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CMS-EXO-18-014 ; CERN-EP-2021-191
First search for exclusive diphoton production at high mass with tagged protons in proton-proton collisions at $\sqrt{s} = $ 13 TeV
Phys. Rev. Lett. 129 (2022) 011801
Abstract: A search for exclusive two-photon production via photon exchange in proton-proton collisions, ${\mathrm{p}}{\mathrm{p}}\to{\mathrm{p}}\gamma\gamma{\mathrm{p}}$ with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons matches the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% CL are $ | \zeta_1 | < $ 2.88 $ \times $ 10$^{-13}$ GeV$^{-4}$ and $ | \zeta_2 | < $ 6.02 $\times$ 10$^{-13}$ GeV$^{-4}$.
Figures & Tables Summary References CMS Publications

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Figure 1:
The process for diphoton production via photon exchange with intact protons in the final state. Several couplings may enter the four-photon shaded area such as a loop (box) of charged fermions or bosons. The model can be extended with intermediate interactions of new physics objects, such as a loop of a heavy charged particle or an $s$-channel process producing a scalar axion-like resonance that decays into two photons.

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Figure 2:
Numbers of simulated and observed events for the various selection regions described in the text. The shaded bands show the statistical uncertainties in the simulated backgrounds added in quadrature. All selection regions are sequential from left to right, with the exception of the inclusive region used in the backgrounds yield correction, thus with a data-to-prediction ratio constrained to unity. The signal region is denoted as "Tight $ {\xi _{\gamma \gamma}^\pm} $''.

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Figure 3:
Invariant mass distribution of the diphoton pairs for the elastic selection region with events satisfying $1- {| \Delta \phi _{\gamma \gamma}/\pi |} < $ 0.005 as described in the text, for data (dots) and MC simulations (histograms). The hatched bands indicate the statistical uncertainties in simulated samples added in quadrature.

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Figure 4:
Two-dimensional limits on the anomalous four-photon couplings, derived from the observed upper limit on the diphoton production cross section. The shaded area depicts the excluded values of the coupling parameters $\zeta _1$ and $\zeta _2$.

