167 research outputs found
A New Phase of Matter: Quark-Gluon Plasma Beyond the Hagedorn Critical Temperature
I retrace the developments from Hagedorn's concept of a limiting temperature
for hadronic matter to the discovery and characterization of the quark-gluon
plasma as a new state of matter. My recollections begin with the transformation
more than 30 years ago of Hagedorn's original concept into its modern
interpretation as the "critical" temperature separating the hadron gas and
quark-gluon plasma phases of strongly interacting matter. This was followed by
the realization that the QCD phase transformation could be studied
experimentally in high-energy nuclear collisions. I describe here my personal
effort to help develop the strangeness experimental signatures of quark and
gluon deconfinement and recall how the experimental program proceeded soon to
investigate this idea, at first at the SPS, then at RHIC, and finally at LHC.
As it is often the case, the experiment finds more than theory predicts, and I
highlight the discovery of the "perfectly" liquid quark-gluon plasma at RHIC. I
conclude with an outline of future opportunities, especially the search for a
critical point in the QCD phase diagram.Comment: To appear in {\em Melting Hadrons, Boiling Quarks} by Rolf Hagedorn
and Johan Rafelski (editor), Springer Publishers, 2015 (open access
Evaluating Frequency, Diagnostic Quality, and Cost of Lyme Borreliosis Testing in Germany: A Retrospective Model Analysis
Background. Data on the economic impact of Lyme borreliosis (LB) on European health care systems is scarce. This project focused on the epidemiology and costs for laboratory testing in LB patients in Germany. Materials and Methods. We performed a sentinel analysis of epidemiological and medicoeconomic data for 2007 and 2008. Data was provided by a German statutory health insurance (DAK) company covering approx. 6.04 million members. In addition, the quality of diagnostic testing for LB in Germany was studied. Results. In 2007 and 2008, the incident diagnosis LB was coded on average for 15,742 out of 6.04 million insured members (0.26%). 20,986 EIAs and 12,558 immunoblots were ordered annually for these patients. For all insured members in the outpatient sector, a total of 174,820 EIAs and 52,280 immunoblots were reimbursed annually to health care providers (cost: 2,600,850€). For Germany, the overall expected cost is estimated at 51,215,105€. However, proficiency testing data questioned test quality and standardization of diagnostic assays used. Conclusion. Findings from this study suggest ongoing issues related to care for LB and may help to improve future LB disease management
Kinetic equation with exact charge conservation
We formulate the kinetic master equation describing the production of charged
particles which are created or destroyed only in pairs due to the conservation
of their Abelian charge.Our equation applies to arbitrary particle
multiplicities and reproduces the equilibrium results for both canonical (rare
particles) and grand canonical (abundant particles) systems. For canonical
systems, the equilibrium multiplicity is much lower and the relaxation time is
much shorter than the naive extrapolation from the grand canonical ensemble
results. Implications for particle chemical equilibration in heavy-ion
collisions are discussed.Comment: 4 Pages in RevTe
Relativistic mass distribution in event-anti-event system and ``realistic'' equation of state for hot hadronic matter
We find the equation of state which gives the value of
the sound velocity in agreement with the ``realistic'' equation of
state for hot hadronic matter suggested by Shuryak, in the framework of a
covariant relativistic statistical mechanics of an event--anti-event system
with small chemical and mass potentials. The relativistic mass distribution for
such a system is obtained and shown to be a good candidate for fitting hadronic
resonances, in agreement with the phenomenological models of Hagedorn, Shuryak,
{\it et al.} This distribution provides a correction to the value of specific
heat 3/2, of the order of 5.5\%, at low temperatures.Comment: 19 pages, report TAUP-2161-9
Recent results in relativistic heavy ion collisions: from ``a new state of matter'' to "the perfect fluid"
Experimental Physics with Relativistic Heavy Ions dates from 1992 when a beam
of 197Au of energy greater than 10A GeV/c first became available at the
Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL)
soon followed in 1994 by a 208Pb beam of 158A GeV/c at the Super Proton
Synchrotron (SPS) at CERN (European Center for Nuclear Research). Previous
