Weak decays of heavy baryons in the light-front approach

In this work, we analyse semi-leptonic and non-leptonic weak decays of the heavy baryons: Λ_b,Ξ_b,?_b and Λ_c,Ξ_c,?_c. For non-leptonic decay modes, we study only the factorizable channels induced by the external Wemission. The two spectator quarks in the baryonic transitions are treated as a diquark and form factors are calculated in the light-front approach. Using the results for form factors, we also calculate some corresponding semi-leptonic and non-leptonic decay widths. We find that our results are comparable with the available experimental data and other theoretical predictions. Decay branching fractions for many channels are found to reach the level 10~(-3)~10~(-2),which is promising for discovery in future measurements at BESIII, LHCb and Belle II. The SU(3) symmetry in semi-leptonic decays is examined and sources of symmetry breaking are discussed.     

<Emphasis Type="Italic">B</Emphasis><Stack><Subscript>s</Subscript><Superscript>0</Superscript></Stack> physics at LHCb

The LHCb experiment is in preparation, to be ready for the start of the LHC. The physics which will be performed by LHCb is reviewed, focussing on what can be learnt fromB _s ⁰ mesons.     

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.     

The lepton flavor violating decay τ ± → μ±μ±μ? at LHCb

The possibility of improving the limit on the branching fraction of the lepton flavor violating decay ?? ^± ?? ??^±??^±??^? at LHCb is discussed. It is shown that a simple, cut-based analysis is sufficient to improve the upper limit on this branching fraction within the lifetime of LHCb.     

Searching for Higgs decays to four bottom quarks at LHCb

We discuss the feasibility of seeing a Higgs boson which decays to four bottom quarks through a pair of (pseudo-)scalars at the LHCb experiment to argue that the use of b-physics triggers and off-line vertex reconstruction, as opposed to jet triggers with b tagging, may be more effective for this signal. Focusing on inclusive production for the Higgs, we find that for light scalar masses below 20 GeV, signal reconstruction efficiencies of order a few percent may be enough for LHCb to find evidence for a Higgs with a dominant 4b decay channel.     

Hadrinoc production of χ c -nesons at LHC

Hadronic production of P-wave charmonium states χ _cJ in hadronic interaction is considered. Using the experimental results of CDF and LHCb collaborations, we show, that contributions of color singlet components are dominant. As for the color octet mechanism, then we show, that contributions from P-wave states can also be observed, while the contribution from S-wave is negligible. The best experimental observables that give information about relative importance of color-singlet and color-octet components are the ratios χ _c2/χ _c1 and χ _c 0/χ _c1.     

Extracting γ and penguin topologies through CP violation in B_{s}^{0}\to J/\psi K_{\mathrm{S}}

The $B_{s}^{0}\to J/\psi K_{\mathrm{S}}$ decay has recently been observed by the CDF collaboration and will be of interest for the LHCb experiment. This channel will offer a new tool to extract the angle γ of the unitarity triangle and to control doubly Cabibbo-suppressed penguin corrections to the determination of sin?2β from the well-known $B_{d}^{0}\to J/\psi K_{\mathrm{S}}$ mode with the help of the U-spin symmetry of strong interactions. While any competitive determination of γ is interesting, the latter aspect is particularly relevant as LHCb will enter a territory of precision which makes the control of doubly Cabibbo-suppressed Standard-Model corrections mandatory. Using the data from CDF and the e ⁺ e ^? B factories as a guideline, we explore the sensitivity for γ and the penguin parameters and point out that the $B_{s}^{0}$ – $\bar{B}_{s}^{0}$ mixing phase φ _s , which is only about ?2° in the Standard Model but may be enhanced through new physics, is a key parameter for these analyses. We find that the mixing-induced CP violation $S(B_{s}^{0}\to J/\psi K_{\mathrm{S}})$ shows an interesting correlation with sin?φ _s , which serves as a target region for the first measurement of this observable at LHCb.     

Charmonium production at the Tevatron and Large Hadron Collider in the Regge limit of QCD

Processes involving direct J/ψ-meson production in proton-antiproton and proton-proton collisions are studied under the assumption of gluon Reggeization in t-channel exchanges and with the aid of the formalism of nonrelativistic quantum chromodynamics. The present calculations are performed in the leading approximation in the strong coupling constant α _s and in the relative quark velocity v. The octet nonperturbative matrix elements for the transition of a c $\bar c$ pair to quarkonium are fixed in fitting the transverse-momentumspectra obtained by the CDF Collaboration for J/ψ mesons at the Tevatron collider. The spectra of J/ψ-meson production at the energies of the Large Hadron Collider are predicted, and the resulting predictions agree well with experimental data obtained by the ATLAS, CMS, and LHCb Collaborations at $\sqrt S $ = 7 TeV.     

Extracting angular correlations from the rare decay \bar Bd \to \bar K*^0 μ + μ − at LHCb

$ \bar Bd \to \bar K*^0 $ μ ⁺ μ ^? is a rare flavor-changing neutral-current decay. It proceeds via a b → s quark transition and is sensitive to many classes of new physics model. In this article the theoretical framework relevant to making a measurement at LHCb, the precision flavor experiment at the Large Hadron Collider, will be introduced. Progress made towards using a full angular analysis to extract A _FB, the forward-backward asymmetry of the μ pair, will be covered and its implications for the precision of the A _FB zero-crossing-point measurement discussed.     

Doubly Charmed Baryon Mass and Wave Function through a Random Walks Method

The mass and the wave function of doubly charmed Ξ_cc⁺⁺ (ccu) baryon are evaluated using Green Function Monte Carlo method to solve the three-body problem with Cornell potential. The mass of Ξ_cc⁺⁺ with spin 1/2 is in a good agreement with the LHCb value. Simulation of the wave function by random walks resulted in a configuration of the quark–diquark type. The radius of Ξ_cc⁺⁺ is much larger than the size needed for a large isospin splitting. The prediction for the Ω_cc mass is presented.     

