CP violation and the widthZ→b \bar b

We discuss the effect of CP-violatingZb $\bar b$ Zb $\bar b$ G andZb $\bar b$ γ couplings on the width Γ(Z→b $\bar b$ X). The presence of such couplings leads in a natural way to an increase of this width relative to the prediction of the standard model. Various strategies of a direct search for such CP-violating couplings by using CP-odd observables are outlined. The number ofZ bosons required to obtain significant information on the couplings in this way is well within the reach of present LEP experiments.     

Is the channelH \to b\bar b observable at LHC?

A detailed study of associated Standard Model Higgs production (WH and ) at the LHC (or a possible upgraded Tevatron collider), where the Higgs boson decays to pairs, is reported for 80m _H <120 gev.=" even=" for=">b-tagging performances of the detector, the signal cannot be cleanly extracted from the background. For an integrated luminosity of 10⁴ pb ^–1 andm _H =100 GeV, one can expect at best 110 reconstructed decays fromWH production, above a resonant background of 150WZ events and a non-resonant background of 4800 events, and 100 reconstructed pairs (of which 50 from decay) from production, above a background of 4000 events. The main difficulty in extracting these two channels is in the expected low signal rate after reconstruction, the need for accurate control of all the background sources and for extremely goodb-tagging performance. Nevertheless, for a few years of running at a luminosity of 10³³ cm^–2s^–1, channel may be the best way to probe the region 80m _H <100>     

One-loop gg\to b\bar{b} effects in the main irreducible background to exclusive H\to b\bar{b} production at the LHC

We calculate the amplitude of $gg\to b\bar{b}$ production for the colour singlet, J _z =0, di-gluon state at $\mathcal{O}(\alpha_{\mathrm{S}}^{2})$ order. We consider the cancellation and a realistic cut-off, of the infrared divergent terms. We show that the one-loop radiative QCD contributions effectively reduce the Born level result for the central exclusive $b\bar{b}$ cross section at the LHC. This process is essentially the only irreducible QCD background to the exclusive $H\to b\bar{b}$ signal.     

Effects of charged Higgs bosons on the processes b→sγ, b→sg1 and b→sℓ+ℓ−

Effects of charged Higgs bosons (H⁺) on various loop-induced processes in the B-meson system are discussed, within the framework of two Higgs doublet models (2HDMs). The H⁺ contribution to the magnetic moment form factor turns out to be very significant and it can distinguish between the two types of 2HDMs. Even with constraints from B_d mixing, both strong enhancements or strong suppressions (in b→sγ) of decay rates are possible. Thus, information from these modes is competitive with, and may soon surpass, restrictions on 2HDMs from B_d mixing. Since (inclusive) b→sγ and b→sg¹ at current limits are not excluded, continued effort to detect them is encouraged.     

Observation of the Ξ(b)(0) baryon

The observation of the bottom, strange baryon Ξ(b)(0) through the decay chain Ξ(b)(0)→Ξ(c)(+)π-, where ΞΞ(c)(+)→Ξ- π+ π+, Ξ-→Λπ-, and Λ→pπ-, is reported by using data corresponding to an integrated luminosity of 4.2 fb(-1) from pp collisions at square root(s)=1.96 TeV recorded with the Collider Detector at Fermilab. A signal of 25.3(-5.4)(+5.6) candidates is observed whose probability of arising from a background fluctuation is 3.6×10(-12), corresponding to 6.8 gaussian standard deviations. The Ξ(b)(0) mass is measured to be 5787.8±5.0(stat)±1.3(syst) MeV/c2. In addition, the Ξ(b)- baryon is observed through the process Ξ(b)-→Ξ(c)(0)π-, where Ξ(c)(0)→Ξ- π+, Ξ-→Λπ-, and Λ→pπ-.     

A $$bb{\bar{b}}{\bar{b}}$$ di-bottomonium at the LHC?

We study the case of a di-bottomonium \(bb{\bar{b}}{\bar{b}}\) particle at the LHC. Its mass and decay width are obtained within a new model of diquark–antidiquark interactions in tetraquarks. The same model solves several open problems on the phenomenology of the experimentally better known X, Z states. We show that the \(bb\bar{b}{\bar{b}}\) tetraquark is expected approximately 100 MeV below threshold, and compare to a recent analysis by LHCb seeking it in the \(\Upsilon \mu \mu \) final state.     

The Λb lifetime in the light front quark model

The enhancement of the Λ_b decay width relative to B decay due to the difference in Fermi motion effects in Λ_band B is calculated in the light front quark model with the simplifying assumption that Λ_bconsists of a heavy quark and a light scalar diquark. In order to explain the large deviation from unity in the experimental result for τ(Λ_b)/τ(B), it is necessary that the diquark be light and the ratio of the squares of the Λ_b and B wave functions at the origin be ?1.     

Variational study of the ground state energy of theE−b 1,b 2 Jahn-Teller system

In this paper a variational method for the ground state energy approximation of theE−b ₁,b ₂ Jahn-Teller system is presented. This method is based on the choice of a suitable variational ground state wave function. This trial wave function — a correlated squeezed state — is used to account for the correlation and anharmonicity of the interaction between the two vibrational modes; the anharmonicity of both modes is taken into account by the squeeze effects of these modes. The ground state of mode 1 in this trial wave function is considered as a linear combination of the two displaced harmonic oscillators. The ground state energies for the linearE - e Jahn-Teller system calculated by this method are not only in good agreement with the exact diagonalization results, but they are also better than those from the previous analytical studies. Another conclusion which results from the presented model is the following one: the squeezing effect of mode 1 for the linearE - e Jahn-Teller system is substantially smaller, in contrast with the results which are presented in the previous analytical studies.     

