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Title: Search for flavor-changing neutral currents in top quark decays t →hc and t →hu in multilepton final states in proton-proton collisions at s =13 TeV with the ATLAS detector

Abstract

Flavor-changing neutral currents are not present in the Standard Model at tree level and are suppressed in loop processes by the unitarity of the Cabibbo-Kobayashi-Maskawa matrix; the corresponding rates for top quark decay processes are experimentally unobservable. Extensions of the Standard Model can generate new flavor-changing neutral current processes, leading to signals which, if observed, would be unambiguous evidence of new interactions. A data set corresponding to an integrated luminosity of 36.1 fb-1 of pp collisions at a center-of-mass energy of s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider is used to search for top quarks decaying to up or charm quarks with the emission of a Higgs boson, with subsequent Higgs boson decay to final states with at least one electron or muon. No signal is observed and limits on the branching fractions B(t→Hc)<0.16% and B(t→Hu)<0.19% at 95% confidence level are obtained (with expected limits of 0.15% in both cases).

Authors:
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Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1480799
DOE Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 98; Journal Issue: 3; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English

Citation Formats

Aaboud, M, Aad, G, Abbott, B, Abdinov, O, Abeloos, B, Abhayasinghe, DK, Abidi, SH, Abouzeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adamczyk, L, Adelman, J, Adersberger, M, Adiguzel, A, Adye, T, Affolder, AA, Afik, Y, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Alberghi, GL, Albert, J, Albicocco, P, Alconada Verzini, MJ, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alhroob, M, Ali, B, Aliev, M, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Alvarez Gonzalez, B, Álvarez Piqueras, D, Alviggi, MG, Amadio, BT, Amaral Coutinho, Y, Ambroz, L, Amelung, C, Amidei, D, Amor Dos Santos, SP, Amoroso, S, Amrouche, CS, Anastopoulos, C, Ancu, LS, Andari, N, Andeen, T, Anders, CF, Anders, JK, Anderson, KJ, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, and Anulli, F. Search for flavor-changing neutral currents in top quark decays t →hc and t →hu in multilepton final states in proton-proton collisions at s =13 TeV with the ATLAS detector. United States: N. p., 2018. Web. doi:10.1103/PhysRevD.98.032002.
Aaboud, M, Aad, G, Abbott, B, Abdinov, O, Abeloos, B, Abhayasinghe, DK, Abidi, SH, Abouzeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adamczyk, L, Adelman, J, Adersberger, M, Adiguzel, A, Adye, T, Affolder, AA, Afik, Y, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Alberghi, GL, Albert, J, Albicocco, P, Alconada Verzini, MJ, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alhroob, M, Ali, B, Aliev, M, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Alvarez Gonzalez, B, Álvarez Piqueras, D, Alviggi, MG, Amadio, BT, Amaral Coutinho, Y, Ambroz, L, Amelung, C, Amidei, D, Amor Dos Santos, SP, Amoroso, S, Amrouche, CS, Anastopoulos, C, Ancu, LS, Andari, N, Andeen, T, Anders, CF, Anders, JK, Anderson, KJ, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, & Anulli, F. Search for flavor-changing neutral currents in top quark decays t →hc and t →hu in multilepton final states in proton-proton collisions at s =13 TeV with the ATLAS detector. United States. doi:10.1103/PhysRevD.98.032002.
