3,973 research outputs found
Recent BES measurements and the hadronic contribution to the QED vacuum polarization
We have updated our evaluation of the hadronic contribution to the running of
the QED fine structure constant using the recent precise measurements of the
e+e- annihilation at the center-of-mass (c.m.s.) energy region between 2.6 and
3.65 GeV performed by the BES collaboration. In the low energy region, around
the rho resonance, we include the recent measurements from the BABAR, CDM-2,
KLOE and SND collaborations. We obtain Delta alpha (5)_had (s) = 0.02750 +/-
0.00033 at s = m_Z^2.Comment: 3 pages, 1 figur
LHCb detector status and commissioning
The LHCb detector status and commissioning is presented.Comment: HCP06 proceedings for reference
Further studies on Bose-Einstein correlations in W-pair decays
Bose-Einstein correlations in W-pair decays are studied using data collected by the ALEPH detector at centre-of-mass energies up to 208 GeV. The analysis presented is based on the comparison of selected events to "mixed" events constructed from the hadronic parts of selected events using the distribution. The data distribution is consistent with predicted when the Bose-Einstein correlations are present only for pions coming from the same W. The JETSET model with the Bose-Einstein correlations between pions from di erent W's is disfavoured
LEP asymmetries and fits of the Standard Model
The lepton and quark asymmetries measured at LEP are presented. The results
of the Standard Model fits to the electoweak data presented at this conference
are given. The top mass obtained from the fit to the LEP data is
GeV; it is when also the
collider, and data are included.Comment: ps file,8 pages, LAPP-EXP-94.0
Virtual effects of light gauginos and higgsinos: a precision electroweak analysis of split supersymmetry
We compute corrections to precision electroweak observables in supersymmetry
in the limit that scalar superpartners are very massive and decoupled. This
leaves charginos and neutralinos and a Standard Model-like Higgs boson as the
only states with unknown mass substantially affecting the analysis. We give
complete formulas for the chargino and neutralino contributions, derive simple
analytic results for the pure gaugino and higgsino cases, and study the general
case. We find that in all circumstances, the precision electroweak fit improves
when the charginos and neutralinos are near the current direct limits. Larger
higgsino and gaugino masses worsen the fit as the theory predictions
asymptotically approach those of the Standard Model. Since the Standard Model
is considered by most to be an adequate fit to the precision electroweak data,
an important corollary to our analysis is that all regions of parameter space
allowed by direct collider constraints are also allowed by precision
electroweak constraints in split supersymmetry.Comment: 22 pages, 5 figures, v2: typos fixed and note adde
Initial-Final-State Interference in the Z line-shape
The uncertainty in the determination of the Z line-shape parameters coming
from the precision of the calculation of the Initial-State Radiation and
Initial--Final-State Interference is 2 10**(-4) for the total cross section
sigma zero(had) at the Z peak, 0.15 MeV for the Z mass M Z, and 0.1 MeV for the
Z width Gamma Z. Corrections to Initial--Final-State Interference beyond
\Order{\alpha^1} are discussed.Comment: 10 pages LaTeX including 2 PostScript figure
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