8964066
A compact beam stop for a rare kaon decay experiment
Abstract We describe the development and testing of a novel beam stop for use in a rare kaon decay experiment at the Brookhaven Alternating Gradient Synchrotron. The beam stop is located inside a dipole spectrometer magnet in close proximity to straw drift chambers and intercepts a high-intensity neutral hadron beam. The design process, involving both Monte Carlo simulations and beam tests of alternative beam-stop shielding arrangements, had the goal of minimizing the leakage of particles from the beam stop and the resulting hit rates in detectors, while preserving maximum acceptance for events of interest. The beam tests consisted of measurements of rates in drift chambers, scintillation counter hodoscopes, a gas threshold Cherenkov counter, and a lead glass array. Measurements were also made with a set of specialized detectors which were sensitive to low-energy neutrons, photons, and charged particles. Comparisons are made between these measurements and a detailed Monte Carlo simulation.
119521709
First observation of the rare decay mode K0(L) ---> e+ e-
In an experiment designed to search for and study very rare two-body decay modes of the K-long, we have observed four examples of the decay K-long -> e+ e-, where the expected background is 0.17+-0.10 events. This observation translates into a branching fraction of 8.7^{+5.7}_{-4.1} X 10^{-12}, consistent with recent theoretical predictions. This result represents by far the smallest branching fraction yet measured in particle physics.
123484670
Search for the presence of H particles in a neutral beam
Abstract A search was made to detect the presence of long-lived H particles in a neutral beam by diffractive dissociation into two lambda particles. Preliminary results are presented.
209905216
Higher statistics measurement of the branching ratio for the decay K0(L) ---> mu mu
15729745
Search for the weak decay of an H dibaryon.
We have searched for a neutral {ital H} dibaryon decaying via {ital H}{r_arrow}{Lambda}{ital n} and {ital H}{r_arrow}{Sigma}{sup 0}{ital n}. Our search has yielded two candidate events from which we set an upper limit on the {ital H} production cross section. Normalizing to the inclusive {Lambda} production cross section, we find ({ital d}{sigma}{sub {ital H}}/{ital d}{Omega})/({ital d}{sigma}{sub {Lambda}}/{ital d}{Omega}){lt}6.3{times}10{sup {minus}6} at 90{percent} C.L., for an {ital H} of mass {approx_equal}2.15 GeV/{ital c}{sup 2}. {copyright} {ital 1996 The American Physical Society.}
38583686
Search for diffractive dissociation of a long-lived H dibaryon.
123264807
DYNAMICAL SYMMETRY BREAKINGS IN QUANTUM CHROMODYNAMICS
Dynamical symmetry breakings in quantum chromodynamics (QCD) are investigated by means of the renormalization-group equations and the Dyson equations. It is shown that: (1) The electromagnetic (and weak) interactions can not be neglected in studying those nonperturbative problems as dynamical symmetry breakings for type-A models in QCD. (2) When the electromagnetic interactions between stratons are taken into account in the weak coupling approximation, dynamical symmetry breakings in QCD occur for many realistic models (type-A models) with QCD asymptotically free. This conclusion may hold beyond the weak coupling approximation of the electromagnetic interactions if there can still be a self-consistent solution of Johnson-Baker-Willey in quantum electrodynamics or β_e has an UV-stable fixed point. e_∞(?)0 (a simple zero of β_e) and e_∞is not too large.
119454200
Testing anomalous gauge couplings of the Higgs boson via weak boson scatterings at the CERN LHC
We propose a sensitive way to test the anomalous HVV couplings ${(V=W}^{\ifmmode\pm\else\textpm\fi{}},{Z}^{0})$ of the Higgs boson $(H),$ which can arise from either the dimension-3 effective operator in a nonlinearly realized Higgs sector or the dimension-6 effective operators in a linearly realized Higgs sector, via studying the VV scattering processes at the CERN LHC. The gold-plated pure leptonic decay modes of the final state weak bosons in the processes $p\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{VVjj}$ are studied. For comparison, we also analyze the constraints from the precision electroweak data, the expected precision of the measurements of the Higgs boson production rate, decay width and branching ratios at the Fermilab Tevatron run-2 and the CERN LHC, and the requirement of unitarity of the S matrix. We show that, with an integrated luminosity of $300{\mathrm{fb}}^{\ensuremath{-}1}$ and sufficient kinematical cuts for suppressing the backgrounds, studying the process $p\stackrel{\ensuremath{\rightarrow}}{p}{W}^{+}{W}^{+}j\stackrel{\ensuremath{\rightarrow}}{j}{l}^{+}\ensuremath{\nu}{l}^{+}\ensuremath{\nu}\mathrm{jj}$ can probe the anomalous HWW couplings at a few tens of percent level for the nonlinearly realized Higgs sector, and at the level of $0.01\char21{}0.08{\mathrm{TeV}}^{\ensuremath{-}1}$ for the linearly realized effective Lagrangian.
119084583
Heavy quarkonium physics
This report is the result of the collaboration and research effort of the Quarkonium Working Group over the last three years. It provides a comprehensive overview of the state of the art in heavy-quarkonium theory and experiment, covering quarkonium spectroscopy, decay, and production, the determination of QCD parameters from quarkonium observables, quarkonia in media, and the effects on quarkonia of physics beyond the Standard Model. An introduction to common theoretical and experimental tools is included. Future opportunities for research in quarkonium physics are also discussed.
17730280
Nonperturbative explanation of the enhancement factors in the QCD sum rule for the ρ meson
Taking the sum rule for the {rho} meson as an example, we study the possibility of explaining the phenomenological enhancement factors for certain terms in the vacuum expectation value of operator product expansion in the QCD sum rule. We take a QCD motivated extended Nambu{endash}Jona-Lasinio model as the low energy effective Lagrangian for QCD with which we calculate the nonperpturbative contributions to the vaccum condensate expansion to obtain the enhancement factors. Our result shows that such nonperturbative contributions can cause large enough enhancement factors which can be consistent with the phenomenological values. {copyright} {ital 1997} {ital The American Physical Society}
8414809
Anomalous gauge interactions of the Higgs boson: precision constraints and weak boson scatterings
Abstract Interaction of Higgs scalar ( H ) with weak gauge bosons ( V = W ± , Z 0 ) is the key to understand electroweak symmetry breaking (EWSB) mechanism. New physics effects in the HVV interactions, as predicted by models of compositeness, supersymmetry and extra dimensions, can be formulated as anomalous couplings via a generic effective Lagrangian. We first show that the existing electroweak precision data already impose nontrivial indirect constraints on the anomalous HVV couplings. Then, we systematically study VV → VV scatterings in the TeV region, via Gold-plated pure leptonic decay modes of the weak bosons. We demonstrate that, even for a light Higgs boson in the mass range 115 GeV≲ m H ≲300 GeV, this process can directly probe the anomalous HVV interactions at the LHC with an integrated luminosity of 300 fb −1 , which further supports the “no-lose” theorem for the LHC to uncover the EWSB mechanism. Comparisons with the constraints from measuring the cross section of VH associate production and the Higgs boson decay width are also presented.