<chapter name="Higgs Processes">
<h2>Higgs Processes</h2>
This page documents Higgs production within and beyond the Standard Model
(SM and BSM for short). This includes several different processes and,
for the BSM scenarios, a large set of parameters that would only be fixed
within a more specific framework such as MSSM. Some choices can be made
irrespective of the particular model:
<flag name="Higgs:cubicWidth" default="off">
The partial width of a Higgs particle to a pair of gauge bosons,
<ei>W^+ W^-</ei> or <ei>Z^0 Z^0</ei>, depends cubically on the
Higgs mass. When selecting the Higgs according to a Breit-Wigner,
so that the actual mass <ei>mHat</ei> does not agree with the
nominal <ei>m_Higgs</ei> one, an ambiguity arises which of the
two to use <ref>Sey95</ref>. The default is to use a linear
dependence on <ei>mHat</ei>, i.e. a width proportional to
<ei>m_Higgs^2 * mHat</ei>, while <code>on</code> gives a
<ei>mHat^3</ei> dependence. This does not affect the widths to
fermions, which only depend linearly on <ei>mHat</ei>.
This flag is used both for SM and BSM Higgs bosons.
</flag>
<flag name="Higgs:runningLoopMass" default="on">
The partial width of a Higgs particle to a pair of gluons or photons,
or a <ei>gamma Z^0</ei> pair, proceeds in part through quark loops,
mainly <ei>b</ei> and <ei>t</ei>. There is some ambiguity what kind
of masses to use. Default is running MSbar ones, but alternatively
fixed pole masses are allowed (as was standard in PYTHIA 6), which
typically gives a noticeably higher cross section for these channels.
(For a decay to a pair of fermions, such as top, the running mass is
used for couplings and the fixed one for phase space.)
</flag>
<flag name="Higgs:clipWings" default="on">
The Breit-Wigner shape of a Higgs is nontrivial, owing to the rapid
width variation with the mass of a Higgs. This implies that a Higgs
of low nominal mass may still acquire a non-negligible high-end tail.
The validity of the calculation may be questioned in these wings.
With this option on, the <code>Higgs:wingsFac</code> value is used to
cut away the wings.
<note>Warning:</note> with this option on, the allowed mass range is
shrunk, but never widened. This can lead to inconsistencies if a run
consists of several subruns with different Higgs masses. The
<code>id:mMin</code> and <code>id:mMax</code> values should therefore be
reset (e.g. to the defaults 50. and 0.) when <code>id:m0</code> is
changed.
</flag>
<parm name="Higgs:wingsFac" default="50." min="0.">
With <code>Higgs:clipWings</code> on, all Higgs masses which deviate
from the nominal one by more than <code>Higgs:wingsFac</code>
times the nominal width are forbidden. This is achieved by setting
the <code>mMin</code> and <code>mMax</code> values of the Higgs states
at initialization. These changes never allow a wider range than already
set by the user, alternatively by the current default values, see
warning above.
</parm>
<p>
One setting is specific to the Standard Model:
<flag name="HiggsSM:NLOWidths" default="on">
The partial width of the SM Higgs particle are multiplied by the
respective factors needed to bring the LO widths encoded in PYTHIA
to the NLO ones recommended by the LHCXSWG. The multiplicative
factors have been derived for a 125 GeV Higgs, but should apply for a
reasonable mass range around that value.
</flag>
<h3>Standard-Model Higgs, basic processes</h3>
This section provides the standard set of processes that can be
run together to provide a reasonably complete overview of possible
production channels for a single SM Higgs.
The main parameter is the choice of Higgs mass, which can be set in the
normal <code>ParticleData</code> database; thereafter the properties
within the SM are essentially fixed.
<flag name="HiggsSM:all" default="off">
Common switch for the group of Higgs production within the Standard Model.
</flag>
<flag name="HiggsSM:ffbar2H" default="off">
Scattering <ei>f fbar → H^0</ei>, where <ei>f</ei> sums over available
flavours except top. Related to the mass-dependent Higgs point coupling
to fermions, so at hadron colliders the bottom contribution will
dominate.
Code 901.
</flag>
<flag name="HiggsSM:gg2H" default="off">
Scattering <ei>g g → H^0</ei> via loop contributions primarily from
top.
Code 902.
</flag>
<flag name="HiggsSM:gmgm2H" default="off">
Scattering <ei>gamma gamma → H^0</ei> via loop contributions primarily
from top and <ei>W</ei>.
Code 903.
</flag>
<flag name="HiggsSM:ffbar2HZ" default="off">
Scattering <ei>f fbar → H^0 Z^0</ei> via <ei>s</ei>-channel <ei>Z^0</ei>
exchange.
Code 904.
</flag>
<flag name="HiggsSM:ffbar2HW" default="off">
Scattering <ei>f fbar → H^0 W^+-</ei> via <ei>s</ei>-channel
<ei>W^+-</ei> exchange.
Code 905.
</flag>
<flag name="HiggsSM:ff2Hff(t:ZZ)" default="off">
Scattering <ei>f f' → H^0 f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
Code 906.
