119115234
Z Boson Asymmetry Measurements at the Tevatron
We present measurements of the forward-backward asymmetry (A_fb) in dilepton pair decays of Z bosons produced in ppbar collisions using the full Tevatron dataset. The CDF experiment extracts a value for the effective weak mixing angle parameter sin^{2}\theta^{l}_{eff} of 0.2315 +/- 0.0010 from the A_fb distribution of dimuon events in 9.2 fb^{-1} of integrated luminosity. From dielectron events in 9.7 fb^{-1} of data, the D0 experiment finds sin^{2}\theta^{l}_{eff} = 0.23106 +/- 0.00053, the world's most precise measurement of sin^{2}\theta^{l}_{eff} from hadron colliders and with light quark couplings.
118474620
Studies of single top quark production at the Tevatron
In this paper we present several measurements of single top quark production from the CDF and D0 experiments at the Tevatron. The various analyses utilize integrated luminosity ranging from 2.1 to 4.8 fb{sup -1}. The results include the observation of single top production with a combined cross section of 2.76{sub -0.47}{sup +0.58} pb for a top quark mass of 170 GeV/c{sup 2}, as well as measurements of top quark polarization and first evidence for t-channel production.
109353411
YO! — A Time‐of‐Arrival Receiver for Removal of Femtosecond Helicity‐Correlated Beam Effects
The G0 parity violation experiment at Jefferson Lab is based on time‐of‐flight measurements, and is sensitive to timing effects between the two electron helicity states of the beam. Photon counters triggered by time‐of‐arrival at the target mandate that timing must be independent of delays associated with different orbits taken by the two helicity states. In addition, the standard 499 MHz beam structure is altered such that 1 of every 16 microbunches are filled, resulting in an arrival frequency of 31.1875 (31) MHz, and an average current of 40 μA. Helicity correction involves identifying and tracking the 31 MHz sub‐harmonic, applying a fast/fine phase correction, and finally producing a clean 31 MHz trigger and a 499 MHz clock train. These signals are phase‐matched to the beam arrival at the target on the order of femtoseconds. The 10 kHz output bandwidth is sufficiently greater than the 30 Hz helicity flip settling time (500 μs). This permits the system to correct each helicity bin for any orbit‐induced...
120340582
Edge imaging in intense beams
The appearance of rings of charge observed near the edge of beams from high-perveance guns is described with a simple ray tracing technique inspired by the particle-core model. We illustrate the technique, which has no analog in light optics, with examples from experiments employing solenoid focusing of an electron beam. The rings of charge result from the combined effects of external focusing and space-charge forces acting on paraxial fringe particles with relatively large initial transverse velocities. The model is independent of the physical mechanisms responsible for the fringe particles. Furthermore, the focal length for edge imaging in a uniform focusing channel is derived using a linearized trajectory equation for the motion of fringe particles. Counterintuitively, the focal length decreases as the beam current increases.
18985470
A search for deeply bound kaonic nuclear states
Abstract We have measured proton and neutron energy spectra by means of time-of-flight (TOF) from 4He( K stopped − , p / n ) reactions (KEK PS E471 experiment). In the proton spectrum, a clear mono-energetic peak was observed under semi-inclusive condition, which was assigned to the formation of a strange tribaryon S0(3115) with isospin T = 1 . The mass and width of the state were deduced to be 3117.7 −2.0 +3.8 ( syst . ) ± 0.9 ( stat . ) MeV / c 2 and 21.6 MeV / c 2 , respectively, and its main decay mode was Σ N N . In the neutron spectrum, a mono-energetic peak was found as the result of a detailed analysis, which was assigned to the formation of another kind of strange tribaryon S+(3140). The mass and width of the state were deduced to be 3140.5 −0.8 +3.0 ( syst . ) ± 2.3 ( stat . ) MeV / c 2 and 21.6 MeV / c 2 , respectively, and its main decay mode was Σ ± N N . The isospin of the state is assigned to be 0. The results are compared with recent theoretical calculations.