h, he, li and be isotopes in the pamela-experiment wolfgang menn university of siegen on behalf of...
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H, He, Li and Be Isotopes H, He, Li and Be Isotopes
in the PAMELA-Experimentin the PAMELA-Experiment
Wolfgang Menn
University of Siegen
On behalf of the PAMELA collaboration
International Conference on Particle Physics and Astrophysics
Moscow 09-Oct-2015
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PAMELAPPayload for ayload for AAntimatter ntimatter MMatter atter EExploration xploration
and and LLight Nucleiight Nuclei AAstrophysicsstrophysics
A wide Range of Measurements:
• Search for Antimatter ( p, He, e+ ) and Dark Matter• Study of Cosmic Ray Propagation: p, He, e-, B, C• Solar Particles• Solar Modulation• Interactions between energetic Particles and the Earth Magnetic Field
We published results in all these fields
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Antiparticles (antiprotons, positrons), secondaries from homogeneously distributed interstellar matter (light nuclei)
PAMELA
Secondary Cosmic RaysSecondary Cosmic Rays
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• Tuning of cosmic-ray propagation models with measurements of secondary/primary flux ratio
• 2H/1H and 3He/4He are complimentary to B/C measurements in constraining propagation models (Coste et al., A&A 539 (2012) A88)
Light Nuclei and IsotopesLight Nuclei and Isotopes
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Adriani et al., ApJ 791 (2014), 93
Tracking performance: σ
x = 14 μm, σ
y = 19 μm
MDR = 250 GV
Modelization of cosmic-ray propagation in the Galaxy
Boron and Carbon Fluxes and B/C RatioBoron and Carbon Fluxes and B/C Ratio
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Adriani et al., ApJ 791 (2014), 93
Tracking performance: σ
x = 14 μm, σ
y = 19 μm
MDR = 250 GV
Modelization of cosmic-ray propagation in the Galaxy
Boron and Carbon Fluxes and B/C RatioBoron and Carbon Fluxes and B/C Ratio
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H, He, Li and Be IsotopesH, He, Li and Be Isotopes
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GF: 21.5 cm2 sr Mass: 470 kgSize: 130x70x70 cm3
Power Budget: 360W
PAMELAPAMELA and its Measured Quantities and its Measured Quantities
Velocity (β) (Multiple dEdx)
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Isotope Measurements with theIsotope Measurements with the Velocity versus Rigidity TechniqueVelocity versus Rigidity Technique
Velocity versus Rigidity Technique:
•Rigidity from spectrometer•Beta from ToF, dEdx, …
Mass Resolution:
β-Measurement Spectrometer
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Spectrometer:microstrip Si tracking system + permanent magnet Measures Rigidity R: R=p / Z∙e -6 layers of silicon microstrip detectors - 3 µm resolution in bending view - magnetic field ~ 0.45 T - → MDR ~ 1 TV
PAMELA Instrument: SpectrometerPAMELA Instrument: Spectrometer
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PAMELA SpectrometerPAMELA Spectrometer
• 6 layers @ 3 µm, 0.45 T → MDR ~1000 GV
•(dR/R)mult ~ (x/X0)/(beta · B·dL)•Silicon Tracker doesn`t need support structure → minimal multiple scattering
~3.5 %
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Time-Of-Flight (TOF): plastic scintillators + PMT-time resolution:~ 300 ps for Z = 1 ~ 100 ps for Z = 2~ 85 ps for Z = 3~ 80 ps for Z = 4
PAMELA Instrument: Time-of-FlightPAMELA Instrument: Time-of-Flight
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ToF: Charge (after conversionfrom dEdx) vs. beta
Charge SelectionCharge Selection
Trk: dEdx vs. Rigidity
Be
Li
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Velocity (ToF) versus Rigidity TechniqueVelocity (ToF) versus Rigidity Technique
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Mass Resolution for Flight Data HeliumMass Resolution for Flight Data Helium
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Velocity versus Rigidity TechniqueVelocity versus Rigidity Technique
PAMELA Tof + SpectrometerExpected Mass Resolution for 4He
4He
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Isotope Measurements with theIsotope Measurements with the Velocity versus Rigidity TechniqueVelocity versus Rigidity Technique
Velocity versus Rigidity Technique:
•Rigidity from spectrometer•Beta from ToF, Cherenkov, dEdx…
Mass Resolution:
β-Measurement Spectrometer
Multiple dE/dXmeasurement
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Electromagnetic W/Si calorimeter44 Si layers (X/Y) +22 W planes380 µm silicon strips, 4224 channels16.3 X0, 0.6 λI
Dynamic range ~1100 mip
PAMELA Instrument: CalorimeterPAMELA Instrument: Calorimeter
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Calorimeter: Truncated Mean MethodCalorimeter: Truncated Mean Method
Only usuable for non-interacting events
Energy loss in each silicon layer of the calorimeter:
Cut away highest 50%
Use the lower 50% (black points) to calculate a mean dEdx
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Refined Selection MethodRefined Selection Method
• Strict Selection: All events with interactions are discarded
• Refined selection: Use information of the „clean“ part in the calorimeter, neglect the lower part
Discarded !
