Thank you, Malte and Noeck, it works perfectly.
I post here another solution, that is interesting because it doesn't use scheme and more easy to understand.
\version "2.19.54"
csl = { \change Staff = "left" }
csr = { \change Staff = "right" }
right = \fixed c' {
\clef treble
\time 2/4
g8-4 \csl g_4 \csr e-3 \csl e_3 \csr
g8-4 \csl g_4 \csr e4-2
\bar "|."
}
left = \fixed c' {
\clef treble
s2
s4 c_2
}
\score {
\new PianoStaff
<<
\new Staff = "right" \right
\new Staff = "left" \left
>>
\layout { }
}