[XeTeX] Accessing mathmatics symbols

[R (Chandra) Chandrasekhar]

Dear Folks,

I am trying out XeTeX (XeTeX 3.141592-0.996 (Web2C 7.5.6)) installed newly from 
TeXLive 2007 source packages for K/Ubuntu Gutsy backported to Feisty.

I have installed the Latin Modern OTF fonts in addition to the lmodern package.

I am having problems getting maths symbols to appear in the output PDF files.

A minimal example is given below:
-------------
\documentclass[a4paper,10pt]{article}
%
\usepackage{fontspec}
\usepackage{xunicode}
\usepackage{xltxtra}
\usepackage[EU1]{fontenc}% Unsure if this is correct
\usepackage{textcomp}
%
\setmainfont{FreeSerif}
\setmathrm{LMRoman10 Regular} % is this really needed?
\defaultfontfeatures{Mapping=tex-text,Scale=MatchLowercase}
%
\begin{document}
$\sqrt{2}$ is an irrational number.
\[
\sum_{i = 1}^{10}i = 55
\]
%
\end{document}
-------------

When I process this file with

xelatex -output-driver="xdvipdfmx -q -E" <filename>

I do not get a square root or capital sigma summation sign.

How can I get them, and what am I doing wrong?

Thank you.

Chandra
22 Jun 07