The 4e PHB was quoted by
@Aldarc and by me upthread. Here it is again (from pp 58, 276):
Sometimes the dice are against you, and you miss your target. Missing isn’t always the end of the story, however. A miss can indicate a splash effect, a glancing blow, or some other incidental effect of a power. . . .
You resolve an attack by comparing the total of your attack roll (1d20 + base attack bonus + attack modifiers) to the appropriate defense score. If your roll is higher than or equal to the defense score, you hit. Otherwise, you miss.
When you hit, you usually deal damage and sometimes produce some other effect. When you’re using a power, the power description tells you what happens when you hit. Some descriptions also say what happens when you miss or when you score a critical hit. . . .
Hit: If the attack roll is higher than or equal to the defense score, the attack hits and deals damage, has a special effect, or both. . . .
Miss: If your attack roll is lower than the defense score, the attack misses. Usually, there’s no effect. Some powers have an effect on a miss, such as dealing half damage.