Robust two-dimensional subrecoil Raman cooling by adiabatic transfer in a tripod atomic system

We demonstrate two-dimensional robust Raman cooling in a four-level tripod system, in which velocity-selective population transfer is achieved by a STIRAP pulse. In contrast to basic 2D Raman cooling with square envelope pulses [Phys. Rev. A 83, 023407 (2011)], the technique presented here allows for a wide variation in the pulse duration and amplitude once the adiabaticity criterion is satisfied. An efficient population transfer together with attaining of a narrow spread of the resonant-velocity group leads to the narrowing of the velocity-distribution spread down to $0.1v_\mathrm{rec}$, corresponding to an effective temperature equal to $0.01 T_\mathrm{rec}$. This robust method opens new possibilities for cooling of neutral atoms.Comment: 8 pages, 3 figure

PEN: a low energy test of lepton universality

Allowed charged $\pi$ meson decays are characterized by simple dynamics, few available decay channels, mainly into leptons, and extremely well controlled radiative and loop corrections. In that sense, pion decays represent a veritable triumph of the standard model (SM) of elementary particles and interactions. This relative theoretical simplicity makes charged pion decays a sensitive means for testing the underlying symmetries and the universality of weak fermion couplings, as well as for studying pion structure and chiral dynamics. Even after considerable recent improvements, experimental precision is lagging far behind that of the theoretical description for pion decays. We review the current state of experimental study of the pion electronic decay $\pi^+ \to e^+\nu_e(\gamma)$, or $\pi_{e2(\gamma)}$, where the $(\gamma)$ indicates inclusion and explicit treatment of radiative decay events. We briefly review the limits on non-SM processes arising from the present level of experimental precision in $\pi_{e2(\gamma)}$ decays. Focusing on the PEN experiment at the Paul Scherrer Institute (PSI), Switzerland, we examine the prospects for further improvement in the near term.Comment: 11 pages, 5 figures; paper presented at the XIII International Conference on Heavy Quarks and Leptons, 22-27 May 2016, Blacksburg, Virginia, US

Precise Measurement of the Pi+ -> Pi0 e+ nu Branching Ratio

Using a large acceptance calorimeter and a stopped pion beam we have made a precise measurement of the rare Pi+ -> Pi0 e+ Nu,(pi_beta) decay branching ratio. We have evaluated the branching ratio by normalizing the number of observed pi_beta decays to the number of observed Pi+ -> e+ Nu, (pi_{e2}) decays. We find the value of Gamma(Pi+ -> Pi0 e+ Nu)/Gamma(total) = [1.036 +/- 0.004(stat.) +/- 0.004(syst.) +/- 0.003(pi_{e2})] x 10^{-8}$, where the first uncertainty is statistical, the second systematic, and the third is the pi_{e2} branching ratio uncertainty. Our result agrees well with the Standard Model prediction.Comment: 4 pages, 5 figures, 1 table, revtex4; changed content; updated analysi

PEN experiment: a precise measurement of the pi+ -> e+ nu decay branching fraction

A new measurement of $B_{\pi e2}$, the $\pi^+ \to e^+\nu(\gamma)$ decay branching ratio, is currently under way at the Paul Scherrer Institute. The present experimental result on $B_{\pi e2}$ constitutes the most accurate test of lepton universality available. The accuracy, however, still lags behind the theoretical precision by over an order of magnitude. Because of the large helicity suppression of the $\pi_{e2}$ decay, its branching ratio is susceptible to significant contributions from new physics, making this decay a particularly suitable subject of study.Comment: 4 pages, 3 figures, talk given at the Tenth Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2009), La Jolla/San Diego, CA, 26-31 May 2009; to appear in Proceedings to be published by the American Institute of Physic

Distribution of Tryptophan-Dependent <I>Yersinia pestis</I> Variants in the Altai Mountain Natural Plague Focus

Carried out is the analysis of spatial location of tryptophan-dependent variants of plague microbe in the territory of Altai mountain plague natural focus. 1166 Y. pestis strains isolated in 1990–2010, were studied as regards nutrient requirements. 140 of them (12 %) were determined as tryptophan-dependent. The highest occurence of such strains was registered in Ulandryk focal region (21.6 % in average). Among strains isolated in Tarkhatin focal region only 2.3 % were tryptophan-dependent, and in Kuray region they were absent. Thus, the data obtained suggest that spatial heterogeneity of Y. pestis subsp. altaica in the focus takes place

Measurements of the reaction pˉp→ϕη\bar{p}p \to \phi \eta of antiproton annihilation at rest at three hydrogen target densities

The proton-antiproton annihilation at rest into the $\phi\eta$ final state was measured for three different target densities: liquid hydrogen, gaseous hydrogen at NTP and at a low pressure of 5 mbar. The yield of this reaction in the liquid hydrogen target is smaller than in the low-pressure gas target. The branching ratios of the $\phi\eta$ channel were calculated on the basis of simultaneous analysis of the three data samples. The branching ratio for annihilation into $\phi\eta$ from the $^3S_1$ protonium state turns out to be about ten times smaller as compared to the one from the $^1P_1$ state.Comment: 10 pages, 3 Postscript figures. Accepted by Physics Letters

The First Case of <I>Yersinia pestis</I> subsp. <I>pestis</I> Isolation in the Territory of the Altai Mountain Natural Plague Focus. Communication 2. Probable Ways and Mechanisms of Plague Agent Main Subspesies Importation into the Territory of the Focus

Analysis of the epizootical situation in the North-West Mongolia and bordering regions of Russia has revealed the fact that plague agent of the main ssp., for the first time ever isolated in the Altai mountain natural plague focus in 2012, is imported from Serkh-Munkh-Khairkhan, which stands approximately 240 km away from it on the straight. It has been demonstrated that possibility of Yersinia pestis ssp. pestis transfer into the territory of Gorny Altai via slow natural migration of infected rodents, lagomorphs and their ectoparasites, as well as transmission by birds or terrestrial varmints in the mountainous environment over that large distance even within the period of several decades, is extremely negligible. The situation is conditioned by the presence of numerous physical-geographical barriers between the two regions involved and ecological peculiarities of the plague vectors and carriers. It is more likely that the agent of the main spp. has appeared in Gorny Altai due to the importation of infected fleas with isabelline wheatear ( Ocenanthe isabellina ) during a spring migration

New data on OZI rule violation in bar{p}p annihilation at rest

The results of a measurement of the ratio R = Y(phi pi+ pi-) / Y(omega pi+ pi-) for antiproton annihilation at rest in a gaseous and in a liquid hydrogen target are presented. It was found that the value of this ratio increases with the decreasing of the dipion mass, which demonstrates the difference in the phi and omega production mechanisms. An indication on the momentum transfer dependence of the apparent OZI rule violation for phi production from the 3S1 initial state was found.Comment: 11 pages, 3 PostScript figures, submitted to Physics Letter