Event Information
The Info class collects various one-of-a-kind information,
some relevant for all events and others for the current event.
An object info is a public member of the Pythia
class, so if you e.g. have declared Pythia pythia, the
Info methods can be accessed by
pythia.info.method(). Most of this is information that
could also be obtained e.g. from the event record, but is here more
directly available. It is primarily intended for processes generated
internally in PYTHIA, but many of the methods would work also for
events fed in via the Les Houches Accord.
List information
void Info::list()
a listing of most of the information set for the current event.
The beams
int Info::idA()
int Info::idB()
the identities of the two beam particles.
double Info::pzA()
double Info::pzB()
the longitudinal momenta of the two beam particles.
double Info::eA()
double Info::eB()
the energies of the two beam particles.
double Info::mA()
double Info::mB()
the masses of the two beam particles.
double Info::eCM()
double Info::s()
the CM energy and its square for the two beams.
Initialization
bool Info::tooLowPTmin()
normally false, but true if the proposed pTmin scale was too low
in timelike or spacelike showers, or in multiparton interactions. In the
former case the pTmin is raised to some minimal value, in the
latter the initialization fails (it is impossible to obtain a minijet
cross section bigger than the nondiffractive one by reducing
pTmin).
The event type
string Info::name()
int Info::code()
the name and code of the process that occurred.
int Info::nFinal()
the number of final-state partons in the hard process.
bool Info::isResolved()
are beam particles resolved, i.e. were PDF's used for the process?
bool Info::isDiffractiveA()
bool Info::isDiffractiveB()
is either beam soft diffractively excited?
bool Info::isDiffractiveC()
is there soft central diffraction (a.k.a. double Pomeron exchange)?
bool Info::isHardDiffractiveA()
bool Info::isHardDiffractiveB()
is either beam hard diffractively excited?
bool Info::isNonDiffractive()
is the process the SoftQCD:nonDiffractive one,
i.e. corresponding to the full inelastic nondiffractive part of the
total cross section. (Note that a hard process, say Z^0
production, normally is nondiffractive, but this is not what we
aim at here, and so the method would return false,
unless the Z^0 had been generated as part of the MPI
machinery for the SoftQCD:nonDiffractive component.)
bool Info::isMinBias()
the same as above, retained for backwards compatibility, but to
be removed in PYTHIA 8.2.
bool Info::isLHA()
has the process been generated from external Les Houches Accord
information?
bool Info::atEndOfFile()
true if a linked Les Houches class refuses to return any further
events, presumably because it has reached the end of the file from
which events have been read in.
bool Info::hasSub()
does the process have a subprocess classification?
Currently only true for nondiffractive and Les Houches events, where
it allows the hardest collision to be identified.
string Info::nameSub()
int Info::codeSub()
int Info::nFinalSub()
the name, code and number of final-state partons in the subprocess
that occurred when hasSub() is true. For a minimum-bias event
the code would always be 101, while codeSub()
would vary depending on the actual hardest interaction, e.g. 111 for
g g → g g. For a Les Houches event the code would
always be 9999, while codeSub() would be the external
user-defined classification code. The methods below would also provide
information for such particular subcollisions.
Hard process initiators
The methods in this sections refer to the two initial partons of the
hard 2 → n process (diffraction excluded; see below).
int Info::id1()
int Info::id2()
the identities of the two partons coming in to the hard process.
double Info::x1()
double Info::x2()
x fractions of the two partons coming in to the hard process.
double Info::y()
double Info::tau()
rapidity and scaled mass-squared of the hard-process subsystem, as
defined by the above x values.
bool Info::isValence1()
bool Info::isValence2()
true if the two hard incoming partons have been picked
to belong to the valence piece of the parton-density distribution,
else false. Should be interpreted with caution.
Information is not set if you switch off parton-level processing.
Hard process parton densities and scales
The methods in this section refer to the partons for which parton
densities have been defined, in order to calculate the cross section
of the hard process (diffraction excluded; see below).
