| 31. |
- Abdallah, J, et al.
(författare)
-
Observation of the muon inner bremsstrahlung at LEP1
- 2008
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:57, s. 499-514
-
Tidskriftsartikel (refereegranskat)abstract
- Muon bremsstrahlung photons converted in front of the DELPHI main tracker (TPC) in dimuon events at LEP1 were studied in two photon kinematic ranges: 0.2< E-gamma <= 1 GeV and transverse momentum with respect to the parent muon p(T) < 40 MeV/c, and 1< E-gamma <= 10 GeV and pT < 80 MeV/c. A good agreement of the observed photon rate with predictions from QED for the muon inner bremsstrahlung was found, contrary to the anomalous soft photon excess that has been observed recently in hadronic Z(0) decays. The obtained ratios of the observed signal to the predicted level of the muon bremsstrahlung are 1.06 +/- 0.12 +/- 0.07 in the photon energy range 0.2< E-gamma <= 1 GeV and 1.04 +/- 0.09 +/- 0.12 in the photon energy range 1< E-gamma <= 10 GeV. The bremsstrahlung dead cone is observed for the first time in the direct photon production at LEP.
|
|
| 32. |
- Abdallah, J., et al.
(författare)
-
Single intermediate vector boson production in e(+)e(-) collisions at root s=183-209 GeV
- 2006
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 45:2, s. 273-289
-
Tidskriftsartikel (refereegranskat)abstract
- The production of single charged and neutral intermediate vector bosons in e(+)e(-) collisions has been studied in the data collected by the DELPHI experiment at LEP at centre-of-mass energies between 183 and 209 GeV, corresponding to an integrated luminosity of about 640 pb(-1). The measured cross-sections for the reactions, determined in limited kinematic regions, are in agreement with the Standard Model predictions.
|
|
| 33. |
- Abdallah, J, et al.
(författare)
-
Determination of heavy quark non-perturbative parametersfrom spectral moments in semileptonic B decays
- 2006
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 45:1, s. 35-59
-
Tidskriftsartikel (refereegranskat)abstract
- Moments of the hadronic invariant mass and of the lepton energy spectra in semileptonic B decays have been determined with the data recorded by the DELPHI detector at LEP. From measurements of the inclusive b-hadron semileptonic decays, and imposing constraints from other measurements on b- and c-quark masses, the first three moments of the lepton energy distribution and of the hadronic mass distribution, have been used to determine parameters which enter into the extraction of vertical bar V-cb vertical bar from the measurement of the inclusive b-hadron semileptonic decay width. The values obtained in the kinetic scheme are: m(b)(1 GeV) = 4.591 +/- 0.062 +/- 0.039 +/- 0.005 GeV/c(2), m(c)(1 GeV) = 1.170 +/- 0.093 +/- 0.055 +/- 0.005 GeV/c(2), m(pi)(2) (1 GeV) = 0.399 +/- 0.048 +/- 0.034 +/- 0.087 GeV2, (p) over tilde (3)(D) = 0.053 +/- 0.017 +/- 0.011 +/- 0.026 GeV3, and include corrections at order 1/m(b)(3). Using these results, and present measurements of the inclusive semileptonic decay partial width of b-hadrons at LEP, an accurate determination of vertical bar V-cb vertical bar is obtained: vertical bar V-cb vertical bar = 0.0421 x (1 +/- 0.014 (meas center dot) +/- 0.014 (fit) +/- 0.015 (th center dot)).
|
|
| 34. |
- Abdallah, J, et al.
(författare)
-
Production of Xi(0)(c) and Xi(b) in Z decays and lifetime measurement of Xi(b)
- 2005
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:44, s. 299-309
-
Tidskriftsartikel (refereegranskat)abstract
- The charmed strange baryon Xi(c)(0) was searched for in the decay channel Xi(c)(0) -> Xi(-)pi(+), and the beauty strange baryon Xi(b) in the inclusive channel Xi(b) -> Xi(-)l(-)(nu) over barX, using the 3.5 million hadronic Z events collected by the DELPHI experiment in the years 1992-1995. The Xi(-) was reconstructed through the decay AT, using a constrained fit method for cascade decays. An iterative discriminant analysis was used for the Xi(c)(0) and Xi(b) selection. The production rates were measured to be f(Xi c)(0) x BR(Xi(c)(0) -> Xi(-)pi(+) = (4.7 +/- 1.4(stat.) +/- 1.1(syst.)) x 10(-4) per hadronic Z decay, and BR(b -> Xi(b))xBR(Xi(b) -> Xi(-)l(-)X) = (3.0 +/- 1.0(stat.) +/- 0.3(syst.)) x 10(-4) for each lepton species (electron or muon). The lifetime of the Xi(b) baryon was measured to be tau(Xi b) = 1.45(-0.43)(+0.55)(stat.)+/- 0.13(syst.) ps. A combination with the previous DELPHI lifetime measurement gives tau(Xi b) = 1.48(-0.31)(+0.40)(stat.)+/- 0.12(syst.) ps.
|
|
| 35. |
- Abdallah, J, et al.
(författare)
-
Charged particle multiplicity in three-jet events and two-gluon systems
- 2005
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; C:44, s. 311-331
-
Tidskriftsartikel (refereegranskat)abstract
- The charged particle multiplicity in hadronic three-jet events from Z decays is investigated. The topology dependence of the event multiplicity is found to be well described by a modified leading logarithmic prediction. A parameter fit of the prediction to the data yields a measurement of the colour factor ratio C-A/C-F with the result C-A/C-F = 2.261 +/- 0.014(stat). +/- 0.036(exp). +/- 0-066(theo). in agreement with the SU(3) expectation of QCD. The quark-related contribution to the event multiplicity is subtracted from the three-jet event multiplicity resulting in a measurement of the multiplicity of two-gluon colour-singlet states over a wide energy range. The ratios r = N-gg(s)/Ng (g) over bar (s) of the gluon and quark multiplicities and r((1)) = N'(gg)(s)/N'g (g) over bar (s) of their derivatives are compared with perturbative calculations. While a good agreement between calculations and data is observed for r((1)), larger deviations are found for r indicating that non-perturbative effects are more important for r than for r((1)).
|
|
| 36. |
|
|
