1. The e+e- collider experiments to search for dark matter
CosPA 2015
KAIST, Daejeon, Korea
October 12 ~ 16, 2015
The e+e- collider experiments to search for dark matter
Kihyeon CHO (KISTI)

2. Contents
Introduction
Search for dark matter at e+e- collider
Summary

3. Introduction

4. Notation Dark photon =A’ = A = AD = U-boson Dark higgs - h’=h0 = HD …
Heavy photon
Dark force
Light dark gauge boson
=A’ = A = AD = U-boson
Dark higgs
- h’=h0 = HD …
Kinetic mixing 2 = 2 = 2 = ’/

5. Dark sector constant Dark sector D = ’ = gD2 /4 Hidden sector
Secluded sector …

6. Dark Matter A’ decay to DM Two body decay Upsilon decay 
Eassig, et al, JHEP 11, 167 (2013). 
Eassig, ArXiv: [hep-ph]
Neutral under SU(3)XSU(2)XU(1)
Two body decay
Upsilon decay
One photon + missing ET

7. e+e- collider Enormous increases in luminosity over last few decays.
~ 2017

8. e+e- collider experiments
CM Energy(GeV)
Date
Place
1. KLOE
1.02
2001~
INFN, Italy
2. BES III
3.78
2007~
Beijing, China
3. BaBar
10.58
1999~2008
SLAC, USA
4. Belle
1999~2010
KEK, Japan
5. Belle II
2017~

9. Search for Dark Matter at e+e- collider9

10. Experiment vs. Dark Sector
Dark Matter
Dark photon
Higg-Strahlung
Heavy flavor lepton
1. KLOE
2 charged lepton+one photon
2 charged lepton + 
+ missing ET(h’)
2. BES III
3. BaBar
one photon + missing ET
2 charge tracks + one photon
3 charged track pairs
4 or more charged tracks
4. Belle
2 charge track + one photon
Two lepton pairs
A lepton pairs + missing ET
5. Belle II
2 Charge Track one photon

11. 1. KLOE Experiment Physics Program
- Kaon physics, Spectroscopy, hadron cross-section,  physics, Dark sector

12. Dark Photon (1/3)
ArXiv: [hep-ph]

13. Dark Photon (2/3) Dark Photon (e+e-) Dark photon (e+e-  & +-)
ArXiv: [hep-ex]

14. Dark Photon (3/3)
ArXiv: [hep-ex]

15. Higgs-Strahlung + missing ET(h’) If Mh’ < MA’
- h’ long-lived invisible
invisible
ArXiv: [hep-ex]

16. 2. BES III Experiment
Zhiyong Wang (2015)

17. Dark Photon
Zhiyong Wang (2015)

18. Zhiyong Wang (2015)

19. Zhiyong Wang (2015)

20. 3. BaBar Experiment
A. Lusiani (2014)

21. Dark Matter (1/2)
One photon + missing ET
A. Lusiani (2014)

22. Dark Matter (2/2)
One photon + missing ET
A. Lusiani (2014)

23. Dark Photon one photon + 
The effective Yukawa coupling (fY) of the b quark to the A0
A. Lusiani (2014)

24. Higgs-Strahlung
A. Lusiani (2014)

25. 4. Belle Experiment
KEK

28. Higgs-Strahlung (1/4) h’ decays depending on Mh’ and MA’ .
To measure the coupling constant of the dark photon to the dark higgs, D
(1) Mh’ > 2MA’ : h’ → A’A’, very low background
Exclusive: 3 charged track pairs with same invariant mass and total energy of event
Inclusive: 2 charged track pairs, same invariant mass, third A from 4 mom. of e+e- system
(2) MA’ < Mh’ < 2MA’: h’ → A’A’*
(3) Mh’ < MA’ : h’ long-lived and h’ → l+l-, π+π-
Mh’
(1)
Mh’=2MA’
h’ → A’A’
(2)
Mh’=MA’
h’ → A’A’*
(3)
h’ → l+l-, π+π-
MA’
ArXiv: [hep-ph]

29. Higgs-Strahlung (2/4) Case (1) Mh’ > 2MA’ : h’ → A’A’,
Prompt of h’ and A’
10 exclusive channels: 3(l+l-), 2(l+l-)(π+π-), 2(π+π-) (l+l-), 3(π+π-) with l=e,
3 inclusive channels: 2(l+l-)X with X dark photon (Missing mass)

30. Higgs-Starahlung (3/4) Background vs. number of events observed
Dark photon
Dark higgs
Background vs. number of events observed
BG: SM 2 processes with  or  final state
Discontinuity at 1.1GeV due to selection criteria

31. Higgs-Strahlung (4/4) Dark photon and Dark higgs distributions

32. Dark Photon Dark photon decays SM particles.
To call a “long-lived gauge boson” instead of dark photon
Same analysis for Higgs-Strahlung
work in progress
Gianluca Inguglia (2015)

33. A’ couples only to heavy-flavor leptons
Brian Shuv and Itai Yavin (arXive: [hep-ph])
If MA’ > 2M
If MA’ < M or sterile neutrinos
work in progress at Belle

34. 5. Belle II Experiment

35. Dark Matter Dark photon decays DM. One photon + missing ET
Full luminosity of 50 ab-1 and 1% trigger fraction
Need a single photon trigger at Belle II
Eassig, et al, JHEP 11, 167 (2013).

36. Dark photon Belle and Belle II detection efficiency for
Eassig, et al, JHEP 11, 167 (2013).

37. Summary
The e+e- collider experiments (KLOE, BESIII, BaBar, Belle) contribute to search for light Dark Matter particles.
Belle II will search for Dark Matter in radiative decays with the trigger.
With 50 ab-1, Belle II may also cross-check any signals discovered by fixed target experiments.

38. Beyond the Standard Model
Standard Model Particles
⇒ Still going
Dark Matter

39. Thank you.

40. Acknowledgement Youngjoon Kwon Patrick Fox Chaehyun Yu Soo-hyeon Nam
Jangho Kim
J. Cooley
Rouven Essig
K.Y. Choi