arXiv subjects

F. Bezrukov

Publications and source records attributed to F. Bezrukov.

27 records · Page 2Linked to original sources

arXiv2003

Dynamical tunneling of bound systems through a potential barrier: complex way to the top

A semiclassical method of complex trajectories for the calculation of the tunneling exponent in systems with many degrees of freedom is further developed. It is supplemented with an easily implementable technique, which enables one to single out the physically relevant trajectory from the whole set of complex classical trajectories. The method is applied to semiclassical transitions of a bound system through a potential barrier. We find that the properties of physically relevant complex trajectories are qualitatively different in the cases of potential tunneling at low energy and dynamical tunneling at energies exceeding the barrier height. Namely, in the case of high energies, the physically relevant complex trajectories describe tunneling via creation of a state close to the top of the barrier. The method is checked against exact solutions of the Schrodinger equation in a quantum mechanical system of two degrees of freedom.

quant-ph↗

arXiv2003

Semiclassical Study of Baryon and Lepton Number Violation in High-Energy Electroweak Collisions

We make use of a semiclassical method for calculating the suppression exponent for topology changing transitions in high-energy electroweak collisions. In the Standard Model these processes are accompanied by violation of baryon and lepton number. By using a suitable computational technique we obtain results for s-wave scattering in a large region of initial data. Our results show that baryon and lepton number violation remains exponentially suppressed up to very high energies of at least 30 sphaleron masses (250 TeV). We also conclude that the known analytic approaches inferred from low energy expansion provide reasonably good approximations up to the sphaleron energy (8 TeV) only.

hep-ph↗

arXiv2003

Suppression of baryon number violation in electroweak collisions: Numerical results

We present a semiclassical study of the suppression of topology changing, baryon number violating transitions induced by particle collisions in the electroweak theory. We find that below the sphaleron energy the suppression exponent is remarkably close to the analytic estimates based on a low energy expansion about the instanton. Above the sphaleron energy, the relevant semiclassical solutions have qualitatively different properties from those below the sphaleron: they correspond to jumps on top of the barrier. Yet these processes remain exponentially suppressed, and, furthermore, the tunneling exponent flattens out in energy. We also derive lower bounds on the tunneling exponent which show that baryon number violation remains exponentially suppressed up to very high energies of at least 30 sphaleron masses (250 TeV).

hep-ph↗

arXiv2003

Theta--instantons in SU(2) Higgs theory

We consider topology changing processes in SU(2)--Higgs theory. In the Standard Model of particle physics they are accompanied by baryon--and lepton--number non--conservation. At fixed energy and multiplicity of initial state, these processes are described by classical Theta--instanton solutions. We describe these solutions and calculate the suppression exponents for the probabilities of the topology changing transitions at relatively low energies.

hep-th↗

arXiv2003

Transmission through a potential barrier in quantum mechanics of multiple degrees of freedom: complex way to the top

A semiclassical method for the calculation of tunneling exponent in systems with many degrees of freedom is developed. We find that corresponding classical solution as function of energy form several branches joint by bifurcation points. A regularization technique is proposed, which enables one to choose physically relevant branches of solutions everywhere in the classically forbidden region and also in the allowed region. At relatively high energy the physical branch describes tunneling via creation of a classical state, close to the top of the barrier. The method is checked against exact solutions of the Schrodinger equation in a quantum mechanical system of two degrees of freedom.

quant-ph↗

arXiv2002

T-Odd Correlations in pi->e nu_e gamma and pi->mu nu_mu gamma Decays

The transverse lepton polarization asymmetry in pi_l2gamma decays may probe T-violating interactions beyond the Standard Model. Dalitz plot distributions of the expected effects are presented and compared to the contribution from the Standard Model final state interactions. We give an example of a phenomenologically viable model, where a considerable contribution to the transverse lepton polarization asymmetry arises.

hep-ph↗

arXiv2002

T-odd Correlations in pi->e nu_e gamma Decay

The transverse lepton polarization asymmetry in pi_e2gamma decay may probe T-violating interactions beyond the Standard Model. Dalitz plot distributions of the expected effects are presented and compared to the contribution from the Standard Model final state interactions. We give an example of a phenomenologically viable model, where a considerable contribution to the transverse lepton polarization asymmetry arises.

hep-ph↗

arXiv2001

Instanton-Like Processes in Particle Collisions: a Numerical Study of the SU(2)-Higgs Theory below the Sphaleron Energy

We use semiclassical methods to calculate the probability of inducing a change of topology via a high-energy collision in the SU(2)-Higgs theory. This probability is determined by a complex solution to a classical boundary value problem on a contour in the complex time plane. In the case of small particle number it is the probability of instanton-like processes in particle collisions. We obtain numerically configurations with the correct topological features and expected properties in the complex time plane. Our work demonstrates the feasibility of the numerical approach to the calculation of instanton-like processes in gauge theories. We present our preliminary results for the suppression factor of topology changing processes, which cover a wide range of incoming particle numbers and energies below the sphaleron energy.

hep-ph↗

arXiv1999

Use of singular classical solutions for calculation of multiparticle cross sections in field theory

A method of reducing the problem of the calculation of tree multiparticle cross sections in $ϕ^4$ theory to the solution of a singular classical Euclidean boundary value problem is introduced. The solutions are obtained numerically in terms of the decomposition in spherical harmonics, and the corresponding estimates of the tree cross sections at arbitrary energies are found. Numerical analysis agrees with analytical results obtained earlier in the limiting cases of large and small energies.

hep-ph↗