5.2 衰变实验的数据分析I -重离子和衰变事件的关联¶

数据：sort.root (按照上一次课件的描述生成root文件）

TTree Branch:

  • timestamp, xstrip, ystrip, de
  • //de- dssd front energy
  • me
  • //mwpc energy, me<0 when no dssd signal

alpha sepctrum:¶

In [1]:
TCanvas *c1 = new TCanvas("c1","c1");
TFile *fin = new TFile("sort1.root");
TTree *tree = (TTree*)fin->Get("tree");
tree->Print();
ULong64_t timestamp;
Int_t xstrip,ystrip;
Float_t me,de;
tree->SetBranchAddress("timestamp",&timestamp);
tree->SetBranchAddress("xstrip",&xstrip);
tree->SetBranchAddress("ystrip",&ystrip);
tree->SetBranchAddress("de",&de);
tree->SetBranchAddress("me",&me);

******************************************************************************
*Tree    :tree      : sorted events                                          *
*Entries :   107136 : Total =         2580874 bytes  File  Size =    1454832 *
*        :          : Tree compression factor =   1.77                       *
******************************************************************************
*Br    0 :timestamp : timestamp/l                                            *
*Entries :   107136 : Total  Size=     860009 bytes  File Size  =     544219 *
*Baskets :       27 : Basket Size=      32000 bytes  Compression=   1.58     *
*............................................................................*
*Br    1 :me        : me/F                                                   *
*Entries :   107136 : Total  Size=     430083 bytes  File Size  =     246434 *
*Baskets :       14 : Basket Size=      32000 bytes  Compression=   1.74     *
*............................................................................*
*Br    2 :de        : de/F                                                   *
*Entries :   107136 : Total  Size=     430083 bytes  File Size  =     379997 *
*Baskets :       14 : Basket Size=      32000 bytes  Compression=   1.13     *
*............................................................................*
*Br    3 :xstrip    : xstrip/I                                               *
*Entries :   107136 : Total  Size=     430155 bytes  File Size  =     133106 *
*Baskets :       14 : Basket Size=      32000 bytes  Compression=   3.23     *
*............................................................................*
*Br    4 :ystrip    : ystrip/I                                               *
*Entries :   107136 : Total  Size=     430155 bytes  File Size  =     149610 *
*Baskets :       14 : Basket Size=      32000 bytes  Compression=   2.87     *
*............................................................................*
In [2]:
//tree->Scan("xstrip:ystrip:timestamp:me","","colsize=30",100,10000);
In [3]:
tree->Draw("de>>hde(3000,0,30000)");//all
tree->Draw("de>>hdem(3000,0,30000)","me>0");//coincide with mwpc
tree->Draw("de>>hdenm(3000,0,30000)","me<0");//mwpc veto
TH1F *hde, *hdem, *hdenm;
hde = (TH1F*)gROOT->FindObject("hde");
hdem = (TH1F*)gROOT->FindObject("hdem");
hdenm = (TH1F*)gROOT->FindObject("hdenm");
hde->Draw();
hdem->SetLineColor(kGreen);
hdenm->SetLineColor(kRed);
hdem->Draw("same");
hdenm->Draw("same");
c1->Draw();
cout<<hdem->Integral(600,750)<<endl;

4172
In [4]:
hdenm->GetXaxis()->SetRangeUser(5000,8000);
hdenm->Draw();
c1->Draw();
In [5]:
tree->Draw("xstrip:ystrip>>(128,0,128,48,0,48)","","colz");
c1->SetLogy(0);
c1->SetLogz(0);
c1->Draw();

按照mwpc上的能量对事件进行分类¶

  • 重离子(Implantation) me>0
  • 衰变粒子(Decay) me<0
    • 还需要veto掉穿出DSSD的轻粒子事件，课件数据已经去掉了这部分事件
In [6]:
struct dssd
{
    Float_t energy;
    Int_t xstrip,ystrip;
};
dssd ds;
multimap<ULong64_t, dssd> mapimp, mapdec;//implantaion, decay

Long64_t nentries = tree->GetEntriesFast();
for (Long64_t jentry=0; jentry<nentries;jentry++) {
    tree->GetEntry(jentry);
        ds.energy = de;
        ds.xstrip = xstrip;
        ds.ystrip = ystrip;
    if(me>0) mapimp.insert(pair<ULong64_t,dssd>(timestamp,ds));
    else mapdec.insert(pair<ULong64_t,dssd>(timestamp,ds));
}
cout<<"The number of implantation/decay : "<<mapimp.size()<<"  "<<mapdec.size()<<endl;

