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.

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- - - - - - - - Overview of HEPData Record - - - - - - - - <br/><br/> <b>Results:</b> <ul> <li><a href="132116?version=1&table=Resultsforchargeasymmetryinclusive">$A_C^{t\bar{t}}$</a> <li><a href="132116?version=1&table=Resultsforchargeasymmetryvsmtt">$A_C^{t\bar{t}}$ vs $m_{t\bar{t}}$</a> <li><a href="132116?version=1&table=Resultsforchargeasymmetryvspttt">$A_C^{t\bar{t}}$ vs $p_{T,t\bar{t}}$</a> <li><a href="132116?version=1&table=Resultsforchargeasymmetryvsbetatt">$A_C^{t\bar{t}}$ vs $\beta_{z,t\bar{t}}$</a> <li><a href="132116?version=1&table=Resultsforleptonicchargeasymmetryinclusive">$A_C^{\ell\bar{\ell}}$</a> <li><a href="132116?version=1&table=Resultsforchargeasymmetryvsllmll">$A_C^{\ell\bar{\ell}}$ vs $m_{\ell\bar{\ell}}$</a> <li><a href="132116?version=1&table=Resultsforchargeasymmetryvsllptll">$A_C^{\ell\bar{\ell}}$ vs $p_{T,\ell\bar{\ell}}$</a> <li><a href="132116?version=1&table=Resultsforchargeasymmetryvsllbetall">$A_C^{\ell\bar{\ell}}$ vs $\beta_{z,\ell\bar{\ell}}$</a> </ul> <b>Bounds on the Wilson coefficients:</b> <ul> <li><a href="132116?version=1&table=BoundsonWilsoncoefficientschargeasymmetryinclusive">$A_C^{t\bar{t}}$</a> <li><a href="132116?version=1&table=BoundsonWilsoncoefficientschargeasymmetryvsmtt">$A_C^{t\bar{t}}$ vs $m_{t\bar{t}}$</a> </ul> <b>Ranking of systematic uncertainties:</b></br> Inclusive:<a href="132116?version=1&table=NPrankingchargeasymmetryinclusive">$A_C^{t\bar{t}}$</a></br> <b>$A_C^{t\bar{t}}$ vs $\beta_{z,t\bar{t}}$:</b> <ul> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsbetattbin0">$\beta_{z,t\bar{t}} \in[0,0.3]$</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsbetattbin1">$\beta_{z,t\bar{t}} \in[0.3,0.6]$</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsbetattbin2">$\beta_{z,t\bar{t}} \in[0.6,0.8]$</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsbetattbin3">$\beta_{z,t\bar{t}} \in[0.8,1]$</a> </ul> <b>$A_C^{t\bar{t}}$ vs $m_{t\bar{t}}$:</b> <ul> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsmttbin0">$m_{t\bar{t}}$ &lt; $500$GeV</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsmttbin1">$m_{t\bar{t}} \in [500,750]$GeV</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsmttbin2">$m_{t\bar{t}} \in [750,1000]$GeV</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsmttbin3">$m_{t\bar{t}} \in [1000,1500]$GeV</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsmttbin4">$m_{t\bar{t}}$ &gt; $1500$GeV</a> </ul> <b>$A_C^{t\bar{t}}$ vs $p_{T,t\bar{t}}$:</b> <ul> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsptttbin0">$p_{T,t\bar{t}} \in [0,30]$GeV</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsptttbin1">$p_{T,t\bar{t}} \in[30,120]$GeV</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsptttbin2">$p_{T,t\bar{t}}$ &gt; $120$GeV</a> </ul> Inclusive leptonic:<a href="132116?version=1&table=NPrankingleptonicchargeasymmetryinclusive">$A_C^{\ell\bar{\ell}}$</a></br> <b>$A_C^{\ell\bar{\ell}}$ vs $\beta_{z,\ell\bar{\ell}}$</b> <ul> <li><a