Cosmic-Ray Lithium and Beryllium Isotopes in the PAMELA-Experiment Wolfgang Menn University of Siegen On behalf of the PAMELA collaboration ICRC 2017 - Busan – 13th July 2017

A wide Range of Measurements: PAMELA Payload for Antimatter Matter Exploration and Light Nuclei Astrophysics 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: Highlight talk by M. Boezio

PAMELA and its Measured Quantities GF: 21.5 cm2 sr Mass: 470 kg Size: 130x70x70 cm3 Power Budget: 360W Velocity (β) (Multiple dEdx)

Isotope Measurements with the Velocity versus Rigidity Technique Rigidity from spectrometer Beta from ToF, dEdx, … Mass Resolution: { { β-Measurement Spectrometer

PAMELA Instrument: 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 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 %

PAMELA Instrument: Time-of-Flight 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

Charge Selection ToF: Charge (after conversion Trk: dEdx vs. 1/beta from dEdx) vs. beta Trk: dEdx vs. 1/beta

Velocity (ToF) versus Rigidity Technique

Mass Resolution for Flight Data Helium 0.29 amu

Mass Resolution for Flight Data Helium PAMELA Tof + Spectrometer Mass Resolution for 4He 4He

Isotope Measurements with the Velocity versus Rigidity Technique Rigidity from spectrometer Beta from ToF, Cherenkov, dEdx… Mass Resolution: { { β-Measurement Spectrometer Multiple dE/dX measurement

PAMELA Instrument: Calorimeter Electromagnetic W/Si calorimeter 44 Si layers (X/Y) +22 W planes 380 µm silicon strips, 4224 channels 16.3 X0, 0.6 λI Dynamic range ~1100 mip

Calorimeter: 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

Multiple dE/dx versus Rigidity Technique

Mass Resolution for 4He

Mass Resolution for 4He More sophisticated method to analyze the calorimeter data NOT used for the analysis presented in this work!

Published: Hydrogen & Helium Isotope Fluxes and Ratio using ToF & Calorimeter (2006 & 2007 Data) Measurements of Cosmic-Ray Hydrogen and Helium Isotopes with the PAMELA experiment ApJ 818, 1, 68 (2016) 

Mass Resolution for Lithium and Beryllium

Mass Resolution: Examples Input: 7Li / 6Li = 1.0

Getting Isotope Counts Compare flight data distributions with „model“ distributions (using Likelihood-Software like TFractionFitter, RooFit…) Model: GEANT4- Simulation of the PAMELA-Experiment Calorimeter: Create simulated dEdx distributions ToF: Create simulated 1/β distributions TFractionFitter: Black Points: Data Red: 6Li Blue: 7Li Grey: 6Li + 7Li → Number of 6Li and 7Li in the histogram

GEANT4 simulation of PAMELA is good, but not 100% perfect... How does a non-perfect model affect the result?

Effect of a “Wrong” Model Distribution Input: 7Li / 6Li = 1.0 Δm Flight= 0.45 amu Quite small effect on the ratio using a wrong „width“

Effect of a “Wrong” Model Distribution Input: 7Li / 6Li = 1.0 Δm Flight = Δm Simulation = 0.45 amu Both Simulated Distributions have a „shift“ Big effect on the ratio!

Deriving the “Shift” Using Flight Data: Beryllium Example: Shift of the simulated calorimeter distribution: Use ToF to select 7Be both for flight data and simulation Compare calorimeter distributions Flight Data Simulated 7Be (+ 9Be for contamination) 7Be + 9Be Be ToF Calorimeter 7Be sel. 7Be sel.

Deriving the “Shift” Using Flight Data: Beryllium Shift of the simulated calorimeter distribution for 7Be Simplification: Shift function is used for simulation of 7Be, 9Be, 10Be

Deriving the “Shift” Using Flight Data: Lithium Example: Shift of the simulated calorimeter distribution: Use ToF to select 6Li and 7Li both for flight data and simulation Compare calorimeter distributions Flight Data Simulated 6Li + 7Li 7Li sel. ToF Calorimeter 7Li sel. 6Li sel. 6Li sel.

Deriving the “Shift” Using Flight Data: Lithium Shift of the simulated calorimeter distribution for 6Li and 7Li Simplification: Shift function is used for simulation of 6Li and 7Li

Deriving Isotopic Fluxes and Ratios Raw counts: Get raw isotope counts using Likelihood method (Simulated distributions are shifted, systematic error of the shift functions is propagated into systematic error of the raw counts) Efficiencies: From simulations, checked with flight data using redundant detectors Livetime Interaction losses Geometry Factor … Propagate systematic errors! So far no isotopic fluxes, only ratios Work in Progress!

Preliminary Results 7Li / 6Li 7Be / (9Be + 10Be)

Summary Momentum resolution of PAMELA spectrometer ca. 3.5 % H and He with Tof & Calorimeter: Analysis ( 0.1 GeV/n – 1.3 GeV/n) published 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 !