Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb−1 of pp collisions at s=13TeV with the ATLAS experiment

The ATLAS collaboration

doi:10.1016/j.physletb.2019.135082

Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb⁻¹ of pp collisions at s=13TeV with the ATLAS experiment

The ATLAS collaboration

Research output: Contribution to journal › Article › peer-review

33 Scopus citations

Abstract

A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb⁻¹ of proton–proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tqγ coupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tuγ coupling of 36 fb (78 fb) and on the branching ratio for t→γu of 2.8×10⁻⁵ (6.1×10⁻⁵). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tcγ coupling of 40 fb (33 fb) and on the branching ratio for t→γc of 22×10⁻⁵ (18×10⁻⁵).

Original language	English (US)
Article number	135082
Journal	Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume	800
DOIs	https://doi.org/10.1016/j.physletb.2019.135082
State	Published - Jan 10 2020
Externally published	Yes

Bibliographical note

Funding Information:
We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS, CEA-DRF/IRFU, France; SRNSFG, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZ?, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, Canarie, CRC and Compute Canada, Canada; COST, ERC, ERDF, Horizon 2020, and Marie Sk?odowska-Curie Actions, European Union; Investissements d' Avenir Labex and Idex, ANR, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF, Greece; BSF-NSF and GIF, Israel; CERCA Programme Generalitat de Catalunya, Spain; The Royal Society and Leverhulme Trust, United Kingdom. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in Ref. [76].

Funding Information:
We acknowledge the support of ANPCyT , Argentina; YerPhI , Armenia; ARC , Australia; BMWFW and FWF , Austria; ANAS , Azerbaijan; SSTC , Belarus; CNPq and FAPESP , Brazil; NSERC , NRC and CFI , Canada; CERN ; CONICYT , Chile; CAS , MOST and NSFC , China; COLCIENCIAS , Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC , Denmark; IN2P3-CNRS , CEA-DRF/IRFU , France; SRNSFG , Georgia; BMBF , HGF , and MPG , Germany; GSRT , Greece; RGC , Hong Kong SAR , China; ISF and Benoziyo Center , Israel; INFN , Italy; MEXT and JSPS , Japan; CNRST , Morocco; NWO , Netherlands; RCN , Norway; MNiSW and NCN , Poland; FCT , Portugal; MNE/IFA , Romania; MES of Russia and NRC KI , Russian Federation; JINR ; MESTD , Serbia; MSSR , Slovakia; ARRS and MIZŠ , Slovenia; DST/NRF , South Africa; MINECO , Spain; SRC and Wallenberg Foundation , Sweden; SERI , SNSF and Cantons of Bern and Geneva , Switzerland; MOST , Taiwan; TAEK , Turkey; STFC , United Kingdom; DOE and NSF , United States of America. In addition, individual groups and members have received support from BCKDF , Canarie , CRC and Compute Canada , Canada; COST , ERC , ERDF , Horizon 2020 , and Marie Skłodowska-Curie Actions , European Union; Investissements d' Avenir Labex and Idex , ANR , France; DFG and AvH Foundation, Germany; Herakleitos , Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF , Greece; BSF-NSF and GIF , Israel; CERCA Programme Generalitat de Catalunya , Spain; The Royal Society and Leverhulme Trust , United Kingdom.

Publisher Copyright:
© 2019 The Author(s)

Publisher link

10.1016/j.physletb.2019.135082

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Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb⁻¹ of pp collisions at s=13TeV with the ATLAS experiment. / The ATLAS collaboration.
In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol. 800, 135082, 10.01.2020.

Research output: Contribution to journal › Article › peer-review

@article{019166817cc74c1d8cd1aca92f561f9e,

title = "Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb−1 of pp collisions at s=13TeV with the ATLAS experiment",

abstract = "A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb−1 of proton–proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tqγ coupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tuγ coupling of 36 fb (78 fb) and on the branching ratio for t→γu of 2.8×10−5 (6.1×10−5). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tcγ coupling of 40 fb (33 fb) and on the branching ratio for t→γc of 22×10−5 (18×10−5).",

