Imperial College London

Alexander Tapper

Faculty of Natural SciencesDepartment of Physics

Professor of Physics
 
 
 
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Contact

 

+44 (0)20 7594 1551a.tapper Website

 
 
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Location

 

508Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

1518 results found

Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Bergauer T, Brandstetter J, Dragicevic M, Eroe J, Del Valle AE, Flechl M, Fruehwirth R, Jeitler M, Krammer N, Kraetschmer I, Liko D, Madlener T, Mikulec I, Rad N, Schieck J, Schoefbeck R, Spanring M, Spitzbart D, Waltenberger W, Wittmann J, Wulz C-E, Zarucki M, Drugakov V, Mossolov V, Suarez Gonzalez J, Darwish MR, De Wolf EA, Di Croce D, Janssen X, Lauwers J, Lelek A, Pieters M, Van Haevermaet H, Van Mechelen P, Van Remortel N, Blekman F, Bols ES, Chhibra SS, D'Hondt J, De Clercq J, Flouris G, Lontkovskyi D, Lowette S, Marchesini I, Moortgat S, Moreels L, Python Q, Skovpen K, Tavernier S, Van Doninck W, Van Mulders P, Van Parijs I, Beghin D, Bilin B, Brun H, Clerbaux B, De Lentdecker G, Delannoy H, Dorney B, Favart L, Grebenyuk A, Kalsi AK, Luetic J, Popov A, Postiau N, Starling E, Thomas L, Vander Velde C, Vanlaer P, Vannerom D, Wang Q, Cornelis T, Dobur D, Fagot A, Gul M, Khvastunov I, Roskas C, Trocino D, Tytgat M, Verbeke W, Vermassen B, Vit M, Zaganidis N, Bondu O, Bruno G, Caputo C, David P, Delaere C, Delcourt M, Giammanco A, Krintiras G, Lemaitre V, Magitteri A, Piotrzkowski K, Prisciandaro J, Saggio A, Marono MV, Vischia P, Zobec J, Alves FL, Alves GA, Correia Silva G, Hensel C, Moraes A, Rebello Teles P, Belchior Batista Das Chagas E, Carvalho W, Chinellato J, Coelho E, Da Costa EM, Da Silveira GG, De Jesus Damiao D, Fonseca De Souza S, Huertas Guativa LM, Malbouisson H, Matos Figueiredo D, Medina Jaime M, Melo De Almeida M, Mora Herrera C, Mundim L, Nogima H, Sanchez Rosas LJ, Santoro A, Sznajder A, Thiel M, Tonelli Manganote EJ, Torres Da Silva De Araujo F, Vilela Pereira A, Ahuja S, Bernardes CA, Calligaris L, De Souza Lemos D, Fernandez Perez Tomei TR, Gregores EM, Mercadante PG, Novaes SF, Padula SS, Aleksandrov A, Hadjiiska R, Iaydjiev P, Marinov A, Misheva M, Rodozov M, Shopova M, Sultanov G, Dimitrov A, Litov L, Pavlov B, Petkov P, Fang W, Gao X, Yuan L, Ahmad M, Chen GM, Chen HS, Chen M, Jiang CH, Leggaet al., 2019, Observation of Two Excited <i>B<sub>c</sub></i><SUP>+</SUP> States and Measurement of the <i>B<sub>c</sub></i><SUP>+</SUP> (2<i>S</i>) Mass in <i>pp</i> Collisions at √<i>s</i>=13 TeV, Publisher: AMER PHYSICAL SOC

