I found the solution on stackoverflow in English, here :
$('#accordion').accordion({
collapsible:true,
beforeActivate: function(event, ui) {
// The accordion believes a panel is being opened
if (ui.newHeader[0]) {
var currHeader = ui.newHeader;
var currContent = currHeader.next('.ui-accordion-content');
// The accordion believes a panel is being closed
} else {
var currHeader = ui.oldHeader;
var currContent = currHeader.next('.ui-accordion-content');
}
// Since we've changed the default behavior, this detects the actual status
var isPanelSelected = currHeader.attr('aria-selected') == 'true';
// Toggle the panel's header
currHeader.toggleClass('ui-corner-all',isPanelSelected).toggleClass('accordion-header-active ui-state-active ui-corner-top',!isPanelSelected).attr('aria-selected',((!isPanelSelected).toString()));
// Toggle the panel's icon
currHeader.children('.ui-icon').toggleClass('ui-icon-triangle-1-e',isPanelSelected).toggleClass('ui-icon-triangle-1-s',!isPanelSelected);
// Toggle the panel's content
currContent.toggleClass('accordion-content-active',!isPanelSelected)
if (isPanelSelected) { currContent.slideUp(); } else { currContent.slideDown(); }
return false; // Cancel the default action
}
});