SpinorVBar[p, m] denotes a \bar{v}(p,m)-spinor that depends on the 4-dimensional momentum p.
Overview, Spinor, SpinorUBar, SpinorU, SpinorV, SpinorUBarD, SpinorUD, SpinorVD, SpinorVBarD.
SpinorVBar[p, m]\bar{v}(p,m)
SpinorVBar[p, m] // FCI // StandardForm
(*Spinor[-Momentum[p], m, 1]*)SpinorVBar[p]\bar{v}(p)
SpinorVBar[p] // FCI // StandardForm
(*Spinor[-Momentum[p], 0, 1]*)SpinorVBar[p] . GS[p]
DiracEquation[%]\bar{v}(p).\left(\bar{\gamma }\cdot \overline{p}\right)
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