共查询到20条相似文献,搜索用时 11 毫秒
1.
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
2.
O. Çakir E. Ateser H. Koru 《The European Physical Journal C - Particles and Fields》2003,28(3):381-388
We study scalar leptoquark production at TESLA and CLIC based colliders. Both direct and resolved contributions to the cross section are examined. We find that the masses of scalar leptoquarks
can be probed up to about 0.9 TeV at TESLA and 2.6 TeV at CLIC.
Received: 10 December 2002 / Revised version: 12 February 2003 / Published online: 31 March 2003 相似文献
3.
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
4.
A. Bartl K. Hohenwarter-Sodek T. Kernreiter H. Rud 《The European Physical Journal C - Particles and Fields》2004,36(4):515-522
We consider the process
at a linear collider with transverse
beam polarization. We investigate the influence of the CP phases on azimuthal asymmetries in
with subsequent two-body decays
and
. We show that triple product correlations involving the transverse
beam polarization vanish if at least one subsequent chargino decay is not observed. We derive this result within the minimal supersymmetric standard model (MSSM) with complex parameters; however, it holds also in the general MSSM with SUSY flavor violation.Received: 29 March 2004, Published online: 30 July 2004 相似文献
5.
V. A. Khoze A. D. Martin M. G. Ryskin W. J. Stirling 《The European Physical Journal C - Particles and Fields》2004,35(2):211-220
The double-diffractive production of
and
mesons, with a rapidity gap on either side, is studied, using both the Regge formalism and the perturbative QCD approach. Due to the rather low scale, the exclusive double-diffractive process
is predicted to dominate, whereas the probability that the incoming protons dissociate is expected to be relatively small. We evaluate the corresponding
production cross sections at the Tevatron and LHC energies. For the double-diffractive process with proton dissociation, it is possible to select events with large transverse momenta transferred through the rapidity gaps, by measuring the transverse energy,
, flows in the proton fragmentation regions. Then the large
provides a scale to justify the use of perturbative QCD, and to allow a spin-parity analysis of the centrally produced system to be performed, by studying the azimuthal angular correlations between the directions of the forward and backward
flows. The central production of the new X(3872) charmonium state is considered.Received: 24 March 2004, Published online: 11 May 2004 相似文献
6.
The DELPHI Collaboration J. Abdallah et al. 《The European Physical Journal C - Particles and Fields》2003,28(1):15-26
Searches for resonant production in e
+
e
-
collisions under the assumption that R-parity is not conserved and that the dominant R-parity violating coupling is or used data recorded by DELPHI in 1997 to 2000 at centre-of-mass energies of 183 to 208 GeV. No deviation from the Standard
Model was observed. Upper limits are given for the and couplings as a function of the sneutrino mass and total width. The limits are especially stringent for sneutrino masses equal
to the centre-of-mass energies with the highest integrated luminosities recorded.
Received: 14 January 2003 / Published online: 14 March 2003 相似文献
7.
D. Bardin 《The European Physical Journal C - Particles and Fields》2002,24(3):373-383
We study predictions for the reaction . The complete one-loop corrections are taken into account and higher order contributions, in particular those for the observed
real photons, are added whenever necessary. The event generator MC, a general-purpose Monte Carlo generator for the process based on the method of exclusive exponentiation, is used as the environment. We extend its applicability to the process ,, where the observation of at least a single is required. The exponentiation is implemented in much the same way as for the s-channel process alone. In particular, all photonic effects present in the case of W exchange, which cannot be included in the s-channel exponentiation scheme, are calculated to a finite order only. The real hard photon matrix element is calculated up
to . Leading logarithmic contributions of the two-loop corrections and one-loop photonic corrections accompanying real single-photon
emission are included. The electroweak corrections are calculated with the DIZET library of the ZFITTER package. Numerical
tests and predictions for typical observables are presented.
Received: 30 October 2001 / Revised version: 5 March 2002 / Published online: 22 May 2002 相似文献
8.