Aaboud, M, Aad, G, Abbott, B, Abdinov, O, Abeloos, B, Abhayasinghe, DK, Abidi, SH, Abouzeid, OS, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adamczyk, L, Adelman, J, Adersberger, M, Adiguzel, A, Adye, T, Affolder, AA, Afik, Y, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Aielli, G, Akatsuka, S, Åkesson, TPA, Akilli, E, Akimov, AV, Alberghi, GL, Albert, J, Albicocco, P, Alconada Verzini, MJ, Alderweireldt, S, Aleksa, M, Aleksandrov, IN, Alexa, C, Alexopoulos, T, Alhroob, M, Ali, B, Aliev, M, Alimonti, G, Alison, J, Alkire, SP, Allaire, C, Allbrooke, BMM, Allen, BW, Allport, PP, Aloisio, A, Alonso, A, Alonso, F, Alpigiani, C, Alshehri, AA, Alstaty, MI, Alvarez Gonzalez, B, Álvarez Piqueras, D, Alviggi, MG, Amadio, BT, Amaral Coutinho, Y, Ambroz, L, Amelung, C, Amidei, D, Amor Dos Santos, SP, Amoroso, S, Amrouche, CS, Anastopoulos, C, Ancu, LS, Andari, N, Andeen, T, Anders, CF, Anders, JK, Anderson, KJ, Andreazza, A, Andrei, V, Anelli, CR, Angelidakis, S, Angelozzi, I, Angerami, A, Anisenkov, AV, Annovi, A, Antel, C, Anthony, MT, Antonelli, M, Antrim, DJA, and Anulli, F. Wed . "Search for flavor-changing neutral currents in top quark decays t →hc and t →hu in multilepton final states in proton-proton collisions at s =13 TeV with the ATLAS detector". United States. doi:10.1103/PhysRevD.98.032002. https://www.osti.gov/servlets/purl/1480799.
@article{osti_1480799,
title = {Search for flavor-changing neutral currents in top quark decays t →hc and t →hu in multilepton final states in proton-proton collisions at s =13 TeV with the ATLAS detector},
author = {Aaboud, M and Aad, G and Abbott, B and Abdinov, O and Abeloos, B and Abhayasinghe, DK and Abidi, SH and Abouzeid, OS and Abraham, NL and Abramowicz, H and Abreu, H and Abulaiti, Y and Acharya, BS and Adachi, S and Adamczyk, L and Adelman, J and Adersberger, M and Adiguzel, A and Adye, T and Affolder, AA and Afik, Y and Agheorghiesei, C and Aguilar-Saavedra, JA and Ahmadov, F and Aielli, G and Akatsuka, S and Åkesson, TPA and Akilli, E and Akimov, AV and Alberghi, GL and Albert, J and Albicocco, P and Alconada Verzini, MJ and Alderweireldt, S and Aleksa, M and Aleksandrov, IN and Alexa, C and Alexopoulos, T and Alhroob, M and Ali, B and Aliev, M and Alimonti, G and Alison, J and Alkire, SP and Allaire, C and Allbrooke, BMM and Allen, BW and Allport, PP and Aloisio, A and Alonso, A and Alonso, F and Alpigiani, C and Alshehri, AA and Alstaty, MI and Alvarez Gonzalez, B and Álvarez Piqueras, D and Alviggi, MG and Amadio, BT and Amaral Coutinho, Y and Ambroz, L and Amelung, C and Amidei, D and Amor Dos Santos, SP and Amoroso, S and Amrouche, CS and Anastopoulos, C and Ancu, LS and Andari, N and Andeen, T and Anders, CF and Anders, JK and Anderson, KJ and Andreazza, A and Andrei, V and Anelli, CR and Angelidakis, S and Angelozzi, I and Angerami, A and Anisenkov, AV and Annovi, A and Antel, C and Anthony, MT and Antonelli, M and Antrim, DJA and Anulli, F},
abstractNote = {Flavor-changing neutral currents are not present in the Standard Model at tree level and are suppressed in loop processes by the unitarity of the Cabibbo-Kobayashi-Maskawa matrix; the corresponding rates for top quark decay processes are experimentally unobservable. Extensions of the Standard Model can generate new flavor-changing neutral current processes, leading to signals which, if observed, would be unambiguous evidence of new interactions. A data set corresponding to an integrated luminosity of 36.1 fb-1 of pp collisions at a center-of-mass energy of s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider is used to search for top quarks decaying to up or charm quarks with the emission of a Higgs boson, with subsequent Higgs boson decay to final states with at least one electron or muon. No signal is observed and limits on the branching fractions B(t→Hc)<0.16% and B(t→Hu)<0.19% at 95% confidence level are obtained (with expected limits of 0.15% in both cases).},
doi = {10.1103/PhysRevD.98.032002},
journal = {Physical Review D},
issn = {2470-0010},
number = 3,
volume = 98,
place = {United States},
year = {2018},
month = {8}
}

Journal Article:

Figures / Tables:

Table 1 Table 1: Variables used to construct the BDT discriminants for the 2lSS and 3l categories. The symbol “×” indicates that this variable is used in the respective BDT. The “best Z candidate” is the opposite-charge lepton pair with same flavor with invariant mass closest to 91.2 GeV; if no suchmore » pair exists, zero is assigned for the invariant mass.« less

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      Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.