Search for new particles leading to Z+jets final states in pp¯ collisions at s=1.96 TeV
Physical Review D American Physical Society (APS) 76:7 (2007) 072006
Abstract:
We present the results of a search for new particles that lead to a Z boson plus jets in pp¯ collisions at s=1.96 TeV using the Collider Detector at Fermilab (CDF II). A data sample with a luminosity of 1.06 fb-1 collected using Z boson decays to ee and μμ is used. We describe a completely data-based method to predict the dominant background from standard model Z+jet events. This method can be similarly applied to other analyses requiring background predictions in multijet environments, as shown when validating the method by predicting the background from W+jets in tt¯ production. No significant excess above the background prediction is observed, and a limit is set using a fourth generation quark model to quantify the acceptance. Assuming BR(b′→bZ)=100% and using a leading-order calculation of the b′ cross section, b′ quark masses below 268 GeV/c2 are excluded at 95% confidence level.Searches for direct pair production of supersymmetric top and supersymmetric bottom quarks in pp¯ collisions at s=1.96 TeV
Physical Review D American Physical Society (APS) 76:7 (2007) 072010
Abstract:
We search for direct pair production of supersymmetric top quarks and supersymmetric bottom quarks in proton-antiproton collisions at s=1.96 TeV, using 295 pb-1 of data recorded by the Collider Detector at Fermilab (CDF II) experiment. The supersymmetric top (supersymmetric bottom) quarks are selected by reconstructing their decay into a charm (bottom) quark and a neutralino, which is assumed to be the lightest supersymmetric particle. The signature of such processes is two energetic heavy-flavor jets and missing transverse energy. The number of events that pass our selection for each search process is consistent with the expected standard model background. By comparing our results to the theoretical production cross sections of the supersymmetric top and supersymmetric bottom quarks in the minimal supersymmetric standard model, we exclude, at a 95% confidence level in the frame of that model, a supersymmetric top quark mass up to 132 GeV/c2 for a neutralino mass of 48 GeV/c2, and a supersymmetric bottom quark mass up to 193 GeV/c2 for a neutralino mass of 40 GeV/c2.Polarizations of J/psi and psi(2S) mesons produced in pp collisions at square root s = 1.96 TeV.
Phys Rev Lett 99:13 (2007) 132001
Abstract:
We have measured the polarizations of J/psi and psi(2S) mesons as functions of their transverse momentum p(T) when they are produced promptly in the rapidity range |y| < 0.6 with p(T) > or =5 GeV/c. The analysis is performed using a data sample with an integrated luminosity of about 800 pb(-1) collected by the CDF II detector. For both vector mesons, we find that the polarizations become increasingly longitudinal as p(T) increases from 5 to 30 GeV/c. These results are compared to the predictions of nonrelativistic quantum chromodynamics and other contemporary models. The effective polarizations of J/psi and psi(2S) mesons from B-hadron decays are also reported.Polarizations of J/ψ and ψ(2S) Mesons Produced in pp¯ Collisions at s=1.96 TeV
Physical Review Letters American Physical Society (APS) 99:13 (2007) 132001
Abstract:
We have measured the polarizations of J/psi and psi(2S) mesons as functions of their transverse momentum p(T) when they are produced promptly in the rapidity range |y| < 0.6 with p(T) > or =5 GeV/c. The analysis is performed using a data sample with an integrated luminosity of about 800 pb(-1) collected by the CDF II detector. For both vector mesons, we find that the polarizations become increasingly longitudinal as p(T) increases from 5 to 30 GeV/c. These results are compared to the predictions of nonrelativistic quantum chromodynamics and other contemporary models. The effective polarizations of J/psi and psi(2S) mesons from B-hadron decays are also reported.Polarizations of J/ψ and ψ(2S) mesons produced in pp̄ collisions at s=1.96TeV
Physical Review Letters 99:13 (2007)