Calculate section

The Calculate section of HEPMDB is accessible only if you are registered. This wiki page will enable you to use the HEPMDB computation frame in order to produce events and 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 will find:

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

Most of the menu commands are straight forward, although a selection have been explained in more detail here.

• 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 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 make sure you have downloaded any results you need to keep before doing this.
• 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 most recent commands. The result of any command will be displayed here, except the computations themselves.

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

The left menu

This is one of the most important menus in 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 subtle differences for MadGraph.

The main part

When the computation is done, the results will be displayed here. In case of an error, the debugging information is also displayed here.

Using CalcHEP

Here, we will review the basic steps for a CalcHEP computation.

You can find a complete tutorial specifically for CalcHEP HERE.

Choosing a model

When using CalcHEP, you first thing you have to do is make sure that the model you wish to use is imported. If it is imported, you will see it in the left panel. If it is not there, click on the Import model option of the CalcHEP drop-down menu. You can import any model uploaded to HEPMDB including any you have uploaded previously.

When your model is imported (when you can see it in the left panel) choose it by selecting it. You are now ready to work with that model.

The batch file

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

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

1. Load batch template: this is a very useful option which loads the template file. The template file contains every possible option as well as some commented out sections which describe various parts of the batch file. Simply change the variables/values so that it calculates what you require and save it.
2. Load from: this allows the user to load the batch file from a file.
3. Save: this does not save to a file! Instead, it tells HEPMDB to use the written batch file for computation.
4. Save As: this only saves to a file. You 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 the 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. Previous results can been found using the history option from the CalcHEP or Menu drop down.

If the job time set by the user is under 2 hours, the calculation will be given priority on HEPMDB.

Using WHIZARD

This only covers 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 import a model and choose it. Note that the WHIZARD models available to use are a lot less numerous than those on CalcHEP. Please upload your own models if you need to. You can import the model via the Import model button then select it in the list 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 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 option. Then, change the variables/values to suit your calculation.
2. Load from: this enable you to load a batch file from a file.
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 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 then have the choice between queuing or not. It is recommended that you choose to queue the calculation, especially for long computation as that allows you to close your internet browser while it is running.

If the job time set by the user is under 2 hours, the calculation will be given priority on HEPMDB.

Using MadGraph

MadGraph works slightly differently. Once again, more comprehensive help should be available soon. If the help you require is not available here, please 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 defines the processes to be processed.
2. param_card.dat: This holds the 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 define the parameters for the run, for example the energy of the beam or which pdf to use.
4. plot_card.dat: With MadGraph it is possible to automatically produce some plots. But with the HEPMDB toolkit and lhe file, this is of little use.

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

Running

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

If the job time set by the user is under 2 hours, the calculation will be given priority on HEPMDB.