2,015 research outputs found
ALICE results on heavy-ion physics at the LHC
ALICE is a multipurpose detector for high-energy nucleus-nucleus physics at the CERN Large Hadron Collider. In November 2010, ALICE took its first Pb-Pb data at the center-of-mass energy of 2.76TeV per nucleon pair; reference
data in proton-proton collisions at the same energy were collected in 2011. This paper gives an overview of the main physics results obtained with these data. In particular, I will present results on identified charged and strange particle transverse momentum spectra, on anisotropic flow of charged particles, on open heavy flavour and quarkonia production in Pb-Pb collisions, compared to pp collisions. These first Pb-Pb results from ALICE at LHC are broadly consistent with expectations based on lower energy RHIC and SPS data. They indicate that matter created in these
collisions, while initially much larger and hotter, still behaves like a very strongly interacting, almost perfect liquid. A brief outlook on the expected results from the
second, higher statistics Pb-Pb run of Fall 2011 will be given as well
Mass modification of D-meson in hot hadronic matter
We evaluate the in-medium and -meson masses in hot hadronic
matter induced by interactions with the light hadron sector described in a
chiral SU(3) model. The effective Lagrangian approach is generalized to SU(4)
to include charmed mesons. We find that the D-mass drops substantially at
finite temperatures and densities, which open the channels of the decay of the
charmonium states (, , ) to pairs in
the thermal medium. The effects of vacuum polarisations from the baryon sector
on the medium modification of the -meson mass relative to those obtained in
the mean field approximation are investigated. The results of the present work
are compared to calculations based on the QCD sum-rule approach, the
quark-meson coupling model, chiral perturbation theory, as well as to studies
of quarkonium dissociation using heavy quark potential from lattice QCD.Comment: 18 pages including 7 figures, minor revision of the text, figure
styles modified, to appear in Phys. Rev.
Geometric Parameterization of Absorption in Heavy Ion Collisions
We calculate the survival probability of particles in various
colliding systems using a Glauber model. An analysis of recent data has
reported a -nucleon breakup cross section of 6.20.7 mb derived
from an exponential fit to the ratio of to Drell-Yan yields as a
function of a simple, linearly-averaged mean path length through the nuclear
medium. Our calculations indicate that, due to the nature of the calculation,
this approach yields an apparent breakup cross section which is systematically
lower than the actual value.Comment: LaTex, 7 pages, 2 figure
The Future of Dancefloors: Building More Flexible, Open and Innovative Clubbing Experiences
Nightclubs across the world are in a state of crisis due to COVID-19, and neither inaction or ‘business as usual’ are viable options if the industry is to survive it.
It has never been more important to question, innovate and re-imagine the status quo
A model-independent analysis of the dependence of the anomalous J/psi suppression on the number of participant nucleons
A recently published experimental dependence of the J/psi to Drell-Yan ratio
on the measured, by a zero degree calorimeter, forward energy E_ZDC in Pb+Pb
collisions at the CERN SPS is analyzed. Using a model-independent approach it
is shown that the data are at variance with an earlier published experimental
dependence of the same quantity on the transverse energy of neutral hadrons
E_T. The discrepancy is related to a moderate centrality region: 100 < N_p <
200 (N_p is the number of participant nucleons) and is peculiar only to the
data obtained within the `minimum bias' analysis (using the `theoretical
Drell-Yan'). This could result from systematic experimental errors in the
minimum bias sample. A possible source of the errors is discussed.Comment: 10 pages, LaTeX, 3 PS-figures. V2: Misprints are correcte
Coherent J/psi production - a novel feature at LHC?
Energy dependence of heavy quarkonia production in hadron-nucleus collisions
is studied in the framework of the Glauber-Gribov theory. We emphasize a change
in the space-time picture of heavy-quark state production on nuclei with
energy. Longitudinally ordered scattering of a heavy-quark system takes place
at low energies, while with increasing energy it transforms to a coherent
scattering of projectile partons on the nuclear target. The characteristic
energy scale for this transition depends on masses and rapidities of produced
particles. For J/psi, produced in the central rapidity region, the transition
happens at RHIC energies. The parameter-free calculation of J/psi in dAu
collisions is in good agreement with recent RHIC data. We use distributions of
gluons in nuclei to predict suppression of heavy quarkonia at LHC.Comment: 13 pages, 4 figures; experimental data and reference included,
conclusions unchanged; to appear in Phys. Lett.
Characterisation of silicon strip detectors with a binary readout chip for X-ray imaging
In this paper we describe the development of a multichannel readout system for X-ray measurements using silicon strip detectors. The developed system is based on a binary readout architecture and optimised for detection of X-rays of energies in the range 6}30 keV. The critical component of the system is the 32-channel front-end chip, RX32N, which has been optimised for low noise performance, small channel to channel variation and high counting rate operation. The performance of the chip is demonstrated by measurements of complex X-ray spectra using silicon strip and pad detectors. The obtained results allow to use the system at room temperature with the detection threshold in the range from 500 to 10 000 electrons, which is enough in many crystallographic and medical imaging applications. ( 2000 Elsevier Scienc
Charmonium suppression at RHIC and SPS: a hadronic baseline
A kinetic equation approach is applied to model anomalous J/psi suppression
at RHIC and SPS by absorption in a hadron resonance gas which successfully
describes statistical hadron production in both experiments. The puzzling
rapidity dependence of the PHENIX data is reproduced as a geometric effect due
to a longer absorption path for J/psi production at forward rapidity.Comment: 16 pages, 6 figures, final version accepted for publication in Phys.
Lett.
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