arXiv subjects

S. N. Gninenko

Publications and source records attributed to S. N. Gninenko.

At least 73 records · Page 4Linked to original sources

arXiv2012

New limits on radiative sterile neutrino decays from a search for single photons in neutrino interactions

It has been recently shown that excess events observed by the LSND and MiniBooNE neutrino experiments could be interpreted as a signal from the radiative decay of a heavy sterile neutrino ν_h produced in ν_μneutral current-like interactions. If the ν_h exist, it would be also produced by the ν_μbeam from the CERN SPS in the neutrino beam line shielding. The ν_h's would penetrate the shielding and be observed through the decay ν_h -> νγ, followed by the photon conversion into e+e- pair in the active target of the NOMAD detector. The ν_h's could be also produced in the iron of the magnetic spectrometer of the CHORUS detector, located just in front of NOMAD. Considering these two sources of ν_h's we set new constraints on ν_h properties and exclude part of the LSND/MiniBooNE ν_h parameter space using bounds on single photons production in neutrino reactions recently reported by the NOMAD collaboration. We find that broad bands in the parameter space are still open for more sensitive searches for the ν_h in future neutrino experiments.

hep-ph↗

arXiv2012

Sterile neutrino decay as a common origin for LSND/MiniBooNe and T2K excess events

We point out that the excess of electron-like neutrino events recently observed by the T2K collaboration may have a common origin with the similar excess events previously reported by the LSND and MiniBooNE experiments and interpreted as a signal from the radiative decays of a sterile neutrino ν_h with the mass around 50 MeV produced in muon neutrino neutral current (NC) interactions. In this work we assumed that the ν_h can also be produced in tau neutrino NC reactions.

hep-ph↗

arXiv2011

Two photon decay of Z' as a probe of Bose symmetry violation at the CERN LHC

The question if the Bose statistics is broken at the TeV scale is discussed. The decay of a new heavy spin 1 gauge boson Z' into two photons, Z'-> 2 gamma, is forbidden by the Bose statistics among other general principles of quantum field theory (Landau-Yang theorem). We point out that the search for this decay can be effectively used to probe the Bose symmetry violation at the CERN LHC.

hep-ph↗

arXiv2011

The LSND/MiniBooNe excess events and heavy neutrino from muon and kaon decays

It has been recently shown that puzzling excess events observed by the LSND and MiniBooNE neutrino experiments could be interpreted as a signal from the radiative decay of a heavy sterile neutrino ($ν_h$) of the mass from 40 to 80 MeV, with a muonic mixing strength $\mix \simeq 10^{-3} - 10^{-2}$, and the lifetime $10^{-11} < τ_h < 10^{-9}$ s. We discuss bounds on $\mix$ obtained from the recent precision measurements with muons and show that they are consistent with the above limits. If the $ν_h$ exists its admixture in the ordinary muon or kaon decay would result in the decay chain $\muhd$ or $\khd$, respectively. We propose a new experiment for a sensitive search for these processes in $μ$ and $K$ decays at rest allowing to either definitively confirm or exclude the existence of the $ν_h$. To our knowledge, no experiment has specifically searched for the signature of radiative decay of massive neutrinos from particles decays as proposed in this work. The search is complementary to the current experimental efforts to clarify the origin of the LSND and MiniBooNE anomalies.

hep-ex↗

arXiv2010

Comments on arXiv:1011.3046 "Muon Capture Constraints on Sterile Neutrino Properties"

It has been very recently reported (McKeen, Pospelov, arXive:1011.3046) that the parameter region suggested for an explanation of the neutrino oscillation results from the LSND, KARMEN and MiniBooNE experiments in terms of the production and radiative decay of a heavy neutrino ($ν_h$) can be ruled out based on the measurements of the radiative muon capture (RMC) on hydrogen. We calculate limits on mixing strength between the $ν_h$ and $ν_μ$ by using results of this experiment, and find out that they essentially disagree with the reported bounds. For the $ν_h$ with mass 60 MeV our limit is worse by a factor of 5, while for 90 MeV it is worse by about two orders of magnitude. We also noticed the wrong behavior of the reported limit curve in the low mass region. The importance of accurate Monte Carlo simulations of the $ν_h$ signal in the RMC experiment is stressed. Our conclusion is that the whole LSND-MiniBooNE parameter region cannot be ruled out by the RMC measurements.