We present a complete one-loop study of the process
and the predicted cross section in a
Linear Collider. A suitable numerical code, PLATONlc, valid for any set of real MSSM parameters, is released. This study and code are complementary to those suitable for dark matter detection through the inverse process
describing neutralino-neutralino annihilation at rest, which were presented previously. If SUSY is realized in nature, both codes should be very helpful in future astrophysical and collider studies of the neutralino sector.Received: 6 November 2003, Published online: 9 January 2004Programme dActions Intégrées Franco-Hellenique, Platon 04100 UM. 相似文献
9.
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 相似文献
10.
We study the interference of resonant Higgs boson exchange in neutralino production in
m+ m-\mu^ + \mu^-
annihilation with longitudinally polarized beams. We use the energy distribution of the decay lepton in the process
[(c)\tilde]0j ? l± [(l)\tilde]-±\tilde{\chi}^0_j \to \ell^{\pm} \tilde{\ell}^\mp
to determine the polarization of the neutralinos. In the CP-conserving minimal supersymmetric standard model a non-vanishing asymmetry in the lepton energy spectrum is caused by the interference of Higgs boson exchange channels with different CP-eigenvalues. The contribution of this interference is large if the heavy neutral bosons H and A are nearly degenerate. We show that the asymmetry can be used to determine the couplings of the neutral Higgs bosons to the neutralinos. In particular, the asymmetry allows one to determine the relative phase of the couplings. We find large asymmetries and cross sections for a set of reference scenarios with nearly degenerate neutral Higgs bosons. 相似文献
11.
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
12.
H.K. Dreiner O. Kittel U. Langenfeld 《The European Physical Journal C - Particles and Fields》2008,54(2):277-284
We analyze the impact of electron and positron beam polarization on radiative neutralino production at the international linear
collider (ILC). We focus on three different mSUGRA scenarios in turn at the Higgs strahlung threshold, the top pair production
threshold, and at 500 GeV. In these scenarios at the corresponding , radiative neutralino production is the only supersymmetric production mechanism that is kinematically allowed. The heavier
neutralinos and charginos as well as the sleptons, squarks and gluinos are too heavy to be pair produced. We calculate the
signal cross section and also the standard model background from radiative neutrino production. For our scenarios, we obtain
significances larger than 10 and signal to background ratios between 2% and 5%, if we have electron beam polarization –0.8 and positron beam polarization –0.3. If we have electron beam polarization of , then the signal is observable with but both the significance and the signal to background ratio are significantly improved for . 相似文献
13.
The CP-violating asymmetries in the
decay, when one of the leptons is polarized, is investigated using the most general form of the effective Hamiltonian. The sensitivity of the CP-violating asymmetries to the new Wilson coefficients is studied.Received: 23 August 2003, Published online: 4 November 2003 相似文献
14.
The H Collaboration 《The European Physical Journal C - Particles and Fields》2004,36(4):441-452
Deep-inelastic positron-proton interactions at low values of Bjorken-x down to
which give rise to high transverse momentum
-mesons are studied with the H1 experiment at HERA. The inclusive cross section for
-mesons produced at small angles with respect to the proton remnant (the forward region) is presented as a function of the transverse momentum and energy of the
and of the four-momentum transfer Q
2 and Bjorken-x. Measurements are also presented of the transverse energy flow in events containing a forward
-meson. Hadronic final state calculations based on QCD models implementing different parton evolution schemes are confronted with the data.Received: 8 April 2004, Revised: 7 July 2004, Published online: 30 July 2004Dedicated to the memory of Krzysztof Rybicki 相似文献
15.
16.
