investigation of different normalization reactions for π collisions at β¦Β Β· 2015. 10. 28.Β Β·...
TRANSCRIPT
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Christopher Fritzsch for the ANKE collaboration
WestfΓ€lische Wilhelms-UniversitΓ€t MΓΌnster, Institut fΓΌr Kernphysik
DPG Heidelberg (HK 37.5)
March 24th, 2015
Investigation of different normalization reactions
for ππ collisions at ANKE
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Christopher Fritzsch DPG Heidelberg March 24th, 2015 1
Motivation
β’ total and differential cross sections of the reaction ππ β 3Heπ are of special interest
β’ indication of a quasi bound state of the 3Heπ-system
β’ high precision data from the ANKE spectrometer at COSY up to π = 15 MeV
β extraction of total and differential cross sections
β careful luminosity determination is necessary
P. Adlarson, European Journal of Physics J. A (2014) 50: 100 DOI 10.1140/epja/i2014-14100-4
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Christopher Fritzsch DPG Heidelberg March 24th, 2015 1
Motivation
β’ total and differential cross sections of the reaction ππ β 3Heπ are of special interest
β’ indication of a quasi bound state of the 3Heπ-system
β’ high precision data from the ANKE spectrometer at COSY up to π = 15 MeV
β extraction of total and differential cross sections
β careful luminosity determination is necessary
P. Adlarson, European Journal of Physics J. A (2014) 50: 100 DOI 10.1140/epja/i2014-14100-4
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Christopher Fritzsch DPG Heidelberg March 24th, 2015 2
ANKE spectrometer
S. Barsov, Nuclear Instruments and Methods in Physics Research A 462 (2001) 364-381
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Christopher Fritzsch DPG Heidelberg March 24th, 2015 2
ANKE spectrometer
S. Barsov, Nuclear Instruments and Methods in Physics Research A 462 (2001) 364-381
ππ β ππ ππ β πππ ππππ
0
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Christopher Fritzsch DPG Heidelberg March 24th, 2015 3
Forward detection system (Fd)
β’ track reconstruction
β one multiwire drift chamber and two multiwire proportional chambers
β’ energy loss measurements
β two layers of scintillator hodoscopes
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Christopher Fritzsch DPG Heidelberg March 24th, 2015 4
Beam time details
flattop 1st supercycle
ππ / (MeV/π) 2nd supercycle
ππ / (MeV/π) 3rd supercycle
ππ / (MeV/π)
0 3120.17(17) 3120.00(22) 3125
2 3146.41(17) 3147.35(17) 3146
3 3148.45(17) 3150.42(17) -------
4 3152.45(17) 3154.49(17) 3157.48(22)
5 3158.71(17) 3162.78(17) 3160.62(22)
6 3168.05(17) 3172.15(17) -------
7 3177.51(17) 3184.87(17) 3204.16(23)
β’ main goals: high precision determination of the π meson mass (ππ β 3HeΞ·) and
studies on the two pion production (ππ β 3Heπ+πβ)
β’ supercycle mode: one supercycle consists of up to 7 different beam momenta
β 19 beam momenta overall
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Christopher Fritzsch DPG Heidelberg March 24th, 2015 4
Beam time details
flattop 1st supercycle
ππ / (MeV/π) 2nd supercycle
ππ / (MeV/π) 3rd supercycle
ππ / (MeV/π)
0 3120.17(17) 3120.00(22) 3125
2 3146.41(17) 3147.35(17) 3146
3 3148.45(17) 3150.42(17) -------
4 3152.45(17) 3154.49(17) 3157.48(22)
5 3158.71(17) 3162.78(17) 3160.62(22)
6 3168.05(17) 3172.15(17) -------
7 3177.51(17) 3184.87(17) 3204.16(23)
below π threshold (ππ β 3Heπ) for a smooth background description
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Christopher Fritzsch
β’ advantages of the ππ-elastic scattering as normalization reaction:
β broad data base of available
differential cross section
β high differential cross sections ensure
good statistics
β excellent signal-to-background ratio
β’ differential cross section as function of
momentum transfer
β independent of beam momentum
β’ ANKE acceptance: βπ‘ = (0.06 β 0.31) (GeV/π)Β²
β’ range for luminosity determination
βπ‘ = 0.08 β 0.26 (GeV/π)Β²
DPG Heidelberg March 24th, 2015 5
Luminosity via ππ β ππ
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Christopher Fritzsch
β’ identification of the reaction via the missing mass technique
Missing Mass = |βp(ejectile)| = |βd(beam) + βp(target) β βd(ejectile)|
β deuterons in the Fd-system
β momentum close to beam momentum
β low momentum transfer onto the target proton
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Identification of ππ β ππ
DPG Heidelberg March 24th, 2015
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Christopher Fritzsch
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Luminosity determination
DPG Heidelberg March 24th, 2015
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Christopher Fritzsch
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Luminosity determination
DPG Heidelberg March 24th, 2015
trigger reduction
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Christopher Fritzsch
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Luminosity determination
DPG Heidelberg March 24th, 2015
trigger reduction
acceptance correction
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Christopher Fritzsch
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Luminosity determination
