Decay Branching Ratios Research Articles

Semileptonic decays of B*, , and with the Bethe–Salpeter method

In this paper we study the semileptonic decays of B*, , and by using the Bethe–Salpeter method with instantaneous approximation. Both the and cases are considered. The largest partial width of these channels is of the order of 10−14 GeV. The branching ratios of these semileptonic decays are also estimated by using the partial width of the one photon decay channel to approximate the total width. For and , the branching ratios are of the order of 10−8 and 10−7, respectively. For , the and channels have the largest branching ratio, which is of the order of 10−6.

The Gigatracker detector of the NA62 experiment at CERN SPS

Abstract The NA62 experiment at the CERN SPS is a fixed target experiment designed to measure the branching ratio of the ultra-rare Kaon decay K + → π + ν ν . The experiment uses an high-momentum K + decay in-flight technique to increase the rejection power of the main background: K + → π + π 0 . The Gigatracker is a hybrid silicon pixel detector, exposed to a 750 MHz high-energy charged hadron beam, built to give an accurate measurement of K + momentum and direction together with an high precision measurement of the beam particle arrival time (115 ps RMS resolution per plane). It comprises three stations placed right before the K + decay region and inserted around two achromats. The detector works in vacuum ( ∼ 1 0 − 6 mbar ) at about − 10 ° C . Each station is made of a 200 μ m thick silicon sensor readout by 10 TDCPix, custom 100 μ m thick ASICs, and cooled by an innovative double circuit silicon micro-channel cooling system. All these parts are designed to minimize the total material budget which, in the final detector, amounts to less than 1.5% X 0 for the three stations. In order to sustain the high rate of incoming particles, each TDCPix, operating in a self triggered mode, is equipped with four 3.2 Gb/s serializers sending data to the detector DAQ system based on a read-out card per TDCPix chip sending trigger-matched hits to 6 PC servers. I will describe the whole detector and present some of the results from data collected during the 2016 NA62 runs.

Investigation ofJ=1states and theirγ-decay behavior inCr52

Background: In the $A\ensuremath{\approx}50$ mass region $M1$ spin-flip transitions are prominent around 9 MeV. An accumulation of ${1}^{\ensuremath{-}}$ states between 5 and 8 MeV generating additional $E1$ strength, also denoted as pygmy dipole resonance, has been established in many nuclei with neutron excess within the last decade.Purpose: The $\ensuremath{\gamma}$-decay behavior of $J=1$ states has been investigated in an NRF experiment. $M1$ excitations have been compared to shell model calculations.Methods: $J=1$ states were excited by quasi-monoenergetic, linearly polarized $\ensuremath{\gamma}$-ray beams generated by laser-Compton backscattering at the $\mathrm{HI}\ensuremath{\gamma}\mathrm{S}$ facility, Durham, NC, USA. Depopulating $\ensuremath{\gamma}$ rays were detected with the multidetector array ${\ensuremath{\gamma}}^{3}$.Results: For eleven beam-energy settings the $\ensuremath{\gamma}$-decay behavior of dipole states was analyzed by a state-to-state analysis and average $\ensuremath{\gamma}$-decay branching ratios have been investigated. 34 parity quantum numbers were assigned to $J=1$ states.Conclusions: Six ${1}^{\ensuremath{-}}$ states and two ${1}^{+}$ states have been investigated in NRF experiments for the first time. The $M1$ strength distribution is in good agreement with shell-model calculations.

Semileptonic decays of Bc meson to P -wave charmonium states

Inspired by a series of unexpected measurements of semileptonic decays mediated via $b\rightarrow c $ charged current interactions, we explore semileptonic $B_c$ decays to the four lightest $P$-wave charmonium states, $\chi_{c0}, \chi_{c1}, \chi_{c2}, h_c$, by the recently developed improved perturbative QCD formalism, in which the charm quark mass effect is included both in the Sudakov factor and the hard kernels. We first directly evaluate the concerned transition form factors with vector and axial-vector currents in the region of small momentum transfer squared, and then recast them to the full kinematical region by adopting the exponential parametrization. The obtained form factors are used to evaluate the semileptonic decay branching ratios, which can reach the order of $10^{-3}$, letting the corresponding measurement appear feasible. For a better analysis, a comparison of our results with the predictions of other models is provided. We also present the ratios between the tau and light lepton branching ratios and the polarization contributions in the relevant processes, which still need experimental tests in the ongoing and forthcoming experiments. Any significant deviations from the Standard Model results may provide some hints of new physics effects.

