Evidence for the charge asymmetry in $pp \rightarrow t\bar{t}$ production at $\sqrt{s}= 13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, G. ; Abbott, B. ; Abbott, D.C. ; et al.
JHEP 08 (2023) 077, 2023.
Inspire Record 2141752 DOI 10.17182/hepdata.132116

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.

47 data tables match query

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.

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Forward - backward charge asymmetry of quark pairs produced at the KEK TRISTAN e+ e- collider

The AMY collaboration Stuart, D. ; Breedon, R.E. ; Chinitz, L.M. ; et al.
Phys.Rev.D 49 (1994) 3098-3105, 1994.
Inspire Record 378569 DOI 10.17182/hepdata.22552

We report on a measurement of the forward-backward charge asymmetry in e+e−→qq¯ at KEK TRISTAN, where the asymmetry is near maximum. We sum over all flavors and measure the asymmetry by determining the charge of the quark jets. In addition we exploit flavor dependencies in the jet charge determination to enhance the contributions of certain flavors. This provides a check on the asymmetries of individual flavors. The measurement agrees with the standard model expectations.

1 data table match query

Forward--backward asymmetry summed over all flavours of quarks.


Measurement of $\Z^0 \to b \bar{b}$ Decay Properties

The L3 collaboration Adeva, B. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 241 (1990) 416-424, 1990.
Inspire Record 295040 DOI 10.17182/hepdata.29716

We have measured the properties of Z 0 → b b decays using a sample of 944 inclusive muon events, corresponding to 18 000 hadron events obtained with the L3 detector at LEP. We measured the partial decay width of the Z 0 into b b , Γ b b =353±48 MeV , and we determined the vector coupling of the Z 0 to the b quark; g rmv 2 (b)=0.095±0.047. We measured the forward-backward charge asymmetry in e + e − → b b events at √ s ≈ M v , and obtained A b b =13.3±9.9% .

1 data table match query

BOTTOM quark charge asymmetry measurement.


Inclusive Electron Production From Heavy Quarks in $e^+ e^-$ Annihilation at 34.6-{GeV} Center-of-mass Energy

The TASSO collaboration Althoff, M. ; Braunschweig, W. ; Kirschfink, F.J. ; et al.
Phys.Lett.B 146 (1984) 443-449, 1984.
Inspire Record 202782 DOI 10.17182/hepdata.30507

The production of electrons by bottom and charm hadrons has been studied in e + e − annihilation at 34.6 GeV center of mass energy. It is observed that the b quark fragmentation function is peaked at large values of the scaling variable z with 〈 z b 〉 = 0.84 +0.15 + 0.15 −0.10 − 0.11 . For c quarks 〈 z c 〉 = 0.57 +0.10 + 0.05 −0.09 − 0.06 is observed. A forward-backward charge asymmetry of A = −0.25 ± 0.22 was measured in b production.

2 data tables match query

THE VALUE OF ASYMMETRY WAS DETERMINED USING A SAMPLE OF PROMPT ELECTRONS.

THE VALUE OF ASYMMETRY WAS DETERMINED USING A SAMPLE OF PROMPT ELECTRONS.


Production and Muonic Decay of Heavy Quarks in e+ e- Annihilation at 34.5-GeV

The TASSO collaboration Althoff, M. ; Braunschweig, W. ; Kirschfink, F.J. ; et al.
Z.Phys.C 22 (1984) 219, 1984.
Inspire Record 194775 DOI 10.17182/hepdata.16252

The production of prompt muons ine+e− annihilation has been studied at centre of mass energies near 34.5 GeV. The measured semi-muonic branching ratios ofb andc quarks areB(b»Xμv) =0.117±0.028±0.01 andB(c→Xμv)=0.082 ±0.012a−0.01+0.02. The fragmentation functions of heavy quarks are hard, <zb>=0.85a−0.12–0.07+0.10+0.02 and <zc> =0.77a−0.07–0.11+0.05+0.03. Limits have been set on flavour changing neutral current decays:B(b→Xµ+µ−) <0.02 andB(b→Xµ+µ− (95% confidence level).

1 data table match query

THE VALUE OF ASYMMETRY WAS DETERMINED USING A SAMPLE OF PROMPT MUONS.


