Motivated by the anomalies present in $b \to u$ and $b \to c$ semileptonic decays, we study the corresponding $B_s \to (K,K^*) τν$ and $B \to πτν$ decays within an effective field theory formalism. Our analysis is based on a strict model dependent assumption, i.e., we assume that $b \to u$ and $b \to c$ transition decays exhibit similar new physics pattern. We give prediction of various observables such as the branching fraction, ratio of branching ratio, lepton side forward-backward asymmetry, longitudinal polarization fraction of the charged lepton and convexity parameter in the standard model and in the presence of vector type new physics couplings.
I discuss how b decays can be used to unravel new physics beyond the Standard Model. Decays second order in the weak interaction involving loops and CP violation are emphasized. This information is complementary to that obtainable with higher energy machines.
We determine the ability of future experiments to observe supersymmetric contributions to the rare decays $B \to X_s γ$ and $B \to X_s l^+l^-$. A global fit to the Wilson coefficients which contribute to these decays is performed from Monte Carlo generated data. This fit is then compared to supersymmetric predictions for several different patterns of the superpartner spectrum.
We study implications of spontaneous CP-violation in minimal susy models for CP-asymmetries in rare $B,\bar B$-decays. In particular, we estimate characteristic values of the angles of the unitarity triangle and show that sizeable CP-violating effects result from $B-\bar B$ mixing only. Significant deviations from the SM predictions are pointed out.
Some mechanisms of supersymmetry breaking result in splitting of the third generation sfermions from the other sfermions. We show that the three-body decay branching ratio of the lighter chargino gives a sensitive probe of the sfermion mass spectrum if the chargino has a large gaugino component.
Beijing Spectrometer (BES) at Beijing Electron Positron Collider (BEPC), IHEP has accumulated 2.5 $\times 10^7$ J/$Ψ$ and plans to increase the number to $10^8 \sim 10^9$ in the near future. In this paper I review and summarize the recent studies on the possibilities of probing for new physics at BES. This includes the theoretical works on and experimental attempt performed at BES in searching for flavor changing neutral current, CP violation and lepton flavor violation in the processes of J/$Ψ$ decays.
We show the 13 TeV proton-proton collider simulation in a $ν$-two-Higgs-doublet-model ($ν$-THDM). The heavy charged Higgs bosons are produced in pairs through the electroweak processes and decay to the light sterile neutrinos. The light sterile neutrino further decays into a jet-like object with a muon in it. This helps us discriminate the signal from the backgrounds with the standard model jets.
The recent CLEO results on on radiative $b$-quark decays are used to derive constraints on anomalous $WWγ$ couplings. These constraints are compared with expectations from $p\bar p\rightarrow e^\pm p\llap/_Tγ+X$ at the Tevatron. The usefulness of exclusive radiative $B$ meson decay channels in probing the $WWγ$ vertex is largely limited by present theoretical uncertainties in the calculation of hadronic matrix elements.
Motivated by a pilot experiment conducted by F.Vannucci et al. during a solar eclipse, we work out the geometry governing the radiative decays of solar neutrinos. Surprisingly, although a smaller proportion of the photons can be detected, the case of strongly non-degenerate neutrinos brings better limits in terms of the fundamental couplings. We advocate satellite-based experiments to improve the sensitivity.
Neutrinoless double beta decay (NDBD) is the only experiment that could probe the Majorana nature of the neutrino. Here we study the theoretical implications of NDBD for models yielding tri-bimaximal lepton mixing like A4 and S4.
