/**************************************************************************
 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

/* $Id$ */

//*-- Author: Andreas Morsch (CERN)

#include "AliEMCALFast.h"
#include <TRandom.h>


ClassImp(AliEMCALFast)

//____________________________________________________________________________


Float_t AliEMCALFast::SmearMomentum(Int_t ind, Float_t p)
{
//
//  The relative momentum error, i.e. (delta p)/p = sqrt (a**2 + (b*p)**2) *
//  10**-2,
//  where typically a = 0.75 and b = 0.16 - 0.24 depending on multiplicity
//  (the lower value is for dn/d(eta) about 2000, and the higher one for 8000)
//
    Float_t pSmeared;
    Float_t a = 0.75;
    Float_t b = 0.24;
    if (ind == 2) b = 0.16;
    
    Float_t sigma = p*TMath::Sqrt(a*a+b*b*p*p)*0.01;
    pSmeared = p + gRandom->Gaus(0., sigma);
    return pSmeared;
}


Float_t AliEMCALFast::Efficiency(Int_t ind, Float_t p)
{
// Tracking efficiency:
// above pt 0.5 GeV practically constant, between 90 and 95 % (agian,
// depending on multplicity)
// below 0.5 GeV goes down to about 70% at 0.2 GeV.
// On top of that there is 90% geometrical acceptance for tracking due
// to TPC (dead zones between readout chambers).  
    Float_t eff = 0.;
// Tracking 
    if (p > 0.5) {
	eff = 0.9;
	if (ind == 2) eff = 0.95;
    } else {
	eff = eff-(0.5-p)*0.2/0.3;
    }
    eff*= 0.9;
// Acceptance    
    return eff;
}