// requires ROOT: http://root.cern.ch/
//
//    usage:            compile using ROOT by: ".L library_e_collision.C+" (note the plus sign)
//
//      By:             Jaideep Singh
//
//      Date:           03/16/07
//
//      descp:          Collisional Energy Loss Parameter Calculator
//
//                      accopanies this technote: http://www.jlab.org/~singhj/docs/radlength_sagdhv130.ps
//
//                      To use this library, place the following line in your macro to load the lib:
//
//                              gSystem->Load("library_e_collision_C.so");
//
//                      Make sure that it has been compiled as described in the usage above.
//                      Make sure that the path is correct in the "Load" command
//
//                      calculated mean and most probable collisional enery loss of electrons 
//                          passing through the elements and the following composite materials:
//                          H2, D2, CO2, SiO2, Na2O, CaO, BaO, SrO, BaO, B2O, K2O, Al2O3, As2O3,
//                          air, kapton, polystyrene, C1720, GE180, H20
//
//                      calcultes the density correction and uses Bethe-Bloch and Landau formulas
//
//      references:     Sternheimer, Berger, Seltzer ATOMIC DATA AND NUCLEAR DATA TABLES 30, 261-71 (1984)
//                      Particle Data Group, "Review of Particle Physics" Phys. Lett. B Vol 592 July 2004
//                      Material Composition Data (NIST 03/07/07): http://physics.nist.gov/cgi-bin/Star/compos.pl
//                      ESTAR (NIST 03/16/07) http://physics.nist.gov/PhysRefData/Star/Text/ESTAR.html

// head files needed to compile macro
#include "TMath.h"
#include "Riostream.h"
#include "library_pc.C"

// Collisional/Ionization loss spectrum "a" scale TSAI71
Double_t fBB_a(Double_t ZA , Double_t beta)
{
	Double_t left = 2.0*TMath::Pi()*pc_NA()*pc_re()*pc_re();  // #*m^2/mol
	left *= 100.0*100.0; 					  // #*cm^2/mol
	Double_t m = pc_m_e("MeV");				  // MeV
	Double_t right = ZA/beta/beta;			          // mol/g
	return left*m*right;	                                  // MeV*cm^2/g
}

// density effect
// See SBS AD & NDT 1984
Double_t fBB_delta(Double_t X, Double_t Xa, Double_t X0, Double_t X1, Double_t delta0, Double_t m)
{
	Double_t tlt = 2.0*TMath::Log(10.0);			// 4.6052
	Double_t a = (delta0 + tlt*(Xa-X0) )/TMath::Power(X1-X0,m);
	Double_t delta = 0.0;
	if      (            X <= X0) {
		delta = delta0*TMath::Power(100.0,X-X0);	//      X <= X0
	}
	else if (X0  <  X && X <  X1) {
		delta = tlt*(X-Xa)+a*TMath::Power(X1-X,m);      // X0 < X <  X1
	}
        else {
		delta = tlt*(X-Xa);				//      X >= X1
	}
	return delta;
}

// Collision/Ionization Loss parameters
// from Sternheimer, Berger, Seltzer ATOMIC DATA AND NUCLEAR DATA TABLES 30, 261-71 (1984)
// material = name of material
// parameter = "I"  , mean ionization potential (eV)
// parameter = "C"  , for density correction
// parameter = "X0" , for density correction
// parameter = "X1" , for density correction
// parameter = "a"  , for density correction
// parameter = "m"  , for density correction
// parameter = "d0" , for density correction
// parameter = "density" , "normal" density of material at room temperature?  g/cm^3
// jacked from NIST database and made by perl script in bethe-bloch directory
Double_t fBB(TString material = "H" , TString parameter = "I")
{
	Double_t ZA = 0.0;
	Double_t  I = 0.0;
	Double_t  I_gas  = 0.0;
	Double_t  I_lors = 0.0;
	Double_t  C = 0.0;
	Double_t X0 = 0.0;
	Double_t X1 = 0.0;
	Double_t  a = 0.0;
	Double_t  m = 0.0;
	Double_t delta0  = 0.0;
	Double_t density = 0.0;
	Double_t output  = 0.0;
// insert "coll_loss_par.C" here

	if (material == "H") {
		ZA = 0.9922;
		 I = 19.2;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -9.5835;
		X0 = 1.8639;
		X1 = 3.2718;
		 a = 0.1409;
		 m = 5.7273;
		delta0  = 0.00;
		density = 8.3748E-05;
	}
	else if (material == "H2") {
		ZA = 0.9922;
		 I = 21.8;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -3.2632;
		X0 = 0.4759;
		X1 = 1.9215;
		 a = 0.1348;
		 m = 5.6249;
		delta0  = 0.00;
		density = 6.0000E-02;
	}