One of the main neutrino oscillation parameters whose value has not been determined very precisely is the leptonic $δ_{CP}$ phase. Since neutrinos have a tiny but finite mass they can undergo decay both visibly and invisibly. The effect of invisible decay of the third mass eigen state $ν_3$ on the sensitivity to $δ_{CP}$ is analysed here using atmospheric neutrino and anti-neutrino events. Effects of detector resolutions and systematic uncertainties are studied to identify the optimum resolutions and efficiencies required by a detector to obtain a significant sensitivity even in presence of de…
We discuss recently reported experimental hints for a bottom squark with mass around 3.5 GeV decaying as sbottom -> charm + lepton + anti-sneutrino. We correlate the sbottom lifetime with the decay rates for bottom -> sbottom + neutrino + anti-sneutrino and bottom -> sbottom + anti-neutrino + sneutrino in the framework of a minimal supersymmetric model extended by right-handed (s)neutrinos. Confronting our results with the well-measured semileptonic branching ratio of B mesons we conclude that the light sbottom interpretation of the experimental anomalies is ruled out, unless m_bottom < m_sbot…
We examine the possibility of observing exotic top quark decays via $R$-Parity violating SUSY interactions in $e^+e^-$ collisions at $\sqrt{s = 500 GeV$. We present cross-sections for $t\bar t$ production followed by the subsequent decay of either the $t$ or $\overline{t}$ via the $R$-Parity violating interaction while the other undergoes the SM decay. We discuss kinematic cuts that allow the exotic SUSY decays to be detected over standard model backgrounds. Discovery limits for $R$-Parity violating couplings in the top sector are presented assuming an integrated luminosity of $100 fb^{-1}$.
We study CP asymmetries in two-body decays of top squarks into neutralinos and sleptons at the LHC. These asymmetries are used to probe the CP phases possibly present in the stop and neutralino sector of the Minimal Supersymmetric Standard Model. Taking into account bounds from experimental electric dipole moment searches, we identify areas in the mSUGRA parameter space where CP asymmetries can be sizeable and discuss the feasibility of their observation at the LHC. As a result, potentially detectable CP asymmetries in stop decays at the LHC are found, motivating further detailed experimental …
A few $B_{d,s}$ and $Λ_b$ decays induced by $b \to s$ transition are studied in the Standard Model and in the framework of the Appelquist, Cheng and Dobrescu (ACD) model, which is a New Physics scenario where a single universal extra dimension is considered. In particular, we investigate the sensitivity of the observables to the radius $R$ of the compactified extra dimension.
We examine the possibility of observing exotic top quark decays via R-violating SUSY interactions at the Fermilab Tevatron and CERN LHC. We present cross-sections for $t\bar t$ production followed by the subsequent decay of either $t$ or $\bar t$ via the R-violating interaction while the other undergoes the SM decay. With suitable kinematic cuts, we find that the exotic decays can possibly be detected over standard model backgrounds at the future runs of the Tevatron and LHC, but not at Run 1 of the Tevatron due to limited statistics. Discovery limits for R-Violating couplings in the top secto…
The exotic decay modes of non-Standard Model Higgs bosons are efficient in probing the hierarchical Two Higgs Doublet Models (2HDM). In particular, the decay mode $H^\pm\to HW^\pm$ serves as a powerful channel in searching for charged Higgses. In this paper, we analyzed the reach for $H^\pm\to HW^\pm \to t\bar{t}W$ at a 100 TeV $pp$ collider, and showed that it extends the reach of the previously studied $ττW$ final states once above the top threshold. Top tagging technique is used, in combination with the boosted decision tree classifier. Almost the entire hierarchical Type-II 2HDM parameter …
The nature of the so-called XYZ states is a long-standing problem. It has been suggested that such particles may be described as compact four-quark states or loosely bound meson molecules. In the present work we analyze the Z_c(') -> eta_c rho decay using both approaches. Such channel might provide useful insights on the nature of the Z_c('), helping discriminating between the two different models.
Anomalous couplings of the $Z$ boson to top quarks are only marginally constrained by direct searches and are still sensitive to new particle dynamics at the TeV scale. Employing an effective field theory approach we consider the dimension-six operators which generate deviations from the standard-model vector and axial-vector interactions. We show that rare $B$ and $K$ meson decays together with electroweak precision observables provide strong constraints on these couplings. We also consider constraints from t-channel single-top production.
