What is QCDLoop?

QCDLoop is a library of one-loop scalar Feynman integrals, evaluated close to four dimensions. First documented in arXiv:0712.1851 and recently in arXiv:1605.03181.

Which integrals QCDLoop compute?

One-loop integrals for tadpole, bubble, triangle and box topologies. For integrals with all massive internal lines the integrals are all known, both analytically and numerically. Therefore we concentrate on integrals with some internal masses vanishing; in general, these integrals contain infra-red and collinear singularities which are here regulated dimensionally.

The general divergent box integral can be calculated using one of sixteen basis integrals which are given here. The general divergent triangle integral can be calculated using one of six triangle basis integrals which are also given here.

What is new in QCDLoop 2.x?

We have redesigned the code in c++, extended the formalism to complex masses, provided a simple mechanim to switch from double to quadruple precision, boosted speed and finally implemented LRU caching algorithms.

Quick startup:

The installation is simple as typing:

./configure && make -j && sudo make install

And calling the library in c++:

double mu2 = 2.0;
std::vector< complex > result(3);
std::vector< double > m = {5.0, 3.0, 1.0};
std::vector< double > p = {2.0, 1.0, 6.0};		  
ql::QCDLoop< complex, double, double > qcdloop;
qcdloop.integral(result,mu2,m,p);

Full instructions are available in the Download section. Doxygen documentation is available here.