href="132116?version=1&tableNPrankingchargeasymmetry=vsllbetallbin0">$\beta_{z,\ell\bar{\ell}} \in [0,0.3]$</a> <li><a href="132116?version=1&tableNPrankingchargeasymmetry=vsllbetallbin1">$\beta_{z,\ell\bar{\ell}} \in [0.3,0.6]$</a> <li><a href="132116?version=1&tableNPrankingchargeasymmetry=vsllbetallbin2">$\beta_{z,\ell\bar{\ell}} \in [0.6,0.8]$</a> <li><a href="132116?version=1&tableNPrankingchargeasymmetry=vsllbetallbin3">$\beta_{z,\ell\bar{\ell}} \in [0.8,1]$</a> </ul> <b>$A_C^{\ell\bar{\ell}}$ vs $m_{\ell\bar{\ell}}$</b> <ul> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsllmllbin0">$m_{\ell\bar{\ell}}$ &lt; $200$GeV</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsllmllbin1">$m_{\ell\bar{\ell}} \in [200,300]$GeV</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsllmllbin2">$m_{\ell\bar{\ell}} \in [300,400]$Ge$</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsllmllbin3">$m_{\ell\bar{\ell}}$ &gt; $400$GeV</a> </ul> <b>$A_C^{\ell\bar{\ell}}$ vs $p_{T,\ell\bar{\ell}}$</b> <ul> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsllptllbin0">$p_{T,\ell\bar{\ell}}\in [0,20]$GeV</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsllptllbin1">$p_{T,\ell\bar{\ell}}\in[20,70]$GeV</a> <li><a href="132116?version=1&table=NPrankingchargeasymmetryvsllptllbin2">$p_{T,\ell\bar{\ell}}$ &gt; $70$GeV</a> </ul> <b>NP correlations:</b> <ul> <li><a href="132116?version=1&table=NPcorrelationschargeasymmetryinclusive">$A_C^{t\bar{t}}$</a> <li><a href="132116?version=1&table=NPcorrelationschargeasymmetryvsmtt">$A_C^{t\bar{t}}$ vs $m_{t\bar{t}}$</a> <li><a href="132116?version=1&table=NPcorrelationschargeasymmetryvspttt">$A_C^{t\bar{t}}$ vs $p_{T,t\bar{t}}$</a> <li><a href="132116?version=1&table=NPcorrelationschargeasymmetryvsbetatt">$A_C^{t\bar{t}}$ vs $\beta_{z,t\bar{t}}$</a> <li><a href="132116?version=1&table=NPcorrelationsleptonicchargeasymmetryinclusive">$A_c^{\ell\bar{\ell}}$</a> <li><a href="132116?version=1&table=NPcorrelationschargeasymmetryvsllmll">$A_c^{\ell\bar{\ell}}$ vs $m_{\ell\bar{\ell}}$</a> <li><a href="132116?version=1&table=NPcorrelationschargeasymmetryvsllptll">$A_C^{\ell\bar{\ell}}$ vs $p_{T,\ell\bar{\ell}}$</a> <li><a href="132116?version=1&table=NPcorrelationschargeasymmetryvsllbetall">$A_C^{\ell\bar{\ell}}$ vs $\beta_{z,\ell\bar{\ell}}$</a> </ul> <b>Covariance matrices:</b> <ul> <li><a href="132116?version=1&table=Covariancematrixchargeasymmetryvsmtt">$A_C^{t\bar{t}}$ vs $m_{t\bar{t}}$</a> <li><a href="132116?version=1&table=Covariancematrixchargeasymmetryvspttt">$A_C^{t\bar{t}}$ vs $p_{T,t\bar{t}}$</a> <li><a href="132116?version=1&table=Covariancematrixchargeasymmetryvsbetatt">$A_C^{t\bar{t}}$ vs $\beta_{z,t\bar{t}}$</a> <li><a href="132116?version=1&table=Covariancematrixleptonicchargeasymmetryvsllmll">$A_c^{\ell\bar{\ell}}$ vs $m_{\ell\bar{\ell}}$</a> <li><a href="132116?version=1&table=Covariancematrixleptonicchargeasymmetryvsllptll">$A_C^{\ell\bar{\ell}}$ vs $p_{T,\ell\bar{\ell}}$</a> <li><a href="132116?version=1&table=Covariancematrixleptonicchargeasymmetryvsllbetall">$A_C^{\ell\bar{\ell}}$ vs $\beta_{z,\ell\bar{\ell}}$</a> </ul>

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.

