Study of exclusive two-photon production of W+W− in pp collisions at √s = 7 TeV and constraints on anomalous quartic gauge couplings

Abstract

A search for exclusive or quasi-exclusive W+W- production by photon-photon interactions, pp→p(∗)W+W-p(∗), at √s = 7 TeV is reported using data collected by the CMS detector with an integrated luminosity of 5.05 inverse femtobarns. Events are selected by requiring a μe vertex with no additional associated charged tracks and dilepton transverse momentum pT (μe) > 30 GeV. Two events passing all selection requirements are observed in the data, compared to a standard model expectation of 2.20.4 signal events with 0.840.15 background. The tail of the dilepton pT distribution is studied for deviations from the standard model. No events are observed with pT (μe) > 100 GeV. Model-independent upper limits are computed and compared to predictions involving anomalous quartic gauge couplings. The limits on the parameters aW0,C/Λ2 with a dipole form factor and an energy cutoff Λcutoff = 500 GeV are of the order of 10−4.

Figures

Figure 1
Figure 1. Transverse momentum distribution of lepton pairs for the γγ→WW process at generator level in the SM (shaded histogram), and for several values of AQGC parameter a0W2, while aCW2 is set to zero (open histograms). In this plots Λ = 500 GeV is the scale for new physics and p is set to 2.0. All distributions are scaled to a integrated luminosity of 5.05 fb-1.
Figure 2 left
Figure 2. Invariant mass distribution of the muon pairs for the elastic selection. The dotted lines indicates the Z peak region. The hatched bands indicate the statistical uncertainty on the simulation.

Figure 3 upper left Figure
Figure 3 upper left Figure
Figure 3. Kinematic distributions for the elastic selection, for the Z region only (70 GeV < m(μμ) < 106 GeV, left column) and with the Z region removed (right column). The acoplanarity of μμ pairs with 0 extra tracks (above), and pT of μμ pairs with 0 extra tracks (below) are shown. The hatched bands indicate the statistical uncertainty on the simulation.

Figure 4 left
Figure 4. Invariant mass distribution of the muon pairs for the dissociation selection. The dotted lines indicates the Z peak region. The hatched bands indicate the statistical uncertainty on the simulation.

Figure 5 left Figure
Figure 5. Kinematic distributions for the proton dissociation selection, for the Z region only (70 GeV < m(μμ) < 106 GeV, left column) and with the Z region removed (right column). The pT of μμ pairs with 0 extra tracks are shown. The hatched bands indicate the statistical uncertainty on the simulation.

Figure 6
Figure 6. Number of additional tracks on the electron-muon primary vertex for events with pT(μe) > 30 GeV. The shaded bands indicate the statistical uncertainty on the background estimation.

Figure 7 left Figure 7 right
Figure 7. .μe invariant mass (left) and acoplanarity (right) for events with 1-6 extra tracks on the μe vertex and pT(μe) > 30 GeV. The shaded bands indicate the statistical uncertainty on the background estimation.

Figure 8 left Figure 8 right
Figure 8. μe invariant mass (left) and acoplanarity (right) for events with 0 extra tracks on the μe vertex and pT(μe) < 30 GeV. The shaded bands indicate the statistical uncertainty on the background estimation.

Figure 9 above left Figure 9 above right Figure 9 below
Figure 9. μe invariant mass (left), acoplanarity (center), and missing transverse energy (right) for events in the signal region with 0 extra tracks on the μe vertex and pT(μe) > 30 GeV. The backgrounds (solid histograms) are stacked with statistical uncertainties indicated by the shaded region, the signal histogram (open histogram) is stacked on top of the backgrounds.

Figure 10 left Figure 10 right
Figure 10. Full pT distribution for events with 0 extra tracks (left) and multiplicity of extra tracks for events with pT(μe) > 100 GeV (right). The backgrounds (solid histograms) are stacked with statistical uncertainties indicated by the shaded region, the signal histogram (open histogram) is stacked on top of the backgrounds. The expected signal is shown for the SM γγ→W+W- signal (solid lines), and for two representative values of the anomalous couplings a0W2 and aCW2 (dotted and dashed lines).

Figure 10
Figure 11. Excluded values of the anomalous coupling parameters a0W2 and aCW2 with \Lambda= 500 GeV.The area outside the solid contour is excluded by this measurement at 95\%~CL, obtained for pT(μ, e) > 20 GeV, η(μ, e) < 2.4, pT(μe) > 100 GeV. The predicted cross sections are rescaled to include the contribution from proton dissociation.

