1,129 research outputs found
The dependence of strange hadron multiplicities on the speed of hadronization
Hadron multiplicities are calculated in the ALCOR model for the Pb+Pb
collisions at CERN SPS energy. Considering the newest experimental results, we
display our prediction obtained from the ALCOR model for stable hadrons
including strange baryons and anti-baryons.Comment: 8 pages, LaTeX in IOP style, appeared in the Proceedings of
Strangeness'97 Conference, Santorini, April 14-18 1997, J. of Physics G23
(1997) 194
Scaling of transverse energies and multiplicities with atomic number and energy in ultrarelativistic nuclear collisions
We compute how the initial energy density and produced gluon, quark and
antiquark numbers scale with atomic number and beam energy in ultrarelativistic
heavy ion collisions. The computation is based on the argument that the effect
of all momentum scales can be estimated by performing the computation at one
transverse momentum scale, the saturation momentum. The initial numbers are
converted to final ones by assuming kinetic thermalisation and adiabatic
expansion. The main emphasis of the study is at LHC and RHIC energies but it is
observed that even at SPS energies this approach leads to results which are not
unreasonable: what is usually described as a completely soft nonperturbative
process can also be described in terms of gluons and quarks. The key element is
the use of the saturation scale.Comment: 13 pages, includes 7 eps-figure
Metal-semiconductor-metal photodetectors on a GeSn-on-insulator platform for 2 µm applications
In this work, the metal-semiconductor-metal photodetectors were demonstrated on the Ge0.91Sn0.09-on-insulator (GeSnOI) platform. The responsivity was 0.24 and 0.06 A/W at wavelengths of 1,600 and 2,003 nm, respectively. Through a systematic study, it is revealed that the photodetectors can potentially detect wavelength beyond 2,200 nm. The dark current density was measured to be 4.6 A/cm2 for GeSnOI waveguide-shaped photodetectors. The 3 dB bandwidth was observed to be 1.26 and 0.81 GHz at 1,550 and 2,000 nm wavelengths, respectively. This work opens up an opportunity for low-cost 2 µm wavelength photodetection on the GeSn/Ge interface-free GeSnOI platform
Pair excitations and the mean field approximation of interacting Bosons, I
In our previous work \cite{GMM1},\cite{GMM2} we introduced a correction to
the mean field approximation of interacting Bosons. This correction describes
the evolution of pairs of particles that leave the condensate and subsequently
evolve on a background formed by the condensate. In \cite{GMM2} we carried out
the analysis assuming that the interactions are independent of the number of
particles . Here we consider the case of stronger interactions. We offer a
new transparent derivation for the evolution of pair excitations. Indeed, we
obtain a pair of linear equations describing their evolution. Furthermore, we
obtain apriory estimates independent of the number of particles and use these
to compare the exact with the approximate dynamics
Hadronization of massive quark matter
We present a fast hadronization model for the constituent quark plasma (CQP)
produced in relativistic heavy ion collisions at SPS. The model is based on
rate equations and on an equation of state inspired by the string
phenomenology. This equation of state has a confining character. We display the
time evolution of the relevant physical quantities during the hadronization
process and the final hadron multiplicities. The results indicate that the
hadronization of CQP is fast.Comment: 12 pages, Latex, 2 EPS figures, contribution to the Proceedings of
the 4th International Conference on Strangeness in Quark Matter (SQM'98),
Padova, Italy, 20-24 July 199
Strange hyperon and antihyperon production from quark and string-rope matter
Hyperon and antihyperon production is investigated using two microscopical
models: {\bf (1)} the fast hadronization of quark matter as given by the ALCOR
model; {\bf (2)} string formation and fragmentation as in the HIJING/B model.
We calculate the particle numbers and momentum distributions for Pb+Pb
collisions at CERN SPS energies in order to compare the two models with each
other and with the available experimental data. We show that these two
theoretical approaches give similar yields for the hyperons, but strongly
differ for antihyperons.Comment: 11 pages, Latex, 3 EPS figures, contribution to the Proceedings of
the 4th International Conference on Strangeness in Quark Matter (SQM'98),
Padova, Italy, 20-24 July 199
Time Dependence of Chemical Freeze-out in Relativistic Heavy Ion Collisions
We investigate chemical and thermal freeze-out time dependencies for strange
particle production for CERN SPS heavy ion collisions in the framework of a
dynamical hadronic transport code. We show that the Lambda yield changes
considerably after hadronization in the case of Pb+Pb collisions, whereas for
smaller system sizes (e.g. S+S) the direct particle production dominates over
production from inelastic rescattering. Chemical freeze-out times for strange
baryons in Pb+Pb are smaller than for non-strange baryons, but they are still
sufficiently long for hadronic rescattering to contribute significantly to the
final Lambda yield. Based on inelastic and elastic cross section estimates we
expect the trend of shorter freeze-out times (chemical and kinetic), and thus
less particle production after hadronization, to continue for multi-strange
baryons.Comment: 10 pages, 7 postscript figure
Transverse Momentum Spectra of and Mesons from Quark Gluon Plasma Hadronization at CERN SPS
A popular derivation of the apparent temperature of the particle transverse
momentum spectra and its inconsistency are considered. An improved formula for
the apparent temperature is discussed. It is shown that recent results on
transverse mass spectra of and mesons support a
hypothesis of statistical production of charmonia at hadronization and suggest
the early thermal freeze-out of these mesons. Using the apparent temperature
formula the collective transverse velocity of the hadronizing quark gluon
plasma is extracted to be . Predictions for transverse mass
spectra of hidden and open charm mesons along with bottomonium at SPS and RHIC
energies are discussed.Comment: Talk given at the Conference ``Strange Quarks in Matter 2001'',
Frankfurt, September 24-29, 200
Possible Evidence of Disoriented Chiral Condensates from the Anomaly in Omega and AntiOmega Abundances at the SPS
No conventional picture of nucleus-nucleus collisions has yet been able to
explain the abundance of Omega and AntiOmega in central collisions between Pb
nuclei at 158 A GeV at the CERN SPS. We argue that such a deviation from
predictions of statistical thermal models and numerical simulations is evidence
that they are produced as topological defects in the form of skyrmions arising
from the formation of disoriented chiral condensates. The estimated domain size
falls in the right range to be consistent with the so far non-observation of
DCC from the distribution of neutral pions.Comment: paper presented at the ICPAQGP-2001, Jaipur, Indi
Second-order corrections to mean field evolution for weakly interacting Bosons. I
Inspired by the works of Rodnianski and Schlein and Wu, we derive a new
nonlinear Schr\"odinger equation that describes a second-order correction to
the usual tensor product (mean-field) approximation for the Hamiltonian
evolution of a many-particle system in Bose-Einstein condensation. We show that
our new equation, if it has solutions with appropriate smoothness and decay
properties, implies a new Fock space estimate. We also show that for an
interaction potential , where is
sufficiently small and , our program can be easily
implemented locally in time. We leave global in time issues, more singular
potentials and sophisticated estimates for a subsequent part (part II) of this
paper
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