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ANALYSIS OF DIFFERENCES ON PSEUDORAPIDITY MULTIPLICITIES
SPECTRUM AT LHC AND UA1/UA5 EXPERIMENTS
Alexandr Dmitriev
Novgorod State University
ATLAS experiment measured lower transverse momentum spectrum of charged
particle multiplicity for proton-proton collisions at 900 GeV e.c.m. than UA1 experiment for
proton-antiproton collisions at same energy. CMS and ALICE experiments confirmed ATLAS
measures. This effect is in clear disagreement with most models, but was predicted by low
constituent model.
Difference between multiplicities was estimated as 20% from analysis of transverse
momentum spectrum. This value has large uncertainty and need to be improved.
To improve estimation of proton-proton and proton-antiproton multiplicity difference,
one should use not only transverse momentum spectrum, but pseudorapidity multiplicities
spectrum. Straightforward comparison of ATLAS and UA1/UA5 data is impossible because
of significantly different kinematic regions of data.
Common parametrizations of transverse momentum spectrum were applied in this
work to make comparison between ATLAS and UA1/UA5 data. Another applied way to
compare data is PYTHIA based parametrisations, then one gets transverse momentum
spectrum at low momentum from generated particles distributions. Improved estimation of
proton-proton and proton-antiproton multiplicity difference is consistent with low constituent
model.
This work is supported by RFBR grant 11-02-01395-a.
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