The Mu2e experiment — Searching for charged lepton flavor violation

Hedges, Michael Thomas

doi:10.1016/j.nima.2022.167589

Title: The Mu2e experiment — Searching for charged lepton flavor violation

Abstract

The Mu2e experiment will search for a Standard Model violating rate of neutrinoless conversion of a muon into an electron in the presence of an aluminum nucleus. Observation of this charged lepton flavor violating process would be an unambiguous sign of new physics. Mu2e will improve upon previous searches for this process by four orders of magnitude. This requires the world’s highest-intensity muon beam, a detector system capable of efficiently reconstructing the 105 MeV/c conversion electron signal, and minimizing sensitivity to background events. A pulsed 8 GeV proton beam strikes a target, producing pions that decay into muons. Beam outside the pulse must be suppressed to $< 1 0^{- 10}$ to reduce beam-related backgrounds. The muon beam is guided from the production target along the transport system and onto the aluminum stopping target. Conversion electrons leave the stopping target and propagate inside a solenoidal magnetic field to the tracker and electromagnetic calorimeter. The tracker is a system of straw tube panels filled with Ar/CO $_{2}$ at 1 atm that tracks particles inside of a solenoidal B-field and measures their momenta with $~ 100$ keV/c resolution to resolve signal events from decay-in-orbit backgrounds. The CsI calorimeter provides $E / p$ and is used to seed the track reconstruction algorithm with $σ_{E} / E ~ 10 %$ and $σ_{t} < 500 ps$ . Additionally, a novel cosmic ray veto with greater than 99.99% efficiency brings the expected number of background events to fewer than one over three years of running. Finally, to normalize the experiment, the stopping target monitor measures the rate of capture photons from muons incident on the stopping target by using a system of high-purity germanium and lanthanum bromide scintillators.

Authors:

^[1]

Purdue Univ., West Lafayette, IN (United States); Mu2e Collaboration et al.

Publication Date:: Fri Oct 14 00:00:00 EDT 2022

Research Org.:: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)

Sponsoring Org.:: USDOE Office of Science (SC), High Energy Physics (HEP); European Union (EU)

Contributing Org.:: Mu2e Collaboration

OSTI Identifier:: 1897098

Report Number(s):: FERMILAB-CONF-22-788-V; arXiv:2210.14317
Journal ID: ISSN 0168-9002; oai:inspirehep.net:2170187; TRN: US2310758

Grant/Contract Number:: AC02-07CH11359; 734303; 822185; 858199; 101003460; 101006726

Resource Type:: Accepted Manuscript

Journal Name:: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment

Additional Journal Information:: Journal Volume: 1045; Journal ID: ISSN 0168-9002

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; Muon conversion clfv

Citation Formats


                    Hedges, Michael Thomas. The Mu2e experiment — Searching for charged lepton flavor violation.  United States: N. p., 2022. 
Web.  doi:10.1016/j.nima.2022.167589.

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                    Hedges, Michael Thomas. The Mu2e experiment — Searching for charged lepton flavor violation.  United States.  https://doi.org/10.1016/j.nima.2022.167589

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                    Hedges, Michael Thomas. Fri .  
"The Mu2e experiment — Searching for charged lepton flavor violation".  United States.  https://doi.org/10.1016/j.nima.2022.167589.  https://www.osti.gov/servlets/purl/1897098.

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@article{osti_1897098,

  title        = {The Mu2e experiment — Searching for charged lepton flavor violation},

  author       = {Hedges, Michael Thomas},

  abstractNote = {The Mu2e experiment will search for a Standard Model violating rate of neutrinoless conversion of a muon into an electron in the presence of an aluminum nucleus. Observation of this charged lepton flavor violating process would be an unambiguous sign of new physics. Mu2e will improve upon previous searches for this process by four orders of magnitude. This requires the world’s highest-intensity muon beam, a detector system capable of efficiently reconstructing the 105 MeV/c conversion electron signal, and minimizing sensitivity to background events. A pulsed 8 GeV proton beam strikes a target, producing pions that decay into muons. Beam outside the pulse must be suppressed to <10–10 to reduce beam-related backgrounds. The muon beam is guided from the production target along the transport system and onto the aluminum stopping target. Conversion electrons leave the stopping target and propagate inside a solenoidal magnetic field to the tracker and electromagnetic calorimeter. The tracker is a system of straw tube panels filled with Ar/CO2 at 1 atm that tracks particles inside of a solenoidal B-field and measures their momenta with ~100 keV/c resolution to resolve signal events from decay-in-orbit backgrounds. The CsI calorimeter provides E/p and is used to seed the track reconstruction algorithm with σE/E~10% and σt<500ps. Additionally, a novel cosmic ray veto with greater than 99.99% efficiency brings the expected number of background events to fewer than one over three years of running. Finally, to normalize the experiment, the stopping target monitor measures the rate of capture photons from muons incident on the stopping target by using a system of high-purity germanium and lanthanum bromide scintillators.},

  doi          = {10.1016/j.nima.2022.167589},

  journal      = {Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment},

  number       = ,

  volume       = 1045,

  place        = {United States},

  year         = {Fri Oct 14 00:00:00 EDT 2022},

  month        = {Fri Oct 14 00:00:00 EDT 2022}

}

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Journal Article:

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Accepted Manuscript (DOE)

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https://doi.org/10.1016/j.nima.2022.167589

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