When new CP-violating interactions are dominated by flavor changing neutral particle exchanges, that may occur in many extensions of the standard model. We examine a type 3 two Higgs doublet model and find that direct CP asymmetries can be as large as about 25% . Time-dependent and time-integrated mixing-induced CP asymmetries up to 85 and 40 %, respectively, are possible without conflict with other constraints. It mainly requirs an enhanced chromo-magnetic dipole $b\to sg$ decay to be close to the present experimental bound.
A non-standard CP-odd Higgs boson could induce a slight (but observable) lepton universality breaking in Upsilon leptonic decays. Moreover, mixing between such a pseudoscalar Higgs boson and $η_b$ states might shift their mass levels, thereby modifying the values of the $M_{Υ(nS)}-M_{η_b(nS)}$ hyperfine spplitings predicted in the standard model. Besides, $η_b$ resonances could be broader than expected with potentially negative consequences for discovery in both $e^+e^-$ and hadron colliders. A scenario with a CP violating Higgs sector is also considered. Finally, further strategies to search …
It had been suggested to probe CP violation in τ \rightarrow νKπ decays with K0 -K ^{-}0 oscillation to produce ACP(τ- \rightarrow νKSπ-) = (0.36\pm0.01)%. BaBar has found ACP(τ- \rightarrow νKSπ-[\geq π0]) = (-0.36 \pm 0.23 \pm 0.11)% - i.e., 2.8 sigma difference with SM prediction. It is discussed, why one needs to probe ACP(τ \rightarrow νKπ), ACP(τ \rightarrow νK2π) and ACP(τ \rightarrow νK3π) separately to establish the existence of New Dynamics and its features. It should be possible at SuperB & Super-Belle experiments.
We argue that a large region of so far unconstrained parameter space for axion-like particles (ALPs), where their couplings to the Standard Model are of order $(0.01\!-\!1)\,\mbox{TeV}^{-1}$, can be explored by searches for the exotic Higgs decays $h\to Za$ and $h\to aa$ in Run-2 of the LHC. Almost the complete region in which ALPs can explain the anomalous magnetic moment of the muon can be probed by searches for these decays with subsequent decay $a\toγγ$, even if the relevant couplings are loop suppressed and the $a\toγγ$ branching ratio is less than~1.
With the primary motivation of probing the quark substructure of scalar mesons, a generalized linear sigma model for the lowest and the next-to-lowest scalar and pseudoscalar mesons is employed to investigate several semi-leptonic decays of $D$ mesons. The free parameters of the model (in its leading approximation) have been previously determined from fits to mass spectra and various low-energy parameters. With these fixed parameters, the model has already given encouraging predictions for different low-energy decays and scattering, as well as for semileptonic decay channels of $D_s^+$ that in…
The disagreement between the standard model prediction and the experimental measurement of muon anomalous magnetic moment can be alleviated by invoking an additional particle which is either a vector boson ($X_1$) or a scalar ($X_0$). This new particle, with the mass $m_X \lesssim 2 m_μ$, can be searched for in the decay $J/ψ\to μ^- μ^+ X$, where $X$ is missing. Our numerical study shows that the search is quite feasible at the BESIII experiment in the parameter space allowed by muon $g-2$ measurements.
Using soft-collinear effective theory we describe at leading order in 1/m_b all the semi-inclusive hadronic B -> XM decays near the endpoint, where an energetic light meson M recoils against an inclusive jet X. We also include the decays involving eta, eta' mesons that receive additional contributions from gluonic operators. The predicted branching ratios and CP asymmetries depend on fewer hadronic parameters than the corresponding two-body B decays. This makes semi-inclusive hadronic B -> XM decays a powerful probe of the potential nonperturbative nature of charming penguins as well as a usef…
The study of inclusive semileptonic decays of $B$ mesons is analyzed from the viewpoint of probing hadron structure and strong interactions. General formulas for the differential decay rates are given in terms of the structure functions in arbitrary frame of reference, taking into account the finite charged lepton mass. These formulas can be used for structure function measurements. The behavior of the structure functions is shown to contain information on the constitution of the $B$ meson and the dynamics of strong interactions. Measurements of the structure functions would reveal the existen…
We show that an angular analysis of B --> V1 V2 decays yields numerous tests for new physics in the decay amplitudes. Unlike direct CP asymmetries, many of these new-physics observables are nonzero even if the strong phase differences vanish. For certain observables, neither time-dependent measurements nor tagging is necessary. Should a signal for new physics be found, one can place a lower limit on the size of the new-physics parameters, as well as on their effect on the measurement of the phase of B0--Bbar0 mixing.
