Bounds on a top quark with charged Higgs decay

If the top quark decays to a charged Higgs boson t→bH⁺, semileptonic decay signatures are suppressed and the mass bounds set by the UA1 top search are evaded. However the charged Higgs decay mode H⁺→τ⁺ν_τ gives a missing-ϱ_T signature; depending on the decay branching fraction and using the UA1 limits on new physics contributions to missing-ϱ_T, we set bounds on the top mass in this scenario. We also evaluate the feasibility of seeking visible-τ-jet signals for top at a pp̄ collider.     

ϒ production at large transverse momentum as a probe of axigluons

Large-p_T production of J/Ψ and ϒ particles is suggested as a sensitive probe of axigluons of mass less than 40 GeV at the CERN collider and 80 GeV at the Tevatron. It is shown that existing CERN collider data on large-p_T ϒ production exclude axigluon masses less than around 20 GeV. At the projected SSC, ϒ and vector toponium production at large p_T through axigluon exchange by far outweighs the QCD contribution over a vast range of axigluon and toponium masses.     

SU(3) predictions for nonleptonicT-meson decays

The predictions ofSU(3) are analyzed for the decays of theT-mesons (T ⁰,T ⁺,T _s ⁺ ). Relations betweenT-meson decay rates are given. Some of these relations may provide important information for searching top mesons.     

Spin effects in two-body hadronic decays of the B c mesons

Spin effects in the weak two-body hadronic decays of the B _c and B _c ^* mesons into J/ψ and ρ(π) mesons are considered within the model of hard one-gluon exchange between quarks at high momentum transfers. It is shown that the polarization of the J/ψ meson in the decays of the B _c ^* meson differs substantially from that in the decays of the B _c ^* meson. The decay widths of the B _c ^* meson differ significantly from the widths of the B _c ^* meson.     

Formfactor effects in exclusiveD andB decays

Recent experimental results on the semileptonicD→K ^* transition seem to be in conflict with quark model expectations. Motivated by this finding we reinvestigate the predictions for exclusiveD andB decays in the relativistic quark model approach. Some of the invariant formfactors relevant for the transition matrix elementsD→K ^* andB→D ^* depend strongly on an explicit quarkmass-dependent integral over the meson wave functions. The dependence of decay rates and spectra in semi-leptonicD andB transitions on this integral is analysed and discussed in detail. Furthermore, we discuss how the predictions of the relativistic quark model for semi-leptonicD andB decays can be tested through measurements of the polarization of the produced vector mesonK ^* andD ^*, respectively. Some remarks on exclusive nonleptonic two-body decays of the heavy mesons are also presented. Finally the theoretical uncertainties for the determination of the K-M matrix element |V _ub | from exclusive semi-leptonic decays are discussed.     

T-odd top partner pair production in the dilepton final states at the LHC in the littlest Higgs Model with T-parity

In the littlest Higgs model with T-parity, we discuss the pair production of the T-odd top partner(T_) that decays almost 100% into the top quark and the lightest T-odd particle(A_H). Considering the current constraints,we investigate the observability of the T-odd top partner pair production through the process pp→T_T_→tt A_HA_H in the final states with two leptons at 14 TeV LHC. We analyze the signal significance and found that the lower limits on the T-odd top partner mass are approximately 1.2 TeV, 1.3 TeV, and 1.4 TeV at the 2σ confidence level at 14 TeV LHC with an integrated luminosities of 30 fb~(-1), 100 fb~(-1), and 300 fb~(-1), respectively. This lower limit can be increased to approximately 1.5(1.6) TeV if we used 1000(3000) fb~(-1) of the integrated luminosity.     

Charged hyperpions,charged higgs bosons and the leptonic decays of the heavy open-top mesonsT b * andT b

We study the leptonic decay modes of the vectorT _b ^* and pseudoscalarT _b t-flavored mesons in the framework of some extended technicolor models and for the standardSU(2)×U(1) model with two complex Higgs doublets. We find that the ratioГ(T _b ^* →? v Г(T →? v) bcan help in discriminating among these models but, unfortunately, the experimental prospects for detecting these decay modes are not very bright.     

