The B Meson

B 介子

Particle 质点	Symbol 符号	Anti- particle 反粒子	Makeup 组成	Rest mass MeV/c² 静止质量 MeV/c²	S	C	B	Lifetime 寿命	Decay Modes 衰变模式
B	B^-	B⁺	bu	5279	0	0	-1	1.5 x10^-12	D⁰ + _
B	B⁰	B⁰	db	5279	0	0	-1	1.5 x10^-12	D⁰ + _
B_s	B_s⁰	B_s⁰	sb	5370	-1	0	-1	1.5 x10^-12	PDG
B_c	B_c⁺	B_c^-	cb	6275	0	0	-1	0.5 x10^-12	PDG

The B-meson contains a b-quark and the least massive variety has a mass about 5.6 times that of a proton. The table summarizes the properties of the B variety which contains the b-quark along with an up or down quark. The more exotic varieties B_s and B_c contain the b-quark along with a strange or charm quark respectively. The study of the B-meson has proven to be fruitful and has merited the operation of "B-factories" at the SLAC and KEK accelerator facilities. At those facilities the violation of CP symmetry in B-meson decay was confirmed in 2001. In B-meson decay the CP violation was found to be a larger effect than in the case of the Kaon decay although it was an effect on rare decays while the Kaon experiments shows a small effect on common decays. The branching ratio for the decay
B⁰ → K⁺ + π^- is only 1.82 x 10^-5, but this decay is 13% more common than its CP' 'mirror image' decay B⁰ → K^- + π⁺ (Griffiths).

Meson diagram

介子图

Table of mesons

介子表

B介子包含一个底夸克，其中最轻的种类质量大约是质子的5.6倍。表总结了包含底夸克并伴有上夸克或下夸克的B介子的性质。更奇特的B_s和B_c介子分别包含底夸克和奇异夸克或粲夸克。对B介子的研究证明是有成效的，并促使在SLAC和KEK加速器设施中建立“B工厂”。在这些设施中，2001年确认了B介子衰变中的CP对称性破坏。在B介子衰变中，CP破坏效应比K介子衰变中的效应更大，尽管它只出现在罕见衰变中，而K介子实验则在常见衰变中显示出较小的效应。B_0 → K^+ + π^-衰变的分支比率为仅1.82×10^-5，但这种衰变比其CP“镜像”衰变B_0 → K^- + π^+更常见，比例高13%（Griffiths）。

Index

Particle concepts

B meson wiki

Griffiths, 2nd Ed sec 1.9, 4.4

索引粒子概念 B 介子网易百科全书 Griffiths, 第二版第1.9节，4.4节

HyperPhysics***** Quantum Physics

HyperPhysics ***** 量子物理

R Nave

Go Back