567 corrections to the <i>f fbar -> h^0</i> one above, and should only be
568 used to study the high-<i>pT</i> tail, while <i>f fbar -> h^0</i>
569 should be used for inclusive production. Only the dominant <i>c</i>
570 and <i>b</i> contributions are included, and generated separately
571 for technical reasons. Note that another first-order process would be
572 <i>q qbar -> h^0 g</i>, which is not explicitly implemented here,
573 but is obtained from showering off the lowest-order process. It does not
574 contain any <i>b</i> at large <i>pT</i>, however, so is less
575 interesting for many applications.
579 <p/><code>flag </code><strong> HiggsBSM:gg2H1bbbar </strong>
580 (<code>default = <strong>off</strong></code>)<br/>
581 Scattering <i>g g -> h^0 b bbar</i>. This process is yet one order
582 higher of the <i>b bbar -> h^0</i> and <i>b g -> h^0 b</i> chain,
583 where now two quarks should be required above some large <i>pT</i>
585 Warning: unfortunately this process is rather slow, owing to a
586 lengthy cross-section expression and inefficient phase-space selection.
590 <p/><code>flag </code><strong> HiggsBSM:qqbar2H1bbbar </strong>
591 (<code>default = <strong>off</strong></code>)<br/>
592 Scattering <i>q qbar -> h^0 b bbar</i> via an <i>s</i>-channel
593 gluon, so closely related to the previous one, but typically less
594 important owing to the smaller rate of (anti)quarks relative to
596 Warning: unfortunately this process is rather slow, owing to a
597 lengthy cross-section expression and inefficient phase-space selection.
601 <p/><code>flag </code><strong> HiggsBSM:gg2H1g(l:t) </strong>
602 (<code>default = <strong>off</strong></code>)<br/>
603 Scattering <i>g g -> h^0 g</i> via loop contributions primarily
608 <p/><code>flag </code><strong> HiggsBSM:qg2H1q(l:t) </strong>
609 (<code>default = <strong>off</strong></code>)<br/>
610 Scattering <i>q g -> h^0 q</i> via loop contributions primarily
611 from top. Not to be confused with the <code>HiggsBSM:qg2H1q</code>
612 process above, with its direct fermion-to-Higgs coupling.
616 <p/><code>flag </code><strong> HiggsBSM:qqbar2H1g(l:t) </strong>
617 (<code>default = <strong>off</strong></code>)<br/>
618 Scattering <i>q qbar -> h^0 g</i> via an <i>s</i>-channel gluon
619 and loop contributions primarily from top. Is strictly speaking a
620 "new" process, not directly derived from <i>g g -> h^0</i>, and
621 could therefore be included in the standard mix without doublecounting,
622 but is numerically negligible.
626 <h4>2) <i>H^0(H_2^0)</i> processes</h4>
628 <p/><code>flag </code><strong> HiggsBSM:qg2H2q </strong>
629 (<code>default = <strong>off</strong></code>)<br/>
630 Scattering <i>q g -> H^0 q</i>. This process gives first-order
631 corrections to the <i>f fbar -> H^0</i> one above, and should only be
632 used to study the high-<i>pT</i> tail, while <i>f fbar -> H^0</i>
633 should be used for inclusive production. Only the dominant <i>c</i>
634 and <i>b</i> contributions are included, and generated separately
635 for technical reasons. Note that another first-order process would be
636 <i>q qbar -> H^0 g</i>, which is not explicitly implemented here,
637 but is obtained from showering off the lowest-order process. It does not
638 contain any <i>b</i> at large <i>pT</i>, however, so is less
639 interesting for many applications.
643 <p/><code>flag </code><strong> HiggsBSM:gg2H2bbbar </strong>
644 (<code>default = <strong>off</strong></code>)<br/>
645 Scattering <i>g g -> H^0 b bbar</i>. This process is yet one order
646 higher of the <i>b bbar -> H^0</i> and <i>b g -> H^0 b</i> chain,
647 where now two quarks should be required above some large <i>pT</i>
649 Warning: unfortunately this process is rather slow, owing to a
650 lengthy cross-section expression and inefficient phase-space selection.
