text: #ifndef _HLTHFAsymmetryFilter_H
  #define _HLTHFAsymmetryFilter_H
  
  
  ///////////////////////////////////////////////////////
  //
  // HLTHFAsymetryFilter
  //
  // Filter definition
  //
  // We perform a selection on HF energy repartition 
  //
  // This filter is primarily used to select Beamgas (aka PKAM) events
  // 
  // An asymmetry parameter, based on the pixel clusters, is computed as follows
  // 
  //  asym1 = E_HF-/(E_HF- + E_HF+) for beam1
  //  asym2 = E_HF+/(E_HF- + E_HF+) for beam2 
  //
  // where E_HF is the total energy of clusters passing a certain threshold (given by eCut_HF_)
  //
  //  Usually for PKAM events, asym1 is close to 1. for B1 BGas events, and close to 0 for B2 BGAS events  
  //
  //
  // More details:
  // http://sviret.web.cern.ch/sviret/Welcome.php?n=CMS.MIB
  //
  // S.Viret: 12/01/2011 (viret@in2p3.fr)
  //
  ///////////////////////////////////////////////////////
  
  
  // system include files
  #include <memory>
  
  // user include files
  #include "DataFormats/HcalRecHit/interface/HcalRecHitCollections.h"
  #include "FWCore/Framework/interface/Frameworkfwd.h"
  #include "FWCore/Framework/interface/Event.h"
  #include "FWCore/Framework/interface/EDFilter.h"
  #include "FWCore/ParameterSet/interface/ParameterSet.h"
  #include "FWCore/ParameterSet/interface/ConfigurationDescriptions.h"
  #include "FWCore/ParameterSet/interface/ParameterSetDescription.h"
  #include "FWCore/Utilities/interface/InputTag.h"
  
  //
  // class decleration
  //
  
  class HLTHFAsymmetryFilter : public edm::EDFilter {
     public:
        explicit HLTHFAsymmetryFilter(const edm::ParameterSet&);
        ~HLTHFAsymmetryFilter();
  
        static void fillDescriptions(edm::ConfigurationDescriptions & descriptions);
        virtual bool filter(edm::Event &, const edm::EventSetup&);
     private:
        // ----------member data ---------------------------
  
   edm::EDGetTokenT<HFRecHitCollection> HFHitsToken_;
   edm::InputTag HFHits_;
   double eCut_HF_;
   double os_asym_;
   double ss_asym_;
  
  };
  
  #endif // _HLTHFAsymmetryFilter_H
  