flavour anomaly



Fields and quanta

field (physics)

standard model of particle physics

force field gauge bosons

scalar bosons

matter field fermions (spinors, Dirac fields)

flavors of fundamental fermions in the
standard model of particle physics:
generation of fermions1st generation2nd generation3d generation
quarks (qq)
up-typeup quark (uu)charm quark (cc)top quark (tt)
down-typedown quark (dd)strange quark (ss)bottom quark (bb)
neutralelectron neutrinomuon neutrinotau neutrino
bound states:
mesonslight mesons:
pion (udu d)
ρ-meson (udu d)
ω-meson (udu d)
ϕ-meson (ss¯s \bar s),
kaon, K*-meson (usu s, dsd s)
eta-meson (uu+dd+ssu u + d d + s s)

charmed heavy mesons:
D-meson (uc u c, dcd c, scs c)
J/ψ-meson (cc¯c \bar c)
bottom heavy mesons:
B-meson (qbq b)
ϒ-meson (bb¯b \bar b)
proton (uud)(u u d)
neutron (udd)(u d d)

(also: antiparticles)

effective particles

hadron (bound states of the above quarks)


minimally extended supersymmetric standard model




dark matter candidates


auxiliary fields



In the current standard model of particle physics the fundamental particles in the three generations of fermions have identical properties from one generation to the next, except for their mass, a state of affairs referred to as lepton flavour universality (LFU). A possible violation of lepton flavour universality is called a flavour anomaly, which would be a sign of “New Physics” (NP) beyond the standard model.

The presence – or not – of flavour anomalies is part of the general flavour problem of the standard model of particle physics.

Flavor universality pertains in particular to (semi-)leptonic decays of bottom quarks, denoted bb (in the third generation), into electron/positron pairs, denoted e +e e^+ e^- (in the first generation) or muon/antimuon pairs, denoted μ +μ \mu^+ \mu^- (in the second generation), the latter two jointly denoted + \ell^+ \ell^- (for “leptons”) in this context.

Since quarks never appear in isolation (due to confinement) but always as bound states to hadrons, decays specifically of bottom quarks manifest themselves in leptonic decays of mesons that contain bbB-mesons, denoted BB

from Cartelle 18

or as leptonic decays of baryons that contain bbLambda baryons, denoted Λ b\Lambda_b (measured only more recently (LHCb 19120.8139)).

Hence flavour universality in the standard model of particle physics demands, for example, that the ratios of decay rates (branching fractions) of B-mesons into electrons are the same as into muons, hence that the ratio

(1)R K=BKμ +μBKe +e R_K \;=\; \frac{ B \to K \mu^+ \mu }{ B \to K e^+ e^- }

(where KK is a kaon, a meson containing a strange quark)

is essentially equal to 1. Any significant departure of this observable from 1 would be a flavour anomaly and would mean that there are fundamental processes at play which are not described by the current standard model of particle physics (“New Physics”).

Moreover, in the standard model the decays involved here are “forbidden” (have vanishing decay rate) at tree level, so that only loop orders contribute to any possible flavour anomaly. But these loop contributions are sensitive to effects from putative undiscovered fundamental particles which “run in the loops” as virtual particles, and which thus may show up as a flavour anomaly even if their mass is too large for them to be seen as scattering products (i.e. as actual, non-virtual particles). This way tests of lepton flavour universality provide a means to potentially detect New Physics with indirect high-luminosity/high-precision experiment (see e.g. Brambilla et al. 14, Section 5 AHRS 20), complementary to the traditional high-energy direct detection measurements.

Notice that the channel R KR_K (1) is just one of many in which flavour anomalies may and have been seen. There are other decay channels of B-mesons and there are also flavour anomalies in decays of, for instance, kaons (Buras 16, Buras 18).

See Alonso 19 for general introduction to an audience with basic background in quantum field theory.

Statistical significance

Indications of flavour anomalies have been observed consistently and with increasing statistical significance around 2.532.5-3 σ in B meson processes in various decay channels and by a number of independent experiments: the LHCb experiment, the Belle experiment and the BaBar experiment:

table grabbed from BGV 19

The global (all channels and experiments combined) tension with the standard model by end of 2018 had statistical significance around 4.14.1 σ (Strumia et al. 17, Cartelle 18, slide 22/25, Dey 18, slide 16/23, HAMN 18, p. 4, Bouchard-Cao-Owen 19). Various authors see the global tension (i.e. of all decay channels jointly) at over 5σ5 \sigma (CCDGMV 17, CFMVV 17 CGMS 18, Dordei 18, slide 12), which traditionally qualifies as detection (see here), some authors already quote 5.3σ5.8σ5.3 \sigma - 5.8 \sigma (ACDGMM 19) or 56σ5-6 \sigma (Kumar-London 19, Kumar 19).

graphics grabbed from Dey 18

This situation was confirmed with the completed measurements presented at Moriond 2019, which showed (Straub 19, Allanach 19) smaller mean discrepancy but also had smaller uncertainty, thus keeping the statistical significance of the apparent anomaly essentially unaffected. But Caria 19, slide 9 reported new measurements by Belle (Belle 1910) according to which the previous statistical significance of 3.8σ3.8 \sigma in the R DR_D channel would decrease to 3.1σ3.1 \sigma or 2.8σ2.8 \sigma (Gambino-Jung-Schacht 19 (6)). See LHCb 19, p. 2 for how the new numbers come about. The statistical significance over all sectors is still seen >4σ\gt 4 \sigma (London 19, p. 7) or 3σ\sim 3\sigma (Jaiswal-Nandi-Patra 20). Moreover, the theoretical prediction is being corrected further away from these measured values (BDKL 20, footnote 1).

