1. Antiproton-proton elastic scattering as a day-1 experiment at HESR
March 14-18, 2011 Darmstadt
Antiproton-proton elastic scattering as a day-1 experiment at HESR
Huagen Xu
IKP: J. Ritman, T. Stockmanns and T. Randriamalala
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2. Outline Introduction to PANDA luminosity monitor
Proposal of the day-1 experiment
Design of the day- 1 experiment
Summary and outlook
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3. 1. Panda luminosity monitor
Goal of Panda luminosity monitor: Integrated luminosity with ~ 3% absolute precision
PANDA facility
Concept: Low t elastic scattering, Coulomb interference region Forward going antiproton, 3 <Θ< 8 mrad 4-layer Si-strip telescope at z~10m 50 um pitch, double sided
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4. The measurable t is limited to a small range!
Performance evaluation with pure elastic events
PANDA
Setting for event generator(DPM):
Plab : 6.2 GeV/c, pure elastic events
Theta_min : °(~1.98mrad)
Events : 5M
Parameters : σel = 18.97mb, σtot = 64.50mb,
b = 11.89(GeV/c)-2, ρ =
t: [ ]
lumi: ~ 0.39%
The measurable t is limited to a small range!
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5. Fixing the parameters is needed to determine the absolute luminosity!
Parameters correlation
Only Lumi free
~0.34%
Both rho & Lumi free
~2.29%
ρ sensitive region
Fixing the parameters is needed to determine the absolute luminosity!
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6. Luminosity uncertainty Luminosity calibration error
2. Proposal of day-1 experiment
Few data existing in PDG for σtot and ρ within PANDA momentum region!
Motivation 1: To determine the parameters for Panda absolute
luminosity calibration
Motivation 2: Physics itself (to obtain accurate values for
the unknown parameters σtot , ρ and b)
Experiment strategy:
luminosity-independent measurement
Luminosity uncertainty
Parameters error
Luminosity calibration error
Error loop should be avoided!
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7. Parameters determination
Typical parameterization
σtot and ρ
b dominant region
Optical point
Optical theorem
Parameterization for slope b
for |t| < 0.8 GeV2 , moderate energies (5-30GeV)
Luminosity independent analysis is feasible!
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8. Large t-range measurement at HESR
Proposed location
Large t-range: GeV2 in order to reduce the parameters effect less than 1% on luminosity determination
Enough space in the early phase running of HESR
Antiproton-proton elastic scattering with coincidence at HESR!
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9. 3. Design of day-1 experiment
Sketch of general design Z θ’
target X Y
α = π/2 - θ’
Forward measurement
Recoils measurement
beam
Kinetic correlation
Background suppression
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10. Recoil arm Requirements for design:
Recoil angle for t:[ – 0.1] GeV2 (~0.4-55MeV)
1.6° °for 1.5 GeV/c
0.9° °for 15.0 GeV/c
Windowless cluster jet target
To measure recoil protons energy and position
Movable detector plane
Active
8 cm
Overlapping
1 cm 1 4 2 3
Beam axis
5cm
24cm
Single sided strip detectors
No. 1 and 2 Si strip sensor:
1000μm with 1.2 mm pitch
No. 3 and 4 Ge strip sensors:
4mm &10mm with 1.2mm pitch
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11. Commissioning at COSY in the next couple of years!
Status of recoil arm
Sensor design is fixed and production will get started by formal order;
Front end electronics solution (conventional commercial FEE modules available);
Mechanical design of vacuum chamber (in consideration)
Cluster jet target (under construction)
Building up a test system for detector test, electronics investigation, calibration study and so on (ongoing);
Commissioning at COSY in the next couple of years!
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12. 4. Summary and Outlook
Dedicated antiproton-proton elastic scattering as a day- 1 experiment at HESR has been proposed;
Design of recoil arm is nearly finished;
The forward arm design will be optimized after commissioning of recoil arm at COSY.
The complete day-1 experiment needs to be performed in the early running phase of HESR.
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13. Thanks for your attention!
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14. In PDG database: few data of σtot and ρ; no data of b;
Dependence of the uncertainty of absolute luminosity on errors of σtot , ρ and b
Err_Lumi vs Err_ σtot
Err_Lumi vs ρ
Err_Lumi vs Err_b
In PDG database: few data of σtot and ρ; no data of b;
The existing data are not sufficient for PANDA absolute luminosity calibration!
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15. Uncertainty of luminosity contributed by σtot
PANDA
Sigtot (mb)
PbarP, 6.2GeV/c
Data of σtot in PDG database
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16. Uncertainty of luminosity contributed by ρ
PANDA
PbarP, 6.2GeV/c
Data of ρ in PDG database
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17. Requirement 1: expected t-range
t:Optical point and b
Nuclear dominated region
t:ρ and σtot
Coulomb-strong region
Known b,ρ and σtot
absolute luminosity <1%
b and dNel/dt|t=0
t: [ ] GeV2
ρ and σtot
t: [ ] GeV2
Luminosity error
< 1% by parameters
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18. Expected t range :
– 0.1 (GeV/c)2
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19. FEE strategy for strip sensors
ASIC-based preamplifier
PCB board-based preamplifier modules
Both self-trigger capable
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20. Recoil arm Recoil angle for t: 0.0008 – 0.1 GeV2 (~0.4-55MeV)
Motor driver
system
18.9°
11°
Cooling plate
Cooling interface
Pump
Source mechanism
Flange 1, 2
Valve
Beam pipe Y
68cm
120cm
Beam height
1.4m
Recoil angle for t: – 0.1 GeV2 (~0.4-55MeV)
1.6° °for 1.5 GeV/c
0.9° °for 15.0 GeV/c
Windowless cluster jet target
Using strip detector to measure recoil protons energy and position
Movable detector plane
Source mechanism for calibration
Separate vacuum chamber
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21. Ratio ρ Typical method ρ sensitive region Optical theorem
PLB 385, 1996, 479 (E760)
NPB 262, 1985, 689
Typical method
ρ sensitive region
Optical theorem
PLB 537, 2002, (E811)
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22. Slope b Measurements for slope b Measure dσ/dt on a large t range
Away from the Coulomb interference region
Traditional parameterization
PR D24,1981,26
PR D50,1994,5518
b sensitive region
|t|<0.8(GeV/c)2, moderate energies(5-30GeV)
0.05<|t|<1.0(GeV/c)2, beam energies (50-175GeV) (good representation for Fermilab data)
Data from SLAC, CERN ISR show even more complicated t dependence
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23. Parameters correlation coefficient
R(rho,L) =
R(sigtot,L) = -1
R(b,L) =
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