scholarly journals Relations between b → cτν decay modes in scalar models

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Stefan Schacht ◽  
Amarjit Soni
Keyword(s):  
Decay Mode ◽  
Semileptonic Decay ◽  
New Physics ◽  
Decay Rates ◽  
Scalar Form Factor ◽  
Scalar Form ◽  
Decay Modes ◽  
Pseudoscalar Mesons ◽  
Quark Level ◽  
Level Transition

Abstract As a consequence of the Ward identity for hadronic matrix elements, we find relations between the differential decay rates of semileptonic decay modes with the underlying quark-level transition b → cτν, which are valid in scalar models. The decay-mode dependent scalar form factor is the only necessary theoretical ingredient for the relations. Otherwise, they combine measurable decay rates as a function of the invariant mass-squared of the lepton pair q2 in such a way that a universal decay-mode independent function is found for decays to vector and pseudoscalar mesons, respectively. This can be applied to the decays $$ B\to {D}^{\ast}\tau v,{B}_s\to {D}_s^{\ast}\tau v,{B}_c\to J/\psi \tau v $$ B → D ∗ τv , B s → D s ∗ τv , B c → J / ψτv and B → Dτv, Bs → Dsτv, Bc → ηcτv, with implications for R(D(*)), $$ R\left({D}_s^{\left(\ast \right)}\right) $$ R D s ∗ , R(J/ψ), R(ηc), and ℬ(Bc → τv). The slope and curvature of the characteristic q2-dependence is proportional to scalar new physics parameters, facilitating their straight forward extraction, complementary to global fits.

scholarly journals Impact of $$b \rightarrow s \ell \ell $$ anomalies on rare charm decays in non-universal $$Z'$$ models

2022 ◽  
Vol 82 (1) ◽  
Author(s):  
Ashutosh Kumar Alok ◽  
Neetu Raj Singh Chundawat ◽  
Dinesh Kumar
Keyword(s):  
New Physics ◽  
Tree Level ◽  
Long Distance ◽  
Charm Decays ◽  
Decay Modes ◽  
The Standard Model ◽  
Quark Level ◽  
Level Transition ◽  
The Impact ◽  
Rare Charm

AbstractIn this work, we study the impact of $$b \rightarrow s \ell \ell $$ b → s ℓ ℓ , $$B_s - \bar{B_s}$$ B s - B s ¯ mixing and neutrino trident measurements on observables in decays induced by $$c \rightarrow u $$ c → u transition in the context of a non-universal $$Z'$$ Z ′ model which generates $$C^{\mathrm{NP}}_{9} <0$$ C 9 NP < 0 and $$C^{\mathrm{NP}}_9 = - \,C^{\mathrm{NP}}_{10} $$ C 9 NP = - C 10 NP new physics scenarios at the tree level. We inspect the effects on $$D^0 \rightarrow \pi ^0 \nu {\bar{\nu }}$$ D 0 → π 0 ν ν ¯ , $$D^+ \rightarrow \pi ^+ \nu {\bar{\nu }}$$ D + → π + ν ν ¯ and $$B_c \rightarrow B^+ \nu {\bar{\nu }} $$ B c → B + ν ν ¯ decays which are induced by the quark level transition $$c \rightarrow u \nu {\bar{\nu }}$$ c → u ν ν ¯ . The fact that the branching ratios of these decays are negligible in the standard model (SM) and the long distance effects are relatively smaller in comparison to their charged dileptons counterparts, they are considered to provide genuine null-tests of SM. Therefore the observation of these modes at the level of current as well as planned experimental sensitivities would imply unambiguous signature of new physics. Using the constraints on $$Z'$$ Z ′ couplings coming from a combined fit to $$b \rightarrow s \ell \ell $$ b → s ℓ ℓ , $$\varDelta M_s$$ Δ M s and neutrino trident data, we find that any meaningful enhancement over the SM value is ruled out in the considered framework. The same is true for $$D - {\bar{D}}$$ D - D ¯ mixing observable $$\varDelta M_D$$ Δ M D along with $$D^0 \rightarrow \mu ^+ \mu ^-$$ D 0 → μ + μ - and $$D^+ \rightarrow \pi ^+ \mu ^+ \mu ^-$$ D + → π + μ + μ - decay modes which are induced through $$c \rightarrow u \mu ^+ \mu ^-$$ c → u μ + μ - transition.