Comprehensive assessments of the situation after Moriond 2019 are given in AHMSN 19, Descotes-Genon 19, Bardhan-Ghosh 19, Alguero 19 and agree that the flavour anomalies have been confirmed:

It appears the reason is that, given the amount of independent measurements (~180!) a smaller deviation because of new physics is easier to accommodate than a large one. Thus the new measurements actually fit better with new physics.

(Axel Maas, reporting from ALPS2019, tweet, 23 Apr 2019)

graphics grabbed from Zupan 19, see also LHCb19, Fig. 5

Similarly Smith 20 on behalf of LHCb 2003.04831 (see also Lopes 20, CERN Courier 200311):

The statistical significances of pull away from the standard model for effective New Physics models:

from Alguero 19
from Koppenburg 20

There is the claim (DGKV 19) that the discrepancy with the standard model increases further if non-trivial hadronic form factors are taken into account:

from Descotes-Genon 19b

and also that the discrepancy increases further with QED-corrections taken into account (Mishra-Mahajan 20,p. 20-21).

If the ongoing evaluation of the data of LHC‘s Run 2 confirms the measurements of Run 1, then the statistical significance of the effect in each decay channel separately should have reached 5 σ (Crivellin et. al 18, p. 12, Zupan 19, 4.6) and hence conventionally count as detection of flavour anomaly (see here), which would make it the first established “new physics” seen at the LHC. More recent extrapolation based on LHCb Collaboration 18 predicts a statistical significance between 6 and 10 σ\sigma by the year 2025 (LKLR 19, p. 12).

In fact, it had been argued prior to the detection of the anomalies (Lyons 13b, Dorigo 15) that due to the specific nature of the experiment, the statistical significance-threshold for detection of anomalies in B meson-decays should not be taken to be 5σ5 \sigma, but just 3σ3 \sigma, hence well exceeded already by the experimentally seen statistical significance:

table taken from Lyons 13b, p. 4

table taken from Dorigo 15, p. 16

This attitude is reflected in SGGJC 19, p. 2:

For some time now, the ratios of semileptonic B-decay rates have appeared to be enhanced with respect to the Standard Model (SM) predictions with a global significance above the evidence threshold.

Status and Outlook

In conclusion, with currently available data, the observed flavour anomalies are possible signs of New Physics beyond the current standard model of particle physics.

graphics taken from Dordei 18, slide 22

from Tuning 20

While the statistical significance of the flavour anomalies in every single decay channel is about 2σ3σ2\sigma - 3 \sigma, the effects are all compatible with each other, with a high joint/global statistical significance:

Garisto 20: Alone, each notable B physics result is only a few-sigma discrepancy. But taken together, the aggregate of the results is—depending on whom you ask—a 5- to 7-sigma deviation from the standard model estimates.

In any case, further and more sensitive experiments are needed to confirm and explore the effect, such as possibly the “HL-LHC” or “HE-LHC” experiment. General outlook, prospects and suggestions for future collider design in this respect are discussed in detail in Allanach-Gripaios-You 17, Crivellin et al. 18.

From Isidori 19, slide 6:

Outlook on the Belle II experiement to confirm the flavour anomalies, if real (HHJLQV 20):

With [[]] Belle II, we are at the brink of a new era in quark flavour physics [...][...] we present a phenomenological study of the potential for Belle II to reveal possible new physics in the inclusive decay channel

(p. 15:) We see that anomalies in the exclusive sector can be confirmed at the level by inclusive measurements if the true values of C 9,10 μNPC_{9,10}^{\mu NP} are at the current best-fit point of the exclusive fits

(p. 16:) After including B sμ +μ B_s \to \mu^+ \mu_-, the reach in the [C 9 μNP,C 10 μNP][C_9^{\mu NP}, C_{10}^{\mu NP}] plane improves considerably. Exclusive anomalies could be confirmed at the level.

(p. 20:) Should the true value of C 9 NPC_9^{NP} and C 10 NPC_{10}^{NP} be at the current best-fit points of the global fits, an analysis of inclusive B¯ X s + \bar B_ \to X_s \ell^+ \ell^- at Belle II with 50ab 150 ab^{-1} of data will exclude the SM point C 9 NP=C 10 NP=0C_9^{NP} = C_{10}^{NP} = 0 at the level of 5\sim 5σ. This again underlines the necessity of a full angular analysis of B¯ X s + \bar B_ \to X_s \ell^+ \ell^- at Belle II.

Relation to other anomalies

There is possibly a relation between the flavour anomalies and the anomalies observed in the anomalous magnetic moment of the electron and/or the muon (e.g. Chiang-Okada 17) which might point to a common origin of these anomalies in the flavour sector (e.g. Crivellin-Hoferichter 20):

graphics from Crivellin-Hoferichter 20

(here “RR” refers to flavour anomalies in various channels, “aa” refers to anomalies in the the anomalous magnetic moments of the electron and the muon, “LFUV” is shoft for “Lepton Flavor Universality Violation”, and the numbers are the statistical significances of the effects seen)

Indeed, leptoquark models preferred by the flavour anomalies (see below) are also a candidate explanation of the anomaly seen at over 4σ\sigma statistical significance in the anomalous magnetic moment of the muon, see there.