We perform a model independent analysis to identify new physics operators which can enhance the branching ratio of $B_s^* \rightarrow μ^+ μ^-$ above its Standard Model (SM) prediction. We find that none of the new physics operators which provide a good fit to $b \rightarrow s μ^+ μ^-$ data can enhance the Br($B_s^* \rightarrow μ^+ μ^-$) above its SM value.
We investigate a new method to probe the helicity of the photon emitted in the b -> s gamma transition. The method relies on the observation of interference effects between two resonance contributions, B -> K*(K gamma) gamma and B -> eta_c(gamma gamma) K or B -> chi_c0(gamma gamma) K to the same final state K gamma gamma. Decays of the type B -> K_res(K gamma) gamma dominate the B -> K gamma gamma yield throughout most of the phase space, and may be accessible at current B meson facilities already.
We discuss the formulation of the general two-Higgs doublet model type III, which incorporates flavor changing neutral scalar interactions (FCNSI) and CP violation from several sources. CP violation can arise either from Yukawa terms or from the Higgs potential, and it can explicit or spontaneous. We discuss the case that includes CP violation with Yukawa textures to control FCNSI and evaluate the CP asymmetry for the decay h-> c-b+ W-, which may allow to test the patterns of FCNSI and CP violation, that arises in these models.
Since decays to four leptons is widely considered a promising way to search for the Higgs particle, we show how the same final state can also be used to search for signals of CP nonconservation. Energy asymmetries and triple correlations are related to parameters in the underlying CP violating effective interaction at the $H^0$-$W$-$W$ and $H^0$-$Z$-$Z$ vertex. Expected size of the effects are shown to be small for both the Sandard Model and its extension with an extra Higgs doublet.
Many of the experiments proposed to look for interference CP violation in neutral B mesons concentrate on tagged decay into CP eigenstates. Aleksan, Dunietz, Kayser and Le Diberder have shown that one can also look for interference CP violation using tagged decays into non-CP eigenstates. In all these methods, one must trace the time dependence of the decays. In this article we discuss a new method to search for interference CP violation by using only time integrated rates into non-CP eigenstates. The method hinges on the comparison between the decays of $Υ(4S)$ into $f f$, $\bar{f} \bar{f}$, …
The evaluation, systematic analysis and numerical study of the semileptonic $τ$-lepton decays with two mesons in the final state has been made in the frame of the standard model extended by right handed neutrinos. In the analysis, heavy-neutrino nondecoupling effects, finite quark masses, quark and meson mixings, finite widths of vector mesons, chiral symmetry breakings in vector-meson--pseudoscalar-meson vertices and effective Higgs-boson--pseudoscalar-meson couplings have been included. Numerical estimates reveal that the decays $τ^-\to e^-π^-π^+$, $τ^-\to e^-K^-K^+$ and $τ^-\to e^-K^0\bar{K…
Several extensions of the Standard Model predict the existence of Long-Lived Neutral Particles (LLNPs) with masses in the multi-GeV range and decay lengths of O(100 m) or longer. These particles could be copiously produced at the LHC, but the decay products cannot be detected with the ATLAS or CMS detectors. MATHUSLA is a proposed large-volume surface detector installed near ATLAS or CMS aimed to probe scenarios with LLNPs which offers good prospects for disentangling the physics underlying two-body decays into visible particles. In this work we focus on LLNP decays into three particles with o…
In this work, we study the lepton number violating W boson and top quark decays via intermediate on-shell Majorana neutrinos Nj into three charged leptons and a light neutrino. We discuss the neutrino oscillation effects present in the decay due to the small mass gap between the heavy neutrino states. We focus on a scenario that contains at least two heavy Majorana neutrinos in the mass range 2-80 GeV. The results indicate that the modulation of the branching ratios as a function of the distance between the vertices may be detected in a future experiment such as High-Luminosity Large Hadron Co…
