共查询到20条相似文献,搜索用时 15 毫秒
1.
We compute the one-loop
-functions describing the renormalisation of the coupling constant
and the frequency parameter
for the real four-dimensional duality-covariant non-commutative
-model, which is renormalisable to all orders. The contribution from the one-loop four-point function is reduced by the one-loop wavefunction renormalisation, but the
-function remains non-negative. Both
and
vanish at the one-loop level for the duality-invariant model characterised by
. Moreover,
also vanishes in the limit
, which defines the standard non-commutative
-quantum field theory. Thus, the limit
exists at least at the one-loop level.Received: 19 March 2004, Published online: 5 May 2004 相似文献
2.
We investigate the phonon thermal conductivity
of doped
based on out-of-plane thermal conductivity measurements. When room temperature is approached the temperature dependence of
strongly deviates from the T-1-decrease which is usually expected for heat transport by acoustic phonons. Instead,
decreases much weaker or even increases with rising temperature. Simple arguments suggest that such unusual temperature dependencies of
are caused by heat transport via dispersive optical phonons.Received: 20 October 2003, Published online: 20 April 2004PACS:
66.70. + f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves - 74.72.Dn La-based cuprates - 44.10. + i Heat conduction 相似文献
3.
J. A. Gracey 《The European Physical Journal C - Particles and Fields》2005,39(1):61-69
We compute the pole mass of the gluon in QCD from the local composite operator formalism at two loops in the
renormalization scheme. For the Yang-Mills theory an estimate of the mass at two loops is
.Received: 25 October 2004, Published online: 17 December 2004 相似文献
4.
We review different definitions of the
parameter describing direct CP-violation in neutral kaon decays, which was precisely measured in recent experiments, and point out the inconsistency of some of them due to a CPT-constraint. The proper comparison of the experimental results to the theoretical computations is discussed.Received: 27 January 2004, Published online: 23 June 2004 相似文献
5.
We present an analysis of the longitudinal
polarization in ultrarelativistic heavy-ion collisions. The polarization of
s coming from the decay chain
exhibits a very well differentiated behavior depending on the production region of the primordial
s. This effect reflects the different values of the
ratio in the QGP region, where nucleon-nucleon interactions take place in a hot and dense environment, and the peripherical region, in which ordinary nucleon-nucleon interactions occur. An increase in the longitudinal
polarization signals a strangeness enhancement which is thought of as a property of the QGP phase.Received: 21 September 2004, Revised: 25 October 2004, Published online: 17 December 2004 相似文献
6.
TaSe3 belongs to a class of low-dimensional materials characterized by the interplay and competition between dimensionality crossover and broken symmetry ground states. A comprehensive study by dc-transport, optical, and angle-resolved photoemission (ARPES) experiments shows that the electronic properties of this compound are strongly anisotropic between the chain and the transverse crystallographic direction. Even though TaSe3 fails to undergo a charge-density-wave (CDW) phase transition, we found evidence for short range order CDW segments, which progressively disappear with decreasing temperature.Received: 27 April 2004, Published online: 23 July 2004PACS:
78.20.-e Optical properties of bulk materials and thin films - 71.30. + h Metal-insulator transitions and other electronic transitions - 71.45.Lr Charge-density-wave systems 相似文献
7.
R. L. Jaffe 《The European Physical Journal C - Particles and Fields》2004,35(2):221-222
In 1997 Diakonov, Petrov, and Polyakov, calculated the width of the exotic baryon that they called
. The prediction,
MeV, has received considerable attention, especially in light of the narrowness of the experimentally reported
resonance. However, there is an arithmetic error in their work: when corrected, the width estimate quoted in that paper should have been
MeV.Received: 29 January 2004, Published online: 5 May 2004 相似文献
8.
Dang Van Soa Takeo Inami Hoang Ngoc Long 《The European Physical Journal C - Particles and Fields》2004,34(3):285-289
We study the production of bileptons, new gauge bosons of lepton number two, in the minimal 3-3-1 model in high energy
collisions. If the bilepton masses are in the range of 300 GeV the reaction will give observable cross-sections in future colliders.Received: 5 August 2003, Published online: 23 March 2004Dang Van Soa: On leave of absence from Department of Physics, Hanoi University of Education, Hanoi, VietnamHoang Ngoc Long: On leave of absence from Institute of Physics, NCST, P.O. Box 429, Bo Ho, Hanoi 10000, Vietnam 相似文献
9.
Ł Bibrzycki L. Leśniak A. P. Szczepaniak 《The European Physical Journal C - Particles and Fields》2004,34(3):335-344
Results of a new analysis of the K + K- photoproduction at two photon energies,
and
, with a particular emphasis on the S-wave production are presented. We show that the proper treatment of all the helicity components of the S- and P-waves enables one to eliminate the reported discrepancies in the extraction of the S-wave photoproduction cross section from the experimental data.Received: 28 August 2003, Revised: 3 February 2004, Published online: 23 March 2004 相似文献
10.
The production of single- and multi-photon events has been studied in the reaction
. The data collected with the DELPHI detector during the years 1999 and 2000 at centre-of-mass energies between 191 GeV and 209 GeV was combined with earlier data to search for phenomena beyond the Standard Model. The measured number of light neutrino families was consistent with three and the absence of an excess of events beyond that predicted by the Standard Model processes was used to set limits on new physics. Both model-independent searches and searches for new processes predicted by supersymmetric and extra-dimensional models have been made. Limits on new non-standard model interactions between neutrinos and electrons were also determined.Received: 31 March 2004, Revised: 14 October 2004, Published online: 7 December 2004 相似文献
11.
