5,413 research outputs found
Proton-proton and deuteron-gold collisions at RHIC
We try to understand recent data on proton-proton and deuteron-gold
collisions at RHIC, employing a modified parton model approach.Comment: Invited talk, given at the XXth Winter Workshop on Nuclear Dynamics,
Trelawny Beach, Jamaica, March 200
A New String Model: NEXUS 3
After discussing conceptual problems with the conventional string model, we
present a new approach, based on a theoretically consistent multiple scattering
formalism.
First results for proton-proton scattering at 158 GeV are discussed.Comment: invited talk given at the 9th Winter Workshop on Nuclear Dynamics,
Breckenridge, Colorado, February 9 - 14, 200
Probing Hadronization with Strangeness
The Omega-bar/Omega ratio originating from string decays is predicted to be
larger than unity in proton-proton interaction at SPS energies. The anti-omega
dominance increases with decreasing beam energy. This surprising behavior is
caused by the combinatorics of quark-antiquark production in small and low-mass
strings. Since this behavior is not found in a statistical description of
hadron production in proton-proton collisions, it may serve as a key observable
to probe the hadronization mechanism in such collisions.Comment: 10 pages, proceedings of the 18th International Winter Workshop on
Nuclear Dynamics, Nassau, Bahamas, January 200
Strange Particles from NEXUS 3
After discussing conceptual problems with the conventional string model, we
present a new approach, based on a theoretically consistent multiple scattering
formalism. First results for strange particle production in proton-proton
scattering at 158 GeV and at 200 GeV (cms) are discussed.Comment: invited talk, given at the Strange Quark Matter Conference, Atlantic
Beach, North Carolina, March 12-17, 200
Constraints on Models for Proton-Proton Scattering from Multi-strange Baryon Data
The recent data on pp collisions at 158 GeV provide severe constraints on
string models: These measurements allow for the first time to determine how
color strings are formed in ultrarelativistic proton-proton collisions.Comment: 8 pages, 17 figure
Formation time dependence of femtoscopic correlations in p+p collisions at =7 TeV
We investigate femtoscopic correlations using the UrQMD approach
combined with a correlation afterburner. The dependence of
correlations on the charged particle multiplicity and formation time in p+p
collisions at = 7 TeV is explored and compared to present ALICE
data. The data allows to constrain the formation time in the string
fragmentation to fm/c.Comment: 9 pages, 2 figure
A Novel Mechanism of H^0 Di-baryon Production in Proton-Proton Interactions from Parton Based Gribov-Regge Theory
A novel mechanism of H^0 and strangelet production in hadronic interactions
within the Gribov-Regge approach is presented. In contrast to traditional
distillation approaches, here the production of multiple (strange) quark bags
does not require large baryon densities or a QGP. The production cross section
increases with center of mass energy. Rapidity and transverse momentum
distributions of the H^0 are predicted for pp collisions at E_lab = 160 AGeV
(SPS) and \sqrt s = 200 AGeV (RHIC). The predicted total H^0 multiplicities are
of order of the Omega-baryon yield and can be accessed by the NA49 and the STAR
experiments.Comment: 4 page
First Physics Results at the Physical Pion Mass from Wilson Twisted Mass Fermions at Maximal Twist
We present physics results from simulations of QCD using dynamical
Wilson twisted mass fermions at the physical value of the pion mass. These
simulations were enabled by the addition of the clover term to the twisted mass
quark action. We show evidence that compared to previous simulations without
this term, the pion mass splitting due to isospin breaking is almost completely
eliminated. Using this new action, we compute the masses and decay constants of
pseudoscalar mesons involving the dynamical up and down as well as valence
strange and charm quarks at one value of the lattice spacing,
fm. Further, we determine renormalized quark masses as well as their
scale-independent ratios, in excellent agreement with other lattice
determinations in the continuum limit. In the baryon sector, we show that the
nucleon mass is compatible with its physical value and that the masses of the
baryons do not show any sign of isospin breaking. Finally, we compute
the electron, muon and tau lepton anomalous magnetic moments and show the
results to be consistent with extrapolations of older ETMC data to the
continuum and physical pion mass limits. We mostly find remarkably good
agreement with phenomenology, even though we cannot take the continuum and
thermodynamic limits.Comment: 45 pages, 15 figure
Satellites and large doping- and temperature-dependence of electronic properties in hole-doped BaFe2As2
Over the last years, superconductivity has been discovered in several
families of iron-based compounds. Despite intense research, even basic
electronic properties of these materials, such as Fermi surfaces, effective
electron masses, or orbital characters are still subject to debate. Here, we
address an issue that has not been considered before, namely the consequences
of dynamical screening of the Coulomb interactions among Fe-d electrons. We
demonstrate its importance not only for correlation satellites seen in
photoemission spectroscopy, but also for the low-energy electronic structure.
From our analysis of the normal phase of BaFe2As2 emerges the picture of a
strongly correlated compound with strongly doping- and temperature-dependent
properties. In the hole overdoped regime, an incoherent metal is found, while
Fermi-liquid behavior is recovered in the undoped compound. At optimal doping,
the self-energy exhibits an unusual square-root energy dependence which leads
to strong band renormalizations near the Fermi level
- …