We report measurements of asymmetries in quasielastic scattering of polarized electrons from polarized He3 at Q2=-0.2 GeV/c)2. We measure AT′=(-2.6±0.9±0.46)% and ATL′=(+1.75±1.2±0.31)%. The asymmetry AT′ depends predominantly on the previously measured neutron magnetic form factor and provides a test of theories of spin-dependent quasielastic scattering. Our result for AT′ is consistent with a previously reported measurement and suggests that the current theoretical picture is incomplete and final-state-interaction and meson-exchange corrections are necessary if the electric form factor of the neutron is to be reliably extracted from the asymmetry of ATL′.
No description provided.
The B0 B¯ 0 average mixing parameter χ has been extracted from eμ and ee events produced in pp¯ collisions at √s =1.8 TeV. In a sample of 900 eμ events, the like-sign to opposite-sign charge ratio R is measured to be 0.556±0.048(stat)−0.042+0.035(syst). In the absence of mixing, the expected value of R would be 0.23±0.06. The corresponding number for 212 ee events is 0.573±0.116(stat)±0.047(syst) with an expected nonmixing value of 0.24±0.07. The observed excess in R leads to a combined determination of χ=0.176±0.031(stat+syst) ±0.032 (model), where the last uncertainty is due to Monte Carlo modeling.
No description provided.
No description provided.
The distribution of nuclei resulting from the annihilation of stopped antiprotons on238U has been studied by an off-line measurement of the residual radioactivity. It was found that the probability of fission exceeds 84% (68% c.l.). The charge and mass distributions of the fission products can be separated into two parts, a more frequent symmetric component originating from high energy fission (excitation energy between 100 MeV and 1 GeV) and an asymmetric component from low energy fission (excitation energy less than 40 MeV).
The measured yields per 1000 stopped PBAR.
We have used the Fermilab 30-in. bubble-chamber-hybrid spectrometer to study neutral-strange-particle production in the interactions of 200-GeV/c protons and π+ and K+ mesons with nuclei of gold, silver, and magnesium. Average multiplicities and inclusive cross sections for K0 and Λ are measured, and a power law is found to give a good description of their A dependence. The exponent characterizing the A dependence is consistent with being the same for K0 and Λ production, and also the same for proton and π+ beams. Average K0 and Λ multiplicities, as well as their ratio, have been measured as functions of the numbers of projectile collisions νp and secondary collisions νs in the nucleus, and indicate that rescattering contributes significantly to enhancement of Λ production but not to K0 production. The properties of events with multiple K0's or Λ's also corroborate this conclusion. K0 rapidities are in the central region and decrease gently with increasing νp, while Λ rapidities are in the target-fragmentation region and are independent of νp. K0 and Λ multiplicities increase with the rapidity loss of the projectile, but their rapidities do not.
No description provided.
No description provided.
No description provided.
Inelastic scattering of 490 GeV μ + from deuterium and xenon nuclei has been studied for x Bj > s .001. The ratio of the xenon/deuterium cross section per nucleon is observed to vary with x Bj , with a depletion in the kinematic range 0.001 < x Bj < 0.025 which exhibits no significant Q 2 dependence. An electromagnetic calorimeter was used to verify the radiative corrections.
Xenon structure function parameterized as being equal to the DEUT structurefunction.
Xenon structure function parameterized by an x-dependent shadowing factor times the DEUT structure function.
This letter reports the full reconstruction of B mesons through the decay chain B±→J/ψ K±, J/ψ→μ+μ−, using data obtained at the Collider Detector at Fermilab in p¯p collisions at √s =1.8 TeV. This exclusive sample, the first observed at a hadron collider, is then used to measure the B-meson cross section, from which we extract the b-quark cross section. We obtain σ=2.8±0.9 (stat) ±1.1(syst) μb for B− mesons with PT>9.0 GeV/c and rapidity ‖y‖<1.0. We obtain σ=6.1±1.9(stat) ±2.4(syst) μb, for b quarks with transverse momentum PT>11.5 GeV/c and rapidity ‖y‖<1.0.
B-meson cross section.
B-quark cross section.
The rate of neutrino- and antineutrino-induced prompt same-sign dimuon production in steel was measured using a sample of μ−μ− events and 25 μ+μ+ events withPμ>9 GeV/c, produced in 1.5 millionvμ and 0.3 million\(\overline {v_\mu}\) induced charged-current events with energies between 30 GeV and 600 GeV. The data were obtained with the Chicago-Columbia-Fermilab-Rochester (CCFR) neutrino detector in the Fermilab Tevatron Quadrupole Triplet Neutrino Beam during experiments E 744 and E 770. After background subtraction, the prompt rate of same-sign dimuon production is (0.53±0.24)×10−4 pervμ charged-current event and (0.52±0.33)×10−4 per\(\overline {v_\mu}\) charged-current event. The kinematic distributions of the same-sign dimuon events after background subtraction are consistent with those of the non-prompt background due to meson decays in the hadron shower of a charged-current event. Calculations ofc\(\bar c\) gluon bremsstrahlung, based on improved measurements of the charm mass parameter and nucleon structure functions by the CCFR collaboration, yield a prompt rate of (0.09±0.39)×10−4 pervμ charged-current event. In this case,c\(\bar c\) gluon bremsstrahlung is probably not an observable source of prompt same-sign dimuons.
Rate of dimuon production per charged current event.
Rate of dimuon production per charged current event.
Results on the multiplicity structure of diffractively excited meson and proton systems in À+/K+p interactions at 250 GeV/c are presented for diffractive masses up to about 9 GeV. The energy dependence of the average charge multiplicity and the shape of the multiplicity distribution in terms of KNO-scaling and negative binomial distribution are investigated. The diffractive systems are compared toe+e−,lh and non-diffractivehh final states as suggested by modern approaches of the Pomeron-hadron collision. Systematic differences are found between diffractive meson and proton systems but also between diffraction and the reactions compared to.
No description provided.
No description provided.
No description provided.
The value of the strong coupling constant,$$\alpha _s (M_{Z^0 } )$$, is determined from a study of 15 d
Differential jet mass distribution for the heavier jet using method T. The data are corrected for the finite acceptance and resolution of the detector and for initial state photon radiation.
Differential jet mass distribution for the jet mass difference using methodT. The data are corrected for the finite acceptance and resolution of the detec tor and for initial state photon radiation.
Differential jet mass distribution for the heavier jet using method M. The data are corrected for the finite acceptance and resolution of the detector and for initial state photon radiation.
A systematic set of measurements of the global transverse energy distributions, dσ/dET and dET/dη, from beams of protons, O16 and Si28 at 14.6A GeV/c, incident on targets ranging from Be to Au is presented. The detector was a semicircular array of lead-glass blocks, covering polar angles 9°<θ<32°, whose total response provides a good measure of the produced particle yield in the central rapidity region of these reactions. Proton-nucleus spectra exhibit a similar shape on the high-energy tail, independent of target, suggesting that produced particles in such events arise mostly from the first collision of the projectile proton. For targets heavier than Cu, the high-energy edges of the oxygen-nucleus spectra, and of the silicon-nucleus spectra, reach ratios consistent with the geometry of central collisions. Angular distributions, dET/dη, are characterized by Gaussian fits, and an acceptance-independent form of the differential cross section is found, based on the maximum value of dET/dη. The projectile dependence of nucleus-nucleus spectra is studied in terms of two very different models: simple energy scaling and the wounded projectile nucleon model of p+A convolutions.
No description provided.
No description provided.
No description provided.
Forum