	else if (material == "He") {
		ZA = 0.4997;
		 I = 41.8;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -11.1393;
		X0 = 2.2017;
		X1 = 3.6122;
		 a = 0.1344;
		 m = 5.8347;
		delta0  = 0.00;
		density = 1.6632E-04;
	}
	else if (material == "Li") {
		ZA = 0.4322;
		 I = 40.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -3.1221;
		X0 = 0.1304;
		X1 = 1.6397;
		 a = 0.9514;
		 m = 2.4993;
		delta0  = 0.14;
		density = 5.3400E-01;
	}
	else if (material == "Be") {
		ZA = 0.4438;
		 I = 63.7;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -2.7847;
		X0 = 0.0592;
		X1 = 1.6922;
		 a = 0.8039;
		 m = 2.4339;
		delta0  = 0.14;
		density = 1.8480E+00;
	}
	else if (material == "B") {
		ZA = 0.4625;
		 I = 76.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -2.8477;
		X0 = 0.0305;
		X1 = 1.9688;
		 a = 0.5622;
		 m = 2.4512;
		delta0  = 0.14;
		density = 2.3700E+00;
	}
	else if (material == "graphite") {
		ZA = 0.4995;
		 I = 78.0;
		 I_gas  = 0.8974;
		 I_lors = 1.0385;
		 C = -2.8680;
		X0 = -0.1780;
		X1 = 2.3415;
		 a = 0.2614;
		 m = 2.8697;
		delta0  = 0.12;
		density = 2.2650E+00;
	}
	else if (material == "C") {
		ZA = 0.4995;
		 I = 78.0;
		 I_gas  = 0.8974;
		 I_lors = 1.0385;
		 C = -2.9925;
		X0 = -0.0351;
		X1 = 2.4860;
		 a = 0.2024;
		 m = 3.0036;
		delta0  = 0.10;
		density = 2.0000E+00;
	}
	else if (material == "amorphous carbon") {
		ZA = 0.4995;
		 I = 78.0;
		 I_gas  = 0.8974;
		 I_lors = 1.0385;
		 C = -3.1550;
		X0 = 0.0480;
		X1 = 2.5387;
		 a = 0.2076;
		 m = 2.9532;
		delta0  = 0.14;
		density = 1.7000E+00;
	}
	else if (material == "N") {
		ZA = 0.4998;
		 I = 82.0;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -10.5400;
		X0 = 1.7378;
		X1 = 4.1323;
		 a = 0.1535;
		 m = 3.2125;
		delta0  = 0.00;
		density = 1.1653E-03;
	}
	else if (material == "O") {
		ZA = 0.5000;
		 I = 95.0;
		 I_gas  = 1.0211;
		 I_lors = 1.1158;
		 C = -10.7004;
		X0 = 1.7541;
		X1 = 4.3213;
		 a = 0.1778;
		 m = 3.2913;
		delta0  = 0.00;
		density = 1.3315E-03;
	}
	else if (material == "F") {
		ZA = 0.4737;
		 I = 115.0;
		 I_gas  = 1.0000;
		 I_lors = 0.9739;
		 C = -10.9653;
		X0 = 1.8433;
		X1 = 4.4096;
		 a = 0.1108;
		 m = 3.2962;
		delta0  = 0.00;
		density = 1.5803E-03;
	}
	else if (material == "Ne") {
		ZA = 0.4956;
		 I = 137.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -11.9041;
		X0 = 2.0735;
		X1 = 4.6421;
		 a = 0.0806;
		 m = 3.5771;
		delta0  = 0.00;
		density = 8.3851E-04;
	}
	else if (material == "Na") {
		ZA = 0.4785;
		 I = 149.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.0526;
		X0 = 0.2880;
		X1 = 3.1962;
		 a = 0.0772;
		 m = 3.6452;
		delta0  = 0.08;
		density = 9.7100E-01;
	}
	else if (material == "Mg") {
		ZA = 0.4937;
		 I = 156.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.5297;
		X0 = 0.1499;
		X1 = 3.0668;
		 a = 0.0816;
		 m = 3.6166;
		delta0  = 0.08;
		density = 1.7400E+00;
	}
	else if (material == "Al") {
		ZA = 0.4818;
		 I = 166.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.2395;
		X0 = 0.1708;
		X1 = 3.0127;
		 a = 0.0802;
		 m = 3.6345;
		delta0  = 0.12;
		density = 2.6989E+00;
	}
	else if (material == "Si") {
		ZA = 0.4985;
		 I = 173.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.4351;
		X0 = 0.2014;
		X1 = 2.8715;
		 a = 0.1492;
		 m = 3.2546;
		delta0  = 0.14;
		density = 2.3300E+00;
	}
	else if (material == "P") {
		ZA = 0.4843;
		 I = 173.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.5214;
		X0 = 0.1696;
		X1 = 2.7815;
		 a = 0.2361;
		 m = 2.9158;
		delta0  = 0.14;
		density = 2.2000E+00;
	}
	else if (material == "S") {
		ZA = 0.4991;
		 I = 180.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.6659;
		X0 = 0.1580;
		X1 = 2.7159;
		 a = 0.3399;
		 m = 2.6456;
		delta0  = 0.14;
		density = 2.0000E+00;
	}
	else if (material == "Cl") {
		ZA = 0.4795;
		 I = 174.0;
		 I_gas  = 1.0000;
		 I_lors = 1.0345;
		 C = -11.1421;
		X0 = 1.5550;
		X1 = 4.2994;
		 a = 0.1985;
		 m = 2.9702;
		delta0  = 0.00;
		density = 2.9947E-03;
	}
	else if (material == "Ar") {
		ZA = 0.4506;
		 I = 188.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -11.9480;
		X0 = 1.7635;
		X1 = 4.4855;
