Measurement Of Branching Ratio Research Articles

Measurements of the top quark branching ratios into channels with leptons and quarks with the ATLAS detector

Measurements of the branching ratios of top quark decays into leptons and jets using events with $t \overline{t}$ (top antitop) pairs are reported. Events were recorded with the ATLAS detector at the LHC in pp collisions at a center-of-mass energy of 7 TeV. The collected data sample corresponds to an integrated luminosity of 4.6 ${\mathrm{fb}}^{-1}$. The measured top quark branching ratios agree with the Standard Model predictions within the measurement uncertainties of a few percent.

Measurement of the branching ratio [formula omitted] with the ATLAS detector

An observation of the Λb0→ψ(2S)Λ0 decay and a comparison of its branching fraction with that of the Λb0→J/ψΛ0 decay has been made with the ATLAS detector in proton–proton collisions at s=8 TeV at the LHC using an integrated luminosity of 20.6 fb−1. The J/ψ and ψ(2S) mesons are reconstructed in their decays to a muon pair, while the Λ0→pπ− decay is exploited for the Λ0 baryon reconstruction. The Λb0 baryons are reconstructed with transverse momentum pT>10 GeV and pseudorapidity |η|<2.1. The measured branching ratio of the Λb0→ψ(2S)Λ0 and Λb0→J/ψΛ0 decays is Γ(Λb0→ψ(2S)Λ0)/Γ(Λb0→J/ψΛ0)=0.501±0.033(stat)±0.019(syst), lower than the expectation from the covariant quark model.

Family gauge boson production at the LHC

Family gauge boson production at the LHC is investigated according to a U(3) family gauge model with twisted family number assignment. In the model we study, a family gauge boson with the lowest mass, A11, interacts only with the first generation leptons and the third generation quarks. (The family numbers are assigned, for example, as (e1,e2,e3)=(e−,μ−,τ−) and (d1,d2,d3)=(b,d,s) [or (d1,d2,d3)=(b,s,d)].) In the model, the family gauge coupling constant is fixed by relating to the electroweak gauge coupling constant. Thus measurements of production cross sections and branching ratios of A11 clearly confirm or rule out the model. We calculate the cross sections of inclusive A11 production and bb¯(tt¯) associated A11 production at s=14 TeV and 100 TeV. With the dielectron production cross section, we discuss the determination of diagonalizing matrix of quark mass matrix, Uu and Ud, respectively.

Precise measurement of branching ratios in theβdecay ofCa38

We present the full description of a measurement of the branching ratios for the $\ensuremath{\beta}$ decay of $^{38}\mathrm{Ca}$. This decay includes five allowed ${0}^{+}\ensuremath{\rightarrow}{1}^{+}$ branches and a superallowed ${0}^{+}\ensuremath{\rightarrow}{0}^{+}$ one. With our new result for the latter, we determine its $ft$ value to be $3062.3\ifmmode\pm\else\textpm\fi{}6.8$ s, a result whose precision (0.2%) is comparable to the precision of the 13 well-known ${0}^{+}\ensuremath{\rightarrow}{0}^{+}$ transitions used up until now for the determination of ${V}_{\text{ud}}$, the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa matrix. The $^{38}\mathrm{Ca}$ superallowed transition thus becomes the first addition to this set of transitions in nearly a decade and the first for which a precise mirror comparison is possible, thus enabling an improved test of the isospin-symmetry-breaking corrections required for the extraction of ${V}_{\text{ud}}$.

Competing C-Br and O-NO Photofission upon Excitation of BrCH2CH2ONO at 193 nm.

