We present measurement of the π0γ*γ, ηγ*γ and η′γ*γ form factors. The π0-form factor is for the first time observed in the space-like region. The transition form factor of the η-meson is determined from its decay modes π+π−π0, π+π−γ and the neutral decay mode γγ. The decay of the η′ is observed in the decay channels ργ, ηπ+π− with η→γγ and in the four charged prong final state stemming from ηπ+π− with the η decaying into π+π−(π0/γ). All form factors agree well with a simple ρ-pole predicted by the vector meson dominance model and also with the QCD inspired Brodsky-Lepage model.
No description provided.
No description provided.
No description provided.
We have searched for resonance production in the reaction γγ→Ks0Kπ. No signal was found for theηc and an upper limit for the radiative with\(\Gamma _{\gamma \gamma }^{\eta _c } \) keV (95% c.l.) is obtained. For the glueball candidate η(1440) (previouslyi) the upper limit\(\Gamma _{\gamma \gamma }^{\eta (1440)} B(\eta (1440) \to K\bar K\pi )< 1.2keV(95\% c.l.)\) is derived. In the tagged data sample resonance formation of a spin 1 state at 1420 MeV is observed, which is absent in the untagged data. The mass and width of this state are consistent with those of thef1(1420); an analysis of decay angular distributions favours positive parity.
Data read from graph.. Additional overall systematic error decreasing from 25% in the lowest mass bins to 15% for M > 2.0 GeV.
In the reaction γγ→KS0KS0 resonance production of thef2− is observed. For the radiative with\(\Gamma _{\gamma \gamma } .B(f'_2\to K\bar K) = 0.11_{ - 0.02}^{ + 0.03}\pm 0.02keV\) is found. The small number of events in thef2,a2 mass region is consistent with the assumption of destructivef2−a2 interference. From the mass distribution we determine the relative phases between the tensor mesons. Upper limits on the radiative widths of the glueball candidatesf2(1720) andX (2220) are derived.
Only bins containing events are included, all others are zero.. Untagged plus single events.. Data read from graph.
Only bins containing events are included, all others are zero.. Untagged events.. Data read from graph.
Corrected for the angular distribution, which is assumed to be sin(theta)**4. Additional systematic error decreasing from 20% in the lowest mass bins to 15% for W > 1.5 GeV.. Data read from graph.
Using the CELLO detector, we have measured cross sections for the processγγ→π+π− in the mass range 0.75–1.9 GeV/c2. A partial wave fit to the data indicates the presence of a sizeableS-wave amplitude with signs of resonant behaviour. Values for the γγ width of thef2(1270) are given, showing the model-dependence of this quantity. At higher dipion masses, the model of Brodsky and Lepage is found to give an order of magnitude description of the data.
No description provided.
No description provided.
Differential cross section data of the CELLO experiment on pair production of muons, taus, and heavy quarks ine+e−-annihilation are presented and analysed, together with our data on Bhabha scattering, in terms of compositeness effects characterized by the mass scale Λ. We discuss difficulties in the combination of limits Λ from different experiments. The appropriate parameter to combine different results turns out to be ɛ=±1/Λ2, which is in contrast to Λ Gaussian distributed.
Errors are combined statistics and systematics.
Errors are combined statistics and systematics.
Errors are combined statistics and systematics.
We have studied the properties of pion production in the reaction γ →3 π + 3 π − in the energy range 1.6⩽ W γγ ⩽7.5 GeV with the CELLO detector at PETRA. We present the topological cross section both for Q 2 ≈0 (anti-tag) and Q 2 ≈0 (single-tag). The Q 2 dependence of the cross section is flatter than the GVDM prediction. The distribution of the production angle of the pions in the CMS peaks at small angles, indicating a peripheral process. In accordance with the VDM picture the p T distribution of the pions manifests an exponential fall-off. Like sign pion pairs were found to be Bose-Einstein correlated. We use this correlation to estimate the spatial dimensions of the interaction region.
No description provided.
No description provided.
No description provided.
The reaction e + e − → τ + τ − has been studied at centre of mass energies between 14.0 and 46.8 GeV with the CELLO detector at the PETRA e + e − collider. We present results for the cross section σ τ and the charge asymmetry A τ . The results are in good agreement with the standard model. We have also measured the topological decay rates BR 1 , BR 3 and BR 5 for the inclusive decay of the τ lepton into one, three and five charge particles. The results confirm and improve earlier CELLO measurements at other energies. We find for the combined values at all energies BR 1 = (84.9 ± 0.4 ± 0.3)%, BR 3 = (15.0 ± 0.4 ± 0.3)% and BR 5 = (0.16 ± 0.13 ± 0.04)%.
