The spectra of strange hadrons are measured in proton-proton collisions, recorded by the CMS experiment at the CERN LHC, at centre-of-mass energies of 0.9 and 7 TeV. The K_{S}, Λ, and Ξ^{–} particles and their antiparticles are reconstructed from their decay topologies and the production rates are measured as functions of rapidity and transverse momentum, pT. The results are compared to other experiments and to predictions of the PYTHIA Monte Carlo program. The pT distributions are found to differ substantially from the PYTHIA results and the production rates exceed the predictions by up to a factor of three.
This paper can be retrieved from several sources including:
The presented results can also be found:
The paper is an updated version of an analysis originally released in the summer of 2010. The twiki for the old (superseded) analysis can be found at PhysicsResultsQCD10007PAS.
Figures from the paper are available below. Right click the image to obtain the .png version and left click to obtain the PDF version. In some cases, the description also contains a link to a root macro file.
Figure 6. K_{S} (top), Λ (middle), and Ξ^{–} (bottom) production per NSD event versus |y| (left) and p_{T} (right). The inner vertical error bars (when visible) show the statistical uncertainties, the outer the statistical and point-to-point systematic uncertainties summed in quadrature. The normalization uncertainty is shown as a band. Three Pythia predictions are overlaid on the |y| distributions. The solid curves in the p_{T} distributions are fits to the Tsallis function as described in the paper. Root macros are available for the K_{S} rapidity distribution, the K_{S} p_{T} distribution, Λ rapidity distribution, the Λ p_{T} distribution, the Ξ^{–} rapidity distribution, and the Ξ^{–} p_{T} distribution. |
Figure 7. Ratio of MC production to data production of K_{S} (top), Λ (middle), and Ξ^{–} (bottom) versus p_{T} at √s = 0.9 TeV (open symbols) and √s = 7 TeV (filled symbols). Results are shown for three Pythia predictions at each centre-of-mass energy. To reduce clutter, the uncertainty, shown as a band, is included for only one of the predictions (D6T) at each energy. This uncertainty includes the statistical and point-to-point systematic uncertainties added in quadrature but does not include the normalization systematic uncertainty. Figure is available in root macro format. |
Figure 8. N(Λ)/N(K_{S}) (left) and N(Ξ^{–})/N(Λ) (right) in NSD events versus p_{T}. The inner vertical error bars (when visible) show the statistical uncertainties, the outer the statistical and all systematic uncertainties summed in quadrature. Results are shown for three Pythia predictions at each centre-of-mass energy. The plots are available in root macro format: left plot and right plot. |
Figure 9. K_{S} (top), Λ (middle), and Ξ^{–} (bottom) production per event versus p_{T}. The error bars on the CMS results show the combined statistical, point-to-point systematic, and normalization systematic uncertainties. The error bars on the CDF (hep-ex/1101.2996), ALICE (hep-ex/1012.3257), and STAR (PRC75,064901,2007) results show the combined statistical and systematic uncertainties. The CMS, CDF, and STAR results are normalized to NSD events while the ALICE results are normalized to all inelastic events. Figure is available in root macro format. |
