Rubber Composition for Tire Tread and Pneumatic Tire

A rubber composition for a tire tread comprising:

• a rubber component containing not less than 30 mass % of a conjugated diene-based rubber (A);
• a silica (B);
• and
• an alkyltriethoxysilane represented by the following formula (1),
• the conjugated diene-based rubber (A) containing not less than 5 mass % of a structural member (a), in which not less than three conjugated diene-based polymer chains (a1) are bonded via a modifier (a2), obtained by a reaction of the conjugated diene-based polymer chains (a1) and the modifier (a2);
• the conjugated diene-based polymer chain (a1) including an isoprene block containing not less than 70 mass % of isoprene units on one terminal and containing an active terminal on the other terminal;
• the modifier (a2) including at least one group selected from an epoxy group and a hydrocarbyloxysilyl group, a total number of the epoxy groups and hydrocarbyloxy groups contained in the hydrocarbyloxysilyl group being not less than three;
• the silica (B) having a nitrogen adsorption specific surface area from 194 to 225 m2/g and a cetyl trimethyl ammonium bromide (CTAB) adsorption specific surface area from 180 to 210 m2/g;
• a content of the silica (B) being from 60 to 150 parts by mass per 100 parts by mass of the rubber component;
• and
• a content of the alkyltriethoxysilane (C) being from 3.0 to 7.0 mass % relative to the silica (B):
• (wherein R is an alkyl group having from 7 to 20 carbons).