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Measurement of identified hadron in pp collisions at = 200GeV

Measurement of identified hadron in pp collisions at = 200GeV. Susumu SATO Japan Society for the Promotion of Science, Research Abroad [BNL] for the PHENIX collaboration. Physics motivations and requirements to measure identified hadron in p+p.

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Measurement of identified hadron in pp collisions at = 200GeV

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  1. Measurement of identified hadron in pp collisions at = 200GeV Susumu SATO Japan Society for the Promotion of Science, Research Abroad [BNL] for the PHENIX collaboration

  2. Physics motivations and requirementsto measure identified hadron in p+p > p+p data gives foot of understanding of hadron production  spectra shape, particle yield, and particle ratio (in this analysis) > Experimentally, the same experimental detector setup and analysis software as those for heavy ion is desirable to minimize systematic uncertainty. > On the other hand, low multiplicity event tends to introduce bias for the event selection. > Phenix has introduced two of new “p+p dedicated” counters, in order to minimize trigger bias, (i) one is to cover more rapidity NTC (1.2<|h|<3.0) (Normalization Trigger Counter), and (ii) the other is T-zero counter(-0.35<h<0.35) to provide start timing for the tracks in the TOF stop counter acceptance, instead of BBC event start timing counter.

  3. [2 Start Counters] (i) T-zero counter (“TZR”) & (ii) Beam Beam Counter (“BBC”) As ordinal event start counter (BBC) covers only forward (3.1<|h| <4) rapidity, For the p+p collision, PHENIX has successfully operated track-by-track start counter (TZR) covering central arm (-0.35<h <0.35) where TOF (stop) counter has acceptance. This enables (i) analysis for events triggered by “NTC” counter(1.2<|h|<3.0), and (ii) further study for the event bias. BBC TZR NTC TOF BBC TZR

  4. Particle identification by the flight time The time difference, DT, between (i) the measured flight time and (ii) the expected time from measured path length and momentum are calculated for each particle.  For p  For K  For p  For back ground For each of positive and negative charged particles, in the momentum slices of DT, particle identification is done with f(x) = “3 gaussian (for p, K, p) + polynominal (for back ground)” fits.

  5. PID typical example(p =1.1 ~ 1.3 GeV/c [200 MeV/c slice]) via TOF-TZR via TOF-BBC Both of the method gives good hadron identification. To study event bias etc., track-by-track starting (TZR) is needed. p+ p+ p K+ p K+ Y-axis: yield [a.u.] p - p - p-bar K- p-bar K- X-axis DT [ns]

  6. Definitions of PID boundaries In the following 3 slides (for pi, K, p respectively), the definition of identification are: in each of 4 graphs (positive via TOF-TZR, positive via TOF-BBC, negative via TOF-TZR, negative via TOF-BBC) (1)Upper points: DT upper boundaries for PID [ns] in 2 sigma (with 0.1 sigma as its error bar) from the mean for THE particle species. (2)Middle points: DT mean [ns] (with error of itself got during the gaussian fitting) for THE particle species. (3)Lower points: DT lower boundaries for PID [ns] in 2 sigma (with 0.1 sigma as its error bar) from the mean for THE particle species.

  7. [Pion]DT boundaries RED: POSITIVEBLUE:NEGATIVE TOF-BBC Y-axis: DT [ns] TOF-TZR In wide range of pt, >2 sigma separation is succeeded. X-axis momentum [GeV/c]

  8. [Kaon]DT boundaries RED: POSITIVEBLUE:NEGATIVE TOF-BBC Y-axis: DT [ns] TOF-TZR In wide range of pt, >2 sigma separation is succeeded. X-axis momentum [GeV/c]

  9. [Proton]DT boundaries RED: POSITIVEBLUE:NEGATIVE TOF-BBC Y-axis: DT [ns] TOF-TZR In wide range of pt, >2 sigma separation is succeeded. X-axis momentum [GeV/c]

  10. [pion] Fitted PID boundaries (by second polynomial) TOF-BBC is used in this analysis for the PID and fiducial selection. Negative Positive

  11. [Kaon] Fitted PID boundaries (by second polynomial) TOF-BBC is used in this analysis for the PID and fiducial selection. Negative Positive

  12. [proton] Fitted PID boundaries (by second polynomial) TOF-BBC is used in this analysis for the PID and fiducial selection. Negative Positive

  13. Fiducial cut Common method with Au+Au data analysis is used. Fiducial difference between p+p and Au+Au due to dead/inactive region gives ~13% error on the yield ratio.

  14. p+ p- K+ K- anti-proton proton Correction function pT [GeV/c]

  15. Pion particle ratio Stat. error: vertical line Sys. error: short horizontal line mark

  16. Kaon particle ratio Stat. error: vertical line Sys. error: short horizontal line mark

  17. Proton particle ratio Stat. error: vertical line Sys. error: short horizontal line mark

  18. More o More than 10 times of the statistics, we have recorded. o Better calibration is in process for the wider range of kinematics coverage. o For further understanding, the event bias study with TZR and NTC is on going. More from

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