author = "{The ATLAS collaboration} and G. Aad and B. Abbott and Abbott, {D. C.} and {Abed Abud}, A. and K. Abeling and Abhayasinghe, {D. K.} and Abidi, {S. H.} and Abouzeid, {O. S.} and Abraham, {N. L.} and H. Abramowicz and H. Abreu and Y. Abulaiti and Acharya, {B. S.} and B. Achkar and S. Adachi and L. Adam and {Adam Bourdarios}, C. and L. Adamczyk and L. Adamek and J. Adelman and M. Adersberger and A. Adiguzel and S. Adorni and T. Adye and Affolder, {A. A.} and Y. Afik and C. Agapopoulou and Agaras, {M. N.} and A. Aggarwal and C. Agheorghiesei and Aguilar-Saavedra, {J. A.} and F. Ahmadov and Ahmed, {W. S.} and X. Ai and G. Aielli and S. Akatsuka and {\AA}kesson, {T. P.A.} and E. Akilli and Akimov, {A. V.} and {Al Khoury}, K. and Alberghi, {G. L.} and J. Albert and {Alconada Verzini}, {M. J.} and S. Alderweireldt and M. Aleksa and Aleksandrov, {I. N.} and C. Alexa and D. Alexandre and T. Alexopoulos and Mahon, {D. J.}",

note = "Funding Information: We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS, CEA-DRF/IRFU, France; SRNSFG, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZ?, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, Canarie, CRC and Compute Canada, Canada; COST, ERC, ERDF, Horizon 2020, and Marie Sk?odowska-Curie Actions, European Union; Investissements d' Avenir Labex and Idex, ANR, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF, Greece; BSF-NSF and GIF, Israel; CERCA Programme Generalitat de Catalunya, Spain; The Royal Society and Leverhulme Trust, United Kingdom. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in Ref. [76]. Funding Information: We acknowledge the support of ANPCyT , Argentina; YerPhI , Armenia; ARC , Australia; BMWFW and FWF , Austria; ANAS , Azerbaijan; SSTC , Belarus; CNPq and FAPESP , Brazil; NSERC , NRC and CFI , Canada; CERN ; CONICYT , Chile; CAS , MOST and NSFC , China; COLCIENCIAS , Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC , Denmark; IN2P3-CNRS , CEA-DRF/IRFU , France; SRNSFG , Georgia; BMBF , HGF , and MPG , Germany; GSRT , Greece; RGC , Hong Kong SAR , China; ISF and Benoziyo Center , Israel; INFN , Italy; MEXT and JSPS , Japan; CNRST , Morocco; NWO , Netherlands; RCN , Norway; MNiSW and NCN , Poland; FCT , Portugal; MNE/IFA , Romania; MES of Russia and NRC KI , Russian Federation; JINR ; MESTD , Serbia; MSSR , Slovakia; ARRS and MIZ{\v S} , Slovenia; DST/NRF , South Africa; MINECO , Spain; SRC and Wallenberg Foundation , Sweden; SERI , SNSF and Cantons of Bern and Geneva , Switzerland; MOST , Taiwan; TAEK , Turkey; STFC , United Kingdom; DOE and NSF , United States of America. In addition, individual groups and members have received support from BCKDF , Canarie , CRC and Compute Canada , Canada; COST , ERC , ERDF , Horizon 2020 , and Marie Sk{\l}odowska-Curie Actions , European Union; Investissements d' Avenir Labex and Idex , ANR , France; DFG and AvH Foundation, Germany; Herakleitos , Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF , Greece; BSF-NSF and GIF , Israel; CERCA Programme Generalitat de Catalunya , Spain; The Royal Society and Leverhulme Trust , United Kingdom. Publisher Copyright: {\textcopyright} 2019 The Author(s)",

year = "2020",

month = jan,

day = "10",

doi = "10.1016/j.physletb.2019.135082",

language = "English (US)",

volume = "800",

journal = "Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics",

issn = "0370-2693",

publisher = "Elsevier B.V.",

}

TY - JOUR

T1 - Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb−1 of pp collisions at s=13TeV with the ATLAS experiment

AU - The ATLAS collaboration

AU - Aad, G.

AU - Abbott, B.

AU - Abbott, D. C.

AU - Abed Abud, A.

AU - Abeling, K.

AU - Abhayasinghe, D. K.

AU - Abidi, S. H.

AU - Abouzeid, O. S.

AU - Abraham, N. L.

AU - Abramowicz, H.

AU - Abreu, H.

AU - Abulaiti, Y.

AU - Acharya, B. S.

AU - Achkar, B.

AU - Adachi, S.

AU - Adam, L.

AU - Adam Bourdarios, C.

AU - Adamczyk, L.

AU - Adamek, L.

AU - Adelman, J.

