29,370 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
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.
LHC Coverage of RPV MSSM with Light Stops
We examine the sensitivity of recent LHC searches to signatures of
supersymmetry with R-parity violation (RPV). Motivated by naturalness of the
Higgs potential, which would favor light third-generation squarks, and the
stringent LHC bounds on spectra in which the gluino or first and second
generation squarks are light, we focus on scenarios dominated by the pair
production of light stops. We consider the various possible direct and cascade
decays of the stop that involve the trilinear RPV operators. We find that in
many cases, the existing searches exclude stops in the natural mass range and
beyond. However, typically there is little or no sensitivity to cases dominated
by UDD operators or LQD operators involving taus. We propose several ideas for
searches which could address the existing gaps in experimental coverage of
these signals.Comment: 41 pages, 12 figures; v2: included new searches (see footnote 10),
minor corrections and improvement
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
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
Flavor SU(3) analysis of charmless B meson decays to two pseudoscalar mesons
Global fits to charmless B --> PP decays in the framework of flavor SU(3)
symmetry are updated and improved without reference to the \sin2\beta measured
from the charmonium decay modes. Fit results directly constrain the
(\bar\rho,\bar\eta) vertex of the unitarity triangle, and are used to predict
the branching ratios and CP asymmetries of all decay modes, including those of
the B_s system. Different schemes of SU(3) breaking in decay amplitude sizes
are analyzed. The major breaking effect between strangeness-conserving and
strangeness-changing decays can be accounted for by including a ratio of decay
constants in tree and color-suppressed amplitudes. The possibility of having a
new physics contribution to K \pi decays is also examined from the data fitting
point of view.Comment: 22 pages and 2 figures; some comments and references added; more
references added, version to appear in journa
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