Motivated by the recent LHCb measurements on $\bar{B}_{s}$ $\to$ $π^{-}K^{*+}$ and $\bar{B}_{s}$ $\to$ $K^{\pm}K^{*\mp}$ decay modes, we revisit the $B_{s}$ $\to$ $PV$ decays within QCD factorization framework. The effects of hard-spectator scattering and annihilation corrections are studied in detail. After performing a $χ^2$-fit on the end-point parameters $X_A^{i,f}$ ($ρ_A^{i,f}$, $ϕ_A^{i,f}$) and $X_H$ ($ρ_H$, $ϕ_H$) with available data, it is found that although some possible mismatches exist, the universalities of $X_A^{i,f}$ and $X_H$ in $B_s$ and $B_{u,d}$ systems are still allowed wit…
We examine the possibility of using rare, 3-body decays of a new neutral gauge boson, \ztwo, to probe its gauge couplings at hadron colliders. Specifically, we study the decays $\ztwo\to W\ellν$ and $\ztwo\to Zν\barν$ and find that much knowledge of the \ztwo\ properties can be obtained from these processes. In particular, these decay modes can yield valuable information on the amount of $Z_1-Z_2$ mixing, on the generation dependence of the \ztwo\ couplings, on the properties of the new generator associated with the \ztwo, as well as being used to distinguish between possible extended models. …
We study the prospects of probing the anomalous $tHq$~($q= u, c$) couplings via SS2L or 3L signatures at the High Luminosity (HL-LHC) run of the 14 TeV CERN collider. We focus on signals of the $tH$ associated production followed by the decay modes $t\to b\ell^{+}ν_{\ell}$ and $H\to WW^{\ast}$, and $t\bar{t}$ production followed by the decay modes $t\to b\ell^{+}ν_{\ell}$ and $\bar{t}\to H(\to WW^{\ast})\bar{q}$, where $\ell=e, μ$. Based on two types of $H\to WW^{\ast}$ decay topologies, one assuming the semileptonic decay mode $H\to WW^{\ast}\to \ell^{+}νjj $ and the other the fully leptonic …
Polarized $Λ_b \to Λγ$ decays at the Z pole are shown to be well suited for probing a large variety of New Physics effects. A new observable is proposed, the angular asymmetry between the $Λ_b$ spin and photon momentum, which is sensitive to the relative strengths of the opposite chirality and Standard Model chirality $b \to s γ$ dipole operators. Combination with the $Λ$ decay polarization asymmetry and comparison with the $Λ_b$ polarization extracted from semileptonic decays allows important tests of the $V-A$ structure of the Standard Model. Modifications of the rates and angular asymmetrie…
Probing Bose-enhanced Inflaton Decay with Gravitational Waves
New York University Abu Dhabi（阿布扎比纽约大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；Kaiping Neutrino Research Center（开平中微子研究中心）；McGill University（麦吉尔大学）
Flavour changing neutral current (FCNC) transitions $c\to uγ$ and $c\to ul^+l^-$ are very rare in the standard model and present an interesting probe for the physics beyond it. We study long distance contamination to these short distance processes in different hadron decays. As the most suitable probe for $c\to uγ$ transition we propose $B_c\to B_u^*γ$ decay. Its detection at the branching ratio well above $10^{-8}$ would signal new physics. The $c\to ul^+l^-$ transition may be probed at high $m_{ll}$ in $D\to πl^+l^-$. The decays $D\to Vγ$ and $D\to Vl^+l^-$ ($V$ is a light vector meson) are …
We consider the radiative transition $ϕ\to f_0 γ$, which is a sensitive probe of the nature of the $f_0(980)$ particle. Using the QCD sum-rule technique, we estimate the branching ratio of such decay mode to be: ${\cal B}(ϕ\to f_0 γ)=(2.7 \pm 1.1) ~ 10^{-4}$, in fair agreement with present experimental data. As for the structure of the $f_0$, the result suggests a sizeable $s {\bar s}$ component; however, this result does not exclude the possibility of further components and allows a more complex structure than indicated by the naive quark model.
