Calculate section

The Calculate section of HEPMDB is accessible only if you're registered. Thanks to this section, you'll be able to use HEPMDB computation frame in order to produce events, compute cross-sections using the various models on the website.

The interface

The interface is divided in four parts:

1. the upper bar, with general menus,
2. the lower frame, with general information on the last operations,
3. the left menu, with the main functions and the program list,
4. the main part, presenting results of computation.

The upper menu

In the upper menu, you'll find:

• A help button,
• The Go to HEPMDB button which brings you back to HEPMDB main page,
• The actual menu.

Most of the menu commands are straight forward. A few precisions might still be needed.

• Remove models: it removes all models that were imported. When a model has been updated, it is necessary to remove the old version this way. There is still no option to remove models individually.
• Reset model list and clear results: This will reset everything to its default state. No results will be kept. You should download them before.
• Show queue on HPCx: as HEPMDB is a shared resource, when you asked for a job, it is put in the queue. This button displays the whole queue.

The lower frame

The lower frame displays information about the last commands. Except for computations, the result of any command will be displayed here.

When something has been queued though, it is necesseray to refresh the display explicitly (through Check submitted jobs button.

The left menu

It might be the most important menu on HEPMDB. The menu is divided in three panels. Each panel correspond to a specific program for computing matrix-elements. CalcHEP and WHIZARD work essentially the same way. There are some subtilities for MadGraph.

The main part

Finally, when the computation is done, it will be displayed here. In case of error, the whole debugging information is displayed there to.

Using CalcHEP

Here, we'll review basic steps with CalcHEP computation. You'll find a complete tutorial specifically for CalcHEP here.

Choosing a model

When using CalcHEP, you first have to choose a model. You can access any model uploaded on HEPMDB but even if your model is uploaded, you'll have to import it through the Import model option of the CalcHEP menu on the left panel.

When your model is imported, or if it is already, select it in the list below. You're now ready to work with it.

The batch file

On HEPMDB, you'll use the batch mode of CalcHEP. The batch file can be edited through the Edit full batch file option.

Besides writing the batch, you'll have four options in the editing window:

1. Load batch template: this is a very useful option loading a template file that contains every possible options. Then, you just have to comment out some lines and change some values.
2. Load from: this is really a load from file button.
3. Save: this does not save to a file! But it tells HEPMDB to use the written batch file for computation.
4. Save As: this only saves to a file. You'll still have to use the Save button to tell HEPMDB to use the batch file.

Running

When your batch file is ready, you can queue the process thanks to the Run Full Batch File button. You can check the status of queued process via Check submitted job. When the computation is done, results will be displayed in the central panel. If not, use the Check submitted job button.

Using WHIZARD

Once again, this is really basic help. More comprehensive help is to come.

Choosing a model

On HEPMDB, WHIZARD usage is very similar to CalcHEP's. You first have to choose a model and import it. Note that WHIZARD are a lot less numerous. But feel free to upload your own models. You can import the model via the Import model button and when it's done, select it in the list below in order to use it.

The batch file

The batch file can be edited through the Edit batch file option.

Besides writing the batch, you'll have four options in the editing window:

1. Load batch template: this is a very useful option loading a template file that contains every possible options. Then, you just have to comment out some lines and change some values.
2. Load from: this is really a load from file button.
3. Save: this does not save to a file! But it tells HEPMDB to use the written batch file for computation.
4. Save As: this only saves to a file. You'll still have to use the Save button to tell HEPMDB to use the batch file.

Running

Push the Run Whizard option to run WHIZARD. You'll have the choice between queuing or not. It is recommanded to choose queuing espacially for long computation as you won't have to keep your internet browser open.

Using MadGraph

MadGraph works a bit differently. Once again, more comprehensive should be available soon. Don't hesitate and search for MadGraph specific help on the internet.

MadGraph cards

MadGraph works with cards. There are four different cards each having a particular role:

1. proc_card_mg5.dat: this will define the processes to be processed.
2. param_card.dat: here are gathered parameters about the model (decays, branching ratios). Note that this file is overwritten by MadGraph after event generation.
3. run_card.dat: in this file, you'll define parameters for the run, like energy of the beam or what pdf to use.
4. plot_card.dat: With MadGraph it is possible to automatically produce some plots. But with HEPMDB toolkit and lhe file, this is of little use.

For all of these files, templates are available, so you don't have to know every parameters. Filling these files and checking the different parameters should be enough in most cases.

Running

For running, just use Run Madgraph button. For now, there is no queuing system for MadGraph so you must stay connected to HEPMDB website while computing.