p/in BRAHMS at forward y Paweł Staszel Jagiellonian University

Analysis concept 1. the analysis utilizes the feature of same pion and proton acceptance in eta vs p T space in the same real time measurement. 2. for a given y bin we calculate p/π ratios on setting by setting basis (same real time measurement) separately for Tof2 pid and Rich pid. 3. in this way all factors like acceptance, tracking efficiencies, trigger normalization cancel out in the ratio. The only remained corrections are specie related which is geant correction (delivered by Flemming) and pid efficiency correction. Thus pid is a crucial part of the analysis

Rich 1. for Rich in first step we parametrize the rich inefficiency vs momentum by studying pions yields in tof2 for tracks with Rich_ring=0. 2. it can be done for low magnetic field settings (430, 608) but already for these fields one reaches the saturation value (~3%) which is then used for higher field settings --> (here we have to relay on that, that the rich is quite stable device at least over a given specie/energy period.)‏ 3. the result found for pions is then extended to kaons (and other species) assuming that Cherenkov radiation depends only on the gamma factor. Corrections: 1. the correction for pions is just the correction for the inefficiency (~3%)‏ 2. the veto protons are corrected for pion+kaon contamination, which is taken as:

Extending inefficiency to other specie

Two methods comparison tof2 pions with rich veto all tof2 pions

Inefficiency versus ring radius

Testing correction for veto protons

Tof2 Tof2 pid approach is similar to that described in Flemming's note on analysis: Rich(veto) information is used to determine kaons in the range where they overlap with pions which leads a relatively clean sample of pions.

Tof2

Tof2 in

protons with false rings

Results

p/π + at

Central vs

pbar/π - at

Central vs

auau and

200 vs 62 for the same μ B

this analysis vs some published is

this analysis vs some published 200, η=3.3

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