</flag>
<flag name="HiggsSM:ff2Hff(t:WW)" default="off">
Scattering <ei>f_1 f_2 → H^0 f_3 f_4</ei> via <ei>W^+ W^-</ei> fusion.
Code 907.
</flag>
<flag name="HiggsSM:gg2Httbar" default="off">
Scattering <ei>g g → H^0 t tbar</ei> via <ei>t tbar</ei> fusion
(or, alternatively put, Higgs radiation off a top line).
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 908.
</flag>
<flag name="HiggsSM:qqbar2Httbar" default="off">
Scattering <ei>q qbar → H^0 t tbar</ei> via <ei>t tbar</ei> fusion
(or, alternatively put, Higgs radiation off a top line).
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 909.
</flag>
<h3>Standard-Model Higgs, further processes</h3>
A number of further production processes has been implemented, that
are specializations of some of the above ones to the high-<ei>pT</ei>
region. The sets therefore could not be used simultaneously
without unphysical double-counting, as further explained below.
They are not switched on by the <code>HiggsSM:all</code> flag, but
have to be switched on for each separate process after due consideration.
<p/>
The first three processes in this section are related to the Higgs
point coupling to fermions, and so primarily are of interest for
<ei>b</ei> quarks. It is here useful to begin by reminding that
a process like <ei>b bbar → H^0</ei> implies that a <ei>b/bbar</ei>
is taken from each incoming hadron, leaving behind its respective
antiparticle. The initial-state showers will then add one
<ei>g → b bbar</ei> branching on either side, so that effectively
the process becomes <ei>g g → H0 b bbar</ei>. This would be the
same basic process as the <ei>g g → H^0 t tbar</ei> one used for top.
The difference is that (a) no PDF's are defined for top and
(b) the shower approach would not be good enough to provide sensible
kinematics for the <ei>H^0 t tbar</ei> subsystem. By contrast, owing
to the <ei>b</ei> being much lighter than the Higgs, multiple
gluon emissions must be resummed for <ei>b</ei>, as is done by PDF's
and showers, in order to obtain a sensible description of the total
production rate, when the <ei>b</ei> quarks predominantly are produced
at small <ei>pT</ei> values.
<flag name="HiggsSM:qg2Hq" default="off">
Scattering <ei>q g → H^0 q</ei>. This process gives first-order
corrections to the <ei>f fbar → H^0</ei> one above, and should only be
used to study the high-<ei>pT</ei> tail, while <ei>f fbar → H^0</ei>
should be used for inclusive production. Only the dominant <ei>c</ei>
and <ei>b</ei> contributions are included, and generated separately
for technical reasons. Note that another first-order process would be
<ei>q qbar → H^0 g</ei>, which is not explicitly implemented here,
but is obtained from showering off the lowest-order process. It does not
contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
interesting for many applications.
Code 911.
</flag>
<flag name="HiggsSM:gg2Hbbbar" default="off">
Scattering <ei>g g → H^0 b bbar</ei>. This process is yet one order
higher of the <ei>b bbar → H^0</ei> and <ei>b g → H^0 b</ei> chain,
where now two quarks should be required above some large <ei>pT</ei>
threshold.
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 912.
</flag>
<flag name="HiggsSM:qqbar2Hbbbar" default="off">
Scattering <ei>q qbar → H^0 b bbar</ei> via an <ei>s</ei>-channel
gluon, so closely related to the previous one, but typically less
important owing to the smaller rate of (anti)quarks relative to
gluons.
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 913.
</flag>
<p/>
The second set of processes are predominantly first-order corrections
to the <ei>g g → H^0</ei> process, again dominated by the top loop.
We here only provide the kinematical expressions obtained in the
limit that the top quark goes to infinity, but scaled to the
finite-top-mass coupling in <ei>g g → H^0</ei>. (Complete loop
expressions are available e.g. in PYTHIA 6.4 but are very lengthy.)
This provides a reasonably accurate description for "intermediate"
<ei>pT</ei> values, but fails when the <ei>pT</ei> scale approaches
the top mass.
<flag name="HiggsSM:gg2Hg(l:t)" default="off">
Scattering <ei>g g → H^0 g</ei> via loop contributions primarily
from top.
Code 914.
</flag>
<flag name="HiggsSM:qg2Hq(l:t)" default="off">
Scattering <ei>q g → H^0 q</ei> via loop contributions primarily
from top. Not to be confused with the <code>HiggsSM:qg2Hq</code>
process above, with its direct fermion-to-Higgs coupling.
Code 915.
</flag>
<flag name="HiggsSM:qqbar2Hg(l:t)" default="off">
Scattering <ei>q qbar → H^0 g</ei> via an <ei>s</ei>-channel gluon
and loop contributions primarily from top. Is strictly speaking a
"new" process, not directly derived from <ei>g g → H^0</ei>, and
could therefore be included in the standard mix without double-counting,
but is numerically negligible.
Code 916.
