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1.
Measurements of the time-dependent CP-asymmetry in the decay
and its charge conjugate by the BELLE and BABAR collaborations currently yield
and
, characterizing the direct and mixing-induced CP-asymmetries, respectively. We study the implication of these measurements on the CKM phenomenology taking into account the available information in the quark mixing sector. Our analysis leads to the results that the ratio |P
c
/T
c
| involving the QCD-penguin and tree amplitudes and the related strong phase difference
in the
decays are quite substantial. Using the isospin symmetry to constrain |P
c
/T
c
| and
, where
parameterizes the penguin-induced contribution, we present a fit of the current data including the measurements of
and
. Our best-fits yield
,
,
,
, and
. At 68% C.L., the ranges are
,
,
,
and
. Currently en vogue dynamical approaches to estimate the hadronic matrix elements in
decays do not provide a good fit of the current data.Received: 5 April 2004, Published online: 14 July 2004A.Ya. Parkhomenko: On leave of absence from Department of Theoretical Physics, Yaroslavl State University, Sovietskaya 14, 150000 Yaroslavl, Russia. 相似文献
2.
We analyze the pion electromagnetic, charged-current, and
transition form factors at timelike momentum transfers q,
GeV2, using a dispersion approach. We discuss in detail the propagator matrix of the photon-vector meson system and define certain reduced amplitudes, or vertex functions, describing the coupling of this system to final states. We then apply the derived analytic expressions to the analysis of the recent
,
, and
data. We find the reduced amplitudes for the coupling of the photon and vector mesons to two pseudoscalars to be constant, independent of s, in the range considered, indicating a freezing of the amplitudes for
GeV. The fit to the form factor data leads to the following values of the Breit-Wigner resonance masses
MeV,
MeV and
MeV, where the errors are only statistical.Received: 8 December 2003, Published online: 23 March 2004T. Paulus: Now at Philips 相似文献
3.
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
4.
The Standard Model constraints on
which can be derived from the
decays are revisited in some depth. As experimental inputs, the
,
decays complemented by the
decays, the CP parameters
and
, and/or the value of
as determined by the global CKM fit are used. The constraints discussed here are model independent in the sense that they rely only on Isospin symmetry, following the Gronau-London proposal. A new bound on
and the function
are introduced. While another bound applied to BABAR results is shown to imply that
is negative. The Grossman-Quinn bound is rediscussed. A close form expression is given for
as a function of the measurements. Various scenarios for the future of the isospin analysis are explored. To probe the Standard Model the
plane is introduced.Received: 17 December 2004, Published online: 25 January 2005 相似文献
5.
The spin-parity analysis of the data on the
annihilation reaction at rest in liquid and in gaseous hydrogen at 3 bar pressure and in flight at
momentum of
MeV/c, collected by the Obelix spectrometer at the LEAR complex of CERN, is presented. The relative branching ratios
and
are obtained. It is also shown that the inclusion of the exotic meson
, JPC = 1- + , mass and width
,
GeV/c2, in its decay to
, improves the fit and some implications of these results are briefly discussed. The relative S and P-wave annihilation percentages in four charged pions at two target densities are obtained.Received: 2 December 2003, Published online: 23 April 2004 相似文献
6.
M. Neubert 《The European Physical Journal C - Particles and Fields》2005,40(2):165-186
Using results on soft-collinear factorization for inclusive B-meson decay distributions, a systematic study of the partial
decay rate with a cut
on photon energy is performed. For values of E
0 below about 1.9 GeV, the rate can be calculated without reference to shape functions using a multi-scale operator product expansion (MSOPE). The transition from the shape-function region to the MSOPE region is studied analytically. The resulting prediction for the
branching ratio depends on three large scales: m
b
,
, and
. Logarithms associated with these scales are resummed at next-to-next-to-leading logarithmic order. While power corrections in
turn out to be small, the sensitivity to the scale
GeV (for
GeV) introduces significant perturbative uncertainties, which so far have been ignored. The new theoretical prediction for the
branching ratio with
GeV is
, where the first error is an estimate of perturbative uncertainties and the second one reflects uncertainties in input parameters. With this cut
of all events are contained. When this fraction is combined with the previously best prediction for the total decay rate, one obtains
, with a somewhat less conservative estimate of parametric uncertainties. The implications of larger theory uncertainties for new physics searches are briefly explored with the example of the type-II two-Higgs-doublet model, for which the lower bound on the charged-Higgs mass is reduced compared with previous estimates to approximately 200 GeV at 95% confidence level.Received: 18 September 2004, Revised: 18 January 2005, Published online: 21 February 2005 相似文献
7.
