Study of π<Superscript>0</Superscript>/γ efficiency using B meson decays in the LHCb experiment

The reconstruction efficiency of photons and neutral pions is measured using the relative yields of reconstructed B ⁺ → J/ψK ^*+(→ K ⁺π⁰) and B ⁺ → J/ψK ⁺ decays. The efficiency is studied using the data set, corresponding to an integrated luminosity of 3 fb^–1, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV.     

Study of π<Superscript>0</Superscript>/γ reconstruction and selection efficiency in the LHCb experiment

The reconstruction efficiency of photons and neutral pions is measured using the relative yields of reconstructed B ⁺ → J/ψK*⁺(→K ⁺π⁰) and B ⁺ → J/ψK ⁺ decays. The efficiency is studied using the data set, corresponding to an integrated luminosity of 3 fb^–1, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV.     

New measurements on physics of <Emphasis Type="Italic">B</Emphasis>-hadrons in ATLAS experiment

Recent results on B-hadron physics in ATLAS are reviewed. A new measurement of CP-violating parameters in B _s → J/ψφ decay is performed on full Run 1 statistics. Branching fraction BR(B _s → μ⁺μ^?) = (0.9 _?0.8 ^+1.1 )×10^?9 is measured, below the Standard Model (SM) prediction.     

37 Years with the light scalar mesons. The learned lessons

Attention is paid to the production mechanisms of light scalars that reveal their nature. We reveal the chiral shielding of the σ(600) meson. We show that the kaon loop mechanism of the ? radiative decays, ratified by experiment, is four-quark transition and points to the four-quark nature of light scalars. We show also that the light scalars are produced in the two photon collisions via four-quark transitions in contrast to the classic P wave tensor qq? mesons that are produced via two-quark transitions γγ → qq?. We study the mechanism of production of the light scalar mesons in the D _s ⁺ → π⁺π^? e ⁺ν decays: D _s ⁺ → ss?e ⁺ν → [σ(600) + f ₀(980)]e ⁺ν → π⁺π^? e ⁺ν, and compare it with the mechanism of production of the light pseudoscalar mesons in the D _s ⁺ → (η/η′)e ⁺ν decays: D _s ⁺ → ss?e ⁺ν → (η/η′)e ⁺ν. As a result we find support to four-quark nature of light scalars. In the end, we outline the future research program.     

b-s Anomaly Decays in Covariant Quark Model

The work is devoted to the study of b-s anomaly decays. We evaluated branching fractions of B → K*μ⁺μ^?, B _s ⁰ → φμ⁺μ^? and B_s→ μ⁺μ^? decays and compared them with available experimental data and with results from other theoretical approaches.     

Possibility of recording rare muonic decays of <Emphasis Type="Italic">B</Emphasis> mesons at the ATLAS detector in the case of LHC operation in the initial-luminosity mode

The possibility of recording the rare muonic decays B _d,s ⁰ → μ ⁺ μ ^? at the ATLAS detector (LHC, CERN) is studied. The question of what results can be expected within the first three years of LHC operation in the initial-luminosity mode is examined. The most important noncombinatorial background processes are listed for rare muonic decays of B mesons.     

Searching for Exotic States with b and c Quarks in D0 Experiment

The latest results of searching for exotic multiquark states with heavy quarks obtained in the D0 experiment (Fermi National Accelerator Laboratory, USA) are presented. In particular, the evidence of existence of a possible four-quark state X(5568) → B _s ⁰ π^±in the cases with hadronic and semileptonic decay channels of B _s ⁰ meson is considered, as well as the results of searching for the five-quark states in the J/ψΛ system.     