Working paper

Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, Brandstetter J, Dragicevic M, Eroe J, Del Valle AE, Flechl M, Fruehwirth R, Ghete VM, Hrubec J, Jeitler M, Krammer N, Kraetschmer I, Liko D, Madlener T, Mikulec I, Rad N, Rohringer H, Schieck J, Schoefbeck R, Spanring M, Spitzbart D, Waltenberger W, Wittmann J, Wulz C-E, Zarucki M, Chekhovsky V, Mossolov V, Gonzalez JS, De Wolf EA, Di Croce D, Janssen X, Lauwers J, Lelek A, Pieters M, Van Haevermaet H, Van Mechelen P, Van Remortel N, Zeid SA, Blekman F, D'Hondt J, De Clercq J, Deroover K, Flouris G, Lontkovskyi D, Lowette S, Marchesini I, Moortgat S, Moreels L, Python Q, Skovpen K, Tavernier S, Van Doninck W, Van Mulders P, Van Parijs I, Beghin D, Bilin B, Brun H, Clerbaux B, De Lentdecker G, Delannoy H, Dorney B, Fasanella G, Favart L, Grebenyuk A, Kalsi AK, Lenzi T, Luetic J, Postiau N, Starling E, Thomas L, Vander Velde C, Vanlaer P, Vannerom D, Wang Q, Cornelis T, Dobur D, Fagot A, Gul M, Khvastunov I, Poyraz D, Roskas C, Trocino D, Tytgat M, Verbeke W, Vermassen B, Vit M, Zaganidis N, Bakhshiansohi H, Bondu O, Bruno G, Caputo C, David P, Delaere C, Delcourt M, Giammanco A, Krintiras G, Lemaitre V, Magitteri A, Piotrzkowski K, Saggio A, Marono MV, Vischia P, Zobec J, Alves FL, Alves GA, Silva GC, Hensel C, Moraes A, Pol ME, Teles PR, Das Chagas EBB, Carvalho W, Chinellato J, Coelho E, Da Costa EM, Da Silveira GG, Damiao DDJ, Martins CDO, De Souza SF, Malbouisson H, Figueiredo DM, De Almeida MM, Herrera CM, Mundim L, Nogima H, Da Silva WLP, Rosas LJS, Santoro A, Sznajder A, Thiel M, Manganote EJT, De Araujo FTDS, Pereira AV, Ahuja S, Bernardes CA, Calligaris L, Tomei TRFP, Gregores EM, Mercadante PG, Novaes SF, Padula SS, Aleksandrov A, Hadjiiska R, Iaydjiev P, Marinov A, Misheva M, Rodozov M, Shopova M, Sultanov G, Dimitrov A, Litov L, Pavlov B, Petkov P, Fang W, Gao X, Yuan L, Ahmad M, Bian JG, Chen GM, Chen HS, Chen M, Chen Y, Jiang CH, Leggat D, Liao H, Liu Z, Shaheen SM, Spiezia A, Tao J, Yazget al., 2019, Measurement of the top quark mass in the all- jets final state at √s =13 TeV and combination with the lepton+jets channel, The European Physical Journal C - Particles and Fields, Vol: 79, ISSN: 1434-6044

A top quark mass measurement is performed using 35.9fb−1 of LHC proton–proton collision data collected with the CMS detector at s√=13TeV . The measurement uses the tt¯ all-jets final state. A kinematic fit is performed to reconstruct the decay of the tt¯ system and suppress the multijet background. Using the ideogram method, the top quark mass ( mt ) is determined, simultaneously constraining an additional jet energy scale factor ( JSF ). The resulting value of mt=172.34±0.20(stat+JSF)±0.70(syst)GeV is in good agreement with previous measurements. In addition, a combined measurement that uses the tt¯ lepton+jets and all-jets final states is presented, using the same mass extraction method, and provides an mt measurement of 172.26±0.07(stat+JSF)±0.61(syst)GeV . This is the first combined mt extraction from the lepton+jets and all-jets channels through a single likelihood function.

Journal article

Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, Brandstetter J, Brondolin E, Dragicevic M, Eroe J, Del Valle AE, Flechl M, Friedl M, Fruehwirth R, Ghete VM, Grossmann J, Hrubec J, Jeitler M, Koenig A, Krammer N, Kraetschmer I, Liko D, Madlener T, Mikulec I, Pree E, Rad N, Rohringer H, Schieck J, Schoefbeck R, Spanring M, Spitzbart D, Taurok A, Waltenberger W, Wittmann J, Wulz C-E, Zarucki M, Chekhovsky V, Mossolov V, Gonzalez JS, De Wolf EA, Di Croce D, Janssen X, Lauwers J, Pieters M, Van De Klundert M, Van Haevermaet H, Van Mechelen P, Van Remortel N, Abu Zeid S, Blekman F, D'Hondt J, De Bruyn I, De Clercq J, Deroover K, Flouris G, Lontkovskyi D, Lowette S, Marchesini I, Moortgat S, Moreels L, Python Q, Skovpen K, Tavernier S, Van Doninck W, Van Mulders P, Van Parijs I, Beghin D, Bilin B, Brun H, Clerbaux B, De Lentdecker G, Delannoy H, Dorney B, Fasanella G, Favart L, Goldouzian R, Grebenyuk A, Kalsi AK, Lenzi T, Luetic J, Seva T, Starling E, Vander Velde C, Vanlaer P, Vannerom D, Yonamine R, Cornelis T, Dobur D, Fagot A, Gul M, Khvastunov I, Poyraz D, Roskas C, Trocino D, Tytgat M, Verbeke W, Vermassen B, Vit M, Zaganidis N, Bakhshiansohi H, Bondu O, Brochet S, Bruno G, Caputo C, Caudron A, David P, De Visscher S, Delaere C, Delcourt M, Francois B, Giammanco A, Krintiras G, Lemaitre V, Magitteri A, Mertens A, Musich M, Piotrzkowski K, Quertenmont L, Saggio A, Marono MV, Wertz S, Zobec J, Alda Junior WL, Alves FL, Alves GA, Brito L, Correia Silva G, Hensel C, Moraes A, Pol ME, Rebello Teles P, Belchior Batista Das Chagas E, Carvalho W, Chinellato J, Coelho E, Da Costa EM, Da Silveira GG, De Jesus Damiao D, Fonseca De Souza S, Malbouisson H, Medina Jaime M, Melo De Almeida M, Mora Herrera C, Mundim L, Nogima H, Sanchez Rosas LJ, Santoro A, Sznajder A, Thiel M, Tonelli Manganote EJ, Torres Da Silva De Araujo F, Vilela Pereira A, Ahuja S, Bernardes CA, Calligaris L, Fernandez Perez Tomei TR, Gregores EM, Mercadante PG, Novaes SF, Padula S, Romero Aet al., 2019, Search for excited leptons in ℓℓγ final states in proton-proton collisions at √s =13 TeV, Journal of High Energy Physics, Vol: 2019, ISSN: 1029-8479

