J. Solano

MEASUREMENTS OF LIFETIMES AND A LIMIT ON THE LIFETIME DIFFERENCE IN THE NEUTRAL D-MESON SYSTEM

Using the large hadroproduced charm sample collected in experiment E791 at Fermilab, we report the first directly measured constraint on the decay-width difference Delta Gamma for the mass eigenstates of the D0-D0bar system. We obtain our result from lifetime measurements of the decays D0 -->K-pi+ and D0 -->K-K+, under the assumption of CP invariance, which implies that the CP eigenstates and the mass eigenstates are the same. The lifetime of D0 -->K-K+ (the CP-even final state is \tau_KK = 0.410 +/- 0.011 +/- 0.006 ps, and the lifetime of D0 -->K-pi+ (an equal mixture of CP-odd and CP-even final states is tau_Kpi = 0.413 +/- 0.003 +/- 0.004 ps. The decay-width difference is Delta Gamma = 2(Gamma_KK - Gamma_Kpi) = 0.04 +/- 0.14 +/- 0.05 ps^-1. We relate these measurements to measurements of mixing in the neutral D-meson system.

Search for rare and forbidden dilepton decays of the D+, Ds+, and D0 charmed mesons

Abstract We report the results of a search for flavor-changing neutral current, lepton-flavor violating, and lepton-number violating decays of D + , D s + , and D 0 mesons (and their antiparticles) into modes containing muons and electrons. Using data from Fermilab charm hadroproduction experiment E791, we examine the π ll and K ll decay modes of D + and D s + and the l + l − decay modes of D 0 . No evidence for any of these decays is found. Therefore, we present branching-fraction upper limits at 90% confidence level for the 24 decay modes examined. Eight of these modes have no previously reported limits, and fourteen are reported with significant improvements over previously published results.

Branching fractions for D0→K+K− and D0→π+π−, and a search for CP violation in D0 decays

Using the large hadroproduced charm sample collected in experiment E791 at Fermilab, we have measured ratios of branching fractions for the two-body singly-Cabibbo-suppressed charged decays of the D0: (D0 -> KK)/(D0 -> Kpi) = 0.109 +- 0.003 +- 0.003, (D0 -> pipi)/(D0 -> Kpi) = 0.040 +- 0.002 +- 0.003, and (D0 -> KK)/(D0 -> pipi) = 2.75 +- 0.15 +- 0.16. We have looked for differences in the decay rates of D0 and D0bar to the CP eigenstates K+K- and pi+pi-, and have measured the CP asymmetry parameters A_CP(K+K-) = -0.010 +- 0.049 +- 0.012 and A_CP(pi+pi-) = -0.049 +- 0.078 +- 0.030, both consistent with zero.

Measurement of the form-factor ratios for

The form factor ratios rv=V(0)/A1(0), r2=A2(0)/A1(0) and r3=A3(0)/A1(0) in the decay D+ -->K* l nu, K* -->K-pi+ have been measured using data from charm hadroproduction experiment E791 at Fermilab. From 3034 (595) signal (background) events in the muon channel, we obtain rv=1.84+-0.11+-0.09, r2=0.75+-0.08+-0.09 and, as a first measurement of r3, we find 0.04+-0.33 +-0.29. The values of the form factor ratios rv and r2 measured for the muon channel are combined with the values of rv and r2 that we have measured in the electron channel. The combined E791 results for the muon and electron channels are rv=1.87+-0.08+-0.07 and r2=0.73+-0.06+-0.08.The form factor ratios rv=V(0)/A1(0), r2=A2(0)/A1(0) and r3=A3(0)/A1(0) in the decay D+ --> K* l nu, K* -->K-pi+ have been measured using data from charm hadroproduction experiment E791 at Fermilab. From 3034 (595) signal (background) events in the muon channel, we obtain rv=1.84+-0.11+-0.09, r2=0.75+-0.08+-0.09 and, as a first measurement of r3, we find 0.04+-0.33 +-0.29. The values of the form factor ratios rv and r2 measured for the muon channel are combined with the values of rv and r2 that we have measured in the electron channel. The combined E791 results for the muon and electron channels are rv=1.87+-0.08+-0.07 and r2=0.73+-0.06+-0.08.

Search for the pentaquark via the P0c̄s→K∗0K−p decay

Abstract We have searched for evidence of the production and decay of a neutral bound-state pentaquark, one of a predicted doublet of states: P 0 c s =| c suud〉 and P − c s =| c sddu〉 . Specifically, we have searched for the decay P 0 c s →K ∗0 K − p in data from Fermilab experiment E791, in which a 500 GeV/c π− beam interacted with nuclear targets. We find mass-dependent upper limits at the 90% confidence level for the ratio of cross section times branching fraction of this decay relative to that for the decay D s − →K ∗0 K − . The upper limits vary between 0.016 and 0.036 for M(P 0 c s ) between 2.75 and 2.91 GeV/c2, assuming a pentaquark lifetime of 0.4 ps.

Asymmetries in the production of Λc+ and Λc− baryons in 500 GeV/cπ− nucleon interactions

We present a measurement of asymmetries in the production of

Asymmetries in the production of Λ0, Ξ−, and Ω− hyperons in 500 GeV/cπ−–nucleon interactions

\Lambda_c^+

Multidimensional resonance analysis of Λc+→pK−π+

and

Measurement of the form-factor ratios for D+s→φℓ+νℓ

\Lambda_c^-

Total forward and differential cross sections of neutral D mesons produced in 500 GeV/ c π − –nucleon interactions

baryons in 500 GeV/c