		 a = 0.1971;
		 m = 2.9618;
		delta0  = 0.00;
		density = 1.6620E-03;
	}
	else if (material == "K") {
		ZA = 0.4860;
		 I = 190.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.6423;
		X0 = 0.3851;
		X1 = 3.1724;
		 a = 0.1983;
		 m = 2.9233;
		delta0  = 0.10;
		density = 8.6200E-01;
	}
	else if (material == "Ca") {
		ZA = 0.4990;
		 I = 191.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.0396;
		X0 = 0.3228;
		X1 = 3.1191;
		 a = 0.1564;
		 m = 3.0745;
		delta0  = 0.14;
		density = 1.5500E+00;
	}
	else if (material == "Sc") {
		ZA = 0.4671;
		 I = 216.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.6949;
		X0 = 0.1640;
		X1 = 3.0593;
		 a = 0.1575;
		 m = 3.0517;
		delta0  = 0.10;
		density = 2.9890E+00;
	}
	else if (material == "Ti") {
		ZA = 0.4595;
		 I = 233.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.4450;
		X0 = 0.0957;
		X1 = 3.0386;
		 a = 0.1566;
		 m = 3.0302;
		delta0  = 0.12;
		density = 4.5400E+00;
	}
	else if (material == "V") {
		ZA = 0.4515;
		 I = 245.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.2659;
		X0 = 0.0691;
		X1 = 3.0322;
		 a = 0.1544;
		 m = 3.0163;
		delta0  = 0.14;
		density = 6.1100E+00;
	}
	else if (material == "Cr") {
		ZA = 0.4616;
		 I = 257.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.1781;
		X0 = 0.0340;
		X1 = 3.0451;
		 a = 0.1542;
		 m = 2.9896;
		delta0  = 0.14;
		density = 7.1800E+00;
	}
	else if (material == "Mn") {
		ZA = 0.4551;
		 I = 272.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.2702;
		X0 = 0.0447;
		X1 = 3.1074;
		 a = 0.1497;
		 m = 2.9796;
		delta0  = 0.14;
		density = 7.4400E+00;
	}
	else if (material == "Fe") {
		ZA = 0.4656;
		 I = 286.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.2911;
		X0 = -0.0012;
		X1 = 3.1531;
		 a = 0.1468;
		 m = 2.9632;
		delta0  = 0.12;
		density = 7.8740E+00;
	}
	else if (material == "Co") {
		ZA = 0.4581;
		 I = 297.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.2601;
		X0 = -0.0187;
		X1 = 3.1790;
		 a = 0.1447;
		 m = 2.9502;
		delta0  = 0.12;
		density = 8.9000E+00;
	}
	else if (material == "Ni") {
		ZA = 0.4771;
		 I = 311.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.3115;
		X0 = -0.0566;
		X1 = 3.1851;
		 a = 0.1650;
		 m = 2.8430;
		delta0  = 0.10;
		density = 8.9020E+00;
	}
	else if (material == "Cu") {
		ZA = 0.4564;
		 I = 322.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.4190;
		X0 = -0.0254;
		X1 = 3.2792;
		 a = 0.1434;
		 m = 2.9044;
		delta0  = 0.08;
		density = 8.9600E+00;
	}
	else if (material == "Zn") {
		ZA = 0.4589;
		 I = 330.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.6906;
		X0 = 0.0049;
		X1 = 3.3668;
		 a = 0.1471;
		 m = 2.8652;
		delta0  = 0.08;
		density = 7.1330E+00;
	}
	else if (material == "Ga") {
		ZA = 0.4446;
		 I = 334.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.9353;
		X0 = 0.2267;
		X1 = 3.5434;
		 a = 0.0944;
		 m = 3.1314;
		delta0  = 0.14;
		density = 5.9040E+00;
	}
	else if (material == "Ge") {
		ZA = 0.4408;
		 I = 350.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.1411;
		X0 = 0.3376;
		X1 = 3.6096;
		 a = 0.0719;
		 m = 3.3306;
		delta0  = 0.14;
		density = 5.3230E+00;
	}
	else if (material == "As") {
		ZA = 0.4405;
		 I = 347.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.0510;
		X0 = 0.1767;
		X1 = 3.5702;
		 a = 0.0663;
		 m = 3.4176;
		delta0  = 0.08;
		density = 5.7300E+00;
	}
	else if (material == "Se") {
		ZA = 0.4306;
		 I = 348.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.3210;
		X0 = 0.2258;
		X1 = 3.6244;
		 a = 0.0657;
		 m = 3.4317;
		delta0  = 0.10;
		density = 4.5000E+00;
	}
	else if (material == "Br") {
		ZA = 0.4380;
		 I = 343.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -11.7307;
		X0 = 1.5262;
		X1 = 4.9899;
		 a = 0.0634;
		 m = 3.4670;
		delta0  = 0.00;
		density = 7.0722E-03;
	}
	else if (material == "Kr") {
		ZA = 0.4296;
		 I = 352.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -12.5115;
		X0 = 1.7158;
		X1 = 5.0748;
		 a = 0.0745;
		 m = 3.4051;
		delta0  = 0.00;
		density = 3.4783E-03;
	}
	else if (material == "Rb") {
		ZA = 0.4329;
		 I = 363.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.4776;
