Ratio Of Branching Fractions Research Articles

Observation of B→D(*) π^(+)π^(-)ℓ^(-)ν Decays in e^(+)e^(-) Collisions at the Υ(4S) Resonance.

We report on measurements of the decays of B¯ mesons into the semileptonic final states B¯→D^(*)π^(+)π^(-)ℓ^(-)ν¯, where D^(*) represents a D or D^(*) meson and ℓ^(-) is an electron or a muon. These measurements are based on 471×10^(6) BB ¯ pairs recorded with the BABAR detector at the SLAC asymmetric B factory PEP-II. We determine the branching fraction ratios R_{π^{+}π^{-}}^{(*)}=B(B[over ¯]→D^{(*)}π^{+}π^{-}ℓ^{-}ν[over ¯])/B(B[over ¯]→D^{(*)}ℓ^{-}ν[over ¯]) using events in which the second B meson is fully reconstructed. We find R_{π^{+}π^{-}}=0.067±0.010±0.008 and R_{π^{+}π^{-}}^{*}=0.019±0.005±0.004, where the first uncertainty is statistical and the second is systematic. Based on these results and assuming isospin invariance, we estimate that B[over ¯]→D^{(*)}ππℓ^{-}ν[over ¯] decays, where π denotes either a π^{±} and π^{0} meson, account for up to half the difference between the measured inclusive semileptonic branching fraction to charm hadrons and the corresponding sum of previously measured exclusive branching fractions.

Study of the [Formula: see text] and [Formula: see text] decays with the ATLAS detector.

The decays B_c^+ rightarrow J/psi D_s^+ and B_c^+ rightarrow J/psi D_s^{*+} are studied with the ATLAS detector at the LHC using a dataset corresponding to integrated luminosities of 4.9 and 20.6 fb^{-1} of pp collisions collected at centre-of-mass energies sqrt{s} = 7 TeV and 8 TeV, respectively. Signal candidates are identified through J/psi rightarrow mu ^+mu ^- and D_s^{(*)+}rightarrow phi pi ^+(gamma /pi ^0) decays. With a two-dimensional likelihood fit involving the B_c^+ reconstructed invariant mass and an angle between the mu ^+ and D_s^+ candidate momenta in the muon pair rest frame, the yields of B_c^+ rightarrow J/psi D_s^+ and B_c^+ rightarrow J/psi D_s^{*+}, and the transverse polarisation fraction in B_c^+ rightarrow J/psi D_s^{*+} decay are measured. The transverse polarisation fraction is determined to be Gamma _{pm pm }(B_c^+ rightarrow J/psi D_s^{*+})/Gamma (B_c^+ rightarrow J/psi D_s^{*+}) = 0.38 pm 0.23 pm 0.07, and the derived ratio of the branching fractions of the two modes is mathcal {B}_{B_c^+ rightarrow J/psi D_s^{*+}}/mathcal {B}_{B_c^+ rightarrow J/psi D_s^+} = 2.8 ,^{+1.2}_{-0.8} pm 0.3, where the first error is statistical and the second is systematic. Finally, a sample of B_c^+rightarrow J/psi pi ^+ decays is used to derive the ratios of branching fractions mathcal {B}_{B_c^+ rightarrow J/psi D_s^+}/mathcal {B}_{B_c^+ rightarrow J/psi pi ^+} = 3.8 pm 1.1 pm 0.4 pm 0.2 and mathcal {B}_{B_c^+ rightarrow J/psi D_s^{*+}}/mathcal {B}_{B_c^+ rightarrow J/psi pi ^+} = 10.4 pm 3.1 pm 1.5 pm 0.6, where the third error corresponds to the uncertainty of the branching fraction of D_s^+rightarrow phi (K^+K^-)pi ^+ decay. The available theoretical predictions are generally consistent with the measurement.

