Abstract
The results of E-190 experiment (project Thermalization) with 50 GeV pro- ton beam irradiation of SVD-2 setup are presented. MC simulation has shown the linear dependence of number of photons detected in electromagnetic calorimeter and the average number of neutral pions. Multiplicity distribution of neutral pion, N0, for total number of particles in the event, Ntot = Nch + N0, are obtained with corrections on the setup accep- tance, triggering and effi ciency of the event reconstruction. The scaled variance of neutral pion fluctuations, ! = D/ , versus total multiplicity is measured. The fluctuations increase at Ntot > 18. According to quantum statistics models this behavior can indicate a pion condensate formation in the high pion multiplicity system. This effect has been observed for the first time.
Highlights
Experiment E-190 is carried out at SVD-2 setup located at U-70 accelerator of IHEP, Protvino [1]
Mark Gorenstein and Viktor Begun have shown in statistical model of the ideal pion gas that the neutral pion number fluctuations begin to grow at the total multiplicity higher than certain threshold value, because in this case the pion system is approached to the Bose-Einstein Condensate (BEC) state [4][5]
The FRITIOF7.02 code (3.5∗104 events) shows that 95% photons are the product of π0 decay, < Nch >= 7.9, < N0 >=2.9, < Nγ >=5.4 in total and < Nγ >=2.5 in ECal
Summary
Experiment E-190 is carried out at SVD-2 setup located at U-70 accelerator of IHEP, Protvino [1]. After the first publication of the evidence the rise of the neutral pion number fluctuations [2] the following upgrades of data analysis have been carried out:. Mark Gorenstein and Viktor Begun have shown in statistical model of the ideal pion gas that the neutral pion number fluctuations begin to grow at the total multiplicity higher than certain threshold value, because in this case the pion system is approached to the Bose-Einstein Condensate (BEC) state [4][5]. This phase transition can be revealed by the scaled variance, ω, which is defined as the ratio of variance, D , of the neutral pion number distribution to their mean value < N0 >, ω = D/ < N0 >. Each distribution is characterized by average, < n0 >, and by standard deviation, σ
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