hep-ph↗

arXiv2009

The MiniBooNE anomaly and heavy neutrino decay

The anomaly in the low energy distribution of quasi-elastic neutrino events reported by the MiniBooNE collaboration is discussed. We show that the observed excess of electron-like events could originate from the production and decay of a heavy neutrino ($ν_h$) in the MiniBooNE detector. The $ν_h$ is created by mixing in $ν_μ$ neutral-current interactions and decays radiatively into $ νγ$ due to a transition magnetic moment between the $ν_h$ and a light neutrino $ν$. The energy measured in the detector arises from the subsequent conversion of the decay photon into a $\pair$ pair within the detector volume. The analysis of the energy and angular distributions of the excess events suggests that the $ν_h$ has a mass around 500 MeV and the lifetime $τ_{ν_h} \lesssim 10^{-9}$ s. Existing experimental data are found to be consistent with a mixing strength between the $ν_h$ and the $ν_μ$ of $|U_{μh}|^2 \simeq (1-4)\times 10^{-3}$ and a $ν_h$ transition magnetic moment of $ μ_{tr} \simeq (1- 6)\times 10^{-9} μ_B$. Finally, we discuss the reason why no significant excess of low energy events has been observed in the recent antineutrino data.

hep-ph↗

arXiv2009

The MiniBooNE anomaly, the decay Ds -> mu+nu and heavy sterile neutrino

It has been recently suggested that the anomalous excess of low-energy electron-like events observed by the MiniBooNE experiment, could be explained by the radiative decay of a heavy sterile neutrino nu_h of the mass around 500 MeV with a muonic mixing strength in the range |U_{μh}|^2 \simeq (1-4)\times 10^{-3}. If such nu_h exists its admixtures in the decay Ds -> mu+nu would result in the decay Ds -> mu+nu_h with the branching fraction \simeq (1.2-5.5)\times 10^{-4}, which is in the experimentally accessible range. Interestingly, the existence of the Ds -> mu+nu_h decay at this level may also explain why the currently measured decay rate of Ds -> mu+nu is slightly higher than the predicted one. This enhances motivation for a sensitive search for this decay mode and makes it interesting and complementary to neutrino experiments probing sterile-active neutrino mixing. Considering, as an example the CLEO-c experiment, we suggest to perform a search for the decay Ds -> mu+nu_h with the analysis of existing data. The discrepancy between the measurements and theoretical description of the decay Ds -> tau+nu is also discussed in brief.

hep-ph↗

arXiv2008

Invisible $Z\prime$ as a probe of extra dimensions at the CERN LHC

A class of extra dimensional models with a warped metric predict tunneling of a massive particle localized on our brane and escaping into additional dimensions. The experimental signature of this effect is the disappearance of the particle from our world, i.e. the particle $\to invisible$ decay. We point out that measurements of $Z\prime \to invisible$ decay width of a new heavy gauge boson $Z\prime$ at the CERN LHC can be effectively used to probe the existence of large extra dimensions. This result enhances motivations for a more sensitive search and study for this decay mode and suggests additional direction for testing extra dimensions in collider experiments.

hep-ph↗

arXiv2008

Formation Of A Cold Antihydrogen Beam in AEGIS For Gravity Measurements

The formation of the antihydrogen beam in the AEGIS experiment through the use of inhomogeneous electric fields is discussed and simulation results including the geometry of the apparatus and realistic hypothesis about the antihydrogen initial conditions are shown. The resulting velocity distribution matches the requirements of the gravity experiment. In particular it is shown that the inhomogeneous electric fields provide radial cooling of the beam during the acceleration.

physics.atom-ph↗

arXiv2008

On search for hidden sector photons in Super-Kamiokande

If hidden sector photons exist, they could be produced through oscillations of photons emitted by the Sun. We show that a search for these particles could be performed in Super-Kamiokande due to the presence in this detector of a large number of photomultiplier's (PMTs) with a relatively low noise and big size. These particles would penetrate the Earth shielding and would be detected by PMTs through their oscillations into real photons inside the PMTs vacuum volume. This would results in an increase of the PMT counting rate and it daily variations depending on the Earth position with respect to the Sun. The proposed search for this effect is sensitive to the photon-hidden photon mixing strength as small as ~10^{-6} for the hidden photon mass region ~10^{-3} - 10^{-1} eV and, in the case of nonobservation, could improve limits recently obtained from photon regeneration laser experiments for this mass region.

hep-ph↗

arXiv2007

Limit on the electric charge-nonconserving $μ^+ \to invisible$ decay

The first limit on the branching ratio of the electric charge-nonconserving invisible muon decay $Br(μ^+ \to invisible) < 5.2 \times 10^{-3}$ is obtained from the recently reported results on new determination of the Fermi constant from muon decays. The results of a feasibility study of a new proposed experiment for a sensitive search for this decay mode at the level of a few parts in 10^{11} are presented. Constrains on the $τ\to invisible$ decay rate are discussed. These leptonic charge-nonconserving processes may hold in four-dimensional world in models with infinite extra dimensions, thus making their searches complementary to collider experiments probing new physics.

hep-ph↗

arXiv2007

Searching for energetic cosmic axions in a laboratory experiment: testing the PVLAS anomaly

Astrophysical sources of energetic gamma rays provide the right conditions for maximal mixing between (pseudo)scalar (axion-like) particles and photons if their coupling is as strong as suggested by the PVLAS claim. This is independent of whether or not the axion interaction is standard at all energies or becomes supressed in the extreme conditions of the stellar interior. The flux of such particles through the Earth could be observed using a metre long, Tesla strength superconducting solenoid thus testing the axion interpretation of the PVLAS anomaly. The rate of events in CAST caused by axions from the Crab pulsar is also estimated for the PVLAS-favoured parameters.

