Electroweak non-resonant NLO corrections to e+ e- -> W+ W- b bbar in the t tbar resonance region

We analyse subleading electroweak effects in the top anti-top resonance production region in e+ e- collisions which arise due to the decay of the top and anti-top quarks into the W+ W- b bbar final state. These are NLO corrections adopting the non-relativistic power counting v ~ alpha_s ~ sqrt(alpha_EW). In contrast to the QCD corrections which have been calculated (almost) up to NNNLO, the parametrically larger NLO electroweak contributions have not been completely known so far, but are mandatory for the required accuracy at a future linear collider. The missing parts of these NLO contributions arise from matching coefficients of non-resonant production-decay operators in unstable-particle effective theory which correspond to off-shell top production and decay and other non-resonant irreducible background processes to t tbar production. We consider the total cross section of the e+ e- -> W+ W- b bbar process and additionally implement cuts on the invariant masses of the W+ b and W- bbar pairs.Comment: LaTeX, 33 pages, 6 figure

Conceptual aspects of QCD factorization in hadronic B decays

I review the meaning of ``QCD factorization'' in hadronic two-body B decays and then discuss recent results of theoretical (rather than phenomenological) nature: the proof of factorization at two loops; the identification of ``chirally enhanced'' power corrections; and the role of annihilation contributions.Comment: 10 pages, LaTeX. Based on talks presented at the UK Phenomenology Workshop on Heavy Flavour and CP Violation, 17 - 22 September 2000, Durham, proceedings to appear in J. Phys. G; the 5th International Symposium on Radiative Corrections (RADCOR2000), Carmel, California, September 11 - 15, 2000; the 4th Workshop on Continuous Advances in QCD, Minneapolis, 12-14 May 2000; the Vth International Workshop on Heavy Quark Physics, Dubna, 6-8 April 200

Electroweak non-resonant corrections to top pair production close to threshold

The production of W+ W- b bbar from e+ e- collisions at energies close to the t tbar threshold is dominated by the resonant process with a nearly on-shell t tbar intermediate state. The W b pairs in the final state can also be reached through the decay of off-shell tops or through background processes containing no or only single top quarks. This non-resonant production starts to contribute at NLO to the W+ W- b bbar total cross section in the non-relativistic power-counting v ~ alpha_s ~ sqrt(alpha_EW). The NLO non-resonant corrections presented in this talk represent the non-trivial NLO electroweak corrections to the e+ e- -> W+ W- b bbar cross section in the top anti-top resonance region. In contrast to the QCD corrections which have been calculated (almost) up to NNNLO, the parametrically larger NLO electroweak contributions have not been completely known so far, but are mandatory for the required accuracy at a future linear collider. We consider the total cross section of the e+ e- -> W+ W- b bbar process and additionally implement cuts on the invariant masses of the W+ b and W- bbar pairs.Comment: Talk presented at the 35th International Conference of High Energy Physics - ICHEP2010, July 22-28, 2010, Paris France. 4 pages, 2 figure

Power counting and effective field theory for charmonium

We hypothesize that the correct power counting for charmonia is in the parameter Lambda_QCD/m_c, but is not based purely on dimensional analysis (as is HQET). This power counting leads to predictions which differ from those resulting from the usual velocity power counting rules of NRQCD. In particular, we show that while Lambda_QCD/m_c power counting preserves the empirically verified predictions of spin symmetry in decays, it also leads to new predictions which include: A hierarchy between spin singlet and triplet octet matrix elements in the J/psi system. A quenching of the net polarization in production at large transverse momentum. No end point enhancement in radiative decays. We discuss explicit tests which can differentiate between the traditional and new theories of NRQCD.Comment: 18 pages, 1 figure Replaced plot of the psi polarization parameter alpha as a function of transverse momentum. Alpha is now closer to zero for large transverse moment

