Golf ball

A golf ball having a spherical core and at least one cover layer covering the spherical core, wherein the spherical core is formed from a rubber composition containing:

• (a) a base rubber,
• (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent,
• (c) a crosslinking initiator and
• (d) a carboxylic acid having a heterocyclic ring and/or a salt thereof,
• provided that the rubber composition further contains (e) a metal compound if only (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms is present as the co-crosslinking agent,
• wherein (d) the carboxylic acid having the heterocyclic ring and/or the salt thereof is a compound represented by the following formula (2), and/or the salt thereof:
• wherein R5 to R8 each independently represent a hydrogen atom, a carboxyl group, halogen,
• a hydroxyl group, an alkyl group, an aryl group, an aralkyl group,
• an alkylaryl group, an alkoxyl group, an amino group which may be substituted, a cyano group,
• or a thiocarboxyl group, and at least one of R5 to R8 is a carboxyl group.