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.     

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.     

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.     

Effect of FCNC mediated <Emphasis Type="Italic">Z</Emphasis> boson on lepton flavor violating decays

We study the three body lepton flavor violating (LFV) decays μ ^?→e ^? e ⁺ e ^?, \(\tau^{-} \to l_{i}^{-} l_{j}^{+} l_{j}^{-}\) and the semileptonic decay τ→μφ in the flavor changing neutral current (FCNC) mediated Z boson model. We also calculate the branching ratios for LFV leptonic B decays, B _d,s →μe, B _d,s →τe, B _d,s →τμ and the conversion of muon to electron in Ti nucleus. The new physics parameter space is constrained by using the experimental limits on μ ^?→e ^? e ⁺ e ^? and τ ^?→μ ^? μ ⁺ μ ^?. We find that the branching ratios for τ→eee and τ→μφ processes could be as large as \({\sim}{\mathcal{O}}(10^{-8})\) and \(\mathrm{Br}(B_{d,s} \to \tau \mu,~ \tau e) \sim {\mathcal{O}}(10^{-10})\). For other LFV B decays the branching ratios are found to be too small to be observed in the near future.     

<Emphasis Type="Italic">B</Emphasis>-meson decays into charmonium states in the ATLAS experiment

The paper presents several recent ATLAS results on the analyses of B-meson decays into charmonium states. These include the measurements of B⁺ mass and the fractions of J/ψ mesons produced in b-hadron decays in pp collisions at \(\sqrt s\) = 13 TeV in the center of mass system. The measured partial widths and polarizations in B _c ⁺ → J/ψD _s ^(*)+ decays and CP-violation parameters in B _s ⁰ → J/ψ? decays in pp collisions at 7 and 8 TeV in the center of mass system are also presented.     

Estimating of CP-violation in <Emphasis Type="Italic">B</Emphasis><Superscript>0</Superscript>→ψ(2<Emphasis Type="Italic">S</Emphasis>)π<Superscript>0</Superscript> decay

I present estimates of CP-violating asymmetries in the non-leptonic charmonium two-body B⁰→ψ(2S)π⁰ decay and the same decays of B⁺→ψ(2S)π⁺ and B⁺→ψ(2S)K⁺ These estimates are based on QCD and improved QCD factorization approach making use of next-to-leading order (NLO) contributions. The CP-violating asymmetry for B⁰→ψ(2S)π⁰ decay is not available, according to the same calculations, it is expected if it can be measured in the future its value will be S_ψ(2S)π0(B⁰ → ψ(2S)π⁰)= 0.662 ± 0.197 and C_ψ(2S)π0(B⁰ → ψ(2S)π⁰)= 0.024 ± 0.007.     

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.     

Analysis of the production of Higgs boson pairs at the one-loop level in the minimal supersymmetric standard model

Within theminimal supersymmetric standardmodel, the amplitudes and total cross sections for the processes e ⁺ e ^? → hh, e ⁺ e ^? → hH, e ⁺ e ^? → HH, and e ⁺ e ^? → AA are calculated in the first order of perturbation theory with allowance for a complete set of one-loop diagrams in the m _e → 0 approximation. Analytic expressions are obtained for the quantities under consideration; numerical results are presented in a graphical form. It is shown that the cross section for the process e ⁺ e ^? → hh is larger than those for the other processes (and is on the same order of magnitude as the cross section for the corresponding processes in the Standard Model). In the case of the collision energy equal to √s = 500 GeV, an integrated luminosity in the region ∫ ? ≥ 500 fb^?1, and a longitudinal polarization of the e ⁺ e ? beams used, 520, 320, and 300 production events are possible in the processes e ⁺ e ^? → hh (at M _h = 115 GeV), e ⁺ e ^? → HH, and e ⁺ e ^? → AA (at M _H,A = 120 GeV), respectively. Even at M _H,A ≈ 500 GeV and √s = 1.5 TeV, not less than 200 events for each of the processes can be accumulated. The cross section for the process e ⁺ e ^? → hH is small (about 10^?2 fb), which complicates the detection of the sought signal significantly.     

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.     

Effect of <Emphasis Type="Italic">Z′</Emphasis>-mediated flavor-changing neutral current on <Emphasis Type="Italic">B</Emphasis> → <Emphasis Type="Italic">ππ</Emphasis> decays

We study the effect of Z′-mediated flavor-changing neutral current on the B → ππ decays. The branching ratios of these decays can be enhanced remarkably in the nonuniversal Z′ model. Our estimated branching ratios B(B ⁰ → π ⁰ π ⁰) are enhanced significantly from their standard model (SM) value. For g′/g = 1, the branching ratios B(B ⁰ → π ⁰ π ⁰) are very close to the recently observed experimental values and for higher values of g′/g branching ratios are more. Our calculated branching ratios B(B ⁰ → π ⁺ π ^?) and B(B ⁺ → π ⁺ π ⁰) are also enhanced from the SM value as well as the recently observed experimental values. These enhancements of branching ratios from their SM value give the possibility of new physics.     