Possible models

Candidate models of “New Physics” beyond the standard model of particle physics that could possibly explain the flavour anomalies (if indeed they are real) includes the following:

Leptoquarks and Grand unified theory

One promising model that could potentially explain the apparently observed flavour anomalies are leptoquarks, which naturally arise in, and hence potentially point to, grand unified theory models, such as notably the Pati-Salam model (Heek-Teresi 18, Heek-Teresi 19)

(see Bauer-Neubert 15, CCDM 16, Crivellin 17, Falkowski17, Mueller 18, Matsuzaki-Nishiwaki 18, Monteux-Rajaraman 18, AMST 18, BDFKFS 18, Crivellin 18, MMR 18, Kumar-London 19, section 2.2.1, MVT 19, AMM 19, MVK 19, Cata-Mannel 19)

From Crivellin 18, p. 2:

the global fit [[ to flavour anomalies ]] even shows compelling evidence for New Physics [[]] The vector leptoquark (LQ) SU(2) LSU(2)_L singlet with hypercharge 4/3-4/3 arising in the famous Pati-Salam model is capable of explaining all the [[flavour ]] anomalies and therefore several attempts to construct a UV completion for this LQ to address the anomalies have been made. It can give a sizeable effect in bc(u)τνb \to c(u)\tau \nu data without violating bounds from bs(d)νν¯b \to s(d)\nu \bar \nu and/or direct searches, provides (at tree level) a C 9=C 10C_9 = - C_{10} solution to bs + b \to s \ell^+ \ell^- data and does not lead to proton decay at any order in perturbation theory.

From GMV 20, Figure 9, showing fits of leptoquark models (labeled S iS_i) to a variety of observables:


Other possible models besides leptoquarks (above) which have been proposed as possible explanations of the apparently observed flavour anomalies include the following:



Early suggestion to look at the R KR_K channel at LHCb are due to

General introduction to the issue is in

  • Simone Bifani, Sebastien Descotes-Genon, Antonio Romero Vidal, Marie-Helene Schune, Review of Lepton Universality tests in B decays, Journal of Physics G: Nuclear and Particle Physics, Volume 46, Number 2 (2018) (arXiv:1809.06229)

  • Rodrigo Alonso, Lepton (non-) unversality in (flavor changing) neutral current B decays, Proceedings of FPCP2019 (arXiv:1907.01716)

and for charm quark physics in

See also

Comprehensive overview of the latest world-averaged results to be found at:

Brief review from the point of view of non-perturbative QCD:

Experimental results

Review and outlook


Outlook for Belle II to confirm the flavour anomalies, if they are real:

  • Tobias Huber, Tobias Hurth, Jack Jenkins, Enrico Lunghi, Qin Qin, K.Keri Vos, Phenomenology of inclusive B¯X s + \bar B \to X_s \ell^+ \ell^- for the Belle II era (arXiv:2007.04191)

Emphasis of non-perturbative effects:

  • Ulrich Nierste, Flavour Anomalies: Phenomenology and BSM Interpretations, talk at Planck 2018, Bonn 2018 (pdf)

  • Saeed Kamali, New physics in inclusive semileptonic BB decays including nonperturbative corrections (arXiv:1811.07393)

Emphasis of higher loop order-effects:

  • Andreas Crivellin, Christoph Greub, Dario Müller, Francesco Saturnino, Importance of Loop Effects in Explaining the Accumulated Evidence for New Physics in B Decays with a Vector Leptoquark, Phys. Rev. Lett. 122, 011805 (2019) (arXiv:1807.02068)

Emphasis of effects of hadronic form factors:

  • Sébastien Descotes-Genon, Alexander Khodjamirian, Javier Virto, Light-Cone Sum Rules for BKπB \to K \pi Form Factors and Applications to Rare Decays (arXiv:1908.02267)

  • Sebastien Descotes-Genon, Light-cone sum rules for BKπB \to K \pi form factorsand applications to rare decays, talk at bsll2019 (pdf, pdf)

Emphasis of QED-corrections:

  • Dayanand Mishra, Namit Mahajan On the Impact of Soft Photons on BK + B \to K \ell^+ \ell^- (arXiv:2010.10853)

Original articles include:

  • Guido D’Amico, Marco Nardecchia, Paolo Panci, Francesco Sannino, Alessandro Strumia, Riccardo Torre, Alfredo Urbano,

    Flavour anomalies after the R K *R_{K^\ast} measurement,

    J. High Energ. Phys. (2017) 2017 (arXiv:1704.05438)

  • Andrea Mauri, Nicola Serra, Rafael Silva Coutinho, Towards establishing Lepton Flavour Universality violation in B¯K¯ * + \bar B \to \bar K^\ast \ell^+ \ell^- decays (arXiv:1805.06401)

  • Bernat Capdevila, Andreas Crivellin, Sébastien Descotes-Genon, Joaquim Matias, Javier Virto, Patterns of New Physics in bs + b \to s \ell^+ \ell^- transitions in the light of recent data, JHEP 1801 (2018) 093 (arXiv:1704.05340)

