Cosmic-rays deuteron identification using the AMS-02 detector

by Sinchul Kang (MS Candidate)

Wednesday May 25, 2016, 1:30 PM → 1:55 PM Asia/Seoul

119호 (제1과학관)

The Alpha Magnetic Spectrometer (AMS-02) is a detector for studying high energy primary cosmic-rays. It was placed on the International Space Station (ISS) on 19 May 2011 and it will take the cosmic-rays data for years. Result of the AMS-02 experiment give high precision data to understand primary cosmic-rays by using the magnet. 
Cosmic-rays consist of almost protons (∼ 91%) and helium nuclei (∼ 8%) and other heavy nuclei (∼ 1%). This study focused on cosmic-ray deuteron. It will be very meaningful to study cosmic-ray deuteron flux. There are interesting physics origins which produce of proton or deuteron at high energies, such as annihilation of dark matters which could produce those particles at particular energies, according to the mass of dark matter.
To study cosmic-ray deuteron, one need to discriminate deuteron from enor- mous amount of proton backgrounds. Proton has same charge as that of deuteron but different mass. Therefore proton and deuteron should be distinguished by using difference of signatures recorded in the detectors. In this study, to maximize the differences of signatures, boosted decision tree (BDT) method based on multivari- ate approaches of statistical hypothesis test is used. There are three BDTs in this study; BDT1, BDT2, BDT3. Since TOF, RICH NaF and RICH aerogel have different velocity resolution in different rigidity region, three BDTs have different rejection powers in each rigidity region. The BDT1 has the highest rejection power in rigidity region from 1 to 3 GV, the BDT2 has the best rejection power in rigidity region from 3 GV to 6 GV and rejection power of the BDT3 is the highest in rigidity region from 6 to 20 GV. The proton rejection power is greater than 100 in rigidity region from 1 to 12 GV, when signal efficiency is 90 %. Most of experiments done so far measured deuteron fluxes with kinetic energy under 1 GeV/n. Therefore this study and result will be helpful to get deuteron flux at higher energy and to provide new physics.

Thesis Advisor: Prof. Dongchul Son