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Search at Babar for a Light Higgs Using Radiative Upsilon Decays

Search at Babar for a Light Higgs Using Radiative Upsilon Decays. Kevin Flood University of Wisconsin On behalf of the Babar Collaboration. Why a Light Higgs?. NMSSM introduces a singlet Higgs which mixes with CP-odd MSSM Higgs to produce a possibly low-mass CP-odd Higgs state A 0

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Search at Babar for a Light Higgs Using Radiative Upsilon Decays

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  1. Search at Babar for a Light Higgs Using Radiative Upsilon Decays Kevin FloodUniversity of Wisconsin On behalf of the Babar Collaboration Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  2. Why a Light Higgs? • NMSSM introduces a singlet Higgs which mixes with CP-odd MSSM Higgs to produce a possibly low-mass CP-odd Higgs state A0 • Scan of NMSSM parameter space for various A0 mass ranges gives possible BR(Y -> gA0) > ~10-4 • Direct searches for M(A0) < 2mb are possible at the B-factories • Depending on M(A0), dominant decays are • A0->t+t-, A0->m+m-, A0->invisible, A0->hadrons • Recent model proposes axion-like state 360 < M(a) < 800 MeV predominantly decaying to di-muons • BR(Y -> ga) ~ 10-5 – 10-6 • Nomura, Thaler arXiv:0810.5397 [hep-ph] A0 Gunion et al, Phys.Rev.D76:051105,2007 Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  3. HyperCP Excess Events S+ -> pm+m- PRL 94, 021801 (2005), hep-ex/0501014 NP SM A0 BF(S+ → pA0, A0→m+m-) = (3.1 ±1.5) x 10-8 +2.4 -1.9 Prob(SM) < ~0.8% Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  4. Light Higgs At B-Factories Di-muon final state dominates for M(A0) < 2M(t) Radiative Upsilon Decays CLEO: Y(1S) -> gA0(mm) l+ PRL 101, 151802 (2008) l- b -> A0s Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  5. Indirect Effects Heng et al, PRD 77, 095012 (2008), 0801.1169 [hep-ph] • b -> sg, b -> sm+m- already constrain large tanb, light A0 scenarios • Points show scan of NMSSM parameter space on BF(b->sm+m-) vs tanb plane • Redpointsallowed by experimental b->sg BF result, blue points excluded BF(b → s m+m-) 10-5 Exp BF(b→ sm+m-)=(4.2±1.2)x10-6 . M(A0) < 5 GeV 5 < M(A0) < 40 GeV M(A0) > 40 GeV 10-6 tanb tanb tanb Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  6. The Babar Detector EMC 6580 CsI(Tl) crystals 1.5 T solenoid DIRC (PID) 144 quartz bars 11000 PMs e+ (3.1 GeV) e- (8.5 GeV) Drift Chamber 40 stereo layers Tracking, dE/dX Instrumented Flux Return Resistive Plate Chambers (Runs1-4) Silicon Vertex Tracker 5 layers, double sided strips Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  7. Babar at the Y(3S) and Y(2S) • PEP-II Y(2S,3S) running December 2007 - April 2008 • Y(3S) ~ 30 fb-1 (~122x106 decays) • Y(2S) ~ 15 fb-1 (~100x106 decays) • Initial Y(3S) results showed at ICHEP 2008 • Observation of hb • UL: Y(3S) -> gA0, A0 -> invisible Y(2S) Y(3S) BB threshold Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  8. Analysis Strategy • Fully reconstruct final state from two oppositely charged tracks and a single energetic photon • only one E*(g) > 0.5 GeV • Kinematic Y(3S) fit • Beam-energy constraint • Beam spot constrained vertex • Fit chi2 probability > 10-6 • Doca in xy-plane < 2 cm • -0.07<Mbeam-MY(3S)<2 GeV • Collinear di-muon, photon • 10 < Ncrys < 50 • 1d fit to reduced mass mR mR Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  9. Signal and Background PDFs • Signal mR PDF from simulated signal events generated at many different mass points • PDF shape parameters interpolated between mass points • Simulation results calibrated using charmonium backgrounds • Background mR PDF determined from fit to Y(4S) data Y(4S) data simulated signal events Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  10. Mass Scan • M(A0) mass scan over ~2000 points • 2M(m) < M(A0) < 9.3 GeV • Signal yield from ML fit in ~300 MeV mR bins • To suppress r0 background, require two identified muons for M(A0) < 1.05 GeV • Muon mis-id as pion ~ 5% Y(1S) J/psi r0 Y(4S) Data • Signal significances from mass fits on 78.5 fb-1Y(4S) data control sample are Gaussian distributed with no significant outliers