Dominant decays of scalar leptoquarks and scalar gluons in the minimal four-color symmetry model

Fermionic and weak decays of the scalar leptoquarks S = S ₁ ⁽⁺⁾ , S ₁ ^(?) , and S _m and the scalar gluons F = F ₁ and F ₂ predicted by the minimal model involving four-color symmetry and the Higgs mechanism of quark-and lepton-mass splitting are considered. The widths and the branching ratios are calculated for these decays, and the results are analyzed versus the couplings and masses of decaying particles. It is shown that, at relatively small mass splittings Δm within scalar doublets (Δm < m _W), the fermionic decays S ₁ ⁽⁺⁾ → tl _j ⁺ , S ₁ ^(?) → v _i \(\tilde b\), S _m → t \(\tilde \nu \) _j, F ₁ → t \(\tilde b\), and F ₂ → t \(\tilde t\), which are characterized by few-GeV widths for m _S, m _F < 1 TeV and decay branching ratios close to unity, are dominant, but that, for Δm > m _W, the weak decays S → S′W and F → F’W compete with the above fermionic decays. In the case of m _S < m _t, the processes S ₁ ⁽⁺⁾ → cl _j ⁺ , S ₁ ^(?) → v _i \(\tilde b\), S _m → bl _j ⁺ , and S _m → c \(\tilde \nu \) _j, whose total branching ratios are Br(S ₁ ⁽⁺⁾ → cl ⁺) ≈ Br(S ₁ ^(?) → v \(\tilde b\)) ≈ 1, Br(S _m → bl ⁺) ≈ 0.9, and Br(S _m → c \(\tilde \nu \)) ≈ 0.1, appear to be dominant decays of scalar leptoquarks. Searches for these decays at LHC and the Tevatron are of interest.     

Measurement of light scalar mesons in many-body decays in the PHENIX experiment at the Relativistic Heavy-Ion Collider

The unique design of the PHENIX detector at the Relativistic Heavy-Ion Collider allows one to detect neutral and charged particles produced in high-energy collisions of heavy ions. This circumstance made it possible to measure many-particle decays of light mesons, such as K _S ⁰ →π⁰π⁰, η→π⁰π^?π⁺, and η→γγ in p + p, d + Au and Au + Au collisions at the energy \(\sqrt {S_{NN} }\) = 200 GeV. The latest results of measuring the differential production cross sections, ratios of particle yields (K _S ⁰ /π⁰ and η/π⁰), and the nuclear modification factors (\(R_{dA}^{K_S }\), R _dA ^η , R _AA ^η ) in a wide range of transverse momenta (from 2 to 12 GeV s^?1) are reported.     

Optical characteristics of radiation from N<Stack><Subscript>2</Subscript><Superscript>*</Superscript></Stack> dimers in a barrier discharge

The spectral and power characteristics of radiation of the second positive system of nitrogen (C ³Π _u → B ³Π _g ) in Ar-N₂ and Ar-N₂-Cl₂ mixtures excited by barrier discharge have been studied experimentally. Addition of argon to N₂ increased the radiation power by sixfold. In the triple mixture Ar-N₂-Cl₂ = 210/0.5/0.005, minor chlorine additions increased the intensity of the C ³Π _u → _B ³Π _g transition by 26% compared to Ar-N₂ mixtures. Radiation power density of 2.7 mW/cm² has been achieved. In both binary and triple mixtures, the second positive system of nitrogen was the major contributor to radiation, while the contributions of the fourth positive system of N ₂ ^* (D ³Σ _u ⁺ → B ³Π _g ), the Vegard-Kaplan transition of N ₂ ^* (A ³Σ _u ⁺ → X ¹Σ _g ⁺ ), and the D′ → A′ band of Cl ₂ ^* were negligibly small.     

