The STAR Collaboration reports precise measurements of the longitudinal double-spin asymmetry, $A_{LL}$, for dijet production with at least one jet at intermediate pseudorapidity $0.8 < η_{\rm jet} < 1.8$ in polarized proton-proton collisions at a center-of-mass energy of 200 GeV. This study explores partons scattered with a longitudinal momentum fraction ($x$) from 0.01 to 0.5, which are predominantly characterized by interactions between high-$x$ valence quarks and low-$x$ gluons. The results are in good agreement with previous measurements at 200 GeV with improved precision and are found to be consistent with the predictions of global analyses that find the gluon polarization to be positive. In contrast, the negative gluon polarization solution from the JAM Collaboration is found to be strongly disfavored.
$A_{LL}$ as a function of parton-level invariant mass for dijets with the East barrel-endcap.
$A_{LL}$ as a function of parton-level invariant mass for dijets with the West barrel-endcap.
$A_{LL}$ as a function of parton-level invariant mass for dijets with the endcap-endcap.
The forward-backward asymmetries of$$e^ + e^ - \to Z^0 \to b\bar b and e^ + e^ - \to Z^0 \to c\bar c$$
Measurement of the asymmetry in b-quark production on the Z0 peak using a two parameter fit, neglecting the effects of B0-BBAR0 mixing.
Measurement of the asymmetry in b-quark production on the Z0 peak using a two parameter fit and correcting for B0-BBAR0 mixing. The second systematic error is due to the uncertainty of the mixing factor.
Measurement of the asymmetry in c-quark production on the Z0 peak using a two parameter fit.
A measurement of the forward--backward asymmetry of $e^{+}e^{-} \to c\bar{c}$ and $e^{+}e^{-} \to b\bar{b}$ on the $Z$ resonance is performed using about 3.5 million hadronic $Z$ decays collected by the DELPHI detector at LEP in the years 1992 to 1995. The heavy quark is tagged by the exclusive reconstruction of several $D$ meson decay modes. The forward--backward asymmetries for $c$ and $b$ quarks at the $Z$ resonance are determined to be: \[ \renewcommand{\arraystretch}{1.6} \begin{array}{rcr@{}l} \Afbc(\sqrt{s} = 91.235 {\rm GeV}) &=& &0.0659 \pm 0.0094 (stat) \pm 0.0035 (syst) \Afbb (\sqrt{s} = 91.235 {\rm GeV}) &=& &0.0762 \pm 0.0194 (stat) \pm 0.0085 (syst) \Afbc(\sqrt{s} = 89.434 {\rm GeV}) &=&-&0.0496 \pm 0.0368 (stat) \pm 0.0053 (syst) \Afbb(\sqrt{s} = 89.434 {\rm GeV}) &=& &0.0567 \pm 0.0756 (stat) \pm 0.0117 (syst) \Afbc(\sqrt{s} = 92.990 {\rm GeV}) &=& &0.1180 \pm 0.0318 (stat) \pm 0.0062 (syst) \Afbb(\sqrt{s} = 92.990 {\rm GeV}) &=& &0.0882 \pm 0.0633 (stat) \pm 0.0122 (syst) \end{array} \] The combination of these results leads to an effective electroweak mixing angle of: SINEFF = 0.2332 \pm 0.0016
No description provided.
The measurements of the Collins and Sivers asymmetries of identified hadrons produced in deep-inelastic scattering of 160 GeV/c muons on a transversely polarised 6LiD target at COMPASS are presented. The results for charged pions and charged and neutral kaons correspond to all data available, which were collected from 2002 to 2004. For all final state particles both the Collins and Sivers asymmetries turn out to be small, compatible with zero within the statistical errors, in line with the previously published results for not identified charged hadrons, and with the expected cancellation between the u- and d-quark contributions.
The Collins and Sivers asymmetry as a function of X for 'ALL' positive pions from the 2003-2004 data.. Errors are statistical only.
The Collins and Sivers asymmetry as a function of PT for 'ALL' positive pions from the 2003-2004 data.. Errors are statistical only.
The Collins and Sivers asymmetry as a function of Z for 'ALL' positive pions from the 2003-2004 data.. Errors are statistical only.
We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process $e^+e^-\rightarrow \pi\pi X$ based on a data set of 62 $\rm{pb}^{-1}$ at the center-of-mass energy $\sqrt{s}=3.65$ GeV collected with the BESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-dependent fragmentation function.
Results of $A_{\rm UL}$ and $A_{\rm UC}$ in each ($z_{1},z_{2}$) and $p_{t}$ bin. The averages $\langle z_i\rangle$, $\langle p_t\rangle$ and $\rm \frac{\langle sin^2\theta_{2}\rangle }{\rm \langle 1+cos^2\theta_{2} \rangle }$ are also given.
Results of $A_{\rm UL}$ and $A_{\rm UC}$ in each ($z_{1},z_{2}$) and $p_{t}$ bin. The averages $\langle z_i\rangle$, $\langle p_t\rangle$ and $\rm \frac{\langle sin^2\theta_{2}\rangle }{\rm \langle 1+cos^2\theta_{2} \rangle }$ are also given.