pioneering measurements at the Berkeley Bevalac in the late 1970's and early
1980's were at much lower bombarding energies (~ 1 A GeV/c) where nuclear
breakup rather than particle production is the dominant inelastic process in
A+A collisions. More recently, starting in 2000, the Relativistic Heavy Ion
Collider (RHIC) at BNL has produced head-on collisions of two 100A GeV beams of
fully stripped Au ions, corresponding to nucleon-nucleon center-of-mass energy,
sqrt(sNN)=200 GeV, total c.m. energy 200A GeV. The objective of this research
program is to produce nuclear matter with extreme density and temperature,
possibly resulting in a state of matter where the quarks and gluons normally
confined inside individual nucleons (r < 1 fm) are free to act over distances
an order of magnitude larger. Progress from the period 1992 to the present will
be reviewed, with reference to previous results from light ion and
proton-proton collisions where appropriate. Emphasis will be placed on the
measurements which formed the basis for the announcements by the two major
laboratories: "A new state of matter", by CERN on Feb 10, 2000 and "The perfect
fluid", by BNL on April 19, 2005.Comment: 62 pages, 39 figures. Review article published in Reports on Progress
in Physics on June 23, 2006. In this published version, mistakes,
typographical errors, and citations have been corrected and a subsection has
been adde
Hadron and hadron-cluster production in a hydrodynamical model including particle evaporation
We discuss the evolution of the mixed phase at RHIC and SPS within
boostinvariant hydrodynamics. In addition to the hydrodynamical expansion, we
also consider evaporation of particles off the surface of the fluid. The
back-reaction of the evaporation process on the dynamics of the fluid shortens
the lifetime of the mixed phase. In our model this lifetime of the mixed phase
is <12 fm/c in Au+Au at RHIC and <6.5 fm/c in Pb+Pb at SPS, even in the limit
of vanishing transverse expansion velocity. Strangeness separation occurs,
especially in events (or at rapidities) with relatively high initial net baryon
and strangeness number, enhancing the multiplicity of MEMOs (multiply strange
nuclear clusters). If antiquarks and antibaryons reach saturation in the course
of the pure QGP or mixed phase, we find that at RHIC the ratio of antideuterons
to deuterons may exceed 0.3 and even anti-helium to helium>0.1. Due to
fluctuations, at RHIC even negative baryon number at midrapidity is possible in
individual events, so that the antibaryon and antibaryon-cluster yields exceed
those of the corresponding baryons and clusters.Comment: 17 pages, Latex, epsfig stylefil
Pion Multiplicity Distribution in Proton-Antiproton Annihilation at Rest
The pion multiplicity distribution is widely believed to reflect the
statistical aspects of annihilation at rest. We try to reproduce it
in a grand canonical picture with explicit conservation of electric charge,
isospin, total angular momentum, and the parity quantum numbers , , and
via the projection operator formalism. Bose statistics is found to be
non-negligible, particularly in fixing the interaction volume. The calculated
pion multiplicity distribution for
turns out to depend strongly on the conservation of the angular momentum and
connected quantum numbers, as well as on the spin state occupation in S-wave
annihilation. However, the empirical Gaussian pion multiplicity distribution
cannot be reproduced. This calls in question either the statistical ansatz or
the rather old data themselves.Comment: 13pages, TPR-94-3
Signatures of Quark-Gluon-Plasma formation in high energy heavy-ion collisions: A critical review
A critical review on signatures of Quark-Gluon-Plasma formation is given and
the current (1998) experimental status is discussed. After giving an
introduction to the properties of QCD matter in both, equilibrium- and
non-equilibrium theories, we focus on observables which may yield experimental
evidence for QGP formation. For each individual observable the discussion is
divided into three sections: first the connection between the respective
observable and QGP formation in terms of the underlying theoretical concepts is
given, then the relevant experimental results are reviewed and finally the
current status concerning the interpretation of both, theory and experiment, is
discussed. A comprehensive summary including an outlook towards RHIC is given
in the final section.Comment: Topical review, submitted to Journal of Physics G: 68 pages,
including 39 figures (revised version: only minor modifications, some
references added
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