The parity-violating asymmetries between a longitudinally-polarized electron beam and an unpolarized deuterium target have been measured recently. The measurement covered two kinematic points in the deep inelastic scattering region and five in the nucleon resonance region. We provide here details of the experimental setup, data analysis, and results on all asymmetry measurements including parity-violating electron asymmetries and those of inclusive pion production and beam-normal asymmetries. The parity-violating deep-inelastic asymmetries were used to extract the electron-quark weak effective couplings, and the resonance asymmetries provided the first evidence for quark-hadron duality in electroweak observables. These electron asymmetries and their interpretation were published earlier, but are presented here in more detail.
Asymmetry results on $\vec e-^2$H parity-violating scattering from the PVDIS experiment at JLab.
Asymmetry results on $\vec e-^2$H parity-violating scattering from the PVDIS experiment at JLab, for RES I settings.
Asymmetry results on $\vec e-^2$H parity-violating scattering from the PVDIS experiment at JLab, for RES II settings.
We report on measurements of hadronic and leptonic cross sections and leptonic forward-backward asymmetries performed with the L3 detector in the years 1993-95. A total luminosity of 103 pb^-1 was collected at centre-of-mass energies \sqrt{s} ~ m_Z and \sqrt{s} ~ m_Z +/- 1.8 GeV which corresponds to 2.5 million hadronic and 245 thousand leptonic events selected. These data lead to a significantly improved determination of Z parameters. From the total cross sections, combined with our measurements in 1990-92, we obtain the final results: m_Z = 91189.8 +/- 3.1 MeV, Gamma_Z = 2502.4 +/- 4.2 MeV, Gamma_had = 1741.1 +/- 3.8 MeV, Gamma_l = 84.14 +/- 0.17 MeV. An invisible width of Gamma_inv = 499.1 +/- 2.9 MeV is derived which in the Standard Model yields for the number of light neutrino species N_nu = 2.978 +/- 0.014. Adding our results on the leptonic forward-backward asymmetries and the tau polarisation, the effective vector and axial-vector coupling constants of the neutral weak current to charged leptons are determined to be \bar{g}_V^l = -0.0397 +/- 0.0017 and \bar{g}_A^l = -0.50153 +/- 0.00053.Including our measurements of the Z -> b \bar{b} forward-backward and quark charge asymmetries a value for the effective electroweak mixing angle of sin^2\bar{\theta}_W = 0.23093 +/- 0.00066 is derived. All these measurements are in good agreement with the Standard Model of electroweak interactions. Using all our measurements of electroweak observables an upper limit on the mass of the Standard Model Higgs boson of m_H < 133 GeV is set at 95% confidence level.
Updated values of coupling constants and electroweak mixing angle.
Cross sections for hadron production from the 1993 data. The first DSYS error is the uncorrelated part of the systematic error. The second DSYS error is from the statistical error on the absolute luminosity. In addition there is a fully correlated multiplicative contribution to the systematic error of 0.039 PCT plus an absolute uncertainty of 3.2pb together with an additional error from the absolute luminosity of 0.105 PCT.
Cross sections for hadron production from the 1994 data. The first DSYS error is the uncorrelated part of the systematic error. The second DSYS error is from the statistical error on the absolute luminosity. In addition there is a fully correlated multiplicative contribution to the systematic error of 0.039 PCT plus an absolute uncertainty of 3.2pb together with an additional error from the absolute luminosity of 0.088 PCT.
Multiplicities in semi-inclusive deep-inelastic scattering are presented for each charge state of \pi^\pm and K^\pm mesons. The data were collected by the HERMES experiment at the HERA storage ring using 27.6 GeV electron and positron beams incident on a hydrogen or deuterium gas target. The results are presented as a function of the kinematic quantities x_B, Q^2, z, and P_h\perp. They represent a unique data set for identified hadrons that will significantly enhance our understanding of the fragmentation of quarks into final-state hadrons in deep-inelastic scattering.
pi+ multiplicities from HERMES, Target: H, Target: D, VM subtracted.
pi- multiplicities from HERMES, Target: H, Target: D, VM subtracted.
K+ multiplicities from HERMES, Target: H, Target: D, VM subtracted.
We present a measurement of the longitudinal spin asymmetry A_|| in photoproduction of pairs of hadrons with high transverse momentum p_T. Data were accumulated by the HERMES experiment using a 27.5 GeV polarized positron beam and a polarized hydrogen target internal to the HERA storage ring. For h+h- pairs with p_T^h_1 > 1.5 GeV/c and p_T^h_2 > 1.0 GeV/c, the measured asymmetry is A_|| = -0.28 +/- 0.12 (stat.) +/- 0.02 (syst.). This negative value is in contrast to the positive asymmetries typically measured in deep inelastic scattering from protons, and is interpreted to arise from a positive gluon polarization.
Asymmetry measurement with a PT cut of 1.5 GeV on the hadron with the higher PT, and 1.0 GeV on the hadron with the lower PT.
