1 INTRODUCTION  
2 METHODOLOGY  
2.1 Data sets  
2.2 Source selection  
2.3 Analysis  
3 THE NATURE OF H α EMITTERS AT $Z\sim2$  
4 MATCHED LY α AND H α EMITTERS: THE LY α ESCAPE FRACTION AT $Z\sim2.23$  
5 H α SFR VS UV AND UV+IR: A CONSISTENT VIEW  
6 SFR VERSUS STELLAR MASS RELATION AND ITS UNCERTAINTIES AT $Z\sim2$  
6.1 The main sequence for H α emitters at $z\sim2$  
6.2 Uncertainties in the SFR-mass relation  
7 CONCLUSIONS