PoS(ICRC2019)509 http://pos.sissa.it/ factors and incorporate the − J factor in a combined analysis. Comparing with current limits, − J ∗ [email protected] [email protected] [email protected] at DM masses above 1TeV. We consider nineteen dSphs with large signatures induced by annihilation of heavy (DM) particles in dwarf spheroidal satel- for high energy gamma-rays and cosmic rays with a wide field of view, which is sensitive to statistical uncertainties of the we find that LHAASO is sensitive toup the to annihilation 100 signatures for TeV. DM masses from several TeV Speaker. lite (dSphs). In this study, we investigate the LHAASO sensitivity to the DM annihilation gamma-rays from 300 GeV to 1 PeV. LHAASO is an ideal experiment to explore the gamma-ray The Large High Altitude Air Shower Observatory (LHAASO) is a next generation observatory ∗ Copyright owned by the author(s) under the terms of the Creative Commons c 36th International Cosmic Ray Conference -ICRC2019- July 24th - August 1st, 2019 Madison, WI, U.S.A. ⃝ Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). Su-Jie Lin Key Laboratory of Particle Astrophysics, Institute ofSciences, High Beijing Energy 100049, Physics, China Chinese AcademyE-mail: of Peng-Fei Yin Key Laboratory of Particle Astrophysics, Institute ofSciences, High Beijing Energy 100049, Physics, China Chinese AcademyE-mail: of Xiao-Jun Bi Prospect for dark matter annihilation signatures from gamma-ray observation of dwarf galaxiesLHAASO by Key Laboratory of Particle Astrophysics, Institute ofSciences, High Beijing Energy 100049, Physics, China Chinese AcademyE-mail: of PoS(ICRC2019)509 E, 2 01 ]). . 7 ◦ ∼ (2.1) , 6 100 , 5 . Xiao-Jun Bi } 5 . TeV are weak TeV. However, 0 . ) , ∼ ) 1 ( int max -factors of nineteen O α θ factor in a combined J { − cos J min − 1 GeV to = ( ) 1 π int . 2 0 of the dSph which is determined α -factors are calculated within an ( , J = J O max ) and large field of view (FOV) ( × θ ∼ ∆Ω γ 1% dE -factor is the integral of the DM density ∼ γ γ ]. These J 9 dE , dN 8 max min E 1 ]. The E 4 ∫ , ⟩ χ 2 v 3 [ m σ factor of dSphs can be derived from the Jeans analysis 2 γ ⟨ − π 1 J dE 4 / γ ) within a solid angle of s = . is the thermal average velocity-weighted DM annihilation cross o dN Φ . ⟩ l v σ , or the maximum angular radius ⟨ ◦ 5 , which are provided by [ . 1 0 is the initial spectrum of photons induced by DM annihilation. In this anal- -factor within a smaller integration angle as of γ factors and include the statistical uncertainties of the J int − dE J α / γ ]. It is composed of a square kilometer particle detector array, a water Cherenkov 2 dN , package to calculate 1 is the DM mass, χ m N) [ The observed gamma-ray flux in a particular energy bin from the pair annihilation of DM in The DM density profile and the Dark matter particles may still annihilate with a moderate rate today and produce high energy Many space-borne detectors and ground-based telescopes have searched for the gamma-ray The large high altitude air shower observatory (LHAASO) is a hybrid cosmic ray and gamma- 35 . ◦ section, and In this analysis, we usedSphs listed the in mean in values Table and statistical uncertainties of the ysis, we assume that thePPPC4DM gamma-ray signature is from a certain annihilation channel and use the integration angle by the outermost member starratio, in we the choose observation. the In order to obtain a large signal-to-background where 2. Analysis method an astrophysical system is the current limits on the annihilation cross section for heavy DM particles above detector array (WCDA), a wide fielddetector Cherenkov array. telescope The array, strong and background a rejection highsr) power threshold of ( shower LHAASO core will benefitis the very very promising high for energy LHAASO gamma-ray tostraints observation explore on of the the dSphs. DM properties annihilation Therefore, of signature it DM heavy and annihilation DM place signatures stringent particles. from con- the In gamma-raydSphs this observations with by analysis large LHAASO. we We investigate consider the nineteen analysis prospects . for squared along the line of sight ( by using the results