The number of implantation/decay : 77675  29461

重离子与衰变事件的关联¶

位置关联¶

  • 一般来说束流在DSSD上有着很宽的位置分布(通过调束，使得束流在注入探测器上有着较宽的分布)，且DSSD的每个pixel面积很小，可以认为束流强度不高时，重离子注入到某一颗粒后在一段不长的时间范围内(称为衰变时间窗)，该颗粒上发生的衰变事件都是由该注入核引起的。换句话说，可将DSSD探测器看成 $x \times y$ 个独立的探测单元，每个单元在衰变时间窗内只有一个重离子注入，并发生衰变。

  • 参数：ht,hx,hy; bt,be,bx,by

  • 位置关联条件： hx==bx && hy==by

时间关联¶

  • 上图中用点线连接的注入(ht)和衰变(bt)事件是真正的注入-衰变关联事件，即$(ht_i,bt_j),i = j$。

当入射束流强度较低时(图.a)¶

  • 在衰变时间窗内，关联事件(注入时间，衰变时间)为

    1. (ht1,bt1)
    1. (ht2,bt2)
    1. (ht3,bt3)

  • 在衰变时间窗内注入和衰变事件都是关联的，时间差$\delta t=bt-ht$服从指数衰减分布。

当入射束流强度较高时，在衰变时间窗内发生的衰变事件可能是由其他重离子的衰变引起的(图.b)。¶

  • 在衰变时间窗内，关联事件(注入时间，衰变时间)为

    1. (ht1,bt1）
    1. (ht2,bt2),(ht2,bt4)
    1. (ht3,bt2),(ht3,bt4),(ht3,bt3)
    1. (ht4,bt4),(ht4,bt3),(ht4,bt5）

  • 事件 $(ht_i,bt_j),i \neq j$ 之间不存在关联关系，此时其时间差 $\delta t=bt-ht$，是不确定的，分布服从均匀分布。

  • 对于衰变时间窗内的关联事件$(ht_i,bt_j),i = j$ ，$\delta t=bt-ht$服从指数衰减分布。

  • 上述两种类型事件在实验上是不可区分的, 衰变时间谱($\delta t$)呈现指数+平台分布。

将不同时刻发生的注入和衰变事件关联起来的方法称为position-time correlation for implantation and decay events。¶

位置关联条件¶

  • 重离子和衰变事件在同一个颗粒的条件为:
hx==bx && hy==by, hz==bz(当粒子注入到多个dssd时);
  • 为了增加探测效率(部分beta粒子会散射到周围的颗粒上)，有时需要将注入和衰变事件的位置关联范围变大，如:
abs(hx-bx)<2 && abs(hx-bx)<2;
  • 对于$\alpha$粒子由于射程很短，一般只用 $\Delta x/\Delta y = 0$ 条件

重新组织事件结构。¶

  • 为了后续的分析，采用如下条件
    • abs(hx-bx)<2 && abs(hx-bx)<2;
    • 衰变时间窗取为: [-twindow ~ +twindow]
In [7]:
//implantation
ULong64_t hts;
Double_t he;
Int_t hx,hy;

//decay events within decay-time window.
Int_t bhit;
ULong64_t bts[1000];
Double_t be[1000];
Int_t bx[1000],by[1000];
Double_t decaytime[1000];

//for alpha-cascade events analysis
Int_t bphit;
ULong64_t bpts[1000];
Double_t bpe[1000];


TFile *fout=new TFile("decay.root","RECREATE");
TTree *tout= new TTree("tree","decay");

tout->Branch("hts",&hts,"hts/l");
tout->Branch("he",&he,"he/D");
tout->Branch("hx",&hx,"hx/I");
tout->Branch("hy",&hy,"hy/I");
tout->Branch("bhit",&bhit,"bhit/I");
tout->Branch("bts",&bts,"bts[bhit]/l");
tout->Branch("be",&be,"be[bhit]/D");
tout->Branch("bx",&bx,"bx[bhit]/I");
tout->Branch("by",&by,"by[bhit]/I");
tout->Branch("decaytime",&decaytime,"decaytime[bhit]/D");
tout->Branch("bphit",&bphit,"bphit/I");
tout->Branch("bpts",&bpts,"bpts[bphit]/l");
tout->Branch("bpe",&bpe,"bpe[bphit]/D");