</flag>
<h3>Beyond-the-Standard-Model Higgs, introduction</h3>
Further Higgs multiplets arise in a number of scenarios. We here
concentrate on the MSSM scenario with two Higgs doublets, but with
flexibility enough that also other two-Higgs-doublet scenarios could
be represented by a suitable choice of parameters. Conventionally the
Higgs states are labeled <ei>h^0, H^0, A^0</ei> and <ei>H^+-</ei>.
If the scalar and pseudocalar states mix the resulting states are
labeled <ei>H_1^0, H_2^0, H_3^0</ei>. In process names and parameter
explanations both notations will be used, but for settings labels
we have adapted the shorthand hybrid notation <code>H1</code> for
<ei>h^0(H_1^0)</ei>, <code>H2</code> for <ei>H^0(H_2^0)</ei> and
<code>A3</code> for <ei>A^0(H_3^0)</ei>. (Recall that the
<code>Settings</code> database does not distinguish upper- and lowercase
characters, so that the user has one thing less to worry about, but here
it causes problems with <ei>h^0</ei> vs. <ei>H^0</ei>.) We leave the issue
of mass ordering between <ei>H^0</ei> and <ei>A^0</ei> open, and thereby
also that of <ei>H_2^0</ei> and <ei>H_3^0</ei>.
<flag name="Higgs:useBSM" default="off">
Master switch to initialize and use the two-Higgs-doublet states.
If off, only the above SM Higgs processes can be used, with couplings
as predicted in the SM. If on, only the below BSM Higgs processes can
be used, with couplings that can be set freely, also found further down
on this page.
</flag>
<h3>Beyond-the-Standard-Model Higgs, basic processes</h3>
This section provides the standard set of processes that can be
run together to provide a reasonably complete overview of possible
production channels for a single neutral Higgs state in a two-doublet
scenarios such as MSSM. The list of processes for neutral states closely
mimics the one found for the SM Higgs. Some of the processes
vanish for a pure pseudoscalar <ei>A^0</ei>, but are kept for flexibility
in cases of mixing with the scalar <ei>h^0</ei> and <ei>H^0</ei> states,
or for use in the context of non-MSSM models. This should work well to
represent e.g. that a small admixture of the "wrong" parity would allow
a process such as <ei>q qbar → A^0 Z^0</ei>, which otherwise is
forbidden. However, note that the loop integrals e.g. for
<ei>g g → h^0/H^0/A^0</ei> are hardcoded to be for scalars for the
former two particles and for a pseudoscalar for the latter one,
so absolute rates would not be correctly represented in the case of
large scalar/pseudoscalar mixing.
<flag name="HiggsBSM:all" default="off">
Common switch for the group of Higgs production beyond the Standard Model,
as listed below.
</flag>
<h4>1) <ei>h^0(H_1^0)</ei> processes</h4>
<flag name="HiggsBSM:allH1" default="off">
Common switch for the group of <ei>h^0(H_1^0)</ei> production processes.
</flag>
<flag name="HiggsBSM:ffbar2H1" default="off">
Scattering <ei>f fbar → h^0(H_1^0)</ei>, where <ei>f</ei> sums over
available flavours except top.
Code 1001.
</flag>
<flag name="HiggsBSM:gg2H1" default="off">
Scattering <ei>g g → h^0(H_1^0)</ei> via loop contributions primarily
from top.
Code 1002.
</flag>
<flag name="HiggsBSM:gmgm2H1" default="off">
Scattering <ei>gamma gamma → h^0(H_1^0)</ei> via loop contributions
primarily from top and <ei>W</ei>.
Code 1003.
</flag>
<flag name="HiggsBSM:ffbar2H1Z" default="off">
Scattering <ei>f fbar → h^0(H_1^0) Z^0</ei> via <ei>s</ei>-channel
<ei>Z^0</ei> exchange.
Code 1004.
</flag>
<flag name="HiggsBSM:ffbar2H1W" default="off">
Scattering <ei>f fbar → h^0(H_1^0) W^+-</ei> via <ei>s</ei>-channel
<ei>W^+-</ei> exchange.
Code 1005.
</flag>
<flag name="HiggsBSM:ff2H1ff(t:ZZ)" default="off">
Scattering <ei>f f' → h^0(H_1^0) f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
Code 1006.
</flag>
<flag name="HiggsBSM:ff2H1ff(t:WW)" default="off">
Scattering <ei>f_1 f_2 → h^0(H_1^0) f_3 f_4</ei> via <ei>W^+ W^-</ei>
fusion.
Code 1007.
</flag>
<flag name="HiggsBSM:gg2H1ttbar" default="off">
Scattering <ei>g g → h^0(H_1^0) t tbar</ei> via <ei>t tbar</ei> fusion
(or, alternatively put, Higgs radiation off a top line).
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1008.
</flag>
<flag name="HiggsBSM:qqbar2H1ttbar" default="off">
Scattering <ei>q qbar → h^0(H_1^0) t tbar</ei> via <ei>t tbar</ei>
fusion (or, alternatively put, Higgs radiation off a top line).
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1009.
<h4>2) <ei>H^0(H_2^0)</ei> processes</h4>
<flag name="HiggsBSM:allH2" default="off">
Common switch for the group of <ei>H^0(H_2^0)</ei> production processes.
