CMS-SUS-18-002

CMS-SUS-18-002 ; CERN-EP-2018-353
Search for supersymmetry in events with a photon, jets, b-jets, and missing transverse momentum in proton-proton collisions at 13 TeV
CMS Collaboration
20 January 2019
Eur. Phys. J. C 79 (2019) 444
Abstract: A search for supersymmetry is presented based on events with at least one photon, jets, and large missing transverse momentum produced in proton-proton collisions at a center-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 35.9 fb$^{-1}$ and were recorded at the LHC with the CMS detector in 2016. The analysis characterizes signal-like events by categorizing the data into various signal regions based on the number of jets, the number of b-tagged jets, and the missing transverse momentum. No significant excess of events is observed with respect to the expectations from standard model processes. Limits are placed on the gluino and top squark pair production cross sections using several simplified models of supersymmetric particle production with gauge-mediated supersymmetry breaking. Depending on the model and the mass of the next-to-lightest supersymmetric particle, the production of gluinos with masses as large as 2120 GeV and the production of top squarks with masses as large as 1230 GeV are excluded at 95% confidence level.
Links: e-print arXiv:1901.06726 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures & Tables	Summary	Additional Figures & Tables	References	CMS Publications

Additional information on efficiencies needed for reinterpretation of these results are available here
Additional technical material for CMS speakers can be found here

Figures
png pdf	Figure 1: Example diagrams depicting the simplified models used, which are defined in the text. The top left diagram depicts the T5qqqqHG model, the top right diagram depicts the T5bbbbZG model, the bottom left diagram depicts the T5ttttZG model, and the bottom right depicts the T6ttZG model.
png pdf	Figure 1-a: Example diagram depicting the simplified T5qqqqHG model.
png pdf	Figure 1-b: Example diagram depicting the simplified T5bbbbZG model.
png pdf	Figure 1-c: Example diagram depicting the simplified T5ttttZG model.
png pdf	Figure 1-d: Example diagram depicting the simplified T6ttZG model.
png pdf	Figure 2: The lost-lepton and ${{{\tau} _\mathrm {h}}}$ event yields as predicted directly from simulation in the signal regions, shown in red, and from the prediction procedure applied to simulated ${{\mathrm {e}}{{\gamma}}}$ or ${{{\mu}}{{\gamma}}}$ events, shown in blue. The error bars correspond to the statistical uncertainties from the limited number of events in simulation. The bottom panel shows the ratio of the simulation expectation (Exp.) and the simulation-based prediction (Pred.). The hashed area shows the expected uncertainties from data-to-simulation correction factors, PDFs, and renormalization and factorization scales. The categories, denoted by dashed lines, are labeled as ${N_{\mathrm {j}}^{\mathrm {b}}}$, where j refers to the number of jets and b refers to the number of b-tagged jets. The numbered bins within each category are the various ${{p_{\mathrm {T}}} ^\text {miss}}$ bins. In each of these regions, the first bin corresponds to 100 $ < {{p_{\mathrm {T}}} ^\text {miss}} < $ 200 GeV, which belongs to a control region. The remaining bins correspond to the signal regions in Table 1.
png pdf	Figure 3: The double ratio $\kappa $ in each ${N_{\text {jets}}} $-$ {N_{{{\mathrm {b}}}\text {-jets}}}$ region for zero-photon events. The filled black circles are the observed $\kappa $ values after subtracting the electroweak contamination based on simulation. The open blue squares are the $\kappa $ values computed directly from simulation. The ratio is shown in the bottom panel, where the shaded region corresponds to the systematic uncertainty in the $\gamma$+jets prediction. In the label ${N_{\mathrm {j}}^{\mathrm {b}}}$, j refers to the number of jets and b refers to the number of b-tagged jets.
png pdf	Figure 4: Observed numbers of events and predicted numbers of events from the various SM backgrounds in the 25 signal regions. The categories, denoted by vertical lines, are labeled as ${N_{\mathrm {j}}^{\mathrm {b}}}$, where j refers to the number of jets and b refers to the number of b-tagged jets. The numbered bins within each category are the various ${{p_{\mathrm {T}}} ^\text {miss}}$ bins, as defined in Table 1. The lower panel shows the ratio of the observed events to the predicted SM background events. The error bars in the lower panel are the quadrature sum of the statistical uncertainty in the observed data and the systematic uncertainty in the predicted backgrounds before the adjustments based on a maximum likelihood fit to data assuming no signal strength.
png pdf	Figure 5: Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the T5qqqqHG (upper left), T5bbbbZG (upper right), T5ttttZG (bottom left), and T6ttZG (bottom right) models. Black lines denote the observed exclusion limit and the uncertainty due to variations of the theoretical prediction of the gluino or top squark pair production cross section. The dashed lines correspond to the region containing 68% of the distribution of the expected exclusion limits under the background-only hypothesis.
png pdf root	Figure 5-a: Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the T5qqqqHG model. Black lines denote the observed exclusion limit and the uncertainty due to variations of the theoretical prediction of the gluino or top squark pair production cross section. The dashed lines correspond to the region containing 68% of the distribution of the expected exclusion limits under the background-only hypothesis.
png pdf root	Figure 5-b: Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the T5bbbbZG model. Black lines denote the observed exclusion limit and the uncertainty due to variations of the theoretical prediction of the gluino or top squark pair production cross section. The dashed lines correspond to the region containing 68% of the distribution of the expected exclusion limits under the background-only hypothesis.
png pdf root	Figure 5-c: Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the T5ttttZG model. Black lines denote the observed exclusion limit and the uncertainty due to variations of the theoretical prediction of the gluino or top squark pair production cross section. The dashed lines correspond to the region containing 68% of the distribution of the expected exclusion limits under the background-only hypothesis.
png pdf root	Figure 5-d: Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the T6ttZG model. Black lines denote the observed exclusion limit and the uncertainty due to variations of the theoretical prediction of the gluino or top squark pair production cross section. The dashed lines correspond to the region containing 68% of the distribution of the expected exclusion limits under the background-only hypothesis.