654 <p/><code>flag </code><strong> HiggsBSM:qqbar2H2bbbar </strong>
655 (<code>default = <strong>off</strong></code>)<br/>
656 Scattering <i>q qbar -> H^0 b bbar</i> via an <i>s</i>-channel
657 gluon, so closely related to the previous one, but typically less
658 important owing to the smaller rate of (anti)quarks relative to
660 Warning: unfortunately this process is rather slow, owing to a
661 lengthy cross-section expression and inefficient phase-space selection.
665 <p/><code>flag </code><strong> HiggsBSM:gg2H2g(l:t) </strong>
666 (<code>default = <strong>off</strong></code>)<br/>
667 Scattering <i>g g -> H^0 g</i> via loop contributions primarily
672 <p/><code>flag </code><strong> HiggsBSM:qg2H2q(l:t) </strong>
673 (<code>default = <strong>off</strong></code>)<br/>
674 Scattering <i>q g -> H^0 q</i> via loop contributions primarily
675 from top. Not to be confused with the <code>HiggsBSM:qg2H1q</code>
676 process above, with its direct fermion-to-Higgs coupling.
680 <p/><code>flag </code><strong> HiggsBSM:qqbar2H2g(l:t) </strong>
681 (<code>default = <strong>off</strong></code>)<br/>
682 Scattering <i>q qbar -> H^0 g</i> via an <i>s</i>-channel gluon
683 and loop contributions primarily from top. Is strictly speaking a
684 "new" process, not directly derived from <i>g g -> H^0</i>, and
685 could therefore be included in the standard mix without doublecounting,
686 but is numerically negligible.
690 <h4>3) <i>A^0(H_3^0)</i> processes</h4>
692 <p/><code>flag </code><strong> HiggsBSM:qg2A3q </strong>
693 (<code>default = <strong>off</strong></code>)<br/>
694 Scattering <i>q g -> A^0 q</i>. This process gives first-order
695 corrections to the <i>f fbar -> A^0</i> one above, and should only be
696 used to study the high-<i>pT</i> tail, while <i>f fbar -> A^0</i>
697 should be used for inclusive production. Only the dominant <i>c</i>
698 and <i>b</i> contributions are included, and generated separately
699 for technical reasons. Note that another first-order process would be
700 <i>q qbar -> A^0 g</i>, which is not explicitly implemented here,
701 but is obtained from showering off the lowest-order process. It does not
702 contain any <i>b</i> at large <i>pT</i>, however, so is less
703 interesting for many applications.
707 <p/><code>flag </code><strong> HiggsBSM:gg2A3bbbar </strong>
708 (<code>default = <strong>off</strong></code>)<br/>
709 Scattering <i>g g -> A^0 b bbar</i>. This process is yet one order
710 higher of the <i>b bbar -> A^0</i> and <i>b g -> A^0 b</i> chain,
711 where now two quarks should be required above some large <i>pT</i>
713 Warning: unfortunately this process is rather slow, owing to a
714 lengthy cross-section expression and inefficient phase-space selection.
718 <p/><code>flag </code><strong> HiggsBSM:qqbar2A3bbbar </strong>
719 (<code>default = <strong>off</strong></code>)<br/>
720 Scattering <i>q qbar -> A^0 b bbar</i> via an <i>s</i>-channel
721 gluon, so closely related to the previous one, but typically less
722 important owing to the smaller rate of (anti)quarks relative to
724 Warning: unfortunately this process is rather slow, owing to a
725 lengthy cross-section expression and inefficient phase-space selection.