Probing the neutrino mass through semileptonic meson decays
IJCLab, Pôle Théorie (Bat. 210), CNRS/IN2P3 et Université Paris-Saclay（巴黎萨克雷大学）；Department of Physics, University of Ljubljana（卢布尔雅那大学）；Jožef Stefan Institute（约瑟夫·斯特凡研究所）
With the first evidence of direct CP violation in $D^0 \to K^+K^-/π^+π^-$ there is a strong reason to probe CP asymmetries in charm baryons in three-body final states $Λ_c \to pπ^+π^-/pK^+K^-$ & $Λ_c \to pK^+π^-$ with $Λ_c \to pK^-π^+$ to calibrate them. Analyzing the Dalitz plots carefully allows to find the 'existence' of New Dynamics (ND) and its `features'. One can test different methods to probe CP asymmetries. Final data from CDF and D0 experiments have advantage by comparing $Λ_c $ with $\bar Λ_c $ directly from $p \bar p $ collisions. LHCb will need more data with $\bar Λ_c$ transition…
Rare leptonic kaon and pion decays $K^+(π^+) \to μ^+\, ν_μ\, e^+ e^-$ can be used to probe a dark photon of mass ${\cal O}(10)$~MeV, with the background coming from the mediation of a virtual photon. This is most relevant for the 16.7-MeV dark photon proposed to explain a 6.8$σ$ anomaly recently observed in $^8$Be transitions by the Atomki Collaboration. We evaluate the reach of future experiments for different scenarios of how the dark photon couples with the standard model particles, and show that a great portion of the preferred 16.7-MeV dark photon parameter space can be decisively probed.…
Supersymmetry with bilinear R-parity violation provides a predictive framework for neutrino masses and mixings in agreement with current neutrino oscillation data. The model leads to striking signals at future colliders through the R-parity violating decays of the lightest supersymmetric particle. Here we study charged scalar lepton decays and demonstrate that if the scalar tau is the LSP (i) it will decay within the detector, despite the smallness of the neutrino masses, (ii) the relative ratio of branching ratios Br({tilde tau}_1 --> e sum nu_i)/ Br({tilde tau}_1 --> mu sum nu_i) is predicte…
We study lepton number violating decays of charged K, D, D_s, B and B_c mesons of the form M^+\to {M'}^-\ell^+\ell^+, induced by the existence of Majorana neutrinos. These processes provide information complementary to neutrinoless double nuclear beta decays, and are sensitive to neutrino masses and lepton mixing. We explore neutrino mass ranges m_N from below 1 eV to several hundred GeV. We find that in many cases the branching ratios are prohibitively small, however in the intermediate range m_π< m_N < m_{B_c}, in specific channels and for specific neutrino masses, the branching ratios can b…
We study the decay rate of process B->K l+ l- (l=e,mu) and some of its other related observables, like forward backward asymmetry (A_{FB}), polarization asymmetry (PA) and CP-asymmetry (A_{CP}) in R-parity violating (R_{p}) Minimal Supersymmetric Standard Model (MSSM). The analysis shows that R_{p}Yukawa coupling products contribute significantly to the branching fraction of B->K l+ l- within 1 sigma and 2 sigma. Study shows that PA and A_{FB} are sensitive enough to R_{p}Yukawa coupling products and turn out to be good predictions for measurement in future experiments.The CP-asymmetry calcula…
The decays $B^\pm\to π^\pm K$ and $B_d\to π^\mp K^\pm$ were observed by the CLEO collaboration last year; they may play an important role to probe the angle $γ$ of the unitarity triangle of the CKM matrix. After a general parametrization of their decay amplitudes within the Standard Model, strategies to constrain and determine the CKM angle $γ$ with the help of the corresponding CP-conserving and CP-violating observables are briefly reviewed. The theoretical accuracy of these methods is limited by certain rescattering and electroweak penguin effects. It is emphasized that the rescattering proc…
We examine whether the parameters in the Higgs sector of the minimal supersymmetric standard model can be determined by detailed study of production cross section and decay branching ratios of the Higgs particle. Assuming that the lightest CP-even Higgs boson ($h$) is observed at a future $e^+ e^-$ linear collider with $\sqrt{s}=300\sim500$GeV, we show that the value of CP-odd scalar mass is determined from the ratio of the two branching ratios, $Br(h\to b\bar{b})$ and $Br(h\to c\bar{c})+Br(h\to gg)$, almost independently of the stop mass scale.