No description provided.
No description provided.
Corrected for radiative effects and background contributions.
We have studied the ρ0 production rate in the reaction ξξ→3π+3π− in the energy range 1.6≦Wγγ≦7.5 GeV with the CELLO detector at PETRA. Our analysis points to a substantial yield of ρ0ρ0π+π− events in particular atWγγ>4.0 GeV. We give cross sections for the ρ02π+2π− and ρ0ρ0π+π− final states and calculate upper limits for the reaction γγ→ρ0ρ0 (1700) →ρ0ρ0π+π−.
Data from CA model analysis.
Data from NCA model analysis.
Upper limits to RHO0 RHO(1700)0 cross section with 95 pct confidence limits. Data read from graph.
The production ofb andc quarks ine+e− annihilation has been studied with the CELLO detector in the range from 35 GeV up to the highest PETRA energies. The heavy quarks have been tagged by their semileptonic decays. The charge asymmetries forb quarks at 35 and 43 GeV have been found to beAb=−(22.2±8.1)% andAb=−(49.1±16.5)%, respectively, using a method incorporating jet variables and their correlations for the separation of the heavy quarks from the back ground of the lighter quarks. Forc quarks we obtainAc=−(12.9±8.8)% andAc=+(7.7±14.0)%, respectively. The axial vector coupling constants of the heavy quarksc andb are found to beac=+(0.29±0.46) andab=−(1.15±0.41) taking\(B^0 \overline {B^0 } \) mixing into account. The results are in agreement with the expectations from the standard model.
BOTTOM quark charge asymmetry.
CHARMED quark charge asymmetry.
We present an analysis of strange particle production frome+e− annihilation into multihadronic final states. The experiment was performed with the CELLO detector at the PETRA storage ring at DESY, the data was taken at a centre of mass energy of 35 GeV with an integrated luminosity of 86 pb−1. The particlesKS0,K*± and Λ have been identified by their characteristic decays, and differential cross sections for their production have been obtained. From a comparison ofKS0 andK*± rates the Lund vector meson suppression parameterV/(V+P)S has been determined.
Errors are statistical only.
Errors are statistical only.
Errors are statistical only.
Results on the reaction γγ → π + π − π 0 π 0 are presented. There is clear evidence for correlated ϱ + ϱ − production. The cross section is much lower than for γγ → ϱ 0 ϱ 0 .
Results using 3 parameter fit (rho+ rho-, rho+- pi+- pi0, and non-resonant 4pi) to data.
Results using 2 parameter fit (rho+ rho-, and non-resonant 4pi) to data.
We have measured the inclusive production of γ, π0 and η ine+e− annihilation at the center of mass energy of 35 GeV. The differential cross sections, extended to the kinematical limit and measured with high accuracy, are found to be in good agreement with previously reported results. Using the measured spectra we determine the average multiplicity for each of these particle species.
No description provided.
Statistical errors only.
Statistical errors only.
A search for single photons, produced in e + e − collisions together with particles interacting only weakly with matter, has been performed using the CELLO detector at the PETRA storage ring. We report on results from data taken at 35 GeV < √ s <46.57 GeV. An upper limit of 8.7 (90% CL) on the number of light neutrino species is set. Combining our result with published results from other e + e − experiments the number of light neutrinos is limited to N v < 4.6 at 90% CL. We also set lower limits on the masses of supersymmetric particles.
TWO RUN AT DIFFERENT ENERGIES COMBINED, 1.26 EVENTS WAS FOUND.
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.
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.
Hadronic events obtained with the CELLO detector at PETRA were compared with first-order QCD predictions using two different models for the fragmentation of quarks and gluons, the Hoyer model and the Lund model. Both models are in reasonable agreement with the data, although they do not completely reproduce the details of many distributions. Several methods have been applied to determine the strong coupling constant α S . Although within one model the value of α S varies by 20% among the different methods, the values determined using the Lund model are 30% or more larger (depending on the method used) than the values determined with the Hoyer model. Our results using the Hoyer model are in agreement with previous results based on this approach.
DATA CORRECTED WITH HOYER MODEL (ALPHA-S=0.15).
DATA CORRECTED WITH LUND MODEL (ALPHA-S=0.25).
No description provided.
Hadronic events obtained with the CELLO detector at PETRA are compared with second order QCD predictions using different models for the fragmentation of quarks and gluons into hadrons. We find that the model dependence in the determination of the strong coupling constant persists when going from first to second order QCD calculations.
