User:Sophie/CE

Channel Description

CE stands for Conversion Electron. This is the primary signal we are searching for at Mu2e. Therefore, ensuring an accurate generator is crucial to us understanding what our signal could look like in our detectors.

Literature

• R. Szafron: https://inspirehep.net/files/ca391cf43844ae4f84155c354c510260 describes the leading log corrected spectrum we use in Mu2e/Offline and Production.

Generator

Conversion electrons can be generated in two ways:

• as endpoints (CeEndpoint) assuming a coherent mono-energetic electron emitted at 104.97 MeV/c
• including leading log (CeMLeadingLog) radiative corrections (see literature).

In the latter case 10 % of the electrons are in a low momentum tail shifted away from the endpoint.

In the figure below we see the generated spectra for the two cases on a log scale:

Functional Forms

The CeEndpoint is a simple delta function at the 104.97 MeV/c endpoint for coherent conversion in an aluminum nucleus.

The endpoint energy is calculated as follows:

with muon mass of 105.66 MeV/c^2 and E_{BE,1s} is the binding energy of the 1s state, and E_{recoil} denotes the nuclear recoil energy.

The generator used to create endpoints is: Offline/EventGenerator/src/CeEndpoint_module.cc. Locations of standard .fcl files are detailed below.

The leading log corrections are derived in the literature noted above:

.

where most of the terms have their usual meaning and E_{max} is the conversion energy and W (E_e) is the non-universal part of the correction.

The generator used to make leading log is: Offline/EventGenerator/src/LeadingLog_module.cc. Locations of standard .fcl files are detailed below.

Generating

Both CeEndpoints and CeMLeadingLog primaries can be made in the same way we generate any other primary process. We utilize the set of muons stopped in target and resample these for a given number of generated conversion electrons.

The .fcl files to produce both are stored in Mu2e/Production/JobConfig.

Jobs can be configured by a user using the gen_Primary.sh stored in Mu2e/Production/Scripts. All the user needs to do is specify the chosen primary e.g.

 gen_Primary.sh --primary CeEndpoint --campaign MDC2020 --pver ah --sver p --type Muminus --njobs 1000 --events 4000

This will generate a total of 4e6 ce endpoints. These can then be mixed with pile-up (using the standard mixing campaign) or digitized and reconstructed using the standard campaigns to produce pure reconstructed conversions.

Contacts

• Current generators written by: Andrei Gaponenko, Sophie Middleton
• Production: Yuri Oksuzian