Theoretical and Experimental High-Energy Physics, Charged Particles Beam Physics, Particle Creation in Subcritical Fields

*Participation in scientific projects: *

EHS-RCBC Collaboration, EHS-NA-22 Collaboration; ZEUS Collaboration

*Publications and reports at conferences:*

Total number of publications – 225, 53 reports

*Membership in editorial boards: *

Editor-in-Chief, Proceedings of the International Workshop
"High Energy Physics and Quantum Field Theory" (QFTHEP), 1993-2000

*Recent Achievements*

*High Energy Physics:*

-For two-body decay kinematics a new set of equations describing boundaries of the physical region
in decays are derived. These features via a graphical representation and implementation of selection
criteria provide an efficient tool for the background suppression in experimental searches for
conventional and exotic (pentaquark, etc.) resonance states.
[ DOI,
pdf]

-An analytical relationship between the statistical significance of an observed signal and the signal width in the case of a large background is obtained. It can help to explain why high-energy experiments may have different conclusions on the existence of new particles. We illustrate our approach using the experimental data on searches for the Θ+(1530) pentaquark state.
[ DOI]

-An empirical principle for the construction of a linear relationship between the total angular momentum and squared-mass of baryons is proposed. Unlike the standard Regge-Chew-Frautschi approach, the constructed trajectories do not have nonlinear behavior. The linear baryonic trajectories are well described by a semiclassical picture based on a spinning relativistic string with tension.
[ DOI]

-ZEUS collaboration: search for QCD instanton induced events and pentaquark production;
setting limits on the effective quark radius; measurement of heavy quark (beauty and charm) production, study of the charm-quark running mass, QCD Analysis of HERA data and other topics.
[ ZEUS Papers]

*Beam Physics:*

-Exact analytical expressions for external 1D and 2D fields of a relativistic bunch of
charged particles with a circular and an elliptical cross section under different boundary
conditions and interaction of the fields with an accelerator structural elements are
derived with the use of the method of images. The new expressions for modified fields are
applied to study image forces acting on the bunch constituents and the bunch as a whole.
The coherent and incoherent tune shifts for an arbitrary bunch displacement from the midplane
are calculated in the framework of an improved linear theory, for both infinite and finite
parallel flat surfaces. For the case of a proton beam, we apply the exact 2D solution for
estimating the intensity of electron field emission activated by the electric field of the
beam in collimators of the future high-luminosity Large Hadron Collider. Calculation shows
that the field emission intensity is very sensitive to a collimator surface roughness.
In addition, with a relatively small and accidental beam displacement from the median path,
about 20% of the collimator half-gap, the emission intensity increases by a factor of 10^7.
[ DOI,
pdf],
[ DOI,
pdf],
[ DOI,
pdf]

*Processes in strong electromagnetic fields:*

-In the framework of the Dirac model of vacuum the creation of е+е−
pairs in a constant and uniform electric field with allowance Coulomb
interaction between е+ and е− is considered. The transmission coefficient
via the energy gap deformed by external field and the electric
fields of particles is calculated in the semiclassical approximation.
The Sauter exponential factor is modified by the exactly calculated
function G(y) accounting Coulomb interaction of particles and changes
in the shape of the potential barrier. When y < 1 the values of G(y)
exceeds unity, testifying the suppression of pair production in comparison
with the predictions of Schwinger and Ritus.
With further increase in the field strength, 1 < y < 2, G(y) tends
to zero and the probability of pair production has increased rapidly.
[ pdf]

-Probabilities of a pair of fermions and bosons creation in a static and spatially uniform
electric field E are represented in the Schwinger formulas by infinite series. It is believed
that in weak fields the main contribution to the probability is given by the first term of series.
We study the mathematical structure of the Schwinger series by using methods developed during last
decades (polylogarithms) and prove that the given series allows an exact summation
and the contribution of remainder growths rapidly with the field strength.
As a rule, it is argued that the pair of particles begin to be produced efficiently from
the vacuum only in the fields of strength E >= E_cr. However, the direct calculation
shows that the Schwinger formula for creation of e+e- pairs is valid only at the field
intensities of E < 0.0291*E_cr. At higher fields, the probability of pair production in an
unit space-time volume exceeds unity.
[ pdf]