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FPS Calibration

FPS Calibration. K.Hiller, DESY Zeuthen Antwerp FPS / VFPS meeting 9/12/2005. Optics of the beam line is well-defined: HERA  Monte Carlo. For the nominal beam the there is a unique relation between proton trajectory and momentum at IP.

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FPS Calibration

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  1. FPS Calibration K.Hiller, DESY Zeuthen Antwerp FPS / VFPS meeting 9/12/2005 • Optics of the beam line is well-defined: HERA  Monte Carlo. • For the nominal beam the there is a unique relation between proton • trajectory and momentum at IP. • At HERA running the proton beam is not at the nominal position. • For momentum reconstruction the measured proton tracks have • to be shifted into the ideal beam line system where the optics is defined

  2. Scattered Proton Trajectory For precise measurement of the proton trajectory a combination of 2 tracking stations is needed  “global track parameters” These “global track parameters” along the ring are uniquely determined by the proton momentum and offset at the IP X(Z,E), X’(Z,E) : global track parameters X(0), X’(0) : proton trajectory at IP AX, BX, CX, DX, GX, HX : optical constants Assume X(0) = 0 since under constraint  enlarge errors In linear machines, containing only dipols and quadrupoles, X and Y projections are completely decoupled  2 independent energy measurements !!!

  3. Calibration of Vertical Pots Kinematic range: 0.1 < Xpom < 0.4 • leading proton by Reggeon/Pion exchange • no well-defined process for calibration • use local or global track “hit pattern” for calibration Local Tracks Global Tracks

  4. Vertical Calibration Constants 2004 81V at ~ 15 mm 90V at ~ 65 mm (detector insert too short  poor data)

  5. Calibration of Horizontal Pots  Diffractive ρ Photoproduction Kinematic range: Xpom < 0.05 γ + p  γ+ p + ρ  γ+ p + π+ + π- Assume soft, quasi-real photon ,  compensate by larger errors !!!

  6. Horizontal Calibration Constants 2004 Both detectors ~ 20 +- 5 mm to the proton orbit

  7. Proton Momentum Vertical Pots: 500 < Ep < 600 GeV 0 < |t| < 0.3 GeV2 Horizontal Pots: Ep > 880 GeV 0.2 < |t| < 1 GeV2

  8. Error Sources 1) real  nominal vertex at IP 2) momentum spread at IP (… emittance) 3) spatial detector resolution 4) calibration constants 5) optical constants (negligible !) 6) beam corrections during the proton fill Error propagation takes into account only 3) + 4) + 6) To account for remaining sources errors of calibration constants are doubled Since the energy is measured in X and Y projections independently on can control the final errors.

  9. Momentum & Angular Errors

  10. Errors – Main Contributions

  11. Errors - Consistency RMS: errors 20 - 30% too small Sigma1/2: mixture of too small/large errors

  12. Calibration Status • 2004 • 1) Survey and geometry JRSU, JR3D: all for 2004 on NDB • (no 2004 tunnel survey – use of ad hoc values ….) • Pot positions JRPP: all on NDB • Optical constants JCDX/Y, JCEX/Y : all on NDB • Calibration constants JCBO: all on NDB • 2005 – much more data • Survey ???? helpful • Pot positions: done – Spaskov • Optical constants: ongoing for 2004/5 e-p • Calibration constants: target H1 meeting Who needs 2005 calibrated FPS data ?

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