Figure 10. Ratio of Λ to K_{S} production (top) and Ξ^{–} to Λ production (bottom) versus p_{T}. The CMS, ALICE (hep-ex/1012.3257), and STAR (PRC75,064901,2007) error bars include statistical and systematic uncertainties. The CDF error bars include the statistical uncertainties for N(Λ)/N(K_{S}) (PRD72,052001,2005) and the statistical and systematic uncertainties for N(Ξ^{–})/N(Λ) (hep-ex/1101.2996). The CDF N(Λ)/N(K_{S}) bin sizes are doubled to reduce fluctuations. For experiments in which the binning for Λ and Ξ^{–} is different (ALICE and STAR), bins are merged to provide common bin ranges in the N(Ξ^{–})/N(Λ) distribution. Figure is available in root macro format. |
Figure 11. Average p_{T} for K_{S} (top), Λ (middle), and Ξ^{–} (bottom), as a function of the centre-of-mass energy. The CMS measurements are for |y| < 2. The other results are from UA5 in ZPC41,179,1988; PhysRept154,247,1987; NPB328,36,1989; NPB258,505,1985; PLB151,309,1985 (ppbar collisions covering |y| < 2.5, |y| < 2, and |y| < 3 for K_{S}, Λ, and Ξ^{–}, respectively), E735 in PRD46,2772,1992 (ppbar collisions using tracks with -0.36<η<1.0), STAR in PRC75,064901,2007 (pp collisions covering |y|<0.5), and ALICE in hep-ex/1012.3257 (pp collisions covering |y| < 0.75 for K_{S} and Λ and |y| < 0.8 for Ξ^{–}).Some points have been slightly offset from the true energy to improve visibility. The vertical bars indicate the statistical and systematic uncertainties (when available) summed in quadrature. Figure is available in root macro format. |
Figure 12. The central rapidity production rate for K_{S} (top), Λ (middle), and Ξ^{–} (bottom), as a function of the centre-of-mass energy. The previous results are from UA5 in ZPC41,179,1988; NPB258,505,1985; (ppbar), CDF in PRD40,3791,1989 (ppbar), STAR in PRC75,064901,2007 (pp), and ALICE in hep-ex/1012.3257 (pp). The CMS, UA5, and STAR results are normalized to NSD events. The CDF results are normalized to events passing their trigger and event selection defined chiefly by activity in both sides of the detector, at least four tracks, and a primary vertex. The ALICE results are normalized to all inelastic events. Some points have been slightly offset from the true energy to improve visibility. The vertical bars indicate the statistical uncertainties for the UA5 and CDF results and the combined statistical and systematic uncertainties for the CMS, ALICE, and STAR results. Figure is available in root macro format. |
Figure 13. The production ratios N(Λ)/N(K_{S}) (left) and N(Ξ^{–})/N(Λ) (right) in NSD events versus |y|. The inner vertical error bars (when visible) show the statistical uncertainties, the outer the statistical and all systematic uncertainties summed in quadrature. Results are shown for three Pythia predictions at each centre-of-mass energy. The plots are available in root macro format: left plot and right plot. |
-- KevinStenson - 20-Apr-2011
I | Attachment | History | Action | Size | Date | Who | Comment |
---|---|---|---|---|---|---|---|
XiMass_selected_data_7.pdf | r1 | manage | 10.2 K | 2011-04-20 - 23:17 | KevinStenson | Cascade mass plot at 7 TeV | |
png | XiMass_selected_data_7.png | r1 | manage | 27.4 K | 2011-04-20 - 23:15 | KevinStenson | Cascade mass plot at 7 TeV |
XiMass_selected_data_900.pdf | r1 | manage | 10.4 K | 2011-04-20 - 23:17 | KevinStenson | Cascade mass plot at 0.9 TeV | |
png | XiMass_selected_data_900.png | r1 | manage | 30.2 K | 2011-04-20 - 23:15 | KevinStenson | Cascade mass plot at 0.9 TeV |
averagept_vs_roots.pdf | r1 | manage | 7.4 K | 2011-04-21 - 19:59 | KevinStenson | Average pT of Kshort, Lambda, and Cascade vs centre-of-mass energy | |
png | averagept_vs_roots.png | r1 | manage | 34.5 K | 2011-04-21 - 19:58 | KevinStenson | Average pT of Kshort, Lambda, and Cascade vs centre-of-mass energy |
dNdy_vs_roots.pdf | r1 | manage | 6.9 K | 2011-04-21 - 20:00 | KevinStenson | Midrapidity production vs centre-of-mass energy | |