Investigations of the synthesis of the superheavy element Z=122

We have identified the most probable projectile-target combination by studying the fusion cross section, evaporation residue cross section, compound nucleus formation probability (${P}_{\mathrm{CN}}$), and survival probability (${P}_{\mathrm{Surv}}$) of different projectile target combinations to synthesize the superheavy element $Z=122$. The selected most probable projectile-target combinations to synthesize the superheavy element $Z=122$ are $\mathrm{Cr}+\mathrm{Cf}$, $\mathrm{Fe}+\mathrm{Cm}$, $\mathrm{Se}+\mathrm{Ra}$, and $\mathrm{As}+\mathrm{Ac}$. Superheavy nuclei may decay through the different decay modes such as spontaneous fission, ternary fission, and cluster decay. We have also studied the half-lives of spontaneous fission, ternary fission, and cluster decay of the predicted nuclei for $Z=122$ and compared with that of alpha decay. This enables us to study the competition between spontaneous fission, ternary fission, cluster decay, and alpha decay in the superheavy nuclei of $Z=122$. The comparision of half lives for different decay modes reveals that alpha decay is having smaller half lives than the other studied decay modes. A detail study of branching ratio of alpha decay with respect to other decay modes also confirms that alpha decay is most dominant decay mode for the isotopes superheavy nuclei $^{307--314}122$ and hence these nuclei can be detected through the alpha decay mode only. We hope that our predictions may be guide for the future experiments in the synthesis of more isotopes of superheavy nuclei $\mathrm{Z}=122$.

Search for pair production of heavy vector-like quarks decaying into high-pTW bosons and top quarks in the lepton-plus-jets final state in pp collisions at sqrt{s}=13 TeV with the ATLAS detector

A search is presented for the pair production of heavy vector-like B quarks, primarily targeting B quark decays into a W boson and a top quark. The search is based on 36.1 fb−1 of pp collisions at sqrt{s}=13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Data are analysed in the lepton-plus-jets final state, characterised by a high-transverse-momentum isolated electron or muon, large missing transverse momentum, and multiple jets, of which at least one is b-tagged. No significant deviation from the Standard Model expectation is observed. The 95% confidence level lower limit on the B mass is 1350 GeV assuming a 100% branching ratio to Wt. In the SU(2) singlet scenario, the lower mass limit is 1170 GeV. The 100% branching ratio limits are found to be also applicable to heavy vector-like X production, with charge +5/3, that decay into Wt. This search is also sensitive to a heavy vector-like B quark decaying into other final states (Zb and Hb) and thus mass limits on B production are set as a function of the decay branching ratios.

One-loop effects of Minimal Supersymmetric Standard Model particles in $e^-e^+\to Zh$ and $e^-e^+\to \nu\bar\nu h$ at the International Linear Collider

The 1-loop effects of the MSSM at the ILC are investigated through numerical analysis. We studied the higgs production processes $e^-e^+\rightarrow Zh$ and $e^-e^+\rightarrow \nu\bar{\nu}h$ at the ILC. It is found that the magnitude of the MSSM contribution through the 1-loop effects is sizable enough to be detected. In the study, three sets of the MSSM parameters are proposed, which are consistent with the observed higgs mass, the muon $g$-$2$, the dark matter abundance and the decay branching ratios of $B$ mesons. In the $e^-e^+\rightarrow Zh$ process, the 1-loop effects of the MSSM are visible and the distinction of the parameter sets is partially possible. For the study of $e^-e^+\rightarrow \nu\bar{\nu}h$, we used the equivalent $\it W$-boson approximation in the evaluation of the 1-loop cross section. While the 1-loop effect of the MSSM is visible, the distinction of the parameter sets might not be possible in this process under the value of realistic luminosity at the ILC.

