// ==========================================
// [初始化阶段] 环境建立与地址绑定
// ==========================================
//建立 ROOT 文件 (TFile)
//创建 数据树 (TTree)

// 定义本地工作区变量（数据中转站）
Int_t    val_pid;
Double_t val_e_true, val_tL, val_tR; // ... 其他变量

// 【建立地址映射】
tree->Branch("pid",    &val_pid,    "pid/I");
tree->Branch("e_true", &val_e_true, "e_true/D");
tree->Branch("tL",     &val_tL,     "tL/D");
tree->Branch("tR",     &val_tR,     "tR/D");

// ==========================================
// [事件循环阶段] 数据刷新与快照填充
// ==========================================
for (从 0 到 总事件数) {
    
    1. 计算/获取逻辑：更新内存变量的内容
       val_pid = 获取粒子ID;
       val_e_true = 获取模拟能量;
       val_tL = 计算左端响应时间;
       val_tR = 计算右端响应时间;
    
    2. 填充事件快照：
       tree->Fill(); 
}
//保存数据到磁盘
tree->Write();  // 将缓冲区内的所有事件批量压缩并写入磁盘
file->Close();  // 关闭文件，安全释放内存连接

void create_tree(){ 
    
  // 1. 常量声明
  const Int_t nEvents = 500000; 
  const Double_t D = 5.0;      // m, 靶到探测器距离
  const Double_t L = 1.0;      // m, 探测器半长
  const Double_t T = 0.05;     // m, 厚度
  const Double_t Lambda = 3.8; // m, 衰减长度
  const Double_t Vsc = 0.075;  // m/ns, 光速

  const Double_t a = 0.83;
  const Double_t b = 2.82;
  const Double_t c = 0.25;
  const Double_t d = 0.93; 

  
  const Double_t En0 = 100.0;    // MeV, 中子平均能量
  const Double_t EnFWHM = 50.0;  // MeV, 中子能量展宽 
  const Double_t Egmean = 15.0;      // MeV, Gamma能量
  const Double_t RatioGamma = 0.3;     

  const Double_t sigt_floor = 0.5;    // 高能端极限 sigma (ns)
  const Double_t sigt_no = 5;    // noise fluctuation
  const Double_t sigt_stat  = 2.0;   // 统计项系数 (ns*sqrt(ADC))  
  const Double_t Walk_AL = 40.0; // ns*sqrt(q), Walk系数: t = t_true + A/sqrt(Q)   
  const Double_t Walk_AR = 45.0; // ns*sqrt(q), Walk系数: t = t_true + A/sqrt(Q)    
    
  const Double_t gL_qe = 10;   //ee to light；
  const Double_t gR_qe = 15;   //ee to light；    
    
  const Double_t Rq = 0.1;     // 相对能量分辨率
  
  const Double_t t0L = 5.5;    
  const Double_t t0R = 20.4;   
  
  const Double_t A_th = 5;   // 阈值 

  // 2. 声明 Tree 中的变量
  Double_t x_true;  // 真实入射位置 (m)
  Double_t e_true;  // 真实能量
  Int_t pid;        // 0: Gamma, 1: Neutron
  Double_t tof_true;// 真实 TOF (ns)
  Double_t tL_true, tR_true;  // 探测器时间  
  Double_t tL, tR;  // 探测器时间
  Double_t qL, qR;  // 探测器能量
  Double_t AL, AR;  // 探测器能量

  // 3. 定义文件与 Tree
  TFile *opf = new TFile("tree.root", "recreate");
  TTree *opt = new TTree("tree", "Simulated Data");
  
  opt->Branch("x_true", &x_true, "x_true/D");
  opt->Branch("e_true", &e_true, "e_true/D");
  opt->Branch("tof_true", &tof_true, "tof_true/D");
  opt->Branch("pid", &pid, "pid/I");
  opt->Branch("tL_true", &tL_true, "tL_true/D");
  opt->Branch("tR_true", &tR_true, "tR_true/D");    
  opt->Branch("tL", &tL, "tL/D");
  opt->Branch("tR", &tR, "tR/D");
  opt->Branch("AL", &AL, "AL/D");
  opt->Branch("AR", &AR, "AR/D");

  TH1D *htof = new TH1D("htof", "Reconstructed time of flight", 1000, 0, 100);
  TRandom3 *gr = new TRandom3(0);

   std::cout << "Starting Simulation..." << std::endl;   

