arXiv subjects

V. V. Petrov

Publications and source records attributed to V. V. Petrov.

At least 19 recordsLinked to original sources

arXiv2018

Precise measurement of $R_{\text{uds}}$ and $R$ between 1.84 and 3.72 GeV at the KEDR detector

The present work continues a series of the KEDR measurements of the $R$ value that started in 2010 at the VEPP-4M $e^+e^-$ collider. By combining new data with our previous results in this energy range we measured the values of $R_{\text{uds}}$ and $R$ at nine center-of-mass energies between 3.08 and 3.72 GeV. The total accuracy is about or better than $2.6\%$ at most of energy points with a systematic uncertainty of about $1.9\%$. Together with the previous precise $R$ measurement at KEDR in the energy range 1.84-3.05 GeV, it constitutes the most detailed high-precision $R$ measurement near the charmonium production threshold.

hep-ex↗

arXiv2018

Measurement of $Γ_{ee}\times\mathcal{B}_{μμ}$ for $ψ(2S)$ meson

The product of the electronic width of the $ψ(2S)$ meson and the branching fraction of its decay to the muon pair was measured in the $e^{+}e^{-} \to ψ(2S) \to μ^{+}μ^{-}$ process using nine data sets corresponding to an integrated luminosity of about 6.5 pb$^{-1}$ collected with the KEDR detector at the VEPP-4M electron-positron collider: \[ Γ_{ee}\times\mathcal{B}_{μμ} = 19.3 \pm 0.3 \pm 0.5 ~\text{eV}. \] Adding the previous KEDR results on hadronic and leptonic channels, the values of the $ψ(2S)$ electronic width were obtained under two assumptions: either with the assumption of lepton universality \[ Γ_{ee} = 2.279 \pm 0.015 \pm 0.042 ~\text{keV} \] or without it, summing up hadronic and three independent leptonic channels: \[ Γ_{ee} = 2.282 \pm 0.015 \pm 0.042 ~\text{keV}. \]

hep-ex↗

arXiv2018

Measurement of $Γ_{ee}(J/ψ)$ with KEDR detector

The product of the electronic width of the $J/ψ$ meson and the branching fractions of its decay to hadrons and electrons has been measured using the KEDR detector at the VEPP-4M $e^+e^-$ collider. The obtained values are: $Γ_{ee}(J/ψ) = 5.550 \pm 0.056 \pm 0.089 \, \text{keV}, $ $Γ_{ee}(J/ψ) \cdot \mathcal{B}_\text{hadrons}(J/ψ) = 4.884 \pm 0.048 \pm 0.078 \, \text{keV}, $ $Γ_{ee}(J/ψ) \cdot \mathcal{B}_{ee}(J/ψ) = 0.3331 \pm 0.0066 \pm 0.0040 \, \text{keV}.$ The uncertainties shown are statistical and systematic, respectively. Using the result presented and the world-average value of the electronic branching fraction, one obtains the total width of the $J/ψ$ meson: $Γ= 92.94 \pm 1.83 \, \text{keV}.$ These results are consistent with the previous experiments.

hep-ex↗

arXiv2016

Measurement of $R$ between 1.84 and 3.05 GeV at the KEDR detector

Using the KEDR detector at the VEPP-4M $e^+e^-$ collider, we have determined the values of $R$ at thirteen points of the center-of-mass energy between 1.84 and 3.05 GeV. The achieved accuracy is about or better than $3.9\%$ at most of the energy points with a systematic uncertainty less than $2.4\%$.

hep-ex↗

arXiv2016

Inversion of Zeeman splitting of exciton states in InGaAs quantum wells

Zeeman splitting of quantum-confined states of excitons in InGaAs quantum wells (QWs) is experimentally found to depend strongly on quantization energy. Moreover, it changes sign when the quantization energy increases with a decrease in the QW width. In the 87-nm QW, the sign change is observed for the excited quantum-confined states, which are above the ground state only by a few meV. A two-step approach for the numerical solution of the two-particle Schroedinger equation, taking into account the Coulomb interaction and valence-band coupling, is used for a theoretical justification of the observed phenomenon. The calculated variation of the g-factor convincingly follows the dependencies obtained in the experiments.

