# Quarks in Particle Decay Equations(OCR A Level Physics)

Author

Katie M

Expertise

Physics

## Balancing Quark transformation equations

• By looking at the transformation of quarks inside the protons and neutrons in beta decay it is possible to analyse the decay of specific quarks inside

#### Beta-minus decay

• In beta-minus decay, one of the neutrons in a nucleus is converted into a proton in a process that may be written as:

n → p + e-

• The neutron, n has the quark composition udd
• The proton, p has the quark composition uud
• So the beta-minus decay must involve a down quark converting to an up quark

d → u + e-

Balancing Charge

• The charge on the left side of the equation is -
• The total charge on the right side is e + (-1)e + 0 = -e
• So, the decay equation is balanced in terms of charge

#### Beta-plus Decay

• In beta-plus decay a proton is converted into a neutron with the emission of a positron and an electron neutrino in a process that may be written as:

p → n + e+ + v

• The proton, p has the quark composition uud
• The neutron, n has the quark composition udd
• So, the beta-plus decay must involve an up quark converting to a down quark

u → d + e+ + v

Balancing Charge

• The charge on the left side of the equation is +
• The total charge on the right side is -e + e + 0 = +e
• So the decay equation is balanced in terms of charge

Charge must be conserved in any reaction or decay equation

#### Worked example

The equation for β decay isUsing the quark model of beta decay, prove that the charge is conserved in this equation.

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