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Measurement of azimuthal asymmetries in inclusive charged dipion production in $e^+e^-$ annihilations at $\sqrt{s}$ = 3.65 GeV

The BESIII collaboration Ablikim, M. ; Achasov, M.N. ; Ai, X.C. ; et al.
Phys.Rev.Lett. 116 (2016) 042001, 2016.
Inspire Record 1384778 DOI 10.17182/hepdata.73802

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.

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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.


Precision Measurement of the Longitudinal Double-spin Asymmetry for Inclusive Jet Production in Polarized Proton Collisions at $\sqrt{s}=200$ GeV

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Phys.Rev.Lett. 115 (2015) 092002, 2015.
Inspire Record 1297229 DOI 10.17182/hepdata.73432

We report a new high-precision measurement of the mid-rapidity inclusive jet longitudinal double-spin asymmetry, $A_{LL}$, in polarized $pp$ collisions at center-of-mass energy $\sqrt{s}=200$ GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep inelastic scattering (DIS), semi-inclusive DIS, and RHIC $pp$ data. The measured asymmetries provide evidence for positive gluon polarization in the Bjorken-$x$ region $x>0.05$.

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Jet neutral energy fraction (NEF) comparing data with simulations, where both are calculated with pT subtraction. This plot shows 8.4 < $p_T$ < 9.9 GeV/c.

Jet neutral energy fraction (NEF) comparing data with simulations, where both are calculated with pT subtraction. This plot shows 26.8 < $p_T$ < 31.6 GeV/c.

Inclusive jet $A_{LL}$ vs. parton jet $p_T$ for |eta|<0.5.

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Measurement of longitudinal spin asymmetries for weak boson production in polarized proton-proton collisions at RHIC

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Phys.Rev.Lett. 113 (2014) 072301, 2014.
Inspire Record 1292792 DOI 10.17182/hepdata.73441

We report measurements of single- and double- spin asymmetries for $W^{\pm}$ and $Z/\gamma^*$ boson production in longitudinally polarized $p+p$ collisions at $\sqrt{s} = 510$ GeV by the STAR experiment at RHIC. The asymmetries for $W^{\pm}$ were measured as a function of the decay lepton pseudorapidity, which provides a theoretically clean probe of the proton's polarized quark distributions at the scale of the $W$ mass. The results are compared to theoretical predictions, constrained by recent polarized deep inelastic scattering measurements, and show a preference for a sizable, positive up antiquark polarization in the range $0.05<x<0.2$.

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$E_T^e$ distribution of $W^{\pm}$ candidate events, background contributions, and sum of backgrounds and W -> ev MC signal. This plot is for Electron |eta|<0.5.

$E_T^e$ distribution of $W^{\pm}$ candidate events, background contributions, and sum of backgrounds and W -> ev MC signal. This plot is for Electron 0.5<|eta|<1.1.

$E_T^e$ distribution of $W^{\pm}$ candidate events, background contributions, and sum of backgrounds and W -> ev MC signal. This plot is for Positron |eta|<0.5.

