An algorithm to resolve γ-rays from charged cosmic rays with DAMPE
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摘要
The DArk Matter Particle Explorer(DAMPE),also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals of DAMPE is to observe Ge V-Te V high energy γ-rays with accurate energy,angular and time resolution,to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to γ-rays,it is challenging to identify γ-rays with sufficiently high efficiency,minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify γ-rays in DAMPE data based on Monte Carlo simulations,using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected γ-ray events at～10 Ge V amounts to less than 1% of the selected sample.Finally,we use flight data to verify the effectiveness of the method by highlighting known γ-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar.
The DArk Matter Particle Explorer(DAMPE),also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals of DAMPE is to observe Ge V-Te V high energy γ-rays with accurate energy,angular and time resolution,to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to γ-rays,it is challenging to identify γ-rays with sufficiently high efficiency,minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify γ-rays in DAMPE data based on Monte Carlo simulations,using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected γ-ray events at～10 Ge V amounts to less than 1% of the selected sample.Finally,we use flight data to verify the effectiveness of the method by highlighting known γ-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar.
The DArk Matter Particle Explorer(DAMPE),also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals of DAMPE is to observe Ge V-Te V high energy γ-rays with accurate energy,angular and time resolution,to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to γ-rays,it is challenging to identify γ-rays with sufficiently high efficiency,minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify γ-rays in DAMPE data based on Monte Carlo simulations,using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected γ-ray events at～10 Ge V amounts to less than 1% of the selected sample.Finally,we use flight data to verify the effectiveness of the method by highlighting known γ-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar.
引文
Abdo,A.A.,Ajello,M.,Antolini,E.,et al.2010,Ap J,720,26
Acero,F.,Ackermann,M.,Ajello,M.,et al.2016,Ap JS,223,26
Ackermann,M.,Ajello,M.,Albert,A.,et al.2015,Ap J,799,86
Agostinelli,S.,Allison,J.,Amako,K.,et al.2003,Nuclear Instruments and Methods in Physics Research A,506,250
Aguilar,M.,Aisa,D.,Alpat,B.,et al.2014,Physical Review Letters,113,221102
Baldini,L.2014,ar Xiv:1407.7631
Barwick,S.W.,Beatty,J.J.,Bower,C.R.,et al.1998,Ap J,498,779
Caraveo,P.A.,Lattanzi,M.G.,Massone,G.,et al.1998,A&A,329,L1
Chang,J.2014,Chinese Journal of Space Science,34,550
Chang,J.,Adams,J.H.,Ahn,H.S.,et al.2008,Advances in Space Research,42,431
Chang,J.,Ambrosi,G.,An,Q.,et al.2017,Astroparticle Physics,95,6
Hobbs,G.B.,Edwards,R.T.,&Manchester,R.N.2006,MNRAS,369,655
Kerr,M.,Ray,P.S.,Johnston,S.,Shannon,R.M.,&Camilo,F.2015,Ap J,814,128
Ray,P.S.,Kerr,M.,Parent,D.,et al.2011,Ap JS,194,17
Wang,C.,Liu,D.,Wei,Y.,et al.2017,Chinese Physics C,41,106201
Wenger,M.,Ochsenbein,F.,Egret,D.,et al.2000,A&AS,143,9
1 The hadronic model QGSP FTFP BERT is used to generate the proton sample considered in this analysis.
2 The intensity of this effect increases towards higher energies in which the higher track multiplicity due to backscattering events from the BGO increases the combinatorial background in each event.
3 We compare the maxima with the coordinates reported in SIMBAD(Wenger et al.2000).
4 http://fermi.gsfc.nasa.gov/ssc/data/access/lat/ephems/.The spin frequency is increased by 4×10-9Hz to improve the accuracy of the ephemeris,according to the Fermi-LAT data covering the period2016–01–01 to 2017–06–01.
Acero,F.,Ackermann,M.,Ajello,M.,et al.2016,Ap JS,223,26
Ackermann,M.,Ajello,M.,Albert,A.,et al.2015,Ap J,799,86
Agostinelli,S.,Allison,J.,Amako,K.,et al.2003,Nuclear Instruments and Methods in Physics Research A,506,250
Aguilar,M.,Aisa,D.,Alpat,B.,et al.2014,Physical Review Letters,113,221102
Baldini,L.2014,ar Xiv:1407.7631
Barwick,S.W.,Beatty,J.J.,Bower,C.R.,et al.1998,Ap J,498,779
Caraveo,P.A.,Lattanzi,M.G.,Massone,G.,et al.1998,A&A,329,L1
Chang,J.2014,Chinese Journal of Space Science,34,550
Chang,J.,Adams,J.H.,Ahn,H.S.,et al.2008,Advances in Space Research,42,431
Chang,J.,Ambrosi,G.,An,Q.,et al.2017,Astroparticle Physics,95,6
Hobbs,G.B.,Edwards,R.T.,&Manchester,R.N.2006,MNRAS,369,655
Kerr,M.,Ray,P.S.,Johnston,S.,Shannon,R.M.,&Camilo,F.2015,Ap J,814,128
Ray,P.S.,Kerr,M.,Parent,D.,et al.2011,Ap JS,194,17
Wang,C.,Liu,D.,Wei,Y.,et al.2017,Chinese Physics C,41,106201
Wenger,M.,Ochsenbein,F.,Egret,D.,et al.2000,A&AS,143,9
1 The hadronic model QGSP FTFP BERT is used to generate the proton sample considered in this analysis.
2 The intensity of this effect increases towards higher energies in which the higher track multiplicity due to backscattering events from the BGO increases the combinatorial background in each event.
3 We compare the maxima with the coordinates reported in SIMBAD(Wenger et al.2000).
4 http://fermi.gsfc.nasa.gov/ssc/data/access/lat/ephems/.The spin frequency is increased by 4×10-9Hz to improve the accuracy of the ephemeris,according to the Fermi-LAT data covering the period2016–01–01 to 2017–06–01.