Recent measurements of $b$-hadron decays show a pattern of consistent tensions with the respective Standard Model (SM) predictions. These tensions appear both in the sector of rare flavour-changing neutral currents and in tree-level semileptonic $b$-hadron decays. Flavour-changing neutral-current decays are loop-suppressed in the SM and are thus very susceptible to contributions from new heavy particles and/or new interactions beyond the SM.
In rare semileptonic decays tensions are observed in measurements of branching fractions and angular observables, as well as in lepton flavour universality tests. Lepton flavour universality is also tested by comparing tree-level $b\to c\ell^-\barν_τ$ processes involving third generation leptons $\ell=τ$ to semileptonic decays with light leptons $\ell=e,μ$ in the final state. These tests also show tensions between measurements and the SM prediction.
Taken together, these tensions constitute the so-called flavour anomalies in $b$-hadron decays, and could be first signs of New Physics (NP) beyond the SM, if established beyond any reasonable doubt. This article reviews both the current experimental status of the flavour anomalies and developments for the relevant theoretical predictions. The review concludes with a discussion of future prospects for the field.
Leptoquarks with masses at the TeV scale have been proposed as possible solutions to flavor anomalies reported in the b-flavor sector. Based on data taken in proton-proton collisions at $\sqrt{s} = 13\,\mathrm{TeV}$ at the LHC, different leptoquark flavors can be probed in various final states. In this article, the results of direct searches for single and pair production of leptoquarks conducted by the ATLAS and CMS Collaborations are summarized.
We show that one can explain the neutral and charged anomalies in B-meson decays in the minimal theory for quark-lepton unification.The implications for flavor violating processes are discussed in detail. Strikingly, experimental observations suggest that the unification of quarks and leptons could be realized below the ${\cal O}(10^2)$ TeV scale.
The $3.1σ$ $R_K$ anomaly after Moriond 2021 and $3.3 σ$ $Δa_μ$ from Fermilab Muon g-2 experiment implicate that the lepton flavor universality violation (LFUV) may play a role in the exploration of new physics. A Flavor Gauged Two-Higgs Doublet Model (FG2HDM) is proposed and investigated in this work. To get rid of the the redundancy in Yukawa coupling of 2HDM-III, a specific U(1) flavor symmetry is introduced. The charge difference between two scalar doublet forbid the appearance of pseudoscalar and hence there are only three particles (a charged and neutral heavy scalar together with a neutr…
The recent results from the Fermilab muon $g-2$ experiment, as well as the persisting hints of lepton flavor universality violation in $B$-meson decays, present a very strong case for flavor-nonuniversal new physics beyond the Standard Model. We assert that a minimal $R$-parity violating supersymmetric scenario with relatively light third-generation sfermions (dubbed as 'RPV3') provides a natural, well-motivated framework for the simultaneous explanation of all flavor anomalies, while being consistent with a multitude of low-energy flavor constraints, as well as with limits from high-energy co…
We study a class of DFSZ-like models for the QCD axion that can address observed anomalies in stellar cooling. Stringent constraints from SN1987A and neutron stars are avoided by suppressed couplings to nucleons, while axion couplings to electrons and photons are sizable. All axion couplings depend on few parameters that also control the extended Higgs sector, in particular lepton flavor-violating couplings of the Standard Model-like Higgs boson $h$. This allows us to correlate axion and Higgs phenomenology, and we find that that ${\rm BR}(h \to τe)$ can be as large as the current experimental…
We discuss the minimal theory for quark-lepton unification at the low scale. In this context, the quarks and leptons are unified in the same representations and neutrino masses are generated through the inverse seesaw mechanism. The properties of the leptoquarks predicted in this theory are discussed in detail and we investigate the predictions for the leptonic and semi-leptonic decays of mesons. We study the possibility to explain the current value of $\mathcal{R}_K$ reported by the LHCb collaboration and the value of the muon anomalous magnetic moment reported by the Muon $g-2$ experiment at…
Heavy flavour physics is well described by the Standard Model with the exception of some measurements which could be pointing to new physics. We briefly review status and prospects of $R(D^{(\ast)})$ and $R(K^{(\ast)})$ anomalies and also address the long standing tension in the $|V_{cb}|$ and $|V_{ub}|$ exclusive/inclusive determinations.