Heavy-Light Mesons in the Nonrelativistic Quark Model Using Laplace Transformation Method

An analytic solution of theN-dimensional radial Schrödinger equation with the combination of vector and scalar potentials via the Laplace transformation method (LTM) is derived. The current potential is extended to encompass the spin hyperfine, spin-orbit, and tensor interactions. The energy eigenvalues and the corresponding eigenfunctions have been obtained in theN-dimensional space. The present results are employed to study the different properties of the heavy-light mesons (HLM). The masses of the scalar, vector, pseudoscalar, and pseudovector forB,Bs,D, andDsmesons have been calculated in the three-dimensional space. The effect of the dimensional number space is discussed on the masses of the HLM. We observed that the meson mass increases with increasing dimensional space. The decay constants of the pseudoscalar and vector mesons have been computed. In addition, the leptonic decay widths and branching ratio for theB+,D+, andBs+mesons have been studied. Therefore, the used method with the current potential gives good results which are in good agreement with experimental data and are improved in comparison with recent theoretical studies.

Analysis of D_s D K^* and D_s D^{*} K^* vertices and branching ratio of B^+rightarrow {K^*}^0 pi ^+

In this paper, the strong form factors and coupling constants of D_sDK^* and D_sD^*K^* vertices are investigated within the three-point QCD sum rules method with and without the SU_{f}(3) symmetry. In this calculation, the contributions of the quark–quark, quark–gluon, and gluon–gluon condensate corrections are considered. As an example of specific application of these coupling constants, the branching ratio of the hadronic decay B^+rightarrow {K^*}^0 pi ^+ is analyzed based on the one-particle-exchange which is one of the phenomenological models. In this model, B decays into a D_s D^* intermediate state, and then these two particles exchange a D (D^*) producing the final K^* and pi mesons. In order to compute the effect of these interactions, the D_s D K^* and D_s D^* K^* form factors are needed.

Decays of the f0(1370) scalar glueball candidate

For a long time doubts have existed on the existence of the f0(1370) meson as an individual object distinct and separated from the σ meson. Decays into π+π− of the f0(1370) are the main source of an isolated structure localized between 1.2 and 1.5 GeV in the π+π− mass spectrum measured in pp Central Exclusive Production (CEP) at s=200GeV at very low four momentum transfer squared ltl. These data confirm in the π+π− decay channel the existence of the f0(1370) as an isolated well identified structure that was previously observed in K+K−, KsKs, 4π0, 2π0π+π− and π+π−π+π− decays measured in pbar annihilations at rest. The decay branching ratios of f0(1370) into σσ, ρρ, ππ, KKbar, ηη relative to ππ decays obtained in analysis of data of pbar annihilations at rest which treat separately f0(1370) and σ are respectively 5.6, 3, 1, 1, 0.02. The decay and production properties of f0(1370) point to a large gg content. CEP interactions at very high energies favour production of 0++ and 2++ mesons. Selection of events with low ltl at both proton vertices suppresses 2++ structures. LHC runs dedicated to pp CEP measurements at low ltl could then provide a unique clean source of all the low energy scalars, cross check the pbar annihilation results and make it clear if and where scalar gluonium is resident and the nature (composition in terms of qqbar, qqqbarqbar, qqbar-qqbar and gg) of f0(500), f0(980), f0(1370), f0(1500) and f0(1710).

