Positron excess?

Physics Department, Tohoku University Physics Department, Tohoku University

（郡　和範）Kazunori Kazunori KohriKohri

－　 From viewpoints of both particle physics and astrophysics －

Positron Excess (PAMELA satellite reported)

Adriani et al, arXiv:0810.4995v1 [astro-ph]

/ ( ~0.6 proton diff usion)e e E

Electron and positron flux by Fermi

Abdo et al, Fermi LAT Collaboration, arXiv:0905.0025, PRL102 (09) 181101

What is the origin of e+e- excess?• Particle-physics origin

• Astrophysical origin

1. Annihilating DM

2. Decaying DM

1. Pulsars

2. Supernova Remnants (SNRs)

3. Gamma-ray burst

See Fuminobu Takahashi’s talks

See also Toshifumi Yamada’s and Patrick Fox’s talk

See Norita Kawanaka’s talk

See also Subir Sarkar’s talk

See Kunihito Ioka, arXiv:0812.4851[astro-ph] or Kawanaka’s talk

BBN, CMB, Gamma-ray, ν, gal. profile

Diffuse-gamma-ray

annisotropy

B/C

annisotropy

Another aspects of annihilating DM

1. Big Bang Nucleosynthesis (BBN)

2. Cosmic Microwave Background (CMB)

3. Gamma-ray background ( gal. and extra-gal.)

4. Neutrinos

5. …

http://map.gsfc.nasa.gov/media/060916

Dark Matter?

2CDM 0.1 h

0

ii

c

Thermal freezeoutBoltzmann equation

frezeout

3

H

nv

2

20.10.1

TeV

v

h

Freezeout / 20T m

Ωχ does not depend on mχ

Kolb & Turner

Predicting TeV Physics!!! 26 33 10 /v cm s

n

s

Positron Excess

Steady-state solution (Hisano etal, ’06)

K(E) and b(E) are taken from (Baltz-Edsjo ’99)

Diffusion model

Flux

Propagating within a few kpc, normalized to fit B/C, Boost Factor (BF) considered for clumpy distributed DM.

0.17propagation ( )/ ( ) 0.7kpc( / GeV)r EK E b E E

Hisano, Kawasaki,

Kohri, Moroi, Nakayama (09)

Positron excess

in DM annihilation

Diffusion model

Fitted to B/C ratio

23 310 /v cm s

Hisano, Kawasaki,

Kohri, Moroi, Nakayama (09)

Electron/positron cutoff

in DM annihilation

Diffusion model

Fitted to B/C ratio

23 310 /v cm s

Residual annihilation of DM even at around BBN or CMB epoch

• To fit the PAMELA and ATIC2/Fermi positron and electron signals,

23 310 /v cm s

2DMD

DMDM DMann

M DMann3 ~

H

v nn

dnHn v n

s s

dn

t

O(103) times larger than canonical value, 26 3

canonical 3 10 /v cm s

1

Big-Bang Nucleosynthesis (BBN)

Big-Bang Nucleosynthesis (BBN)

Very strong cosmological tools to study long-lived particles with lifetime of 0.01 sec – 1012 sec

Theoretical predictions are constrained by observational D, 3He, 4He, 6Li and 7Li abundances with their conservative errors.

44

38

1

18

16

1

5

10

12

2

- 4

10 GeV

10 GeV

10 GeV

200 MeV

3 M

time

10 sec

10 sec

10 sec

10 sec

0.1 sec

1 sec

10 s

eV

0.5 MeV

1ec

10 se

eV

0.1 eV

1

"temper

c

0

at ur

e"

eV13

.7 Gyr

Thermal history of the UniverseThermal history of the Universe

Planck scale

GUT phase transition?

Electroweak phase transition

QCD phase transition

Neutrino decoupling

Electron-positron annihilation

Matter-radiation equality

Photon decoupling (CMB)

Big bang

Present

Inflation and Reheating

Baryogenesis?

