855 research outputs found
Top-Down Approach to Unified Supergravity Models
We introduce a new approach for studying unified supergravity models. In this
approach all the parameters of the grand unified theory (GUT) are fixed by
imposing the corresponding number of low energy observables. This determines
the remaining particle spectrum whose dependence on the low energy observables
can now be investigated. We also include some SUSY threshold corrections that
have previously been neglected. In particular the SUSY threshold corrections to
the fermion masses can have a significant impact on the Yukawa coupling
unification.Comment: 19 pages, uuencoded compressed ps file, DESY 94-057 (paper format
corrected
Hemodynamic performance of different stent strategies for coronary bifurcations. Evaluation with a mathematical model
Purpose: Best percutaneous treatment strategy for lesions in coronary bifurcations is an ongoing subject of debate. There is limited data that analyses the effect of the different bifurcation strategies on coronary flow. Our aim is to evaluate the influence of different bifurcation stenting strategies on hemodynamic parameters, both in the main vessel (MV) and side branch (SB)
NN,N\Delta Couplings and the Quark Model
We examine mass-corrected SU(6) symmetry predictions in the quark model
relating vector, axial-vector and strong NN and N\Delta couplings, and
demonstrate that the experimental N\Delta value is significantly higher than
predicted in each case. Nevertheless the Goldberger-Treiman relation is
satisfied in both sectors. Possible origins of the discrepancy of the quark
model predictions with experiment are discussed.Comment: 22 pg. Latex file, figures available by reques
PPPC 4 DM ID: A Poor Particle Physicist Cookbook for Dark Matter Indirect Detection
We provide ingredients and recipes for computing signals of TeV-scale Dark
Matter annihilations and decays in the Galaxy and beyond. For each DM channel,
we present the energy spectra of electrons and positrons, antiprotons,
antideuterons, gamma rays, neutrinos and antineutrinos e, mu, tau at
production, computed by high-statistics simulations. We estimate the Monte
Carlo uncertainty by comparing the results yielded by the Pythia and Herwig
event generators. We then provide the propagation functions for charged
particles in the Galaxy, for several DM distribution profiles and sets of
propagation parameters. Propagation of electrons and positrons is performed
with an improved semi-analytic method that takes into account
position-dependent energy losses in the Milky Way. Using such propagation
functions, we compute the energy spectra of electrons and positrons,
antiprotons and antideuterons at the location of the Earth. We then present the
gamma ray fluxes, both from prompt emission and from Inverse Compton scattering
in the galactic halo. Finally, we provide the spectra of extragalactic gamma
rays. All results are available in numerical form and ready to be consumed.Comment: 57 pages with many figures and tables. v4: updated to include a 125
higgs boson, computation and discussion of extragalactic spectra corrected,
some other typos fixed; all these corrections and updates are reflected on
the numerical ingredients available at
http://www.marcocirelli.net/PPPC4DMID.html they correspond to Release 2.
Higher Resonance Contamination of pi NN Couplings Obtained Via the Three-Point Function Method in QCD Sum Rules
We investigate the size of potential higher pseudoscalar resonance
contaminations of the estimates of isospin-conserving and isospin-violating
couplings obtained using the 3-point function method in QCD sum rules.
For the isospin-conserving case it is shown that conventional models of the
isovector pseudoscalar spectral function imply resonance decay constants large
enough to create significant contaminations, and that assuming these models are
incorrect, and that the decay constants are actually much smaller, implies
physically implausible values for the flavor-breaking quark condensate ratios.
