重子数减去轻子数的差

B − L

quantum number (difference between the baryon number and the lepton number), conserved in some grand unified theories even when baryon and lepton numbers are not separately conserved

在粒子物理学中，重子数减去轻子数的差，顾名思义，就是一个粒子或系统中，重子数减去轻子数之后所得的量子数，而这量子数又记做。