arXiv subjects

A. V. Sidorov

Publications and source records attributed to A. V. Sidorov.

At least 19 recordsLinked to original sources

arXiv2019

Detection of true Gaussian shaped pulses at high count rates

A new true Gaussian digital shaper of detector pulses is tested and compared to the standard trapezoidal shaper in terms of output count rate, amplitude resolution and biasing the output shaped pulses. The true Gaussian shaper allows for shaping detector pulses into a symmetrical form which width can be considerably less than their rise time. Standard trapezoidal shapers cannot provide such short pulses. Therefore, the dead time of the true Gaussian shaper can be considerably reduced in regards to that of trapezoidal shaper. The output count rate of the true Gaussian and trapezoidal pulses are compared in a wide range of input count rates. The maximal output count rate of the true Gaussian shaper has been found to exceed in several times the rate of the trapezoidal shapers. The true Gaussian shapers provide better resolution and biasing-free measurements of pulse amplitudes at high count rates. The tests have been performed by modeling output signals of silicon drift detector (SDD) VITUS H7 equipped with AXAS-D pre-amplifier developed by KETEK GmbH for measurements of soft X-ray spectra at high count rates.

physics.ins-det↗

arXiv2018

True Gaussian shaping for high count rate measurements of pulse amplitudes

A digital shaper for high-count-rate detection and amplitude measurement of pulses is proposed and analysed in this paper. The proposed shaper converts pulses with a short leading edge and a long exponential tail into a true Gaussian form. The width of Gaussian pulses can be several times smaller than the rise time of the input pulses, i.e. considerably shorter than the undistorted output pulses provided by standard shapers. Therefore, the proposed true Gaussian shaper resolves strongly overlapped pulses better and provides a higher output count rate. The capabilities of the proposed true Gaussian shaper are analysed with real and simulated output signals of a silicon drift detector of soft X-ray radiation, operating at a high count rate of the collected quanta. Our analysis shows that true Gaussian shapers can increase the count rate of spectrometer systems several times compared with the widely used trapezoidal shapers, while maintaining their amplitude resolution.

physics.ins-det↗

arXiv2018

Observation of extreme-ultraviolet light emission from an expanding plasma jet with multiply-charged argon or xenon ions

We report the first direct demonstration of possibility to generate the extreme ultraviolet (EUV) radiation with a freely expanding jet of dense plasma with multiply-charged ions supported by high-power microwaves. The detected emission power is about 20 W at 18--50 nm for argon and xenon and 0.3 W at 13--17 nm for xenon. The discharge with a peak electron density up to $3\times 10^{16}\,$cm$^{-3}$ and a characteristic size of $150\,μ$m is supported by a focused radiation of a recently developed gyrotron with unique characteristics, 250~kW output power at 250~GHz, operating in a relatively long (50$\,μ$s) pulse mode. Up-scaling of these experimental results gives grounds for development of a point-like kilowatt-level EUV source for a high-resolution lithography able to fulfill requirements of the microelectronics industry.

physics.plasm-ph↗

arXiv2018

Asymptotics of the contour of the stationary phase and efficient evaluation of the Mellin-Barnes integral for the F_3 structure function

A new approximation is proposed for the contour of the stationary phase of the Mellin--Barnes integrals in the case of its finite asymptotic behavior as ${\rm Re} z\to -\infty$. The efficiency of application of the proposed contour and the quadratic approximation to the contour of the stationary phase is compared by the example of the inverse Mellin transform for the structure function $F_3$. It is shown that, although for a small number of terms $N$ in quadrature formulas used to calculate integrals along these contours, the quadratic contour is more efficient, but for $N>20$ the asymptotic stationary phase integration contour gives better accuracy. The case of the $Q^2$-dependence of the $F_3$ structure function is also considered.

hep-ph↗

arXiv2015

Polarized nonsinglet {Delta q}_3 and nonsinglet fragmentation function D^{pi+}_{u_v} in the analytic approach to QCD

We discuss the application of an analytic approach called the analytic perturbation theory (APT) to the QCD analysis of DIS data. In particular, the results of the QCD analysis of a set of `fake' data on the polarized nonsinglet Delta{q3} and the nonsinglet fragmentation function D^{pi+}_{u_v} by using the Q^2-evolution within the APT are considered. The `fake' data are constructed based on parametrization of the polarized PDF and nonsinglet combination of the pion fragmentation functions. We confirm that APT can be successfully applied to QCD analysis of Delta{q_3}(x,Q^2) and D^{pi+}_{u_v}(z,Q^2) and that the inequality Lambda_{APT} > Lambda_{PT} obtained previously for the xF3(x) structure function takes place.

