arXiv subjects

T. Affolder

Publications and source records attributed to T. Affolder.

28 records · Page 2Linked to original sources

arXiv2000

Direct Measurement of the W Boson Width in ppbar Collisions at roots = 1.8 TeV

This Letter describes a direct measurement of the $W$ boson total decay width, $\gw$, using the Collider Detector at Fermilab. The measurement uses an integrated luminosity of $90\invpb$, collected during the 1994--1995 run of the Fermilab Tevatron $p\pbar$ collider. The width is determined by normalizing predicted signal and background distributions to 49844 $\wenu$ candidates and 21806 $\wmunu$ candidates in the transverse-mass region $M_T<200\gev$ and then fitting the predicted shape to the 438 electron events and 196 muon events in the high-$M_T$ region, $100<M_T<200\gev$. The result is $Γ_W=2.04\pm0.11$(stat)$\pm0.09$(syst)GeV.

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arXiv2000

Limits on Gravitino Production and New Processes with Large Missing Transverse Energy in p-pbar Collisions at sqrt(s)=1.8 TeV

Events collected by the Collider Detector at Fermilab (CDF) with an energetic jet plus large missing transverse energy can be used to search for physics beyond the Standard Model. We see no deviations from the expected background and set upper limits on the production of new processes. We consider in addition the production of light gravitinos within the framework of the Gauge Mediated Supersymmetry Breaking models and set a limit at 95% confidence level on the breaking scale sqrt(F) >= 217 GeV, which excludes gravitino masses smaller than 1.1x10^-5 eV/c^2.

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arXiv2000

Search for New Particles Decaying to top-antitop in proton-antiproton collisions at squareroot(s)=1.8 TeV

We use 106 $\ipb$ of data collected with the Collider Detector at Fermilab to search for narrow-width, vector particles decaying to a top and an anti-top quark. Model independent upper limits on the cross section for narrow, vector resonances decaying to $\ttbar$ are presented. At the 95% confidence level, we exclude the existence of a leptophobic $\zpr$ boson in a model of topcolor-assisted technicolor with mass $M_{\zpr}$ $<$ 480 $\gev$ for natural width $Γ$ = 0.012 $M_{\zpr}$, and $M_{\zpr}$ $<$ 780 $\gev$ for $Γ$ = 0.04 $M_{\zpr}$.

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arXiv2000

The Transverse Momentum and Total Cross Section of E+ E- Pairs in the Z-Boson Region from P Anti-P Collisions at s**(1/2) = 1.8-Tev

The transverse momentum and total cross section of e^+e^- pairs in the Z-boson region of 66<M_{ee}<116 GeV$/c^2$ from $p\bar{p}$ collisions at $\sqrt{s}=1.8$ TeV are measured using 110 pb^{-1} of collisions taken by the Collider Detector at Fermilab during 1992-1995. The total cross section is measured to be $248 \pm 11$ pb. The differential transverse momentum cross section is compared with calculations that match quantum chromodynamics perturbation theory at high transverse momentum with the gluon resummation formalism at low transverse momentum.

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arXiv1999

A Measurement of the Differential Dijet Mass Cross Section in p-pbar Collisions at sqrt{s}=1.8 TeV

We present a measurement of the cross section for production of two or more jets as a function of dijet mass, based on an integrated luminosity of 86 pb^-1 collected with the Collider Detector at Fermilab. Our dijet mass spectrum is described within errors by next-to-leading order QCD predictions using CTEQ4HJ parton distributions, and is in good agreement with a similar measurement from the D0 experiment.

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arXiv1999

Production of Y(1S) Mesons from chib Decays in pp(bar) Collisions at sqrt(s)=1.8 TeV

We have reconstructed the radiative decays $χ_{b}(1P) \to Υ(1S) γ$ and $χ_{b}(2P) \to Υ(1S) γ$ in $p \bar{p}$ collisions at $\sqrt{s} = 1.8$ TeV, and measured the fraction of $Υ(1S)$ mesons that originate from these decays. For $Υ(1S)$ mesons with $p^Υ_{T}>8.0$ GeV/$c$, the fractions that come from $χ_{b}(1P)$ and $χ_{b}(2P)$ decays are $(27.1\pm6.9(stat)\pm4.4(sys))%$ and $(10.5\pm4.4(stat)\pm1.4(sys))%$, respectively. We have derived the fraction of directly produced $Υ(1S)$ mesons to be $(50.9\pm8.2(stat)\pm9.0(sys))%$.

