Added beampipe v23a, short version of v21h

macro/pipe/fair/recalculate_BP.C

+using namespace std;
+
+void recalculate_BP(double maxZ)
+{
+    double phi = (1.2-0.435)*TMath::DegToRad(); // this rotation angle stays
+    double c = cos(phi);
+    double s = sin(phi);
+    double orig_half_length = 7230.; // original half length
+    double orig_T_x = 134.85;  // original translation in X when placing psd_tube
+    double orig_T_z = 10808.8; // original translation in Z when placing psd_tube
+
+    // placing psd_tube at origin
+    double S0_x = 0.;
+    double S0_z = -1.*orig_half_length;
+    double F0_x = 0.;
+    double F0_z = orig_half_length;
+
+    // after rotation around Y at origin:
+    double S1_x =  c*S0_x + s*S0_z;
+    double S1_z = -s*S0_x + c*S0_z;
+    double F1_x =  c*F0_x + s*F0_z;
+    double F1_z = -s*F0_x + c*F0_z;
+
+    // after original translation
+    double S2_x = S1_x + orig_T_x;
+    double S2_z = S1_z + orig_T_z;
+    double F2_x = F1_x + orig_T_x;
+    double F2_z = F1_z + orig_T_z;
+
+    // parameterization of line between S2 and F2: z = k*x + q
+    double k = (F2_z - S2_z)/(F2_x - S2_x);
+    double q = S2_z - k*S2_x;
+
+    // now using specified max Z of the F3 find its X 
+    double S3_x = S2_x;
+    double S3_z = S2_z;
+    double F3_z = maxZ;
+    double F3_x = (F3_z - q)/k;
+
+    // new half-length of tube
+    double new_half_length = 0.5*sqrt(pow(F3_x-S3_x,2) + pow(F3_z-S3_z,2));
+    double new_T_x = 0.5*(F3_x + S3_x);
+    double new_T_z = 0.5*(F3_z + S3_z);
+
+    cout << "New half-length: " << new_half_length << endl
+         << "New Trans [ " << new_T_x << " , 0., " << new_T_z << " ]" << endl;
+
+}
\ No newline at end of file

pipe/pipe_v23a.geo.info

+Beam pipe design taken from v21h (@ 12 AGeV/c)
+only small modification in ctr_psd_tube and psd_tube_s and vacuum_psd_tube_s
+to end the beam-pipe at z=9800 (for the middle of beampipe)
+this is needed to allow simulation with FSD without any hole