B→πτν¯τdecay in the context of type II 2HDM

In this manuscript the B -> pi tau nu decay is investigated in the context of the 2HDM type II extension of the SM. In particular, predictions for the ratio of semileptonic branching fractions from l = tau and l = electron, muon are produced and an exclusion based on the MSSM parameters tan beta and mH+ from a preliminary Belle measurement are reported. An alternative variable to the ratio of branching fractions that could offer increased sensitivity is discussed that could result in increased sensitivity to rule out contributions from additional scalar mediators.

Indirect reach of heavy MSSM Higgs bosons by precision measurements at future lepton colliders

In the Minimal Supersymmetric Standard Model (MSSM), the bottom Yukawa coupling of the Higgs boson can considerably deviate from its Standard Model prediction due to nondecoupling effects. We point out that the ratio of the Higgs boson decay branching fraction to a bottom quark pair and that to a W-boson pair from the same production channel is particularly sensitive to large additional MSSM Higgs boson mass regions at future electron–positron colliders. Based on this precision measurement, we explicitly show the indirect discovery reach of the additional Higgs bosons according to planned programs of the International Linear Collider.

Measurement of the branching ratio ofB¯→D(*)τ−ν¯τrelative toB¯→D(*)ℓ−ν¯ℓdecays with hadronic tagging at Belle

We report a measurement of the branching fraction ratios R(D(*)) of Bbar -> D(*) tau- nubar_tau relative to Bbar -> D()* l- nubar_l (where l = e or mu) using the full Belle data sample of 772 x 10^6 BBbar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. The measured values are R(D)= 0.375 +- 0.064(stat.) +- 0.026(syst.) and R(D*) = 0.293 +- 0.038(stat.) +- 0.015(syst.). The analysis uses hadronic reconstruction of the tag-side B meson and purely leptonic tau decays. The results are consistent with earlier measurements and do not show a significant deviation from the standard model prediction.

B→Dlνform factors at nonzero recoil and extraction of|Vcb|

We present a lattice QCD calculation of the $B \rightarrow D l \nu$ semileptonic decay form factors $f_+(q^2)$ and $f_0(q^2)$ for the entire physical $q^2$ range. Non-relativistic QCD (NRQCD) bottom quarks and Highly Improved Staggered Quark (HISQ) charm and light quarks are employed together with $N_f = 2+1$ MILC gauge configurations. A joint fit to our lattice and BaBar experimental data allows an extraction of the CKM matrix element $|V_{cb}|$. We also determine the phenomenologically interesting ratio $R(D) = {\cal B}(B \rightarrow D \tau \nu_\tau) / {\cal B}(B \rightarrow D l \nu_l)$ ($l = e, \mu$). We find $|V_{cb}|_{excl.}^{B \rightarrow D} = 0.0402(17)(13)$, where the first error consists of the lattice simulation errors and the experimental statistical error and the second error is the experimental systematic error. For the branching fraction ratio we find $R(D) = 0.300(8)$.

Measurement of the ratio of branching fractions B(B[over ¯]^{0}→D^{*+}τ^{-}ν[over ¯]_{τ})/B(B[over ¯]^{0}→D^{*+}μ^{-}ν[over ¯]_{μ}).

The branching fraction ratio R(D^{*})≡B(B[over ¯]^{0}→D^{*+}τ^{-}ν[over ¯]_{τ})/B(B[over ¯]^{0}→D^{*+}μ^{-}ν[over ¯]_{μ}) is measured using a sample of proton-proton collision data corresponding to 3.0 fb^{-1} of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ^{-}→μ^{-}ν[over ¯]_{μ}ν_{τ}. The semitauonic decay is sensitive to contributions from non-standard-model particles that preferentially couple to the third generation of fermions, in particular, Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate B[over ¯]^{0} decays gives R(D^{*})=0.336±0.027(stat)±0.030(syst). This result, which is the first measurement of this quantity at a hadron collider, is 2.1 standard deviations larger than the value expected from lepton universality in the standard model.

