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Abstract:

Inclusive momentum distributions of charged particles in restricted cones around jet axes were measured in dijet events with invariant dijet masses in the range 80 to 600 GeV/c2. Events were produced at the Fermilab Tevatron in pp collisions with a center of mass energy of 1.8 TeV and recorded by the Collider Detector at Fermilab. The results were compared to perturbative QCD calculations carried out in the framework of the modified leading log approximation (MLLA) and assuming local parton-hadron duality. It was shown that the data follow theoretical predictions quite well over the whole range of the jet energies included in this analysis. We extracted the MLLA cutoff scale Qe f f and found a value of 230±40 MeV. The theoretical prediction of Ejetsin θc scaling, where u c is the cone opening angle, was experimentally observed for the first time. From the MLLA fits to the data, two more parameters were extracted: the ratio of parton multiplicities in gluon and quark jets, r = Npartonsg-jet /Npartonsq-jet = 1.9±0.5, and the ratio of the number of charged hadrons to the number of predicted partons in a jet, KLPHDcharged=Nhadronscharged/Npartons=0.56±0.10.

Abstract:

Using 13.5 fb^-1 of e⁺e^- annihilation data collected with the CLEO II detector, we have observed a narrow resonance decaying to D*s⁺ Ï€⁰ with a mass near 2.46 GeV/c². The search for such a state was motivated by the recent discovery by the BaBar Collaboration of a narrow state at 2.32 GeV/c ², the D*sJ(2317)⁺, that decays to D s⁺ Ï€⁰. Reconstructing the Ds ⁺ Ï€⁰ and D*s⁺ Ï€⁰ final states in CLEO data, we observe peaks in both of the corresponding reconstructed mass difference distributions, ΔM(D sÏ€⁰) = M(DsÏ€⁰) - M(D s) and ΔM(D*s Ï€⁰) = M(D*s Ï€⁰) - M(D*s), both of them at values near 350 MeV/c². We interpret these peaks as signatures of two distinct states, the D*sJ(2317)⁺ plus a new state, designated as the DsJ(2463)⁺. Because of the similar ΔM values, each of these states represents a source of background for the other if photons are lost, ignored or added. A quantitative accounting of these reflections confirms that both states exist. We have measured the mean mass differences 〈ΔM(Ds Ï€⁰)〉 = 350.0 ±1.2 (stat) ± 1.0 (syst) MeV/c² for the D*sJ(2317)⁺ state, and 〈ΔM(D* s Ï€⁰)〉 = 351.2 ± 1.7 (stat) ± 1.0 (syst) MeV/c² for the new DsJ(2463)⁺ state. We have also searched, but find no evidence, for decays of the two states via the channels D*s⁺ γ, Ds⁺ γ, and Ds⁺ Ï€⁺ Ï€^-. The observations of the two states at 2.32 and 2.46 GeV/c², in the D s⁺ Ï€⁰ and D*s⁺ Ï€⁰ decay channels, respectively, are consistent with their interpretations as csÌ„ mesons with an orbital angular momentum L = 1 and spin and parity J^P = 0⁺ and 1⁺. © 2003 The American Physical Society.

Abstract:

We have searched for the baryon-containing radiative penguin decays B ^-→Λp̄γ and B^-→ Σ^0-pγ, using a sample of 9.7 × 10⁶ BBÌ„ events collected at the Y(45) with the CLEO detector. We find no evidence for either, and set 90% confidence level upper limits of B(B ^-→Λp̄γ) + 0.3B(B ^-→Σ^0-±è̄γ)±Õ·¡Î³ >2.0 GeV<3.3×10^-6, [B(B^-→Σ ^0-p̄γ) + 0-4B(B^-→Λ±è̄γ)±Õ ·¡Î³>2.0Gev<6.4×10⁶. From the latter, we estimate B(B →Xsγ²â,³Ýs containing baryons) ·¡Î³>2.0 GeV<3.8×10^-5. This limit implies upper limits on corrections to CLEO's recent measurement of branching fraction, mean photon energy, and variance in photon energy from b→sγ that are less than half the combined statistical and systematic errors quoted on these quantities. © 2003 The American Physical Society.

Abstract:

We report on a search for the flavor-changing neutral current decay D ⁰→µ⁺µ^- in pp^- collisions at √s = 1.96 TeV using 65 pb^-1 of data collected by the CDF II experiment at the Fermilab Tevatron Collider. A displaced-track trigger selects long-lived D⁰ candidates in the D⁰→µ ⁺µ^- search channel, the kinematically similar D ⁰→П⁺p^- channel used for normalization, the Cabibbo-favored D⁰K^-П^- channel used to optimize the selection criteria in an unbiased manner, and their charge conjugates. Finding no signal events in the D⁰→µ⁺µ^- search window, we set an upper limit on the branching fraction B(D⁰→µ⁺µ^-)≤2.5×10^-6 (3.3×10^-6) at the 90% (95%) confidence level.