arXiv subjects

S. Smirnov

Publications and source records attributed to S. Smirnov.

10 recordsLinked to original sources

arXiv2019

Identification of particles with Lorentz factor up to $10^{4}$ with Transition Radiation Detectors based on micro-strip silicon detectors

This work is dedicated to the study of a technique for hadron identification in the TeV momentum range, based on the simultaneous measurement of the energies and of the emission angles of the Transition Radiation (TR) X-rays with respect to the radiating particles. A detector setup has been built and tested with particles in a wide range of Lorentz factors (from about $10^3$ to about $4 \times 10^4$ crossing different types of radiators. The measured double-differential (in energy and angle) spectra of the TR photons are in a reasonably good agreement with TR simulation predictions.

physics.ins-det↗

arXiv2016

Test beam studies of the TRD prototype filled with different gas mixtures based on Xe, Kr, and Ar

Towards the end of LHC Run1, gas leaks were observed in some parts of the Transition Radiation Tracker (TRT) of ATLAS. Due to these leaks, primary Xenon based gas mixture was replaced with Argon based mixture in various parts. Test-beam studies with a dedicated Transition Radiation Detector (TRD) prototype were carried out in 2015 in order to understand transition radiation performance with mixtures based on Argon and Krypton. We present and discuss the results of these test-beam studies with different active gas compositions.

physics.ins-det↗

arXiv2016

Blocking transport resonances via Kondo entanglement in quantum dots

Many-body entanglement is at the heart of the Kondo effect, which has its hallmark in quantum dots as a zero-bias conductance peak at low temperatures. It signals the emergence of a conducting singlet state formed by a localized dot degree of freedom and conduction electrons. Carbon nanotubes offer the possibility to study the emergence of the Kondo entanglement by tuning many-body correlations with a gate voltage. Here we quantitatively show an undiscovered side of Kondo correlations, which counterintuitively tend to block conduction channels: inelastic cotunneling lines in the magnetospectrum of a carbon nanotube strikingly disappear when tuning the gate voltage. Considering the global \SUT\ $\otimes $ \SUT\ symmetry of a carbon nanotube coupled to leads, we find that only resonances involving flips of the Kramers pseudospins, associated to this symmetry, are observed at temperatures and voltages below the corresponding Kondo scale. Our results demonstrate the robust formation of entangled many-body states with no net pseudospin.

cond-mat.mes-hall↗

arXiv2015

Broken SU(4) symmetry in a Kondo-correlated carbon nanotube

Understanding the interplay between many-body phenomena and non-equilibrium in systems with entangled spin and orbital degrees of freedom is a central objective in nano-electronics. We demonstrate that the combination of Coulomb interaction, spin-orbit coupling and valley mixing results in a particular selection of the inelastic virtual processes contributing to the Kondo resonance in carbon nanotubes at low temperatures. This effect is dictated by conjugation properties of the underlying carbon nanotube spectrum at zero and finite magnetic field. Our measurements on a clean carbon nanotube are complemented by calculations based on a new approach to the non-equilibrium Kondo problem which well reproduces the rich experimental observations in Kondo transport.

cond-mat.mes-hall↗

arXiv2009

Packing dimension of mean porous measures

We prove that the packing dimension of any mean porous Radon measure on $\mathbb R^d$ may be estimated from above by a function which depends on mean porosity. The upper bound tends to $d-1$ as mean porosity tends to its maximum value. This result was stated in \cite{BS}, and in a weaker form in \cite{JJ1}, but the proofs are not correct. Quite surprisingly, it turns out that mean porous measures are not necessarily approximable by mean porous sets. We verify this by constructing an example of a mean porous measure $μ$ on $\mathbb R$ such that $μ(A)=0$ for all mean porous sets $A\subset\mathbb R$.

math.CA↗

arXiv2008

Harmonic measure and SLE

In this paper we rigorously compute the average multifractal spectrum of harmonic measure on the boundary of SLE clusters.

math.CV↗

arXiv2007

Bloch's theory in periodic structures with Rashba's spin-orbit interaction

We consider a two-dimensional electron gas with Rashba's spin-orbit interaction and two in-plane potentials superimposed along directions perpendicular to each other. The first of these potentials is assumed to be a general periodic potential while the second one is totally arbitrary. A general form for Bloch's amplitude is found and an eigen-value problem for the band structure of the system is derived. We apply the general result to the two particular cases in which either the second potential represents a harmonic in-plane confinement or it is zero. We find that for a harmonic confinement regions of the Brillouin zone with high polarizations are associated with the ones of large group velocity.

cond-mat.mes-hall↗

arXiv2007

Random conformal snowflakes

In many problems of classical analysis extremal configurations appear to exhibit complicated fractal structure. This makes it much harder to describe extremals and to attack such problems. Many of these problems are related to the multifractal analysis of harmonic measure. We argue that, searching for extremals in such problems, one should work with random fractals rather than deterministic ones. We introduce a new class of fractals random conformal snowflakes and investigate its properties developing tools to estimate spectra and showing that extremals can be found in this class. As an application we significantly improve known estimates from below on the extremal behaviour of harmonic measure, showing how to constuct a rather simple snowflake, which has a spectrum quite close to the conjectured extremal value.

math.CV↗

arXiv2001

Linux-Based Toolkit in the VEPP-4 Control System

The control system of the VEPP-4 facility was designed more than fifteen years ago and based on the home-developed CAMAC-embedded minicomputers Odrenok [1]. Five years ago, all computers were connected via Ethernet network. This step allowed us to force an integration of PCs into the VEPP-4 control system. This paper reviews new tools running on the PCs under Linux. The beam diagnostics tool described in this paper provides the data about position and dimensions of e-/e+ beams from CCD matrix controller via 100-Mbit Ethernet. The next tool provides measuring of beam energy at the VEPP-4M collider using a well-known method of resonance depolarization by the observation of the polarization degree on the effect of internal scattering of particles. Data visualization tools are based on CERN ROOT framework. Hardware and software aspects of the systems are presented in this paper.

physics.acc-ph↗

arXiv2001

Database and Channel Access on the VEPP-4

The VEPP-4 control system was designed almost 20 years ago as CAMAC-based distributed control system. Today the main peculiarity of the upgraded VEPP-4 control system is the employment of obsolete CAMAC-embedded 24-bit Odrenok computers in the middle (process) level. The communication software is developed to provide an effective interaction between user (operator) applications on the high level and executive programs in the middle level. The communication software is Linux-based and includes the Application Server and Device Servers. The Application Server provides channel and database access for user applications. The Device Servers provide interaction with the hardware. The backend database server is based on PostgreSQL. This paper describes the structure of the VEPP-4 control system database and data/channel access procedures.

physics.acc-ph↗