This study characterizes two of the primary photodissociation channels of 2-bromoethyl nitrite, BrCH2CH2ONO, at 193 nm and the subsequent unimolecular dissociation channels of the nascent vibrationally excited BrCH2CH2O radicals produced from the O-NO bond photofission. We use a crossed laser-molecular beam scattering apparatus with electron bombardment detection. Upon photodissociation of BrCH2CH2ONO at 193 nm, the measured branching ratio between primary O-NO photofission and C-Br photofission is 3.9:1 (O-NO/C-Br). The measured O-NO photofission recoil kinetic energy distribution (P(ET)) peaks near 30 kcal/mol and extends from 20 to 50 kcal/mol. We use the O-NO photofission P(ET) to characterize the internal energy distribution in the nascent ground-electronic-state BrCH2CH2O radicals. At 193 nm, all of the BrCH2CH2O radicals are formed with enough internal energy to unimolecularly dissociate to CH2Br + H2CO or to BrCH2CHO + H. We also investigated the possibility of the BrCH2CH2O → CH2CHO + HBr reaction arising from the vibrationally excited BrCH2CH2O radicals produced from O-NO primary photodissociation. Signal strengths at HBr(+), however, demonstrate that the vinoxy product does not have HBr as a cofragment, so the BrCH2CH2O → HBr + vinoxy channel is negligible compared to the CH2Br + H2CO channel. We also report our computational prediction of the unimolecular dissociation channels of the vibrational excited CH2CH2ONO radical resulting from C-Br bond photofission. Our theoretical calculations on the ground-state CH2CH2ONO potential energy surface at the G4//B3LYP/6-311++G(3df,2p) level of theory give the energetics of the zero-point corrected minima and transition states. The lowest accessible barrier height for the unimolecular dissociation of CH2CH2ONO is a 12.7 kcal/mol barrier from the cis-ONO conformer, yielding NO2 + ethene. Our measured internal energy distribution of the nascent CH2CH2ONO radicals together with this computational result suggests that the CH2CH2ONO radicals will dissociate to NO2 + ethene, with a small possible branching to NO + oxirane.

Ion-pair dissociation of highly excited carbon clusters, size and charge effects

SynopsisIon-pair dissociation of a highly excited molecule is a relaxation process giving rise to emission of anionic and cationic fragments. We present first measurements of ion-pair dissociation of carbon clusters. We found that ion- pair relaxation is an ubiquitous, although very small, relaxation channel common to all sizes and charges of Cq+n species produced in high velocity C+n-He collisions. Quantitative interpretation of measured branching ratios is conducted on the basis of a statistical approach i.e through listing of all possible final states.

Note on the newly observedY(4220)resonance

The BES III Collaboration has recently observed a vector resonance in the ${\ensuremath{\chi}}_{c0}\ensuremath{\omega}$ channel, at a mass of about 4220 MeV, named $Y(4220)$. Hints of a similar structure appear in the ${h}_{c}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ channel. We find that the two observations are likely due to the same state, which we identify with one of the expected diquark-antidiquark resonances with orbital quantum number $L=1$. This assignment fulfills heavy quark spin conservation. The measured branching ratio of the $Y(4220)$ into ${\ensuremath{\chi}}_{c0}\ensuremath{\omega}$ and ${h}_{c}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ is compatible with the prediction for such a tetraquark state.

Scalar leptoquarks and the rareBmeson decays

We study some rare decays of $B$ meson involving the quark level transition $b \to q l^+l^- (q=d,s)$ in the scalar leptoquark model. We constrain the leptoquark parameter space using the recently measured branching ratios of $B_{s,d} \to \mu^+ \mu^-$ processes. Using such parameters, we obtain the branching ratios, direct CP violation parameters and isospin asymmetries in $B \to K \mu^+ \mu^-$ and $B \to \pi \mu^+ \mu^-$ processes. We also obtain the branching ratios for some lepton flavour violating decays $B \to l_i^+ l_j^-$. We find that the various anomalies associated with the isospin asymmetries of $B \to K \mu^+ \mu^-$ process can be explained in the scalar leptoquark model.

Spectroscopic and radiative properties of Sm3+ ions in zinc borophosphate glasses

The paper reports on the preparation and characterization of Sm3+ doped zinc borophosphate (ZBP) glasses. The density was measured and the corresponding molar volume was evaluated. The present glass system was investigated by the XRD, optical absorption, photoluminescence, decay curves and FTIR analysis. The Judd–Ofelt theory has been used to evaluate the JO intensity parameters (Ω2,4,6) and calculated oscillator strengths (ƒcal). Using JO intensity parameters, various radiative parameters such as transition probability (AR), radiative lifetime (τR), measured lifetime (τm), calculated branching ratios (βR), measured branching ratios (βm) have been calculated for the excited 4G5/2 level. The nature of the decay curves of 4G5/2 level for different Sm3+ ion concentration in all ZBP glasses has been analyzed and the lifetimes are noticed to decrease with increase of concentration.

