The exclusive B_s\rightarrow \phi \ell^+ \ell^- decay in the two Higgs doublet models

We study the differential branching ratio, the branching ratio and the forward-backward asymmetry for exclusive decay in the two Higgs doublet model. We analyze the dependences of these quantities on the model parameters and show that these observables are highly sensitive to new physics and hence may provide a powerful probe of the SM and beyond. Received: 27 March 2002 / Revised version: 3 July 2002 / Published online: 20 September 2002 RID="a" ID="a" e-mail: gurerk@newton.physics.metu.edu.tr RID="b" ID="b" e-mail: gsevgur@metu.edu.tr     

Heavy charged Higgs boson production at next generation $\gamma\gamma$ colliders

We investigate the scope of all relevant production modes of charged Higgs bosons in the MSSM, with mass larger than the one of the top quark, at future Linear Colliders operating in mode at the TeV energy scale. Final states with one or two bosons are considered, as produced by both tree- and loop-level interactions. Received: 8 November 2002 / Revised version: 12 February 2003 / Published online: 13 May 2003 RID="a" ID="a" e-mail: stefano.moretti@cern.ch RID="b" ID="b" e-mail: kanemu@post.kek.jp     

Towards high-precision predictions for the MSSM Higgs sector

The status of the evaluation of the MSSM Higgs sector is reviewed. The phenomenological impact of recently obtained corrections is discussed. In particular it is shown that the upper bound on m_h within the MSSM is shifted upwards. Consequently, lower limits on obtained by confronting the upper bound as function of with the lower bound on m_h from Higgs searches are significantly weakened. Furthermore, th e region in the M_A--plane where the coupling of the lightest Higgs boson to down-type fermions is suppressed is modified. The presently not calculated higher-order corrections to the Higgs-boson mass matrix are estimated to shift the mass of the lightest Higgs boson by up to 3 GeV. Received: 12 December 2002 / Published online: 3 March 2003 RID="a" ID="a" e-mail: giuseppe.degrassi@roma3.infn.it RID="b" ID="b" e-mail: Sven.Heinemeyer@physik.uni-muenchen.de RID="c" ID="c" e-mail: hollik@mppmu.mpg.de RID="d" ID="d" e-mail: slavich@mppmu.mpg.de RID="e" ID="e" e-mail: Georg.Weiglein@durham.ac.uk     

QCD saturation and $\gamma^{*}$-$\gamma^{*}$ scattering

Two photon collisions at high energy have an important theoretical advantage: the simplicity of the initial state, which gives us a unique opportunity to calculate these processes for large virtualities of both photons in the perturbative QCD approach. In this paper we study QCD saturation in two photon collisions in the framework of the Glauber-Mueller approach. The Glauber-Mueller formula is derived emphasising the impact parameter dependence (b_t) of the dipole-dipole amplitude. It is shown that non-perturbative QCD contributions are needed to describe the large b _t behaviour, and the way how to deal with them is suggested. Our approach can be viewed as the model for the saturation in which the entire impact parameter dependence is determined by the initial conditions. The unitarity bound for the total cross section, its energy dependence as well as predictions for future experiments are discussed. It is argued that the total cross section increases faster than any power of in a wide range of energy or x, namely -, where reflects the x dependence of the gluon density and is the pion mass. Received: 22 November 2002 / Revised version: 27 January 2003 / Published online: 5 May 2003 RID="a" ID="a" e-mail: kozlov@post.tau.ac.il RID="b" ID="b" e-mail: leving@post.tau.ac.il and levin@mail.desy.de     

Fourth generation effects in processes induced by the $b \rightarrow s$ transition

We study the effects of sequential fourth quark generation in rare decays induced by the transition and in B _s ⁰- mixing. Using the experimental values on the branching ratios of the and decays, the allowed regions for and are determined as a function of the t ^' quark mass. Received: 3 April 2003 / Published online: 2 June 2003 RID="a" ID="a" e-mail: taliev@metu.edu.tr RID="b" ID="b" e-mail: ozpineci@ictp.trieste.it RID="c" ID="c" e-mail: savci@metu.edu.tr     

World-line techniques for resumming gluon radiative corrections at the cross-section level