Driven by the recent experimental hints of lepton-flavor-universality violation in the bottom-quark sector, we consider a simple extension of the Standard Model (SM) with an additional vector leptoquark $V_{\rm LQ}({\bf 3},{\bf 1},2/3)$ and a scalar diquark $S_{\rm DQ}({\bf 6},{\bf 1},4/3)$ under the SM gauge group $SU(3)_c\times SU(2)_L\times U(1)_Y$, in order to simultaneously explain the $b \to s \ell^+ \ell^-$ (with $\ell=e,μ$) and $b \to c l^- \bar ν_l$ (with $l=e,μ,τ$) flavor anomalies, as well as to generate small neutrino masses through a two-loop radiative mechanism. We perform a glob…
We develop an economical theoretical framework for combined explanations of the flavor physics anomalies involving muons: $(g-2)_μ$, $R_{K^{(*)}}$, and $b \to s μ^+ μ^-$ angular distributions and branching ratios, that was first initiated by some of us in Ref. [1]. The Standard Model (SM) is supplemented with a lepton-flavored $\mathrm{U}(1)_X$ gauge group. The $\mathrm{U}(1)_X$ gauge boson with the mass of $\mathcal{O}(0.1)$ GeV resolves the $(g-2)_μ$ tension. A TeV-scale leptoquark, charged under the $\mathrm{U}(1)_X$, carries a muon number and mediates $B$-decays without prompting charged l…
We analyze the recent hints of lepton flavor universality violation in both charged-current and neutral-current rare decays of $B$-mesons in an $R$-parity violating supersymmetric scenario. Motivated by simplicity and minimality, we had earlier postulated the third-generation superpartners to be the lightest (calling the scenario "RPV3") and explicitly showed that it preserves gauge coupling unification and of course has the usual attribute of naturally addressing the Higgs radiative stability. Here we show that both $R_{D^{(*)}}$ and $R_{K^{(*)}}$ flavor anomalies can be addressed in this RPV…
The updated measurements from the LHCb and SH0ES collaborations have respectively strengthened the deviations of the ratio $R_{K}$ in rare semi-leptonic $B$-meson decays and the present-day Hubble parameter $H_0$ in the Universe, implying tantalizing hints of new physics beyond the Standard Model. In this paper, we consider a simple flavor-specific two-Higgs-doublet model, where the long-standing $R_{K^{(*)}}$ anomalies can be addressed by a one-flavor right-handed neutrino. One of the intriguing predictions resulting from the parameter space for the $R_{K^{(*)}}$ resolution under flavor- and …
Using Soft-Collinear Effective Theory, we develop the transverse-momentum-dependent factorization formalism for heavy flavor dijet production in polarized-proton-electron collisions. We consider heavy flavor mass corrections in the collinear-soft and jet functions, as well as the associated evolution equations. Using this formalism, we generate a prediction for the gluon Sivers asymmetry for charm and bottom dijet production at the future Electron-Ion Collider. Furthermore, we compare theoretical predictions with and without the inclusion of finite quark masses. We find that the heavy flavor m…
Heavy flavor production at the future Electron-Ion Collider (EIC) will allow us to precisely determine the quark/gluon fragmentation processes in vacuum and the nuclear medium especially within the poorly constrained kinematic region. Heavy flavor hadron and jet reconstruction with the recent EIC detector design have been studies in simulation. Results of corresponding physics projections such as the flavor dependent hadron nuclear modification factor $R_{eA}$ in electron+nucleus collisions will be shown. The statistical precision obtained by these proposed heavy flavor measurements for the fu…
In these proceedings, we report on the production of various open heavy-flavor hadrons and quarkonia in Au+Au collisions at sNN = 200GeV from the STAR experiment.
We review our transverse momentum dependent factorization and resummation formalism for heavy flavor dijet production at the EIC. In this formalism, we have calculated the heavy flavor mass corrections in the collinear-soft and jet functions, and in the resummed expression for the cross section. By establishing this formalism, we then study the effects of the mass corrections by providing predictions at the EIC for the massive case and for the case where the mass is neglected. We find that the heavy flavor mass effects can give sizable corrections to the predicted asymmetry.
We proposed a unified framework to describe the interactions of the observed $T_{cc}$, $P_c$, and $P_{cs}$ within a quark level interaction in our previous work. In this work, we generalize our framework to the loosely bound hadronic molecules composed of heavy flavor di-hadrons with strangeness. We predict the possible $D^{(*)}D^{(*)}_s$ molecular states in the SU(3) limit with the masses of the $P_c$ states as the inputs. We also investigate the baryon-meson and baryon-baryon systems and consider the SU(3) breaking effect in their flavor wave functions. We generalize our isospin criterion of…
Recent high precision determinations of $V_{us}$ and $V_{ud}$ indicate towards anomalies in the first row of the CKM matrix. Namely, determination of $V_{ud}$ from superallowed beta decays and of $V_{us}$ from kaon decays imply a violation of first row unitarity at about $4σ$ level. Moreover, there is tension between determinations of $V_{us}$ obtained from leptonic $K\mu2$ and semileptonic $K\ell3$ kaon decays. These discrepancies can be explained if there exist extra vector-like quarks at the TeV scale, which have large enough mixings with the lighter quarks. In particular, extra vector-like…
In recent years, exciting (indirect) hints for physics beyond the Standard Model (SM) have been accumulated. In particular, semi-leptonic $B$ decays show deviations from the SM predictions, which, due to the ratios $R(K^{(*)})$ and $R(D^{(*)})$ are obviously related to lepton flavour universality violation (LFUV). However, {we point out} there are more anomalies which admit an interpretation in terms of LFUV: The anomalous magnetic moment of the muon, the Cabibbo angle anomaly, the CMS measurements of non-resonant di-electrons, the difference of the forward-backward asymmetry in $B\to D^*\ellν…
Heavy-flavored hadrons are unique probes to study the properties of hot and dense QCD medium produced in ultra-relativistic heavy-ion collisions at RHIC and the LHC. Transverse spherocity is one of the event-topology variables used to separate jetty and isotropic events from the pool of event samples. This study aims to understand the production dynamics of heavy-flavors through the transverse momentum spectra, double differential yield and mean transverse momentum of J/$ψ$, $\rm D^{0}$ and $Λ_{c}^{+}$ as a function of charged-particle multiplicity and transverse spherocity. Further to investi…
