1,718 research outputs found
Analytic Amplitudes for Hadronic Forward Scattering : COMPETE Update
We consider several classes of analytic parametrizations of hadronic
scattering amplitudes, and compare their predictions to all available forward
data in hadron-hadron, gamma-p and gamma-gamma reactions. Although these
parametrizations are very close for SQRTs larger than 9 GeV, it turns out that
they differ markedly at low energy, where a universal Pomeron term like ln**2 s
enables one to extend the fit down to SQRTs equal to 4 GeV. We present
predictions on the total cross sections and on the ratio of the real part to
the imaginary part of the elastic amplitude (RHO parameter) for present and
future pp and antipp colliders, and on total cross sections for gamma-p into
hadrons at cosmic-ray energies and for gamma-gamma into hadrons up to SQRTs
equal to 1 TeV.Comment: 3 pages, 3 tables. To be published in the Proceedings of the 31st
International Conference on High Energy Physics (ICHEP 2002), Amsterdam, The
Netherlands, 24-31 July 200
Reanalysis-driven climate simulation over CORDEX North America domain using the Canadian Regional Climate Model, version 5: model performance evaluation
The performance of reanalysis-driven Canadian Regional Climate Model, version 5 (CRCM5) in reproducing the present climate over the North American COordinated Regional climate Downscaling EXperiment domain for the 1989–2008 period has been assessed in comparison with several observation-based datasets. The model reproduces satisfactorily the near-surface temperature and precipitation characteristics over most part of North America. Coastal and mountainous zones remain problematic: a cold bias (2–6 °C) prevails over Rocky Mountains in summertime and all year-round over Mexico; winter precipitation in mountainous coastal regions is overestimated. The precipitation patterns related to the North American Monsoon are well reproduced, except on its northern limit. The spatial and temporal structure of the Great Plains Low-Level Jet is well reproduced by the model; however, the night-time precipitation maximum in the jet area is underestimated. The performance of CRCM5 was assessed against earlier CRCM versions and other RCMs. CRCM5 is shown to have been substantially improved compared to CRCM3 and CRCM4 in terms of seasonal mean statistics, and to be comparable to other modern RCMs
Forward observables at RHIC, the Tevatron run II and the LHC
We present predictions on the total cross sections and on the ratio of the
real part to the imaginary part of the elastic amplitude (rho parameter) for
present and future pp and pbar p colliders, and on total cross sections for
gamma p -> hadrons at cosmic-ray energies and for gamma gamma -> hadrons up to
sqrt(s)=1 TeV.
These predictions are based on a study of many possible analytic
parametrisations and invoke the current hadronic dataset at t=0. The
uncertainties on total cross sections, including the systematic theoretical
errors, reach 1% at RHIC, 3% at the Tevatron, and 10% at the LHC, whereas those
on the rho parameter are respectively 10%, 17%, and 26%.Comment: 11 pages, 2 figures, LaTeX, presented at the Second International
"Cetraro" Workshop & NATO Advanced Research Workshop "Diffraction 2002",
Alushta, Crimea, Ukraine, August 31 - September 6, 200
Elastic and scattering in the models of unitarized pomeron
Elastic scattering amplitudes dominated by the Pomeron singularity which obey
the principal unitarity bounds at high energies are constructed and analyzed.
Confronting the models of double and triple (at ) Pomeron pole
(supplemented by some terms responsible for the low energy behaviour) with
existing experimental data on and total and differential cross
sections at GeV and GeV we are able to tune
the form of the Pomeron singularity. Actually the good agreement with those
data is received for both models though the behaviour given by the dipole model
is more preferable in some aspects. The predictions made for the LHC energy
values display, however, the quite noticeable difference between the
predictions of models at GeV. Apparently the future
results of TOTEM will be more conclusive to make a true choice.Comment: Revtex4, 8 pages, 5 figures. Text is improved, no changes in figures
and conclusions. Version to be published in Phys. Rev.
Associative production of B_c and D mesons at LHC
It is shown that the study of correlations in the associative production of
B_c and D mesons at LHC allows to obtain the essential information about the
B_c production mechanism.Comment: 14 pages, 10 figures. Some misprints have been removed in the last
version. The reference to CTEQ pdf has been adde
Forward Physics at the LHC (Elba 2010)
The papers review the main theoretical and experimental aspects of the
Forward Physics at the Large Hadron Collider
First-principles study of lattice instabilities in the ferromagnetic martensite NiMnGa
The phonon dispersion relations and elastic constants for ferromagnetic
NiMnGa in the cubic and tetragonally distorted Heusler structures are
computed using density-functional and density-functional perturbation theory
within the spin-polarized generalized-gradient approximation. For
, the TA tranverse acoustic branch along and
symmetry-related directions displays a dynamical instability at a wavevector
that depends on . Through examination of the Fermi-surface nesting and
electron-phonon coupling, this is identified as a Kohn anomaly. In the parent
cubic phase the computed tetragonal shear elastic constant,
C=(CC)/2, is close to zero, indicating a marginal
elastic instability towards a uniform tetragonal distortion. We conclude that
the cubic Heusler structure is unstable against a family of energy-lowering
distortions produced by the coupling between a uniform tetragonal distortion
and the corresponding modulation. The computed relation between the
ratio and the modulation wavevector is in excellent agreement with
structural data on the premartensitic ( = 1) and martensitic ( =
0.94) phases of NiMnGa.Comment: submitted to Phys. Rev.
Influence of intermartensitic transitions on transport properties of Ni2.16Mn0.84Ga alloy
Magnetic, transport, and x-ray diffraction measurements of ferromagnetic
shape memory alloy NiMnGa revealed that this alloy undergoes
an intermartensitic transition upon cooling, whereas no such a transition is
observed upon subsequent heating. The difference in the modulation of the
martensite forming upon cooling from the high-temperature austenitic state
[5-layered (5M) martensite], and the martensite forming upon the
intermartensitic transition [7-layered (7M) martensite] strongly affects the
magnetic and transport properties of the alloy and results in a large thermal
hysteresis of the resistivity and magnetization . The
intermartensitic transition has an especially marked influence on the transport
properties, as is evident from a large difference in the resistivity of the 5M
and 7M martensite, , which is larger than the jump of resistivity at
the martensitic transition from the cubic austenitic phase to the monoclinic 5M
martensitic phase. We assume that this significant difference in between
the martensitic phases is accounted for by nesting features of the Fermi
surface. It is also suggested that the nesting hypothesis can explain the
uncommon behavior of the resistivity at the martensitic transition, observed in
stoichiometric and near-stoichiometric Ni-Mn-Ga alloys.Comment: 7 pages, 6 figures, REVTEX
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