A search is presented for excited electrons and muons in ℓℓγ final states at the LHC. The search is based on a data sample corresponding to an integrated luminosity of 35.9 fb−1 of proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector in 2016. This is the first search for excited leptons at s√ = 13 TeV. The observation is consistent with the standard model background prediction, and the most stringent exclusion limits to date are set on the excited lepton mass and the compositeness scale, at 95% confidence level. Excited electrons and muons are excluded for masses below 3.9 and 3.8 TeV, respectively, under the assumption that the excited lepton mass equals the compositeness scale. The best observed limit on the compositeness scale is obtained with an excited lepton mass of around 1.0 TeV, excluding values below 25 TeV for both excited electrons and muons.

Journal article

Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, Brandstetter J, Dragicevic M, Eroe J, Del Valle AE, Flechl M, Fruehwirth R, Ghete VM, Hrubec J, Jeitler M, Krammer N, Kraetschmer I, Liko D, Madlener T, Mikulec I, Rad N, Rohringer H, Schieck J, Schoefbeck R, Spanring M, Spitzbart D, Taurok A, Waltenberger W, Wittmann J, Wulz C-E, Zarucki M, Chekhovsky V, Mossolov V, Gonzalez JS, De Wolf EA, Di Croce D, Janssen X, Lauwers J, Pieters M, Van Haevermaet H, Van Mechelen P, Van Remortel N, Abu Zeid S, Blekman F, D'Hondt J, De Clercq J, Deroover K, Flouris G, Lontkovskyi D, Lowette S, Marchesini I, Moortgat S, Moreels L, Python Q, Skovpen K, Tavernier S, Van Doninck W, Van Mulders P, Van Parijs I, Beghin D, Bilin B, Brun H, Clerbaux B, De Lentdecker G, Delannoy H, Dorney B, Fasanella G, Favart L, Goldouzian R, Grebenyuk A, Kalsi AK, Lenzi T, Luetic J, Postiau N, Starling E, Thomas L, Vander Velde C, Vanlaer P, Vannerom D, Wang Q, Cornelis T, Dobur D, Fagot A, Gul M, Khvastunov I, Poyraz D, Roskas C, Trocino D, Tytgat M, Verbeke W, Vermassen B, Vit M, Zaganidis N, Bakhshiansohi H, Bondu O, Brochet S, Bruno G, Caputo C, David P, Delaere C, Delcourt M, Giammanco A, Krintiras G, Lemaitre V, Magitteri A, Piotrzkowski K, Saggio A, Marono MV, Wertz S, Zobec J, Alves FL, Alves GA, Correa Martins Junior M, Correia Silva G, Hensel C, Moraes A, Pol ME, Rebello Teles P, Belchior Batista Das Chagas E, Carvalho W, Chinellato J, Coelho E, Da Costa EM, Da Silveira GG, De Jesus Damiao D, De Oliveira Martins C, Fonseca De Souza S, Malbouisson H, Matos Figueiredo D, Melo De Almeida M, Mora Herrera C, Mundim L, Nogima H, Prado Da Silva WL, Sanchez Rosas LJ, Santoro A, Sznajder A, Thiel M, Tonelli Manganote EJ, Torres Da Silva De Araujo F, Vilela Pereira A, Ahuja S, Bernardes CA, Calligaris L, Fernandez Perez Tomei TR, Gregores EM, Mercadante PG, Novaes SF, Padula SS, Aleksandrov A, Hadjiiska R, Iaydjiev P, Marinov A, Misheva M, Rodozov M, Shopova M, Sultanov G, Dimitrov A, Litet al., 2019, Combination of Searches for Higgs Boson Pair Production in Proton-Proton Collisions at √s =13 TeV, Physical Review Letters, Vol: 122, ISSN: 0031-9007