ULong64_t twindow = 20000000000;//20s, 时间窗长度 > 10*T1/2
Int_t n=0;
for(auto ia = mapimp.begin(); ia!=mapimp.end();ia++) {
     hts = ia->first;
     he = ia->second.energy;
     hx = ia->second.xstrip;
     hy = ia->second.ystrip;
     auto ib1 = mapdec.lower_bound(ia->first - twindow/2.); // for negative decaytime
     auto ib2 = mapdec.upper_bound(ia->first + twindow); // for positive decaytime  
     bhit = 0;
     bphit = 0;
     if(ib1==mapdec.end()) continue;
     for( ; ib1!=mapdec.end() && ib1!=ib2; ib1++) { 
        Int_t delx = abs(ib1->second.xstrip - hx);
        Int_t dely = abs(ib1->second.ystrip - hy); 
        if(delx < 2 && dely < 2) {//deltaX,deltaY =0/-1/+1
            bts[bhit] = ib1->first;
            be[bhit] = ib1->second.energy;
            bx[bhit] = ib1->second.xstrip;
            by[bhit] = ib1->second.ystrip;            
            decaytime[bhit] = Long64_t(ib1->first - hts)/1.e6;//ms
            //for alpha-cascade events analysis
            if(decaytime[bhit]>0 && delx ==0 && dely ==0) {
                bpts[bphit] = ib1->first;
                bpe[bphit] = ib1->second.energy;
                bphit++;
            }
            bhit++;
        }
     }
    if(bhit>0) tout->Fill();
    n++;
    if(n%1000 == 0) cout<<".";
}
cout<<endl;
cout<<"Done!"<<endl;
tout->Write();
fout->Close();

.............................................................................
Done!
In [8]:
TFile *fdecay = new TFile("decay.root");
TTree *tree = (TTree *)fdecay->Get("tree");
tree->Print();

******************************************************************************
*Tree    :tree      : decay                                                  *
*Entries :    39009 : Total =         4507222 bytes  File  Size =    2059578 *
*        :          : Tree compression factor =   2.19                       *
******************************************************************************
*Br    0 :hts       : hts/l                                                  *
*Entries :    39009 : Total  Size=     313277 bytes  File Size  =     202832 *
*Baskets :       10 : Basket Size=      32000 bytes  Compression=   1.54     *
*............................................................................*
*Br    1 :he        : he/D                                                   *
*Entries :    39009 : Total  Size=     313263 bytes  File Size  =     175783 *
*Baskets :       10 : Basket Size=      32000 bytes  Compression=   1.78     *
*............................................................................*
*Br    2 :hx        : hx/I                                                   *
*Entries :    39009 : Total  Size=     156854 bytes  File Size  =      48248 *
*Baskets :        5 : Basket Size=      32000 bytes  Compression=   3.24     *
*............................................................................*
*Br    3 :hy        : hy/I                                                   *
*Entries :    39009 : Total  Size=     156854 bytes  File Size  =      52315 *
*Baskets :        5 : Basket Size=      32000 bytes  Compression=   2.99     *
*............................................................................*
*Br    4 :bhit      : bhit/I                                                 *
*Entries :    39009 : Total  Size=     156872 bytes  File Size  =      19718 *
*Baskets :        5 : Basket Size=      32000 bytes  Compression=   7.93     *
*............................................................................*
*Br    5 :bts       : bts[bhit]/l                                            *
*Entries :    39009 : Total  Size=     631982 bytes  File Size  =     295938 *
*Baskets :       25 : Basket Size=      32000 bytes  Compression=   2.13     *
*............................................................................*
*Br    6 :be        : be[bhit]/D                                             *
*Entries :    39009 : Total  Size=     631953 bytes  File Size  =     262652 *
*Baskets :       25 : Basket Size=      32000 bytes  Compression=   2.40     *
*............................................................................*
*Br    7 :bx        : bx[bhit]/I                                             *
*Entries :    39009 : Total  Size=     394707 bytes  File Size  =     137063 *
*Baskets :       18 : Basket Size=      32000 bytes  Compression=   2.87     *
*............................................................................*
*Br    8 :by        : by[bhit]/I                                             *
*Entries :    39009 : Total  Size=     394707 bytes  File Size  =     141034 *
*Baskets :       18 : Basket Size=      32000 bytes  Compression=   2.79     *
*............................................................................*
*Br    9 :decaytime : decaytime[bhit]/D                                      *
*Entries :    39009 : Total  Size=     632156 bytes  File Size  =     476584 *
*Baskets :       25 : Basket Size=      32000 bytes  Compression=   1.32     *
*............................................................................*
*Br   10 :bphit     : bphit/I                                                *
*Entries :    39009 : Total  Size=     156881 bytes  File Size  =      18370 *
*Baskets :        5 : Basket Size=      32000 bytes  Compression=   8.51     *
*............................................................................*
*Br   11 :bpts      : bpts[bphit]/l                                          *
*Entries :    39009 : Total  Size=     283918 bytes  File Size  =     123035 *
*Baskets :       14 : Basket Size=      32000 bytes  Compression=   2.30     *
*............................................................................*
*Br   12 :bpe       : bpe[bphit]/D                                           *
*Entries :    39009 : Total  Size=     283900 bytes  File Size  =     103025 *
*Baskets :       14 : Basket Size=      32000 bytes  Compression=   2.75     *
*............................................................................*