We employ the Polyakov world-line path-integral version of QCD to identify and resum at leading perturbative order enhanced radiative gluon contributions to the Drell-Yan type ( pair annihilation) cross-sections. We emphasize that this is the first time that world-line techniques are applied to cross-section calculations. Received: 10 June 2002 / Published online: 31 October 2002 RID="a" ID="a" e-mail: akaranik@cc.uoa.gr RID="b" ID="b" e-mail: cktorid@cc.uoa.gr RID="c" ID="c" e-mail: stefanis@tp2.ruhr-uni-bochum.de     

Quantisation of $\theta$-expanded non-commutative QED

We analyse two new versions of -expanded non-commutative quantum electrodynamics up to first order in and first loop order. In the first version we expand the bosonic sector using the Seiberg-Witten map, leaving the fermions unexpanded. In the second version we leave both bosons and fermions unexpanded. The analysis shows that the Seiberg-Witten map is a field redefinition at first order in . However, at higher order in the Seiberg-Witten map cannot be regarded as a field redefinition. We find that the initial action of any -expanded massless non-commutative QED must include one extra term proportional to which we identify by loop calculations. Received: 3 July 2002 / Published online: 7 October 2002 RID="a" ID="a" e-mail: jesper@hep.itp.tuwien.ac.at Work supported by The Danish Research Agency. RID="b" ID="b" e-mail: raimar.wulkenhaar@mis.mpg.de Schloe?mann fellow     

Probing the Majorana mass scale of right-handed neutrinos in mSUGRA

We discuss the perspectives of testing the right-handed Majorana mass scale M_R of the SUSY see-saw model in the mSUGRA framework. Lepton-flavor violating low energy processes are analyzed in recently proposed post-LEP benchmark scenarios, taking into account present uncertainties and future developments in the neutrino sector. Non-observation of in the next-generation PSI experiment will provide upper bounds on M_R of the order of GeV, while on the other hand, a positive signal for at SUPERKEKB or the LHC may determine M_R for a given mSUGRA scenario with an accuracy of a factor of 2. Received: 14 June 2002 / Revised version: 7 January 2003 / Published online: 14 April 2003 RID="a" ID="a" e-mail: deppisch@physik.uni-wuerzburg.de RID="b" ID="b" e-mail: paes@physik.uni-wuerzburg.de RID="c" ID="c" e-mail: asredelb@physik.uni-wuerzburg.de RID="d" ID="d" e-mail: rueckl@physik.uni-wuerzburg.de RID="e" ID="e" e-mail: shimizu@eken.phys.nagoya-u.ac.jp     

Time-ordered perturbation theory on non-commutative spacetime II: Unitarity

We examine the unitarity issue in the recently proposed time-ordered perturbation theory on noncommutative (NC) spacetime. We show that unitarity is preserved as long as the interaction Lagrangian is explicitly hermitian. We explain why it makes sense to distinguish the hermiticity of the Lagrangian from that of the action in perturbative NC field theory and how this requirement fits in this framework. Received: 25 June 2002 / Published online: 30 August 2002 RID="a" ID="a" e-mail: liaoy@itp.uni-leipzig.de RID="b" ID="b" e-mail: sibold@itp.uni-leipzig.de     

Interaction of coupled higher order nonlinear Schrödinger equation solitons

The novel inelastic collision properties of two-soliton interaction for an n-component coupled higher order nonlinear Schr?dinger equation are studied. Some interesting features of three soliton interactions, related to the integrability of the n-component coupled higher order nonlinear Schr?dinger equation are also discussed. Received 17 April 2002 Published online 2 October 2002 RID="a" ID="a"e-mail: abhijit@iitg.ernet.in RID="b" ID="b"e-mail: sasanka@iitg.ernet.in RID="c" ID="c"e-mail: sudipta@iitg.ernet.in     

The radiative return at $\phi$- and B-factories: small-angle photon emission at next-to-leading order

