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1.
E. Boos H.-U. Martyn G. Moortgat-Pick M. Sachwitz A. Sherstnev P. M. Zerwas 《The European Physical Journal C - Particles and Fields》2003,30(3):395-407
The basic parameters of supersymmetric theories can be determined at future e
+
e
- linear colliders with high precision. We investigate in this report how polarisation measurements in
and
or
decays to
leptons and t quarks plus neutralinos or charginos can be used to measure
(in particular for large values) and to determine the trilinear couplings
, A
t
and A
b
in sfermion pair production.Received: 17 April 2003, Revised: 3 July 2003, Published online: 29 August 2003 相似文献
2.
Multijet production rates in neutral current deep inelastic scattering have been measured in the range of exchanged boson
virtualities
. The data were taken at the ep collider HERA with centre-of-mass energy
using the ZEUS detector and correspond to an integrated luminosity of
. Jets were identified in the Breit frame using the kT cluster algorithm in the longitudinally invariant inclusive mode. Measurements of differential dijet and trijet cross sections
are presented as functions of jet transverse energy (
), pseudorapidity (
) and Q2 with
and
. Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant
, determined from the ratio of the trijet to dijet cross sections, is
.
Received: 1 April 2005, Revised: 28 June 2005, Published online: 30 August 2005 相似文献
3.
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
4.
Di-jet production is studied in collisions of quasi-real photons at e + e- centre-of-mass energies
from 189 to 209 GeV at LEP. The data were collected with the OPAL detector. Jets are reconstructed using an inclusive
-clustering algorithm for all cross-section measurements presented. A cone jet algorithm is used in addition to study the different structure of the jets resulting from either of the algorithms. The inclusive di-jet cross-section is measured as a function of the mean transverse energy
of the two leading jets, and as a function of the estimated fraction of the photon momentum carried by the parton entering the hard sub-process,
, for different regions of
. Angular distributions in di-jet events are measured and used to demonstrate the dominance of quark and gluon initiated processes in different regions of phase space. Furthermore the inclusive di-jet cross-section as a function of
and
is presented, where
is the jet pseudo-rapidity. Different regions of the
-
-space are explored to study and control the influence of an underlying event. The results are compared to next-to-leading order perturbative QCD calculations and to the predictions of the leading order Monte Carlo generator PYTHIA.Received: 20 December 2002, Published online: 17 October 2003 相似文献
5.
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
6.
Measurements of on-shell ZZ production are described, using data from the DELPHI experiment at LEP in e
+
e
- collisions at centre-of-mass energies between 183 and 209 GeV, corresponding to an integrated luminosity of about 665 pb-1. Results obtained in each of the final states
,
,
,
,
, l
+
l
-
l
+
l
-, and
(with
) are presented. The measured production cross-sections are consistent with the Standard Model expectations. These results update and supersede those already published at 183 and 189 GeV.Received: 3 March 2002, Revised: 28 May 2003, Published online: 19 September 2003 相似文献
7.
The H Collaboration 《The European Physical Journal C - Particles and Fields》2003,29(4):497-513
Inclusive jet cross sections are measured in photoproduction at HERA using the H1 detector. The data sample of
events in the kinematic range of photon virtualities
and photon-proton centre-of-mass energies
represents an integrated luminosity of
. Jets are defined using the inclusive
algorithm. Single- and multi-differential cross sections are measured as functions of jet transverse energy ET jet and pseudorapidity
in the domain
and
. The cross sections are found to be in good agreement with next-to-leading order perturbative QCD calculations corrected for fragmentation and underlying event effects. The cross section differential in ET jet, which varies by six orders of magnitude over the measured range, is compared with similar distributions from
colliders at equal and higher energies.Received: 24 February 2003, Revised: 26 May 2003, Published online: 11 July 2003 相似文献
8.
production in
interactions has been detected via its decays into
,K
+
K
-
K
+
K
- and
in the data taken with the DELPHI detector at LEP1 and LEP2 energies. The two-photon radiative width averaged over all observed decay channels is
= 13.9
2.0 (stat.)
1.4(syst.)
2.7 (BR) keV. No direct decay channel
has been observed. An upper limit
< 5.5 keV at 95% confidence level has been evaluated for this decay mode.Received: 3 July 2003, Published online: 7 November 2003 相似文献
9.
A model describing the leptoproduction of
mesons is considered. For the amplitude of the photon dissociation into a
pair, the light-cone wave function is used. Scattering of the colorless
pair off the nucleon is computed within reggeon exchange phenomenology. The transition of the scattered quark and antiquark into the final
meson is treated with the aid of the parton-hadron duality concept. Numerical calculations of
and r0400 describe the world data at Q2 < 4 GeV2 rather reasonably. The calculations of the
meson spin density matrix show that the computed matrix elements except r0400 are in good agreement with the available experimental data at Q2 up to 8 GeV2 and the total mass of the
system greater than 4 GeV. The Regge phenomenology predictions at the highest experimentally available energies agree with both the HERA data and calculations performed within the perturbative QCD approach even for very high Q2 (
-20 GeV2). The predicted scale of the S-channel helicity non-conservation is in reasonable agreement with the experimental data.Received: 18 September 2003, Revised: 17 December 2003, Published online: 13 February 2004 相似文献
10.
