The existence of three flavors of fundamental fermions is one of the great mysteries of the standard model of particle physics. At the same time it is at the basis of a variety of exciting phenomena, such as CP violation and neutrino flavor oscillations. Hints are mounting that the assumption of lepton universality and charged lepton flavour conservation, as currently incorporated in the standard model, may not be valid. We report on our test of charged lepton flavour conservation in the decay of B mesons, as measured at LHCb

Kappert, Rosa

Onderwater, Cornelis

Pellegrino, Antonio

van Veghel, Maarten

Wiersema, Garbrand

ARTS repository - University of Groningen

   University of GroningenB(s)→eμ: search for lepton flavour violation at LHCbOnderwater, Cornelis; Pellegrino, Antonio; Kappert, Rosa; Wiersema, Garbrand; van Veghel,MaartenIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2016Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Onderwater, C., Pellegrino, A., Kappert, R., Wiersema, G., & van Veghel, M. (2016). B(s)→eμ: search forlepton flavour violation at LHCb. Poster session presented at Physics@FOM, Veldhoven, Netherlands.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 21-06-2022  founded in 1614B(s)→eμ: search for lepton flavour violation at LHCbRosa Kappert, Gerco Onderwater, Antonio Pellegrino, Maarten van Veghel, Garbrand WiersemaUniversity of Groningen and NikhefIntroduction LFV Searches at LHCbExcellent particle identification and momentum resolution make LHCb an ideal environment to search for rare decays. We investigate LFV through decays of heavy B and D mesons into muon-electron pairs. Earlier LHCb results (90% CL) for the branching ratios were reported:● Br(B0→eμ)  < 2.8x10-9 (1 fb-1)● Br(Bs0→eμ) < 1.1x10-8 (1 fb-1)● Br(D0→eμ) < 1.3x10-8 (3 fb-1)The analysis of Br(B(s)→eμ) for the 2011 & 2012 3fb-1 data is expected to be finalized soon.Lepton (Flavour) UniversalityThe weak interaction strength is the same for all lepton flavours. This is referred to as lepton universality. Contrary to quark flavour mixing, lepton flavour mixing seems to be exclusive for the neutrinos, notably neutrino oscillations. Flavour mixing of the charged leptons has not been observed, and is predicted to be unmeasurably small by the Standard Model. Experimental observation of charged lepton flavour mixing would thus unambi-guously signal new physics.Flavour physics is the study of the interactions that distinguish between the three different copies of fundamental fermions. Within the Standard Model quarks, leptons, and neutrinos appear in three flavours, and only the interaction with the Higgs boson distinguishes these flavours, leading to flavour non-universality.Through the years a clear understanding of the underlying mechanism of flavour mixing and flavour non-universality has emerged, and this mechanism has been successfully verified in experiments.However, flavour physics still represents one of the most puzzling and, at the same time, interesting aspects of particle physics, summarized by two open questions:● What determines the observed pattern of masses and mixing angles of quarks and leptons?● Which are the sources of flavour symmetry breaking accessible at low energies?Answering these questions is a key part of the more general program of investigating the nature of physics beyond the Standard Model.Hints for Lepton Non-UniversalityRecent experimental data in high energy physics hint toward violation of Lepton Universality in semi-leptonic decays. The statistically most significant results are for (with ℓ=e,μ):● B→D*ℓνℓ3.8σ 1,2,3● B→Dℓνℓ2.0σ 1,2,3● B→Kℓ+ℓ– 2.6σ 3● h→μτ 2.5σ 4,51BaBar, 2Belle, 3LHCb, 4ATLAS, 5CMSViolation of lepton universality necessarily leads to lepton flavour violation, as no known symmetry principle can protect the one in the absence of the other.Implications & ProspectsSeveral models attempt to explain the observed non-universality, while meeting limits on decays such as B(s)0 → μμ and severe constrains from e.g. μ→eγ and μ→eee. Some of these models predict LFV signals within reach of LHCb†. Interesting links exist with the pp→γγ (750GeV) excess‡, and the (g-2)μ anomaly¶. New measurements will help to constrain these models.†e.g. Leptoquarks: Sahoo, Mohanta, arXiv:1512.04657; new interactions: Glashow, Guadagnoli, Lane, Phys. Rev. Lett. 114, 091801 (2015) ‡e.g. Two Higgs doublet: Bizot, Davidson, Frigerio, Kneur, arXiv:1512.08508¶,e.g. Doubly charged scalar: Chakrabortty,  Ghosh,  Mondal,  Srivastava, arXiv:1512.03581

