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1.
D. Bećirević Ph. Boucaud V. Giménez V. Lubicz M. Papinutto 《The European Physical Journal C - Particles and Fields》2004,37(3):315-321
We report our results for the bag parameter B
K
obtained from the quenched simulations on the lattice with Wilson fermions for three values of the lattice spacing. We implemented the method by which no subtraction of the mixing with other four-fermion
operators is needed. Our final result, in terms of the renormalization group invariant bag parameter, is
.Received: 9 July 2004, Revised: 27 July 2004, Published online: 21 September 2004 相似文献
2.
The quark mass function
in QCD is revisited, using a gluon propagator in the form 1/(k
2 + m
g
2) plus
, where the second (IR) term gives linear confinement for m
g
= 0 in the instantaneous limit, being another scale. To find
we propose a new (differential) form of the Dyson-Schwinger equation (DSE) for
, based on an infinitesimal subtractive renormalization via a differential operator which lowers the degree of divergence in integration on the RHS, by two units. This warrants
in the integrand since its k-dependence is no longer sensitive to the principal term (p-k)2 in the quark propagator. The simplified DSE (which incorporates the Ward-Takahashi (WT) identity in the Landau gauge) is satisfied for large p
2 by
=
, except for Log factors. The limit p
2 = 0 determines
. A third limit, p
2 = -m
0
2, defines the dynamical mass m
0 via
. After two checks (
MeV and
=
), for
with
MeV, the T-dependent DSE is used in the real time formalism to determine the critical index
analytically, with the IR term partly serving as the H-field. We find
MeV and check the vanishing of
and
at T
c.Received: 31 August 2004, Published online: 11 January 2005PACS:
24.85. + p, 12.38.Lg, 12.38.AwA.N. Mitra: Permanent address: 244 Tagore Park, Delhi-110009, India. 相似文献
3.
Inclusive cross-sections for gluon jet production are studied numerically in the perturbative QCD pomeron model for pA and central AA collisions at high energies. Two forms for the inclusive cross-sections, with and without emission from the triple pomeron vertex, are compared. The difference was found to reduce to a numerical factor
for momenta below the saturation momentum Q
s. Above Q
s no difference was found at all. For pA collisions the gluon spectrum was found to be
at momenta k below Q
s and
above it. For central AA collisions it was found to be
at momenta k below Q
s and
above it. At large k the spectrum goes like
, flattening with energy. The multiplicities turned out to be proportional to A
0.7 for pA collisions and A for central AA collisions with a good precision. In the latter case they are becoming more peaked at the center with the growth of energy. Their absolute values are high and grow rapidly with energy in accordance with the high value of the BFKL intercept.Received: 12 October 2004, Revised: 22 November 2004, Published online: 21 January 2005 相似文献
4.
The production rates and substructure of jets have been studied in charged current deep inelastic e
+
p scattering for Q
2 > 200 GeV2 with the ZEUS detector at HERA using an integrated luminosity of 110.5 pb-1. Inclusive jet cross sections are presented for jets with transverse energies
GeV and pseudorapidities in the range
. Dijet cross sections are presented for events with a jet having
GeV and a second jet having
GeV. Measurements of the mean subjet multiplicity,
, of the inclusive jet sample are presented. Predictions based on parton-shower Monte Carlo models and next-to-leading-order QCD calculations are compared to the measurements. The value of
, determined from
at
for jets with
GeV, is
. The mean subjet multiplicity as a function of Q
2 is found to be consistent with that measured in NC DIS.Received: 5 June 2003, Published online: 10 October 2003 相似文献
5.