hep-ph↗

arXiv2014

The QCD analysis of the combined set for the F_3 structure function data based on the analytic approach

We apply analytic perturbation theory to the QCD analysis of the xF_3(x,Q^2) structure function considering a combined set of deep inelastic scattering data presented by several collaborations, and extract values of the scale parameter Lambda_{QCD}, the parameters of the form of the xF_3 structure function, and the x-shape of the higher twist contribution. We study the difference between the results obtained within the standard perturbative and analytic approaches in comparison with the experimental errors and state that the greatest difference occurs for large x.

hep-ph↗

arXiv2013

The QCD analysis of xF_3 structure function based on the analytic approach

We apply analytic perturbation theory to the QCD analysis of the xF_3 structure function data of the CCFR collaboration. We use different approaches for the leading order Q^2 evolution of the xF_3 structure function and compare the extracted values of the parameter Lambda_QCD and the shape of the higher twistcontribution. Our consideration is based on the Jacobi polynomial expansion method of the unpolarized structure function. The analysis shows that the analytic approach provides reasonable results in the leading order QCD analysis.

hep-ph↗

arXiv2007

Relation between the x-dependence of Higher Twist Contribution to $F_3$ and $g_1^p - g_1^n$ in the Light of the Recent Experimental Data

We compare the recent results on the higher twist (HT) contribution to the nonsinglet combination $g_1^p - g_1^n$ of the polarized proton and neutron structure functions with that one to the unpolarized structure function $F_3$ using the assumption that the HT contributions to the Gross-Llewellyn Smith and the Bjorken sum rules are similar. We have found, that the relation ${1/3}h^{F_3}(x) \approx \frac{6}{g_A}h^{g_1^p - g_1^n}(x)$ is valid for $x \geq 0.2$ in the case of NLO QCD approximation for the leading term parts of the structure functions.

hep-ph↗

arXiv2007

Fixation of theoretical ambiguities in the improved fits to $xF_3$ CCFR data at the next-to-next-to-leading order and beyond

Using the results for the NNLO QCD corrections to anomalous dimensions of odd $xF_3$ Mellin moments and N$^3$LO corrections to their coefficient functions we improve our previous analysis of the CCFR'97 data for $xF_3$. The possibility of extracting from the fits of $1/Q^2$-corrections is analysed using three independent models,including infrared renormalon one. Theoretical quetion of applicability of the renormalon-type inspired large-$β_0$ approximation for estimating corrections to the coefficient functions of odd $xF_3$ and even non-singlet $F_2$ moments are considered. The comparison with [1/1] Padé estimates is given. The obtained NLO and NNLO values of $α_s(M_Z)$ are supporting the results of our less definite previous analysis and are in agreement with the world average value $α_s(M_Z)\approx 0.118$. We also present first N$^3$LO extraction of $α_s(M_Z)$. The interplay between higher-order perturbative QCD corrections and $1/Q^2$-terms is demonstrated. The results of our studies are compared with those obtained recently using the NNLO model of the kernel of DGLAP equation and with the results of the NNLO fits to CCFR'97 $xF_3$ data, performed by the Bernstein polynomial technique.

hep-ph↗

arXiv2006

Higher twists in polarized DIS and the size of the constituent quark

The spontaneous breaking of chiral symmetry implies the presence of a short-distance scale in the QCD vacuum, which phenomenologically may be associated with the "size" of the constituent quark, rho ~ 0.3 fm. We discuss the role of this scale in the matrix elements of the twist-4 and 3 quark-gluon operators determining the leading power (1/Q^2-) corrections to the moments of the nucleon spin structure functions. We argue that the flavor-nonsinglet twist-4 matrix element, f_2^{u - d}, has a sizable negative value of the order rho^{-2}, due to the presence of sea quarks with virtualities ~ rho^{-2} in the proton wave function. The twist-3 matrix element, d_2, is not related to the scale rho^{-2}. Our arguments support the results of previous calculations of the matrix elements in the instanton vacuum model. We show that this qualitative picture is in agreement with the phenomenological higher-twist correction extracted from an NLO QCD fit to the world data on g_1^p and g_1^n, which include recent data from the Jefferson Lab Hall A and COMPASS experiments. We comment on the implications of the short-distance scale rho for quark-hadron duality and the x-dependence of higher-twist contributions.

hep-ph↗

arXiv2005

On the Relation Between x-dependence of the Higher Twist Contribution to F_3 and g_1^p - g_1^n