EventDisplays.png
Event displays. Displays of the two selected candidate events.

Figure 7 left Figure 7 right
Figure 7 left Figure 7 right
Figure 7 left Figure 7 right
Event displays. Display of the first selected candidate event showing all tracks in the event (left), and only tracks from the e-mu primary vertex (right).

Figure 7 left Figure 7 right
Figure 7 left Figure 7 right
Figure 7 left Figure 7 right
Event displays. Display of the second selected candidate event showing all tracks in the event (left), and only tracks from the e-mu primary vertex (right).

Topic attachments
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PDFpdf CMS_2D_limit_v3.pdf r1 manage 15.2 K 2013-06-03 - 08:50 JonathanHollar  
PNGpng EventDisplays.png r1 manage 86.4 K 2013-02-04 - 10:21 JonathanHollar  
PNGpng Run163402_RhoPhi_NoPUTracks.png r1 manage 71.9 K 2013-04-28 - 14:49 JonathanHollar  
PNGpng Run163402_RhoPhi_WithPUTracks.png r1 manage 72.9 K 2013-04-28 - 14:51 JonathanHollar  
PNGpng Run163402_RhoZ_NoPUTracks.png r1 manage 48.8 K 2013-04-28 - 14:49 JonathanHollar  
PNGpng Run163402_RhoZ_WithPUTracks.png r1 manage 50.8 K 2013-04-28 - 14:52 JonathanHollar  
PNGpng Run163402_ThreeD_NoPUTracks.png r1 manage 72.2 K 2013-04-28 - 14:49 JonathanHollar  
PNGpng Run163402_ThreeD_WithPUTracks.png r1 manage 72.7 K 2013-04-28 - 14:53 JonathanHollar  
PNGpng Run177201_RhoPhi_NoPUTracks.png r1 manage 72.6 K 2013-04-28 - 14:50 JonathanHollar  
PNGpng Run177201_RhoPhi_WithPUTracks.png r1 manage 73.7 K 2013-04-28 - 14:53 JonathanHollar  
PNGpng Run177201_RhoZ_NoPUTracks.png r1 manage 49.1 K 2013-04-28 - 14:50 JonathanHollar  
PNGpng Run177201_RhoZ_WithPUTracks.png r1 manage 50.9 K 2013-04-28 - 14:53 JonathanHollar  
PNGpng Run177201_ThreeD_NoPUTracks.png r1 manage 65.5 K 2013-04-28 - 14:51 JonathanHollar  
PNGpng Run177201_ThreeD_WithPUTracks.png r1 manage 64.9 K 2013-04-28 - 14:54 JonathanHollar  
PDFpdf dphiemu_0tracks_pt30_unblind_final.pdf r1 manage 15.7 K 2013-06-03 - 08:50 JonathanHollar  
PDFpdf dphiemu_0tracks_ptlessthan30_final.pdf r1 manage 16.7 K 2013-06-03 - 08:51 JonathanHollar  
PDFpdf dphiemu_1to6tracks_pt30_final.pdf r1 manage 16.3 K 2013-06-03 - 08:51 JonathanHollar  
PDFpdf dphimumu_0tracks_elastic_Z_final.pdf r1 manage 22.0 K 2013-06-03 - 09:02 JonathanHollar  
PDFpdf dphimumu_0tracks_elastic_Z_logscale_final.pdf r1 manage 22.1 K 2013-06-03 - 09:02 JonathanHollar  
PDFpdf dphimumu_0tracks_elastic_noZ_final.pdf r1 manage 21.9 K 2013-06-03 - 09:01 JonathanHollar  
PDFpdf dphimumu_0tracks_elastic_noZ_logscale_final.pdf r1 manage 22.4 K 2013-06-03 - 09:14 JonathanHollar  
PDFpdf memu_0tracks_pt30_unblind_final.pdf r1 manage 15.1 K 2013-06-03 - 08:53 JonathanHollar  
PDFpdf memu_0tracks_ptlessthan30_final.pdf r1 manage 15.9 K 2013-06-03 - 08:53 JonathanHollar  
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PDFpdf mmumu_0tracks_elastic_final.pdf r1 manage 21.8 K 2013-06-03 - 09:02 JonathanHollar  
PDFpdf mmumu_0tracks_inelastic_logscale_final.pdf r1 manage 23.1 K 2013-06-03 - 09:49 JonathanHollar  
