Studying the possibility of recovering np and nn helicity amplitudes on the basis of \vec p + \vec d and \vec n + \vec d scattering data at intermediate energies

In this work, we study the possibility of direct recovery of np helicity amplitudes, which are unknown at incident neutron energies T _n > 1.1 GeV, and nn helicity amplitudes, which are unknown at any energy, from data on $\vec p + \vec d$ and $\vec n + \vec d$ scattering. For the inversion of $\vec N + \vec d$ data, we use formulas that relate N _d- and NN amplitudes derived in terms of a refined Glauber model. It is found that the critical factors for solving the inverse problem under study are the accuracy and completeness of the set of input $\vec N + \vec d$ observables.     

Model-independent analysis of Higgs spin and CP properties in the process \boldsymbol{e}^{+} \boldsymbol{e}^{-} \to\boldsymbol{t}\bar{\boldsymbol{t}} \boldsymbol{\Phi}

In this paper we investigate methods to study the $t\bar{t}$ Higgs coupling. The spin and CP properties of a Higgs boson are analysed in a model-independent way in its associated production with a $t\bar{t}$ pair in high-energy e ⁺ e ^? collisions. We study the prospects of establishing the CP quantum numbers of the Higgs boson in the CP-conserving case as well as those of determining the CP-mixing if CP is violated. We explore in this analysis the combined use of the total cross section and its energy dependence, the polarisation asymmetry of the top quark and the up-down asymmetry of the antitop with respect to the top–electron plane. We find that combining all three observables remarkably reduces the error on the determination of the CP properties of the Higgs Yukawa coupling. Furthermore, the top polarisation asymmetry and the ratio of cross sections at different collider energies are shown to be sensitive to the spin of the particle produced in association with the top-quark pair.     

The phase and pole structure of the N*(1535) in \piN \rightarrow \piN and \gammaN \rightarrow \piN

The nature of some baryonic resonances is still an unresolved issue. The case of the N ^*(1535) is particularly interesting in this respect due to the nearby $ \eta$ N threshold and interference with the N ^*(1650) . The N ^*(1535) has been described as a threshold effect, as a genuine 3-quark resonance, or as dynamically generated from the interaction of the octet of baryons with the octet of mesons. In the scheme of dynamical generation, predictions for the interaction of the N ^*(1535) with the photon can be made. In this study, we simultaneously analyze the role of the N ^*(1535) in the $ \pi$ N $ \rightarrow$ $ \pi$ N and $ \gamma$ N $ \rightarrow$ $ \pi$ N reactions and compare to the respective amplitudes from partial-wave analyses. This test is very sensitive to the meson-baryon components of the N ^*(1535) .     

Effects of the mixing of scalar and pseudoscalar Higgs bosons in the process e^ + e^ - \to e^ + e^ - b\bar b at a future linear electron-positron collider

The sensitivity of data on the process $e^ + e^ - \to e^ + e^ - b\bar b$ at a future linear electron-positron collider to the deviation of the coupling of the Higgs boson to b quarks from the Standard Model predictions owing to the presence of a pseudoscalar Higgs boson state is analyzed for a collision energy of $\sqrt s = 500 Gev$ . The admixture of a new hypothetical pseudoscalar Higgs boson state in the $Hb\bar b$ vertex is parametrized in the form m _b /v(a + iγ ₅ b). On the basis of an analysis of data on the process $e^ + e^ - \to e^ + e^ - b\bar b$ , it is shown that experiments at the future linear collider TESLA will make it possible to constrain the parameters Δa = a ? 1 and b as ?0.056 ≤ Δa ≤ 0.055 and ?0.32 ≤ b ≤ 0.32, respectively.     