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arXiv1999

Measurement of the Helicity of W Bosons in Top Quark Decays

We use the transverse momentum spectrum of leptons in the decay chain t-->bW with W-->l nu to measure the helicity of the W bosons in the top quark rest frame. Our measurement uses a ttbar sample isolated in 106 +/- 4 inverse picobarns of data collected in ppbar collisions at sqrt(s)=1.8 TeV with the CDF detector at the Fermilab Tevatron. Assuming a standard V--A weak decay, we find that the fraction of W's with zero helicity in the top rest frame is F_0 = 0.91 +/- 0.37 (stat) +/- 0.13 (syst), consistent with the standard model prediction of F_0=0.70 for a top mass of 175 GeV/c**2.

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arXiv1999

Search for a Fourth-Generation Quark More Massive than the Z0 Boson in ppbar Collisions at sqrt(s) = 1.8 TeV

We present the results of a search for pair production of a fourth-generation charge -1/3 quark (b') in sqrt(s)=1.8 TeV ppbar collisions using 88 pb^(-1) of data obtained with the Collider Detector at Fermilab. We assume that both quarks decay via the flavor-changing neutral current process b' -> bZ and that the b' mass is greater than m_Z + m_b. We studied the decay mode b'b'bar -> ZZ b bbar where one Z0 decays into e^+e^- or mu^+ mu^- and the other decays hadronically, giving a signature of two leptons plus jets. An upper limit on the cross section of ppbar -> b'b'bar times [BR (b' -> bZ)]^2 is established as a function of the b' mass. We exclude at 95% confidence level a b' quark with mass between 100 and 199 GeV/c^2 for BR(b' -> bZ) = 100%.

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arXiv1999

Measurement of b Quark Fragmentation Fractions in p-pbar Collisions at sqrt(s)=1.8 TeV

We have studied the production of B hadrons in 1.8-TeV p-pbar collisions. We present measurements of the fragmentation fractions, f_u, f_d, f_s and f_baryon, of produced b quarks that yield B^+, B^0, B^0_s and Lambda_b hadrons. Reconstruction of several electron-charm final states yields f_s/(f_u+f_d)=0.213+/-0.068 and f_baryon/(f_u+f_d)=0.118+/-0.042, assuming f_u=f_d. If all B hadrons produced in p-pbar collisions cascade to one of these four hadrons, we determine f_u=f_d=0.375+/-0.023, f_s=0.160+/-0.044 and f_baryon=0.090+/-0.029. If we do not assume f_u=f_d, we find f_d/f_u=0.84+/-0.16.

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arXiv1999

Measurement of the B0 anti-B0 oscillation frequency using l- D*+ pairs and lepton flavor tags

The oscillation frequency Delta-md of B0 anti-B0 mixing is measured using the partially reconstructed semileptonic decay anti-B0 -> l- nubar D*+ X. The data sample was collected with the CDF detector at the Fermilab Tevatron collider during 1992 - 1995 by triggering on the existence of two lepton candidates in an event, and corresponds to about 110 pb-1 of pbar p collisions at sqrt(s) = 1.8 TeV. We estimate the proper decay time of the anti-B0 meson from the measured decay length and reconstructed momentum of the l- D*+ system. The charge of the lepton in the final state identifies the flavor of the anti-B0 meson at its decay. The second lepton in the event is used to infer the flavor of the anti-B0 meson at production. We measure the oscillation frequency to be Delta-md = 0.516 +/- 0.099 +0.029 -0.035 ps-1, where the first uncertainty is statistical and the second is systematic.

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