arXiv subjects

M. G. Kozlov

Publications and source records attributed to M. G. Kozlov.

At least 109 records · Page 6Linked to original sources

arXiv2008

Flavour physics of leptons and dipole moments

This chapter of the report of the ``Flavour in the era of the LHC'' Workshop discusses the theoretical, phenomenological and experimental issues related to flavour phenomena in the charged lepton sector and in flavour-conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavour structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the Standard Model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.

hep-ph↗

arXiv2007

A new approach for testing variations of fundamental constants over cosmic epochs using FIR fine-structure lines

Aims. To obtain limits on the variation of the fine-structure constant alpha and the electron-to-proton mass ratio mu over different cosmological epochs. Methods. A new approach based on the comparison of redshifts of far infrared (FIR) fine-structure lines and low-lying rotational transitions in CO is proposed which is in principle more sensitive by a factor of 10 compared to QSO metal absorption lines. Results. Estimations of the quotient F = alpha^2/mu obtained for two distant quasars J1148+5251 (z = 6.42) and BR1202-0725 (z = 4.69) provide Delta F/F = (0.1+/-1.0)10^{-4} and (1.4+/-1.5)10^{-4}, respectively. The obtained limits are consistent with no variation of physical constants at the level of 0.01% over a period of 13 Gyr. Conclusions. Upcoming observations of quasars and distant galaxies in FIR fine-structure lines of different species and in CO low rotational lines at the SOFIA, HSO, and ALMA are expected to improve the current limit by, at least, an order of magnitude.

astro-ph↗

arXiv2007

Enhanced sensitivity to variation of the fine structure constant and m_p/m_e in diatomic molecules

Sensitivity to temporal variation of the fundamental constants may be strongly enhanced in transitions between narrow close levels of different nature. This enhancement may be realized in a large number of molecules due to cancelation between the ground state fine structure omega_f and vibrational interval omega_v (omega=omega_f - n omega_v is close to zero, delta omega/omega= K (2 delta alpha/alpha +0.5 delta mu/mu), K >>1, mu=m_p/m_e). The intervals between the levels are conveniently located in microwave frequency range and the level widths are very small. Required accuracy of the shift measurements is about 0.01-1 Hz. As examples, we consider molecules Cl_2+, CuS, IrC, SiBr and HfF+.

physics.atom-ph↗

arXiv2007

Using Molecules to Measure Nuclear Spin-Dependent Parity Violation

Nuclear spin-dependent parity violation arises from weak interactions between electrons and nucleons, and from nuclear anapole moments. We outline a method to measure such effects, using a Stark-interference technique to determine the mixing between opposite-parity rotational/hyperfine levels of ground-state molecules. The technique is applicable to nuclei over a wide range of atomic number, in diatomic species that are theoretically tractable for interpretation. This should provide data on anapole moments of many nuclei, and on previously unmeasured neutral weak couplings.

physics.atom-ph↗

arXiv2007

Transition frequency shifts with fine structure constant variation for Fe II: Breit and core-valence correlation correction

Transition frequencies of Fe II ion are known to be very sensitive to variation of the fine structure constant α. The resonance absorption lines of Fe II from objects at cosmological distances are used in a search for the possible variation of αin cause of cosmic time. In this paper we calculated the dependence of the transition frequencies on α^2 (q-factors) for Fe II ion. We found corrections to these coefficients from valence-valence and core-valence correlations and from the Breit interaction. Both the core-valence correlation and Breit corrections to the q-factors appeared to be larger than had been anticipated previously. Nevertheless our calculation confirms that the Fe II absorption lines seen in quasar spectra have large q-factors of both signs and thus the ion Fe II alone can be used in the search for the α-variation at different cosmological epochs.

physics.atom-ph↗

arXiv2007

High-precision calculations of In I and Sn II atomic properties

We use all-order relativistic many-body perturbation theory to study 5s^2 nl configurations of In I and Sn II. Energies, E1-amplitudes, and hyperfine constants are calculated using all-order method, which accounts for single and double excitations of the Dirac-Fock wave functions.

physics.atom-ph↗

arXiv2007

Enhanced sensitivity to time-variation of m_p/m_e in the inversion spectrum of ammonia

We calculate the sensitivity of the inversion spectrum of ammonia to possible time-variation of the ratio of the proton mass to the electron mass, mu=m_p/m_e. For the inversion transition (lambda= 1.25 cm^{-1}) the relative frequency shift is significantly enhanced: delta(omega)/omega=-4.46, delta(mu)/mu. This enhancement allows one to increase sensitivity to the time-variation of mu using NH_3 spectra for high redshift objects. We use published data on microwave spectra of the object B0218+357 to place the limit delta(mu)/mu =(0.6 +/- 1.9) 10^{-6} at redshift z=0.6847; this limit is several times better than the limits obtained by different methods and may be significantly improved. Assuming linear time dependence we obtain dot{mu}/mu=(-1 +/- 3) 10^{-16} yr^{-1}.