		X0 = 0.5737;
		X1 = 3.7995;
		 a = 0.0726;
		 m = 3.4177;
		delta0  = 0.14;
		density = 1.5320E+00;
	}
	else if (material == "Sr") {
		ZA = 0.4337;
		 I = 366.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.9867;
		X0 = 0.4585;
		X1 = 3.6778;
		 a = 0.0717;
		 m = 3.4435;
		delta0  = 0.14;
		density = 2.5400E+00;
	}
	else if (material == "Y") {
		ZA = 0.4387;
		 I = 379.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.4801;
		X0 = 0.3608;
		X1 = 3.5542;
		 a = 0.0714;
		 m = 3.4585;
		delta0  = 0.14;
		density = 4.4690E+00;
	}
	else if (material == "Zr") {
		ZA = 0.4385;
		 I = 393.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.1774;
		X0 = 0.2957;
		X1 = 3.4890;
		 a = 0.0718;
		 m = 3.4533;
		delta0  = 0.14;
		density = 6.5060E+00;
	}
	else if (material == "Nb") {
		ZA = 0.4413;
		 I = 417.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.0141;
		X0 = 0.1785;
		X1 = 3.2201;
		 a = 0.1388;
		 m = 3.0930;
		delta0  = 0.14;
		density = 8.5700E+00;
	}
	else if (material == "Mo") {
		ZA = 0.4378;
		 I = 424.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.8793;
		X0 = 0.2267;
		X1 = 3.2784;
		 a = 0.1052;
		 m = 3.2549;
		delta0  = 0.14;
		density = 1.0220E+01;
	}
	else if (material == "Tc") {
		ZA = 0.4392;
		 I = 428.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.7769;
		X0 = 0.0949;
		X1 = 3.1253;
		 a = 0.1657;
		 m = 2.9738;
		delta0  = 0.14;
		density = 1.1500E+01;
	}
	else if (material == "Ru") {
		ZA = 0.4353;
		 I = 441.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.7694;
		X0 = 0.0599;
		X1 = 3.0834;
		 a = 0.1934;
		 m = 2.8707;
		delta0  = 0.14;
		density = 1.2410E+01;
	}
	else if (material == "Rh") {
		ZA = 0.4373;
		 I = 449.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.8008;
		X0 = 0.0576;
		X1 = 3.1069;
		 a = 0.1920;
		 m = 2.8633;
		delta0  = 0.14;
		density = 1.2410E+01;
	}
	else if (material == "Pd") {
		ZA = 0.4323;
		 I = 470.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -4.9358;
		X0 = 0.0563;
		X1 = 3.0555;
		 a = 0.2418;
		 m = 2.7239;
		delta0  = 0.14;
		density = 1.2020E+01;
	}
	else if (material == "Ag") {
		ZA = 0.4357;
		 I = 470.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.0630;
		X0 = 0.0657;
		X1 = 3.1074;
		 a = 0.2459;
		 m = 2.6899;
		delta0  = 0.14;
		density = 1.0500E+01;
	}
	else if (material == "Cd") {
		ZA = 0.4270;
		 I = 469.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.2727;
		X0 = 0.1281;
		X1 = 3.1667;
		 a = 0.2461;
		 m = 2.6772;
		delta0  = 0.14;
		density = 8.6500E+00;
	}
	else if (material == "In") {
		ZA = 0.4268;
		 I = 488.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.5211;
		X0 = 0.2406;
		X1 = 3.2032;
		 a = 0.2388;
		 m = 2.7144;
		delta0  = 0.14;
		density = 7.3100E+00;
	}
	else if (material == "Sn") {
		ZA = 0.4213;
		 I = 488.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.5340;
		X0 = 0.2879;
		X1 = 3.2959;
		 a = 0.1869;
		 m = 2.8576;
		delta0  = 0.14;
		density = 7.3100E+00;
	}
	else if (material == "Sb") {
		ZA = 0.4189;
		 I = 487.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.6241;
		X0 = 0.3189;
		X1 = 3.3489;
		 a = 0.1665;
		 m = 2.9319;
		delta0  = 0.14;
		density = 6.6910E+00;
	}
	else if (material == "Te") {
		ZA = 0.4075;
		 I = 485.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.7131;
		X0 = 0.3296;
		X1 = 3.4418;
		 a = 0.1381;
		 m = 3.0354;
		delta0  = 0.14;
		density = 6.2400E+00;
	}
	else if (material == "I") {
		ZA = 0.4176;
		 I = 491.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.9488;
		X0 = 0.0549;
		X1 = 3.2596;
		 a = 0.2377;
		 m = 2.7276;
		delta0  = 0.00;
		density = 4.9300E+00;
	}
	else if (material == "Xe") {
		ZA = 0.4113;
		 I = 482.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -12.7281;
		X0 = 1.5630;
		X1 = 4.7371;
		 a = 0.2331;
		 m = 2.7414;
		delta0  = 0.00;
		density = 5.4854E-03;
	}
	else if (material == "Cs") {
		ZA = 0.4138;
		 I = 488.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.9135;
		X0 = 0.5473;
		X1 = 3.5914;
		 a = 0.1823;
		 m = 2.8866;
		delta0  = 0.14;
		density = 1.8730E+00;
	}
	else if (material == "Ba") {
		ZA = 0.4078;