  • Alejandro Celis, Javier Fuentes-Martin, Avelino Vicente, Javier Virto, Gauge-invariant implications of the LHCb measurements on Lepton-Flavour Non-Universality, Phys. Rev. D 96, 035026 (2017) (arXiv:1704.05672)

  • Monika Blanke, Andreas Crivellin, Stefan de Boer, Teppei Kitahara, Marta Moscati, Ulrich Nierste, Ivan Nišandžić, Impact of polarization observables and B cτνB_c \to \tau \nu on new physics explanations of the bcτνb \to c \tau \nu anomaly (arXiv:1811.09603)

  • Monika Blanke, Andreas Crivellin, Stefan de Boer, Teppei Kitahara, Marta Moscati, Ulrich Nierste, Ivan Nišandžić, Addendum: “Impact of polarization observables and B cτνB_c \to \tau \nu on new physics explanations of the bcτνb \to c \tau \nu anomaly” (arXiv:1905.08253)

  • Jacky Kumar, David London, New physics in bse +e b \to s e^+ e^-?, Phys. Rev. D 99, 073008 (2019) (arXiv:1901.04516, doi:10.1103/PhysRevD.99.073008)

  • Domagoj Leljak, Blazenka Melic, Monalisa Patra, On lepton flavour universality in semileptonic B cη c,J/ψB_c \to \eta_c, J/\psi decays (arXiv:1901.08368)

  • Rui-Xiang Shi, Li-Sheng Geng, Benjamín Grinstein, Sebastian Jäger, Jorge Martin Camalich, Revisiting the new-physics interpretation of the bcτνb \to c \tau \nu data (arXiv:1905.08498)

Cautionary remarks include

In contrast, an argument that the threshold statistical significance for flavour anomalies should be taken to be 3σ3\sigma instead of 5σ5 \sigma is made in

Discussion of possible bdb \to d anomalies:

  • Aleksey V. Rusov, Probing New Physics in bdb \to d Transitions (arXiv:1911.12819)

In hadronic decays

  • Marzia Bordone, Nico Gubernari, Tobias Huber, Martin Jung, Danny van Dyk, A puzzle in B¯0(s)→D+(s){π−,K−} decays and extraction of the fs/fd fragmentation fraction (arXiv:2007.10338)

  • Syuhei Iguro, Teppei Kitahara, Implications for new physics from novel puzzle in B¯0(s)→D(∗)+(s){π−,K−} decays (arXiv:2008.01086)

  • Eleftheria Malami, Exploring New Physics in B→πK Decays (arXiv:2008.08468)

Relation to (g2)(g-2)-anomalies

Beyond their possible common origin in leptoquarks, further possible joint explanation of flavour anomalies and the anomalies observed in the muon anomalous magnetic moment:

  • Cheng-Wei Chiang, Hiroshi Okada, A simple model for explaining muon-related anomalies and dark matter (arXiv:1711.07365)

  • Junichiro Kawamura, Stuart Raby, Andreas Trautner, Complete Vector-like Fourth Family and new U(1)U(1)' for Muon Anomalies (arXiv:1906.11297)

  • Lorenzo Calibbi, M.L. López-Ibáñez, Aurora Melis, Oscar Vives, Muon and electron g2g-2 and lepton masses in flavor models (arXiv:2003.06633)

  • A. S. de Jesus, S. Kovalenko, F. S. Queiroz, K. Sinha, C. Siqueira, Vector-Like Leptons and Inert Scalar Triplet: Lepton Flavor Violation, g2g-2 and Collider Searches (arXiv:2004.01200)

  • Shaikh Saad, Combined explanations of (g2) μ(g-2)_\mu, R D *R_{D^\ast}, R K *R_{K^\ast} anomalies in a two-loop radiative neutrino mass model (arXiv:2005.04352)

  • K. S. Babu, P. S. Bhupal Dev, Sudip Jana, Anil Thapa, Unified Framework for BB-Anomalies, Muon g2g-2, and Neutrino Masses (arXiv:2009.01771)

Possible explanations/models

General EFT parameterization

General effective field theory parametrization:

  • T. Hurth, A. Arbey, F. Mahmoudi, S. Neshatpour, New global fits to bsb \to s data with all relevant parameters, Proceedings of the Seventh Workshop on Theory, Phenomenology and Experiments in Flavour Physics, Capri, 8-10 June 2018 (arXiv:1812.07602)

  • Srimoy Bhattacharya, Aritra Biswas, Zaineb Calcuttawala, Sunando Kumar Patra, An in-depth analysis of bc(s)b \to c(s) semileptonic observables with possible μτ\mu \to \tau mixing (arXiv:1902.02796)

  • Marcel Algueró, Bernat Capdevila, Sébastien Descotes-Genon, Pere Masjuan, Joaquim Matias, What R KR_K and Q 5Q_5 can tell us about New Physics in bsb \to s \ell \ell transitions? (arXiv:1902.04900)

  • Marcel Algueró, Bernat Capdevila, Andreas Crivellin, Sébastien Descotes-Genon, Pere Masjuan, Joaquim Matias, Javier Virto, Addendum: “Patterns of New Physics in bs + b \to s \ell^+ \ell^- transitions in the light of recent data” (arXiv:1903.09578)

  • Ashutosh Kumar Alok, Amol Dighe, Shireen Gangal, Dinesh Kumar, Continuing search for new physics in bμssb \to \mu s s decays: two operators at a time (arXiv:1903.09617)

