The probability density function (PDF) is constructed from the time distributions of signal and backgrounds and the relations among time, time uncertainty, mass, and mass difference variables.

根据信号、本底的时间分布以及时间、时间误差、质量、质量差等变量之间的关系，构建概率密度函数。

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The difference in speed also means a difference in mass of 50%.

VOA: special.2009.01.20

The frequency at which it happens is related to a small but significant difference between the mass of the particle and its antiparticle.

ECONOMIST: Cosmology and particle physics

To assess the contribution from melting ice sheets, scientists try to measure "mass balance, " which is the difference between the annual snow that falls on the permanent ice sheets each year, and the total mass of ice that melts or breaks off the sheets.

WSJ: Polar Ice Sheets Melt at Faster Pace

On average, men have 40% more fat-free mass than women, which is similar to the difference in gorillas, a species in which males unquestionably compete with other males for exclusive sexual access to females.

ECONOMIST: Masculine traits