We consider the decay of a generic resonance to two visible particles and any number of invisible particles. We show that the shape of the invariant mass distribution of the two visible particles is sensitive to both the mass spectrum of the new particles, as well as the decay topology. We provide the analytical formulas describing the invariant mass shapes for the nine simplest topologies (with up to two invisible particles in the final state). Any such distribution can be simply categorized by its endpoint, peak location and curvature, which are typically sufficient to discriminate among the…
We explore the anomalous right-handed $\bar{t}sW$ and $\bar{t}bW$ couplings using $ B \to X_s γ$ and $B \to X_s l^+ l^-$ decays induced by the flavour-changing penguin diagrams. The anomalous $\bar{t}sW$ coupling can yield 10% enhancement of the $B \to X_s l^+ l^-$ decay rate under the constraint from the present $B \to X_s γ$ data, while it does not affect the forward-backward asymmetry of the charged lepton. The allowed region for anomalous $\bar{t}bW$ coupling by the $ B \to X_s γ$ constraint is two-fold, the small value region and the large value region. Though the effect of the small anom…
The experimental prospects for precise measurements of the leptonic decays B_u -> tau nu / mu nu, B_s -> mu+ mu-, D -> mu nu and D_s -> mu nu / tau nu are very promising. Double ratios involving four of these decays can be defined in which the dependence on the values of the decay constants is essentially eliminated, thus enabling complementary measurements of the CKM matrix element V_ub with a small theoretical error. We quantify the experimental error in a possible future measurement of |V_ub| using this approach, and show that it is competitive with the anticipated precision from the conven…
$SU(2)_L$-invariance links charged dilepton $\bar q\,q^\prime\,\ell^+\,\ell^-$ and dineutrino $\bar q\, q^\prime\, \barν\,ν$ couplings. This connection can be established using the Standard Model Effective Field Theory framework, and allows to perform complementary experimental tests of lepton universality and charged lepton flavor conservation with flavor-summed dineutrino observables. We present its phenomenological implications for the branching ratios of rare charm decays $c\to u\,ν\,\barν$ and rare $B$ decays $b\to s\,\barν\,ν$ decays.
Probing scalar and pseudoscalar new physics using rare kaon decays
INFN-Sezione di Napoli（意大利国家核物理研究所那不勒斯分部）；Indian Institute of Technology Delhi（德里印度理工学院）；Université Claude Bernard Lyon 1, CNRS/IN2P3, Institut de Physique des 2 Infinis de Lyon（里昂第一大学，法国国家科学研究中心/法国国家粒子物理研究所，里昂双无穷物理研究所）；CERN（欧洲核子研究组织）；Institut Universitaire de France (IUF)（法国高等研究院）
Motivated by the recent hints of lepton flavor universality violation observed in semileptonic $B$ decays, we analyze how to test flavor and helicity structures of the corresponding amplitudes in view of future data. We show that the general assumption that such non-standard effects are controlled by a $U(2)_q \times U(2)_\ell$ flavor symmetry, minimally broken as in the Standard Model Yukawa sector, leads to stringent predictions on leptonic and semileptonic $B$ decays. Future measurements of $R_{D^{(*)}}$, $R_{K^{(*)}}$, ${\mathcal B}(\bar B_{c,u}\to \ell \bar ν)$, ${\mathcal B}(\bar B \to π…
