Forward Beamline Simulation (short overview)

1. Forward Beamline Simulation(short overview) V.Andreev LPI, Moscow 1. Introduction 2. Dead material description 3. Active detectors 4. Summary Diffraction and the (V)FPS Antwerpen 09 December 2005

2. Introduction • List of persons who gave contribution to H1SIM (Forward beamline): • M.Kapishin, H.Mahlke-Krueger, A.Kutov, B.List , • A.Fedotov, A.Zhokin, V.Solochenko, P.Van Michelen, • U.Duenger, K.H. Hiller , V.Andreev. • Two important things need to take into account: • a) dead material description (“close” as possible to reality) • for active detectors (FTS and FNC); • b) correct magnet's position and field description for right particle's trajectory reconstruction (FPS and VFPS detectors).

3. Dead material • Example of quadrupolesdescription

4. Such “detailed” description was done only up to ~ 110 m with inserting correct beampipe shape, quadrupoles, dipoles, flanges and all others dead material (this is important for FTS and FNC). • Behind FNC calorimeter very simple dead material description was used (like “tube” shape for beampipe and also for magnet elements) because the very precise magnet field description is more important for VFPS.

5. Active Detectors (FTS and FNC) • ForwardTaggingSystem (FTS)

6. FTS 28 m • View of two FTS stations

7. example of H1SIM simulation (present setup) and comparison with real data (R.Weber – diffractive rho production with DIFFVMgenerator)

8. Xv=0.0 cm sum diss ela Yv=0.0 cm Xv=0.23 cm sum ela diss Yv=0.67 cm Xv=0.23 cm sum diss ela Yv=0.67 cm tilt_x=-0.8 mrad tilt_y=0.8 mrad

9. ela sum diss • Tuning procedure (decreasing GEANT energy cuts in some dead material and put two scintillator counters of 90-th FTS station into correct position ) present sum diss ela “tuned”

10. Short conclusion for this part • H1SIM (at least forward part ) is tuning for the nominal vertex (Xv=0.0 cm and Yv=0.0 cm) for electron case and (Xv=0.75 cm and Yv=0.0 cm) for positron case and for zero tilt in IP. • In real life there are vertex shift (Xv=0.23 cm, Yv=0.68 cm) and beam tilt (tilt_x= -0.8 mrad ,tilt_y = 0.8 mrad). • Simple possibility to “resolve” this problem was suggested by B.List : put all “forward” particles into nominal simulation vertex (with Xv=0.0 cm, Yv=0.0 cm and zero beam tilt).

11. FPS and VFPS stations • Slice at 100 m from IP (inline generator p=883.2-920.0 GeV, theta=0.0-0.126 deg and phi=0.0-360 deg) for events with dP > 0.1 MeV standart JGDO “improve” JGDO

12. present JBPS “improve” JBPS • Slice at 220 m for the same inline generator and dP < 0.01 MeV and presence hit in VFPS station (influence of the kick magnet)

13. Vx = 0.75 cm Vx = 0.37 cm • Slice at 220 m for the same inline generator and dP < 0.01 MeV and presence hit in VFPS station (different vertex position )

14. z illustrated by the next scetch: s z2 • the problem which was realized in present description of magnet's position behind 100 m is s2 z2 z1 z1 s1 real magnet position we have (z1,z2) magnet position coordinates instead of (z1,z2) which should be and shift about several cm at 220 m H1

15. Summary • Present H1SIM version doesn't give full relevant description of the Forward beamline. • Problem with response of FTS stations (could be solved by the simple way). • Need to revise magnet's position behind 100 m (VFPS). • Absence description of PToF, FTi1 and Fti2 in present H1SIM version.