Decay D0 Research Articles

Search for leptonic decays ofD0mesons

We search for the flavor-changing neutral current decays D0\to mu+mu- and D0\to e+e-, and for the lepton-flavor violating decays D0\to e\pm mu\mp using 660 fb^-1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We find no evidence for any of these decays. We obtain significantly improved upper limits on the branching fractions: B(D0\to mu+mu-)<1.4x10-7, B(D0\to e+e-)<7.9x10-8, and B(D0\to e+mu-)+B(D0\to mu+e-)<2.6x10-7 at 90% confidence level.

MiniBooNE anomaly, the decayDs+→μ+νμand heavy sterile neutrino

It has been recently suggested that the anomalous excess of low-energy electron-like events observed by the MiniBooNE experiment, could be explained by the radiative decay of a heavy sterile neutrino nu_h of the mass around 500 MeV with a muonic mixing strength in the range |U_{\mu h}|^2 \simeq (1-4)\times 10^{-3}. If such nu_h exists its admixtures in the decay Ds -> mu+nu would result in the decay Ds -> mu+nu_h with the branching fraction \simeq (1.2-5.5)\times 10^{-4}, which is in the experimentally accessible range. Interestingly, the existence of the Ds -> mu+nu_h decay at this level may also explain why the currently measured decay rate of Ds -> mu+nu is slightly higher than the predicted one. This enhances motivation for a sensitive search for this decay mode and makes it interesting and complementary to neutrino experiments probing sterile-active neutrino mixing. Considering, as an example the CLEO-c experiment, we suggest to perform a search for the decay Ds -> mu+nu_h with the analysis of existing data. The discrepancy between the measurements and theoretical description of the decay Ds -> tau+nu is also discussed in brief.

Measurement ofD0−D¯0Mixing from a Time-Dependent Amplitude Analysis ofD0→K+π−π0Decays

We present evidence of $D^0$-$\bar{D^0}$ mixing using a time-dependent amplitude analysis of the decay D0->K+pi-pi0 in a data sample of 384 fb^-1 collected with the BaBar detector at the PEP-II e+e- collider at SLAC. Assuming CP conservation, we measure the mixing parameters x'_{Kpipi0} = [2.61^{+0.57}_{-0.68} (stat.) +- 0.39 (syst.)]%, y'_{Kpipi0} = [-0.06 ^{+0.55}_{-0.64} (stat.) +- 0.34 (syst.)]%. The confidence level for the data to be consistent with the no-mixing hypothesis is 0.1%, including systematic uncertainties. This result is inconsistent with the no-mixing hypothesis with a significance of 3.2 standard deviations. We find no evidence of CP violation in mixing.

Can scalar leptoquarks explain the [formula omitted] puzzle?

Motivated by the disagreement between experimental and lattice QCD results on the Ds decay constant we systematically reinvestigate role of leptoquarks in charm meson decays. We consider scalar leptoquarks that transform as a weak interaction triplet, doublet, or singlet in a model independent approach, and also argue that in a particular class of SU(5) GUT models these leptoquark states, contained in the 45-dimensional Higgs representation, could be safe against proton decay bounds. Using the current experimental measurements in τ, kaon and charm sectors, we find that scalar leptoquarks cannot naturally explain the Ds→μν and Ds→τν decay widths simultaneously. While any contributions of the triplet leptoquarks are already excluded, the singlets could only contribute significantly to the Ds→τν width. Finally, a moderate improvement of the experimental upper bound on the D0→μ+μ− decay width could exclude the doublet contribution to the Ds→μν, while present experimental data limits its mass to be below 1.4 TeV. Possible new signatures at present and near future experiments are also briefly discussed.

Study of the semileptonic decayDs+→f0(980)e+νand implications forBs0→J/ψf0

Using e+e- -> Ds^-Ds^{*+} and Ds^{*-}Ds^+ interactions at 4170 MeV collected with the CLEO-c detector, we investigate the semileptonic decays Ds+ -> f0(980) e+ nu, and Ds+ -> phi e+ nu. By examining the decay rates as functions of the four-momentum transfer squared, q^2, we measure the ratio [dB/dq^2(Ds+ -> f0(980) e+ nu) B(f0 -> pi+pi-)]/[dB/dq^2(Ds+ -> phi e+ nu)B(phi -> K+K-)] at q^2 of zero to be (42 +/- 11)%. This ratio has been predicted to equal the rate ratio [B(Bs -> J/psi f_0)B(f0 -> pi+pi-)]/[B(Bs -> J/psi phi)B(phi -> K+K-)], thus indicating that the CP eigenstate J/psi f0 could be useful for measuring CP violation via Bs mixing. Assuming a simple pole model for the form factor |f+(q^2)| in the f0 e+ nu decay, we find a pole mass of (1.7 {+4.5} {-0.7} +/- 0.2) GeV. We also determine the f0 mass and width as (977 {+11}{-9} +/- 1) MeV, and (91{+30}{-22}+/- 3) MeV, respectively. In addition, we present updated results for B(Ds+ -> f0(980) e+ nu) B(f0 -> pi+pi-)=(0.20 +/- 0.03 +/- 0.01)%, and B}(Ds+ -> phi e+ nu)=(2.36 +/- 0.23 +/- 0.13)%.

