513 research outputs found
Soft-Gluon Angular Screening in Heavy-Quark Fragmentation
A method to measure the suppression of soft-gluon radiation by a heavy quark
("dead cone") is discussed. We analyse this QCD phenomenon in the framework of
the HERA experiment using Monte Carlo simulations.Comment: 13 pages, 8 eps figures, submitted to Phys. Lett.
Local properties of local multiplicity distributions in hadronic Z decay
Preliminary results on local multiplicity fluctuations in hadronic Z decays are presented. The data were obtained using the L3 detector at LEP. It is investigated to what extent Monte-Carlo models, which are tuned to reproduce global event-shape variables and single-particle inclusive distributions, can describe the local fluctuations measured by means of bunching parameters.Preliminary results on local multiplicity fluctuations in hadronic Z decays are presented. The data were obtained using the L3 detector at LEP. It is investigated to what extent Monte-Carlo models, which are tuned to reproduce global event-shape variables and single-particle inclusive distributions, can describe the local fluctuations measured by means of bunching parameters
Current-Target Correlations as a Probe of Delta_G/G in Polarized Deep Inelastic Scattering
The measurement of the polarized gluon distribution function Delta_G/G using
current-target correlations in the Breit frame of deep inelastic scattering is
proposed. The approach is illustrated using a Monte Carlo simulation of
polarized -collisions for HERA energies.Comment: 8 pages, 3 eps figures, submitted to Phys. Lett.
Multiplicities, fluctuations and QCD: Interplay between soft and hard physics?
Multiplicity fluctuations are studied both globaly (in terms of high-order
moments) and locally (in terms of small phase-space intervals). The ratio of
cumulant factorial to factorial moments of the charged-particle multiplicity
distribution shows a quasi-oscillatory behaviour similar to that predicted by
the NNLLA of perturbative QCD. However, an analysis of the sub-jet multiplicity
distribution at perturbative scales shows that these oscillations cannot be
related to the NNLLA prediction. We investigate how it is possible to reproduce
the oscillations within the framework of Monte-Carlo models. Furthermore, local
multiplicity fluctuations in angular phase-space intervals are compared with
Monte-Carlo models and with first-order QCD predictions. While JETSET
reproduces the experimental data very well, the predictions of the Double
Leading Log Approximations and estimates obtained in Modified Leading Log
Approximations deviate significantly from the data.Comment: 11 pages, 11 eps figures, Presented at the XXVII Symposium on
Multiparticle Dynamics, September 8-12, 1997 Frascati-Rome, Ital
Bose-Einstein Correlations in at a Linear Collider
We show that the most popular method to simulate Bose-Einstein (BE) interference effects predicts negligible correlations between identical pions originating from the hadronic decay of different W's produced in e+e- -> W+W- -> 4 jets at typical linear collider energies
Selection and reconstruction of the top quarks in the all-hadronic decays at a Linear Collider
A method of reconstruction of the top quarks produced in the process E+E- ->
t\bar{t} -> 6 jets at a Linear Collider (LC) is proposed. The approach does not
involve a kinematic fit, as well as assumptions on the invariant masses of the
dijets originating from the decays of W bosons and, therefore, the method is
expected to be less sensitive to theoretical and experimental uncertainties on
the top-mass measurement than traditional reconstruction methods. For the first
time, the reconstruction of the top quarks was investigated using the full LC
detector simulation after taking into account the background arising from QCD
multi-jet production.Comment: 22 pages, including 13 figures and 3 table
Generelized Parton Distributions in light meson production
We analyze light meson electroproduction within the handbag model, where the
amplitude factorizes into Generelized Parton Distributions (GPDs) and a hard
scattering part. The cross sections and spin asymmetries for various vector and
pseudoscalar mesons are analyzed. We discuss what information on hadron
structure can be obtained from GPDs.Comment: Latex, 14 pages, 12 figures, Presented at the 5th joint International
HADRON STRUCTURE '11 Conference, June 27- July 1, 2011, Tatranska Strba
(Slovak Republic
X-ray and neutron diffraction studies of coupled structural phase transitions in DyBaCoO
A structural transition at K from the to phase
is found to coincide with an anomaly of resistivity. Another structural phase
transition doubling the lattice parameter , which has been postulated
earlier to accompany a low-temperature magnetic transition in
TbBaCoO, is observed in a single crystal DbBaCoO by
means of the X-ray and neutron diffraction. The low temperature phase does not
belong to the space group that has been chosen earlier as the highest
subgroup of the . The transition is of the first order with the
temperature hysteresis, between and K, which
probably explains anomalous magnetic properties in this temperature range.Comment: 6 pages, 4 figure
The longitudinal cross section of vector meson electroproduction
We analyze electroproduction of light vector mesons (V=rho, phi and omega) at
small Bjorken-x in the handbag approach in which the process factorizes into
general parton distributions and partonic subprocesses. The latter are
calculated in the modified perturbative approach where the transverse momenta
of the quark and antiquark forming the vector meson are retained and Sudakov
suppressions are taken into account. Modeling the generalized parton
distributions through double distributions and using simple Gaussian
wavefunctions for the vector mesons, we compute the longitudinal cross sections
at large photon virtualities. The results are in fair agreement with the
findings of recent experiments performed at HERA and HERMES.Comment: 27 pages, 20 figures, using LATEX with graphic
Bose-Einstein Correlations and Color Reconnection in W-pair production
We propose a systematic study of Bose-Einstein correlations between identical
hadrons coming from different W decays. Experimentally accessible signatures of
these correlations as well as of possible color reconnection effects are
discussed on the basis of two-particle inclusive densities.Comment: 24 pages, 9 eps figures, submitted to Eur. J. Phys.
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