The search for an additional heavy gauge boson Z′ is described. The models considered are based on either a superstring-motivated E 6 or on a left-right symmetry and assume a minimal Higgs sector. Cross sections and asymmetries measured with the L3 detector in the vicinity of the Z resonance during the 1990 and 1991 running periods are used to determine limits on the Z-Z′ gauge boson mixing angle and on the Z′ mass. For Z′ masses above the direct limits, we obtain the following allowed ranges of the mixing angle, θ M at the 95% confidence level: −0.004 ⪕ θ M ⪕ 0.015 for the χ model, −0.003 ⪕ θ M ⪕ 0.020 for the ψ model, −0.029 ⪕ θ M ⪕ 0.010 for the η model, −0.002 ⪕ θ M ⪕ 0.020 for the LR model,
Data taken during 1990.
Data taken during 1991.
We have measured the forward-backward asymmetry in e + e − → b b and e + e − → c c processes using hadronic events containing muons or electrons. The data sample corresponds to 4100000 hadronic decays of the Z 0 . From a fit to the single lepton and dilepton p and p T spectra, we determine A b b =0.086±0.015±0.007 and A c c =0.083±0.038±0.027 at the effective center-of-mass energy √ s =91.24 GeV. These measurements yield a value of the electroweak mixing angle sin 2 θ w =0.2336±0.0029 .
No description provided.
No description provided.
No description provided.
The product of the $\Lambda_b^0$ ($\overline{B}^0$) differential production cross-section and the branching fraction of the decay $\Lambda_b^0\rightarrow J/\psi pK^-$ ($\overline{B}^0\rightarrow J/\psi\overline{K}^*(892)^0$) is measured as a function of the beauty hadron transverse momentum, $p_{\rm T}$, and rapidity, $y$. The kinematic region of the measurements is $p_{\rm T}<20~{\rm GeV}/c$ and $2.0<y<4.5$. The measurements use a data sample corresponding to an integrated luminosity of $3~{\rm fb}^{-1}$ collected by the LHCb detector in $pp$ collisions at centre-of-mass energies $\sqrt{s}=7~{\rm TeV}$ in 2011 and $\sqrt{s}=8~{\rm TeV}$ in 2012. Based on previous LHCb results of the fragmentation fraction ratio, $f_{\Lambda_B^0}/f_d$, the branching fraction of the decay $\Lambda_b^0\rightarrow J/\psi pK^-$ is measured to be \begin{equation*} \mathcal{B}(\Lambda_b^0\rightarrow J/\psi pK^-)= (3.17\pm0.04\pm0.07\pm0.34^{+0.45}_{-0.28})\times10^{-4}, \end{equation*} where the first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the branching fraction of the decay $\overline{B}^0\rightarrow J/\psi\overline{K}^*(892)^0$, and the fourth is due to the knowledge of $f_{\Lambda_b^0}/f_d$. The sum of the asymmetries in the production and decay between $\Lambda_b^0$ and $\overline{\Lambda}_b^0$ is also measured as a function of $p_{\rm T}$ and $y$. The previously published branching fraction of $\Lambda_b^0\rightarrow J/\psi p\pi^-$, relative to that of $\Lambda_b^0\rightarrow J/\psi pK^-$, is updated. The branching fractions of $\Lambda_b^0\rightarrow P_c^+(\rightarrow J/\psi p)K^-$ are determined.
Asymmetries $a_{\rm p+d}$ $(\%)$ of $\Lambda_b^0$ and $\overline{\Lambda}_b^0$ in bins of $p_\rm{T}$ for the 2011 and 2012 samples.
Asymmetries $a_{\rm p+d}$ $(\%)$ of $\Lambda_b^0$ and $\overline{\Lambda}_b^0$ in bins of $y$ for the 2011 and 2012 samples.
