On the anomalous large transverse energy events observed in proton-lead scattering

It has been shown that a study of correlation between the average rapidity, 〈y〉, and transverse energy,E _T , can be used to distinguish between different origins of large transverse energy events observed inp-Pb scattering in the HELIOS experiment. If the largeE _T events are to be attributed to a nuclear dependence of structure functions then the hard scattering picture implies a positive correlation among the above two quantities, contrary to that seen in experiment.     

Search for supersymmetry at the LHC in events with jets and missing transverse energy

A search for events with jets and missing transverse energy is performed in a data sample of pp collisions collected at √s=7 TeV by the CMS experiment at the LHC. The analyzed data sample corresponds to an integrated luminosity of 1.14 fb(-1). In this search, a kinematic variable α(T) is used as the main discriminator between events with genuine and misreconstructed missing transverse energy. No excess of events over the standard model expectation is found. Exclusion limits in the parameter space of the constrained minimal supersymmetric extension of the standard model are set. In this model, squark masses below 1.1 TeV are excluded at 95% C.L. Gluino masses below 1.1 TeV are also ruled out at 95% C.L. for values of the universal scalar mass parameter below 500 GeV.     

Top-quark mass measurement using events with missing transverse energy and jets at CDF

We present a measurement of the top-quark mass using a sample of t ?t events in 5.7 fb(-1) of integrated luminosity from p ?p collisions at the Fermilab Tevatron with √s=1.96 TeV and collected by the CDF II Detector. We select events having large missing transverse energy, and four, five, or six jets with at least one jet tagged as coming from a b quark, and reject events with identified charged leptons. This analysis considers events from the semileptonic t ?t decay channel, including events that contain tau leptons. The measurement is based on a multidimensional template method. We fit the data to signal templates of varying top-quark masses and background templates, and measure a top-quark mass of M(top)=172.32±2.4(stat)±1.0(syst) GeV/c(2).     

Observation of events with an isolated high energy lepton and missing transverse momentum at HERA

A search for events with an imbalance in transverse momentum and with isolated high energy leptons has been carried out at the positron-proton collider HERA. One event with an and five events with a are found together with evidence for undetected particles carrying transverse momentum. Within the Standard Model the dominant origin of events with this kind of topology is the production of W bosons with subsequent leptonic decay. Three of the six events are within measurement errors found in a region of phase space likely to be populated by this process, while the remaining events show kinematic properties which are atypical of all Standard Model processes considered. Received: 9 June 1998 / Published online: 26 August 1998     

Glueball-Pomeron identity and the transverse structure of two-jet events

We discuss the transverse structure of two-jet events within a scheme à la Harari-Freund, using Dual Field Theory as a guide. We point out that the situation is quite different from current two-random-walk models based on uncorrelated-jet pictures of multiparticle production, and that it also differs in a natural way from standardf iteration schemes leading to Pomeronf identity. It then follows that recent criticism based on the role of transverse dimensions cannot be applied to the “gluonic” Pomeron of Dual Field Theory.     

Ground-state entanglement in a three-spin transverse Ising model with energy current

The ground-state entanglement associated with a three-spin transverse Ising model is studied. By introducing an energy current into the system, a quantum phase transition to energy-current phase may be presented with the variation of external magnetic field; and the ground-state entanglement varies suddenly at the critical point of quantum phase transition. In our model, the introduction of energy current makes the entanglement between any two qubits become maximally robust.     

Statistical hadronization model and transverse momentum spectra of hadrons in high energy collisions

A detailed analysis of transverse momentum spectra of several identified hadrons in high energy collisions within the canonical framework of the statistical model of hadronization is performed. The study of particle momentum spectra requires an extension of the statistical model formalism used to handle particle multiplicities, which is described in detail starting from a microcanonical treatment of single hadronizing clusters. Also, a new treatment of extra strangeness suppression is presented which is based on the enforcement of fixed numbers of pairs in the primary hadrons. The considered center-of-mass energies range from to 30 GeV in hadronic collisions ( and Kp) and from 15 to 35 GeV in collisions. The effect of the decay chain following hadron generation is accurately and exhaustively taken into account by a newly proposed numerical method. The exact conservation at low energy and the increasing hard parton emission at high energy bound the validity of the presently taken approach within a limited center-of-mass energy range. However, within this region, a clear consistency is found between the temperature parameter extracted from the present analysis and that obtained from fits to average hadron multiplicities in the same collision systems. This finding indicates that in the hadronization process the production of different particle species and their momentum spectra are two closely related phenomena governed by one parameter. Received: 31 October 2001 / Published online: 15 February 2002     

Search for diphoton events with large missing transverse energy in 7 TeV proton-proton collisions with the ATLAS detector

A search for diphoton events with large missing transverse energy is presented. The data were collected with the ATLAS detector in proton-proton collisions at √s=7 TeV at the CERN Large Hadron Collider and correspond to an integrated luminosity of 3.1 pb?1. No excess of such events is observed above the standard model background prediction. In the context of a specific model with one universal extra dimension with compactification radius R and gravity-induced decays, values of 1/R<729 GeV are excluded at 95% C. L., providing the most sensitive limit on this model to date.     

Missing spots in low energy electron diffraction

Recent attempts to justify the use, after appropriate data averaging, of kinematical theory in surface structure determination by LEED, make it important to be able to distinguish truly kinematical features from those which can also be predicted from entirely general symmetry arguments. Such arguments are therefore developed formally into a set of rules determining the consequences of symmetry for LEED patterns. In particular the conditions for missing spots due to the presence of glide planes are given. It is pointed out that in some circumstances the isotropic scatterer model leads to spurious selection rules, that will not be satisfied in general.     

On the nonergodicity of the transverse magnetization in the transverse Ising model

The nonergodic behavior exhibited by the transverse spin correlation function _q=0 ^xx (t) the transverse Ising model obtained as the solution of approximate kinetic equations (derived on the basis of Résibois and De Leener's method), is shown to be an intrinsic property of the model and not the result of the approximations made in the derivation of the kinetic equations.Chargé de Recherches au Fonds National Belge de la Recherche Scientifique.     

Ultra-high energy neutrino-nucleon and neutrino-electron cross-sections in the standard model,in supersymmetric and superstring models

The neutrino-nucleon cross-section is calculated for energies up to 10¹⁵ GeV in the framework of the standard model assuming that the nucleon structure functionF ₂(x, Q ²) goes like ln²(a/x) asx→0. The cross-sections forv _μ e ^?(v _e e ^?)-interactions rise linearly with energy up toE _ν～10⁷ GeV and amount at this energy to ～10% of the neutrino-nucleon cross-section. The νN-cross-sections with production of supersymmetric particles in the framework of a supersymmetric model with minimal particle content are estimated. Photino-nucleon and photino-electron interactions are considered for masses of the squarks and sleptons in the range of 80–300 GeV. In superstring inspired unified models an estimation is made of the νN-interaction with an exchange of light leptoquarks.