arXiv subjects

The Fermilab E791 Collaboration

Publications and source records attributed to The Fermilab E791 Collaboration.

4 recordsLinked to original sources

arXiv1999

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 τ_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.

hep-ex↗

arXiv1997

A search for D0-D0bar mixing and doubly-Cabibbo-suppressed decays of the D0 in hadronic final states

We present results of a search for D0-D0bar mixing and doubly-Cabibbo-suppressed decays of the D0 in Fermilab experiment E791, a fixed-target charm hadroproduction experiment. We look for evidence of mixing in the decay chain D* -> pi D0 -> (K pi or K pi pi pi). If the charge of the pion from the D* decay is the same as the charge of the kaon from the D decay (a ``wrong-sign'' event), mixing may have occurred. Mixing can be distinguished from other sources of wrong-sign events (such as doubly-Cabibbo-suppressed decays) by analyzing the distribution of decay times. We see no evidence of mixing. Allowing for possible CP violation, our results for r_{mix}, the ratio of mixed to unmixed decays, are r_{mix}(D0bar -> D0)=(0.18_{-0.39}^{+0.43} +- 0.17)% and r_{mix}(D0 -> D0bar)=(0.70_{-0.53}^{+0.58} +- 0.18)%. The sensitivity of these results is comparable to that of previous measurements, but the assumptions made in fitting the data are notably more general. We present results from many fits to our data under various assumptions. If we assume r_{mix} = 0, we find that the ratios of doubly Cabibbo-suppressed decays to Cabibbo-favored decays are r_{dcs}(K pi) =(0.68_{-0.33}^{+0.34} +- 0.07)% and r_{dcs}(K pi pi pi)=(0.25_{-0.34}^{+0.36} +- 0.03)%.

hep-ex↗

arXiv1997

Branching Fractions for D0 -> K+K- and D0 -> pi+pi-, 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.

hep-ex↗

arXiv1997

The doubly Cabibbo-suppressed decay $D^+\to K^+ π^- π^+$

We report the observation of the doubly Cabibbo-suppressed decay $D^+\to K^+ π^- π^+$ in data from Fermilab charm hadroproduction experiment E791. With a signal of 59 \pm 13 events we measured the ratio of the branching fraction for this mode to that of the Cabibbo-favored decay $D^+\to K^- π^+ π^+$ to be $B(D^+ \to K^+ π^- π^+) / B(D^+ \to K^- π^+ π^+) = (7.7 \pm 1.7 \pm 0.8) \times 10^{-3}$. A Dalitz plot analysis was performed to search for resonant structures.

hep-ex↗