Logging on as a logon with sysadmin Server roles   and executing the following sql statement :

 select * from sys.sysprocesses

 will return sysprocesses of all users on the server .

 Logging on as a logon with with db_datareader permissions on a database    and executing the following sql statement :

 select * from sys.sysprocesses

 will only return the users process.

 This is because , if a user does not have VIEW SERVER STATE permission on the server , the user will only view their own session.

 The syntax to grant permission is

 GRANT VIEW SERVER STATE TO user

Ref:Jack Vamvas (http://www.sqlserver-dba.com)