maddump

MadDump thick targets

Asked by Suchita

Dear MadGraph team,

I wish to know whether one can account for the thickness of target with MadDump settings. I see that in the settings one can provide the x, y co-ordinates of the detector, the distance between target and detector and something called depth of the detector.

Thus, it is not clear to me whether the depth of the detector is the same as a the depth of the target or it is really the depth of the detector itself? Thus, is the detector is placed at a distance Ldet from target and the depth of the detector itself is Lz, is the total active volume

(Ldet + Lz ) \times x_det \times y_det ?

In this case, the thickness of the target is not accounted for. Can one account for the thickness of the target in MadDump via the settings, if so how?

best,
Suchita.

Question information

Language:
English Edit question
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maddump Edit question
Assignee:
Luca Edit question
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Luca (lbuono) said : 		#1

Dear Suchita,

MadDump relies on the assumption that the primary interactions occur at a localised point.
The size of the target should be indeed very small compared to the distance between the
target and the detector in the characteristic searches the tool was designed for.
Therefore, the finite size of the target (which for the scopes of our tools means
that the interaction point can be displaced) should represent a second--order effect,
that is neglected in MadDump.
The parameter "depth" represents really just the detector dimension along the
original beam-axis of the beam-dump, while x and y are its dimensions in the transverse
plane (if the parallelepiped shape is selected).
The active volume is given by
depth*x*y
for this configuration. The distance between the target and the detector does not affect the active volume,
as it is interpreted as the (macroscopically) distance travelled by the particles produced at the primary interaction point
before reaching the detector surface.

Best,
Luca

Revision history for this message
Suchita (suchita-kulkarni) said : 		#2

Thanks Luca, this clarifies it.

I asked this question for two reasons:

1) In the MadDump write up there is some discussion about depth of the target and hence I wanted to confirm that the depth in the MadDump settings does not refer to this.

2) More importantly, for long lived/displaced decays, one need to account for the probability that the BSM particle produced has not decayed inside the target if I understand fixed target experiments correctly. However, as I understand from your message I will have to manually reject such events. Which can of course be done. Such rejection will be relevant for small lifetimes.

I have one additional question, I was yesterday trying to generate fig. 2 from https://arxiv.org/pdf/0906.0580.pdf. This is an electron beam on target which produces A' and A' decays visibly. MadDump settings won't allow me to generate such a process. In this case, there is no interaction e.g. via DIS or electron, it's just an A' decay which is detected e.g. via spectrometer/calorimeter. Is there a way to generate e.g.

ep > epA', A' > mu+ mu-

in MadDump?

As an alternative I could try to simulate it in MadGraph and then put acceptance cuts with proper normalisation, however it will be nice to have a common setup for all kinds of decays hence this question.

I thank you again for the prompt reply.

Can you help with this problem?

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