We present a measurement of the electron charge asymmetry in ppbar->W+X->enu+X events at a center of mass energy of 1.96 TeV using 0.75 fb-1 of data collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron transverse momentum and pseudorapidity in the interval (-3.2, 3.2) and is compared with expectations from next-to-leading order calculations in perturbative quantum chromodynamics. These measurements will allow more accurate determinations of the proton parton distribution functions.
Folded electron charged asymmetry.
We report the first measurement of the lepton forward-backward asymmetry ${\cal A}_{\rm FB}$ as a function of the squared four-momentum of the dilepton system, $q^2$, for the electroweak penguin process $B \rightarrow X_s \ell^+ \ell^-$ with a sum of exclusive final states, where $\ell$ is an electron or a muon and $X_s$ is a hadronic recoil system with an $s$ quark. The results are based on a data sample containing $772\times10^6$ $B\bar{B}$ pairs recorded at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. ${\cal A}_{\rm FB}$ for the inclusive $B \rightarrow X_s \ell^+ \ell^-$ is extrapolated from the sum of 10 exclusive $X_s$ states whose invariant mass is less than 2 GeV/$c^2$. For $q^2 > 10.2$ GeV$^2$/$c^2$, ${\cal A}_{\rm FB} < 0$ is excluded at the 2.3$\sigma$ level, where $\sigma$ is the standard deviation. For $q^2 < 4.3$ GeV$^2$/$c^2$, the result is within 1.8$\sigma$ of the Standard Model theoretical expectation.
The value of ASYM(FB) obtained from the fit in each of the four Q**2 bins.
A search for the leptonic charge asymmetry ($A_\text{c}^{\ell}$) of top-quark$-$antiquark pair production in association with a $W$ boson ($t\bar{t}W$) is presented. The search is performed using final states with exactly three charged light leptons (electrons or muons) and is based on $\sqrt{s} = 13$ TeV proton$-$proton collision data collected with the ATLAS detector at the Large Hadron Collider at CERN during the years 2015$-$2018, corresponding to an integrated luminosity of 139 fb$^{-1}$. A profile-likelihood fit to the event yields in multiple regions corresponding to positive and negative differences between the pseudorapidities of the charged leptons from top-quark and top-antiquark decays is used to extract the charge asymmetry. At reconstruction level, the asymmetry is found to be $-0.123 \pm 0.136$ (stat.) $\pm \, 0.051$ (syst.). An unfolding procedure is applied to convert the result at reconstruction level into a charge-asymmetry value in a fiducial volume at particle level with the result of $-0.112 \pm 0.170$ (stat.) $\pm \, 0.054$ (syst.). The Standard Model expectations for these two observables are calculated using Monte Carlo simulations with next-to-leading-order plus parton shower precision in quantum chromodynamics and including next-to-leading-order electroweak corrections. They are $-0.084 \, ^{+0.005}_{-0.003}$ (scale) $\pm\, 0.006$ (MC stat.) and $-0.063 \, ^{+0.007}_{-0.004}$ (scale) $\pm\, 0.004$ (MC stat.) respectively, and in agreement with the measurements.
Measured values of the leptonic charge asymmetry ($A_c^{\ell}$) in ttW production in the three lepton channel. Results are given at reconstruction level and at particle level. Expected values are obtained using the Sherpa MC generator.
We present a measurement of the forward-backward charge asymmetry ($A_{FB}$) in $p\bar{p} \to Z/\gamma^{*}+X \to e^+e^-+X$ events at a center-of-mass energy of 1.96 TeV using 1.1 fb$^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron collider. $A_{FB}$ is measured as a function of the invariant mass of the electron-positron pair, and found to be consistent with the standard model prediction. We use the $A_{FB}$ measurement to extract the effective weak mixing angle sin$^2\Theta^{eff}_W = 0.2327 \pm 0.0018 (stat.) \pm 0.0006 (syst.)$.
Unfolded forward-backward asymmetry as a function of the di-electron mass.
We report the double helicity asymmetry, $A_{LL}^{J/\psi}$, in inclusive $J/\psi$ production at forward rapidity as a function of transverse momentum $p_T$ and rapidity $|y|$. The data analyzed were taken during $\sqrt{s}=510$ GeV longitudinally polarized $p
$A_{LL}^{J/\psi}$ as a function of $p_T$ or $|y|$. $N_{J/\psi}^{2\sigma}$ is the $J/\psi$ counting within its $2\sigma$ mass window. The column of Type A systematic uncertainties are a statistically weighted quadratic combination of the background fraction and run grouping uncertainties. $\Delta A_{LL}$ (Rel. Lumi.) is the global systematic uncertainty from relative luminosity measurements. $\Delta A_{LL}$ (Polarization) is the systematic uncertainty from the beam polarization measurement: a zero indicates an uncertainty $< 0.001$.
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