Search for new phenomena in final states with an energetic jet and large missing transverse momentum in $pp$ collisions at $\sqrt{s}=13$ TeV using the ATLAS detector

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Search for new phenomena in final states with an energetic jet and large missing transverse momentum in $pp$ collisions at $\sqrt{s}=13$ TeV using the ATLAS detector Phys. Rev. D 94 (2016) 032005 26 April 2016
Contact: ATLAS Exotics conveners
e-print arXiv:1604.07773 - internal	pdf from arXiv
Inspire record	-
Figures Auxiliary Material	-
Abstract
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton--proton collision data corresponding to an integrated luminosity of 3.2 fb${}^{-1}$ at $\sqrt{s}=13$ TeV collected in 2015 with the ATLAS detector at the Large Hadron Collider. Events are required to have at least one jet with a transverse momentum above 250 GeV and no leptons. Several signal regions are considered with increasing missing-transverse-momentum requirements between $E_{\rm T}^{\rm miss} >250$ GeV and $E_{\rm T}^{\rm miss} > 700$ GeV. Good agreement is observed between the number of events in data and Standard Model predictions. The results are translated into exclusion limits in models with large extra spatial dimensions, pair production of weakly interacting dark-matter candidates, and the production of supersymmetric particles in several compressed scenarios.
Figures
Figure 01a: A generic diagram for the pair production of squarks with the decay mode squark → q + neutralino. The presence of a jet from initial-state radiation is also indicated for illustration purposes. png (142kB) pdf (5kB)
Figure 01b: Diagram for the pair production of weakly interacting massive particles, with a leptophobic Z'-like mediator A with axial-vector couplings exchanged in the s-channel. The presence of a jet from initial-state radiation is also indicated for illustration purposes. png (123kB) pdf (11kB)
Figure 02a: The measured E_T^miss distribution in the W(→μν)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties in the background predictions as determined by the global fit to the data in the control regions. The contributions from multijets and non-collision backgrounds are negligible and are not shown in the figures. png (244kB) pdf (73kB)
Figure 02b: The measured leading jet p_T distribution in the W(→μν)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties in the background predictions as determined by the global fit to the data in the control regions. The contributions from multijets and non-collision backgrounds are negligible and are not shown in the figures. png (249kB) pdf (76kB)
Figure 02c: The measured E_T^miss distribution in the W(→eν)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties in the background predictions as determined by the global fit to the data in the control regions. The contributions from multijets and non-collision backgrounds are negligible and are not shown in the figures. png (243kB) pdf (71kB)
Figure 02d: The measured leading jet p_T distribution in the W(→e;ν)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties in the background predictions as determined by the global fit to the data in the control regions. The contributions from multijets and non-collision backgrounds are negligible and are not shown in the figures. png (247kB) pdf (77kB)
Figure 02e: The measured E_T^miss distribution in the Z(→μμ)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties in the background predictions as determined by the global fit to the data in the control regions. The contributions from multijets and non-collision backgrounds are negligible and are not shown in the figures. png (245kB) pdf (68kB)
Figure 02f: The measured leading jet p_T distribution in the Z(→μμ)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties in the background predictions as determined by the global fit to the data in the control regions. The contributions from multijets and non-collision backgrounds are negligible and are not shown in the figures. png (247kB) pdf (71kB)
Figure 03a: Measured distribution of the E_T^miss for the IM1 selection compared to the SM predictions. The latter are normalized with normalization factors as determined by the global fit that considers exclusive E_T^miss regions. For illustration purposes, the distributions of different ADD, SUSY, and WIMP scenarios are included. The error bands in the ratio shown in the lower panel include both the statistical and systematic uncertainties in the background expectations. The contributions from multijets and non-collision backgrounds are negligible and not shown in the figures. png (288kB) pdf (77kB)