English

B(s)→eμ: search for lepton flavour violation at LHCb

NARCIS 

Proceedings - University of Groningen

   University of GroningenB(s)→eμ: search for lepton flavour violation at LHCbOnderwater, Cornelis; Pellegrino, Antonio; Kappert, Rosa; Wiersema, Garbrand; van Veghel,MaartenIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2016Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Onderwater, C., Pellegrino, A., Kappert, R., Wiersema, G., & van Veghel, M. (2016). B(s)→eμ: search forlepton flavour violation at LHCb. Poster session presented at Physics@FOM, Veldhoven, Netherlands.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 04-06-2022  founded in 1614B(s)→eμ: search for lepton flavour violation at LHCbRosa Kappert, Gerco Onderwater, Antonio Pellegrino, Maarten van Veghel, Garbrand WiersemaUniversity of Groningen and NikhefIntroduction LFV Searches at LHCbExcellent particle identification and momentum resolution make LHCb an ideal environment to search for rare decays. We investigate LFV through decays of heavy B and D mesons into muon-electron pairs. Earlier LHCb results (90% CL) for the branching ratios were reported:● Br(B0→eμ)  < 2.8x10-9 (1 fb-1)● Br(Bs0→eμ) < 1.1x10-8 (1 fb-1)● Br(D0→eμ) < 1.3x10-8 (3 fb-1)The analysis of Br(B(s)→eμ) for the 2011 & 2012 3fb-1 data is expected to be finalized soon.Lepton (Flavour) UniversalityThe weak interaction strength is the same for all lepton flavours. This is referred to as lepton universality. Contrary to quark flavour mixing, lepton flavour mixing seems to be exclusive for the neutrinos, notably neutrino oscillations. Flavour mixing of the charged leptons has not been observed, and is predicted to be unmeasurably small by the Standard Model. Experimental observation of charged lepton flavour mixing would thus unambi-guously signal new physics.Flavour physics is the study of the interactions that distinguish between the three different copies of fundamental fermions. Within the Standard Model quarks, leptons, and neutrinos appear in three flavours, and only the interaction with the Higgs boson distinguishes these flavours, leading to flavour non-universality.Through the years a clear understanding of the underlying mechanism of flavour mixing and flavour non-universality has emerged, and this mechanism has been successfully verified in experiments.However, flavour physics still represents one of the most puzzling and, at the same time, interesting aspects of particle physics, summarized by two open questions:● What determines the observed pattern of masses and mixing angles of quarks and leptons?● Which are the sources of flavour symmetry breaking accessible at low energies?Answering these questions is a key part of the more general program of investigating the nature of physics beyond the Standard Model.Hints for Lepton Non-UniversalityRecent experimental data in high energy physics hint toward violation of Lepton Universality in semi-leptonic decays. The statistically most significant results are for (with ℓ=e,μ):● B→D*ℓνℓ3.8σ 1,2,3● B→Dℓνℓ2.0σ 1,2,3● B→Kℓ+ℓ– 2.6σ 3● h→μτ 2.5σ 4,51BaBar, 2Belle, 3LHCb, 4ATLAS, 5CMSViolation of lepton universality necessarily leads to lepton flavour violation, as no known symmetry principle can protect the one in the absence of the other.Implications & ProspectsSeveral models attempt to explain the observed non-universality, while meeting limits on decays such as B(s)0 → μμ and severe constrains from e.g. μ→eγ and μ→eee. Some of these models predict LFV signals within reach of LHCb†. Interesting links exist with the pp→γγ (750GeV) excess‡, and the (g-2)μ anomaly¶. New measurements will help to constrain these models.†e.g. Leptoquarks: Sahoo, Mohanta, arXiv:1512.04657; new interactions: Glashow, Guadagnoli, Lane, Phys. Rev. Lett. 114, 091801 (2015) ‡e.g. Two Higgs doublet: Bizot, Davidson, Frigerio, Kneur, arXiv:1512.08508¶,e.g. Doubly charged scalar: Chakrabortty,  Ghosh,  Mondal,  Srivastava, arXiv:1512.03581