B¯0decay intoD0andf0(500),f0(980),a0(980),ρandB¯s0decay intoD0andκ(800),K*0

We make predictions for ratios of branching fractions of $\bar B^0$ decays into $D^0$ and the scalar mesons $f_0(500)$, $f_0(980)$, $a_0(980)$, plus $\bar B^0_s$ decay into $D^0$ and $\kappa(800)$. We also compare the $\pi^+ \pi^-$ production in the scalar channel with that observed in the $\rho$ channel and make predictions for the $\bar B^0_s$ decay into $D^0$ and $K^*(892)$, comparing the strength of this channel with that of $\kappa(800)$ production. The work is based on results of the chiral unitary approach where the scalar resonances are generated from the pseudoscalar-pseudoscalar interaction. Up to an arbitrary normalization, the mass distributions and rates for decays into the scalar resonances are predicted with no free parameters. Comparison with experimental data is done when available.

Measurement of the [Formula: see text] production cross-section in proton-proton collisions via the decay [Formula: see text

The production of the eta _c (1S) state in proton-proton collisions is probed via its decay to the poverline{p} final state with the LHCb detector, in the rapidity range 2.0 < y < 4.5 and in the meson transverse-momentum range p_mathrm{T} > 6.5 mathrm{{,GeV/}{ c}} . The cross-section for prompt production of eta _c (1S) mesons relative to the prompt {{ J}}/{psi } cross-section is measured, for the first time, to be sigma _{eta _c (1S)}/sigma _{{{{ J}}/{psi }}} = 1.74, pm ,0.29, pm , 0.28, pm ,0.18 _{{mathcal{B}}} at a centre-of-mass energy {sqrt{s}} = 7 {~mathrm{TeV}} using data corresponding to an integrated luminosity of 0.7 fb^{-1}, and sigma _{eta _c (1S)}/sigma _{{{{ J}}/{psi }}} = 1.60 pm 0.29 pm 0.25 pm 0.17 _{{mathcal{B}}} at {sqrt{s}} = 8 {~mathrm{TeV}} using 2.0 fb^{-1}. The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the eta _c (1S) and {{ J}}/{psi } decays to the poverline{p} final state. In addition, the inclusive branching fraction of {b} -hadron decays into eta _c (1S) mesons is measured, for the first time, to be {mathcal{B}}( b {rightarrow } eta _c X ) = (4.88, pm ,0.64, pm ,0.29, pm , 0.67 _{{mathcal{B}}}) times 10^{-3}, where the third uncertainty includes also the uncertainty on the {{ J}}/{psi } inclusive branching fraction from {b} -hadron decays. The difference between the {{ J}}/{psi } and eta _c (1S) meson masses is determined to be 114.7 pm 1.5 pm 0.1 {mathrm {,MeV!/}c^2} .

Clues for flavor from rare lepton and quark decays

Flavor symmetries successfully explain lepton and quark masses and mixings yet it is usually hard to distinguish different models that predict the same mixing angles. Further experimental input could be available, if the agents of flavor breaking are sufficiently low in mass and detectable or if new physics with non-trivial flavor charges is sufficiently low in mass and detectable. The recent hint for lepton-nonuniversality in the ratio of branching fractions B → Kμμ over B → Kee, R K , suggests the latter, at least for indirect detection via rare decays. We demonstrate the discriminating power of the rare decay data on flavor model building taking into account viable leptonic mixings and show how correlations with other observables exist in leptoquark models. We give expectations for branching ratios B → Kℓℓ′, B (s) → ℓℓ′ and ℓ → ℓ′γ, and Higgs decays h → ℓℓ′.

