1. Search for a Light Particle HyangKyu Park CHEP, KyungPook National Univ. HEP Seminar, KISTI Sep. 29, 2009

2. Motivations for a Light Particle Search  Recent astroparticle observations: ATIC, PAMELA and etc.  Light Higgs particle in Next-to-Minimal SUSY B-factory is complementary to LHC.  HyperCP exotic event Belle, BaBar, CLEO, D0 and E391a experiments These topics are highly connected each other.

3. Search for a Light Particle from Particle Decays  Many experiments have searched for a light boson:

4. Astroparticle Observation: The ATIC Instrument & Program ATIC 2 Flight from McMurdo 2002 Total of 4 flights – 3 successful Goal: measure CR fluxes of electrons, protons, and nuclei to ~ 1 TeV Instrument not optimized for electron detection.

5. Astroparticle Observation: ATIC Results ATIC 1+2  Significance of bump for ATIC1+2 is about 3.8   This caused considerable excitement and speculation.  Recently analyized Flight 4 data shows same “bump” and significance of ATIC1+2+4 is 5.1   Dashed line indicates expected electron spectrum extrapolated from lower energy ATIC 1+2+4 Preliminary ATIC 1 ATIC 2 ATIC 4 Preliminary

6. Astroparticle Observation: PAMELA Satellite Experiment Launched in Spring 2007 A High Energy Electron Event Magnetic Spectrometer measure sign of charge and momentum Goal: measure e+/e-, p/, He /anti- He, etc. as well as spectra

7. Astroparticle Observation: Anti-Proton Fraction (PAMELA) Nothing surprising seen in anti-proton / proton ratio Anti-proton abundance consistent with expectations for secondary CR production off the Interstellar Medium

8. Astroparticle Observation: PAMELA Positron Fraction Unexpected! Positron fraction increases above 10 GeV! Note that Geomagnetic cut-off of primary cosmic rays is O(10 GeV) Data below 10 GeV is dominated by trapped radiation and fluxes are sensitive to Solar Cycle ATIC Electron Spectra & PAMELA e + Fraction caused excitement in 2008!

9. Plausible Explanation for ATIC & PAMELA  ATIC: excess in e + + e - spectrum between 300 GeV and 800 GeV.  PAMELA: excess in e + spectrum from 10 GeV to 100 GeV. No excess in proton and anti-proton spectrum  Dark matter annihilation mediated by a extra gauge boson (U- boson), mass e + e -, μ + μ - U U DM

10. NMSSM (Next-to-Minimal SUSY SM)   problem in MSSM (Minimal Supersymmetric Standard Model)  The simplest possible extension of the MSSM: –Introduce just one extra gauge-singlet Higgs field N. –This is common in string models. –All the good properties of MSSM are preserved.  Higgs bosons in NMSSM h 0, H 0, A 0, H +,H -, s 0, a 0  LEP access at M 2b ~100 GeV is well described: (Note: The mass of the lightest Higgs in MSSM < 130 GeV) [R. Dermisek & J. Gunion, PRD 73, 111701(2006)]

11. Light Higgs Search at D0  gg → h→aa, a→μ + μ -, τ + τ -  Search Range: 0.214 GeV≤ m A ≤ 20 GeV 2μ 2τ channel

12. Light Higgs Search at BaBar  Υ(2S,3S)→γa, a→μ + μ -  Search Range: 0.212 GeV≤ m A ≤ 9.3 GeV

13. Light Higgs Search at CLEO  Υ(1S)→γa, a→ μ + μ -, τ + τ -  Search Range: 0.212 GeV≤ m A ≤ ~9.0 GeV

14. Light Particle Search at Belle HyperCP exotic event, X(214)  B decays  e + e - collisions Eventually both analysese move to general light particle search.

15. Introduction : HyperCP Exotic Event, X(214) Observation of 3 events for  +  p  +  - decays H.K.Park et al. (HyperCP Collaboration), PRL 94, 021801 (2005)  Mass of X(214) : 214.3 MeV/c 2  Possible interpretations –Sgoldstino (pseudo-scalar): D.S.Gorbunov and V.A.Rubakov, PRD 73, 035002 (2006) –Low mass Higgs: X.-G.He, J.Tandean and G.Valencia, PRL 98, 081802 (2007) –U-boson (vector particle): M. Reece and L.-T. Wang JHEP 0907, 51 (2009), C.-H. Chen, C.-Q. Geng and C.-W. Kao, Phys. Lett. B 663, 100 (2008).