PDFpdf nextratracks_pt100_AQGCunblind_final.pdf r1 manage 16.9 K 2013-06-03 - 09:38 JonathanHollar  
PDFpdf nextratracks_pt30_final.pdf r1 manage 16.8 K 2013-06-03 - 08:54 JonathanHollar  
PDFpdf pfmet_0tracks_pt30_unblind_final.pdf r1 manage 15.5 K 2013-06-03 - 09:28 JonathanHollar  
PNGpng plotsfeb21_CMS_2D_limit_v3.png r1 manage 25.6 K 2013-06-03 - 08:55 JonathanHollar  
PNGpng plotsfeb21_dphiemu_0tracks_pt30_unblind_final.png r1 manage 22.7 K 2013-06-03 - 08:55 JonathanHollar  
PNGpng plotsfeb21_dphiemu_0tracks_ptlessthan30_final.png r1 manage 25.4 K 2013-06-03 - 09:03 JonathanHollar  
PNGpng plotsfeb21_dphiemu_1to6tracks_pt30_final.png r1 manage 25.5 K 2013-06-03 - 08:56 JonathanHollar  
PNGpng plotsfeb21_dphimumu_0tracks_elastic_Z_logscale_final.png r1 manage 35.4 K 2013-06-03 - 09:10 JonathanHollar  
PNGpng plotsfeb21_dphimumu_0tracks_elastic_noZ_logscale_final.png r1 manage 36.8 K 2013-06-03 - 09:09 JonathanHollar  
PNGpng plotsfeb21_memu_0tracks_pt30_unblind_final.png r1 manage 23.4 K 2013-06-03 - 09:03 JonathanHollar  
PNGpng plotsfeb21_memu_0tracks_ptlessthan30_final.png r1 manage 25.1 K 2013-06-03 - 09:27 JonathanHollar  
PNGpng plotsfeb21_memu_1to6tracks_pt30_final.png r1 manage 26.6 K 2013-06-03 - 09:04 JonathanHollar  
PNGpng plotsfeb21_mmumu_0tracks_elastic_final.png r1 manage 27.2 K 2013-06-03 - 09:05 JonathanHollar  
PNGpng plotsfeb21_mmumu_0tracks_inelastic_logscale_final.png r1 manage 30.3 K 2013-06-03 - 09:50 JonathanHollar  
PNGpng plotsfeb21_nextratracks_pt100_AQGCunblind_final.png r1 manage 33.2 K 2013-06-03 - 09:41 JonathanHollar  
PNGpng plotsfeb21_nextratracks_pt30_final.png r1 manage 26.6 K 2013-06-03 - 09:22 JonathanHollar  
PNGpng plotsfeb21_pfmet_0tracks_pt30_unblind_final.png r1 manage 23.0 K 2013-06-03 - 09:30 JonathanHollar  
PNGpng plotsfeb21_pt_GEN_no-cuts_weight_lin.png r1 manage 26.3 K 2013-06-03 - 08:57 JonathanHollar  
PNGpng plotsfeb21_ptemu_0tracks_AQGCunblind_final.png r1 manage 33.4 K 2013-06-03 - 09:37 JonathanHollar  
PNGpng plotsfeb21_ptmumu_0tracks_elastic_Z_final.png r1 manage 31.8 K 2013-06-03 - 09:10 JonathanHollar  
PNGpng plotsfeb21_ptmumu_0tracks_elastic_noZ_final.png r1 manage 32.2 K 2013-06-03 - 09:10 JonathanHollar  
PNGpng plotsfeb21_ptmumu_0tracks_inelastic_Z_logscale_final.png r1 manage 33.4 K 2013-06-03 - 09:11 JonathanHollar  
PNGpng plotsfeb21_ptmumu_0tracks_inelastic_noZ_logscale_final.png r1 manage 34.7 K 2013-06-03 - 09:11 JonathanHollar  
PDFpdf pt_GEN_no-cuts_weight_lin.pdf r3 r2 r1 manage 14.7 K 2013-06-03 - 08:59 JonathanHollar  
PDFpdf ptemu_0tracks_AQGCunblind_final.pdf r1 manage 16.3 K 2013-06-03 - 09:38 JonathanHollar  
PDFpdf ptmumu_0tracks_elastic_Z_final.pdf r1 manage 19.6 K 2013-06-03 - 09:09 JonathanHollar  
PDFpdf ptmumu_0tracks_elastic_noZ_final.pdf r1 manage 19.4 K 2013-06-03 - 09:09 JonathanHollar  
PDFpdf ptmumu_0tracks_inelastic_Z_logscale_final.pdf r1 manage 20.8 K 2013-06-03 - 09:12 JonathanHollar  
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Topic revision: r4 - 2013-06-03 - JonathanHollar
 
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