skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Spin-dependent μ → e conversion

Abstract

The experimental sensitivity to μ→e conversion on nuclei is expected to improve by four orders of magnitude in coming years. Here, we consider the impact of μ→e flavour-changing tensor and axial-vector four-fermion operators which couple to the spin of nucleons. Such operators, which have not previously been considered, contribute to μ→e conversion in three ways: in nuclei with spin they mediate a spin-dependent transition; in all nuclei they contribute to the coherent (A 2-enhanced) spin-independent conversion via finite recoil effects and via loop mixing with dipole, scalar, and vector operators. Furthermore, we estimate the spin-dependent rate in Aluminium (the target of the upcoming COMET and Mu2e experiments), show that the loop effects give the greatest sensitivity to tensor and axial-vector operators involving first-generation quarks, and discuss the complementarity of the spin-dependent and independent contributions to μ→e conversion.

Authors:
 [1];  [2]; ORCiD logo [3]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Centre National de la Recherche Scientifique (CNRS)/IN2P3 Computing Center (IN2P3), Villeurbonne (France). Inst. of Nuclear Physics of Lyon (IPNL)
  3. Osaka Univ. (Japan). Dept. of Physics
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC). Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1360714
Report Number(s):
LA-UR-17-21718
Journal ID: ISSN 0370-2693
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 771; Journal Issue: C; Journal ID: ISSN 0370-2693
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Atomic and Nuclear Physics

Citation Formats

Cirigliano, Vincenzo, Davidson, Sacha, and Kuno, Yoshitaka. Spin-dependent μ → e conversion. United States: N. p., 2017. Web. doi:10.1016/j.physletb.2017.05.053.
Cirigliano, Vincenzo, Davidson, Sacha, & Kuno, Yoshitaka. Spin-dependent μ → e conversion. United States. doi:10.1016/j.physletb.2017.05.053.
Cirigliano, Vincenzo, Davidson, Sacha, and Kuno, Yoshitaka. Mon . "Spin-dependent μ → e conversion". United States. doi:10.1016/j.physletb.2017.05.053. https://www.osti.gov/servlets/purl/1360714.
@article{osti_1360714,
title = {Spin-dependent μ → e conversion},
author = {Cirigliano, Vincenzo and Davidson, Sacha and Kuno, Yoshitaka},
abstractNote = {The experimental sensitivity to μ→e conversion on nuclei is expected to improve by four orders of magnitude in coming years. Here, we consider the impact of μ→e flavour-changing tensor and axial-vector four-fermion operators which couple to the spin of nucleons. Such operators, which have not previously been considered, contribute to μ→e conversion in three ways: in nuclei with spin they mediate a spin-dependent transition; in all nuclei they contribute to the coherent (A2-enhanced) spin-independent conversion via finite recoil effects and via loop mixing with dipole, scalar, and vector operators. Furthermore, we estimate the spin-dependent rate in Aluminium (the target of the upcoming COMET and Mu2e experiments), show that the loop effects give the greatest sensitivity to tensor and axial-vector operators involving first-generation quarks, and discuss the complementarity of the spin-dependent and independent contributions to μ→e conversion.},
doi = {10.1016/j.physletb.2017.05.053},
journal = {Physics Letters. Section B},
number = C,
volume = 771,
place = {United States},
year = {Mon May 22 00:00:00 EDT 2017},
month = {Mon May 22 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 3works
Citation information provided by
Web of Science

Save / Share:
  • Charge asymmetry in the processes e +e → μ +μ γ and e +e → π +π γ is measured using 232 fb –1 of data collected with the BABAR detector at e +e center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial- and final-state radiation (FSR). The asymmetry is determined as a function of the invariant mass of the final-state tracks from production threshold to a few GeV/c 2. Itmore » is compared to the expectation from QED for e +e → μ +μ γ, and from theoretical models for e +e → π +π γ. A clear interference pattern is observed in e +e → π +π γ, particularly in the vicinity of the f 2(1270) resonance. As a result, the inferred rate of lowest-order FSR production is consistent with the QED expectation for e +e → μ +μ γ, and is negligibly small for e +e → π +π γ.« less
  • We present searches for the rare decay modes D⁰→e⁺e⁻, D0→μ⁺μ⁻, and D⁰→e ±μ in continuum e⁺e⁻→cc¯ events recorded by the BABAR detector in a data sample that corresponds to an integrated luminosity of 468 fb⁻¹. These decays are highly Glashow–Iliopoulos–Maiani suppressed but may be enhanced in several extensions of the standard model. Our observed event yields are consistent with the expected backgrounds. An excess is seen in the D⁰→μ⁺μ⁻ channel, although the observed yield is consistent with an upward background fluctuation at the 5% level. Using the Feldman–Cousins method, we set the following 90% confidence level intervals on themore » branching fractions: B(D⁰→e⁺e⁻)<1.7×10⁻⁷, B(D⁰→μ⁺μ⁻) within [0.6,8.1]×10⁻⁷, and B(D⁰→e ±μ )<3.3×10⁻⁷.« less
    Cited by 4
  • We describe a proposed experiment to search for Charged Lepton Flavor Violation (CLFV) using stopped muons at Fermilab. A primary Proton beam will strike a gold target, producing pions which decay to muons. Low-momentum negative muons will be collected, selected, and transported by a custom arrangement of solenoidal magnets and collimators. Muons will stop in thin foil targets, creating muonic atoms with significant nuclear overlap. Mu2e will search for the coherent conversion of nuclear bound muons to electrons, with an experimental signature of a single mono-energetic electron. Conversion electrons will be detected and measured in a low-mass straw tracker andmore » a crystal calorimeter. Mu2e will have a sensitivity four orders of magnitude better than the most sensitive published result for μ → e conversion, and will have complementary physics reach to LHC experiments and μ → eγ decay experiments such as MEG.« less
  • This paper presents a full simulation study of the measurement of the production cross section(ZH) of the Higgsstrahlung process e+e- ZH and the Higgs boson mass (MH) at the International Linear Collider (ILC), using events in which a Higgs boson recoils against a Z boson decaying into a pair of muons or electrons. The analysis is carried out for three center-of-mass energiesps =250, 350, and 500 GeV, and two beam polarizations e L e+ R and e Re+L , for which the polarizationsof e and e+ are Pe-; Pe+ =(-80%, +30%) and (+80%, -30%), respectively. Assuming an integrated luminosity ofmore » 250 fb1 for each beam polarization at ps = 250 GeV, where the best lepton momentum resolution is obtainable, ZH and MH can be determined with a precision of 2.5%and 37 MeV for e L e+R and 2.9% and 41 MeV for e-Re+L , respectively. Regarding a 20 year ILC physics program, the expected precisions for the HZZ coupling and MH are estimated to be 0.4% and 14MeV, respectively. The event selection is designed to optimize the precisions of ZH and MH while minimizing the bias on the measured ZH due to discrepancy in signal efficiencies among Higgs decay modes. For the first time, model independence has been demonstrated to a sub-percent level for the ZH measurement at each of the three center-of-mass energies. The results presented show the impact of center-of-mass energy and beam polarization on the evaluated precisons and serve as« less