Dissertations of the University of Groningen

   University of GroningenB(s)→eμ: search for lepton flavour violation at LHCbOnderwater, Cornelis; Pellegrino, Antonio; Kappert, Rosa; Wiersema, Garbrand; van Veghel,MaartenIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2016Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Onderwater, C., Pellegrino, A., Kappert, R., Wiersema, G., & van Veghel, M. (2016). B(s)→eμ: search forlepton flavour violation at LHCb. Poster session presented at Physics@FOM, Veldhoven, Netherlands.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 09-09-2023  founded in 1614B(s)→eμ: search for lepton flavour violation at LHCbRosa Kappert, Gerco Onderwater, Antonio Pellegrino, Maarten van Veghel, Garbrand WiersemaUniversity of Groningen and NikhefIntroduction LFV Searches at LHCbExcellent particle identification and momentum resolution make LHCb an ideal environment to search for rare decays. We investigate LFV through decays of heavy B and D mesons into muon-electron pairs. Earlier LHCb results (90% CL) for the branching ratios were reported:● Br(B0→eμ)  < 2.8x10-9 (1 fb-1)● Br(Bs0→eμ) < 1.1x10-8 (1 fb-1)● Br(D0→eμ) < 1.3x10-8 (3 fb-1)The analysis of Br(B(s)→eμ) for the 2011 & 2012 3fb-1 data is expected to be finalized soon.Lepton (Flavour) UniversalityThe weak interaction strength is the same for all lepton flavours. This is referred to as lepton universality. Contrary to quark flavour mixing, lepton flavour mixing seems to be exclusive for the neutrinos, notably neutrino oscillations. Flavour mixing of the charged leptons has not been observed, and is predicted to be unmeasurably small by the Standard Model. Experimental observation of charged lepton flavour mixing would thus unambi-guously signal new physics.Flavour physics is the study of the interactions that distinguish between the three different copies of fundamental fermions. Within the Standard Model quarks, leptons, and neutrinos appear in three flavours, and only the interaction with the Higgs boson distinguishes these flavours, leading to flavour non-universality.Through the years a clear understanding of the underlying mechanism of flavour mixing and flavour non-universality has emerged, and this mechanism has been successfully verified in experiments.However, flavour physics still represents one of the most puzzling and, at the same time, interesting aspects of particle physics, summarized by two open questions:● What determines the observed pattern of masses and mixing angles of quarks and leptons?● Which are the sources of flavour symmetry breaking accessible at low energies?Answering these questions is a key part of the more general program of investigating the nature of physics beyond the Standard Model.Hints for Lepton Non-UniversalityRecent experimental data in high energy physics hint toward violation of Lepton Universality in semi-leptonic decays. The statistically most significant results are for (with ℓ=e,μ):● B→D*ℓνℓ3.8σ 1,2,3● B→Dℓνℓ2.0σ 1,2,3● B→Kℓ+ℓ– 2.6σ 3● h→μτ 2.5σ 4,51BaBar, 2Belle, 3LHCb, 4ATLAS, 5CMSViolation of lepton universality necessarily leads to lepton flavour violation, as no known symmetry principle can protect the one in the absence of the other.Implications & ProspectsSeveral models attempt to explain the observed non-universality, while meeting limits on decays such as B(s)0 → μμ and severe constrains from e.g. μ→eγ and μ→eee. Some of these models predict LFV signals within reach of LHCb†. Interesting links exist with the pp→γγ (750GeV) excess‡, and the (g-2)μ anomaly¶. New measurements will help to constrain these models.†e.g. Leptoquarks: Sahoo, Mohanta, arXiv:1512.04657; new interactions: Glashow, Guadagnoli, Lane, Phys. Rev. Lett. 114, 091801 (2015) ‡e.g. Two Higgs doublet: Bizot, Davidson, Frigerio, Kneur, arXiv:1512.08508¶,e.g. Doubly charged scalar: Chakrabortty,  Ghosh,  Mondal,  Srivastava, arXiv:1512.03581