</flag>
<flag name="HiggsBSM:ffbar2H2" default="off">
Scattering <ei>f fbar → H^0(H_2^0)</ei>, where <ei>f</ei> sums over
available flavours except top.
Code 1021.
</flag>
<flag name="HiggsBSM:gg2H2" default="off">
Scattering <ei>g g → H^0(H_2^0)</ei> via loop contributions primarily
from top.
Code 1022.
</flag>
<flag name="HiggsBSM:gmgm2H2" default="off">
Scattering <ei>gamma gamma → H^0(H_2^0)</ei> via loop contributions
primarily from top and <ei>W</ei>.
Code 1023.
</flag>
<flag name="HiggsBSM:ffbar2H2Z" default="off">
Scattering <ei>f fbar → H^0(H_2^0) Z^0</ei> via <ei>s</ei>-channel
<ei>Z^0</ei> exchange.
Code 1024.
</flag>
<flag name="HiggsBSM:ffbar2H2W" default="off">
Scattering <ei>f fbar → H^0(H_2^0) W^+-</ei> via <ei>s</ei>-channel
<ei>W^+-</ei> exchange.
Code 1025.
</flag>
<flag name="HiggsBSM:ff2H2ff(t:ZZ)" default="off">
Scattering <ei>f f' → H^0(H_2^0) f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
Code 1026.
</flag>
<flag name="HiggsBSM:ff2H2ff(t:WW)" default="off">
Scattering <ei>f_1 f_2 → H^0(H_2^0) f_3 f_4</ei> via <ei>W^+ W^-</ei>
fusion.
Code 1027.
</flag>
<flag name="HiggsBSM:gg2H2ttbar" default="off">
Scattering <ei>g g → H^0(H_2^0) t tbar</ei> via <ei>t tbar</ei> fusion
(or, alternatively put, Higgs radiation off a top line).
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1028.
</flag>
<flag name="HiggsBSM:qqbar2H2ttbar" default="off">
Scattering <ei>q qbar → H^0(H_2^0) t tbar</ei> via <ei>t tbar</ei>
fusion (or, alternatively put, Higgs radiation off a top line).
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1029.
<h4>3) <ei>A^0(H_3^0)</ei> processes</h4>
<flag name="HiggsBSM:allA3" default="off">
Common switch for the group of <ei>A^0(H_3^0)</ei> production processes.
</flag>
<flag name="HiggsBSM:ffbar2A3" default="off">
Scattering <ei>f fbar → A^0(H_3^0)</ei>, where <ei>f</ei> sums over
available flavours except top.
Code 1041.
</flag>
<flag name="HiggsBSM:gg2A3" default="off">
Scattering <ei>g g → A^0(A_3^0)</ei> via loop contributions primarily
from top.
Code 1042.
</flag>
<flag name="HiggsBSM:gmgm2A3" default="off">
Scattering <ei>gamma gamma → A^0(A_3^0)</ei> via loop contributions
primarily from top and <ei>W</ei>.
Code 1043.
</flag>
<flag name="HiggsBSM:ffbar2A3Z" default="off">
Scattering <ei>f fbar → A^0(A_3^0) Z^0</ei> via <ei>s</ei>-channel
<ei>Z^0</ei> exchange.
Code 1044.
</flag>
<flag name="HiggsBSM:ffbar2A3W" default="off">
Scattering <ei>f fbar → A^0(A_3^0) W^+-</ei> via <ei>s</ei>-channel
<ei>W^+-</ei> exchange.
Code 1045.
</flag>
<flag name="HiggsBSM:ff2A3ff(t:ZZ)" default="off">
Scattering <ei>f f' → A^0(A_3^0) f f'</ei> via <ei>Z^0 Z^0</ei> fusion.
Code 1046.
</flag>
<flag name="HiggsBSM:ff2A3ff(t:WW)" default="off">
Scattering <ei>f_1 f_2 → A^0(A_3^0) f_3 f_4</ei> via <ei>W^+ W^-</ei>
fusion. Code 1047.
</flag>
<flag name="HiggsBSM:gg2A3ttbar" default="off">
Scattering <ei>g g → A^0(A_3^0) t tbar</ei> via <ei>t tbar</ei> fusion
(or, alternatively put, Higgs radiation off a top line).
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1048.
</flag>
<flag name="HiggsBSM:qqbar2A3ttbar" default="off">
Scattering <ei>q qbar → A^0(A_3^0) t tbar</ei> via <ei>t tbar</ei>
fusion (or, alternatively put, Higgs radiation off a top line).
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1049.
<h4>4) <ei>H+-</ei> processes</h4>
<flag name="HiggsBSM:allH+-" default="off">
Common switch for the group of <ei>H^+-</ei> production processes.
</flag>
<flag name="HiggsBSM:ffbar2H+-" default="off">
Scattering <ei>f fbar' → H^+-</ei>, where <ei>f, fbar'</ei> sums over
available incoming flavours. Since couplings are assumed
generation-diagonal, in practice this means <ei>c sbar → H^+</ei>
and <ei>s cbar → H^-</ei>.