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
11.
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
12.
The ZEUS inclusive differential cross-section data from HERA, for charged and neutral current processes taken with e + and e- beams, together with differential cross-section data on inclusive jet production in e + p scattering and dijet production in
scattering, have been used in a new NLO QCD analysis to extract the parton distribution functions of the proton. The input of jet-production data constrains the gluon and allows an accurate extraction of
at NLO;
An additional uncertainty from the choice of scales is estimated as
. This is the first extraction of
from HERA data alone. 相似文献
13.
14.
Searches for stable, hadronizing scalar quarks and gluinos are performed using the data collected with the ALEPH detector at LEP. Gluon splitting into a gluino or a squark pair is searched for at centre-of-mass energies around the Z resonance, in the e + e-
and
processes. Stable squark pair production, and stop pair production with subsequent decays into a stable gluino,
, are also directly searched for at centre-of-mass energies from 183 to 209 GeV. Altogether, stable hadronizing stop (sbottom) quarks are excluded up to masses of 95 (92)
, and stable hadronizing gluinos are excluded up to 26.9
, at 95% confidence level. In the framework of R-parity-conserving supersymmetric models in which the gluino and the stop quark are the two lightest supersymmetric particles, a 95% C.L. lower limit of 80
is set on the stop quark mass.Received: 23 May 2003, Published online: 24 October 2003 相似文献
15.
Multi-ring signatures of
appearance via the oscillation
are formulated for a water Cherenkov detector. These signatures are appropriate for long-baseline neutrino experiments operating at relatively high neutrino energies
GeV that emphasize the matter effect. The NC background is less for selected multi-ring events than for 1e-like events, and may be directly estimated from the data. Our results suggest that best sensitivity to
and to the sign of
can be reached with baselines over some 6000 km.Received: 14 April 2003, Revised: 19 June 2003, Published online: 26 September 2003M.A. Kubantsev: Now at Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA 相似文献
16.
The production of
, D0, D + , Ds + and
charm hadrons and their antiparticles in e p scattering at HERA was measured with the ZEUS detector using an integrated luminosity of
. The measurement has been performed in the photoproduction regime with the exchanged-photon virtuality
and for photon-proton centre-of-mass energies in the range
. The charm hadrons were reconstructed in the range of transverse momentum
and pseudorapidity
. The production cross sections were used to determine the ratio of neutral and charged D-meson production rates,
, the strangeness-suppression factor,
, and the fraction of charged D mesons produced in a vector state,
. The measured
and
values agree with those obtained in deep inelastic scattering and in e + e- annihilations. The measured
value is smaller than, but consistent with, the previous measurements. The fractions of c quarks hadronising as a particular charm hadron,
, were derived in the given kinematic range. The measured open-charm fragmentation fractions are consistent with previous
results, although the measured
is smaller and
is larger than those obtained in e + e- annihilations. These results generally support the hypothesis that fragmentation proceeds independently of the hard sub-process.
Received: 12 August 2005, Revised: 8 September 2005, Published online: 6 October 2005 相似文献
17.
The hadronic photon structure function
is measured from data taken with the ALEPH detector at LEP. At centre-of-mass energies between
and
an integrated luminosity of
is analyzed in two ranges of Q2 with
GeV2 and 67.2 GeV2. Detector effects and acceptance are corrected for with a Tikhonov unfolding procedure. The results are compared to theoretical predictions and measurements from other experiments.Received: 12 June 2003, Published online: 11 August 2003 相似文献
18.
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
19.
M. Benayoun P. David L. DelBuono Ph Leruste H. B. O'Connell 《The European Physical Journal C - Particles and Fields》2003,29(3):397-411
We analyze a pion form factor formulation which fulfills the Analyticity requirement within the Hidden Local Symmetry (HLS)
Model. This implies an s-dependent dressing of the
VMD coupling and an account of several coupled channels. The corresponding function
provides nice fits of the pion form factor data from s=-0.25 to s=1 GeV2. It is shown that the coupling to
has little effect, while
improves significantly the fit probability below the
mass. No need for additional states like
shows up in this invariant-mass range. All parameters, except for the subtraction polynomial coefficients, are fixed from
the rest of the HLS phenomenology. The fits show consistency with the expected behaviour of
at s=0 up to
and with the phase shift data on
from threshold to somewhat above the
mass. The
sector is also examined in relation with recent data from CMD-2.
Received: 13 January 2003, Revised: 12 March 2003, Published online: 2 June 2003 相似文献
20.
A study of Z-boson pair production in e + e- annihilation at center-of-mass energies between 190 GeV and 209 GeV is reported. Final states containing only leptons, (
and
), quark and lepton pairs, (
,
) and only hadrons (
) are considered. In all states with at least one Z boson decaying hadronically, lifetime, lepton and event-shape tags are used to separate
pairs from
final states. Limits on anomalous ZZ
and ZZZ couplings are derived from the measured cross sections and from event kinematics using an optimal observable method. Limits on low scale gravity with large extra dimensions are derived from the cross sections and their dependence on polar angle.Received: 14 July 2003, Published online: 18 December 2003 相似文献