Heavy ion and decay correlation in the same pixel $\Delta x=0$ and $\Delta y=0$¶

In [9]:
TCut cdxdy00 = "abs(bx-hx)==0 && abs(by-hy)==0";
tree->Draw("be:decaytime>>(200,0,2e4,300,5000,8000)",cdxdy00,"colz");
c1->Draw();

$^{211}Ac$的衰变时间分布¶

  • 指数+均匀分布！
In [10]:
TCut cAc211a = "be>7400 && be<7510 && decaytime>0";
tree->Draw("decaytime>>hdtAc211a(200,0,2e4)",cdxdy00 && cAc211a,"colz");
c1->SetLogy();
c1->Draw();

Heavy ion and decay correlation with $\Delta x=\pm 1$ and $\Delta y=\pm 1$¶

  • no correlation
In [11]:
TCut cdxdy11 = "abs(bx-hx)==1 && abs(by-hy)==1  && decaytime>0";
TCut cAc211 = "be>7400 && be<7510";
tree->Draw("decaytime>>hdtAc211b(200,0,2e4)",cdxdy11 && cAc211,"colz");
c1->SetLogy();
c1->Draw();

Heavy ion and decay correlation with $\Delta x=\pm 1$ or $\Delta y=\pm 1$¶

  • negligible
In [12]:
TCut cdxdy0110 = "abs(bx-hx) + abs(by-hy)==1 && decaytime>0";
TCut cAc211 = "be>7400 && be<7510";
tree->Draw("decaytime>>hdtAc211c(200,0,2e4)",cdxdy0110 && cAc211,"colz");
c1->SetLogy();
c1->Draw();

从半衰期曲线的对比看，关联主要在相同的颗粒上, 相同颗粒外几乎没有关联粒子。¶

  • 在下面的处理中只用 $\Delta x/\Delta y = 0$的条件

  • 对不同能量，不同类型的粒子，由于在探测器中的射程和散射程度的不同，关联的位置范围都有可能不同。

  • 应进行上述检验确定合理的位置关联范围。

减去20个半衰期以后的平台本底¶

  • 对于低计数的区域拟合要使用"L"选项
    • https://zhihuanli.github.io/Experimental-Data-Analysis-Course/chapt5/fitting_LS_LH.html
In [13]:
TF1 *fp01 = new TF1("fp01","pol0",1.5e4,2e4);
hdtAc211a->Fit(fp01,"LR");
Double_t p01 = fp01->GetParameter(0);
c1->SetLogy();
c1->Draw();

 FCN=32.4205 FROM MIGRAD    STATUS=CONVERGED      53 CALLS          54 TOTAL
                     EDM=6.37252e-07    STRATEGY= 1      ERROR MATRIX ACCURATE 
  EXT PARAMETER                                   STEP         FIRST   
  NO.   NAME      VALUE            ERROR          SIZE      DERIVATIVE 
   1  p0           1.77985e+00   1.88664e-01   7.38324e-04  -4.23124e-03
                               ERR DEF= 0.5