AN EFFECTIVE LAGRANGIAN CALCULATION OF THE SEMILEPTONIC DECAY MODES OF THE τ LEPTON

1990 ◽  
Vol 05 (14) ◽  
pp. 2737-2753 ◽  
Author(s):  
ERIC BRAATEN ◽  
ROBERT J. OAKES ◽  
SZE-MAN TSE
Keyword(s):  
Vector Meson ◽  
Ad Hoc ◽  
Semileptonic Decay ◽  
Branching Fractions ◽  
Decay Rates ◽  
Coupling Constants ◽  
Vector Meson Dominance ◽  
Decay Modes ◽  
Effective Lagrangian ◽  
Pseudoscalar Mesons

The semileptonic decay rates of the τ lepton into final states containing up to three pseudoscalar mesons are calculated using a general low energy effective Lagrangian for pseudoscalar and vector mesons with U (3)× U (3) chiral symmetry. Symmetry breaking is taken into account in the meson masses and mixing angles. All of the coupling constants in the Lagrangian are determined empirically from vector meson decay data without additional ad hoc hypotheses such as vector meson dominance. The results compare well with the measured decay rates where data are available. No unexpectedly large branching fractions are found that might account for the “missing” decay modes of the τ.

scholarly journals Relativistic calculations of R(D(∗)), R(Ds(∗)), R(ηc) and R(J/ψ)

2020 ◽  
Vol 35 (17) ◽  
pp. 2050076
Author(s):  
Tian Zhou ◽  
Tianhong Wang ◽  
Yue Jiang ◽  
Xiao-Ze Tan ◽  
Geng Li ◽  
...  
Keyword(s):  
Experimental Data ◽  
Standard Model ◽  
Semileptonic Decay ◽  
Form Factors ◽  
Relativistic Correction ◽  
New Physics ◽  
Decay Rates ◽  
The Standard Model ◽  
Model Predictions

Recently, the deviation of the ratios [Formula: see text], [Formula: see text] and [Formula: see text] have been found between experimental data and the Standard Model predictions, which may be the hint of new physics. In this work, we calculate these ratios within the Standard Model by using the improved instantaneous Bethe–Salpeter method. The emphasis is pad to the relativistic correction of the form factors. The results are [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text], which are consistent with predictions of other models and the experimental data. The semileptonic decay rates and corresponding form factors at zero recoil are also given.

scholarly journals The $$ \overline{B} $$ → π form factors from QCD and their impact on |Vub|

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Domagoj Leljak ◽  
Blaženka Melić ◽  
Danny van Dyk
Keyword(s):  
Form Factor ◽  
Lattice Qcd ◽  
Sum Rules ◽  
Semileptonic Decay ◽  
Form Factors ◽  
Scalar Form Factor ◽  
Small Momentum Transfer ◽  
Scalar Form ◽  
Sum Rule ◽  
First Time

Abstract We revisit light-cone sum rules with pion distribution amplitudes to determine the full set of local $$ \overline{B} $$ B ¯ → π form factors. To this end, we determine all duality threshold parameters from a Bayesian fit for the first time. Our results, obtained at small momentum transfer q2, are extrapolated to large q2 where they agree with precise lattice QCD results. We find that a modification to the commonly used BCL parametrization is crucial to interpolate the scalar form factor between the two q2 regions. We provide numerical results for the form factor parameters — including their covariance — based on simultaneous fit of all three form factors to both the sum rule and lattice QCD results. Our predictions for the form factors agree well with measurements of the q2 spectrum of the semileptonic decay $$ {\overline{B}}^0\to {\pi}^{+}{\mathrm{\ell}}^{-}{\overline{\nu}}_{\mathrm{\ell}} $$ B ¯ 0 → π + ℓ − ν ¯ ℓ . From the world average of the latter we obtain |Vub| = (3.77 ± 0.15) · 10−3, which is in agreement with the most recent inclusive determination at the 1 σ level.