DPG Heidelberg March 24th, 2015
trigger reduction
acceptance correction
efficiency correction
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Christopher Fritzsch
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Luminosity determination
DPG Heidelberg March 24th, 2015
acceptance correction
trigger reduction efficiency correction
dead time correction
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Christopher Fritzsch
β’ luminosity should be independent of momentum transfer
β’ determination performed for 18 momentum transfer bins (Ξπ‘ = 0.01 (GeV/π)2)
β for each of the 19 beam momenta
β’ luminosity precision achieved:
ΞπΏstat = 1%
ΞπΏsys = 6%
β’ improvement by at least a
factor of two
β’ relative normalization via the
reactions ππ β πspecπ by
determination of the number of
spectator protons in the
Fd-system
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Results for ππ β ππ
DPG Heidelberg March 24th, 2015
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Christopher Fritzsch
β’ luminosity should be independent of momentum transfer
β’ determination performed for 18 momentum transfer bins (Ξπ‘ = 0.01 (GeV/π)2)
β for each of the 19 beam momenta
β’ luminosity precision achieved:
ΞπΏstat = 1%
ΞπΏsys = 6%
β’ improvement by at least a
factor of two
β’ relative normalization via the
reactions ππ β πspecπ by
determination of the number of
spectator protons in the
Fd-system
8
Results for ππ β ππ
DPG Heidelberg March 24th, 2015
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Christopher Fritzsch
β’ luminosity should be independent of momentum transfer
β’ determination performed for 18 momentum transfer bins (Ξπ‘ = 0.01 (GeV/π)2)
β for each of the 19 beam momenta
β’ luminosity precision achieved:
ΞπΏstat = 1%
ΞπΏsys = 6%
β’ improvement by at least a
factor of two
β’ relative normalization via the
reactions ππ β πspecπ by
determination of the number of
spectator protons in the
Fd-system
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Results for ππ β ππ
DPG Heidelberg March 24th, 2015
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Christopher Fritzsch DPG Heidelberg March 24th, 2015 9
Luminosity via ππ β πππ ππππ0
β’ to verify the results of the ππ-elastic scattering
β independent normalization required
β reaction used: ππ β ππspecπ0
β’ πspec = half of beam momentum + fermi motion
β’ identification of the ππ pairs in the Fd-system
β time-of-flight measurement
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Christopher Fritzsch 10
Identification of πππ πππ pairs
DPG Heidelberg March 24th, 2015
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Christopher Fritzsch 10
Identification of πππ πππ pairs
DPG Heidelberg March 24th, 2015
ππ (fast π)
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Christopher Fritzsch 10
Identification of πππ πππ pairs
DPG Heidelberg March 24th, 2015
ππ (slow π)
ππ (fast π)
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Christopher Fritzsch 10
Identification of πππ πππ pairs
DPG Heidelberg March 24th, 2015
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Christopher Fritzsch 10
Identification of πππ πππ pairs
DPG Heidelberg March 24th, 2015
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Christopher Fritzsch 11 DPG Heidelberg March 24th, 2015
Identification of πππ πππ pairs
m2π0 = 0.0182 (GeV/πΒ²)Β²
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Christopher Fritzsch 12 DPG Heidelberg March 24th, 2015
Background description
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Christopher Fritzsch 13 DPG Heidelberg March 24th, 2015
Background description
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Christopher Fritzsch
β’ accurate signal background substraction
β’ next steps:
β’ determination of correction terms
- acceptance
- dead time
- shadow effect
- β¦
β’ calculation of uncertainties
β’ luminosity determination
for every beam momentum
β’ compare results with
ππ-elastic scattering
14 DPG Heidelberg March 24th, 2015
Preliminary results
m2π0 = 0.0182 (GeV/πΒ²)Β²
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Christopher Fritzsch
β’ luminosities were determined via ππ-elastic scattering for 18 momentum transfer bins
for each of the 19 beam momenta
β’ precision of ΞπΏstat = 1% and ΞπΏsys = 6% achieved
β improvement by at least a factor of two compared to previous calculations
β’ luminosities already used to determine differential and double differential cross
sections for ππ β Β³Heπ+πβ
β’ relative normalization via spectator protons of reactions of the type ππ β ππ ππππ
β’ ongoing analysis:
β’ independent luminosity determination using the reaction ππ β πππ ππππ0
β’ identification of πππ πππ pairs and background description by time-of-flight
measurements
β’ next steps: - determination of correction terms
- luminosity determination for every beam momentum
DPG Heidelberg March 24th, 2015 15
Summary & Outlook
M. Mielke et al., European Journal of Physics J. A50 (2014) 102
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Christopher Fritzsch
Thank you for your attention!
DPG Heidelberg March 24th, 2015
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Christopher Fritzsch DPG Heidelberg March 24th, 2015
Additional slide