729 <p/><code>flag </code><strong> HiggsBSM:gg2A3g(l:t) </strong>
730 (<code>default = <strong>off</strong></code>)<br/>
731 Scattering <i>g g -> A^0 g</i> via loop contributions primarily
736 <p/><code>flag </code><strong> HiggsBSM:qg2A3q(l:t) </strong>
737 (<code>default = <strong>off</strong></code>)<br/>
738 Scattering <i>q g -> A^0 q</i> via loop contributions primarily
739 from top. Not to be confused with the <code>HiggsBSM:qg2H1q</code>
740 process above, with its direct fermion-to-Higgs coupling.
744 <p/><code>flag </code><strong> HiggsBSM:qqbar2A3g(l:t) </strong>
745 (<code>default = <strong>off</strong></code>)<br/>
746 Scattering <i>q qbar -> A^0 g</i> via an <i>s</i>-channel gluon
747 and loop contributions primarily from top. Is strictly speaking a
748 "new" process, not directly derived from <i>g g -> A^0</i>, and
749 could therefore be included in the standard mix without doublecounting,
750 but is numerically negligible.
754 <h3>Parameters for Beyond-the-Standard-Model Higgs production and decay</h3>
756 This section offers a big flexibility to set couplings of the various
757 Higgs states to fermions and gauge bosons, and also to each other.
758 The intention is that, for scenarios like MSSM, you should use standard
759 input from the <a href="SUSYLesHouchesAccord.html" target="page">SUSY Les Houches
760 Accord</a>, rather than having to set it all yourself. In other cases,
761 however, the freedom is there for you to use. Kindly note that some
762 of the internal calculations of partial widths from the parameters provided
763 do not include mixing between the scalar and pseudoscalar states.
766 Masses would be set in the <code>ParticleData</code> database,
767 while couplings are set below. When possible, the couplings of the Higgs
768 states are normalized to the corresponding coupling within the SM.
769 When not, their values within the MSSM are indicated, from which
770 it should be straightforward to understand what to use instead.
771 The exception is some couplings that vanish also in the MSSM, where the
772 normalization has been defined in close analogy with nonvanishing ones.
773 Some parameter names are asymmetric but crossing can always be used,
774 i.e. the coupling for <i>A^0 -> H^0 Z^0</i> obviously is also valid
775 for <i>H^0 -> A^0 Z^0</i> and <i>Z^0 -> H^0 A^0</i>.
776 Note that couplings usually appear quadratically in matrix elements.
778 <p/><code>parm </code><strong> HiggsH1:coup2d </strong>
779 (<code>default = <strong>1.</strong></code>)<br/>
780 The <i>h^0(H_1^0)</i> coupling to down-type quarks.
783 <p/><code>parm </code><strong> HiggsH1:coup2u </strong>
784 (<code>default = <strong>1.</strong></code>)<br/>
785 The <i>h^0(H_1^0)</i> coupling to up-type quarks.
788 <p/><code>parm </code><strong> HiggsH1:coup2l </strong>
789 (<code>default = <strong>1.</strong></code>)<br/>
790 The <i>h^0(H_1^0)</i> coupling to (charged) leptons.
793 <p/><code>parm </code><strong> HiggsH1:coup2Z </strong>
794 (<code>default = <strong>1.</strong></code>)<br/>
795 The <i>h^0(H_1^0)</i> coupling to <i>Z^0</i>.
798 <p/><code>parm </code><strong> HiggsH1:coup2W </strong>
799 (<code>default = <strong>1.</strong></code>)<br/>
800 The <i>h^0(H_1^0)</i> coupling to <i>W^+-</i>.
803 <p/><code>parm </code><strong> HiggsH1:coup2Hchg </strong>
804 (<code>default = <strong>0.</strong></code>)<br/>
805 The <i>h^0(H_1^0)</i> coupling to <i>H^+-</i> (in loops).
806 Is <i>sin(beta - alpha) + cos(2 beta) sin(beta + alpha) /
807 (2 cos^2theta_W)</i> in the MSSM.