Determination of theD0→K−π+π0andD0→K−π+π+π−coherence factors and average strong-phase differences using quantum-correlated measurements

The first measurements of the coherence factors (R_Kpipi0 and R_K3pi) and the average strong-phase differences (delta_D^Kpipi0 and delta_D^K3pi) for D0->K-pi+pi0 and D0->K-pi+pi+pi- are presented. These parameters can be used to improve the determination of the unitarity triangle angle gamma in B^- -> DK^- decays, where D is a D^0 or Dbar^0 meson decaying to the same final state. The measurements are made using quantum-correlated, fully-reconstructed D^0Dbar^0 pairs produced in e+e- collisions at the psi(3770) resonance. The measured values are: R_Kpipi0=0.84+/-0.07, delta_D^Kpipi0=(227+14-17) deg, $R_K3pi=0.33+0.20-0.23, and delta_D^K3pi=(114+26-23) deg. These results indicate significant coherence in the decay D0->K-pi+pi0, whereas lower coherence is observed in the decay D0->K-pi+pi+pi-. The analysis also results in a small improvement in the knowledge of other D-meson parameters, in particular the strong-phase difference for D0->K-pi+, delta_D^Kpi, and the mixing parameter, y.

Inclusive hadron yields fromDs+decays

We study the inclusive decays of Ds+ mesons, using data collected near the Ds*+ Ds- peak production energy E_cm=4170 MeV by the CLEO-c detector. We report the inclusive yields of Ds+ decays to K^+ X, K^- X, KS0 X, pi^+ X, pi^- X, pi^0 X, eta X, eta' X, phi X, omega X and f0(980) X, and also decays into pairs of kaons, Ds+ -> KK-bar X. Using these measurements, we obtain an overview of Ds+ decays.

RADIATIVE LEPTONIC DECAY OF Ds AND D MESONS

The radiative leptonic decays Ds → μνμγ and D → μνμγ are investigated at the tree level within the relativistic independent quark model based on the confining potential in the scalar–vector harmonic form. The branching ratios for these decays in the vanishing lepton mass limit are obtained as ℬr(Ds → μνμγ) = 4.94×10-4 and ℬr(D → μνμγ) = 3.34×10-5, which includes the contributions of the internal bremsstrahlung and structure dependent diagrams at the level of the quark constituents. Finally, the photon energy spectra as predicted here is found to be symmetric about the peak value of the photon energy at [Formula: see text].

Dalitz plot analysis ofDs+→K+K−π+

We perform a Dalitz plot analysis of the decay Ds to K+K-pi+ with the CLEO-c data set of 586/pb of e+e- collisions accumulated at sqrt(s) = 4.17 GeV. This corresponds to about 0.57 million D_s+D_s(*)- pairs from which we select 14400 candidates with a background of roughly 15%. In contrast to previous measurements we find good agreement with our data only by including an additional f_0(1370)pi+ contribution. We measure the magnitude, phase, and fit fraction of K*(892) K+, phi(1020)pi+, K0*(1430)K+, f_0(980)pi+, f_0(1710)pi+, and f_0(1370)pi+ contributions and limit the possible contributions of other KK and Kpi resonances that could appear in this decay.

Leptoquark on [formula omitted], FCNC and LFV

Motivated by the disagreement between the experimental data and lattice calculations on the decay constant of the Ds meson, we investigate leptoquark (LQ) contributions to the purely leptonic decays of a pseudoscalar (P). We concentrate on the LQs which only couple to the second-generation quarks before the electroweak symmetry breaking and we discuss in detail how flavor symmetry breaking effects are brought into the extension of the Standard Model after the spontaneous symmetry breaking. We show that the assumption of the hermiticity for the fermion mass matrices cannot only reproduce the correct Cabibbo–Kobayashi–Maskawa and Maki–Nakagawa–Sakata matrices, but also reduce the number of independent flavor mixing matrices and lead to VfR=VfL with L (R) denoting the chirality of the f-type fermion. Accordingly, it is found that the decays Ds,d→ℓ+ν, B+→τ+ν and Bc→ℓ+ν have a strong correlation in parameters. We predict that the decay constant of the Bc meson calculated by the lattice could be less than the experimental data by 23%. Intriguingly, the resultant upper limits of branching ratios for D→μ+μ− and τ→μ(π0,η,η′,ρ,ω) are found to be around 5.1×10−7 and (2.6,1.5,0.6,7.4,4.8)×10−8, which are below and close to the current experimental upper bounds, respectively.