This Letter describes a search for Higgs boson pair production using the combined results from four final states: bbγγ, bbττ, bbbb, and bbVV, where V represents a W or Z boson. The search is performed using data collected in 2016 by the CMS experiment from LHC proton-proton collisions at √s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. Limits are set on the Higgs boson pair production cross section. A 95% confidence level observed (expected) upper limit on the nonresonant production cross section is set at 22.2 (12.8) times the standard model value. A search for narrow resonances decaying to Higgs boson pairs is also performed in the mass range 250–3000 GeV. No evidence for a signal is observed, and upper limits are set on the resonance production cross section.

Journal article

Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, Brandstetter J, Brondolin E, Dragicevic M, Eroe J, Del Valle AE, Flechl M, Friedl M, Fruehwirth R, Ghete VM, Grossmann J, Hrubec J, Jeitler M, Koenig A, Krammer N, Kraetschmer I, Liko D, Madlener T, Mikulec I, Pree E, Rad N, Rohringer H, Schieck J, Schoefbeck R, Spanring M, Spitzbart D, Taurok A, Waltenberger W, Wittmann J, Wulz C-E, Zarucki M, Chekhovsky V, Mossolov V, Gonzalez JS, De Wolf EA, Di Croce D, Janssen X, Lauwers J, Pieters M, Van De Klundert M, Van Haevermaet H, Van Mechelen P, Van Remortel N, Abu Zeid S, Blekman F, D'Hondt J, De Bruyn I, De Clercq J, Deroover K, Flouris G, Lontkovskyi D, Lowette S, Marchesini I, Moortgat S, Moreels L, Python Q, Skovpen K, Tavernier S, Van Doninck W, Van Mulders P, Van Parijs I, Beghin D, Bilin B, Brun H, Clerbaux B, De Lentdecker G, Delannoy H, Dorney B, Fasanella G, Favart L, Goldouzian R, Grebenyuk A, Kalsi AK, Lenzi T, Luetic J, Seva T, Starling E, Vander Velde C, Vanlaer P, Vannerom D, Yonamine R, Cornelis T, Dobur D, Fagot A, Gul M, Khvastunov I, Poyraz D, Roskas C, Trocino D, Tytgat M, Verbeke W, Vermassen B, Vit M, Zaganidis N, Bakhshiansohi H, Bondu O, Brochet S, Bruno G, Caputo C, Caudron A, David P, De Visscher S, Delaere C, Delcourt M, Francois B, Giammanco A, Krintiras G, Lemaitre V, Magitteri A, Mertens A, Musich M, Piotrzkowski K, Quertenmont L, Saggio A, Marono MV, Wertz S, Zobec J, Alda Junior WL, Alves FL, Alves GA, Brito L, Correia Silva G, Hensel C, Moraes A, Pol ME, Rebello Teles P, Belchior Batista Das Chagas E, Carvalho W, Chinellato J, Coelho E, Da Costa EM, Da Silveira GG, De Jesus Damiao D, Fonseca De Souza S, Malbouisson H, Medina Jaime M, Melo De Almeida M, Mora Herrera C, Mundim L, Nogima H, Sanchez Rosas LJ, Santoro A, Sznajder A, Thiel M, Tonelli Manganote EJ, Torres Da Silva De Araujo F, Vilela Pereira A, Ahuja S, Bernardes CA, Calligaris A, Fernandez Perez Tomei TR, Gregores EM, Mercadante PG, Novaes SF, Padula SS, Romeroet al., 2019, Measurement of exclusive ϒ photoproduction from protons in pPb collisions at √sNN =5.02 Tev, The European Physical Journal C - Particles and Fields, Vol: 79, ISSN: 1434-6044

The exclusive photoproduction of ϒ(nS) meson states from protons, γ p → ϒ(nS) p (with n = 1, 2, 3), is studied in ultraperipheral pPb collisions at a centre-of-mass energy per nucleon pair of √sNN = 5.02 TeV. The measurement is performed using the ϒ(nS) → μ+μ− decay mode, with data collected by the CMS experiment corresponding to an integrated luminosity of 32.6 nb−1. Differential cross sections as functions of the ϒ(nS) transverse momentum squared p2 T, and rapidity y, are presented. The ϒ(1S) photoproduction cross section is extracted in the rapidity range|y| < 2.2, which corresponds to photon–proton centre-ofmass energies in the range 91 < Wγ p < 826 GeV. The data are compared to theoretical predictions based on perturbative quantum chromodynamics and to previous measurements.

Journal article

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