We discuss the time-dependent CP asymmetry of the decay
in an extension of the standard model with both a two Higgs doublet and additional fourth-generation quarks. We show that, although the standard model with a two Higgs doublet and the standard model with fourth-generation quarks alone are not likely to largely change the effective
from the decay
, the model with both an additional Higgs doublet and fourth-generation quarks can easily account for the possible large negative value of
without conflicting with other experimental constraints. In this model, additional large CP violating effects may arise from the flavor-changing Yukawa interactions between neutral Higgs bosons and the heavy fourth-generation down type quark, which can modify the QCD penguin contributions. With the constraints obtained from
processes such as
and
, this model can lead to an effective
as large as - 0.4 in the CP asymmetry of
.Received: 25 March 2004, Revised: 20 April 2004, Published online: 18 June 2004 相似文献
8.
A. Bartl H. Fraas O. Kittel W. Majerotto 《The European Physical Journal C - Particles and Fields》2004,36(2):233-243
We study CP-sensitive observables in the neutralino production
and the subsequent two-body decays of the neutralino
and of the Z boson
. We identify the CP-odd elements of the Z boson density matrix and propose CP-sensitive triple-product asymmetries. We calculate these observables and the cross sections in the minimal supersymmetric standard model with complex parameters and M
1 for an e
+
e
- linear collider with
GeV and longitudinally polarized beams. We show that the asymmetries can reach
for
and
for
and discuss the feasibility of measuring these asymmetries.Received: 4 February 2004, Revised: 17 May 2004, Published online: 2 July 2004 相似文献
9.
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
10.
A resonance search has been made in the
invariant-mass spectrum with the ZEUS detector at HERA using an integrated luminosity of
. The decay channels
and
(and the corresponding antiparticle decays) were used to identify
mesons. No resonance structure was observed in the
mass spectrum from more than 60 000 reconstructed
mesons. The results are not compatible with a report of the H1 Collaboration of a charmed pentaquark,
.Received: 14 September 2004, Revised: 29 September 2004, Published online: 9 November 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.
The CP asymmetries of the decay
, which originates from
flavor-changing neutral-current processes, and its CP-averaged branching ratio BR
offer interesting avenues to explore flavor physics. We show that we may characterize this channel, within the standard model, in a theoretically clean manner through a surface in observable space. In order to extract the relevant information from BR
, further information is required, which is provided by the
system and the SU(3) flavor symmetry, where we include the leading factorizable SU(3)-breaking corrections and discuss how experimental insights into non-factorizable effects can be obtained. We point out that the standard model implies a lower bound for BR
, which is very close to its current experimental upper bound, thereby suggesting that this decay should soon be observed. Moreover, we explore the implications for color suppression in the
system, and convert the data for these modes in a peculiar standard-model pattern for the CP-violating
observables.Received: 3 August 2004, Published online: 15 November 2004 相似文献
13.
The anomalous weak dipole moments of the
lepton are measured in a data sample collected by ALEPH from 1990 to 1995 corresponding to an integrated luminosity of 155 pb-1. Tau leptons produced in the reaction
at energies close to the
mass are studied using their semileptonic decays to
,
,
or
. The real and imaginary components of both the anomalous weak magnetic dipole moment and the CP-violating anomalous weak electric dipole moment,
,
,
and
, are measured simultaneously by means of a likelihood fit built from the full differential cross section. No evidence of new physics is found. The following bounds are obtained (95% CL):
,
,
, and
.Received: 25 September 2002, Published online: 29 August 2003 相似文献
14.