These partons would normally agree with the
ones above, the initiators of the 2 → n process, but it
does not have to be so. Currently the one counterexample is POWHEG
events [Ali10]. Here the original hard process could be
2 → (n-1). The NLO machinery at times would add an
initial-state branching to give a 2 → n process with a
changed initial state. In that case the values in this section
refer to the original 2 → (n-1) state and the initiator
ones above to the complete2 → n process. The
Info::list() printout will contain a warning in such cases.
For external events in the Les Houches format, the pdf information
is obtained from the optional #pdf line. When this
information is absent, the parton identities and x values agree
with the initiator ones above, while the pdf values are unknown and
therefore set to vanish. The alpha_s and alpha_em
values are part of the compulsory information. The factorization and
renormalization scales are both equated with the one compulsory scale
value in the Les Houches standard, except when a #pdf
line provides the factorization scale separately. If alpha_s,
alpha_em or the compulsory scale value are negative at input
then new values are defined as for internal processes.
int Info::id1pdf()
int Info::id2pdf()
the identities of the two partons for which parton density values
are defined.
double Info::x1pdf()
double Info::x2pdf()
x fractions of the two partons for which parton density values
are defined.
double Info::pdf1()
double Info::pdf2()
parton densities x*f(x,Q^2) evaluated for the two incoming
partons; could be used e.g. for reweighting purposes in conjunction
with the idpdf, xpdf and QFac
methods. Events obtained from external programs or files may not
contain this information and, if so, 0 is returned.
double Info::QFac()
double Info::Q2Fac()
the Q or Q^2 factorization scale at which the
densities were evaluated.
double Info::alphaS()
double Info::alphaEM()
the alpha_strong and alpha_electromagnetic values used
for the hard process.
double Info::QRen()
double Info::Q2Ren()
the Q or Q^2 renormalization scale at which
alpha_strong and alpha_electromagnetic were evaluated.
double Info::scalup()
returns the stored SCALUP value for Les Houches events,
and else zero. It may agree with both the QFac() and
QRen() values, as explained above. However, to repeat,
should the input SCALUP scale be negative, separate positive
factorization and renormalization scales are calculated and set as for
internally generated events. Furthermore, when PDF info is supplied for
the Les Houches event, the factorization scale is set by this PDF info
(scalePDF), which can disagree with SCALUP.
Hard process kinematics
The methods in this section provide info on the kinematics of the hard
processes, with special emphasis on 2 → 2 (diffraction excluded;
see below).
double Info::mHat()
double Info::sHat()
the invariant mass and its square for the hard process.
double Info::tHat()
double Info::uHat()
the remaining two Mandelstam variables; only defined for 2 → 2
processes.
double Info::pTHat()
double Info::pT2Hat()
transverse momentum and its square in the rest frame of a 2 → 2
processes.
double Info::m3Hat()
double Info::m4Hat()
the masses of the two outgoing particles in a 2 → 2 processes.
double Info::thetaHat()
double Info::phiHat()
the polar and azimuthal scattering angles in the rest frame of
a 2 → 2 process.
Soft Diffraction
Information on the primary elastic or
diffractive process
(A B → A B, X1 B, A X2, X1 X2, A X B) can be obtained with
the methods in the "Hard process kinematics" section above. The
variables here obviously are s, t, u, ... rather than
sHat, tHat, uHat, ..., but the method names remain to avoid
unnecessary duplication. Most other methods are irrelevant for a
primary elastic/diffractive process.
Central diffraction A B → A X B is a 2 → 3
process, and therefore most of the 2 → 2 variables are
no longer relevant. The tHat() and uHat()
methods instead return the two t values at the A → A
and B → B vertices, and pTHat() the average
transverse momentum of the three outgoing "particles", while
thetaHat() and phiHat() are undefined.