The radiative return offers the unique possibility for a measurement of the cross section of electron-positron annihilation into hadrons over a wide range of energies. The large luminosity of present - and B-factories easily compensates for the additional factor of due to the emission of a hard photon. Final states with photons at large angles can be easily identified. The rate for events with collinear photons, however, is enhanced by a large logarithm and allows, in particular at lower energies, for a complementary measurement. The Monte Carlo generator PHOKHARA, which includes next-to-leading order corrections from virtual and real photon emission, has been extended from large photon angles into the collinear region, using recent results for the virtual corrections. In addition, the present version includes final state radiation for muon and pion pair production and final states with four pions. Implications for the experimental analysis at three typical energies, 1.02, 4 and 10.6 GeV, are presented: the magnitude of these new corrections is studied, possibilities for the separation of initial and final state radiation are proposed, and the differences with respect to the previous treatment based on structure functions are investigated. Received: 16 December 2002 / Published online: 26 February 2003 RID="a" ID="a" e-mail: czyz@us.edu.pl RID="b" ID="b" e-mail: grzel@joy.phys.us.edu.pl, Supported in part by "Marie Curie Training Site" at Karlsruhe University RID="c" ID="c" e-mail: jk@particle.uni-karlsruhe.de RID="d" ID="d" e-mail: german.rodrigo@cern.ch, Supported in part by E.U. TMR grant HPMF-CT-2000-00989     

Confronting spectral functions from ee annihilation and $\tau$ decays: consequences for the muon magnetic moment

Vacuum polarization integrals involve the vector spectral functions which can be experimentally determined from two sources: (i) e ⁺ e ^- annihilation cross sections and (ii) hadronic decays. Recently results with comparable precision have become available from CMD-2 on one side, and ALEPH, CLEO and OPAL on the other. The comparison of the respective spectral functions involves a correction from isospin-breaking effects, which is evaluated. After the correction it is found that the dominant spectral functions do not agree within experimental and theoretical uncertainties. Some disagreement is also found for the spectral functions. The consequences of these discrepancies for vacuum polarization calculations are presented, with the emphasis on the muon anomalous magnetic moment. The work includes a complete re-evaluation of all exclusive cross sections, taking into account the most recent data that became available in particular from the Novosibirsk experiments and applying corrections for the missing radiative corrections. The values found for the lowest-order hadronic vacuum polarization contributions are where the errors have been separated according to their sources: experimental, missing radiative corrections in e ⁺ e ^- data, and isospin breaking. The Standard Model predictions for the muon magnetic anomaly read where the errors account for the hadronic, light-by-light scattering and electroweak contributions. We observe deviations with the recent BNL measurement at the 3.0 (e ⁺ e ^- ) and 0.9 () level, when adding experimental and theoretical errors in quadrature. Received: 27 August 2002 / Revised version: 10 January 2003 / Published online: 26 February 2003 RID="a" ID="a" e-mail: davier@lal.in2p3.fr RID="b" ID="b" e-mail: simon.eidelman@cern.ch RID="c" ID="c" e-mail: hoecker@lal.in2p3.fr RID="d" ID="d" e-mail: zhangzq@lal.in2p3.fr     

Coulomb interference in high-energy pp and $\bar p p$ scattering

An analysis of the Coulombic amplitude and its interference with the nuclear amplitude which is driven by the three-component pomeron is presented. It is shown that different approaches towards the evaluation of the Coulomb phase give approximately uniform results at all energies and the differences are negligible at RHIC and LHC energies. We show that the use of the amplitude which was fitted to accommodate the nucleon data only (in the region (GeV²)), combined with the Coulomb amplitude, reproduces the existing data in the Coulomb interference domain quite accurately without any adjustment of the parameters. As a consequence, we predict the differential cross section in the region of the Coulomb nucleon interference for both RHIC and LHC energies. Received: 3 June 2002 / Revised version: 27 February 2003 / Published online: 5 May 2003 RID="a" ID="a" e-mail: petrov@mx.ihep.su RID="b" ID="b" e-mail: predazzi@to.infn.it RID="c" ID="c" e-mail: prokudin@to.infn.it     

Explicit model realizing parton-hadron duality

An explicit model realizing parton-hadron duality and fitting the data is suggested. Complex nonlinear Regge trajectories are important ingredients of the model. The inclusion of Δ and N^* trajectories should account for all resonances in the direct channel. The exotic trajectory is responsible for the smooth background. Received: 7 June 2002 / Accepted: 3 July 2002 / Published online: 10 December 2002 RID="a" ID="a"e-mail: fiore@cs.infn.it RID="b" ID="b"e-mail: flachi@ifae.es RID="c" ID="c"e-mail: jenk@gluk.org RID="d" ID="d"e-mail: sasha@len.uzhgorod.ua RID="e" ID="e"e-mail: vladimir@cfif.ist.utl.pt Communicated by V.V. Anisovich     

