Prospects of a baryon instability search in neutron-antineutron oscillations

The purpose of this article is to review the current status and the future prospects for an experimental neutron-antineutron transition search. Traditional and new experimental techniques are discussed here. In the n {r_arrow} {anti n} search in experiments at existing reactors, it would be possible to increase the discovery potential up to four orders of magnitude for vacuum n {r_arrow} {anti n} transitions relative to the existing experimental level or to achieve the limit of {tau}{sub n-{anti n}{sup {approximately}}} 10{sup 10}s.. With dedicated future reactors and an ultimate experimental layout, it might be possible to reach the limit of 10{sup 11}s. Significant progress in an intranuclear n {r_arrow} {anti n} transition search expected to be made during the next decade by the SuperKamiokande and Icarus detectors. It can be matched, or even exceeded, in a new alternative approach, where unstable long-lived isotopes of technetium are searched in non radioactive deep-mined ores

Prospects for baryon instability search with long-lived isotopes

In this paper we consider the possibility of observation of baryon instability processes occurring inside nuclei by searching for the remnants of such processes that could have been accumulated in nature as mm long-lived isotopes. As an example, we discuss here the possible detection of traces of {sup 97}Tc, {sup 98}Tc, and {sup 99}Tc in deep-mined nonradioactive tin ores

Limits on \boldmath n {\bar n} oscillations from nuclear stability

The relationship between the lower limit on the nuclear stability lifetime as derived from the non disappearance of `stable` nuclei ($T_{d}~\gtrsim~5.4~\times~10^{31}$ yr), and the lower limit thus implied on the oscillation time $(\tau_{n \bar n})$ of a possibly underlying neutron-antineutron oscillation process, is clarified by studying the time evolution of the nuclear decay within a simple model which respects unitarity. The order-of-magnitude result $\tau_{n \bar n} \approx 2 (T_{d}/\Gamma_{\bar n})^{1/2} > 2 \times 10^{8}$ sec, where $\Gamma_{\bar n}$ is a typical $\bar n$ nuclear annihilation width, agrees as expected with the limit on $\tau_{n \bar n}$ established by several detailed nuclear physics calculations, but sharply disagreeing by 15 orders of magnitude with a claim published recently in Phys. Rev. CRAP.Comment: 8 pages; this PRC version (accepted for publication, November 4 1999) differs from the original version only by a few minor editorial change

Trap with ultracold neutrons as a detector of dark matter particles with long-range forces

The possibility of using a trap with ultracold neutrons as a detector of dark matter particles with long-range forces is considered. The basic advantage of the proposed method lies in possibility of detecting the recoil energy 10-7 eV. The restrictions on parameters of Yukawa type interaction potential between dark matter particles and a neutron are presented for different dark matter densities on the Earth. The assumption concerned with long-range interaction of dark matter particles and ordinary matter leads to a substantial enhancement of cross section at low energy. Consequently, there arises a possibility of capture and accumulation of dark matter in a gravitational field of the Earth. Rough estimation of accumulation of low-energy dark matter on the Earth is discussed. The first experimental restrictions for existence of dark matter with long-range forces on the Earth are presented.Comment: 17 pages, 6 figure

Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF

The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described

Determination of the number of light neutrino species from single photon production at LEP

A determination of the number of light neutrino families performed by measuring the cross section of single photon production in \ee\ collision near the \Zo\ resonance is reported. From an integrated luminosity of $100~\mathrm{pb^{-1}}$, collected during the years 1991--94, we have observed 2091 single photon candidates with an energy above 1~\GeV\ in the polar angular region $45^\circ < \theta_\gamma < 135^\circ$. From a maximum likelihood fit to the single photon cross section, the \Zo\ decay width into invisible particles is measured to be \Ginv = 498 \pm 12 \mathrm{(stat)} \pm 12 \mathrm{(sys)~MeV}. Using the Standard Model couplings of neutrinos to the \Zo, the number of light neutrino species is determined to be $N_\nu = 2.98 \pm 0.07 (\mathrm{stat}) \pm 0.07 (\mathrm{sys}).

Search for R-Parity Breaking Sneutrino Exchange at LEP

We report on a search for R--parity breaking effects due to supersymmetric tau--sneutrino exchange in the reactions e+e- to e+e- and e+e- to mu+mu- at centre--of--mass energies from 91~{\GeV} to 172~{\GeV}, using the L3 detector at LEP. No evidence for deviations from the Standard Model expectations of the measured cross sections and forward--backward asymmetries for these reactions is found. Upper limits for the couplings $\lambda_{131}$ and $\lambda_{232}$ for sneutrino masses up to m_{\SNT} \leq 190~\GeV are determined from an analysis of the expected effects due to tau sneutrino exchange

Local multiplicity fluctuations in hadronic Z decay

Local multiplicity fluctuations in hadronic Z decays are studied using the L3 detector at LEP. Bunching parameters are used for the first time in addition to the normalised factorial moment method. The bunching parameters directly demonstrate that the fluctuations in rapidity are multifractal. Monte Carlo models show overall agreement with the data, reproducing the trend, although not always the magnitude, of the factorial moments and bunching parameters

Angular multiplicity fluctuations in hadronic Z decays and comparison to QCD models and analytical calculations

Local multiplicity fluctuations in angular phase space intervals are studied using factorial moments measured in hadronic events at \sqrt{s}\simeq 91.2\GeV, which were collected by the L3 detector at LEP in 1994. Parton shower Monte Carlo programs agree well with the data. On the other hand, first-order QCD calculations in the Double Leading Log Approximation and the Modified Leading Log Approximation are found to deviate significantly from the data