cond-mat.mes-hall↗

arXiv2016

Excitons in asymmetric quantum wells

Resonance dielectric response of excitons is studied for the high-quality GaAs/InGaAs heterostructures with wide asymmetric quantum wells (QWs). To highlight effects of the QW asymmetry, we have grown and studied several heterostructures with nominally square QWs as well as with triangle-like QWs. Several quantum confined exciton states are experimentally observed as narrow exciton resonances with various profiles. A standard approach for the phenomenological analysis of the profiles is generalized by introducing of different phase shifts for the light waves reflected from the QWs at different exciton resonances. Perfect agreement of the phenomenological fit to the experimentally observed exciton spectra for high-quality structures allowed us to obtain reliable parameters of the exciton resonances including the exciton transition energies, the radiative broadenings, and the phase shifts. A direct numerical solution of Schrödinger equation for the heavy-hole excitons in asymmetric QWs is used for microscopic modeling of the exciton resonances. Remarkable agreement with the experiment is achieved when the effect of indium segregation during the heterostructure growth is taken into account. The segregation results in a modification of the potential profile, in particular, in an asymmetry of the nominally square QWs.

cond-mat.mes-hall↗

arXiv2015

Measurement of $R_{\text{uds}}$ and $R$ between 3.12 and 3.72 GeV at the KEDR detector

Using the KEDR detector at the VEPP-4M $e^+e^-$ collider, we have measured the values of $R_{\text{uds}}$ and $R$ at seven points of the center-of-mass energy between 3.12 and 3.72 GeV. The total achieved accuracy is about or better than $3.3\%$ at most of energy points with a systematic uncertainty of about $2.1\%$. At the moment it is the most accurate measurement of $R(s)$ in this energy range.

hep-ex↗

arXiv2015

Spin-noise-based magnetometry of an $n$-doped GaAs microcavity in the field of elliptically polarized light

Recently reported optical nuclear orientation in the $n$-doped GaAs microcavity under pumping in nominal transparency region of the crystal [Appl. Phys. Lett. $\mathbf{106}$, 242405 (2015)] has arisen a number of questions, the main of them concerning mechanisms of angular momentum transfer from the light to the nuclear spin system and the nature of the light-related magnetic fields accompanying the optical nuclear polarization. In this paper, we use the spin noise spectroscopy for magnetometric purposes, particularly, to study effective fields acting upon electron spin system of an $n$-GaAs layer inside a high-Q microcavity in the presence of elliptically polarized probe beam. In addition to the external magnetic field applied to the sample in the Voigt geometry and the Overhauser field created by optically oriented nuclei, the spin noise spectrum reveals an additional effective, "optical," magnetic field produced by elliptically polarized probe itself. This field is directed along the light propagation axis, with its sign being determined by the sign of the probe helicity and its magnitude depending on degree of circular polarization and intensity of the probe beam. We analyze properties of this optical magnetic field and suggest that it results from the optical Stark effect in the field of the elliptically polarized electromagnetic wave.

cond-mat.mes-hall↗

arXiv2015

Excitons in square quantum wells: microscopic modeling and experiment

The binding energy and the corresponding wave function of excitons in GaAs-based finite square quantum wells (QWs) are calculated by the direct numerical solution of the three-dimensional Schroedinger equation. The precise results for the lowest exciton state are obtained by the Hamiltonian discretization using the high-order finite-difference scheme. The microscopic calculations are compared with the results obtained by the standard variational approach. The exciton binding energies found by two methods coincide within 0.1 meV for the wide range of QW widths. The radiative decay rate is calculated for QWs of various widths using the exciton wave functions obtained by direct and variational methods. The radiative decay rates are confronted with the experimental data measured for high-quality GaAs/AlGaAs and InGaAs/GaAs QW heterostructures grown by molecular beam epitaxy. The calculated and measured values are in good agreement, though slight differences with earlier calculations of the radiative decay rate are observed.

