B meson

B +
classification
Boson Hadron Meson
properties
electric charge	1  e (+1.602 10 −19  C )
Resting energy	5279.32 (14)  MeV
Spin parity	0 -
Isospin	1/2 (z component +1/2)
Beauty	+1
average lifespan	1.638 (4) · 10 −12  s
Interactions	strong weak electromagnetic gravitation
Quark composition	${\displaystyle u{\bar {b}}}$, 1 up and 1 anti-bottom

B 0
classification
Boson Hadron Meson
properties
electric charge	neutral
Resting energy	5279.63 (15)  MeV
Spin parity	0 -
Isospin	1/2 (z component -1/2)
Beauty	+1
average lifespan	1.520 (4) · 10 −12  s
Interactions	strong weak electromagnetic gravitation
Quark composition	${\displaystyle d{\bar {b}}}$, 1 down and 1 anti-bottom

The four B mesons (B for bottom quark ) contain a heavy bottom anti-quark and a light u or d quark , or the corresponding antiparticles : ${\displaystyle {\bar {b}}}$

	B anti-mesons		B mesons
	${\displaystyle B^{-}\!\,}$	${\displaystyle {\bar {B}}^{0}}$	${\displaystyle B^{0}\!\,}$	${\displaystyle B^{+}\!\,}$
Isospin ${\displaystyle I_{z}}$	-½	+ ½	-½	+ ½
Quark composition	${\displaystyle {\bar {u}}}$	${\displaystyle {\bar {d}}}$	${\displaystyle d\!\,}$	${\displaystyle u\!\,}$
	${\displaystyle b\!\,}$	${\displaystyle b\!\,}$	${\displaystyle {\bar {b}}}$	${\displaystyle {\bar {b}}}$
Bottomness ${\displaystyle B'}$	−1		+1

They were in 1983 with the CLEO - particle detector at CESR - storage ring of Cornell University in New Jersey ( USA discovered).

properties

B mesons have a mass of 5.2789  GeV / c ² ( ) or 5.2792 GeV / c ² ( and ) and a lifetime of 1.6 · 10 ⁻¹²  s ( ) or 1.5 · 10 ^{- 12}  s ( , ).  ${\displaystyle B^{\pm }}$ ${\displaystyle B^{0}}$ ${\displaystyle {\bar {B^{0}}}}$ ${\displaystyle B^{\pm }}$ ${\displaystyle B^{0}}$ ${\displaystyle {\bar {B^{0}}}}$

All B mesons have roughly the same masses because the main contribution comes from the heavy b quark or its antiparticle, and roughly the same decay times because the b quark mainly decays into a c or u quark.

The mechanism of the CP violation (according to the CPT theorem equivalent to the violation of the symmetry against time reversal ) is investigated on the - system , similar to the previous one in the system of kaons (the equivalents of the B mesons, if one uses the bottom quark a strange quark replaced). ${\displaystyle B^{0}}$ ${\displaystyle {\bar {B^{0}}}}$

B mesons with charm or strangeness

B s 0
classification
Boson Hadron Meson
properties
electric charge	neutral
Resting energy	5366.89 (19)  MeV
Spin parity	0 -
Isospin	0
Strangeness	−1
Beauty	+1
average lifespan	1.509 (4) · 10 −12  s
Interactions	strong weak electromagnetic gravitation
Quark composition	${\displaystyle s{\bar {b}}}$, 1 Strange and 1 Anti-Bottom

B c +
classification
Boson Hadron Meson
properties
electric charge	1  e (+1.602 10 −19  C )
Resting energy	6274.9 (8)  MeV
Spin parity	0 -
Isospin	0
Charm	+1
Beauty	+1
average lifespan	0.507 (9) · 10 −12  s
Interactions	strong weak electromagnetic gravitation
Quark composition	${\displaystyle c{\bar {b}}}$, 1 charm and 1 anti-bottom

In addition, B mesons with charm or strangeness are also referred to as those mesons that contain a bottom anti-quark, but instead of an up or down quark, a charm or strange quark, or each the corresponding antiparticles:

	B-anti-mesons with ...		B mesons with ...
	${\displaystyle B_{c}^{-}\!\,}$	${\displaystyle {\bar {B}}_{s}^{0}}$	${\displaystyle B_{s}^{0}\!\,}$	${\displaystyle B_{c}^{+}\!\,}$
… Charm ${\displaystyle C}$	−1	0	0	+1
... strangeness ${\displaystyle S}$	0	+1	−1	0
Quark composition	${\displaystyle {\bar {c}}}$	${\displaystyle {\bar {s}}}$	${\displaystyle s\!\,}$	${\displaystyle c\!\,}$
	${\displaystyle b\!\,}$	${\displaystyle b\!\,}$	${\displaystyle {\bar {b}}}$	${\displaystyle {\bar {b}}}$
Bottomness ${\displaystyle B'}$	−1		+1

See also

• List of mesons
• B factory

literature

• Bogdan Povh , Klaus Rith , Christoph Scholz, Frank Zetsche: Particles and Cores. An introduction to the physical concepts . 7th edition Springer, Berlin 2006, ISBN 978-3-540-36685-0 , p. 194.
• P. Koppenburg, Z. Dolezal, M. Smizanska: Rare decays of b hadrons . In: Scholarpedia . tape 11 , no. 6 , 2016, p. 32643. , Doi : 10.4249 / scholarpedia.32643 ( scholarpedia.org ).

Web links

• Heavy Flavor Averaging Group Current data collection on the physics of heavy quarks

References and comments

1. ↑ ^{a b c d} The information on the particle properties (info box) are, unless otherwise stated, taken from:
   M. Tanabashi et al .: 2018 Review of Particle Physics. In: Phys. Rev. D 98, 030001 (2018). Particle Data Group, accessed June 6, 2018 . 
2. ↑ For comparison: the heaviest quark, the t-quark, has a mass of 170.9 GeV / c ² .