		 I = 491.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.3153;
		X0 = 0.4190;
		X1 = 3.4547;
		 a = 0.1827;
		 m = 2.8906;
		delta0  = 0.14;
		density = 3.5000E+00;
	}
	else if (material == "La") {
		ZA = 0.4104;
		 I = 501.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.7850;
		X0 = 0.3161;
		X1 = 3.3293;
		 a = 0.1859;
		 m = 2.8828;
		delta0  = 0.14;
		density = 6.1540E+00;
	}
	else if (material == "Ce") {
		ZA = 0.4139;
		 I = 523.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.7837;
		X0 = 0.2713;
		X1 = 3.3432;
		 a = 0.1888;
		 m = 2.8592;
		delta0  = 0.14;
		density = 6.6570E+00;
	}
	else if (material == "Pr") {
		ZA = 0.4187;
		 I = 535.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.8096;
		X0 = 0.2333;
		X1 = 3.2773;
		 a = 0.2326;
		 m = 2.7331;
		delta0  = 0.14;
		density = 6.7100E+00;
	}
	else if (material == "Nd") {
		ZA = 0.4160;
		 I = 546.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.8290;
		X0 = 0.1984;
		X1 = 3.3063;
		 a = 0.2353;
		 m = 2.7050;
		delta0  = 0.14;
		density = 6.9000E+00;
	}
	else if (material == "Pm") {
		ZA = 0.4209;
		 I = 560.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.8224;
		X0 = 0.1627;
		X1 = 3.3199;
		 a = 0.2428;
		 m = 2.6674;
		delta0  = 0.14;
		density = 7.2200E+00;
	}
	else if (material == "Sm") {
		ZA = 0.4123;
		 I = 574.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.8597;
		X0 = 0.1520;
		X1 = 3.3460;
		 a = 0.2470;
		 m = 2.6403;
		delta0  = 0.14;
		density = 7.4600E+00;
	}
	else if (material == "Eu") {
		ZA = 0.4146;
		 I = 580.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.2278;
		X0 = 0.1888;
		X1 = 3.4633;
		 a = 0.2445;
		 m = 2.6245;
		delta0  = 0.14;
		density = 5.2430E+00;
	}
	else if (material == "Gd") {
		ZA = 0.4070;
		 I = 591.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.8738;
		X0 = 0.1058;
		X1 = 3.3932;
		 a = 0.2511;
		 m = 2.5977;
		delta0  = 0.14;
		density = 7.9004E+00;
	}
	else if (material == "Tb") {
		ZA = 0.4090;
		 I = 614.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.9045;
		X0 = 0.0947;
		X1 = 3.4224;
		 a = 0.2445;
		 m = 2.6056;
		delta0  = 0.14;
		density = 8.2290E+00;
	}
	else if (material == "Dy") {
		ZA = 0.4062;
		 I = 628.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.9183;
		X0 = 0.0822;
		X1 = 3.4474;
		 a = 0.2467;
		 m = 2.5849;
		delta0  = 0.14;
		density = 8.5500E+00;
	}
	else if (material == "Ho") {
		ZA = 0.4062;
		 I = 650.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.9587;
		X0 = 0.0761;
		X1 = 3.4782;
		 a = 0.2464;
		 m = 2.5726;
		delta0  = 0.14;
		density = 8.7950E+00;
	}
	else if (material == "Er") {
		ZA = 0.4066;
		 I = 658.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.9521;
		X0 = 0.0684;
		X1 = 3.4922;
		 a = 0.2482;
		 m = 2.5573;
		delta0  = 0.14;
		density = 9.0660E+00;
	}
	else if (material == "Tm") {
		ZA = 0.4084;
		 I = 674.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.9677;
		X0 = 0.0812;
		X1 = 3.5085;
		 a = 0.2489;
		 m = 2.5469;
		delta0  = 0.14;
		density = 9.3210E+00;
	}
	else if (material == "Yb") {
		ZA = 0.4045;
		 I = 684.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.3325;
		X0 = 0.1199;
		X1 = 3.6246;
		 a = 0.2530;
		 m = 2.5141;
		delta0  = 0.14;
		density = 6.7300E+00;
	}
	else if (material == "Lu") {
		ZA = 0.4058;
		 I = 694.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.9785;
		X0 = 0.1560;
		X1 = 3.5218;
		 a = 0.2403;
		 m = 2.6543;
		delta0  = 0.14;
		density = 9.8400E+00;
	}
	else if (material == "Ha") {
		ZA = 0.4034;
		 I = 705.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.7139;
		X0 = 0.1965;
		X1 = 3.4337;
		 a = 0.2292;
		 m = 2.6155;
		delta0  = 0.14;
		density = 1.3310E+01;
	}
	else if (material == "Ta") {
		ZA = 0.4034;
		 I = 718.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.5262;
		X0 = 0.2117;
		X1 = 3.4805;
		 a = 0.1780;
		 m = 2.7623;
		delta0  = 0.14;
		density = 1.6654E+01;
	}
	else if (material == "W") {
		ZA = 0.4025;
		 I = 727.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.4059;
		X0 = 0.2167;
		X1 = 3.4960;
		 a = 0.1551;
		 m = 2.8447;
		delta0  = 0.14;
		density = 1.9300E+01;