Figure 03b: Measured distribution of the leading-jet p_T for the IM1 selection compared to the SM predictions. The latter are normalized with normalization factors as determined by the global fit that considers exclusive E_T^miss regions. For illustration purposes, the distributions of different ADD, SUSY, and WIMP scenarios are included. The error bands in the ratio shown in the lower panel include both the statistical and systematic uncertainties in the background expectations. The contributions from multijets and non-collision backgrounds are negligible and not shown in the figures. png (299kB) pdf (82kB)
Figure 03c: Measured distribution of the leading-jet η for the IM1 selection compared to the SM predictions. The latter are normalized with normalization factors as determined by the global fit that considers exclusive E_T^miss regions. For illustration purposes, the distributions of different ADD, SUSY, and WIMP scenarios are included. The error bands in the ratio shown in the lower panel include both the statistical and systematic uncertainties in the background expectations. The contributions from multijets and non-collision backgrounds are negligible and not shown in the figures. png (245kB) pdf (70kB)
Figure 03d: Measured distribution of the jet multiplicity for the IM1 selection compared to the SM predictions. The latter are normalized with normalization factors as determined by the global fit that considers exclusive E_T^miss regions. For illustration purposes, the distributions of different ADD, SUSY, and WIMP scenarios are included. The error bands in the ratio shown in the lower panel include both the statistical and systematic uncertainties in the background expectations. The contributions from multijets and non-collision backgrounds are negligible and not shown in the figures. png (231kB) pdf (63kB)
Figure 03e: Measured distribution of the second-leading-jet p_T for the IM1 selection compared to the SM predictions. The latter are normalized with normalization factors as determined by the global fit that considers exclusive E_T^miss regions. For illustration purposes, the distributions of different ADD, SUSY, and WIMP scenarios are included. The error bands in the ratio shown in the lower panel include both the statistical and systematic uncertainties in the background expectations. The contributions from multijets and non-collision backgrounds are negligible and not shown in the figures. png (305kB) pdf (81kB)
Figure 03f: Measured distribution of the third-leading-jet p_T for the IM1 selection compared to the SM predictions. The latter are normalized with normalization factors as determined by the global fit that considers exclusive E_T^miss regions. For illustration purposes, the distributions of different ADD, SUSY, and WIMP scenarios are included. The error bands in the ratio shown in the lower panel include both the statistical and systematic uncertainties in the background expectations. The contributions from multijets and non-collision backgrounds are negligible and not shown in the figures. png (281kB) pdf (74kB)
Figure 04: Observed and expected 95% CL lower limits on the fundamental Planck scale in 4+n dimensions, M_D, as a function of the number of extra dimensions. The shaded area around the expected limit indicates the expected ±1σ range of limits in the absence of a signal. Finally, the thin dashed line shows the 95% CL observed limits after the suppression of the events with ŝ > M_D² (damping) is applied, as described in the text. The results from this analysis are compared to previous results from the ATLAS Collaboration at √s = 8 TeV. png (205kB) pdf (48kB)
Figure 05: Excluded region at the 95% CL in the (stop, neutralino) mass plane for the decay channel stop → charm-quark + neutralino (BR=100%). The dotted lines around the observed limit indicate the range of observed limits corresponding to ±1σ variations of the NLO SUSY cross-section predictions. The shaded area around the expected limit indicates the expected ±1σ ranges of limits in the absence of a signal. The results from this analysis are compared to previous results from the ATLAS Collaboration at √s = 8 TeV. png (312kB) pdf (64kB)
Figure 06a: Exclusion region at 95% CL as a function of squark mass and the squark-neutralino mass difference for the decay channel sbottom → bottom-quark + neutralino. The dotted lines around the observed limit indicate the range of observed limits corresponding to ±1σ variations of the NLO SUSY cross-section predictions. The shaded area around the expected limit indicates the expected ±1σ ranges of limits in the absence of a signal. png (300kB) pdf (50kB)
Figure 06b: Exclusion region at 95% CL as a function of squark mass and the squark-neutralino mass difference for the decay channel squark → quark + neutralino (quark = u, d, c, s). The dotted lines around the observed limit indicate the range of observed limits corresponding to ±1σ variations of the NLO SUSY cross-section predictions. The shaded area around the expected limit indicates the expected ±1σ ranges of limits in the absence of a signal. png (305kB) pdf (50kB)
