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On Fitting Manuela Cirilli. Roma, 25 novembre 2002Manuela CirilliFIT/2 * Global 6 parameters fit: * 2 Fermi-Dirac functions with fixed KT * constant background.

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Presentation on theme: "On Fitting Manuela Cirilli. Roma, 25 novembre 2002Manuela CirilliFIT/2 * Global 6 parameters fit: * 2 Fermi-Dirac functions with fixed KT * constant background."— Presentation transcript:

1 On Fitting Manuela Cirilli

2 Roma, 25 novembre 2002Manuela CirilliFIT/2 * Global 6 parameters fit: * 2 Fermi-Dirac functions with fixed KT * constant background * Global 8 parameters fit: * 2 Fermi-Dirac functions with KT as free parameters * constant background * Rising and falling edge fit: * 1 Fermi-Dirac with KT as free parameters + constant background * Fit options: * 2 fit ? * Log likelihood? * It is crucial to establish a reliable and agreed on method * Global 6 parameters fit: * 2 Fermi-Dirac functions with fixed KT * constant background * Global 8 parameters fit: * 2 Fermi-Dirac functions with KT as free parameters * constant background * Rising and falling edge fit: * 1 Fermi-Dirac with KT as free parameters + constant background * Fit options: * 2 fit ? * Log likelihood? * It is crucial to establish a reliable and agreed on method TDC spectrum fits

3 Roma, 25 novembre 2002Manuela CirilliFIT/3 * Standard 2 option 6 parameters fit Tmax=1305 T0= Tmax=1305 T0= * 2 steps: * Bounded fit * Log likelihood * 2 steps: * Bounded fit * Log likelihood Tmax= 1308 T0= Tmax= 1308 T0= 407.7

4 Roma, 25 novembre 2002Manuela CirilliFIT/4 * Standard 2 option 6 parameters fit Tmax= 1346 T0= Tmax= 1346 T0= * 2 steps: * Bounded fit * Log likelihood * 2 steps: * Bounded fit * Log likelihood Tmax= 1350 T0= Tmax= 1350 T0= 414.7

5 Roma, 25 novembre 2002Manuela CirilliFIT/5 6 parameters fit * The problem lies in the KT values

6 Roma, 25 novembre 2002Manuela CirilliFIT/6 A better way: 8 parameters fit * Better 2 /ndf * Less dependence on the fit options * This is implemented in calib, together with automatic search of input parameters to the fit * Works really fine! …is this the end of the story? * Better 2 /ndf * Less dependence on the fit options * This is implemented in calib, together with automatic search of input parameters to the fit * Works really fine! …is this the end of the story?

7 Roma, 25 novembre 2002Manuela CirilliFIT/7 Lets try and fit T 0 and T max separately

8 Roma, 25 novembre 2002Manuela CirilliFIT/8 Difference in T 0 * T 0 (8 parameters) - T 0 (rising edge) * Look at a good-behaved chamber (BIS) * T 0 (8 parameters) - T 0 (rising edge) * Look at a good-behaved chamber (BIS)ML2ML2 T0=1.9 counts T0=1.9 countsML1ML1 T0=2.06 counts T0=2.06 counts

9 Roma, 25 novembre 2002Manuela CirilliFIT/9 Difference in T max * T max (8 parameters) - T max (rising edge) * Look at a good-behaved chamber (BIS) * T max (8 parameters) - T max (rising edge) * Look at a good-behaved chamber (BIS)ML2ML2 Tmax=-2.2 counts Tmax=-2.2 counts ML1ML1 Tmax=-2.6 counts Tmax=-2.6 counts

10 Roma, 25 novembre 2002Manuela CirilliFIT/10 Stability of the T 0 fit * Wide region of stability for regular spectra for regular spectra * Wide region of stability for regular spectra for regular spectra T0T0 T fit 2 /ndf

11 Roma, 25 novembre 2002Manuela CirilliFIT/11 Stability of the T max fit * Wide region of stability for regular spectra for regular spectra * Wide region of stability for regular spectra for regular spectra T max T fit 2 /ndf

12 Roma, 25 novembre 2002Manuela CirilliFIT/12 * The separate fit of T0 and Tmax seems the best option * Stability studies to be done on large number of runs/chambers and on high rate spectra * Study the cases of not well behaved spectra * The separate fit of T0 and Tmax seems the best option * Stability studies to be done on large number of runs/chambers and on high rate spectra * Study the cases of not well behaved spectra Conclusions


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