27,083 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
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
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
Triggering on hard probes in heavy ion collisions with CMS
We present a study of the CMS trigger system in heavy-ion collisions.
Concentrating on two physics channels, dimuons from decays of quarkonia and
single jets, we evaluate a possible trigger strategy for Pb+Pb running that
relies on event selection solely in the High-Level Trigger (HLT). The study is
based on measurements of the timing performance of the offline algorithms and
event-size distributions using full simulations. Using a trigger simulation
chain, we compare the physics reach for the jet and dimuon channels using
online selection in the HLT to minimum bias running. The results demonstrate
the crucial role the HLT will play for CMS heavy-ion physics.Comment: 4 pages, 4 fugures, contribution to QM'06 conferenc
Dihadron correlations in PbPb collisions at 2.76 TeV with CMS
Measurements of charged dihadron DeltaEta-DeltaPhi correlations from the CMS
collaboration are presented for PbPb collisions at a center-of-mass energy of
2.76 TeV per nucleon pair over a broad range of pseudorapidity and the full
range of azimuthal angle. A significant correlated yield is observed for pairs
of particles with small DeltaPhi but large longitudinal separation DeltaEta,
commonly known as the "ridge". The ridge persists up to at least |DeltaEta| = 4
and the dependence of the ridge region shape and yield on collision centrality
and transverse momentum has been measured. A Fourier analysis of the long-range
two-particle correlation is presented and discussed in the context of higher
order flow coefficients.Comment: Proceedings of presentation given at Quark Matter 201
Isospin constraints from/on B->pipi
The Standard Model constraints on alpha which can be derived from the B->
pipi decays are revisited in some depth. As experimental inputs, the three
branching ratios, the two CP parameters Spipi and Cpipi and/or the value of
alpha 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 B00 and the
function C00(B00) are introduced. The Grossman-Quinn bound is rediscussed. A
close form expression is given for alpha as a function of the measurements.
Various scenarii for the future of the isospin analysis are explored. To probe
the Standard Model the (B00,C00) plane is introduced.Comment: 25 pages, 8 figures, Submitted to Eur. Phys. J.
The First Year IceCube-DeepCore Results
The IceCube Neutrino Observatory includes a tightly spaced inner array in the
deepest ice, called DeepCore, which gives access to low-energy neutrinos with a
sizable surrounding cosmic ray muon veto. Designed to be sensitive to neutrinos
at energies as low as 10 GeV, DeepCore will be used to study diverse physics
topics with neutrino signatures, such as dark matter annihilations and
atmospheric neutrino oscillations. The first year of DeepCore physics
data-taking has been completed, and the first observation of atmospheric
neutrino-induced cascades with IceCube and DeepCore are presented.Comment: 4 pages, 3 figures, TAUP 2011 (Journal of Physics: Conference Series
(JCPS)
Production of J/psi Mesons at HERA
Inelastic and diffractive production of J/psi mesons at HERA is reviewed. The
data on inelastic photoproduction are described well within errors by the
Colour Singlet Model in next-to-leading order. A search for colour octet
processes predicted within the NRQCD/factorisation approach is conducted in
many regions of phase space. No unambiguous evidence has been found to date.
Diffractive elastic production of J/psi mesons has been measured in the limit
of photoproduction up to the highest photon proton center of mass energies. The
increase of the cross section is described by pQCD models. At larger Q^2, the W
dependence is found to be similar to that observed in photoproduction. First
analyses of data at high t yield a powerlike dependence on |t|. A LO BFKL
calculation gives a good description of the data.Comment: 14 pages, 12 figures, contribution to Ringberg 200
Rho Meson Diffraction off Au Nuclei
The STAR Ultra Peripheral Collisions program has collected a substantial
sample of mesons and for the first time at RHIC energies it has been
able to extract the distribution of momentum transfer t from diffractive
elastic scattering off the Au ion. The resulting diffraction pattern is
consistent with coherent scattering off a nuclear object the size of the Au
nuclei. Measurements of this nature can offer insights and guidance to the
ongoing preparations for the new electron ion programs.Comment: 8 pages 11 figures, submitted to the proceedings of the 28th Winter
Workshop on Nuclear Dynamic
Strange Particle Production Mechanisms in Proton-Proton Collisions at RHIC
We present data on strange particle production in elementary proton-proton
collisions at RHIC energies. Comparison to leading order and next-to-leading
order (NLO) calculations shows that the fragmentation process is flavor
dependent and that higherorder corrections are needed to describe all spectra,
in particular at these collision energies, which are modest compared to the
Tevatron energies. A model (EPOS) which takes into account multiple scattering
between projectile constituents seems to describe the data best.Comment: 4 pages, 4 figures, QM2005 poster proceedings, updated according to
referee repor
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