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Light Resonances and the Low-$q^2$ Bin of $R_{K^*}$

LHCb has reported hints of lepton-flavor universality violation in the rare decays B → K$^{(*)}$ℓ$^{+}$ℓ$^{−}$, both in high- and low-q$^{2}$ bins. Although the high-q$^{2}$ hint may be explained by new short-ranged interactions, the low-q$^{2}$ one cannot. We thus explore the possibility that the l...

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Autores principales: Altmannshofer, Wolfgang, Baker, Michael J., Gori, Stefania, Harnik, Roni, Pospelov, Maxim, Stamou, Emmanuel, Thamm, Andrea
Lenguaje:eng
Publicado: 2017
Materias:
Acceso en línea:https://dx.doi.org/10.1007/JHEP03(2018)188
http://cds.cern.ch/record/2295716
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author Altmannshofer, Wolfgang
Baker, Michael J.
Gori, Stefania
Harnik, Roni
Pospelov, Maxim
Stamou, Emmanuel
Thamm, Andrea
author_facet Altmannshofer, Wolfgang
Baker, Michael J.
Gori, Stefania
Harnik, Roni
Pospelov, Maxim
Stamou, Emmanuel
Thamm, Andrea
author_sort Altmannshofer, Wolfgang
collection CERN
description LHCb has reported hints of lepton-flavor universality violation in the rare decays B → K$^{(*)}$ℓ$^{+}$ℓ$^{−}$, both in high- and low-q$^{2}$ bins. Although the high-q$^{2}$ hint may be explained by new short-ranged interactions, the low-q$^{2}$ one cannot. We thus explore the possibility that the latter is explained by a new light resonance. We find that LHCb’s central value of $ {R}_{K^{*}} $ in the low-q$^{2}$ bin is achievable in a restricted parameter space of new-physics scenarios in which the new, light resonance decays preferentially to electrons and has a mass within approximately 10 MeV of the di-muon threshold. Interestingly, such an explanation can have a kinematic origin and does not require a source of lepton-flavor universality violation. A model-independent prediction is a narrow peak in the differential B → K$^{*}$e$^{+}$e$^{−}$ rate close to the di-muon threshold. If such a peak is observed, other observables, such as the differential B → Ke$^{+}$e$^{−}$ rate and R$_{K}$ , may be employed to distinguish between models. However, if a low-mass resonance is not observed and the low-q$^{2}$ anomaly increases in significance, then the case for an experimental origin of the lepton-flavor universality violating anomalies would be strengthened. To further explore this, we also point out that, in analogy to J/ψ decays, e$^{+}$e$^{−}$ and μ$^{+}$μ$^{−}$ decays of ϕ mesons can be used as a cross check of lepton-flavor universality by LHCb with 5 fb$^{−1}$ of integrated luminosity.
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spelling cern-22957162023-03-14T18:32:39Zdoi:10.1007/JHEP03(2018)188http://cds.cern.ch/record/2295716engAltmannshofer, WolfgangBaker, Michael J.Gori, StefaniaHarnik, RoniPospelov, MaximStamou, EmmanuelThamm, AndreaLight Resonances and the Low-$q^2$ Bin of $R_{K^*}$hep-exParticle Physics - Experimenthep-phParticle Physics - PhenomenologyLHCb has reported hints of lepton-flavor universality violation in the rare decays B → K$^{(*)}$ℓ$^{+}$ℓ$^{−}$, both in high- and low-q$^{2}$ bins. Although the high-q$^{2}$ hint may be explained by new short-ranged interactions, the low-q$^{2}$ one cannot. We thus explore the possibility that the latter is explained by a new light resonance. We find that LHCb’s central value of $ {R}_{K^{*}} $ in the low-q$^{2}$ bin is achievable in a restricted parameter space of new-physics scenarios in which the new, light resonance decays preferentially to electrons and has a mass within approximately 10 MeV of the di-muon threshold. Interestingly, such an explanation can have a kinematic origin and does not require a source of lepton-flavor universality violation. A model-independent prediction is a narrow peak in the differential B → K$^{*}$e$^{+}$e$^{−}$ rate close to the di-muon threshold. If such a peak is observed, other observables, such as the differential B → Ke$^{+}$e$^{−}$ rate and R$_{K}$ , may be employed to distinguish between models. However, if a low-mass resonance is not observed and the low-q$^{2}$ anomaly increases in significance, then the case for an experimental origin of the lepton-flavor universality violating anomalies would be strengthened. To further explore this, we also point out that, in analogy to J/ψ decays, e$^{+}$e$^{−}$ and μ$^{+}$μ$^{−}$ decays of ϕ mesons can be used as a cross check of lepton-flavor universality by LHCb with 5 fb$^{−1}$ of integrated luminosity.LHCb has reported hints of lepton-flavor universality violation in the rare decays $B \to K^{(*)} \ell^+\ell^-$, both in high- and low-$q^2$ bins. Although the high-$q^2$ hint may be explained by new short-ranged interactions, the low-$q^2$ one cannot. We thus explore the possibility that the latter is explained by a new light resonance. We find that LHCb's central value of $R_{K^*}$ in the low-$q^2$ bin is achievable in a restricted parameter space of new-physics scenarios in which the new, light resonance decays preferentially to electrons and has a mass within approximately $10$ MeV of the di-muon threshold. Interestingly, such an explanation can have a kinematic origin and does not require a source of lepton-flavor universality violation. A model-independent prediction is a narrow peak in the differential $B \to K^* e^+e^-$ rate close to the di-muon threshold. If such a peak is observed, other observables, such as the differential $B \to K e^+e^-$ rate and $R_K$, may be employed to distinguish between models. However, if a low-mass resonance is not observed and the low-$q^2$ anomaly increases in significance, then the case for an experimental origin of the lepton-flavor universality violating anomalies would be strengthened. To further explore this, we also point out that, in analogy to $J/\psi$ decays, $e^+e^-$ and $\mu^+\mu^-$ decays of $\phi$ mesons can be used as a cross check of lepton-flavor universality by LHCb with $5$ fb$^{-1}$ of integrated luminosity.arXiv:1711.07494FERMILAB-PUB-17-523-TCERN-TH-2017-240MITP/17-083ZU-TH-35/17oai:cds.cern.ch:22957162017-11-20
spellingShingle hep-ex
Particle Physics - Experiment
hep-ph
Particle Physics - Phenomenology
Altmannshofer, Wolfgang
Baker, Michael J.
Gori, Stefania
Harnik, Roni
Pospelov, Maxim
Stamou, Emmanuel
Thamm, Andrea
Light Resonances and the Low-$q^2$ Bin of $R_{K^*}$
title Light Resonances and the Low-$q^2$ Bin of $R_{K^*}$
title_full Light Resonances and the Low-$q^2$ Bin of $R_{K^*}$
title_fullStr Light Resonances and the Low-$q^2$ Bin of $R_{K^*}$
title_full_unstemmed Light Resonances and the Low-$q^2$ Bin of $R_{K^*}$
title_short Light Resonances and the Low-$q^2$ Bin of $R_{K^*}$
title_sort light resonances and the low-$q^2$ bin of $r_{k^*}$
topic hep-ex
Particle Physics - Experiment
hep-ph
Particle Physics - Phenomenology
url https://dx.doi.org/10.1007/JHEP03(2018)188
http://cds.cern.ch/record/2295716
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