While the primary interaction does not contain a hard process,
the diffractive subsystems can contain them, but need not.
Specifically, double diffraction can contain two separate hard
subprocesses, which breaks the methods above. Most of them have been
expanded with an optional argument to address properties of diffractive
subsystems. This argument can take four values:
- 0 : default argument, used for normal nondiffractive events or
the primary elastic/diffractive process (see above);
- 1 : the X1 system in single diffraction
A B → X1 B or double diffraction A B → X1 X2;
- 2 : the X2 system in single diffraction
A B → A X2 or double diffraction A B → X1 X2;
- 3 : the X system in central diffraction
A B → A X B.
The argument is defined for all of the methods in the three sections above,
"Hard process initiators", "Hard process parton densities and scales" and
"Hard process kinematics", with the exception of the isValence
methods. Also the four final methods of "The event type" section, the
...Sub() methods, take this argument. But recall that they
will only provide meaningful answers, firstly if there is a system of the
requested type, and secondly if there is a hard subprocess in this system.
A simple check for this is that id1() has to be nonvanishing.
The methods below this section do not currently provide information
specific to diffractive subsystems, e.g. the MPI information is not
bookkept in such cases.
Hard Diffraction
Information on the momentum fraction taken from the beam
and the momentum transfer in the hard diffractive process.
Note that when side A is diffractively exited, then the Pomeron
has been taken from side B and vice versa.
double Info::xPomeronA()
double Info::xPomeronB()
x fractions of momenta carried by the Pomeron in the hard
diffractive process.
double Info::tPomeronA()
double Info::tPomeronB()
The momentum transfer t in the hard diffractive process.
Photons from lepton beams
Information about the kinematics of photon-photon collisions from lepton
beams.
double Info::eCMsub()
Collision energy of the gamma-gamma sub-system.
double Info::xGammaA()
double Info::xGammaB()
x fractions of lepton momenta carried by the photons.
double Info::Q2GammaA()
double Info::Q2GammaB()
Virtualities of the photons emitted by the leptons.
double Info::thetaScatLepA()
double Info::thetaScatLepB()
Scattering angles of the leptons wrt. the beam direction.
int Info::photonMode()
Type of photon process, see
Photoproduction for details.
Event weight and activity
double Info::weight()
weight assigned to the current event. Is normally 1 and thus
uninteresting. However, there are several cases where one may have
nontrivial event weights. These weights must the be used e.g. when
filling histograms.
(i) In the
PhaseSpace:increaseMaximum = off default strategy,
an event with a differential cross-section above the assumed one
(in a given phase-space point) is assigned a weight correspondingly
above unity. This should happen only very rarely, if at all, and so
could normally be disregarded.
(ii) The User Hooks class offers
the possibility to bias the selection of phase space points, which
means that events come with a compensating weight, stored here.
(iii) For Les Houches events some strategies allow negative weights,
which then after unweighting lead to events with weight -1. There are
also Les Houches strategies where no unweighting is done, so events
come with a weight. Specifically, for strategies +4 and
-4, the event weight is in units of pb. (Internally in mb,
but converted at output.)
double Info::weightSum()
Sum of weights accumulated during the run. For unweighted events this
agrees with the number of generated events. In order to obtain
histograms normalized "per event", at the end of a run, histogram
contents should be divided by this weight. (And additionally
divided by the bin width.) Normalization to cross section also
required multiplication by sigmaGen() below.
int Info::lhaStrategy()
normally 0, but if Les Houches events are input then it gives the
event weighting strategy, see
Les Houches Accord.
int Info::nISR()
int Info::nFSRinProc()
int Info::nFSRinRes()
the number of emissions in the initial-state showering, in the final-state
showering excluding resonance decays, and in the final-state showering
inside resonance decays, respectively.
double Info::pTmaxMPI()
double Info::pTmaxISR()
double Info::pTmaxFSR()
Maximum pT scales set for MPI, ISR and FSR, given the
process type and scale choice for the hard interactions. The actual
evolution will run down from these scales.
double Info::pTnow()
The current pT scale in the combined MPI, ISR and FSR evolution.