Four-Leptonic Decays of Charged and Neutral <Emphasis Type="Italic">B</Emphasis> Mesons within the Standard Model

The branching ratios and differential distributions for the four-leptonic decays \({B^ - } \to {\mu ^ + }{\mu ^ - }{\bar v_e}{e^ - }\), \({B^ - } \to {e^ + }{e^ - }{\bar v_\mu }{\mu ^ - }\), and \({B^ - } \to {\mu ^ + }{\bar v_\mu }{\mu ^ - }{\mu ^ - }\) are calculated within the Standard Model. The branching ratios for the rare decays B_d,s → e⁺e^?μ⁺μ^? and B_d,s → μ⁺μ^?μ⁺μ^? are estimated. Methods for testing the lepton universality in rare multileptonic decays of charged and neutral B mesons are proposed.     

Measurement of polarization angular coefficients in <Emphasis Type="Italic">Z</Emphasis> boson leptonic decays with ATLAS at the LHC

This paper presents the complete set of polarization angular coefficients A _0?7 describing lepton angular distributions in Z boson decay, which were measured at the ATLAS experiment in proton–proton collisions with the energy √s = 8 TeV. Theoretical values for the difference A ₀ ? A ₂ calculated in the fixed-order QCD perturbation theory O(α _s ² ), demonstrate significant deviation from the measured data, which indicates the necessity of taking into account higher order corrections. The evidence of nonzero coefficients A _5,6,7 was obtained for the first time, in accordance with theoretical calculations in O(α _s ² ) approximation. Measurement of the polarization angular coefficients A _i is important for subsequent precision measurement of parameters of the electroweak model at the LHC, such as the sine of Weinberg electroweak mixing angle sin² θ _W and the W boson mass.     

High-frequency EPR of Cr<Superscript>2+</Superscript> ions in CdGa<Subscript>2</Subscript>S<Subscript>4</Subscript>

High-frequency broad-band (65–240 GHz) EPR is used to study impurity centers of bivalent chromium in a CdGa₂S₄ crystal. It is found that the EPR spectra correspond to tetragonal symmetry. The spin Hamiltonian H = βB · g · S + B ₂ ⁰ O ₂ ⁰ + B ₄ ⁰ O ₄ ⁰ + B ₄ ⁴ O ₄ ⁴ with the parameters B ₂ ⁰ =23659±2 MHz, B ₄ ⁰ =1.9±1 MHz, |B ₄ ⁴ |=54.2±2 MHz, g_‖=1.93±0.02, and g_⊥=1.99±0.02 is used to describe the observed spectra. It is concluded that chromium ions occupy one of the tetrahedrally coordinated cation positions.     

Study of η–η′ mixing in <Emphasis Type="Italic">B</Emphasis>-meson decay with the LHCb detector

The first ever observation of the decay process B⁰ → J/ψη′ is described. The branching ratios were measured for the decay processes B_(s) → J/ψη(′), and the η–η′ mixing angles were determined on this basis. The first indication of the occurrence of the decay process B_s → ψ(2S)η′ is presented. The respective analysis was performed on the basis of data accumulated with the LHCb detector in proton–proton collisions at the c.m. collision energies of 7 and 8 TeV and the integrated luminosity of 3 fb^?1.     

Radiative decays at LHCb

Precise measurements on rare radiative B decays are performed with the LHCb experiment at LHC. The LHCb results regarding the ratio of branching fractions for two radiative decays, B ⁰ → K ^*0 γ and B _s → ?γ, the direct CP asymmetry in B ⁰ → K ^*0 γ decay channel and the observation of the photon polarization in the B ^± → K ^±π^?π^± γ decay, are included. The first two measurements were performed in 1 fb^–1 of pp collisions data and the third one in 3 fb^–1 of data, respectively.     

Dipole moment functions for electronic transitions from ion-pair states of the second tier of molecular iodine

The emission spectra caused by the transitions from the ion-pair states and f0 _g ⁺ and G1_g of the I₂ molecule are obtained by excitation of individual rovibronic levels of the molecule by the method of optical-optical double resonance. The emission spectra from the state F0 _u ⁺ populated due to collisions I₂(f) + I₂(X) are also measured. By modeling the experimental emission spectra, the dipole moment functions for the electronic transitions f _g ⁺ -B0 _u ⁺ , A0 _u ⁺ , and B″0 _u ⁺ ; G1_g-A0 _u ⁺ and B″0 _u ⁺ ; and F0 _u ⁺ -X0 _g ⁺ and a′0 _g ⁺ of the iodine molecule are reconstructed.     

