I would like to add one simple arc in the chart section like a circle:
vis.append(\"circle\")
.style(\"stroke\", \"gray\")
.style(\"fill\", \"white\"
D3 uses a path generator for arcs. If you don't want to data-drive your arc just define the arc generator and add some methods...
var arc = d3.svg.arc()
.innerRadius(50)
.outerRadius(70)
.startAngle(45 * (Math.PI/180)) //convert from degs to radians
.endAngle(3) //just radians
vis.append("path")
.attr("d", arc)
.attr("transform", "translate(50,50)")
You can see a demo here: http://jsfiddle.net/h9XNz/