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Дата изменения: Wed Aug 9 20:40:47 2000
Дата индексирования: Mon Oct 1 22:46:36 2012
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Quark-gluon interaction.

The interaction of a gluon with a quark is described by the following term of Lagrangian (.5):

$$S_{QqG}= g \int G^{\alpha}_{\mu}(x) \bar{q}(x)\gamma^{\mu} \hat{t}_{\alpha} q(x) \, d^4x\;.$$

Applying the Fourier transformation and substituting $\bar{q} = q^+\gamma^0$ we get

$$S_{QqG}= g (2\pi)^4 \int \delta(p_1+p_2+p_3) G^{\alpha}_{\mu... ...gamma^{\mu} \hat{t}_{\alpha} q(p_2) \, d^4p_1 d^4p_2 d^4p_3\;;$$

$$\frac{\delta S_{QqG}} {\delta q^+_i(p_1)\delta q^j(p_2) \del... ...(p_1+p_2+p_3) (\hat{t}_{\alpha})^i_j \gamma^0\gamma^{\mu_3}\;.$$

The factor $(2\pi)^4 \delta(p_1+p_2+p_3) (\hat{t}_{\alpha})^i_j \gamma^0$ is substituted by CompHEP  automatically. Thus, the quark-gluon interaction is implemented in the CompHEP  Vertex table as the following record:

A1	A2	A3	A4	Factor	Lorentz part
Q	q	G		GG	G(m3)

where $q$ and $Q$ are designations for a quark and a corresponding antiquark.