4,702 research outputs found
Relative particle yield fluctuations in Pb-Pb collisions at TeV
First results on K/, p/ and K/p fluctuations are obtained with the
ALICE detector at the CERN LHC as a function of centrality in Pb-Pb collisions
at TeV. The observable , which is
defined in terms of the moments of particle multiplicity distributions, is used
to quantify the magnitude of dynamical fluctuations of relative particle yields
and also provides insight into the correlation between particle pairs. This
study is based on a novel experimental technique, called the Identity Method,
which allows one to measure the moments of multiplicity distributions in case
of incomplete particle identification. The results for p/ show a change of
sign in from positive to negative towards more peripheral
collisions. For central collisions, the results follow the smooth trend of the
data at lower energies and exhibits a change in sign for
p/ and K/p.Comment: 19 pages, 4 captioned figures, 2 tables, authors from page 14,
published, figures at http://aliceinfo.cern.ch/ArtSubmission/node/413
production in Pb-Pb collisions at TeV
A measurement of the production of prompt baryons in
Pb-Pb collisions at TeV with the ALICE detector at
the LHC is reported. The and were reconstructed at midrapidity () via the hadronic decay
channel (and
charge conjugate) in the transverse momentum and centrality intervals GeV/ and 0-80%. The /D ratio, which
is sensitive to the charm quark hadronisation mechanisms in the medium, is
measured and found to be larger than the ratio measured in minimum-bias pp
collisions at TeV and in p-Pb collisions at TeV. In particular, the values in p-Pb and Pb-Pb collisions differ by
about two standard deviations of the combined statistical and systematic
uncertainties in the common interval covered by the measurements in
the two collision system. The /D ratio is also
compared with model calculations including different implementations of charm
quark hadronisation. The measured ratio is reproduced by models implementing a
pure coalescence scenario, while adding a fragmentation contribution leads to
an underestimation. The nuclear modification factor,
, is also presented. The measured values of the of
, D and non-strange D mesons are compatible
within the combined statistical and systematic uncertainties. They show,
however, a hint of a hierarchy , conceivable with a contribution
of recombination mechanisms to charm hadron formation in the medium.Comment: 19 pages, 3 captioned figures, 1 table, authors from page 14,
published, figures at http://alice-publications.web.cern.ch/node/469
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