Tables
png pdf	Table 1: Predicted and observed event yields for each of the 25 exclusive signal regions.

Summary

A search for gluino and top squark pair production is presented, based on a proton-proton collision dataset at a center-of-mass energy of 13 TeV recorded with the CMS detector in 2016. The data correspond to an integrated luminosity of 35.9 fb$^{-1}$. Events are required to have at least one isolated photon with transverse momentum $p_{\mathrm{T}}>$ 100 GeV, two jets with $p_{\mathrm{T}}>$ 30 GeV and pseudorapidity $| \eta | < $ 2.4, and missing transverse momentum $p_{\mathrm{T}}^{\text{miss}}>$ 200 GeV.

The data are categorized into 25 exclusive signal regions based on the number of jets, the number of b-tagged jets, and $p_{\mathrm{T}}^{\text{miss}}$. Background yields from the standard model processes are predicted using simulation and data control regions. The observed event yields are found to be consistent with expectations from the standard model processes within the uncertainties.

Results are interpreted in the context of simplified models. Four such models are studied, three of which involve gluino pair production and one of which involves top squark pair production. All models assume a gauge-mediated supersymmetry (SUSY) breaking scenario, in which the lightest SUSY particle is a gravitino ($ \tilde{\mathrm{G}}$). We consider scenarios in which the gluino decays to a neutralino $\tilde{\chi}^{0}_{1}$ and a pair of light-flavor quarks (T5qqqqHG), bottom quarks (T5bbbbZG), or top quarks (T5ttttZG). In the T5qqqqHG model, the $\tilde{\chi}^{0}_{1}$ decays with equal probability either to a photon and a $ \tilde{\mathrm{G}}$ or to a Higgs boson and a $ \tilde{\mathrm{G}}$. In the T5bbbbZG and T5ttttZG models, the $\tilde{\chi}^{0}_{1}$ decays with equal probability either to a photon and a $ \tilde{\mathrm{G}}$ or to a Z boson and a $ \tilde{\mathrm{G}}$. In the top squark pair production model (T6ttZG), top squarks decay to a top quark and $\tilde{\chi}^{0}_{1}$, and the $\tilde{\chi}^{0}_{1}$ decays with equal probability either to a photon and a $ \tilde{\mathrm{G}}$ or to a Z boson and a $ \tilde{\mathrm{G}}$.

Using the cross sections for SUSY pair production calculated at next-to-leading order plus next-to-leading logarithmic accuracy, we place 95% confidence level lower limits on the gluino mass as large as 2120 GeV, depending on the model and the $m_{\tilde{\chi}^{0}_{1}}$ value, and limits on the top squark mass as large as 1230 GeV, depending on the $m_{\tilde{\chi}^{0}_{1}}$ value. These results significantly improve upon those from previous searches for SUSY with photons.