The STAR Collaboration reports measurements of the transverse single-spin asymmetries, $A_N$, for inclusive jets and identified `hadrons within jets' production at midrapidity from transversely polarized $pp$ collisions at $\sqrt{s}$ = 200 GeV, based on data recorded in 2012 and 2015. The inclusive jet asymmetry measurements include $A_N$ for inclusive jets and $A_N$ for jets containing a charged pion carrying a momentum fraction $z>0.3$ of the jet momentum. The identified hadron within jet asymmetry measurements include the Collins effect for charged pions, kaons and protons, and the Collins-like effect for charged pions. The measured asymmetries are determined for several distinct kinematic regions, characterized by the jet transverse momentum $p_{T}$ and pseudorapidity $\eta$, as well as the hadron momentum fraction $z$ and momentum transverse to the jet axis $j_{T}$. These results probe higher momentum scales ($Q^{2}$ up to $\sim$ 900 GeV$^{2}$) than current, semi-inclusive deep inelastic scattering measurements, and they provide new constraints on quark transversity in the proton and enable tests of evolution, universality and factorization breaking in the transverse-momentum-dependent formalism.
Inclusive jet asymmetries, $A_{UT}^{\sin(\phi_{S})}$, as a function of particle jet-$p_{T}$. The bars show the statistical uncertainties, while the size of the boxes represents the systematic uncertainties on $A_{UT}^{\sin(\phi_{S})}$ (vertical) and jet-$p_{T}$ (horizontal). The top panel shows results for jets that scatter forward relative to the polarized beam ($x_{F} > 0$).
Inclusive jet asymmetries, $A_{UT}^{\sin(\phi_{S})}$, as a function of particle jet-$p_{T}$. The bars show the statistical uncertainties, while the size of the boxes represents the systematic uncertainties on $A_{UT}^{\sin(\phi_{S})}$ (vertical) and jet-$p_{T}$ (horizontal). the bottom panel shows jets that scatter backward to the polarized beam ($x_{F} < 0$).
Inclusive jet asymmetries, $A_{UT}^{\sin(\phi_{S})}$, as a function of particle jet-$p_{T}$ for jets that contain a charged pion with $z > 0.3$. The blue circles are for jets containing a high-$z$ $\pi^{+}$, while red squares are for jets containing a high-$z$ $\pi^{-}$.
No description provided.
No description provided.
During 1993 and 1995 LEP was run at 3 energies near the Z$^0$peak in order to give improved measurements of the mass and width of the resonance. During 1994, LEP o
Cross section and forward-backward asymmetry in the E+ E- channel for the 1993 data. The polar angle is 44 to 136 degrees. Additional systematic error for cross section of 0.46 PCT (efficiencies and backgrounds) and 0.29 PCT (absolute luminosity). Additional systematic error for the asymmetry of 0.0026.
Cross section and forward-backward asymmetry in the E+ E- channel for the 1994 data. The polar angle is 44 to 136 degrees. Additional systematic error for cross section of 0.52 PCT (efficiencies and backgrounds) and 0.14 PCT (absolute luminosity). Additional systematic error for the asymmetry of 0.0021.
Cross section and forward-backward asymmetry in the E+ E- channel for the 1995 data. The polar angle is 44 to 136 degrees. Additional systematic error for cross section of 0.52 PCT (efficiencies and backgrounds) and 0.14 PCT (absolute luminosity). Additional systematic error for the asymmetry of 0.0020.
Measured forward backward asymmetries.
Forward-backward s-quark asymmetries from the separate processes.
Final s-quark forward-backward asymmetries.