Mixing of <Emphasis Type="Italic">K</Emphasis><Superscript>0</Superscript> and <Emphasis Type="Italic">B</Emphasis><Superscript>0</Superscript> neutral mesons within the minimum supersymmetry model

Mixing of K ⁰ and B ⁰ mesons is studied in the scope of the minimum supersymmetry model (MSSM) with a type II Yukawa sector and explicit violation of CP invariance in the Higgs potential. The mixing parameters Δm _LS and ? are calculated in the limit of the low-energy four-fermion approximation with a charged Higgs boson exchange. It is shown that supersymmetric effects are very small for K ⁰ mesons and may be quite significant for B _s ⁰ and B _d ⁰ mesons, which imposes constraints on the MSSM parameter space.     

The origin of frustration of magnetic coupling in the NiFeCrO<Subscript>4</Subscript> ferrite

The magnetostriction of the NiFeCrO₄ ferrite is investigated for the first time. It is found that the frustration of magnetic coupling occurs only in the B sublattice of the NiFeCrO₄ ferrite, whereas the A sublattice has a usual magnetic structure. The inference is made that the frustration of magnetic coupling in the B sublattice is caused not only by the negative direct BB exchange interaction Cr _B ³⁺ -Cr _B ³⁺ but also by the positive indirect AB exchange interaction Fe _A ³⁺ -O^2?-Cr _B ³⁺ . Reasoning from the experimental data and an analysis of the exchange interactions in the NiFeCrO₄ ferrite sample, it is demonstrated for the first time that the magnetic moments of Fe _A ³⁺ ions in this ferrite deviate from collinearity. It is established that, at low temperatures, the B sublattice of the NiFeCrO₄ ferrite is responsible for the total magnetic moment n_0exp.     

Integral characteristics of vibronic-spin-orbit interactions in a phosphorus-containing analogue of the fluorene molecule

The strengths (P ₀₀ ^s )² and F _VSO ² of the transitions from the triplet sublevels s = z, y, and x of the electronic state ³A″ of the phenyldibenzophosphole (DB(P-Ph)) molecule are calculated taking into account the intramolecular spin-orbit (SO) and joint vibronic-spin-orbit (VSO) interactions. The contributions to the vibronic transition strengths from the SO interactions in different structural elements of the molecule (the C atoms of the dibenzene framework, the P atom, and the Ph substituent) are determined. The effect of the nonplanar nuclear configuration of the DB(P-Ph) molecule on the values of F _VSO ^s is investigated. The radiative deactivation rate constants of the k _rad ^s triplet sublevels T ^s are estimated. It is found that the vibrations of the A′(B₁) symmetry in the fine-structure phosphorescence spectrum of DB(P-Ph) occur due to both the SO coupling exclusively in the P atom and the T ^x → S₀ transition (the x axis is perpendicular to the planar dibenzene framework of the molecule) with a high (preferential) population of this triplet sublevel.     

QRPA coordinate space calculations of 2<Superscript>+</Superscript> states in <Emphasis Type="Italic">N</Emphasis>=20 isotones

The first 2⁺ states in N=20 isotones are studied within the self-consistent quasiparticle random phase approximation based on the Green’s function method. The residual interaction between quasiparticles with full velocity dependence is consistently derived from the Skyrme interaction plus pairing interaction energy density functional. The B(E2, 0 ₁ ⁺ → 2 ₁ ⁺ ) transition probabilities and the excitation energies of the first 2⁺ states are well described within a single framework. We discuss mainly the microscopic origin of the anomalously large B(E2) value and the very low excitation energy in ³²Mg.