Figure 07a: 95% CL exclusion contours in the m_χ-m_A parameter plane. The solid (dashed) curve shows the median of the observed (expected) limit, while the bands indicate the ±1σ theory uncertainties in the observed limit and ±1σ range of the expected limit in the absence of a signal. The red curve corresponds to the expected relic density. The region excluded due to perturbativity, defined by m_χ > √π/2m_A, is indicated by the hatched area. png (385kB) pdf (55kB)
Figure 07b: A comparison of the inferred limits to the constraints from direct detection experiments on the spin-dependent WIMP--proton scattering cross section in the context of the Z'-like simplified model with axial-vector couplings. Unlike in the m_χ-m_A parameter plane, the limits are shown at 90% CL. The results from this analysis, excluding the region to the left of the contour, are compared with limits from the XENON100, LUX, and PICO experiments. The comparison is model-dependent and solely valid in the context of this model, assuming minimal mediator width and the coupling values g_q = 1/4 and g_χ = 1. png (294kB) pdf (49kB)
Auxiliary figures and tables
Figure 01a: The measured m_T distribution in the W(→μν)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties on the background predictions. The shape difference observed in the dimuon invariant mass between data and simulation does not have an impact in this analysis. png (230kB) pdf (69kB)
Figure 01b: The measured number of jets distribution in the W(→μν)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties on the background predictions. The shape difference observed in the dimuon invariant mass between data and simulation does not have an impact in this analysis. png (203kB) pdf (61kB)
Figure 01c: The measured m_T distribution in the W(→eν)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties on the background predictions. The shape difference observed in the dimuon invariant mass between data and simulation does not have an impact in this analysis. png (246kB) pdf (79kB)
Figure 01d: The measured number of jets distribution in the W(→eν)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties on the background predictions. The shape difference observed in the dimuon invariant mass between data and simulation does not have an impact in this analysis. png (199kB) pdf (61kB)
Figure 01e: The measured m_μμ distribution in the Z(→μμ)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties on the background predictions. The shape difference observed in the dimuon invariant mass between data and simulation does not have an impact in this analysis. png (256kB) pdf (73kB)
Figure 01f: The measured number of jets distribution in the Z(→μμ)+jets control region, for the IM1 selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit as performed in exclusive E_T^miss bins. The error bands in the ratios include the statistical and experimental uncertainties on the background predictions. The shape difference observed in the dimuon invariant mass between data and simulation does not have an impact in this analysis. png (198kB) pdf (60kB)
Figure 02: Measured distribution of the Δφ(jets, p⃗_T^miss) for the IM1 selection compared to the SM expectations. The latter is normalized, with normalization factors as determined by the global fit that considers exclusive E_T^miss regions. For illustration purposes, the distributions of different ADD, SUSY, and WIMP scenarios are included. The error bands in the ratios shown in the lower panel include both the statistical and systematic uncertainties in the background expectations. png (262kB) pdf (77kB)
Figure 03a: Measured distribution of the E_T^miss in the multijets control region for the IM1 selection compared to the SM expectations. The latter is normalized, with normalization factors as determined by the global fit that considers exclusive E_T^miss regions. The jet smearing method requires the normalization of the smeared data in a multijets-enriched control region. For the monojet-like selection, this region is defined with a similar E_T^miss and leading jet p_T cuts, but inverting the Δφ(jets, p⃗_T^miss) cut, now requiring it to be less than 0.4. The error bands in the ratio shown in the lower panel include both the statistical and systematic uncertainties in the background expectations. The multijets background expectation includes both the statistical and a 100% systematic uncertainty. png (231kB) pdf (67kB)
Figure 03b: Measured distribution of the number of jets in the multijets control region for the IM1 selection compared to the SM expectations. The latter is normalized, with normalization factors as determined by the global fit that considers exclusive E_T^miss regions. The jet smearing method requires the normalization of the smeared data in a multijets-enriched control region. For the monojet-like selection, this region is defined with a similar E_T^miss and leading jet p_T cuts, but inverting the Δφ(jets, p⃗_T^miss) cut, now requiring it to be less than 0.4. The error bands in the ratio shown in the lower panel include both the statistical and systematic uncertainties in the background expectations. The multijets background expectation includes both the statistical and a 100% systematic uncertainty. png (216kB) pdf (60kB)
