H, He, Li and Be Isotopes in the PAMELA-Experiment Wolfgang Menn University of Siegen On behalf of the PAMELA collaboration International Conference on.

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

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

Antiparticles (antiprotons, positrons), secondaries from homogeneously distributed interstellar matter (light nuclei)

PAMELA

Secondary Cosmic RaysSecondary Cosmic Rays

• 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

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

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

H, He, Li and Be IsotopesH, He, Li and Be Isotopes

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)

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

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

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 %

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

ToF: Charge (after conversionfrom dEdx) vs. beta

Charge SelectionCharge Selection

Trk: dEdx vs. Rigidity

Be

Li

Velocity (ToF) versus Rigidity TechniqueVelocity (ToF) versus Rigidity Technique

Mass Resolution for Flight Data HeliumMass Resolution for Flight Data Helium

Velocity versus Rigidity TechniqueVelocity versus Rigidity Technique

PAMELA Tof + SpectrometerExpected Mass Resolution for 4He

4He

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

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

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

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 !

Multiple dE/dx versus Rigidity TechniqueMultiple dE/dx versus Rigidity Technique

Mass Resolution with Calorimeter “Truncated Mean”Mass Resolution with Calorimeter “Truncated Mean”

44HeHe

Mass Resolution For LithiumMass Resolution For Lithium

Mass Resolution For BerylliumMass Resolution For Beryllium

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

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

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

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

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)

Hydrogen Isotope Fluxes and Ratio Hydrogen Isotope Fluxes and Ratio using ToF & Calorimeter (2006 & 2007 Data)using ToF & Calorimeter (2006 & 2007 Data)

Preliminary

Helium Isotope Fluxes and Ratio Helium Isotope Fluxes and Ratio using ToF & Calorimeter (2006 & 2007 Data)using ToF & Calorimeter (2006 & 2007 Data)

Preliminary

Lithium & BerylliumLithium & BerylliumFlight Data 2006 – 2014Flight Data 2006 – 2014

Lithium: ToFLithium: ToF2006 – 2014 Data2006 – 2014 Data

GEANT4 simulationTFractionFitter

Lithium: Calorimeter “Truncated Mean” MethodLithium: Calorimeter “Truncated Mean” Method2006 – 2014 Data2006 – 2014 Data

GEANT4 simulation TFractionFitter

6Li 7Li

Beryllium: ToFBeryllium: ToF2006 – 2014 Data2006 – 2014 Data

GEANT4 simulationTFractionFitter

Beryllium: Calorimeter “Truncated Mean” MethodBeryllium: Calorimeter “Truncated Mean” Method2006 – 2014 Data2006 – 2014 Data

GEANT4 simulationTFractionFitter

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

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

Measurements of Lithium IsotopesMeasurements of Lithium Isotopes

Measurements of Beryllium IsotopesMeasurements of Beryllium Isotopes

7Be / (9Be + 10Be)

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…

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!

Mass resolution with “Bethe-Bloch-Chi²” MethodMass resolution with “Bethe-Bloch-Chi²” Method

44HeHe

Different methods still under test, work in progress…

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 !

Backup Slides

BESS BESS MDR = 200 GVB = 0.5 TL = 1 m

ISOMAX Mass Resolution For BerylliumISOMAX Mass Resolution For Beryllium

Comparison ToF & CalorimeterComparison ToF & Calorimeter

2.5 – 2.7 GV ToF Calorimeter:

Truncated mean

Chi² B.-B.

ISOMAX Mass ResolutionISOMAX Mass Resolution

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!

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

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 %