Useful for classification in user hooks,
but not once the event has been evolved.
double Info::mergingWeight()
combined leading-order merging weight assigned to the current event, if
tree-level multi-jet merging (i.e.
CKKW-L or
UMEPS merging) is attempted.
If tree-level multi-jet merging is performed, all histograms should be
filled with this weight, as discussed in
CKKW-L Merging and
UMEPS Merging.
double Info::mergingWeightNLO()
combined NLO merging weight assigned to the current event, if
NLO multi-jet merging (i.e.
NL3 or
UNLOPS merging) is attempted.
If NLO multi-jet merging is performed, all histograms should be filled
with this weight, as discussed in
NLO Merging.
Multiparton interactions
As already noted, these methods do not make sense for diffractive
topologies, and should not be used there. Partly this is physics,
but mainly it is for technical reasons, e.g. that double diffraction
involves two separate systems that would have to be bookkept as such.
double Info::a0MPI()
The value of a0 when an x-dependent matter profile is used,
MultipartonInteractions:bProfile = 4.
double Info::bMPI()
The impact parameter b assumed for the current collision when
multiparton interactions are simulated. Is not expressed in any physical
size (like fm), but only rescaled so that the average should be unity
for minimum-bias events (meaning less than that for events with hard
processes).
double Info::enhanceMPI()
The choice of impact parameter implies an enhancement or depletion of
the rate of subsequent interactions, as given by this number. Again
the average is normalized to be unity for minimum-bias events (meaning
more than that for events with hard processes).
double Info::enhanceMPIavg()
The average enhancement factor expected for hard processes in those
cases where it can be calculated already at initialization, i.e. excluding
the x-dependent b profile.
int Info::nMPI()
The number of hard interactions in the current event. Is 0 for elastic
and diffractive events, and else at least 1, with more possible from
multiparton interactions.
int Info::codeMPI(int i)
double Info::pTMPI(int i)
the process code and transverse momentum of the i'th
subprocess, with i in the range from 0 to
nMPI() - 1. The values for subprocess 0 is redundant with
information already provided above.
int Info::iAMPI(int i)
int Info::iBMPI(int i)
are normally zero. However, if the i'th subprocess is
a rescattering, i.e. either or both incoming partons come from the
outgoing state of previous scatterings, they give the position in the
event record of the outgoing-state parton that rescatters.
iAMPI and iBMPI then denote partons coming from
the first or second beam, respectively.
double Info::eMPI(int i)
The enhancement or depletion of the rate of the i'th
subprocess. Is primarily of interest for the
MultipartonInteractions:bProfile = 4 option, where the
size of the proton depends on the x values of the colliding
partons. Note that eMPI(0) = enhanceMPI().
double Info::bMPIold()
double Info::enhanceMPIold()
double Info::enhanceMPIoldavg()
These methods are only relevant for hard diffraction with the requirement
of no MPI in the hadron-hadron collision. Then an impact parameter
and associated enhancement factor is picked for this collision, but
afterwards overwritten when the Pomeron-hadron subcollision is considered.
In such cases the old hadron-hadron values can be found here, while
bMPI, enhanceMPI and enhanceMPIavg
provide the new Pomeron-hadron ones.
Cross sections
Here are the currently available methods related to the event sample
as a whole, for the default value i = 0, and otherwise for
the specific process code provided as argument. This is the number
obtained with Info::code(), while the further subdivision
given by Info::codeSub() is not bookkept. While continuously
updated during the run, it is recommended only to study these properties
at the end of the event generation, when the full statistics is available.