Determination of the branching fractions of B S 0 → D S ∓ K ∓ and B 0 → D S − K +

Measurements are presented of the branching fractions of the decays B-s(0) -> D-s(-/+) K--/+ and B-0 -> Ds-K+ relative to the decays B-s(0) -> D-s(-)pi(+) and B-0 -> D-s(-)pi(+), respectively. The data used correspond to an integrated luminosity of 3.0 fb(-1) of proton-proton collisions. The ratios of branching fractions are B(B-s(0) -> D-s(-/+) K--/+)/B(B-s(0) -> D-s(-)pi(+)) = 0.0752 +/- 0.0015 +/- 0.0019 and B(B-0 -> Ds-K+)/B(B-0 -> D-pi(+)) = 0.0129 +/- 0.0005 +/- 0.0008, where the uncertainties are statistical and systematic, respectively.

Measurement of theD0→π−e+νedifferential decay branching fraction as a function ofq2and study of form factor parametrizations

Based on a sample of 500 million $e^+e^- \to c\bar c$ events recorded by the BaBar detector at c.m. energies of close to 10.6 GeV, we report on a study of the decay $D^0 \to \pi^- e^+ \nu_e$. We measure the ratio of branching fractions $R_D = {\cal B}(D^0 \to \pi^- e^+ \nu_e)/{\cal B}(D^0 \to K^- \pi^+) = 0.0713 \pm 0.0017_{stat.} \pm 0.0024_{syst.}$, and use the present world average for ${\cal B}(D^0 \to K^- \pi^+)$ to obtain ${\cal B}(D^0 \to \pi^- e^+ \nu_e) = (2.770 \pm 0.068_{{\rm stat.}} \pm 0.092_{{\rm syst.}} \pm 0.037_{{\rm ext.}})\times 10^{-3}$ where the third error accounts for the uncertainty on the branching fraction for the reference channel. The measured dependence of the differential branching fraction on $q^2$, the four-momentum transfer squared between the $D$ and the $\pi$ meson, is compared to various theoretical predictions for the hadronic form factor, $f_{+,D}^{\pi}(q^2)$, and the normalization $|V_{cd}| \times f_{+,D}^{\pi}(q^2=0)=0.1374\pm0.0038_{{\rm stat.}} \pm0.0022_{{\rm syst.}} \pm0.0009_{{\rm ext.}}$ is extracted from a fit to data. Using the most recent LQCD prediction of $f_{+,D}^{\pi}(q^2=0)=0.666 \pm 0.029$, we obtain $|V_{cd}|=0.206 \pm 0.007_{\rm exp.} \pm 0.009_{\rm LQCD}$. Assuming instead, $|V_{cd}|=|V_{us}|=0.2252 \pm 0.0009$, we obtain $f_{+,D}^{\pi}(q^2=0)=0.610 \pm 0.020_{\rm exp.} \pm 0.005_{\rm ext.}$. The $q^2$ dependence of $f_{+,D}^{\pi}(q^2)$ is compared to a variety of multi-pole parameterizations. This information is applied to $B^0 \to \pi^- e^+ \nu_e$ decays and, combined with an earlier $B^0 \to \pi^- e^+ \nu_e$ measurement by BaBar, is used to derive estimates of $|V_{ub}|$.

Measurement of the production cross section ratio σ(χb2(1P))/σ(χb1(1P)) in pp collisions at [formula omitted

A measurement of the production cross section ratio σ(χb2(1P))/σ(χb1(1P)) is presented. The χb1(1P) and χb2(1P) bottomonium states, promptly produced in pp collisions at s=8 TeV, are detected by the CMS experiment at the CERN LHC through their radiative decays χb1,2(1P)→ϒ(1S)+γ. The emitted photons are measured through their conversion to e+e− pairs, whose reconstruction allows the two states to be resolved. The ϒ(1S) is measured through its decay to two muons. An event sample corresponding to an integrated luminosity of 20.7 fb−1 is used to measure the cross section ratio in a phase-space region defined by the photon pseudorapidity, |ηγ|<1.0; the ϒ(1S) rapidity, |yϒ|<1.5; and the ϒ(1S) transverse momentum, 7<pTϒ<40 GeV. The cross section ratio shows no significant dependence on the ϒ(1S) transverse momentum, with a measured average value of 0.85±0.07(stat+syst)±0.08(BF), where the first uncertainty is the combination of the experimental statistical and systematic uncertainties and the second is from the uncertainty in the ratio of the χb branching fractions.

