23 research outputs found
Recent results from Yakutsk experiment: development of EAS, energy spectrum and primary particle mass composition in the energy region of 10^15-10^19 eV
Experimental data obtained at the Yakutsk array after the modernization in
1993 are analyzed. The characteristics of EAS longitudinal and radial
development found from the charged particle flux and EAS Cherenkov light
registered at the Yakutsk complex array are presented. The energy spectrum of
EAS obtained from Cherenkov light and an estimate of the PCR mass composition
are presented.Comment: 10 pages, 11 figures. Invited talk on XIV ISVHECRI; to be published
in Nucl. Phys. B (Proc. Supply
The spectrum features of UHECRs below and surrounding GZK
The energy spectrum of UHECRs is discussed on the basis of the Yakutsk array
database analysis. In the region E=0.1 to 30 EeV the showers are detected under
trigger-500, while at energies above 30 EeV the whole acceptance area for
trigger-1000 is used in order to utilize all the data available in the region
of GZK cutoff.Comment: Invited talk at CRIS2004: GZK and surroundings, Catania, Italy,
31.05.04. To appear in Nucl. Phys. B Proc. Supp
A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments
We measured the inclusive electron-proton cross section in the nucleon
resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2
with the CLAS detector. The large acceptance of CLAS allowed for the first time
the measurement of the cross section in a large, contiguous two-dimensional
range of Q**2 and x, making it possible to perform an integration of the data
at fixed Q**2 over the whole significant x-interval. From these data we
extracted the structure function F2 and, by including other world data, we
studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate
higher twist contributions. The small statistical and systematic uncertainties
of the CLAS data allow a precise extraction of the higher twists and demand
significant improvements in theoretical predictions for a meaningful comparison
with new experimental results.Comment: revtex4 18 pp., 12 figure
Exclusive meson electroproduction from hydrogen at CLAS
The longitudinal and transverse components of the cross section for the reaction were measured in Hall B at Jefferson
Laboratory using the CLAS detector. The data were taken with a 4.247 GeV
electron beam and were analyzed in a range of from 0.2 to 0.6 and of
from 1.5 to 3.0 GeV. The data are compared to a Regge model based on
effective hadronic degrees of freedom and to a calculation based on Generalized
Parton Distributions. It is found that the transverse part of the cross section
is well described by the former approach while the longitudinal part can be
reproduced by the latter.Comment: 6 pages, 4 figure
Tensor Polarization of the phi meson Photoproduced at High t
As part of a measurement of the cross section of meson photoproduction
to high momentum transfer, we measured the polar angular decay distribution of
the outgoing in the channel in the
center-of-mass frame (the helicity frame). We find that s-channel helicity
conservation (SCHC) holds in the kinematical range where -channel exchange
dominates (up to GeV for =3.6 GeV). Above this
momentum, -channel production of a meson dominates and induces a
violation of SCHC. The deduced value of the coupling constant lies in
the upper range of previously reported values.Comment: 6 pages; 5 figure
Proton source size measurements in the eA → e'ppX reaction
Two-proton correlations at small relative momentum
q
were studied in the
e
A
(
3
H
e
,
4
H
e
,
C
,
F
e
)
→
e
′
p
p
X
reaction at
E
0
=
4.46
G
e
V
using the CLAS detector at Jefferson Lab. The enhancement of the correlation function at small
q
was found to be in accordance with theoretical expectations. Sizes of the emission region were extracted, and proved to be dependent on
A
and on the proton momentum. The size of the two-proton emission region for He was measured in
e
A
reactions for the first time
Measurement of the proton spin structure function g<sub>1</sub>(x,Q<sup>2</sup>) for Q<sup>2</sup> from 0.15 to 1.6 GeV<sup>2</sup> with CLAS
Double-polarization asymmetries for inclusive ep scattering were measured at Jefferson Lab using 2.6 and 4.3 GeV longitudinally polarized electrons incident on a longitudinally polarized NH3 target in the CLAS detector. The polarized structure function g(1)(x,Q(2)) was extracted throughout the nucleon resonance region and into the deep inelastic regime, for Q(2)=0.15-1.64 GeV2. The contributions to the first moment Gamma(1)(Q(2))=integralg(1)(x,Q(2)) dx were determined up to Q(2)=1.2 GeV2. Using a parametrization for g(1) in the unmeasured low x regions, the complete first moment was estimated over this Q(2) region. A rapid change in Gamma(1) is observed for Q(2) lt 1 GeV2, with a sign change near Q(2)=0.3 GeV2, indicating dominant contributions from the resonance region. At Q(2)=1.2 GeV2 our data are below the perturbative QCD evolved scaling value