810 <p/><code>parm </code><strong> HiggsH2:coup2d </strong>
811 (<code>default = <strong>1.</strong></code>)<br/>
812 The <i>H^0(H_2^0)</i> coupling to down-type quarks.
815 <p/><code>parm </code><strong> HiggsH2:coup2u </strong>
816 (<code>default = <strong>1.</strong></code>)<br/>
817 The <i>H^0(H_2^0)</i> coupling to up-type quarks.
820 <p/><code>parm </code><strong> HiggsH2:coup2l </strong>
821 (<code>default = <strong>1.</strong></code>)<br/>
822 The <i>H^0(H_2^0)</i> coupling to (charged) leptons.
825 <p/><code>parm </code><strong> HiggsH2:coup2Z </strong>
826 (<code>default = <strong>1.</strong></code>)<br/>
827 The <i>H^0(H_2^0)</i> coupling to <i>Z^0</i>.
830 <p/><code>parm </code><strong> HiggsH2:coup2W </strong>
831 (<code>default = <strong>1.</strong></code>)<br/>
832 The <i>H^0(H_2^0)</i> coupling to <i>W^+-</i>.
835 <p/><code>parm </code><strong> HiggsH2:coup2Hchg </strong>
836 (<code>default = <strong>0.</strong></code>)<br/>
837 The <i>H^0(H_2^0)</i> coupling to <i>H^+-</i> (in loops).
838 Is <i>cos(beta - alpha) + cos(2 beta) cos(beta + alpha) /
839 (2 cos^2theta_W)</i> in the MSSM.
842 <p/><code>parm </code><strong> HiggsH2:coup2H1H1 </strong>
843 (<code>default = <strong>1.</strong></code>)<br/>
844 The <i>H^0(H_2^0)</i> coupling to a <i>h^0(H_1^0)</i> pair.
845 Is <i>cos(2 alpha) cos(beta + alpha) - 2 sin(2 alpha)
846 sin(beta + alpha)</i> in the MSSM.