scholarly journals THE ROLE OF $K^*_0(1430)$ IN D → PK AND τ → KPντ DECAYS

1999 ◽  
Vol 14 (26) ◽  
pp. 4161-4175 ◽  
Author(s):  
S. FAJFER ◽  
J. ZUPAN
Keyword(s):  
Experimental Data ◽  
Form Factor ◽  
Matrix Element ◽  
Scalar Meson ◽  
Final State Interaction ◽  
Form Factors ◽  
Decay Rates ◽  
Scalar Form Factor ◽  
Meson Resonance ◽  
Scalar Form

We consider the scalar form factor in the weak current matrix element <PK|jμ|0>, P=π, η, η′. It obtains the contributions from the scalar meson resonance [Formula: see text] and from the scalar projection of the vector meson K*(892) resonance. We analyze decay amplitudes of the Cabibbo suppressed decays D → KP, P=π, η, η′ using the factorization approach. The form factors of the relevant matrix elements are described by assuming the dominance of nearby resonances. The annihilation contribution in these decays arises from the matrix element <PK|jμ|0>. All the required parameters are experimentally known except the scalar meson [Formula: see text] decay constant. We fit the decay amplitudes and we find that final state interaction improves the agreement with the experimental data. Then we extract bounds on scalar form factor parameters and compare them with the experimental data obtained in the analyses of K→πeνe and K→πμνμ. The same scalar form factor is present in the τ → KPντ decay, with P=π, η, η′. Using the obtained bounds we investigate the significance of the scalar meson form factor in the τ→ KPντ, P=π, η, η′ decay rates and spectra. We find that the [Formula: see text] scalar meson dominates in the τ→Kη′ντ decay spectrum.

scholarly journals The role of right-handed neutrinos in b → cτ (πντ, ρντ, μ$$ \overline{\nu} $$μντ)$$ \overline{\nu} $$τ from visible final-state kinematics

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Neus Penalva ◽  
Eliecer Hernández ◽  
Juan Nieves
Keyword(s):  
Semileptonic Decay ◽  
Massive Particle ◽  
New Physics ◽  
Experimental Information ◽  
Final State ◽  
Spin Asymmetries ◽  
Decay Modes ◽  
Lepton Flavor ◽  
Rule Out

Abstract In the context of lepton flavor universality violation (LFUV) studies, we fully derive a general tensor formalism to investigate the role that left- and right-handed neutrino new-physics (NP) terms may have in b → cτ$$ \overline{\nu} $$ ν ¯ τ transitions. We present, for several extensions of the Standard Model (SM), numerical results for the Λb → Λcτ$$ \overline{\nu} $$ ν ¯ τ semileptonic decay, which is expected to be measured with precision at the LHCb. This reaction can be a new source of experimental information that can help to confirm, or maybe rule out, LFUV presently seen in $$ \overline{B} $$ B ¯ meson decays. The present study analyzes observables that can help in distinguishing between different NP scenarios that otherwise provide very similar results for the branching ratios, which are our currently best hints for LFUV. Since the τ lepton is very short-lived, we consider three subsequent τ-decay modes, two hadronic πντ and ρντ and one leptonic μ$$ \overline{\nu} $$ ν ¯ μντ, which have been previously studied for $$ \overline{B} $$ B ¯ → D(*) decays. Within the tensor formalism that we have developed in previous works, we re-obtain the expressions for the differential decay width written in terms of visible (experimentally accessible) variables of the massive particle created in the τ decay. There are seven different τ angular and spin asymmetries that are defined in this way and that can be extracted from experiment. Those asymmetries provide observables that can help in constraining possible SM extensions.

