168 research outputs found
Measurement of the proton and deuteron structure functions, F2p and F2d, and of the ratio sigma(L)/sigma(T)
The muon-proton and muon-deuteron inclusive deep inelastic scattering cross
sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q2 <
75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results
are based on the full data set collected by the New Muon Collaboration,
including the data taken with a small angle trigger. The extracted values of
the structure functions F2p and F2d are in good agreement with those from other
experiments. The data cover a sufficient range of y to allow the determination
of the ratio of the longitudinally to transversely polarised virtual photon
absorption cross sections, R= sigma(L)/sigma(T), for 0.002 < x < 0.12 . The
values of R are compatible with a perturbative QCD prediction; they agree with
earlier measurements and extend to smaller x.Comment: In this replacement the erroneously quoted R values in tables 3-6 for
x>0.12, and R1990 values in tables 5-6 for all x, have been corrected, and
the cross sections in tables 3-4 have been adapted. Everything else,
including the structure functions F2, remained unchanged. 22 pages, LateX,
including figures, with two .sty files, and three separate f2tab.tex files
for the F2-tables. Accepted for publication in Nucl.Phys.B 199
AIBIIICVI 2 (A = Cu, Ag; B = Ga, In; C = S, Se, Te) based photonic crystal superlattices: Optical properties
In this study, we present an investigation of the optical properties and band structures for the photonic structures based on AIBIIICVI 2 with a Fibonacci sequence that can act as a multi-wavelength birefringent filter. The filtering wavelengths are analyzed by the indices concerning the quasi-periodicity of a Fibonacci sequence and the average lattice parameter. The transmittances of filtering wavelengths can be tuned by varying structure parameters such as the lengths of poled domains, filling factor, and dispersion relation. In our simulation, we employed the finite-difference time domain (FDTD) technique, which implies a solution from Maxwell equation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
Inverse bremsstrahlung contributions to Drell-Yan like processes
The contribution of the sub-process in
hadron-hadron interactions is considered. It is a part of one-loop electroweak
radiative corrections for the Drell-Yan production of lepton pairs at hadron
colliders. It is shown that this contribution should be taken into account
aiming at the 1% accuracy of the Drell-Yan process theoretical description.
Both the neutral and charged current cases are evaluated. Numerical results are
presented for typical conditions of LHC experiments.Comment: 11 pages, 8 figure
The proton and deuteron F_2 structure function at low Q^2
Measurements of the proton and deuteron structure functions are
presented. The data, taken at Jefferson Lab Hall C, span the four-momentum
transfer range GeV, and Bjorken values from 0.009 to
0.45, thus extending the knowledge of to low values of at low .
Next-to-next-to-leading order calculations using recent parton distribution
functions start to deviate from the data for GeV at the low and
high -values. Down to the lowest value of , the structure function is
in good agreement with a parameterization of based on data that have been
taken at much higher values of or much lower values of , and which is
constrained by data at the photon point. The ratio of the deuteron and proton
structure functions at low remains well described by a logarithmic
dependence on at low .Comment: 3 figures, submitted pape
Production of para-- and orthopositronium at relativistic heavy ion colliders
We consider the ortho-- and parapositronium production in the process Ps where A is a nucleus with the charge number Z. The inclusive cross
section and the energy distribution of the relativistic Ps are calculated which
are of primary interest from the experimental point of view. The accuracy of
the corresponding cross sections is given by omitting terms for the para--Ps and for the ortho--Ps production
where and 16 for the RHIC and the LHC. Within this
accuracy the multiphoton (Coulomb) corrections are taken into account. We show
that the RHIC and the LHC will be Ps factories with a productions rate of about
relativistic Ps per day. The fraction of the ortho--Ps is
expected to be of the same order as that of the para--Ps for Au--Au and Pb--Pb
collisions.Comment: 22 pages, 5 figures, RevTeX, misprint correcte
The Fermion Self-Energy during Inflation
We compute the one loop fermion self-energy for massless Dirac + Einstein in
the presence of a locally de Sitter background. We employ dimensional
regularization and obtain a fully renormalized result by absorbing all
divergences with BPHZ counterterms. An interesting technical aspect of this
computation is the need for a noninvariant counterterm owing to the breaking of
de Sitter invariance by our gauge condition. Our result can be used in the
quantum-corrected Dirac equation to search for inflation-enhanced quantum
effects from gravitons, analogous to those which have been found for massless,
minimally coupled scalars.Comment: 63 pages, 3 figures (uses axodraw.sty), LaTeX 2epsilon. Revised
version (to appear in Classical and Quantum Gravity) corrects some typoes and
contains some new reference
R_b and New Physics: A Comprehensive Analysis
We survey the implications for new physics of the discrepancy between the LEP
measurement of and its Standard Model prediction. Two broad classes of
models are considered: () those in which new Z\bbar b couplings arise at
tree level, through or -quark mixing with new particles, and ()
those in which new scalars and fermions alter the Z \bbar b vertex at one
loop. We keep our analysis as general as possible in order to systematically
determine what kinds of features can produce corrections to of the right
sign and magnitude. We are able to identify several successful mechanisms,
which include most of those which have been recently been proposed in the
literature, as well as some earlier proposals (\eg\ supersymmetric models). By
seeing how such models appear as special cases of our general treatment we are
able to shed light on the reason for, and the robustness of, their ability to
explain .Comment: 60 pages, 8 figures, plain tex, uses epsf. Final version to appear in
Phys. Rev. D; propgating sign error corrected in eqs. 78, 87, 88, 89, 98, and
107; results unchange
Longitudinal-Transverse Separations of Structure Functions at Low for Hydrogen and Deuterium
We report on a study of the longitudinal to transverse cross section ratio,
, at low values of and , as determined from
inclusive inelastic electron-hydrogen and electron-deuterium scattering data
from Jefferson Lab Hall C spanning the four-momentum transfer range 0.06 GeV. Even at the lowest values of , remains
nearly constant and does not disappear with decreasing , as expected. We
find a nearly identical behaviour for hydrogen and deuterium.Comment: 4 pages, 2 gigure
Measurement of the proton and the deuteron structure functions F2p and F2d
The proton and deuteron structure functions F2p and F2d were measured in the
kinematic range 0.006<x<0.6 and 0.5<Q^2<75 GeV^2, by inclusive deep inelastic
muon scattering at 90, 120, 200 and 280 GeV. The measurements are in good
agreement with earlier high precision results. The present and earlier results
together have been parametrised to give descriptions of the proton and deuteron
structure functions F2 and their uncertainties over the range 0.006<x<0.9.Comment: 22 pages, using LATEX, 12pt, epsfig.sty, rotating.sty; 2 tables and 6
figures uuencoded compressed tar files in f2fig.uu (Corrected two values of
Table 3 into c3=-35.01 and c4=44.43 for "Upper F2p".
Accurate Measurement of F2d/F2p and Rd-Rp
Results are presented for F2d/F2p and Rd-Rp from simultaneous measurements of
deep inelastic muon scattering on hydrogen and deuterium targets, at 90, 120,
200 and 280 GeV. The difference Rd-Rp, determined in the range 0.002<x<0.4 at
an average Q^2 of 5 GeV^2, is compatible with zero. The x and Q^2 dependence of
F2d/F2p was measured in the kinematic range 0.001<x<0.8 and 0.1<Q^2<145 GeV^2
with small statistical and systematic errors. For x>0.1 the ratio decreases
with Q^2.Comment: 29 pages, LateX, including figures, prepared with uufiles, arriving
with .sty files as used, figures .eps files and a table .tex file. Accepted
for publication in Nucl.Phys.B 199
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