Additional Figures
png pdf	Additional Figure 1: Comparison of predicted and true MC yields for the misidentified photon background after parameterizing the misidentification rate as a function of ${Q_{\text {mult}}}$ and electron ${p_{\mathrm {T}}}$. The bottom panel shows the ratio of the MC expectation (Exp.) and the MC-based prediction (Pred.). The hashed area shows various systematic uncertainties associated with the prediction.
png pdf	Additional Figure 2: The ${N_{\text {jets}}}$ distribution for predicted SM processes and observed data in a region corresponding to $ {N_{\text {b-jets}}} \geq $ 1 and $ {{p_{\mathrm {T}}} ^\text {miss}} > $ 450 GeV. The two solid lines show the ${N_{\text {jets}}}$ distribution for two representative T5qqqqHG signal scenarios.
png pdf	Additional Figure 3: The ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for predicted SM processes and observed data in a region corresponding to $ {N_{\text {b-jets}}} = $ 0 and 2 $ \leq {N_{\text {jets}}} \leq $ 4. The two solid lines show the ${{p_{\mathrm {T}}} ^\text {miss}}$ distribution for two representative T5qqqqHG signal scenarios.
png pdf	Additional Figure 4: The ${N_{\text {jets}}}$ distribution for predicted SM processes and observed data in a region corresponding to $ {N_{\text {b-jets}}} \geq $ 1 and $ {{p_{\mathrm {T}}} ^\text {miss}} > $ 450 GeV. The two solid lines show the ${N_{\text {jets}}}$ distribution for two representative T5bbbbZG signal scenarios.
png pdf	Additional Figure 5: The ${N_{\text {jets}}}$ distribution for predicted SM processes and observed data in a region corresponding to $ {N_{\text {b-jets}}} \geq $ 1 and $ {{p_{\mathrm {T}}} ^\text {miss}} > $ 450 GeV. The two solid lines show the ${N_{\text {jets}}}$ distribution for two representative T5ttttZG signal scenarios.
png pdf	Additional Figure 6: The ${N_{\text {jets}}}$ distribution for predicted SM processes and observed data in a region corresponding to $ {N_{\text {b-jets}}} \geq $ 1 and $ {{p_{\mathrm {T}}} ^\text {miss}} > $ 450 GeV. The two solid lines show the ${N_{\text {jets}}}$ distribution for two representative T6ttZG signal scenarios.
png pdf root	Additional Figure 7: The pre-fit background covariance matrix.
png pdf root	Additional Figure 8: The pre-fit background correlation matrix.

Additional Tables
png pdf	Additional Table 1: Event yields for each step of the event selection process for representative models of gluino pair production with $m_{{\mathrm {\tilde{g}}}} = $ 1800 GeV . The $ {\tilde{\chi}^{0}_{1}} $ mass is expressed in units of GeV. The yields are scaled to an integrated luminosity of 35.9 fb$^{-1}$.