png | dNdy_vs_roots.png | r1 | manage | 33.0 K | 2011-04-21 - 20:00 | KevinStenson | Midrapidity production vs centre-of-mass energy |
c | fig10.C | r1 | manage | 39.7 K | 2011-04-21 - 22:51 | KevinStenson | Production ratios vs pT compared to other experiments |
c | fig11.C | r1 | manage | 31.6 K | 2011-04-21 - 22:51 | KevinStenson | Average pT of Kshort, Lambda, and Cascade vs centre-of-mass energy |
c | fig12.C | r1 | manage | 22.9 K | 2011-04-21 - 22:52 | KevinStenson | Midrapidity production vs centre-of-mass energy |
c | fig13_left.C | r1 | manage | 31.1 K | 2011-04-21 - 22:52 | KevinStenson | Lambda/Kshort vs rapidity |
c | fig13_right.C | r1 | manage | 32.4 K | 2011-04-21 - 22:53 | KevinStenson | Cascade/Lambda vs rapidity |
c | fig6_botleft.C | r1 | manage | 33.1 K | 2011-04-21 - 22:47 | KevinStenson | Cascade rapidity distribution |
c | fig6_botright.C | r1 | manage | 245.0 K | 2011-04-21 - 22:47 | KevinStenson | Cascade pT distribution |
c | fig6_midleft.C | r1 | manage | 32.5 K | 2011-04-21 - 22:48 | KevinStenson | Lambda rapidity distribution |
c | fig6_midright.C | r1 | manage | 250.7 K | 2011-04-21 - 22:48 | KevinStenson | Lambda pT distribution |
c | fig6_topleft.C | r1 | manage | 31.9 K | 2011-04-21 - 22:48 | KevinStenson | Kshort rapidity distribution |
c | fig6_topright.C | r1 | manage | 236.2 K | 2011-04-21 - 22:48 | KevinStenson | Kshort pT distribution |
c | fig7.C | r1 | manage | 194.2 K | 2011-04-21 - 22:49 | KevinStenson | Ratio of MC to data pT distributions for Kshort, Lambda, and Cascade |
c | fig8_left.C | r1 | manage | 61.3 K | 2011-04-21 - 22:49 | KevinStenson | Lambda/Kshort vs pT |
c | fig8_right.C | r1 | manage | 59.6 K | 2011-04-21 - 22:50 | KevinStenson | Cascade/Lambda vs pT |
c | fig9.C | r1 | manage | 52.9 K | 2011-04-21 - 22:51 | KevinStenson | pT distributions compared to other experiments |
ks_yield_data_7000.pdf | r1 | manage | 15.5 K | 2011-04-20 - 23:16 | KevinStenson | Kshort mass plot at 7 TeV | |
png | ks_yield_data_7000.png | r1 | manage | 29.1 K | 2011-04-20 - 23:13 | KevinStenson | Kshort mass plot at 7 TeV |
ks_yield_data_900.pdf | r1 | manage | 15.5 K | 2011-04-20 - 23:15 | KevinStenson | Kshort mass plot at 0.9 TeV | |
png | ks_yield_data_900.png | r1 | manage | 29.7 K | 2011-04-20 - 23:12 | KevinStenson | Kshort mass plot at 0.9 TeV |
kslife_sum_log.pdf | r1 | manage | 16.1 K | 2011-04-20 - 23:49 | KevinStenson | Kshort lifetime distribution | |
png | kslife_sum_log.png | r1 | manage | 30.2 K | 2011-04-20 - 23:48 | KevinStenson | Kshort lifetime distribution |
kspt_cor_data_perevt_log.pdf | r1 | manage | 17.5 K | 2011-04-21 - 19:46 | KevinStenson | Kshort pT distribution | |
png | kspt_cor_data_perevt_log.png | r1 | manage | 35.7 K | 2011-04-21 - 19:46 | KevinStenson | Kshort pT distribution |
ksy_cor_datamc_perevt.pdf | r1 | manage | 6.2 K | 2011-04-21 - 19:45 | KevinStenson | Kshort rapidity distribution | |
png | ksy_cor_datamc_perevt.png | r1 | manage | 29.2 K | 2011-04-21 - 19:45 | KevinStenson | Kshort rapidity distribution |
lamOverKsMC_pt_sys.pdf | r1 | manage | 10.3 K | 2011-04-21 - 19:55 | KevinStenson | Lambda/Kshort vs pT | |
png | lamOverKsMC_pt_sys.png | r1 | manage | 41.3 K | 2011-04-21 - 19:54 | KevinStenson | Lambda/Kshort vs pT |
lamOverKsMC_y_sys.pdf | r1 | manage | 6.1 K | 2011-04-21 - 21:06 | KevinStenson | Lambda/Kshort vs rapidity | |
png | lamOverKsMC_y_sys.png | r1 | manage | 22.6 K | 2011-04-21 - 21:05 | KevinStenson | Lambda/Kshort vs rapidity |
lam_yield_data_7000.pdf | r1 | manage | 13.2 K | 2011-04-20 - 23:17 | KevinStenson | Lambda mass plot at 7 TeV | |
