CMS-PAS-EXO-16-017

CMS-PAS-EXO-16-017
Search for dark matter in association with a boosted top quark in the hadronic final state at $\sqrt{s}= $ 13 TeV
CMS Collaboration
June 2016

Abstract: A search for dark matter is conducted in events with large missing transverse energy and a hadronically decaying, boosted top quark. This study is performed using proton-proton collision data collected by the CMS detector, corresponding to an integrated luminosity of 2.3 fb$^{-1}$. No significant deviations from standard model predictions are observed and limits are placed on the production of inivisible bosons coupling to dark matter particles.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Example of monotop production via a neutral flavor-changing current.
png pdf	Figure 2-a: Comparison between data and Monte Carlo simulation in the control regions before and after performing the simultaneous fit to the different control regions and signal region. Plot (a) corresponds to the dielectron control region, and plot (b) corresponds to the dimuon control region. Plot (c) corresponds to the single photon control region. The blue solid line represents the sum of the SM background contributions normalized to the post-fit yield. The red solid line represents the sum of the SM background contributions normalized to the theoretical prediction. The stacked histograms show the individual SM background distributions after the fit is performed. The last bin contains overflow events. The gray band indicates the post-fit uncertainty after propagating all the systematic uncertainties in the fit.
png pdf	Figure 2-b: Comparison between data and Monte Carlo simulation in the control regions before and after performing the simultaneous fit to the different control regions and signal region. Plot (a) corresponds to the dielectron control region, and plot (b) corresponds to the dimuon control region. Plot (c) corresponds to the single photon control region. The blue solid line represents the sum of the SM background contributions normalized to the post-fit yield. The red solid line represents the sum of the SM background contributions normalized to the theoretical prediction. The stacked histograms show the individual SM background distributions after the fit is performed. The last bin contains overflow events. The gray band indicates the post-fit uncertainty after propagating all the systematic uncertainties in the fit.
png pdf	Figure 2-c: Comparison between data and Monte Carlo simulation in the control regions before and after performing the simultaneous fit to the different control regions and signal region. Plot (a) corresponds to the dielectron control region, and plot (b) corresponds to the dimuon control region. Plot (c) corresponds to the single photon control region. The blue solid line represents the sum of the SM background contributions normalized to the post-fit yield. The red solid line represents the sum of the SM background contributions normalized to the theoretical prediction. The stacked histograms show the individual SM background distributions after the fit is performed. The last bin contains overflow events. The gray band indicates the post-fit uncertainty after propagating all the systematic uncertainties in the fit.
png pdf	Figure 3-a: Comparison between data and Monte Carlo simulation in the control regions before and after performing the simultaneous fit to the different control regions and signal region. Plot (a) corresponds to the single electron anti-$b$-tagged control region and plot (b) corresponds to the single muon anti-$b$-tagged control region. The blue solid line represents the sum of the SM background contributions normalized to the post-fit yield. The red solid line represents the sum of the SM background contributions normalized to the theoretical prediction. The stacked histograms show the individual SM background distributions after the fit is performed. The last bin contains overflow events. The gray band represents the post-fit uncertainty propagating all the systematics through.
png pdf	Figure 3-b: Comparison between data and Monte Carlo simulation in the control regions before and after performing the simultaneous fit to the different control regions and signal region. Plot (a) corresponds to the single electron anti-$b$-tagged control region and plot (b) corresponds to the single muon anti-$b$-tagged control region. The blue solid line represents the sum of the SM background contributions normalized to the post-fit yield. The red solid line represents the sum of the SM background contributions normalized to the theoretical prediction. The stacked histograms show the individual SM background distributions after the fit is performed. The last bin contains overflow events. The gray band represents the post-fit uncertainty propagating all the systematics through.
png pdf	Figure 4-a: Comparison between data and Monte Carlo simulation in the control regions before and after performing the simultaneous fit to the different control regions and signal region. Plot (a) corresponds to the single electron $b$-tagged control region and plot (b) corresponds to the single muon $b$-tagged control region. The blue solid line represents the sum of the SM background contributions normalized to the post-fit yield. The red solid line represents the sum of the SM background contributions normalized to the theoretical prediction. The stacked histograms show the individual SM background distributions after the fit is performed. The last bin contains overflow events. The gray band represents the post-fit uncertainty propagating all the systematics through.
png pdf	Figure 4-b: Comparison between data and Monte Carlo simulation in the control regions before and after performing the simultaneous fit to the different control regions and signal region. Plot (a) corresponds to the single electron $b$-tagged control region and plot (b) corresponds to the single muon $b$-tagged control region. The blue solid line represents the sum of the SM background contributions normalized to the post-fit yield. The red solid line represents the sum of the SM background contributions normalized to the theoretical prediction. The stacked histograms show the individual SM background distributions after the fit is performed. The last bin contains overflow events. The gray band represents the post-fit uncertainty propagating all the systematics through.
png pdf	Figure 5: Distribution of ${E_{\mathrm {T}}^{\text {miss}}}$ from SM backgrounds superimposed to data in the signal region. The stacked histograms show the individual SM background distributions after the fit is performed. The blue solid line represents the sum of the SM background contributions normalized to the post-fit yield. The red solid line represents the sum of the SM background contributions normalized to the theoretical prediction. The last bin contains overflow events. The gray bands indicate the post-fit uncertainty on the background, assuming no signal. For comparison, the ${E_{\mathrm {T}}^{\text {miss}}}$ distribution from the FCNC signal model with $m_V= $ 900 GeV and $a_\text {FC} = b_\text {FC} = $ 0.1 is shown.
png pdf	Figure 6-a: Results assuming a FCNC interpretation of the monotop signature. Shown are upper limits as a function of the mass of the vector field $V$, assuming fixed $a_\text {FC} = b_\text {FC}= $ 0.1 . the limits are placed at a confidence level of 95%. a: limits on the inclusive cross section for monotop production; b: limits on $\sigma /\sigma _\text {theory}$. With the assumptions on $a_\text {FC}, b_\text {FC}$, the model is excluded in the range 300 $ < M_V < $ 1100 GeV.
png pdf	Figure 6-b: Results assuming a FCNC interpretation of the monotop signature. Shown are upper limits as a function of the mass of the vector field $V$, assuming fixed $a_\text {FC} = b_\text {FC}= $ 0.1 . the limits are placed at a confidence level of 95%. a: limits on the inclusive cross section for monotop production; b: limits on $\sigma /\sigma _\text {theory}$. With the assumptions on $a_\text {FC}, b_\text {FC}$, the model is excluded in the range 300 $ < M_V < $ 1100 GeV.

