Indirect dark matter searchCurrent status and report

Yen­Hsun Lin (林彥勳 )Nat'l Chiao Tung Univ., Taiwan

江門中微子實驗黃皮書進展研討會8/4~8/9, 廈門

Neutrino flux from DM in the Sun

● The neutrino flux from DM annihilation in the Sun is given by:

● The is related to the DM particle property: σχp, the DM-nucleon cross section

● Spectrum dN/dE can be generated by WimpSim

Total annihilation rate

Neutrino spectrum @ solar core

JCAP 08, 021 (2008)

How evolves?

● The DM number evolution equation in the Sun

● The solution:

Self-interaction Self-interactioninduced evaporation

Gravitational capture Evaporation

Annihilation

Gravitational capture

● DM particles in the Halo attracted by solar gravity therefore scatter with nucleus and captured

● Two types of DM-nucleus interaction: 1) spin-dependent and 2) spin-independent

G

DM capture rate

● Spin-dependent:

● Spin-independent:

Phys.Rept. 267, 195 (1996)Phys.Rept. 405, 279 (2005)

DM capture ratearXiv:1312.6048

σχp

= 1 pb σχp

= 1 pb

Evaporation

● The captured DM particles scattered with the nucleus in the Sun and gains kinetic energy thus escapes

DM evaporation rate

● The evaporation rate:

Ce

σχp

= 10−4 pb

Left is for spin-dependent and spin-independent is similar.

JCAP 07, 010 (2013)

Astrophys. J. 321, 560 (1987)Nucl. Phys. B 283, 681 (1987)

Self-interaction, S.I.

● The Halo DM particles scatter with the DM already captured by the Sun● Both captured

● One captured, the other escapes

● Both escapes (self-eject)

PRD 80, 063501 (2009)

S.I. induced evaporation

● It's not one of the three situations mentioned before

● Explored by no one before as far as we know

DM number inside the Sun

Y.-H. Lin, Talk@ICHEP 2014

Total annihilation rate

● directly matters to the ν signal

● Actually not only related to σχp also σχχ

Y.-H. Lin, Talk@ICHEP 2014

Event rate estimation

● The neutrino event rate can be estimated:

Detector effective area

We used IC-PINGU's to calculate

Detector effective volume ν

e

νμ

arXiv:1401.2046

Mton

Mton

Let's have a look @

● With mχ > 5 GeV, the evaporation mass

● The most popular channels examined are: τ, ν, W...etc.

Hard channel Soft channel

High energy neutrino from annihilation/decay producthighest fewest

C. Rott, Talk@CosPA 2013

Disfavored by current galactic constraints

See review article arXiv:1202.1454 for further details

We expected...

● JUNO detector has ~ 20 kton effective volume

● By examining the hard spectrum

● We can expect the JUNO σχp-sensitivity by projecting the results from PRD 84, 036007 (2011)

Unfortunately...

● Evaporation occurs while ● Current galactic constraints favor leptophillic dominant

channels, but they are not realistic● The JUNO effective volume is not such large @ GeV level ● JUNO detector is designed to have better performance @

MeV level

IceCube JUNO

Effective voume 3-5 Mton <20 kton

Sensitive flavor All

Event rate (yr-1) ~7000 (Cas+Tra) <2

Around Eν ~ GeV

If JUNO is capable running @ GeV constantly all year

Soft spectrum revisited

● So far, the problems raised when we focus on hard spectrum signal● How about soft spectrum? Is it really non-detectable @ detector?

?1 GeV 100 GeV

Soft HardRecently...

MeVPRD 34,2206(1986)Nucl.Phys.B304,877(1987)

Considered as non-detectable

Pion multiplication

HadronsB

f = 64.79%

Goes to hard spectrum

Solar core

Annu.Rev.Nucl.Sci. 23, 395 (1973)

if survives

Continuous hadronic interaction

in the medium and energy lossPion decay at rest

Eν up to 52.8 MeV

Coulomb absorp-tion, no contribu-tion

negligible contribution

Pion

stop

pin

g p

oi n

t

Low energy neutrino from hadronic shower

Pion yieldPion yield at the production point as a function of DM mass m

χ

JCAP 08, 011 (2013)

ν-yield from π multiplication

PRD 88, 055005 (2013)JCAP 08, 011 (2013)

ν-yield @ Solar core

● Taking mχ = 10 GeV to avoid evaporation● Examining spectra from b and τ channels ● Higher mχ is achievable→Severe attenuation happens @ TeV

arXiv:1312.6048

Disadvantage to ICDC

No affect to MeV ν-yield: Advantage to JUNO

ν-yield @ JUNO

● Settings are the same as previous: ν-yield per annihilation

Soft spectrum10 - 100 MeV

Hard spectrum1 - 10 GeV

Hard spectrum1 - 10 GeV

Soft spectrum10 - 100 MeV

arXiv:1312.6048

Event rate re-estimation

● The high ν-yield is now @ MeV range● Thus:

● ν cross section can be approximated as:

● We can estimate the event rate in JUNO per year with (no S.I.):

10 MeV

100 MeV

PRD 60, 053003 (1999)Phys.Lett.B 564, 42 (2003)PRD 88, 055005 (2013)

~0.39 yr-1

Current status

● The soft spectrum has high ν-yield● MeV neutrinos produced via DM-DM annihila-

tion is potentially detectable in JUNO● At MeV energy, JUNO has maximum effective

volume● We estimated the neutrino event rate per year

in JUNO● By the unique spectrum shape, we can further

examine different DM scenarios

Further steps and discussions

● ν cross section is approximated not exactly calculated or from fine MC simulation

● Event rate is just a rough estimation, careful calculation required

● Backgrounds ● Angular/energy resolutions ● Day/night effects ● Manuscript not updated yet!!!● ……● Stay tuned!

Haven't analyzed yet!!!