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Register a new userSearch for New Physics in Photon-Lepton Events in pbar-p Collisions at root-s= 1.8 TeV
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We present the results of a search in pbar-p collisions at root-s=1.8 TeV for anomalous production of events containing a photon and a lepton (e or mu), both with large transverse energy, using 86 pb-1 of data collected with the Collider Detector at Fermilab during the 1994-95 collider run at the Fermilab Tevatron. The presence of large missing transverse energy, additional photons, or additional leptons in these events is also analyzed. The results are consistent with standard model expectations, with the possible exception of photon-lepton events with large missing transverse energy, for which the observed total is 16 events and the expected mean total is 7.6 pm 0.7 events.
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We present a search for new phenomena in events with two reconstructed $Z$ bosons and large missing transverse momentum, sensitive to processes $pbar{p}rightarrow X_2X_2 rightarrow Z Z X_1 X_1$, where $X_2$ is an unstable particle decaying as $X_2rightarrow ZX_1$ and $X_1$ is undetected. The particles $X_1$ and $X_2$ may be, among other possibilities, fourth generation neutrinos or supersymmetric particles. We study the final state in which one $Z$ boson decays to two charged leptons and the second decays hadronically. In data corresponding to an integrated luminosity of 4.2 fb$^{-1}$ from proton-antiproton collisions recorded by the CDF II detector at the Tevatron, with center-of-mass energy of 1.96 TeV, we find agreement between data and standard-model backgrounds. We calculate 95% confidence level upper limits on the cross section of the process $pbar{p}rightarrow X_2X_2 rightarrow Z Z X_1 X_1$ ranging from 50 fb to 1 pb, depending on the masses of $X_1$ and $X_2$.
We present the results of a search for pair production of a heavy top-like (t) quark decaying to Wq final states using data corresponding to an integrated luminosity of 5.6 fb-1 collected by the CDF II detector in pp collisions at {surd}s = 1.96 TeV. We perform parallel searches for t to Wb and t to Wq (where q is a generic down-type quark) in events containing a lepton and four or more jets. By performing a fit to the two-dimensional distribution of total transverse energy versus reconstructed t quark mass, we set upper limits on the t bar{t} production cross section and exclude a standard model fourth-generation t quark decaying to W b (W q) with mass below 358 (340) GeV/c2 at 95% CL.
A search for a narrow Higgs boson resonance in the diphoton mass spectrum is presented based on data corresponding to 7.0 fb^-1 of integrated luminosity from p-pbar collisions at sqrt(s) = 1.96 TeV collected by the CDF experiment. No evidence of such a resonance is observed, and upper limits are set on the cross section times branching ratio of the resonant state as a function of Higgs boson mass. The limits are interpreted in the context of the standard model and one fermiophobic benchmark model where the data exclude fermiophobic Higgs bosons with masses below 114 GeV/c^2 at a 95% Bayesian credibility level.
We have measured deconfined hadronic volumes, $4.4 < V < 13.0$ fm$^{3}$, produced by a one dimensional (1D) expansion. These volumes are directly proportional to the charged particle pseudorapidity densities $6.75 < dN_{c}/deta < 20.2$. The hadronization temperature is $T = 179.5 pm 5$ (syst) MeV. Using Bjorkens 1D model,the hadronization energy density is $epsilon_{F} = 1.10 pm 0.26$ (stat) GeV/fm$^{3}$ corresponding to an excitation of $24.8 pm 6.2$ (stat) quark-gluon degrees of freedom.
A set of inclusive cross sections at zero rapidity is presented for p-pbar interactions at center of mass energy sqrt(s)=1.8 TeV. Six particle cross sections are corrected for secondary contributions from decays of higher mass resonances in order to produce a set of primary cross sections. The primary cross sections per spin state are well described by d(sigma^p)/dy|_(y=0)= 0.721*(pi*lambdabar_(pi)^2)*exp(-m/T), where m is the particle rest mass, T=hbar*c/r_h, and r_h=0.97 fm. The deuterium production cross section is also described if r_h is replaced by r_A=r_h*A^(1/3). The same exponential in m and T describes primary charm fractions in e+e- collisions at least up to the J/Psi mass. There is no significant evidence for strangeness or charm suppression if only primary production of light hadrons is considered. There is evidence that the primary cross section for each particle may have the same value for pp and pbar-p collisions and that it may have nearly constant values between sqrt(s)=63 GeV and sqrt(s)=1800 GeV. Fits to the final state transverse momenta of the particles using a gas model favor a temperature T=132 MeV, a chemical potential mu=129 MeV, and a transverse flow of the gas with beta_f=0.27.
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