FORWARD - BACKWARD CHARGE ASYMMETRY IN e+ e- ---> HADRON JETS

The AMY collaboration Stuart, D. ; Breedon, R.E. ; Kim, G.N. ; et al.
Phys.Rev.Lett. 64 (1990) 983, 1990.
Inspire Record 283082 DOI 10.17182/hepdata.19965

The forward-backward asymmetry of quarks produced in e+e− annihilations, summed over all flavors, is measured at √s between 50 and 60.8 GeV. Methods of determining the charge direction of jet pairs are discussed. The asymmetry is found to agree with the five-flavor standard model.

1 data table match query

Forward backward asymmetry summed over all flavours of quarks.


Spin correlation in t anti-t production from p anti-p collisions at S**(1/2) = 1.8-TeV

The D0 collaboration Abbott, B. ; Abolins, M. ; Abramov, V. ; et al.
Phys.Rev.Lett. 85 (2000) 256-261, 2000.
Inspire Record 524260 DOI 10.17182/hepdata.42996

The D0 collaboration has performed a study of spin correlation in tt-bar production for the process tt-bar to bb-bar W^+W^-, where the W bosons decay to e-nu or mu-nu. A sample of six events was collected during an exposure of the D0 detector to an integrated luminosity of approximately 125 pb^-1 of sqrt{s}=1.8 TeV pp-bar collisions. The standard model (SM) predicts that the short lifetime of the top quark ensures the transmission of any spin information at production to the tt-bar decay products. The degree of spin correlation is characterized by a correlation coefficient k. We find that k>-0.25 at the 68% confidence level, in agreement with the SM prediction of k=0.88.

1 data table match query

No description provided.


Measurement of the forward backward asymmetry of c and b quarks at the Z pole using reconstructed D mesons.

The DELPHI collaboration Abreu, P. ; Adye, T. ; Adzic, P. ; et al.
Eur.Phys.J.C 10 (1999) 219-237, 1999.
Inspire Record 495464 DOI 10.17182/hepdata.49295

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

1 data table match query

No description provided.


Observation of Transverse Spin-Dependent Azimuthal Correlations of Charged Pion Pairs in $p^\uparrow+p$ at $\sqrt{s}=200$ GeV

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Phys.Rev.Lett. 115 (2015) 242501, 2015.
Inspire Record 1357596 DOI 10.17182/hepdata.73282

We report the observation of transverse polarization-dependent azimuthal correlations in charged pion pair production with the STAR experiment in $p^\uparrow+p$ collisions at RHIC. These correlations directly probe quark transversity distributions. We measure signals in excess of five standard deviations at high transverse momenta, at high pseudorapidities eta>0.5, and for pair masses around the mass of the rho-meson. This is the first direct transversity measurement in p+p collisions. Comparing the results to data from lepton-nucleon scattering will test the universality of these spin-dependent quantities.

15 data tables match query

$p_T$ asymmetries, $\eta$ < 0, maximum opening angle of 0.2.

$<M_{inv}>$ asymmetries, $\eta$ < 0, maximum opening angle of 0.2.

$p_T$ asymmetries, $\eta$ > 0, maximum opening angle 0.2.

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Measurement of the $\Lambda_b$ polarization and angular parameters in $\Lambda_b\to J/\psi\, \Lambda$ decays from pp collisions at $\sqrt{s}=$ 7 and 8 TeV

The CMS collaboration Sirunyan, Albert M ; Tumasyan, Armen ; Adam, Wolfgang ; et al.
Phys.Rev.D 97 (2018) 072010, 2018.
Inspire Record 1654926 DOI 10.17182/hepdata.83664

An analysis of the decay $\Lambda_b \to J/\psi(\to\mu^+\mu^-)\Lambda(\to p \pi^-)$ decay is performed to measure the $\Lambda_b$ polarization and three angular parameters in data from pp collisions at $\sqrt{s} =$ 7 and 8 TeV, collected by the CMS experiment at the LHC. The $\Lambda_b$ polarization is measured to be 0.00 $\pm$ 0.06 (stat) $\pm$ 0.06 (syst) and the parity-violating asymmetry parameter is determined to be 0.14 $\pm$ 0.14 (stat) $\pm$ 0.10 (syst). The measurements are compared to various theoretical predictions, including those from perturbative quantum chromodynamics.

2 data tables match query

The measured values of the angular parameters and the $\Lambda_b$ polarization.

Correlation matrix for the fitted parameters.