Results for the Cabibbo suppressed semileptonic decays D 0 → π − e + ν and D 0 → π − μ + ν (charge conjugates are implied) are reported by Fermilab photoproduction experiment E687. We find 45.4 ± 13.3 events in the electron mode and 45.6 ± 11.8 in the muon mode. The relative branching ratio BR (D 0 →π − l + v) BR (D 0 →K − l + v) for the combined sample is measured to be 0.101 ± 0.020 (stat.) ± 0.003 (syst.) 14 .
CONST(C=V-CD and CONST(C=V-CS) are the Cabibbo-Kobayashi-Maskawa matrix elemets.
We report measurements of charm particle production asymmetries from the Fermilab photoproduction experiment E687. An asymmetry in the rate of production of charm versus anticharm particles is expected to arise primarily from fragmentation effects. We observe statistically significant asymmetries in the photoproduction of D + , D ∗+ and D 0 mesons and find small (but statistically weak) asymmetries in the production of the D s + meson and the Λ c + baryon. Our inclusive photoproduction asymmetries are compared to predictions from nonperturbative models of charm quark fragmentation.
Production asymmetry. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table. SIG(C=ANTI-CHARM) denotes the reaction with anti-charm production.
Antiparticle/particle production ratio. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table. SIG(C=ANTI-CHARM) denotes the reaction with anti-charm production.
Production asymmetry for particles produced in association with a D*(2010)+-. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table.
We report on the study of charm baryons decaying to Λ c + : Λ c ★+ (2625) → Λ c + π + π − , Λ c ★+ (2593) → Λ c + π + π − , Σ c 0 → Λ c + π − and Σ c ++ → Λ c + π + . We present a confirmation of the state Λ c ∗+ (2593) and determine its mass difference to be M ( Λ c ★+ (2593)) − M ( Λ c + ) = 309.2 ± 0.7 ± 0.3 MeV/ c 2 . We determine the lower limit on the resonant branching ratio to be BR (Λ c ★+ (2593) → Σ c π ± Λ c ★+ (2593) → Λ c + π + π − ) > 0.51 (90% c.l.). We also measure the mass differences M ( Σ c 0 ) − M ( Λ c + ) = 166.6±0.5±0.6 MeV/ c 2 and M ( Σ c ++ ) − M ( Λ c + ) = 167.6±0.6±0.6 MeV/ c 2 . Finally, we measure the relative photoproduction cross sections for Λ c ★+ and Σ c with respect to the (inclusive) photoproduction cross section for Λ c + .
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Charged hadronic four-body decays of D 0 mesons have been studied in the E687 photoproduction experiment at Fermilab. Branching ratios relative to the D 0 → K − π + π + π − decay mode for the Cabibbo-suppressed decays D 0 → π − π + π − π + , D 0 → K − K + π − π + have been measured and the first evidence of the D 0 → K − K + K − π + decay mode is reported. An analysis of the D 0 → K − K + π − π + resonance structure is also presented.
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We report evidence for the Cabibbo-suppressed decay of the charm baryon Λ c + into the final state pK − K + . The analysis is performed on data collected by high energy photoproduction experiment E687 during the 1990–1991 Fermilab fixed target run. The branching ratio of the decay Λ c + → pK − K + relative to the non-suppressed Λ c + → pK − π + is measured to be BR( pK − K + / pK − π + ) = 0.096 ± 0.029 ± 0.010. The upper limit of the decay into pø relative to the inclusive pK − K + decay is measured to be BR( pø / pK − K + < 58% at the 90% confidence level.
Branching ratio of Cabibbo-suppressed and resolved modes.
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The yields and average transverse momenta of pions, kaons, and antiprotons produced at the Fermilab p¯p collider at s=300, 540, 1000, and 1800 GeV are presented and compared with data from the energies reached at the CERN collider. We also present data on the dependence of average transverse momentum 〈pt〉 and particle ratios as a function of charged particle density dNcdη; data for particle densities as high as six times the average value, corresponding to a Bjorken energy density 6 GeV/fm3, are reported. These data are relevant to the search for quark-gluon phase of QCD.
PT RANGE FROM 0 TO INFINITY.
PT RANGE FROM 0 TO INFINITY.
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The KS0KS0π0 system has been studied in the exclusive reaction π−p→KS0KS0π0n at 21.4 GeV/c. Evidence for the production of the f1(1285) and the η(1460) is presented. The η(1460) is produced away from minimum momentum transfer in the presence of nonresonant K*K (S-wave) production and phase-space background. The observed mass, width, and decay properties of the η(1460) are consistent with those attributed to the ι(1460) observed in radiative Jψ decay.
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The hadronic production of charmed states was studied in a two-arm spectrometer using a 205-GeV/c negative-pion beam incident upon a beryllium target. One arm, filled with dense absorber, triggered the detectors upon the passage of a muon with a moderate transverse momentum and a total momentum of at least 4 GeV/c. The other arm was an open-geometry magnetic spectrometer which had both neutral- and charged-particle identification capabilities. The apparatus, the data, and an invariant-mass-plot search for evidence of charmed-meson production through several charged-particle decay modes are described. The Kπ, Kππ, and Kπππ mass plots fail to reveal significant D-meson signals. Based upon the Kπ mass plots, the 95%-confidence upper limit on the DD¯ production cross section is found to be less than 51 μb per nucleon for the production models tested. A search for evidence of charged-D* production yields 30±16 combinations above background in association with the expected trigger muon charge. Interpreted as a D* signal, this excess corresponds to a model-dependent inclusive DD¯ production cross section of 34±18−9+14 μb per nucleon. Model-dependent upper limits on the ratio of the F to D cross sections are also presented.
Uncorrelated model for charmed mesons production.
'Correlated' model for pair of charmed mesons production.
Uncorrelated model for D/S+- mesons production.
A coupled channel analysis has been carried out using a new amplitude analysis of the K 0 s K 0 s system produced in the reaction π − p→K 0 s K 0 s n at 22 GeV/ c , which contained about 40 000 new events in the low- t region (| t − t min |<0.1 GeV 2 ). Here only the I G =0 + , J PC =2 ++ amplitude from this analysis is considered, together with available data from other experiments in channels with the same quantum numbers in order to determine which 2 ++ isoscalar mesons have significant pseudoscalar-pseudoscalar couplings. It is found that four poles, f(1270), f'(1525), θ(1690), and f r (1810), are needed, plus a smooth background in order to fit these data; the need for the θ(1690) depends on the J/ψ radiative decay alone, and the f r (1810) is seen only in hadronic production.
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Inclusive cross sections for π 0 , K s 0 , Λ 0 and Λ 0 production in 100, 200 and 360 GeV /c π − p interactions are presented and compared with data at other energies. Invariant cross sections for γ, K s 0 , Λ 0 and Λ 0 production are presented in terms of Feynman x , the rapidity y , and transverse momentum squared, p T 2 . A comparison of the observed γ spectrum is made with the spectra computed assuming that the π 0 momentum distribution is identical to that of the observed π + or π − .
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