189 lines
6.4 KiB
C
189 lines
6.4 KiB
C
// fit_a1c0_zcorr.C
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// ---------------------------------------------------------------------------
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// Linear-regression fit of the anode-only (A1C0) PC-z against the reference z,
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// to extract the per-detector scale + offset corrections used by a1c1_zcorr()
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// in TrackRecon.C.
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//
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// WORKFLOW
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// 1. Set the 4 correction params to 0 (the default in TrackRecon.C now) and
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// run all SOURCE runs so the A1C0 benchmark histograms hold the RAW,
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// uncorrected anode-only z vs the reference z.
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// 2. hadd the per-run outputs into one file (e.g. Output_av/all.root).
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// 3. root -l -b -q 'fit_a1c0_zcorr.C("Output_av/all.root")'
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//
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// MODEL
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// The benchmark TH2s are filled as (x = reference/truth z, y = z_a1c0 raw).
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// Profiling y over x and fitting y = A*x + B gives the linear trend.
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// a1c1_zcorr does z_corr = z_a1c0*(1-scale) - off, and we want z_corr = x,
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// so: scale = 1 - 1/A off = B/A
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// (Equivalent to OLS on the scatter; the profile gives clean per-bin means
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// and avoids the per-event spread destabilising the fit.)
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//
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// CAVEAT
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// Smaller residual width alone is NOT proof of a correct scale: as scale->1
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// the estimate collapses to a constant. The fit below pins the slope, so the
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// corrected A1C0-vs-ref slope should come out ~1 by construction. Always
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// re-run with the printed params and confirm the corrected slope is ~1.
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// ---------------------------------------------------------------------------
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#include <TFile.h>
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#include <TH2.h>
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#include <TProfile.h>
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#include <TF1.h>
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#include <TKey.h>
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#include <TDirectory.h>
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#include <iostream>
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#include <string>
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#include <vector>
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// Recursively search a directory tree for the first TH2 whose name matches.
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static TH2 *findTH2(TDirectory *dir, const std::string &name)
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{
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// direct hit in this directory
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if (TObject *o = dir->Get(name.c_str()))
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if (o->InheritsFrom(TH2::Class()))
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return static_cast<TH2 *>(o);
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TIter next(dir->GetListOfKeys());
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while (TKey *key = static_cast<TKey *>(next()))
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{
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TObject *obj = key->ReadObj();
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if (obj->InheritsFrom(TDirectory::Class()))
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{
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if (TH2 *h = findTH2(static_cast<TDirectory *>(obj), name))
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return h;
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}
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else if (obj->InheritsFrom(TH2::Class()) && name == obj->GetName())
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{
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return static_cast<TH2 *>(obj);
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}
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}
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return nullptr;
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}
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// Try a list of candidate histogram names, fit the first one found.
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// Returns true and sets scale/off on success.
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static bool fitOne(TFile *f, const char *label,
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const std::vector<std::string> &candidates,
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double fitlo, double fithi,
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double &scale, double &off)
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{
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TH2 *h2 = nullptr;
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std::string used;
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for (const auto &nm : candidates)
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{
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h2 = findTH2(f, nm);
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if (h2)
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{
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used = nm;
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break;
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}
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}
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if (!h2)
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{
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std::cout << "[" << label << "] none of the candidate histograms were found:\n";
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for (const auto &nm : candidates)
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std::cout << " " << nm << "\n";
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return false;
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}
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// ProfileX: mean of y (z_a1c0) in each x (reference) bin.
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TProfile *prof = h2->ProfileX((used + "_pfx").c_str());
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if (prof->GetEntries() < 1)
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{
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std::cout << "[" << label << "] profile from '" << used << "' is empty.\n";
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return false;
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}
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TF1 fpol("fpol", "pol1", fitlo, fithi);
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prof->Fit(&fpol, "QR"); // Quiet, restrict to range
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double B = fpol.GetParameter(0); // intercept
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double A = fpol.GetParameter(1); // slope
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double Aerr = fpol.GetParError(1);
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if (A == 0.0)
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{
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std::cout << "[" << label << "] degenerate slope (A=0), cannot invert.\n";
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return false;
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}
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scale = 1.0 - 1.0 / A;
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off = B / A;
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std::cout << "------------------------------------------------------------\n";
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std::cout << "[" << label << "] hist: " << used << "\n";
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std::cout << " entries (2D) : " << (Long64_t)h2->GetEntries() << "\n";
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std::cout << " fit range : [" << fitlo << ", " << fithi << "] mm\n";
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std::cout << " z_a1c0 = A*z_ref + B\n";
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std::cout << " A (slope) : " << A << " +/- " << Aerr << "\n";
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std::cout << " B (intercept) : " << B << " mm\n";
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std::cout << " => scale = 1-1/A : " << scale << "\n";
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std::cout << " off = B/A : " << off << " mm\n";
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return true;
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}
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void fit_a1c0_zcorr(const char *filename,
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double fitlo = -150.0, double fithi = 150.0)
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{
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TFile *f = TFile::Open(filename, "READ");
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if (!f || f->IsZombie())
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{
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std::cerr << "Cannot open file: " << filename << std::endl;
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return;
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}
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std::cout << "\n==================== A1C0 z-correction fit ====================\n";
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std::cout << "file: " << filename << "\n";
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double scale_qqq = 0, off_qqq = 0, scale_sx3 = 0, off_sx3 = 0;
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// QQQ: only a _vs_ref benchmark is filled (A1C2 crossover is the truth).
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bool okQ = fitOne(f, "QQQ",
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{"Benchmark_QQQ_PCZ_A1C0_Hyb_vs_ref",
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"Benchmark_QQQ_PCZ_A1C0_vs_ref",
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"Benchmark_QQQ_PCZ_A1C0_Hyb_vs_qqqpczguess"},
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fitlo, fithi, scale_qqq, off_qqq);
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// SX3: prefer the source-run geometric guess (fixed-vertex truth), fall
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// back to the A1C2 reference.
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bool okS = fitOne(f, "SX3",
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{"Benchmark_SX3_PCZ_A1C0_Hyb_vs_sx3pczguess",
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"Benchmark_SX3_PCZ_A1C0_Hyb_vs_ref",
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"Benchmark_SX3_PCZ_A1C0_vs_sx3pczguess"},
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fitlo, fithi, scale_sx3, off_sx3);
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std::cout << "\n==================== paste-ready output ====================\n";
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if (okQ || okS)
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{
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std::cout << "// --- TrackRecon.C Begin() dataset block ---\n";
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if (okQ)
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{
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std::cout << "double a1c1_z_scale_qqq = " << scale_qqq << ";\n";
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std::cout << "double a1c1_z_off_qqq = " << off_qqq << ";\n";
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}
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if (okS)
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{
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std::cout << "double a1c1_z_scale_sx3 = " << scale_sx3 << ";\n";
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std::cout << "double a1c1_z_off_sx3 = " << off_sx3 << ";\n";
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}
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std::cout << "\n// --- or as environment overrides ---\n";
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if (okQ)
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{
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std::cout << "export A1C1_Z_SCALE_QQQ=" << scale_qqq << "\n";
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std::cout << "export A1C1_Z_OFF_QQQ=" << off_qqq << "\n";
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}
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if (okS)
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{
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std::cout << "export A1C1_Z_SCALE_SX3=" << scale_sx3 << "\n";
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std::cout << "export A1C1_Z_OFF_SX3=" << off_sx3 << "\n";
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}
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}
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else
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{
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std::cout << "No histograms fitted -- check the file and run with source data.\n";
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}
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std::cout << "============================================================\n\n";
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f->Close();
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}
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