  // 4. 事件循环
  for(int i = 0; i < nEvents; i++){
      
     // --- 进度条提示输出 (每5%刷新一次) ---
    if (i % (nEvents / 20) == 0) {
        Double_t progress = (Double_t)i / nEvents * 100;
        std::cout << "\rProcessing: " << (int)progress << "% completed..." << std::flush;
    }     
    // --- 生成真值 ---
    x_true = gr->Uniform(-L, L);
    Double_t y_prime = gr->Uniform(-T/2.0, T/2.0); // 深度 y'
    Double_t dis = TMath::Sqrt(pow(D + y_prime, 2) + pow(x_true, 2)); // 真实距离
      
    Double_t E_dep = 0; // 沉积能量 (产生光信号的能量)
    if(gr->Uniform() < RatioGamma) { // Gamma
       pid = 0;
       e_true = gr->Exp(Egmean);
       tof_true = 3.333 * dis; // m -> ns
       E_dep = e_true;// Gamma沉积能量 
    } else { // Neutron
        pid = 1;
        e_true = En0; //中子能量，
        if(e_true <= 0) continue;
        tof_true = 72.3 / TMath::Sqrt(e_true) * dis ;
        E_dep = e_true;//中子能量沉积
    }

    // --- 探测器响应 ---
    // 时间信号
     
    tL_true = tof_true + (L + x_true)/Vsc + t0L; // x 定义方向
    
    tL = gr->Gaus(tL_true, sigt_floor);
    
    tR_true = tof_true + (L - x_true)/Vsc + t0R;
    tR = gr->Gaus(tR_true, sigt_floor);
      
    // 能量信号
    // 此处简化：暂不考虑反冲质子能量分布

    Double_t Q = E_dep; 
    qL = (Q/2.0) * TMath::Exp(-(L + x_true)/Lambda);
    qL = gr->Gaus(qL, qL * Rq/2.35);
    AL = gL_qe * qL;
    
    qR = (Q/2.0) * TMath::Exp(-(L - x_true)/Lambda);
    qR = gr->Gaus(qR, qR * Rq/2.35);
    AR = gR_qe * qR;

    if (AL < 0 || AR < 0) continue; 
      
    // 在线重构 
    double tof_rec = (tL + tR)/2.0; 
      
    htof->Fill(tof_rec); //填充histogram 
    //5.将计算好的变量值填到Tree中
    opt->Fill(); 
  }
  // 完成后输出 100%
  std::cout << "\rProcessing: 100% completed!      " << std::endl;    
  // 6.将数据写入root文件中
  htof->Write();
  opt->Write();
  opf->Close();

  std::cout << "Data saved to tree.root" << std::endl;    
}

create_tree();

Starting Simulation...
Processing: 100% completed!      
Data saved to tree.root

//%jsroot on

TFile *ipf = new TFile("tree.root");//root -l tree.root
ipf->ls()//ROOT 环境下 > .ls

TFile**		tree.root	
 TFile*		tree.root	
  KEY: TTree	tree;2	Simulated Data [current cycle]
  KEY: TTree	tree;1	Simulated Data [backup cycle]
  KEY: TH1D	htof;1	Reconstructed time of flight

//观察tree的结构
tree->Print()

******************************************************************************
*Tree    :tree      : Simulated Data                                         *
*Entries :   500000 : Total =        38111950 bytes  File  Size =   30674091 *
*        :          : Tree compression factor =   1.24                       *
******************************************************************************
*Br    0 :x_true    : x_true/D                                               *
*Entries :   500000 : Total  Size=    4011942 bytes  File Size  =    2797027 *
*Baskets :      125 : Basket Size=    3368960 bytes  Compression=   1.43     *
*............................................................................*
*Br    1 :e_true    : e_true/D                                               *
*Entries :   500000 : Total  Size=    4011942 bytes  File Size  =    1437266 *
*Baskets :      125 : Basket Size=    3368960 bytes  Compression=   2.79     *
*............................................................................*
*Br    2 :tof_true  : tof_true/D                                             *
*Entries :   500000 : Total  Size=    4012200 bytes  File Size  =    3556188 *
*Baskets :      125 : Basket Size=    3368960 bytes  Compression=   1.13     *
*............................................................................*
*Br    3 :pid       : pid/I                                                  *
*Entries :   500000 : Total  Size=    2005967 bytes  File Size  =     211716 *
*Baskets :       63 : Basket Size=    1684480 bytes  Compression=   9.47     *
*............................................................................*
*Br    4 :tL_true   : tL_true/D                                              *
*Entries :   500000 : Total  Size=    4012071 bytes  File Size  =    3773792 *
*Baskets :      125 : Basket Size=    3368960 bytes  Compression=   1.06     *
*............................................................................*
*Br    5 :tR_true   : tR_true/D                                              *
*Entries :   500000 : Total  Size=    4012071 bytes  File Size  =    3762401 *
*Baskets :      125 : Basket Size=    3368960 bytes  Compression=   1.07     *
*............................................................................*
*Br    6 :tL        : tL/D                                                   *
*Entries :   500000 : Total  Size=    4011337 bytes  File Size  =    3774018 *
*Baskets :      124 : Basket Size=    3368448 bytes  Compression=   1.06     *
*............................................................................*
*Br    7 :tR        : tR/D                                                   *
*Entries :   500000 : Total  Size=    4011337 bytes  File Size  =    3764227 *
*Baskets :      124 : Basket Size=    3368448 bytes  Compression=   1.06     *
*............................................................................*
*Br    8 :AL        : AL/D                                                   *
*Entries :   500000 : Total  Size=    4011337 bytes  File Size  =    3795368 *
*Baskets :      124 : Basket Size=    3368448 bytes  Compression=   1.06     *
*............................................................................*
*Br    9 :AR        : AR/D                                                   *
*Entries :   500000 : Total  Size=    4011337 bytes  File Size  =    3792262 *
*Baskets :      124 : Basket Size=    3368448 bytes  Compression=   1.06     *
*............................................................................*