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Experimental investigation of transverse spin asymmetries in muon-p SIDIS processes: Sivers asymmetries

The COMPASS collaboration Adolph, C. ; Alekseev, M.G. ; Alexakhin, V.Yu. ; et al.
Phys.Lett.B 717 (2012) 383-389, 2012.
Inspire Record 1115721 DOI 10.17182/hepdata.59737

The COMPASS Collaboration at CERN has measured the transverse spin azimuthal asymmetry of charged hadrons produced in semi-inclusive deep inelastic scattering using a 160 GeV positive muon beam and a transversely polarised NH_3 target. The Sivers asymmetry of the proton has been extracted in the Bjorken x range 0.003<x<0.7. The new measurements have small statistical and systematic uncertainties of a few percent and confirm with considerably better accuracy the previous COMPASS measurement. The Sivers asymmetry is found to be compatible with zero for negative hadrons and positive for positive hadrons, a clear indication of a spin-orbit coupling of quarks in a transversely polarised proton. As compared to measurements at lower energy, a smaller Sivers asymmetry for positive hadrons is found in the region x > 0.03. The asymmetry is different from zero and positive also in the low x region, where sea-quarks dominate. The kinematic dependence of the asymmetry has also been investigated and results are given for various intervals of hadron and virtual photon fractional energy. In contrast to the case of the Collins asymmetry, the results on the Sivers asymmetry suggest a strong dependence on the four-momentum transfer to the nucleon, in agreement with the most recent calculations.

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The Sivers asymmetry, from the 2010 data set, for positive hadrons as a function of X for full range. Also shown are the mean values of other variables plus the correlation with the Collins data measurments.

The Sivers asymmetry, from the 2010 data set, for negative hadrons as a function of X for full range. Also shown are the mean values of other variables plus the correlation with the Collins data measurments.

The Sivers asymmetry, from the 2010 data set, for positive hadrons as a function of PT for full range. Also shown are the mean values of other variables plus the correlation with the Collins data measurments.

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Experimental investigation of transverse spin asymmetries in muon-p SIDIS processes: Collins asymmetries

The COMPASS collaboration Adolph, C. ; Alekseev, M.G. ; Alexakhin, V.Yu. ; et al.
Phys.Lett.B 717 (2012) 376-382, 2012.
Inspire Record 1115720 DOI 10.17182/hepdata.59732

The COMPASS Collaboration at CERN has measured the transverse spin azimuthal asymmetry of charged hadrons produced in semi-inclusive deep inelastic scattering using a 160 GeV positive muon beam and a transversely polarised NH_3 target. The Collins asymmetry of the proton was extracted in the Bjorken x range 0.003<x<0.7. These new measurements confirm with higher accuracy previous measurements from the COMPASS and HERMES collaborations, which exhibit a definite effect in the valence quark region. The asymmetries for negative and positive hadrons are similar in magnitude and opposite in sign. They are compatible with model calculations in which the u-quark transversity is opposite in sign and somewhat larger than the d-quark transversity distribution function. The asymmetry is extracted as a function of Bjorken $x$, the relative hadron energy $z$ and the hadron transverse momentum p_T^h. The high statistics and quality of the data also allow for more detailed investigations of the dependence on the kinematic variables. These studies confirm the leading-twist nature of the Collins asymmetry.

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The Collins asymmetry, from the 2010 data set, for positive hadrons as a function of X for full range. Also shown are the mean values of other variables plus the correlation with the Sivers data measurments.

The Collins asymmetry, from the 2010 data set, for negative hadrons as a function of X for full range. Also shown are the mean values of other variables plus the correlation with the Sivers data measurments.

The Collins asymmetry, from the 2010 data set, for positive hadrons as a function of PT for full range. Also shown are the mean values of other variables plus the correlation with the Sivers data measurments.

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Flavour Separation of Helicity Distributions from Deep Inelastic Muon-Deuteron Scattering

The COMPASS collaboration Alekseev, M. ; Alexakhin, V.Yu. ; Alexandrov, Yu. ; et al.
Phys.Lett.B 680 (2009) 217-224, 2009.
Inspire Record 820721 DOI 10.17182/hepdata.55300