Rare radiative exclusive B decays in soft-collinear effective theory

We consider rare radiative B decays such as B -> K^* gamma or B -> rho gamma in soft-collinear effective theory, and show that the decay amplitudes are factorized to all orders in alpha_s and at leading order in Lambda/m_b.By employing two-step matching, we classify the operators for radiative B decays in powers of a small parameter lambda(~ \sqrt{Lambda/m_b}) and obtain the relevant operators to order lambda in SCET_I. These operators are constructed with or without spectator quarks including the four-quark operators contributing to annihilation and W-exchange channels. And we employ SCET_II where the small parameter becomes of order Lambda/m_b, and evolve the operators in order to compute the decay amplitudes for rare radiative decays in soft-collinear effective theory. We show explictly that the contributions from the annihilation channels and the W-exchange channels vanish at leading order in SCET. We present the factorized result for the decay amplitudes in rare radiative B decays at leading order in SCET, and at next-to-leading order in alpha_s.Comment: v2: 31 pages, 11 figures. An appendix is added about the quark mass effects on radiative B decay

Kinematic Enhancement of Non-Perturbative Corrections to Quarkonium Production

In this letter we address issues involved in quarkonium production near the boundaries of phase space. It is shown that higher-order non-perturbative contributions are enhanced in this kinematic region and lead to a breakdown of the non-relativistic (NRQCD) expansion. This breakdown is a consequence of sensitivity to the kinematics of soft gluon radiation and to the difference between partonic and hadronic phase space. We show how these large corrections can be resummed giving the dominant contribution to the cross section. The resummation leads to the introduction of non-perturbative, universal distribution functions. We discuss the importance of these shape functions for several observables, in particular the energy distribution of photo-produced $J/\psi$ close to the endpoint.Comment: Latex 13 page

Risk assessment of MRSA isolates from swine using a diagnostic DNA microarray

The aim of this study was to support a risk assessment of MRSA-isolates from swine using a diagnostic DNA-microarray to detect virulence-, toxin- and resistance related genes. In comparison with other species like poultry, cattle and humans there were only few isolates with virulence genes

Quarkonium momentum distributions in photoproduction and B decay

According to our present understanding many $J/\psi$ production processes proceed through a coloured $c\bar{c}$ state followed by the emission of soft particles in the quarkonium rest frame. The kinematic effect of soft particle emission is usually a higher-order effect in the non-relativistic expansion, but becomes important near the kinematic endpoint of quarkonium energy (momentum) distributions. In an intermediate region a systematic resummation of the non-relativistic expansion leads to the introduction of so-called `shape functions'. In this paper we provide an implementation of the kinematic effect of soft gluon emission which is consistent with the non-relativistic shape function formalism in the region where it is applicable and which models the extreme endpoint region. We then apply the model to photoproduction of $J/\psi$ and $J/\psi$ production in $B$ meson decay. A satisfactory description of $B$ decay data is obtained. For inelastic charmonium photoproduction we conclude that a sensible comparison of theory with data requires a transverse momentum cut larger than the currently used 1 GeV.Comment: latex, 45 pages; (v2) some typos corrected, version to appear in PR

Radiative B decays to the axial KK mesons at next-to-leading order

We calculate the branching ratios of $B\to K_1\gamma$ at next-to-leading order (NLO) of $\alpha_s$ where $K_1$ is the orbitally excited axial vector meson. The NLO decay amplitude is divided into the vertex correction and the hard spectator interaction part. The one is proportional to the weak form factor of $B\to K_1$ transition while the other is a convolution between light-cone distribution amplitudes and hard scattering kernel. Using the light-cone sum rule results for the form factor, we have \calB(B^0\to K_1^0(1270)\gamma)=(0.828\pm0.335)\times 10^{-5} and \calB(B^0\to K_1^0(1400)\gamma)=(0.393\pm0.151)\times 10^{-5}.Comment: 17pages, 4 figures. Minor changes, typos corrected. PRD accepted versio

External Operators and Anomalous Dimensions in Soft-Collinear Effective Theory

It has recently been argued that soft-collinear effective theory for processes involving both soft and collinear partons contains a new soft-collinear mode, which can communicate between the soft and collinear sectors of the theory. The formalism incorporating the corresponding fields into the effective Lagrangian is extended to include external current and four-quark operators relevant to weak interactions. An explicit calculation of the anomalous dimensions of these operators reveals that soft-collinear modes are needed for correctly describing the ultraviolet behavior of the effective theory.Comment: 15 pages, 2 figure