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.     

Production of ϒ meon in pp colliion at $$\qrt $$ = 7 and 8 TeV in the LHCb experiment

The LHCb results on the production of ? mesons in pp collisions at \(\sqrt s\) = 7 and 8 TeV are briefly reviewed.     

<Emphasis Type="Italic">Z</Emphasis> <Superscript>+</Superscript>(4430): Nonexotic interpretation

The possibility of describing the charged charmonium-like state Z⁺(4430) as the kinematical rescattering effect is examined. This approach makes it possible to avoid the introduction of exotic hadron states in the model, and one describes structures in the ψ(2S)π⁺ mass spectrum by the presence of the D_s^(*)′ resonance in a hidden intermediate state. The resulting model predictions are compared with the results obtained by the LHCb Collaboration.     

Study of the B_c→B_sπ decay with the perturbative QCD approach

The Bc→Bsπ decay is studied with the perturbative QCD approach. Three types of wave functions for Bsmeson are considered.The transition form factor FBc→Bs0(0) and the branching ratio Br(Bc→Bsπ)aresensitivetothemodelofthe Bsmeson wave functions.With appropriate inputs, our estimate on Br(Bc→Bsπ) is comparable with the recent LHCb measurement. A clear signal of Bc→Bsπ decay should be easily observed at the Large Hadron Collider.     

Lepton-number violating decays of heavy mesons

The experimental observation of lepton-number violating processes would unambiguously indicate the Majorana nature of neutrinos. Various ΔL=2 processes for pseudoscalar meson M ₁ decays to another pseudoscalar meson M ₂ and two charged leptons ? ₁, ? ₂ (\(M_{1}^{+}\rightarrow \ell_{1}^{+}\ell_{2}^{+}M_{2}^{-}\)) have been studied extensively. Extending the existing literature on the studies of these kinds of process, we consider the rare decays of heavy mesons to a vector meson or a pseudoscalar meson. These processes have not been searched for experimentally, while they may have sizable decay rates. We calculate their branching fractions and propose to search for these decay modes in the current and forthcoming experiments, in particular at the LHCb.     

Weak decays of doubly heavy baryons: “decay constants”

Inspired by the recent observation of the Ξ_c~+_c~+)by the LHCb Collaboration, we explore the "decay constants" of doubly heavy baryons in the framework of QCD sum rules. With the Ξ_cc),Ξ_(bc),Ξ_(bb), and ?_(cc),?_(bc),?_(bb) baryons interpolated by three-quark operators, we calculate the correlation functions using the operator product expansion and include the contributions from operators up to dimension six. On the hadron side, we consider both contributions from the lowest-lying states with JP=1/2~+ and from negative parity baryons with JP=1/2~-. We find that the results are stable and the contaminations from negative parity baryons are not severe. These results are ingredients for the QCD study of weak decays and other properties of doubly-heavy baryons.     

Constraints on supersymmetry from LHC data on SUSY searches and Higgs bosons combined with cosmology and direct dark matter searches

The ATLAS and CMS experiments did not find evidence for Supersymmetry using close to 5/fb of published LHC data at a center-of-mass energy of 7 TeV. We combine these LHC data with data on $B^{0}_{s}\to \mu^{+}\mu^{-}$ (LHCb experiment), the relic density (WMAP and other cosmological data) and upper limits on the dark matter scattering cross sections on nuclei (XENON100 data). The excluded regions in the constrained Minimal Supersymmetric SM (CMSSM) lead to gluinos excluded below 1270 GeV and dark matter candidates below 220 GeV for values of the scalar masses (m ₀) below 1500 GeV. For large m ₀ values the limits of the gluinos and the dark matter candidate are reduced to 970 GeV and 130 GeV, respectively. If a Higgs mass of 125 GeV is imposed in the fit, the preferred SUSY region is above this excluded region, but the size of the preferred region is strongly dependent on the assumed theoretical error.     

Prospects for studying penguin decays in LHCb experiments

Investigation of loop penguin decays of beauty hadrons seems promising in testing the predictions of the Standard Model of electroweak and strong interactions and in seeking new phenomena beyond the Standard Model. The possibility of studying the radiative penguin decays B ⁰ → K*⁰ γ, B ⁰ _s → ?γ, and B ⁰ → ωγ and the gluonic penguin decays B ⁰ → ?K ⁰ _S and B ⁰ _s → ?? in LHCb experiments is discussed.     

Modern trends in methods of charged particle identification at high energies

The survey is devoted to methods of charged particle identification at high energies that are based on measurements of the angle of Cherenkov radiation (ring imaging Cherenkov counters — RICH), of time of flight (TOF) and propagation (TOP), and of ionization energy loss (dE/dx). As an example, some operating spectrometers are considered (LHCb, ALICE, COMPASS, Belle, and BaBar) together with proposed ones (Belle-2 and PANDA) in which new achievements of recent years are introduced.     

B s →μ + μ − decay in the R-parity violating minimal supergravity

We study B _s →μ ⁺ μ ^? in the context of the R-parity violating minimal supergravity in the high-tan?β regime. We find that the lowest value of the branching ratio can go well below the present LHCb sensitivity and hence B _s →μ ⁺ μ ^? can even be invisible to the LHC. We also find that the present upper bound on Br?(B _s →μ ⁺ μ ^?) puts strong constraint on the minimal supergravity parameter space. The constraints become more severe if the upper bound is close to its standard model prediction.