Ground-state and pairing-vibrational bands with equal quadrupole collectivity inXe124

The nuclear structure of $^{124}\mathrm{Xe}$ has been investigated via measurements of the ${\ensuremath{\beta}}^{+}$/EC decay of $^{124}\mathrm{Cs}$ with the $8\ensuremath{\pi}\ensuremath{\gamma}$-ray spectrometer at the TRIUMF-ISAC facility. The data collected have enabled branching ratio measurements of weak, low-energy transitions from highly excited states, and the ${2}^{+}\ensuremath{\rightarrow}{0}^{+}$ in-band transitions have been observed. Combining these results with those from a previous Coulomb excitation study, $B(E2;{2}_{3}^{+}\ensuremath{\rightarrow}{0}_{2}^{+})=78(13)$ W.u. and $B(E2;{2}_{4}^{+}\ensuremath{\rightarrow}{0}_{3}^{+})=53(12)$ W.u. were determined. The ${0}_{3}^{+}$ state, in particular, is interpreted as the main fragment of the proton-pairing vibrational band identified in a previous $^{122}\mathrm{Te}$($^{3}\mathrm{He},n$)$^{124}\mathrm{Xe}$ measurement, and has quadrupole collectivity equal to, within uncertainty, that of the ground-state band.

Using U spin to extract γ from charmless B → PPP decays

Some years ago, a method was proposed for measuring the CP-violating phase gamma using pairs of two-body decays that are related by U-spin reflection (d <-> s). In this paper we adapt this method to charmless B -> PPP decays. Time-dependent Dalitz-plot analyses of these three-body decays are required for the measurement of the mixing-induced CP asymmetries. However, isobar analyses of the decay amplitudes are not necessary. A potential advantage of using three-body decays is that the effects of U-spin breaking may be reduced by averaging over the Dalitz plot. This can be tested independently using the measurements of direct CP asymmetries and branching ratios in three-body charged B decays.

Superallowed0+→0+nuclearβdecays: 2014 critical survey, with precise results forVudand CKM unitarity

A new critical survey is presented of all half-life, decay-energy and branching-ratio measurements related to 20 superallowed 0+ --> 0+ beta decays. Included are 222 individual measurements of comparable precision obtained from 177 published references. Compared with our last review in 2008, we have added results from 24 new publications and eliminated 9 references, the results from which having been superseded by much more precise modern data. We obtain world-average ft-values for each of the eighteen transitions that have a complete set of data, then apply radiative and isospin-symmetry-breaking corrections to extract corrected Ft values. Fourteen of these Ft values now have a precision of order 0.1% or better. In the process of obtaining these results we carefully evaluate the available calculations of the isospin-symmetry-breaking corrections by testing the extent to which they lead to Ft values consistent with conservation of the vector current (CVC). Only one set of calculations satisfactorily meets this condition. The resultant average Ft value, when combined with the muon liftime, yields the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, Vud = 0.97417 +/- 0.00021. The unitarity test on the top row of the matrix becomes |Vud|^2 + |Vus|^2 + |Vub|^2 = 0.99978 +/- 0.00055 if the Particle Data Group recommended value for Vus is used. However, recent lattice QCD calculations, not included yet in the PDG evaluation, have introduced some inconsistency into kaon-decay measurements of Vus and Vus/Vud. We examine the impact of these new results on the unitarity test and conclude that there is no evidence of any statistically significant violation of unitarity. Finally, from the Ft-value data we also set limits on the possible existence of scalar interactions.

Radiative properties and luminescence spectra of Sm3+ ion in zinc–aluminum–sodium-phosphate (ZANP) glasses

The fluorescence properties of different concentrations of Sm3+ doped zinc–aluminum–sodium-phosphate (ZANP) glasses were studied by the XRD, SEM, FTIR, TG–DTA, optical absorption, photoluminescence and decay cure analysis. X-ray diffraction profiles and SEM images confirmed the amorphous nature of the glass samples. Structural information of these glass matrices was provided by FTIR spectrum. Judd–Ofelt (J–O) theory was applied to the experimental oscillator strengths to evaluate three phenomenological J–O intensity parameters, Ωλ (λ=2, 4 and 6). Using J–O intensity parameters and emission spectra, various radiative parameters such as radiative transition probabilities (AR), radiative lifetimes (τR), calculated and measured branching ratios (βR and βm), effective bandwidths (Δλeff) and stimulated emission cross-sections (σP) were calculated for observed emission transitions. The intensity of emission transitions with the variation of Sm3+ ion concentration was studied. The nature of decay curves of 4G5/2 level for different Sm3+ ion concentrations in ZANP glass was analyzed and obtained measured lifetimes (τexp). Quantum efficiency of 4G5/2 level was calculated based on experimental and measured radiative lifetimes (τexp and τR).

Dipole strength distributions from HIGS Experiments

A series of photon scattering experiments has been performed on the double-beta decay partners 76 Ge and 76 Se, in order to investigate their dipole response up to the neutron separation threshold. Gamma-ray beams from bremsstrahlung at the S-DALINAC and from Compton-backscattering at HIGS have been used to measure absolute cross sections and parities of dipole excited states, respectively. The HIGS data allows for indirect measurement of averaged branching ratios, which leads to significant corrections in the observed excitation cross sections. Results are compared to statistical calculations, to test photon strength functions and the Axel-Brink hypothesis.

