Higgs Boson Decay into a Pair of Leptons

The decay of a Higgs boson into a pair of W bosons h --> W^+W^-, is a dominant mode for Higgs boson masses above 135 GeV. At hadron colliders, searches for this decay focus on channels in which both W bosons decay leptonically into charged leptons, h --> W^+ W^- --> l^+ l^- plus missing energy. We show that semileptonic decays of heavy flavors are an important background to this signal. Lepton isolation provides too little suppression of heavy flavor contributions, and an additional 4 to 8 orders-of-magnitude suppression must come from physics cuts. An increase of the cut on the the minimum transverse momentum of non-leading leptons in multilepton events is one effective way to achieve the needed suppression, without appreciable loss of the Higgs boson signal.Comment: 4 pages, 2 figures, 1 table. AIP style file. Paper presented by Ed Berger. To be published in the proceedings of the 9th Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2006), Rio Grande, Puerto Rico, May 30-June 3, 200

Isolated leptons from heavy flavor decays: Theory and data

Events with isolated leptons play a prominent role in signatures of new physics phenomena at high energy collider physics facilities. In earlier publications, we examine the standard model contribution to isolated lepton production from bottom and charm mesons and baryons through their semileptonic decays (b, c -> l + X), showing that this source can overwhelm the effects of other standard model processes in some kinematic domains. In this paper, we show that we obtain good agreement with recent Tevatron collider data, both validating our simulations and showing that we underestimate the magnitude of the heavy-flavor contribution to the isolated lepton yields. We also show that the isolation requirement acts as a narrow bandpass filter on the momentum of the isolated lepton, and we illustrate the effect of this filter on the background to Higgs boson observation in the dilepton mode. We introduce and justify a new rule of thumb: isolated electrons and muons from heavy flavor decay are produced with roughly the same distributions as b and c quarks, but with 1/200 times the rates of b and c production, respectively.Comment: 12 pg, revtex, 5 fig, corrected typo

Associated Higgs plus vector boson test of a fermiophobic Higgs boson

Production in association with an electroweak vector boson V is a distinctive mode of production for a Higgs boson H without tree-level couplings to fermions, known as a fermiophobic Higgs boson. We focus on HV associated production with H decay into a pair of photons, and V into a pair of jets, with the goal of distinguishing a fermiophobic Higgs boson from the standard model Higgs boson. Performing a simulation of the signal and pertinent QCD backgrounds, and using the same event selection cuts employed by the LHC ATLAS Collaboration, we argue that existing LHC data at 7 TeV with 4.9 fb^{-1} of integrated luminosity may distinguish a fermiophobic Higgs boson from a standard model Higgs boson near 125 GeV at about 1.9 standard deviation signal significance (1.9 sigma) per experiment. At 8 TeV we show that associated production could yield 2.8 sigma significance per experiment with 10 fb^{-1} of data.Comment: 5 pgs., 4 figs, version to appear in Phys. Rev.

Historical Arabic Dialectology: Interpreting the Sources

The description of historical Arabic dialects brings with it a whole plethora of challenges. The most important one is that there are no native speakers left of these dialects, with the consequence that researchers have to rely on written sources in order to discover more about the historical stages of Arabic dialects. These sources are often hard to find and even harder to interpret. This chapter will address some of these challenges, from the interpretation of Arabic orthographical habits in writing the dialect, the use of text editions, and the (un)reliability of historical sources, to the use of Latin transcription or alphabets other than the Arabic for writing the Arabic language. The chapter illustrates these issues with samples of Arabic dialect materials from various periods and origins