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File indexing completed on 2024-04-06 12:31:19
0001 // 0002 // 0003 // File: src/Vector_Resolution.cc 0004 // Purpose: Calculate resolutions in p, phi, eta. 0005 // Created: Jul, 2000, sss, based on run 1 mass analysis code. 0006 // 0007 // CMSSW File : src/Vector_Resolution.cc 0008 // Original Author : Scott Stuart Snyder <snyder@bnl.gov> for D0 0009 // Imported to CMSSW by Haryo Sumowidagdo <Suharyo.Sumowidagdo@cern.ch> 0010 // 0011 0012 /** 0013 @file Vector_Resolution.cc 0014 0015 @brief Calculate and represent resolution for a vector 0016 of momentum \f$p\f$, pseudorapidity \f$\eta\f$, and azimuthal 0017 angle \f$\phi\f$. See the documentation for the header file 0018 Vector_Resolution.h for details. 0019 0020 @author Scott Stuart Snyder <snyder@bnl.gov> 0021 0022 @par Creation date: 0023 Jul 2000. 0024 0025 @par Modification History: 0026 Apr 2009: Haryo Sumowidagdo <Suharyo.Sumowidagdo@cern.ch>: 0027 Imported to CMSSW.<br> 0028 Nov 2009: Haryo Sumowidagdo <Suharyo.Sumowidagdo@cern.ch>: 0029 Added doxygen tags for automatic generation of documentation. 0030 0031 @par Terms of Usage: 0032 With consent for the original author (Scott Snyder). 0033 0034 */ 0035 0036 #include "TopQuarkAnalysis/TopHitFit/interface/Vector_Resolution.h" 0037 #include "TopQuarkAnalysis/TopHitFit/interface/fourvec.h" 0038 #include <cmath> 0039 #include <ostream> 0040 #include <cctype> 0041 0042 using std::isspace; 0043 using std::ostream; 0044 using std::string; 0045 0046 namespace { 0047 0048 /** 0049 @brief Helper function: extract the <i>i</i>-th slash-separated field 0050 from a string. 0051 0052 @param s The string to analyze. 0053 0054 @param i The field number, starting from 0. 0055 */ 0056 string field(string s, int i) 0057 // 0058 // Purpose: Extract the Ith slash-separated field from S. 0059 // 0060 // Inputs: 0061 // s - The string to analyze. 0062 // i - Field number (starting with 0). 0063 // 0064 // Returns: 0065 // Field I of S. 0066 // 0067 { 0068 string::size_type pos = 0; 0069 while (i > 0) { 0070 pos = s.find('/', pos); 0071 if (pos == string::npos) 0072 return ""; 0073 ++pos; 0074 --i; 0075 } 0076 0077 string::size_type pos2 = s.find('/', pos + 1); 0078 if (pos2 != string::npos) 0079 pos2 = pos2 - pos; 0080 0081 while (pos < pos2 && isspace(s[pos])) 0082 ++pos; 0083 0084 return s.substr(pos, pos2); 0085 } 0086 0087 } // unnamed namespace 0088 0089 namespace hitfit { 0090 0091 Vector_Resolution::Vector_Resolution() 0092 // 0093 // Purpose: Default constructor. Create a vector resolution object with 0094 // infinite precision.v 0095 // 0096 : _p_res("0,0,0"), 0097 _eta_res("0,0,0"), 0098 _phi_res("0,0,0"), 0099 _use_et(false) 0100 0101 {} 0102 0103 Vector_Resolution::Vector_Resolution(std::string s) 0104 // 0105 // Purpose: Constructor. 0106 // 0107 // Inputs: 0108 // s - String encoding the resolution parameters, as described 0109 // in the comments in the header. 0110 // 0111 : _p_res(field(s, 0)), _eta_res(field(s, 1)), _phi_res(field(s, 2)), _use_et(field(s, 3) == "et") {} 0112 0113 Vector_Resolution::Vector_Resolution(const Resolution& p_res, 0114 const Resolution& eta_res, 0115 const Resolution& phi_res, 0116 bool use_et /*= false*/) 0117 // 0118 // Purpose: Constructor from individual resolution objects. 