Code 1061.
</flag>
<flag name="HiggsBSM:bg2H+-t" default="off">
Scattering <ei>b g → H^+ tbar</ei>. At hadron colliders this is the
dominant process for single-charged-Higgs production.
Code 1062.
</flag>
<h4>5) Higgs-pair processes</h4>
<flag name="HiggsBSM:allHpair" default="off">
Common switch for the group of Higgs pair-production processes.
</flag>
<flag name="HiggsBSM:ffbar2A3H1" default="off">
Scattering <ei>f fbar → A^0(H_3) h^0(H_1)</ei>.
Code 1081.
</flag>
<flag name="HiggsBSM:ffbar2A3H2" default="off">
Scattering <ei>f fbar → A^0(H_3) H^0(H_2)</ei>.
Code 1082.
</flag>
<flag name="HiggsBSM:ffbar2H+-H1" default="off">
Scattering <ei>f fbar → H^+- h^0(H_1)</ei>.
Code 1083.
</flag>
<flag name="HiggsBSM:ffbar2H+-H2" default="off">
Scattering <ei>f fbar → H^+- H^0(H_2)</ei>.
Code 1084.
</flag>
<flag name="HiggsBSM:ffbar2H+H-" default="off">
Scattering <ei>f fbar → H+ H-</ei>.
Code 1085.
</flag>
<h3>Beyond-the-Standard-Model Higgs, further processes</h3>
This section mimics the above section on "Standard-Model Higgs,
further processes", i.e. it contains higher-order corrections
to the processes already listed. The two sets therefore could not
be used simultaneously without unphysical double-counting.
They are not controlled by any group flag, but have to be switched
on for each separate process after due consideration. We refer to
the standard-model description for a set of further comments on
the processes.
<h4>1) <ei>h^0(H_1^0)</ei> processes</h4>
<flag name="HiggsBSM:qg2H1q" default="off">
Scattering <ei>q g → h^0 q</ei>. This process gives first-order
corrections to the <ei>f fbar → h^0</ei> one above, and should only be
used to study the high-<ei>pT</ei> tail, while <ei>f fbar → h^0</ei>
should be used for inclusive production. Only the dominant <ei>c</ei>
and <ei>b</ei> contributions are included, and generated separately
for technical reasons. Note that another first-order process would be
<ei>q qbar → h^0 g</ei>, which is not explicitly implemented here,
but is obtained from showering off the lowest-order process. It does not
contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
interesting for many applications.
Code 1011.
</flag>
<flag name="HiggsBSM:gg2H1bbbar" default="off">
Scattering <ei>g g → h^0 b bbar</ei>. This process is yet one order
higher of the <ei>b bbar → h^0</ei> and <ei>b g → h^0 b</ei> chain,
where now two quarks should be required above some large <ei>pT</ei>
threshold.
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1012.
</flag>
<flag name="HiggsBSM:qqbar2H1bbbar" default="off">
Scattering <ei>q qbar → h^0 b bbar</ei> via an <ei>s</ei>-channel
gluon, so closely related to the previous one, but typically less
important owing to the smaller rate of (anti)quarks relative to
gluons.
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1013.
</flag>
<flag name="HiggsBSM:gg2H1g(l:t)" default="off">
Scattering <ei>g g → h^0 g</ei> via loop contributions primarily
from top.
Code 1014.
</flag>
<flag name="HiggsBSM:qg2H1q(l:t)" default="off">
Scattering <ei>q g → h^0 q</ei> via loop contributions primarily
from top. Not to be confused with the <code>HiggsBSM:qg2H1q</code>
process above, with its direct fermion-to-Higgs coupling.
Code 1015.
</flag>
<flag name="HiggsBSM:qqbar2H1g(l:t)" default="off">
Scattering <ei>q qbar → h^0 g</ei> via an <ei>s</ei>-channel gluon
and loop contributions primarily from top. Is strictly speaking a
"new" process, not directly derived from <ei>g g → h^0</ei>, and
could therefore be included in the standard mix without double-counting,
but is numerically negligible.
Code 1016.
</flag>
<h4>2) <ei>H^0(H_2^0)</ei> processes</h4>
<flag name="HiggsBSM:qg2H2q" default="off">
Scattering <ei>q g → H^0 q</ei>. This process gives first-order
corrections to the <ei>f fbar → H^0</ei> one above, and should only be
used to study the high-<ei>pT</ei> tail, while <ei>f fbar → H^0</ei>
should be used for inclusive production. Only the dominant <ei>c</ei>
and <ei>b</ei> contributions are included, and generated separately
for technical reasons. Note that another first-order process would be
<ei>q qbar → H^0 g</ei>, which is not explicitly implemented here,
but is obtained from showering off the lowest-order process. It does not
contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
interesting for many applications.
Code 1031.
</flag>
<flag name="HiggsBSM:gg2H2bbbar" default="off">
Scattering <ei>g g → H^0 b bbar</ei>. This process is yet one order
higher of the <ei>b bbar → H^0</ei> and <ei>b g → H^0 b</ei> chain,
where now two quarks should be required above some large <ei>pT</ei>
threshold.
