Forward Beamline Simulation (short overview)

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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 quadrupoles description

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• 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)

• Forward Tagging System (FTS)

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• View of two FTS stations

FTS 28 m
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• example of H1SIM simulation (present setup) and
  comparison with real data (R.Weber diffractive
  rho production with DIFFVM generator)

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Xv0.0 cm
sum
diss
ela
Yv0.0 cm
Xv0.23 cm
sum
ela
diss
Yv0.67 cm
Xv0.23 cm
sum
diss
ela
Yv0.67 cm
tilt_x-0.8 mrad
tilt_y0.8 mrad
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• Tuning procedure (decreasing GEANT energy cuts in
  some dead material and put two scintillator
  counters of 90-th FTS station into correct
  position )

ela
sum
diss
present
sum
diss
ela
tuned
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Short conclusion for this part

• H1SIM (at least forward part ) is tuning for the
  nominal vertex (Xv0.0 cm and Yv0.0
  cm) for electron case and (Xv0.75 cm and Yv0.0
  cm) for positron case and for zero
  tilt in IP.
• In real life there are vertex shift (Xv0.23 cm,
  Yv0.68 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
  Xv0.0 cm, Yv0.0 cm and zero beam tilt).
  

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FPS and VFPS stations

• Slice at 100 m from IP (inline generator
  p883.2-920.0 GeV, theta0.0-0.126 deg and
  phi0.0-360 deg) for events with dP gt
  0.1 MeV

standart JGDO
improve JGDO
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• Slice at 220 m for the same inline generator and
  dP lt 0.01 MeV and presence hit in VFPS station
  (influence of the kick magnet)

present JBPS
improve JBPS
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• Slice at 220 m for the same inline generator and
  dP lt 0.01 MeV and presence hit in VFPS station
  (different vertex position )

Vx 0.75 cm
Vx 0.37 cm
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• the problem which was realized in present
  description of magnet's position behind 100 m is

z
illustrated by the next scetch
s
z2
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
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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.