tree->Show(10);//显示指定的事件数据 event=10

======> EVENT:10
 x_true          = -0.746245
 e_true          = 100
 tof_true        = 36.644
 pid             = 1
 tL_true         = 45.5274
 tR_true         = 80.3272
 tL              = 46.0796
 tR              = 80.2509
 AL              = 470.406
 AR              = 500.379

tree->Scan("x_true:e_true:tof_true:pid:tL:tR:AL:AR","","",10,10);

************************************************************************************************************
*    Row   *    x_true *    e_true *  tof_true *       pid *        tL *        tR *        AL *        AR *
************************************************************************************************************
*       10 * -0.746245 *       100 * 36.643961 *         1 * 46.079593 * 80.250888 * 470.40624 *  500.3791 *
*       11 * -0.926384 *       100 * 36.659505 *         1 * 43.760717 * 83.046770 * 479.98667 * 430.03453 *
*       12 * 0.0953839 *       100 * 36.210595 *         1 * 55.893525 * 69.558013 * 394.79357 * 591.15340 *
*       13 * 0.3093909 *       100 * 36.176069 *         1 * 59.183832 * 66.666512 * 392.44258 * 641.17039 *
*       14 * -0.958320 *       100 * 36.950511 *         1 * 42.570520 * 83.084246 * 519.85725 * 441.99134 *
*       15 * -0.760824 *       100 * 36.399884 *         1 * 45.660114 * 80.248237 * 453.88114 * 418.91337 *
*       16 * -0.018517 * 4.0821660 * 16.627294 *         0 * 35.755004 * 51.052217 * 16.760023 * 23.442220 *
*       17 * -0.632558 *       100 * 36.430165 *         1 * 45.983321 * 78.262556 * 448.97570 * 466.07457 *
*       18 * -0.143903 *       100 * 36.278417 *         1 * 53.069224 * 71.807450 * 396.81997 * 580.17878 *
*       19 * 0.2871965 *       100 * 36.094508 *         1 * 59.458789 * 67.066652 * 353.29347 * 647.69140 *
************************************************************************************************************

TCanvas *c1 = new TCanvas();//* 在ROOT环境下可省略
c1->Clear();//* 在ROOT环境下可省略

tree->Draw("tR-tL>>(100,-15,50");
c1->Draw(); //* 在ROOT环境下可省略

tree->Draw("tof_true>>(1000,0,100)","");//实际飞行时间
c1->Draw();

TH1D *hh = (TH1D*) ipf->Get("htof"); //在代码中得到文件内数据指针的方法，在ROOT环境下课直接用 htof->Draw()
hh->Draw();//画图
c1->Draw();

c1->Clear();
c1->Divide(2,1);
c1->cd(1);
tree->Draw("tof_true:x_true >> h1(400, -1.10, 1.10, 400, 15, 60)", "", "colz");
c1->cd(2);
tree->Draw("tof_true/sqrt(pow(5.05,2)+pow(x_true,2)):x_true >> h2(400, -1.10, 1.10, 400, 2.5, 11", "", "colz");
c1->Draw();

c1->Clear();
c1->Divide(2,1);
c1->cd(1);
tree->Draw("x_true:tR-tL >> h3(200, -20, 50, 200, -1.1, 1.1)", "", "colz");
c1->cd(2);
tree->Draw("log(AL/AR):x_true","","colz");
c1->Draw();

.L create_tree_hw.cc

create_tree_hw();

Starting Simulation...
Processing: 100% completed!      
Data saved to tree_hw.root

