We present measurements of the B+ meson total cross section and differential cross section $d\sigma/ dp_T$. The measurements use a $98\pm 4$ pb^{-1} sample of $p \bar p$ collisions at $\sqrt{s}=1.8$ TeV collected by the CDF detector. Charged $B$ meson candidates are reconstructed through the decay $B^{\pm} \to J/\psi K^{\pm}$ with $J/\psi\to \mu^+ \mu^-$. The total cross section, measured in the central rapidity region $|y|<1.0$ for $p_T(B)>6.0$ GeV/$c$, is $3.6 \pm 0.6 ({\rm stat} \oplus {\rm syst)} \mu$b. The measured differential cross section is substantially larger than typical QCD predictions calculated to next-to-leading order.
Measured differential cross section for B+ production. The first (DSYS) error is the PT dependent systematic error and the second is the full correlated systematic error.
The total integrated B+ meson cross section. The first error is the combined statistical and PT dependent systematic error. The DSYS error is the fully correlated systematic error.
The charged-particle multiplicity distribution is measured for all hadronic events as well as for light-quark and b-quark events produced in e+e- collisions at the Z pole. Moments of the charged-particle multiplicity distributions are calculated. The H moments of the multiplicity distributions are studied, and their quasi-oscillations as a function of the rank of the moment are investigated.
Moments of the charged particle multiplicity distribution with KOS and LAMBDA decay for all events.
Moments of the charged particle multiplicity distribution without KOS and LAMBDA decay for all events.
Moments of the charged particle multiplicity distribution with KOS and LAMBDA decay for light quark events.
Double-tag events in two-photon collisions are studied using the L3 detector at LEP centre-of-mass energies from root(s)=189 GeV to 209 GeV. The cross sections of the e+e- -> e+e- hadrons and gamma*gamma* -> hadrons processes are measured as a function of the photon virtualities, Q1^2 and Q2^2, of the two-photon mass, W_gammagamma, and of the variable Y=ln(W_gammagamma^2/(Q1 Q2)), for an average photon virtuality <Q2> = 16 GeV2. The results are in agreement with next-to-leading order calculations for the process gamma*gamma* -> q qbar in the interval 2 <= Y <= 5. An excess is observed in the interval 5 < Y <= 7, corresponding to W_gammagamma greater than 40 GeV . This may be interpreted as a sign of resolved photon QCD processes or the onset of BFKL phenomena.
Differential cross section as a function of the photon virtualities Qi**2. Here Q1 is the virtuality w.r.t the electron vertex, and Q2 w.r.t the positron vertex. Data are given both before and after radiative corrections.
Differential cross section as a function of W, the invariant mas of the virtual GAMMA*GAMMA* system. Data are given both before and after radiative corrections.
Differential cross section as a function of the variable LN(W**2/Q1*Q2). Data are given both before and after radiative corrections.
We present a study of pp¯ collisions at s=1800 and 630 GeV collected using a minimum bias trigger by the CDF experiment in which the data set is divided into two classes corresponding to “soft” and “hard” interactions. For each subsample, the analysis includes measurements of the multiplicity, transverse momentum (pT) spectrum, and the average pT and event-by-event pT dispersion as a function of multiplicity. A comparison of results shows distinct differences in the behavior of the two samples as a function of the center of mass (c.m.) energy. We find evidence that the properties of the soft sample are invariant as a function of c.m. energy.
Charged multiplicity at $\sqrt{s} = 630~\text{GeV}$, $|\eta| < 1$, $p_T > 0.4~\text{GeV}$.
Charged multiplicity at $\sqrt{s} = 1800~\text{GeV}$, $|\eta| < 1$, $p_T > 0.4~\text{GeV}$.
$\langle p_\perp \rangle$ vs. multiplicity at $\sqrt{s} = 630~\text{GeV}$, $|\eta| < 1$, $p_T > 0.4~\text{GeV}$.
We report the first measurement of inclusive antiproton production at mid-rapidity in Au+Au collisions at 130 GeV by the STAR experiment at RHIC. The antiproton transverse mass distributions in the measured transverse momentum range of 0.25 < pT < 0.95 GeV/c are found to fall less steeply for more central collisions. The extrapolated antiproton rapidity density is found to scale approximately with the negative hadron multiplicity density.
Tranverse mass distributions for different centralities
Antiproton fit parameters and yields. Systematic errors are 10%.
Antiproton fit parameters and yields. Systematic errors are 10%.