0119 // 0120 // Inputs: 0121 // p_res - Momentum resolution object. 0122 // eta_res - Eta resolution object. 0123 // phi_res - Phi resolution object. 0124 // use_et - If true, momentum resolution is based on pt, not p. 0125 // 0126 : _p_res(p_res), _eta_res(eta_res), _phi_res(phi_res), _use_et(use_et) {} 0127 0128 const Resolution& Vector_Resolution::p_res() const 0129 // 0130 // Purpose: Return the momentum resolution object. 0131 // 0132 // Returns: 0133 // The momentum resolution object. 0134 // 0135 { 0136 return _p_res; 0137 } 0138 0139 const Resolution& Vector_Resolution::eta_res() const 0140 // 0141 // Purpose: Return the eta resolution object. 0142 // 0143 // Returns: 0144 // The eta resolution object. 0145 // 0146 { 0147 return _eta_res; 0148 } 0149 0150 const Resolution& Vector_Resolution::phi_res() const 0151 // 0152 // Purpose: Return the phi resolution object. 0153 // 0154 // Returns: 0155 // The phi resolution object. 0156 // 0157 { 0158 return _phi_res; 0159 } 0160 0161 bool Vector_Resolution::use_et() const 0162 // 0163 // Purpose: Return the use_et flag. 0164 // 0165 // Returns: 0166 // The use_et flag. 0167 // 0168 { 0169 return _use_et; 0170 } 0171 0172 namespace { 0173 0174 /** 0175 @brief Helper function: calculate the uncertainty/resolution \f$\sigma\f$ 0176 for the momentum of a four-momentum. 0177 0178 @param v The four-momentum. 0179 0180 @param res The resolution object. 0181 0182 @param use_et If <b>TRUE</b> then use \f$p_{T}\f$ instead of \f$p\f$ 0183 for momentum resolution. 0184 */ 0185 double find_sigma(const Fourvec& v, const Resolution& res, bool use_et) 0186 // 0187 // Purpose: Helper for *_sigma functions below. 0188 // 0189 // Inputs: 0190 // v - The 4-vector. 0191 // res - The resolution object. 0192 // use_et - Use_et flag. 0193 // 0194 // Returns: 0195 // The result of res.sigma() (not corrected for e/et difference). 0196 // 0197 { 0198 double ee = use_et ? v.perp() : v.e(); // ??? is perp() correct here? 0199 return res.sigma(ee); 0200 } 0201 0202 } // unnamed namespace 0203 0204 double Vector_Resolution::p_sigma(const Fourvec& v) const 0205 // 0206 // Purpose: Calculate momentum resolution for 4-vector V. 0207 // 0208 // Inputs: 0209 // v - The 4-vector. 0210 // 0211 // Returns: 0212 // The momentum resolution for 4-vector V. 0213 // 0214 { 0215 double sig = find_sigma(v, _p_res, _use_et); 0216 if (_use_et) { 0217 if (_p_res.inverse()) { 0218 sig *= v.perp() / v.e(); 0219 } else { 0220 sig *= v.e() / v.perp(); 0221 } 0222 } 0223 return sig; 0224 } 0225 0226 double Vector_Resolution::eta_sigma(const Fourvec& v) const 0227 // 0228 // Purpose: Calculate eta resolution for 4-vector V. 0229 // 0230 // Inputs: 0231 // v - The 4-vector. 0232 // 0233 // Returns: 0234 // The eta resolution for 4-vector V. 0235 // 0236 { 0237 return find_sigma(v, _eta_res, _use_et); 0238 } 0239 0240 double Vector_Resolution::phi_sigma(const Fourvec& v) const 0241 // 0242 // Purpose: Calculate phi resolution for 4-vector V. 0243 // 0244 // Inputs: 0245 // v - The 4-vector. 