Coherence ofu\bar u andd\bar d final states: Possible influence onZ 0 decay width ande + e − annihilation cross section

The decay width of theZ ⁰ associated with its coupling tou andd quarks is usually expressed as the incoherent sum of the widths into \(u\bar u\) and \(d\bar d\) final states, \(\Gamma (u\bar u) + \Gamma (d\bar d)\) . We examine a specific correction to this estimate arising from the coherence of the \(u\bar u\) and \(d\bar d\) systems, dictated by isospin symmetry. The decay width is written in the alternative form Γ(G=+1)+Γ(G=?1), which recognises that final hadronic states can be classified according to even and odd G-parity. Assuming that states withG=+1(?1) evolve from configurations containing even (odd) numbers ofG=?1 systems, and considering various multiplicity distributions for such systems, small corrections are obtained relative to the conventional estimate. A similar analysis applied to the cross section for \(e^ + e^ - \to u\bar u, d\bar d\) yields small energy-dependent corrections to the parameter R.     

Decay energy of183Re→183W

The electron capture decay energy of¹⁸³Re has been determined from the fraction ofK-capture in the transition to the 453.08 keV level in¹⁸³W by delayed coincidences. From this value the total decay energy from₁₈₃Re→¹⁸³W is obtained to beQ=555 _?7 ⁺⁹ keV according to the theory ofBrysk andRose with corrections ofBahcall. The resulting logft values and consequences for the decay scheme are discussed.     

Wino and zino production inp\bar p collisions: first order supersymmetric QCD corrections

We compute the first order supersymmetric QCD correction to wino \((\tilde W)\) and zino \((\tilde Z)\) production in \(p\bar p\) collisions via subprocesses involving two massless partons inside the nucleon or one massless parton and a massive SUSY parton (squark or gluino). The first order SQCD corrections to the rapidity dependence at CERN collider and Tevatron energies are found large (K～2). The rates are important (～10^?2 nb at \(\sqrt s = 630\) GeV and ～10^?1 nb at \(\sqrt s = 2\) TeV), as soon as the \((\tilde W)\) and \((\tilde Z)\) production by squarks is allowed. Transverse momentum distributions are also given and their shape is found very sensitive to the presence of SUSY partons inside the nucleon.     

Single decay-lepton angular distributions in polarizede + e − →\overline {tt} and simple angular asymmetries as a measure of CP-violating top dipole couplingsand simple angular asymmetries as a measure of CP-violating top dipole couplings

In the presence of an electric dipole coupling of $\overline {tt} $ to a photon, and an analogous ‘weak’ dipole coupling to the Z, CP violation in the process e⁺e^? → $\overline {tt} $ results in modified polarization of the top and the anti-top. This polarization can be analyzed by studying the angular distributions of decay charged leptons when the top or anti-top decays leptonically. Analytic expressions are presented for these distributions when eithert or $\overline t $ decays leptonically, including $\mathcal{O}$ (α_s) QCD corrections in the soft-gluon approximation. The angular distributions are insensitive to anomalous interactions in top decay. Two types of simple CP-violating polar-angle asymmetries and two azimuthal asymmetries, which do not need the full reconstruction of thet or $\overline t $ , are studied. Independent 90% CL limits that may be obtained on the real and imaginary parts of the electric and weak dipole couplings at a linear collider operating at √ s = 500 GeV with integrated luminosity 500 fb^? and also at √s = 1000 GeV with integrated luminosity 1000 fb^? have been evaluated. The effect of longitudinal electron and/or positron beam polarizations has been included.     

TheW-boson width

The analytic formulae for the partial decay widthW ⁺→ \(f_1 \bar f_2 \) are presented including the 1-loop electroweak and QCD corrections for arbitrary masses of the fermions. Numerical results are discussed for the physically interesting cases \(W^ + \to t\bar b\) and for the decay into a heavy leptonl ⁺ and a neutrino of a fourth fermion generation. Also the results for the totalW width and the partial width into light fermion pairs are listed.     

