P. Gagnon

Asymmetries between the production of D+ and D− mesons from 500 GeV/c π−-nucleus interactions as a function of xF and pt2

Abstract We present measurements of the production of Ds− mesons relative to Ds+ mesons as functions of xF and of pt2 for a sample of 2445 Ds decays to φπ. The Ds mesons were produced in Fermilab experiment E791 with 500 GeV/c π− mesons incident on one platinum and four carbon foil targets. The acceptance-corrected integrated asymmetry in the xF range −0.1 to 0.5 for Ds± mesons is 0.032 ± 0.022 ± 0.022, consistent with no net asymmetry. We compare the results as functions of xF and pt2 to predictions and to the large production asymmetry observed for D± mesons in the same experiment. These comparisons support the hypothesis that production asymmetries come from the fragmentation process and not from the charm quark production itself.

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.

Search for CP violation in charged D meson decays

Abstract We report results of a search for CP violation in the singly Cabibbo-suppressed decays D + → K − K + π + , φπ + , K ∗ (892) 0 K + , and π − π + π + based on data from the charm hadroproduction experiment E791 at Fermilab. We search for a difference in the D + and D − decay rates for each of the final states. No evidence for a difference is seen. The decay rate asymmetry parameters ( A CP ), defined as the difference in the D + and D − decay rates divided by the sum of the decay rates, are measured to be: A CP ( KKπ ) = −0.014±0.029, A CP ( φπ ) = −0.028±0.036, A CP (K ∗ (892)K) = −0.010±0.050 and A CP ( πππ ) = −0.017±0.042.We report results of a search for CP violation in the singly Cabibbosuppressed decays D → KKπ, φπ, K(892)0K+, and πππ based on data from the charm hadroproduction experiment E791 at Fermilab. We search for a difference in the D and D decay rates for each of the final states. No evidence for a difference is seen. The decay rate asymmetry parameters (ACP ), defined as the difference in the D + and D decay rates divided by the sum of the decay rates, are measured to be: ACP (KKπ) = −0.014 ± 0.029, ACP (φπ) = −0.028 ± 0.036, ACP (K(892)K) = −0.010 ± 0.050, and ACP (πππ) = −0.017 ± 0.042. PACS numbers: 11.30.Er, 12.15.Ji, 13.25.Ft, 14.40.Lb Typeset using REVTEX

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: n(D0 -> KK)/(D0 -> Kpi) = 0.109 +- 0.003 +- 0.003, n(D0 -> pipi)/(D0 -> Kpi) = 0.040 +- 0.002 +- 0.003, and n(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 nA_CP(K+K-) = -0.010 +- 0.049 +- 0.012 and nA_CP(pi+pi-) = -0.049 +- 0.078 +- 0.030, both consistent with zero.

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

Abstract We present a measurement of asymmetries in the production of Λ c + and Λ c − baryons in 500xa0GeV/ c π − -nucleon interactions from the E791 experiment at Fermilab. The asymmetries were measured as functions of Feynman x ( x F ) and transverse momentum squared ( p T 2 ) using a sample of 1 819±62 Λ c s observed in the decay channel Λ c + → pK − π + . We observe more Λ c + than Λ c − baryons, with an asymmetry of (12.7±3.4±1.3)% independent of x F and p T 2 in our kinematical range (−0.1⩽ x F ⩽0.6 and 0.0⩽ p T 2 ⩽8.0xa0(GeV/ c ) 2 ). This Λ c asymmetry measurement is the first with data in both the positive and negative x F regions.We present a measurement of asymmetries in the production of

Multidimensional resonance analysis of Λc+→pK−π+

Lambda_c^+

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

and

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

Lambda_c^-

Mass splitting and production of Σc0 and Σc++ measured in 500 GeV π− -N interactions

baryons in 500 GeV/c