TFile *ipfm = new TFile("tree_hw.root");
c1->Clear();
c1->Divide(1,1);

tree->Draw("tL-tL_true:AL>>(400,0,600,200,0,50)","","colz");
c1->Draw();

void draw_gamma_cut() {
   TCutG *cutg = new TCutG("cut_gamma",15);
   cutg->SetVarX("tL+tR");
   cutg->SetVarY("sqrt(AL*AR)");
   cutg->SetTitle("Graph");
   cutg->SetFillStyle(1000);
   cutg->SetPoint(0,86.7586,588.026);
   cutg->SetPoint(1,87.9764,331.974);
   cutg->SetPoint(2,89.803,105.395);
   cutg->SetPoint(3,96.5007,7.76315);
   cutg->SetPoint(4,118.116,-12.5);
   cutg->SetPoint(5,131.816,-3.28948);
   cutg->SetPoint(6,128.771,15.1316);
   cutg->SetPoint(7,113.549,28.0263);
   cutg->SetPoint(8,101.981,55.6579);
   cutg->SetPoint(9,96.1963,156.974);
   cutg->SetPoint(10,94.6741,304.342);
   cutg->SetPoint(11,94.0652,503.289);
   cutg->SetPoint(12,92.8474,591.711);
   cutg->SetPoint(13,85.8453,586.184);
   cutg->SetPoint(14,86.7586,588.026);
        
    // 注意：在分析代码中调用时，通常不需要它自动 Draw()
    cutg->Draw("L"); 
}

TCanvas *c2 = new TCanvas("tof-q","tof-q",1000,300);
c2->Divide(3,1);
c2->cd(1);
tree->Draw("sqrt(AL*AR):tL_true+tR_true>>h1(400,80,200,500,0,600)","","colz");
c2->cd(2);
tree->Draw("sqrt(AL*AR):tL+tR>>h2(400,80,250,500,0,600)","","colz");
draw_gamma_cut();
c2->cd(3);
tree->Draw("sqrt(AL*AR):tL+tR>>h3(400,80,250,500,0,600)","cut_gamma","colz");
c2->Draw();

// 在终端执行，假设 x 为横坐标变量，y 为纵坐标变量
tree->Draw("y:x", "", "colz");

1.1 用TTree 结构存储事件数据¶

1. 目的¶

2、实验设置与物理原理¶

2.1. 几何设置¶

2.2. 信号读出¶

2.3. 物理公式¶

3. ROOT 文件结构 (TTree) — 数据生成与存储机制¶

3.1 TTree的数据存储¶

3.2 TTree 的 Branch 接口参数 (基础变量)¶

3.3 TTree 核心操作机制¶

3.4 存入TTree的事件信息¶

3. 模拟代码¶

4. 运行与分析¶

练习：¶

4.1. 查看ROOT文件¶

4.2 查看事件数据¶

4.3 查看相对位置分布¶

4.4：TOF¶

4.5 飞行时间与位置的二维关联¶

4.6 位置¶

5. 作业¶

6. 考虑作业中修正后的结果¶

6.1 Timewalk¶

gamma事件选择¶

附录：CERN ROOT Graphic Cut (TCutG) 指南¶

1. 建立上下文：绘制散点图¶

2. 交互式创建与重命名¶

3. 保存与复用 (.C 脚本)¶

4. 在 ROOT 终端直接调用¶

5. 在循环代码中引用 (C++ Loop)¶

1.1 用TTree 结构存储事件数据¶

1. 目的¶

2、 实验设置与物理原理¶

2.1. 几何设置¶

2.2. 信号读出¶

2.3. 物理公式¶

3. ROOT 文件结构 (TTree) — 数据生成与存储机制¶

3.1 TTree的数据存储¶

3.2 TTree 的 Branch 接口参数 (基础变量)¶

3.3 TTree 核心操作机制¶

3.4 存入TTree的事件信息¶

3. 模拟代码¶

4. 运行与分析¶

练习：¶

4.1. 查看ROOT文件¶

4.2 查看事件数据¶

4.3 查看相对位置分布¶

4.4：TOF¶

4.5 飞行时间与位置的二维关联¶

4.6 位置¶

5. 作业¶

6. 考虑作业中修正后的结果¶

6.1 Timewalk¶

gamma事件选择¶

附录：CERN ROOT Graphic Cut (TCutG) 指南¶

1. 建立上下文：绘制散点图¶

2. 交互式创建与重命名¶

3. 保存与复用 (.C 脚本)¶

4. 在 ROOT 终端直接调用¶

5. 在循环代码中引用 (C++ Loop)¶

2、实验设置与物理原理¶