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// -*- C++ -*-
//
// SimpleAlphaEM.cc is a part of ThePEG - Toolkit for HEP Event Generation
// Copyright (C) 1999-2011 Leif Lonnblad
//
// ThePEG is licenced under version 2 of the GPL, see COPYING for details.
// Please respect the MCnet academic guidelines, see GUIDELINES for details.
//
//
// This is the implementation of the non-inlined, non-templated member
// functions of the SimpleAlphaEM class.
//
#include "SimpleAlphaEM.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/StandardModel/StandardModelBase.h"
using namespace ThePEG;
IBPtr SimpleAlphaEM::clone() const {
return new_ptr(*this);
}
IBPtr SimpleAlphaEM::fullclone() const {
return new_ptr(*this);
}
double SimpleAlphaEM::value(Energy2 scale, const StandardModelBase & sm) const {
useMe();
double alem = sm.alphaEM();
double alem3pi = alem/(3.0*Constants::pi);
double rpigg;
double Q2 = scaleFactor()*scale/GeV2;
if(Q2<=2e-6)
rpigg=0.;
else if ( Q2 < 0.09 )
rpigg = alem3pi*(13.4916 + log(Q2)) + 0.00835*log(1.0 + Q2);
else if ( Q2 < 9.0 )
rpigg=alem3pi*(16.3200 + 2.0*log(Q2)) + 0.00238*log(1.0 + 3.927*Q2);
else if ( Q2 < 10000.0 )
rpigg=alem3pi*(13.4955 + 3.0*log(Q2)) + 0.00165 + 0.00299*log(1.0 + Q2);
else
rpigg=alem3pi*(13.4955 + 3.0*log(Q2)) + 0.00221 + 0.00293*log(1.0 + Q2);
return alem/(1.0-rpigg);
}
NoPIOClassDescription<SimpleAlphaEM> SimpleAlphaEM::initSimpleAlphaEM;
void SimpleAlphaEM::Init() {
static ClassDocumentation<SimpleAlphaEM> interfaceDocumentation
("This class implements a running \\f$\\alpha_{\\mbox{EM}}\\f$ according "
"to Buckhardt et al.",
"In the running of $\\alpha_{EM}$, the parametrization of "
"H.~Buckhardt et al. was used. See \\cite{KLEISSCERN9808v3pp129}.",
"\\bibitem{KLEISSCERN9808v3pp129} R.~Kleiss et al, "
"CERN 89-08, vol.~3, pp 129-131.");
}
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