astro-ph↗

arXiv2007

Relativistic corrections to isotope shift in light ions

We calculate isotope mass shift for several light ions using Dirac wave functions and mass shift operator with relativistic corrections of the order of $(αZ)^2$. Calculated relativistic corrections to the specific mass shift vary from a fraction of a percent for Carbon, to 2% for Magnesium. Relativistic corrections to the normal mass shift are typically smaller. Interestingly, the final relativistic mass shifts for the levels of one multiplet appear to be even closer than for non-relativistic operator. That can be important for the astrophysical search for possible $α$-variation, where isotope shift is a source of important systematic error. Our calculations show that for levels of the same multiplet this systematics is negligible and they can be used as probes for $α$-variation.

astro-ph↗

arXiv2006

Proposal for a sensitive search for electric dipole moment of electron with matrix-isolated radicals

We propose using matrix-isolated paramagnetic diatomic molecules to search for the electric dipole moment of electron (eEDM). As was suggested by Shapiro in 1968, the eEDM leads to a magnetization of a sample in the external electric field. In a typical condensed matter experiment, the effective field on the unpaired electron is of the same order of magnitude as the laboratory field, typically about $10^{5}$V/cm. We exploit the fact that the effective electric field inside heavy polar molecules is in the order of $10^{10}$V/cm. This leads to a huge enhancement of the Shapiro effect. Statistical sensitivity of the proposed experiment may allow one to improve the current limit on eEDM by three orders of magnitude in few hours accumulation time.

physics.atom-ph↗

arXiv2006

Laboratory spectroscopy and the search for space-time variation of the fine structure constant using QSO spectra

Theories unifying gravity with other interactions suggest spatial and temporal variation of fundamental ``constants'' in the Universe. A change in the fine structure constant, alpha, could be detected via shifts in the frequencies of atomic transitions in quasar absorption systems. Previous studies of three independent samples of data, containing 143 absorption systems spread from 2 to 10 billion years after big bang, hint that alpha was smaller 7 - 11 billion years ago. To continue this study we urgently need accurate laboratory measurements of atomic transition frequencies. In this paper, we present a current list of transitions of importance to the search for alpha variation. They are E1 transitions to the ground state in several different atoms and ions, with wavelengths ranging from around 900 - 6000 Angstroms, and require an accuracy of better than 10^(-4) Angstroms. We also discuss isotope shift measurements that are needed in order to resolve systematic effects in the study. Researchers who are interested in performing these measurements should contact the authors directly.

physics.atom-ph↗

arXiv2006

Proof of the multi-Regge form of QCD amplitudes with gluon exchanges in the NLA

The multi--Regge form of QCD amplitudes with gluon exchanges is proved in the next-to-leading approximation. The proof is based on the bootstrap relations, which are required for the compatibility of this form with the s-channel unitarity. We show that the fulfillment of all these relations ensures the Reggeized form of energy dependent radiative corrections order by order in perturbation theory. Then we prove that all these relations are fulfilled if several bootstrap conditions on the Reggeon vertices and trajectory hold true. Now all these conditions are checked and proved to be satisfied.

hep-ph↗

arXiv2005

Calculation of isotope shifts and relativistic shifts in CI, CII, CIII and CIV

We present an accurate ab initio method of calculating isotope shifts and relativistic shifts in atomic spectra. We test the method on neutral carbon and three carbon ions. The relativistic shift of carbon lines may allow them to be included in analyses of quasar absorption spectra that seek to measure possible variations in the fine structure constant, alpha, over the lifetime of the Universe. Carbon isotope shifts can be used to measure isotope abundances in gas clouds: isotope abundances are potentially an important source of systematic error in the alpha-variation studies. These abundances are also needed to study nuclear reactions in stars and supernovae, and test models of chemical evolution of the Universe.

physics.atom-ph↗

arXiv2005

Improved calculation of relativistic shift and isotope shift in Mg I

We present an ab initio method of calculation of isotope shift and relativistic shift in atoms with a few valence electrons. It is based on an energy calculation involving combination of the configuration interaction method and many-body perturbation theory. This work is motivated by analyses of quasar absorption spectra that suggest that the fine structure constant, alpha, was smaller at an early epoch. Relativistic shifts are needed to measure this variation of alpha, while isotope shifts are needed to resolve systematic effects in this study. The isotope shifts can also be used to measure isotopic abundances in gas clouds in the early universe, which are needed to study nuclear reactions in stars and supernovae and test models of chemical evolution. This paper shows that isotope shift in magnesium can be calculated to very high precision using our new method.

