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N. V. Krasnikov

Publications and source records attributed to N. V. Krasnikov.

At least 91 records · Page 5Linked to original sources
arXiv2003

Extra dimensions and invisible decay of orthopositronium

We point out that some models with infinite additional dimension(s) of Randall-Sundrum type predict the disappearance of orthopositronium (o-Ps) into additional dimension(s). The experimental signature of this effect is the o-Ps -> invisible decay of orthopositronium which may occur at a rate within three orders of magnitude of the present experimental upper limit. This result enhances existing motivations for a more sensitive search for this decay mode and suggests additional directions for testing extra dimensions in non accelerator experiments.

hep-ph↗
arXiv2002

Invisible decay of orthopositronium vs extra dimensions

In models of Randall-Sundrum type orthopositronium (o-Ps) can disappear due to tunnelling into additional dimension(s). The experimental signature of this effect is the invisible decay of orthopositronium. We point out that this process may occur at a rate within two or three orders of magnitude of the present experimental upper limit. We discuss this in details and stress that the existence of invisible decay of orthopositronium in vacuum could explain the o-Ps decay rate puzzle. Thus, our result enhances the existing motivation and justifies efforts for a more sensitive search for o-Ps->invisible decay in a near future experiment. Possible manifestations of new physics in other rare (exotic) decays of orthopositronium are also discussed.

hep-ph↗
arXiv2002

Uncertainties and Discovery Potential in Planned Experiments

We describe a method for estimation of the discovery potential on new physics in planned experiments. The effective significance of signal for given probability of observation is proposed for planned experiments instead of the usual significances S_1 = n_s/sqrt{n_b} and S_2 = n_s/sqrt{n_s+n_b}, where n_s and n_b are the average numbers of signal and background events. Application of the test of equal-probability allows to estimate the exclusion limits on new physics. We also estimate the influence of systematic uncertainty related to nonexact knowledge of signal and background cross sections on the discovery probability of new physics in planned experiments. An account of such systematics is very essential in the search for supersymmetry at LHC.

hep-ph↗
arXiv2001

LHC(CMS) SUSY discovery potential for the case of nonuniversal gaugino masses

We investigate squark and gluino pair production at LHC(CMS) for the case of nonuniversal gaugino masses. Visibility of signal by an excess over SM background in $(n \geq 2)jets + E^{miss}_T + (m \geq leptons)$ events depends rather strongly on the relation between LSP, gluino and squark masses and it decreases with the increase of LSP mass. For relatively heavy LSP mass close to squark or gluino masses it is possible to detect SUSY for $(m_{\tilde{q}}, m_{\tilde{g}}) \leq (1 - 1.5)$ TeV.}

hep-ph↗
arXiv2001

Confidence Intervals for Poisson Distribution Parameter

Results of numerical procedure of constructing confidence intervals for parameter of the Poisson distribution of signal events in the presence of background events with known value of parameter of Poisson distribution are presented. It is shown that the used procedure has both the Bayesian and frequentist interpretations. Also the possibility to construct a continuous analogue of the Poisson distribution to search the bounds of confidence intervals for the parameter of the Poisson distribution is discussed.

hep-ex↗
arXiv2001

Probing lepton flavour violation in $ν_μ + N \to τ+ ...$ scattering and $μ\to tau$ conversion on nucleons

We study lepton flavour-violating interactions which could result in the $τ$-lepton production in the $ν_μN$ scattering or in $μ\to τ$ conversion on nucleons at high energies. Phenomenological bounds on the strength of $\barτν_μ\bar{q}q^{'}$ interactions are extracted from the combined result of the NOMAD and CHORUS experiments on searching for $ν_μ - ν_τ$ oscillations. Some of these bounds supersede limits from rare decays. We also propose a ``missing energy'' type experiment searching for $μ- τ$ conversion on nucleons. The experiment can be performed at a present accelerator or at a future neutrino factory.

hep-ph↗
arXiv2001

The muon anomalous magnetic moment and a new light gauge boson

It is shown that the 2.6 $σ$ discrepancy between the predicted and recently measured value of the anomalous magnetic moment of positive muons could be explained by the existence of a new light gauge boson X with a mass $M_X \leq O(5) GeV$. Phenomenological bounds on the X coupling are discussed.