High-precision efficiency calibration of a high-purity co-axial germanium detector

A high-purity co-axial germanium detector has been calibrated in efficiency to a precision of about 0.15% over a wide energy range. High-precision scans of the detector crystal and γ-ray source measurements have been compared to Monte-Carlo simulations to adjust the dimensions of a detector model. For this purpose, standard calibration sources and short-lived online sources have been used. The resulting efficiency calibration reaches the precision needed e.g. for branching ratio measurements of super-allowed β decays for tests of the weak-interaction standard model.

CP violation measurements in B mesons at Belle

We present recent measurements of time-dependent CP asymmetries in two neutral B decay modes: B0 → η'K0 and B0 → ωK°S. The measured values of mixing-induced (sin 2ϕ1eff) and direct CP violation parameters are: Sη'Ko = +0.68 ± 0.07stat ± 0.03syst, Aη'K0 = +0.03 ± 0.05stat ± 0.04syst and SωK0S = +0.91 ± 0.32stat ± 0.05syst, AωK0S = -0.36 ± 0.19stat ± 0.05syst, respectively. These results are fully consistent with the current world average of sin 2ϕ1 measured in b → cc̄s transitions, and represent the most accurate measurements in these modes up-to- date. In addition, we present a new preliminary update on branching ratio measurement in B0 → π0π0 decay mode, the result of which: ℬ(B0 → π0π0) = (0.90 ± 0.12stat ± 0.10syst) × 10−6 represents an important ingredient in a ππSU(2) isospin analysis, used to experimentally extract ϕ2 angle from B → ππ measurements. To obtain CP violation parameters (ℬ(B0 → π0π0)) the final data set of 772 × 106 (751.5 × 106) BB̄ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric e+e− collider in Japan (3.5 × 8.0GeV) is used.

Measurement of the absolute branching ratio of the K+ → π+π−π+ (γ) decay with the KLOE detector

The absolute branching ratio of the K+ → π+π−π+ (γ) decay, inclusive of final- state radiation, has been measured using ~17 million tagged K+ mesons collected with the KLOE detector at DAΦNE, the Frascati ϕ-factory. The result is:BR(K+ → π+π−π+ (γ)) = 0.05565 ± 0.00031stat ± 0.00025syst

B+c physics at LHCb

We present recent LHCb results in B+c physics with four topics. Using 3fb−1 of data collected in 2011 and 2012 produced in pp collisions, a baryonic decay mode, B+c → J/ψpp̄π+, is observed for the first time. With 1fb−1 of data collected in 2011, the first measurement of the relative branching ratio B(B+c → J/ψμ+)/B(B+c → J/ψμ+νμ) is performed. With 2fb−1 of data collected in 2012, the lifetime of the B+c meson is measured with the semileptonic decay B+c → J/ψμ+νμ. Finally, evidence is presented for the decay B+c → J/ψ3π+2π− using pp collision data, corresponding to an integrated luminosity of 3fb−1.

Studying the lepton number and lepton flavor violating $D^0\to e^\pm\mu^\mp$ and $D^+_{d/s}\to \pi(K)^+e^\pm\mu^\mp$ decays

The rare D decays are sensitive to new physics involving the up quark sector such as certain R-parity violating supersymmetric models. We study the lepton number and lepton flavor violating [Formula: see text] and [Formula: see text] decays in the supersymmetry without R-parity. From the best experimental upper limits of these decay branching ratios, we derive constraints on the relevant coupling products for the first time, and examine their contributions to relevant branching ratios and dileptonic invariant mass spectra. We find that all branching ratios are very sensitive to moduli of the squark exchange coupling products. Accurate measurements of these decay branching ratios in the future experiments at LHC and BESIII could give very strong bounds on relevant lepton number and lepton flavor violating coupling products.

Measurement of the absolute branching ratio of the [formula omitted] decay with the KLOE detector

The absolute branching ratio of the K+→π+π−π+(γ) decay, inclusive of final-state radiation, has been measured using ∼17 million tagged K+ mesons collected with the KLOE detector at DAΦNE, the Frascati ϕ-factory. The result is:BR(K+→π+π−π+(γ))=0.05565±0.00031stat±0.00025syst a factor ≃ 5 more precise with respect to the previous result. This work completes the program of precision measurements of the dominant kaon branching ratios at KLOE.