K^0_S production in \tau decays

From a sample of about 160k candidates collected with the ALEPH detector at LEP between 1991 and 1995, lepton decays involving are studied. The associated production in decays is also investigated. The branching ratios are measured for the inclusive decay , where can be anything, and for the exclusive decays The decay is studied for the first time, giving a branching ratio The channels , , , , and are also investigated. In addition, mass spectra in the and final states are analysed to provide information on the intermediate states produced in the decays. Received: 6 January 1998 / Published online: 15 May 1998     

Inclusive decays and lifetimes of doubly-charmed baryons

The analysis of singly-charmed hadrons has been extended to the case of doubly-charmed baryons, , and . Doubly-charmed baryons are described as a system containing a heavy cc diquark and a light quark, as in the case of a heavy–light meson. This leads to preasymptotic effects in semileptonic and nonleptonic decays that are essentially proportional to the meson wave function. Interplay between preasymptotic effects in semileptonic and/or nonleptonic decay rates leads to very clear predictions for semileptonic branching ratios and lifetimes of doubly-charmed baryons. Received: 21 January 1999 / Published online: 20 May 1999     

Search for B --> h(*)nunu[over ] decays at Belle

We present a search for the rare decays B --> h(*)nunu[over ], where h(*) stands for a light meson. A data sample of 535 x 10{6} BB[over ] pairs collected with the Belle detector at the KEKB e{+}e{-} collider is used. Signal candidates are required to have an accompanying B meson fully reconstructed in a hadronic mode and signal side particles consistent with a single h(*) meson. No significant signal is observed and we set upper limits on the branching fractions at 90% confidence level. The limits on B{0} --> K{*0}nunu[over ] and B{+} --> K{+}nunu[over ] decays are more stringent than the previous constraints, while the first searches for B{0} --> K{0}nunu[over ], pi{0}nunu[over ], rho{0}nunu[over ], varphinunu[over ] and B{+} --> K{*+}nunu[over ], rho{+}nunu[over ] are reported.     

Measurement of the b baryon lifetime and branching fractions in Z decays

Using approximately 4 million hadronic Z decays recorded with the aleph detector from 1991 through 1995, the lifetime of the b baryon is measured with three independent methods. From the impact parameter distribution of candidate leptons in 1063 events with combinations, the average b baryon lifetime is measured to be ps. From a sample of 193 fully reconstructed candidates correlated with a lepton and a sample of 46 combinations, the lifetime is measured to be ps. The product branching fractions to these final states are % for the first sample and % for the second and third samples combined. Received: 15 August 1997 / Online publication: March 10, 1998     

Measurement of the {\rm\bf B_{\bf d}^{\bf 0}- {\bf \bar{B}}_{\bf d}^{\bf 0}} oscillation frequency

Time-dependent mixing is studied using about two million hadronic Z decays registered by L3 in 1994 and 1995. For this study three techniques are used. Tagging of the b-quark charge at decay time is performed by identifying leptons from semileptonic B decays. The flavour of the b quark at production time is determined from the charge of the lepton in the opposite hemisphere or by using a jet-charge technique. The proper time of the B-particle decay is obtained by reconstructing the production and decay vertices or by a measurement of the lepton impact parameter. The combined result for the frequency of meson oscillations is Received: 20 February 1998 / Revised version: 23 March 1998 / Published online: 12 August 1998     

A search for a narrow radial excitation of the $\mathrm{D}^{*\pm}$ Meson

A sample of 3.73 million hadronic Z decays, recorded with the OPAL detector at LEP in the years 1991–95, has been used to search for a narrow resonance corresponding to the decay of the meson into . The mesons are reconstructed in the decay channel with . No evidence for a narrow resonance is found. A limit on the production of narrow in hadronic Z decays is derived: Received: 16 January 2001 / Published online: 28 May 2001     

Observation of the decay B(0)-->D(+/-)D(*-/+)

We report the first observation of the decay B(0)-->D(+/-)D(*-/+) with the Belle detector at the KEKB e(+)e(-) Collider operated at the Upsilon(4S) resonance. The sum of branching fractions B(B(0)-->D(+)D(*-))+B(B(0)-->D(-)D(*+)) is measured to be (1.17+/-0.26(+0.22)(-0.25))x10(-3) using the full reconstruction method where both charmed mesons from B0 decays are reconstructed. A consistent value [(1.48+/-0.38(+0.28)(-0.31))x10(-3)] is obtained using a partial reconstruction technique that uses only the slow pion from the D(*-)-->D(-0)pi(-) decay and a fully reconstructed D(+) to reconstruct the B(0).     