A new evaluation of the hadronic vacuum polarization contribution to the muon magnetic moment is presented. We take into account the reanalysis of the low-energy e
+
e
-annihilation cross section into hadrons by the CMD-2 Collaboration. The agreement between e
+
e
-and
spectral functions in the
channel is found to be much improved. Nevertheless, significant discrepancies remain in the center-of-mass energy range between 0.85 and
, so that we refrain from averaging the two data sets. 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 corresponding Standard Model predictions for the muon magnetic anomaly read
where the errors account for the hadronic, light-by-light (LBL) scattering and electroweak contributions. The deviations from the measurement at BNL are found to be
(1.9
) and
(0.7
) for the e
+
e
-- and
-based estimates, respectively, where the second error is from the LBL contribution and the third one from the BNL measurement.Received: 7 September 2003, Published online: 30 October 2003 相似文献
6.
The recent observations of f
0(980) in charmless B decays motivate further studies of scalar particle and glueball production in these processes. Amplitudes for charmless two-body B decays involving the members of the scalar nonet are presented based on the symmetries of the dominant penguin contribution. Different scenarios for the lightest scalar nonet are investigated in view of the presently available data. We describe the evidence from B decays for f
0(1500) with a flavor octet like mixing and the hints towards the members of the
nonet of lowest mass. There is further support for the hypothesis of a broad 0 + + glueball acting as coherent background especially in
. The estimated B decay rates into gluonic mesons represent a sizable fraction of the theoretically derived decay rate for
.Received: 23 April 2004, Revised: 27 October 2004, Published online: 21 December 2004Work supported in part by the Schweizerischer Nationalfonds. 相似文献
7.
Cross sections for e
+
p charged current deep inelastic scattering at a centre-of-mass energy of
have been determined with an integrated luminosity of
collected with the ZEUS detector at HERA. The differential cross sections
,
and
for
are presented. In addition,
has been measured in the kinematic range
and . The predictions of the Standard Model agree well with the measured cross sections. The mass of the W boson propagator is determined to be
from a fit to
. The chiral structure of the Standard Model is also investigated in terms of the (1-y)2 dependence of the double-differential cross section. The structure-function
has been extracted by combining the measurements presented here with previous ZEUS results from e
-
p scattering, extending the measurement obtained in a neutrino-nucleus scattering experiment to a significantly higher Q
2 region.Received: 17 July 2003, Published online: 12 November 2003
a supported by the Natural Sciences and Engineering Research Council
of Canada (NSERC)
b supported by the German
Federal Ministry for Education and Research (BMBF), under contract numbers HZ1GUA 2,
HZ1GUB 0, HZ1PDA 5, HZ1VFA 5
c supported by the
MINERVA Gesellschaft für Forschung GmbH, the Israel Science Foundation, the U.S.-Israel
Binational Science Foundation and the Benozyio Center for High Energy Physics
d supported by
the German-Israeli Foundation and the Israel Science Foundation
e supported
by the Italian National Institute for Nuclear Physics (INFN)
f supported
by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and its grants
for Scientific Research
g supported by the
Korean Ministry of Education and Korea Science and Engineering Foundation
h supported
by the Netherlands Foundation for Research on Matter (FOM)
i supported by the
Polish State Committee for Scientific Research, grant no. 620/E-77/SPUB-M/DESY/P-03/DZ 247/2000-2002
j partially
supported by the German Federal Ministry for Education and Research (BMBF)
k supported by
the Fund for Fundamental Research of Russian Ministry for Science and Education and by
the German Federal Ministry for Education and Research (BMBF)
l supported by the
Spanish Ministry of Education and Science through funds provided by CICYT
m supported by
the Particle Physics and Astronomy Research Council, UK
n supported by the
US Department of Energy
o supported by the US
National Science Foundation
p supported by the
Polish State Committee for Scientific Research, grant no. 112/E-356/SPUB-M/DESY/P-03/DZ 301/2000-2002, 2 P03B 13922
q supported by the Polish State Committee for Scientific Research, grant no. 115/E-343/SPUB-M/DESY/P-03/DZ 121/2001-2002, 2 P03B 07022 相似文献
8.