  • Marco Ciuchini, António M. Coutinho, Marco Fedele, Enrico Franco, Ayan Paul, Luca Silvestrini, Mauro Valli, New Physics in bs + b \to s \ell^+ \ell^- confronts new data on Lepton Universality (arXiv:1903.09632)

  • Jason Aebischer, Wolfgang Altmannshofer, Diego Guadagnoli, Meril Reboud, Peter Stangl, David M. Straub, B-decay discrepancies after Moriond 2019 (arXiv:1903.10434)

  • Alakabha Datta, Jacky Kumar, David London, The BB Anomalies and New Physics in bse +e b \to s e^+ e^- (arXiv:1903.10086)

  • Ashutosh Kumar Alok, Dinesh Kumar, Suman Kumbhakar, S Uma Sankar, Impact of D *D^\ast polarization measurement on solutions to R DR_D-R D *R_{D^\ast} anomalies (arXiv:1903.10486)

  • Pere Arnan, Andreas Crivellin, Marco Fedele, Federico Mescia, Generic Loop Effects of New Scalars and Fermions in bs + b \to s \ell^+ \ell^- and a Vector-like 4th Generation (arXiv:1904.05890)

  • A. Arbey, T. Hurth, F. Mahmoudi, D. Martinez Santos, S. Neshatpour, Update on the bsb \to s anomalies (arXiv:1904.08399)

  • Pouya Asadi, David Shih, Maximizing the Impact of New Physics in bcτνb \to c \tau \nu Anomalies, (arXiv:1905.03311)

  • J. E. Chavez-Saab, Marxil Sánchez, Genaro Toledo, R D *R_{D^\ast} or R D πR_{D_\pi}: closing the theoretical gap? (arXiv:1905.03394)

  • Suman Kumbhakar, Ashutosh Kumar Alok, Dinesh Kumar, S Uma Sankar, Resolving R DR_D and R D *R_{D^\ast} anomalies (arXiv:1905.03513)

  • Jyoti Saini, Dinesh Kumar, Shireen Gangal, S. B. Dasm, Probing signatures of beyond standard model physics through B s *μ +μ B_s^\ast \to \mu^+ \mu^- decay (arXiv:1905.03933)

  • David London, CP Violation in B¯ 0D *+ ν¯ \bar B^0 \to D^{\ast +} \ell^- \bar \nu_\ell (arXiv:1906.07752)

  • Marta Moscati, New Physics in bcτνb \to c \tau \nu: Impact of Polarisation Observables and B cτνB_c \to \tau \nu (arXiv:1906.08035)

  • Damir Becirevic, Marco Fedele, Ivan Nisandzic, Andrey Tayduganov, Lepton Flavor Universality tests through angular observables of B¯D (*)ν¯\bar B \to D^{(\ast) \ell \bar \nu} decay modes (arXiv:1907.02257)

  • Ashutosh Kumar Alok, Suman Kumbhakar, S. Uma Sankar, Discriminating new physics scenarios in b→sμ+μ− via transverse polarization asymmetry of K∗ in B→K∗μ+μ− decay (arXiv:2001.04395)

  • Suman Kumbhakar, Ashutosh Kumar Alok, Dinesh Kumar, S. Uma Sankar, New Physics solutions for bcτν¯b \to c \tau \bar \nu anomalies after Moriond 2019 (arXiv:2001.06344)

  • Florian U. Bernlochner, Stephan Duell, Zoltan Ligeti, Michele Papucci, Dean J. Robinson, Das ist der HAMMER: Consistent new physics interpretations of semileptonic decays (arXiv:2002.00020)

  • Andrei Angelescu, Darius A. Faroughy, Olcyr Sumensari, Lepton Flavor Violation and Dilepton Tails at the LHC (arXiv:2002.05684)

  • Kingman Cheung, Zhuo-Ran Huang, Hua-Dong Li, Cai-Dian Lü, Ying-nan Mao, Ru-Ying Tang, Revisit to the bcτνb \to c \tau \nu transition: in and beyond the SM (arXiv:2002.07272)

  • Soumia Lebbal, Noureddine Mebarki, Jamal Mimouni, Lepton Flavor Universality Violation in a 331 Model in bsl +l b \to s l^+ l^- Processes (arXiv:2003.03230)

  • Rafael Aoude, Tobias Hurth, Sophie Renner, William Shepherd, The impact of flavour data on global fits of the MFV SMEFT (arXiv:2003.05432)

  • Aritra Biswas, Soumitra Nandi, Ipsita Ray, Sunando Kumar Patra, New physics in bsb\to s \ell \ell decays with complex Wilson coefficients (arXiv:2004.14687)

  • Bhubanjyoti Bhattacharya, Alakabha Datta, Saeed Kamali, David London, A Measurable Angular Distribution for B¯D *τ ν¯ τ\bar B \to D^\ast \tau^- \bar \nu_\tau Decays (arXiv:2005.03032)

  • N. Penalva, E. Hernández, J. Nieves, B¯ cη c\bar B_c \to \eta_c, B¯ cJ/ψ\bar B_c \to J/\psi and B¯D (*)\bar B \to D^{(\ast)} semileptonic decays including new physics (arXiv:2007.12590)

In relation to electroweak precision measurements:

  • Lina Alasfar, Aleksandr Azatov, Jorge de Blas, Ayan Paul, Mauro Valli, B anomalies under the lens of electroweak precision (arXiv:2007.04400)


explanation via assumption of leptoquarks:

  • Martin Bauer, Matthias Neubert, One Leptoquark to Rule Them All: A Minimal Explanation for R D (*)R_{D^{(\ast)}}, R KR_K and (g2) μ(g-2)_\mu, Phys. Rev. Lett. 116, 141802 (2016) (arXiv:1511.01900)

  • Yi Cai, John Gargalionis, Michael A. Schmidt, Raymond R. Volkas, Reconsidering the One Leptoquark solution: flavor anomalies and neutrino mass (arXiv:1704.05849)

  • Estefania Coluccio Leskow, Andreas Crivellin, Giancarlo D’Ambrosio, Dario Müller, (g2) μ(g-2)_\mu, Lepton Flavour Violation and Z Decays with Leptoquarks: Correlations and Future Prospects, Phys. Rev. D 95, 055018 (2017) (arXiv:1612.06858)

  • Andreas Crivellin, New Physics in Flavour Observables (arXiv:1706.00929)

  • Adam Falkowski, Leptoquarks strike back, November 2017

  • Dario Müller, Leptoquarks in Flavour Physics, EPJ Web of Conferences 179, 01015 (2018) (arXiv:1801.03380)

  • Shinya Matsuzaki, Kenji Nishiwaki, Kei Yamamoto, Simultaneous interpretation of K and B anomalies in terms of chiral-flavorful vectors (arXiv:1806.02312)

  • Angelo Monteux, Arvind Rajaraman, B Anomalies and Leptoquarks at the LHC: Beyond the Lepton-Quark Final State, Phys. Rev. D 98, 115032 (2018) (arXiv:1803.05962)

  • Ufuk Aydemir, Djordje Minic, Chen Sun, Tatsu Takeuchi, BB-decay anomalies and scalar leptoquarks in unified Pati-Salam models from noncommutative geometry, JHEP 09 (2018) 117 (arXiv:1804.05844)

  • Damir Bečirević, Ilja Doršner, Svjetlana Fajfer, Nejc Košnik, Darius A. Faroughy, Olcyr Sumensari, Scalar leptoquarks from GUT to accommodate the BB-physics anomalies, Phys. Rev. D 98, 055003 (2018) (arXiv:1806.05689)

  • Jacky Kumar, David London, Ryoutaro Watanabe, Combined Explanations of the bsμ +μ b \to s \mu^+ \mu^- and bcτ ν¯b \to c \tau^- \bar \nu Anomalies: a General Model Analysis, Phys. Rev. D 99, 015007 (2019) (arXiv:1806.07403)

    (reviewed in Kumar 19)

  • Tanumoy Mandal, Subhadip Mitra, Swapnil Raz, R D (*)R_{D^{(\ast)}} in minimal leptoquark scenarios: impact of interference on the exclusion limits from LHC data (arXiv:1811.03561)

  • Jason Aebischer, Andreas Crivellin, Christoph Greub, QCD Improved Matching for Semi-Leptonic B Decays with Leptoquarks (arXiv:1811.08907)

  • Michael J. Baker, Javier Fuentes-Martin, Gino Isidori, Matthias König, High-pT Signatures in Vector-Leptoquark Models (arXiv:1901.10480)

  • Ivo de Medeiros Varzielas, Jim Talbert, Simplified Models of Flavourful Leptoquarks (arXiv:1901.10484)

  • Natascia Vignaroli, Seeking leptoquarks in the tt¯t \bar t plus missing energy channel at the high-luminosity LHC (arXiv:1808.10309)

  • Ufuk Aydemir, Tanumoy Mandal, Subhadip Mitra, Addressing the R D (*)R_{D^{(\ast)}} anomalies with an S1 leptoquark from SO(10)SO(10) grand unification, Phys. Rev. D 101, 015011 (2020) (arXiv:1902.08108)

  • Ivo de Medeiros Varzielas, Stephen F. King, Origin of Yukawa couplings for Higgs and leptoquarks (arXiv:1902.09266)

  • Oscar Cata, Thomas Mannel, Linking lepton number violation with BB anomalies (arXiv:1903.01799)

  • Bhubanjyoti Bhattacharya, Alakabha Datta, Saeed Kamali, David London, CP Violation in B¯ 0D *+μ ν¯ μ\bar B^0 \to D^{\ast +} \mu^- \bar \nu_\mu (arXiv:1903.02567)

  • Han Yan, Ya-Dong Yang, Xing-Bo Yuan, Phenomenology of bcτν¯b \to c \tau \bar \nu decays in a scalar leptoquark model (arXiv:1905.01795)

  • Alakabha Datta, Divya Sachdeva, John Waite, A unified explanation of bsμ =μ b \to s\mu^= \mu^- anomalies, neutrino masses and BπKB \to \pi K puzzle (arXiv:1905.04046)

  • Andrei Angelescu, Single Leptoquark Solutions to the BB-physics Anomalies, contribution to the 2019 EW session of the 54th Rencontres de Moriond (arXiv:1905.06044)

  • Oleg Popov, Michael A. Schmidt, Graham White, R 2R_2 as a single leptoquark solution to R D (*)R_{D^{(\ast)}} and R K (*)R_{K^{(\ast)}} (arXiv:1905.06339)

