Express \(4 x ^ { 2 } - 24 x + p\) in the form \(a ( x + b ) ^ { 2 } + c\), where \(a\) and \(b\) are integers and \(c\) is to be given in terms of the constant \(p\).
Hence or otherwise find the set of values of \(p\) for which the equation \(4 x ^ { 2 } - 24 x + p = 0\) has no real roots.