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1032.
</flag>
<flag name="HiggsBSM:qqbar2H2bbbar" default="off">
Scattering <ei>q qbar → H^0 b bbar</ei> via an <ei>s</ei>-channel
gluon, so closely related to the previous one, but typically less
important owing to the smaller rate of (anti)quarks relative to
gluons.
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1033.
</flag>
<flag name="HiggsBSM:gg2H2g(l:t)" default="off">
Scattering <ei>g g → H^0 g</ei> via loop contributions primarily
from top.
Code 1034.
</flag>
<flag name="HiggsBSM:qg2H2q(l:t)" default="off">
Scattering <ei>q g → H^0 q</ei> via loop contributions primarily
from top. Not to be confused with the <code>HiggsBSM:qg2H1q</code>
process above, with its direct fermion-to-Higgs coupling.
Code 1035.
</flag>
<flag name="HiggsBSM:qqbar2H2g(l:t)" default="off">
Scattering <ei>q qbar → H^0 g</ei> via an <ei>s</ei>-channel gluon
and loop contributions primarily from top. Is strictly speaking a
"new" process, not directly derived from <ei>g g → H^0</ei>, and
could therefore be included in the standard mix without double-counting,
but is numerically negligible.
Code 1036.
</flag>
<h4>3) <ei>A^0(H_3^0)</ei> processes</h4>
<flag name="HiggsBSM:qg2A3q" default="off">
Scattering <ei>q g → A^0 q</ei>. This process gives first-order
corrections to the <ei>f fbar → A^0</ei> one above, and should only be
used to study the high-<ei>pT</ei> tail, while <ei>f fbar → A^0</ei>
should be used for inclusive production. Only the dominant <ei>c</ei>
and <ei>b</ei> contributions are included, and generated separately
for technical reasons. Note that another first-order process would be
<ei>q qbar → A^0 g</ei>, which is not explicitly implemented here,
but is obtained from showering off the lowest-order process. It does not
contain any <ei>b</ei> at large <ei>pT</ei>, however, so is less
interesting for many applications.
Code 1051.
</flag>
<flag name="HiggsBSM:gg2A3bbbar" default="off">
Scattering <ei>g g → A^0 b bbar</ei>. This process is yet one order
higher of the <ei>b bbar → A^0</ei> and <ei>b g → A^0 b</ei> chain,
where now two quarks should be required above some large <ei>pT</ei>
threshold.
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1052.
</flag>
<flag name="HiggsBSM:qqbar2A3bbbar" default="off">
Scattering <ei>q qbar → A^0 b bbar</ei> via an <ei>s</ei>-channel
gluon, so closely related to the previous one, but typically less
important owing to the smaller rate of (anti)quarks relative to
gluons.
Warning: unfortunately this process is rather slow, owing to a
lengthy cross-section expression and inefficient phase-space selection.
Code 1053.
</flag>
<flag name="HiggsBSM:gg2A3g(l:t)" default="off">
Scattering <ei>g g → A^0 g</ei> via loop contributions primarily
from top.
Code 1054.
</flag>
<flag name="HiggsBSM:qg2A3q(l:t)" default="off">
Scattering <ei>q g → A^0 q</ei> via loop contributions primarily
from top. Not to be confused with the <code>HiggsBSM:qg2H1q</code>
process above, with its direct fermion-to-Higgs coupling.
Code 1055.
</flag>
<flag name="HiggsBSM:qqbar2A3g(l:t)" default="off">
Scattering <ei>q qbar → A^0 g</ei> via an <ei>s</ei>-channel gluon
and loop contributions primarily from top. Is strictly speaking a
"new" process, not directly derived from <ei>g g → A^0</ei>, and
could therefore be included in the standard mix without double-counting,
but is numerically negligible.
Code 1056.
</flag>
<h3>Parameters for Beyond-the-Standard-Model Higgs production and decay</h3>
This section offers a big flexibility to set couplings of the various
Higgs states to fermions and gauge bosons, and also to each other.
The intention is that, for scenarios like MSSM, you should use standard
input from the <aloc href="SUSYLesHouchesAccord">SUSY Les Houches
Accord</aloc>, rather than having to set it all yourself. In other cases,
however, the freedom is there for you to use. Kindly note that some
of the internal calculations of partial widths from the parameters provided
do not include mixing between the scalar and pseudoscalar states.
<p/>
Masses would be set in the <code>ParticleData</code> database,
while couplings are set below. When possible, the couplings of the Higgs
states are normalized to the corresponding coupling within the SM.
When not, their values within the MSSM are indicated, from which
it should be straightforward to understand what to use instead.
The exception is some couplings that vanish also in the MSSM, where the
normalization has been defined in close analogy with nonvanishing ones.
Some parameter names are asymmetric but crossing can always be used,
i.e. the coupling for <ei>A^0 → H^0 Z^0</ei> obviously is also valid
for <ei>H^0 → A^0 Z^0</ei> and <ei>Z^0 → H^0 A^0</ei>.
Note that couplings usually appear quadratically in matrix elements.
