CMS-PAS-SUS-18-002

CMS-PAS-SUS-18-002
Search for supersymmetry in events with a photon, jets, and missing transverse momentum in proton-proton collisions at 13 TeV
CMS Collaboration
September 2018

Abstract: A search for supersymmetry is presented based on events with at least one photon, multiple jets, and large missing transverse momentum produced in proton-proton collisions at a center-of-mass energy of $\sqrt{s}= $ 13 TeV. The data correspond to an integrated luminosity of 35.9 fb$^{-1}$ and were recorded by the CMS detector in 2016 at the LHC. 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 missing transverse momentum. No significant excess of events is observed with respect to expectations from standard model processes. Limits are placed on gluino, top squark, and neutralino masses using several simplified models of pair production of supersymmetric particles with gauge-mediated supersymmetry breaking. Depending on the model and the mass of the next-to-lightest supersymmetric particle, gluino masses as large as 2120 GeV and top squark masses as large as 1230 GeV are excluded.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, EPJC 79 (2019) 444. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Example Feynman diagrams depicting the simplified models used. 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 Feynman diagrams depicting the simplified models used. 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-b: Example Feynman diagrams depicting the simplified models used. 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-c: Example Feynman diagrams depicting the simplified models used. 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-d: Example Feynman diagrams depicting the simplified models used. 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 2: The lost-lepton and ${\tau _{\text {had}}}$ 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 parton distribution functions, renormalization and factorization scale uncertainties, and data-to-simulation correction factor uncertainties. 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 is used for SM predictions. Note that the kinematic variable requirements used to derive the average transfer factors are different from those used to define the search regions. Expectations and predictions are compatible within uncertainties.
png pdf	Figure 3: Validation of the double ratio $\kappa $ in each ${N_{\text {jets}}} - {N_{{{\mathrm {b}}}\text {-jets}}}$ region for zero photon events. The black points are the observed $\kappa $ values after subtracting the electroweak contamination based on the simulation. The blue points are the $\kappa $ values computed directly from the simulation. The ratio is shown in the bottom panel, where the hashed region corresponds to the systematic uncertainty in the ${\gamma}$+jets prediction. In the label ${N_{\mathrm {j}}^{\mathrm {b}}}$, $\mathrm{j}$ refers to the number of jets and b refers to the number of b-tagged jets.
png pdf	Figure 4: Distribution of predicted SM background events from various sources and observed events in each of the 25 signal regions. 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. The lower pane shows the ratio of observed events to predicted SM background events. The error bars in the lower pane are the quadrature sum of the statistical uncertainty in the observed data and the systematic uncertainty in the predicted backgrounds before adjustments based on a maximum likelihood fit to data assuming a signal strength of zero. The observed event yields are consistent with the predicted SM backgrounds within one standard deviation in all bins except bin 2, as discussed in the text.
png pdf	Figure 5: Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the (upper left) T5qqqqHG, (upper right) T5bbbbZG, (bottom left) T5ttttZG, and (bottom right) T6ttZG 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	Figure 5-a: Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the (upper left) T5qqqqHG, (upper right) T5bbbbZG, (bottom left) T5ttttZG, and (bottom right) T6ttZG 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	Figure 5-b: Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the (upper left) T5qqqqHG, (upper right) T5bbbbZG, (bottom left) T5ttttZG, and (bottom right) T6ttZG 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	Figure 5-c: Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the (upper left) T5qqqqHG, (upper right) T5bbbbZG, (bottom left) T5ttttZG, and (bottom right) T6ttZG 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	Figure 5-d: Observed and expected 95% CL upper limits for gluino or top squark pair production cross sections for the (upper left) T5qqqqHG, (upper right) T5bbbbZG, (bottom left) T5ttttZG, and (bottom right) T6ttZG 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.

Tables
png pdf	Table 1: Predicted and observed event yields for each signal region.

Summary

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

The data are categorized into 25 independent signal regions based on the number of jets, the number of b-tagged jets, and ${p_{\mathrm{T}}^{\text{miss}}}$. Background yields from standard model processes are predicted using simulation and data control regions. The observed event yields are found to be consistent with expectations from the SM processes within 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 breaking scenario, in which the lightest supersymmetric particle is a gravitino. 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 either to a photon and gravitino $\tilde{\mathrm{G}}$ or to a Higgs boson and $\tilde{\mathrm{G}}$, with branching fraction 50%. In the T5bbbbZG and T5ttttZG models, the $\tilde{\chi}^0_1$ decays either to a photon and $\tilde{\mathrm{G}}$ or to a Z boson and $\tilde{\mathrm{G}}$, with branching fraction 50%. 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 to a photon and $\tilde{\mathrm{G}}$ or to a Z boson and $\tilde{\mathrm{G}}$ with a branching fraction of 50%.

Using the next-to-leading-order plus next-to-leading-logarithmic cross sections for supersymmetric pair production, we place 95% confidence level upper limits on the gluino mass as large as 2120 GeV, depending on the model and ${m_{\tilde{\chi}^0_1}} $, and limits on the top squark mass as large as 1230 GeV, depending on ${m_{\tilde{\chi}^0_1}} $. These results improve upon those from previous searches for supersymmetry with photons [26,27].