849 <p/><code>parm </code><strong> HiggsH2:coup2A3A3 </strong>
850 (<code>default = <strong>1.</strong></code>)<br/>
851 The <i>H^0(H_2^0)</i> coupling to an <i>A^0(H_3^0)</i> pair.
852 Is <i>cos(2 beta) cos(beta + alpha)</i> in the MSSM.
855 <p/><code>parm </code><strong> HiggsH2:coup2H1Z </strong>
856 (<code>default = <strong>0.</strong></code>)<br/>
857 The <i>H^0(H_2^0)</i> coupling to a <i>h^0(H_1^0) Z^0</i> pair.
858 Vanishes in the MSSM.
861 <p/><code>parm </code><strong> HiggsH2:coup2A3H1 </strong>
862 (<code>default = <strong>0.</strong></code>)<br/>
863 The <i>H^0(H_2^0)</i> coupling to an <i>A^0(H_3^0) h^0(H_1^0)</i> pair.
864 Vanishes in the MSSM.
867 <p/><code>parm </code><strong> HiggsH2:coup2HchgW </strong>
868 (<code>default = <strong>0.</strong></code>)<br/>
869 The <i>H^0(H_2^0)</i> coupling to a <i>H^+- W-+</i> pair.
870 Is <i>sin(beta - alpha)</i> in the MSSM.
873 <p/><code>parm </code><strong> HiggsA3:coup2d </strong>
874 (<code>default = <strong>1.</strong></code>)<br/>
875 The <i>A^0(H_3^0)</i> coupling to down-type quarks.
878 <p/><code>parm </code><strong> HiggsA3:coup2u </strong>
879 (<code>default = <strong>1.</strong></code>)<br/>
880 The <i>A^0(H_3^0)</i> coupling to up-type quarks.
883 <p/><code>parm </code><strong> HiggsA3:coup2l </strong>
884 (<code>default = <strong>1.</strong></code>)<br/>
885 The <i>A^0(H_3^0)</i> coupling to (charged) leptons.
888 <p/><code>parm </code><strong> HiggsA3:coup2H1Z </strong>
889 (<code>default = <strong>1.</strong></code>)<br/>
890 The <i>A^0(H_3^0)</i> coupling to a <i>h^0(H_1^0) Z^0</i> pair.
891 Is <i>cos(beta - alpha)</i> in the MSSM.
894 <p/><code>parm </code><strong> HiggsA3:coup2H2Z </strong>
895 (<code>default = <strong>1.</strong></code>)<br/>
896 The <i>A^0(H_3^0)</i> coupling to a <i>H^0(H_2^0) Z^0</i> pair.
897 Is <i>sin(beta - alpha)</i> in the MSSM.
900 <p/><code>parm </code><strong> HiggsA3:coup2Z </strong>
901 (<code>default = <strong>0.</strong></code>)<br/>
902 The <i>A^0(H_3^0)</i> coupling to <i>Z^0</i>.
903 Vanishes in the MSSM.
906 <p/><code>parm </code><strong> HiggsA3:coup2W </strong>
907 (<code>default = <strong>0.</strong></code>)<br/>
908 The <i>A^0(H_3^0)</i> coupling to <i>W^+-</i>.
909 Vanishes in the MSSM.
912 <p/><code>parm </code><strong> HiggsA3:coup2H1H1 </strong>
913 (<code>default = <strong>0.</strong></code>)<br/>
914 The <i>A^0(H_3^0)</i> coupling to a <i>h^0(H_1^0)</i> pair.
915 Vanishes in the MSSM.
918 <p/><code>parm </code><strong> HiggsA3:coup2Hchg </strong>
919 (<code>default = <strong>0.</strong></code>)<br/>
920 The <i>A^0(H_3^0)</i> coupling to <i>H^+-</i>.
921 Vanishes in the MSSM.
924 <p/><code>parm </code><strong> HiggsA3:coup2HchgW </strong>
925 (<code>default = <strong>1.</strong></code>)<br/>
926 The <i>A^0(H_3^0)</i> coupling to a <i>H^+- W-+</i> pair.
930 <p/><code>parm </code><strong> HiggsHchg:tanBeta </strong>
931 (<code>default = <strong>5.</strong></code>)<br/>
932 The <i>tan(beta)</i> value, which leads to an enhancement of the
933 <i>H^+-</i> coupling to down-type fermions and suppression to
934 up-type ones. The same angle also appears in many other places,
935 but this particular parameter is only used for the charged-Higgs case.
938 <p/><code>parm </code><strong> HiggsHchg:coup2H1W </strong>
939 (<code>default = <strong>1.</strong></code>)<br/>
940 The <i>H^+-</i> coupling to a <i>h^0(H_1^0) W^+-</i> pair.
941 Is <i>cos(beta - alpha)</i> in the MSSM.
944 <p/><code>parm </code><strong> HiggsHchg:coup2H2W </strong>
945 (<code>default = <strong>0.</strong></code>)<br/>
946 The <i>H^+-</i> coupling to a <i>H^0(H_2^0) W^+-</i> pair.
947 Is <i>sin(beta - alpha)</i> in the MSSM.
951 Another set of parameters are not used in the production stage but
952 exclusively for the description of angular distributions in decays.
954 <p/><code>mode </code><strong> HiggsH1:parity </strong>
955 (<code>default = <strong>1</strong></code>; <code>minimum = 0</code>; <code>maximum = 3</code>)<br/>
956 possibility to modify angular decay correlations in the decay of a
957 <i>h^0(H_1)</i> decay <i>Z^0 Z^0</i> or <i>W^+ W^-</i> to four
958 fermions. Currently it does not affect the partial width of the
959 channels, which is only based on the above parameters.
960 <br/><code>option </code><strong> 0</strong> : isotropic decays.