References
1	F. Zwicky	Die Rotverschiebung von extragalaktischen Nebeln	Helv. Phys. Acta 6 (1933)110
2	V. C. Rubin and W. K. Ford Jr	Rotation of the Andromeda nebula from a spectroscopic survey of emission regions	Astrophys. J. 159 (1970) 379
3	R. Barbieri and G. F. Giudice	Upper bounds on supersymmetric particle masses	NPB 306 (1988) 63
4	S. Dimopoulos and G. F. Giudice	Naturalness constraints in supersymmetric theories with nonuniversal soft terms	PLB 357 (1995) 573	hep-ph/9507282
5	R. Barbieri and D. Pappadopulo	S-particles at their naturalness limits	JHEP 10 (2009) 061	0906.4546
6	M. Papucci, J. T. Ruderman, and A. Weiler	Natural SUSY endures	JHEP 09 (2012) 035	1110.6926
7	CMS Collaboration	Measurements of properties of the Higgs boson decaying into the four-lepton final state in pp collisions at $ \sqrt{s}= $ 13 TeV	JHEP 11 (2017) 047	CMS-HIG-16-041 1706.09936
8	ATLAS and CMS Collaborations	Combined measurement of the Higgs boson mass in $ pp $ collisions at $ \sqrt{s}= $ 7 and 8 TeV with the ATLAS and CMS experiments	PRL 114 (2015) 191803	1503.07589
9	P. Ramond	Dual theory for free fermions	PRD 3 (1971) 2415
10	\relax Yu. A. Golfand and E. P. Likhtman	Extension of the algebra of Poincar$ \'e $ group generators and violation of P invariance	JEPTL 13 (1971)323
11	A. Neveu and J. H. Schwarz	Factorizable dual model of pions	NPB 31 (1971) 86
12	D. V. Volkov and V. P. Akulov	Possible universal neutrino interaction	JEPTL 16 (1972)438
13	J. Wess and B. Zumino	A Lagrangian model invariant under supergauge transformations	PLB 49 (1974) 52
14	J. Wess and B. Zumino	Supergauge transformations in four dimensions	NPB 70 (1974) 39
15	P. Fayet	Supergauge invariant extension of the Higgs mechanism and a model for the electron and its neutrino	NPB 90 (1975) 104
16	H. P. Nilles	Supersymmetry, supergravity and particle physics	Phys. Rep. 110 (1984) 1
17	G. R. Farrar and P. Fayet	Phenomenology of the production, decay, and detection of new hadronic states associated with supersymmetry	PLB 76 (1978) 575
18	P. Meade, N. Seiberg, and D. Shih	General gauge mediation	Prog. Theor. Phys. Suppl. 177 (2009) 143	0801.3278
19	S. Deser and B. Zumino	Broken supersymmetry and supergravity	PRL 38 (1977) 1433
20	E. Cremmer et al.	Super-Higgs effect in supergravity with general scalar interactions	PLB 79 (1978) 231
21	N. Arkani-Hamed et al.	MARMOSET: The path from LHC data to the new standard model via on-shell effective theories		hep-ph/0703088
22	J. Alwall, P. C. Schuster, and N. Toro	Simplified models for a first characterization of new physics at the LHC	PRD 79 (2009) 075020	0810.3921
23	J. Alwall, M.-P. Le, M. Lisanti, and J. G. Wacker	Model-independent jets plus missing energy searches	PRD 79 (2009) 015005	0809.3264
24	D. Alves et al.	Simplified models for LHC new physics searches	JPG 39 (2012) 105005	1105.2838
25	CMS Collaboration	Interpretation of searches for supersymmetry with simplified models	PRD 88 (2013) 052017	CMS-SUS-11-016 1301.2175
26	CMS Collaboration	CMS luminosity measurements for the 2016 data taking period	CMS-PAS-LUM-17-001	CMS-PAS-LUM-17-001
27	CMS Collaboration	Search for gauge-mediated supersymmetry in events with at least one photon and missing transverse momentum in pp collisions at $ \sqrt{s} = $ 13 TeV	PLB 780 (2018) 118	CMS-SUS-16-046 1711.08008
28	CMS Collaboration	Search for supersymmetry in events with at least one photon, missing transverse momentum, and large transverse event activity in proton-proton collisions at $ \sqrt{s}= $ 13 TeV	JHEP 12 (2017) 142	CMS-SUS-16-047 1707.06193
29	ATLAS Collaboration	Search for supersymmetry in a final state containing two photons and missing transverse momentum in $ \sqrt{s} = 13 TeV pp $ collisions at the LHC using the ATLAS detector	EPJC 76 (2016) 517	1606.09150
30	ATLAS Collaboration	Search for photonic signatures of gauge-mediated supersymmetry in 13 $ TeV pp $ collisions with the ATLAS detector	PRD 97 (2018) 092006	1802.03158
31	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
32	CMS Collaboration	The CMS trigger system	JINST 12 (2017) P01020	CMS-TRG-12-001 1609.02366
33	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
34	A. Kalogeropoulos and J. Alwall	The SysCalc code: A tool to derive theoretical systematic uncertainties		1801.08401
35	P. Artoisenet, R. Frederix, O. Mattelaer, and R. Rietkerk	Automatic spin-entangled decays of heavy resonances in Monte Carlo simulations	JHEP 03 (2013) 015	1212.3460
