Nicole Kelley

Positron clouds within thunderstorms

We report the observation of two isolated clouds of positrons inside an active thunderstorm. These observations were made by the Airborne Detector for Energetic Lightning Emissions (ADELE), an array of six gamma-ray detectors, which flew on a Gulfstream V jet aircraft through the top of an active thunderstorm in August 2009. ADELE recorded two 511 keV gamma-ray count rate enhancements, 35 seconds apart, each lasting approximately 0.2 seconds. The enhancements, which were about a factor of 12 above background, were both accompanied by electrical activity as measured by a flat-plate antenna on the underside of the aircraft. The energy spectra were consistent with a source mostly composed of positron annihilation gamma rays, with a prominent 511 keV line clearly visible in the data. Model fits to the data suggest that the aircraft was briefly immersed in clouds of positrons, more than a kilometer across. It is not clear how the positron clouds were created within the thunderstorm, but it is possible they were caused by the presence of the aircraft in the electrified environment.

Study of e + e − → H 0 A 0 production and the constraint on dark matter density

This paper reports the results of a study of the supersymmetric neutral heavy Higgs boson production process e{sup +}e{sup -}{yields}H{sup 0}A{sup 0} at {radical}(s)=1 TeV performed using fully simulated and reconstructed events. The adopted parameters for the supersymmetric models are compatible with the relic dark matter density if this is due to neutralinos annihilating through the A{sup 0} boson in the early universe. The accuracies on the heavy Higgs boson masses, widths, and decay branching fractions are estimated to be {delta}M{sub A{sup 0}}/M{sub A{sup 0}}=0.0024 {delta}{gamma}{sub A{sup 0}}/{gamma}{sub A{sup 0}}=0.19, {delta}BR(A{sup 0}{yields}bb)/BR(A{sup 0}{yields}bb)=0.07, and {delta}BR(A{sup 0}{yields}{tau}{sup +}{tau}{sup -})/BR(A{sup 0}{yields}{tau}{sup +}{tau}{sup -})=0.15 These results, combined with other measurements from the LHC and an e{sup +}e{sup -} collider, allow the supersymmetric dark matter density to be inferred to a relative accuracy {delta}{omega}{sub {chi}}h{sup 2}/{omega}{sub {chi}}h{sup 2}=0.08.