Diagnosing lepton-nonuniversality in b → sℓℓ

Ratios of branching fractions of semileptonic B decays, (B → Hμμ) over (B → Hee) with H = K, K ∗, X s , K 0(1430), ϕ, . . . are sensitive probes of lepton universality. In the Standard Model, the underlying flavor changing neutral current process b → sℓℓ is lepton flavor universal. However models with new flavor violating physics above the weak scale can give substantial non-universal contributions. The leading contributions from such new physics can be parametrized by effective dimension six operators involving left- or right-handed quarks. We show that in the double ratios $$ {R_X}_{{}_s}/{R}_K $$ , R K ∗/R K and R ϕ /R K the dependence on new physics coupling to left-handed quarks cancels out. Thus a measurement of any of these double ratios is a clean probe of flavor nonuniversal physics coupling to right-handed quarks. We also point out that the observables $$ {R_X}_{{}_s} $$ , R K ∗, $$ {R}_K{{}_{{}_0}}_{(1430)} $$ and R ϕ depend on the same combination of Wilson coefficients and therefore satisfy simple consistency relations.

Study of η − η′ mixing from measurement of B (s) 0 → J/ψη(′) decay rates

A study of $B^0$~and $B^0_s$ meson decays into $J/\psi\eta$~and $J/\psi\eta^{\prime}$ final states is performed using a data set of proton-proton collisions at centre-of-mass energies of 7 and 8TeV, collected by the LHCb experiment and corresponding to 3.0fb$^{-1}$ of integrated luminosity. The decay $B^0 \rightarrow J/\psi \eta^{\prime}$ is observed for thefirst time. The following ratios of branching fractions are measured: $$ \frac{\mathcal{B}(B^0 \rightarrow J/\psi \eta^{\prime})}{\mathcal{B}(B^0_s \rightarrow J/\psi \eta^{\prime})} = (2.28\pm0.65\,(stat)\,\pm0.10\,(syst)\,\pm0.13\,(f_{s}/f_{d}))\times10^{-2},$$ $$ \frac{\mathcal{B}(B^0 \rightarrow J/\psi \eta)}{\mathcal{B}(B^0_s \rightarrow J/\psi \eta)} = (1.85\pm0.61\,(stat)\,\pm0.09\,(syst)\,\pm0.11\,(f_{s}/f_{d}))\times10^{-2},$$ where the third uncertainty is related to the present knowledge of $f_{s}/f_{d}$, the ratio between the probabilities for a $b$ quark to form a $B^0_s$ or $B^0$ meson. The branching fraction ratios are used to determine the parameters of $\eta-\eta^{\prime}$ meson mixing. In addition, the first evidence for the decay $B^0_s \rightarrow \psi(2S) \eta^{\prime}$ is reported, and the relative branching fraction is measured, $$\frac{\mathcal{B}(B^0_s \rightarrow \psi(2S) \eta^{\prime})}{\mathcal{B}(B^0_s \rightarrow J/\psi \eta^{\prime})} = (38.7\pm9.0\,(stat)\,\pm1.3\,(syst)\,\pm0.9(\mathcal{B}))\times10^{-2},$$ where the third uncertainty is due to the limited knowledge of the branching fractions of $J/\psi$ and $\psi(2S)$~mesons.

Test of lepton universality using b+ → K+ℓ+ℓ- decays.

