arXiv subjects

H. J. Lipkin

Publications and source records attributed to H. J. Lipkin.

9 recordsLinked to original sources

arXiv2003

Implications of a DK Molecule at 2.32 GeV

We discuss the implications of a possible quasinuclear DK bound state at 2.32 GeV. Evidence for such a state was recently reported in D_s^+pi^o by the BaBar Collaboration. We first note that a conventional quark model c-sbar assignment is implausible, and then consider other options involving multiquark systems. An I=0 c sbar n nbar baryonium assignment is one possibility. We instead favor a DK meson molecule assignment, which can account for the mass and quantum numbers of this state. The higher-mass scalar c-sbar state expected at 2.48 GeV is predicted to have a very large DK coupling, which would encourage formation of an I=0 DK molecule. Isospin mixing is expected in hadron molecules, and a dominantly I=0 DK state with some I=1 admixture could explain both the narrow total width of the 2.32 GeV state as well as the observed decay to D_s^+ pi^o. Additional measurements that can be used to test this and related scenarios are discussed.

hep-ph↗

arXiv2002

Puzzles in Cabibbo-Suppressed Charm Decays

We identify two Cabibbo suppressed $D^+$ decay modes with anomalously high branching ratios which are not simply explained by any model. All standard model diagrams that can contribute to these decays are related by symmetries to diagrams for other decays that do not show any such enhancement. If these high branching ratios are confirmed by more precise experiments, they may require new physics to explain them. Anomalies in $D_s$ decays and tests for possible violation of G-parity are discussed.

hep-ph↗

arXiv2000

The contribution of $Σ^* \to Λπ$ to measured $Λ$ polarization

Calculations of the polarization of $Λ$ and $\barΛ$ particles after fragmentation of a polarized quark produced in processes like $Z$-decay and deep inelastic polarized lepton scattering must include $Λ$ and $\barΛ$ produced as decay products of $Σ^0$ and $Σ^*$ as well as those produced directly. These decay contributions are significant and not feasibly included in theoretical calculations based on QCD without additional input from other experimental data. Furthermore these contributions depend on the spin structure of the $Σ^0$ or $Σ^*$ and are not directly related to the structure function of the $Λ$

hep-ph↗

arXiv1999

Expected Polarization of $Λ$ particles produced in deep inelastic polarized lepton scattering

We calculate the polarization of Lambda and Anti-Lambda particles produced in deep inelastic polarized lepton scattering. We use two models: the naive quark model and a model in which SU(3)$_F$ symmetry is used to deduce the spin structure of SU(3) octet hyperons from that of the proton. We perform the calculations for Lambda and Anti-Lambda produced directly or as decay products of $Σ^0$ and $Σ^*$.

hep-ph↗

arXiv1997

Penguins, Trees and Final State Interactions in B Decays in Broken SU3

The availability of data on $B_s$ decays to strange quasi-two-body final states, either with or without charmonium opens new possibilities for understanding different contributions of weak diagrams and in particular the relative contributions of tree and penguin diagrams. Corresponding $B_d$ and $B_s$ decays to charge conjugate final states are equal in the SU(3) symmetry limit and the dominant SU(3) breaking mechanism is given by ratios of CKM matrix elements. Final State Interactions effects should be small, because strong interactions conserve $C$ and should tend to cancel in ratios between charge conjugate states. Particularly interesting implications of decays into final states containing $η$ and $η'$ are discussed.

hep-ph↗

arXiv1995

How to Search for Pentaquarks in High Energy Hadronic Interactions

The strange-anticharmed Pentaquark is a $uud\bar{c}s$ or $udd\bar{c}s$ five-quark baryon that is expected to be either a narrow resonance, or possibly even stable against strong and electromagnetic decay. We describe this hyperon here, its structure, binding energy and lifetime, resonance width, production mechanisms, production cross sections, and decay modes. We describe techniques to reduce backgrounds in search experiments and to optimize the conditions for Pentaquark observation. Possibilities for enhancing the signal over background in Pentaquark searches are investigated by examining predictions for detailed momentum and angular distributions in multiparticle final states. General model-independent predictions are presented as well as those from two models: a loosely bound $D_{s}^-N$ molecule and a strongly-bound five-quark system. Fermilab E791 data, currently being analyzed, may have marginal statistics for showing definitive signals. Future experiments in the spirit of the recent CHARM2000 workshop, such as FNAL E781 and CERN CHEOPS with $10^6-10^7$ reconstructed charmed baryon events, should have sensitivity to determine whether or not the Pentaquark exists.

hep-ph↗

arXiv1995

Topology, Locality, and Aharonov-Bohm Effect with Neutrons

Recent neutron interferometry experiments have been interpreted as demonstrating a new topological phenomenon similar in principle to the usual Aharonov-Bohm (AB) effect, but with the neutron's magnetic moment replacing the electron's charge. We show that the new phenomenon, called Scalar AB (SAB) effect, follows from an ordinary local interaction, contrary to the usual AB effect, and we argue that the SAB effect is not a topological effect by any useful definition. We find that SAB actually measures an apparently novel spin autocorrelation whose operator equations of motion contain the local torque in the magnetic field. We note that the same remarks apply to the Aharonov-Casher effect.

quant-ph↗

arXiv1994

Pentaquark Search with Energetic Hadron Beams

The strange-anticharmed Pentaquark is a uud(cbar)s or udd(cbar)s five-quark baryon that is expected to be either a narrow resonance, or possibly even stable against strong decay. We describe this hyperon here; its structure, binding energy and lifetime, resonance width, production mechanisms and decay modes. We estimate production cross sections, techniques to reduce backgrounds in search experiments, and how to optimize experiments to observe it. Possibilities for enhancing the signal over background in Pentaquark searches are investigated by examining predictions for detailed momentum and angular distributions in multiparticle final states. General model-independent predictions are presented as well as those from two models: a loosely bound Ds-N "deuteron" and a strongly-bound five-quark model. Fermilab E791 data, currently being analysed, may be marginal for showing definitive signals. Future experiments with more than 10^5 reconstructed charmed baryon events should have sensitivity to determine whether or not the Pentaquark exists.

hep-ph↗

arXiv1993

Resonant Tunneling and the Pauli Principle

A new method based on modified optical Bloch equations is proposed for studying resonant tunneling in semiconductor heterostructures. The method manifestly takes account of electrons' statistics, which enables to investigate the influence of the Pauli principle on resonant tunneling in presence of inelastic scattering. Being applied to evaluation of the resonant current in semiconductor heterostructures, our approach predicts considerable deviations from the one-electron picture.

cond-mat↗