The reactions ee->ee+pi0+X and ee->ee+K0s+X are studied using data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 202 GeV. Inclusive differential cross sections are measured as a function of the particle transverse momentum pt and the pseudo-rapidity. For pt < 1.5 GeV, the pi0 and K0s differential cross sections are described by an exponential, typical of soft hadronic processes. For pt > 1.5 GeV, the cross sections show the presence of perturbative QCD processes, described by a power-law. The data are compared to Monte Carlo predictions and to NLO QCD calculations.
The PI0 differential cross section as a function of PT.
The PI0 differential cross section as a function of pseudorapidity.
The K0S differential cross section as a function of PT.
We present a search for new heavy particles, $X$, which decay via $X \to WZ \to e\nu +jj$ in $p{\bar p}$ collisions at $\sqrt{s}$ = 1.8 TeV. No evidence is found for production of $X$ in 110 pb$^{-1}$ of data collected by the Collider Detector at Fermilab. Limits are set at the 95% C.L. on the mass and the production of new heavy charged vector bosons which decay via $W'\to WZ$ in extended gauge models as a function of the width, $\Gamma (W')$, and mixing factor between the $W'$ and the Standard Model $W$ bosons.
CONST(NAME=XI) is the mixing factor between WPRIME and W-boson.
The growth and development of “charged particle jets” produced in proton-antiproton collisions at 1.8 TeV are studied over a transverse momentum range from 0.5 GeV/c to 50 GeV/c. A variety of leading (highest transverse momentum) charged jet observables are compared with the QCD Monte Carlo models HERWIG, ISAJET, and PYTHIA. The models describe fairly well the multiplicity distribution of charged particles within the leading charged jet, the size of the leading charged jet, the radial distribution of charged particles and transverse momentum around the leading charged jet direction, and the momentum distribution of charged particles within the leading charged jet. The direction of the leading “charged particle jet” in each event is used to define three regions of η−φ space. The “toward” region contains the leading “charged particle jet,” while the “away” region, on the average, contains the away-side jet. The “transverse” region is perpendicular to the plane of the hard 2-to-2 scattering and is very sensitive to the “underlying event” component of the QCD Monte Carlo models. HERWIG, ISAJET, and PYTHIA with their default parameters do not describe correctly all the properties of the “transverse” region.
Average number of charged particles as a function of the relative azimuthal angle between the individual charged particle and the overall leading jet angle.
Average scalar PT sum of charged particles as a function of the relative azimuthal angle between the individual charged particle for 3 different lower limits of the leading jet PT. and the overall jet angle.
The average number of toward(DPHI < 60 DEG), transverse (DPHI 60 TO 120 DEG) and away (DPHI > 120 DEG) charged particles as a function of the PT of the leading charged jet. The data in this table are from the Min-Bias events.
The first measurements of light antinucleus production in Au+Au collisions at RHIC are reported. The observed production rates for antideuterons and antihelions are much larger than in lower energy nucleus-nucleus collisions. A coalescence model analysis of the yields indicates that there is little or no increase in the antinucleon freeze-out volume compared to collisions at SPS energy. These analyses also indicate that the antihelion freeze-out volume is smaller than the antideuteron freeze-out volume.
Coalescence parameters $B_2$ and $B_3$ in Au+Au collisions at 130 GeV.
Invariant yields of $\overline{d}$ and $\overline{p}$. Systematic errors are estimated to be 15%.
Invariant yields of $^3\overline{\mathrm{He}}$ and $\overline{p}$. Systematic errors are estimated to be 15%.
We report on a measurement of the mean charged-particle multiplicity of jets in dijet events with dijet masses in the range 80–630GeV/c2, produced at the Tevatron in pp¯ collisions with s=1.8TeV and recorded by the Collider Detector at Fermilab. The data are fit to perturbative-QCD calculations carried out in the framework of the modified leading log approximation and the hypothesis of local parton-hadron duality. The fit yields values for two parameters in that framework: the ratio of parton multiplicities in gluon and quark jets, $r≡N_{partons}^{g−jet} / N_{partons}^{q−jet} = 1.7 \pm 0.3$, and the ratio of the number of charged hadrons to the number of partons in a jet, $K_{LPHD}^{charged} ≡ N_{hadrons}^{charged} / N_{partons} = 0.57 \pm 0.11$.
Measured values of inclusive charged particle multiplicity per jet for jets falling in restricted cones with opening angles 0.17, 0.28 and 0.47 radians. Note that the systematic errors are strongly correlated.
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