<parm name="HiggsH1:coup2d" default="1.">
The <ei>h^0(H_1^0)</ei> coupling to down-type quarks.
</parm>
<parm name="HiggsH1:coup2u" default="1.">
The <ei>h^0(H_1^0)</ei> coupling to up-type quarks.
</parm>
<parm name="HiggsH1:coup2l" default="1.">
The <ei>h^0(H_1^0)</ei> coupling to (charged) leptons.
</parm>
<parm name="HiggsH1:coup2Z" default="1.">
The <ei>h^0(H_1^0)</ei> coupling to <ei>Z^0</ei>.
</parm>
<parm name="HiggsH1:coup2W" default="1.">
The <ei>h^0(H_1^0)</ei> coupling to <ei>W^+-</ei>.
</parm>
<parm name="HiggsH1:coup2Hchg" default="0.">
The <ei>h^0(H_1^0)</ei> coupling to <ei>H^+-</ei> (in loops).
Is <ei>sin(beta - alpha) + cos(2 beta) sin(beta + alpha) /
(2 cos^2theta_W)</ei> in the MSSM.
</parm>
<parm name="HiggsH2:coup2d" default="1.">
The <ei>H^0(H_2^0)</ei> coupling to down-type quarks.
</parm>
<parm name="HiggsH2:coup2u" default="1.">
The <ei>H^0(H_2^0)</ei> coupling to up-type quarks.
</parm>
<parm name="HiggsH2:coup2l" default="1.">
The <ei>H^0(H_2^0)</ei> coupling to (charged) leptons.
</parm>
<parm name="HiggsH2:coup2Z" default="1.">
The <ei>H^0(H_2^0)</ei> coupling to <ei>Z^0</ei>.
</parm>
<parm name="HiggsH2:coup2W" default="1.">
The <ei>H^0(H_2^0)</ei> coupling to <ei>W^+-</ei>.
</parm>
<parm name="HiggsH2:coup2Hchg" default="0.">
The <ei>H^0(H_2^0)</ei> coupling to <ei>H^+-</ei> (in loops).
Is <ei>cos(beta - alpha) + cos(2 beta) cos(beta + alpha) /
(2 cos^2theta_W)</ei> in the MSSM.
</parm>
<parm name="HiggsH2:coup2H1H1" default="1.">
The <ei>H^0(H_2^0)</ei> coupling to a <ei>h^0(H_1^0)</ei> pair.
Is <ei>cos(2 alpha) cos(beta + alpha) - 2 sin(2 alpha)
sin(beta + alpha)</ei> in the MSSM.
</parm>
<parm name="HiggsH2:coup2A3A3" default="1.">
The <ei>H^0(H_2^0)</ei> coupling to an <ei>A^0(H_3^0)</ei> pair.
Is <ei>cos(2 beta) cos(beta + alpha)</ei> in the MSSM.
</parm>
<parm name="HiggsH2:coup2H1Z" default="0.">
The <ei>H^0(H_2^0)</ei> coupling to a <ei>h^0(H_1^0) Z^0</ei> pair.
Vanishes in the MSSM.
</parm>
<parm name="HiggsH2:coup2A3H1" default="0.">
The <ei>H^0(H_2^0)</ei> coupling to an <ei>A^0(H_3^0) h^0(H_1^0)</ei> pair.
Vanishes in the MSSM.
</parm>
<parm name="HiggsH2:coup2HchgW" default="0.">
The <ei>H^0(H_2^0)</ei> coupling to a <ei>H^+- W-+</ei> pair.
Is <ei>sin(beta - alpha)</ei> in the MSSM.
</parm>
<parm name="HiggsA3:coup2d" default="1.">
The <ei>A^0(H_3^0)</ei> coupling to down-type quarks.
</parm>
<parm name="HiggsA3:coup2u" default="1.">
The <ei>A^0(H_3^0)</ei> coupling to up-type quarks.
</parm>
<parm name="HiggsA3:coup2l" default="1.">
The <ei>A^0(H_3^0)</ei> coupling to (charged) leptons.
</parm>
<parm name="HiggsA3:coup2H1Z" default="1.">
The <ei>A^0(H_3^0)</ei> coupling to a <ei>h^0(H_1^0) Z^0</ei> pair.
Is <ei>cos(beta - alpha)</ei> in the MSSM.
</parm>
<parm name="HiggsA3:coup2H2Z" default="1.">
The <ei>A^0(H_3^0)</ei> coupling to a <ei>H^0(H_2^0) Z^0</ei> pair.
Is <ei>sin(beta - alpha)</ei> in the MSSM.
</parm>
<parm name="HiggsA3:coup2Z" default="0.">
The <ei>A^0(H_3^0)</ei> coupling to <ei>Z^0</ei>.
Vanishes in the MSSM.
</parm>
<parm name="HiggsA3:coup2W" default="0.">
The <ei>A^0(H_3^0)</ei> coupling to <ei>W^+-</ei>.
Vanishes in the MSSM.
</parm>
<parm name="HiggsA3:coup2H1H1" default="0.">
The <ei>A^0(H_3^0)</ei> coupling to a <ei>h^0(H_1^0)</ei> pair.
