An efficient conjugate directions method without linear minimization Manevich, A.I.; Boudinov, E.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2000, Letnik:
455, Številka:
3
Journal Article
Recenzirano
Odprti dostop
An algorithm of conjugate directions for unconstrained minimization is presented, called Single-Step Conjugate Directions Method (SSCDM) that differs from the known algorithms in the following ...points: (1) only one step is made on each iteration, without the linear searches of a minimum; (2) each step includes simultaneous displacements along all conjugate directions found on previous steps (instead of consequent steps along each conjugate vector); (3) each new conjugate direction is determined by the general procedure of construction of conjugate vectors, without assumption that minima along the conjugate directions were reached on previous steps. These features of the algorithm eliminate high sensitivity to computation errors pertinent to usual methods of conjugate directions and simultaneously significantly reduce the running time. Performance of the algorithm is demonstrated by applying it to a set of standard test-functions and solving a problem of high-energy physics with a Monte-Carlo-type objective function.
Operation, optimisation, and performance of the DELPHI RICH detectors Albrecht, E.; van Apeldoorn, G.; Augustinus, A. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
1999, Letnik:
433, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
The Ring Imaging Cherenkov detectors of DELPHI represent a large-scale particle identification system which covers almost the full angular acceptance of DELPHI. The combination of liquid and gas ...radiators (C
4F
10, C
5F
12, and C
6F
14) provides particle identification over the whole secondary particle momentum spectrum at LEP I and LEP II. Continuing optimisation on the hardware as well as on the online and offline software level have resulted in a stable operation of the complete detector system for more than five years at full physics performance.
2+1-dimensional Yang–Mills theory is reinterpreted in terms of metrics on 3-manifolds. The dual gluons are related to diffeomorphisms of the 3-manifolds. Monopoles are identified with points where ...the Ricci tensor has triply degenerate eigenvalues. The dual gluons have the desired interaction with these monopoles. This would give a mass for the dual gluons resulting in confinement.
Searches for pair production of gauginos and squarks in $e^{+} e^{-}$ collisions at a centre-of-mass energy of 189 GeV have been performed on data corresponding to an integrated luminosity of 158 ...pb$^{-1}$ collected by the DELPHI detector at LEP. The data were analyzed under the assumption of non-conservation of \mbox{$R$-parity} through a single dominant $\bar{U} \bar{D} \bar{D}$~coupling between squarks and quarks. Typical final states contain between 4 and 10 jets with or without additional leptons. No excess of data above Standard Model expectations was observed. The results were used to constrain domains of the MSSM parameter space and derive limits on the masses of supersymmetric particles. The following mass limits at 95\% CL were obtained from these searches: \begin{itemize} \item neutralino mass: $m_{\tilde{\chi^0_{1}}} \ge 32$ GeV \item chargino mass: $m_{\tilde{\chi^+_{1}}} \ge 94 $ GeV \item stop and sbottom mass (indirect decay) with $\Delta M 5$ GeV: $m_{\tilde{t_{1}}} \ge 74$ GeV, for $\Phi_{mix}=0$ rad $m_{\tilde{t_{1}}} \ge 59$ GeV, for $\Phi_{mix}=0.98 $ rad $m_{\tilde{b_{1}}} \ge 72$ GeV, for $\Phi_{mix}=0$ rad. \end{itemize} The angle $\phi_{mix}$ is the mixing angle between left and right handed quarks.
The DELPHI detector at LEP has collected 54 pb −1 of data at a centre-of-mass energy around 183 GeV during 1997, 158 pb −1 around 189 GeV during 1998, and 187 pb −1 between 192 and 200 GeV during ...1999. These data were used to measure the average charged particle multiplicity in e + e − →b b ̄ events, 〈n〉 b b ̄ , and the difference δ bl between 〈n〉 b b ̄ and the multiplicity, 〈n〉 l l ̄ , in generic light quark (u,d,s) events: δ bl (183 GeV) =4.55±1.31( stat )±0.73( syst ) , δ bl (189 GeV) =4.43±0.85( stat )±0.61( syst ) , δ bl (200 GeV) =3.39±0.89( stat )±1.01( syst ) . This result is consistent with QCD predictions, while it is inconsistent with calculations assuming that the multiplicity accompanying the decay of a heavy quark is independent of the mass of the quark itself. (Elsevier)
The rapidity-rank structure of \ppb pairs is used to analyze the mechanism of baryon production in hadronic \zz decay. The relative occurrence of the rapidity-ordered configuration \pmpb, where $M$ ...is a meson, and that of \ppb adjacent pairs is compared. The data are found to be consistent with predictions from a mechanism producing adjacent-rank \ppb pairs, without requiring `string-ordered' \pmpb configurations. An upper limit of 15\% at 90\% confidence is determined for the \pmpb contribution.
The study of the directional dependence of two-particle correlations in the hadronic decays of the $Z^0$ boson is performed using the data collected by the DELPHI experiment in the 1992--1995 running ...periods. The comparison between the transverse, $R_{\perp}$, and longitudinal, $R_{\parallel}$, correlation radii confirms the string model prediction that the transverse correlation length is smaller than the longitudinal one, with the measured values of $R_{\perp}=0.53\pm 0.08\,\mathrm{fm}$ and $R_{\parallel}=0.85\pm 0.08\,\mathrm{fm}$, for selected $Z^0\rightarrow q\bar{q}$ events.
The ratio of the CKM quark-mixing matrix elements |V_{ub}|/|V_{cb}|has been measured using B hadron semileptonic decays.The analysis is based on a novel technique, recently proposed by theoreticians, ...that uses the reconstructed mass M_X ofthe secondary hadronic system produced in association with an identified lepton.Since B rightarrow X_u \ell \bar \nu transitions are characterisedby hadronic masses below those of the $D$ mesons produced inB \rightarrow X_c \ell \bar \nu transitions, events with a reconstructed value of M_X significantly below the D massare selected.Further signal enrichments are obtained using thetopology of reconstructed decays and hadron identification.A fit to the numbers of decays in the b\to u enriched and depleted samples with M_X above and below 1.6 GeV/c^2and to the shapes of the lepton energy distribution in the Brest frame gives |V_{ub}|/|V_{cb}|= \mathrm{0.103^{+0.011}_{-0.012}~(stat.)\pm0.016~(syst.)\pm0.010~(mo del)}%The model dependance of $b \rightarrow u \ell \bar \nu$%is significantly reduced with this method.and, correspondingly, a charmless semileptonic $B$ decay branching fractionof BR($B \rightarrow X_u \ell \bar \nu) = \mathrm{(1.57 \pm 0.35~(stat.)\pm0.48~(syst.)\pm0.27~(model))\times 10^{-3}}$.
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