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     

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     

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 contribution of off-shell gluons to the structure functions F 2 and F_{\mathrm {L}}^c and the unintegrated gluon distributions

We calculate the perturbative parts of the structure functions F ₂ ^c and for a gluon target having non-zero transverse momentum squared at order . The results of the double convolution (with respect to the Bjorken variable and the transverse momentum) of the perturbative part and the unintegrated gluon densities are compared with the HERA experimental data for F ₂ ^c . The contribution from the structure function ranges in 10-30% of that of F ₂ ^c at the kinematical range of the HERA experiments. Received: 18 April 2002 / Revised version: 24 July 2002 / Published online: 7 October 2002 RID="a" ID="a" e-mail: kotikov@sunse.jinr.ru RID="b" ID="b" e-mail: gonzalo@fpaxp1.usc.es     

High-spin states in the <Superscript>97</Superscript>Tc nucleus

High-spin states in the ⁹⁷Tc nucleus have been studied by in-beam γ-ray spectroscopy with the reaction ⁸²Se(¹⁹F,4nγ) at 68 MeV incident energy. Excited states have been observed up to about 8 MeV excitation and spin 43/2. The observed level scheme is compared with results of shell model calculations. Received: 22 November 2002 / Accepted: 23 December 2002 / Published online: 18 March 2003 RID="a" ID="a"e-mail: bucurescu@tandem.nipne.ro RID="b" ID="b"Present address: INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy. RID="b" ID="b"Present address: INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy. RID="b" ID="b"Present address: INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy. RID="c" ID="c"Present address: Università di Padova, Padova, Italy. Communicated by C. Signorini     

Candidates for chiral doublet bands in 136Nd

The even-even nucleus ¹³⁶Nd was studied via in-beam γ-ray spectroscopy using the ¹⁶O + ¹²⁵Te reaction at 100 MeV and the EUROBALL array. One new dipole band was observed. Together with a previously identified dipole band, whose position in the level scheme is revised, the new band forms a doublet structure similar to the recently observed chiral bands in the odd-odd neighboring nuclei. This would be the first case of a chiral doublet in an even-even nucleus. Received: 23 May 2002 / Accepted: 30 September 2002 / Published online: 27 November 2002 RID="a" ID="a"e-mail: costel.petrache@unicam.it RID="b" ID="b"Present address: Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. RID="c" ID="c"Present address: Gesellschaft für Schwerionenforschung D-64291 Darmstadt, Germany. Communicated by C. Signorini     

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     

Deconstruction of gauge symmetry breaking by discrete symmetry and G unification

We deconstruct the non-supersymmetric SU(5) breaking by discrete symmetry on the space-time and in the Higgs mechanism deconstruction scenario. Also we explain the subtle point of how to exactly match the continuum results with the latticized results on the quotient space S ¹ /Z ₂ and . We also propose an effective deconstruction scenario and discuss the gauge symmetry breaking by the discrete symmetry on the theory space in this approach. As an application, we suggest the G^N unification where G^N is broken down to by the bifundamental link fields and the doublet-triplet splitting can be achieved. Received: 10 October 2002 / Revised version: 23 March 2003 / Published online: 13 May 2003 RID="a" ID="a" Current address: School of Natural Sciences, Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540, USA e-mail: tli@sns.ias.edu RID="b" ID="b" e-mail: liutao@sas.upenn.edu     

UCN production in superfluid helium

Ultra-cold neutrons (UCN) are produced in superfluid helium by single- and multi-phonon excitation. The UCN production rate density R _II via multiphonons can be larger than that by one-phonon excitation R _I being due to the dependence of the incident neutron spectral flux density dφ/dλ on the wavelength λ. Received: 28 March 2002 / Accepted: 19 December 2002 / Published online: 11 March 2003 RID="a" ID="a"e-mail: wschott@e18.physik.tu-muenchen.de RID="b" ID="b"On leave of absence from PNPI, Gatchina, Russia Communicated by T. Walcher     

Rotational bands and signature inversion phenomena in πh9/2⊗νi13/2 and πi13/2⊗νi13/2 structures in odd-odd 176Ir