The individual process results are not available if
a second hard process has been
chosen, but can be gleaned from the pythia.stat() output.
vector<int> Info::codesHard()
returns a vector with all the process codes set up for the current run,
i.e. the valid nonzero arguments for the five methods below.
string Info::nameProc(int i = 0)
returns the process name for process code i.
long Info::nTried(int i = 0)
long Info::nSelected(int i = 0)
long Info::nAccepted(int i = 0)
the total number of tried phase-space points, selected hard processes
and finally accepted events, summed over all allowed processes
(i = 0) or for the given process.
The first number is only intended for a study of the phase-space selection
efficiency. The last two numbers usually only disagree if the user introduces
some veto during the event-generation process; then the former is the number
of acceptable events found by PYTHIA and the latter the number that also
were approved by the user. If you set a
second hard process there may also be a mismatch.
double Info::sigmaGen(int i = 0)
double Info::sigmaErr(int i = 0)
the estimated cross section and its estimated error,
summed over all allowed processes (i = 0) or for the given
process, in units of mb. The numbers refer to the accepted event sample
above, i.e. after any user veto.
Loop counters
Mainly for internal/debug purposes, a number of loop counters from
various parts of the program are stored in the Info class,
so that one can keep track of how the event generation is progressing.
This may be especially useful in the context of the
User Hooks facility.
int Info::getCounter(int i)
the method that gives you access to the value of the various loop
counters.
argument i : the counter number you want to access:
argumentoption 0 - 9 : counters that refer to the run as a whole,
i.e. are set 0 at the beginning of the run and then only can increase.
argumentoption 0 : the number of successful constructor calls for the
Pythia class (can only be 0 or 1).
argumentoption 1 : the number of times a Pythia::init()
call has been begun.
argumentoption 2 : the number of times a Pythia::init()
call has been completed successfully.
argumentoption 3 : the number of times a Pythia::next()
call has been begun.
argumentoption 4 : the number of times a Pythia::next()
call has been completed successfully.
argumentoption 10 - 19 : counters that refer to each individual event,
and are reset and updated in the top-level Pythia::next()
method.
argumentoption 10 : the number of times the selection of a new hard
process has been begun. Normally this should only happen once, unless a
user veto is set to abort the current process and try a new one.
argumentoption 11 : the number of times the selection of a new hard
process has been completed successfully.
argumentoption 12 : as 11, but additionally the process should
survive any user veto and go on to the parton- and hadron-level stages.
argumentoption 13 : as 11, but additionally the process should
survive the parton- and hadron-level stage and any user cuts.
argumentoption 14 : the number of times the loop over parton- and
hadron-level processing has begun for a hard process. Is reset each
time counter 12 above is reached.
argumentoption 15 : the number of times the above loop has successfully
completed the parton-level step.
argumentoption 16 : the number of times the above loop has successfully
completed the checks and user vetoes after the parton-level step.
argumentoption 17 : the number of times the above loop has successfully
completed the hadron-level step.
argumentoption 18 : the number of times the above loop has successfully
completed the checks and user vetoes after the hadron-level step.
argumentoption 20 - 39 : counters that refer to a local part of the
individual event, and are reset at the beginning of this part.
argumentoption 20 : the current system being processed in
PartonLevel::next(). Is almost always 1, but for double
diffraction the two diffractive systems are 1 and 2, respectively.
argumentoption 21 : the number of times the processing of the
current system (see above) has begun.
argumentoption 22 : the number of times a step has begun in the
combined MPI/ISR/FSR evolution downwards in pT
for the current system.
argumentoption 23 : the number of times MPI has been selected for the
downwards step above.
argumentoption 24 : the number of times ISR has been selected for the
downwards step above.
argumentoption 25 : the number of times FSR has been selected for the
downwards step above.
argumentoption 26 : the number of times MPI has been accepted as the
downwards step above, after the vetoes.
argumentoption 27 : the number of times ISR has been accepted as the
downwards step above, after the vetoes.
argumentoption 28 : the number of times FSR has been accepted as the
downwards step above, after the vetoes.