Big-Bang Nucleosynthesis (BBN)

17(~10 sec)

cf) 1 GeV ~ 1013K

Radiation

Matter

Scenario of BBN

1) 1 MeV ( 1sec)T t , , e,n p

Weak interaction is in equilibrium

en e p

n

p

n QExp

n T

(Q 1.29 MeV)n pm m

cf) 1 MeV ~ 1010K

2) ~ 1 MeV ( ~ 1 sec)T tFeezeout of weak interaction

•Weak interaction rate

•Hubble expansion rate

5 4~ ~ / n p n p e Wn T m

2( )~ /

( )

pl

a tH T M

a t

33

4~

0.8 MeV

p

W

T M T

H M

( 0.8 MeV ) fH T T / is fixedn pn n

freezeout

n

p f

n QExp

n T

cf) 1 MeV ~ 1010K

QExp

T

freezeout

1

7n

p

n

n

4 He4

N

pB

mY

4 He

N

n

mfreezeout

freezeout

2( / )0.25

( / ) +1( )

n p

n pn p

n n

n nn n

He4 mass fraction

4 Hen

npp

4He/ 2nn n

3) ~ 0.1 MeV ( ~ 100 sec)T t

p n D 2.2 MeVDT B

3/ 2/ 16.3( / ) exp[ / ] 0.01 D H N Dn n T m B T

4) 0.1 MeV ( 100 sec)T t

3

3

44

, +n

( He ) +n ( He+

H

e p)

e

H

D D T p

T D D3A little and He are left as cold ashes D

There is no stable nuclei for A=5,8. Mass 7 nuclei are produced a little.4

4

7

73

He +

He He

L

+

i

Be

T

7e

7e +LiB e

cf) 0.1 MeV ~ 109K

64 LHe i+ D

Time evolution of light elementsTime evolution of light elements

He4

D

Li7

Li6

He3

Observational Light Element Observational Light Element AbundancesAbundances

pY 0.2516 0.004 Peimbert,Lridiana,

Peimbert(2007)Izotov,Thuan, Stasinska (2007)

5D/ H (2.82 0.26) 10

Melendez,Ramirez(2004)

7sy10 st.log Li/ H 9.90 0 ( 0.35.09 )

O’Meara et al. (2006)

sy6

s7Li/ Li 0.046 0. ( 0.106022 ) Asplund et al(2006)

3He/ D 0.83 0.27 Geiss and Gloeckler (2003)

Fukugita, Kawasaki (2006)

SBBN

( / )Bn n

10

WMAP (6.225 0.160) 10 ( / )Bn n

Annihilation or decay during/after BBN epoch

Massive particle decaying/annihilating during/after BBN epoch produces high energy photons, hadrons, and neutrinos

Destruction/production/dilution of light elements

Severer constraints on the number density

Sato and Kobayashi (1977), Lindley (1984,1985), Khlopov and Linde (1984)

Ellis, Kim, Nanopoulos, (1984); Ellis, Nanopoulos, Sarkar (1985)

Kawasaki and Sato (1987)

Reno and Seckel (1988), Dimopoulos, Esmailzadeh, Hall, Starkman (1988)

Kawasaki, Moroi (1994), Sigl et al (95), Holtmann et al (97)

Jedamzik (2000), Kawasaki, Kohri, Moroi (2001), Kohri(2001), Cyburt, Ellis, Fields, Olive (2003)

Kawasaki, Kohri, Moroi(04), Jedamzik (06)

Electromagnetic mode

x

D + p + n

He3/D >~ O(1)

and / or e emissionDM DM

Hadronic modeHadronic mode

0

,

,

2

p pq q

n nDM DM W

Z

strongweakn p n pn p

Extraordinary inter-conversion reactions between n Extraordinary inter-conversion reactions between n

and pand p

Hadron induced exchange

/n p n pEven after freeze-out of n/p in SBBN

More He4, D, Li7 …

cf) 0n p 0p n

（（ I) Early stage of BBN I) Early stage of BBN (T > 0.1MeV)Reno and Seckel (1988) Kohri

(2001)

(II) Late stage of BBN (T < 0.1MeV)Hadronic showers and “Hadro-dissociation” S. Dimopoulos et al. (1988)

fE E n (p)

Kawasaki, Kohri, Moroi (2004)

Non-thermal Li, Be Production by energetic nucleons or photons Dimopoulos et al (1989)

34 +X

N (or ) + HHe

Te

+ X

4 6T + He + [8.4 Li MeV]n

3 4 6 He + He + [7.0 L V]i Mep

4 4 *N (or ) + He He +X

4 4 6 7 7He +He Li, Li, Be + ...