On the Quasi-linear Elliptic PDE {-\nabla \cdot ( \nabla{u}/ \sqrt{1-| \nabla{u} |^2}) = 4 \pi \sum_k a_k \delta_{s_k}} in Physics and Geometry

It is shown that for each finite number N of Dirac measures ${\delta_{s_n}}$ supported at points ${s_n \in {\mathbb R}^3}$ with given amplitudes ${a_n \in {\mathbb R} \backslash\{0\}}$ there exists a unique real-valued function ${u \in C^{0, 1}({\mathbb R}^3)}$ , vanishing at infinity, which distributionally solves the quasi-linear elliptic partial differential equation of divergence form ${-\nabla \cdot ( \nabla{u}/ \sqrt{1-| \nabla{u} |^2}) = 4 \pi \sum_{n=1}^N a_n \delta_{s_n}}$ . Moreover, ${u \in C^{\omega}({\mathbb R}^3\backslash \{s_n\}_{n=1}^N)}$ . The result can be interpreted in at least two ways: (a) for any number N of point charges of arbitrary magnitude and sign at prescribed locations s _n in three-dimensional Euclidean space there exists a unique electrostatic field which satisfies the Maxwell-Born-Infeld field equations smoothly away from the point charges and vanishes as |s| ?? ??; (b) for any number N of integral mean curvatures assigned to locations ${s_n \in {\mathbb R}^3 \subset{\mathbb R}^{1, 3}}$ there exists a unique asymptotically flat, almost everywhere space-like maximal slice with point defects of Minkowski spacetime ${{\mathbb R}^{1, 3}}$ , having lightcone singularities over the s _n but being smooth otherwise, and whose height function vanishes as |s| ?? ??. No struts between the point singularities ever occur.     

First search for double- \beta decay of platinum by ultra-low background HP Ge \gamma spectrometry

A search for double- $ \beta$ processes in ¹⁹⁰Pt and ¹⁹⁸Pt was realized with the help of ultra-low background HP Ge 468cm^3 $ \gamma$ spectrometer in the underground Gran Sasso National Laboratories of the INFN (Italy). After 1815 h of data taking with 42.5g platinum sample, T _1/2 limits on 2 $ \beta$ processes in ¹⁹⁰Pt ( $ \varepsilon$ $ \beta^{+}_{}$ and 2 $ \varepsilon$ have been established on the level of 10¹⁴-10¹⁶y, 3 to 4 orders of magnitude higher than those known previously. In particular, a possible resonant double-electron capture in ¹⁹⁰Pt was restricted on the level of 2.9×10¹⁶ y at 90% C.L. In addition, T _1/2 limit on 2 $ \beta^{-}_{}$ decay of ¹⁹⁸Pt (2 $ \nu$ +0 $ \nu$ ) to the 2⁺ ₁ excited level of ¹⁹⁸Hg has been set at the first time: T _1/2 > 3.5×10¹⁸ y. The radiopurity level of the used platinum sample is reported.     

Phenomenological model for the \overline{{K}}N \rightarrow K \Xi reaction

A phenomenological model for the $ \overline{{K}}$ N $ \rightarrow$ K $ \Xi$ reaction is suggested. The model includes s and u channel exchanges by $ \Lambda$ , $ \Sigma$ , $ \Sigma$ (1385) , and $ \Lambda$ (1520) and s channel exchanges by above-threshold hyperonic resonances. The explicit expression for the propagator for a particle with spin 7/2 is presented. High-mass and high-spin resonances play a significant role in the process. We deal with the whole set of existing experimental data on the cross-sections and polarizations in the energy range from the threshold to 2.8GeV in the center-of-mass system and reach a good agreement with experiments. Applications of the model to other elementary reactions of $ \Xi$ production and to $ \Xi$ hypernuclear spectroscopy are briefly discussed.     