AU - Adersberger, M.

AU - Adiguzel, A.

AU - Adorni, S.

AU - Adye, T.

AU - Affolder, A. A.

AU - Afik, Y.

AU - Agapopoulou, C.

AU - Agaras, M. N.

AU - Aggarwal, A.

AU - Agheorghiesei, C.

AU - Aguilar-Saavedra, J. A.

AU - Ahmadov, F.

AU - Ahmed, W. S.

AU - Ai, X.

AU - Aielli, G.

AU - Akatsuka, S.

AU - Åkesson, T. P.A.

AU - Akilli, E.

AU - Akimov, A. V.

AU - Al Khoury, K.

AU - Alberghi, G. L.

AU - Albert, J.

AU - Alconada Verzini, M. J.

AU - Alderweireldt, S.

AU - Aleksa, M.

AU - Aleksandrov, I. N.

AU - Alexa, C.

AU - Alexandre, D.

AU - Alexopoulos, T.

AU - Mahon, D. J.

N1 - Funding Information: We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS, CEA-DRF/IRFU, France; SRNSFG, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZ?, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, Canarie, CRC and Compute Canada, Canada; COST, ERC, ERDF, Horizon 2020, and Marie Sk?odowska-Curie Actions, European Union; Investissements d' Avenir Labex and Idex, ANR, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF, Greece; BSF-NSF and GIF, Israel; CERCA Programme Generalitat de Catalunya, Spain; The Royal Society and Leverhulme Trust, United Kingdom. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in Ref. [76]. Funding Information: We acknowledge the support of ANPCyT , Argentina; YerPhI , Armenia; ARC , Australia; BMWFW and FWF , Austria; ANAS , Azerbaijan; SSTC , Belarus; CNPq and FAPESP , Brazil; NSERC , NRC and CFI , Canada; CERN ; CONICYT , Chile; CAS , MOST and NSFC , China; COLCIENCIAS , Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC , Denmark; IN2P3-CNRS , CEA-DRF/IRFU , France; SRNSFG , Georgia; BMBF , HGF , and MPG , Germany; GSRT , Greece; RGC , Hong Kong SAR , China; ISF and Benoziyo Center , Israel; INFN , Italy; MEXT and JSPS , Japan; CNRST , Morocco; NWO , Netherlands; RCN , Norway; MNiSW and NCN , Poland; FCT , Portugal; MNE/IFA , Romania; MES of Russia and NRC KI , Russian Federation; JINR ; MESTD , Serbia; MSSR , Slovakia; ARRS and MIZŠ , Slovenia; DST/NRF , South Africa; MINECO , Spain; SRC and Wallenberg Foundation , Sweden; SERI , SNSF and Cantons of Bern and Geneva , Switzerland; MOST , Taiwan; TAEK , Turkey; STFC , United Kingdom; DOE and NSF , United States of America. In addition, individual groups and members have received support from BCKDF , Canarie , CRC and Compute Canada , Canada; COST , ERC , ERDF , Horizon 2020 , and Marie Skłodowska-Curie Actions , European Union; Investissements d' Avenir Labex and Idex , ANR , France; DFG and AvH Foundation, Germany; Herakleitos , Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF , Greece; BSF-NSF and GIF , Israel; CERCA Programme Generalitat de Catalunya , Spain; The Royal Society and Leverhulme Trust , United Kingdom. Publisher Copyright: © 2019 The Author(s)

PY - 2020/1/10

Y1 - 2020/1/10

N2 - A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb−1 of proton–proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tqγ coupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tuγ coupling of 36 fb (78 fb) and on the branching ratio for t→γu of 2.8×10−5 (6.1×10−5). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tcγ coupling of 40 fb (33 fb) and on the branching ratio for t→γc of 22×10−5 (18×10−5).

AB - A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb−1 of proton–proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tqγ coupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tuγ coupling of 36 fb (78 fb) and on the branching ratio for t→γu of 2.8×10−5 (6.1×10−5). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tcγ coupling of 40 fb (33 fb) and on the branching ratio for t→γc of 22×10−5 (18×10−5).

UR - http://www.scopus.com/inward/record.url?scp=85075235650&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85075235650&partnerID=8YFLogxK

U2 - 10.1016/j.physletb.2019.135082

DO - 10.1016/j.physletb.2019.135082

M3 - Article

AN - SCOPUS:85075235650

SN - 0370-2693

VL - 800

JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

M1 - 135082

ER -