An experimental investigation of the reaction γ p → p p p at photon energies 4.7 ⩽ E γ ⩽ 6.6 GeV is described. The main results are the measurement of the cross section as a function of energy, a discussion of the main dynamical features of the reaction and the observation of a narrow p p mass state at 2.024 ± 0.005 GeV with a width of 29 ± 13 MeV.
OBSERVATION OF THIS CHANNEL AS A CONSISTENCY CHECK ON THE NORMALIZATION.
No description provided.
MEASUREMENTS OF CROSS SECTIONS OF MASS SIGNALS AT 1.94 AND 2.024 GEV, EVALUATE BY FITTING TWO BREIT WIGNERS AND CONSTANT BACKGROUND TO (AP P) MASS SPECTRUM. ERRORS ARE STATISTICAL ONLY.
Cross section and pp¯ in variant mass distribution of the reaction γp→pp¯p are presented. Further evidence for a narrow pp¯ mass state at 2.023 GeV will be given.
Axis error includes +- 0.0/0.0 contribution (?////SYSTEMATIC ERRORS HAVE BEEN FOLDED IN QUADRATURE WITH STATISTICAL ERRORS).
Axis error includes +- 0.0/0.0 contribution (?////SYSTEMATIC ERRORS HAVE BEEN FOLDED IN QUADRATURE WITH STATISTICAL ERRORS).
Axis error includes +- 0.0/0.0 contribution (?////SYSTEMATIC ERRORS HAVE BEEN FOLDED IN QUADRATURE WITH STATISTICAL ERRORS).
We have studied the reactions e + e − → e + e − , e + e − → γγ , e + e − → μ + μ − , and e + e − → τ + τ − in the centre-of-mass (CM) energy range from 39.8 to 45.2 GeV using the CELLO detector at PETRA. Upper limits on the partial widths for new spin 0 bosons with masses both within and above the energy range covered are determined. No evidence for contributions of such new particles has been observed up to the highest PETRA energies in a model independent way. Under the assumptions of recently suggested models relating the existence of spin 0 bosons to the radiative width Γ τ of the Z 0 we exclude such bosons at the 95% confidence level for masses below the Z 0 -mass if Γ τ > 20 MeV.
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Figure actually gives the 95 PCT CL upper limits of the coupling constants for each process as a function of the mass of the intermediate spin zero boson.
The total e + e − annihilation onto hadron has been measured at CM energies between 33.00 and 36.72 GeV and between 38.66 and 46.78 GeV in steps of 20 and 30 MeV respectively. The average of the ratio R = σ ( e + e − → hadrons )/ σ is 〈 R 〉=3.85±0.12 and 〈 R 〉=4.04±0.10 for the two energy ranges. The systematic error on 〈 R 〉 is 0.31. Both values are consistent with the expectation for the known coloured quarks u, d, s, c and b. No evidence was found for the production of new quarks. If the largest fluctuation in R is interpreted as a narrow resonance, it corresponds to a product of the electronic width and the hadronic branching ratio Γ ee B had >2.9 keV at the 95% confidence level, well below the value expected for the toponium vector ground state with charge 2 3 e . The observed number of aplanar final states rules out the continuum production of a a new heavy flavour with pointlike cross section up to a CM energy of 45.4 GeV for a quarck charge of 1 3 e . and up to 46.6 GeV for 2 3 e at the 95% confidence level.
ENERGY SCANS IN 20(30) MEV STEPS.
No description provided.
The e + e − → τ + τ − process has been measured using the CELLO detector at a mean total centre of mass energy of 34.2 GeV using essentially all the decay channels of the τ lepton. The measured cross section yields R τ =1.03±0.05 (stat)±0.07 (syst). Topological branching fraction are given for τ → 1, 3 or 5 charged tracks. The angular distribution shows a clear 1 + cos 2 θ dependance with a forward-backward asymmetry of -0.103 ± 0.052 corresponding to an axial-vector coupling a τ of the τ to the weak neutral current given by a τ =−1.12 ± 0.57.
No description provided.
No description provided.
Forward-backward asymmetry based on 1 + (cos(theta))**2 + bcos(theta) fit for angular distribution.
The differential cross sections of the reactions e + e − → e + e − and e + e − → λλ are measured at energies between 33.0 and 36.7 GeV. The results agree with the predictions of quantum electrodynamics. A comparison with the standard model of electroweak interaction yields sin 2 θ W = 0.25 ± 0.13.
No description provided.
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Using both charged and neutral components, 2600 multihadronic e + e − annihilation events, recorded at 34 GeV by the CELLO detector at PETRA, have been analysed in a calometric approach. The fraction of energy carried by gamma rays is measured to be f γ = (26.0 ± 0.4 (stat) ± 4.0 (syst)%. The neutral energy flow is seen to follow closely the overall energy flow. From the corrected oblateness distribution, a first order determination of α s is performed. The result is α s = 0.16 ± 0.01 (stat) ± 0.03 (syst).
No description provided.
The topology of hadronic e + e − annihilation events has been analysed using the sphericity tensor and a cluster method. Comparison with quark models including gluon bremsstrahlung yields good agreement with the data. The strong-coupling constant is determined in 1st order QCD to be α S =0.19±0.04 (stat) ± 0.04 (syst.) at 22 GeV and α S =0.16 ±0.02± 0.03 at 34 GeV. The differential cross section with respect to the energy fraction carried by the most energetic parton agrees with the prediction of QCD, but cannot be reproduced by a scalar gluon model. These results are stable against variations of the transverse momentum distribution of the fragmentation function within the quoted errors.
No description provided.
We have measured at PETRA the process e γ → e + hadrons at an average Q 2 value of 9 GeV 2 / c 2 . The total number of observed events attributed to this process is 215. Our data are compared to calculations based on the estimation of the photon structure function F 2 in the quark parton model and in QCD.
No description provided.
Two photon final states in e + e − annihilation have been analyzed at CM energies around 34 GeV. Good agreement with QED is observed. Lower limits for the QED cutoff parameters of Λ + > 59 GeV and Λ - > 44 GeV are determined. A search for two photons with missing energy yields an upper limit for the production of neutral particles which decay into a photon and a non-interacting particle. Constraints on the mass and the coupling strength of supersymmetric photinos are discussed.
Cross section for ABS(cos(theta)) <0.85.
No description provided.
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