Effects of scalar and pseudoscalar Higgs bosons in the process e^ + e^ - \to b\bar bv\bar v at the LEP II collider

The possibility of setting constraints on the couplings of the scalar or pseudoscalar Higgs boson to b quarks on the basis of data on the process $e^ + e^ - \to b\bar bv\bar v$ at the LEP II collider is investigated. The mixing of the scalar and the hypothetical pseudoscalar Higgs boson in the $Hb\bar b$ vertex is parametrized in the form $\frac{{m_b }}{v}(a + i\gamma _5 b)$ . An analysis of the differential distributions for the process $e^ + e^ - \to b\bar bv\bar v$ reveals that the contribution of the fusion subprocess WW → H in the channel involving an electron neutrino enhances the sensitivity of data to the parameters under analysis. It is shown that the LEP II data at $\sqrt s = 200$ GeV and $\smallint \mathcal{L}dt = 600 pb^{ - 1} $ per experiment would make it possible to constrain the parameters Δa = a ? 1 and b as follows: ?0.75 ≤ Δa ≤ 1.4 at b = 0 and free Δa and ?0.97 ≤ b ≤ 0.97 at Δa = 0 and free b.     

Corrections of order O(\bar \alpha \bar \alpha _s ) and O(\overline \alpha ^2 ) to the \bar bb-decay width of the neutral Higgs boson

Analytical expressions are presented for contributions of order $O(\overline \alpha \overline \alpha _s )$ and $O(\overline \alpha ^2 )$ to the $\bar bb$ -decay width of the neutral Higgs boson of the standard model of electroweak interactions. The numerical value of the mixed QED and QCD correction of order $O(\overline \alpha \overline \alpha _s )$ is comparable to other computed terms in the perturbation series.     

Mixings and CP violations of theB^0 - \bar B^0 system in the four-generation model

We study the mixings and CP violations in the \(B^0 - \bar B^0 \) system together with the \(K^0 - \bar K^0 \) one in the four-generation model, taking into account the ARGUS data for the \(B_d^0 - \bar B_d^0 \) mixing. We take typical six cases of the mixing hierarchy and search for the allowed regions of three phases in the 4×4KM matrix. The CP violating parameter ? _K in the \(K^0 - \bar K^0 \) system gives a severe constraint for the phases, and the smaller mixing than that in the three-generation model is predicted for the \(B_s^0 - \bar B_s^0 \) system. The asymmetry parameters for the two-body non-leptonic decays of theB ⁰ and \(\bar B^0 \) mesons are also predicted.     

The standard model process e^ + e^ - \to \nu \bar \nu b\bar b and its Higgs signal at LEP II

We present and study the results for the standard model process $e^ + e^ - \to \nu \bar \nu b\bar b$ at c.m. energies 150 ≤ √s(GeV) ≤ 240 and for Higgs boson masses 60 GeV ≤ m _H ≤ 110 GeV, obtained from all tree-level diagrams and including the most important radiative corrections. The matrix elements have been calculated by the ‘spinor bracket’ method without neglecting masses, which is presented in detail. The √s-dependence and the interference properties of the Higgs boson contributions and of various coherent background contributions to the total cross section are examined and compared. The important differential distributions for the Higgs boson and the background components are studied, providing information useful for choosing cuts in Higgs searches. We also examine the effect of a minimal set of cuts and evaluate the importance of the WW fusion for detecting a higher mass Higgs boson at LEP II.     

Alternative technique for Standard Model estimation of the rare kaon decay branchings \left. {BR(K \to \pi \nu \bar \nu )} \right|_{SM}

We estimate $BR(K \to \pi \nu \bar \nu )$ in the context of the Standard Model by fitting for λ _t≡V _tdV _ts ^* of the “kaon unitarity triangle” relation. To find the vertex of this triangle, we fit data from |? _K|, the CP-violating parameter describing K mixing, and a _ψ,K , the CP-violating asymmetry in B _d ⁰ → J/ψK ⁰ decays, and obtain the values $\left. {BR(K \to \pi \nu \bar \nu )} \right|_{SM} = (7.07 \pm 1.03) \times 10^{ - 11} $ and $\left. {BR(K_L^0 \to \pi ^0 \nu \bar \nu )} \right|_{SM} = (2.60 \pm 0.52) \times 10^{ - 11} $ . Our estimate is independent of the CKM matrix element V _cb and of the ratio of B-mixing frequencies ${{\Delta m_{B_s } } \mathord{\left/ {\vphantom {{\Delta m_{B_s } } {\Delta m_{B_d } }}} \right. \kern-0em} {\Delta m_{B_d } }}$ . We also use the constraint estimation of λ _t with additional data from $\Delta m_{B_d } $ and |V _ub|. This combined analysis slightly increases the precision of the rate estimation of $K^ + \to \pi ^ + \nu \bar \nu $ and $K_L^0 \to \pi ^0 \nu \bar \nu $ (by ?10 and ?20%, respectively). The measured value of $BR(K^ + \to \pi ^ + \nu \bar \nu )$ can be compared both to this estimate and to predictions made from ${{\Delta m_{B_s } } \mathord{\left/ {\vphantom {{\Delta m_{B_s } } {\Delta m_{B_d } }}} \right. \kern-0em} {\Delta m_{B_d } }}$ .     

