A measurement of the QCD jet-broadening parameter 〈QT〉 is described for high-ET jet data in the central calorimeter of the Collider Detector at Fermilab. As an alternate approach to clustering analysis, this method involves the use of a global event parameter which is free from the ambiguities associated with the definition and separation of individual clusters. The parameter QT is defined as the scalar sum of the transverse momentum perpendicular to the transverse thrust axis. Parton-level QCD predictions are made for 〈QT〉 as a function of ET, the total transverse energy in the events, and suggest that a measurement would show a dependence on the running of the strong coupling constant αs. Comparisons are made to first-order QCD parton-level calculations, as well as to fully evolved and hadronized leading-log simulations. The data are well described by the QCD predictions.
A small asymmetry in the systematic uncertainty has been ignored. Given here are the average values.
The single-spin asymmetry $A_N(PP)$ for inclusive $\pi^0$ production at 0.5 < Pt< 2 GeV/c by 200-GeV transversely-polarized antiprotons on protons has been measured at Fermilab over a wide range of xp. We observe that AN (15P) has the same sign, a similar $x_F$ dependence, and about half the magnitude as $A_N(PP)$ for $\pi^0$ production by protons. We also present the ratio of the spin-averaged cross sections for $\pi^0$ production by antiprotons and by protons.
No description provided.
P P data are taken from Adams et al, Fermilab-Pub-91/13-E.
Ratio of the spin averaged invariant cross section for PI0 production in p p and pbar p interactions.
The spin asymmetryAN for inclusive π0 production by 200-GeV transversely-polarized protons on a liquid hydrogen target has been measured at Fermilab over a wide range ofxF, with 0.5<pT<2 GeV/c. AtxF>0.3, the asymmetry rises with increasingxF and reaches a value ofAN=0.15±0.03 in the region 0.6<xF<0.8. This result provides new input regarding the question of the internal spin structure of transversely-polarized protons.
No description provided.
False asymmetry calculated for events with average beam polarization of zero.
No description provided.
A measurement of the single-spin asymmetry A N in p↑ + p→ π 0 + X at 200 GeV with x F = 0 shows a transition in the production process from a “ low -x T ” regime with A N = 0, through an intermediate region of negative asymmetry, to a “ high -x T ” regime with A N > 0.3. This transition occurs at x T ≈ 0.4 and is consistent with x T -scaling of A N in pion production using polarized beams or targets from √− s =5.2 to 19.4 GeV. Results for A N in η production by polarized protons and in π 0 production by polarized antiprotons are also presented.
Statistical errors only.
Statistical errors only.
Statistical errors only.
We have measured the polarization of D*, the energy dependence of the polarization, and the spin-density matrix of D* in e+e− annihilation at a center-of-mass energy of 29 GeV using the Time Projection Chamber detector at the SLAC storage ring PEP. In 147 pb−1 of data we see no strong evidence for polarization, alignment, or final-state interactions in this fragmentation process.
Polarization is the factor alpha(z) in the expression d width (D*-->D pi)/domega = C(1+alpha(z)cos(theta)**2).
Spin density matrices for D* --> D0 pi+.
The production of μ−e+ dileptons by muon neutrinos is studied in a high-statistics bubble-chamber experiment. The experiment consisted of exposing the Fermilab 15-ft bubble chamber filled with a heavy Ne-H2 mix to a wideband neutrino beam. In a total sample of 146 700±11 700 charged-current interactions, 461 events with an e+(Pe+>300 MeV/c) and a μ− are observed. The rate for μ−e+ dilepton production in measured to be (0.42±0.06)%. The energy dependence of this rate is presented. The kinematic distributions for the μ−e+ events are consistent with charm production and subsequent semileptonic decay. A total of 60 KS0 and 31 Λ0 decays were observed in the μ−e+ event sample. The measured rates for neutral-strange-particle production are 0.78±0.12 K0K¯0's and 0.19±0.04 Λ0's per μ−e+ event. Finally, rates for Λc+, D0, and D+ production in charged-current νμ interactions are derived. They are found to be (4−2+10)%, (1.7−0.7+0.5)%, and (1.3−0.5+0.4)%, respectively.
No description provided.
No description provided.
No description provided.
The production ofπ0 andη mesons has been studied in the reactions20Ne +Al at 350 MeV/u and40Ar + Ca at 1.0 GeV/u. Rapidity distributions and transverse momentum spectra have been measured and are compared to thermal distributions.
THE SPECTRUM (1/PT)*D(SIG)/D(PT) HAS BEEN FITTED BY A THERMAL DISTRIBUTION SQRT(MT)*EXP(-SLOPE*MT).
THE SPECTRUM (1/PT)*D(SIG)/D(PT) HAS BEEN FITTED BY A THERMAL DISTRIBUTION SQRT(MT)*EXP(-SLOPE*MT).
The production of π±,K±,p has been measured in p+Be and p+Au collisions for comparison with central Si+Au collisions. The inverse slope parameters T0 obtained by an exponential fit to the invariant cross sections in transverse mass are found to be, T0p,K+,ππ∼140–160 MeV in p+A collisions, whereas in central Si+Au collisions, T0p,K+∼200–220 MeV >T0ππ∼140–160 MeV at midrapidity. The π± and K+ distributions are shifted backwards in p+Au compared with p+Be. A gradual increase of (dn/dy)K+ per projectile nucleon is observed from p+Be to p+Au to central Si+Au collisions, while pions show no significant increase.
No description provided.
No description provided.
No description provided.
The reactionγγ→3π+3π- has been studied usig the JADE detector at PETRA. The topological cross sectionσ(γγ→3π+3π-) was measured in the CM energy range 1.5–5.5 GeV. The production ofρ0,s was observed and the average number ofρ0,s per event measured. The contributions of the subprocessesγγ→ρ02π+2π-,γγ→ρ0ρ0π+2π- andγγ→ 3π+3π- (phase space) were studied and 95% C.L. upper limits for the cross sectionσ(γγ→ρ0ρ0π+π- determined. Finally the Bose-Einstein correlation for pairs of like signed pions was observed. A fit to a standard parametrization gave results consistent with other studies of this effect in pion systems.
Topological cross section.
Fractions of events for different final states resulting from the extended liklihood fit using incoherent weights.
Fractions of events for different final states resulting from the extended liklihood fit using coherent weights.
The multiplicity distributions of charged particles in restricted rapidity intervals inZ0 hadronic decays measured by the DELPHI detector are presented. The data reveal a shoulder structure, best visible for intervals of intermediate size, i.e. for rapidity limits around ±1.5. The whole set of distributions including the shoulder structure is reproduced by the Lund Parton Shower model. The structure is found to be due to important contributions from 3-and 4-jet events with a hard gluon jet. A different model, based on the concept of independently produced groups of particles, “clans”, fluctuating both in number per event and particle content per clan, has also been used to analyse the present data. The results show that for each interval of rapidity the average number of clans per event is approximately the same as at lower energies.
Data for both hemispheres.
Data for both hemispheres.
Data for both hemispheres.
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