ASYMMETRY FOR DATA CORRECTED WITH IF MODEL (ALPHA-S=0.12).
ASSYMETRY FOR DATA CORRECTED WITH SF MODEL (ALPHA-S=0.19).
No description provided.
A search for multihadronic events produced with two energetic leptons has been performed at PETRA using 130 pb −1 accumulated by the CELLO detector at 35 GeV ⩽ √ s ⩽46.8 GeV. Three μ + μ − , eleven e + e − and three eμ events were observed. The mesured yields an dthe event characteristics are in good agreement with the expectation for the α 4 QED processes e + e − → ℓ + ℓ − q q and from semileptonic decays of pairs of heavy quarks.
No description provided.
The reactions e + e − →γγγ and e + e − →γγγγ have been studied at center-of-mass energies between 35 and 46.8 GeV with an integrated luninosity of about 130 pb −1 accumulated with the CELLO detector at PETRA. The measurements are compared to QED calculations up to third and fourth orders of perturbation theory. Excellent agreement is observed.
No description provided.
The e + e − → μ + μ − reaction has been studied at centre of mass energies ranging between 38.3 abd 46.8 GeV with the CELLO detector at PETRA. We present results on the cross section and the charge asymmetry for this channel. Combining all the data at the average energy 〈 s 〉=43 GeV we obtain R μμ =〈 σ μμ / σ 0 〉=0.98±0.04±0.04, 〈 A μμ 〉=(−14.1±3.7±1.0)%, where σ 0 is the QED cross section and A μμ is the charge asymmetry corrected for pure radiative effects. These results are in good agreement with the expected values of R μμ =1.01 and A μμ =−14.5% at that energy.
Mu-pair cross sections.
Corrected angular distributions with data sample divided into two energy regions with means 39 and 44 GeV and total energy region.
Forward-backward asymmetry.
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.
We have measured the total normalized cross section R for the process e + e − → hadrons at centre-of-mass energies between 14.0 and 46.8 GeV based on an integrated luminosity of 60.3 pb −1 . The data are well described by the standard SU(3) c ⊗SU(2) L ⊗U(1) model with the production of the five known quarks. No open production of a sixth quark with charge 2/3 or 1/3 occurs below a centre-of-mass energy of 46.6 or 46.3 GeV, respectively. A fitting procedure which takes the correlations between measurements into account was used to determine the electroweak mixing angle sin 2 θ w and the strong coupling constant α s ( S ) in second-order QCD. We applied this procedure to the CELLO data and in addition included the data from other experiments at PETRA and PEP. Both fits give consistent results. The fit to the combined data yields α s (34 2 GeV 2 ) = 0.165±0.030, and sin 2 θ w = 0.236±0.020. Fixing sin 2 θ w at the world average value of 0.23 yields α s (34 2 GeV 2 ) = 0.169±0.025.
No description provided.
No description provided.
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.
No description provided.
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.
Differential cross sections fore+e−→e+e−, τ+, τ- measured with the CELLO detector at\(\left\langle {\sqrt s } \right\rangle= 34.2GeV\) have been analyzed for electroweak contributions. Vector and axial vector coupling constants were obtained in a simultaneous fit to the three differential cross sections assuming a universal weak interaction for the charged leptons. The results,v2=−0.12±0.33 anda2=1.22±0.47, are in good agreement with predictions from the standardSU(2)×U(1) model for\(\sin ^2 \theta _w= 0.228\). Combining this result with neutrino-electron scattering data gives a unique axial vector dominated solution for the leptonic weak couplings. Assuming the validity of the standard model, a value of\(\sin ^2 \theta _w= 0.21_{ - 0.09}^{ + 0.14}\) is obtained for the electroweak mixing angle. Additional vector currents are not observed (C<0.031 is obtained at the 95% C.L.).
No description provided.
Combined MU and TAU asymmetry. See PL 114B(1982)282 (<a href=http://durpdg.dur.ac.uk/scripts/reacsearch.csh/TESTREAC/red+1234> RED = 1234 </a>) and ZP C14(1982)283 (<a href=http://durpdg.dur.ac.uk/scripts/reacsearch.csh/TESTREAC/red+1245> RED = 1245 </a>) for individual asymmetry measurements.
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.
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.