Measurement of the branching fractions and CP asymmetry of B--->D(0)((CP))K- decays with the BABAR detector

We present a study of B--->D(0)(CP)K- decays, where D(0)(CP) is reconstructed in CP-even channels, based on a sample of 88.8 x 10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II e(+)e(-) storage ring. We measure the ratio of Cabibbo-suppressed to Cabibbo-favored branching fractions B(B--->D(0)(CP)K-)/B(B--->D(0)(CP)pi(-))=[8.8+/-1.6(stat)+/-0.5(syst)]x10(-2) and the CP asymmetry A(CP)=0.07+/-0.17(stat)+/-0.06(syst). We also measure B(B--->D0K-)/B(B--->D0pi(-))=[8.31+/-0.35(stat)+/-0.20(syst)]x10(-2) using a sample of 61.0 x 10(6) BB pairs.     

Measurement of the bottom quark contribution to nonphotonic electron production in p + p collisions at √s=200 GeV

The contribution of B meson decays to nonphotonic electrons, which are mainly produced by the semileptonic decays of heavy-flavor mesons, in p + p collisions at √s=200 GeV has been measured using azimuthal correlations between nonphotonic electrons and hadrons. The extracted B decay contribution is approximately 50% at a transverse momentum of pT≥5 GeV/c. These measurements constrain the nuclear modification factor for electrons from B and D meson decays. The result indicates that B meson production in heavy ion collisions is also suppressed at high pT.     

Search for CP violation in the decay B0-->D*+/-D-/+

We report a search for CP-violating asymmetry in B0-->D(*+/-)D-/+ decays. The analysis employs two methods of B0 reconstruction: full and partial. In the full reconstruction method all daughter particles of the B0 are required to be detected; the partial reconstruction technique requires a fully reconstructed D- and only a slow pion from the D(*+)-->D0pi(+)(slow) decay. From a fit to the distribution of the time interval corresponding to the distance between two B meson decay points we calculate the CP-violating parameters and find the significance of nonzero CP asymmetry to be 2.7 standard deviations.     

Recent results from NA48/2

Recent results on radiative K± decays from the NA48/2 experiment are reported.From the full NA48/2 data set,about a million K±→π±π0γ decays were reconstructed.Based on this sample,the first measurement of the interference between direct photon emission and inner bremsstrahlung in K±→π±π0γ decays was performed.Stringent limits on CP violation in this decay were also set.In addition,a precise measurement of the branching fraction of K±→π±γγ is presented.This measurement was based on a data sample of more than 1000 event candidates.Also the related decay K±→π±e+e-γ has first been observed.Results of the measurement of the decay rate and the decay parameter c are summarized.     

Measurement of the ratio of B+ and B0 meson lifetimes

The ratio of the B+ and B0 meson lifetimes was measured using data collected in 2002-2004 by the D0 experiment in Run II of the Fermilab Tevatron Collider. These mesons were reconstructed in B-->mu(+)nuD(*-)X decays, which are dominated by B0 and B-->mu(+)nuD 0X decays, which are dominated by B+. The ratio of lifetimes is measured to be tau(+)/tau(0)=1.080+/-0.016(stat)+/-0.014(syst).     

Method for determining the D0-D0 mixing parameters

We propose a new method to determine the mass and width differences of the two D meson mass eigenstates as well as the CP violating parameters associated with D0-D[over ]0 mixing. We show that an accurate measurement of all the mixing parameters is possible for an arbitrary CP violating phase, by combining observables from a time dependent study of D decays to a doubly Cabibbo suppressed mode with information from a CP eigenstate. As an example we consider D0-->K*0pi0 decays where the K*0 is reconstructed in both K+pi- and K(S)pi0. We also show that decays to the CP eigenstate D-->K+K- together with D-->K+pi- decays can be used to extract all the mixing parameters. There is a fourfold ambiguity in the solutions for x and y in both the cases. A combined analysis using D0-->K*0pi0 and D-->K+K- can also be used to reduce the ambiguity in the determination of parameters.     

Observation of D+ → K(+)η(') and search for CP violation in D+ → π(+)η(') decays

We report the first observation of the doubly Cabibbo-suppressed decays D(+)→K(+)η((')) using a 791 fb(-1) data sample collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The ratio of the branching fractions of doubly Cabibbo-suppressed relative to singly Cabibbo-suppressed D(+)→π(+)η((')) decays are B(D(+)→K(+)η)/B(D(+)→π(+)η)=(3.06±0.43±0.14)% and B(D(+)→K(+)η')/B(D(+)→π(+)η')=(3.77±0.39±0.10)%. From these, we find that the relative final-state phase difference between the tree and annihilation amplitudes in D(+) decays, δ(TA), is (72±9)° or (288±9)°. We also report the most precise measurements of CP asymmetries to date: A(CP)(D(+)→π(+)η)=(+1.74±1.13±0.19)% and A(CP)(D(+)→π(+)η')=(-0.12±1.12±0.17)%.     