We present a LO evaluation of helicity densities of valence, \Delta u_v+\Delta d_v, non-strange sea, \Delta\bar{u}+\Delta\bar{d}, and strange quarks, \Delta s (assumed to be equal to \Delta\bar{s}). They have been obtained from the inclusive asymmetry A_{3,d} and the semi-inclusive asymmetries A^{\pi+}_{1,d}, A^{\pi-}_{1,d}, A^{K+}_{1,d}, A^{K-}_{1,d} measured in polarised deep inelastic muon-deuteron scattering. The full deuteron statistics of COMPASS (years 2002-2004 and 2006) has been used. The data cover the range Q^2 > 1 (GeV/c)^2 and 0.004<x<0.3. Both non-strange densities are found to be in a good agreement with previous measurements. The distribution of \Delta s(x) is compatible with zero in the whole measured range, in contrast to the shape of the strange quark helicity distribution obtained in most LO and NLO QCD fits. The sensitivity of the values of \Delta s(x) upon the choice of fragmentation functions used in the derivation is discussed.

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Inclusive asymmetry as a function of X.

Charged pion and kaon semi-inclusive asymmetries as functions of X.

Correlations coefficients of the unfolded asymmetries.

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Deep inelastic scattering with leading protons or large rapidity gaps at HERA

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
Nucl.Phys.B 816 (2009) 1-61, 2009.
Inspire Record 804915 DOI 10.17182/hepdata.52860

The dissociation of virtual photons, $\gamma^{\star} p \to X p$, in events with a large rapidity gap between $X$ and the outgoing proton, as well as in events in which the leading proton was directly measured, has been studied with the ZEUS detector at HERA. The data cover photon virtualities $Q^2>2$ GeV$^2$ and $\gamma^{\star} p$ centre-of-mass energies $40&lt;W&lt;240$ GeV, with $M_X>2$ GeV, where $M_X$ is the mass of the hadronic final state, $X$. Leading protons were detected in the ZEUS leading proton spectrometer. The cross section is presented as a function of $t$, the squared four-momentum transfer at the proton vertex and $\Phi$, the azimuthal angle between the positron scattering plane and the proton scattering plane. It is also shown as a function of $Q^2$ and $\xpom$, the fraction of the proton's momentum carried by the diffractive exchange, as well as $\beta$, the Bjorken variable defined with respect to the diffractive exchange.

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The differential cross section DSIG/DT for the LRG and the LPS data samples.

The fitted exponential slope of the T distribution as a function of X(NAME=POMERON).

The fitted exponential slope of the T distribution as a function of X(NAME=POMERON).

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Collins and Sivers asymmetries for pions and kaons in muon-deuteron DIS

The COMPASS collaboration Alekseev, M. ; Alexakhin, V.Yu. ; Alexandrov, Yu. ; et al.
Phys.Lett.B 673 (2009) 127-135, 2009.
Inspire Record 779473 DOI 10.17182/hepdata.48532

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.

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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.

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Measurement of K0(S), Lambda, anti-Lambda production at HERA

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
Eur.Phys.J.C 51 (2007) 1-23, 2007.
Inspire Record 734144 DOI 10.17182/hepdata.45796

The production of the neutral strange hadrons $K^{0}_{S}$, $\Lambda$ and $\bar{\Lambda}$ has been measured in $ep$ collisions at HERA using the ZEUS detector. Cross sections, baryon-to-meson ratios, relative yields of strange and charged light hadrons, $\Lambda$ ($\bar{\Lambda}$) asymmetry and polarization have been measured in three kinematic regions: $Q^2 > 25 \gev^2$: $5 < Q^2 < 25 \gev^2$: and in photoproduction ($Q^2 \simeq 0$). In photoproduction the presence of two hadronic jets, each with at least $5 \gev$ transverse energy, was required. The measurements agree in general with Monte Carlo models and are consistent with measurements made at $e^+ e^-$ colliders, except for an enhancement of baryon relative to meson production in photoproduction.

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Differential K0S cross section in DIS events as a function of transverse momentum (lab). for Q**2 from 5 to 25 GeV**2.

Differential K0S cross section in DIS events as a function of transverse momentum (lab). for Q**2 > 25 GeV**2.

Differential K0S cross section in DIS events as a function of pseudorapidity (lab). for Q**2 from 5 to 25 GeV**2.

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