cond-mat.mes-hall↗

arXiv2015

Multiple quantum beats of quantum confined exciton states in InGaAs/GaAs quantum well

Multiple quantum beats of a system of the coherently excited quantum confined exciton states in a high-quality heterostructure with a wide InGaAs/GaAs quantum well are experimentally detected by the spectrally resolved pump-probe method for the first time. The beat signal is observed as at positive as at negative delays between the pump and probe pulses. A theoretical model is developed, which allows one to attribute the QBs at negative delay to the four-wave mixing (FWM) signal detected at the non-standard direction. The beat signal is strongly enhanced by the interference of the FWM wave with the polarization created by the probe pulse. At positive delay, the QBs are due to the mutual interference of the quantum confined exciton states. Several QB frequencies are observed in the experiments, which coincide with the interlevel spacings in the exciton system. The decay time for QBs is of order of several picoseconds at both the positive and negative delays. They are close to the relaxation time of exciton population that allows one to consider the exciton depopulation as the main mechanism of the coherence relaxation in the system under study.

cond-mat.mes-hall↗

arXiv2015

Nontrivial relaxation dynamics of excitons in high-quality InGaAs/GaAs quantum wells

Photoluminescence (PL) and reflectivity spectra of a high-quality InGaAs/GaAs quantum well structure reveal a series of ultra-narrow peaks attributed to the quantum confined exciton states. The intensity of these peaks decreases as a function of temperature, while the linewidths demonstrate a complex and peculiar behavior. At low pumping the widths of all peaks remain quite narrow ($< 0.1$ meV) in the whole temperature range studied, $4 - 30K$. At the stronger pumping, the linewidth first increases and than drops down with the temperature rise. Pump-probe experiments show two characteristic time scales in the exciton decay, $< 10$ps and $15 - 45ns$, respectively. We interpret all these data by an interplay between the exciton recombination within the light cone, the exciton relaxation from a non-radiative reservoir to the light cone, and the thermal dissociation of the non-radiative excitons. The broadening of the low energy exciton lines is governed by the radiative recombination and scattering with reservoir excitons while for the higher energy states the linewidths are also dependent on the acoustic phonon relaxation processes.

cond-mat.mes-hall↗

arXiv2014

Effect of irradiation by He+ and Ga+ ions on 2D-exciton susceptibility of the InGaAs/GaAs quantum-well structures

The effect of irradiation by 30-keV Ga+ and 35-keV He+ ions (in relatively small doses) on the excitonic reflectivity spectra of single InGaAs/GaAs quantum-well structures is studied. It is found that the irradiation results in decreasing intensity and broadening of the excitonic resonances in the reflectivity spectra for all the doses. It is shown that these changes are not related to a decrease of the exciton transition oscillator strength and, therefore, to the irradiation-induced destruction of the excitonic states, but can be rather ascribed to a common cause, namely, to inhomogeneous broadening of the excitonic resonances proportional to the exposure dose.A tentative model of the irradiation-induced broadening is considered, with the mechanism of the process being a consequence of scat-tering of the 2D excitons by structural defects associated with Ga(In) and As vacancies arising upon collisions of the high-energy ions with regular atoms of the crystal structure. The model is used to compare experimental dependence of efficiency of the Ga+-ion-induced broad-ening on distance of the quantum well from the irradiated surface with a similar dependence calculated using the Monte-Carlo technique. A discrepancy between the results of simulation and experimental data is discussed.

cond-mat.mes-hall↗

arXiv2014

Readout Optical System of Sapphire Disks intended for Long-Term Data Storage

The development of long-term data storage technology is one of the urging problems of our time. This paper presents the results of implementation of technical solution for long-term data storage technology proposed a few years ago on the basis of single crystal sapphire. It is shown that the problem of reading data through a substrate of negative single crystal sapphire can be solved by using for reading a special optical system with a plate of positive single crystal quartz. The experimental results confirm the efficiency of the proposed method of compensation.

