126188523
Low Divergence Beam in Proton West
122051077
Results from experiments of crystal extraction of 900 GeV proton beams from the Tevatron Collider
The extraction of a small flux of primary protons from a collider in a parasitic manner is very attractive for a number of fixed target applications. The key requirements of the extracted beam are small average currents with relatively small temporal variations. At this time a bent crystal is installed in the Tevatron Collider which is designed to channel protons down an instrumented beam abort transfer line. In this paper the results of experiments with this crystal are presented. The impact on the high energy physics collider detectors of the crystal as a collimator and the transverse mechanism necessary to deposit the protons into the crystal for alignment purposes are described.
38493149
Position Determination of High Energy Photons in Lead Glass
Two 25 element SF5 lead glass Cerenkov counter arrays have been used in the study of photon and ¿° production in pN collisions at Fermilab. The method used to identify shower patterns, and the determination of the position of the photon in the lead glass arrays in the energy range 2-32 GeV is presented. The method enables the spatial position of photons in this energy range width to be measured with a resolution of ¿ = 0.25 inches.
95691104
Preparing crystals for channeling experiments at high energies
Abstract On the basis of the experience of silicon crystal preparation for two Fermilab experiments on particle channeling (E761 and E853) the requirements for the crystal perfection for high energy physics experiments are discussed. Techniques which provide the cutting, orientation with high accuracy and test the quality of the initial and completed crystals are presented.
120121929
Characteristics of the radiation damage seen in the silicon microstrip detector of Fermilab experiment E771
The central region of the silicon microstrip detector used in Fermilab experiment E771 was subjected to a peak fluence of 9.5 × 1013 p/cm2 induced by 800 GeV protons over a two-month period. Fourteen 300 μm thick planes manufactured by Micron Semiconductor were operated at bias voltages ranging from 84 to 109 V. Analysis of data from low intensity beam triggers taken near the end of the run shows that the mean pulse height from our amplifiers began to decline at a fluence of approximately 2 × 1013 p/cm2 and fell to near zero by 6 × 1013 p/cm2. We show that the use of fast amplifiers contributed to this early loss of signal.
124276644
Cross sections for the reactions anti-p + p ---> pi-plus + pi-minus and k-plus + k-minus near 2 gev/c
122070076
Muon trigger electronics for hadron collider experiments
Abstract Trigger electronics designed and constructed for the SDC muon system are described briefly and results of beam tests carried out at KEK are presented. The implementation is based on custom VLSI designs in 1.2 μm CMOS. The performance characteristics of the circuits were measured and confirmed to meet specifications. Designs based on this approach are applicable to future collider experiments.
55399019
Massive spin-2 states as the origin of the top quark forward-backward asymmetry
We show that the anomalously large top quark forward-backward asymmetry observed by CDF and DØ can naturally be accommodated in models with flavor-violating couplings of a new massive spin-2 state to quarks. Regardless of its origin, the lowest-order couplings of a spin-2 boson to fermions are analogous to the coupling of the graviton to energy/momentum, leading to strong sensitivity of the effects associated with its virtual exchange to the energy scales at hand. Precisely due to this fact, the observed dependence of the asymmetry on the $ t\overline t $ invariant mass fits nicely into the proposed framework. In particular, we find a vast parameter space which can lead to the central value for the observed forward-backward asymmetry in the high mass bin.
56563443
On Limit Cycles in Supersymmetric Theories
Abstract Contrary to popular belief conformality does not require zero beta functions. This follows from the work of Jack and Osborn, and examples in non-supersymmetric theories were recently found by some of us. In this Letter we show that such examples are absent in unitary N = 1 supersymmetric four-dimensional field theories. More specifically, we show to all orders in perturbation theory that the beta-function vector field of such theories does not admit limit cycles. A corollary of our result is that unitary N = 1 supersymmetric four-dimensional theories cannot be superscale-invariant without being superconformal.
2024174
Bottom-quark forward-backward asymmetry in the standard model and beyond.
We computed the bottom-quark forward-backward asymmetry at the Tevatron in the standard model (SM) and for several new physics scenarios. Near the Z pole, the SM bottom asymmetry is dominated by tree level exchanges of electroweak gauge bosons. While above the Z pole, next-to-leading order QCD dominates the SM asymmetry as was the case with the top-quark forward-backward asymmetry. Light new physics, M(NP)≲150  GeV, can cause significant deviations from the SM prediction for the bottom asymmetry. The bottom asymmetry can be used to distinguish between competing new physics (NP) explanations of the top asymmetry based on how the NP interferes with s-channel gluon and Z exchange.
172822549
Inclusive J / $\psi$ Production at D0