cern.ch

Measurement of antiproton production in ${\rm p He}$ collisions at $\sqrt{s_{NN}}=110$ GeV

[to restricted-access page]

Abstract

The cross-section for prompt antiproton production in collisions of protons with an energy of $6.5$ TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set corresponding to an integrated luminosity of $0.5\,nb^{-1}$. The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between $12$ and $110\,\mathrm{GeV/}c$, represent the first direct determination of the antiproton production cross-section in ${\rm p He}$ collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.

Figures and captions

Two-dimensional template fit to the PID distribution of negatively charged tracks for a particular bin ( $ 21.4 < p < 24.4 {\mathrm{\,GeV\!/}c} $, $1.2 < p_{\mathrm{ T}} < 1.5 {\mathrm{\,GeV\!/}c} $). The ( $\mathrm{DLL_{pK}}$ , $\mathrm{DLL_{p\pi }}$ ) distribution, shown in the top plot, is fitted to determine the relative contribution of $\pi ^-$ , $ K ^-$ and $\overline p $ particles, using simulation to determine the template distributions and the fraction of fake tracks (which are barely visible). In the bottom plot, the result of the fit is projected into the variable $\arg{(\mathrm{DLL_{pK}} + i\, \mathrm{DLL_{p\pi }} )}$.

dllPlo[..].pdf [21 KiB]
HiDef png [229 KiB]
Thumbnail [88 KiB]
*.C file
dllPlot_paper.pdf
phiPID[..].pdf [18 KiB]
HiDef png [148 KiB]
Thumbnail [51 KiB] *.C file
phiPID_paper.pdf

Distributions of (left) momentum and (right) transverse momentum for (top) single electron and single positron candidates, and (bottom) background-subtracted electron candidates, compared with the distributions in simulation, which are normalized to the data yield.

elekin[..].pdf [34 KiB]
HiDef png [368 KiB]
Thumbnail [101 KiB]
*.C file
elekin_paper.pdf

Antiproton production cross-section per He nucleus as a function of momentum, integrated over various $ p_{\mathrm{ T}}$ regions. The data points are compared with predictions from theoretical models. The uncertainties on the data points are uncorrelated only, while the shaded area indicates the correlated uncertainty.

IntRes[..].pdf [22 KiB]
HiDef png [702 KiB]
Thumbnail [182 KiB]
*.C file
IntResult_paper.pdf

Animated gif made out of all figures.

PAPER-2018-031.gif
Thumbnail
thumbnail_PAPER-2018-031.gif

Tables and captions

Relative uncertainties on the $\overline p $ production cross-section. The ranges refer to the variation among kinematic bins.

Table_1.pdf [33 KiB]
HiDef png [110 KiB]
Thumbnail [15 KiB]
tex code
Table_1.pdf

Numerical results for the measured prompt $\overline p $ production cross-section. The reported values are the double-differential cross-section $\mathrm{d}^2\sigma/\mathrm{d}p\,\mathrm{d}p_{\mathrm{T}}$ per He nucleus in the laboratory frame, averaged over the given kinematic range of each bin. The uncertainty is split into an uncorrelated uncertainty $\delta_{\text{uncorr}}$, and an uncertainty $\delta_{\text{corr}}$ which is fully correlated among the kinematic bins. For both uncertainties, the systematic uncertainty, dominant for most bins, and the statistical uncertainty, are added in quadrature. The average value within each bin is also reported for $ p$ , $ p_{\mathrm{ T}}$ and $x$-Feynman $ x_{\mathrm{F}} =2\,p_Z^*/\sqrt{s_{\scriptscriptstyle\rm NN}} $, where $p_Z^*$ is the longitudinal $\overline p $ momentum in the proton-nucleon center-of-mass system. These average values are obtained from simulation, to avoid biases from reconstruction effects and given the good agreement with data observed for the simulated kinematic spectra.

Table_2.pdf [1 KiB]
HiDef png [0 KiB]
Thumbnail [0 KiB]
tex code
Table_2.pdf

Supplementary Material [file]

Supplementary material full pdf

supple[..].pdf [234 KiB]
supplementary.pdf

This ZIP file contains supplemetary material for the publication LHCb-PAPER-2018-031. The files are: supplementary.pdf : An overview of the extra figures *.pdf, *.png, *.eps : The figures in variuous formats

Fig4.pdf [19 KiB]
HiDef png [295 KiB]
Thumbnail [87 KiB]
*C file
Fig4.pdf
Fig5.pdf [14 KiB]
HiDef png [155 KiB]
Thumbnail [56 KiB]
*C file
Fig5.pdf
Fig6.pdf [18 KiB]
HiDef png [526 KiB]
Thumbnail [116 KiB]
*C file
Fig6.pdf
Fig7.pdf [27 KiB]
HiDef png [868 KiB]
Thumbnail [179 KiB]
*C file
Fig7.pdf
Fig8a.pdf [12 KiB]
HiDef png [111 KiB]
Thumbnail [46 KiB]
*C file
Fig8a.pdf
Fig8b.pdf [68 KiB]
HiDef png [1 MiB]
Thumbnail [288 KiB]
*C file
Fig8b.pdf
Fig9.pdf [25 KiB]
HiDef png [381 KiB]
Thumbnail [173 KiB]
*C file
Fig9.pdf

Created on 09 December 2018.Citation count from INSPIRE on 18 December 2018.