Difference between revisions of "Meson"

Revision as of 14:24, 18 July 2019

Key Stage 5

Meaning

Mesons are a type of hadron consisting of a quark-antiquark pair.

About Mesons

Mesons have a very short half life, decaying via the weak nuclear interaction or though the quark-antiquark pair annihilating one another.

Mesons consisting of the quarks; up-quark, down-quark and strange-quark are divided into two main categories; π-mesons and k-mesonss.

K-mesons have a strangeness of +1 or -1. However, π-mesons do not carry strangeness.

Mesons are affected by the:

Determining Meson Composition

NB: You do not need to memorise the exact composition of a given meson. However, you should be able to determine the quark composition given the charge and strangeness of the meson and by remembering the properties of the up-quark, down-quark and strange-quark.

Mesons can be shown in the following diagram:

The composition of these mesons can be determined given their charge and strangeness.

Examples

This table is for referencing the properties of the quarks.
Quark	Charge	Strangeness
Up-quark	\(q=+\frac{2}{3}\)	\(S=0\)
Antiup-quark	\(q=-\frac{2}{3}\)	\(S=0\)
Down-quark	\(q=-\frac{1}{3}\)	\(S=0\)
Antidown-quark	\(q=+\frac{1}{3}\)	\(S=0\)
Strange-quark	\(q=-\frac{1}{3}\)	\(S=-1\)
Antistrange-quark	\(q=+\frac{1}{3}\)	\(S=+1\)

Determine the composition of the π⁺	Determine the composition of the K^-
π⁺ has a strangeness of 0, therefore it contains no strange-quark or antistrange-quark. π⁺ has a positive charge. This can be achieved with one charge of \(+\frac{2}{3}\) (an up-quark) and \(+\frac{1}{3}\) (an antidown-quark). Therefore \(π^+ = u + \bar{d}\) An up-antidown pair.	K^- has a strangeness of -1, therefore it contains a strange-quark. K^- has a negative charge. This can be achieved with one its strange-quark with an charge of [[\(-\frac{1}{3}\) and another charge of \(-\frac{2}{3}\) (an antiup-quark). Therefore \(K^- = S + \bar{u}\) A strange-antiup pair.

@@ Line 29: / Line 29: @@
 | style="height:20px; width:200px; text-align:center;"|[[Electrical Charge|'''Charge''']]
 | style="height:20px; width:200px; text-align:center;"|'''[[Strangeness]]'''
-|-
-| style="height:20px; width:200px; text-align:center;"|
-[[Strange-quark]]
-| style="height:20px; width:200px; text-align:center;"|<math>q=-\frac{1}{3}</math>
-| style="height:20px; width:200px; text-align:center;"|<math>S=-1</math>
-|-
-| style="height:20px; width:200px; text-align:center;"|
-[[Antistrange-quark]]
-| style="height:20px; width:200px; text-align:center;"|<math>q=+\frac{1}{3}</math>
-| style="height:20px; width:200px; text-align:center;"|<math>S=+1</math>
 |-
 | style="height:20px; width:200px; text-align:center;"|
@@ Line 70: / Line 56: @@
 | style="height:20px; width:200px; text-align:center;"|<math>S=0</math>
+|-
+| style="height:20px; width:200px; text-align:center;"|
+[[Strange-quark]]
+| style="height:20px; width:200px; text-align:center;"|<math>q=-\frac{1}{3}</math>
+| style="height:20px; width:200px; text-align:center;"|<math>S=-1</math>
+|-
+| style="height:20px; width:200px; text-align:center;"|
+[[Antistrange-quark]]
+| style="height:20px; width:200px; text-align:center;"|<math>q=+\frac{1}{3}</math>
+| style="height:20px; width:200px; text-align:center;"|<math>S=+1</math>
 |}