TheZ-width in the two Higgs doublet model

Effects from an extended Higgs sector on the partial widths \(\Gamma _{{\rm Z} \to b\bar b} \) and \(\Gamma _{{\rm Z} \to \tau ^ + \tau ^ - } \) are analysed with emphasis on enhanced Yukawa couplings to the fermions with the weak isospinT ₃=?1/2. Contributions from charged and neutral Higgs bosons are incorporated. Vertex corrections from a heavy top quark and from charged Higgs bosons are always negative. One can however find regions in the parameter space where neutral Higgs bosons lead to positive vertex corrections. The charged Higgs bosons decouple from the ratio \(\Gamma ^{_{{\rm Z} \to \tau ^ + \tau ^ - } } /\Gamma ^{_{{\rm Z} \to \mu ^ + \mu ^ - } } \) if their mass is beyond 80 GeV. This ratio is then sensitive to the neutral sector only.     

A new model forN \bar N annihilation

A new quark model forN \(\bar N\) annihilation is proposed. It is argued that a linear superposition of the so-called³P₀ and³S₁ models is more consistent with QCD and the inclusion of quark degrees of freedom inNN scattering, and is also suggested by the data. A comparison is made, in Born approximation, with the angular distribution for \(p\bar p \to \Lambda \bar \Lambda \) .     

Conserved-vector-current hypothesis and the\bar v_e e^ - \to \pi ^ - \pi ^0 process

Based on the conserved-vector-current (CVC) hypothesis and a four-ρ-resonance unitary and analytic VMD model of the pion electromagnetic form factor, theσ _tot(E _v ^lab ) and dσdE _π ^lab of the weak \(\bar v_e e^ - \to \pi ^ - \pi ^0\) process are predicted theoretically for the first time. Their experimental approval could verify the CVC hypothesis for all energies above the two-pion threshold. Since, unlike the electromagnetic e⁺e^?→π⁺π^? process, there is no isoscalar vector-meson contribution to the weak \(\bar v_e e^ - \to \pi ^ - \pi ^0\) reaction, accurate measurements of theσ _tot(E _v ^lab ) that moreover is strengthened with energyE _v ^lab linearly could solve now a widely discussed problem of the mass specification of the first excited state of theρ(770) meson. As a by-product, an equality \(\sigma _{tot} (\bar v_e e^ - \to \pi ^ - \pi ^0 ) = \sigma _{tot} (e^ + e^ - \to \pi ^ - \pi ^0 )\) is predicted for \(\sqrt s \approx 70 GeV\) .     

