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1 | /////////////////////////////////////////////////////////////////////////// |
2 | // | |
3 | // Copyright 2010 | |
4 | // | |
5 | // This file is part of starlight. | |
6 | // | |
7 | // starlight is free software: you can redistribute it and/or modify | |
8 | // it under the terms of the GNU General Public License as published by | |
9 | // the Free Software Foundation, either version 3 of the License, or | |
10 | // (at your option) any later version. | |
11 | // | |
12 | // starlight is distributed in the hope that it will be useful, | |
13 | // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | // GNU General Public License for more details. | |
16 | // | |
17 | // You should have received a copy of the GNU General Public License | |
18 | // along with starlight. If not, see <http://www.gnu.org/licenses/>. | |
19 | // | |
20 | /////////////////////////////////////////////////////////////////////////// | |
21 | // | |
22 | // File and Version Information: | |
23 | // $Rev:: 45 $: revision of last commit | |
24 | // $Author:: bgrube $: author of last commit | |
25 | // $Date:: 2011-02-27 20:52:35 +0100 #$: date of last commit | |
26 | // | |
27 | // Description: | |
28 | // | |
29 | // | |
30 | // | |
31 | /////////////////////////////////////////////////////////////////////////// | |
32 | ||
33 | ||
34 | #include <iostream> | |
35 | #include <fstream> | |
36 | #include <cmath> | |
37 | ||
38 | #include "starlightconstants.h" | |
39 | #include "incoherentVMCrossSection.h" | |
40 | ||
41 | ||
42 | using namespace std; | |
43 | using namespace starlightConstants; | |
44 | ||
45 | ||
46 | //______________________________________________________________________________ | |
47 | incoherentVMCrossSection::incoherentVMCrossSection(const beamBeamSystem& bbsystem) | |
48 | :photonNucleusCrossSection(bbsystem) | |
49 | { | |
50 | _narrowYmax = inputParametersInstance.maxRapidity(); | |
51 | _narrowYmin = -1.0*_narrowYmax; | |
52 | _narrowNumY = inputParametersInstance.nmbRapidityBins(); | |
53 | _Ep = inputParametersInstance.protonEnergy(); | |
54 | } | |
55 | ||
56 | ||
57 | //______________________________________________________________________________ | |
58 | incoherentVMCrossSection::~incoherentVMCrossSection() | |
59 | { } | |
60 | ||
61 | ||
62 | //______________________________________________________________________________ | |
63 | void | |
64 | incoherentVMCrossSection::crossSectionCalculation(const double) // _bwnormsave (unused) | |
65 | { | |
66 | // This subroutine calculates the vector meson cross section assuming | |
67 | // a narrow resonance. For reference, see STAR Note 386. | |
68 | ||
69 | // double Av,Wgp,cs,cvma; | |
70 | double W,dY; | |
71 | double y1,y2,y12,ega1,ega2,ega12; | |
72 | // double t,tmin,tmax; | |
73 | double csgA1,csgA2,csgA12,int_r,dR,rate; | |
74 | double Wgp,csVN,csVA; | |
75 | double tmp; | |
76 | // double ax,bx; | |
77 | double Eth; | |
78 | int J,NY; | |
79 | // int K,NGAUSS; | |
80 | ||
81 | NY = _narrowNumY; | |
82 | dY = (_narrowYmax-_narrowYmin)/double(NY); | |
83 | ||
84 | cout<<" Using Narrow Resonance ..."<<endl; | |
85 | ||
86 | W = getChannelMass(); | |
87 | Eth=0.5*(((W+protonMass)*(W+protonMass)- | |
88 | protonMass*protonMass)/(_Ep+sqrt(_Ep*_Ep-protonMass*protonMass))); | |
89 | ||
90 | cout<<" gamma+nucleon Threshold: "<<Eth<<endl; | |
91 | int_r=0.; | |
92 | ||
93 | tmp = 0.0; | |
94 | ||
95 | for(J=0;J<=(NY-1);J++){ | |
96 | ||
97 | y1 = _narrowYmin + double(J)*dY; | |
98 | y2 = _narrowYmin + double(J+1)*dY; | |
99 | y12 = 0.5*(y1+y2); | |
100 | ||
101 | ega1 = 0.5*W*exp(y1); | |
102 | ega2 = 0.5*W*exp(y2); | |
103 | ega12 = 0.5*W*exp(y12); | |
104 | ||
105 | if(ega1 < Eth) | |
106 | continue; | |
107 | if(ega2 > maxPhotonEnergy()) | |
108 | continue; | |
109 | ||
110 | // First point | |
111 | Wgp = sqrt(2.*ega1*(_Ep+sqrt(_Ep*_Ep-starlightConstants::protonMass*starlightConstants::protonMass)) | |
112 | +starlightConstants::protonMass*starlightConstants::protonMass); | |
113 | csVN = sigma_N(Wgp); | |
114 | csVA = sigma_A(csVN); | |
115 | csgA1 = (csVA/csVN)*sigmagp(Wgp); | |
116 | if( getbbs().beam1().A() == 1 || getbbs().beam2().A()==1 ){ | |
117 | csgA1 = sigmagp(Wgp); | |
118 | } | |
119 | ||
120 | // Middle point | |
121 | Wgp = sqrt(2.*ega12*(_Ep+sqrt(_Ep*_Ep-starlightConstants::protonMass*starlightConstants::protonMass)) | |
122 | +starlightConstants::protonMass*starlightConstants::protonMass); | |
123 | csVN = sigma_N(Wgp); | |
124 | csVA = sigma_A(csVN); | |
125 | csgA12 = (csVA/csVN)*sigmagp(Wgp); | |
126 | if( getbbs().beam1().A() == 1 || getbbs().beam2().A()==1 ){ | |
127 | csgA12 = sigmagp(Wgp); | |
128 | } | |
129 | ||
130 | // Last point | |
131 | Wgp = sqrt(2.*ega2*(_Ep+sqrt(_Ep*_Ep-starlightConstants::protonMass*starlightConstants::protonMass)) | |
132 | +starlightConstants::protonMass*starlightConstants::protonMass); | |
133 | csVN = sigma_N(Wgp); | |
134 | csVA = sigma_A(csVN); | |
135 | csgA2 = (csVA/csVN)*sigmagp(Wgp); | |
136 | if( getbbs().beam1().A() == 1 || getbbs().beam2().A()==1 ){ | |
137 | csgA2 = sigmagp(Wgp); | |
138 | } | |
139 | ||
140 | dR = ega1*photonFlux(ega1)*csgA1; | |
141 | dR = dR + 4*ega12*photonFlux(ega12)*csgA12; | |
142 | dR = dR + ega2*photonFlux(ega2)*csgA2; | |
143 | dR = dR*(dY/6.); | |
144 | ||
145 | // cout<<" y: "<<y12<<" egamma: "<<ega12<<" flux: "<<photonFlux(ega12)<<" sigma_gA: "<<10000000.*csgA12<<" dsig/dy (microb): "<<10000.*dR/dY<<endl; | |
146 | ||
147 | // The 2 accounts for the 2 beams | |
148 | if(getbbs().beam1().A()==getbbs().beam2().A()){ | |
149 | dR = 2.*dR; | |
150 | } | |
151 | ||
152 | int_r = int_r+dR; | |
153 | ||
154 | } | |
155 | rate=luminosity()*int_r; | |
156 | cout<<" Cross section (mb): " <<10.*int_r<<endl; | |
157 | } |