Figure 04a: The leading jet p_T distribution of the data events passing the signal region selection without the tight cleaning criteria applied on the leading jet. The Standard Model background indicated in the plots corresponds to the estimates obtained for the analysis signal region, including tight jet quality requirements. The jet selection inefficiency of the cleaning selection is O(1%), which is negligible compared to the observed excess in data. This demonstrates the necessity of a strong non-collision background suppression for this analysis. png (34kB) pdf (49kB)
Figure 04b: The leading jet φ distribution of the data events passing the signal region selection without the tight cleaning criteria applied on the leading jet. The φ distribution shows a typical azimuthal structure of beam-induced backgrounds. The Standard Model background indicated in the plots corresponds to the estimates obtained for the analysis signal region, including tight jet quality requirements. The jet selection inefficiency of the cleaning selection is O(1%), which is negligible compared to the observed excess in data. This demonstrates the necessity of a strong non-collision background suppression for this analysis. png (149kB) pdf (47kB)
Figure 05a: Observed events in the W(→μν)+jets, W(→eν)+jets, and Z(→μμ)+jets control regions and signal regions for the IM1 selection compared to the background predictions. The latter include the global normalization factors extracted from the corresponding fit. The error bands in the ratios include the statistical and experimental uncertainties on the background predictions. png (172kB) pdf (59kB)
Figure 05b: Observed events in the W(→μν)+jets, W(→eν)+jets, and Z(→μμ)+jets control regions and signal regions for the IM7 selection compared to the background predictions. The latter include the global normalization factors extracted from the corresponding fit. The error bands in the ratios include the statistical and experimental uncertainties on the background predictions. png (201kB) pdf (60kB)
Figure 05c: Observed events in the W(→μν)+jets, W(→eν)+jets, and Z(→μμ)+jets control regions and signal regions for the EM1 selection compared to the background predictions. The latter include the global normalization factors extracted from the corresponding fit. The error bands in the ratios include the statistical and experimental uncertainties on the background predictions. png (173kB) pdf (59kB)
Figure 05d: Observed events in the W(→μν)+jets, W(→eν)+jets, and Z(→μμ)+jets control regions and signal regions for the EM4 selection compared to the background predictions. The latter include the global normalization factors extracted from the corresponding fit. The error bands in the ratios include the statistical and experimental uncertainties on the background predictions. png (176kB) pdf (60kB)
Figure 06: The ratios of the observed and expected 95% CL upper limits on cross section to the predicted signal cross section for the Z'-like model with axial-vector couplings and m_χ = 150 GeV, m_A = 1 TeV, for different choices of the coupling g=g_q=g_χ. The yellow band indicates the expected ±1σ ranges of limits in the absence of a signal. Minimal mediator width is assumed. png (247kB) pdf (48kB)
Figure 07: A comparison of the inferred limits to the constraints from direct detection experiments on the spin-dependent WIMP-neutron scattering cross section in the context of the Z'-like simplified model with axial-vector couplings. The results from this analysis, excluding the region to the left of the contour, are compared with limits from the LUX experiment. All limits are shown at 90% CL. The comparison is valid solely in the context if this model, assuming minimal mediator width and the coupling values g_q = 1/4 and g_χ = 1. png (229kB) pdf (46kB)
Figure 08: The ratios of the observed and expected 95% CL upper limits on cross section to the predicted signal cross section in the m_χ-m_A parameter plane for a simplified model with an axial-vector mediator, Dirac DM and couplings g_q = 1/4 and g_χ = 1. Minimal mediator width is assumed. The solid (dashed) curve shows the median of the observed (expected) limit, while the dotted bands indicate the ±1σ theory uncertainties on the observed limit and ±1σ range of the expected limit in the absence of a signal. These ratios do not correspond to the rescaling factors for the coupling values since the mediator width would change in such cases and thus modify the acceptance. The red curve corresponds to the parameters where the correct DM relic abundance is obtained from standard thermal freeze-out for the chosen couplings. The region towards lower DM masses or higher mediator masses corresponds to DM overproduction. The region excluded due to perturbativity, defined by m_χ > √π/2m_A, is indicated by the hatched area. png (426kB) pdf (64kB)
