We have directly measured the ZZ-gamma and Z-gamma-gamma couplings by studying p pbar --> l+ l- gamma + X, (l = e, mu) events at the CM energy of 1.8$TeV with the D0 detector at the Fermilab Tevatron Collider. A fit to the transverse energy spectrum of the photon in the signal events, based on the data set corresponding to an integrated luminosity of 13.9 pb~-1 ($13.3 pb~-1) for the electron (muon) channel, yields the following 95% confidence level limits on the anomalous CP-conserving ZZ-gamma couplings: -1.9 < h~Z_30 < 1.8 (h~Z_40 = 0), and -0.5 < h~Z_40 < 0.5 (h~Z_30 = 0), for a form-factor scale Lambda = 500 GeV. Limits for the Z-gamma-gamma$ couplings and CP-violating couplings are also discussed.
The anomalous CP-conserving Z Z GAMMA. CONST(NAME=SCALE) is the model parameter, used in the modification of the couplings as follows: h = hi0/(1 + M(gamma Z)**2/CONT(NAME=SCALE)**2)**n. See article for details.
The DO collaboration reports on a search for the Standard Model top quark in pbar-p collisions at Sqrt(s)=1.8TeV at the Fermilab Tevatron, with an integrated luminosity of approximately 50pb-1. We have searched for t-tbar production in the dilepton and single-lepton decay channels, with and without tagging of b-quark jets. We observed 17 events with an expected background of 3.8+/-0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2.0E-6 (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measure its mass to be 199~+19_21 (stat.)+/- 22 (syst.)GeV/c**2 and its production cross section to be 6.4 +/- 2.2 pb.
Cross section refers to top quark mass equal 199. (+19, -21, +- 22) GeV.
The decay τ−→π−−+vτ has been studied using data collected with the OPAL detector at LEP during 1992 and 1993. The hadronic structure functions for this decay are measured model independently assuming G-parity invariance and neglecting scalar currents. Simultaneously the parity violating asymmetry parameter is determined to be\(\gamma VA = 1.08 _{ - 0.41- 0.25}^{ + 0.46+ 0.14} \), consistent with the Standard Model prediction of γVA=1 for left-handed tau neutrinos. Models of Kühn and Santamaria and of Isgur et al. are used to fit distributions of the invariant 3π mass as well as 2π mass projections of the Dalitz plot. The model dependent mass and width of thea1 resonance are measured to be\(m_{a_1 }= 1.266 \pm 0.014_{ - 0.002}^{ + 0.012} \) GeV and\(\Gamma _{a_1 }= 0.610 \pm 0.049_{ - 0.019}^{ + 0.053} \) GeV for the Kühn and Santamaria model and\(m_{a_1 }= 1.202 \pm 0.009_{ - 0.001}^{ + 0.009} \) GeV and\(\Gamma _{a_1 }= 0.422 \pm 0.023_{ - 0.004}^{ + 0.033} \) GeV for the Isgur et al. model. The model dependent values obtained for the parity violating asymmetry parameter are γVA=0.87±0.27−0.06+0.05 for the Kühn and Santamaria model and γVA=1.10±0.31−0.14+0.13 for the Isgur et al. model. Within the Isgur et al. model the ratio of theS-andD-wave amplitudes is measured to beD/S=−0.09±0.03±0.01.
See paper for definition of four weak decay formfactors : wa, wc, wd, we. For TAU+-.
Here ASYM is parity violating asymmetry parameter gamma_VA = 2g_v*g_A/(g_v **2+g_A**2) (see paper).
Using about 950000 hadronic events collected during 1991 and 1992 with the ALEPH detector, the ratios r b = α s b α s udsc and r uds = α s uds α s cb have been measured in order to test the flavour independence of the strong coupling constant α s . The analysis is based on event-shape variables using the full hadronic sample, two b -quark samples enriched by lepton tagging and lifetime tagging, and a light-quark sample enriched by lifetime antitagging. The combined results are r b = 1.002±0.023 and r uds = 0.971 ± 0.023.
No description provided.
