Measuring masses in semi-invisible final states at electron-positron colliders

Mass measurement of a particle whose decay products including invisible particles is a challenging task at colliders. For a new physics model involving a dark matter candidate N and a Z2 symmetry that stabilizes it, a typical new process at e+e− colliders is the pair production e+e−→YY¯ followed by...

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Bibliographic Details
Published in:Physical review. D 2017-04, Vol.95 (7), Article 075037
Main Authors: Xiang, Qian-Fei, Bi, Xiao-Jun, Yan, Qi-Shu, Yin, Peng-Fei, Yu, Zhao-Huan
Format: Article
Language:English
Subjects:
Dark matter
Electron-positron accelerators
Energy conservation
Kinematic equations
Pair production
Particle decay
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Summary:Mass measurement of a particle whose decay products including invisible particles is a challenging task at colliders. For a new physics model involving a dark matter candidate N and a Z2 symmetry that stabilizes it, a typical new process at e+e− colliders is the pair production e+e−→YY¯ followed by decay processes Y→aN and Y¯→bN¯, where a and b are visible but N is invisible. In this work, we propose a new method to measure the physical masses in this topology by making use of the kinematic equations given by momentum-energy conservation and on-shell conditions. For each event, the solvability of these equations determines a limited region on the trial mY−mN plane. The edge of this region can be used to define two variables, mYedge and mNedge, whose distributions are utilized to derive the measurement values of mY and mN. The measurement deviations and uncertainties are also estimated after including detector effects and background contamination.
ISSN:2470-0010
2470-0029
DOI:10.1103/PhysRevD.95.075037