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Search for light Higgs in Y(1S) → gamma tau + tau -

Search for light Higgs in Y(1S) → gamma tau + tau -. Nasra Sultana & Tomasz Skwarnicki. Motivation.

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Search for light Higgs in Y(1S) → gamma tau + tau -

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  1. Search for light Higgs in Y(1S)→ gamma tau+tau- Nasra Sultana & Tomasz Skwarnicki

  2. Motivation • Some NMSSM models (Dermisek, Gunion, McElrath: hep-ph/0612031) predict existence of a new non-SM-like higgs boson a0 (pseudo-scalar) with ma < 2mb to avoid fine-tuning of parameters in electroweak symmetry breaking • Such light higgs avoids the LEP limit mH > 100GeV based on e+e- →ZH(→bb) searches since its mass is below the threshold for decay to bb. • In this scenario also SM-like higgs boson h (scalar) also avoids the LEP lower mass limit since Br(h→ bb) is much smaller than Br(h →a0a0) • The perfect place to search for a0 is in radiative decays of Upsilon meson, Υ → g a0. • Such an a0 decays predominantly into heaviest pair of fermions available (Br(a0→ t+t-)~0.9 for ma>2mt) • We have studied the decay Υ → ga0followed bya0→ t+t-

  3. Previous and new approach • Previously we used Y(2S)->p+p-Y(1S) • We now switched to directly produced Y(1S) resonances: • 21M Y(1S); previously 9M Y(2S) * BR(p+p-) = 1M Y(1S) • Keep cuts the same except that don’t need to reconstruct p+p- (gain in efficiency) • Larger background due to continuum e+e- -> t+t-

  4. e+e- → p+p-Υ(1S) Υ (1S)→ ga0, a0→ t+t- signal MonteCarlo 10,000 events for each mass BKH’s fix to MC energy resolution is on Peaks are fitted with a Crystal Ball function Signal MC: Photon Energy distribution for various ma ma = 4 GeV ma = 5 GeV ma = 6 GeV ma = 7 GeV ma = 8 GeV ma = 8.5 GeV ma = 9 GeV ma = 9.15 GeV ma = 9.30 GeV ma = 9.35 GeV

  5. Efficiencyobtained from fits to signal MC and interpolated for the regions in between. Fits to MC data (previous slide) Polynomial fit to interpolate to other photon energies (used in calculation of upper limits on signal BR) new Plotted efficiencies based on phase-space MC Multiply them by 0.91 to account for 1+cos2θgdistribution for Υ→ga Old (p+p-)

  6. Energy resolutionobtained from fits to signal MC (points) and interpolation to other energies (solid line). Factor from fits to our MC Obtained by BKH and Selina (CBX 02-22) from fits to single g MC (before the MC resolution fix)

  7. Photon spectrum with binning comparable to expected signal width 21M Υ(1S)

  8. p+p- approach

  9. Comparison with our previous results Previous Results New Results

  10. From Dermisek, Gunion, McElrath: hep-ph/0612031 NMSSM consistent with all previous results CLEO III We have improved ULs by about an order of magnitude or more. We are constraining NMSSM models. Many models with 2mt<ma<7.5 GeV (represented by red points) ruled out by our results.

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