The Physics Vector package -* ========================== -* The Physics Vector package consists of five classes: -* - TVector2 -* - TVector3 -* - TRotation -* - TLorentzVector -* - TLorentzRotation -* It is a combination of CLHEPs Vector package written by -* Leif Lonnblad, Andreas Nilsson and Evgueni Tcherniaev -* and a ROOT package written by Pasha Murat. -* for CLHEP see: http://wwwinfo.cern.ch/asd/lhc++/clhep/ -* Adaption to ROOT by Peter Malzacher *
TLorentzVector v1; // initialized
by (0., 0., 0., 0.)
TLorentzVector v2(1., 1., 1., 1.);
TLorentzVector v3(v1);
TLorentzVector v4(TVector3(1., 2., 3.),4.);
For backward compatibility there are two constructors from an Double_t
and Float_t C array.
Double_t xx =v.X();
...
Double_t tt = v.T();
Double_t px = v.Px();
...
Double_t ee = v.E();
The components of TLorentzVector can also accessed by index:
xx = v(0); or
xx = v[0];
yy = v(1);
yy = v[1];
zz = v(2);
zz = v[2];
tt = v(3);
tt = v[3];
You can use the Vect() member function to get the vector component of TLorentzVector:
TVector3 p = v.Vect();
For setting components also two sets of member functions can be used:
SetX(),.., SetPx(),..:
v.SetX(1.); or
v.SetPx(1.);
...
...
v.SetT(1.);
v.SetE(1.);
To set more the one component by one call you can use the SetVect() function for the TVector3 part or SetXYZT(), SetPxPyPzE(). For convenience there is also a SetXYZM():
v.SetVect(TVector3(1,2,3));
v.SetXYZT(x,y,z,t);
v.SetPxPyPzE(px,py,pz,e);
v.SetXYZM(x,y,z,m); // ->
v=(x,y,z,e=Sqrt(x*x+y*y+z*z+m*m))
Double_t m, theta, cost, phi, pp, pp2, ppv2, pp2v2;
m = v.Rho();
t = v.Theta();
cost = v.CosTheta();
phi = v.Phi();
v.SetRho(10.);
v.SetTheta(TMath::Pi()*.3);
v.SetPhi(TMath::Pi());
or get information about the r-coordinate in cylindrical systems:
Double_t pp, pp2, ppv2, pp2v2;
pp = v.Perp(); // get transvers component
pp2 = v.Perp2(); // get transverse component squared
ppv2 = v.Perp(v1); // get
transvers component with
// respect to another vector
pp2v2 = v.Perp(v1);
for convenience there are two more set functions SetPtEtaPhiE(pt,eta,phi,e); and SetPtEtaPhiM(pt,eta,phi,m);
v3 = -v1;
v1 = v2+v3;
v1+= v3;
v1 = v2 + v3;
v1-= v3;
if (v1 == v2) {...}
if(v1 != v3) {...}
Double_t s, s2;
s = v1.Dot(v2); // scalar
product
s = v1*v2; // scalar product
s2 = v.Mag2(); or s2 = v.M2();
s = v.Mag();
s = v.M();
Since in case of momentum and energy the magnitude has the meaning of invariant mass TLorentzVector provides the more meaningful aliases M2() and M();
The member functions Beta() and Gamma() returns beta and gamma = 1/Sqrt(1-beta*beta).
The member function Boost() performs a boost transformation from the rod frame to the original frame. BoostVector() returns a TVector3 of the spatial components divided by the time component:
TVector3 b;
v.Boost(bx,by,bz);
v.Boost(b);
b = v.BoostVector(); // b=(x/t,y/t,z/t)
Double_t pcone = v.Plus();
Double_t mcone = v.Minus();
CAVEAT: The values returned are T{+,-}Z. It is known that some authors find it easier to define these components as (T{+,-}Z)/sqrt(2). Thus check what definition is used in the physics you're working in and adapt your code accordingly.
TLorentzRotation l;
v.Transform(l);
v = l*v; or
v *= l; // Attention v = l*v
virtual void | TObject::DoError(int level, const char* location, const char* fmt, va_list va) const |
void | TObject::MakeZombie() |
static TObject::(anonymous) | TObject::kBitMask | |
static TObject::EStatusBits | TObject::kCanDelete | |
static TObject::EStatusBits | TObject::kCannotPick | |
static TObject::EStatusBits | TObject::kHasUUID | |
static TObject::EStatusBits | TObject::kInvalidObject | |
static TObject::(anonymous) | TObject::kIsOnHeap | |
static TObject::EStatusBits | TObject::kIsReferenced | |
static TObject::EStatusBits | TObject::kMustCleanup | |
static TLorentzVector::(anonymous) | kNUM_COORDINATES | |
static TObject::EStatusBits | TObject::kNoContextMenu | |
static TObject::(anonymous) | TObject::kNotDeleted | |
static TObject::EStatusBits | TObject::kObjInCanvas | |
static TObject::(anonymous) | TObject::kOverwrite | |
static TLorentzVector::(anonymous) | kSIZE | |
static TObject::(anonymous) | TObject::kSingleKey | |
static TLorentzVector::(anonymous) | kT | |
static TObject::(anonymous) | TObject::kWriteDelete | |
static TLorentzVector::(anonymous) | kX | |
static TLorentzVector::(anonymous) | kY | |
static TLorentzVector::(anonymous) | kZ | |
static TObject::(anonymous) | TObject::kZombie |