2,324 research outputs found
Transverse Momentum Spectra of Pions in Particle and Nuclear Collisions and Some Ratio-Behaviours: Towards A Combinational Approach
The nature of transverse momentum dependence of the inclusive cross-sections
for secondary pions produced in high energy hadronic(), hadronuclear()
and nuclear() collisions has here been exhaustively investigated for a
varied range of interactions in a unified way with the help of a master
formula. This formula evolved from a new combination of the basic Hagedorn's
model for particle(pion) production in PP scattering at ISR range of energies,
a phenomenological approach proposed by Peitzmann for converting the results of
reactions to those for either or collisions, and a specific
form of parametrization for mass number-dependence of the nuclear cross
sections. This grand combination of models(GCM) is then applied to analyse the
assorted extensive data on various high energy collisions. The nature of
qualitative agreement between measurements and calculations on both the
inclusive cross-sections for production of pions, and some ratios of them as
well, is quite satisfactory. The modest successes that we achieve here in
dealing with the massive data-sets are somewhat encouraging in view of the
diversity of the reactions and the very wide range of interaction energies.Comment: 19 pages, 19 figure
Experimental feeding validates nanofluidic array technology for DNA detection of ungulate prey in wolf scats
The study of carnivores' diet is a key component to enhance knowledge on the ecology of predators and their effect on prey populations. Although molecular approaches to detect prey DNA in carnivore scats are improving, the validation of their accuracy, a prerequisite for reliable applications within ecological frameworks, is still lagging behind the methodological advances. Indeed, variation in detection probability among prey species can occur, representing a potentially insidious source of bias in food-habit studies of carnivores. Calibration of DNA-based methods involves the
optimization of specificity and sensitivity and, whereas priority is usually given to the former to avoid false positives, sensitivity is rarely investigated so that false negatives may be largely overlooked. We conducted feeding trials with captive wolves (Canis lupus) to validate a nanofluidic array technology recently developed for the detection of multiple prey species in scats. Using 371 scat samples from 12 wolves fed with a single-prey diet, the sensitivity of our nanofluidic array method varied between 0.45 and 0.95 for the six main ungulate prey species. The method sensitivity was enhanced by using multiple markers per species and by a relatively low threshold of number of amplifying markers required to confirm a detection. Yet, at least two markers should be used to avoid false positives. By acknowledging sources of bias in sensitivity to reliably interpret the results of DNA-based dietary methods, our study highlights the relevance of feeding experiments to optimally calibrate the relative thresholds to define a positive detection and investigate the occurrence and extent of biases in sensitivity
QCD corrections to the t-->H+b decay within the minimal supersymmetric standard model
I present the contribution of gluinos and scalar quarks to the decay rate of
the top quark into a charged Higgs boson and a bottom quark within the minimal
supersymmetric standard model, including the mixing of the scalar partners of
the left- and right-handed top quark. I show that for certain values of the
supersymmetric parameters the standard QCD loop corrections to this decay mode
are diminished or enhanced by several 10 per cent. I show that not only a small
value of 3 GeV for the gluino mass (small mass window) but also much larger
values of several hundreds of GeV's have a non-neglible effect on this decay
rate, against general belief. Last but not least, if the ratio of the vacuum
expectation values of the Higgs bosons are taken in the limit of I
obtain a drastic enhancement due to a \ dependence in the couplings.Comment: UQAM-PHE-94/01, 6 pages, plain tex, 4 figures not included, available
under request via mail or fa
Production in Au+Au and pp Collisions at = 200GeV at STAR
Mid-rapidity and are
measured in Au+Au and pp collisions at =200GeV using the STAR
detector at RHIC. The mass is systematically shifted at small
transverse momentum for both Au+Au and pp collisions. The
transverse mass spectra are measured in Au+Au collisions at different
centralities and in pp collisions. The mean transverse momentum
as a function of the collision centrality is compared to those of identified
, and . The and ratios are
compared to measurements in A+A, , , collisions at
various colliding energies. The physics implications of these measurements are
also discussed.Comment: 6 pages, 4 figures, proceedings of Strange Quarks in Matter
(SQM2003), Atlantic Beach, USA, to be published in J. Phys.
Examination of direct-photon and pion production in proton-nucleon collisions
We present a study of inclusive direct-photon and pion production in hadronic
interactions, focusing on a comparison of the ratio of gamma/pi0 yields with
expectations from next-to-leading order perturbative QCD (NLO pQCD). We also
examine the impact of a phenomenological model involving k_T smearing (which
approximates effects of additional soft-gluon emission) on absolute predictions
for photon and pion production and their ratio.Comment: 20 pages, 12 figures. Minor changes in wording and in figure
Relevance of baseline hard proton-proton spectra for high-energy nucleus-nucleus physics
We discuss three different cases of hard inclusive spectra in proton-proton
collisions: high single hadron production at 20 GeV and
at = 62.4 GeV, and direct photon production at = 200 GeV;
with regard to their relevance for the search of Quark Gluon Plasma signals in
A+A collisions at SPS and RHIC energies.Comment: Proceeds. Hot Quarks 2004 Int. Workshop on the Physics of
Ultrarelativistic Nucleus-Nucleus Collisions. 26 pages. 26 figs. [minor
corrs., refs. added
Multiple Interactions in Two-Photon Collisions
We compute cross sections for events where two pairs of partons scatter off
each other in the same reaction, giving rise to at least 3
high--{\mbox{}} jets. Unlike in {\mbox{}}\ collisions we find
the signal to lie well above the background from higher order QCD processes. If
the usual ``eikonaliztion" assumption is correct, the signal should be readily
observable at LEP2, and might already be detectable in data taken at TRISTAN.Comment: 8 pages, plain LaTeX, 2 figures (not included). A compressed PS file
of the entire paper, including figures, can be obtained via anonymous ftp
from ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-921.ps.
Inclusive Dielectron Cross Sections in p+p and p+d Interactions at Beam Energies from 1.04 to 4.88 GeV
Measurements of dielectron production in p+p and p+d collisions with beam
kinetic energies from 1.04 to 4.88 GeV are presented. The differential cross
section is presented as a function of invariant pair mass, transverse momentum,
and rapidity. The shapes of the mass spectra and their evolution with beam
energy provide information about the relative importance of the various
dielectron production mechanisms in this energy regime. The p+d to p+p ratio of
the dielectron yield is also presented as a function of invariant pair mass,
transverse momentum, and rapidity. The shapes of the transverse momentum and
rapidity spectra from the p+d and p+p systems are found to be similar to one
another for each of the beam energies studied. The beam energy dependence of
the integrated cross sections is also presented.Comment: 15 pages and 16 figure
Signals for Double Parton Scattering at the Fermilab Tevatron
Four double-parton scattering processes are examined at the Fermilab Tevatron
energy. With optimized kinematical cuts and realistic parton level simulation
for both signals and backgrounds, we find large samples of four-jet and
three-jet+one-photon events with signal to background ratio being 20\%-30\%,
and much cleaner signals from two-jet+two-photon and two-jet+ final
states. The last channel may provide the first unambiguous observation of
multiple parton interactions, even with the existing data sample accumulated by
the Tevatron collider experiments.Comment: 7 pages, plain LaTeX, 2 tables, no figures. A compressed PS file is
available by anonymous ftp at
ftp://phenom.physics.wisc.edu/pub/preprints/1996/madph-96-945.ps.
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