-- BhawnaGomber - 2014-11-03

# Search for new phenomena in monophoton final states in proton-proton collisions at √s = 8 TeV

## Abstract

Results are presented from a search for new physics in final states containing a photon and missing transverse momentum. The data correspond to an integrated luminosity of 19.6 fb-1 collected in proton-proton collisions at √s =8 TeV with the CMS experiment at the CERN LHC. No deviation from the standard model predictions is observed for these final states. New, improved limits are set on dark matter production and on parameters of models with large extra dimensions. In particular, the first limits on branon production at a hadron collider are found and significantly extend previous limits from LEP. A cross section upper limit of 14.0 fb is set at the 95% confidence level for events with a monophoton final state with photon transverse momentum greater than 145 GeV and missing transverse momentum greater than 140 GeV.

## Approved Plots from EXO-12-047 ( click on plot to get .pdf )

Figure Abbreviated Caption
Photon transverse momentum distribution for the candidate sample, compared with estimated contribtuions from Standard model backgrounds and a prediction from ADD signal for $M_{D}$ = 2 TeV and $n$ = 3. The bottom panel shows the ratio of data over expected events based on combined statistical and systematic uncertainty.
The MET distribution for the candidate sample, compared with estimated contributions from SM background and a prediction from ADD signal for $M_{D}$ = 2 TeV and $n$ = 3. The bottom panel shows the ratio of data over expected events based on combined statistical and systematic uncertainty.
Summary of estimated backgrounds and observed total number of candidates for 19.6 fb-1 of 2012 data. Backgrounds listed as Others include $W\mu\nu$, $Z(ll)+\gamma$, $\gamma\gamma$ and $\gamma$+jet. A scale factor has been applied on backgrounds estimated from MC and k factor have been applied on $Z(\nu\nu)+\gamma$ and $W(l\nu)+\gamma$ backgrounds.
Model-independent 95% confidence level upper limits on a signal cross section times acceptance for counting experiments as a function of the cut on the photon transverse momentum.
Observed (expected) model-independent 95% and 90% confidence level upper limits on a signal cross section times acceptance for counting experiments as a function of the cut on the photon transverse momentum.
Limits on $M_{D}$ as a function of extra dimensions, compared to LO results from similar searches at the Tevatron and LEP along with the CMS 7 TeV results.
The 95% confidence level observed and expected limits on the ADD cross section as a function of $M_{D}$ and extra dimensions.
The 90% confidence level upper limits on the $\chi$-nucleon cross section as a function of $M_{\chi}$ for spin independent scattering. Also shown are the limits from selected experiments with published results along with CMS 7 and 8 TeV results.
This table summarizes the theoretical dark-matter production cross section (where generated photon transverse momentum is greater than 130 GeV and cut-off scale $\Lambda$ is 10 TeV), observed(expected) 90% confidence level upper limits on the dark matter production cross section where a photon with pT greater than 130 GeV is radiated by one of the incoming quarks, 90% confidence level observed(expected) lower limits on the cut-off scale $\Lambda$ and the 90% confidence level observed(expected) upper limits on the $\chi$-nucleon cross section for the vector operator as a function of the dark-matter mass.
The 90% confidence level upper limits on the $\chi$-nucleon cross section as a function of $M_{\chi}$ for spin dependent scattering. Also shown are the limits from selected experiments with published results along with CMS 7 and 8 TeV results.
This table summarizes the theoretical dark-matter production cross section (where generated photon transverse momentum is greater than 130 GeV and cut-off scale $\Lambda$ is 10 TeV), observed(expected) 90% confidence level upper limits on the dark matter production cross section where a photon with pT greater than 130 GeV is radiated by one of the incoming quark, 90% confidence level observed(expected) lower limits on the cut-off scale $\Lambda$ and the 90% confidence level observed(expected) upper limits on the $\chi$-nucleon cross section for the axial vector operator as a function of the dark-matter mass.
Observed limits on the DM mediator mass divided by coupling, $M/\sqrt{g_{\chi}g_{q}}$ as a function of the mediator mass $M$, assuming vector interactions, for DM particle masses of 50 GeV and 500 GeV. The width, $\Gamma$, of the mediator is varied between $M/8\pi$ and $M/3$. The dashed lines show contours of constant coupling.
The 95% confidence level upper limits on the Branon cross sections as a function of branon mass.
The 95% confidence level upper limits on the branon brane tension as a function of branon mass. Also shown is the LEP limits.
The 95% confidence level observed and expected upper limits on the branon brane tension $f$ as a function of the branon mass $M_{B}$ .

## Other Unpublished Results ( click on plot to get .pdf )

 Photon transverse momentum distribution in the $Z\gamma$ control region. Data is depicted as solid circles with error bars. Standard model backgrounds are shown as colored histograms and the shaded band is their uncertainty. The bottom panel shows the ratio of data over expected events based on combined statistical and systematic uncertainty. Missing transverse energy distribution in the $Z\gamma$ control region. Data is depicted as solid circles with error bars. Standard model backgrounds are shown as colored histograms and the shaded band is their uncertainty. The bottom panel shows the ratio of data over expected events based on combined statistical and systematic uncertainty. Photon transverse momentum distribution in the $W\gamma$ control region. Data is depicted as solid circles with error bars. Standard model backgrounds are shown as colored histograms and the shaded band is their uncertainty. The bottom panel shows the ratio of data over expected events based on combined statistical and systematic uncertainty. Missing transverse energy distribution in the $W\gamma$ control region. Data is depicted as solid circles with error bars. Standard model backgrounds are shown as colored histograms and the shaded band is their uncertainty. The bottom panel shows the ratio of data over expected events based on combined statistical and systematic uncertainty. 3-D view of the highest photon $p_{T}$ candidate event. Info: run:event:lumisection =207454:771:1095163126; Photon Pt = 653 GeV; MET = 716 GeV Rho-Phi view of the highest photon $p_{T}$ candidate event. Info: run:event:lumisection =207454:771:1095163126; Photon Pt = 653 GeV; MET = 716 GeV Absolute value of the log10 of pvalue for the candidate sample, compared with estimated contributions from Standard model backgrounds and a prediction from ADD signal for $M_{D}$ = 2 TeV and $n$ = 3 . The bottom panel shows the ratio of data over expected events based on combined statistical and systematic uncertainty. Recalculated minimized MET distribution for the candidate sample, compared with estimated contributions from Standard model backgrounds and a prediction from ADD signal for $M_{D}$ = 2 TeV and $n$ = 3. The bottom panel shows the ratio of data over expected events based on combined statistical and systematic uncertainty. 3-D view of the QCD event. Info: run:event:lumisection = 194050:698:652513020; Jet Pt = 965 GeV Rho-Phi view of the QCD event. Info: run:event:lumisection = 194050:698:652513020; Jet Pt = 965 GeV Model-independent 90% confidence level upper limits on a signal cross section times acceptance for counting experiments as a function of the cut on the photon transverse momentum.
Topic attachments
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pdf ADD.pdf r1 manage 17.7 K 2014-11-05 - 21:38 BhawnaGomber
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Topic revision: r4 - 2014-11-17 - JuanAlcaraz

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