I'm trying to work through a scattering calculation in the Peskin QFT textbook in chapter 5, specifically getting equation 5.10. They take two bracketed terms(adsbygoogle = window.adsbygoogle || []).push({});

[itex]

4[p'^{\mu}p^{\nu}+p'^{\nu}p^{\mu}-g^{\mu\nu}(p \cdot p'+m_e^2)]

[/itex]

and

[itex]

4[k_{\mu}k'_{\nu}+k_{\nu}k'_{\mu}-g_{\mu\nu}(k \cdot k'+m_{\mu}^2)]

[/itex]

they set [itex]m_e=0[/itex] and take the dot product of these two to get

[itex]

{32e^4}[(p \cdot k)(p' \cdot k')+(p \cdot k')(p' \cdot k)+m^2_{\mu}(p \cdot p')]

[/itex]

When I do this I get

[itex]

16[2(p' \cdot k)(p \cdot k')+2(k \cdot p)(p' \cdot k')-3(p' \cdot p)(k' \cdot k)-(p' \cdot p)m^2_{\mu}]

[/itex]

In this scattering problem the two incoming momenta are [itex]p[/itex] and [itex]p'[/itex] and outgoing [itex]k[/itex] and [itex]k'[/itex], so working in the COM frame I suspect there is a reduction you can make but I can't figure out what it is. Any help is appreciated!

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# A Trouble with Peskin QFT textbook

Have something to add?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**