First observation of the decay Bˉs0→D0K∗0\bar{B}^0_s \to D^0 K^{*0} and a measurement of the ratio of branching fractions B(Bˉs0→D0K∗0)B(Bˉ0→D0ρ0)\frac{{\cal B}(\bar{B}^0_s \to D^0 K^{*0})}{{\cal B}(\bar{B}^0 \to D^0 \rho^0)}

The first observation of the decay $\bar{B}^0_s \to D^0 K^{*0}$ using $pp$ data collected by the LHCb detector at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 36 pb$^{-1}$, is reported. A signal of $34.4 \pm 6.8$ events is obtained and the absence of signal is rejected with a statistical significance of more than nine standard deviations. The $\bar{B}^0_s \to D^0 K^{*0}$ branching fraction is measured relative to that of $\bar{B}^0 \to D^0 \rho^0$: $\frac{{\cal B}(\bar{B}^0_s \to D^0 K^{*0})}{{\cal B}(\bar{B}^0 \to D^0 \rho^0)} = 1.48 \pm 0.34 \pm 0.15 \pm 0.12$, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the ratio of the $B^0$ and $B^0_s$ hadronisation fractions.Comment: 10 pages, 3 figures, submitted to Phys. Lett. B; ISSN 0370-269

Prompt K_short production in pp collisions at sqrt(s)=0.9 TeV

The production of K_short mesons in pp collisions at a centre-of-mass energy of 0.9 TeV is studied with the LHCb detector at the Large Hadron Collider. The luminosity of the analysed sample is determined using a novel technique, involving measurements of the beam currents, sizes and positions, and is found to be 6.8 +/- 1.0 microbarn^-1. The differential prompt K_short production cross-section is measured as a function of the K_short transverse momentum and rapidity in the region 0 < pT < 1.6 GeV/c and 2.5 < y < 4.0. The data are found to be in reasonable agreement with previous measurements and generator expectations.Comment: 6+18 pages, 6 figures, updated author lis

Modernization of the x-band epr spectrometer bruker elexsys e580 for dynamic nuclear polarization

To study the effects of dynamic nuclear polarization (DNP) in the X-band (microwave frequency of 9 GHz), using the capabilities provided by commercial EPR equipment, a part of the EPR spectrometer associated with the excitation and detection of double electron-nuclear resonance signals (ENDOR) has been modernized. Using the developed preamplifier of NMR signals, a homemade “Kazan Nova II”NMR spectrometer was implemented into the radio frequency path of the EPR spectrometer. The tuning and matching circuits made it possible to observe the NMR and DNP signals on protons in the frequency range 14.5–15.2 MHz. The performance of the DNP equipment was tested for a solution of the stable nitroxyl radical TEMPOL in benzene and a crude oil sample. The DNP effects caused by the Overhauser and solid effects were observed. The modernization of the existing EPR equipment creates a basis for further expanding its capabilities to study DNP effects in various systems at different conditions (in the pulsed mode of saturation of the EPR lines, with the temperature lowering, under the action of optical excitation, etc)

Multipurpose portable q-band bridge

The paper describes the design, implementation, and technical characteristics of a portable Q-band microwave (mw) bridge based on the Gunn diode with the potential use for electron paramagnetic resonance (EPR) and dynamic nuclear polarization (DNP) spectroscopies. The mw frequency can be electronically adjusted in the range of 36–38 GHz with the maximal mw output of 120 mW and electronic attenuation of 0–60 dB. The value of the mw frequency can be stabilized and changed via automatic frequency control for direct and alternating current. A self-written Matlab-based program allows tuning and operating the bridge through the RS-485 interface. Examples of the EPR spectra implemented into the magnetic system of the Bruker ESP300 commercial spectrometer are shown

Experimental evidences of the shape-induced structural distortion of SrTiO3 single crystals from impurity Mn4+ ions electron paramagnetic resonance

A study of high-quality SrTiO3 single crystals doped with the Mn4+ ions in the cubic phase (T > 105 K) with X-band electron paramagnetic resonance reveals direct correspondence between a shape of a sample and magnetic anisotropy of the impurity Mn4+ centers. In particular, for a sample with the shape of a square base rectangular prism, a size of (a × a × h) and faces perpendicular to the crystallographic directions, zero-field splitting parameter D is approximately proportional to (a / h − 1) quantity. Temperature dependence of D indicates that this peculiar symmetry lowering is a feature characteristic for the cubic Fm3m phase of the strontium titanate. Diminishing of the D value with the decrease of the surface roughness for a thin (001)-oriented SrTiO3:Mn platelet shows that the observed effect originates from the sample surface

Symmetry breaking in single-crystal SrTiO<inf>3</inf>plates: EPR manifestations

Results of the electron paramagnetic resonance (EPR) studies of Fe3+ and Mn4+ impurity centers in high-quality single-crystal SrTiO3 plates with thickness h < 1 mm are presented. Impurities served the paramagnetic probes of the crystal structure. Analysis of the collected data indicates that the symmetry of the crystal structure of thin (001) and (110) oriented strontium titanate plates above 105 K lowers in the bulk from the cubic to tetragonal. The structure of this high-temperature tetragonal state is different from that of the conventional low-temperature antiferrodistorsive phase and has not been reported for SrTiO3 before. It is shown that the effect does not originate from the residual stress; its magnitude and particular manifestations depend on plate orientation, surface quality and geometry of a sample. Peculiarities of the observed phenomenon are presented and the possible scenario of its realization is discussed

First observation of Bs → J/ψf0(980) decays

Using data collected with the LHCb detector in proton–proton collisions at a centre-of-mass energy of 7 TeV, the hadronic decay is observed. This CP eigenstate mode could be used to measure mixing-induced CP violation in the system. Using a fit to the π+π− mass spectrum with interfering resonances gives . In the interval ±90 MeV around 980 MeV, corresponding to approximately two full f0 widths we also find , where in both cases the uncertainties are statistical and systematic, respectively