	}
	else if (material == "Re") {
		ZA = 0.4028;
		 I = 736.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.3445;
		X0 = 0.0559;
		X1 = 3.4845;
		 a = 0.1518;
		 m = 2.8627;
		delta0  = 0.08;
		density = 2.1020E+01;
	}
	else if (material == "Os") {
		ZA = 0.3996;
		 I = 746.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.3083;
		X0 = 0.0891;
		X1 = 3.5414;
		 a = 0.1275;
		 m = 2.9608;
		delta0  = 0.10;
		density = 2.2570E+01;
	}
	else if (material == "Ir") {
		ZA = 0.4006;
		 I = 757.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.3418;
		X0 = 0.0819;
		X1 = 3.5480;
		 a = 0.1269;
		 m = 2.9658;
		delta0  = 0.10;
		density = 2.2420E+01;
	}
	else if (material == "Pt") {
		ZA = 0.3998;
		 I = 790.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.4732;
		X0 = 0.1484;
		X1 = 3.6212;
		 a = 0.1113;
		 m = 3.0417;
		delta0  = 0.12;
		density = 2.1450E+01;
	}
	else if (material == "Au") {
		ZA = 0.4011;
		 I = 790.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.5747;
		X0 = 0.2021;
		X1 = 3.6979;
		 a = 0.0976;
		 m = 3.1101;
		delta0  = 0.14;
		density = 1.9320E+01;
	}
	else if (material == "Hg") {
		ZA = 0.3988;
		 I = 800.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.9605;
		X0 = 0.2756;
		X1 = 3.7275;
		 a = 0.1101;
		 m = 3.0519;
		delta0  = 0.14;
		density = 1.3546E+01;
	}
	else if (material == "Tl") {
		ZA = 0.3963;
		 I = 810.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.1365;
		X0 = 0.3491;
		X1 = 3.8044;
		 a = 0.0945;
		 m = 3.1450;
		delta0  = 0.14;
		density = 1.1720E+01;
	}
	else if (material == "Pb") {
		ZA = 0.3958;
		 I = 823.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.2018;
		X0 = 0.3776;
		X1 = 3.8073;
		 a = 0.0936;
		 m = 3.1608;
		delta0  = 0.14;
		density = 1.1350E+01;
	}
	else if (material == "Bi") {
		ZA = 0.3972;
		 I = 823.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.3505;
		X0 = 0.4152;
		X1 = 3.8248;
		 a = 0.0941;
		 m = 3.1671;
		delta0  = 0.14;
		density = 9.7470E+00;
	}
	else if (material == "Po") {
		ZA = 0.4019;
		 I = 830.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.4003;
		X0 = 0.4267;
		X1 = 3.8293;
		 a = 0.0928;
		 m = 3.1830;
		delta0  = 0.14;
		density = 9.3200E+00;
	}
	else if (material == "Rn") {
		ZA = 0.3874;
		 I = 794.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -13.2839;
		X0 = 1.5368;
		X1 = 4.9889;
		 a = 0.2080;
		 m = 2.7409;
		delta0  = 0.00;
		density = 9.0662E-03;
	}
	else if (material == "Ra") {
		ZA = 0.3893;
		 I = 826.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -7.0452;
		X0 = 0.5991;
		X1 = 3.9428;
		 a = 0.0880;
		 m = 3.2454;
		delta0  = 0.14;
		density = 5.0000E+00;
	}
	else if (material == "Ac") {
		ZA = 0.3920;
		 I = 841.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.3742;
		X0 = 0.4559;
		X1 = 3.7966;
		 a = 0.0857;
		 m = 3.2683;
		delta0  = 0.14;
		density = 1.0070E+01;
	}
	else if (material == "Th") {
		ZA = 0.3879;
		 I = 847.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.2473;
		X0 = 0.4202;
		X1 = 3.7681;
		 a = 0.0866;
		 m = 3.2610;
		delta0  = 0.14;
		density = 1.1720E+01;
	}
	else if (material == "Pa") {
		ZA = 0.3939;
		 I = 878.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.0327;
		X0 = 0.3144;
		X1 = 3.5079;
		 a = 0.1477;
		 m = 2.9845;
		delta0  = 0.14;
		density = 1.5370E+01;
	}
	else if (material == "U") {
		ZA = 0.3865;
		 I = 890.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.8694;
		X0 = 0.2260;
		X1 = 3.3721;
		 a = 0.1968;
		 m = 2.8171;
		delta0  = 0.14;
		density = 1.8950E+01;
	}
	else if (material == "Np") {
		ZA = 0.3923;
		 I = 902.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.8149;
		X0 = 0.1869;
		X1 = 3.3690;
		 a = 0.1974;
		 m = 2.8082;
		delta0  = 0.14;
		density = 2.0250E+01;
	}
	else if (material == "Pu") {
		ZA = 0.3932;
		 I = 921.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -5.8748;
		X0 = 0.1557;
		X1 = 3.3981;
		 a = 0.2042;
		 m = 2.7679;
		delta0  = 0.14;
		density = 1.9840E+01;
	}
	else if (material == "Am") {
		ZA = 0.3908;
		 I = 934.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.2813;
		X0 = 0.2274;
		X1 = 3.5021;
		 a = 0.2031;
