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121.
We establish upper limits on branching fractions for B0 decays to final states where the decay products are purely invisible (i.e., no observable final state particles) and for B0 decays to nunugamma. Within the standard model, these decays have branching fractions that are below current experimental sensitivity, but various models of physics beyond the standard model predict significant contributions from these channels. Using 88.5 x 10(6) BB pairs collected at the Upsilon(4S) resonance by the BABAR experiment at the PEP-II e(+)e- storage ring at the Stanford Linear Accelerator Center, we establish upper limits at the 90% confidence level of 22 x 10(-5) for the branching fraction of B0-->invisible and 4.7 x 10(-5) for the branching fraction of B0-->nunugamma.  相似文献   
122.
We have measured the time-dependent decay rate for the process B-->J/psiK(*0) (892) in a sample of about 88x10(6) Upsilon(4S)-->B(-)B decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. In this sample we study flavor-tagged events in which one neutral B meson is reconstructed in the J/psiK(*0) or J/psi(-)K(*0) final state. We measure the coefficients of the cosine and sine terms in the time-dependent asymmetries for J/psiK(*0) and J/psi(-)K(*0), find them to be consistent with the standard model expectations, and set upper limits at 90% confidence level (C.L.) on the decay amplitude ratios |A((-)B(0)-->J/psiK(*0))|/|A(B0-->J/psiK(*0))|<0.26 and |A(B0-->J/psi(-)K(*0))|/|A((-)B(0)-->J/psi(-)K(*0))|<0.32. For a single ratio of wrong-flavor to favored amplitudes for B0 and (-)B(0) combined, we obtain an upper limit of 0.25 at 90% C.L.  相似文献   
123.
We present a measurement of the time-dependent CP asymmetry for the neutral B-meson decay B0-->phiK0. We use a sample of approximately 114 x 10(6) B-meson pairs taken at the Upsilon(4S) resonance with the BABAR detector at the PEP-II B-meson factory at SLAC. We reconstruct the CP eigenstates phiK0S and phiK0L, where phi-->K+K-, K0S-->pi+pi-, and K0L is observed via its hadronic interactions. The other B meson in the event is tagged as either a B0 or Bbar0 from its decay products. The values of the CP-violation parameters are SphiK=0.47+/-0.34(stat)+0.08-0.06(syst) and CphiK=0.01+/-0.33(stat)+/-0.10(syst).  相似文献   
124.
We describe a measurement of the direct CP asymmetry between inclusive b-->s gamma and b-->s gamma decays. This asymmetry is expected to be less than 0.01 in the standard model, but could be enhanced up to about 0.10 by new physics contributions. We use a sample of 89 x 10(6) BB pairs recorded with the BABAR detector at SLAC PEP-II, from which we reconstruct a set of 12 exclusive b-->s gamma final states containing one charged or neutral kaon and one to three pions. We measure an asymmetry of A(CP)(b-->s gamma)=0.025+/-0.050(stat)+/-0.015(syst), corresponding to an allowed range of -0.06s gamma)<+0.11 at 90% confidence level.  相似文献   
125.
We report the observation of the B meson decay B+/- -->J/psietaK+/- and evidence for the decay B0-->J/psietaK0S, using 90 x 10(6) BB; events collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II e+e- asymmetric-energy storage ring. We obtain branching fractions of B(B+/- -->J/psietaK+/-) = [10.8 +/- 2.3(stat) +/- 2.4(syst)] x 10(-5) and B(B0-->J/psietaK0S) = [8.4 +/- 2.6(stat) +/- 2.7(syst)] x 10(-5). We search for the new narrow mass state, the X(3872), recently reported by the Belle Collaboration, in the decay B+/- -->X(3872)K+/-,X(3872)-->J/psieta and determine an upper limit of B[B +/- -->X(3872)K+/- -->J/psietaK+/-] < 7.7 x 10(-6) at 90% confidence level.  相似文献   
126.
We present a study of the decay B--->D(*0)K(*-) based on a sample of 86 x 10(6) Upsilon(4S)-->BBmacr; decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We measure the branching fraction B(B--->D(*0)K(*-))=(8.3+/-1.1(stat)+/-1.0(syst)) x 10(-4), and the fraction of longitudinal polarization in this decay to be Gamma(L)/Gamma=0.86+/-0.06(stat)+/-0.03(syst).  相似文献   
127.
We have observed the decays B--> phiK and phiK(*) in a sample of over 45 million B mesons collected with the BABAR detector at the PEP-II collider. The measured branching fractions are B(B+--> phiK+) = (7.7(+1.6)(-1.4)+/-0.8)x10(-6), B(B0--> phiK0) = (8.1(+3.1)(-2.5)+/-0.8)x10(-6), B(B+--> phiK(*+)) = (9.7(+4.2)(-3.4)+/-1.7)x10(-6), and B(B0--> phiK(*0)) = (8.7(+2.5)(-2.1)+/-1.1)x10(-6). We also report the upper limit B(B+--> phipi(+))<1.4x10(-6) ( 90% C.L.).  相似文献   
128.
We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88 x 10(6) Upsilon(4S)-->B(-)B decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We study events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B(0) or B(-0) from its decay products. The amplitude of the CP asymmetry, which in the standard model is proportional to sin2beta, is derived from the decay-time distributions in such events. We measure sin2beta=0.741+/-0.067(stat)+/-0.034(syst) and |lambda|=0.948+/-0.051(stat)+/-0.030(syst). The magnitude of lambda is consistent with unity, in agreement with the standard model expectation of no direct CP violation in these modes.  相似文献   
129.
A search for the lepton-flavor-violating decay of the tau into three charged leptons has been performed using 91.5 fb(-1) of data collected at an e(+)e(-)center-of-mass energy around 10.58 GeV with the BABAR detector at the SLAC storage ring PEP-II. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1-3)x10(-7) at 90% confidence level.  相似文献   
130.
We report the observation of decays B{0}-->D{s}{(*)+}pi- and B{0}-->D{s}{(*)-}K+ in a sample of 230 x 10(6) Upsilon(4S)-->BB[over] events recorded with the BABAR detector at the SLAC PEP-II asymmetric-energy e+ e- storage ring. We measure the branching fractions B(B{0}-->D{s}{+}pi-)=(1.3+/-0.3(stat)+/-0.2(syst))x10(-5), B(B{0}-->D{s}{-} K+)=(2.5+/-0.4(stat)+/-0.4(syst))x10(-5), B(B{0}-->D{s}{*+}pi-)=(2.8+/-0.6(stat)+/-0.5(syst))x10(-5), and B(B{0}-->D{s}{*-}K+)=(2.0+/-0.5(stat)+/-0.4(syst))x10(-5). The significances of the measurements to differ from zero are 5, 9, 6, and 5 standard deviations, respectively. This is the first observation of B{0}-->D{s}{+}pi-, B{0}-->D{s}{*+}pi-, and B{0}-->D{s}{*-}K+ decays.  相似文献   
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