scholarly journals The low-energy effective theory of axions and ALPs

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Martin Bauer ◽  
Matthias Neubert ◽  
Sophie Renner ◽  
Marvin Schnubel ◽  
Andrea Thamm
Keyword(s):  
High Energy ◽  
New Physics ◽  
Mass Scale ◽  
Low Energy ◽  
Effective Theory ◽  
Loop Order ◽  
Flavor Changing ◽  
Effective Lagrangian ◽  
Anomalous Dimensions ◽  
Pseudoscalar Mesons

Abstract Axions and axion-like particles (ALPs) are well-motivated low-energy relics of high-energy extensions of the Standard Model, which interact with the known particles through higher-dimensional operators suppressed by the mass scale Λ of the new-physics sector. Starting from the most general dimension-5 interactions, we discuss in detail the evolution of the ALP couplings from the new-physics scale to energies at and below the scale of electroweak symmetry breaking. We derive the relevant anomalous dimensions at two-loop order in gauge couplings and one-loop order in Yukawa interactions, carefully considering the treatment of a redundant operator involving an ALP coupling to the Higgs current. We account for one-loop (and partially two-loop) matching contributions at the weak scale, including in particular flavor-changing effects. The relations between different equivalent forms of the effective Lagrangian are discussed in detail. We also construct the effective chiral Lagrangian for an ALP interacting with photons and light pseudoscalar mesons, pointing out important differences with the corresponding Lagrangian for the QCD axion.

scholarly journals Search forD0−D¯0mixing using doubly flavor tagged semileptonic decay modes

2007 ◽  
Vol 76 (1) ◽  
Author(s):  
B. Aubert ◽  
M. Bona ◽  
D. Boutigny ◽  
Y. Karyotakis ◽  
J. P. Lees ◽  
...  
Keyword(s):  
Semileptonic Decay ◽  
Decay Modes

scholarly journals Dark Photon Searches at BESIII

2018 ◽  
Vol 46 ◽  
pp. 1860046 ◽  
Author(s):  
Dayong Wang
Keyword(s):  
Degrees Of Freedom ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Gauge Bosons ◽  
Data Set ◽  
Decay Modes ◽  
Dark Photon ◽  
The Standard Model ◽  
New Type ◽  
Low Mass

Many models beyond the Standard Model, motivated by the recent astrophysical anomalies, predict a new type of weak-interacting degrees of freedom. Typical models include the possibility of the low-mass dark gauge bosons of a few GeV and thus making them accessible at the BESIII experiment running at the tau-charm region. The BESIII has recently searched such dark bosons in several decay modes using the high statistics data set collected at charmonium resonaces. This talk will summarize the recent BESIII results of these dark photon searches and related new physics studies.

scholarly journals Study of Rare Mesonic Decays Involving Di-Neutrinos in Their Final State

2018 ◽  
Vol 2018 ◽  
pp. 1-20
Author(s):  
Azeem Mir ◽  
Farida Tahir ◽  
Shakeel Mahmood ◽  
Shi- Hai Dong
Keyword(s):  
Branching Fractions ◽  
New Physics ◽  
Supersymmetric Model ◽  
Final State ◽  
Yukawa Couplings ◽  
Leptonic Decays ◽  
Pseudoscalar Mesons ◽  
Theoretical Predictions ◽  
Minimal Supersymmetric Model

We have studied phenomenological implication of R-parity violating (Rp) Minimal Supersymmetric Model (MSSM) via analyses of pure leptonic (M→νν¯) and semileptonic decays of pseudoscalar mesons (M→Xνν¯). These analyses involve comparison between theoretical predictions made by Rp MSSM and the Standard Model (SM) with the experimental results like branching fractions (Br) of the said process. We have found, in general, that Rp contribution dominates over the SM contribution, i.e., by a factor of 10 for the pure leptonic decays of KL,S and by 102 and 104 in case of Bs and Bd, respectively. Furthermore, the limits obtained on Rp Yukawa couplings (λαkβ′λαkγ′⁎) by using Br  (M→Xνν¯) are used to calculate Br  (M→νν¯). This demonstrates the role of Rp MSSM as a viable model for the study of new physics contribution in rare decays at places like Super B factories, KOTO (J-PARC) and NA62 at CERN.

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