Summary

A search for dark matter in the monotop final state is performed. The data is found to be in agreement with the Standard Model prediction. Results are interpreted in terms of dark matter particles produced via a neutral flavor-changing interaction. Assuming couplings of $a_\text{FC} = b_\text{FC} =$ 0.1, the flavor-changing neutral current is excluded for mediator masses of 300 $ < M_\phi < $ 1100 GeV. Compared to previous CMS searches for monotop production, the exclusion mass range is extended.

References
1	Planck Collaboration	Planck 2015 results. XIII. Cosmological parameters		1502.01589
2	CDF Collaboration	Search for a Dark Matter Candidate Produced in Association with a Single Top Quark in $ p\overline{p} $ Collisions at $ \sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV} $	PRL 108 (May, 2012) 201802
3	CMS Collaboration	Search for Monotop Signatures in Proton-Proton Collisions at $ \sqrt{s}=8\text{ }\text{ }\mathrm{TeV} $	PRL 114 (Mar, 2015) 101801
4	CMS Collaboration	Search for monotop in the muon channel in proton-proton collisions at 8 TeV
5	ATLAS Collaboration	Search for invisible particles produced in association with single-top-quarks in proton–proton collisions at $ \sqrt{s}=8\text{ }\text{ }\mathrm{TeV} $ with the ATLAS detector	EPJC 75 (2015) 79
6	I. Boucheneb, G. Cacciapaglia, A. Deandrea, and B. Fuks	Revisiting monotop production at the LHC	Journal of High Energy Physics 2015 (2015), no. 1, 1--24
7	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
8	CMS Collaboration	Particle--Flow Event Reconstruction in CMS and Performance for Jets, Taus, and $ E_{\mathrm{T}}^{\text{miss}} $	CDS
9	M. Cacciari, G. P. Salam, and G. Soyez	The Anti-k(t) jet clustering algorithm	JHEP 04 (2008) 063	0802.1189
10	CMS Collaboration	A Cambridge-Aachen (C-A) based Jet Algorithm for boosted top-jet tagging	CDS
11	D. Bertolini, P. Harris, M. Low, and N. Tran	Pileup per particle identification	JHEP 10 (2014) 1--22	1407.6013
12	CMS Collaboration	Determination of jet energy calibration and transverse momentum resolution in CMS	Journal of Instrumentation 6 (November, 2011) 11002	CMS-JME-10-011 1107.4277
13	A. Larkoski, S. Marzani, G. Soyez, and J. Thaler	Soft drop	JHEP 146 (2014)	1402.2657
14	CMS Collaboration	Identification of b-quark jets with the CMS experiment	JINST 8 (2012) P04013
15	CMS Collaboration	Performance of b tagging at $ \sqrt{s} = 8 $$ TeV $ in multijet, $ \mathrm{t}\bar{\mathrm{t}} $, and boosted topology events.	CMS-PAS-BTV-13-001	CMS-PAS-BTV-13-001
16	J. Thaler and K. Tilburg	Identifying boosted objects with N-subjettiness	JHEP 15 (2011)	1011.2268
17	CMS Collaboration	Reconstruction and identification of $ \tau $ lepton decays to hadrons and $ \nu_\tau $ at CMS	JINST 11 (Oct, 2015) P01019. 72 p
18	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 1407 (2014) 079	1405.0301
19	T. Sj\"ostrand et al.	An Introduction to PYTHIA 8.2	CPC 191 (2015) 159--177	1410.3012
20	R. Frederix and S. Frixione	Merging meets matching in MC@NLO	JHEP 12 (2012) 061	1209.6215