Figure 09: The highest E_T^miss monojet event in the 2015 ATLAS data (Event 606734214, Run 279284). A jet with p_T of 973 GeV, indicated by the green and red bars corresponding to the energy deposition in the calorimeters, is balanced by a E_T^miss of 954 GeV, shown as the red arrow. Tracks with p_T above 2 GeV are displayed in the inner detector. png (2MB) pdf (539kB)
Table 01: Data and background predictions in the signal and control regions before and after the fit is performed for the EM1 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (572kB) pdf (236kB)
Table 02: Data and background predictions in the signal and control regions before and after the fit is performed for the EM2 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (570kB) pdf (232kB)
Table 03: Data and background predictions in the signal and control regions before and after the fit is performed for the EM3 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (553kB) pdf (224kB)
Table 04: Data and background predictions in the signal and control regions before and after the fit is performed for the EM4 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (541kB) pdf (217kB)
Table 05: Data and background predictions in the signal and control regions before and after the fit is performed for the EM5 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (495kB) pdf (196kB)
Table 06: Data and background predictions in the signal and control regions before and after the fit is performed for the EM6 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (488kB) pdf (192kB)
Table 07: Data and background predictions in the signal and control regions before and after the fit is performed for the EM7 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (487kB) pdf (192kB)
Table 08: Data and background predictions in the signal and control regions before and after the fit is performed for the IM1 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (595kB) pdf (253kB)
Table 09: Data and background predictions in the signal and control regions before and after the fit is performed for the IM2 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (583kB) pdf (242kB)
Table 10: Data and background predictions in the signal and control regions before and after the fit is performed for the IM3 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (564kB) pdf (236kB)
Table 11: Data and background predictions in the signal and control regions before and after the fit is performed for the IM4 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (559kB) pdf (231kB)
Table 12: Data and background predictions in the signal and control regions before and after the fit is performed for the IM5 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (512kB) pdf (206kB)
Table 13: Data and background predictions in the signal and control regions before and after the fit is performed for the IM6 selection. The background predictions include both the statistical and systematic uncertainties. The individual uncertainties are correlated and do not necessarily add in quadrature to the total background uncertainty. png (503kB) pdf (200kB)
Table 14: Number of accepted events after the application of the monojet-like selection criteria for different SUSY signals. Three different SUSY scenarios for squark pair production are presented: squark → q + neutralino (m(squark) = 650 GeV, m(neutralino) = 645 GeV), sbottom → b + neutralino (m(squark) = 350 GeV, m(neutralino) = 345 GeV), stop → c + neutralino (m(squark) = 350 GeV, m(neutralino) = 345 GeV). The number of signal events corresponds to the expectations for a total integrated luminosity of 3.2 fb^-1. The 'All' row is after the application of a generator-level filter applying a E_T^miss > 100 GeV requirement at truth level. For each cut level the expected events and acceptance at reconstructed level are given. png (420kB) pdf (208kB)
Table 15: Number of accepted events after the application of the monojet-like selection criteria for a couple of representative WIMP and ADD signals. For the WIMP a simplified axial-vector model (m_χ = 150 GeV, m_A = 1 TeV) is presented. For ADD a model with n = 3, M_D = 4.1 TeV is shown. The number of signal events corresponds to the expectations for a total integrated luminosity of 3.2 fb^-1. In the case of ADD, 'All' row is after the application of a generator-level filter applying a jet p_T > 100 GeV requirement at truth level. For each cut level the expected events and acceptance at reconstructed level are given. png (341kB) pdf (176kB)

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