Precise measurements of the spin structure functions of the proton $g_1^p(x,Q^2)$ and deuteron $g_1^d(x,Q^2)$ are presented over the kinematic range $0.0041 \leq x \leq 0.9$ and $0.18 $ GeV$^2$ $\leq Q^2 \leq 20$ GeV$^2$. The data were collected at the HERMES experiment at DESY, in deep-inelastic scattering of 27.6 GeV longitudinally polarized positrons off longitudinally polarized hydrogen and deuterium gas targets internal to the HERA storage ring. The neutron spin structure function $g_1^n$ is extracted by combining proton and deuteron data. The integrals of $g_1^{p,d}$ at $Q^2=5$ GeV$^2$ are evaluated over the measured $x$ range. Neglecting any possible contribution to the $g_1^d$ integral from the region $x \leq 0.021$, a value of $0.330 \pm 0.011\mathrm{(theo.)}\pm0.025\mathrm{(exp.)}\pm 0.028$(evol.) is obtained for the flavor-singlet axial charge $a_0$ in a leading-twist NNLO analysis.
Integrals of G1 for P, DEUT and N targets.. The second DSYS systematic error is due to the uncertainty in the parameterizations (R, F2, A2, Azz, omegaD).. The third DSYS systematic error is due to the uncertainty in evolving to a common Q**2.
Integrals of G1 for the Non-Singlet contributions.. The second DSYS systematic error is due to the uncertainty in the parameterizations (R, F2, A2, Azz, omegaD).. The third DSYS systematic error is due to the uncertainty in evolving to a common Q**2. Axis error includes +- 5.2/5.2 contribution.
Integrals of G1 over different X ranges for P target at various Q*2 values. The second DSYS systematic error is due to the uncertainty in the parameterizations (R, F2, A2, Azz, omegaD).. The third DSYS systematic error is due to the uncertainty in evolving to a common Q**2. Axis error includes +- 5.2/5.2 contribution.
A measurement of the beam-spin asymmetry in the azimuthal distribution of pions produced in semi-inclusive deep-inelastic scattering off protons is presented. The measurement was performed using the {HERMES} spectrometer with a hydrogen gas target and the longitudinally polarized 27.6 GeV positron beam of HERA. The sinusoidal amplitude of the dependence of the asymmetry on the angle $\phi$ of the hadron production plane around the virtual photon direction relative to the lepton scattering plane was measured for $\pi^+,\pi^-$ and $\pi^0$ mesons. The dependence of this amplitude on the Bjorken scaling variable and on the pion fractional energy and transverse momentum is presented. The results are compared to theoretical model calculations.
Beam SSA as a function of Z, X, hadronic PT and Q**2.
Beam SSA as a function of Z, X, hadronic PT and Q**2.
Beam SSA as a function of Z, X, hadronic PT and Q**2.
We have performed a high-statistics measurement of Bhabha scattering and of the production of hadrons in electron-positron annihilation at PETRA energies (12 GeV<~s<~36.7 GeV). Combining the results with measurements of μ+μ− and τ+τ− production enables us to compare our results with electroweak theory. We find sin2θw=0.27±0.08. This is in good agreement with the value obtained from neutrino experiments which were carried out in entirely different kinematic regions.
No description provided.
No description provided.
ASYMMETRY WAS USED.
The differential cross sections for lepton pair production in e+e− annihilation at 29 GeV have been measured and found to be in good agreement with the standard model of the electroweak interaction. With the assumption of e−μ−τ universality, the weak neutral-current couplings are determined to be ga2=0.23±0.05 and gv2=0.03±0.04.
Numerical values supplied by M.Levi.
Data requested from authors.
Extrapolated to full angular range.
By combining results from the MARK-J at PETRA on Bhabha scattering, μ + μ - and τ + τ - production with recent world data from neutrino-electron scattering experiments, we determine unique values for the leptonic weak neutral current coupling constants g V and g A in the framework of electroweak models containing a single Z 0 . In contrast to previous analyses, we only use data from purely leptonic interactions, and therefore avoid the inherent uncertainties resulting from the use of hadronic targets. From the MARK-J data alone in the context of the standard SU(2) ⊗ U (1) model of Glashow, Weinberg and Salam, we find sin 2 θ W =0.24±0.11.
No description provided.
No description provided.
No description provided.
The processes e + e − → e + e − and μ + μ − have been studied at PETRA using the JADE detector. The data, which were collected at s -values of up to 1300 GeV 2 have been analysed in terms of an electro-weak extension of QED to obtain values for the weak vector and axial vector couplings in the lepton sector. The values obtained agree with the predictions of the standard Salam-Weinberg model and the data are further analysed in terms of this model to obtain the limits 0.10 < sin 2 ϑ w < 0.40 (68% CL). The mass of the neutral weak gauge boson is deduced to be greater than 51 GeV/ c 2 .
No description provided.
No description provided.
No description provided.
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