Quark-diagram estimates ofCP violation in two-body baryonicB_d^0 - \bar B_d^0 decays

CP violation in partial-decay-rate asymmetries are examined for some two-body baryonic decays of \(B_d^0 - \bar B_d^0 \) system. We discuss two feasible experimental circumstances: the symmetrice ⁺ e ^? collisions (i) on theZ ⁰ resonance to produce incoherent \(B_d^0 \bar B_d^0 \) states, and (ii) just above the ?(4S) resonance to produceC=even \(B_d^0 \bar B_d^0 \) states. Using the quark-diagram scheme, we estimate the branching ratios of those decays, and the numbers ofb \(\bar b\) pairs needed for testing theCP-violating effects for 3σ signature. We find that the promising channels may beB _d ⁰ , \(\bar B_d^0 \to p\bar p\) , \(\Delta ^ + \bar \Delta ^ - \) , \(p\bar \Delta ^ - \) , \(\Delta ^ + \bar p\) , \(n\bar n\) , \(\Delta ^0 \bar \Delta ^0 \) , \(n\bar \Delta ^0 \) , \(\Delta ^0 \bar n\) , \(\Sigma _c^ + \bar \Sigma _c^ - \) , \(\Lambda _c^ + \bar \Lambda _c^ - \) , \(\Sigma _c^ + \bar \Lambda _c^ - \) , \(\Lambda _c^ + \bar \Sigma _c^ - \) , \(\Sigma _c^0 \bar \Sigma _c^0 \) , \(\Xi _c^0 \bar \Xi _c^0 \) , which should be interesting for experimental observation.     

Factorizable electroweak \mathcal{O}(\alpha) corrections for top quark pair production and decay at a linear e^+e^- collider

We calculate the standard model predictions for top quark pair production and decay into six fermions at a linear e⁺e^- collider. We include the factorizable electroweak $\mathcal{O}(\alpha)$ corrections in the pole approximation and QED corrections due to the initial state radiation in the structure function approach. The effects of the radiative corrections on the predictions are illustrated by showing numerical results for two selected six-fermion reactions $e^+e^-\rightarrow b\nu_{\mu}\mu^+\bar{b}\mu^-\bar{\nu}_\mu$ and $e^+e^-\rightarrow b\nu_{\mu}\mu^+\bar{b}d\bar{u}$ .     

ARCLUS—A new jet clustering algorithm inspired by the Colour Dipole Model

A new jet clustering algorithm-Arclus-is presented. The main difference between this and conventional algorithms is that while the latter in each step join two clusters into one,Arclus joins three clusters into two. The performance ofArclus in terms of the size of hadronization corrections is studied for some jet-reconstruction tasks ine ⁺ e ^? andep collisions, and is found to be as good as or, for some tasks inep collisions, better than conventional clustering algorithms.     

O(α s ) corrections to the polar angle dependence of the longitudinal spin–spin correlation asymmetry in e^{+}e^{-}\to q\bar{q}

We provide analytical results for the O(α _s ) corrections to the polar angle dependence of the longitudinal spin–spin correlation asymmetry in $e^{+}e^{-}\to q\bar{q}$ . For top quark pair production the O(α _s ) corrections to the longitudinal spin–spin asymmetry are strongly polar angle dependent and can amount up to ?4% in the q ²-range from above $t\bar{t}$ threshold up to $\sqrt{q^{2}}=1000\ \mbox {GeV}$ . The O(α _s ) radiative corrections to the correlation asymmetry are below ≈1% in the forward direction where the cross section is largest. In the $e^{+}e^{-}\to b\bar{b}$ case the O(α _s ) corrections reduce the asymmetry value from its m _b =0 value of ?100% to approximately ?96% for q ²-values around the Z peak and are practically independent of the value of the polar angle θ. This reduction can be traced to finite anomalous contributions from residual mass effects which survive the m _b →0 limit. We discuss the role of the anomalous contributions and the pattern of how they contribute to spin-flip and non-flip terms.     

Long distance effects inb→s exclusive decays

We estimate long distance corrections to radiativeB →K ^*γ and to non leptonicB→Kπ,B→K ^*π,B→Kσ,B→K ^*σ,B→KΦ andB→K ^*Φ decays generated by the ( \(\overline b\) c) ( \(\overline c\) s) part of the non leptonic weak Hamiltonian. While vanishing in the vacuum saturation approximation, these corrections are finite if one includes single particle charmed states between the currents in the Hamiltonian. We find small effects in radiative decays, but significant contributions to several non leptonic processes.     