Analysis of transverse momentum distributions forpp interactions at 360 GeV/c in the framework of a quark-diquark fragmentation model

Using a quark-diquark fragmentation model, in which either the Field-Feynman or the Lund model is coupled with a quark-diquark distribution function, we study transverse momentum distributions,p _T, for the inclusive reactionspp→hadron +anything at 360 GeV/c. We find that a primordial mean transverse momentum 〈k _T〉?0.4 GeV/c can well reproduce thep _T ² distributions of charged hadrons, π⁰,K _s ⁰ , Λ⁰,K ^* and Σ^* and the Feynmanx?p _T correlations. We confirm that a diquark in a proton plays an important rôle in reproducing thex?p _T correlation of Λ⁰.     

Nonfactorizable contributions to hadronic decays of charm mesons in the Cabibbo-suppressed modes

We investigate nonfactorizable contributions to charm meson decays into D → ππ/K K?/K K?*/K? K*/D → K*K?* modes. Obtaining the contributions from spectatorquark diagrams for N _c = 3, we determine the nonfactorizable isospin amplitudes required to explain the data for these modes. For these decays, we observe that ππ, πρ, decay modes favor a nonfactorizable-isospin-amplitudes ratio A ₀ ^nf /A ₂ ^nf equal to (1.123±0.158) and for K K?, K K?*, K? K* and K*K?* modes, the ratio of nonfactorizable amplitudes A ₀ ^nf and A ₁ ^nf turns out to be unity.     

Charmed particle production in hadron-hadron collisions

In the framework of Quark-Gluon-String Model developed recently in ITEP we calculate spectra of charmed particlesD,D _s,Λ_c,Ξ_c,Ω_c in hadron-hadron collisions taking into account the decays ofS-wave resonances like D^*,D_s ^*,Σ_c,Σ_c ^*,Ξ_c ^*,Ξ_c ^′, and Ω_c ^*. We describe the bulk of the existing data onD, D^*, adΛ _c production in πp andpp collisions and predict the yield of charmed particlesin Σ^?p and Ξ^?p reactions at hyperon beam energies of 340 GeV/c and 600 GeV/c. Because of significant production of baryon resonances our predictions for unfavored fragmentation differ from predictions of other models which do not take resonance production into account.     

CP violation in decay rates of charged bottom mesons

In the standard theory we discuss a mechanism of interference between two different tree-level charged current amplitudes to induce CP violation. The asymmetry between conjugate Cabibbo disfavoured modes of charged bottom meson decays is considered. Estimates for two-body decays ofB _u andB _c are presented. We find thatB _u ^? →D ^?+D ₀ ^* , for instance, can give a big CP asymmetry with values ≈1–50%, depending on the angle and phase parameters.     

Production of vector and tensor mesons in proton-proton collisions at\sqrt s = 52.5 GeV

Inclusive production of ?⁰,f, andg ⁰ mesons and ofK _s ⁰ ,K ^*0 (892), ? andK ^*0(1430)mesons has been measured at <y>～2.6 and <p _T >～1.1 GeV/c in proton-proton interactions at \(\sqrt s = 52.5\) GeV. The negative particle from the two-body decays of these resonances were identified by a threshold Cerenkov counter and used for triggering. Starting from the measured differential cross section, total inclusive cross sections for the vector and tensor mesons were determined using various parametrizations for they andp _T dependence of the differential cross section. The experimental results are discussed in the framework of production models based on the parton picture. The strangeness suppresion factor λ=(0.30±0.10) due toSU(3) symmetry breaking of the quark sea is derived.     

Multiple quantum coherences: New NMR tools to study materials and living systems

Intermolecular multiple-quantum coherences have been proven in recent years to provide a novel contrast mechanism to study heterogeneity in liquid systems. This subject represents a source of remarkable interest in the fields of physics of matter and biomedicine. Recent results achieved on intermolecular double-quantum signal transverse relaxation decay in confined liquid systems (such as in vivo bone marrow in trabecular bone, and doped water in glass capillary pipes) are reported and discussed in this paper. Correlated two-dimensional spectroscopy revamped by asymmetricz-gradient echo detection-like sequences were implemented in order to perform intermolecular doublequantum transverse relaxationT _2DQ andT _2DQ ^* measurements. Our experimental results indicated that the relationshipT _2,n ^* =T ₂ ^* /n betweenn-quantum transverse relaxation time and the conventional singlequantumT ₂ ^* only applies for homogeneous systems and fails in the case of highly heterogeneous systems like porous systems.     

