I don't believe that you can.

Instead, consider protecting access to your batcheable class and provide a service class that calls the constructor for you, passing in the batch size, and then you call 

    global static class myService {
        global static void RunMyBatch(Integer batchSize) {
            myBatch theBatch = new myBatch (batchSize); // Batch size in constructor
            Database.executeBatch(theBatch, batchSize);
        }
    }