3T, He4He

4He Energy loss

① T(He3) – He4 collision

② He4 – He4 collision

Jedamzik (2000)

Residual annihilation of DM even at around BBN epoch

• To fit the PAMELA and ATIC2/Fermi positron and electron signals ,

• At least it must emit charged leptons

• It might also emit hadrons

23 310 /v cm s

Electromagnetic cascade shower is induced

Hadronic cascade shower is induced

Hadron emission by residual annihilation in BBN epoch

Hisano, Kawasaki, Kohri, Moroi, Nakayama (09)

Charged-lepton (e+e-) emission by residual annihilation in BBN epoch

Hisano, Kawasaki, Kohri, Moroi, Nakayama (09)

Residual annihilation and CMB

• Energy injection affects the recombination history of the Universe

• Changing the ionization fraction affects CMB anisotropy very sensitively

Belicov and Hooper (09); Galli, Iocco, Bertone, Melchiorri (09); Huetsi, Hektor, Raidal (09) Cirelli, Iocco, Panci (09); Slatyer, Padmanabhan, Finkbeiner (09); Kanzaki, Kawasaki, Nakayama (09)

Constraint from CMB anisotropyKanzaki, Kawasaki, Nakayama (09)

What is the origin of Boost Factor (BF~103)

• BF = <σv>obs / <σv>canonical

• Local enhancement of DM density in astrophys

• Sommerfeld effectLight particle exchange annihilation for m < αmDM

(a kind of bound state formation, see also Hisano-Matsumoto-Nojiri (03) )

Non-perturbative effect

Enhancement of cross section <σv>~10-23 cm3/s without

breaking Unitarity and perturbation theory

Arkani-Hamed et al (08)

Velocity-dependent annihilation cross section?• Sommerfeld or Breit-Wigner enhancement

• The constraint from BBN and CMB is nontrivial

0~ with n=1,2,3,4, ...( / ) ...nvv c

See Zavala, Vogelsberger, White (09) for the constraint from μ-distortion of CMB

initial initial (f or kinetically-decoupling DM)~ ( / ) 1 v v T T 1/ 2

(f or kinetically-thermalized DM)~( / ) <<1 v T M

Hisano, Kawasaki, Kohri, Nakayama, arXiv:0810.1892 [hep-ph]

Gamma-ray signal from DM annihilation

Gamma-ray flux

5 5

2 2

b

Averaged over

ProfileNavarro-Frank-White (NFW): cusp structure

( 1 1.5)pr p Isothermal (iso): core structure

01/ [1 ( / ) ] ( 2)qr r q

Kawasaki, Kohri, Nakayama (09)

Gamma-ray signal from GC by DM annihilation

Results by Meade et al Meade, Papucci, Strumia, Volansky, arXiv:0905.0430

Gamma-ray obs by Fermi LAT Abdo et al, 0908.1171

22 60b

: ucleon-enhancement f actorM n

Kawasaki, Kohri, Nakayama (09)

Extragalactic diffuse Gamma-ray by DM annihilation

Neutrinos from galactic center expected by PAMELA/ATIC2

• Detecting up-going muons in Kamioka

• Annihilation (upper panel) and decay (lower panel)

• Direct-neutrino emission modes with NFW are excluded

Hisano, Kawasaki, Kohri, Nakayama (08)

Hisano, Nakayama Yang(09)

Astrophysical origin?

• Supernova Remnants (SNRs)

• Pulsar

• GRB

i. A local and old unknown SNR with ns<2 in radiative phase

ii. Statistically-known SNRs with (re)acceleration of secondary positron

Fujita, Kohri, Yamazaki, Ioka (09)

Ahlers, Mertsch, Sarkar (09)

See Kawanaka’s talk

See Kunihito Ioka, arXiv:0812.4851[astro-ph]

An old SNR near the Earth

• Proton was accelerated at a local SNR (<200 pc) in a dense gas cloud (n~50/cc) 106 years ago

• p-p collision produces pions electrons and positrons which propagated for 106 years

• The cloud had alrerady disappeared (see Loop I, Local Buble as its vestige)

• Antiproton was also produced

s s A,upp

photon index in radiative phase can be

n ~v / v 2

Fujita, Kohri, Yamazaki, Ioka, arXiv:0903.5298 

• Source spectrum

• Spectrum

• Diffusion length

Fitted to Fermi by local SNR modelFujita, Kohri, Yamazaki, Ioka, arXiv:0903.5298 

Fitted to Fermi by local SNR model

• Antiproton

Fujita, Kohri, Yamazaki, Ioka, arXiv:0903.5298 

Fitted to Fermi by pp collision model

• B/C is also increasing?

Mertsch and Sarkar, arXiv:0905.3152v3

HEAO-3-C2

ATIC-2

CREAM

Summary

• Annihilation scenarios may have some problems to agree with BBN, CMB, and gamma-ray background

• It should be nontrivial to remove these discrepancies even if we adopt Sommerfeld or Breit-Wigner enhancement mechanism

• For astrophysical origin, so far we have not excluded a possible peculiar object such as a local and old SNR near the solar system.