Yii CJuiSlider is not displayed on the layout page

Question

I'm trying to display a standard Yii widget [CJuiSlider] on the layout page for ranking prices (price "from" and price "to") :

<strong style="margin-bottom: 8px; display: block;">Price</strong>
<span style="color: grey">from</span>
<input type="text" name="filter[price_min]" id="price-from" /> &nbsp;
<span style="color: grey">to</span>
<input type="text" name="filter[price_max]" id="price-to" />
<span style="color: grey">$</span>
<?php
    // This values in widget - only for test
    $this->widget('zii.widgets.jui.CJuiSlider', array(
        'options'=>array(
            'range' => true,
            'min' => 10,
            'max' => 20,
            'values' => array( 10, 20 ),
            'slide'=>'js:function(event, ui) {
                    $("#price-from").val(ui.values[0]);
                    $("#price-to").val(ui.values[1]);
            }',
    ),
));
?>

But this widget is not displayed :( In the source HTML code I see that:

<div id="yw1"></div>

In what could be a bug/problem? Many thanks in advance!