of the kinematic observation of stellar velocities (see e.g. Refs. [ 1. Introduction standard model particles, which couldAmong lead these to signatures, the detectable gamma-ray signatures photon in isspheroidal an astrophysical satellites ideal observations. (dSphs) tool to are explore very theannihilation, nature promising because of to they DM. are search Dwarf large for galactic DMis the substructures no gamma-ray with significant signature high DM gamma-ray from densities. emission DM searching Since from for there the the astrophysical DM signature process is in almost dSphs, background-free. it is expectedsignature that from DM annihilation in a wide energy range from ray observatory located at 4410 m above sea level near Daocheng, Sichuan province, China ( Short Title for header due to the low statistic of photons at high energies. 29 PoS(ICRC2019)509 . ≡ p eff A Q , the (2.2) 50% 3 ]. ∼ = 9 γ ε Xiao-Jun Bi ), maximum min eff E for r / ) 5 4 3 4 4 1 8 7 2 2 4 9 6 3 2 3 5 4 2 9 max ...... − , 11% 0 0 0 0 0 2 0 0 0 1 0 1 0 0 1 0 0 0 0 obs E . J ]. For the four dSphs is the primary proton cm 0                    dE 8 2 10 ) 2 4 6 0 8 1 9 8 0 3 4 9 4 5 9 9 4 9 5 ...... Ω to E log ( 18 17 17 19 18 18 16 17 18 16 16 16 19 17 20 17 19 18 19 GeV p dtd is introduced to include the ]. We also list the effective ) Φ 04% . E 1 10 . ( 0 p 1 . ε · are survival ratios of gamma-rays 47 53 13 31 30 28 45 23 16 07 35 70 43 53 37 = . . . . . − . . . . . − . . − . . . − max -factors are taken from Ref. [ p θ J )) in LHAASO are calculated. Assum- cr t ε 13% ζ ( . S . ◦ zen 40 ], the and θ 8 varies from , 60 ∼ γ ε E eff γ 399377442 0 451 0 348 1 346372 0 0 0 357 0 403 432449455 0 430 0 1 352398 0 0 303 0 314327 0 299 1 ...... r ( ε 0 0 . In each energy bin with p eff N is the angular resolution of LHAASO and varies A 6TeV 2 . c · 0 θ ) . E ], where 54 0 61 0 ( 505632 0 90 0 92 0 56 0 79 0 30 0 15 0 0 0 08 0 18 0 921323 0 05 0 0 0 . . )] 22 95 ...... of the dSphs are taken from Ref. [ p . . 0 1 } 11 2 5 (deg) (year) (deg) ( c DEC. 36 − − Φ 0.278% for above is smaller than θ · max , p θ ∼ cr ε int zen ζ p θ α ε T { 0 to show their visibility. It is defined as the fraction of observation 02 14 20 64 37 22 022974 33 05 34 23 76 57 12 12 23 12 79 63 7726 16 7187 51 34 63 51 28 67 32 ...... ∫ . 1 RA. (deg) 33 max ∆Ω 238 168 186 260 247 152 173 172 344 151 153 158 132 162 227 210 ( ∫ -factors are not given in Ref. [ is taken to be one year in this analysis, and -factor and J J max T cos min E E I 202 − II 194 ⋆ ∫ with the increased energy of the incoming photon. The effective area 1 ⋆ [ ⋆ ⋆ ◦ = ). The 1 × . B 0 π ¨ otes I max 2 and signature number from DM annihilation θ Draco Leo II Source Leo IV to Sextans discrimination is crucial for this analysis. The energy-dependent quality factor of dSphs in Table Bo Draco II Pisces II B = Ursa Minor ◦ p Ursa Major I from the direction of a dSph is given by Ursa Major II eff 2 II / Canes Venatici Coma Berenices r Canes Venatici B γ ∆Ω The astrophysical properties of nineteen dSphs within the LHAASO FOV. The listed columns for for WCDA is estimated in Ref. [ p ε We assume a series of mimic observations to investigate the LHAASO sensitivity to the The √ and randomly generate the mimic event count / γ contributions of heavier primaryangle cosmic-ray of particles. The integral is performed within a solid expected flux described by a single power-law. An additional factor ing the null result of the DMB signature in the mimic observation, we take a Poisson sampling around with from time during which the zenith angle ε and primary protons. It is shown that where observational time gamma-ray signature from DM annihilation. The expectedray background particles number induced by cosmic- depending on the energy andtime zenith ratio angle and is taken from Ref. [ For a conservative analysis, we set Table 1: Short Title for header each dSph are theangular name, radius right ( ascension (RA.), declination (DEC.), effective time ratio ( marked with asterisks whose PoS(ICRC2019)509 - ◦ J 29 (2.3) . For ∼ ⟩ -factor v J σ ⟨ Xiao-Jun Bi , is take to be 2 j is taken to be p σ 2 ε ) ]. Furthermore, / 2 N 11 )] , . In the researches j , 1 B . -factor into account. | obs 2 J J S . Both the individual ( , while ( − 10 ∼ C.L. for given L W log 50% + − ) j J W ∼ annihilation channel from one 95% ( . j γ 10 ¯ -factors and favorable locations b ε at J b L log and [ 95 − for ⟩ in the mimic observation, we require − e v τ σ 95 × + ⟨ S j τ , 1TeV πσ − 2 factor in the analysis, which would loosen the µ √ + − j , J -th dSph, respectively, µ . This improvement can be attributed to the larger j 3 1 around 5 , obs ¯ t J t ∼ ) are the observed mean values and standard deviations , 1% 2 ¯ j b 10 b ( σ -th dSph is defined as j is adjusted to maximize ln ) j J and × ( ) ) ] to take the statistical uncertainty of the j , 10 i j 13 N obs , , log J i j , ( discrimination of LHAASO. The area of WCDA, which is about 4.5 12 ⟩ -th energy bin and B i 10 | v . p i j 1 σ / S ⟨ log γ ( ]. We investigate the sensitivities to the DM annihilation cross section i j is always larger than 14 p L -factor and is located near the center of the FOV of LHAASO. But it does not ε i J ] adopted here is more conservative than that provided by Ref. [ ∏ p 16 ε = represent the , . j j j 15 L in this analysis. This difference would provide provide another improvement factor of L j and ∏ i = We consider the statistical uncertainty of the Our results show that the combined sensitivity is dominated by Segue 1, Ursa Major II and In this analysis, we investigate the DM annihilation signatures from nineteen dSphs, which are A likelihood ratio test is performed to explore the possible excess in the mimic observation. For a 95% C.L. upper limit on the DM signature flux 278% . . Note that tot 0 2 the joint analysis with severalL dSphs, the procedure is similar by adopting a combined likelihood sensitivities for each dSph anddSphs the are calculated. combined As sensitivity an from example,mimic a we observation show joint in the Fig. analysis results for for the all the selected of HAWC [ ∼ ∼ for the high-latitude bright sources such as Ursa Major II, LHAASO located at the latitude of expected sensitivity. Even so, theconstraints expected placed sensitivity by HAWC of by LHAASO a factor is of still better than thetimes current larger than that of HAWC, would provide an improvement factor of for five annihilation channels, including Triangulum II. This is because that these three dSphs have large that the log-likelihood with the DMcan contribution obtain decreases the by limit 2.71/2 on from the its DM maximum. annihilation Then cross we section 3. LHAASO Sensitivities located in the FOV of LHAASO withFour favored more declination angles dSphs and are have significant consideredsearches DM (Draco contents. of II, HAWC Leo [ V, Pisces II and Willman 1), compared with the effective area and better would be more sensitive than HAWC. This would also improve the the LHAASO senstitivity. where We use the method in Refs. [ Short Title for header The likelihood in all energy bins for the of the J factor. For given in the FOV of LHAASO.not The significantly affect sensitivities the for combined other limit.almost selected Among the dSphs the largest selected are nineteen much dSphs, weakertotally Triangulum II and dominated has would the combined sensitivity,factor has since large Triangulum statistical uncertainty. II Therefore, is the an analysis taking ultra-faint the dSph uncertainty of and the its the Poisson distribution, PoS(ICRC2019)509 . ], 2 14 channels, Xiao-Jun Bi ¯ b b at 95% confi- at DM masses ⟩ v 1 σ and − ⟨ s − 3 W cm + -factors, including Segue 24 W J ], VERITAS Segue 1 limit − , − 18 100 10 τ + ∼ τ Sextans Triangulum II Ursa Major I Ursa Major II Ursa Minor Willman 1 for the [TeV] 10 1 TeV to 100 TeV. 8 TeV DM Hercules Leo I Leo II Leo IV Leo V Pisces II Segue I m 4 ∼ ¯ b channel. The solid blue line represents the combined ∼ annihilation channel is the most strong among all the and − τ + τ ], HESS combined dSph limit [ Bootes I Canes Venatici I Canes Venatici II Coma Berenices Draco Draco II Combined channels, LHAASO has a very strong capability to search for 3 TeV _ ], are also shown for comparison. 17 b b ¯ t t ∼ 1 20 , -22 -23 -24 -25 -26 -27 -18 -19 -20 -21