36	M. Czakon and A. Mitov	Top++: A program for the calculation of the top-pair cross-section at hadron colliders	CPC 185 (2014) 2930	1112.5675
37	R. Gavin, Y. Li, F. Petriello, and S. Quackenbush	W physics at the LHC with FEWZ 2.1	CPC 184 (2013) 208	1201.5896
38	R. Gavin, Y. Li, F. Petriello, and S. Quackenbush	FEWZ 2.0: A code for hadronic Z production at next-to-next-to-leading order	CPC 182 (2011) 2388	1011.3540
39	NNPDF Collaboration	Parton distributions for the LHC Run II	JHEP 04 (2015) 040	1410.8849
40	T. Sjostrand et al.	An introduction to PYTHIA 8.2	CPC 191 (2015) 159	1410.3012
41	CMS Collaboration	Event generator tunes obtained from underlying event and multiparton scattering measurements	EPJC 76 (2016) 155	CMS-GEN-14-001 1512.00815
42	J. Alwall et al.	Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions	EPJC 53 (2008) 473	0706.2569
43	R. Frederix and S. Frixione	Merging meets matching in MC@NLO	JHEP 12 (2012) 061	1209.6215
44	W. Beenakker, R. Hopker, M. Spira, and P. M. Zerwas	Squark and gluino production at hadron colliders	NPB 492 (1997) 51	hep-ph/9610490
45	A. Kulesza and L. Motyka	Threshold resummation for squark-antisquark and gluino-pair production at the LHC	PRL 102 (2009) 111802	0807.2405
46	A. Kulesza and L. Motyka	Soft gluon resummation for the production of gluino-gluino and squark-antisquark pairs at the LHC	PRD 80 (2009) 095004	0905.4749
47	W. Beenakker et al.	Soft-gluon resummation for squark and gluino hadroproduction	JHEP 12 (2009) 041	0909.4418
48	W. Beenakker et al.	Squark and gluino hadroproduction	Int. J. Mod. Phys. A 26 (2011) 2637	1105.1110
49	GEANT4 Collaboration	GEANT4--a simulation toolkit	NIMA 506 (2003) 250
50	S. Abdullin et al.	The fast simulation of the CMS detector at LHC	J. Phys. Conf. Ser. 331 (2011) 032049
51	A. Giammanco	The fast simulation of the CMS experiment	J. Phys. Conf. Ser. 513 (2014) 022012
52	CMS Collaboration	Particle-flow reconstruction and global event description with the CMS detector	JINST 12 (2017) P10003	CMS-PRF-14-001 1706.04965
53	CMS Collaboration	Performance of electron reconstruction and selection with the CMS detector in proton-proton collisions at $ \sqrt{s}= $ 8 TeV	JINST 10 (2015) P06005	CMS-EGM-13-001 1502.02701
54	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 1502.02702
55	CMS Collaboration	Performance of the CMS muon detector and muon reconstruction with proton-proton collisions at $ \sqrt{s}= $ 13 TeV	JINST 13 (2018) P06015	CMS-MUO-16-001 1804.04528
56	M. Cacciari, G. P. Salam, and G. Soyez	The anti-$ {k_{\mathrm{T}}} $ jet clustering algorithm	JHEP 04 (2008) 063	0802.1189
57	M. Cacciari, G. P. Salam, and G. Soyez	FastJet user manual	EPJC 72 (2012) 1896	1111.6097
58	CMS Collaboration	Jet algorithms performance in 13 TeV data	CMS-PAS-JME-16-003	CMS-PAS-JME-16-003
59	CMS Collaboration	Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV	JINST 12 (2017) P02014	CMS-JME-13-004 1607.03663
60	M. Cacciari and G. P. Salam	Pileup subtraction using jet areas	PLB 659 (2008) 119	0707.1378
61	CMS Collaboration	Identification of heavy-flavour jets with the CMS detector in pp collisions at 13 TeV	JINST 13 (2018) P05011	CMS-BTV-16-002 1712.07158
62	K. Rehermann and B. Tweedie	Efficient identification of boosted semileptonic top quarks at the LHC	JHEP 03 (2011) 059	1007.2221
63	CMS Collaboration	Performance of missing energy reconstruction in 13 TeV pp collision data using the CMS detector	CMS-PAS-JME-16-004	CMS-PAS-JME-16-004
64	M. Cacciari et al.	The $ t\bar{t} $ cross-section at 1.8 TeV and 1.96 TeV: a study of the systematics due to parton densities and scale dependence	JHEP 04 (2004) 068	hep-ph/0303085
65	S. Catani, D. de Florian, M. Grazzini, and P. Nason	Soft gluon resummation for Higgs boson production at hadron colliders	JHEP 07 (2003) 028	hep-ph/0306211
66	A. Denner, S. Dittmaier, M. Hecht, and C. Pasold	NLO QCD and electroweak corrections to $ Z+\gamma $ production with leptonic Z-boson decays	JHEP 02 (2016) 057	1510.08742
67	CMS Collaboration	Search for supersymmetry in multijet events with missing transverse momentum in proton-proton collisions at 13 TeV	PRD 96 (2017) 032003	CMS-SUS-16-033 1704.07781
68	G. Cowan, K. Cranmer, E. Gross, and O. Vitells	Asymptotic formulae for likelihood-based tests of new physics	EPJC 71 (2011) 1554	1007.1727
69	T. Junk	Confidence level computation for combining searches with small statistics	NIMA 434 (1999) 435	hep-ex/9902006
70	A. L. Read	Presentation of search results: the CLs technique	JPG 28 (2002) 2693