SU(3) symmetry breaking in charmed baryon decays

We explore the breaking effects of the SU(3) flavor symmetry in the singly Cabibbo-suppressed anti-triplet charmed baryon decays of mathbf{B}_crightarrow mathbf{B}_n M, with mathbf{B}_c=(Xi _c^0,Xi _c^+,Lambda _c^+) and mathbf{B}_n(M) the baryon (pseudo-scalar) octets. We find that these breaking effects can be used to account for the experimental data on the decay branching ratios of {mathcal {B}}(Lambda _c^+rightarrow Sigma ^{0} K^{+},Lambda ^{0} K^{+}) and R'_{K/pi }={mathcal {B}}(Xi ^0_c rightarrow Xi ^- K^+)/{mathcal {B}}(Xi ^0_c rightarrow Xi ^- pi ^+). In addition, we obtain that {mathcal {B}}(Xi _{c}^{0} rightarrow Xi ^{-} K^{+},Sigma ^{-} pi ^{+})=(4.6 pm 1.7,12.8 pm 3.1)times 10^{-4}, {mathcal {B}}(Xi _c^0rightarrow pK^-,Sigma ^+pi ^-)=(3.0 pm 1.0, 5.2 pm 1.6)times 10^{-4} and {mathcal {B}}(Xi _c^+rightarrow Sigma ^{0(+)} pi ^{+(0)})=(10.3 pm 1.7)times 10^{-4}, which all receive significant contributions from the breaking effects, and can be tested by the BESIII and LHCb experiments.

H-COUP: A program for one-loop corrected Higgs boson couplings in non-minimal Higgs sectors

We describe a numerical calculation tool H-COUP33The webpage of H-COUP is given in http://www-het.phys.sci.osaka-u.ac.jp/~kanemu/HCOUP_HP1013/HCOUP_HP.html, where one can download the set of source files of H-COUP_1.0. written in Fortran, which provides one-loop electroweak corrected vertices for the discovered Higgs boson h(125) in various Higgs sectors. The renormalization is based on the improved on-shell scheme without gauge dependence. In the first version H-COUP_1.0, the following models are included, namely, the Higgs singlet model, four types (Type-I, Type-II, Type-X, Type-Y) of two Higgs doublet models with a softly-broken Z2 symmetry and the inert doublet model. We first briefly introduce these models and then explain how to install and run this tool in an individual machine. A sample of numerical outputs is provided for user information. Program summaryProgram title: H-COUPProgram Files doi: http://dx.doi.org/10.17632/f88szmrj5x.1Licensing provisions: GPLv3Programming language: Fortran90Nature of problem: One-loop electroweak corrected vertices for the discovered Higgs boson h(125) are numerically calculated in the Higgs singlet model, four types (Type-I, Type-II, Type-X, Type-Y) of two Higgs doublet models with a softly-broken Z2 symmetry and the inert doublet model. The renormalization is based on the improved on-shell scheme without gauge dependence. Loop induced decay rates, i.e., h→γγ, h→Zγ and h→gg are also computed in these extended Higgs sectors at leading order.Solution method: All one-loop integrals for one-, two- and three-point functions are analytically expressed by using Passarino–Veltman functions in a systematic way, and their numerical values are calculated through the LoopTools. One-loop corrected h(125) vertices are then numerically provided in terms of form factors which are obtained by decomposing their Lorentz structure.Additional comments including restrictions and unusual features: In the version 1.0, QCD corrections are not included in the calculation of the h(125) vertices as well as the loop induced decay rates. In addition, the total width, decay branching ratios and cross sections are not outputted automatically. Details of these issues are described in Sec. VII of this manual.

Gamma-ray branching ratios in the decay of 49Cr

The $\gamma$ -decay branching ratios of 49V have been studied in the $\beta$ /EC decay of 49Cr. The $\gamma$ -ray spectrum has been measured with a 70% relative efficiency co-axial germanium detector calibrated in efficiency with a precision of about 0.5%. The primary result is the measurement of the relative branching ratios of the three main $\gamma$ rays in the decay of 49Cr. Large discrepancies were found with a previous experimental work. The 49Cr sample was produced by proton impact on a ZrO2 target and collected at the ISOLDE facility of CERN and enabled us to re-evaluate the decay scheme of 49Cr. The new data allow the use of this nucleus for future high-precision calibration work.