University of Groningen

   University of GroningenB(s)→eμ: search for lepton flavour violation at LHCbOnderwater, Cornelis; Pellegrino, Antonio; Kappert, Rosa; Wiersema, Garbrand; van Veghel,MaartenIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2016Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Onderwater, C., Pellegrino, A., Kappert, R., Wiersema, G., & van Veghel, M. (2016). B(s)→eμ: search forlepton flavour violation at LHCb. Poster session presented at Physics@FOM, Veldhoven, Netherlands.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 12-11-2019  founded in 1614B(s)→eμ: search for lepton flavour violation at LHCbRosa Kappert, Gerco Onderwater, Antonio Pellegrino, Maarten van Veghel, Garbrand WiersemaUniversity of Groningen and NikhefIntroduction LFV Searches at LHCbExcellent particle identification and momentum resolution make LHCb an ideal environment to search for rare decays. We investigate LFV through decays of heavy B and D mesons into muon-electron pairs. Earlier LHCb results (90% CL) for the branching ratios were reported:● Br(B0→eμ)  < 2.8x10-9 (1 fb-1)● Br(Bs0→eμ) < 1.1x10-8 (1 fb-1)● Br(D0→eμ) < 1.3x10-8 (3 fb-1)The analysis of Br(B(s)→eμ) for the 2011 & 2012 3fb-1 data is expected to be finalized soon.Lepton (Flavour) UniversalityThe weak interaction strength is the same for all lepton flavours. This is referred to as lepton universality. Contrary to quark flavour mixing, lepton flavour mixing seems to be exclusive for the neutrinos, notably neutrino oscillations. Flavour mixing of the charged leptons has not been observed, and is predicted to be unmeasurably small by the Standard Model. Experimental observation of charged lepton flavour mixing would thus unambi-guously signal new physics.Flavour physics is the study of the interactions that distinguish between the three different copies of fundamental fermions. Within the Standard Model quarks, leptons, and neutrinos appear in three flavours, and only the interaction with the Higgs boson distinguishes these flavours, leading to flavour non-universality.Through the years a clear understanding of the underlying mechanism of flavour mixing and flavour non-universality has emerged, and this mechanism has been successfully verified in experiments.However, flavour physics still represents one of the most puzzling and, at the same time, interesting aspects of particle physics, summarized by two open questions:● What determines the observed pattern of masses and mixing angles of quarks and leptons?● Which are the sources of flavour symmetry breaking accessible at low energies?Answering these questions is a key part of the more general program of investigating the nature of physics beyond the Standard Model.Hints for Lepton Non-UniversalityRecent experimental data in high energy physics hint toward violation of Lepton Universality in semi-leptonic decays. The statistically most significant results are for (with ℓ=e,μ):● B→D*ℓνℓ 3.8σ 1,2,3● B→Dℓνℓ 2.0σ 1,2,3● B→Kℓ+ℓ– 2.6σ 3● h→μτ 2.5σ 4,51BaBar, 2Belle, 3LHCb, 4ATLAS, 5CMSViolation of lepton universality necessarily leads to lepton flavour violation, as no known symmetry principle can protect the one in the absence of the other.Implications & ProspectsSeveral models attempt to explain the observed non-universality, while meeting limits on decays such as B(s)0 → μμ and severe constrains from e.g. μ→eγ and μ→eee. Some of these models predict LFV signals within reach of LHCb†. Interesting links exist with the pp→γγ (750GeV) excess‡, and the (g-2)μ anomaly¶. New measurements will help to constrain these models.†e.g. Leptoquarks: Sahoo, Mohanta, arXiv:1512.04657; new interactions: Glashow, Guadagnoli, Lane, Phys. Rev. Lett. 114, 091801 (2015) ‡e.g. Two Higgs doublet: Bizot, Davidson, Frigerio, Kneur, arXiv:1512.08508¶,e.g. Doubly charged scalar: Chakrabortty,  Ghosh,  Mondal,  Srivastava, arXiv:1512.03581

