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1 | /************************************************************************** |
| 2 | * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. * |
| 3 | * * |
| 4 | * Author: The ALICE Off-line Project. * |
| 5 | * Contributors are mentioned in the code where appropriate. * |
| 6 | * * |
| 7 | * Permission to use, copy, modify and distribute this software and its * |
| 8 | * documentation strictly for non-commercial purposes is hereby granted * |
| 9 | * without fee, provided that the above copyright notice appears in all * |
| 10 | * copies and that both the copyright notice and this permission notice * |
| 11 | * appear in the supporting documentation. The authors make no claims * |
| 12 | * about the suitability of this software for any purpose. It is * |
| 13 | * provided "as is" without express or implied warranty. * |
| 14 | **************************************************************************/ |
| 15 | |
| 16 | //-----------------------------------------------------------------// |
| 17 | // // |
| 18 | // Implementation of the TOF PID class // |
| 19 | // Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch // |
| 20 | // // |
| 21 | //-----------------------------------------------------------------// |
| 22 | |
| 23 | #include "TMath.h" |
| 24 | #include "AliLog.h" |
| 25 | |
| 26 | #include "AliTOFPIDResponse.h" |
| 27 | |
| 28 | ClassImp(AliTOFPIDResponse) |
| 29 | |
| 30 | //_________________________________________________________________________ |
| 31 | AliTOFPIDResponse::AliTOFPIDResponse(): |
| 32 | fSigma(0), |
| 33 | fPmax(0), // zero at 0.5 GeV/c for pp |
| 34 | fTime0(0) |
| 35 | { |
| 36 | } |
| 37 | //_________________________________________________________________________ |
| 38 | AliTOFPIDResponse::AliTOFPIDResponse(Double_t *param): |
| 39 | fSigma(param[0]), |
| 40 | fPmax(0), // zero at 0.5 GeV/c for pp |
| 41 | fTime0(0) |
| 42 | { |
| 43 | // |
| 44 | // The main constructor |
| 45 | // |
| 46 | // |
| 47 | |
| 48 | //fPmax=TMath::Exp(-0.5*3*3)/fSigma; // ~3 sigma at 0.5 GeV/c for PbPb |
| 49 | } |
| 50 | //_________________________________________________________________________ |
| 51 | Double_t |
| 52 | AliTOFPIDResponse::GetMismatchProbability(Double_t p, Double_t mass) const { |
| 53 | // |
| 54 | // Returns the probability of mismatching |
| 55 | // assuming 1/(p*beta)^2 scaling |
| 56 | // |
| 57 | const Double_t km=0.5; // "reference" momentum (GeV/c) |
| 58 | |
| 59 | Double_t ref2=km*km*km*km/(km*km + mass*mass);// "reference" (p*beta)^2 |
| 60 | Double_t p2beta2=p*p*p*p/(p*p + mass*mass); |
| 61 | |
| 62 | return fPmax*ref2/p2beta2; |
| 63 | } |
| 64 | //_________________________________________________________________________ |
| 65 | Double_t AliTOFPIDResponse::GetExpectedSigma(Float_t mom, Float_t time, Float_t mass) const { |
| 66 | // |
| 67 | // Return the expected sigma of the PID signal for the specified |
| 68 | // particle type. |
| 69 | // If the operation is not possible, return a negative value. |
| 70 | // |
| 71 | |
| 72 | Double_t dpp = 0.01; //mean relative pt resolution; |
| 73 | if (mom>0.5) dpp = 0.01*mom; |
| 74 | |
| 75 | |
| 76 | Double_t sigma = dpp*time/(1.+ mom*mom/(mass*mass)); |
| 77 | |
| 78 | return TMath::Sqrt(sigma*sigma + fSigma*fSigma); |
| 79 | } |
| 80 | |
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