  • Andreas Crivellin, Francesco Saturnino, Explaining the Flavor Anomalies with a Vector Leptoquark (Moriond 2019 update) (arXiv:1906.01222)

  • Michal Malinský, Lepton non-universality in BB-decays in the minimal leptoquark gauge model (arXiv:1906.09174)

  • Jordan Bernigaud, Ivo de Medeiros Varzielas, Jim Talbert, Finite Family Groups for Fermionic and Leptoquark Mixing Patterns (arXiv:1906.11270)

  • Junichiro Kawamura, Stuart Raby, Andreas Trautner, Complete Vector-like Fourth Family and new U(1)U(1)' for Muon Anomalies (arXiv:1906.11297)

  • Leandro Da Rold, Federico Lamagna, A vector leptoquark for the B-physics anomalies from a composite GUT (arXiv:1906.11666)

  • Jacky Kumar, Combined explanation of the B-anomalies, Proceedings for FPCP 2019 (arXiv:1907.00416)

    (review of KumarLondonWatanabe18)

  • C. Hati, J. Kriewald, J. Orloff, A.M. Teixeira, A nonunitary interpretation for a single vector leptoquark combined explanation to the B-decay anomalies (arXiv:1907.05511)

  • Javier Fuentes-Martin, Gino Isidori, Matthias König, Nudzeim Selimovic, Vector Leptoquarks Beyond Tree Level (arxiv:1910.13474)

  • Shaikh Saad, Anil Thapa, A Common Origin of Neutrino Masses and R D *R_{D^\ast}, R K *R_{K^\ast} Anomalies (arXiv:2004.07880)

  • P. S. Bhupal Dev, Rukmani Mohanta, Sudhanwa Patra, Suchismita Sahoo, Unified explanation of flavor anomalies, radiative neutrino mass and ANITA anomalous events in a vector leptoquark model (arXiv:2004.09464)

  • Suman Kumbhakar, Rukmani Mohanta, Investigating the effect of U 1U_1 vector leptoquark on buτν¯b \to u \tau \bar\nu mediated B decays (arXiv:2008.04016)

  • Valerio Gherardi, David Marzocca, Elena Venturini, Low-energy phenomenology of scalar leptoquarks at one-loop accuracy (arXiv:2008.09548)

leptoquarks within a Randall-Sundrum model:

leptoquarks particularly as fields in a grand unified theory:

  • Julian Heeck, Daniele Teresi, Pati-Salam explanations of the B-meson anomalies, JHEP 12 (2018) 103 (arXiv:1808.07492)

  • Julian Heeck, Daniele Teresi, Pati-Salam and lepton universality in B decays (arXiv:1905.05211)

  • Shyam Balaji, Michael A. Schmidt, A unified SU(4)SU(4) theory for the R D (*)R_D^{(\ast)} and R K (*)R_K^{(\ast)} anomalies (arXiv:1911.08873)

and in relation to axions:

  • Javier Fuentes-Martin, Mario Reig, Avelino Vicente, 4321… axion! (arXiv:1907.02550)

leptoquarks as possible explanation also of the anomalies seen in the ANITA experiment

  • Bhavesh Chauhan, Subhendra Mohanty, A common leptoquark solution of flavor and ANITA anomalies (arXiv:1812.00919)


explanations via assumption of Z'-bosons:

  • Rhorry Gauld, Florian Goertz, Ulrich Haisch, An explicit Z’-boson explanation of the BK *μ +μ B \to K^\ast \mu^+ \mu^- anomaly, JHEP01(2014)069 (arXiv:1310.1082)

  • Richard H. Benavides, Luis Muñoz, William A. Ponce, Oscar Rodríguez, Eduardo Rojas, Minimal Z Z^\prime models for flavor anomalies (arXiv:1812.05077)

  • G. D’Ambrosio, A. M. Iyer, F. Piccinini, A.D. Polosa, Confronting BB anomalies with atomic physics (arXiv:1902.00893)

  • P. Ko, Takaaki Nomura, Chaehyun Yu, bsμ +μ b \to s \mu^+ \mu^- anomalies and related phenomenology in U(1) B 3x μL μx τL τU(1)_{B_{3-x_\mu L_\mu - x_\tau L_\tau}} flavor gauge models (arXiv:1902.06107)

  • Joe Davighi, Connecting neutral current BB anomalies with the heaviness of the third family, Contribution to the 2019 QCD session of the 54th Rencontres de Moriond (arXiv:1905.06073)

  • Wolfgang Altmannshofer, Joe Davighi, Marco Nardecchia, Gauging the accidental symmetries of the Standard Model, and implications for the flavour anomalies (arXiv:1909.02021)

  • Ben Allanach, U(1) B 3L 2U(1)_{B_3-L_2} Explanation of the Neutral Current BB−Anomalies (arXiv:2009.02197)

Dark matter

Possible joint explanation of the flavour anomalies and dark matter:

  • Basabendu Barman, Debasish Borah, Lopamudra Mukherjee, Soumitra Nandi, Correlating the anomalous results in bsb \to s decays with inert Higgs doublet dark matter and muon (g2)(g-2), Phys. Rev. D 100, 115010 (2019) (arXiv:1808.06639)

  • Seungwon Baek, Scalar dark matter behind bsμμb \to s \mu \mu anomaly (arXiv:1901.04761)