Charmonium rescattering effects in \psi(2S) \rightarrow \gamma \eta_{c}^{} decay

Charmonium rescattering effects in the M1 transition of $ \psi$ (2S) $ \rightarrow$ $ \gamma$ $ \eta_{c}^{}$ are investigated by modeling a $ \chi_{{cJ}}^{}$ or J/ $ \psi$ rescattering into a $ \eta_{c}^{}$ final state. The absorptive and dispersive part of the transition amplitudes for the rescattering loops of $ \eta$ $ \psi$ ( $ \gamma^{{\ast}}_{}$ ) and $ \gamma$ $ \chi$ ( $ \psi$ ) are separately evaluated. The numerical results show that the contribution from the $ \gamma$ $ \chi$ ( $ \psi$ ) rescattering process is negligible. Compared with the virtual D $ \bar{{D}}$ (D ^*) rescattering processes, the $ \eta$ $ \psi$ ( $ \gamma^{{\ast}}_{}$ ) process may be regarded as the next-leading order of the hadronic loop mechanism, which only offers the partial decay width of ～ 0.045 keV to the $ \psi$ (2S) $ \rightarrow$ $ \gamma$ $ \eta_{c}^{}$ .     

B^0 - \bar B^0 mixing within and beyond the standard model

The standard model with three fermion families is found to be compatible with the Argus observation of a relatively large amount of \(B_{^d }^0 - \bar B_d^0 \) mixing provided that the top quark is rather heavy. From an analysis of the existing information on mixing angles, and of the constraints imposed by the kaon system, in particular by the ε parameter, we conclude that almost certainlym _t <45 GeV and probablym _t >90 GeV. In view of the Argus result the standard model unambiguously leads to the prediction of a nearly maximal amount of \(B_{^s }^0 - \bar B_s^0 \) mixing. Apart from the rather obvious case of a fourth family of quarks, most “minimal” extensions of the standard model preserve the prediction of a large \(B_{^s }^0 - \bar B_s^0 \) mixing. We discuss \(B^0 - \bar B^0 \) mixing in minimal supersymmetric models compatible with the UA1 lower bounds on gluino and squark masses. Contributions from charged Higgs exchange in the box diagrams are also discussed. While supersymmetry (although marginally) and charged Higgses can lead to an appreciable enhancement of \(B^0 - \bar B^0 \) mixing, minimal left-right symmetric models actually predict a modest suppression of the effect with respect to the standard model.     

High-spin excitations of the odd-odd 88 37Rb51 and 86 35Br51 nuclei: \pip3/2 \nud5/2 and \pif5/2 \nud5/2 residual interactions

The odd-odd ⁸⁸ ₃₇Rb₅₁ and ⁸⁶ ₃₅Br₅₁ nuclei have been produced as fission fragments in the fusion reaction ¹⁸O$ + $²⁰⁸Pb at 85MeV bombarding energy and studied with the Euroball IV array. Their high-spin level schemes have been built from the triple $ \gamma$ -ray coincidence data and $ \gamma$ - $ \gamma$ angular correlations have been analyzed in order to assign spin and parity values to many observed states. The proposed configurations involve proton excitations from three sub-shells located close to the Fermi levels, $ \pi$ p _3/2 , $ \pi$ f _5/2 , and $ \pi$ g _9/2 , the $ \nu$ d _5/2 neutron acting as a spectator. The residual $ \pi$ $ \nu$ interactions are extracted from the multiplets of states resulting from the $ \pi$ p _3/2 $ \nu$ d _5/2 and $ \pi$ f _5/2 $ \nu$ d _5/2 configurations. The empirical values of the latter are discussed and compared to those known in two similar configurations having j _p = j _n with l _p = l _n + 1 , where the role of the tensor force had been highlighted.     

Mass mixing,CP violation and left-right symmetry for heavy neutral mesons

We investigate \(M^0 - \bar M^0 \) mixing and CP violation in the minimal left-right symmetric gauge model with spontaneous P and CP violation. The dominant contributions to the mixing amplitude including QCD corrections are calculated explicitly for \(B^0 - \bar B^0 \) . While the amount of mixing is not much changed with respect to the standard model leftright symmetry can give rise to significantly larger CP violation in the \(B_s^0 - \bar B_s^0 \) system (up to two orders of magnitude for the dilepton charge asymmetry). Sizable CP violating effects require that the left-right contribution to theK _L K _S mass difference has the same sign as the standard model contribution. We also comment on \(D^0 - \bar D^0 \) mixing including a careful discussion of the standard model prediction for the short distance part.