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Search for a Light Particle

Search for a Light Particle. HyangKyu Park CHEP, KyungPook National Univ. N&P, COEX Oct. 13, 200 9. 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.

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Search for a Light Particle

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  1. Search for a Light Particle HyangKyu Park CHEP, KyungPook National Univ. N&P, COEX Oct. 13, 2009

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

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

  6. Astroparticle Observation:PAMELA Satellite Experiment A High Energy Electron Event Launched in Spring 2007 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. U DM U DM 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 < ~1 GeV.U-boson -> e+ e- , μ+ μ-

  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 MSSMare preserved. • Higgs bosons in NMSSMh0, H0, A0, H+,H-, s0, a0 • LEP access at M2b~100 GeV is welldescribed: (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≤ mA ≤ 20 GeV 2μ 2τ channel

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

  13. Light Higgs Search at CLEO • Υ(1S)→γa, a→ μ+μ-, τ+τ- • Search Range: 0.212 GeV≤ mA ≤ ~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 +- decaysH.K.Park et al. (HyperCP Collaboration), PRL 94, 021801 (2005) Mass of X(214) : 214.3 MeV/c2 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.  + X0 + X0 X0  Properties of HyperCP event, X(214) • Use B( + → pX0, X0 → +) and the uncertainty of muon g-2 • Then, check the X0 contribution for the following processes: +    X0 Extract the couplings of s→dX0 and X0 → + Either pseudo-scalar or axial vector particle is allowed in present data. ~10-15 s (~10-7 MeV)

  17. 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)

  18. X(214) Search in E391a@KEK Use the mode, KL→π0π0X, X →γγ:Assume that the X is a sgoldstiono particle (psedo-scalar) Upper Limit Two photon invariant mass

  19. 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 X0S.V.Demidov and D.S.Gorbunov, JETP 84, 479 (2006) B(D   X0, X0 +-) = 10-9 ~ 10-6 B(B  K* X0, X0 +-) = 10-9 ~ 10-6 B(B   X0, X0 +-) = 10-9 ~ 10-7 The listed channels above are possible for low mass Higgs search in NMSSM (Next-to-Minimal SUSYSM) The listed channels can be used for a light particle search in model independent.

  20. Large sample of (4S)  BB-bar : 657M BB-bar pairs B  K*0X0, K*0 K+-, X0 +- B  0X0, 0 +-, X0 +- Assume that X0 is a scalar (or psedo-scalar) particle (spin 0) or vector (or axial-vector) particle (spin 1) Decay modes

  21. Signal efficiency X0 window defined with dimuon mass resolution 214.3  3  (0.5 (HyperCP) + resol. (Belle)) [MeV/c2] 211.5 MeV/c2 < M+- < 217.1 MeV/c2

  22. Background Study Counting method Use MC samples of continuum and BB-bar which are larger than data sample B  K*0X0 - Shaded region is X0 window B  0X0 • Fitting method • Fit MC data in sideband region (sideband is defined as 5 ~ 10 in E-Mbc) B  K*0X0 B  0X0

  23. Systematic and Upper limit No event is observed inthe signal region. B  K*0X0 B  0X0 23

  24. Expected B.F as sgoldstino S.V.Demidov and D.S.Gorbunov, JETP Letters, 2006, vol. 84, No. 9, pp479-484 September 10-13 2009 JPS Search for a light particle at Belle 24

  25. 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 sC.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 ≤ mx≤ 300 MeV Upper limit doesn’t change in these life times. September 10-13 2009 JPS Search for a light particle at Belle 25

  26. X(214) Search with e+e- collisions (I) • Use the process e+ e- →γ X, X →μ+μ- • Signal and background processes (e+ e- X0) ~ 1 pb to 5 ab @ s = 10 GeV [D. S. Gorbunov and V. A. Rubakov, PRD 73, 035002 (2006)]

  27. 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

  28. 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

  29. Backup Slides

  30. Systematic : 214.3 MeV/c2 and vector September 10-13 2009 JPS Search for a light particle at Belle 30

  31. Systematic : 214.3 MeV/c2 and scalar September 10-13 2009 JPS Search for a light particle at Belle 31

  32. Lifetime scan : 214.3 MeV/c2 As a Scalar As a Vector September 10-13 2009 JPS Search for a light particle at Belle 32

  33.    X0 X0 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KX0, X0+- No QED background, e+e- +- B((1S)  X0, X0+-) ~10-8 [Michelangelo Mangano & Paolo Nason, hep-ph/0704.1719,CERN-PH-TH/2007-062]

  34. 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 P0 and scalar S0The masses of P0 and S0 are generally arbitrary. Perhaps < a few GeV or a few MeV • P0 and S0can couple with SM particles, quarks, leptons and gauge bosons. • Interactions of sgoldstinos P0 and S0with quarks are given by Neutral current FCNC at tree level

  35. sgoldstino (II) • If the masses of P0 and S0are 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) Al : soft mass term (~100 GeV)

  36. Event Selection (I)

  37. Kinematic variables, E and Mbc, cut applied E = EB* - Ebeam* (Mbc)2 = (MES)2 = (Ebeam*)2 - |pB*|2Ebeam* : beam energy,pB* and EB* : momentum and energy of B candidate Event selection (II) signal box sideband region

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