  • D.G. Cerdeno, A. Cheek, P. Martin-Ramiro, J.M. Moreno, B anomalies and dark matter: a complex connection (arXiv:1902.01789)

  • Anirban Biswas, Avirup Shaw, Reconciling dark matter, R K (*)R_{K^{(\ast)}} anomalies and (g2) μ(g-2)_\mu in an L μL τL_\mu-L_\tau scenario (arXiv:1903.08745)

  • Da Huang, António P. Morais, Rui Santos, Anomalies in BB Decays and Muon g2g-2 from Dark Loops (arXiv:2007.05082)


Realization in F-theory of GUT-models with Z'-bosons and/or [leptoquarks]] addressing the flavour anomalies and the (g-2) anomalies:

  • Miguel Crispim Romao, Stephen F. King, George K. Leontaris, Non-universal ZZ' from Fluxed GUTs, Physics Letters B Volume 782, 10 July 2018, Pages 353-361 (arXiv:1710.02349)

  • A. Karozas, G. K. Leontaris, I. Tavellaris, N. D. Vlachos, On the LHC signatures of SU(5)×U(1)SU(5) \times U(1)' F-theory motivated models (arXiv:2007.05936)


Other possible explanations of the flavour anomalies:

composite Higgs boson:

  • David Marzocca, Addressing the B-physics anomalies in a fundamental Composite Higgs Model, JHEP07(2018)121 (arXiv:1803.10972)

  • Andreas Crivellin, Dario Müller, Christoph Wiegand, bs + b \to s \ell^+ \ell^- Transitions in Two-Higgs-Doublet Models (arXiv:1903.10440)

  • Peter Stangl, Flavour anomalies and (fundamental) partial compositeness (arXiv:1907.05158)

right-handed neutrino:

  • Carlo Marzo, Luca Marzola, Martti Raidal, Common explanation to the R K (*)R_{K^{(\ast)}}, R K (*)R_{K^{(\ast)}} and ϵ/ϵ\epsilon'/\epsilon anomalies in a 3HDM+ν R\nu_R and connections to neutrino physics (arXiv:1901.08290)

  • Luigi Delle Rose, Shaaban Khalil, Simon J.D. King, Stefano Moretti, R KR_K and R K *R_{K^\ast} in an Aligned 2HDM with Right-Handed Neutrinos (arXiv:1903.11146)

  • Rusa Mandal, Clara Murgui, Ana Peñuelas, Antonio Pich, The role of right-handed neutrinos in bcτν¯b \to c \tau \bar \nu anomalies (arXiv:2004.06726)


  • Dris Boubaa, Shaaban Khalil, Stefano Moretti, Explaining B decays anomalies in SUSY models (arXiv:2004.07939)

MSSM with R-parity-violation

  • Dong-Yang Wang, Ya-Dong Yang, Xing-Bo Yuan, bcτν¯b \to c \tau \bar \nu decays in supersymmetry with R-parity violation (arXiv:1905.08784)

  • Quan-Yi Hu, Lin-Lin Huang, Explaining bs + b\to s \ell^+ \ell^- data by sneutrinos in the R-parity violating MSSM (arXiv:1912.03676)

  • Quan-Yi Hu, Ya-Dong Yang, Min-Di Zheng, Revisiting the B-physics anomalies in R-parity violating MSSM (arXiv:2002.09875)

  • Wolfgang Altmannshofer, P. S. Bhupal Dev, Amarjit Soni, Yicong Sui, Addressing R D *R_{D^\ast}, R K *R_{K^\ast}, muon g2g-2 and ANITA anomalies in a minimal R-parity violating supersymmetric framework (arXiv:2002.12910)

Horava-Witten theory-type KK-compactification:

  • Jong-Phil Lee, BB anomalies in the nonminimal universal extra dimension model (arXiv:1906.07345)

Exotic Higgs field couplings to a hidden sector:

Application of holographic QCD to B-meson physics and flavour anomalies

Application of holographic QCD (holographic light front QCD) to B-meson physics and flavour anomalies:

  • Ruben Sandapen, Mohammad Ahmady, Predicting radiative B decays to vector mesons in holographic QCD (arXiv:1306.5352)

  • Mohammad Ahmady, R. Campbell, S. Lord, Ruben Sandapen, Predicting the BρB \to \rho form factors using AdS/QCD Distribution Amplitudes for the ρ\rho meson, Phys. Rev. D88 (2013) 074031 (arXiv:1308.3694)

  • Mohammad Ahmady, Dan Hatfield, Sébastien Lord, Ruben Sandapen, Effect of cc¯c \bar c resonances in the branching ratio and forward-backward asymmetry of the decay BK *μ +μ B \to K^\ast\mu^+ \mu^-

  • Mohammad Ahmady, Alexandre Leger, Zoe McIntyre, Alexander Morrison, Ruben Sandapen, Probing transition form factors in the rare BK *νν¯B \to K^\ast \nu \bar \nu decay, Phys. Rev. D 98, 053002 (2018) (arXiv:1805.02940)

  • Mohammad Ahmady, Holographic light-front QCD in B meson phenomenology, PoS DIS2013 (2013) 182 (arXiv:2001.00266)

Last revised on October 23, 2020 at 04:11:21. See the history of this page for a list of all contributions to it.