Associative open charm photoproduction $$\gamma + N \to Y_c + \bar D_c (\bar D_c^ * ), Y_c = \Lambda _c^ + or \Sigma _c $$

We analyze polarization effects in associative photoproduction of pseudoscalar\((\bar D_c )\) and vector\((\bar D_c^ * )\) charmed mesons in exclusive processes\(\gamma + N \to Y_c + \bar D_c , Y_c = \Lambda _c^ + , \Sigma _c \). We calculate the differential cross section and all polarization observables in framework of au effective Lagrangian approach. In case of collinear kinematics it is possible to give model independent predictions for polarization observables in case of\(\bar D_c \) production, and the analysis for\(\bar D_c^ * \) is largely simplified.     

Polarization correlations in thee^ - + e^ + \to \Lambda + \widetilde\Sigma ^0 process

In this work consequences of interference between weak neutral and electromagnetic currents for the \(e^ - e^ + \to \Lambda \widetilde\Sigma ^0 \) process are discussed. Quantitative estimates show that effects related to the polarization correlations and asymmetries of exit angles for final particles in this process are, for presently attainable energies of colliding beams, of the order of several percent. In principle, this allows one to establish details of the interaction.     

\bar v_e + d \to \bar v_e + n + pat reactor energies

The deuteron disintegration process \(\bar v_e + d \to \bar v_e + n + p\) is calculated at reactor energies using the antineutrino spectra given by various authors. Numerical results are presented and compared with the experimental and other theoretical results.     

QCD corrections to the reactionp + \bar p \to W + \gamma + X

The complete order α _S QCD corrections to the cross section and differential distributions for \(p + \bar p \to W + \gamma + X\) are presented. At the quark level this involves the computation of the contributions from the reactions \(q + \bar q \to W + \gamma + g and q(\bar q) + g \to W + \gamma + q + (\bar q)\) . We discuss how these corrections modify the factorization property of the lowest order amplitude and give results for future experiments at CERN and Fermilab.     

Overview of the CKM physics opportunities beyond K^ + \to \pi ^ + \nu \bar \nu

A new experiment CKM is accepted by Fermilab for a very sensitive study of rare kaon decay $K^ + \to \pi ^ + \nu \bar \nu $ on an intense separated kaon beam. The high quality of the beam and CKM setup make it possible to perform an important set of other kaon-decay measurements in parallel with the main research program: (1) the search for new physics effects beyond the Standard Model (search for new P, S, T interactions and lepton flavor violation in kaon decays); (2) further search for direct CP violation in charged kaon decays; (3) study of low-energy hadron physics in pure conditions of decay processes (K ⁺ → π ⁺ l ⁺ l ^?; ππlν _l; π ⁰ γγ, etc.). The expected results of these studies are compared with other experimental programs.     

A kinematically complete measurement of K^+ \to \pi^+ \pi^0 \pi^0 decays

In a kinematically complete setting, the decays of stopped were measured. In the frame work of the Weinberg polynomial expansion, the coefficients up to quadratic terms were deduced. The results are in good agreement with previous measurements and consistent with CP conservation expectations. The empirical rule is violated. Received: 16 October 1999 / Published online: 27 January 2000     

\pi\pi correlations in \gamma + A reactions

Preliminary differential cross-sections of the reactions and with A = ¹ H, ¹² C, and ^nat Pb are presented. A significant nuclear-mass dependence of the invariant-mass distribution is found in the channel. The dependence is not observed in the channel. The in-medium observation in the channel is consistent with an in-medium modification of the interaction in the I = J = 0 channel, changing width and pole position of a resonant state.Received: 30 September 2002, Published online: 22 October 2003PACS: 13.60.Le Meson production - 21.65. + f Nuclear matterJ.G. Messchendorp: For the TAPS and A2 Collaborations     

Suggestion for Einstein-Podolsky-Rosen experiments using reactions likee^ + e^ - \to \Lambda \bar \Lambda \to \pi ^ - p\pi ^ + \bar p

Since weakly decaying particles are their own polarimeters, reactions like \(\eta _c \to \Lambda \bar \Lambda , \psi \to \Lambda \bar \Lambda ,e^ + e^ - \to \mu ^ + \mu ^ -\) , etc. are interesting for testing the non-locality of quantum mechanical predictions. Although such reactions, in principle, do not exclude all classes of hidden variable theories, they can be used to complement current experiments with external polarimeters. The reaction \(\eta _c \to \Lambda \bar \Lambda \to \pi ^ - p\pi ^{ + - } \bar p\) is conceptually the simplest and most useful as agedanken experiment, although it has not yet been seen experimentally. The reaction \(e^ + e^ - \to \Lambda \bar \Lambda \to \pi ^ - p\pi ^ + \bar p\) near threshold or at the φ resonance can be used for essentially the same test. This is feasible with presently available data and would be the first EPR experiment involving weak interactions.     

Recent results on the {K^-_{\rm stop} + A\rightarrow \Sigma^\pm + \pi^\mp + A^{\prime}} reaction with FINUDA

A study of the $K^-_{\rm stop}A\rightarrow \Sigma^\pm\pi^\mp A^{\prime}$ reaction in some p-shell nuclei, i.e., ^6,7Li, ⁹Be, ¹³C and ¹⁶O, performed by the FINUDA experiment, is reported.     

Electroweak asymmetries in the processe^ - + e^ + \to \tilde f + \tilde f in various gauge models

The creation of a pair of scalar fermion partners accompanying the annihilation of arbitrarily polarized electrons and positrons is studied in the gauge models SU(2)× U(l), SU(2)_L× SU(2)_R× U(1), and SU(3)× U(1). Different electroweak asymmetries are found and analyzed in detail (right-left asymmetry a_rl, P-even transversal spin asymmetry a₁ and P-odd asymmetry A₂) for the e^–e⁺-beam energies s=40–360 GeV and the Weinberg parameter values 0.21 sin²_W0.27. The computations show that the presence of weak neutral currents also leads to noticeable electroweak asymmetries, which are sensible to the choice of the gauge model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 78–82, May, 1989.     

Calculation of pure annihilation type decay B^+ \to D_s^+ \phi

The rare decay can occur only via annihilation-type diagrams in the standard model. We calculated this decay in the perturbative QCD approach with Sudakov resummation. We found that the branching ratio of is of order ; this may be measured in the near future by the KEK and SLAC B factories. The small branching ratio predicted in the standard model makes this channel sensitive to new physics contributions. Received: 16 January 2002 / Published online: 5 April 2002