The uncertainties in estimating the hadronic production of the B
c
meson are studied in the framework of the complete
approach of perturbative QCD and the gluon-gluon fusion mechanism. Quantitative comparisons of the production at TEVATRON and LHC are made. Considering the detectors at TEVATRON and LHC, we have also estimated the production with proper kinematic cuts. Based on the results, we conclude that the experimental studies of the B
c
meson at the two colliders will be complementary and mutually stimulative. We find that as the CM energy is increasing from RUN-I to RUN-II at TEVATRON, the production cross section increases by about
.Received: 21 July 2004, Published online: 18 November 2004PACS:
12.38.Bx, 13.85.Ni, 14.40.Nd, 14.40.Lb 相似文献
9.
10.
J. Gasser B. Kubis N. Paver M. Verbeni 《The European Physical Journal C - Particles and Fields》2005,40(2):205-227
Motivated by recent experimental results and ongoing measurements, we review the chiral perturbation theory prediction for
decays. Special emphasis is given to the stability of the inner bremsstrahlung-dominated relative branching ratio versus the K
e3 form factors, and on the separation of the structure-dependent amplitude in differential distributions over the phase space. For the structure-dependent terms, an assessment of the order p
6 corrections is given, in particular, a full next-to-leading order calculation of the axial component is performed. The experimental analysis of the photon energy spectrum is discussed, and other potentially useful distributions are introduced.Received: 9 December 2004, Published online: 21 February 2005PACS:
13.20.Eb, 11.30.Rd, 12.39.Fe 相似文献
11.
We have calculated the next-to-leading order cross sections for the inclusive production of D
* mesons in
collisions at HERA in two approaches using massive or massless charm quarks. The usual massive theory for the direct cross section with charm quarks only in the final state was transformed into a massive theory with
subtraction by subtracting the mass divergent and additional finite terms calculated earlier in connection with the process
. This theory approaches the massless theory with increasing transverse momentum. The difference between the massive and the massless approach with
subtraction is studied in detail in those kinematic regions relevant for comparison with experimental data. With these results and including the resolved cross section which is dominated by the part originating from the charm in the photon, we compute the fully inclusive
cross section and compare it with preliminary data from the ZEUS collaboration at HERA. We find on average good agreement.Received: 5 October 2004, Published online: 26 November 2004 相似文献
12.
Constraints on the whole spectrum of lepton flavor violating vertices are shown in the context of the standard two Higgs doublet model. The vertex involving the e-
mixing is much more constrained than the others, and the decays proportional to such a vertex are usually very suppressed. On the other hand, bounds on the quark sector are obtained from leptonic decays of the Bd,s0 mesons and from
. We emphasize that although the Bd0-
mixing restricts severely the d-b mixing vertex, the upper bound for this vertex could still give a sizable contribution to the decay
with respect to the standard model contribution, from which we see that such a vertex could still play a role in the phenomenology.Received: 16 September 2004, Published online: 26 April 2005PACS:
12.60.Fr, 12.15.Mm, 12.15.Ff, 11.30.Hv 相似文献
13.
V. A. Khoze A. D. Martin M. G. Ryskin 《The European Physical Journal C - Particles and Fields》2004,34(3):327-334
We study the central diffractive production of the (three neutral) Higgs bosons, with a rapidity gap on either side, in an MSSM scenario with CP-violation. We consider the
and
decay for the light H1 boson and the four b-jet final state for the heavy H2 and H3 bosons, and discuss the corresponding backgrounds. A direct indication of the existence of CP-violation can come from the observation of either an azimuthal asymmetry in the angular distribution of the tagged forward protons (for the exclusive
process) or of a
contribution in the azimuthal correlation between the transverse energy flows in the proton fragmentation regions for the process with the diffractive dissociation of both incoming protons (
). We emphasise the advantage of reactions with the rapidity gaps (that is, production by pomeron-pomeron fusion) to probe CP-parity and to determine the quantum numbers of the produced central object.Received: 16 January 2004, Published online: 31 March 2004 相似文献
14.
