arXiv subjects

R. H. Dalitz

Publications and source records attributed to R. H. Dalitz.

5 recordsLinked to original sources

arXiv2000

Local Realistic Theories and Quantum Mechanics for the two-neutral-kaon system

The predictions of local realistic theories for the observables concerning the evolution of a $K^0\bar{K}^0$ quantum entangled pair (created in the decay of the $ϕ$-meson) are discussed. It is shown, in agreement with Bell's theorem, that the most general local hidden-variable model fails in reproducing the whole set of quantum-mechanical joint probabilities. We achieve these conclusion by employing two different approaches. In a first one the local realistic observables are deduced from the most general premises concerning locality and realism, and Bell-like inequalities are not employed. The other approach makes use of Bell's inequalities. Within the former scheme, under particular conditions for the detection times, the discrepancy between quantum mechanics and local realism for the time-dependent asymmetry turns out to be not less than 20%. The same incompatibility can be made evident by means of a Bell-type test by employing both Wigner's and (once properly normalized probabilities are used) Clauser-Holt-Shimony-Holt's inequalities. Because of the relatively low experimental accuracy, the data obtained by the CPLEAR collaboration for the asymmetry parameter do not allow for a decisive test of local realism. Such a test, both with and without the use of Bell's inequalities, should be feasible in the future at the Frascati $Φ$-factory.

quant-ph↗

arXiv1998

Test of Analysis Method for Top-Antitop Production and Decay Events

We have carried out Monte Carlo calculations on two sets of randomly generated QCD events due to $p\bar{p} \to t \bar{t}$ with top mass $m_t = 170$ GeV, one set leading to $e^+e^-$ or $e^{\pm}μ^{\mp}$ or $μ^+μ^-$ 2jets (dilepton) and the other leading to $e^{\pm}$ or $μ^{\pm}$ 4jets (unilepton) configurations, in order to test the likelihood methods we have proposed for determining the top mass by analyses of these two sets of configurations. For the set of unilepton events, our method gives a very efficient and quite sharp measure of the top mass lying several GeV below the input mass. For the dilepton set, our method gives a much broader and markedly asymmetric distribution for the top mass estimates, 75% of them lying below 170 GeV, but the dilepton data will have much lower background than unilepton data. We then illustrate these methods by applying them to the data available from CDF in 1995 and discuss the results obtained in relation to the results for the sets of Monte Carlo events. The dilepton events yield masses spread widely, over 140 to 180 GeV, generally lower than the unilepton events, which cluster around $175\pm 8$ GeV. In an appendix, we discuss the nature of the additional ``slow'' $μ^{+}$ observed in one CDF dilepton event, concluding that it is most probably a ``tertiary lepton'' resulting from the decay sequence $b\to c + hadrons$, followed by $c\to s μ^{+} ν$.

hep-ph↗

arXiv1995

Top Mass Analyses for the Reported Top-Antitop Production and Decay Events

We have analyzed the available data on $p\bar{p}\,\rightarrow\, t\, \bar{t}$ followed by the decays ($t\rightarrow bW^{+},\: \bar{t}\rightarrow \bar{b}W^{-}$) which lead to $e^{\pm}μ^{\mp}2 \mathrm{jets}$ or $l^{\pm}4 \mathrm{jets}$ configurations, using a likelihood method we proposed earlier. The outcome is compared with the recent CDF analysis. In an appendix, we discuss the nature of the additional ``slow'' $μ^{+}$ observed in one CDF dilepton event, concluding that it is most probably a ``tertiary lepton'' resulting from the decay sequence $b\rightarrow c +\mathrm{hadrons}$, followed by $c\rightarrow s μ^{+} ν$.

hep-ph↗

arXiv1993

Where is Top?

Possibilities are discussed for determining the top quark mass $m_t$ from observations on the decay processes for top-antitop pairs produced in antiproton-proton collisions, assuming that the $t \to bW^+$ decay channel is dominant and much faster than hadronization. The final states $t \bar{t} \to \bar{b} b μ^\pm e^\mp$ provide the most striking signal, with little background, but they are rare ($\approx 2/81$). If all candidate events prove to be from $t \bar{t}$, an estimate follows for $P(m_t|rate)$, the probability distribution for $m_t$. The one reported configuration allows an independent estimate for $P(m_t|μ^\pm e^\mp \,2jets)$. These two distributions are compatible,yielding an estimate of about 122 GeV. Decay events ``1 energetic lepton($l$) + 4jets'' should appear twelve times as often as ``$μ^\pm e^\mp \,2jets$'' events and can be analysed to give estimates for $P(m_t|l\, 4jets)$. There may be background from non-top events but suitable cuts on the data and our analysis procedure together reduce this to a low level. The rate observed for these events does not appear to be as large as this factor 12. Identification of either or both of the $(b \bar{b})$ jets would be a great step forward. We advocate an energetic approach to the analysis of individual events on an event by event basis, with the hope of finding a subgroup of events with a common mass estimate.

hep-ph↗

arXiv1992

On Observing Top Quark Production at the Tevatron

A technique for separating top quark production from Standard Model background events is introduced. It is applicable to the channel in which one top quark decays semi-leptonically and its anti-quark decays hadronically into three jets, or vice versa. The method is shown to discriminate dramatically between Monte Carlo generated events with and without simulated top quarks of mass around 120 GeV and above. The simulations were performed with CDF detector characteristics incorporated, showing that the method is applicable to existing data.

hep-ph↗