   University of GroningenB(s)→eμ: search for lepton flavour violation at LHCbOnderwater, Cornelis; Pellegrino, Antonio; Kappert, Rosa; Wiersema, Garbrand; van Veghel,MaartenIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2016Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Onderwater, C., Pellegrino, A., Kappert, R., Wiersema, G., & van Veghel, M. (2016). B(s)→eμ: search forlepton flavour violation at LHCb. Poster session presented at Physics@FOM, Veldhoven, Netherlands.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 05-06-2022  founded in 1614B(s)→eμ: search for lepton flavour violation at LHCbRosa Kappert, Gerco Onderwater, Antonio Pellegrino, Maarten van Veghel, Garbrand WiersemaUniversity of Groningen and NikhefIntroduction LFV Searches at LHCbExcellent particle identification and momentum resolution make LHCb an ideal environment to search for rare decays. We investigate LFV through decays of heavy B and D mesons into muon-electron pairs. Earlier LHCb results (90% CL) for the branching ratios were reported:● Br(B0→eμ)  < 2.8x10-9 (1 fb-1)● Br(Bs0→eμ) < 1.1x10-8 (1 fb-1)● Br(D0→eμ) < 1.3x10-8 (3 fb-1)The analysis of Br(B(s)→eμ) for the 2011 & 2012 3fb-1 data is expected to be finalized soon.Lepton (Flavour) UniversalityThe weak interaction strength is the same for all lepton flavours. This is referred to as lepton universality. Contrary to quark flavour mixing, lepton flavour mixing seems to be exclusive for the neutrinos, notably neutrino oscillations. Flavour mixing of the charged leptons has not been observed, and is predicted to be unmeasurably small by the Standard Model. Experimental observation of charged lepton flavour mixing would thus unambi-guously signal new physics.Flavour physics is the study of the interactions that distinguish between the three different copies of fundamental fermions. Within the Standard Model quarks, leptons, and neutrinos appear in three flavours, and only the interaction with the Higgs boson distinguishes these flavours, leading to flavour non-universality.Through the years a clear understanding of the underlying mechanism of flavour mixing and flavour non-universality has emerged, and this mechanism has been successfully verified in experiments.However, flavour physics still represents one of the most puzzling and, at the same time, interesting aspects of particle physics, summarized by two open questions:● What determines the observed pattern of masses and mixing angles of quarks and leptons?● Which are the sources of flavour symmetry breaking accessible at low energies?Answering these questions is a key part of the more general program of investigating the nature of physics beyond the Standard Model.Hints for Lepton Non-UniversalityRecent experimental data in high energy physics hint toward violation of Lepton Universality in semi-leptonic decays. The statistically most significant results are for (with ℓ=e,μ):● B→D*ℓνℓ3.8σ 1,2,3● B→Dℓνℓ2.0σ 1,2,3● B→Kℓ+ℓ– 2.6σ 3● h→μτ 2.5σ 4,51BaBar, 2Belle, 3LHCb, 4ATLAS, 5CMSViolation of lepton universality necessarily leads to lepton flavour violation, as no known symmetry principle can protect the one in the absence of the other.Implications & ProspectsSeveral models attempt to explain the observed non-universality, while meeting limits on decays such as B(s)0 → μμ and severe constrains from e.g. μ→eγ and μ→eee. Some of these models predict LFV signals within reach of LHCb†. Interesting links exist with the pp→γγ (750GeV) excess‡, and the (g-2)μ anomaly¶. New measurements will help to constrain these models.†e.g. Leptoquarks: Sahoo, Mohanta, arXiv:1512.04657; new interactions: Glashow, Guadagnoli, Lane, Phys. Rev. Lett. 114, 091801 (2015) ‡e.g. Two Higgs doublet: Bizot, Davidson, Frigerio, Kneur, arXiv:1512.08508¶,e.g. Doubly charged scalar: Chakrabortty,  Ghosh,  Mondal,  Srivastava, arXiv:1512.03581

