φ meson

Phi meson (φ)
classification
Boson Hadron Meson
properties
electric charge	neutral
Resting energy	(1019.461 ± 0.016)  MeV
Spin parity	1 -
Isospin	0
average lifespan	1.55 ± 0.01 × 10 −22  s
Decay width	(4.249 ± 0.013)  MeV
Quark composition	Strange - Anti-Strange

The φ-meson , also Phi-meson , a meson consisting of a strange quark and the corresponding anti quark is and spin  1 has (Vektormeson). ${\displaystyle s}$ ${\displaystyle {\bar {s}}}$

Since the φ meson u. a. contains a strange quark, it is one of the strange particles . Since it consists of a quark and its antiquark, it is also a quarkonium .

description

In the quark model, the φ and ω mesons are mixtures of the three quark antiquark states u u , d d and s s of the up, down and strange quarks. Both mixtures each have a hypercharge and an isospin and are in the same place in the multiplet of the vector mesons as the neutral ρ meson . ${\displaystyle Y=0}$ ${\displaystyle I=0}$ ${\displaystyle \rho ^{0}}$

The three mutually orthogonal linear combinations of the above Quark-antiquark states are identified as follows:

${\displaystyle (u{\bar {u}}-d{\bar {d}})/{\sqrt {2}}}$with the meson ${\displaystyle \rho ^{0}}$

${\displaystyle (u{\bar {u}}+d{\bar {d}}-2s{\bar {s}})/{\sqrt {6}}}$with , a state of the ω meson in the SU (3) octet ${\displaystyle \omega _{8}}$

${\displaystyle (u{\bar {u}}+d{\bar {d}}+s{\bar {s}})/{\sqrt {3}}}$with , a state of the ω meson in the SU (3) singlet. ${\displaystyle \omega _{1}}$

The physical ( mass ) states φ and ω result in turn as linear combinations of and : ${\displaystyle \omega _{8}}$ ${\displaystyle \omega _{1}}$

${\displaystyle \left({\begin{array}{cc}\cos \theta _{\mathrm {V} }&-\sin \theta _{\mathrm {V} }\\\sin \theta _{\mathrm {V} }&\cos \theta _{\mathrm {V} }\end{array}}\right)\left({\begin{array}{c}\omega _{8}\\\omega _{1}\end{array}}\right)=\left({\begin{array}{c}\varphi \\\omega \end{array}}\right).}$

The mixing angle introduced in this way has an experimental value which, at around 39 °, almost corresponds to the ideal mixing angle of ≈35.3 ° ( ). So the φ meson is composed almost exclusively of a Strange anti-strange quark pair, and the flavor - wave function can be written as ${\displaystyle \theta _{V}}$ ${\displaystyle \tan \theta _{V}=1/{\sqrt {2}}}$

${\displaystyle |\varphi \rangle \approx |s{\bar {s}}\rangle }$.

The φ meson was first detected in 1963 at the Lawrence Radiation Laboratory in kaon - proton reactions.

Decay channels

φ mesons decay under the strong force . The decay takes place mainly in two kaons , either the charged Κ ⁺ / Κ ^- (48.9%) or the neutral Κ ⁰ _L / Κ ⁰ _S (34.2%), and to a lesser extent either into a ρ meson and one pion or in three pions (15.32%). The latter two decay channels in mesons without strangeness should actually be dominant due to their higher Q value , but are suppressed by the OZI rule .

particularities

Due to the mixing effects of the pseudoscalar η-mesons , the φ-meson is the lightest meson that consists of a strange-antistrange quark pair.

See also

• List of mesons

Individual evidence

1. ↑ The information on the particle properties (Infobox) 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. ↑ Reviews - Quark Model (PDF; 644 kB) from 2010 Review of Particle Physics, K. Nakamura et al. (Particle Data Group), J. Phys. G 37, 075021 (2010)
3. ↑ P. Schlein et al. : Quantum Numbers of a 1020-MeV KK ̅ Resonance . In: Phys. Rev. Lett. No. 10 , 1963, pp. 368-371 , doi : 10.1103 / PhysRevLett.10.368 .
4. ↑ N. Nakamura et al . (2010): Particle listings - φ (PDF; 217 kB)