First flavor-tagged determination of bounds on mixing-induced CP violation in Bs0 --> J/psiphi decays

This Letter describes the first determination of bounds on the CP-violation parameter 2beta(s) using B(s)(0) decays in which the flavor of the bottom meson at production is identified. The result is based on approximately 2000 B(s)(0)-->J/psiphi decays reconstructed in a 1.35 fb(-1) data sample collected with the CDF II detector using pp collisions produced at the Fermilab Tevatron. We report confidence regions in the two-dimensional space of 2beta(s) and the decay-width difference DeltaGamma. Assuming the standard model predictions of 2beta(s) and DeltaGamma, the probability of a deviation as large as the level of the observed data is 15%, corresponding to 1.5 Gaussian standard deviations.     

Spin correlations in production and decay of charginos

We study the production of charginos with polarized beams and the subsequent decays and , including the complete spin correlations between production and decay. Analytical formulae are presented for the joint spin-density matrix of the charginos, for the chargino decay matrix and for the differential cross section of the combined processes of production and decays. We present numerical results for pair production of the lighter chargino with unpolarized beams and the leptonic decay of into the lightest neutralino . The lepton angular distribution and the forward-backward asymmetry are studied in four representative scenarios for GeV and GeV. Received: 28 April 1998 / Revised version: 18 June 1998 / Published online: 8 September 1998     

Observation of B+-->psi(3770)K+

We report the first observation of the decay B+-->psi(3770)K+ where the psi(3770) is reconstructed in the D0(-)D(0) and D+D- decay channels. The obtained branching fraction is B(B+-->psi(3770)K+)=(0.48+/-0.11+/-0.07)x10(-3). We have measured the branching fraction for the decay B+-->D0(-)D0K+ to be (1.17+/-0.21+/-0.15)x10(-3) and set a 90% confidence level upper limit of 0.90 x 10(-3) for the decay B+-->D+D-K+. We also present the results of a search for possible decays to D(-)D and D0(-)D(0)pi(0) of the recently observed X(3872) particle. The analysis is based on 88 fb(-1) of data collected at the Upsilon(4S) resonance by the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider.     

Production and decay of Omegac0

We present an analysis of inclusive Omega(c)(0) baryon production and decays in 230.5 fb(-1) of data recorded with the BABAR detector. Omega(c)(0) baryons are reconstructed in four final states (Omega(-)pi(+), Omega(-)pi(+)pi(0), Omega(-)pi(+)pi(+)pi(-), Xi(-)K(-)pi(+)pi(+)) and the corresponding ratios of branching fractions are measured. We also measure the momentum spectrum in the e(+)e(-) center-of-mass frame. From the spectrum, we observe Omega(c)(0) production from B decays and in cc events, and extract the two rates of production.     

Measurement of time-dependent CP asymmetries in B0-->D(*)+/-D+/- decays

We present a first measurement of CP asymmetries in neutral B decays to D+D-, and updated CP asymmetry measurements in decays to D(*+)D- and D(*-)D+. We use fully reconstructed decays collected in a data sample of (232+/-3) x 10(6) gamma(4S)-->BB events in the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We determine the time-dependent asymmetry parameters to be SD(*+)(D-)=-0.54+/-0.35+/-0.07, CD(*+)(D-)=0.09+/-0.25+/-0.06, SD(*-)(D+)=-0.29+/-0.33+/-0.07, CD(*-)(D+)=0.17+/-0.24+/-0.04, SD+(D-)=-0.29+/-0.63+/-0.06, and CD+(D-)=0.11+/-0.35+/-0.06, where in each case the first error is statistical and the second error is systematic.     

Study of B-->D(*)sJ +-D(*) decays

We report a study of D(*)(sJ)(2317)(+) and D(sJ)(2460)(+) meson production in B decays. We observe the decays B+-->D((*)+)(sJ)D ((*)0) and B0-->D((*)+)(sJ)D((*)-) with the subsequent decays D(*)(sJ)(2317)(+)-->D(+)(s)pi(0), D(sJ)(2460)(+)-->D(+)(s)gamma, and D(sJ)(2460)(+)-->D(*+)(s)pi(0). Based on a data sample of 122.1 x 10(6) BB pairs collected with the BABAR detector at the PEP-II B factory, we obtain branching fractions for these modes, including the previously unseen decays B-->D((*)+)(sJ)D(*). In addition, we perform an angular analysis of D(sJ)(2460)(+)-->D(+)(s)gamma decays to test the different D(sJ)(2460)(+) spin hypotheses.