		 m = 2.7615;
		delta0  = 0.14;
		density = 1.3670E+01;
	}
	else if (material == "Cm") {
		ZA = 0.3886;
		 I = 939.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.3097;
		X0 = 0.2484;
		X1 = 3.5160;
		 a = 0.2026;
		 m = 2.7579;
		delta0  = 0.14;
		density = 1.3510E+01;
	}
	else if (material == "Bk") {
		ZA = 0.3926;
		 I = 952.0;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -6.2912;
		X0 = 0.2378;
		X1 = 3.5186;
		 a = 0.2019;
		 m = 2.7560;
		delta0  = 0.14;
		density = 1.4000E+01;
	}
	else if (material == "air") {
		ZA = 0.4992;
		 I = 85.7;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -10.5961;
		X0 = 1.7418;
		X1 = 4.2759;
		 a = 0.1091;
		 m = 3.3994;
		delta0  = 0.00;
		density = 1.2048E-03;
	}
	else if (material == "Al2O3") {
		ZA = 0.4904;
		 I = 145.2;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -3.5682;
		X0 = 0.0402;
		X1 = 2.8665;
		 a = 0.0850;
		 m = 3.5458;
		delta0  = 0.00;
		density = 3.9700E+00;
	}
	else if (material == "B2O3") {
		ZA = 0.4884;
		 I = 99.6;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -3.6027;
		X0 = 0.1843;
		X1 = 2.7379;
		 a = 0.1155;
		 m = 3.3832;
		delta0  = 0.00;
		density = 1.8120E+00;
	}
	else if (material == "CaO") {
		ZA = 0.4993;
		 I = 176.1;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -4.1209;
		X0 = -0.0172;
		X1 = 3.0171;
		 a = 0.1213;
		 m = 3.1936;
		delta0  = 0.00;
		density = 3.3000E+00;
	}
	else if (material == "CaSO4") {
		ZA = 0.4995;
		 I = 152.3;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -3.9388;
		X0 = 0.0587;
		X1 = 3.1229;
		 a = 0.0771;
		 m = 3.4495;
		delta0  = 0.00;
		density = 2.9600E+00;
	}
	else if (material == "CO2") {
		ZA = 0.4999;
		 I = 85.0;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -10.1537;
		X0 = 1.6294;
		X1 = 4.1825;
		 a = 0.1177;
		 m = 3.3227;
		delta0  = 0.00;
		density = 1.8421E-03;
	}
	else if (material == "pyrex") {
		ZA = 0.4971;
		 I = 134.0;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -3.9708;
		X0 = 0.1479;
		X1 = 2.9933;
		 a = 0.0827;
		 m = 3.5224;
		delta0  = 0.00;
		density = 2.2300E+00;
	}
	else if (material == "kapton") {
		ZA = 0.5126;
		 I = 79.6;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -3.3497;
		X0 = 0.1509;
		X1 = 2.5631;
		 a = 0.1597;
		 m = 3.1921;
		delta0  = 0.00;
		density = 1.4200E+00;
	}
	else if (material == "MgO") {
		ZA = 0.4962;
		 I = 143.8;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -3.6404;
		X0 = 0.0575;
		X1 = 2.8580;
		 a = 0.0831;
		 m = 3.5968;
		delta0  = 0.00;
		density = 3.5800E+00;
	}
	else if (material == "CH4") {
		ZA = 0.6233;
		 I = 41.7;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -9.5243;
		X0 = 1.6263;
		X1 = 3.9716;
		 a = 0.0925;
		 m = 3.6257;
		delta0  = 0.00;
		density = 6.6715E-04;
	}
	else if (material == "polystyrene") {
		ZA = 0.5377;
		 I = 68.7;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -3.2999;
		X0 = 0.1647;
		X1 = 2.5031;
		 a = 0.1645;
		 m = 3.2224;
		delta0  = 0.00;
		density = 1.0600E+00;
	}
	else if (material == "K2O") {
		ZA = 0.4883;
		 I = 189.9;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -4.6463;
		X0 = 0.0480;
		X1 = 3.0110;
		 a = 0.1679;
		 m = 3.0121;
		delta0  = 0.00;
		density = 2.3200E+00;
	}
	else if (material == "SiO2") {
		ZA = 0.4993;
		 I = 139.2;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -4.0029;
		X0 = 0.1385;
		X1 = 3.0025;
		 a = 0.0841;
		 m = 3.5064;
		delta0  = 0.00;
		density = 2.3200E+00;
	}
	else if (material == "Na2O") {
		ZA = 0.4840;
		 I = 148.8;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -4.1892;
		X0 = 0.1652;
		X1 = 2.9793;
		 a = 0.0750;
		 m = 3.6943;
		delta0  = 0.00;
		density = 2.2700E+00;
	}
	else if (material == "water") {
		ZA = 0.5551;
		 I = 75.0;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -3.5017;
		X0 = 0.2400;
		X1 = 2.8004;
		 a = 0.0912;
		 m = 3.4773;
		delta0  = 0.00;
		density = 1.0000E+00;
	}
	else if (material == "water vapor") {
		ZA = 0.5551;
		 I = 71.6;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -10.5962;
		X0 = 1.7952;
		X1 = 4.3437;
		 a = 0.0810;
		 m = 3.5901;
		delta0  = 0.00;
		density = 7.5618E-04;
	}