Compressible bag model and the phase structure

The phase structure of hadrons and the quark-gluon plasma is investigated by two types of equation of state of the hadrons, namely the ideal hadron gas model and the compressible bag model. It is pointed out that, while the ideal gas model produces an unrealistic extra hadron phase, the compressible bag model gives the expected and reasonable phase diagram even if the rich hadron spectrum is taken into account. Received: 22 February 2002 / Revised version: 28 June 2002 / Published online: 20 September 2002 RID="a" ID="a" e-mail: kagiyama@sci.kagoshima-u.ac.jp RID="b" ID="b" e-mail: kumamoto@cosmos01.cla.kagoshima-u.ac.jp RID="c" ID="c" e-mail: minaka@edu.kagoshima-u.ac.jp RID="d" ID="d" e-mail: nakamura@sci.kagoshima-u.ac.jp RID="e" ID="e" e-mail: ohkura@cosmos01.cla.kagoshima-u.ac.jp RID="f" ID="f" e-mail: yamaguchi@cosmos01.cla.kagoshima-u.ac.jp     

How well can we reconstruct the $t\bar{t}$ system near its threshold at future ee linear colliders?

We developed a new method for the full kinematical reconstruction of the system near its threshold at future linear e ⁺ e ^- colliders. In the core of the method lies likelihood fitting which is designed to improve measurement accuracies of the kinematical variables that specify the final states resulting from decays. The improvement is demonstrated by applying this method to a Monte Carlo sample generated with various experimental effects including beamstrahlung, finite acceptance and resolution of the detector system, etc. In most cases the fit takes a broad non-Gaussian distribution of a given kinematical variable to a nearly Gaussian shape, thereby justifying phenomenological analyses based on simple Gaussian smearing of the parton-level momenta. The standard deviations of the resultant distributions of various kinematical variables are given in order to facilitate such phenomenological analyses. A possible application of the kinematical fitting method and its expected impact are also discussed. Received: 4 March 2003 / Published online: 23 May 2003 RID="a" ID="a" e-mail: ikematsu@post.kek.jp RID="b" ID="b" e-mail: fujiik@jlcuxf.kek.jp RID="c" ID="c" e-mail: hioki@ias.tokushima-u.ac.jp RID="d" ID="d" e-mail: sumino@tuhep.phys.tohoku.ac.jp RID="e" ID="e" e-mail: tohrut@hiroshima-u.ac.jp     

Two-photon annihilation into baryon-antibaryon pairs

We study the handbag contribution to two-photon annihilation into baryon-antibaryon pairs at large energy and momentum transfer. We derive factorization of the process amplitude into a hard subprocess and form factors describing the soft transition, assuming that the process is dominated by configurations where the (anti)quark approximately carries the full momentum of the (anti)baryon. The form factors represent moments of time-like generalized parton distributions, so-called distribution amplitudes. A characteristic feature of the handbag mechanism is the absence of isospin-two components in the final state, which in combination with flavor symmetry provides relations among the form factors for the members of the lowest-lying baryon octet. Assuming dominance of the handbag contribution, we can describe current experimental data with form factors of plausible size, and predict the cross sections of presently unmeasured channels. Received: 3 July 2002 / Revised version: 7 October 2002 / Published online: 20 November 2002 RID="a" ID="a" e-mail: mdiehl@physik.rwth-aachen.de RID="b" ID="b" e-mail: kroll@physik.uni-wuppertal.de RID="c" ID="c" e-mail: cvogt@nordita.dk     

On decoupling of massless modes in NCOS theories

We revisit the decoupling phenomenon of massless modes in non-commutative open string (NCOS) theories. We check the decoupling by explicit computation in (2+1) or higher dimensional NCOS theories and recapitulate the validity of the decoupling to all orders in perturbation theory. Received: 23 April 2002 / Published online: 25 October 2002 RID="a" ID="a" e-mail: hyun@phya.yonsei.ac.kr RID="b" ID="b" e-mail: sangmin@newton.skku.ac.kr RID="c" ID="c" e-mail: hshin@kias.re.kr