Cosmic Ray Excess From MultiComponent Dark Matter


 Posy Watson
 6 months ago
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1 Cosmic Ray Excess From MultiComponent Dark Matter Da Huang Physics Department, LeCosPA PRD89, (2014) [arxiv: ] PRD91, (2015) [arxiv: ] Mod. Phys. Lett. A 30 (2015) 35, In collaboration with C.Q. Geng, L.H. Tsai and C. Lai 1
2 Content Motivation and Review of Experimental Status General Phenomenological Analysis Two Component Decaying DM Diffuse γray Prediction Summary 2
3 Motivation Recently, AMS02 published a series of new measurements of the positron fraction spectrum, showing an uprise above 10 GeV. AMS02 Positron Fraction Spectrum Confirm the observation by many previous experiments, such as PAMELA, FermiLAT, AMS 01, et al.. Different from usual astrophysical expection: decreasing power law 3
4 Motivation The excess was also observed in the total e + +e  flux spectrum by PAMELA, FermiLAT and AMS02. FemiLAT e + +e  Spectrum Conventional expectation: decreasing power law 4
5 Motivation Moreover, both the AMS02 positron fraction spectrum and the FemiLAT total e + +e  flux spectrum showed some substructure around 100 GeV. AMS02 Positron Fraction Spectrum FemiLAT e + +e  Spectrum Substructure? 5
6 Motivation In the new release, AMS02 also gave the spectra of e + (e  ) flux and total (e + +e  ) flux. e + (e  ) flux: Spectrum hardening above ~30 GeV 6
7 Motivation Positron fraction : first evidence that positron fraction stops increasing with energy above ~200 GeV Total e + +e  flux: good fit with a single power law at high energy AMS02 Positron Fraction Spectrum AMS02 Spectrum of (e + +e  ) flux 7
8 Motivation All the excesses indicate that there are additional positron and/or electron sources beyond our current knowledge, either in astrophysical or particle physical origin. In literature, there are two compelling candidate origin for these excesses: Pulsars and Dark Matter. In this talk, I concentrate on the decaying dark matter interpretation for this AMS02/FermiLAT excess Requirement the TeV DM lifetime τ DM ~O(10 26 )s >> τ Universe ~ O(10 17 )s 8
9 Decaying DM: Status Previous Studies concentrated on the SingleComponent Decaying DM models with the dominant decay channels e + e , μ + μ , τ + τ ,W + W , b + b , Their general conclusion is that such models cannot explain the AMS02 positron fraction and FermiLAT total e + +e  flux simultaneously. Jin et al APJ (2013) arxiv: ; Yuan, et.al. arxiv: MultiComponent DM 9
10 Further Constraints on Decaying DM The measured antiproton spectrum agrees with the prediction of the conventional astrophysical theory well 10
11 Further Constraints on Decaying DM Recent analysis with the new AMS02 data confirmed this conclusion. Giesen et al ICAP(2015); Iin et al. PRD (2015); Kappl et al JCAP(2015). Leptophilic DM 11
12 Decaying DM: General Formula e  (e + ) flux: Primary electron flux: assumed to be broken power law Br = : Secondary e  (e + ) produced in propagation, computed by GALPROP κ 1,2 denotes the uncertainty in normalization of backgrounds. 12
13 TwoComponent Decaying DM DM Source Term: ρ(x): DM density distribution, here we use isothermal profile τ i : DM lifetime M i : DM Mass Half Density DM decay process : DM Injection Spectra: with condition: 13
14 TwoComponent Decaying DM Normalized Injection Spectra for Electrons : : obtained with the simulation by PYTHIA After e + /e  are produced from DM decays, they would propagate in the Galaxy, which is solved numerically by GALPROP 14
15 TwoComponent Decaying DM Observations: The excess of total e + +e  flux by FermiLAT extends to 1 TeV, so at least one DM cutoff should be larger than 1 TeV; The substructure at around 100 GeV observed by both AMS02 and FermiLAT AMS02 Positron Fraction Spectrum FemiLAT e + +e  Spectrum One DM drop at 100GeV Substructure? 15
16 TwoComponent Decaying DM The observations above indicates that DM at least contains two components, with E c1 > 1000 GeV and E c2 100 GeV. For generic discussion, we take two DMs cutoffs E ci and masses M i as follows: E c1 M 1 E c2 M GeV 3030 GeV 100 GeV 416 GeV 16
17 TwoComponent Decaying DM Fitting Results: Conclusion: DoubleComponent DM decaying mainly via twobody leptonic decay CAN fit to AMS02 positron fraction and FermiLAT total 2nd flux LeCosPA simultaneously. 17
18 Update with New AMS02 Data Recently, we update our analysis of twocomponent decaying DM model with the AMS02 positron fraction and total (e + +e  ) flux. C. Lai, DH, C. Q. Geng, MPLA 30 (2015) 35, Advantage: reduce the systematic uncertainties of fit 18
19 Update with New AMS02 Data Total e + +e  Flux Positron Fraction Spectrum All the cases fit the AMS02 dataset very well. 19
20 Diffuse γray Constraint Previous studies showed that the diffuse γray measured by FermiLAT could already give strong constraint to decaying DM Cirelli et al PRD(2012); Essig et al. PRD (2009); Ibe et al(2013), ; Cirelli & Panci, NPB (2009); Question: Does our twocomponent DM (or multicomponent DM) scenario still survive after the consideration of diffuse γray constraints? Strategy: We compute total various diffuse γray spectrum, including the ones from twocomponent DM decays, which is compared with the FermiLAT data. Total Predictions of Phen. Model! 20
21 Model Prediction to Diffuse γray Substructure? Conclusion: With the parameters fitted by AMS02 and Fermi LAT, the predicted γ ray is still allowed by the FermiLAT measurement. 21
22 Summary In this talk we investigate the multicomponent decaying Dark Matter model to explain AMS02 and FermiLAT e + /e  excesses, and show that two DM components are enough to explain the data. We also use the AMS data to update our analysis of twocomponent DM model, and show that it can also provide a good fit. We also show that the predicted diffuse γray spectrum agrees with that observed by FermiLAT. 22
23 23
24 SingleComponent Decaying DM Χ 2 Fitting Results: 24
25 Update with New AMS02 Data Total e + +e  Flux Positron Fraction Spectrum All the cases fit the AMS02 data very well 2DM alive Observation: if E ch < 1 TeV, the positron fraction begins decreasing at ~200 GeV, as claimed by AMS02, but it cannot explain the total (e + +e  ) flux at high energies. 25
26 Propagation Parameters 26