   University of GroningenB(s)→eμ: search for lepton flavour violation at LHCbOnderwater, Cornelis; Pellegrino, Antonio; Kappert, Rosa; Wiersema, Garbrand; van Veghel,MaartenIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2016Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Onderwater, C., Pellegrino, A., Kappert, R., Wiersema, G., & van Veghel, M. (2016). B(s)→eμ: search forlepton flavour violation at LHCb. Poster session presented at Physics@FOM, Veldhoven, Netherlands.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 30-10-2023  founded in 1614B(s)→eμ: search for lepton flavour violation at LHCbRosa Kappert, Gerco Onderwater, Antonio Pellegrino, Maarten van Veghel, Garbrand WiersemaUniversity of Groningen and NikhefIntroduction LFV Searches at LHCbExcellent particle identification and momentum resolution make LHCb an ideal environment to search for rare decays. We investigate LFV through decays of heavy B and D mesons into muon-electron pairs. Earlier LHCb results (90% CL) for the branching ratios were reported:● Br(B0→eμ)  < 2.8x10-9 (1 fb-1)● Br(Bs0→eμ) < 1.1x10-8 (1 fb-1)● Br(D0→eμ) < 1.3x10-8 (3 fb-1)The analysis of Br(B(s)→eμ) for the 2011 & 2012 3fb-1 data is expected to be finalized soon.Lepton (Flavour) UniversalityThe weak interaction strength is the same for all lepton flavours. This is referred to as lepton universality. Contrary to quark flavour mixing, lepton flavour mixing seems to be exclusive for the neutrinos, notably neutrino oscillations. Flavour mixing of the charged leptons has not been observed, and is predicted to be unmeasurably small by the Standard Model. Experimental observation of charged lepton flavour mixing would thus unambi-guously signal new physics.Flavour physics is the study of the interactions that distinguish between the three different copies of fundamental fermions. Within the Standard Model quarks, leptons, and neutrinos appear in three flavours, and only the interaction with the Higgs boson distinguishes these flavours, leading to flavour non-universality.Through the years a clear understanding of the underlying mechanism of flavour mixing and flavour non-universality has emerged, and this mechanism has been successfully verified in experiments.However, flavour physics still represents one of the most puzzling and, at the same time, interesting aspects of particle physics, summarized by two open questions:● What determines the observed pattern of masses and mixing angles of quarks and leptons?● Which are the sources of flavour symmetry breaking accessible at low energies?Answering these questions is a key part of the more general program of investigating the nature of physics beyond the Standard Model.Hints for Lepton Non-UniversalityRecent experimental data in high energy physics hint toward violation of Lepton Universality in semi-leptonic decays. The statistically most significant results are for (with ℓ=e,μ):● B→D*ℓνℓ3.8σ 1,2,3● B→Dℓνℓ2.0σ 1,2,3● B→Kℓ+ℓ– 2.6σ 3● h→μτ 2.5σ 4,51BaBar, 2Belle, 3LHCb, 4ATLAS, 5CMSViolation of lepton universality necessarily leads to lepton flavour violation, as no known symmetry principle can protect the one in the absence of the other.Implications & ProspectsSeveral models attempt to explain the observed non-universality, while meeting limits on decays such as B(s)0 → μμ and severe constrains from e.g. μ→eγ and μ→eee. Some of these models predict LFV signals within reach of LHCb†. Interesting links exist with the pp→γγ (750GeV) excess‡, and the (g-2)μ anomaly¶. New measurements will help to constrain these models.†e.g. Leptoquarks: Sahoo, Mohanta, arXiv:1512.04657; new interactions: Glashow, Guadagnoli, Lane, Phys. Rev. Lett. 114, 091801 (2015) ‡e.g. Two Higgs doublet: Bizot, Davidson, Frigerio, Kneur, arXiv:1512.08508¶,e.g. Doubly charged scalar: Chakrabortty,  Ghosh,  Mondal,  Srivastava, arXiv:1512.03581