指数 + 平台拟合¶

  • 拟合$\alpha$ 或 $\beta$-衰变时间谱时，为了避免获取死时间的影响，通常选择 decaytime>1ms的条件
In [14]:
TF1 *fdecay1 = new TF1("fdecay1","[0]+[1]*TMath::Exp(-x*TMath::Log(2.)/[2])",1,1e4);//skip 1ms
fdecay1->FixParameter(0,p01);
fdecay1->SetParameter(2,1e2);
hdtAc211a->Fit(fdecay1,"RL");
cout<<endl;
cout<<"half-life of 211Ac is "<<fdecay1->GetParameter(2)<<" +/- "<<fdecay1->GetParError(2)<<" ms"<<endl;
c1->SetLogy();
c1->Draw();

 FCN=52.6145 FROM MIGRAD    STATUS=CONVERGED     138 CALLS         139 TOTAL
                     EDM=9.13665e-10    STRATEGY= 1      ERROR MATRIX ACCURATE 
  EXT PARAMETER                                   STEP         FIRST   
  NO.   NAME      VALUE            ERROR          SIZE      DERIVATIVE 
   1  p0           1.77985e+00     fixed    
   2  p1           6.07619e+02   1.89243e+01   6.55598e-02  -2.12807e-06
   3  p2           2.53200e+02   5.92143e+00   2.05334e-02  -6.95988e-06
                               ERR DEF= 0.5

half-life of 211Ac is 253.2 +/- 5.92143 ms

$\alpha$ 能谱减本底¶

  • 取前5*decaytime范围作为来自于全部衰变+本底贡献的alpha

  • 取远处20-25*decaytime范围作为来自于本底贡献的alpha

  • 前两者相减作为来自衰变的alpha

  • 蓝色为本底alpha，红色为减本底后的alpha能谱

  • 在下面的图中只有半衰期小于1s的能量大于7400keV的$\alpha$ ($^{211,212}$Ac)减去了正确的本底。

    • 半衰期更长的alpha谱，应该取更长的衰变时间范围，本底区也应该相应后移。
In [15]:
tree->Draw("be>>hbeall(300,5000,8000)",cdxdy00 && "decaytime<5*250");
tree->Draw("be>>hbebkg(300,5000,8000)",cdxdy00 && "decaytime>20*250 && decaytime<25*250");
TH1F *hbeall = (TH1F*)gROOT->FindObject("hbeall");
TH1F *hbebkg = (TH1F*)gROOT->FindObject("hbebkg");
TH1F *hbenet = new TH1F("hbenet","energy_background subtracted",300,5000,8000);
hbenet->Add(hbeall,hbebkg,1,-1);
hbenet->SetLineColor(kRed);
hbeall->SetLineColor(kGreen);
hbeall->Draw();
hbebkg->Draw("same");
hbenet->Draw("same");
c1->SetLogy(0);
c1->Draw();

减负衰变时间本底¶

  • 衰变时间为负的事件：即衰变先发生，母核生成在后，这样的事件在物理上是不可能的。因此与负衰变时间关联的事件可视为随机本底事件。
In [16]:
TCut cdxdy00 = "abs(bx-hx)==0 && abs(by-hy)==0";
tree->Draw("be:decaytime>>(300,-1e4,2e4,300,5000,8000)",cdxdy00,"colz");
c1->Draw();
In [17]:
TCut cAc211a = "be>7400 && be<7510";
tree->Draw("decaytime>>hdtAc211d(300,-1e4,2e4)",cdxdy00 && cAc211a,"colz");
c1->SetLogy();
c1->Draw();
In [18]:
TF1 *fp01d = new TF1("fp01d","pol0",-0.8e4,-0.3e4);
hdtAc211d->Fit(fp01d,"LR");
Double_t p01d = fp01d->GetParameter(0);
c1->SetLogy();
c1->Draw();

 FCN=27.3895 FROM MIGRAD    STATUS=CONVERGED      53 CALLS          54 TOTAL
                     EDM=1.7046e-07    STRATEGY= 1      ERROR MATRIX ACCURATE 
  EXT PARAMETER                                   STEP         FIRST   
  NO.   NAME      VALUE            ERROR          SIZE      DERIVATIVE 
   1  p0           1.57993e+00   1.77756e-01   6.42253e-04  -2.32267e-03
                               ERR DEF= 0.5
In [19]:
TF1 *fdecay2 = new TF1("fdecay2","[0]+[1]*TMath::Exp(-x*TMath::Log(2.)/[2])",1,1e4);
fdecay2->FixParameter(0,p01d);
fdecay2->SetParameter(2,1e2);
hdtAc211d->Fit(fdecay2,"RL");
cout<<endl;
cout<<"half-life of 211Ac is "<<fdecay2->GetParameter(2)<<" +/- "<<fdecay2->GetParError(2)<<" ms"<<endl;
c1->SetLogy();
c1->Draw();

