Search for a heavy neutral gauge boson in the dielectron channel with 5.4 fb−1 of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:mi>p</mml:mi><mml:mover accent="true"><mml:mi>p</mml:mi><mml:mo>¯</mml:mo></mml:mover></mml:math> collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"><mml:msqrt><mml:mi>s</mml:mi></mml:msqrt><mml:mo>=</mml:mo><mml:mn>1.96</mml:mn><mml:mtext> TeV</mml:mtext></mml:math>

We report the results of a search for a heavy neutral gauge boson Z′ decaying into the dielectron final state using data corresponding to an integrated luminosity of 5.4 fb−1 collected by the D0 experiment at the Fermilab Tevatron Collider. No significant excess above the standard model prediction is observed in the dielectron invariant-mass spectrum. We set 95σ(pp¯→Z′)×BR(Z′→ee) depending on the dielectron invariant mass. These cross section limits are used to determine lower mass limits for Z′ bosons in a variety of models. For the sequential standard model Z′ boson a lower mass limit of 1023 GeV is obtained.