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TCFIT : using testV0 from TCFit.cxx. Use macro in $StRoot/StarRoot/TCFITV0::Test() It generates D 0 (decayLength taken randomly in exp(c ) : D0Len = D0Tau*C*D0Gama*D0Beta; double dist = gRandom->Exp(D0Len);
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Use macro in $StRoot/StarRoot/TCFITV0::Test() • It generates D0 (decayLength taken randomly in exp(c) : D0Len = D0Tau*C*D0Gama*D0Beta; double dist = gRandom->Exp(D0Len); • It let decay the D0 in KPi and uses later the TCFit class to re-construct the initial D0 • The TCFit class return slength (which is positive) and the error associated • In the macro, Victor compared the decayLength from TCFit with the initial decayLength • I used 20k D0 in the following plots
Decay length (input) • similar as the plot from Spiros’s MIT talk (see next slide)
D0 decay length D0->K+pi counts ~1 c Decay Length in X-Y plane cm • Used <pt>~1GeV • 1 GeV/ =0 D0 has • Un-boost in Collider ! • Mean R-f value ~ 70 mm 4
There is a clear correlation between decay length generated and the decay length reco (red line) • The decay length that TcFit returns is either positive or negative : • There might be a ‘signed’ decay so we have to make sure to compare with what the helix swimming returns (decay in plane XY or decay 3D)
matching • Except the negative values that TCFIT returns, it • matches well with the input decayLength
Test with MuKpi macro • In the macro, I filled now : • The decay from linear fit (slength) • The decay calculated by the Helix swimming (3 methods : Global parameters (decayXY), DcaGeometry(decayXYC) and THelixTrack(decayXYT) • The decay from TCFIT (slength_tcfit) • I used here 100 D0 with vertex fixed at (0,0,0) • I noticed that it gives better results than the vertex position I used before (at (0.1,0.2,0.3)) • I do not have plots, only comparison.
Comparison with GEANT : few events decayXY decay3d ************************************************************************************ * Row * decayXY * decayXYC * decayXYT * slength * slength_t * eveId * ************************************************************************************ * 0 * 0.0639654 * 0.0636852 * 0.0697509 * -0.082695 * 0.0779094 * 1 * * 1 * 0.0624416 * 0.0621775 * 0.0787873 * -0.082695 * 0.0779452 * 1 * * 2 * 0.0077134 * 0.0076759 * 0.0376531 * -0.010074 * -0.006489 * 2 * * 3 * 0.0085079 * 0.0084608 * 0.0558257 * -0.010074 * -0.006558 * 2 * * 4 * 0.0138766 * 0.0138436 * 0.0167018 * 0.0025418 * -0.015083 * 3 * * 5 * 0.0106651 * 0.0106221 * 0.0138436 * 0.0025418 * -0.015086 * 3 * * 6 * 1.6370849 * 1.6046876 * 1.9076843 * -0.303399 * 0.3939315 * 4 * * 7 * 0.0957023 * 0.0957561 * 0.1005115 * -0.053309 * 0.0990436 * 5 * * 8 * 0.0936700 * 0.0937298 * 0.0957561 * -0.053309 * 0.0991125 * 5 * * 9 * 0.0135957 * 0.0136085 * 0.0141907 * 0.0036865 * -0.003121 * 9 * * 10 * 0.0141550 * 0.0141907 * 0.0136085 * 0.0036865 * -0.003135 * 9 * ************************************************ * Row * eve * TMath::Sq * TMath::Sq * ************************************************ * 0 * 1 * 0.0616972 * 0.0770033 * * 1 * 2 * 0.0118082 * 0.0132884 * * 2 * 3 * 0.0324287 * 0.0380093 * * 3 * 4 * 0.0588259 * 0.0620812 * * 4 * 5 * 0.0726091 * 0.0984998 * * 5 * 6 * 0.0023527 * 0.0025653 * * 6 * 7 * 0.0138945 * 0.0139567 * * 7 * 8 * 0.2153165 * 0.3037138 * * 8 * 9 * 0.0483147 * 0.0551986 * • slength_tcfit seems agree with the 3 others methods (event 1, event 5) for some case • All are agrees also for some events (event 1 is good)
