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# MCgrid: Interpolation tools for NLO event generators

## Examples

You can download a tarball containing the following examples in the Downloads section. The examples tarballs are named MCgridYExamples-X.X.X, where Y is the major MCgrid version and X.X.X specifies the Rivet version they are compatible with. You can check what Rivet version you are using with rivet-config --version. Note that only for Rivet v.2.2.0 or more recent the examples include fastNLO setups. But they can easily be adapted for earlier versions.

MCgrid is independent of the Monte Carlo event generator, as long as the generator can generate output in the .hepmc format (see HepMC). We provide Sherpa configuration files for generating your own .hepmc files, but it is easy to adapt the examples to other generators.

Unpack the tarball using tar -xzf examples.tar.gz and change into the unpacked directory (cd examples). When MCgrid and its dependencies are installed, you can use the provided Makefile to compile and install the included analyses: make plugin && make install.

With make test you can compile a simple test program to convolute APPLgrids you have produced with the examples below. You can use ./applgrid-test path/to/grid.root to generate a histogram with scale variations. If you run into an exception here, make sure that APPLgrid has been configured to link against Hoppet. You can also try applgrid2yoda, which is a bit more convenient. For convoluting fastNLO tables, you can use their in-house fnlo-tk-yodaout binary.

For more detailed instructions on how to make and use the examples, have a look into the included README file.

### Basic

In the templates folder you will find MCGRID_BASIC.cc, which is an empty Rivet analysis demonstrating the minimal modifications required to enable MCgrid. You can use it as a cheat sheet when you modify an analysis yourself.

### CDF $Z$ rapidity

This example provides the modified Rivet analysis CDF_2009_S8383952. It projects out the $Z$ rapidity in Drell-Yan production with a Tevatron-like beam setup.

This analysis comes with a Sherpa Runcard that included the modified CDF_2009_S8383952 analysis. If you have Sherpa in your path, run it using

cd CDF_2009_S8383952
make plugin-...
make install
[make install-applgrid]
Sherpa -f Run.dat
Sherpa -f Run.dat


This will generate an APPLgrid/fastNLO table in ./mcgrid.

### ATLAS $Z$ $p_T$

This one is very similar to the CDF $Z$ rapidity example. It is based on the Rivet analysis ATLAS_2011_S9131140. Besides generating a grid for the $Z$ $p_T$ distribution, it makes another one for the total cross section.

### CMS Inclusive Jets

This example is a modification of a CMS inclusive jet analysis CMS_2011_S9086218. It is intended as a demonstration of the MCGrid::BinnedGrid class, which complements the BinnedHistogram of Rivet.