Search for Higgs boson decays to beyond-the-Standard-Model light bosons in four-lepton events with the ATLAS detector at sqrt{s}=13 TeV

A search is conducted for a beyond-the-Standard-Model boson using events where a Higgs boson with mass 125 GeV decays to four leptons (ℓ = e or μ). This decay is presumed to occur via an intermediate state which contains one or two on-shell, promptly decaying bosons: H → ZX/XX → 4ℓ, where X is a new vector boson Zd or pseudoscalar a with mass between 1 and 60 GeV. The search uses pp collision data collected with the ATLAS detector at the LHC with an integrated luminosity of 36.1 fb−1 at a centre-of-mass energy sqrt{s}=13 TeV. No significant excess of events above Standard Model background predictions is observed; therefore, upper limits at 95% confidence level are set on modelindependent fiducial cross-sections, and on the Higgs boson decay branching ratios to vector and pseudoscalar bosons in two benchmark models.

Decays A→Zγγ and ϕ→Zγγ ( ϕ=h , H ) in two-Higgs doublet models

The one-loop contributions to the decays of the $CP$-odd and $CP$-even scalar bosons $A\ensuremath{\rightarrow}Z\ensuremath{\gamma}\ensuremath{\gamma}$ and $\ensuremath{\phi}\ensuremath{\rightarrow}Z\ensuremath{\gamma}\ensuremath{\gamma}$ ($\ensuremath{\phi}=h$, $H$) are calculated within the framework of $CP$-conserving two-Higgs doublet models (THDMs), where they are induced by box and reducible Feynman diagrams. The behavior of the corresponding branching ratios are then analyzed within the type-II THDM in a region of the parameter space around the alignment limit and still consistent with experimental data. It is found that the $A\ensuremath{\rightarrow}Z\ensuremath{\gamma}\ensuremath{\gamma}$ branching ratio is only relevant when ${m}_{A}>{m}_{H}+{m}_{Z}$, but it is negligible otherwise. For ${m}_{A}>600\text{ }\text{ }\mathrm{GeV}$ and ${t}_{\ensuremath{\beta}}\ensuremath{\simeq}O(1)$, $\mathrm{BR}(A\ensuremath{\rightarrow}Z\ensuremath{\gamma}\ensuremath{\gamma})$ can reach values of the order of ${10}^{\ensuremath{-}5}\ensuremath{-}{10}^{\ensuremath{-}4}$, but it decreases by about 1 order of magnitude as ${t}_{\ensuremath{\beta}}$ increases up to 10. A similar behavior is followed by the $H\ensuremath{\rightarrow}Z\ensuremath{\gamma}\ensuremath{\gamma}$ decay, which only has a non-negligible branching ratio when ${m}_{H}>{m}_{A}+{m}_{Z}$ and can reach the level of ${10}^{\ensuremath{-}4}\ensuremath{-}{10}^{\ensuremath{-}3}$ for ${m}_{H}>600\text{ }\text{ }\mathrm{GeV}$ and ${t}_{\ensuremath{\beta}}\ensuremath{\simeq}O(1)$. We also estimated the branching ratios of these rare decays in the type-I THDM, where they can be about 1 order of magnitude larger than in type-II THDM. As far as the $h\ensuremath{\rightarrow}Z\ensuremath{\gamma}\ensuremath{\gamma}$ decay is concerned, since the properties of this scalar boson must be nearly identical to those of the SM Higgs boson, the $h\ensuremath{\rightarrow}Z\ensuremath{\gamma}\ensuremath{\gamma}$ branching ratio does not deviate significantly from the SM prediction, where it is negligibly small, of the order of ${10}^{\ensuremath{-}9}$. This result is in agreement with previous calculations.

