The process pp → pl+l−p(∗), with l+l− a muon or an electron pair produced at midrapidity with mass larger than 110 GeV, has been observed for the first time at the LHC in pp collisions at √s = 13TeV. One of the two scattered protons is measured in the CMS-TOTEM precision proton spectrometer (CT-PPS), which operated for the first time in 2016. The second proton either remains intact or is excited and then dissociates into a low-mass state p∗, which is undetected. The measurement is based on an integrated luminosity of 9.4 fb−1 collected during standard, high-luminosity LHC operation. A total of 12 μ+μ− and 8 e+e− pairs with m(l+l−) > 110GeV, and matching forward proton kinematics, are observed, with expected backgrounds of 1.49 ± 0.07 (stat) ± 0.53 (syst) and 2.36 ± 0.09 (stat) ± 0.47 (syst), respectively. This corresponds to an excess of more than five standard deviations over the expected background. The present result constitutes the first observation of proton-tagged γγ collisions at the electroweak scale. This measurement also demonstrates that CT-PPS performs according to the design specifications.
Observation of proton-tagged, central (semi)exclusive production of high-mass lepton pairs in pp collisions at 13 TeV with the CMS-TOTEM precision proton spectrometer
Ravera, F.;Amapane, N.;Argiro, S.;Bellan, R.;Costa, M.;Covarelli, R.;Kiani, B.;Migliore, E.;Monaco, V.;Monteil, E.;Obertino, M. M.;Pacher, L.;Pinna Angioni, G. L.;Romero, A.;Sacchi, R.;Sola, V.;Solano, A.;Rumerio, P.;
2018-01-01
Abstract
The process pp → pl+l−p(∗), with l+l− a muon or an electron pair produced at midrapidity with mass larger than 110 GeV, has been observed for the first time at the LHC in pp collisions at √s = 13TeV. One of the two scattered protons is measured in the CMS-TOTEM precision proton spectrometer (CT-PPS), which operated for the first time in 2016. The second proton either remains intact or is excited and then dissociates into a low-mass state p∗, which is undetected. The measurement is based on an integrated luminosity of 9.4 fb−1 collected during standard, high-luminosity LHC operation. A total of 12 μ+μ− and 8 e+e− pairs with m(l+l−) > 110GeV, and matching forward proton kinematics, are observed, with expected backgrounds of 1.49 ± 0.07 (stat) ± 0.53 (syst) and 2.36 ± 0.09 (stat) ± 0.47 (syst), respectively. This corresponds to an excess of more than five standard deviations over the expected background. The present result constitutes the first observation of proton-tagged γγ collisions at the electroweak scale. This measurement also demonstrates that CT-PPS performs according to the design specifications.File | Dimensione | Formato | |
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3.CMS2018_Article_ObservationOfProton-taggedCent.pdf
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