Constraints on dark matter annihilation and decay from ν e cascades

Transcription

1 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

2 Cosmic rays observed by PAMELA/Fermi Figure: Fermi/LAT Collaboration, arxiv:

3 Existing galactic constraints (ann.) DM DM e e, NFW profile DM DM Μ Μ, NFW profile DM DM Τ Τ, NFW profile GC VLT ds Γ GC VLT ds Γ GC VLT Σv in cm 3 sec GC Γ GR Γ Σv in cm 3 sec Ν GC Γ GR Γ Σv in cm 3 sec Ν ds Γ GC Γ GR Γ Figure: Meade et al., arxiv:

4 Existing galactic constraints (ann.) DM DM e e, NFW profile DM DM Μ Μ, NFW profile DM DM Τ Τ, NFW profile GC VLT ds Γ GC VLT ds Γ GC VLT Σv in cm 3 sec GC Γ GR Γ Σv in cm 3 sec Ν GC Γ GR Γ Σv in cm 3 sec Ν ds Γ GC Γ GR Γ Figure: Meade et al., arxiv: ν µ -induced upgoing muon at Super-K provides most robust constraint (Hisano, Nakayama, Yang, arxiv: )

5 Existing galactic constraints (decay) DM 4Μ, NFW profile DM Μ Μ, NFW profile DM Τ Τ, NFW profile DM life time Τ in sec GR Γ Ν DM life time Τ in sec GR Γ Ν GC Γ ds Γ DM life time Τ in sec GR Γ Ν GC Γ ds Γ GC Γ ds Γ Figure: Meade et al., arxiv:

6 Existing galactic constraints (decay) DM 4Μ, NFW profile DM Μ Μ, NFW profile DM Τ Τ, NFW profile DM life time Τ in sec GR Γ Ν DM life time Τ in sec GR Γ Ν GC Γ ds Γ DM life time Τ in sec GR Γ Ν GC Γ ds Γ GC Γ ds Γ Figure: Meade et al., arxiv: Rising cross-section and effective volume gives strong constraint at higher masses

7 Improving ν constraints with DeepCore 1000 Μ Μ Boost Σ Limit PAMELA Figure: Spolyar, et al. arxiv:

8 Rationale for cascade search Suppressed muon background higher significance of galactic signal

9 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)

10 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.)

11 Rationale for cascade search (cont d) φ 2 1 ν x E (m sec sr 1 GeV 2 ν 3 ) (a) 2 x νµ ν µ ν e 0.5 x ν e 10 1 This Work HKKM04 Bartol Fluka E ν (GeV) Figure: Honda et al., arxiv:astro-ph/

12 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

13 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)

14 5 DeepCore-years χ 2 for DM DM µ + µ ] [ cm 3 /s σv m [GeV]

15 5 DeepCore-year χ 2 for DM µ + µ τ [s] m [GeV] 0.0

16 Discrepancy in exposure Significance s2 b increases with exposure

17 Discrepancy in exposure Significance s2 b increases with exposure Shape of χ 2 map changed by accumulation of background, but significance always improves.

18 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

19 100 DeepCore-years χ 2 for DM DM µ + µ ] [ cm 3 /s σv m [GeV]

20 100 DeepCore-years χ 2 for DM µ + µ τ [s] m [GeV] 0.0

21 Summary Not yet competing with background, because not enough counts (according to my treatment)! Cascade search should surpass contained-muon events...

22 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