For the isospin-violating case it is shown explicitly that such resonance
contamination is unavoidably present and precludes using the 3-point function
method as a means of estimating the at present unmeasured isospin-violating
couplings.Comment: 8 page
Implementation of synthetic fast-ion loss detector and imaging heavy ion beam probe diagnostics in the 3D hybrid kinetic-MHD code MEGA
A synthetic fast-ion loss (FIL) detector and an imaging Heavy Ion Beam Probe (i-HIBP) have been implemented in the 3D hybrid kinetic-magnetohydrodynamic code MEGA. First synthetic measurements from these two diagnostics have been obtained for neutral beam injection-driven Alfvén Eigenmode (AE) simulated with MEGA. The synthetic FILs show a strong correlation with the AE amplitude. This correlation is observed in the phase-space, represented in coordinates (Pϕ, E), being toroidal canonical momentum and energy, respectively. FILs and the energy exchange diagrams of the confined population are connected with lines of constant E′, a linear combination of E and Pϕ. First i-HIBP synthetic signals also have been computed for the simulated AE, showing displacements in the strike line of the order of ∼1 mm, above the expected resolution in the i-HIBP scintillator of ∼100 μm
Search for Higgs bosons decaying to tautau pairs in ppbar collisions at sqrt(s) = 1.96 TeV
We present a search for the production of neutral Higgs bosons decaying into
tautau pairs in ppbar collisions at a center-of-mass energy of 1.96 TeV. The
data, corresponding to an integrated luminosity of 5.4 fb-1, were collected by
the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the
95% C.L. on the product of production cross section and branching ratio for a
scalar resonance decaying into tautau pairs, and we then interpret these limits
as limits on the production of Higgs bosons in the minimal supersymmetric
standard model (MSSM) and as constraints in the MSSM parameter space.Comment: 7 pages, 5 figures, submitted to PL
Measurement of the photon-jet production differential cross section in collisions at \sqrt{s}=1.96~\TeV
We present measurements of the differential cross section dsigma/dpT_gamma
for the inclusive production of a photon in association with a b-quark jet for
photons with rapidities |y_gamma|< 1.0 and 30<pT_gamma <300 GeV, as well as for
photons with 1.5<|y_gamma|< 2.5 and 30< pT_gamma <200 GeV, where pT_gamma is
the photon transverse momentum. The b-quark jets are required to have pT>15 GeV
and rapidity |y_jet| < 1.5. The results are based on data corresponding to an
integrated luminosity of 8.7 fb^-1, recorded with the D0 detector at the
Fermilab Tevatron Collider at sqrt(s)=1.96 TeV. The measured cross
sections are compared with next-to-leading order perturbative QCD calculations
using different sets of parton distribution functions as well as to predictions
based on the kT-factorization QCD approach, and those from the Sherpa and
Pythia Monte Carlo event generators.Comment: 10 pages, 9 figures, submitted to Phys. Lett.
Limits on anomalous trilinear gauge boson couplings from WW, WZ and Wgamma production in pp-bar collisions at sqrt{s}=1.96 TeV
We present final searches of the anomalous gammaWW and ZWW trilinear gauge
boson couplings from WW and WZ production using lepton plus dijet final states
and a combination with results from Wgamma, WW, and WZ production with leptonic
final states. The analyzed data correspond to up to 8.6/fb of integrated
luminosity collected by the D0 detector in pp-bar collisions at sqrt{s}=1.96
TeV. We set the most stringent limits at a hadron collider to date assuming two
different relations between the anomalous coupling parameters
Delta\kappa_\gamma, lambda, and Delta g_1^Z for a cutoff energy scale Lambda=2
TeV. The combined 68% C.L. limits are -0.057<Delta\kappa_\gamma<0.154,
-0.015<lambda<0.028, and -0.008<Delta g_1^Z<0.054 for the LEP parameterization,
and -0.007<Delta\kappa<0.081 and -0.017<lambda<0.028 for the equal couplings
parameterization. We also present the most stringent limits of the W boson
magnetic dipole and electric quadrupole moments.Comment: 10 pages, 5 figures, submitted to PL
Measurement of three-jet differential cross sections d sigma-3jet / d M-3jet in p anti-p collisions at sqrt(s)=1.96 TeV
We present the first measurement of the inclusive three-jet differential
cross section as a function of the invariant mass of the three jets with the
largest transverse momenta in an event in p anti-p collisions at sqrt(s) = 1.96
TeV. The measurement is made in different rapidity regions and for different
jet transverse momentum requirements and is based on a data set corresponding
to an integrated luminosity of 0.7 fb^{-1} collected with the D0 detector at
the Fermilab Tevatron Collider. The results are used to test the three-jet
matrix elements in perturbative QCD calculations at next-to-leading order in
the strong coupling constant. The data allow discrimination between
parametrizations of the parton distribution functions of the proton.Comment: 10 pages, 4 figures, 2 tables, submitted to Phys. Lett. B, corrected
chi2 values for NNPD
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