Vanishes in the MSSM.
</parm>
<parm name="HiggsA3:coup2Hchg" default="0.">
The <ei>A^0(H_3^0)</ei> coupling to <ei>H^+-</ei>.
Vanishes in the MSSM.
</parm>
<parm name="HiggsA3:coup2HchgW" default="1.">
The <ei>A^0(H_3^0)</ei> coupling to a <ei>H^+- W-+</ei> pair.
Is 1 in the MSSM.
</parm>
<parm name="HiggsHchg:tanBeta" default="5.">
The <ei>tan(beta)</ei> value, which leads to an enhancement of the
<ei>H^+-</ei> coupling to down-type fermions and suppression to
up-type ones. The same angle also appears in many other places,
but this particular parameter is only used for the charged-Higgs case.
</parm>
<parm name="HiggsHchg:coup2H1W" default="1.">
The <ei>H^+-</ei> coupling to a <ei>h^0(H_1^0) W^+-</ei> pair.
Is <ei>cos(beta - alpha)</ei> in the MSSM.
</parm>
<parm name="HiggsHchg:coup2H2W" default="0.">
The <ei>H^+-</ei> coupling to a <ei>H^0(H_2^0) W^+-</ei> pair.
Is <ei>sin(beta - alpha)</ei> in the MSSM.
</parm>
<p/>
Another set of parameters are not used in the production stage but
exclusively for the description of angular distributions in decays.
<modepick name="HiggsH1:parity" default="1" min="0" max="3">
possibility to modify angular decay correlations in the decay of a
<ei>h^0(H_1)</ei> decay <ei>Z^0 Z^0</ei> or <ei>W^+ W^-</ei> to four
fermions. Currently it does not affect the partial width of the
channels, which is only based on the above parameters.
<option value="0">isotropic decays.</option>
<option value="1">assuming the <ei>h^0(H_1)</ei> is a pure scalar
(CP-even), as in the MSSM.</option>
<option value="2">assuming the <ei>h^0(H_1)</ei> is a pure pseudoscalar
(CP-odd).</option>
<option value="3">assuming the <ei>h^0(H_1)</ei> is a mixture of the two,
including the CP-violating interference term. The parameter
<ei>eta</ei>, see below, sets the strength of the CP-odd admixture,
with the interference term being proportional to <ei>eta</ei>
and the CP-odd one to <ei>eta^2</ei>.</option>
</modepick>
<parm name="HiggsH1:etaParity" default="0.">
The <ei>eta</ei> value of CP-violation in the
<code>HiggsSM:parity = 3</code> option.
</parm>
<modepick name="HiggsH2:parity" default="1" min="0" max="3">
possibility to modify angular decay correlations in the decay of a
<ei>H^0(H_2)</ei> decay <ei>Z^0 Z^0</ei> or <ei>W^+ W^-</ei> to four
fermions. Currently it does not affect the partial width of the
channels, which is only based on the above parameters.
<option value="0">isotropic decays.</option>
<option value="1">assuming the <ei>H^0(H_2)</ei> is a pure scalar
(CP-even), as in the MSSM.</option>
<option value="2">assuming the <ei>H^0(H_2)</ei> is a pure pseudoscalar
(CP-odd).</option>
<option value="3">assuming the <ei>H^0(H_2)</ei> is a mixture of the two,
including the CP-violating interference term. The parameter
<ei>eta</ei>, see below, sets the strength of the CP-odd admixture,
with the interference term being proportional to <ei>eta</ei>
and the CP-odd one to <ei>eta^2</ei>.</option>
</modepick>
<parm name="HiggsH2:etaParity" default="0.">
The <ei>eta</ei> value of CP-violation in the
<code>HiggsSM:parity = 3</code> option.
</parm>
<modepick name="HiggsA3:parity" default="2" min="0" max="3">
possibility to modify angular decay correlations in the decay of a
<ei>A^0(H_3)</ei> decay <ei>Z^0 Z^0</ei> or <ei>W^+ W^-</ei> to four
fermions. Currently it does not affect the partial width of the
channels, which is only based on the above parameters.
<option value="0">isotropic decays.</option>
<option value="1">assuming the <ei>A^0(H_3)</ei> is a pure scalar
(CP-even).</option>
<option value="2">assuming the <ei>A^0(H_3)</ei> is a pure pseudoscalar
(CP-odd), as in the MSSM.</option>
<option value="3">assuming the <ei>A^0(H_3)</ei> is a mixture of the two,
including the CP-violating interference term. The parameter
<ei>eta</ei>, see below, sets the strength of the CP-odd admixture,
with the interference term being proportional to <ei>eta</ei>
and the CP-odd one to <ei>eta^2</ei>.</option>
</modepick>
<parm name="HiggsA3:etaParity" default="0.">
The <ei>eta</ei> value of CP-violation in the
<code>HiggsSM:parity = 3</code> option.
</parm>
</chapter>
<!-- Copyright (C) 2014 Torbjorn Sjostrand -->
Marcin Chrzaszcz