21	M. L. Mangano, M. Moretti, F. Piccinini, and M. Treccani	Matching matrix elements and shower evolution for top-quark production in hadronic collisions	JHEP 0701 (2007) 013	hep-ph/0611129
22	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
23	C. Oleari	The POWHEG BOX	Nuclear Physics B Proceedings Supplements 205 (August, 2010) 36--41	1007.3893
24	S. Agostinelli, J. Allison, K. Amako et al.	Geant4 - a simulation toolkit	Nucl.Instrum.Meth. 506 (2003), no. 3, 250 -- 303
25	CMS Collaboration	Performance of Photon Reconstruction and Identification with the CMS Detector in Proton-Proton Collisions at sqrt(s) = 8 TeV	JINST 10 (2015), no. 08, P08010	CMS-EGM-14-001 1502.02702
26	CMS Collaboration	Data-Driven Estimation of the Invisible Z Backgrund to the SUSY MET Plus Jets Search	Technical Report CMS-PAS-SUS-08-002, CERN, Geneva
27	J. H. Kuhn, A. Kulesza, S. Pozzorini, and M. Schulze	Electroweak corrections to hadronic photon production at large transverse momenta	JHEP 03 (2006) 059	hep-ph/0508253
28	S. Kallweit et al.	NLO electroweak automation and precise predictions for W+multijet production at the LHC	JHEP 04 (2015) 012	1412.5157
29	S. Kallweit et al.	NLO QCD+EW automation and precise predictions for V+multijet production	in 50th Rencontres de Moriond on QCD and High Energy Interactions La Thuile, Italy, March 21-28, 2015 2015	1505.05704
30	S. Kallweit et al.	NLO QCD+EW predictions for V+jets including off-shell vector-boson decays and multijet merging		1511.08692
31	NNPDF Collaboration	Parton distributions for the LHC Run II	JHEP 04 (2015) 040	1410.8849
32	CMS Collaboration	Differential cross section measurements for the production of a W boson in association with jets in proton-proton collisions at $ \sqrt{s} $=7 TeV	CDS
33	CMS Collaboration	Measurement of the production cross section for a W boson and two b jets in pp collisions at $ \sqrt{s} $=7 TeV	CDS
34	CMS Collaboration	Measurements of jet multiplicity and differential production cross sections of Z+jets events in proton-proton collisions at $ \sqrt{s} $=7 TeV	CDS
35	CMS Collaboration	Measurement of the production cross sections for a Z boson and one or more b jets in pp collisions at $ \sqrt{s} $=7 TeV	CDS
36	CMS Collaboration	First measurement of the differential cross section for ttbar production in the dilepton final state at sqrts = 13 TeV	CMS-PAS-TOP-15-010	CMS-PAS-TOP-15-010
37	CMS Collaboration	Measurement of the ZZ production cross section in $ \ell\ell\ell'\ell' $ decays in pp collisions at $ \sqrt{s} = 13 $ TeV	CMS-PAS-SMP-15-005	CMS-PAS-SMP-15-005
38	CMS Collaboration	Measurement of the WZ production cross section in pp collisions at $ \sqrt{s} = 13 $ TeV	CMS-PAS-SMP-15-006	CMS-PAS-SMP-15-006
39	CMS Collaboration	Performance of the CMS missing transverse momentum reconstruction in pp data at $ \sqrt{s} $ = 8 TeV	JINST 10 (2015), no. 02, P02006	CMS-JME-13-003 1411.0511
40	CMS Collaboration	CMS Luminosity Measurement for the 2015 Data Taking Period	CMS-PAS-LUM-15-001	CMS-PAS-LUM-15-001
41	A. L. Read	Presentation of search results: the CLs technique	Journal of Physics G: Nuclear and Particle Physics 28 (2002), no. 10