A. Bredenstein S. Dittmaier M. Roth 《The European Physical Journal C - Particles and Fields》2005,44(1):27-49
The
electroweak radiative corrections to
within the electroweak standard model are calculated in double-pole approximation (DPA). Virtual corrections are treated in DPA, leading to a classification into factorizable and non-factorizable contributions, and real-photonic corrections are based on complete lowest-order matrix elements for
. Soft and collinear singularities appearing in the virtual and real corrections are combined alternatively in two different ways, namely by using the dipole subtraction method or by applying phase-space slicing. The radiative corrections are implemented in a Monte Carlo generator called Coffer
- the computer code can be obtained from the authors upon request - which optionally includes anomalous triple and quartic gauge-boson couplings in addition and performs a convolution over realistic spectra of the photon beams. A detailed survey of numerical results comprises
corrections to integrated cross sections as well as to angular, energy, and invariant-mass distributions. Particular attention is paid to the issue of collinear safety in the observables.Received: 3 June 2005, Published online: 5 August 2005 相似文献
17.
S. Alekhin V. Borodulin A. Çelikel M. Kantar S. Sultansoy 《The European Physical Journal C - Particles and Fields》1999,11(2):301-307
The recent proposals concerning the usage of the real polarized gamma beam, obtained by Compton backscattering of the laser
photons off the electron beams from either the linear or circular accelerators were considered. The heavy quark photoproduction
process, which gives a unique opportunity to measure the polarized gluon distribution, was investigated.
Received: 22 March 1999 / Revised version: 17 June 1999 / Published online: 14 October 1999 相似文献
18.
A. Bredenstein S. Dittmaier M. Roth 《The European Physical Journal C - Particles and Fields》2004,36(3):341-363
We have constructed a Monte Carlo generator (the corresponding FORTRAN code can be obtained from the authors upon request) for lowest-order predictions for the processes
and
in the standard model and extensions thereof by an effective
coupling as well as anomalous triple and quartic gauge-boson couplings. Polarization is fully supported, and a realistic photon beam spectrum can be taken into account. For the processes
all helicity amplitudes are explicitly given in a compact form. The presented numerical results contain, in particular, a survey of cross sections for representative final states and their comparison to results obtained with the program package Whizard/Madgraph. The impact of a realistic beam spectrum on cross sections and distributions is illustrated. Moreover, the size of various contributions to cross sections, such as from weak charged- or neutral-current, or from strong interactions, is analyzed. Particular attention is paid to W-pair production channels
where we investigate the impact of background diagrams, possible definitions of the W-pair signal, and the issue of gauge-invariance violation caused by finite gauge-boson widths. Finally, the effects of triple and quartic anomalous gauge-boson couplings on cross sections as well as the possibility to constrain these anomalous couplings at future
colliders are discussed.Received: 19 May 2004, Published online: 16 July 2004 相似文献
19.
We have calculated the next-to-leading order cross section for the inclusive production of charm quarks as a function of
the transverse momentum pT and the rapidity in two approaches using massive or massless charm quarks. For the single-resolved cross section we have
derived the massless limit from the massive theory. We find that this limit differs from the genuine massless version with
factorization by finite corrections. By adjusting subtraction terms we establish a massive theory with subtraction which approaches the massless theory very fast with increasing transverse momentum. With these results and including
the equivalent results for the direct cross section obtained previously as well as double-resolved contributions, we calculate
the inclusive cross section in collisions using realistic evolved non-perturbative fragmentation functions and compare with recent data from the LEP collaborations
ALEPH, L3 and OPAL. We find good agreement.
Received: 14 February 2003 / Published online: 5 May 2003 相似文献
20.
The ALEPH Collaboration A. Heister et al. 《The European Physical Journal C - Particles and Fields》2003,28(1):1-13
Events containing only energetic photons are analysed in a sample of of data recorded from collisions at centre-of-mass energies between 189 and 209 GeV by the ALEPH detector at LEP. The and cross sections are measured and found to be in agreement with the standard model predictions. The number of light
neutrino generations is determined to be . Upper limits are derived on the cross sections for photon production in the context of several supersymmetric models. Limits
are also set on the parameters of models with extra spatial dimensions, with contact interactions and with excited electrons.
Received: 27 May 2002 / Published online: 14 March 2003 相似文献