Here:
 - M isn't visible,
 - S is "/usr/bin/tlm-sessiond"
 - U is "/bin/sh -l /etc/session.d/user-session"

##########################################################################################
#  FIRST SESSION: ALL'S RIGHT
##########################################################################################
# systemctl status user-1000.slice
● user-1000.slice
   Loaded: loaded
   Active: active since lun. 2015-03-30 04:37:22 PDT; 19h ago
   CGroup: /user.slice/user-1000.slice
           ├─session-c1.scope
           │ ├─ 573 /usr/bin/tlm-sessiond
           │ ├─ 708 /bin/sh -l /etc/session.d/user-session
           │ └─1140 /usr/bin/tz-launcher -c /usr/share/applications/tizen/launcher.conf /home/alice/.applications/desktop
           └─user@1000.service
             ├─613 /usr/lib/systemd/systemd --user
             ├─615 (sd-pam)
             ├─pulseaudio.service
             │ ├─1081 /usr/bin/pulseaudio --daemonize=no
             │ └─1086 /usr/libexec/pulse/gconf-helper
             ├─xwalk.service
             │ ├─1072 /usr/lib64/xwalk/xwalk --external-extensions-path=/usr/lib64/tizen-extensions-crosswalk
             │ ├─1074 /usr/lib64/xwalk/xwalk --type=zygote
             │ ├─1094 /usr/lib64/xwalk/xwalk --type=gpu-process --channel=1072.0.284773123 --gpu-no-context-lost --use-gl=egl --supports-dual-gp...
             │ └─1106 /usr/lib64/xwalk/xwalk --type=gpu-broker
             ├─dbus.service
             │ └─645 /usr/bin/dbus-daemon --session --address=systemd: --nofork --systemd-activation
             └─amd_session_agent.service
               └─639 /usr/bin/amd_session_agent

(removed here not interesting lines)

##########################################################################################
#  AFTER RE-LAUNCH
##########################################################################################

# systemctl status user-1000.slice
● user-1000.slice
   Loaded: loaded
   Active: inactive (dead) since mar. 2015-03-31 00:37:41 PDT; 11s ago
   CGroup: /user.slice/user-1000.slice
           └─session-c7.scope
             ├─1427 /usr/bin/tlm-sessiond
             ├─1443 /bin/sh -l /etc/session.d/user-session
             └─1460 /usr/bin/tz-launcher -c /usr/share/applications/tizen/launcher.conf /home/alice/.applications/desktop

mars 31 00:37:41 lenovo06 systemd[613]: Closed D-Bus Session Message Bus Socket.
mars 31 00:37:41 lenovo06 systemd[613]: Stopping -.slice.
mars 31 00:37:41 lenovo06 systemd[613]: Removed slice -.slice.
mars 31 00:37:41 lenovo06 systemd[613]: Starting Shutdown.
mars 31 00:37:41 lenovo06 systemd[613]: Reached target Shutdown.
mars 31 00:37:41 lenovo06 systemd[613]: Starting Exit the Session...
mars 31 00:37:41 lenovo06 systemd[613]: Received SIGRTMIN+24 from PID 1438 (kill).
mars 31 00:37:41 lenovo06 systemd[615]: pam_unix(systemd-user:session): session closed for user alice
mars 31 00:37:41 lenovo06 systemd[1]: Stopping user-1000.slice.
mars 31 00:37:41 lenovo06 systemd[1]: Removed slice user-1000.slice.


# systemctl status user@1000.service
● user@1000.service - User Manager for UID 1000
   Loaded: loaded (/usr/lib/systemd/system/user@.service; static)
   Active: inactive (dead)

mars 31 00:37:41 lenovo06 systemd[613]: Stopping D-Bus Session Message Bus Socket.
mars 31 00:37:41 lenovo06 systemd[613]: Closed D-Bus Session Message Bus Socket.
mars 31 00:37:41 lenovo06 systemd[613]: Stopping -.slice.
mars 31 00:37:41 lenovo06 systemd[613]: Removed slice -.slice.
mars 31 00:37:41 lenovo06 systemd[613]: Starting Shutdown.
mars 31 00:37:41 lenovo06 systemd[613]: Reached target Shutdown.
mars 31 00:37:41 lenovo06 systemd[613]: Starting Exit the Session...
mars 31 00:37:41 lenovo06 systemd[613]: Received SIGRTMIN+24 from PID 1438 (kill).
mars 31 00:37:41 lenovo06 systemd[615]: pam_unix(systemd-user:session): session closed for user alice
mars 31 00:37:41 lenovo06 systemd[1]: Stopped User Manager for UID 1000.