arXiv subjects

Alexander A. Penin

Publications and source records attributed to Alexander A. Penin.

28 records · Page 2Linked to original sources

arXiv2012

Nonrelativistic effective field theory of unstable top

We develop a new nonrelativistic effective field theory of $ρ$NRQCD [1] to describe the finite lifetime effects in the threshold production of top quark-antiquark pairs. The theory is based on the expansion in a parameter $ρ=1-m_W/m_t$ characterizing the dynamics of the top-quark decay. Within this framework we compute the nonresonant contribution to the total cross section of the top quark-antiquark threshold production in electron-positron annihilation up to the next-to-next-to-leading order. Our method naturally resolves the problem of spurious divergences in the analysis of the unstable top production.

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arXiv2012

Threshold production of unstable top

We develop a systematic approach to describe the finite lifetime effects in the threshold production of top quark-antiquark pairs. It is based on the nonrelativistic effective field theory with an additional scale rho^(1/2) m_t characterizing the dynamics of the top-quark decay, which involves a new expansion parameter rho=1-m_W/m_t. Our method naturally resolves the problem of spurious divergences in the analysis of the unstable top production. Within this framework we compute the next-to-leading nonresonant contribution to the total cross section of the top quark-antiquark threshold production in electron-positron annihilation through high-order expansion in rho and confirm the recently obtained result. We extend the analysis to the next-to-next-to-leading O(alpha_s) nonresonant contribution which is derived in the leading order in rho. The dominant nonresonant contribution to the top-antitop threshold production in hadronic collisions is also obtained.

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arXiv2009

Quantum Hall Effect in Quantum Electrodynamics

We consider the quantum Hall effect in quantum electrodynamics and find a deviation from the quantum mechanical prediction for the Hall conductivity due to radiative antiscreening of electric charge in an external magnetic field. A weak universal dependence of the von Klitzing constant on the magnetic field strength, which can possibly be observed in a dedicated experiment, is predicted.

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arXiv2008

Two-Loop Electroweak Logarithms in Four-Fermion Processes at High Energy

We present the complete analytical result for the two-loop logarithmically enhanced contributions to the high energy asymptotic behavior of the vector form factor and the four-fermion cross section in a spontaneously broken SU(2) gauge model. On the basis of this result we derive the dominant two-loop electroweak corrections to the neutral current four-fermion processes at high energies. Previously neglected effects of the gauge boson mass difference are included through the next-to-next-to-leading logarithmic approximation.

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arXiv2008

Two-Loop Electroweak Logarithms

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arXiv2005

Two-Loop Sudakov Form Factor in a Theory with Mass Gap

The two-loop Sudakov form factor is computed in a U(1) model with a massive gauge boson and a $U(1)\times U(1)$ model with mass gap. We analyze the result in the context of hard and infrared evolution equations and establish a matching procedure which relates the theories with and without mass gap setting the stage for the complete calculation of the dominant two-loop corrections to electroweak processes at high energy.

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arXiv2003

Heavy-quarkonium creation and annihilation with O(alpha_s^3 ln(alpha_s)) accuracy

We calculate the O(alpha_s^3 ln(alpha_s)) contributions to the heavy-quarkonium production and annihilation rates. Our result sheds new light on the structure of the high-order perturbative corrections and opens a new perspective for a high-precision theoretical analysis. We also determine the three-loop anomalous dimensions of the nonrelativistic vector and pseudoscalar currents.

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arXiv2001

Nonabelian alpha_s^3/(m_q r^2) heavy-quark-antiquark potential

We calculate the leading mass-suppressed two-loop contribution, proportional to alpha_s^3/(m_q r^2), to the potential of a heavy quark-antiquark system. This contribution originates in the nonabelian nature of quantum chromodynamics (QCD) and has no analogue in quantum electrodynamics (QED). For this purpose, we elaborate a technique based on the implementation of the threshold expansion within the effective theory of nonrelativistic QCD (NRQCD). We discuss phenomenological implications of our result for heavy-quarkonium physics. We also confirm a previous result for the two-loop O(alpha_s^2) correction to the static potential.

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arXiv2000

Order alpha^7 ln(1/alpha) Contribution to Positronium Hyperfine Splitting

The logarithmically enhanced alpha^7 ln(1/alpha) contribution to the hyperfine splitting of the positronium ground-state energy levels is calculated in the framework of dimensionally regularized nonrelativistic quantum electrodynamics. The correction is negative and amounts to about 1/3 of the leading logarithmic alpha^7 ln^2(1/alpha) one. The discrepancy between the experimental measurements and the theoretical prediction is reduced.

hep-ph↗

arXiv2000

Order alpha^3 ln(1/alpha) Corrections to Positronium Decays

The logarithmically enhanced alpha^3 ln(1/alpha) corrections to the para- and orthopositronium decay widths are calculated in the framework of dimensionally regularized nonrelativistic quantum electrodynamics.In the case of parapositronium, the correction is negative, approximately doubles the effect of the leading logarithmic alpha^3 ln^2(1/alpha) one, and is comparable to the nonlogarithmic O(alpha^2) one. As for orthopositronium, the correction is positive and almost cancels the alpha^3 ln^2(1/alpha) one. The uncertainties in the theoretical predictions for the decay widths are reduced.

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