STARPHENIX Comparison Differences in the analyses Richard Seto

STAR-PHENIX Comparison Differences in the analyses Richard Seto Collected slides from Charlie, dipali etc

p-p @ 200 Ge. V 9/30/2020 pp comparison 2

Min Bias d + Au @ 200 Ge. V d. Au min bias comparison 9/30/2020 3

d. Au 9/30/2020 d. Au comparison 4

Au-Au data Au. Au comp arison 9/30/2020 5

comments • Au. Au – PP same – Au. Au star higher than phenix – all centralities – HENCE • Rcp should be same in both exps – it is • R_AA will be different - phenix suppressed Star not (this is what is seen) – When does hard scattering come in? • d. A – pp same – d. Au • Central: star slightly higher than phenix. • peripheral- nominal agreement – HENCE • Rcp different in the two experiments with phenix showing suppression • Rd. A different in two experiments with phenix showing suppression • STAR shows no suppression in both (IS THIS TRUE? ) – Rd. Au phenix is shows “suppression!!!? ” 9/30/2020 6

More comments • PHENIX higher than STAR in ALL AU-AU and Central d. Au • PHENIX and STAR “agree” in pp and peripheral d. Au • PHENIX lower than star on high multiplcity events – Multiplcity dependent problem? – Embedding or efficiency? ? 9/30/2020 7

d. Au 9/30/2020 8

AU-Au Current Status of the Run 2 Discrepancy Looking at the integrated yield numbers d. N/dy • Publications from Run 2 Au+Au data at 200 Ge. V – STAR in PL B 612 (April 2005) 181 -189 – PHENIX in PR C 72 (July 2005) 014903 • One common centrality bin and minimum bias data can be directly compared using exponential fitting Centrality STAR d. N/dy PHENIX d. N/dy STAR T PHENIX T 0 - 10% 6. 65 +/- 0. 35 +/- 0. 73 3. 94 +/- 0. 60 +/- 0. 62 357 +/- 14 +/- 39 376 +/- 24 +/- 20 Mininum Bias 2. 40 +/- 0. 07 +/- 0. 26 1. 34 +/- 0. 09 +/- 0. 21 353 +/- 9 +/- 39 366 +/- 11 +/- 18 Run 2 discrepancy factors for d. N/dy 1. 69 +/- 0. 27 (0 - 10% centrality) 1. 79 +/- 0. 13 (minimum bias) 9/30/2020 statistical errors only 9

Update from QM’ 05 Presentations • Both STAR and PHENIX presented Run 4 yield results – Both stated that their Run 4 results agreed with their Run 2 results By inference the integrated yield discrepancy persists for Run 4 – Questions were asked about the STAR-PHENIX discrepancy Obvious interest in getting this discrepancy resolved – STAR had a back-up slide not shown quoting a Rafelski et al. preprint which questioned the lowest PHENIX m. T data point in 0 -10% centrality (that back-up slide will be shown later in this presentation) • STAR and PHENIX presented the first v 2 results for the – STAR’s result tended to be higher than PHENIX’s result but the error bars are too large to conclude that there is a discrepancy – The yield discrepancy may diminish the credence of the v 2 quotes ? • PHENIX declined to show Rd. Au results for the • STAR declined to show Run 4 RAA results for the but PHENIX did show Run 4 RAA results claiming suppression – In its Run 2 paper STAR had shown an absence of suppression for the 9/30/2020 10

RAA and RCP From Run 2 STAR (PLB figure) STAR sees almost the same RCP ~0. 5 for the as PHENIX in the Run 2 data STAR sees no RAA suppression for the in the 0 -5% centrality bin from Run 2 for the p. T range 1. 5 to 3. 4 Ge. V/c STAR sees RAA ~1. 5 enhancement for the in the 60 -80% centrality bin for the p. T range 1. 5 to 3. 4 Ge. V/c 9/30/2020 11

RAA and RCP from Run 4 PHENIX (QM’ 05 prelim figures) PHENIX claims RAA ~0. 4 suppression for the in the 0 -10% centrality bin for the p. T range 1. 5 to 2. 1 Ge. V/c comparable to effect seen in the p 0 Suppression decreases in the 60 -90% bin, again comparable to the p 0 RCP for the comparable to what STAR has published for Run 2 9/30/2020 12

Update on RCP 2. 5 Ratio 2. 0 1. 5 Rd. Au RAA(60~80/pp) RAA(05/pp) 1. 0 0. 5 STAR Preliminary Talk by Xiangzhou Cai 0. 0 0. 5 1. 0 1. 5 2. 0 2. 5 3. 0 3. 5 4. 0 PT (Ge. V/c 2 ) PHENIX Preliminary: Talk by D. Pal The RCP is well below proton or lambda RCP. Consistent with NCQ scaling expectations. a discrepancy arises between PHENIX and STAR RAA (RAA ≠ RCP) 9/30/2020 13

Question about Rd. Au for the in PHENIX Values appear to be systematically low? 9/30/2020 14

Unshown STAR Backup Slide from QM’ 05 (but it shows what they are thinking) Johann Rafelski etc. nucl-th/0412072 0 - 10% centrality STAR data 0 - 10% centrality PHENIX data 0 - 10% centrality STAR and PHENIX 9/30/2020 Rafelski et al. conjecture that the lowest PHENIX m. T data point is a factor of 1. 5 too low and this drives the low d. N/dy value for PHENIX. Since STAR has more low m. T data, then STAR’s result is more believable My opinion (see next slide): By using a linear plot Rafelski et al. obscure the difference in normalization at the higher m. T points. Rafelski et al. also ignore the minimum bias data discrepancy. 15