Y(4S) Data Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  11. Y(3S) Mass Scan Fit Results arXiv:0902.2176 M(A0) < 1 GeV All Masses 4 < M(A0) < 9.3 GeV 1 < M(A0) < 4 GeV Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  12. Sytematic Uncertainties and Significance • PDF systematics • ± 1 sigma PDF parameter variations • Signal width correction • calibrated from J/psi data/MC • Peaking background mean, width, tail • Fit bias sBF ~ 0.02 x 10-6 • Efficiency corrections ~ 2-10% • Y(3S) counting ~ 1% • Signal significance distribution (stat+sys) in Y(3S) data shows no significant outliers • No excess signal events observed at HyperCP mass ~214 MeV • Most significant upward fluctuations (~3s) at 4.94 GeV and 0.426 GeV • ~80% probability to see one >3s result for number of points here J/psi veto psi(2S) veto Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  13. BF Upper Limits (90% CL, Stat+Sys) All Masses M(A0) < 1 GeV next most significant signal, 0.426 GeV J/psi veto psi(2S) veto 1 < M(A0) < 4 GeV 4 < M(A0) < 9.3 GeV most signifi-cant signal, 4.94 GeV psi(2S) veto J/psi veto Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  14. Most Significant Mass Region Fit (4.940 GeV) BF(4.940) = (1.9 ± 0.7 ± 0.1) x 10-6 Significance = 3.0 (stat+sys) Total fit Background Signal Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  15. Second Most Significant Mass Region Fit (0.426 GeV) BF(0.426) = (3.1 ± 1.1 ± 0.3) x 10-6 Significance = 2.9 (stat+sys) Total fit Background Signal Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  16. Mass Fit in the HyperCP Signal Region (0.214 GeV) +0.43 BF(0.214) = (0.12 ± 0.17) x 10-6 -0.41 BF(0.214) < 0.8 x 10-6 (90% CL) Total fit Background Signal M(A0)=0.214 GeV mR=0.034 GeV Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  17. hb Mass Region Fit • No significant signal observed • BF[Y(3S)->ghb]x BF[hb->mm] = (0.2 ± 3.0 ± 0.9) x 10-6 • BF[hb->mm] = (0.0 ± 0.6 ± 0.2) x 10-2 • BR[hb->mm] < 0.8% (90% CL) • Assuming Babar’s measurement BR[Y(3S)->ghb] = (4.8 ± 0.5 ± 1.2) x 10-4 Total fit Bkgd Signal e+e- →gISR Y(1S) hb Y(3S) → gcb(2P) cb(2P) → gY(1S) Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  18. Y(3S) -> gA0, A0 -> invisible arXiv:0808.0017 • Dominant A0 decay mode may be invisible, e.g. to neutralino LSP pair • Fit for missing mass in events with a high-energy photon with energy consistent with 0 < M(A0) < 7.8 GeV • No significant signal seen anywhere, limits similar to di-muon results 10-5 10-6 Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  19. Experimental Limits: M(A0) < 2M(t) A0→mm A0→invisible A0 A0 High UL High UL Low UL Low UL Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  20. Experimental Limits: 2M(t) < M(A0) < 7.5GeV A0→mm A0→invisible A0 A0 High UL High UL Low UL Low UL Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  21. Experimental Limits: 7.5 < M(A0) < 8.8 GeV A0→mm A0→invisible A0 A0 High UL Low UL High UL Low UL Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  22. Experimental Limits: M(A0) > 8.8 GeV A0→mm A0→invisible results do not extend to the highest mass range A0 High UL Low UL Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  23. Experimental Limits:0.36 < M(A0) < 0.8 GeV (Axion Model Mass Range) A0→mm A0→invisible Axion Model BF Range A0 Upper Limit High UL Low UL Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

  24. Conclusions • No significant Y(3S) -> gA0, A0 -> mm signal observed • ~2000 mass points 2mm< M(A0) < 9.3 GeV • Conference note at arXiv:0902.2176 [hep-ex] • Upper limits (90% CL) range from (0.25-5.2) x 10-6 • Generally lower upper limits than CLEO by a factor of ~2 • No significant signal at HyperCP mass (di-muon threshold) • BF[Y(3S)->gA0 (214)] < 0.8 x 10-6 (90% CL) • No evidence of hb->mm decays • BR[hb->mm] < 0.8% (90% CL) • Y(3S) -> gA0, A0 -> invisible UL (0.7-31) x 10-6 (90% CL) • ICHEP 2008 conference note at arXiv:0808.0017 [hep-ex] • Other Babar searches for A0 proceeding • Y(2S) -> gA0, A0 -> mm • ~20% better sensitivity than Y(3S) • Y(2S, 3S) -> gA0, A0 -> tt • Y(2S, 3S) -> gA0, A0->hadrons • b -> s A0, A0 -> mm Aspen Winter Workshop Kevin Flood 8-14 Feb 2009

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