In the framework of QCD factorization, we study
decays. In order to more reliably determine the phenomenological parameters X
H and X
A arising from end-point divergences in the hard spectator scattering and weak annihilation contributions, we use the global analysis for twelve
and VP decay modes, such as
,
,
,
, et cetera, but excluding the modes whose (dominant) internal quark-level process is
. Based on the global analysis, we critically investigate possible magnitudes of X
H,A and find that both large and small X
H,A terms are allowed by the global fit. In the case of the large X
H,A effects, the standard model (SM) prediction of the branching ratios (BRs) for
is large and well consistent with the experimental results. In contrast, in the case of the small X
H,A effects, the SM prediction for these BRs is smaller than the experimental data. Motivated by the recent Belle measurement of
through
, if we take into account possible new physics effects on the quark-level process
, we can explicitly show that these large BRs can be understood even in the small X
H,A case. Specifically, we present two new physics scenarios: R-parity violating SUSY and R-parity conserving SUSY.Received: 28 April 2004, Revised: 12 July 2004, Published online: 7 September 2004 相似文献
15.
We explore CP violation in
decay processes in the presence of the anomalous right-handed
and
couplings. The complex anomalous top coupling can be a source of new CP violation and may lead to a deviation of the observed weak phase in
decays, which accounts for the present disagreement of the observed
between
and
decays. Direct CP violation is also predicted.
Received: 27 November 2002, Revised: 28 March 2003, Published online: 2 June 2003 相似文献
16.
Cirigliano V. Ecker G. Neufeld H. Pich A. 《The European Physical Journal C - Particles and Fields》2004,33(3):369-396
We perform a complete analysis of isospin breaking in
amplitudes in chiral perturbation theory, including both strong isospin violation (
) and electromagnetic corrections to next-to-leading order in the low-energy expansion. The unknown chiral couplings are estimated at leading order in the 1/Nc expansion. We study the impact of isospin breaking on CP conserving amplitudes and rescattering phases. In particular, we extract the effective couplings g8 and g27 from a fit to
branching ratios, finding small deviations from the isospin-limit case. The ratio
measuring the
enhancement is found to decrease from
in the isospin limit to
in the presence of isospin breaking. We also analyze the effect of isospin violation on the CP violation parameter
, finding a destructive interference between three different sources of isospin violation. Within the uncertainties of large-Nc estimates for the low-energy constants, the isospin violating correction for
is below 15%.Received: 21 November 2003, Published online: 4 February 2004Work supported in part by IHP-RTN, Contract No. HPRN-CT2002-00311 (EURIDICE) and by Acciones Integradas, Project No. 19/2003 (Austria), HU2002-0044 (MCYT, Spain) 相似文献
17.
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
18.
D. V. Bugg 《The European Physical Journal C - Particles and Fields》2004,36(2):161-168
A partial wave analysis of PS185 data for
is presented. A 3
S
1 cusp is identified in the inverse process
at threshold, using detailed balance to deduce cross sections from
. Partial wave amplitudes for
3
P
0, 3
F
3, 3
D
3 and 3
G
3 exhibit a behaviour very similar to resonances observed in Crystal Barrel data. With this identification, the
data then provide evidence for a new I = 0, J
PC
= 1- resonance with mass
MeV,
MeV, coupling to both 3
S
1 and 3
D
1.Received: 4 June 2004, Published online: 9 July 2004 相似文献
19.
M. Benayoun P. David L. DelBuono Ph Leruste H. B. O’Connell 《The European Physical Journal C - Particles and Fields》2003,31(4):525-547
We examine the decay modes
within the context of the hidden local symmetry (HLS) model. Using numerical information derived in previous fits to the
and Ve
+
e
- decay modes in isolation and the
lineshape determined in a previous fit to the pion form factor, we show that all aspects of these decays can be predicted with fair accuracy. Freeing some parameters does not improve the picture. This is interpreted as strong evidence in favor of the box anomaly in the
decays, which occurs at precisely the level expected. We also construct the set of equations defining the amplitudes for
and
at the chiral limit, as predicted from the anomalous HLS Lagrangian appropriately broken. This provides a set of four equations depending on only one parameter, instead of three for the traditional set. This is also shown to match the (two-angle, two-decay-constant)
-
mixing scheme recently proposed and is also fairly well fulfilled by the data. The information returned from the fits also matches expectations from previously published fits to the
decay modes in isolation.Received: 29 June 2003, Revised: 17 September 2003, Published online: 4 November 2003 相似文献
20.
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