We compare the higher twist (HT) contribution to the unpolarized structure function $F_3$ with that one to the nonsinglet combination g_1^p - g_1^n of the polarized proton and neutron structure functions using the assumption that the HT contributions to the Gross-Llewellyn Smith and the Bjorken sum rules are similar. We have found, that the relation 1/3x h^{xF_3}(x) ~ 6/g_A h^{g_1^p - g_1^n}(x) is valid for x > 0.1 and for x > 0.2 in the case of LO and NLO QCD approximations, respectively.

hep-ph↗

arXiv2004

The Role of Higher Twist in Determining Polarized Parton Densities from DIS data

Different methods to extract the polarized parton densities from the world polarized DIS data are considered. The higher twist corrections $h^N(x)/Q^2$ to the spin dependent proton and neutron $g_1$ structure functions are found to be non-negligible and important in the QCD analysis of the present experimental data. Their role in determining the polarized parton densities in the framework of the different approaches is discussed.

hep-ph↗

arXiv2004

Higher twists in spin structure functions from a "constituent quark" point of view

We discuss the implications of a "constituent quark" structure of the nucleon for the leading (1/Q^2-) power corrections to the spin structure functions. Our basic assumption is the presence of quark-gluon correlations in the nucleon wave function, whose size, rho ~ 0.3 fm, is small compared to the nucleon radius, R (two-scale picture). We argue that in this picture the isovector twist-4 matrix element in the proton has a sizable negative value, M_N^2 |f_2^{u - d}| ~ rho^{-2}, while the twist-3 matrix elements are small, M_N^2 d_2 ~ R^{-2}. These findings are in agreement with the result of a QCD fit to the g_1 world data, including recent neutron data from HERMES and Jefferson Lab Hall A, which gives M_N^2 f_2^{u - d} = -0.28 +/- 0.08 GeV^2.

hep-ph↗

arXiv2003

Importance of Higher Twist Corrections in Polarized DIS

The higher twist corrections $h^N(x)/Q^2$ to the spin dependent proton and neutron $g_1$ structure functions are extracted from the world data on $g_1(x,Q^2)$ in a model independent way and found to be non-negligible. Their role in determining the polarized parton densities in the nucleon is discussed. It is also considered how the results are influenced by the recent JLab and HERMES/d inclusive DIS data.

hep-ph↗

arXiv2003

On the Role of Higher Twist in Polarized Deep Inelastic Scattering

The higher twist corrections $h^N(x)/Q^2$ to the spin dependent proton and neutron structure functions $g_1^N(x, Q^2)$ are extracted in a model independent way from experimental data on $g_1^N$ and found to be non-negligible. It is shown that the NLO QCD polarized parton densities determined from the data on g1, including higher twist effects, are in good agreement with those found earlier from our analysis of the data on g1/F1 and A1 where higher twist effects are negligible. On the contrary, the LO QCD polarized parton densities obtained from the data on g1, including higher twist, differ significantly from our previous results.

hep-ph↗

arXiv2002

N^3LO fits to xF_3 data : $α_s$ vs 1/Q^2 contributions

The results of approximate N$^$3LO and detailed NNLO fits to $xF_3$ data of the CCFR'97 collaboration are presented. We demonstrate that $1/Q^2$ non-perturbative corrections to $xF_3$ modeled by three independent procedures are shadowed by perturbative QCD effects, starting at the NNLO. Special attention is paid to revealing the role of the recently calculated NNLO corrections to the anomalous dimensions and $N^3$LO corrections to the coefficient functions of odd moments of $xF_3$ with $n\leq 13$. The related values of $α_s(M_Z)$ are extracted.

hep-ph↗

arXiv2002

Next-to-next-to-leading order fits to CCFR'97 $xF_3$ data and infrared renormalons

We briefly summarize the outcomes of our recent improved fits to the experimental data of CCFR collaboration for $xF_3$ structure function of $νN$ deep-inelastic scattering at the next-to-next-to-leading order. Special attention is paid to the extraction of $α_s(M_Z)$ and the parameter of the infrared renormalon model for $1/Q^2$-correction at different orders of perturbation theory. The results can be of interest for planning similar studies using possible future data of Neutrino Factories.

hep-ph↗

arXiv2002

A New Evaluation of Polarized Parton Densities in the Nucleon

We present a new leading and next-to-leading QCD analysis of the world data on inclusive polarized deep inelastic scattering. A new set of polarized parton densities is extracted from the data and the sensitivity of the results to the newly incorporated SLAC/E155 proton data is discussed.

hep-ph↗