Inclusive and differential measurements of the top-antitop ($t\bar{t}$) charge asymmetry $A_\text{C}^{t\bar{t}}$ and the leptonic asymmetry $A_\text{C}^{\ell\bar{\ell}}$ are presented in proton-proton collisions at $\sqrt{s} = 13$ TeV recorded by the ATLAS experiment at the CERN Large Hadron Collider. The measurement uses the complete Run 2 dataset, corresponding to an integrated luminosity of 139 fb$^{-1}$, combines data in the single-lepton and dilepton channels, and employs reconstruction techniques adapted to both the resolved and boosted topologies. A Bayesian unfolding procedure is performed to correct for detector resolution and acceptance effects. The combined inclusive $t\bar{t}$ charge asymmetry is measured to be $A_\text{C}^{t\bar{t}} = 0.0068 \pm 0.0015$, which differs from zero by 4.7 standard deviations. Differential measurements are performed as a function of the invariant mass, transverse momentum and longitudinal boost of the $t\bar{t}$ system. Both the inclusive and differential measurements are found to be compatible with the Standard Model predictions, at next-to-next-to-leading order in quantum chromodynamics perturbation theory with next-to-leading-order electroweak corrections. The measurements are interpreted in the framework of the Standard Model effective field theory, placing competitive bounds on several Wilson coefficients.
The unfolded inclusive charge asymmetry. The measured values are given with statistical and systematic uncertainties. The SM theory predictions calculated at NNLO in QCD and NLO in EW theory are listed, and the impact of the linear term of the Wilson coefficient on the $A_C^{t\bar{t}}$ prediction is shown for two different values. The scale uncertainty is obtained by varying renormalisation and factorisation scales independently by a factor of 2 or 0.5 around $\mu_0$ to calculate the maximum and minimum value of the asymmetry, respectively. The nominal value $\mu_0$ is chosen as $H_T/4$. The variations in which one scale is multiplied by 2 while the other scale is divided by 2 are excluded. Finally, the scale and MC integration uncertainties are added in quadrature.
The unfolded differential charge asymmetry as a function of the invariant mass of the top pair system. The measured values are given with statistical and systematic uncertainties. The SM theory predictions calculated at NNLO in QCD and NLO in EW theory are listed, and the impact of the linear term of the Wilson coefficient on the $A_C^{t\bar{t}}$ prediction is shown for two different values. The scale uncertainty is obtained by varying renormalisation and factorisation scales independently by a factor of 2 or 0.5 around $\mu_0$ to calculate the maximum and minimum value of the asymmetry, respectively. The nominal value $\mu_0$ is chosen as $H_T/4$. The variations in which one scale is multiplied by 2 while the other scale is divided by 2 are excluded. Finally, the scale and MC integration uncertainties are added in quadrature.
The unfolded differential charge asymmetry as a function of the transverse momentum of the top pair system. The measured values are given with statistical and systematic uncertainties. The SM theory predictions calculated at NNLO in QCD and NLO in EW theory are listed. The scale uncertainty is obtained by varying renormalisation and factorisation scales independently by a factor of 2 or 0.5 around $\mu_0$ to calculate the maximum and minimum value of the asymmetry, respectively. The nominal value $\mu_0$ is chosen as $H_T/4$. The variations in which one scale is multiplied by 2 while the other scale is divided by 2 are excluded. Finally, the scale and MC integration uncertainties are added in quadrature.
We have measured the forward-backward asymmetry in Z 0 → b b decays using hadronic events containing muons and electrons. The data sample corresponds to 118 200 hadronic events at √ s ≈ M z . From a fit to the single and dilepton p and P ⊥ spectra, we determine A b b =0.130 −0.042 +0.044 including the correction for B 0 − B 0 mixing.
Observed asymmetry from fit to single and dilepton P and PT spectra assuming no mixing.
Asymmetry corrected for the effects of mixing using the L3 observed mixing parameter chi(B) = 0.178 +0.049,-0.040.
Using the data recorded with the L3 detector at LEP, we study the process e + e − → μ + μ − ( γ ) for events with hard initial-state photon radiation. The effective centre-of-mass energies of the muons range from 50 GeV to 86 GeV. The data sample corresponds to an integrated luminosity of 103.5 pb −1 and yields 293 muon-pair events with a hard photon along the beam direction. The events are used to determine the cross sections and the forward-backward charge asymmetries at centre-of-mass energies below the Z resonance.
Forward-Backward Asymmetry from fit as function of the reduced centre-of-mass energy.
Background corrected Forward-Backward Asymmetry as function of the reduced centre-of-mass energy.
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