The ^109,111,113Rh nuclei have been produced as fission fragments in the fusion reaction ¹⁸O + ²⁰⁸Pb at 85 MeV. Their level schemes have been built from gamma-rays detected using the Euroball IV array. High-spin states of the neutron-rich ^111,113Rh nuclei have been identified for the first time. Several rotational bands with the odd proton occupying the πg _9/2, πp _1/2 and π(g _7/2/d _5/2) sub-shells have been observed. A band of low-energy transitions has been identified at excitation energy around 2 MeV in ^109,111Rh, which can be interpreted in terms of three-quasiparticle excitation, πg _9/2νh _11/2νg _7/2/d _5/2. In addition another structure built on states located at low excitation energy (608 keV in ¹¹¹Rh, 570 keV in ¹¹³Rh) points out that, as already observed in the lighter isotopes ^107,109Rh, triaxial deformation plays a role in the neutron-rich Rh isotopes well beyond the mid-shell. Received: 15 July 2002 / Accepted: 9 October 2002 / Published online: 3 December 2002 RID="a" ID="a"e-mail: porquet@csnsm.in2p3.fr RID="b" ID="b"Present address: CSNSM IN2P3-CNRS and Université Paris-Sud 91405 Orsay, France. RID="c" ID="c"Present address: CEA/Saclay, DSM/DAPNIA/SPhN, 91191 Gif-sur-Yvette Cedex, France. Communicated by D. Schwalm     

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     

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     

The classical nucleation rate in two dimensions

In many systems in condensed matter physics and quantum field theory, first order phase transitions are initiated by the nucleation of bubbles of the stable phase. In homogeneous nucleation theory the nucleation rate can be written in the form of the Arrhenius law: . Here is the energy of the critical bubble, and the prefactor can be expressed in terms of the determinant of the operator of fluctuations near the critical bubble state. In general it is not possible to find explicit expressions for and . If the difference between the energies of the stable and metastable vacua is small, the constant can be determined within the leading approximation in , which is an extension of the ”thin wall approximation”. We have done this calculation for the case of a model with a real-valued order parameter in two dimensions. Received: 11 September 2002 / Revised version: 30 October 2002 / Published online: 24 January 2003 RID="a" ID="a" e-mail: munsteg@uni-muenster.de RID="b" ID="b" e-mail: rut@ifttp.bas-net.by ^* Present address: Universit?t Essen, Fachbereich 7 - Physik, Universit?tsstr. 5, 45117 Essen, Germany     

First evidence for triaxial superdeformation in 161Lu and 162Lu

High-spin states in ¹⁶¹Lu and ¹⁶²Lu have been investigated using the GASP γ-ray spectrometer array. Excited states in these nuclei have been populated through the ¹⁰⁰Mo(⁶⁵Cu, xn) reaction at a beam energy of 260 MeV. Four presumably triaxial superdeformed bands, three in ¹⁶²Lu and one in ¹⁶¹Lu, have been observed. This is the first evidence for triaxial superdeformation in the two isotopes. Received: 18 October 2002 / Accepted: 21 November 2002 / Published online: 4 February 2003 RID="a" ID="a"e-mail: bringel@iskp.uni-bonn.de RID="b" ID="b"Present address: Wright Nuclear Structure Laboratory, Yale University, New Haven, CT 06520, USA. RID="c" ID="c"Present address: Physik Department, Technische Universit?t München, James Franck Str., D-85748 Garching, Germany. Communicated by D. Schwalm     

Instabilities of an electron cloud in a Penning trap

We have measured the storage instabilities of electrons in a Penning trap at low magnetic fields. These measurements are carried out as a function of the trapping voltage, for different magnetic fields. It is seen that these instabilities occur at the same positions when the trapping voltage is expressed as a percentage of the maximum voltage, given by the stability limit. The characteristic frequencies at which these instabilities occur, obey a relation that is given by n _zω _z + n ₊ω ₊ + n _-ω _- = 0, where ω _z, ω ₊ and ω _- are the axial, perturbed cyclotron and the magnetron frequencies of the trapped electrons respectively, and the n's are integers. The reason for these instabilities are attributed to higher order static perturbations in the trapping potential. Received 5 August 2002 / Received in final form 14 October 2002 Published online 17 December 2002 RID="a" ID="a"Present address: Dept. of Physics, Rampurhat College, Rampurhat, Birbhum, West Bengal, India. RID="b" ID="b"e-mail: werth@mail.uni-mainz.de     