png | lam_yield_data_7000.png | r1 | manage | 30.2 K | 2011-04-20 - 23:14 | KevinStenson | Lambda mass plot at 7 TeV |
lam_yield_data_900.pdf | r1 | manage | 13.3 K | 2011-04-20 - 23:16 | KevinStenson | Lambda mass plot at 0.9 TeV | |
png | lam_yield_data_900.png | r1 | manage | 29.3 K | 2011-04-20 - 23:14 | KevinStenson | Lambda mass plot at 0.9 TeV |
lamlife_sum_log.pdf | r1 | manage | 17.0 K | 2011-04-20 - 23:50 | KevinStenson | Lambda lifetime distribution | |
png | lamlife_sum_log.png | r1 | manage | 32.5 K | 2011-04-20 - 23:49 | KevinStenson | Lambda lifetime distribution |
lampt_cor_data_perevt_log.pdf | r1 | manage | 18.2 K | 2011-04-21 - 19:49 | KevinStenson | Lambda pT distribution | |
png | lampt_cor_data_perevt_log.png | r1 | manage | 36.2 K | 2011-04-21 - 19:49 | KevinStenson | Lambda pT distribution |
lamy_cor_datamc_perevt.pdf | r1 | manage | 6.4 K | 2011-04-21 - 19:47 | KevinStenson | Lambda rapidity distribution | |
png | lamy_cor_datamc_perevt.png | r1 | manage | 28.2 K | 2011-04-21 - 19:47 | KevinStenson | Lambda rapidity distribution |
pt_datadata_comp.pdf | r1 | manage | 18.9 K | 2011-04-21 - 19:57 | KevinStenson | pT distributions compared to other experiments | |
png | pt_datadata_comp.png | r1 | manage | 49.2 K | 2011-04-21 - 19:56 | KevinStenson | pT distributions compared to other experiments |
pt_datamc_comp.pdf | r1 | manage | 17.5 K | 2011-04-21 - 19:54 | KevinStenson | Ratio of MC to data pT distributions for Kshort, Lambda, and Cascade | |
png | pt_datamc_comp.png | r1 | manage | 63.5 K | 2011-04-21 - 19:53 | KevinStenson | Ratio of MC to data pT distributions for Kshort, Lambda, and Cascade |
ptrat_datadata_comp.pdf | r1 | manage | 17.0 K | 2011-04-21 - 19:57 | KevinStenson | Production ratios vs pT compared to other experiments | |
png | ptrat_datadata_comp.png | r1 | manage | 43.0 K | 2011-04-21 - 19:57 | KevinStenson | Production ratios vs pT compared to other experiments |
v0effpt_sum.pdf | r1 | manage | 10.2 K | 2011-04-20 - 23:47 | KevinStenson | Efficiency vs pT for Kshort, Lambda, and Cascade | |
png | v0effpt_sum.png | r1 | manage | 28.6 K | 2011-04-20 - 23:46 | KevinStenson | Efficiency vs pT for Kshort, Lambda, and Cascade |
v0effy_sum.pdf | r1 | manage | 6.3 K | 2011-04-20 - 23:48 | KevinStenson | Efficiency vs |y| for Kshort, Lambda, and Cascade | |
png | v0effy_sum.png | r1 | manage | 22.0 K | 2011-04-20 - 23:47 | KevinStenson | Efficiency vs |y| for Kshort, Lambda, and Cascade |
xiOverLamMC_pt_sys.pdf | r1 | manage | 9.8 K | 2011-04-21 - 19:55 | KevinStenson | Cascade/Lambda vs pT | |
png | xiOverLamMC_pt_sys.png | r1 | manage | 36.9 K | 2011-04-21 - 19:55 | KevinStenson | Cascade/Lambda vs pT |
xiOverLamMC_y_sys.pdf | r1 | manage | 6.4 K | 2011-04-21 - 21:07 | KevinStenson | Cascade/Lambda vs rapidity | |
png | xiOverLamMC_y_sys.png | r1 | manage | 24.8 K | 2011-04-21 - 21:06 | KevinStenson | Cascade/Lambda vs rapidity |
xilife_sum_log.pdf | r1 | manage | 14.1 K | 2011-04-20 - 23:51 | KevinStenson | Cascade lifetime distribution | |
png | xilife_sum_log.png | r1 | manage | 29.8 K | 2011-04-20 - 23:50 | KevinStenson | Cascade lifetime distribution |
xipt_cor_data_perevt_log.pdf | r1 | manage | 18.4 K | 2011-04-21 - 19:51 | KevinStenson | Cascade pT distribution | |
png | xipt_cor_data_perevt_log.png | r1 | manage | 38.4 K | 2011-04-21 - 19:50 | KevinStenson | Cascade pT distribution |
xiy_cor_datamc_perevt.pdf | r1 | manage | 6.6 K | 2011-04-21 - 19:50 | KevinStenson | Cascade rapidity distribution | |
png | xiy_cor_datamc_perevt.png | r1 | manage | 27.8 K | 2011-04-21 - 19:50 | KevinStenson | Cascade rapidity distribution |