Uncertainty quantification of neutron multiplication factors of light water reactor fuels during depletion

ABSTRACT Nuclear data-induced uncertainties of infinite neutron multiplication factors (k ∞) during fuel depletion are quantified in a single cell and a 3×3 multi-cell including burnable absorbers. Uncertainties of reaction cross sections, fission yields, decay half-lives and decay branching ratios provided in the JENDL libraries are taken into account. Hundred percent uncertainties are assumed to nuclear data to which uncertainty information are not provided in JENDL. Uncertainties propagation calculations are carried out with the adjoint-based procedure, and required sensitivity profiles of k ∞ with respect to these nuclear data are efficiently calculated by the depletion perturbation theory. Covariance matrices for fission yields and decay data in a simplified burnup chain are successfully generated by the stochastic-based procedure. k ∞ uncertainties of about 0.6% during fuel depletion are obtained, and it is shown that actinoids reaction cross sections are dominant contributors. Nuclide-wise decomposition of the uncertainties and observation of component-wise sensitivity profiles provide physical interpretations. By virtue of the adjoint-based procedure, several parametric surveys are also conducted. Contributions of uncertainties in fission products (FPs) nuclides are quantified, and important nuclides and energy ranges are identified for further evaluation of nuclear data of FP nuclides. Effect of cooling period on k ∞ uncertainties is also discussed.

Study of Electromagnetic Properties of Light Baryons in the Hypercentral Approach

Light flavour baryons are studied in a non-relativistic potential model with colour Coulomb plus linear confinement potential using a simple variational method. The ground-state masses and magnetic moments of the light baryons are computed using a spin- and isospin-dependent potential. We extend our scheme to predict the transition magnetic moments of $B_{(J^P={3/2}^+)} \rightarrow B_{(J^P={1/2}^+)}\gamma$ processes. We also compute the radiative decay widths and branching ratios of light baryons. A comparison of our results with those of other works and experimental data is also presented.

Neutron Lifetime and Axial Coupling Connection.

Experimental studies of neutron decay, n→peν[over ¯], exhibit two anomalies. The first is a 8.6(2.1)s, roughly 4σ difference between the average beam measured neutron lifetime, τ_{n}^{beam}=888.0(2.0) s, and the more precise average trapped ultracold neutron determination, τ_{n}^{trap}=879.4(6) s. The second is a 5σ difference between the pre2002 average axial coupling, g_{A}, as measured in neutron decay asymmetries g_{A}^{pre2002}=1.2637(21), and the more recent, post2002, average g_{A}^{post2002}=1.2755(11), where, following the UCNA Collaboration division, experiments are classified by the date of their most recent result. In this Letter, we correlate those τ_{n} and g_{A} values using a (slightly) updated relation τ_{n}(1+3g_{A}^{2})=5172.0(1.1) s. Consistency with that relation and better precision suggest τ_{n}^{favored}=879.4(6) s and g_{A}^{favored}=1.2755(11) as preferred values for those parameters. Comparisons of g_{A}^{favored} with recent lattice QCD and muonic hydrogen capture results are made. A general constraint on exotic neutron decay branching ratios, <0.27%, is discussed and applied to a recently proposed solution to the neutron lifetime puzzle.

Decay modes of superheavy nuclei Z = 124

It is important to study the different decay modes of superheavy nuclei such as spontaneous fission, ternary fission and cluster decay. We studied the spontaneous fission, ternary fission and cluster decay of predicted isotopes of superheavy nuclei [Formula: see text] and compared with that of alpha decay. This enables us to study the competition between spontaneous fission, ternary fission, cluster decay and alpha decay in the superheavy nuclei [Formula: see text]. We have studied the half-lives and decay constants of different decay modes. We have also studied the branching ratio of alpha decay with respect to other decay modes. This study reveals that alpha decay is the most dominant decay mode for the superheavy nuclei [Formula: see text] and hence these nuclei can be detected through the alpha decay mode only.

Four-body decays of B meson with lepton number violation

The existence of heavy meson lepton number violating (LNV) processes shows the Majorana nature of the neutrino. Much of this theoretical and experimental researche focuses on this type of decay. Four-body epton-number violation (LNV) processes of the B meson may have sizable branching ratios as they share the same vertex and mixing parameters with the three-body case. Mixing parameters between the heavy Majorana neutrino and charged leptons extracted from the three-body case can be used to constrain the branching ratios of four-body decays of the B meson. So we can update the upper limits of these mixing parameters with new experimental data of the three-body LNV decays. We also analyze using the updated parameters and estimate some channels’ reconstruction events using current experimental data from Belle.