We have observed five new decay modes of the charmed baryon Λc+ using data collected with the CLEO II detector. Four decay modes, Λc+→pK¯0η, Ληπ+, Σ+η, and Σ*+η, are first observations of final states with an η meson, while the fifth mode, Λc+→ΛK¯0K+, requires the creation of an ss¯ quark pair. We measure the branching fractions of these modes relative to Λc+→pK−π+ to be 0.25±0.04±0.04, 0.35±0.05±0.06, 0.11±0.03±0.02, 0.17±0.04±0.03, and 0.12±0.02±0.02, respectively.
Integrated luminosity of 3.25 fb-1 have used, which corresponds to about 4 million C CBAR events.. Here X=P(LAMBDA/C)/sqrt(Ebeam**2-M(LAMBDA/C)**2).
Integrated luminosity of 3.25 fb-1 have used, which corresponds to about 4 million C CBAR events.. Here X=P(LAMBDA/C)/sqrt(Ebeam**2-M(LAMBDA/C)**2).
Integrated luminosity of 3.25 fb-1 have used, which corresponds to about 4 million C CBAR events.. Here X=P(LAMBDA/C)/sqrt(Ebeam**2-M(LAMBDA/C)**2).
Inclusive π±, K± and\((p,\bar p)\) differential cross-sections in hadronic decays of the Z have been measured as a function ofz=Phadron/Pbeam, the scaled momentum. The results are based on approximately 520 000 events measured by the ALEPH detector at LEP during 1992. Charged particles are identified by their rate of ionization energy loss in the ALEPH Time Projection Chamber. The position, ξ*, of the peak in the ln(1/z) distribution is determined, and the evolution of the peak position with centre-of-mass energy is compared with the prediction of QCD.
No description provided.
No description provided.
No description provided.
We have studied the production of D*± mesons in a sample of 1.25 million multihadronic decays of the Z0, in which 1969 candidates have been identified. We have determined the total multiplicity of charged D* mesons in multihadronic Z0 decays to be
No description provided.
Multiplicity data uncorrected for decay branching ratios.
No description provided.
Using data collected by the CLEO II detector, we have observed two states decaying to Λc+π+π−. Relative to the Λc+, their mass splittings are measured to be +307.5±0.4±1.0 and +342.2±0.2±0.5MeV/c2, respectively; this represents the first measurement of the less massive state. These two states are consistent with being orbitally excited, isospin zero Λc+ states.
CONST(NAME=EPS) is the parameter of the Peterson fragmentation function (C.Peterson et al., PR D27, 105 (1983)) D(N)/D(Z) = FD(Z) = const * (1/Z)*1/(1 - (1/Z)-CONST(NAME=EPS)/(1-Z))**2. Charged conjugated states are understood.
Charged conjugated states are understood.
Charged conjugated states are understood.
The transverse-longitudinal asymmetry ATL′ in He→3(e→, e′) quasielastic scattering at momentum transfer Q2=0.14 (GeV/c)2 has been measured to be 1.52 ± 0.55(stat) ± 0.15(syst)%. The plane wave impulse approximation (PWIA) prediction for this measurement ranges from 2.1% to 2.9%, where the variation is due to uncertainty in the initial state wave function, nucleon form factors, and off-shell prescription. The data may suggest a suppression with respect to the PWIA, which has also been observed for the unpolarized longitudinal response function.
QUASIELASTIC REACTION.
Using the CLEO II detector at CESR, we have observed two charmed states, where the higher mass state decays to D 0 π + and to D ∗0 π + , while the lower mass state decays to D ∗0 π + , but not to D 0 π + . The masses and widths were measured to be 2425±2±2 MeV/c 2 and 26 −7−4 +8+4 MeV/c 2 for the lower mass state, and 2463±3±3 MeV/c 2 and 27 −8−5 +11+5 MeV/c 2 for the higher mass state. Properties of these states, including their decay angular distributions and spin-parity assignments have been studied. The results of this analysis support the identification of these states as the charged L = 1 D 1 (2420) + and D 2 ∗ (2460) + , respectively. The isospin mass splittings between these states and their neutral partners have also been measured. This is the first full reconstruction of any decay mode of the D 1 (2420) + and the first observation of the decay of D 2 ∗ (2460) + to D ∗0 π + .
CONST(NAME=EPS) is the parameter of the Peterson fragmentation function (C.Peterson et al., PR D27, 105 (1983)) D(N)/D(Z) = FD(Z) = const * (1/Z)*1/(1 - (1/Z)-CONST(NAME=EPS)/(1-Z))**2. Charged conjugate states are undestood.
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