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Search for a Light Particle

This seminar discusses the motivations and recent developments in the search for light particles, focusing on evidence from astroparticle observations such as ATIC and PAMELA. Key topics include the significance of recent findings, implications of the light Higgs particle within the Next-to-Minimal Supersymmetry (NMSSM) framework, and results from various experiments such as Belle, BaBar, and CLEO. The interplay between dark matter models and observed particle decays is emphasized, highlighting the potential of light bosons in explaining anomalies in cosmic ray spectra.

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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. 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 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. 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

  17. 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)

  18.  + 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)

  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, KL→π0π0X, X →γγ:Assume that the X is a sgoldstiono particle (psedo-scalar) Upper Limit Two photon invariant mass

  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 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.

  22. 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

  23. Event Selection (I)

  24. 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

  25. 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

  26. 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

  27. Systematic and Upper limit No event is observed inthe signal region. B  K*0X0 B  0X0 27

  28. 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 28

  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 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 29

  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- X0) ~ 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/c2 and vector September 10-13 2009 JPS Search for a light particle at Belle 35

  36. Systematic : 214.3 MeV/c2 and scalar September 10-13 2009 JPS Search for a light particle at Belle 36

  37. Lifetime scan : 214.3 MeV/c2 As a Scalar As a Vector September 10-13 2009 JPS Search for a light particle at Belle 37

  38.    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]

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