104 research outputs found
Polarised deep inelastic scattering accompanied by a forward jet as a probe of the resummation
We argue that the production of forward jets in polarised deep inelastic
scattering can be a useful tool for probing the double resummation
effects which control the polarised deep inelastic scattering for small values
of the Bjorken parameter . We solve the corresponding integral equations
generating the double resummation and calculate the differential
structure function describing the forward jet production in the small
regime which can possibly be probed by the polarised HERA measurements. We show
that these structure functions should exhibit the characteristic increase with
decreasing , where denotes the longitudinal momentum fraction of
the parent proton carried by a jet, and we quantify this increase.Comment: 13 pages, latex, 5 figure
Spin structure function g_1 at low x: status and plans
A brief review of measurements and expectations concerning the spin structure
function g_1 of the nucleon at low values of the scaling variable x is given.Comment: 4 pages, 3 figures. Invited talk presented at the ``International
Workshop on the Spin Structure of the Proton and Polarized Collider
Physics'', ECT*, Trento, Italy, July 23-28, 200
Unified description of the non-singlet spin dependent structure function incorporating Altarelli-Parisi evolution and the double logarithmic effects at low
A unified equation for the non-singlet spin dependent structure function
which incorporates the complete leading order
Altarelli-Parisi evolution at finite and double logarithmic
effects at is formulated. The solution of this equation reasonably
agrees with the recent data obtained by the Spin Muon Collaboration.Comment: 10 pages, plain LATEX, 3 eps figures. Corrected: several misprints
and a calculation error leading to negligible changes in fig. 2 and 3. To
appear in Phys. Lett.
Spin dependent structure function g_1 at low x and low Q^2
Theoretical description of the spin dependent structure function g_1(x,Q^2)
in the region of low values of x and Q^2 is presented. It contains the Vector
Meson Dominance contribution and the QCD improved parton model suitably
extended to the low Q^2 domain. Theoretical predictions are compared with the
recent experimental data in the low x, low Q^2 region
Shadowing, Binding and Off-Shell Effects in Nuclear Deep Inelastic Scattering
We present a unified description of nuclear deep inelastic scattering (DIS)
over the whole region of the Bjorken variable. Our approach is based on
a relativistically covariant formalism which uses analytical properties of
quark correlators. In the laboratory frame it naturally incorporates two
mechanisms of DIS: (I) scattering from quarks and antiquarks in the target and
(II) production of quark-antiquark pairs followed by interactions with the
target. We first calculate structure functions of the free nucleon and develop
a model for the quark spectral functions. We show that mechanism (II) is
responsible for the sea quark content of the nucleon while mechanism (I)
governs the valence part of the nucleon structure functions. We find that the
coherent interaction of pairs with nucleons in the nucleus leads to
shadowing at small and discuss this effect in detail. In the large
region DIS takes place mainly on a single nucleon. There we focus on the
derivation of the convolution model. We point out that the off-shell properties
of the bound nucleon structure function give rise to sizable nuclear effects.Comment: 29 pages (and 10 figures available as hard copies from Authors),
REVTE
Low , Low Region in Electroproduction an Overview
We summarise existing experimental and theoretical knowledge on the structure
function in the region of low and low . The constraints on the
behaviour of structure functions in the limit are listed.
Phenomenological low parametrisations of the are collected and
their dynamical content is discussed. The high energy photoproduction and
nuclear shadowing are also briefly described. Recent update of the low ,
low experimental data is given.Comment: 28 pages Warsaw university preprint number IFD/1/199
A unified BFKL and GLAP description of data
We argue that the use of the universal unintegrated gluon distribution and
the (or high energy) factorization theorem provides the natural framework
for describing observables at small x. We introduce a coupled pair of evolution
equations for the unintegrated gluon distribution and the sea quark
distribution which incorporate both the resummed leading BFKL
contributions and the resummed leading GLAP contributions. We solve
these unified equations in the perturbative QCD domain using simple parametic
forms of the nonperturbative part of the integrated distributions. With only
two (physically motivated) input parameters we find that this
factorization approach gives an excellent description of the measurements of
at HERA. In this way the unified evolution equations allow us to
determine the gluon and sea quark distributions and, moreover, to see the x
domain where the resummed effects become significant. We use
factorization to predict the longitudinal structure function and
the charm component of .Comment: 25 pages, LaTeX, 9 figure
Spin asymmetry A_1^d and the spin-dependent structure function g_1^d of the deuteron at low values of x and Q^2
We present a precise measurement of the deuteron longitudinal spin asymmetry
A_1^d and of the deuteron spin-dependent structure function g_1^d at Q^2 < 1
GeV^2 and 4*10^-5 < x < 2.5*10^-2 based on the data collected by the COMPASS
experiment at CERN during the years 2002 and 2003. The statistical precision is
tenfold better than that of the previous measurement in this region. The
measured A_1^d and g_1^d are found to be consistent with zero in the whole
range of x.Comment: 17 pages, 10 figure
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
QED Corrections to Deep Inelastic Scattering with Tagged Photons at HERA
We calculate the QED corrections to deep inelastic scattering with tagged
photons at HERA in the leading logarithmic approximation. Due to the special
experimental setup, two large scales appear in the calculation that lead to two
large logarithms of comparable size. The relation of our formalism to the
conventional structure function formalism is outlined. We present some
numerical results and compare with previous calculations.Comment: 7 pages, REVTeX, 2 figures; published versio
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