My question comes from the textbook by Peskin & Schroeder, the integral (19.26): ∫d2k(2π)2e−ik⋅(y−z)i⧸kk2=−∂̸(i4πlog(y−z)2)
Question: how to derive the formula from the left hand side to the right hand side ?
If considering the identity (3.117) and set m=0, I have ∫d2k(2π)2ik⋅γk2e−ik⋅(y−z)=i∂̸(DR(y−z)) here DR(y−z)=∫d2k(2π)2ik2e−ik⋅(y−z) the 2-vector: kμ=(k0,k1) and owing to the massless condition:(k0)2=(k1)2. set κ≡k1.therefore I got ∫+∞−∞dk1(2π)[12k0e−i[k0(y−z)0−k1(y−z)1]+1−2k0e−i[−k0(y−z)0−k1(y−z)1]]=−i4π 2∫+∞−∞sin(κ(y−z)0)κeiκ(y−z)1dκ
But I failed to get the log-term from the above formula.
NOTE I found a related answer A four-dimensional integral in Peskin & Schroeder
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