1,043 research outputs found
Production and rescattering of strange baryons at SPS energies in a transport model with hadron potentials
A mean-field potential version of the Ultra-relativistic Quantum Molecular
Dynamics (UrQMD) model is used to investigate the production of strange
baryons, especially the s and s, from heavy ion
collisions at SPS energies. It is found that, with the consideration of both
formed and pre-formed hadron potentials in UrQMD, the transverse mass and
longitudinal rapidity distributions of experimental data of both s and
s can be quantitatively explained fairly well. Our
investigation also shows that both the production mechanism and the
rescattering process of hadrons play important roles in the final yield of
strange baryons.Comment: 15 pages, 7 figure
Anomalous behavior of pion production in high energy particle collisions
A shape of invariant differential cross section for charged hadron production
as function of transverse momentum measured in various collider experiments is
analyzed. Contrary to the behavior of produced charged kaons, protons and
antiprotons, the pion spectra require an anomalously high contribution of an
exponential term to describe the shape.Comment: 4 pages, 6 figure
Coherent Production of Pairs of Parabosons of Order 2
A parameter-free statistical model is used to study multiplicity signatures
for coherent production of charged-pairs of parabosons of order p=2 in
comparison with those arising in the case of ordinary bosons, p=1. Two
non-negative real parameters arise because "ab" and "ba" are fundamentally
distinct pair operators of charge "+1", A-quanta and charge "-1", B-quanta
parabosons. In 3D plots of P(q)_m = "The probability of m paraboson
charged-pairs and q positive parabosons" versus and , the p=1
curve is found to lie on the relatively narrow 2D p=2 surface.Comment: 25 pages, 16 figures, no macro
Neutrino emission from dark matter annihilation/decay in light of cosmic and data
A self-consistent global fitting method based on the Markov Chain Monte Carlo
technique to study the dark matter (DM) property associated with the cosmic ray
electron/positron excesses was developed in our previous work. In this work we
further improve the previous study to include the hadronic branching ratio of
DM annihilation/decay. The PAMELA data are employed to constrain
the hadronic branching ratio. We find that the 95% () upper limits of
the quark branching ratio allowed by the PAMELA data is for DM annihilation and for DM decay respectively. This
result shows that the DM coupling to pure leptons is indeed favored by the
current data. Based on the global fitting results, we further study the
neutrino emission from DM in the Galactic center. Our predicted neutrino flux
is some smaller than previous works since the constraint from -rays is
involved. However, it is still capable to be detected by the forth-coming
neutrino detector such as IceCube. The improved points of the present study
compared with previous works include: 1) the DM parameters, both the particle
physical ones and astrophysical ones, are derived in a global fitting way, 2)
constraints from various species of data sets, including -rays and
antiprotons are included, and 3) the expectation of neutrino emission is fully
self-consistent.Comment: 13 pages, 2 figures, 1 table; Published in IJMPA 201
Dijet Cross Section and Longitudinal Double Spin Asymmetry Measurements in Polarized Proton-proton Collisions at \sqrt{s}=200 GeV at STAR
These proceedings show the preliminary results of the dijet cross sections
and the dijet longitudinal double spin asymmetries A_LL in polarized
proton-proton collisions at \sqrt{s} = 200 GeV at the mid-rapidity |eta| < 0.8.
The integrated luminosity of 5.39 pb^{-1} collected during RHIC Run-6 was used
in the measurements. The preliminary results are presented as functions of the
dijet invariant mass M_jj. The dijet cross sections are in agreement with
next-to-leading-order pQCD predictions. The A_LL is compared with theoretical
predictions based on various parameterizations of polarized parton
distributions of the proton. Projected precision of data analyzed to date from
Run-9 are shown.Comment: 8 pages, 5 figures, Proceedings of the SPIN2010 conference (Juelich,
Germany, 2010
More loosely bound hadron molecules at CDF?
