3,718 research outputs found
Combining real and virtual Higgs boson mass constraints
Within the framework of the standard model we observe that there is a
significant discrepancy between the most precise boson decay asymmetry
measurement and the limit from direct searches for Higgs boson production.
Using methods inspired by the Particle Data Group we explore the possible
effect on fits of the Higgs boson mass. In each case the central value and the
95% confidence level upper limit increase significantly relative to the
conventional fit. The results suggest caution in drawing conclusions about the
Higgs boson mass from the existing data.Comment: 11 pages, Latex. Citations are added and paper is otherwise
reconciled with version to be published in Physical Review Letter
The Indirect Limit on the Standard Model Higgs Boson Mass from the Precision FERMILAB, LEP and SLD Data
Standard Model fits are performed on the most recent leptonic and b quark Z
decay data from LEP and SLD, and FERMILAB data on top quark production, to
obtain and . Poor fits are obtained, with confidence levels
2%. Removing the b quark data improves markedly the quality of the fits and
reduces the 95% CL upper limit on by 50 GeV.Comment: 6 pages 3 tables i figur
The spin dependence of an weak interaction in the decay of hypernuclei
From an analysis of 468 hypernuclei (HFs) with ranges > 120 μ m, the non-mesic to π--mesic ratio (Q-) for ΛHe and ΛHe5 HFs was found to be 1.37 ± 0.17 and 1.58± 0.20 respectively. This data, together with results on ΛHe4 and heavy hypernuclei, has been used to deduce spin dependences for Λn and ΛP weak interactions in decay of hypernuclei. It is found that the rates for triplet and singlet interactions between Λ and neutron are 22 ΓΛ and 11 ΓΛ and for Λ and proton are 8.2 ΓΛ and 5.5 ΓΛ respectively, where ΓΛ is the decay rate of Λ. The total decay rates for ΛHe4 and ΛHe5 are 1.28 ΓΛ and 0.99 ΓΛ and the non-mesic decay rates are 0.17 ΓΛ and 0.51 ΓΛ respectively
An analytical program for fermion pair production in e+e- annihilation
We describe how to use {\tt ZFITTER}, a program based on a semi-analytical approach to fermion pair production in e^+ e^- annihilation and Bhabha scattering. A flexible treatment of complete {\cal O}(\alpha) QED corrections, also including higher orders, allows for three calculational {\bf chains} with different realistic sets of restrictions in the photon phase space. {\tt ZFITTER} consists of several {\bf branches} with varying assumptions on the underlying hard scattering process. One includes complete {\cal O}(\alpha) weak loop corrections with a resummation of leading higher-order terms. Alternatively, an ansatz inspired from S-matrix theory, or several model-independent effective Born cross sections may be convoluted. The program calculates cross sections, forward-backward asymmetries, and for \tau~pair production also the final-state polarization. Various {\bf interfaces} allow fits to be performed with different sets of free parameters
Partial-wave analysis of the eta pi+ pi- system produced in the reaction pi-p --> eta pi+ pi- n at 18 GeV/c
A partial-wave analysis of 9082 eta pi+ pi- n events produced in the reaction
pi- p --> eta pi+ pi- n at 18.3 GeV/c has been carried out using data from
experiment 852 at Brookhaven National Laboratory. The data are dominated by
J^{PC} = 0^{-+} partial waves consistent with observation of the eta(1295) and
the eta(1440). The mass and width of the eta(1295) were determined to be 1282
+- 5 MeV and 66 +- 13 Mev respectively while the eta(1440) was observed with a
mass of 1404 +- 6 MeV and width of 80 +- 21 MeV. Other partial waves of
importance include the 1++ and the 1+- waves. Results of the partial wave
analysis are combined with results of other experiments to estimate f1(1285)
branching fractions. These values are considerably different from current
values determined without the aid of amplitude analyses.Comment: 22 pages, 8 figure
The ratio of non-mesic to π<SUP>-</SUP>-mesic decay of light hyperfragments
A new method of obtaining the charge spectrum of light hyperfragments from their residual range distribution is described. This method has been used to determine the ratio (Q-) of non-mesic to π--mesic decay of light hyperfragments. The values of Q- for hyperfragments of different charges are found to be in good agreement with theoretical calculations of Dalitz
Precision Physics at LEP
1 - Introduction
2 - Small-Angle Bhabha Scattering and the Luminosity Measurement
3 - Z^0 Physics
4 - Fits to Precision Data
5 - Physics at LEP2
6 - ConclusionsComment: Review paper to appear in the RIVISTA DEL NUOVO CIMENTO; 160 pages,
LateX, 70 eps figures include
Study of Spin and Decay-Plane Correlations of W Bosons in the e+e- -> W+W- Process at LEP
Data collected at LEP at centre-of-mass energies \sqrt(s) = 189 - 209 GeV are
used to study correlations of the spin of W bosons using e+e- -> W+W- -> lnqq~
events. Spin correlations are favoured by data, and found to agree with the
Standard Model predictions. In addition, correlations between the W-boson decay
planes are studied in e+e- -> W+W- -> lnqq~ and e+e- -> W+W- -> qq~qq~ events.
Decay-plane correlations, consistent with zero and with the Standard Model
predictions, are measured
Search for Branons at LEP
We search, in the context of extra-dimension scenarios, for the possible
existence of brane fluctuations, called branons. Events with a single photon or
a single Z-boson and missing energy and momentum collected with the L3 detector
in e^+ e^- collisions at centre-of-mass energies sqrt{s}=189-209$ GeV are
analysed. No excess over the Standard Model expectations is found and a lower
limit at 95% confidence level of 103 GeV is derived for the mass of branons,
for a scenario with small brane tensions. Alternatively, under the assumption
of a light branon, brane tensions below 180 GeV are excluded
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