We present evidence for the exclusive reaction e+e−→Ds±Ds*∓, observed with the Mark III detector at the SLAC storage ring SPEAR. The Ds± is reconstructed in the φπ± decay mode, while the Ds*∓ is detected as a narrow peak in the recoil-mass distribution. The mass of the Ds* is found to be 2109.3±2.1±3.1 MeV/c2, yielding a Ds*−Ds mass difference of 137.9±2.1±4.3 MeV/c2. The width of the Ds* is <22 MeV/c2 at the 90%-confidence level. The observed signal corresponds to σ(e+e−→Ds+Ds*−+Ds−Ds*+)B(Ds+→φπ+)=30±6±11 pb at s=4.14 GeV.
No description provided.
We have studied backward baryon and meson production in π−p→pπ+π−π− at 8.0 GeV/c using a streamer chamber triggered by the detection of a fast forward proton. Our data sample (1227 events) displays prominent N*ρ and N*f quasi-two-body production. These states are investigated with regard to the peripheral nature of the production mechanism and sequential decay of the excited baryon and meson systems. The quasi-two-body production of N*ρ and N*f intermediate states is consistent with u-channel proton exchange as the dominant production mechanism. In the π+π−π− mass distribution we observe a 3- to 4- standard-deviation enhancement at M3π=1897±17 MeV/c2 with full width at half maximum = 110 ± 82 MeV/c2, but find no but find no evidence for backward A1 or A2 production. We observe Δ++(1232) production in the pπ+ effective mass distribution.
In π − p interactions at 9 GeV/ c and 12 GeV/ c , the forward production of N ∗ 1680 and N ∗ 1520 has been observed with features of nucleon exchange. The production of Δ1232 is strongly suppressed.
We have analyzed backward meson production in the reaction π − p → p f π + π − π − at 9 GeV/ c and 12 GeV/ c incident π − momenta, from an experiment performed at the CERN Ω Spectrometer using a fast proton (p f ) trigger device. We find strong production of quasi-two-body processes N ∗ ϱ and N ∗ f with a production mechanism consistent with u -channel nucleon exchange. At a lower level, we observe N ∗ π processes with a 3-body baryon decay through Δ(1232)π. In the (3π) − system, we find evidence for A 1 − and clear A 2 − backward production with similar cross sections (≈0.5 μb).
A new technique is applied to data collected at the ψ(3770) resonance to derive charmed-D-meson branching fractions without relying on the measurement of D-production cross sections. Measurements are presented for three decay modes of the D0 (K−π+, D−π−π+π+, and K−π+π0 and four decay modes of the D+ (K−π+π+,K−π+π+π0,KS0π+, and KS0π+π0). The resulting branching fractions are significantly larger than previous measurements.
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Pairs of τ leptons produced at s=3.77 GeV have been studied in eμ, ee, and μμ final states. The leptonic branching ratios have been measured to be B(τ→eνν)=(18.2±0.7±0.5)% and B(τ→μνν)=(18.0±1.0±0.6)%. Limits have been set for the two-body decays τ→eG and τ→μG, where G is a light Goldstone boson.
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We have studied backward meson and baryon production in π−p→nπ+π− at 8 GeV/c using a streamer chamber triggered by the detection of the interaction of the neutron in thick-plate optical spark chambers. Our data sample of 866 events is dominated by the quasi-two-body final states Δ−(1232)π+, nρ0, and nf0. We study the differential and total backward cross sections for these states and the decay angular distributions of the resonances. The results for the Δ− and ρ0 indicate that both nucleon and Δ exchange in the u channel are important in their production, while f0 production is, as expected, consistent with nucleon exchange.
We have studied the backward production of ω 0 mesons in the u -channel I u = 1 2 exchange reaction π − p → N 0 (1680) ω 0 at 9 GeV/ c and 12 GeV/ c incident momenta. The data come from an experiment performed at the CERN Omega Spectrometer using a fast proton trigger device. The backward production of the η 0 meson has also been observed and the coupling constant ratio g η NN / g π NN has been estimated.
Evidence is presented for a narrow state, called ξ, in the decay modes J/ψ→γξ, ξ→K+K−, and ξ→KS0KS0. In the K+K− mode, the ξ has a mass of 2.230±0.006±0.014 GeV/c2, a width of Γ=0.026−0.016+0.020± 0.017 GeV/c2, a product branching ratio of (4.2−1.4+1.7±0.8)×10 −5, and a statistical significance of ∼4.5 standard deviations. In the KS0KS0 mode, it has a mass of 2.232±0.007±0.007 GeV/c2, a width of Γ=0.018−0.015+0.023± 0.010 GeV/c2, a product branching ratio of (3.1−1.3+1.6±0.7)×10 −5, and a statistical significance of ∼3.6 standard deviations. Limits on ξ decay to other final states are presented.
No description provided.
We have found 431 events of the reaction K+d→K0pps at 3.8−GeVc K+ beam momentum in a 295 000-frame exposure of the Argonne National Laboratory 30-in. deuterium-filled bubble chamber. The event sample consists of one- and two-prong events with a visible K0 decaying to π+π− The total and differential cross sections are found after correction for unseen K0's and for efficiencies in the scanning-measuring-fitting chain. Comparisons of the data are made to an SU(3) sum rule, a Regge model, and data for K−p→K¯0n.
No description provided.
GLAUBER SCREENING AND PAULI EXCLUSION PRINCIPLE CORRECTIONS ARE REQUIRED TO YIELD THE K+ N CHARGE EXCHANGE CROSS SECTION. THE GLAUBER CORRECTION IMPLIES AN INCREASE IN THE CROSS SECTIONS BY THE FACTOR 1.016. THE PAULI CORRECTION IS SLIGHT EXCEPT AT LOW -T (<0.2 GEV**2) WHERE IT IS LARGE AND UNCERTAIN.
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