9,988 research outputs found
Quantitative Study of Geometrical Scaling in Deep Inelastic Scattering at HERA
We propose a method to assess the quality of geometrical scaling in Deep
Inelastic Scattering and apply it to the combined HERA data on
cross-section. Using two different approaches based on Bjorken binning and
binning in scattering energy , we show that geometrical
scaling in variable works well up to Bjorken 's
0.1. The corresponding value of exponent is 0.32 -- 0.34.Comment: 18 pages, 11 figures, version accepted in JHEP, new discussion of
experimental error
Ioffe Time in Double Logarithmic Approximation
We analyze the light cone (Ioffe) time structure of the gluon distribution
function in the double logarithmic approximation. We show that due to QCD
evolution Ioffe equation is modified. The characteristic light cone time of the
gluons does not increase as fast with increasing energy (decreasing Bjorken x)
as predicted by the parton distributions exhibiting Bjorken scaling due to the
increase of the transverse momenta of the gluons in the DGLAP ladder.Comment: 13 pages, 1 figur
Parton Sum Rules and Improved Scaling Variable
The effect from quark masses and transversal motion on the Gottfried,
Bjorken, and Ellis-Jaffe sum rules is examined by using a quark-parton model of
nucleon structure functions based on an improved scaling variable. Its use
results in corrections to the Gottfried, Bjorken, and Ellis-Jaffe sum rules. We
use the Brodsky-Huang-Lepage prescription of light-cone wavefunctions to
estimate the size of the corrections. We constrain our choice of parameters by
the roughly known higher twist corrections to the Bjorken sum rule and find
that the resulting corrections to the Gottfried and Ellis-Jaffe sum rules are
relevant, though not large enough to explain the observed sum rule violations.Comment: latex, with 1 postscript figure, to be published in Phys.Lett.
Prescriptions for the scaling variable of the nucleon structure function in nuclei
We tested several choices of the in-medium value of the Bjorken scaling
variable assuming the nucleon structure function in nucleus to be the same as
that of free nucleon. The results unambiguously show that it is different.Comment: 11 pages, 3 figures, 1 tabl
Geometrical Scaling of Direct-Photon Production in Hadron Collisions from RHIC to the LHC
We consider pp, dAu and AuAu production of photons at RHIC energies, and PbPb
collisions at LHC energy. We show that the inclusive spectrum of photons in the
transverse momentum range of 1 GeV < pT <= 4 GeV satisfies geometric scaling.
Geometric scaling is a property of hadronic interactions predicted by theories
of gluon saturation, and expresses rates in terms of dimensionless ratios of
the transverse momentum to saturation momentum. We show excellent agreement
with geometric scaling with the only input being the previously measured
dependence of the saturation momentum upon Bjorken x and centrality.Comment: 12 pages, 4 figure
The Parton Model and its Applications
This is a review of the program we started in 1968 to understand and
generalize Bjorken scaling and Feynman's parton model in a canonical quantum
field theory. It is shown that the parton model proposed for deep inelastic
electron scatterings can be derived if a transverse momentum cutoff is imposed
on all particles in the theory so that the impulse approximation holds. The
deep inelastic electron-positron annihilation into a nucleon plus anything else
is related by the crossing symmetry of quantum field theory to the deep
inelastic electron-nucleon scattering. We have investigated the implication of
crossing symmetry and found that the structure functions satisfy a scaling
behavior analogous to the Bjorken limit for deep inelastic electron scattering.
We then find that massive lepton pair production in collisions of two high
energy hadrons can be treated by the parton model with an interesting scaling
behavior for the differential cross sections. This turns out to be the first
example of a class of hard processes involving two initial hadrons.Comment: Contribution to a book to be published by World Scientific for the
occasion of 50 Years of Quarks. 17 pages, 4 figure
Confinement and scaling in deep inelastic scattering
We show that parton confinement in the final state generates large
corrections to Bjorken scaling, thus leaving less room for the logarithmic
corrections. In particular, the -scaling violations at large are
entirely described in terms of power corrections. For treatment of these
non-perturbative effects, we derive a new expansion in powers of for
the structure function that is free of infra-red singularities and which
reduces corrections to the leading term. The leading term represents scattering
from an off-mass-shell parton, which keeps the same virtual mass in the final
state. It is found that this quasi-free term is a function of a new variable
, which coincides with the Bjorken variable for . The
two variables are very different, however, at finite . In particular, the
variable depends on the invariant mass of the spectator particles.
Analysis of the data at large shows excellent scaling in the variable , and determines the value of the diquark mass to be close to zero. -scaling allows us to extract the structure function near the elastic
threshold. It is found to behave as . Predictions for the
structure functions based on -scaling are made.Comment: Discussion of target mass corrections is added. Accepted for
publication in Phys. Rev.
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