Oscillations in the B-s(0)- <(B-s(0))over bar> system were studied in events selected from about 4.3 million hadronic Z(0) decays registered by DELPHI between 1992 and 2000. This paper presents ...updates of two published analyses (11, 12). The first analysis, which utilizes leptons emitted with large momentum transverse to a jet, was improved by means of a better algorithm for the vertex reconstuction and a new algorithm for flavour-tagging at production time. The second analysis, which utilizes D-s-lepton events, was improved by optimizing the treatment of proper time resolution. No signal of B-s(0) oscillations was observed and limits on the mass difference between the physical B-s(0) states were obtained to be: Deltam(s)>8.0 ps-1 at the 95% C.L. with a sensitivity of Deltam(s)= 9.1 ps(-1) in the high p(t) lepton analysis and Deltam(s)>4.9 ps(-1) at the 95% C.L. with a sensitivity of Deltam(s)=8.6 ps(-1) in the D-s-lepton analysis. Previously published results on these analyses are superseded. The combination of these results with those obtained in other independent analyses previously performed in DELPHI (D-s-hadron, exclusive B-s(0), inclusive vertex) gives: Deltam(s)>8.5 ps(-1) at the 95% C.L. with a sensitivity of Deltam(s)=12.0 ps(-1).
Searches for H Z production with the Higgs boson decaying into an invisible final state were performed using the data collected by the DELPHI experiment at centre-of-mass energies between 188 GeV and ...209 GeV. Both hadronic and leptonic final states of the Z boson were analysed. In addition to the search for a heavy Higgs boson, a dedicated search for a light Higgs boson down to 40 GeV/c2 was performed. No signal was found. Assuming the Standard Model HZ production cross-section, the mass limit for invisibly decaying Higgs bosons is 112.1 GeV/c2 at 95% confidence level. An interpretation in the Minimal Supersymmetric extension of the Standard Model (MSSM) and in a Majoron model is also given.
In a study of the reaction
e
−
e
+
→
W
−
W
+
with the DELPHI detector, the probabilities of the two W particles occurring in the joint polarisation states transverse–transverse (
TT
), ...longitudinal–transverse plus transverse–longitudinal (
LT
) and longitudinal–longitudinal (
LL
) have been determined using the final states
(
l
=
e
,
μ
). The two-particle joint polarisation probabilities, i.e. the spin density matrix elements
ρ
TT
,
ρ
LT
,
ρ
LL
, are measured as functions of the
W
−
production angle,
, at an average reaction energy of 198.2 GeV. Averaged over all
, the following joint probabilities are obtained:
These results are in agreement with the Standard Model predictions of 63.0%, 28.9% and 8.1%, respectively. The related polarisation cross-sections
σ
TT
,
σ
LT
and
σ
LL
are also presented.
Searches for HZ production with the Higgs boson decaying into an invisible final state were performed using the data collected by the DELPHI experiment at centre-of-mass energies between 188 GeV and ...209 GeV. Both hadronic and leptonic final states of the Z boson were analysed. In addition to the search for a heavy Higgs boson, a dedicated search for a light Higgs boson down to 40 GeV/c2 was performed. No signal was found. Assuming the Standard Model HZ production cross-section, the mass limit for invisibly decaying Higgs bosons is 112.1 GeV/c2 at 95% confidence level. An interpretation in the Minimal Supersymmetric extension of the Standard Model (MSSM) and in a Majoron model is also given.
Higgs boson production with subsequent decay to photons was searched for in the data collected by the DELPHI detector at centre-of-mass energies between 183 GeV and 209 GeV, corresponding to a total ...integrated luminosity of nearly 650 pb-1. No evidence for a signal was found, and limits were set on h0Z0 and h0A0 production with h0 decay to photons. These results were used to exclude regions in the parameter space of fermiophobic scenarios of Two Higgs Doublet Models.
The form factor of A(o)(b) baryons is estimated using 3.46 x 10(6) hadronic Z decays collected by the DELPM experiment between 1992 and 1995. Charmed A(c)(+) baryons fully reconstructed in the ...pK(-)pi(+), pK(o)(s), and Api(+)pi(+)pi(-) modes, are associated to a c S lepton with opposite charge in order to select A(o)(b) --> A(c)(+)l(-)v(l) decays. From a combined likelihood and event rate fit to the b C distribution of the Isgur-Wise variable w, and using the Heavy Quark Effective Theory (HQET), the slope of the b-baryon form factor is measured to be p(2)=2.03+/-0.46(stat)(-1.00)(+0.72)(syst). The exclusive semileptonic branching fraction Br(A(b)(o) --> A(c)(+)l(-)v(l)) can be derived from p(2) and is found to be (5.0(-0.8)(+1.1)(stat)(-1.2)(+1.6) (syst))%. Limits on other branching fractions are also obtained. (C) 2004 Published by Elsevier B.V.
Shashlik calorimeter prototypes for a linear collider Benvenuti, A.C.; Britvich, I.; Camporesi, T. ...
1999 IEEE Nuclear Science Symposium. Conference Record. 1999 Nuclear Science Symposium and Medical Imaging Conference (Cat. No.99CH37019),
1999, Letnik:
1
Conference Proceeding
Two techniques for longitudinal segmentation of shashlik calorimeters are proposed. Results concerning energy resolution, impact point reconstruction and e//spl pi/ separation are reported.
Hadronic event shape distributions are determined from data in e+e- collisions between 183 and 207 GeV. From these the strong coupling alpha_s is extracted in O(alpha_s^2), NLLA and matched ...O(alpha_s^2)+NLLA theory. Hadronisation corrections evaluated with fragmentation model generators as well as an analytical power ansatz are applied. Comparing these measurements to those obtained at and around M_Z allows a combined measurement of alpha_s from all DELPHI data and a test of the energy dependence of the strong coupling.
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