argumentoption 29 : the number of times a step has begun in the
separate (optional) FSR evolution downwards in pT
for the current system.
argumentoption 30 : the number of times FSR has been selected for the
downwards step above.
argumentoption 31 : the number of times FSR has been accepted as the
downwards step above, after the vetoes.
argumentoption 40 - 49 : counters that are unused (currently), and
that therefore are free to use, with the help of the two methods below.
void Info::setCounter(int i, int value = 0)
set the above counters to a given value. Only to be used by you
for the unassigned counters 40 - 49.
argument i : the counter number, see above.
argument value (default = 0) : set the counter to this number;
normally the default value is what you want.
void Info::addCounter(int i, int value = 0)
increase the above counters by a given amount. Only to be used by you
for the unassigned counters 40 - 49.
argument i : the counter number, see above.
argument value (default = 1) : increase the counter by this amount;
normally the default value is what you want.
Parton shower history
The following methods are mainly intended for internal use,
e.g. for matrix-element matching.
void Info::hasHistory(bool hasHistoryIn)
bool Info::hasHistory()
set/get knowledge whether the likely shower history of an event
has been traced.
void Info::zNowISR(bool zNowIn)
double Info::zNowISR()
set/get value of z in latest ISR branching.
void Info::pT2NowISR(bool pT2NowIn)
double Info::pT2NowISR()
set/get value of pT^2 in latest ISR branching.
Les Houches Event File 3.0 information
Les Houches Event files can conform to version 1.0 and version 3.0
of the standard (version 2.0 having been extended to 3.0). The LHEF version
of an input file can can be accessed by
int Info::LHEFversion()
The Info class also provides a suitable interface to
the information stored after reading Les Houches Event files in the
updated format [But14]. An example main program using LHEF 3.0
information is main38.cc.
LHEF 3.0 offers new features both in the initialisation and the event sections
of the input files. Possible information include extended
use of XML tags in the <header> and
<init> blocks. The LHEF 3.0 information is stored
in a series struct's:
-- The <initrwgt> tag is a container
tag for weight and weightgroup tags. This information is stored
internally in LHAinitrwgt.
Currently, there is no dedicated
output for this tag. However, all the information stored in the tag can
be retrieved by using the Info class member pointer
LHAinitrwgt Info::initrwgt.
-- Multiple <weightgroup> tags:
Container tag for weight tags. Currently, there is no dedicated
output for this tag. However, all the information stored in the tag can
be retrieved by using the Info class member pointer
vector<LHAweightgroups> * Info::weightgroups.
-- Multiple <weight> tags: Tag defining
auxiliary information on an event weight, e.g. the identifier and information
on what the weight represents. All the information stored in the tag can
be retrieved by using the Info class member pointer
vector<LHAweightgroups> * Info::init_weights. This vector
contains all <weight> tags in the
<initrwgt> container and its subcontainer
<weightgroup> tags. The size of the vector can be accessed
through the method
int Info::getInitrwgtSize()
-- Multiple <generator> tags: Store
information on the generators used in the event generation. All the
information stored in the tag can be retrieved by using the
Info class member pointer
vector<LHAgenerators> * Info::generators. More easy-to-use
output functions are available. The size of this vector can be obtained from
int Info::getGeneratorSize()
The complete header can be obtained with the Info class
member string getHeaderBlock().
The contents of a <generator> tag can be accessed through
the method
string Info::getGeneratorValue(unsigned int n = 0)
Return the contents of the n'th <generator> tag in
the vector of tags.
Attributes of the <generator> tag (e.g. the generator
name and version) can be accessed via
string Info::getGeneratorAttribute(unsigned int n, string key, bool doRemoveWhitespace = false)
Return the value of the generator attribute named key for
the n'th generator in the vector. Setting doRemoveWhitespace to
true will return the value, stripped of any whitespace. An empty string is
returned if the attribute named key does not exist.