We describe the spectra and decays of
and
atoms within a non-relativistic effective field theory. The evaluations of the energy shifts and widths are performed at next-to-leading order in isospin symmetry breaking. We provide general formulae for all S-states, and discuss the states with angular momentum one in some detail. The prediction for the lifetime of the
atom in its ground state yields
s.Received: 9 May 2004, Published online: 23 July 2004 相似文献
12.
We compute the cross section for exclusive double-diffractive
production at the Tevatron,
, and the LHC. We evaluate both the gg and
-channel exchange contributions to the process. The observation of exclusive
production at the Tevatron will provide a check on the model predictions and offer an opportunity to confirm the expectations for exclusive double-diffractive Higgs production at the LHC.Received: 10 September 2004, Revised: 8 October 2004, Published online: 1 December 2004 相似文献
13.
Dilepton production in heavy ion collisions in the intermediate mass region (IMR) has consistently shown an excess over theoretical estimates. An attempt to understand this discrepancy between the observed dilepton pairs and the theoretical estimate is made here through the production of the
meson and estimates obtained by NRQCD calculations. We find that
production offers a satisfactory quantitative picture for explaining the discrepancy.Received: 13 August 2003, Revised: 9 February 2004, Published online: 23 March 2004 相似文献
14.
We study the peripheral ion collisions at LHC energies where a nucleus is excited to a discrete state and then emits
-rays. Large nuclear Lorenz factors allow the observation of high-energy photons up to a few tens GeV and in the angular region of a few hundred micro-radians from the beam direction. These photons can be used to tagg events with particle production in the central rapidity region in ultra-peripheral collisions. To detect these photons it is necessary to have an electromagnetic detector in front of the zero-degree calorimeter in LHC experiments.Received: 10 February 2004, Revised: 9 March 2004, Published online: 14 September 2004PACS:
25.75.-q Relativistic heavy-ion collisions - 25.75.Dw Particle and resonance production 相似文献
15.
This study of gauge field theories on
-deformed Minkowski spacetime extends previous work on field theories on this example of a non-commutative spacetime. We construct deformed gauge theories for arbitrary compact Lie groups using the concept of enveloping algebra-valued gauge transformations and the Seiberg-Witten formalism. Derivative-valued gauge fields lead to field strength tensors as the sum of curvature- and torsion-like terms. We construct the Lagrangians explicitly to first order in the deformation parameter. This is the first example of a gauge theory that possesses a deformed Lorentz covariance.Received: 17 December 2003, Revised: 6 May 2004, Published online: 23 June 2004 相似文献
16.
17.
V. A. Khoze A. D. Martin M. G. Ryskin W. J. Stirling 《The European Physical Journal C - Particles and Fields》2005,39(2):163-171
We consider the prompt hadroproduction of
and the
states caused by the fusion of a symmetric colour-octet state, (gg)8s
, and an additional gluon. The cross sections are calculated in leading-order perturbative QCD. We find a considerable enhancement in comparison with previous perturbative QCD predictions. Indeed, the resulting cross sections are found to be consistent with the values measured at the Tevatron and RHIC, without the need to invoke non-perturbative colour-octet type of contributions.Received: 16 October 2004, Revised: 10 November 2004, Published online: 11 January 2005 相似文献
18.
Recently, we have reported photoassociation of laser-cooled Rb and Cs atoms, decay of the RbCs photoassociation resonances
to high levels of the
state, and reexcitation to vibronic levels of the
state [Kerman et al. , Phys. Rev. Lett. 92, 033004; 153001 (2004)]. Considering the reexcitation spectrum, we report here a preliminary analysis of perturbations in
the c state by high levels of the
and low levels of the
state. Mixing with the B state provides the singlet character needed to stimulate decay to v = 0 of the
ground state. We conclude that an experimental procedure that involves photoassociation of laser-cooled atoms, radiative
decay, and stimulated Raman transfer to the ground electronic state is a feasible method for producing translationally, rotationally,
vibrationally and electronically cold RbCs molecules.
Electronic supplementary material to this article is available at and is accessible for authorized users.
Received: 1 September 2004, Published online: 23 November 2004
PACS:
33.80.Ps Optical cooling of molecules; trapping - 34.50.Gb Electronic excitation and ionization of molecules; intermediate
molecular states (including lifetimes, state mixing, etc.) - 33.20.Kf Visible spectra - 34.20.-b Interatomic and intermolecular
potentials and forces, potential energy surfaces for collisions - 33.15.Pw Fine and hyperfine structure
A supplementary table (Tab. I) is only available in electronic form at http: //www.eurphysj.org 相似文献
19.
We present a new ab initio theoretical formulation to calculate
and hence the positron annihilation rates directly from the onshell and offshell (half) scattering amplitudes. The method does not require any explicit use of the scattering wave function and is formally exact within the framework of the well established Lippmann-Schwinger equation. It could serve as an effective tool as all the T-, K-, and S-matrix formulations, yield directly the scattering amplitudes; not the wave function. Numerical test of the method is presented considering sample static calculations in positron-hydrogen and positron-helium systems.Received: 15 January 2004, Published online: 15 April 2004PACS:
03.65.Nk Scattering theory - 34.85. + x Positron scattering - 71.60. + z Positron states - 78.70.Bj Positron annihilation 相似文献
20.
P. Aurenche Rahul Basu M. Fontannaz R. M. Godbole 《The European Physical Journal C - Particles and Fields》2004,34(3):277-284
We present a next-to-leading order calculation of the cross section for the leptoproduction of large-
hadrons and we compare our predictions with H1 data on the forward production of
. We find large higher order corrections and an important sensitivity to the renormalization and factorization scales. These large corrections are shown to arise in part from BFKL-like diagrams at the lowest order.Received: 9 January 2004, Published online: 19 March 2004 相似文献