The reaction (e+e−→μ+μ−) has been measured between\(\sqrt S= 14.0\) and\(\sqrt S= 36.4\). The total cross section result is in good agreement with the QED prediction and the following Λ values have been obtained:Λ+=186 GeV,Λ−=101 GeV. The angular distribution at high energy (\(\left( {\left. {\left\langle {\sqrt S } \right.} \right\rangle= 34.2 GeV} \right)\)) shows a fitted charge asymmetry of −0.064±0.064 in agreement with theW-S model prediction of −0.092, corresponding to an axial coupling parametera2=4ga2=0.69±0.69.
No description provided.
No description provided.
Errors include contribution from systematics. Result based on fit(1 + cos(theta)**2 + q cos(theta)) to corrected angular distribution.
Measurements of energy weighted angular correlations in electron positron annihilations at c.m. energies of 22 GeV and 34 GeV are presented.
ENERGY-ENERGY CORRELATIONS FOR FINAL STATE PARTICLES.
ENERGY-ENERGY CORRELATIONS FOR PRIMORDIAL HADRONS.
ASSYMETRY IN ENERGY CORRELATIONS FOR FINAL STATE PARTICLES.
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 production of thef0 in two photon collisions, with the subsequent decayf0→π+π− has been observed in the CELLO detector at PETRA. Thef0 peak was found to lie on a dipion continuum and to be shifted downwards in mass by ≃50 MeV/c2. The ππ mass spectrum from 0.8 to 1.5 GeV/c2 was well fitted by the model of Mennessier using only a unitarised Born amplitude and helicity 2f0 amplitude. The previously observed mass shift and distortion of thef0 peak are explained by strong interference between the Born andf0 amplitudes. The only free parameter in the fit of the data to the model is the radiative widthΓγγ(f0). It was found that:Γγγ(f0)=2.5±0.1±0.5 keV where the first (second) quoted errors are statistical (systematic).
Data read from graph.
Data read from graph.
We have determined the cross section for γγ→π+π+π−π− in a way free of assumptions about the relative contributions fromρ0ρ0,ρ02π and 4π (uncorrelated phase space). We find a sharp onset above threshold and a rather high cross section of about 200 nb aroundWγγ=1.5 GeV which consists to about 40% ofρ0ρ0 production with sizeable contributions fromρ02π and 4π (PS). The total cross section as well as theρ0ρ0 content fall rather fast at higher c.m. energies. Attempts to explain this behaviour in terms of production of known resonances are not successful so far. The angular distributions do not show any significant structure pointing to resonance formation in the 4π-system. Only theρ0-meson is observed in the moment analysis. The decay distributions of theρ0 for forward produced rhos are fairly consistent with helicity conservation of the produced rhos in accordance with the VDM picture.
No description provided.
RESULTS OF DECOMPOSITION OF THE CROSS SECTION INTO RHO RHO, RHO 2PI, AND 4PI(PHASE SPACE) USING TWO WIDE W BINS. SEE TEXT OF PAPER FOR DISCUSSION OF FITS.
RESULTS OF DECOMPOSITION OF THE CROSS SECTION INTO THE RHO RHO, RHO PI, AND 4PI (PHASE SPACE) USING SMALL W BINS. SEE TEXT OF PAPER FOR DISCUSSION OF FITS.
The photonic part of multihadronice+e− annihilation events has been analyzed at a c.m. energy of 34 GeV. The photonic energy fraction per event is determined to befγ=0.251±0.003 (stat.) ±0.04 (syste.). The neutral and charged components of the events are analyzed separately revealing close similarity in thrust axis directions and momentum distributions in agreement with the hypothesis that most photons result from π0 decay. π0's are reconstructed separately and used to determine the inclusive cross section. Comparing these cross sections with lower energy data from SPEAR we find some indication for scaling violation.
No description provided.
No description provided.
We have measured the scale invariant inclusive photon and π0 cross sections atW=14, 22 and 34 GeV. A comparison with π± data shows no significant difference between neutral and charged pion production. Comparing the integrated cross sections in thex range 0.15<x<1.0 we observe a considerable decrease from 14 GeV to 34 GeV with a statistical significance of 1.5 standard deviations. This is compatible with the expectations for scaling violations from QCD.
NUMERICAL VALUES OF DATA SUPPLIED BY H. OBERLACK.
NUMERICAL VALUES OF DATA SUPPLIED BY H. OBERLACK.
NUMERICAL VALUES OF DATA SUPPLIED BY H. OBERLACK.
None
CONTINUOUS COVERAGE OF THREE ENERGY RANGES (33.00 TO 33.80, 34.00 TO 35.26 AND 36.08 TO 36.72 GEV PLUS SEVEN ADDITIONAL DATA POINTS AROUND 35.7 GEV).
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