16. sgoldstino (I)  In SUSY, spontaneous SUSY breaking generates Goldstone fermion (Goldstino), which gives the longitudinal component of gravitino. There should exist superpartners of Goldstino: sgoldstinos, pseudoscalar P 0 and scalar S 0 The masses of P 0 and S 0 are generally arbitrary. Perhaps < a few GeV or a few MeV  P 0 and S 0 can couple with SM particles, quarks, leptons and gauge bosons.  Interactions of sgoldstinos P 0 and S 0 with quarks are given by FCNC at tree level Neutral current

17. sgoldstino (II)  If the masses of P 0 and S 0 are less than two pion masses, they can decay into photon or lepton pairs (D.S. Gorbunov, Nucl. Phys. B602 (2001) 213). F : SUSY breaking scale, M  : order of photino mass (~100 GeV) A l : soft mass term (~100 GeV)

18. Properties of HyperCP event, X(214)  Use B(  + → pX 0, X 0 →     ) and the uncertainty of muon g-2  Then, check the X 0 contribution for the following processes:    Extract the couplings of s→dX 0 and X 0 →     X0X0 X0X0  X0X0   X0X0  Either pseudo-scalar or axial vector particle is allowed in present data.  ~10 -15 s (  ~10 -7 MeV)  

19. X(214) Search in Other Experiments  Hadron collider: –D0 Experiment (PRL 103, 061801 (2009))  e + e - collider –BaBar (PRL 103, 081803 (2009)) –CLEO (PRL 101, 151802 (2008))  Fixed Target –E391a@KEK (PRL 102, 051802(2009)) –E949@BNL (PRD 79, 092004(2009)) –KTeV@FNAL (ongoing analysis)

20. X(214) Search in E391a@KEK  Use the mode, K L →π 0 π 0 X, X → γγ: Assume that the X is a sgoldstiono particle (psedo-scalar) Two photon invariant mass Upper Limit

21. Possible Decay Modes for X(214) in Heavy Quark Decays  Possible decay modes for sgoldstino in SUSY –Pseudo-scalar B and D meson decays to vector meson and X 0 S.V.Demidov and D.S.Gorbunov, JETP 84, 479 (2006) B(D   X 0, X 0   +  - ) = 10 -9 ~ 10 -6 B(B  K* X 0, X 0   +  - ) = 10 -9 ~ 10 -6 B(B   X 0, X 0   +  - ) = 10 -9 ~ 10 -7  The listed channels above are possible for low mass Higgs search in NMSSM (Next-to-Minimal SUSY SM )  The listed channels can be used for a light particle search in model independent.

22.  Large sample of  (4S)  BB-bar : 657M BB-bar pairs B  K* 0 X 0, K* 0  K +  -, X 0   +  - B   0 X 0,  0   +  -, X 0   +  -  Assume that X 0 is a scalar (or psedo-scalar) particle (spin 0) or vector (or axial-vector) particle (spin 1) Decay modes

23. Event Selection (I) Charged trackSelection requirement Good charged track dr < 1.0 cm |dz| < 5.0 cm electron eid > 0.9 P lab > 0.395 GeV/c muon  id > 0.95 P lab > 0.690 GeV/c Kaon kid > 0.6 pion remaining tracks after selecting the lepton and K tracks K* 0 0.815 GeV/c 2 < M K*0 < 0.975 GeV/c 2 00 0.633 GeV/c 2 < M  0 < 0.908 GeV/c 2 best B minimum  2 value of four charged tracks

24.  Kinematic variables,  E and M bc, cut applied –  E = E B * - E beam * –(M bc ) 2 = (M ES ) 2 = (E beam *) 2 - |p B *| 2 E beam * : beam energy, p B * and E B * : momentum and energy of B candidate Event selection (II) signal box sideband region

25. Signal efficiency  X 0 window defined with dimuon mass resolution 214.3  3  (0.5 (HyperCP) + resol. (Belle)) [MeV/c 2 ] 211.5 MeV/c 2 < M  +  - < 217.1 MeV/c 2 Decay modes X 0 as a Scalar particleX 0 as a Vector particle Dimuon mass resolution [keV/c 2 ] Signal efficiency (  ) Dimuon mass resolution [keV/c 2 ] Signal efficiency (  ) B  K* 0 X 0 427  14 26.3 % B   0 X 0 428  15 23.5 %

26. Background Study B  K* 0 X 0 B   0 X 0 B  K* 0 X 0 B   0 X 0  Counting method –Use MC samples of continuum and BB-bar which are larger than data sample Fitting method Fit MC data in sideband region (sideband is defined as 5  ~ 10  in  E-M bc ) Decay modeFitting the sidebandCounting B  K* 0 X 0 0.13 +0.04 -0.03 0 B   0 X 0 0.11 +0.03 -0.02 0 - Shaded region is X 0 window

27. Systematic and Upper limit  No event is observed in the signal region. 27 B  K* 0 X 0 B   0 X 0 Decay modes Systematic X 0 as a Scalar particleX 0 as a Vector particle B  K* 0 X 0 5.2 % B   0 X 0 5.7 % Decay modes Upper limit @ 90% C.L. X 0 as a Scalar particleX 0 as a Vector particle B  K* 0 X 0 2.01  10 -8 B   0 X 0 1.51  10 -8

28. Expected B.F as sgoldstino September 10-13 2009 JPSSearch for a light particle at Belle28 S.V.Demidov and D.S.Gorbunov, JETP Letters, 2006, vol. 84, No. 9, pp479-484

29. Upper limits vs. Lifetime  Constraints on Lifetime for X(214) –1.7  10 -15 s   x  2.5  10 -11 s D.S.Gorbunov and V.A.Rubakov, PRD 73, 035002 (2006) –1.7  10 -15 s   x  4  10 -14 s C.Q. Geng, Y.K. Hsiao, PLB 632, 215-218 (2006)  We choose lifetimes for this search as follows : 0 s, 10 -15 s, and 10 -12 s  Now we are focusing on general light particle search: 212 MeV ≤ m x ≤ 300 MeV September 10-13 2009 JPSSearch for a light particle at Belle29 Upper limit doesn’t change in these life times.