961 <br/><code>option </code><strong> 1</strong> : assuming the <i>h^0(H_1)</i> is a pure scalar
962 (CP-even), as in the MSSM.
963 <br/><code>option </code><strong> 2</strong> : assuming the <i>h^0(H_1)</i> is a pure pseudoscalar
965 <br/><code>option </code><strong> 3</strong> : assuming the <i>h^0(H_1)</i> is a mixture of the two,
966 including the CP-violating interference term. The parameter
967 <i>eta</i>, see below, sets the strength of the CP-odd admixture,
968 with the interference term being proportional to <i>eta</i>
969 and the CP-odd one to <i>eta^2</i>.
972 <p/><code>parm </code><strong> HiggsH1:etaParity </strong>
973 (<code>default = <strong>0.</strong></code>)<br/>
974 The <i>eta</i> value of CP-violation in the
975 <code>HiggsSM:parity = 3</code> option.
978 <p/><code>mode </code><strong> HiggsH2:parity </strong>
979 (<code>default = <strong>1</strong></code>; <code>minimum = 0</code>; <code>maximum = 3</code>)<br/>
980 possibility to modify angular decay correlations in the decay of a
981 <i>H^0(H_2)</i> decay <i>Z^0 Z^0</i> or <i>W^+ W^-</i> to four
982 fermions. Currently it does not affect the partial width of the
983 channels, which is only based on the above parameters.
984 <br/><code>option </code><strong> 0</strong> : isotropic decays.
985 <br/><code>option </code><strong> 1</strong> : assuming the <i>H^0(H_2)</i> is a pure scalar
986 (CP-even), as in the MSSM.
987 <br/><code>option </code><strong> 2</strong> : assuming the <i>H^0(H_2)</i> is a pure pseudoscalar
989 <br/><code>option </code><strong> 3</strong> : assuming the <i>H^0(H_2)</i> is a mixture of the two,
990 including the CP-violating interference term. The parameter
991 <i>eta</i>, see below, sets the strength of the CP-odd admixture,
992 with the interference term being proportional to <i>eta</i>
993 and the CP-odd one to <i>eta^2</i>.
996 <p/><code>parm </code><strong> HiggsH2:etaParity </strong>
997 (<code>default = <strong>0.</strong></code>)<br/>
998 The <i>eta</i> value of CP-violation in the
999 <code>HiggsSM:parity = 3</code> option.
1002 <p/><code>mode </code><strong> HiggsA3:parity </strong>
1003 (<code>default = <strong>2</strong></code>; <code>minimum = 0</code>; <code>maximum = 3</code>)<br/>
1004 possibility to modify angular decay correlations in the decay of a
1005 <i>A^0(H_3)</i> decay <i>Z^0 Z^0</i> or <i>W^+ W^-</i> to four
1006 fermions. Currently it does not affect the partial width of the
1007 channels, which is only based on the above parameters.
1008 <br/><code>option </code><strong> 0</strong> : isotropic decays.
1009 <br/><code>option </code><strong> 1</strong> : assuming the <i>A^0(H_3)</i> is a pure scalar
1011 <br/><code>option </code><strong> 2</strong> : assuming the <i>A^0(H_3)</i> is a pure pseudoscalar
1012 (CP-odd), as in the MSSM.
1013 <br/><code>option </code><strong> 3</strong> : assuming the <i>A^0(H_3)</i> is a mixture of the two,
1014 including the CP-violating interference term. The parameter
1015 <i>eta</i>, see below, sets the strength of the CP-odd admixture,
1016 with the interference term being proportional to <i>eta</i>
1017 and the CP-odd one to <i>eta^2</i>.
1020 <p/><code>parm </code><strong> HiggsA3:etaParity </strong>
1021 (<code>default = <strong>0.</strong></code>)<br/>
1022 The <i>eta</i> value of CP-violation in the
1023 <code>HiggsSM:parity = 3</code> option.
1029 <!-- Copyright (C) 2010 Torbjorn Sjostrand -->