hep-ph↗
arXiv2001

The LHC (CMS) Discovery Potential for Models with Effective Supersymmetry and Nonuniversal Gaugino Masses

We investigate squark and gluino pair production at LHC (CMS) with subsequent decays into quarks, leptons and LSP in models with effective supersymmetry where third generation of squarks is relatively light while the first two generations of squarks are heavy. We consider the general case of nonuniversal gaugino masses. Visibility of signal by an excess over SM background in (n \geq 2)jets + (m \geq 0)leptons + E^{miss}_T events depends rather strongly on the relation between LSP, second neutralino, gluino and squark masses and it decreases with the increase of LSP mass. We find that for relatively heavy gluino it is very difficult to detect SUSY signal even for light 3^{rd} generation squarks (m_{\tilde q_3}\le 1 TeV) if the LSP mass is closed to the 3^{rd} generation squark mass.

hep-ph↗
arXiv2000

Running coupling at small momenta, renormalization schemes and renormalons

We suggest a method of summing the perturbation theory (PT) asymptotic series related to infrared (IR) renormalons in QCD by using special renormalization schemes in which the running coupling can be integrated over the region of small momenta. For the method to work, one should consider higher order PT corrections to the standard bubble-chain diagrams. High-order corrections allow one to choose a scheme in which the coupling evolution can smoothly be extrapolated to small momenta. In such schemes the sum of an (extended) IR-renormalon asymptotic series is defined as an integral of the running coupling over the IR region. We give explicit examples of renormalization schemes in QCD which can be used for summing IR-renormalon asymptotic series according to our definition.

hep-ph↗
arXiv2000

On the Confidence Interval for the parameter of Poisson Distribution

The possibility of construction of continuous analogue of Poisson distribution with the search of bounds of confidence intervals for parameter of Poisson distribution is discussed. Also, in the article is shown that the true value of a parameter of Poisson distribution for the observed value $\hat x$ has Gamma distribution with the scale parameter, which is equal to one, and the shape parameter, which is equal to $\hat x$. The results of numerical construction of confidence intervals are presented.

physics.data-an↗
arXiv2000

Tau neutrino magnetic moments from the Super-Kamiokande and $ν$ e-scattering data

Combined results on $ν_μ\to ν_τ$ oscillations and $νe$-scattering from the Super-Kamiokande and LAMPF experiments, respectively, limit the Dirac $ν_τ$ diagonal magnetic moment to $μ_{ν_τ} < 1.9\times 10^{-9} μ_{B}$. For the scheme with 3 Majorana neutrinos the LAMPF results allow the limitation of effective $ν_τ$ magnetic moment to $μ_{ν_τ} < 7.6 \times 10^{-10}μ_{B}$. The moments in the scheme with additional Majorana light sterile neutrinos as well as experiments on stimulated radiative neutrino conversion are also discussed.

hep-ph↗
arXiv2000

The Reach of LHC (CMS) for Models with Effective Supersymmetry and Nonuniversal Gaugino Masses

We investigate squark and gluino pair production at LHC (CMS) with subsequent decays into quarks, leptons and LSP in models with effective supersymmetry where third generation of squarks is relatively light while the first two generations of squarks are heavy. We consider the general case of nonuniversal gaugino masses. Visibility of signal by an excess over SM background in $(n \geq 2)jets + (m \geq 0)leptons + E^{miss}_T$ events depends rather strongly on the relation between LSP, second neutralino, gluino and squark masses and it decreases with the increase of LSP mass.

hep-ph↗
arXiv1999

Observability and Probability of Discovery in Future Experiments

We propose a method to estimate the probability of new physics discovery in future high energy physics experiments. Physics simulation gives both the average numbers $ $ of background and $ $ of signal events. We find that the proper definition of the significance is $S_{12} = \sqrt{ + } - \sqrt{ }$ in comparison with often used significances $S_1 = \displaystyle \frac{ }{\sqrt{ }}$ and $S_2 = \displaystyle \frac{ }{\sqrt{ + }}$. We propose a method for taking into account systematic uncertainties related to nonexact knowledge of background and signal cross sections. An account of such systematics is very essential in the search for supersymmetry at LHC. We propose a method for estimation of exclusion limits on new physics in future experiments. We also estimate the probability of new physics discovery in future experiments taking into account systematical errors.

hep-ph↗