Generally this are neutrophil markers: CD16 CD11b, CD14, CD66b,

http://www.biolegend.com/cell_markers

The most frequently used one (in clinical hematology analysis) is... granularity.  In other words a particular forward scatter x side-scatter population on a flow cytometer.  That works so well, it's sufficient for clinical diagnostic purposes.  You can certainly trust the scatter properties alone for research purposes. 

Thanks for the input, but I should have been more clear in my question. I am looking for markers that differentiate immature neutrophils from mature neutrophils. I am familiar with the normal neutrophil markers, but I don't know which are absent on immature neutrophils. 

Definitely you should be more specific ;)

As for the neutrophils,  "young" neutrophils have low expression of CD16 (but you have to be careful - low CD16 expression can be also observed on apoptotic cells).