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Summary of K*(892) analysis, PhD thesis C. Hoehne archiv.ub.uni-marburg.de/diss/z2003/0627/

Summary of K*(892) analysis, PhD thesis C. Hoehne http://archiv.ub.uni-marburg.de/diss/z2003/0627/ CERN EDMS Id 816035. analyzed data samples method, corrections results for pp results for CC, SiSi Appendix: Comparison of pion and kaon analysis to NA49-pp-group.

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Summary of K*(892) analysis, PhD thesis C. Hoehne archiv.ub.uni-marburg.de/diss/z2003/0627/

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  1. Summary of K*(892) analysis, PhD thesis C. Hoehne http://archiv.ub.uni-marburg.de/diss/z2003/0627/ CERN EDMS Id 816035 • analyzed data samples • method, corrections • results for pp • results for CC, SiSi • Appendix: Comparison of pion and kaon analysis to NA49-pp-group

  2. Analyzed datasets for pp collisions: • Corrections in order to extract yields for minimum bias p+p collisions (basically corresponding to yields for inelastic pp-collisions): • multiplicity dependent scaling of events in order to correct for trigger bias • scaling in order to correct for „0-track events“ in the N49 acceptance • global empty target run subtraction • (For comparison to results with more complicated and detailed corrections see Appendix.) • In addition: study of p+p events at different inelasticity

  3. Analyzed datasets for CC and SiSi collisions: • C target thickness of 3.05 mm corresponds to 2.4% interaction length, Si target thickness of 5.02 mm to 4.4%. • centrality selection was: (15.3 ± 2.4)% for C+C and (12.2 ± 1.8)% for SiSi • Number of wounded nucleons (VENUS): 14 ± 2 for C+C, 37 ± 3 for SiSi

  4. Fraction of C, N and Al, Si, P in beam selection: • C – N intensity ratio: 69:31 • Al – Si – P intensity ratio: 35:41:24

  5. K*(892) extracted using the invariant mass method • invariant mass calculated for real and mixed events • distribution normalized to number of entries • subtracted • yield extraction by comparison to simulation • undershoot structure due to mixing of K, pi from K* from different events – well described by simulation! K*(892)

  6. Investigation of correlations due to higher lying resonances, in particular the K*2(1430) • higher lying resonances expected (see literature) with exponential dependence of the yield on the mass

  7. Investigation of correlations due to higher lying resonances, in particular the K*2(1430) • implement in simulation and investigate the effect • only K*2(1430) shows a small effect in the K*(892) invariant mass spectrum • baseline (solid line) pulled down in comparison to simulation without (dashed line)

  8. Investigation of correlations due to higher lying resonances, in particular the K*2(1430) • simulations performed with different fractions of the K*2(1430) compared to the K*(892) • best fit value compares well to expectation from the exponential dependence of the yield on the mass

  9. For the extraction of the yield K*2(1430) is taken into account • integrated spectra

  10. For the extraction of the yield K*2(1430) is taken into account • example spectra for more restricted kinematical bins as used for the extraction of pt- and y-spectra • phantastic quality of K*(892) signal in pp data!

  11. Investigation of reflections from other resonances in the invariant mass spectrum • misidentification of kaons and pions due to selection by dE/dx in a measured band around the Bethe-Bloch value • if e.g. a proton from a D(1232) decay is misidentified as K and combined with the partner pion, correlated structures appear in the background

  12. Investigation of reflections from other resonances in the invariant mass spectrum • these reflections generate distortions in the remaining background after the event-mix subtraction • difficult to quantify • investigate by changing selection criteria

  13. Investigation of reflections from other resonances in the invariant mass spectrum • pp data rather insensitive – always high quality • strong effect seen for CC, SiSi • with strict selection criteria (and reduced misidentification) the remaining background clearly improves

  14. Selection criteria of kaons and pions: • momentum range (4-50) GeV/c for a reasonable dE/dx identification • upper pt-cut of 1.5 GeV/c (pp) or 1 GeV/c (CC, SiSi), because for this range fitted dE/dx positions were available • lower cut on the number of measured points on track Npoints, standard = 30, best K* results in CC, SiSifor Npoints > 100 • particle identification by selecting tracks from a fixed c∙sdE/dx window around the mean dE/dx value from fits, standard c=1.5, best K* results in CC, SiSi for C=1.5 for pions and (-0.5, 1.5) ∙sdE/dx for kaons • cuts are varied for the extraction of systematic errors • (same for subtraction of remaining background in the invariant mass signal if necessary)