10 10 10 10 10 10 10 10 10 10

] s [cm v> < σ

-1 3 and − 2 TeV µ + ∼ µ The individual expected sensitivities to the DM annihilation cross section We would like to thank Min Zha, Yan-Jin Wang, Yi-Qing Guo, Ying-Ying Guo, Han-Rong Wu In this analysis, we investigate the sensitivity to the DM annihilation cross section for five DM The photon number in the very high energy region is expected to be small, therefore the sta- The LHAASO sensitivity for the ] and MAGIC Segue 1 limit [ 19 dence level for nineteen dSphs of one year for the b and Zhi-Guo Yao for helpful and engaging discussions. This work is supported by the National Key 1, Ursa Major II and Triangulumcross II. section, Compared with LHAASO the is current more constraints sensitive on at the DM DM masses annihilation from several TeV upAcknowledgments to 100 TeV. 4. Conclusion annihilation channels by the LHAASO gamma-ray observationLHAASO of combined dSphs. sensitivity Our is results dominated show by that three the dSphs with large channels, because of the hard initial photon spectrum. It reaches the annihilation signatures for DM masses from tistical fluctuation in the mimic observationobservations should under be the taken null into hypothesis. account.tainment The bands We of median perform the values 500 combined and mimic sensitivities the for five two-sided DM 68% annihilation channels and are 95% shown con- in Fig. into account is importantenough and kinematic data. avoids the overestimation of the sensitivity for the dSph without The current constraints from five dSph observations, including the[ HAWC combined limit [ above TeV. Compared with the currentmore constraints sensitive placed by above other experiments, LHAASO is also Figure 1: sensitivity. Short Title for header Fermi-LAT combined dSph limit [ respectively. For the PoS(ICRC2019)509 , ], − µ 17 + µ 100 100 t, ¯ ¯ b, t Xiao-Jun Bi ]. 20 HAWC w/o TriII HAWC w/ TriII MAGIC Segue1 VERITAS Combined HESS Segue1 VERITAS Combined HAWC w/o TriII HAWC w/ TriII [TeV] [TeV] 10 10 DM DM m m 100 ], Fermi-LAT combined limit [ Thermal Relic DM Thermal Relic DM LHAASO 95% Containment LHAASO 68% Containment LHAASO Combined Fermi Combined LHAASO 95% Containment LHAASO 68% Containment LHAASO Combined 14 - τ VERITAS Combined HAWC w/o TriII HAWC w/ TriII MAGIC Segue1 - + τ t t ] and MAGIC Segue 1 limit [ 1 1 18 -21 -22 -23 -24 -25 -26 -27 -21 -22 -23 -24 -25 -26 -27

10 10 10 10 10 10 10 10 10 10 10 10 10 10

] s [cm v> < ] s [cm v> < σ σ

-1 3 -1 3 [TeV] 10 DM m 5 100 100 Thermal Relic DM LHAASO 95% Containment LHAASO 68% Containment LHAASO Combined Fermi Combined - W + VERITAS Combined HAWC w/o TriII HAWC w/ TriII MAGIC Segue1 HAWC w/o TriII HAWC w/ TriII HESS Segue1 MAGIC Segue1 VERITAS Combined W 1 -24 -25 -26 -27 -21 -22 -23

10 10 10 10 10 10 10

] s [cm v> < σ

-1 3 [TeV] [TeV] 10 10 DM DM m m ], HESS combined dSph limit [ 19 Thermal Relic DM Thermal Relic DM LHAASO 95% Containment LHAASO 68% Containment LHAASO Combined Fermi Combined LHAASO 95% Containment LHAASO 68% Containment LHAASO Combined Fermi Combined . Also shown are the HAWC combined limits [ − W - µ _ + + µ b b 1 1 The LHAASO median combined sensitivities (red solid lines), and two-sided 68% (yellow bands) -25 -26 -27 -23 -24 -25 -26 -27 -21 -22 -23 -24 -21 -22

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] s [cm v> < ] s [cm v> < σ σ