30. X(214) Search with e + e - collisions (I)  Use the process e + e - →γ X, X →μ + μ -  Signal and background processes  (e + e -   X 0 ) ~ 1 pb to 5 ab @  s = 10 GeV [D. S. Gorbunov and V. A. Rubakov, PRD 73, 035002 (2006)]

31. X(214) Search with e + e - collisions (II)  Background and systematics are studying  Initial goal is for X(214) search, and move to search for general mass and life times

32. Summary  Recent astroparticle observation would suggest a light gauge boson with masses in MeV to GeV range.  There is no evidence for a light Higgs boson in NMSSM so far.  There have been searches including the Belle for HyperCP exotic event with mass 214.3 MeV. No evidence is found.  A super-B factory would be a good place to search for a light particle in even LHC era

33. Once the X(214) is confirmed, I will provide wine and cheese to people here !

34. Backup Slides

35. Systematic : 214.3 MeV/c 2 and vector Decay modeK* 0 X 0 0X00X0 Source ＼ lifetime 0 s10 -15 s10 -12 s0 s10 -15 s10 -12 s Integrated Luminosity (N BB-bar )1.4 % Signal efficiency Muon ID3.0 %2.9 %3.0 %2.9 % charged kaon ID0.8 % --- charged pion ID0.5 % 0.7 % Tracking4.2 % 4.3 % MC statistics0.1 % Cut variables M bc 0.7 %0.3 %0.7%0.6 % 0.5 % EE 0.7 %0.3 %0.7 %0.6 % 0.5 % K* 0 mass0.7 %0.3 %0.7 %---  0 mass ---0.6 % 0.5 % Total5.6 %5.4 %5.6 %5.5 % September 10-13 2009 JPS35Search for a light particle at Belle

36. Systematic : 214.3 MeV/c 2 and scalar Decay modeK* 0 X 0 0X00X0 Source ＼ lifetime 0 s10 -15 s10 -12 s0 s10 -15 s10 -12 s Integrated Luminosity (N BB-bar )1.4 % Signal efficiency Muon ID3.0 %2.9 % charged kaon ID0.8 % --- charged pion ID0.5 % 0.7 % Tracking3.8 %4.2 % 4.4 %4.3 % MC statistics0.1 % Cut variables M bc 0.6 %0.5 %0.3 %0.9 %0.3 %0.4 % EE 0.6 %0.5 %0.4 %0.9 %0.3 %0.4% K* 0 mass0.6 %0.5 %0.4 %---  0 mass ---0.9 %0.3 %0.5% Total5.2 %5.4 % 5.7 %5.4 %5.5 % September 10-13 2009 JPS36Search for a light particle at Belle

37. Lifetime scan : 214.3 MeV/c 2 September 10-13 2009 JPSSearch for a light particle at Belle37 K* 0 X 0 Lifetime0 s10 -15 s10 -12 s Mass resol. [keV/c 2 ] 427.3  14.3424.4  14.4534.1  24.8 Mass region [MeV/c 2 ](211.5, 217.1)(211.6, 217.2)(211.3, 217.5) efficiency (26.3  0.1)%(26.4  0.1)%(26.1  0.1)% 0X00X0 Mass resol. [keV/c 2 ] 427.7  15.1424.5  14.7536.9  25.9 Mass region [MeV/c 2 ](211.5, 217.1)(211.6, 217.2)(211.3, 217.5) efficiency (23.5  0.1)%(23.8  0.1)%(23.6  0.1)% K* 0 X 0 Lifetime0 s10 -15 s10 -12 s Mass resol. [keV/c 2 ] 425.1  14.4426.5  14.5535.8  74.9 Mass region [MeV/c 2 ](211.6, 217.2) (211.3, 217.5) efficiency (26.3  0.1)% (26.4  0.1)% 0X00X0 Mass resol. [keV/c 2 ] 424.9  14.7428.7  15.0538.0  25.0 Mass region [MeV/c 2 ](211.6, 217.2) (211.3, 217.5) efficiency (23.6  0.1)%(23.8  0.1)%(23.4  0.1)% As a Scalar As a Vector

38. Possible decay modes for Further Search in NMSSM model  e + e -   (4S)   +  -  (1S), e + e -   (3S)   +  -  (1S)  One may still look for this mode, B  K X 0, X 0  +  - B(  (1S)   X 0, X 0  +  - ) ~10 -8   X0X0 X0X0   No QED background, e + e -    +  - [Michelangelo Mangano & Paolo Nason, hep-ph/0704.1719,CERN-PH-TH/2007-062]