.
Eur. Phys. J. C 72 (2012) 2168
The Λˉ/Λ and Λˉ/K0S production ratios are measured by the LHCb detector from 0.3nb−1 of pp collisions delivered by the LHC at √s=0.9\,TeV and 1.8nb−1 at √s=7\,TeV. Both ratios are presented as a function of transverse momentum, pT, and rapidity, y, in the ranges {0.15<pT<2.50GeV/c} and {2.0<y<4.5}. Results at the two energies are in good agreement as a function of rapidity loss, Δy=ybeam−y, and are consistent with previous measurements. The ratio Λˉ/Λ, measuring the transport of baryon number from the collision into the detector, is smaller in data than predicted in simulation, particularly at high rapidity. The ratio Λˉ/K0S, measuring the baryon-to-meson suppression in strange quark hadronisation, is significantly larger than expected.
(Note, eps versions are available under attachments).
Caption |
Figure |
The Fisher discriminant FIP in 0.5 million Monte Carlo simulated minimum bias events at √s = 7 TeV for KS0. |
|
The Fisher discriminant FIP in 0.5 million Monte Carlo simulated minimum bias events at √s = 7 TeV for Λ. |
|
Invariant mass peaks for Λ in the range 0.25 < pT < 2.50 GeV/c & 2.5 < y < 3.0 at √s = 0.9TeV with field up. Signal yields, N, are found from fits (solid curves) with a double Gaussian peak with common mean, μ, over a linear background (dashed lines). The width, σ, is computed as the quadratic average of the two Gaussian widths weighted by their signal fractions. |
|
Invariant mass peaks for KS0 in the range 0.65 < pT < 1.00GeV/c & 3.5 < y < 4.0 at √s = 0.9TeV with field up. Signal yields, N, are found from fits (solid curves) with a double Gaussian peak with common mean, μ, over a linear background (dashed lines). The width, σ, is computed as the quadratic average of the two Gaussian widths weighted by their signal fractions. |
|
Transverse momentum for KS0 in data and Monte Carlo at sqrt(s) = 7 TeV. The difference between data and Monte Carlo is reduced by weighting the simulated candidates. |
|
Rapidity distributions for KS0 in data and Monte Carlo at sqrt(s) = 7 TeV. The difference between data and Monte Carlo is reduced by weighting the simulated candidates. |
|
The double ratio (Λ/Λ)Data/(Λ/Λ)MC is shown as a function of the material traversed, in units of radiation length. Flat line fits, shown together with their respective χ2 probabilities, give no evidence of a bias. |
|
The double ratio (Λ/KS0)Data/(Λ/KS0)MC is shown as a function of the material traversed, in units of radiation length. Flat line fits, shown together with their respective χ2 probabilities, give no evidence of a bias. |
|
The ratio Λ/Λ from the full analysis procedure at √s = 0.9 TeV, shown as a function of rapidity, compared across intervals of transverse momentum. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/Λ from the full analysis procedure at √s = 7 TeV, shown as a function of rapidity, compared across intervals of transverse momentum. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/KS0 from the full analysis procedure at √s = 0.9 TeV, shown as a function of rapidity, compared across intervals of transverse momentum. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/KS0 from the full analysis procedure at √s = 7 TeV, shown as a function of rapidity, compared across intervals of transverse momentum. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/Λ at √s = 0.9 TeV compared with the predictions of the LHCb MC, Perugia 0 and Perugia NOCR as a function of rapidity. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/Λ at √s = 0.9 TeV compared with the predictions of the LHCb MC, Perugia 0 and Perugia NOCR as a function of transverse momentum. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/KS0 at √s = 0.9 TeV compared with the predictions of the LHCb MC, Perugia 0 and Perugia NOCR as a function of rapidity. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/KS0 at √s = 0.9 TeV compared with the predictions of the LHCb MC, Perugia 0 and Perugia NOCR as a function of transverse momentum. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/Λ at √s = 7 TeV compared with the predictions of the LHCb MC, Perugia 0 and Perugia NOCR as a function of rapidity. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/Λ at √s = 7 TeV compared with the predictions of the LHCb MC, Perugia 0 and Perugia NOCR as a function of transverse momentum. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/KS0 at √s = 7 TeV compared with the predictions of the LHCb MC, Perugia 0 and Perugia NOCR as a function of rapidity. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/KS0 at √s = 7 TeV compared with the predictions of the LHCb MC, Perugia 0 and Perugia NOCR as a function of transverse momentum. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/Λ from LHCb is compared at both √s = 0.9TeV (triangles) and 7TeV (circles) with the published results from STAR[1] (squares) as a function of rapidity loss, ∆y = ybeam − y. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|
The ratio Λ/KS0 from LHCb is compared at both √s = 0.9TeV (triangles) and 7TeV (circles) with the published results from STAR[1] (squares) as a function of rapidity loss, ∆y = ybeam − y. Vertical lines show the combined statistical and systematic uncertainties and the short horizontal bars (where visible) show the statistical component. |
|