From the
Z decays recorded in 1994 and 1995 by the DELPHI detector at LEP, the charged particle multiplicity of weakly decaying
B hadrons was measured to be:
4.97±0.03±0.06
excluding the
K
0 and
Λ ...decay products.
A first measurement is reported of the longitudinal proton structure function FL(X, Q(2)) at the ep collider HERA. It is based on inclusive deep inelastic e(+)p scattering cross section measurements ...with a positron beam energy of 27.5 GeV and proton beam energies of 920, 575 and 460 GeV. Employing the energy dependence of the cross section, FL is measured in a range of squared four-momentum transfers 12 <= Q2 <=, 90 GeV2 and low Bjorken x 0.00024 <= x <= 0.0036. The F-L values agree with higher order QCD calculations based on parton densities obtained using cross section data previously measured at HERA. (C) 2008 Elsevier B.V. All rights reserved.
Inclusive production of D* mesons in deep-inelastic ep scattering at HERA is studied in the range 5 < Q(2) < 100 GeV2 of the photon virtuality and 0.02 < y < 0.7 of the inelasticity of the scattering ...process. The observed phase space for the D* meson is (pT) (D*) > 1.25 GeV and |eta( D*)| < 1.8. The data sample corresponds to an integrated luminosity of 348 pb(-1) collected with the H1 detector. Single and double differential cross sections are measured and the charm contribution F-2(c (c) over bar) to the proton structure function F-2 is determined. The results are compared to perturbative QCD predictions at next-to-leading order implementing different schemes for the charm mass treatment and with Monte Carlo models based on leading order matrix elements with parton showers.
Current achievements of the DELPHI ring imaging Cherenkov detector Adam, W; Albrecht, E; Allen, D ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
03/1996, Letnik:
371, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The DELPHI experiment has already collected 2.5 million Z
0 decays with the ring imaging Cherenkov detector (RICH) operational. This detector, covering most of the solid angle, is designed to perform
...π
K
separation from 0.8 to 20 GeV/
c and K/p separation from 0.8 to 35 GeV/
c. After a brief detector description we discuss the actual operating conditions, the data monitoring and the signal treatment. The collected data from Z
0 decays and the detector response to signals from the calibration system are used to evaluate the performance of the RICH system.
Muon pair production in the process \(e^+e^-\to e^+e^-\mu^+\mu^-\) is studied using the data taken at LEP1 (\(\sqrt{s}\simeq m_Z\)) with the DELPHI detector during the years 1992-1995. The ...corresponding integrated luminosity is 138.5 pb\(^{-1}\). The QED predictions have been tested over the whole \(Q^2\) range accessible at LEP1 (from several GeV\(^2/c^4\) to several hundred GeV\(^2/c^4\)) by comparing experimental distributions with distributions resulting from Monte Carlo simulations using various generators. Selected events are used to extract the leptonic photon structure function \(F_2^\gamma\). Azimuthal correlations are used to obtain information on additional structure functions, \(F_A^\gamma\) and \(F_B^\gamma\), which originate from interference terms of the scattering amplitudes. The measured ratios \(F_A^\gamma/F_2^\gamma\) and \(F_B^\gamma/F_2^\gamma\) are significantly different from zero and consistent with QED predictions.
Performance of the ring imaging Cherenkov detector of DELPHI Adam, W.; Albrecht, E.; Allen, D. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
12/1995, Letnik:
367, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The general purpose particle detector DELPHI at the Large Electron Positron collider at CERN was built to give the complete information of each event. DELPHI uses ring imaging Cherenkov counters to ...provide hadron identification in most of the momentum range below 45 GeV/
c and over almost the full solid angle. Charged particles traversing gaseous and liquid fluorocarbon radiators create photons used for Cherenkov angle reconstruction. Some of the design features of the detector will be presented, with emphasis on the experience which was gained in the operation of these large systems. The hadron identification power of the ring imaging Cherenkov detector closely meets the main design values. Data processing and performance of the detector will be discussed using dimuon events collected during 1994. Pion rejection factors for kaon tagging will be shown.
Data taken by the DELPHI experiment at centre-of-mass energies of 183 GeV and 189 GeV with a total integrated luminosity of 212 pb-1 have been used to search for the supersymmetric partners of the ...electrons, muons, and taus in the context of the Minimal Supersymmetric Standard Model (MSSM). The decay topologies searched for were the direct decay (ℓ̃ → ℓx̃), producing acoplanar lepton pairs plus missing energy, and the cascade decay (ℓ → ℓx̃0 2 → ℓγx̃0 1), producing acoplanar lepton and photon pairs plus missing energy. The observed number of events is in agreement with Standard Model predictions. The 95% CL excluded mass limits for selectrons, smuons and staus are mẽ ≤ 87 GeV/c2, mμ̃ ≤ 80 GeV/c2 and mτ̃ 75 GeV/c2, respectively, for values of μ=-200 GeV/c2 and tanβ=1.5.
A search for physics beyond the Standard Model in neutral current deep inelastic scattering at high negative four-momentum transfer squared Q(2) is performed in e(+/-)p collisions at HERA. The ...differential cross section d sigma/dQ(2), measured using the full H1 data sample corresponding to an integrated luminosity of 446 pb(-1), is compared to the Standard Model prediction. No significant deviation is observed. Limits on various models predicting new phenomena at high Q(2) are derived. For general four-fermion eeqq contact interaction models, lower limits on the compositeness scale A are set in the range 3.6 TeV to 7.2 TeV. Leptoquarks with masses M-LQ and couplings lambda are constrained to M-LQ/lambda > 0.41-1.86 TeV and limits on squarks in R-parity violating supersymmetric models are derived. A lower limit on the gravitational scale in 4 + n dimensions of M-S > 0.9 TeV is established for low-scale quantum gravity effects in models with large extra dimensions. For the light quark radius an upper bound of R-q < 0.65 . 10(-18) m is determined. (C) 2011 Elsevier B.V. All rights reserved.
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