H. Vogel

Semileptonic decay of the B meson

Abstract Using the CUSB detector we have measured the production of electrons from the decay B→eνX. We obtain a branching ratio for B→eνX of (13.2±0.8±1.4)%. The observed energy spectrum of the electrons implies that the coupling (bc)W dominates over (bu)W. An upper limit Γ( B → e ν X u ) Γ( B → e ν X c ) at 90% confidence level is obtained, where Xc contains a c-quark and Xu contains no charmed particles.

Inclusive K0 production in e+ e− annihilation at the upsilon resonances

We report on inclusive K0 production in the region of the upsilon resonances (9.4–10.6 GeV). The K0 yield for the resonances and continuum below the BB threshold is found to be constant at 0.82 ± 0.10 K0 per observed hadronic event. At the ϒ(4S), however, the K0 yield is significantly higher, 1.58 ± 0.35. This increase in K0 production and the differential cross section dσ/dp of kaons are consistent with BB decay of the ϒ(4S) resonance with the bottom quarks subsequently decaying primarily into charmed quarks.

Dark radiation constraints on minicharged particles in models with a hidden photon

We compute the thermalization of a hidden sector consisting of minicharged fermions (MCPs) and massless hidden photons in the early Universe. The precise measurement of the anisotropies of the cosmic microwave background (CMB) by Planck and the relic abundance of light nuclei produced during big bang nucleosynthesis (BBN) constrain the amount of dark radiation of this hidden sector through the effective number of neutrino species, Neff. This study presents novel and accurate predictions of dark radiation in the strongly and weakly coupled regime for a wide range of model parameters. We give the value of Neff for MCP masses between ~ 100 keV and 10 GeV and minicharges in the range 10?11?1. Our results can be used to constrain MCPs with the current data and they are also a valuable indicator for future experimental searches, should the hint for dark radiation manifest itself in the next release of Plancks data.

Photodiode readout for scintillating crystals of BGO and Nal(Tl)

Abstract We present first results using a photodiode readout for BGO and Nal(Tl) crystals. The measurements indicate that photodiodes might replace photomultiplier tubes in electromagnetic calorimetry. Using commercial photodiodes, a noise equivalent r.m.s. error of 1–2 MeV has been observed. Limitations and possible future improvements are discussed.

A measurement of the semileptonic decay of B mesons into muons

Abstract We have observed muons from the semileptonic decay B → Xμν where B meson are produced in e+e− annihilations into hadrons at the γ(4S) resonance (10.58 GeV). We obtain a branching ratio of (11.2 ± 0.9 ± 1.0)% for B → Xμν. We have also measured the production of energetic muons in hadronic e+e− annihilations in the energy region above the γ(4S) from 10.6 GeV to 11.2 GeV.

Observation of direct photons in ϒ and ϒ′ decays and determination of the QCD scale parameter

Abstract Using the CUSB detector, we have measured the high energy direct photon spectrum from ϒ and ϒ′ decays. These photons are assumed to arise from the decays ϒ,ϒ′ → γgg. We determine the ration >(gggg/>(ggg) to be 0.0299 ± 0.0059 for the ϒ and 0.0337 ± 0.0114 for the ϒ′. From these results we obtain: αs = 0.226−0.042+0.067, λ MS = 116 −57 +105 MeV for ϒ → γgg, and αS = 0.197−0.055+0.123, λ MS = 80 −59 +195 MeV for ϒ′ → gggg.

Search for Higgs scalars in upsilon decays

Abstract We have searched for the decay of ϒs into a monochromatic photon accompanied by other particles as a signal for the reaction ϒ → γ +Higgs. Two different methods are presented both with null result. While we are not sensitive to the branching ratios predicted by the standard model with a minimal Higgs content, we can put limits on the possible values of the lowest Higgs mass and the ratio of the vacuum expectation values for more complex models. Our results are also of interest with respect to the ξ(2.2) being a Higgs in the context of such models.

A study of hadronic decays of the ϒ

Abstract We present a detailed study of the decays ϒ ′ → π + π − ϒ and ϒ ′ → π 0 π 0 ϒ , where the ϒ decays subsequently to e + e − or μ + μ − . The results are obtained from a sample of 146 000 ϒ′ decays observed with the CUSB detector at the Cornell Electron Storage Ring. We derive branching fractions of (18.9 ± 2.6)% for ϒ ′ → π ′ π − ϒ and (10.3 ± 2.3)% for ϒ ′ → π 0 π 0 ϒ , and determined partial widths for these decays. Invariant mass and angular distributions of both the π + π − and π 0 π 0 systems are presented. We also set a limit on the branching fraction for ϒ ′ → ηϒ of less than 0.2% at the 90% confidence level.

Neutrino propagation in media: Flavor, helicity, and pair correlations

Neutrinos propagating in media (matter and electromagnetic fields) undergo flavor and helicity oscillations, where helicity transitions are instigated both by electromagnetic fields and matter currents. In addition, it has been shown that correlations between neutrinos and antineutrinos of opposite momentum can build up in anisotropic media. We re-derive the neutrino equations of motion in the mean-field approximation for homogeneous yet anisotropic media, confirming previous results except for a small correction in the Majorana case. Furthermore, we derive the mean-field Hamiltonian induced by neutrino electromagnetic interactions. We also provide a phenomenological discussion of pair correlations in comparison with helicity correlations.

Minicharged Particles from the Sun: A Cutting-Edge Bound

We study the impact on the Sun of an exotic energy-loss channel caused by plasmon decay into fermionic minicharged particles with charge e and mass mf . We compare solar models with this extra emission to helioseismological and neutrino data, obtaining a bound < 2:2 10 14 (95% CL) for mf . 25 eV. Our result is comparable to previous limits from the cooling of globular cluster stars, while at the same time it is better understood and takes theoretical and observational errors into account.