To obtain information on cross sections, the following two methods can be
used
int Info::nProcessesLHEF()
return the number of processes for which the cross section is stored.
double Info::sigmaLHEF(int iProcess)
return the cross section of the iProcess'th process.
Possible information also includes extended use of XML tags in the
<event> blocks:
-- The <rwgt> tag is a container
tag for wgt tags. Currently, there is no dedicated
output for this tag. It can however be retrieved by using the
Info class member pointer
LHArwgt Info::rwgt.
-- Multiple <wgt> tags: Tag defining
the event weight in the detailed version of LHEF 3.0. All the information
stored in the tag can be retrieved by using the Info class
member pointer vector<LHAwgt> * Info::weights_detailed.
More easy-to-use output functions are available. The size of this vector
can be obtained from
unsigned int Info::getWeightsDetailedSize()
A convenient access point to the information stored in the
<wgt> tags is the Info class member
vector<double> Info::weights_detailed_vector. The
entries of this vector are ordered according to how <wgt>
tags appear in the event block.
The contents of a <wgt> tag can be accessed through the
method
double Info::getWeightsDetailedValue(string n)
Return the value of the n'th <wgt> tag in the
event.
Attributes of the <wgt> tag (e.g. the weight
id) can be accessed via
string Info::getWeightsDetailedAttribute(string n, string key, bool doRemoveWhitespace = false)
Return the value of the wgt attribute named key for
the n'th wgt in the vector. Setting doRemoveWhitespace to
true will return the value, stripped of any whitespace. An empty string is
returned if the attribute named key does not exist.
-- The <weights> tag: Tag containing
a vector of double entries for weights in the compressed version
of LHEF 3.0. All the information stored in the tag can be retrieved by using
the Info class member pointer LHAweights *
Info::weights and the vector vector<double>
Info::weights_compressed. More easy-to-use output functions are
available. The size of this vector can be obtained from
unsigned int Info::getWeightsCompressedSize()
The n'th weight can be accessed through the method
double Info::getWeightsCompressedValue(unsigned int n)
Attributes of the <weights> tag (not normally used) can be
accessed via
string Info::getWeightsCompressedAttribute(string key, bool doRemoveWhitespace = false)
Return the value of the <weights> tag's attribute
named key. Setting doRemoveWhitespace to
true will return the value, stripped of any whitespace. An empty string is
returned if the attribute named key does not exist.
-- The <scales> tag: Contains information
on different scales used by the matrix element generator. All the information
stored in the tag can be retrieved by using the Info class
member pointer LHAweights * Info::scales. More easy-to-use
output functions are available. The contents of the scales tag can be
obtained from
string Info::getScalesValue()
However, note that the actual scale values are stored as attributes (called
e.g. muf or mur). Attributes of the
<scales> tag can be accessed via
double Info::getScalesAttribute(string key)
Return the value of the <scales> tag's attribute
named key. Not-a-number will be returned if the attribute
named key does not exist.
Finally, arbitrary attributes of the <event> tag are
supported. Attributes of the <event> tag can be accessed by
string Info::getEventAttribute(string key, bool doRemoveWhitespace = false)
return the value of the event attribute named key. Setting
doRemoveWhitespace to true will return the value, stripped of
any whitespace. An empty string is returned if the attribute named
key does not exist.
Additional comments appearing in the <event> tag
can be obtained with the Info class member
string getEventComments().
Header information
A simple string key/value store, mainly intended for accessing
information that is stored in the header block of Les Houches Event
(LHE) files. In principle, any LHAup derived class can set
this header information, which can then be read out later. Although the
naming convention is arbitrary, in practice, it is dictated by the
XML-like format of LHE files, see
Les Houches Accord for more details.
string Info::header(string key)
return the header named key
vector <string> Info::headerKeys()
return a vector of all header key names
void Info::setHeader(string key, string val)
set the header named key with the contents of val