The forward-backward charge asymmetry for the process e + e − → b b ̄ → μ ± + hadrons has been measured using the JADE detector at PETRA. An asymmetry of (−22.8 ± 6.0 ± 2.5)% was observed at an average center of mass energy of 34.6 GeV. For comparison, an asymmetry of −25.2% is expected on the basis of the standard Glashow-Salam-Weinberg model.
THE VALUE OF CONST HAVE BEEN RESCALED TO DEFINITION I3(Q) = 1/2 BY OPY.
We present a measurement of the forward-backward charge asymmetry in hadronic decays of the Z 0 using data collected with the OPAL detector at LEP. The forward-backward charge asymmetry was measured using a weight function method which gave the number of forward events on a statistical basis. In a data sample of 448 942 hadronic Z 0 decays, we have observed a charge asymmetry of A h = 0.040±0.004 (stat.)±0.006 (syst.)±0.002 (B 0 B 0 mix.), taking into account the effect of B 0 B 0 mixing. In the framework of the standard model, this asymmetry corresponds to an effective weak mixing angle averaged over five quark flavours of sin 2 θ W = 0.2321 ± 0.0017 ( stat. ) ± 0.0027 ( syst. ) ± 0.0009 (B 0 B 0 mix.). The result agrees with the value obtained from the Z 0 line shape and lepton pair forward-backward asymmetry.
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The second systematic error is due to the uncertainty in the correction for B.BBAR mixing which had been applied to the data.
We have studied the production of charged D ∗ mesons in e + e − annihilation at an average center-of-mass energy of 58.0 GeV. Charged D ∗ mesons were identified using two independent methods; the mass-difference method and the detection of the low transverse-momentum pion. The forward-backward asymmetry of the charm quark production was measured to be A c = −0.61±0.13(stat.)±0.08(syst.). The cross section of inclusive D ∗ production was found to be σ(e + e − →D ∗ ± +X) = 24.5 ± 5.3 ( stat. )±3.0( syst. ) pb. If we assume the standard model prediction for the charm quark production, we obtain the branching ratio for the charm quark to produce a charged D ∗ meson to be Br (c→D ∗+ + X) = (22±5( stat. )±3( syst. ))% .
Forward-backward asymmetry of charm quarks at the lowest order.
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This paper presents measurements of the production of Ds- mesons relative to Ds+ mesons as functions of x_F and square of p_t for a sample of 2445 Ds decays to phi pi. The Ds mesons were produced in Fermilab experiment E791 with 500 GeV/c pi- mesons incident on one platinum and four carbon foil targets. The acceptance-corrected integrated asymmetry in the x_F range -0.1 to 0.5 for Ds+- mesons is 0.032 +- 0.022 +- 0.022, consistent with no net asymmetry. The results, as functions of x_F and square of p_t, are compared to predictions and to the large production asymmetry observed for D+- mesons in the same experiment. These comparisons support the hypothesis that production asymmetries come from the fragmentation process and not from the charm quark production itself.
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We present a measurement of asymmetries in the production of $\Lambda_c^+$ and $\Lambda_c^-$ baryons in 500 GeV/c $\pi^-$--nucleon interactions from the E791 experiment at Fermilab. The asymmetries were measured as functions of Feynman x ($x_F$) and transverse momentum squared ($p_T^2$) using a sample of $1819 \pm 62$ $\Lambda_c$'s observed in the decay channel $\Lambda_c \to pK^-\pi^+$. We observe more $\Lambda_c^+$ than $\Lambda_c^-$ baryons, with an asymmetry of $(12.7\pm3.4\pm1.3) %$ independent of $x_F$ and $p_T^2$ in our kinematical range $(-0.1 < x_F < 0.6$ and $0.0 < p_T^2 < 8.0 (GeV/c)^2$). This $\Lambda_c$ asymmetry measurement is the first with data in both the positive and negative $x_F$ regions.
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Using data from Fermilab fixed-target experiment E769, we have measured particle-antiparticle production asymmetries for Lambda0 hyperons in 250 GeV/c pi+-, K+- and p -- nucleon interactions. The asymmetries are measured as functions of Feynman-x (x_F) and p_t^2 over the ranges -0.12<=x_F<=0.12 and 0<=p_t^2<=3 (GeV/c)^2 (for positive beam) and -0.12<=x_F<=0.4 and 0<=p_t^2<=10 (GeV/c)^2 (for negative beam). We find substantial asymmetries, even at x_F around zero. We also observe leading-particle-type asymmetries. These latter effects are qualitatively as expected from valence-quark content of the target and variety of projectiles studied.
LAMBDA production asymmetries versus XL for the positive beams.
LAMBDA production asymmetries versus PT**2 for the positive beams.
LAMBDA production asymmetries versus XL for the negative beams.
Using data from Fermilab fixed-target experiment E791, we have measured particle-antiparticle production asymmetries for lambda zero, cascade minus, and omega minus hyperons in pi minus-nucleon interactions at 500 GeV/c. The asymmetries are measured as functions of Feynman-x (x_F) and pt^2 over the ranges of -0.12 GE x_F LE 0.12 and 0 GE pt^2 LE 4 (GeV/c)^2. We find substantial asymmetries, even at x_F = 0. We also observe leading-particle- type asymmetries which qualitatively agree with theoretical predictions.
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A forward-backward asymmetry A , consistent with that expected from the γ − Z 0 interference term in the process e + e − → q q , is observed in the laboratory production angular distribution of high-momentum ∧ baryons. The data were collected with the High Resolution Spectrometer at PEP. The asymmetry for ∧ baryons with fractional energy z= 2E s greater than 0.3 is A = (−23± 8 plusmn ; 2)%.
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Data read from graph.
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