1. The e+e- collider experiment to search for Dark Matter Kihyeon CHO (KISTI) LHC Physics Workshop 2015 Konkuk University, Seoul, Korea August 4 ~ 6, 2015

2. Contents Dark matter at e+e- collider Search for Dark Matter at e+e- collider Summary 2

3. Dark Matter at e+e- Collider 3

4. Why Dark Matter? Dark Matter is an evidence of BSM Physics. Its mass is not well constrained. Weak-scale DM has lots of attention: –Weak-scale, masses, couplings ⇒ correct abundance –Good candidates in models designed to understand the weak scale –Huge experimental efforts (direct detection, LHC,...) Up to now, not too much new physics at the LHC ⇒ We must look everywhere we can do for DM. 4

5. Dark Matter at fixed target experiments Recently 6 fixed target experiments have been approved. They will cover region between 1MeV/c 2 ~1GeV/c 2. All experiments use prompt decays & A → l + l - HPS & DarkLight use displacement decays, too. 5 Eassig, et al, JHEP 11, 167 (2013).

6. Dark Matter at e+e- collider Fixed CM energy Sensitive to light DM: a few MeV/c 2 ~ 5GeV/c 2 Relatively free from unitarity or validity of EFT Clean signal and low background Both prompt decay and displacement decay 6

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

8. e+e- collider experiments 8 ExperimentsCM Energy(GeV)DatePlace 1. KLOE1.022001~INFN, Italy 2. BES III3.782007~Beijing, China 3. BaBar10.581999~2008SLAC, USA 4. Belle10.581999~2010KEK, Japan 5. Belle II10.582017~KEK, Japan

9. Nomenclature Dark photon –Heavy photon –Dark force –Light dark gauge boson =A’ = A = A D = U-boson Dark higgs - h’=h 0 = H D … Kinetic mixing  2 =  2 =  2 =  ’/  9

10. Dark sector constant –  D =  ’ = g D 2 /4  Dark sector –Hidden sector –Secluded sector –… 10

11. Dark Sector 11 8 gluons W + W - Z 0  H A’h’  Standard Model Dark Sector  -Z 0 mixing  -A’ mixing (…)

12. Dark Matter (1/3) 12  A’ decay to DM Eassig, ArXiv: 1309.5084 [hep-ph] Upsilon decay Two body decay Eassig, et al, JHEP 11, 167 (2013). Neutral under SU(3)XSU(2)XU(1)

13. Dark Matter (2/3) The plane of with different characteristic single photon and missing E T signals A’ mediator 13 Off-shell heavy mediator Invisible and on-shell off-shell mediator Eassig, et al, JHEP 11, 167 (2013).

14. Dark Matter (3/3) A’ decays to dark matter on-shell or off-shell with different gamma spectrum –Radiative production in e+e- collision –Only one photon in the final state with Requires high single photon trigger –Not available in Belle, –The BaBar implemented a single photon trigger (arXive: 0808.0017[hep-ex]) –On-going discussions for Belle II 14

15. Search for Dark Matter at e+e- collider 15

16. e+e- Collider Experiments ExperimentDark MatterDark photonHigg-StrahlungHeavy flavor lepton 1. KLOE 2 charged lepton+one photon 2 charged lepton +   + missing E T (h’) 2. BES III 2 charged lepton+one photon 3. BaBarone photon + missing E T 2 charge tracks + one photon 3 charged track pairs 4 or more charged tracks 4. Belle2 charge track + one photon 3 charged track pairs Two lepton pairs A lepton pairs + missing E T 5. Belle IIone photon + missing E T 2 Charge Track one photon 3 charged track pairs Two lepton pairs A lepton pairs + missing E T

17. 1. KLOE Experiment 17 Physics Program - Kaon physics, Spectroscopy, hadron cross-section,  physics, Dark sector

18. Dark Photon (1/3) 18 ArXiv: 0903.0363 [hep-ph]

19. Dark Photon (2/3) Dark Photon (  e + e - ) Dark photon (e + e -  &  +  -  ) 19 ArXiv: 1501.05517 [hep-ex]

20. 20 ArXiv: 1501.05517 [hep-ex] Dark Photon (3/3)

21. Higgs-Strahlung  + missing E T (h’) If M h’ < M A’ - h’ long-lived invisible 21 invisible ArXiv: 1501.05517 [hep-ex]

22. 2. BES III Experiment 22 Zhiyong Wang (2015)

23. Dark Photon 23 Zhiyong Wang (2015)

24. 24 Zhiyong Wang (2015)

25. 25 Zhiyong Wang (2015)