On the correlation between supercooling,superheating and kinetic arrest in a magnetic glass Pr<Subscript>0.5</Subscript>Ca<Subscript>0.5</Subscript>Mn<Subscript>0.975</Subscript>Al<Subscript>0.025</Subscript>O<Subscript>3</Subscript>

We report a quantitative investigation of the magnetic field-temperature phase diagram by taking into account a simple phenomenological model arising out of the interplay of kinetic arrest and thermodynamic transitions in a magnetic glass Pr_0.5Ca_0.5Mn_0.975Al_0.025O₃, through magnetization measurements. Such studies are necessary as kinetic arrest plays an important role in the formation of “magnetic glasses”, which has been observed in systems undergoing first order magnetic phase transitions. It has been shown that disorder in a system results in the formation kinetic arrest (H _K ,T _K ) band, like supercooling (H ^*,T ^*) and superheating (H ^**,T ^**) band. Quantitative proofs are given to show that (H _K ,T _K ) band is anticorrelated with (H ^*,T ^*) and (H ^**,T ^**) bands, while the later two are correlated among themselves. Analysis of time dependence of magnetization at different temperatures is carried out to establish the fact that the kinetic arrested state is different from the supercooled state.     

Pseudogap and its temperature dependence in YBCO from the data of resistance measurements

The temperature dependence of the excess conductivity Δσ for Δσ = A(1 ? T/T^*)exp(Δ^*/T) (YBCO) epitaxial films is analyzed. The excess conductivity is determined from the difference between the normal resistance extrapolated to the low-temperature range and the measured resistance. It is demonstrated that the temperature dependence of the excess conductivity is adequately described by the relationship Δσ = A(1 ? T/T^*)exp(Δ^*/T). The pseudogap width and its temperature dependence are calculated under the assumption that the temperature behavior of the excess conductivity is associated with the formation of the pseudogap at temperatures well above the critical temperature T _c of superconductivity. The results obtained are compared with the available experimental and theoretical data. The crossover to fluctuation conductivity near the critical temperature T _c is discussed.     

Supersymmetric signature in quarkonium decays

We calculate the heavy quarkonium decay widths for decays to scalar fermion-scalar antifermion pairs. In the light of the supersymmetric interpretation of the recently observed monojets, these decays could be observable in the forthcoming e⁺−e⁻ colliding beam machines. The scalar lepton-scalar antilepton pairs produced by toponium decays is comparable to those produced by direct photon exchanges. The decays of the scalar pair into an electron-positron (or muon-antimuon) pair (carrying about one-half of the total beam energy) together with the missing photinos will be a clean signature of supersymmetry.     

Constraints on cosmologically regenerated gravitinos

Cosmological constraints on the regenerated abundance of gravitinos as a function of the maximum reheating temperature T_h are examined. We combine the bound that arises in order for stable photinos produced by gravitino decays to not overdominate the mass density of the universe together with that inferred from the distortions produced in the cosmic microwave background radiation as well as constraints from the observed deuterium and ³He abundances. This suffices to constrain T_h to be below between 10¹⁷ and 10¹⁰ GeV for gravitions in the mass below ～ 10 TeV. More massive gravitinos, however, could be produced at T_h<10¹⁴ GeV.     

Discriminating scalar and pseudoscalar weak bosons via toponium → γ + boson

The production of Higg's or neutral technipion spin-zero bosons (szb) in toponium decay is examined. Different methods for determining the parity of these bosons are discussed. The decay width Γ(m³S₁ → γ + szb) is very sensitive to the parity of the szb and it is shown how comparing the widths of different toponium states can be used to determine the szb parity. The method is applicable for a szb within 30% of the toponium mass.     

Study of B<Subscript>s</Subscript>→D<Subscript>sJ</Subscript>(2317,2460)lν̄ semileptonic decays in the CQM model

Assuming D^* _sJ(2317) and D_sJ(2460) to be the (0⁺,1⁺) chiral partners of the regular particles D_s(1968) and D^* _s(2112), we calculate the semileptonic decays of B_s to D_s(1968), D^* _s(2112), D_sJ ^*(2317) and D_sJ(2460) in terms of the constituent quark meson model. The large branching ratios of the semileptonic decays of B_s to D_sJ ^*(2317) and D_sJ(2460) indicate that these two semileptonic decays should be seen in future experiments. PACS 12.25.Ft; 12.38.Lg; 12.39.Fe; 12.39.Hg