The charge asymmetry of leptons from {ital W}-boson decay has been measured using {ital {bar p}p} data from the Collider Detector at Fermilab at {radical}{ital s} =1.8 TeV. The observed asymmetry is ...well described by most of the available parton distributions.
The acceptance of chorionic villus sampling (CVS) for monitoring pregnancies at risk for chromosomal and genetic disorders was studied from its introduction in the Centre for Clinical Genetics in ...Rotterdam in 1984 until 1988. Special attention was given to increasing acceptance in the group with advanced maternal age (AMA) (12.6% CVS in 1984, 52.2% CVS in 1988) and the group with a high genetic risk (HGR) (42.7% in 1984, 86.7% in 1988). The odds-growth-rate in CVS was 1.64 and 1.67 respectively, which was not significantly different. The relatively limited use of CVS at AMA is most likely determined by the fact that a considerable number of patients are referred too late in pregnancy to have the option of CVS.
An analysis of proton-antiproton collisions at {radical}{ital s} =1.8 TeV recorded with the Collider Detector at Fermilab (CDF) yields {sigma}({ital p{bar p}}{r arrow}{ital WX}){ital B}({ital W}{r ...arrow}{mu}{nu})=2.21{plus minus}0.22 nb and {sigma}({ital p{bar p}}{r arrow}{ital ZX}){ital B}({ital Z} {r arrow}{mu}{sup +}{mu}{sup {minus})}=0.226{plus minus}0.032 nb. The ratio is {ital R}{sub {mu}}={sigma}{sub {ital W}B}({ital W}{r arrow}{mu}{nu})/{sigma}{sub {ital Z}B}({ital Z}{r arrow}{mu}{sup +}{mu}{sup {minus}})=9.8{plus minus}1.2. Combining with previous CDF electron results gives {sigma}{sub {ital W}B}({ital W}{r arrow}{ital l}{nu})=2.20{plus minus}0.20 nb, {sigma}{sub {ital Z}B}({ital Z}{r arrow}{ital l}{sup +}{ital l{minus}})=0.214{plus minus}0.023 nb, and {ital R}{sub {ital l}}=10.0{plus minus}0.8. We extract the ratios of the coupling constants {ital g}{sub {mu}}/{ital g}{sub {ital e}} and {ital g}{sub {tau}}/{ital g}{sub {mu}}. Using standard model assumptions we deduce the inverse branching ratio {ital B}{sup {minus}1}({ital W}{r arrow}{ital l}{nu}), the width {Gamma}({ital W}), and a decay-mode-independent lower bound on the top quark mass of 45 GeV/{ital c}{sup 2} (95% C.L.).
This letter reports the full reconstruction of {ital B} mesons through the decay chain {ital B}{sup {plus minus}}{r arrow}{ital J}/{psi} {ital K}{sup {plus minus}}, {ital J}/{psi}{r arrow}{mu}{sup ...+}{mu}{sup {minus}}, using data obtained at the Collider Detector at Fermilab in {ital {bar p}p} collisions at {radical}{ital s} =1.8 TeV. This exclusive sample, the first observed at a hadron collider, is then used to measure the {ital B}-meson cross section, from which we extract the {ital b}-quark cross section. We obtain {sigma}=2.8{plus minus}0.9 (stat) {plus minus}1.1(syst) {mu}b for {ital B}{sup {minus}} mesons with {ital P}{sub {ital T}}{gt}9.0 GeV/{ital c} and rapidity {vert bar}{ital y}{vert bar}{lt}1.0. We obtain {sigma}=6.1{plus minus}1.9(stat) {plus minus}2.4(syst) {mu}b, for {ital b} quarks with transverse momentum {ital P}{sub {ital T}}{gt}11.5 GeV/{ital c} and rapidity {vert bar}{ital y}{vert bar}{lt}1.0.
We have observed over 10{sup 2} events of the type {ital W}{r arrow}{tau}{nu} followed by {tau}{r arrow} hadrons, where the taus are identified by their decay into one or three charged particles. We ...measure the cross section times branching ratio for {ital p{bar p}}{r arrow}{ital W}{r arrow}{tau}{nu} and compare it to the value for {ital W}{r arrow}{ital e}{nu} to directly measure the ratio of weak coupling constants {ital g}{sub {tau}}/{ital g}{sub {ital e}}. We find {ital g}{sub {tau}}/{ital g}{sub {ital e}}=0.97{plus minus}0.07, consistent with lepton universality.
The {ital B}{sup 0} {ital {bar B}} {sup 0} average mixing parameter {chi} has been extracted from {ital e}{mu} and {ital ee} events produced in {ital p{bar p}} collisions at {radical}{ital s} =1.8 ...TeV. In a sample of 900 {ital e}{mu} events, the like-sign to opposite-sign charge ratio {ital R} is measured to be 0.556{plus minus}0.048(stat){sub {minus}0.042}{sup +0.035}(syst). In the absence of mixing, the expected value of {ital R} would be 0.23{plus minus}0.06. The corresponding number for 212 {ital ee} events is 0.573{plus minus}0.116(stat){plus minus}0.047(syst) with an expected nonmixing value of 0.24{plus minus}0.07. The observed excess in {ital R} leads to a combined determination of {chi}=0.176{plus minus}0.031(stat+syst) {plus minus}0.032 (model), where the last uncertainty is due to Monte Carlo modeling.
Int.J.Mod.Phys. A18 (2003) 1357-1364 Top quark-antiquark ($t\bar t$) pairs will be produced copiously at the
Tevatron collider and in huge numbers at the LHC. This will make possible
detailed ...investigations of the properties and interactions of this quark
flavor. The analysis and interpretation of future data requires precise
predictions of the hadronic production of $t\bar t$ pairs and of their
subsequent decays. In this talk the reactions $p {\bar p}, p p \to t{\bar t} +
X \to l^+ l'^- + X$ are considered and results are presented of our calculation
of the dilepton angular distribution at next-to-leading order QCD, keeping the
full dependence on the spins of the intermediate $t\bar{t}$ state. The angular
distribution is determined for different choices of reference axes that can be
identified with the $t$ and $\bar t$ spin axes. While the QCD corrections to
the leading-order distribution turn out to be small in the case of the LHC, we
find them to be sizeable in the case of the Tevatron and find, moreover, the
angular distribution to be sensitive to the parton content of the proton.
We present a measurement of the cross section for production of isolated prompt photons in {ital {bar p}p} collisions at {radical}{ital s} =1.8 TeV. The cross section, measured as a function of ...transverse momentum ({ital P}{sub {ital T}}), agrees qualitatively with QCD calculations but has a steeper slope at low {ital P}{sub {ital T}}.
We have searched for the production of a neutral gauge boson ({ital Z}{prime}) with mass above 100 GeV/{ital c}{sup 2} in {ital {bar p}p} collisions with the Collider Detector at fermilab. We present ...a 95% confidence level (C.L.) limit on the {ital Z}{prime}{r arrow}{mu}{sup +}{mu}{sup {minus}} production cross section. We combine the {ital Z}{prime} limit with that from our previous dielectron search; the combined result sets a limit of {ital M}{sub {ital Z}{prime}}{gt}412 GeV/{ital c}{sup 2} 95% C.L., assuming standard-model coupling strengths. In addition, the absence of any evidence for an effective muon-quark contact interaction is used to set a lower limit of 1.6 TeV (95% C.L.) on an associated muon-quark compositeness scale.
PDF