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	Y. A. Gol'fand 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	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
27	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
28	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
29	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
30	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
31	CMS Collaboration	The CMS trigger system	JINST 12 (2017) P01020	CMS-TRG-12-001 1609.02366
32	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
33	M. Beneke, P. Falgari, S. Klein, and C. Schwinn	Hadronic top-quark pair production with NNLL threshold resummation	NPB 855 (2012) 695	1109.1536
34	M. Cacciari et al.	Top-pair production at hadron colliders with next-to-next-to-leading logarithmic soft-gluon resummation	PLB 710 (2012) 612	1111.5869
35	P. Barnreuther, M. Czakon, and A. Mitov	Percent-level-precision physics at the Tevatron: Next-to-next-to-leading order QCD corrections to $ q\bar{q}\to t\bar{t} + X $	PRL 109 (2012) 132001	1204.5201
36	M. Czakon and A. Mitov	NNLO corrections to top-pair production at hadron colliders: the all-fermionic scattering channels	JHEP 12 (2012) 054	1207.0236
37	M. Czakon and A. Mitov	NNLO corrections to top pair production at hadron colliders: the quark-gluon reaction	JHEP 01 (2013) 080	1210.6832
38	M. Czakon, P. Fiedler, and A. Mitov	Total top-quark pair-production cross section at hadron colliders through $ O(\alpha_S^4) $	PRL 110 (2013) 252004	1303.6254
39	R. Gavin, Y. Li, F. Petriello, and S. Quackenbush	W physics at the LHC with FEWZ 2.1	CPC 184 (2013) 208	1201.5896
40	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
41	R. Frederix and S. Frixione	Merging meets matching in MC@NLO	JHEP 12 (2012) 061	1209.6215
42	A. Kalogeropoulos and J. Alwall	The SysCalc code: A tool to derive theoretical systematic uncertainties		1801.08401
43	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
44	NNPDF Collaboration	Parton distributions for the LHC Run II	JHEP 04 (2015) 040	1410.8849
45	T. Sjostrand et al.	An introduction to PYTHIA 8.2	CPC 191 (2015) 159	1410.3012
46	CMS Collaboration	Event generator tunes obtained from underlying event and multiparton scattering measurements	EPJC76 (2016), no. 3, 155	CMS-GEN-14-001 1512.00815
47	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
48	W. Beenakker, R. Hopker, M. Spira, and P. M. Zerwas	Squark and gluino production at hadron colliders	NPB 492 (1997) 51	hep-ph/9610490
49	A. Kulesza and L. Motyka	Threshold resummation for squark-antisquark and gluino-pair production at the LHC	PRL 102 (2009) 111802	0807.2405
50	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
51	W. Beenakker et al.	Soft-gluon resummation for squark and gluino hadroproduction	JHEP 12 (2009) 041	0909.4418
52	W. Beenakker et al.	Squark and gluino hadroproduction	Int. J. Mod. Phys. A 26 (2011) 2637	1105.1110
53	GEANT4 Collaboration	GEANT4---a simulation toolkit	NIMA 506 (2003) 250
54	CMS Collaboration	The fast simulation of the CMS detector at LHC	J. Phys. Conf. Ser. 331 (2011) 032049
55	CMS Collaboration	Particle-flow reconstruction and global event description with the CMS detector	JINST 12 (2017) P10003	CMS-PRF-14-001 1706.04965
56	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
57	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
58	CMS Collaboration	The performance of the CMS muon detector in proton-proton collisions at $ \sqrt{s} = $ 7 TeV at the LHC	JINST 8 (2013) P11002	CMS-MUO-11-001 1306.6905
59	M. Cacciari, G. P. Salam, and G. Soyez	The anti-$ {k_{\mathrm{T}}} $ jet clustering algorithm	JHEP 04 (2008) 063	0802.1189
60	M. Cacciari, G. P. Salam, and G. Soyez	FastJet user manual	EPJC 72 (2012) 1896	1111.6097
61	CMS Collaboration	Jet performance in pp collisions at $ \sqrt{s}= $ 7 ~TeV	CDS
62	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
63	M. Cacciari and G. P. Salam	Pileup subtraction using jet areas	PLB 659 (2008) 119	0707.1378
64	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
65	K. Rehermann and B. Tweedie	Efficient identification of boosted semileptonic top quarks at the LHC	JHEP 03 (2011) 059	1007.2221
66	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
67	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
68	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
69	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
70	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
71	G. Cowan, K. Cranmer, E. Gross, and O. Vitells	Asymptotic formulae for likelihood-based tests of new physics	EPJC 71 (2011) 1554	1007.1727
72	T. Junk	Confidence level computation for combining searches with small statistics	NIMA 434 (1999) 435	hep-ex/9902006
73	A. L. Read	Presentation of search results: the CLs technique	JPG 28 (2002) 2693