A universal Regge pole model for all vector meson exclusive photoproduction by real and virtual photons

A model based on a dipole pomeron framework for exclusive vector meson photoproduction by real and virtual photons shows very good agreement with the experimental data. This model does not violate unitarity constraints and describes in a universal manner all the available data for , , , and vector meson photoproduction in the region of energies and photon virtualities . Received: 18 December 2001 / Published online: 25 October 2002 RID="a" ID="a" e-mail: martynov@bitp.kiev.ua 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     

Transfer reactions and sub-barrier fusion in 40Ca + 90, 96Zr

The two systems ⁴⁰Ca + ^90,96Zr have been studied by measuring nucleon transfer reactions at two energies near the Coulomb barrier, thus complementing the available sub-barrier fusion cross-sections. Angular distributions for various transfer channels have been determined. Significantly larger neutron transfer cross-sections are found for the target ⁹⁶Zr that exhibits the larger enhancement in the sub-barrier fusion cross-sections. All data have been analyzed with a new model for heavy-ion collisions that calculates simultaneously transfer cross-sections, fusion excitation functions and barrier distributions. The model gives a good account of both transfer and fusion data. Received: 2 May 2002 / Accepted: 4 June 2002 / Published online: 26 November 2002 RID="a" ID="a"e-mail: montagnoli@pd.infn.it, Fax +39049 8277102, Tel. +39049 8277117. RID="b" ID="b"On leave from the China Institute for Atomic Energy, 102413 Beijing, China. Communicated by C. Signorini     

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     

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     

Production of high quality shocks for equation of state experiments

In this paper we describe the quality requirements that a shock wave must fulfil to make equation of state (EOS) measurements possible: planarity, no-preheating and stationarity of the shock. Experimental measurements have been performed at the Max Planck Institut für Quantenoptik (Garching). We also present simple analytical models that allow to verify shock stationarity and absence of preheating. Received 17 June 2002 Published online 21 January 2003 RID="a" ID="a"e-mail: batani@mib.infn.it RID="b" ID="b"Present address: Pro-beam, Behrinsta?e 6, 85152 Planegg b. München, Germany. RID="c" ID="c"UMR 7605     

On the effective lagrangian in spinor electrodynamics with added violation of Lorentz and <Emphasis Type="Italic">CPT</Emphasis>-symmetries

We consider quantum electrodynamics with additional coupling of spinor fields to the space-time independent axial vector violating both Lorentz and CPT-symmetries. The Fock-Schwinger proper-time method is used to calculate the one-loop effective action up to the second order in the axial vector and to all orders in the space-time independent electromagnetic field strength. We find that the Chern-Simons term is not radiatively induced and that the effective action is CPT-invariant in the given approximation. Received: 29 January 2003 / Published online: 24 March 2003 RID="a" ID="a" e-mail: sitenko@itp.unibe.ch RID="b" ID="b" e-mail: rulik@to.infn.it     

On the instanton-induced portion of the nucleon strangeness II: the MIT model beyond the linearized approximation

If instantons are introduced into the MIT bag model in such a way that the bag radii are allowed to vary, the MIT bag interior can accommodate an instanton density which is by an order of magnitude larger than in the case when the radii are fixed (although it is still significantly smaller than in the non-perturbative QCD vacuum). The instanton contribution to the baryon mass shifts is also correspondingly larger. The instanton-induced part of the scalar strangeness of the nucleon MIT bag is an order of magnitude larger than found previously, within the linearized approximation. The decrease of the model radii (which is associated with the increase of the instanton density) is very favorable from the standpoint of nuclear physics. Received: 7 February 2003 / Revised version: 1 April 2003 / Published online: 23 May 2003 RID="a" ID="a" e-mail: klabucar@phy.hr RID="b" ID="b" e-mail: kkumer@phy.hr RID="c" ID="c" e-mail: dmekter@rudjer.irb.hr RID="d" ID="d" e-mail: bp@phy.hr. Present address: Faculty of Civil Engineering, University of Rijeka, HR-51000 Rijeka, Croatia     

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     

Antideuteron production in proton-proton and proton-nucleus collisions

The experimental data of the antideuteron production in proton-proton and proton-nucleus collisions are analyzed within a simple model based on the diagrammatic approach to the coalescence model. This model is shown to be able to reproduce most of the existing data without any additional parameter. Received: 18 April 2002 / Accepted: 30 August 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: duperray@isn.in2p3.fr RID="b" ID="b"e-mail: protasov@isn.in2p3.fr RID="c" ID="c"e-mail: avoronin@aha.ru Communicated by A. Molinari     

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     

The QCD pomeron in ultraperipheral heavy ion collisions: I. The double $J/\Psi$ production

