Search for anomalous production of multiple leptons in association with W and Z bosons at CDF
(2012)
Search for anomalous production of multiple leptons in association with W and Z bosons at CDF
ArXiv 1202.126 (2012)
Abstract:
This paper presents a search for anomalous production of multiple low-energy leptons in association with a W or Z boson using events collected at the CDF experiment corresponding to 5.1 fb$^{-1}$ of integrated luminosity. This search is sensitive to a wide range of topologies with low-momentum leptons, including those with the leptons near one another. The observed rates of production of additional electrons and muons are compared with the standard model predictions. No indications of phenomena beyond the standard model are found. A 95% confidence level limit is presented on the production cross section for a benchmark model of supersymmetric hidden-valley Higgs production. Particle identification efficiencies are also provided to enable the calculation of limits on additional models.Search for the rare radiative decay W→πγ in pp̄ collisions at √s=1.96TeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 85:3 (2012)
Abstract:
We present a search for the rare radiative decay W ±→ π ±γ using data corresponding to an integrated luminosity of 4.3fb -1 of proton-antiproton collisions at a center-of-mass energy of 1.96 TeV collected by the CDF experiment at Fermilab. As no statistically significant signal is observed, we set a 95%-confidence-level upper limit on the relative branching fraction Γ(W ±→π ±γ)/Γ(W ±→e ±ν) at 6.4×10 -5, a factor of 10 improvement over the previous limit. © 2012 American Physical Society.A weak compact jet in a soft state of Cygnus X-1
Monthly Notices of the Royal Astronomical Society 419:4 (2012) 3194-3199
Abstract:
We present evidence for the presence of a weak compact jet during a soft X-ray state of Cygnus X-1. Very-high-resolution radio observations were taken with the VLBA, EVN and MERLIN during a hard-to-soft spectral state change, showing the hard state jet to be suppressed by a factor of about 3-5 in radio flux and unresolved to direct imaging observations (i.e. ≲1 mas at 4cm). High time-resolution X-ray observations with the RXTE-PCA were also taken during the radio monitoring period, showing the source to make the transition from the hard state to a softer state (via an intermediate state), although the source may never have reached the canonical soft state. Using astrometric very long baseline interferometry (VLBI) analysis and removing proper motion, parallax and orbital motion signatures, the residual positions show a scatter of ∼0.2 mas (at 4cm) and ∼3 mas (at 13cm) along the position angle of the known jet axis; these residuals suggest that there is a weak unresolved outflow, with varying size or opacity, during intermediate and soft X-ray states. Furthermore, no evidence was found for extended knots or shocks forming within the jet during the state transition, suggesting that the change in outflow rate may not be sufficiently high to produce superluminal knots. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.Galaxy Zoo: Building the low-mass end of the red sequence with local post-starburst galaxies
Monthly Notices of the Royal Astronomical Society 420:2 (2012) 1684-1692