0246 // 0247 // Returns: 0248 // The phi resolution for 4-vector V. 0249 // 0250 { 0251 return find_sigma(v, _phi_res, _use_et); 0252 } 0253 0254 namespace { 0255 0256 /** 0257 @brief Helper function: smear the pseudorapidity of a four-momentum 0258 0259 @param v The four-momentum to smear. 0260 0261 @param ee The energy for \f$sigma\f$ calculation. 0262 0263 @param res The resolution object, giving the amount of smearing. 0264 0265 @param engine The underlying random number generator. 0266 */ 0267 void smear_eta(Fourvec& v, double ee, const Resolution& res, CLHEP::HepRandomEngine& engine) 0268 // 0269 // Purpose: Smear the eta direction of V. 0270 // 0271 // Inputs: 0272 // v - The 4-vector to smear. 0273 // ee - Energy for sigma calculation. 0274 // res - The resolution object, giving the amount of smearing. 0275 // engine - The underlying RNG. 0276 // 0277 // Outputs: 0278 // v - The smeared 4-vector. 0279 // 0280 { 0281 double rot = res.pick(0, ee, engine); 0282 roteta(v, rot); 0283 } 0284 0285 /** 0286 @brief Helper function: smear the azimuthal angle of a four-momentum 0287 0288 @param v The four-momentum to smear. 0289 0290 @param ee The energy for \f$sigma\f$ calculation. 0291 0292 @param res The resolution object, giving the amount of smearing. 0293 0294 @param engine The underlying random number generator. 0295 */ 0296 void smear_phi(Fourvec& v, double ee, const Resolution& res, CLHEP::HepRandomEngine& engine) 0297 // 0298 // Purpose: Smear the phi direction of V. 0299 // 0300 // Inputs: 0301 // v - The 4-vector to smear. 0302 // ee - Energy for sigma calculation. 0303 // res - The resolution object, giving the amount of smearing. 0304 // engine - The underlying RNG. 0305 // 0306 // Outputs: 0307 // v - The smeared 4-vector. 0308 // 0309 { 0310 double rot = res.pick(0, ee, engine); 0311 v.rotateZ(rot); 0312 } 0313 0314 } // unnamed namespace 0315 0316 void Vector_Resolution::smear(Fourvec& v, CLHEP::HepRandomEngine& engine, bool do_smear_dir /*= false*/) const 0317 // 0318 // Purpose: Smear a 4-vector according to the resolutions. 0319 // 0320 // Inputs: 0321 // v - The 4-vector to smear. 0322 // engine - The underlying RNG. 0323 // do_smear_dir- If false, only smear the energy. 0324 // 0325 // Outputs: 0326 // v - The smeared 4-vector. 0327 // 0328 { 0329 double ee = _use_et ? v.perp() : v.e(); // ??? is perp() correct? 0330 v *= _p_res.pick(ee, ee, engine) / ee; 0331 0332 if (do_smear_dir) { 0333 smear_eta(v, ee, _eta_res, engine); 0334 smear_phi(v, ee, _phi_res, engine); 0335 } 0336 } 0337 0338 /** 0339 @brief Output stream operator, print the content of this Vector_Resolution 0340 object to an output stream. 0341 0342 @param s The stream to which to write. 0343 0344 @param r The instance of Vector_Resolution to be printed. 0345 */ 0346 std::ostream& operator<<(std::ostream& s, const Vector_Resolution& r) 0347 // 0348 // Purpose: Dump this object to S. 0349 // 0350 // Inputs: 0351 // s - The stream to which to write. 0352 // r - The object to dump. 0353 // 0354 // Returns: 0355 // The stream S. 0356 // 0357 { 0358 s << r._p_res << "/ " << r._eta_res << "/ " << r._phi_res; 0359 if (r._use_et) 0360 s << "/et"; 0361 s << "\n"; 0362 return s; 0363 } 0364 0365 } // namespace hitfit
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