apex:inputHidden value="{!$CurrentPage.parameters.par}" NOT WORK

Hello

I have a method to pass the values into page 2
But the inputHidden dont work. Why???

APEX:

public PageReference modifier(){

PageReference pageRef= new PageReference('/apex/BBBBPage2');
pageRef.getParameters().put('par' ,jobInfoMail);

pageRef.setRedirect(true);
return pageRef;
}

VISUALFORCE:

.........

function prepopulate(){

var getOPTNomJob = document.getElementById("{!$Component.theform.block01.nomJobOP}").innerHTML;
document.getElementById("{!$Component.theform.block01.nomJobIP}").value= getOPTNomJob ;

}

..........  
 

<apex:inputHidden value="{!$CurrentPage.parameters.par}" id="nomJobOP"/><br />
    Nom Job.:&nbsp;<apex:inputText id="nomJobIP" value="{!nomJob}" onclick="prepopulate();return false;"/><br /><br />

Thank you