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Multiple dE/dx versus Rigidity TechniqueMultiple dE/dx versus Rigidity Technique
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Mass Resolution with Calorimeter “Truncated Mean”Mass Resolution with Calorimeter “Truncated Mean”
44HeHe
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Mass Resolution For LithiumMass Resolution For Lithium
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Mass Resolution For BerylliumMass Resolution For Beryllium
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Getting Isotope Counts (ToF)Getting Isotope Counts (ToF)
•Compare flight data distributions with „model“ distributions
•ToF H & He: 1/β distributions are gaussian => do a gaussian fit
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Getting Isotope Counts (ToF)Getting Isotope Counts (ToF)
•ToF Li & Be: Work in progress…• Create simulated 1/β distributions • Compare flight data distributions with „model“ using Likelihood-Software like TFractionFitter, RooFit…
TFractionFitter:Black Points: Data Red / Blue / Green: Isotopes Grey: Sum
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Getting Isotope Counts (Calorimeter)Getting Isotope Counts (Calorimeter)
•Truncated mean dEdx distributions are not gaussian•Model: Use GEANT4- Simulation of the PAMELA-Experiment•Create simulated distributions of truncated mean dEdx
TFractionFitter:Black Points: Data Red / Blue / Green: Isotopes Grey: Sum
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Getting the Efficiency in the CalorimeterGetting the Efficiency in the Calorimeter
•GEANT4- Simulation of the PAMELA-Experiment (Example: 3He and 4He)•Derive Efficiency for specific set of selection cuts
Flight Data Tracker dEdx
4He
3He
Flight Data 1/β
4He
3He
Flight Data ToF dEdx
4He
3He
3He 4He
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Deriving Isotopic Fluxes and Ratios for H and HeDeriving Isotopic Fluxes and Ratios for H and He
•Efficiencies
•Livetime
•Interaction losses•Geometry Factor
•Unfolding
Make Use of ToF Analysis published
• „Measurement of the Isotopic Composition of Hydrogen and Helium Nuclei in Cosmic Rays with the PAMELA Experiment“ O. Adriani et al., ApJ, 770, 2, (2013)
• Measurement of hydrogen and helium isotopes flux in galactic cosmic rays with the PAMELA experiment V. Formato et al. NIM A, 742, p. 273–275 (2014)
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Hydrogen Isotope Fluxes and Ratio Hydrogen Isotope Fluxes and Ratio using ToF & Calorimeter (2006 & 2007 Data)using ToF & Calorimeter (2006 & 2007 Data)
Preliminary
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Helium Isotope Fluxes and Ratio Helium Isotope Fluxes and Ratio using ToF & Calorimeter (2006 & 2007 Data)using ToF & Calorimeter (2006 & 2007 Data)
Preliminary
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Lithium & BerylliumLithium & BerylliumFlight Data 2006 – 2014Flight Data 2006 – 2014
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Lithium: ToFLithium: ToF2006 – 2014 Data2006 – 2014 Data
GEANT4 simulationTFractionFitter
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Lithium: Calorimeter “Truncated Mean” MethodLithium: Calorimeter “Truncated Mean” Method2006 – 2014 Data2006 – 2014 Data
GEANT4 simulation TFractionFitter
6Li 7Li
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Beryllium: ToFBeryllium: ToF2006 – 2014 Data2006 – 2014 Data
GEANT4 simulationTFractionFitter
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Beryllium: Calorimeter “Truncated Mean” MethodBeryllium: Calorimeter “Truncated Mean” Method2006 – 2014 Data2006 – 2014 Data
GEANT4 simulationTFractionFitter
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So far no isotopic fluxes, only ratiosWork in Progress!
