[1] Univ Milano Bicocca, Dipartimento Fis, I-20126 Milan, Italy
[2] Ist Nazl Fis Nucl, Sez Milano, I-20126 Milan, Italy
[3] Univ S Carolina, Dept Phys & Astron, Columbia, SC 29208 USA
[4] Lab Nazl Gran Sasso, I-67010 Assergi, Aquila, Italy
[5] Univ Florence, Dipartimento Fis, I-50125 Florence, Italy
[6] Ist Nazl Fis Nucl, Sez Firenze, I-50125 Florence, Italy
[7] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Dept Mat Sci & Engn, Berkeley, CA 94720 USA
[8] Univ Zaragoza, Lab Nucl & High Energy Phys, Zaragoza 50009, Spain
[9] Leiden Univ, Kamerlingh Onnes Lab, NL-2300 RA Leiden, Netherlands
[10] Univ Insubria, Dipartimento Sci Chim Fis & Matemat, I-22100 Como, Italy
[11] Ist Nazl Fis Nucl, Sez Milano, I-22100 Como, Italy
[12] Lab Nazl Legnaro, I-35020 Legnaro, Padova, Italy