The year 2016 marks the 60th anniversary of the Joint Institute for Nuclear Research (JINR) in Dubna, an international intergovernmental organization for basic research in the fields of elementary particles, atomic nuclei, and condensed matter. Highly productive advances over this long road clearly show that the international basis and diversity of research guarantees successful development (and maintenance) of fundamental science. This is especially important for experimental research. In this review, the most significant achievements are briefly described with an attempt to look into the future (seven to ten years ahead) and show the role of JINR in solution of highly important problems in elementary particle physics, which is a fundamental field of modern natural sciences. This glimpse of the future is full of justified optimism.

The Joint Institute for Nuclear Research in Experimental Physics of Elementary Particles

Search for the flavour-changing neutral-current decay D0 → μ+μ−

In contrast with $B^0-\bar B^0$, $B_s-\bar B_s$ mixing where the standard model (SM) contributions overwhelm that of new physics beyond standard model (BSM), a measured relatively large $D^0-\bar D^0$ mixing where the SM contribution is negligible, definitely implies the existence of new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the rare decay $D^0\to \mu^+\mu^-$ could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of new physics BSM in the leptonic decays of $D^0$, concretely we discuss the contributions of unparticle or an extra gauge boson $Z'$ while imposing the constraints set by fitting the $D^0-\bar D^0$ mixing data. We find that the long-distance SM effects for $D^0\to l\bar l$ still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as $D^0\to \mu^{\pm}e^{\mp}$, the new physics contribution would be significant.

Searching for New Physics in $D^0\rightarrow \mu^+\mu^-,\; e^+e^-, \;\mu^{\pm}e^{\mp}$ at BES and/or Super Charm-Tau Factory

The report on a search for beauty particles produced in π − -nucleon interactions at s ≃ 26 GeV at the CERN Ω′ spectrometer. Data were collected using the WA92 apparatus, which included a high-resolution imaging detector and a system for triggering on secondary vertices. The search for beauty decays using conventional analysis procedures is described and a new event-selection method, based on neural-network techniques, is presented. Results obtained with the new and the conventional methods are compared.

Results from the WA92 experiment

In contrast with B0-B?0, Bs-B?s mixing where the standard model (SM) contributions overwhelm that of the new physics beyond standard model (BSM), a measured relatively large D0-D?0 mixing where the SM contribution is negligible, definitely implies the existence of the new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the decay mode D0??+?? could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of the new physics BSM in the leptonic decays of D0. Concretely we discuss the contributions of unparticle or an extra gauge boson Z' while imposing the constraints set by fitting the D0-D?0 mixing data. We find that the long-distance SM effects for D0 ?ll? still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as D0???e, the new physics contribution would be significant.

M. Verzocchi

Papers

Search for the decay D0 → μ+μ−