Sensitivity of the pQCD deuteron structure to the nucleon form factors

We discuss the applicability of pQCD to the elastic scattering of electrons on protons and deuterons. We analyze the Q²-dependence of the reduced deuteron form factor, taking into account the recent data on the electric proton form factor and we find that the value of the QCD-scale parameter Λ differs essentially from the value Λ = 0.1 GeV, previously found using the dipole parametrization of the electromagnetic nucleon form factors G_E and G_M. Moreover, the predicted scaling behavior of the reduced deuteron form factor cannot be recovered in the Dirac and Pauli representations for the nucleon electromagnetic form factors. Received: 14 October 2002 / Accepted: 12 November 2002 / Published online: 11 March 2003 RID="a" ID="a"Permanent address: National Science Center KFTI, 310108 Kharkov, Ukraine. RID="b" ID="b"e-mail: etomasi@cea.fr Communicated by V.V. Anisovich     

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     

Confinement and mass gap in abelian gauge

First, we present a simple confining abelian pure gauge theory. Classically, its kinetic term is not positive definite, and it contains a simple UV regularized F⁴ interaction. This provokes the formation of a condensate such that, at the saddle point of the effective potential, the wave function normalization constant of the abelian gauge fields vanishes exactly. Then we study SU(2) pure Yang-Mills theory in an abelian gauge and introduce an auxiliary field for a BRST invariant condensate of dimension 2, which renders the charged sector massive. Under simple assumptions its effective low energy theory reduces to the confining abelian model discussed before, and the VEV of is seen to scale correctly with the renormalization point. Under these assumptions, the confinement condition Z _eff = 0 also holds for the massive charged sector, which suppresses the couplings of the charged fields to the abelian gauge bosons in the infrared regime. Received: 27 November 2002 / Published online: 14 April 2003 RID="a" ID="a" e-mail: Ulrich.Ellwanger@th.u-psud.fr RID="b" ID="b" e-mail: Nicolas.Wschebor@th.u-psud.fr ^* Unité Mixte de Recherche - CNRS - UMR 8627     

High-spin structure of the neutron-rich odd-odd 106, 108 45Rh and 110, 112 47Ag isotopes

The ^{106, 108}Rh and ^{110, 112}Ag nuclei have been produced as fission fragments following the fusion reaction ²⁸Si + ¹⁷⁶Yb at 145 MeV bombarding energy and studied with the Eurogam2 array. The yrast high-spin states of these four odd-odd nuclei, which are observed for the first time, consist of rotational bands in which the odd proton occupies the πg _9/2 subshell and the odd neutron the νh _11/2 subshell. Their behaviour as a function of spin values does not vary with the number of neutrons: as observed in the odd-N neighbouring nuclei, the motion of the odd neutron remains decoupled from the motion of the core, from N = 61 to N = 65. Moreover, the staggering observed in the yrast bands of odd-odd isotopes is strongly reduced as compared to the large values displayed by the rotational bands built on the πg _9/2 subshell in the odd-A Rh and Ag isotopes. The results of particle-rotor calculations indicate that this reduction is related to a change of the core deformation. Received: 1 June 2001 / Accepted: 23 July 2002 / Published online: 10 December 2002 RID="a" ID="a"e-mail: porquet@csnsm.in2p3.fr RID="b" ID="b"Present address: CSNSM IN2P3-CNRS and Université Paris-Sud 91405 Orsay, France. RID="c" ID="c"Present address: NAC, Faure, ZA 7131, South Africa. RID="d" ID="d"Present address: Department of Nuclear Physics, ANU, Canberra ACT 0200, Australia. Communicated by D. Schwalm