In a recent paper we have proposed a method to estimate the prompt production
cross section of X(3872) at the Tevatron assuming that this particle is a
loosely bound molecule of a D and a D*bar meson. Under this hypothesis we find
that it is impossible to explain the high prompt production cross section found
by CDF at sigma(X(3872)) \sim 30-70 nb as our theoretical prediction is about
300 times smaller than the measured one. Following our work, Artoisenet and
Braaten, have suggested that final state interactions in the DD*bar system
might be so strong to push the result we obtained for the cross section up to
the experimental value. Relying on their conclusions we show that the
production of another very narrow loosely bound molecule, the X_s=D_s D_s*bar,
could be similarly enhanced. X_s should then be detectable at CDF with a mass
of 4080 MeV and a prompt production cross section of sigma(X_s) \sim 1-3 nb.Comment: Minor revisions made. To appear in Phys Lett
Quantum Number Density Asymmetries Within QCD Jets Correlated With Lambda Polarization
The observation of jets in a variety of hard-scattering processes has allowed
the quantitative study of perturbative quantum chromodynamics (PQCD) by
comparing detailed theoretical predictions with a wide range of experimental
data. This paper examines how some important, nonperturbative, facets of QCD
involving the internal dynamical structure of jets can be studied by measuring
the spin orientation of Lambda particles produced in these jets. The
measurement of the transverse polarization for an individual Lambda within a
QCD jet permits the definition of spin-directed asymmetries in local quantum
number densities in rapidity space (such as charge, strangeness and baryon
number densities) involving neighboring hadrons in the jet. These asymmetries
can only be generated by soft, nonperturbative dynamical mechanisms and such
measurements can provide insight not otherwise accessible into the color
rearrangement that occurs during the hadronization stage of the fragmentation
process.Comment: The replacement manuscript contains a new abstract, five pages of
additional material and a revised version of Fig.
Theoretical Aspects of Particle Production
These lectures describe some of the latest data on particle production in
high-energy collisions and compare them with theoretical calculations and
models based on QCD. The main topics covered are: fragmentation functions and
factorization, small-x fragmentation, hadronization models, differences between
quark and gluon fragmentation, current and target fragmentation in deep
inelastic scattering, and heavy quark fragmentation.Comment: 26 pages, 27 figures. Lectures at International Summer School on
Particle Production Spanning MeV and TeV Energies, Nijmegen, The Netherlands,
August 199
The physical environment and multi-professional teamwork in three newly built stroke units
Purpose: To explore multi-professional teamwork in relation to the physical environment in three newly built or renovated stroke units. Materials and methods: An observational study was undertaken. The participants were all staff members of a multi-professional team working in the reviewed stroke units. The data were collected using behavioural mapping and semi-structured observations, and they were analysed by content analysis and descriptive statistics. Results: Out of all the observations in the behavioural mapping, very few were of two or more members from the team together with a patient. None of the included stroke units had a co-location for all the members of the multi-professional team. Three main categories emerged from the analysis of the interviews: (i) the hub of the unit; (ii) the division of places; and (iii) power imbalance. All the categories reflected the teamwork in relation to parts of the physical environment. Conclusion: The design of the physical environment is important for multi-professional teamwork. Emphasis must be placed on better understanding the impact of the physical environment and on incorporating the evidence related to multi-professional teamwork during the design of stroke units.IMPLICATIONS FOR REHABILITATION Understanding the link between the physical environment and effective teamwork can lead to more tailored and supportive design solutions. The design of the physical environment should be considered as a vital part of effective teamwork in stroke units. The physical environment should include shared workstations, allowing team members to meet and communicate face to face
Wroclaw neutrino event generator
A neutrino event generator developed by the Wroclaw Neutrino Group is
described. The physical models included in the generator are discussed and
illustrated with the results of simulations. The considered processes are
quasi-elastic scattering and pion production modelled by combining the
resonance excitation and deep inelastic scattering.Comment: Talk given at 2nd Scandanavian Neutrino Workshop (SNOW 2006),
Stockholm, Sweden, 2-6 May 2006. 3 pages, 6 figure
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