The H Collaboration 《The European Physical Journal C - Particles and Fields》2004,37(2):141-159
Triple differential dijet cross sections in
interactions are presented in the region of photon virtualities 2 < Q
2 < 80 GeV2, inelasticities 0.1 < y < 0.85, jet transverse energies E
*
T 1 > 7 GeV, E
*
T 2 > 5 GeV, and pseudorapidities
. The measurements are made in the
centre-of-mass frame, using an integrated luminosity of 57 pb-1. The data are compared with NLO QCD calculations and LO Monte Carlo programs with and without a resolved virtual photon contribution. NLO QCD calculations fail to describe the region of low Q
2 and low jet transverse energies, in contrast to a LO Monte Carlo generator which includes direct and resolved photon interactions with both transversely and longitudinally polarised photons. Initial and final state parton showers are tested as a mechanism for including higher order QCD effects in low E
T
jet production.Received: 13 January 2004, Revised: 21 July 2004, Published online: 18 August 2004 相似文献
15.
We use an appropriate combination of moments of finite energy sum rules in QCD in order to compute the B
q
-meson decay constants f
B
and
. We perform the calculation using a two-loop computation of the imaginary part of the pseudoscalar two point function in terms of the running bottom quark mass. The results are stable against the so-called QCD duality threshold, and they are in agreement with the estimates obtained from Borel transform QCD sum rules and lattice computations.Received: 28 July 2004, Revised: 10 September 2004, Published online: 23 November 2004PACS:
12.38.Bx, 12.38.LgSupported by MCYT-FEDER under contract FPA2002-00612. 相似文献
16.
A. Bartl H. Fraas T. Kernreiter O. Kittel 《The European Physical Journal C - Particles and Fields》2004,33(3):433-442
We define a CP-sensitive asymmetry in the sfermion decays
, based on triple product correlations between the momenta of the outgoing fermions. We study this asymmetry in the MSSM with complex parameters. We show that the asymmetry is sensitive to the phases of the parameters and M1. The leading contribution stems from the decay chain
, for which we obtain analytic formulae for the amplitude squared. The asymmetry can go up to
for
, and up to
for
. We also estimate the rates necessary to measure the asymmetry.Received: 2 July 2003, Revised: 7 November 2003, Published online: 13 February 2004 相似文献
17.
J. Cao Z. Xiong J. M. Yang 《The European Physical Journal C - Particles and Fields》2004,32(2):245-252
In the supersymmetric seesaw model, large flavor mixings of sleptons induce the lepton flavor violating (LFV) interactions
(
), which give rise to various LFV processes. In this work we examine the LFV decays
. Subject to the constraints from the existing neutrino oscillation data and the experimental bounds on the decays
, these LFV Z-decays are found to be sizable, and among them the largest-rate channel
can occur with a branching ratio of 10-8 and may be accessible at the LHC or GigaZ experiment.Received: 1 September 2003, Published online: 20 November 2003 相似文献
18.
The difference of vector and axial-vector charged current correlators is analyzed by means of QCD sum rules. The contribution of 10-dimensional 4-quark condensates is calculated and its value is estimated within the framework of the factorization hypothesis. It is compared to the result obtained from an operator fit of Borel sum rules in the complex q
2-plane, calculated from experimental data on hadronic
-decays. This fit gives accurate values of the light quark condensate and the quark-gluon mixed condensate. The size of the high-order operators and the convergence of the operator series are discussed.Received: 10 May 2004, Revised: 7 September 2004, Published online: 18 November 2004 相似文献
19.
We review CP-violating effects in
jet and
4 jet decays, assuming the presence of CP-violating effective
and
couplings. Longitudinal beam polarization is included in the studies. We propose a direct search for such CP-violating couplings by using various CP-odd observables. The data of a future linear collider running at the Z-resonance in the so-called GigaZ option should give significant information on the couplings. Finally we show that stringent bounds on the mass of excited b quarks can be derived if appropriate couplings are of a size characteristic of a strong interaction.Received: 21 August 2003, Published online: 20 November 2003 相似文献
20.
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