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Table 1:
Description of the selection stages applied on the photon and proton kinematic variables, and used in this study.
To summarize, the CMS-TOTEM precision proton spectrometer has proven the feasibility of continuously operating a near-beam proton spectrometer at a high-luminosity hadron collider. The first search for the ${\mathrm{p}}{\mathrm{p}}\to{\mathrm{p}}\gamma\gamma{\mathrm{p}}$ process with forward proton tags is presented. The search uses an integrated luminosity of 9.4 fb$^{-1}$ of proton-proton collisions collected at a 13 TeV center-of-mass energy at the LHC during 2016. No events are observed with a pair of proton tracks compatible with the diphoton kinematic properties with an expected background of 0.23 and 0.43 events for the 2 and 3 standard deviations windows, respectively. This provides the first limit for the standard model light-by-light production cross section at a scale of hundreds of GeV, and places limits on anomalous couplings for the four-photon interaction based on an effective field theory extension of the standard model.
1 S. L. Adler Photon splitting and photon dispersion in a strong magnetic field Annals Phys. 67 (1971) 599
2 G. Jarlskog et al. Measurement of Delbrück scattering and observation of photon splitting at high energies PRD 8 (1973) 3813
3 R. N. Li, A. I. Mil'shtein, and V. M. Strakhovenko Splitting of a high-energy photon in a strong Coulomb field J. Exp. Theor. Phys. 85 (1997) 1049 hep-ph/9704230
4 PVLAS Collaboration Limits on low energy photon-photon scattering from an experiment on magnetic vacuum birefringence PRD 78 (2008) 032006 0805.3036
5 R. S. Van Dyck, P. B. Schwinberg, and H. G. Dehmelt New high precision comparison of electron and positron G factors PRL 59 (1987) 26
6 Muon g--2 Collaboration Final report of the muon E821 anomalous magnetic moment measurement at BNL PRD 73 (2006) 072003 hep-ex/0602035
7 Muon g-2 Collaboration Measurement of the positive muon anomalous magnetic moment to 0.46 ppm PRL 126 (2021) 141801 2104.03281
8 D. d'Enterria and G. G. da Silveira Observing light-by-light scattering at the Large Hadron Collider PRL 111 (2013) 080405 1305.7142
9 ATLAS Collaboration Observation of light-by-light scattering in ultraperipheral Pb+Pb collisions with the ATLAS detector PRL 123 (2019) 052001 1904.03536
10 CMS Collaboration Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV PLB 797 (2019) 134826 CMS-FSQ-16-012
11 ATLAS Collaboration Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC NP 13 (2017) 852 1702.01625
12 A. J. Baltz The physics of ultraperipheral collisions at the LHC PR 458 (2008) 1 0706.3356
13 E. Chapon, C. Royon, and O. Kepka Anomalous quartic WW$ \gamma\gamma $, ZZ$ \gamma\gamma $, and trilinear WW$ \gamma $ couplings in two-photon processes at high luminosity at the LHC PRD 81 (2010) 074003 0912.5161
14 I. Sahin and S. C. Inan Probe of unparticles at the LHC in exclusive two lepton and two photon production via photon-photon fusion JHEP 09 (2009) 069 0907.3290
15 R. S. Gupta Probing quartic neutral gauge boson couplings using diffractive photon fusion at the LHC PRD 85 (2012) 014006 1111.3354
16 L. N. Epele et al. Looking for magnetic monopoles at LHC with diphoton events EPJPlus 127 (2012) 60 1205.6120
17 S. Fichet et al. Probing new physics in diphoton production with proton tagging at the Large Hadron Collider PRD 89 (2014) 114004 1312.5153
18 H. Sun Large extra dimension effects through light-by-light scattering at the CERN LHC EPJC 74 (2014) 2977 1406.3897
19 S. Fichet Shining light on polarizable dark particles JHEP 04 (2017) 088 1609.01762
20 S. Fichet et al. Light-by-light scattering with intact protons at the LHC: from standard model to new physics JHEP 02 (2015) 165 1411.6629
21 CMS Collaboration Study of exclusive two-photon production of W$ ^+ $W$ ^- $ in pp collisions at $ \sqrt{s} = $ 7 TeV and constraints on anomalous quartic gauge couplings JHEP 07 (2013) 116 CMS-FSQ-12-010
22 CMS Collaboration Evidence for exclusive $ \gamma\gamma \to $ W$ ^+ $W$ ^- $ production and constraints on anomalous quartic gauge couplings in pp collisions at $ \sqrt{s}= $ 7 and 8 TeV JHEP 08 (2016) 119 CMS-FSQ-13-008
23 ATLAS Collaboration Measurement of exclusive $ \gamma\gamma\rightarrow $ W$ ^+ $W$ ^- $ production and search for exclusive higgs boson production in pp collisions at $ \sqrt{s} = $ 8 TeV using the ATLAS detector PRD 94 (2016) 032011 1607.03745
24 CMS Collaboration HEPData record for this analysis link
25 CMS Collaboration The CMS trigger system JINST 12 (2017) P01020 CMS-TRG-12-001
26 CMS Collaboration The CMS experiment at the CERN LHC JINST 3 (2008) S08004 CMS-00-001
27 CMS-TOTEM Collaboration CMS-TOTEM Precision Proton Spectrometer CERN-LHCC-2014-021, TOTEM-TDR-003, CMS-TDR-13
28 J. Kašpar Alignment of CT-PPS detectors in 2016, before TS2 CERN-TOTEM-NOTE 2017-001
29 F. Nemes LHC optics determination with proton tracks measured in the CT-PPS detectors in 2016, before TS2 CERN-TOTEM-NOTE 2017-002
30 CMS-TOTEM Collaboration 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 JHEP 07 (2018) 153 1803.04496
31 CMS Collaboration Search for high-mass diphoton resonances in proton-proton collisions at 13 TeV and combination with 8 TeV search PLB 767 (2017) 147 CMS-EXO-16-027
32 CMS Collaboration Electron and photon reconstruction and identification with the CMS experiment at the CERN LHC JINST 16 (2021) P05014 CMS-EGM-17-001
33 CMS Collaboration Performance of photon reconstruction and identification with the CMS detector in proton-proton collisions at $ \sqrt{s} = $ 8 TeV JINST 10 (2015) P08010 CMS-EGM-14-001
34 J. Alwall et al. The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations JHEP 07 (2014) 079 1405.0301
35 NNPDF Collaboration Parton distributions for the LHC Run II JHEP 04 (2015) 040 1410.8849
36 T. Sjostrand et al. An introduction to PYTHIA 8.2 CPC 191 (2015) 159 1410.3012
37 M. Boonekamp et al. FPMC: A generator for forward physics 2011 1102.2531
38 GEANT4 Collaboration GEANT4--a simulation toolkit NIMA 506 (2003) 250
39 CMS Collaboration Proton reconstruction with the Precision Proton Spectrometer (PPS) in Run 2 CDS
40 CMS Collaboration Precision luminosity measurement in proton-proton collisions at $ \sqrt{s} = $ 13 TeV in 2015 and 2016 at CMS EPJC 81 (2021) 800 CMS-LUM-17-003
41 L. A. Harland-Lang, V. A. Khoze, and M. G. Ryskin Exclusive physics at the LHC with SuperChic 2 EPJC 76 (2016) 9 1508.02718
42 L. A. Harland-Lang, V. A. Khoze, and M. G. Ryskin The photon PDF in events with rapidity gaps EPJC 76 (2016) 255 1601.03772
43 G. Cowan, K. Cranmer, E. Gross, and O. Vitells Asymptotic formulae for likelihood-based tests of new physics EPJC 71 (2011) 1554 1007.1727
44 T. Junk Confidence level computation for combining searches with small statistics NIMA 434 (1999) 435 hep-ex/9902006
45 A. L. Read Presentation of search results: the CL$ _\mathrm{s} $ technique in Durham IPPP Workshop: Advanced Statistical Techniques in Particle Physics, p. 2693 Durham, UK, March, 2002 [JPG 28 (2002) 2693]
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