The contribution of the QCD pomeron to the process is discussed. We focus on the photon-photon collision, with the quasi-real photon coming from the Weizs?cker-Williams spectrum of the nuclei. We calculate the cross section for this process considering the solution of the LLA BFKL equation at zero momentum transfer using a small t approximation for the differential cross section of the subprocess. Furthermore, the impa ct of non-leading corrections to the BFKL equation is also analyzed. In both cases the cross section is found to increase with the energy, predicting considerable values for the LHC energies. Moreover, we compare our results with the Born two-gluon approximation, which is energy independent at the photon level. Our results indicate that the experimental analyses of this process can be useful to discriminate the QCD dynamics at high energies. Received: 12 December 2002 / Published online: 7 March 2003 RID="a" ID="a" e-mail: barros@ufpel.tche.br RID="b" ID="b" e-mail: magnus@if.ufrgs.br     

On the finite size corrections to some random matching problems

We get back to the computation of the leading finite size corrections to some random link matching problems, first adressed by Mézard and Parisi [J. Phys. France 48, 1451 (1987)]. In the so-called bipartite case, their result is in contradiction with subsequent works. We show that they made some mistakes, and correcting them, we get the expected result. In the non bipartite case, we agree with their result but push the analytical treatment further. Received 28 April 2002 Published online 14 October 2002 RID="a" ID="a"e-mail: giorgio.parisi@roma1.infn.it RID="b" ID="b"e-mail: matthieu.ratieville@roma1.infn.it     

Recursive actions for scalar theories

We introduce a class of self-interacting scalar theories in which the various coupling constants obey a recursive relation. These imply a particularly simple form for the generating function of the Feynman amplitudes with vanishing external momenta, as well as for the effective potential. In addition we discuss an interesting duality inherent in these models. Specializing to the case of zero spacetime dimensions we find intriguing nullification properties for the amplitudes. Received: 19 December 2001 / Published online: 5 May 2003 RID="a" ID="a" e-mail: chrisd@sci.kun.nl RID="b" ID="b" e-mail: kleiss@sci.kun.nl RID="c" ID="c" e-mail: petros@sci.kun.nl RID="d" ID="d" e-mail: andrevh@sci.kun.nl RID="e" ID="e" e-mail: papadopo@alice.nuclear.demokritos.gr     

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     

Spin structure function g 1 (x, Q) and the DHGHY integral I(Q) at low Q: predictions from the GVMD model

Theoretical predictions for the polarized nucleon structure function g ₁ (x, Q ² ) at low Q² are obtained in the framework of the generalized vector meson dominance model. Contributions from both light and heavy vector mesons are evaluated. In the photoproduction limit the first moment of g₁ is related to the static properties of the nucleon via the Drell-Hearn-Gerasimov-Hosoda-Yamamoto sum rule. This property is employed to fix the magnitude of the light vector meson contribution to g₁, using the recent measurements in the region of baryonic resonances. The results are compared to the data on g ₁ (x, Q ² ). Finally, the DHGHY moment function I(Q ² ) is calculated, and our theoretical predictions are confronted with the recent preliminary data obtained at the Jefferson Laboratory. Received: 9 July 2002 / Published online: 7 October 2002 RID="a" ID="a" e-mail: badelek@fuw.edu.pl RID="b" ID="b" e-mail: jan.kwiecinski@ifj.edu.pl RID="c" ID="c" e-mail: ziaja@tsl.uu.se     

Deconstructing scalar QED at zero and finite temperature

We calculate the effective potential for the WLPNGB in a world with a circular latticized extra dimension. The mass of the Wilson line pseudo-Nambu-Goldstone boson (WLPNGB) is calculated from the one-loop quantum effect of scalar fields at zero and finite temperature. We show that a series expansion by the modified Bessel functions is useful to calculate the one-loop effective potentials. Received: 24 January 2003 / Published online: 14 April 2003 RID="a" ID="a" e-mail: b1834@sty.cc.yamaguchi-u.ac.jp RID="b" ID="b" e-mail: b1795@sty.cc.yamaguchi-u.ac.jp RID="c" ID="c" e-mail: shiraish@po.cc.yamaguchi-u.ac.jp     

Experimental tests of non-perturbative pion wave functions

We use the transverse-momentum dependence of the cross section for the diffractive dissociation of high energy pions to two jets to study some non-perturbative light-cone wave functions of the pion. We compare the predictions for this distribution by Gaussian and Coulomb wave functions as well as the wave function derived from a solution of the light-cone Hamiltonian in the singlet model. We conclude that this experimentally measured information provides a powerful tool for these studies. Received: 15 January 2003 / Published online: 14 April 2003 RID="a" ID="a" e-mail: ashery@tauphy.tau.ac.il RID="b" ID="b" e-mail: pauli@mpi-hd.mpg.de