3,798 research outputs found
Heavy-flavour production in Pb-Pb collisions at the LHC, measured with the ALICE detector
We present the first results from the ALICE experiment on the nuclear
modification factors for heavy-flavour hadron production in Pb-Pb collisions at
sqrt{s_NN}=2.76 TeV. Using proton-proton and lead-lead collision samples at
sqrt{s}=7 TeV and sqrt{s_NN}=2.76 TeV, respectively, nuclear modification
factors R_AA(pt) were measured for D mesons at central rapidity (via displaced
decay vertex reconstruction), and for electrons and muons, at central and
forward rapidity, respectively.Comment: 8 pages, 5 figures, plenary talk at Quark Matter 2011, Annecy, Franc
Investigation of charm and beauty production via semileptonic decays of heavy-flavour hadrons in pp at 7 TeV and Pb--Pb at 2.76 TeV with ALICE
Electron spectra measured with ALICE at mid-rapidity are used to study the
production of hadrons carrying a charm or a beauty quark. The production cross
section of electrons from heavy-flavour hadron decays is measured in pp
collisions at =7 TeV. Electrons from the beauty decays are identified
via the displacement from the interaction vertex. From the electron spectra
measured in Pb--Pb collisions, we determine the nuclear modification factor,
which is sensitive to the heavy-quark energy loss in a hot strongly interacting
medium.Comment: Quark Matter 2011 proceeding
Computer simulation of pulsed field gel runs allows the quantitation of radiation-induced double-strand breaks in yeast
A procedure for the quantification of double-strand breaks in yeast is presented that utilizes pulsed field gel electrophoresis (PFGE) and a comparison of the observed DNA mass distribution in the gel lanes with calculated distributions. Calculation of profiles is performed as follows. If double-strand breaks are produced by sparsely ionizing radiation, one can assume that they are distributed randomly in the genome, and the resulting DNA mass distribution in molecular length can be predicted by means of a random breakage model. The input data for the computation of molecular length profiles are the breakage frequency per unit length, , as adjustable parameter, and the molecular lengths of the intact chromosomes. The obtained DNA mass distributions in molecular length must then be transformed into distributions of DNA mass in migration distance. This requires a calibration of molecular length vs. migration distance that is specific for the gel lane in question. The computed profiles are then folded with a Lorentz distribution with adjusted spread parameter to account for and broadening. The DNA profiles are calculated for different breakage frequencies and for different values of , and the parameters resulting in the best fit of the calculated to the observed profile are determined
Charm diffusion in a pion gas implementing unitarity, chiral and heavy quark symmetries
We compute the charm drag and diffusion coefficients in a hot pion gas, such
as is formed in a Heavy Ion Collision after the system cools sufficiently to
transit into the hadron phase. We fully exploit Heavy Quark Effective Theory
(with both D and D* mesons as elementary degrees of freedom during the
collision) and Chiral Perturbation Theory, and employ standard unitarization to
reach higher temperatures. We find that a certain friction and shear diffusion
coefficients are almost p-independent at fixed temperature which simplifies
phenomenological analysis. At the higher end of reliability of our calculation,
T about 150 MeV, we report a charm relaxation length of some 40 fm, in
agreement with the model estimate of He, Fries and Rapp. The momentum of a
1-GeV charm quark decreases about 50 MeV per Fermi when crossing the hadron
phase.Comment: 23 pages, 29 figure
D meson nuclear modification factors in Pb-Pb collisions at {\surd}sNN = 2.76 TeV, measured with the ALICE detector
The ALICE experiment has measured the D meson production in pp and Pb-Pb
collisions at the LHC at {\surd}s = 7 and 2.76 TeV and {\surd}sNN = 2.76 TeV
respectively, via the exclusive reconstruction of hadronic decay channels. The
analyses of the D0{\to}K-pi+ and D+{\to}K-pi+pi+ channels will be described and
the preliminary results for the D0 and D+ nuclear modification factor will be
presented.Comment: Proceedings of Quark Matter 2011 conference. 4 pages, 4 figures. The
slides of the talk can be found at the link:
http://indico.cern.ch/materialDisplay.py?contribId=591&sessionId=53&materialId=slides&confId=3024
Review of SIS Experimental Results on Strangeness
>A review of meson emission in heavy ion collisions at incident energies
around 1 -- 2 GeV is presented. It is shown how the shape of the
spectra and the various particle yields vary with system size, with centrality
and with incident energy. A statistical model assuming thermal and chemical
equilibrium and exact strangeness conservation (i.e. strangeness conservation
per collision) explains most of the observed features.
Emphasis is put onto the study of and emission. In the framework
of this statistical model it is shown that the experimentally observed equality
of and rates at threshold corrected energies is due to a crossing of two excitation functions. Furthermore,
the independence of the to ratio on the number of participating
nucleons observed between 1 and 10 GeV is consistent with this model.
The observed flow effects are beyond the scope of this model.Comment: 10 pages, 9 figures, Strangeness 2000, V International Conference on
Strangeness in Quark Matter, July, 2000, Berkeley, Californi
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