#### $\vert \mathit q_{{{\mathit p}}}~+~\mathit q_{{{\overline{\mathit p}}}}\vert /{{\mathit e}}$

A test of $\mathit CPT$ invariance. Note that the comparison of the ${{\overline{\mathit p}}}$ and ${{\mathit p}}$ charge-to-mass ratios given above is much better determined. See also a similar test involving the electron.
VALUE CL% DOCUMENT ID TECN  COMMENT
$\bf{<7 \times 10^{-10}}$ 90 1
 2011
SPEC ${{\overline{\mathit p}}}{{\mathit e}^{-}}{}^{}\mathrm {He}$ atom
• • We do not use the following data for averages, fits, limits, etc. • •
$<2 \times 10^{-9}$ 90 1
 2006
SPEC ${{\overline{\mathit p}}}{{\mathit e}^{-}}$ He atom
$<1.0 \times 10^{-8}$ 90 1
 2003
SPEC ${{\overline{\mathit p}}}{{\mathit e}^{-}}$ ${}^{4}\mathrm {He}$, ${{\overline{\mathit p}}}{{\mathit e}^{-}}$ ${}^{3}\mathrm {He}$
$<6 \times 10^{-8}$ 90 1
 2001
SPEC ${{\overline{\mathit p}}}{{\mathit e}^{-}}{}^{}\mathrm {He}$ atom
$<5 \times 10^{-7}$ 2
 1999
SPEC ${{\overline{\mathit p}}}{{\mathit e}^{-}}{}^{}\mathrm {He}$ atom
$<2 \times 10^{-5}$ 3
 1992
RVUE
 1 HORI 2001 , HORI 2003 , HORI 2006 , and HORI 2011 use the more-precisely-known constraint on the ${{\overline{\mathit p}}}$ charge-to-mass ratio of GABRIELSE 1999 (see above) to get their results. Their results are not independent of the HORI 2001 , HORI 2003 , HORI 2006 , and HORI 2011 values for $\vert {\mathit m}_{{{\mathit p}}}−{\mathit m}_{{{\overline{\mathit p}}}}\vert /{\mathit m}_{{{\mathit p}}}$, above.
 2 TORII 1999 uses the more-precisely-known constraint on the ${{\overline{\mathit p}}}$ charge-to-mass ratio of GABRIELSE 1995 (see above) to get this result. This is not independent of the TORII 1999 value for $\vert {\mathit m}_{{{\mathit p}}}−{\mathit m}_{{{\overline{\mathit p}}}}\vert /{\mathit m}_{{{\mathit p}}}$, above.
 3 HUGHES 1992 uses recent measurements of Rydberg-energy and cyclotron-frequency ratios.
Conservation Laws:
$\mathit CPT$ INVARIANCE
References:
 HORI 2011
NAT 475 484 Two-Photon Laser Spectroscopy of Antiprotonic Helium and the Antiproton-to-Electron Mass Ratio
 HORI 2006
PRL 96 243401 Determination of the Antiproton-to-Electron Mass Ratio by Precision Laser Spectroscopy of ${{\overline{\mathit p}}}{}^{}\mathrm {He}{+}$
 HORI 2003
PRL 91 123401 Direct Measurement of Transition Frequencies in Isolated ${{\overline{\mathit p}}}$ He${}^{+}$ Atoms, and New $\mathit CPT$-Violation Limits on the Antiproton Charge and Mass
 HORI 2001
PRL 87 093401 Sub-ppm Laser Spectroscopy of Antiprotonic Helium and $\mathit CPT$-Violation Limit on the Antiprotonic Charge and Mass
 TORII 1999
PR A59 223 Laser Measurements of the Density Shifts of Resonance Lines in Antiprotonic Helium Atoms and Stringent Constraint on the Antiproton Charge and Mass
 HUGHES 1992
PRL 69 578 Electric Charges of Positrons and Antiprotons