Measuring D0D̄0 mixing in D → f0(980)K* and more**Supported by National Natural Science Foundation of China (10735080, 10625525)

We investigate the D0D̄0 mixing through the doubly Cabibbo suppressed (DCS) channel D0 → f0(980)K*0 and its charge conjugate channel, in which the K*0 meson is reconstructed in both K+π− and KSπ0 final state. Although the decay D0 → f0(980)K* has a small branching ratio, the final state mesons are relatively easy to identify. The f0(980) meson can be replaced by the S-wave π+π− state, or a longitudinally polarized vector meson ρ0. All mixing parameters, including the mass difference and decay width difference, can be extracted by studying the time-dependent decay width of these channels. We show that the method is valid in all regions for mixing parameters and it does not depend on the strong phase difference.

Study of the decayDs+→K+K−e+νe

Using 214 fb-1 of data recorded by the Babar detector at the PEPII electron-positron collider, we study the decay Ds+ --> K+ K- e+ nu. Except for a small S-wave contribution, the events with K+K- masses in the range 1.01-1.03 GeV/c2 correspond to phi mesons. For Ds+ --> phi e+ nu decays, we measure the relative normalization of the Lorentz invariant form factors at q2=0, rV=V(0)/A1(0)=1.849 +/- 0.060 +/- 0.095, r2=A2(0)/A1(0)=0.763 +/- 0.071 +/- 0.065 and the pol e mass of the axial-vector form factors mA=(2.28^{+0.23}_{-0.18}+/- 0.18) GeV/c2. Within the same K+K- mass range, we also measure the relative branching fraction B(Ds+ --> K + K- e+ nu)/B(Ds+ --> K+ K- pi+)=0.558 +/- 0.007 +/- 0.016, from which we obtain the total branching fraction B(Ds+ --> phi e+ nu) = (2.61 +/- 0.03 +/- 0.08 +/- 0.15)* 10^{-2}. By comparing this value with the predicted decay rate, we extract A1(0) = 0.607 +/- 0.011 +/- 0.019 +/- 0.018. The stated uncertainties are statistical, systematic, and from external inputs.

Charm mixing from BABAR**Supported by Università di Pisa and INFN. Also Supported by U.S. Department of Energy and SLAC, Stanford University

We present recent results from BABAR experiment for D0-D̄0 mixing measurements. Mixing parameters can be measured in different ways using different D0 decay modes, here we discuss the most sensitive analyses such as D0 → K+π− where we had the first evidence of charm mixing, the measurement of the ratio of lifetimes of the decays D0 → K+K− and D0 → π+π− relative to D0 → K−π+, the time dependent Dalitz plot analysis of D0 → K+π−π0. New limits on CP-violating time-integrated asymmetries in D0 → K+K− and D0 → π+π− are also discussed. The analyses presented are based on 384 fb−1 data collected with the BABAR detector at the PEP-II asymmetric B Factory.

First Observation of the DecayDs+→pn¯

Using e+e--->Ds*-Ds+ data collected near the peak Ds production energy, Ecm=4170 MeV, with the CLEO-c detector, we present the first observation of the decay Ds+-->pn. We measure a branching fraction B(Ds+-->pn)=(1.30+/-0.36(-0.16)+0.12)x10(-3). This is the first observation of a charmed meson decaying into a baryon-antibaryon final state.

The use of quantum-correlated D0 decays for φ3 measurement

We report the results of the Monte-Carlo study of the method to determine the CKM angle phi3 using Dalitz plot analysis of D0 decay from B->DK process. Our main goal is to find the optimal strategy for a model-independent phi3 extraction. We find that the analysis using decays of CP-tagged D mesons only cannot provide a completely model-independent measurement in the case of limited data sample. The procedure involving binned analysis of B->DK and psi(3770)->(K0 pi+ pi-)_D (K0 pi+ pi-)_D decays is proposed, that allows to reach the phi3 precision comparable to unbinned model-dependent fit.