cs.ET↗

arXiv2014

Measurement of $J/ψ\toγη_{\rm c}$ decay rate and $η_{\rm c}$ parameters at KEDR

Using the inclusive photon spectrum based on a data sample collected at the $J/ψ$ peak with the KEDR detector at the VEPP-4M $e^+e^-$ collider, we measured the rate of the radiative decay $J/ψ\toγη_{\rm c}$ as well as $η_{\rm c}$ mass and width. Taking into account an asymmetric photon lineshape we obtained $Γ^0_{γη_{\rm c}}=2.98\pm0.18 \phantom{|}^{+0.15}_{-0.33}$ keV, $M_{η_{\rm c}} = 2983.5 \pm 1.4 \phantom{|}^{+1.6}_{-3.6}$ MeV/$c^2$, $Γ_{η_{\rm c}} = 27.2 \pm 3.1 \phantom{|}^{+5.4}_{-2.6}$ MeV.

hep-ex↗

arXiv2014

Extremely low inhomogeneous broadening of exciton lines in shallow (In,Ga)As/GaAs quantum wells

We study radiative linewidth of exciton resonance in shallow In$_x$Ga$_{1-x}$As/GaAs single quantum wells as a function of indium concentration in the range $x=0.02...0.10$ and well thickness in the range $L_Z=1...30$ nm using the method of Brewster reflection spectroscopy. Record linewidths of heavy-hole exciton resonance of about 130...180 $μ$eV are measured in reflection spectra for single quantum wells with $L_Z=2$ nm and $x=0.02$ at temperature 9 K. In these spectra, the non-radiative linewidth including inhomogeneous broadening can be comparable or even less than radiative linewidth. It is shown that radiative linewidth weakly depends on $x$ and $L_Z$ in these ranges. In multiple-quantum-well Bragg structure with ten periods radiative linewidth exceeds inhomogeneous broadening by 4 times.

cond-mat.mes-hall↗

arXiv2014

All-optical NMR in semiconductors provided by resonant cooling of nuclear spins interacting with electrons in the resonant spin amplification regime

Resonant cooling of different nuclear isotopes manifested in optically-induced nuclear magnetic resonances (NMR) is observed in n-doped CdTe/(Cd,Mg)Te and ZnSe/(Zn,Mg)Se quantum wells and for donor-bound electrons in ZnSe:F and GaAs epilayers. By time-resolved Kerr rotation used in the regime of resonant spin amplification we can expand the range of magnetic fields where the effect can be observed up to nuclear Larmor frequencies of 170 kHz. The mechanism of the resonant cooling of the nuclear spin system is analyzed theoretically. The developed approach allows us to model the resonant spin amplification signals with NMR resonances.

cond-mat.mes-hall↗

arXiv2014

Measurement of the ratio of the leptonic widths $Γ_{ee}/Γ_{μμ}$ for the $J/ψ$ meson

The ratio of the electron and muon widths of the $J/ψ$ meson has been measured using direct $J/ψ$ decays in the KEDR experiment at the VEPP-4M electron-positron collider. The result $Γ_{ee}(J/ψ)/Γ_{μμ}(J/ψ)=1.0022\pm0.0044\pm0.0048\ (0.65\%)$ is in good agreement with the lepton universality. The experience collected during this analysis will be used for a $J/ψ$ lepton width determination with up to 1% accuracy.

hep-ex↗

arXiv2013

Parameters of charmonium states from KEDR

We report results of experiments performed with the KEDR detector at the VEPP-4M $e^+e^-$ collider. They include final results for the mass and other parameters of the $J/ψ$, $ψ(2S)$ and $ψ(3770)$ and $J/ψ\toγη_c$ branching fraction determination.

hep-ex↗