Recursion operator and bäcklund transformations for the Ruijsenaars-Toda lattice

We exhibit the recursion operator and the whole class of Bäcklund transformations for a relativistic version of the Toda lattice recently introduced by Ruijsenaars. These results allow us to prove the complete integrability of the system.     

Distorted Wave Effects of the 1b3g Orbital in Ethylene

We study the unexpected distorted wave effects of the 1b3g orbital in ethylene using a high resolution binary (e,2e) electron momentum spectrometer,at an impact energy of 800eV plus the binding energy (8-22eV) with symmetric non-coplanar kinematics.The experimental monentum profile of the 1b3g orbital is obtained and compared with the data previously measured at an impact energy of 1200 eV plus the binding energy.Also,the experimental momentum profiles of the 1b3g orbital are compared with the theoretical momentum distributions calculated by using Hartree-Fock and density functional theory methods.The experimental momentum profiles of the 1b3g orbital of ethylene at different impact energies show that the cross section of the orbital below the momentum p-1 a.u.is higher for lower impact energies.     

Study on the Decay b→sγ in theMultiscale Walking Tchnicolor Model

We invesdgate the correction to the branching ratio of decay b→sγ from the Pseudo-Goldstone bosons (PGBs) in the multiscale walking technicolor model (MWTCM). Tbe correction is found so large that we can not explain the recentCLEO data lf topcolor is further introduced. the branching ratio in the topcolor assisted MWTCM will be in agreement with the CLEO data for a certain range of the model-allowed parameter space.     

Fluctuation-dominated kinetics in the a+b→0 reaction between immobile particles

We consider the accumulation of immobile particles landing on a one-dimensional lattice and annihilating via the A + B 0 bimolecular reaction. Here we focus on short-range interactions with cutoff. We investigate through computer simulations both the kinetics of the particles' accumulation and also their spatial distribution. The relation between the exponents describing the growth of the particles' concentration and the correlation length of their distribution shows that the kinetics of accumulation is fluctuation-dominated.This work is dedicated to Prof. George H. Weiss.     

Analysis of the Λb → Λ?+?? transition in the SM4 using form factors from full QCD

Using the responsible form factors calculated via full QCD, we analyze the ?? _b ?? ???⁺?^? transition in the standard model containing fourth-generation quarks (SM4). We discuss the effects of the presence of the t?? fourth-family quark on related observables like branching ratio, forward-backward asymmetry, baryon polarization as well as double-lepton polarization asymmetries. We also compare our results with those obtained in the SM as well as with predictions of the SM4 but using form factors calculated within heavy-quark effective theory. The obtained results on the branching ratio indicate that the ? transition is more probable in full QCD comparing to the heavy-quark effective theory. It is also shown that the results on all considered observables in the SM4 deviate considerably from the SM predictions when m _t?? ?? 400 GeV.     

b MESONS

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Re-study of the contribution of scalar potential and spectra of c, b and b(c) families

We indicated in our previous work that for QED the role of the scalar potential which appears at the loop level is much smaller than that of the vector potential and is in fact negligible. But the situation is different for QCD, one reason is that the loop effects are more significant because α s is much larger than α, and second the non-perturbative QCD effects may induce a sizable scalar potential. In this work, we study phenomenologically the contribution of the scalar potential to the spectra of charmonia, bottomonia and b(c) families. Taking into account both vector and scalar potentials, by fitting the well measured charmonia and bottomonia spectra, we re-fix the relevant parameters and test them by calculating other states of not only the charmonia and bottomonia families, but also the b family. We also consider the Lamb shift of the spectra.     

Physics beyond the Standard Model through b → s μ ?+? μ ? transition

A comprehensive study of the impact of new-physics operators with different Lorentz structures on decays involving the b ?? s ?? ^?+? ?? ^? transition is performed. The effects of new vector?Caxial vector (VA), scalar?Cpseudoscalar (SP) and tensor (T) interactions on the differential branching ratios, forward?Cbackward asymmetries (A _FB??s), and direct CP asymmetries of ${\bar B}_{\rm s}^0 \to \mu^+ \mu^-$ , ${\bar B}_{\rm d}^0 \to$ $ X_{\rm s} \mu^+ \mu^-$ , ${\bar B}_{\rm s}^0 \to \mu^+ \mu^- \gamma$ , ${\bar B}_{\rm d}^0 \to {\bar K} \mu^+ \mu^-$ , and ${\bar B}_{\rm d}^0\to {\bar{K}^*} \mu^+ \mu^-$ are examined. In ${\bar B}_{\rm d}^0\to {\bar{K}^*} \mu^+ \mu^-$ , we also explore the longitudinal polarization fraction f _L and the angular asymmetries $A_{\rm T}^{(2)}$ and A _LT, the direct CP asymmetries in them, as well as the triple-product CP asymmetries $A_{\rm T}^{\rm (im)}$ and $A^{\rm (im)}_{\rm LT}$ . While the new VA operators can significantly enhance most of the observables beyond the Standard Model predictions, the SP and T operators can do this only for A _FB in ${\bar B}_{\rm d}^0 \to {\bar K} \mu^+ \mu^-$ .