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

• Main Authors: Sirunyan, A. M., Tumasyan, A. R., Adam, Wolfgang, Ambrogi, Federico, Asilar, Ece, Md. Ali, Mohd. Adli
• Format: Article
• Language: English; English; English
• Published: Springer Verlag 2018
• Subjects: Q Science (General); QC Physics
• Online Access: http://irep.iium.edu.my/70412/1/70412_Observation%20of%20proton-tagged%2C%20central%20%28semi%29exclusive_article.pdf; http://irep.iium.edu.my/70412/7/70412_Observation%20of%20proton-tagged%2C%20central%20%28semi%29exclusive_scopus.pdf; http://irep.iium.edu.my/70412/8/70412_Observation%20of%20proton-tagged%2C%20central%20%28semi%29exclusive_wos.pdf; http://irep.iium.edu.my/70412/; https://link.springer.com/content/pdf/10.1007%2FJHEP07%282018%29153.pdf
• Institution: Universiti Islam Antarabangsa Malaysia

The process pp → p` +` −p (∗) , with ` +` − 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 = 13 TeV. 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(` +` −) > 110 GeV, 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.