N. Horwitz

Model-independent determination of the strong-phase difference between D0 and D⊃̄0→KS,L0h+h- (h=π, K) and its impact on the measurement of the CKM angle γ/Φ3

We report the first determination of the relative strong-phase difference between D0→KS,L0K+K- and D 0→KS,L0K+K-. In addition, we present updated measurements of the relative strong-phase difference between D0→KS,L0π+π- and D 0→KS,L0π+π-. Both measurements exploit the quantum coherence between a pair of D0 and D 0 mesons produced from ψ(3770) decays. The strong-phase differences measured are important for determining the Cabibbo-Kobayashi-Maskawa angle γ/ϕ3 in B-→K-D˜0 decays, where D˜0 is a D0 or D 0 meson decaying to KS0h+h- (h=π, K), in a manner independent of the model assumed to describe the D0→KS0h+h- decay. Using our results, the uncertainty in γ/ϕ3 due to the error on the strong-phase difference is expected to be between 1.7° and 3.9° for an analysis using B-→K-D˜0, D˜0→KS0π+π- decays, and between 3.2° and 3.9° for an analysis based on B-→K-D˜0, D˜0→KS0K+K- decays. A measurement is also presented of the CP-odd fraction, F-, of the decay D0→KS0K+K- in the region of the ϕ→K+K- resonance. We find that in a region within 0.01  GeV2/c4 of the nominal ϕ mass squared F->0.91 at the 90% confidence level.

Limits on rare exclusive decays of B mesons

Abstract We have set upper limits for rare exclusive decays of B mesons arising from higher order processes in the standard model of electroweak interactions. Such decays may occur via “penguin diagrams” in B decay. We also set an upper limit on a lepton-number-violating decay mode of the neutral B meson.

Updated measurement of the strong phase in D0→K+π- decay using quantum correlations in e+e-→D0D̄0 at CLEO

We analyze a sample of 3 million quantum-correlated D0 D0bar pairs from 818 pb^-1 of e+e- collision data collected with the CLEO-c detector at E_cm = 3.77 GeV, to give an updated measurement of \cos\delta and a first determination of \sin\delta, where \delta is the relative strong phase between doubly Cabibbo-suppressed D0 --> K+pi- and Cabibbo-favored D0bar --> K+pi- decay amplitudes. With no inputs from other experiments, we find \cos\delta = 0.81 +0.22+0.07 -0.18-0.05, \sin\delta = -0.01 +- 0.41 +- 0.04, and |\delta| = 10 +28+13 -53-0 degrees. By including external measurements of mixing parameters, we find alternative values of \cos\delta = 1.15 +0.19+0.00 -0.17-0.08, \sin\delta = 0.56 +0.32+0.21 -0.31-0.20, and \delta = (18 +11-17) degrees. Our results can be used to improve the world average uncertainty on the mixing parameter y by approximately 10%.

Measurement of the isospin mass splitting Ξ+cΞ0c

Abstract Using the CLEO detector, we present a measurement of the mass of the charged charmed strange baryon Ξ + c and its neutral counterpart the Ξ 0 c . The Ξ + c is observed through its decay to Ξ - π + π + , and its mass is measured to be (2467±3±4) MeV. The isospin mass splitting of the Ξ c system is found to be M ( Ξ + c )- M ( Ξ 0 c )=(−5±4±1)MeV.

A measurement of the tau lifetime

The tau lepton lifetime is measured using four different methods with the DELPHI detector. Three measurements using one prong decays are combined, accounting for correlations, resulting in ττ=298 ±7 (stat.)±4 (syst.) fs while the decay length distribution of three prong decays gives ππ=298±13 (stat)±(syst.) fs. The combined result is ττ=298±7 fs. The ratio of the Fermi coupling constant from tau decay relative to that from muon decay is found to be 0.985±0.013, compatible with lepton universality.

Determination of B(Ds+) via observation of Ds+l+1/2

Using the CLEO detector at the Cornell Electron Storage Ring (CESR), we have determined the ratio {Gamma}({ital D}{sub {ital s}}{sup +}{r arrow}{phi}{ital l}{sup +}{nu})/{Gamma}({ital D}{sub {ital s}}{sup +} {r arrow}{phi}{pi}{sup +})=0.49{plus minus}0.10{sub {minus}0.14}{sup +0.10}. We use this measurement to derive {ital B}({ital D}{sub {ital s}}{sup +}{r arrow}{phi}{pi}{sup +}).

Measurement of γγ widths of charmonium states

Abstract Using the CLEO detector at the Cornell Electron Storage Ring, we have searched for two-photon production of charmonium in four-track final states. We have measured Γ γγ ( η c )=5.9 +2.1 −1.8 ±1.9 keV, and we have obtained 95% CL upper limits of Γ γγ ( X c 0 ) Γ γγ ( X c 2 )

Limits on the production of large transverse momentum direct photons deduced from the measurement of low-mass electron pairs

Abstract The hadronic production of electron pairs with masses between 200 and 500 MeV and large transverse momentum has been measured at the CERN Intersecting Storage Rings (ISR). The expected relation between low-mass electron pairs and real photons is used to determine the direct hadronic production of photons. Contrary to indications from some previous experiments, the observed spectrum is consistent with expectations from the decay of known mesons, and leads to a value for the ratio of direct photons to π 0 of γ / π 0 = (0.55 ± 0.92)% for 2 p T s 〉 = 55 GeV.

First observation of inclusive ψ production in ψ decays

The branching ratio for inclusive ψ production in ψ(1S) decays is measured to be (0.11 ± 0.04 ± 0.02)%.

Observation on pp → 3π°, 2π°η° at rest☆

Abstract Annihilations have been observed of anti-protons stopped in liquid hydrogen yielding 3π° and 3π°η°, with a ratio 3π°: 2π°η° of 0.81 ± 0.08. The Dalitz plot of 2100 3π°-events exhibits structures somewhat similar to those observed in p n →2π − π + (at rest); viz: depopulation at the center, enhancement at small M2(2π°) and at about 2.35 (GeV/c2)2.