A measurement of the ratio of the branching fractions of the B(+) → K(+)μ(+)μ(-) and B(+) → K(+)e(+)e(-) decays is presented using proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb(-1), recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. The value of the ratio of branching fractions for the dilepton invariant mass squared range 1 < q(2) < 6 GeV(2)/c(4) is measured to be 0.745(-0.074)(+0.090)(stat) ± 0.036(syst). This value is the most precise measurement of the ratio of branching fractions to date and is compatible with the standard model prediction within 2.6 standard deviations.

Bs→Kℓνform factors from lattice QCD

We report the first lattice QCD calculation of the form factors for the standard model tree-level decay $B_s\to K \ell\nu$. In combination with future measurement, this calculation will provide an alternative exclusive semileptonic determination of $|V_{ub}|$. We compare our results with previous model calculations, make predictions for differential decay rates and branching fractions, and predict the ratio of differential branching fractions between $B_s\to K\tau\nu$ and $B_s\to K\mu\nu$. We also present standard model predictions for differential decay rate forward-backward asymmetries, polarization fractions, and calculate potentially useful ratios of $B_s\to K$ form factors with those of the fictitious $B_s\to\eta_s$ decay. Our lattice simulations utilize NRQCD $b$ and HISQ light quarks on a subset of the MILC Collaboration's $2+1$ asqtad gauge configurations, including two lattice spacings and a range of light quark masses.

Measurement of the ratio ofBc+branching fractions toJ/ψπ+andJ/ψμ+νμfinal states

The first measurement that relates semileptonic and hadronic decay rates of the $B_c^+$ meson is performed using proton-proton collision data corresponding to 1.0 fb$^{-1}$ of integrated luminosity collected with the LHCb detector. The measured value of the ratio of branching fractions, ${\cal B}(B_c^+ \to J/\psi \pi^+)/{\cal B}(B_c^+\to J/\psi\mu^+\nu_\mu)=0.0469 \pm 0.0028 (stat.) \pm 0.0046 (syst.)$, is at the lower end of available theoretical predictions.

Measurement of the ratio [formula omitted] in pp collisions at [formula omitted

The ratio of the top-quark branching fractions R=B(t→Wb)/B(t→Wq), where the denominator includes the sum over all down-type quarks (q=b,s,d), is measured in the tt¯ dilepton final state with proton–proton collision data at s=8 TeV from an integrated luminosity of 19.7 fb−1, collected with the CMS detector. In order to quantify the purity of the signal sample, the cross section is measured by fitting the observed jet multiplicity, thereby constraining the signal and background contributions. By counting the number of b jets per event, an unconstrained value of R=1.014±0.003(stat.)±0.032(syst.) is measured, in a good agreement with current precision measurements in electroweak and flavour sectors. A lower limit R>0.955 at the 95% confidence level is obtained after requiring R≤1, and a lower limit on the Cabibbo–Kobayashi–Maskawa matrix element |Vtb|>0.975 is set at 95% confidence level. The result is combined with a previous CMS measurement of the t-channel single-top-quark cross section to determine the top-quark total decay width, Γt=1.36±0.02(stat.)−0.11+0.14(syst.) GeV.

Measurement of B(t→Wb)/B(t→Wq) in top-quark-pair decays using dilepton events and the full CDF Run II data set.

We present a measurement of the ratio of the top-quark branching fractions R=B(t→Wb)/B(t→Wq), where q represents any quark flavor, in events with two charged leptons, imbalance in total transverse energy, and at least two jets. The measurement uses proton-antiproton collision data at center-of-mass energy 1.96TeV, corresponding to an integrated luminosity of 8.7 fb^{-1} collected with the Collider Detector at Fermilab during Run II of the Tevatron. We measure R to be 0.87±0.07, and extract the magnitude of the top-bottom quark coupling to be |V_{tb}|=0.93±0.04, assuming three generations of quarks. Under these assumptions, a lower limit of |V_{tb}|>0.85(0.87) at 95% (90%) credibility level is set.