 FCN=52.6114 FROM MIGRAD    STATUS=CONVERGED     137 CALLS         138 TOTAL
                     EDM=8.41325e-08    STRATEGY= 1      ERROR MATRIX ACCURATE 
  EXT PARAMETER                                   STEP         FIRST   
  NO.   NAME      VALUE            ERROR          SIZE      DERIVATIVE 
   1  p0           1.57993e+00     fixed    
   2  p1           6.05513e+02   1.88295e+01   6.52003e-02  -9.64404e-06
   3  p2           2.54654e+02   5.93702e+00   2.05807e-02   2.19015e-05
                               ERR DEF= 0.5

half-life of 211Ac is 254.654 +/- 5.93702 ms

$\alpha$能谱减本底¶

  • 减去负时间本底
  • 蓝色为本底alpha，红色为减本底后的alpha能谱
  • 相比于正衰变时间本底，负时间本底不受衰变时间范围的影响。
In [20]:
TCut cdxdy00 = "abs(bx-hx)==0 && abs(by-hy)==0";
tree->Draw("be>>hbealln(300,5000,8000)",cdxdy00 && "decaytime>0 && decaytime<5*250");
TH1F *hbealln = (TH1F*)gROOT->FindObject("hbealln");
tree->Draw("be>>hbebkgn(300,5000,8000)",cdxdy00 && "decaytime>-5*250-300 && decaytime<-300");
TH1F *hbebkgn = (TH1F*)gROOT->FindObject("hbebkgn");
TH1F *hbenetn = new TH1F("hbenetn","energy_background subtracted",300,5000,8000);
hbenetn->Add(hbealln,hbebkgn,1,-1);
hbenetn->SetLineColor(kRed);
hbealln->SetLineColor(kGreen);
hbealln->Draw();
hbebkgn->Draw("same");
hbenetn->Draw("same");
c1->SetLogy(0);
c1->Draw();

寻找下一级衰变事件¶

  • $^{211}Ac$衰变子核$^{207}$Fr可通过$\alpha$衰变继续衰变到$^{203}At$.
  • 从衰变链下端的已知核($A_p,Z_p$)向上推，可以确定未知衰变核($A_N,Z_N$)的属性($A_N=A_p+4，Z_N=Z_p+2$)

  • 由于重离子只注入在DSSD的表面，每一级的$\alpha$探测效率为50%，即两级$\alpha$衰变的探测效率为25%。

在衰变时间窗内，将满足条件的所有衰变事件存入数组¶

选择事件：decaytime>0 && bx==hx && by==hy

  • 注入事件：hts
  • 衰变事件：bphit, bpe[bphit], bpt[bphit]

两级关联条件：¶

  • 第一级：
bpts[0]-ht<700 //ms
  • 第二级：
    • 原则上时间范围应大于三倍第二级半衰期以上。
bpts[1]-bpts[0]<19*1000 //ms
In [21]:
tree->Draw("bphit","bphit>0");
c1->SetLogy();
c1->Draw();

母核α-子核α能量关联图，包含逃逸事件¶

  • 可以看到 $^{207}Fr$的 6767keV的 $\alpha$, 与 $^{211}Ac$的 7477keV的 $\alpha$ 关联。
In [22]:
TCut cs1 = "bphit>1 && (bpts[0]-hts)/1.e6<700"; 
TCut cs2 = "(bpts[1]-bpts[0])/1.e6<19000";
tree->Draw("bpe[1]:bpe[0]>>hbe12(200,6000,8000,200,6000,8000)",cs1&&cs2,"colz");
c1->SetLogy(0);
c1->Draw();

207Fr衰变时间¶

  • 因为时间范围小于207Fr的半衰期，无法通过拟合得到可靠的半衰期。
In [23]:
TCut cecut = "abs(bpe[1]-6767)<50 && abs(bpe[0]-7477)<50";
tree->Draw("(bpts[1]-bpts[0])/1.e6>>hdt12(100,0,20000)",cs1&&cs2&&cecut ,"colz");
c1->SetLogy();
c1->Draw();