Measurement of the Diffractive Structure Function of the Antiproton in Proton-Antiproton Collisions at √ s = 1800 and 630 GeV

A measurement of the effective diffractive structure function Ffi of the antiproton obtained from a study of single diffractive dijet events produced in association with a leading antiproton in pp collisions at the center-of-mass energy y/s = 1800 and 630 GeV is presented. Inclusive samples of single diffractive events were collected during the Tevatron collider run of 1995—1996 using the Collider Detector at Fermilab (CDF) by triggering on a leading antiproton detected in a forward Roman Pot spectrometer. From these samples, single diffractive dijet subsamples were selected by requiring two or more jets with transverse energy ET \u3e 7 GeV in an event. From the dijet data samples, an effective leading order diffractive structure function Ffi of the antiproton is extracted. In the kinematic region of antiproton fractional momentum loss 0.035 \u3c £ \u3c 0.095, four-momentum transfer squared \t\ \u3c 1.0 GeV2 and (3 = xp/£, \u3c 0.5, where xp is the Bjorken scaling variable of the struck parton the antiproton, Ffi(/?,£) is found to have the form Fg (/?,£) oc /r 10±01£-0 9±01 yfs = 1800 GeV. To address the question of QCD factorization in diffraction processes, i.e. universality of the diffractive structure function, several comparisons are made on the measured Ffi. In comparisons with expectations based on results obtained in diffractive deep inelastic scattering experiments at HERA, Ffi measured in this analysis is found to be smaller by approximately an order of magnitude, indicating a breakdown of QCD factorization in diffraction processes. In comparisons with results obtained in pp collisions at y/s = 630 GeV, the ratio in normalization of the measured Ffi at the two energies is found to be R_mo_ = 1.3 ± 0.2(stat)^o3(syst). This is compatible with the factorization expectation of unity, but is also in agreement within errors with predictions in the range 1.6—1.8 from phenomenological models that explain the suppression of the diffractive structure function in pp collisions relative to that collisions. Comparisons with results from a study of dijet events by double pomeron exchange and single diffractive events containing a J/ip meson by the CDF collaboration, and with results from a study of single diffractive dijet events obtained by the UA8 collaboration in pp collisions at y/s = 630 GeV are also presented

Analysis Of The Permeability Spectra Of Spinel Ferrite Composites Using Mixing Rules

Magnetic permeability spectra of composite materials containing spinel ferrites (Ni-Zn or Mn-Zn types) have been studied using a permeability dispersion formula by the numerical analysis. The variation of d.c. permeability and the frequency dispersion parameters due to domain wall and gyromagnetic spin resonances with particle content were evaluated using two mixing rules, Coherent Model Approximation (CMA) and Maxwell-Garnet Approximation (MGA) assuming the isotropic particle shape. The variation of d.c. permeability with particle content for spinel ferrite composite can be predicted by the CMA and MGA using the permeability value of embedded ferrite. The dc susceptibility and resonance frequency of domain wall and spin components estimated by the numerical analysis can also be qualitatively described by the CMA and MGA. The type of frequency dispersion, relaxation or resonance, for domain wall and spin components can be analyzed by the estimated damping factors. © 2013 IEEE

Probing Compressed Bottom Squarks with Boosted Jets and Shape Analysis

A feasibility study is presented for the search of the lightest bottom squark (sbottom) in a compressed scenario, where its mass difference from the lightest neutralino is 5 GeV. Two separate studies are performed: $(1)$ final state containing two VBF-like tagging jets, missing transverse energy, and zero or one $b$-tagged jet; and $(2)$ final state consisting of initial state radiation (ISR) jet, missing transverse energy, and at least one $b$-tagged jet. An analysis of the shape of the missing transverse energy distribution for signal and background is performed in each case, leading to significant improvement over a cut and count analysis, especially after incorporating the consideration of systematics and pileup. The shape analysis in the VBF-like tagging jet study leads to a $3\sigma$ exclusion potential of sbottoms with mass up to $530 \, (462)$ GeV for an integrated luminosity of $300$ fb$^{-1}$ at 14 TeV, with $5\%$ systematics and PU $= 0 \, (50)$.Comment: 5 pages, 4 figures. Discussions and references updated, reach for PU=50 case give

Energy Calibration of b-Quark Jets with Z->b-bbar Decays at the Tevatron Collider

The energy measurement of jets produced by b-quarks at hadron colliders suffers from biases due to the peculiarities of the hadronization and decay of the originating B hadron. The impact of these effects can be estimated by reconstructing the mass of Z boson decays into pairs of b-quark jets. From a sample of 584 pb-1 of data collected by the CDF experiment in 1.96 TeV proton-antiproton collisions at the Tevatron collider, we show how the Z signal can be identified and measured. Using the reconstructed mass of Z candidates we determine a jet energy scale factor for b-quark jets with a precision better than 2%. This measurement allows a reduction of one of the dominant source of uncertainty in analyses based on high transverse momentum b-quark jets. We also determine, as a cross-check of our analysis, the Z boson cross section in hadronic collisions using the b-bbar final state as sigma x B(Z->b-bbar) = 1578 +636 -410 pb.Comment: 35 pages, 9 figures, submitted to Nuclear Instruments and Methods in Physics Research Section

Electromagnetic Properties Of Metal Granular Composite Materials For EMC Applications

Electromagnetic properties of copper and Fe55Ni45alloy (Permalloy) composite materials have been studied by measuring the relative complex permeability (µr = µr’– jµr”), and permittivity (Σr = Σr’– jΣr”) spectra over the microwave range, as well as the a.c. electrical conductivity σac spectra. The variation of σac and Σr with particle content shows the insulator-metal transition due to the percolation effect. The effective cluster model can be applied to the percolation effect in permittivity. The permeability spectra in Permalloy composites, which contain the percolated particles, can be affected by the eddy current effect. The permeability relaxation frequency of Permalloy composites shifts to the higher frequencies by the oxidation of embedded particle surfaces. © 2012 IEEE