Studies of Cosmic-Ray Proton from DAMPE Chuan Yue *, Jing-Jing Zang, Tie-Kuang Dong, Antonio Surdo, Stefania Vitillo on behalf of the DAMPE Collaboration *speaker: yuechuan@pmo.ac.cn 2017.07.17 BUSAN, KOREA
Introduction The Structure of DAMPE Data Sample Proton Selection Criteria Efficiency Validations Background & Acceptance Preliminary Proton Flux of DAMPE Conclusions Outlines 2
(Y. S. Yoon et al., CREAM, 2017) (C. Patrignani et al., PDG, 2016) Introduction Interesting Scientific Issues: Proton Flux Hardening at ~200-400 GeV? Other Structures beyond TeV Range? Unknown Acceleration Mechanisms? Nearby Sources? Modification of Propagation Models? Proton Flux Measurements AMS02,ATIC-2,PAMELA,CREAM 3
Altitude: ~ 500 km Origins and Propagations of Cosmic-Rays Gamma-ray Astronomy Dark Matter Indirected Detection Orbit Information: Sub-Detectors: Sun-synchronous Orbit Launch Date: Dec.17th, 2015 Main Scientific Goals: DArk Matter Particle Explorer (DAMPE) DAMPE Collaboration: Purple Mountain Observatory, National Space Science Center, Inst. High Energy Physics, Inst. Modern Physics, University of Science and Technology Geneva University Bari, Lecce, Perugia (Universities and INFN) Plastic Scintillator strip Detector (PSD): charge (Z) measurement Silicon-Tungsten tracKer-converter (STK): track reconstruction; gamma-converter; Z measurement BGO imaging Energy CALorimeter (BGO-ECAL): energy measurement; lepton/hadron identification NeUtron Detector (NUD): high energy lepton/hadron identification 4
Data Sample: Jan. 1st 2016 to May. 31st 2017 Data Sample × 3 10 6000 Number of Events / Day 5000 4000 2 . 626 × 10 9 Total Events: 3000 2000 Preliminary 1000 0 0 100 200 300 400 500 Day Number (from Jan. 1st 2016) 5
Cut 1: High Energy Trigger (G3) Cut 2: STK Track Selection Cut 3: Cross PSD (track-PSD match) Cut 4: Cross BGO (track-BGO match) Particle Identification Cut 5: charge identification Cut 6: e/p separation Cut 0: BgoEnergy > 20 GeV Proton Selection Criteria Number of Events 8 10 Cut-0 Preliminary Cut-1 7 10 Cut-2 Cut-3 6 10 Cut-4 Cut-5 5 Cut-6 10 4 10 3 10 2 10 Event Selection 10 3 2 4 10 10 10 BGO Energy (GeV) Total Proton Candidates (BGO_E >20 GeV): 1 . 574 × 10 7 6
latitudes <20deg and 1/2048 at high latitudes) (unbias trigger pre-scaled by 1/512 at low the limited statistics of unbias trigger events. Uncertainty due to the threshold calibration and Systematic Error: ~ 8% HighEnergy Trigger Efficiency By applying proton selections to unbias sample, 1.2 HighEnergy Trigger Efficiency ε trigger = N he | unb MonteCarlo Proton 1 On-Orbit Proton N unb 0.8 Preliminary 0.6 0.4 0.2 0 3 Trigger Logics of DAMPE, see CRD117 2 4 10 10 10 10 BGO Energy (GeV) or DAMPE mission paper arXiv:1706.08453 HE Trigger Efficiency of Proton 7
Systematic Error: ~ 2.5% Track Reconstruction Efficiency Yes Typical Proton with ‘Good’ Reconstructed Shower-Axis 1.2 Track Reconstruction Efficiency Using shower-axis based proton selections to check STK track reconstruction efficiency, 1 0.8 ε track = N track | shower-axis Preliminary 0.6 N shower-axis MonteCarlo Proton On-Orbit Proton 0.4 0.2 Track Efficiency of Proton 0 3 2 4 10 10 10 10 BGO Energy (GeV) 8
Sideview of PSD, see Zhang’s poster CRD98 PSD Charge Reconstruction X Layer-1 Layer-2 Z Number of Events On-Orbit Data 3000 Preliminary MC Proton+Helium MC Proton 2500 MC Helium 2000 BGO_E ~ 445 - 560 GeV 1500 1000 500 0 0 2 4 6 8 10 12 14 16 18 20 PSD Energy (MeV) Combined PSD spectrum for protons and helium nuclei 9