  15. Extraction of yields • adjust a simulation to the measured invariant mass spectrum (c2-minimization), extract yield from scaling factor d: Nsignal = d∙Nsim • F = braching ratio • pid = particle identification probabability from dE/dx cut • as statistics is not sufficient for a binning in y and pt, 1/Dy and 1/Dpt are replaced by fy anf fpt if integrating over y or pt respectively; fy and fpt are then extrapolation factors from the used y- and pt-range to the full y-range or infinity • the simulation contains corrections for the geometrical acceptance (including the Npoints cut) and kaon decay in flight

  16. K*(892) acceptance • no embedding simulations done as efficiency losses due to track density are negligible for pp, CC, and SiSi interactions Note: underlying acceptance corrections for pions and kaons, and inflight-decay corrections for kaons also used for the extraction of pion and kaon yields using dE/dx fits

  17. Kinematic distributions and yields in minimum bias p+p collisions • determination of the mass of K*(892) (width fixed to 50 MeV)

  18. Kinematic distributions and yields in minimum bias p+p collisions • transverse momentum distributions

  19. Kinematic distributions and yields in minimum bias p+p collisions • rapidity distributions

  20. Kinematic distributions and yields in minimum bias p+p collisions • systematic errors determined by variation of analysis cuts

  21. Kinematic distributions and yields in minimum bias p+p collisions • systematic errors determined by variation of analysis cuts

  22. Summary table of results

  23. Comparison to other experiments

  24. Comparison to other experiments

  25. Integrated yields in C+C and Si+Si collisions • statistics lacking for the extraction of kinematic distributions • estimate of total yield, assume rapidity distribution as for K, pt-spectra (slope) as for f-meson • extract number of K*(892) in large acceptance: 3.1 < y < 4.7 and pt < 1.5 GeV/c • appr. 6% error of extrapolation to full acceptance taking unknown distributions into account • variation of cuts and background estimate for systematic errors: 15% at most • statistical errors 15-20% • combined error 30%

  26. K*(892)

  27. K*(892)

  28. Summary of results:

  29. Appendix: Comparison of my pp-analysis with results from the NA49-pp-group Multiplicities of pions and kaons: Claudia: systematic errors of 5% on p and 10% on K NA49: systematic errors on K are given xF dependent: 2.2% … 12.2 %

  30. NA49 pp data • Difference of sophisticated empty target run subtraction and trigger bias correction method to an (older) method applying multiplicity dependent cross section weighting factors or even simple overall scaling • → estimate systematic error due to this correction • p-production • published data: Eur. Phys. J. C 45, 343–381 (2006) • → sophisticated trigger bias correction and empty target run subtraction • PhD thesis, C. Höhne, http://archiv.ub.uni-marburg.de/diss/z2003/0627/ • → multiplicity dependent scaling of events in order to correct for trigger bias, global empty target run subtraction • 4p yields: • EPJC <p+> = 3.018 <p-> = 2.360 • PhD <p+> = 3.07±0.01 ± 0.15 <p-> = 2.33 ±0.01 ±0.12

  31. pt- / mt ditribution at midrapidity • PhD • T at midrapidity (2.77 < y < 3.23), fitted to data points from 0.3 GeV < (mt-m0) < 1.3 GeV • p+ T = 167±1±10 MeV • p- T = 166±1.5±10 MeV • EPJC • see figure

  32. numerical values not given in the paper no direct comparison possible

  33. y-distribution

  34. f production • published data: Physics Letters B 491 (2000) 59–66 • → no correction for y- and mt-distribution (if I remember correctly) • → 4p yield scaled down by ratio of minimum bias pp event trigger (28.9 mb) and known inelastic pp cross section (31.7 mb) • PhD thesis, C. Höhne, http://archiv.ub.uni-marburg.de/diss/z2003/0627/ • → multiplicity dependent scaling of events in order to correct for trigger bias, global empty target run subtraction • 4p yields • PLB <f> = 0.012±0.0015 • PhD <f> = 0.0129±0.0002±0.0013

  35. mt-distribution PLB (y-range: 2.9 – 4.4) T = 169±17 MeV PhD (y-range 2.9 – 4) T = 164±4±10 MeV

  36. y-distribution PLB sy = 0.89 ± 0.06 PhD sy = 0.95 ± 0.02 ± 0.04

  37. Comparison to other experiments

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