Constraints on dark matter annihilation and decay from ν e cascades Sourav Mandal (w/ Hitoshi Murayama) IPMU/UC-Berkeley sourav.mandal@berkeley.edu 2009/7/15
Cosmic rays observed by PAMELA/Fermi Figure: Fermi/LAT Collaboration, arxiv:0905.0025
Existing galactic constraints (ann.) DM DM e e, NFW profile DM DM Μ Μ, NFW profile DM DM Τ Τ, NFW profile 10 20 GC VLT ds Γ 10 20 GC VLT ds Γ 10 20 GC VLT Σv in cm 3 sec 10 22 10 24 GC Γ GR Γ Σv in cm 3 sec 10 22 10 24 Ν GC Γ GR Γ Σv in cm 3 sec 10 22 10 24 Ν ds Γ GC Γ GR Γ 10 26 10 26 10 26 Figure: Meade et al., arxiv:0905.0480
Existing galactic constraints (ann.) DM DM e e, NFW profile DM DM Μ Μ, NFW profile DM DM Τ Τ, NFW profile 10 20 GC VLT ds Γ 10 20 GC VLT ds Γ 10 20 GC VLT Σv in cm 3 sec 10 22 10 24 GC Γ GR Γ Σv in cm 3 sec 10 22 10 24 Ν GC Γ GR Γ Σv in cm 3 sec 10 22 10 24 Ν ds Γ GC Γ GR Γ 10 26 10 26 10 26 Figure: Meade et al., arxiv:0905.0480 ν µ -induced upgoing muon at Super-K provides most robust constraint (Hisano, Nakayama, Yang, arxiv:0905.2075)
Existing galactic constraints (decay) DM 4Μ, NFW profile DM Μ Μ, NFW profile DM Τ Τ, NFW profile 10 27 10 27 10 27 DM life time Τ in sec 10 26 10 25 10 24 GR Γ Ν DM life time Τ in sec 10 26 10 25 10 24 GR Γ Ν GC Γ ds Γ DM life time Τ in sec 10 26 10 25 10 24 GR Γ Ν GC Γ ds Γ GC Γ ds Γ 10 23 10 23 10 23 Figure: Meade et al., arxiv:0905.0480
Existing galactic constraints (decay) DM 4Μ, NFW profile DM Μ Μ, NFW profile DM Τ Τ, NFW profile 10 27 10 27 10 27 DM life time Τ in sec 10 26 10 25 10 24 GR Γ Ν DM life time Τ in sec 10 26 10 25 10 24 GR Γ Ν GC Γ ds Γ DM life time Τ in sec 10 26 10 25 10 24 GR Γ Ν GC Γ ds Γ GC Γ ds Γ 10 23 10 23 10 23 Figure: Meade et al., arxiv:0905.0480 Rising cross-section and effective volume gives strong constraint at higher masses
Improving ν constraints with DeepCore 1000 Μ Μ Boost 500 100 50 2 Σ Limit PAMELA 10 500 1000 1500 2000 2500 3000 3500 Figure: Spolyar, et al. arxiv:0905.4764
Rationale for cascade search Suppressed muon background higher significance of galactic signal
Rationale for cascade search Suppressed muon background higher significance of galactic signal Why not reduce the ν background, by selecting for cascade events (mostly ν e )? Background is reduced 5 10 (ν µ contributes cascades through NC)
Rationale for cascade search Suppressed muon background higher significance of galactic signal Why not reduce the ν background, by selecting for cascade events (mostly ν e )? Background is reduced 5 10 (ν µ contributes cascades through NC) Last week at RC, IceCube announced ability to reliably identify cascade-type events in simulation (Middell, et al.)
Rationale for cascade search (cont d) φ 2 1 ν x E (m sec sr 1 GeV 2 ν 3 ) 10 3 10 2 (a) 2 x νµ ν µ ν e 0.5 x ν e 10 1 This Work HKKM04 Bartol Fluka 10 1 10 0 10 1 10 2 10 3 E ν (GeV) Figure: Honda et al., arxiv:astro-ph/0611418
Simulation Follow prescription of Spolyar, et al.: Observe half-sky (Ω = 2π) towards galactic center w/ NFW profile Assert atmospheric ν background Simulate final states with PYTHIA, track products down to 10 GeV
Simulation Follow prescription of Spolyar, et al.: Observe half-sky (Ω = 2π) towards galactic center w/ NFW profile Assert atmospheric ν background Simulate final states with PYTHIA, track products down to 10 GeV Use geometric volume of DeepCore as effective volume (smaller than effective volume for contained muon) Also consider diffuse flux limit approaching unitarity limit ( 100 TeV), useful for certain SUSY models (e.g., GMSB hidden sector)
Annihilation @ 5 DeepCore-years 10 21 χ 2 for DM DM µ + µ 5.0 4.5 4.0 3.5 ] [ cm 3 /s 10 23 3.0 2.5 σv 2.0 10 25 10 5 m [GeV] 1.5 1.0 0.5 0.0
Decay @ 5 DeepCore-year χ 2 for DM µ + µ 5.0 4.5 10 27 4.0 3.5 3.0 τ [s] 2.5 10 25 2.0 1.5 1.0 0.5 10 23 10 5 m [GeV] 0.0
Discrepancy in exposure Significance s2 b increases with exposure
Discrepancy in exposure Significance s2 b increases with exposure Shape of χ 2 map changed by accumulation of background, but significance always improves.
Discrepancy in exposure Significance s2 b increases with exposure Shape of χ 2 map changed by accumulation of background, but significance always improves. Use same cross-section νn and source flux, so must resolve discrepancy with authors of original paper... For low exposure, still match performance at m =100 GeV
Annihilation @ 100 DeepCore-years 10 21 χ 2 for DM DM µ + µ 5.0 4.5 4.0 3.5 ] [ cm 3 /s 10 23 3.0 2.5 σv 2.0 10 25 10 5 m [GeV] 1.5 1.0 0.5 0.0
Decay @ 100 DeepCore-years χ 2 for DM µ + µ 5.0 4.5 10 27 4.0 3.5 3.0 τ [s] 2.5 10 25 2.0 1.5 1.0 0.5 10 23 10 5 m [GeV] 0.0
Summary Not yet competing with background, because not enough counts (according to my treatment)! Cascade search should surpass contained-muon events...
Summary Not yet competing with background, because not enough counts (according to my treatment)! Cascade search should surpass contained-muon events... Nonetheless, strong overall constraints on DM annihilation and decay Diffuse flux limit can put very strong constraint on decays of superheavy DM, but would need much larger volume with muon-veto