Li and Be spectra: Measurement of Lithium and Beryllium cosmic-ray abundances by the PAMELA experiment (ICRC 2015)
•Efficiencies•Livetime•Interaction losses•Geometry Factor•…
Deriving Isotopic Fluxes and Ratios for Li and BeDeriving Isotopic Fluxes and Ratios for Li and Be
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Getting the Efficiency in the CalorimeterGetting the Efficiency in the Calorimeter
•GEANT4- Simulation of the PAMELA-Experiment • Derive Efficiency for specific set of selection cuts
Check with flight data:•Use redundant detectors to select flight data 6Li and 7Li•Derive Efficiency in the same way as for simulated data
ToF–β vs. R ToF-dEdx vs. R Trk-dEdx vs. R
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Measurements of Lithium IsotopesMeasurements of Lithium Isotopes
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Measurements of Beryllium IsotopesMeasurements of Beryllium Isotopes
7Be / (9Be + 10Be)
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Measurements of Beryllium Isotopes (2)Measurements of Beryllium Isotopes (2)
Difficult: Separate 9Be and 10Be…
Large systematic error…
Probably we need to use „Chi²-Method“ (or TMVA etc.) to get a better mass resolution…
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Alternative Analysis: Make Use of Particle’s SlowdownAlternative Analysis: Make Use of Particle’s Slowdown
Move the calculated Bethe-Bloch-Curve for a given Mass through the measured Data and calculate a Chi² value
The best Chi² wins!
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Mass resolution with “Bethe-Bloch-Chi²” MethodMass resolution with “Bethe-Bloch-Chi²” Method
44HeHe
Different methods still under test, work in progress…
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SummarySummary
•Momentum resolution of PAMELA spectrometer ca. 3.5 % •H and He with Tof & Calorimeter: Analysis ( 0.1 GeV/n – 1.3 GeV/n) ready to publish •Li and Be with ToF & Calorimeter: Results show that PAMELA will be able to provide new data for Lithium and Beryllium isotopes up to ~ 1.2 GeV/n
Thank You !Thank You !
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Backup Slides
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BESS BESS MDR = 200 GVB = 0.5 TL = 1 m
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ISOMAX Mass Resolution For BerylliumISOMAX Mass Resolution For Beryllium
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Comparison ToF & CalorimeterComparison ToF & Calorimeter
2.5 – 2.7 GV ToF Calorimeter:
Truncated mean
Chi² B.-B.
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ISOMAX Mass ResolutionISOMAX Mass Resolution
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AMS-01AMS-01
R=5.56 GV MDReff=32 GV
each track layer = 0.65 % X0(PAMELA 0.32 %)
Expected He4 mass resolution:0.4 amu @ 2GV
Data looks worse!
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Definition of “non interacting”Definition of “non interacting”
• qtot= Total energy loss in each layer• qtrack: Energy loss in the three strips closest to the track• Perfect event: qtrack/qtot = 1
Old selection (until ICRC 2013): Integral qtrack/qtot > 0.9
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PAMELA SpectrometerPAMELA Spectrometer
• 6 layers @ 3 µm, 0.45 T → MDR ~1000 GV
CERN Beam TestProton Data
•(dR/R)mult ~ (x/X0)/(beta · B·dL)•Silicon Tracker doesn`t need support structure → minimal multiple scattering
~3.5 %