hep-ph↗

arXiv2007

Search for millicharged particles in reactor neutrino experiments: a probe of the PVLAS anomaly

It has been recently suggested that the vacuum magnetic dichroism observed by the PVLAS experiment could be explained by the pair production of a new light, m ~0.1 eV, millicharged, q ~ 3 10^{-6} e, fermions. In addition, it has been pointed out that millicharged particles with q > 10^{-9} e appear naturally in models based on the string theory. We show that low energy reactor neutrino experiments provide a sensitive probe of millicharged particles. Considering, as an example, recent results of the TEXONO experiment searching for neutrino magnetic moment, a new upper bound q < 10^{-5} e for the mass region m < 1 keV is derived. These results enhance motivations for a more sensitive search for such particles in near future experiments. Furthemore, a direct experimental limit on the electric charge of the electron antineutrino q < 3.7 10^{-12} e is obtained.

hep-ph↗

arXiv2005

Development of a high-efficiency pulsed slow positron beam for measurements with orthopositronium in vacuum

We have developed a high-efficiency pulsed slow positron beam for experiments with orthopositronium in vacuum. The new pulsing scheme is based on a double-gap coaxial buncher powered by an RF pulse of appropriate shape. The modulation of the positron velocity in the two gaps is used to adjust their time-of-flight to a target. This pulsing scheme allows to minimize non-linear aberrations in the bunching process and to efficiently compress positron pulses with an initial pulse duration ranging from 300 to 50 ns into bunches of 2.3 to 0.4 ns width, respectively, with a repetition period of 1 mks. The compression ratio achieved is ~100, which is a factor 5 better than has been previously obtained with slow positron beams based on a single buncher. Requirements on the degree, to which the moderated positrons should be mono-energetic and on the precision of the waveform generation are presented. Possible applications of the new pulsed positron beam for measurements of thin films are discussed.

physics.acc-ph↗

arXiv2004

A new experiment to search for the invisible decay of the orthopositronium

We propose an experiment to search for invisible decays of orthopositronium (o-Ps) with a 90% confidence sensitivity in the branching ratio as low as $10^{-8}$. Evidence for this decay mode would unambigously signal new physics: either the existence of extra--dimensions or fractionally charged particles or new light gauge bosons. The experimental approach and the detector components of the proposed experiment are described.

hep-ex↗

arXiv2003

An apparatus to search for mirror dark matter via the invisible decay of orthopositronium in vacuum

Mirror matter is a possible dark matter candidate. It is predicted to exist if parity is an unbroken symmetry of the vacuum. The existence of the mirror matter, which in addition to gravity is coupled to our world through photon-mirror photon mixing, would result in orthopositronium (o-Ps) to mirror orthopositronium (o-Ps') oscillations. The experimental signature of this effect is the invisible decay of o-Ps in vacuum. This paper describes the design of the new experiment for a search for the o-Ps -> invisible decay in vacuum with a sensitivity in the branching ratio of Br(o-Ps -> invisible)\simeq 10^{-7}, which is an order of magnitude better than the present limit on this decay mode from the Big Bang Nucleosynthesis. The experiment is based on a high-efficiency pulsed slow positron beam, which is also applicable for other experiments with o-Ps, and (with some modifications) for applied studies. Details of the experimental design and of a new pulsing method, as well as preliminary results on requirements for the pulsed beam components are presented. The effects of o-Ps collisions with the cavity walls as well as the influence of external fields on the o-Ps to o-Ps' oscillation probability are also discussed.

hep-ex↗

arXiv2003

Prospects of detecting massive isosinglet neutrino at LHC in the CMS detector

A possibility to search for a heavy isosinglet (sterile) neutrino using its decay mode $ν_s \to l^{\pm} + 2 jets$ in the $S$ - channel production $pp \to W^* + X \to l^{\pm}ν_s + X$ in the CMS experiment is studied. The only assumption about the heavy neutrino is its nonzero mixing with $ν_e$ or $ν_μ$. The corresponding CMS discovery potential expressed in terms of the heavy neutrino mass and the mixing parameter between the heavy and light neutrino is determined. It is shown that the heavy neutrino with a mass up to 800 $GeV$ could be detected in CMS. We also investigate the production of the heavy neutrino $N_l$ mixed with $ν_e$ and/or $ν_μ$ in the $SU_C(3) \otimes SU_L(2) \otimes SU_R(2)\otimes U(1)$ model through the reaction $pp \to W_R + X \to l^{\pm}N_l + X$ with the same heavy neutrino decay channel as above. We find that for $M_{W_R} < 3 TeV$ it is possible to discover the heavy neutrino with a mass up to $0.75 \cdot M_{W_R}$.

hep-ph↗

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↗