Evidence forD0−D¯0Mixing Using the CDF II Detector

We measure the time dependence of the ratio of decay rates for the rare decay D0→K+π− to the Cabibbo-favored decay D0→K−π+. A signal of 12.7×103 D0→K+π− decays was obtained using the Collider Detector at Fermilab II detector at the Fermilab Tevatron with an integrated luminosity of 1.5 fb−1. We measure the D0−D¯0 mixing parameters (RD,y′,x′2), and find that the data are inconsistent with the no-mixing hypothesis with a probability equivalent to 3.8 Gaussian standard deviations.Received 11 December 2007DOI:https://doi.org/10.1103/PhysRevLett.100.121802©2008 American Physical Society

Study of the DecayBs0→Ds(*)Ds(*)

We report a study of the decay Bs(0)-->Ds(*)Ds(*) using a data sample corresponding to 1.3 fb(-1) of integrated luminosity collected by the D0 experiment in 2002-2006 during run II of the Fermilab Tevatron collider. One Ds(*) meson was partially reconstructed in the decay Ds-->phi mu nu, and the other Ds(*) meson was identified using the decay Ds-->phi pi where no attempt was made to distinguish Ds and Ds(*) states. For the branching fraction Br(Bs(0)-->Ds(*)Ds(*)) we obtain a 90% C.L. range [0.002,0.080] and central value 0.039(-0.017)(+0.019)(stat)(-0.015)(+0.016)(syst). This was subsequently used to make the most precise estimate of the width difference DeltaGamma(s)CP in the Bs(0)-Bs(0) system: DeltaGamma(s)CP/Gamma(s)=0.079(-0.035)(+0.038)(stat)(-0.030)(+0.031)(syst).

Suppressed Decays ofDs+Mesons to Two Pseudoscalar Mesons

Using data collected near the D{s}{*+}D{s}{-} peak production energy E_{cm}=4170 MeV by the CLEO-c detector, we study the decays of D{s}{+} mesons to two pseudoscalar mesons. We report on searches for the singly Cabibbo-suppressed D{s}{+} decay modes K{+}eta, K{+}eta', pi{+}K{S}{0}, K{+}pi{0}, and the isospin-forbidden decay mode D{s}{+}-->pi{+}pi{0}. We normalize with respect to the Cabibbo-favored D{s}{+} modes pi{+}eta, pi{+}eta', and K{+}K{S}{0}, and obtain ratios of branching fractions: B(D{s}{+}-->K{+}eta)/B(D{s}{+}-->pi{+}eta)=(8.9+/-1.5+/-0.4)%, B(D{s}{+}-->K{+}eta')/B(D{s}{+}-->pi{+}eta')=(4.2+/-1.3+/-0.3)%, B(D{s}{+}-->pi{+}K{S}{0})/B(D{s}{+}-->K{+}K{S}{0})=(8.2+/-0.9+/-0.2)%, B(D{s}{+}-->K{+}pi{0})/B(D{s}{+}-->K{+}K{S}{0})=(5.5+/-1.3+/-0.7)%, and B(D{s}{+}-->pi{+}pi{0})/B(D{s}{+}-->K{+}K{S}{0})<4.1% at 90% C.L., where the uncertainties are statistical and systematic, respectively.

Measurement of the hadronic form factor inD0→K−e+νedecays

The shape of the hadronic form factor f+(q2) in the decay D0 --> K- e+ nue has been measured in a model independent analysis and compared with theoretical calculations. We use 75 fb(-1) of data recorded by the BABAR detector at the PEPII electron-positron collider. The corresponding decay branching fraction, relative to the decay D0 --> K- pi+, has also been measured to be RD = BR(D0 --> K- e+ nue)/BR(D0 --> K- pi+) = 0.927 +/- 0.007 +/- 0.012. From these results, and using the present world average value for BR(D0 --> K- pi+), the normalization of the form factor at q2=0 is determined to be f+(0)=0.727 +/- 0.007 +/- 0.005 +/- 0.007 where the uncertainties are statistical, systematic, and from external inputs, respectively.

Bias-stress induced threshold voltage and drain current instability in 4H–SiC DMOSFETs

In this work, the instability of n-channel 4H–SiC double-implanted metal–oxide–semiconductor field-effect-transistors (DMOSFETs) was studied, in terms of threshold-voltage ( V TH) shifts and drain–source current ( I DS) transients, for different gate bias stress durations of range 100–5500 s. At room temperature, for positive gate bias stress, the V TH shift and I DS decay increase with increasing stress time. The V TH shift and the I DS decay were recovered by negative gate bias stress. It is believed that the instability in device behavior during positive gate bias stress is due to capture of electrons by the SiC/gate dielectric interface traps and the gate dielectric near interface traps. Elevated temperature measurements have indicated a decrease in V TH and an increase in I DS with increasing stress time possibly due to mobile positive ions in the gate dielectric.