Where do I find the definition of the search field

I am in the processing of modifying the text fields in discourse using the jquery.ime plugin. I simply find the corresponding handlebar template and add the required javascript code. But I cannot find the hbs file containing the definition of search text field that appears at the top of the page. Can somebody please tell where can I find this definition?

It’s here, and it is a Widget. So you can’t find it in .hbs template files.