Systematic Error: ~ 2% Systematic Error: ~ 4% PSD Charge Efficiency With the help of STK, a “pure” proton sample can be selected for estimating the charge selection efficiencies of proton for PSD layer-1 and layer-2. (see Stefania Vitillo’s poster CRD097) 1.2 1.2 PSD (layer-1) Charge Efficiency PSD (layer-2) Charge Efficiency Preliminary Preliminary MonteCarlo Proton MonteCarlo Proton 1.1 1.1 On-Orbit Proton On-Orbit Proton 1 1 0.9 0.9 0.8 0.8 0.7 0.7 0.6 0.6 0.5 0.5 0.4 0.4 3 3 2 4 2 4 10 10 10 10 10 10 10 10 BGO Energy (GeV) BGO Energy (GeV) Charge Selection Efficiencies of Proton for PSD layer-1 and layer2 10
Background Helium contamination is estimated using Helium Background (%) χ χ 2 2 / ndf / ndf 29.43 / 25 29.43 / 25 Preliminary 5 ± ± p0 p0 3.597 3.597 0.128 0.128 Template-Fit based on MC simulation data ± ± p1 p1 -31 -31 0.3 0.3 ± ± p2 p2 30.08 30.08 0.43 0.43 ± ± p3 p3 4 -8.766 -8.766 0.367 0.367 < 2% for BGO_E from 20 GeV to 10 TeV ± ± p4 p4 11.25 11.25 0.05 0.05 ± ± p5 p5 -5.14 -5.14 0.02 0.02 ± ± p6 p6 0.6342 0.6342 0.0034 0.0034 3 2 10 4 10 4 1 HESS IceCube sub-TeV ankle sub-TeV ankle p p 1 particle/m 2 s 1 particle/m 2 s Akeno 0 3 Tibet 2 4 10 10 10 10 2 10 2 He/2 He/2 BGO Energy (GeV) AGASA HiRes E 2 dN/dE (GeV m -2 s -1 sr -1 ) E 2 dN/dE (GeV m -2 s -1 sr -1 ) e - (or e +/- ) e - (or e +/- ) Auger Helium Background 10 0 10 0 e + e + knee knee all-particle all-particle 1 particle/m 2 yr 1 particle/m 2 yr 10 -2 10 -2 Electrons can be easily eliminated given EGB EGB ankle ankle - - p p 1 particle/km 2 yr 1 particle/km 2 yr the thick calorimeter (32 radiation lengths) ν ν CREAM 10 -4 10 -4 ATIC < 1% for BGO_E from 20 GeV to 10 TeV AMS-02 GZK cutoff GZK cutoff PAMELA Fermi-LAT 10 -6 10 -6 10 -2 10 -2 10 0 10 0 10 2 10 2 10 4 10 4 10 6 10 6 10 8 10 8 10 10 10 10 10 12 10 12 E (GeV/particle) E (GeV/particle) 11
Charge Identification: ~ 4.5% Particle Identification Cut 0: BgoEnergy > 20 GeV Cut 1: High Energy Trigger (G3) Cut 2: STK Track Selection Cut 4: Cross BGO (track-BGO match) Cut 3: Cross PSD (track-PSD match) Cut 5: charge identification Cut 6: e/p separation Systematic Errors: HE Tigger: ~ 8% Track Reconstruction: ~ 2.5% Effective Acceptance Sr) 2 0.05 Proton Effective Acceptance (m Preliminary 0.04 χ χ 2 2 / ndf / ndf 63.99 / 59 63.99 / 59 ± ± p0 p0 0.4687 0.4687 0.0054 0.0054 0.03 ± ± p1 p1 -2.337 -2.337 0.008 0.008 ± ± p2 p2 1.119 1.119 0.007 0.007 ± ± p3 p3 -0.152 -0.152 0.001 0.001 ± ± p4 p4 -0.7298 -0.7298 0.0027 0.0027 0.02 ± ± p5 p5 0.1428 0.1428 0.0011 0.0011 ± ± p6 p6 -0.00249 -0.00249 0.00008 0.00008 0.01 0 2 3 4 10 10 10 Primary Energy (GeV) Proton Effective Acceptance 12
Preliminary Proton Flux Does not include uncertainties from absolute energy measurement Flux × E 2.7 (m − 2 sr − 1 s − 1 GeV 1.7 ) Preliminary 4 10 AMS-02 (2015) PAMELA (2011) ATIC-2 (2009) CREAM-III (2017) DAMPE Preliminary 3 10 3 2 4 1 10 10 10 10 Kinetic Energy (GeV) Preliminary Proton Flux of DAMPE, Compared with Previous Experiments 13
The DAMPE detector was successfully launched into a sun-synchronous orbit at the altitude of 500 km on Dec. 17th 2015 A proton selection criteria is developed and the cut efficiencies obtained by MC simulations are validated with on-orbit data. The preliminary Proton flux has been reported for the range 50 GeV ‒ 10 TeV (talk CRD096 by Paolo Bernardini for Helium analysis) The hardening of Proton flux at E_k ~ 200 GeV has been observed More studies about systematics including energy uncertainties are in processing In the near future, the Proton flux measurement will be extended up to 100 TeV Conclusions Preliminary 14
Thanks for your attentions!
Recommend
More recommend
