26,502 research outputs found
Review of Final LEP Results or A Tribute to LEP
After a comment on the performance of LEP some highlights of the LEP1 and
LEP2 physics programmes are reviewed. The talk concentrates on the precision
measurements at the Z resonance, two fermion production above the Z, W+W-
production, ZZ production, indirect limits on the Higgs mass, LEP contributions
to the exploration of the CKM matrix, and on the LEP measurements of alpha_s.Comment: Proceedings of the XX International Symposium on Lepton and Photon
Interactions at High Energies Rome, Italy, July 200
Remarks Concerning the Study of Four-Jet Events from Hadronic Decays of the Z0
The angular correlations of four-jet events from hadronic decays of the Z0
have been studied in the past mainly to extract from them the fundamental
constants of quantum chromodynamics called colour factors. Previous studies
have used all the available phase-space in order to maximize statistics. In
this note we want to point out the possibility that significant differences
between experiment and theory in restricted regions of phase-space might have
escaped detection. Such differences could be a harbinger of the existence of
new particles. Some preliminary results are presented.Comment: 9 pages, 3 figure
New NLO Parametrizations of the Parton Distributions in Real Photons
We present new NLO sets of parton distributions in real photons based on a
scheme invariant definition of the non-perturbative input. We compare the
theoretical predictions with LEP data and a best fit allows us to constrain the
parameters of the distributions. The shape of the gluon distribution is poorly
constrained and we consider the possibility to measure it in photoproduction
experiments. Three parametrizations which aim to take into account the
scattering of LEP data are proposed. They are compared to other NLO
parametrizations.Comment: 38 pages, 23 Postscript figures, fig. 6,7,8,9 improved, comparisons
with other NLO parametrizations, added reference
A new gamma*-p / pbar-p factorization test in diffraction, valid below Q^2 about 6 GeV^2
One of the key experimental issues in high energy hadron physics is the
extent to which data from the diffractive interaction mechanism may be
described by a factorized formula which is the product of a universal term
describing the probability of finding a Pomeron in a proton (loosely referred
to as the "Pomeron flux-factor") and a term decribing the Pomeron's interaction
with the other incident proton. In the present paper, after demonstrating that
existing data on diffractive gamma*-p and pbar-p interactions show that the
Pomeron flux-factor is not universal, we present the results of a new test of
factorization in these interactions which does not rely on universality of the
flux-factor. The test is satisfied to within ~20% for 1 < Q^2 ~ 6 GeV^2 and
beta < 0.2 in the gamma*-p interactions, suggesting that the resons for
non-universality of the flux-factor have a limited effect on the factorization
itself. However, a clear breakdown of this test is observed at larger Q^2.
Kharzeev and Levin suggest that this can be attributed to the onset of QCD
evolution effects in the Pomeron's structure. The breakdown occurs in a Q^2
region which agrees with their estimates of a small Pomeron size.Comment: 20 pages, 7 Encapsulated Postscript figures, LaTex, submitted to
European Phisical Journal
B Physics at the Z0 Resonance
B physics results from e+ e- annihilation at the Z0 resonance are reviewed. A
vast program is summarised, including the study of B+, B0d, B0s and b baryon
lifetimes, the time dependence of B0d and B0s oscillations, the width
difference in the B0s system, and the measurements of the magnitudes of the CKM
matrix elements Vcb and Vub.Comment: 17 pages, 8 figures, presented at the UK Phenomenology Workshop on
Heavy Flavour and CP Violation, 17-22 September 200
The neutrino velocity anomaly as an explanation of the missing observation of neutrinos in coincidence with GRB
The search for neutrinos emitted in coincidence with Gamma-Bay Burst has been
so far unsuccessfully. In this paper we show that the recent result reported by
the OPERA Collaboration on an early arrival time of muon neutrinos with respect
to the one computed assuming the speed of light in vacuum could explain the
null search for neutrinos in coincidence with Gamma-Ray Burst
Recent Low x and Diffractive Collider Data
Selected recent data from collider experiments pertaining to the
understanding of QCD at low Bjorken-x are reviewed. The status of QCD and Regge
factorisation in hard diffractive interactions is discussed in terms of data
from HERA and the Tevatron. The possibility of anomalous behaviour in the
total cross section is confronted with the most recent
measurements from LEP. Data from all three colliders that are sensitive to
possible BFKL effects are presented and different interpretations are
discussed.Comment: 9 pages, introductory talk from the 1999 Durham Phenomenology
Workshop on Collider Physic
On the physics and technology of gaseous particle detectors
Despite an already long and fruitful history, gaseous elementary-particle
detectors remain today an important mainstay of high-energy and nuclear physics
experiments and of radiation detection in general. In here we briefly describe
some of the gaseous detector's main technologies and applications, along with
some unsolved gas-discharge physics aspects of practical relevance.Comment: Submitted to Plasma Sources in Science and Technolog
Constraining the Unitarity Triangle with B -> V gamma
We discuss the exclusive radiative decays , , and in QCD factorization within the Standard
Model. The analysis is based on the heavy-quark limit of QCD. Our results for
these decays are complete to next-to-leading order in QCD and to leading order
in the heavy-quark limit. Special emphasis is placed on constraining the
CKM-unitarity triangle from these observables. We propose a theoretically clean
method to determine CKM parameters from the ratio of the decay
spectrum to the branching fraction of . The method is based on
the cancellation of soft hadronic form factors in the large energy limit, which
occurs in a suitable region of phase space. The ratio of the
and branching fractions determines the side of the
standard unitarity triangle with reduced hadronic uncertainties. The recent
Babar bound on implies , with the
limiting uncertainty coming only from the SU(3) breaking form factor ratio
. This constraint is already getting competitive with the constraint from
- mixing. Phenomenological implications from
isospin-breaking effects are briefly discussed.Comment: 23 pages, 8 figure
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