-1 3 -1 3 , and W − τ + VERITAS Segue 1 limit [ Figure 2: and 95% (green bands) containment bands ofτ one year for five annihilation channels, including b Short Title for header PoS(ICRC2019)509 ]. , 742 , (2015) PoS The Most , JCAP Phys. Rev. , , Xiao-Jun Bi 115 ]. ]. ]. 1606.04898 [ (2011) 051 1408.0002 [ Indirect Dark Matter Phys. Rev. Lett. PPPC 4 DM ID: A Poor ]. , Nucl. Instrum. Meth. A 1103 Weak Corrections are , (2016) 047 1009.0224 [ 1611.03184 [ JCAP 1609 (2015) 74 , 801 JCAP (2011) 019 1706.01277 Dwarf annihilation and decay , [ (2017) 110 ]. 1103 834 Dark matter substructure modelling and sensitivity 6 Astrophys. J. ]. JCAP , (2018) 154 , ]. ]. . 853 0709.1510 [ Astrophys. J. A ’Baedecker’ for the dark matter annihilation signal , Searching for Dark Matter Annihilation in Recently Discovered ]. (2010) 249 1701.01778 1508.04370 [ [ Searching for Dark Matter Annihilation from Dwarf Astrophys. J. 34 (2008) 614 The Large High Altitude Air Shower Observatory (LHAASO) Science White Gamma/Proton separation study for the LHAASO-WCDA detector A future project at Tibet: The large high altitude air shower observatory Status of LHAASO updates from ARGO-YBJ , Observation of the crab with the hawc gamma-ray observatory ]. . New method for gamma/hadron separation in hawc using neural networks Dark Matter Limits From Dwarf Spheroidal Galaxies with The HAWC . 678 astro-ph/0311145 [ 0902.4715 (2017) 39 [ (2016) 991 ]. 843 Chin. Phys. C (2018) 842 , . 1503.02641 Astrophys. J. [ , 1905.02773 -LAT collaboration, -LAT, DES collaboration, , (2009) 014 (2004) 123501 ICRC2015 69 ERMI ERMI 1012.4515 HAWC collaboration, HAWC collaboration, LHAASO collaboration, F F LHAASO collaboration, LHAASO collaboration, LHAASO collaboration, A. U. Abeysekara et al., Astrophys. J. Spheroidal Galaxies with Six Years of Fermi Large Area Telescope Data PoS Milky Way Satellites with Fermi-LAT Gamma-Ray Observatory Paper Relevant for Dark Matter Indirect Detection D Dark Matter Dominated Galaxies: Predicted Gamma-rayDwarfs Signals from the Faintest Milky Way G. D. Martinez, J. S. Bullock,Detection M. from Kaplinghat, Dwarf L. Satellites: E. Joint Strigari Expectations0906 and from R. Astrophysics and Trotta, Supersymmetry A. Geringer-Sameth, S. M. Koushiappas andemission M. profiles Walker, for dark matter experiments M. Hütten, C. Combet, G. Maierof and the D. Cherenkov Maurin, Telescope Array to Galactic dark halos ICRC2017 231301 M. Cirelli, G. Corcella, A. Hektor, G. Hutsi, M. Kadastik, P. Panci[ et al., P. Ciafaloni, D. Comelli, A. Riotto, F. Sala, A. Strumia and A. Urbano, N. W. Evans, F. Ferrer and S. Sarkar, L. E. Strigari, S. M. Koushiappas, J. S. Bullock, M. Kaplinghat, J. D. Simon, M. Geha et al., (LHAASO) Particle Physicist Cookbook for Dark Matter Indirect Detection (2014) 95 D Program of China (Grant No. 2016YFA0400200), the National Natural Science Foundation & [9] [7] [8] [4] [5] [6] [3] [1] [2] [16] [13] [14] [15] [12] [10] [11] of China (Grant Nos. U1738209,Top-Notch 11851303, Young Professionals. 11835009), and the National Program for Support of References R Short Title for header PoS(ICRC2019)509 , 1602 ]. Xiao-Jun Bi JCAP , 1310.0828 [ ]. (2014) 042001 1410.2589 [ 89 7 Phys. Rev. D ]. , (2014) 112012 90 Limits to Dark Matter Annihilation Cross-Section from a 1202.2144 [ Phys. Rev. D Dark matter constraints from observations of 25 Milky Way satellite ]. , VERITAS Deep Observations of the Dwarf Spheroidal Galaxy Segue 1 Search for dark matter annihilation signatures in H.E.S.S. observations of -LAT collaboration, (2012) 062001 85 1601.06590 ERMI [ -LAT collaboration, ERMI MAGIC,F F H.E.S.S. collaboration, VERITAS collaboration, Combined Analysis of MAGIC and Fermi-LAT Observations of Dwarf Satellite Galaxies Dwarf Spheroidal Galaxies Phys. Rev. D (2016) 039 galaxies with the Fermi Large Area Telescope [19] [20] [17] [18] Short Title for header