Determination of quark-antiquark component of the photon wave function for <Emphasis Type="Italic">u,d, s</Emphasis> quarks

Based on the data for the transitions π⁰, η, η′ → γγ*(Q²) and reactions of the e⁺e^? annihilations e⁺e^? → ρ⁰, ω, ? and e⁺e^? → hadrons at 1<E _e+e? <3.7 GeV, we determine the light-quark components of the photon wave function \(\gamma * (Q^2 ) \to q\bar q(q = u,d,s)\) for the region 0 ? Q² ? 1 (GeV/c)².     

Annihilation semileptonic decays of <Emphasis Type="Italic">B</Emphasis> mesons and the model dependence on the choice of the distribution amplitude

The rare semileptonic B-meson decay B → ??⁺?^? is considered. The partial decay rate integrated over the 1–8 GeV² interval of the dilepton invariant mass squared is computed with a 10% systematic uncertainty arising from the model dependence of the distribution amplitude. The purely perturbative contribution to the decay probability amounts to ? ～ 10^?12, which suggests that the LHC experiments could observe the B → ??⁺?^? decay in a few years of data taking.     

Measurement of cross sections for processes involving <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> annihilation to hadrons at the VEPP-2M collider

Results obtained by measuring, in experiments at the VEPP-2M e ⁺ e ^? collider with the CMD-2 and SND detectors at the Novosibirsk Institute of Nuclear Physics, cross sections for e ⁺ e ^? → hadrons annihilation processes at energies in the range 360 ≤ √s ≤ 1380 MeV are surveyed. The measured cross sections and the vector-meson parameters deduced from an analysis of these cross sections are presented. The cross section for the process e ⁺ e ^? → π ⁺ π ^? is compared with the spectral function for the decay τ ^? → π ^? π ⁰ ν _τ.     

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.     

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.     

Energy scan of cross sections for <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>–</Superscript> annihilation into quarkonia and light hadrons in the Belle experiment

The cross sections of the reactions e⁺e^– → ?(nS)π⁺π^? (n = 1, 2,3) and e⁺e^– → h _b (nP)π⁺π^? (n = 1, 2) are measured as a function of the cms collision energy from their thresholds up to 11.02 GeV using the data of the Belle experiment operating at the KEKB e⁺e^– collider. The peaks of the ?(10 860) and ?(11020) resonances are observed in the cross sections with an insignificant contribution of the continuum. The decay ?(11020) → h _b (nP)π⁺π^? is found to fully proceed through intermediate isovector states Z _b (10610) and Z _b (10650).     

Effects of Final State Interactions in Pure Annihilation Decay of B+ → D+K0*

The decay of the B ⁺ meson to the D ⁺ and K ⁰* mesons is a pure annihilation decay. For this reason, in the framework of the quantum chromodynamics factorization (QCDF) approach, this decay has a small amplitude and a small branching ratio. In this research we find that, before the D ⁺ and K ⁰* mesons are produced in the final states, pair mesons such as D _s ⁺* and D _s ⁺ρ⁰ are produced. The intermediate-state mesons via the exchange of K ⁰(K ⁰*) and D ⁺(D ⁺*) go to the D ⁺ and K ⁰* final state mesons. However we calculate the B ₊ → D ⁺ K ⁰* decay in two different frameworks. The first framework is the QCDF method and the second one is final state interaction (FSI). The experimental branching ratio of B ₊ → D ₊ K ⁰* decay is less than 3 × 10^–6, and our results obtained by the QCDF method and FSI are (0.35 ± 0.04) × 10^–6 and (2.94 ± 0.10) × 10^–6, respectively.     

Method for taking into account hard-photon emission in four-fermion processes

A method for taking into account hard-photon emission in four-fermion processes proceeding in the s channel is described. The application of this method is exemplified by numerically estimating one-loop electroweak corrections to observables (cross sections and asymmetries) of the reaction e^?e⁺ → μ^?μ⁺(γ) involving longitudinally polarized electrons and proceeding at energies below the Z-resonance energy.     

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.     

Production of exotic Λ hypernuclei via mesonic beams

We study the production of neutron-rich hypernuclei _Λ ¹² Be, _Λ ¹⁶ C, and _Λ ¹⁰ Li by the (π^?, K⁺) and (K^?, π⁺) reactions in flight and treat two different mechanisms of production. The first mechanism is a two-step process with meson charge exchange (e.g., π^?p → π⁰n, π⁰p → K⁺Λ). The other mechanism is one-step production (π^?p → K⁺Σ^?) proceeding via a small Σ^? component, arising in Λ hypernuclei due to ΛN–ΣN coupling, as a doorway state. Typically, the two-step mechanism is more productive. The forward differential cross section of the ¹⁰B(π^?,K⁺) reaction is about 70 nb/sr at an incident momentum of 1.05 GeV/c. On the other hand, the one-step process can serve as a direct measurement of the Σ admixture if the two-step contribution is suppressed by a suitable choice of the reaction kinematics.