physics.atom-ph↗

arXiv2005

Atomic CP-violating polarizability

Searches for CP violating effects in atoms and molecules provide important constrains on competing extensions to the standard model of elementary particles. In particular, CP violation in an atom leads to the CP-odd (T,P-odd) polarizability $β^\mathrm{CP}$: a magnetic moment $μ^\mathrm{CP}$ is induced by an electric field $\mathcal{E}_0$ applied to an atom, $μ^\mathrm{CP} = β^\mathrm{CP} \mathcal{E}_0 $. We estimate the CP-violating polarizability for rare-gas (diamagnetic) atoms He through Rn. We relate betaCP to the permanent electric dipole moment (EDM) of the electron and to the scalar constant of the CP-odd electron-nucleus interaction. The analysis is carried out using the third-order perturbation theory and the Dirac-Hartree-Fock formalism. We find that, as a function of nuclear charge Z, betaCP scales steeply as Z^5 R(Z), where slowly-varying R(Z) is a relativistic enhancement factor. Finally, we evaluate a feasibility of setting a limit on electron EDM by measuring CP-violating magnetization of liquid Xe. We find that such an experiment could provide competitive bounds on electron EDM only if the present level of experimental sensitivity to ultra-weak magnetic fields [Kominis et al., Nature 422, 596 (2003)] is improved by several orders of magnitude.

hep-ex↗

arXiv2004

Space-time variation of the fine structure constant and evolution of isotope abundances

At present several groups are analyzing astrophysical data in a search for time-variation of the fine structure constant $α$. Here we discuss how to exclude systematic effects caused by the changes in the isotope abundances during the evolution of the universe. We suggest using particular combinations of the transition frequencies of O II, Al II, Al III, Si II and Mn II as anchors, which are insensitive to $α$-variation and to changes in isotope abundances. These anchors can be used to determine the cosmological redshift. Then, one can use other combinations of frequencies as probes for the time-variation of $α$ and another set as probes for the isotopic abundances. In this way it is possible to eliminate one source of the systematic errors in the search for $α$-variation and get new information about evolution of the isotopes. On the level of accuracy that has already been reached in the search for $α$-variation it is possible to see ~10% changes in isotope abundances of Si and Ni.

astro-ph↗

arXiv2003

Configuration interaction calculation for the isotope shift in Mg I

We present an ab initio method of calculation of isotope shift in atoms with a few valence electrons, based on the configuration-interaction calculation of energy. The main motivation for developing the method comes from the need to analyze whether differences in isotope abundance in early universe can contribute to the observed anomalies in quasar absorption spectra. The current best explanation for these anomalies is the assumption that the fine structure constant, alpha, was smaller at early epoch. We show that we can calculate the isotope shift in magnesium with good accuracy.

physics.atom-ph↗

arXiv2003

Unusually large polarizabilities and "new" atomic states in Ba

Electric polarizabilities of four low-J even-parity states and three low-J odd-parity states of atomic barium in the range $35,600 $ to $36,000\ $cm$^{-1}$ are investigated. The states of interest are excited (in an atomic beam) via an intermediate odd-parity state with a sequence of two laser pulses. The odd-parity states can be excited due to the Stark-induced mixing with even-parity states. The polarizabilities are measured via direct spectroscopy on the second-stage transition. Several states have tensor and scalar polarizabilities that exceed the values that might be expected from the known energy levels of barium by more than two orders of magnitude. Two of the Stark-induced transitions cannot be identified from the known energy spectrum of barium. The observations suggest the existence of as yet unidentified odd-parity energy states, whose energies and angular momenta are determined in the present experiment. A tentative identification of these states as [Xe]$6s8p ^3P_{0,2}$ is suggested.

physics.atom-ph↗

arXiv2003

Radiative Corrections to QCD Amplitudes in Quasi-Multi-Regge Kinematics

Radiative corrections to QCD amplitudes in the quasi-multi-Regge kinematics are interesting in particular since the Reggeized form of these amplitudes is used in the derivation of the NLO BFKL. This form is a hypothesis which must be at least carefully checked, if not proved. We calculate the radiative corrections in the one-loop approximation using the s-channel unitarity. Compatibility of the Reggeized form of the amplitudes with the s-channel unitarity requires fulfillment of the set of nonlinear equations for the Reggeon vertices. We show that these equations are satisfied.

hep-ph↗