26. 3. BaBar Experiment 26 A. Lusiani (2014)

27. Dark Matter (1/2) A. Lusiani (2014)

28. Dark Matter (2/2) A. Lusiani (2014)

29. Dark Photon 29 A. Lusiani (2014)

30. Higgs-Strahlung 30 A. Lusiani (2014)

31. 4. Belle Experiment 31 KE K

32. 32

33. 33

34. Higgs-Strahlung (1/4) 34 h’ decays depending on M h’ and M A’. To measure the coupling constant of the dark photon to the dark higgs,  D 1) M h’ > 2M A’ : 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) M A’ < M h’ < 2M A’ : h’ → A’A’* 3) M h’ < M A’ : h’ long-lived and h’ → l + l -, π + π - ArXiv: 0903.0363 [hep-ph] M h’ M A’ M h’ =2M A’ M h’ =M A’ h’ → A’A’ h’ → A’A’* h’ → l + l -, π + π -

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

36. Higgs-Starahlung (3/4) Background vs. number of events observed –BG: SM 2  processes with  or  final state –Discontinuity at 1.1GeV due to selection criteria 36 Dark photon Dark higgs

37. Higgs-Strahlung (4/4) 37 Dark photon and Dark higgs distributions Dark photon Dark higgs Dark photon

38. Dark Photon 38 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)

39. A’ couples only to heavy-flavor leptons Brian Shuv and Itai Yavin (arXive: 1403.2727[hep-ph]) – If M A’ > 2M  If M A’ < M  or sterile neutrinos  work in progress at Belle

40. 5. Belle II Experiment 40

41. Dark Matter Dark photon decays DM. Mono-energetic photon signature Full luminosity 50 ab -1 and 1% trigger fraction Need a single photon trigger at Belle II 41 Eassig, et al, JHEP 11, 167 (2013).

42. Dark photon (1/3) 42 To set A’ limit a few MeV/c 2 ~ 7GeV/c 2 Dark photon decays SM particles: or hadrons Igal Jaegle (2014)

43. Dark photon (2/3) MC simulation of signal signature –Off-shell –On-shell or hadrons 43 Igal Jaegle (2014)

44. Dark photon (3/3) Belle and Belle II detection efficiency for 44 Eassig, et al, JHEP 11, 167 (2013).

45. Background Study 45

46. Background Mode MC @ Belle/BaBar –Does not included Cross Section check using MadGraph

47. Total Cross Section Cross Section (pb) Sqrt(s)/2 (GeV) Z W+ Total

48. 5 diagrams

49. Cross Section (pb) Sqrt(s)/2 (GeV) Total

50. 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. 50

51. Beyond the Standard Model 51 Dark Matter Standard Model Particles ⇒ Still going

52. Acknowledgement Youngjoon Kwon Patrick Fox Chaehyun Yu Soo-hyeon Nam Jangho Kim J. Cooley Rouven Essig K.Y. Choi 52

53. Thank you. 53

54. Appendix: Dark Matter Research Cluster Title: Dark matter research cluster based on computational science Object: To meet researchers between government institutes (KISTI+KASI) + anyone (Universities, Industries, IBS, …) Source: NST ( 국가과학기술연구회, National research council of Science & Technology) Fund: 50,000,0000 won/year * 2years Usage: Just for seminar/workshop and meeting Date: 2015.9.1~2017.8.31 Status: proposal 54

55. 우주의 비밀 물질의 근원표준모형 한국천문연구원 KISTI 우주의 구성 암흑물질 계산과학 기반 암흑물질 클러스터 대학 ( 인력 양성 )

56. 암흑 물질 탐색 연구 클러스터 구축 - 우주론에서 암흑물질 탐색 계산 연구 - 관측데이터 활용 연구 ( 가속기 충돌 실험 ) - 고에너지 가속기 실험 / 시뮬레이션 데이터활용 암흑물질 탐색 연구 - 슈퍼컴 활용 현상론적 모델 제시 가속기 우주론 슈퍼컴퓨터, GSDC( 대용량데이터센터 ), 첨단연구망 인프라(KISTI)인프라(KISTI) 과제목표과제목표 궁극적목표궁극적목표 계산과학 기반 국가 R&D 융합 연구의 선도 56 천제 관측 데이터 장비 인프라 ( 천문연 ) 인프라 KISTI/ 천문연 / 대학 천문연 /KISTI/ 대학 빅 데이터 일본 KEK 의 Belle/Belle II 가속기 실험 데이터, MC 시뮬레이션 데이터, 천체 관측 데이터 등 연구내용연구내용 계산과학 기반