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
The process pp$$\to\ell^+\ell^-$$p$$^{(*)}$$, with $$\ell^+\ell^-$$ 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 $$\sqrt{s} =$$ 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 $$\mu^+\mu^-$$ and 8 e$^+$$e$$^-$ pairs with $$m(\ell^{+}\ell^{-}) >$$ 110 GeV, and matching forward proton kinematics, are observed, with expected backgrounds of 1.49 $$\pm$$ 0.07 (stat) $$\pm$$ 0.53 (syst) and 2.36 $$\pm$$ 0.09 (stat) $$\pm$$ 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 $$\gamma\gamma$$ collisions at the electroweak scale. Furthermore, this measurement also demonstrates that CT-PPS performs according to the design specifications.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP); USDOE National Nuclear Security Administration (NNSA)
- Contributing Organization:
- The CMS collaboration; The TOTEM collaboration
- Grant/Contract Number:
- AC02-07CH11359; AC52-07NA27344
- OSTI ID:
- 1454715
- Alternate ID(s):
- OSTI ID: 1888102
- Report Number(s):
- FERMILAB-PUB-18-278-CMS; CMS-PPS-17-001; TOTEM-2018-001; CERN-EP-2018-014; arXiv:1803.04496; LLNL-JRNL-819451; 1662293; TRN: US1901108
- Journal Information:
- Journal of High Energy Physics (Online), Vol. 2018, Issue 7; ISSN 1029-8479
- Publisher:
- Springer NatureCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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