University of Groningen Research Database

  
 University of Groningen
B(s)→eμ: search for lepton flavour violation at LHCb
Onderwater, Cornelis; Pellegrino, Antonio; Kappert, Rosa; Wiersema, Garbrand; van Veghel,
Maarten
IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from
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Onderwater, C., Pellegrino, A., Kappert, R., Wiersema, G., & van Veghel, M. (2016). B(s)→eμ: search for
lepton flavour violation at LHCb. Poster session presented at Physics@FOM, Veldhoven, Netherlands.
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B(s)→eμ: search for lepton flavour violation at LHCb
Rosa Kappert, Gerco Onderwater, Antonio Pellegrino, Maarten van Veghel, Garbrand Wiersema
University of Groningen and Nikhef
Introduction LFV Searches at LHCb
Excellent particle identification and 
momentum resolution make LHCb 
an ideal environment to search for 
rare decays. We investigate LFV 
through decays of heavy B and D 
mesons into muon-electron pairs. 
Earlier LHCb results (90% CL) for 
the branching ratios were reported:
● Br(B0→eμ)  < 2.8x10-9 (1 fb-1)
● Br(Bs0→eμ) < 1.1x10-8 (1 fb-1)
● Br(D0→eμ) < 1.3x10-8 (3 fb-1)
The analysis of Br(B(s)→eμ) for the 
2011 & 2012 3fb-1 data is expected 
to be finalized soon.
Lepton (Flavour) Universality
The weak interaction strength is the 
same for all lepton flavours. This is 
referred to as lepton universality. 
Contrary to quark flavour mixing, 
lepton flavour mixing seems to be 
exclusive for the neutrinos, notably 
neutrino oscillations. Flavour mixing 
of the charged leptons has not been 
observed, and is predicted to be 
unmeasurably small by the 
Standard Model. Experimental 
observation of charged lepton 
flavour mixing would thus unambi-
guously signal new physics.
Flavour physics is the study of the interactions that 
distinguish between the three different copies of 
fundamental fermions. Within the Standard Model 
quarks, leptons, and neutrinos appear in three 
flavours, and only the interaction with the Higgs 
boson distinguishes these flavours, leading to flavour 
non-universality.
Through the years a clear understanding of the 
underlying mechanism of flavour mixing and flavour 
non-universality has emerged, and this mechanism 
has been successfully verified in experiments.
However, flavour physics still represents one of the 
most puzzling and, at the same time, interesting 
aspects of particle physics, summarized by two open 
questions:
● What determines the observed pattern of masses 
and mixing angles of quarks and leptons?
● Which are the sources of flavour symmetry 
breaking accessible at low energies?
Answering these questions is a key part of the more 
general program of investigating the nature of physics 
beyond the Standard Model.
Hints for Lepton Non-Universality
Recent experimental data in high 
energy physics hint toward violation 
of Lepton Universality in semi-
leptonic decays. The statistically 
most significant results are for (with 
ℓ=e,μ):
● B→D*ℓνℓ 3.8σ 1,2,3
● B→Dℓνℓ 2.0σ 1,2,3
● B→Kℓ+ℓ– 2.6σ 3
● h→μτ 2.5σ 4,5
1BaBar, 2Belle, 3LHCb, 4ATLAS, 5CMS
Violation of lepton universality 
necessarily leads to lepton flavour 
violation, as no known symmetry 
principle can protect the one in the 
absence of the other.
Implications & Prospects
Several models attempt to explain 
the observed non-universality, while 
meeting limits on decays such as 
B(s)
0 → μμ and severe constrains 
from e.g. μ→eγ and μ→eee. Some 
of these models predict LFV signals 
within reach of LHCb†. Interesting 
links exist with the pp→γγ (750GeV) 
excess‡, and the (g-2)μ anomaly
¶. 
New measurements will help to 
constrain these models.
†e.g. Leptoquarks: Sahoo, Mohanta, arXiv:1512.04657; 
new interactions: Glashow, Guadagnoli, Lane, Phys. 
Rev. Lett. 114, 091801 (2015) 
‡e.g. Two Higgs doublet: Bizot, Davidson, Frigerio, 
Kneur, arXiv:1512.08508
¶,e.g. Doubly charged scalar: Chakrabortty,  Ghosh,  
Mondal,  Srivastava, arXiv:1512.03581


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B(s)→eμ: search for lepton flavour violation at LHCb

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