Toward the theory of electron and positron states in dielectric clusters

Analytical expressions for the binding energy of electrons and positrons in dielectric clusters, analyzed in this work, neglect the elastic effects. Therefore, we present the density-functional theory for neutral liquid clusters that experience the spontaneous deformation. Using the 1/R-expansion, R being the cluster radius, the exact analytical expressions for the size corrections to the chemical potential, surface tension, and atomic density are derived from the condition of mechanical equilibrium. The problem of calculating these corrections is reduced to calculating the quantities for a liquid with a flat surface. The size compression and tension of density occur in the 1/R and 1/R ² orders respectively. The sizes of charged rigid and elastic critical clusters, for which the electron or positron binding energy is close to zero, are calculated for Xe _N ^? , Kr _N ^? , Ar _N ^? , Ne _N ⁺ , He _N ⁺ . The calculations show significant contribution of self-compression to the binding energy of the excess electron in contrast to the positron.     

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.     

Benchmark cross sections forp \bar p collisions at 1.8 TeV

High-energyp \(\bar p\) collisions provide many quantitative tests of the standard model. Of particular interest are “hard scattering” processes, which test not only standard model matrix elements and higher order perturbative corrections, but also the distributions of quarks and gluons in the colliding hadrons. We present detailed comparisons of data from the CERNSp \(\bar p\) S collider with theory, incorporating up-to-date parton distributions derived from recent deep inelastic scattering data. Encouraged by the excellent agreement between data and theory at \(\sqrt s \) =630GeV, we present a complete set of “benchmark” predictions for the FNALp \(\bar p\) collider at \(\sqrt s \) =1.8TeV.     

Radiative open charm decay of the Y(3940) , Z(3930) , X(4160) resonances

We determine the radiative decay amplitudes for the decay into D^* and $ \bar{{D}}$ $ \gamma$ , or D ^* _s and $ \bar{{D}}_{s}^{}$ $ \gamma$ of some of the charmonium-like states classified as X , Y , Z resonances, plus some other hidden charm states which are dynamically generated from the interaction of vector mesons with charm. The mass distributions as a function of the $ \bar{{D}}$ $ \gamma$ or $ \bar{{D}}_{s}^{}$ $ \gamma$ invariant mass show a peculiar behavior as a consequence of the D ^* $ \bar{{D}}^{*}_{}$ nature of these states. The experimental search of these magnitudes can shed light on the nature of these states.     

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) .     

CP-violating asymmetries in penguin-inducedB-meson decays beyond the leading logarithmic approximation

We investigate CP-violating phenomena both in semi-inclusive and exclusive penguin-inducedB-meson decays by using low energy effective Hamiltonians for |ΔB|=1, ΔC=ΔU=0 transitions including leading and next-to-leading order OCD corrections. In particular, we discuss the renormalization scheme dependences arising beyond the leading order and their explicit cancellation for the physical transition amplitudes. In order to estimate the hadronic matrix elements needed for the exclusive penguin modes, we apply both the Bauer, Stech, Wirbel model and the meson model of Brodsky and Lepage. Numerical results are presented for semi-inclusive \(b \to q'\bar qq(q',q \in \{ d,s\} )\) modes and the exclusive decaysB ^?→K ^? K ⁰, \(B^ - \to \pi ^ - \bar K^0 \) , and \(B_d^0 \to K^0 \bar K^0 \) .     

{\Xi} Hypernucler States Predicted by the New Interaction Model ESC08c

The features of the new interaction model ESC08c in ${\Lambda N}$ , ${\Sigma N}$ and ${\Xi N}$ channels are demonstrated single hyperon potentials ${U_Y(Y=\Lambda, \Sigma, \Xi)}$ in nuclear matter on the basis of the G-matrix theory. (K ^?, K ⁺) productions of ${\Xi}$ hypernuclei are studied with ${\Xi}$ -nucleus folding potentials.     

Search for the K L 0 → π0ν \tilde v decay at the INEP U-70 accelerator: The KLOD project

The rare decay K _L ⁰ → π⁰ν $ \tilde v $ branching ratio measurement is one of the clearest Standard Model test. Calculations based on the SM predict Br(K _L ⁰ → π⁰ν $ \tilde v $ ) ≈ 2.8 × 10^?11, but the most accurate experimental value Br(K _L ⁰ → π⁰ν $ \tilde v $ ) < 6.7 × 10^?8 (90% C.L.). We present design of a new experimental setup KLOD (U-70 accelerator, IHEP, Protvino) for K _L ⁰ → π⁰ν $ \tilde v $ branching ratio measurement. Sensitivity of the KLOD experiment will be enough for registration of 2.4 events K _L ⁰ → π⁰ν $ \tilde v $ for every 10 days of the data taking (according to SM predictions).