	else if (material == "As2O3") {
		ZA = 0.4549;
		 I = 276.6;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -4.9606;
		X0 = 0.2000;
		X1 = 3.0000;
		 a = 0.1840;
		 m = 3.0000;
		delta0  = 0.00;
		density = 3.8600E+00;
	}
	else if (material == "BaO") {
		ZA = 0.4174;
		 I = 451.1;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -5.6349;
		X0 = 0.3370;
		X1 = 3.0000;
		 a = 0.2162;
		 m = 3.0000;
		delta0  = 0.00;
		density = 5.7000E+00;
	}
	else if (material == "SrO") {
		ZA = 0.4439;
		 I = 326.4;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -4.9259;
		X0 = 0.2000;
		X1 = 3.0000;
		 a = 0.1824;
		 m = 3.0000;
		delta0  = 0.00;
		density = 5.7000E+00;
	}
	else if (material == "C1720") {
		ZA = 0.4967;
		 I = 141.0;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -3.9477;
		X0 = 0.2000;
		X1 = 3.0000;
		 a = 0.1379;
		 m = 3.0000;
		delta0  = 0.00;
		density = 2.5300E+00;
	}
	else if (material == "GE180") {
		ZA = 0.4829;
		 I = 171.8;
		 I_gas  = 1.0000;
		 I_lors = 1.0000;
		 C = -4.2834;
		X0 = 0.2000;
		X1 = 3.0000;
		 a = 0.1532;
		 m = 3.0000;
		delta0  = 0.00;
		density = 2.7600E+00;
	}
	else if (material == "He3") {
		ZA = 0.6631;
		 I = 41.8;
		 I_gas  = 1.0000;
		 I_lors = 1.1300;
		 C = -11.1393;
		X0 = 2.2017;
		X1 = 3.6122;
		 a = 0.1344;
		 m = 5.8347;
		delta0  = 0.00;
		density = 1.2533E-04;
	}

// end insert here
	else
	{	cerr << "(fBB) Unknown material: " << material << endl;	}
	if (parameter == "I")
	{	output = I;	}
	else if (parameter == "ZA")
	{	output = ZA;	}
	else if (parameter == "C")
	{	output = C;	}
	else if (parameter == "X0")
	{	output = X0;	}
	else if (parameter == "X1")
	{	output = X1;	}
	else if (parameter == "a")
	{	output = a;	}
	else if (parameter == "m")
	{	output = m;	}
	else if (parameter == "delta0")
	{	output = delta0;	}
	else if (parameter == "density")
	{	output = density;	}
	else if (parameter == "I_gas")
	{	output = I_gas;		}
	else if (parameter == "I_lors")
	{	output = I_lors;	}
	else
	{	cerr << "(fBB) Unknown paramter: " << parameter << endl;	}
	return output;
}

// mean or most probable collisonal loss in MeV for ELECTRON beams only
// (positrons, protons, & alphas all require a different formula)
// material = name of material
// p = momentum of electron in MeV*c
// rho = density in g/cm^3
// xthick = thickness of material in cm
// type = "mean" for mean loss calculated from Bethe-Bloch equation
// type = "mp"   for most probably loss calculated by Landau
Double_t collision_loss(TString material, Double_t p, Double_t rho, Double_t xthick, TString type = "mp")
{
	Double_t ZA = fBB(material,"ZA"); 			// mol/g
	Double_t  I = fBB(material,"I")/1.0E6;			// eV -> MeV
	Double_t me = pc_m_e("MeV");				// MeV
	Double_t gamma = TMath::Sqrt(1.0+p*p/me/me);
	Double_t beta = TMath::Sqrt(1.0-1.0/gamma/gamma);
	Double_t xi = fBB_a(ZA,beta)*rho*xthick;		// (MeV/cm^2/g)*(g/cm^3)*(cm) = MeV

	Double_t X = TMath::Log10(p/me);
	Double_t m = fBB(material,"m");
	Double_t C = fBB(material,"C");
	Double_t rho0  = fBB(material,"density"); 		// g/cm^3
	Double_t X_rho = 0.5*TMath::Log10(rho/rho0);		// shift due to density difference
	Double_t Xa = -C/2.0/TMath::Log(10.0) - X_rho;
	Double_t X0 = fBB(material,"X0")      - X_rho;
	Double_t X1 = fBB(material,"X1")      - X_rho;
	Double_t delta0 = fBB(material,"delta0");
 	Double_t delta  = fBB_delta(X,Xa,X0,X1,delta0,m);

	Double_t term1 = 2.0*TMath::Log(p/I);
	Double_t g = 0.0;
	if (type == "mode" || type == "most" || type == "mp" || type == "most probable" || type == "landau") {
		g  = TMath::Log(2.0*xi/me);
		g -= beta*beta;
		g += 0.198;  // this term wrong in original Landau paper
	}
	else {
		Double_t F = (1.0+2.0/gamma-1.0/gamma/gamma)*TMath::Log(2.0);
		F -= 0.125*(1.0-1.0/gamma)*(1.0-1.0/gamma);
		F -= 1.0/gamma/gamma;
		g = TMath::Log(gamma-1.0) - F;
	}
//	cout << "xi   = " << xi << endl;
//	cout << "beta = " << beta << endl;
//	cout << "xi*beta^2 = " << xi*beta*beta << endl;
//	cout << "X    = " << X << endl;
//	cout << "term1          = " << term1 << endl;
//	cout << "density effect = " << delta << endl;
//	cout << "g              = " << g << endl;
	return xi*(term1 - delta + g);
}