Compact Muon Solenoid
LHC, CERN
Visit us: CMS Public Website, CMS Physics ;
Contact us: CMS Publications Committee
| CMS-SUS-19-002 ; CERN-EP-2019-196 | ||
| Search for supersymmetry with a compressed mass spectrum in events with a soft $\tau$ lepton, a highly energetic jet, and large missing transverse momentum in proton-proton collisions at $\sqrt{s} =$ 13 TeV | ||
| CMS Collaboration | ||
| 2 October 2019 | ||
| Phys. Rev. Lett. 124 (2020) 041803 | ||
| Abstract: The first search for supersymmetry in events with an experimental signature of one soft, hadronically decaying $ \tau $ lepton, one energetic jet from initial-state radiation, and large transverse momentum imbalance is presented. These event signatures are consistent with direct or indirect production of scalar $ \tau $ leptons ($\tilde{\tau}$) in supersymmetric models that exhibit coannihilation between the $\tilde{\tau}$ and the lightest neutralino ($\tilde{\chi}^0_1$), and that could generate the observed relic density of dark matter. The data correspond to an integrated luminosity of 77.2 fb$^{-1}$ of proton-proton collisions at $\sqrt{s} = $ 13 TeV collected with the CMS detector at the LHC in 2016 and 2017. The results are interpreted in a supersymmetric scenario with a small mass difference ($\delta$) between the chargino ($\tilde{\chi}^{\pm}_1$) or next-to-lightest neutralino ($\tilde{\chi}^0_2$), and the $\tilde{\chi}^0_1$. The mass of the $\tilde{\tau}$ is assumed to be the average of the $\tilde{\chi}^{\pm}_1$ and $\tilde{\chi}^0_1$ masses. The data are consistent with standard model background predictions. Upper limits at 95% confidence level are set on the sum of the $\tilde{\chi}^{\pm}_1$, $\tilde{\chi}^0_2$, and $\tilde{\tau}$ production cross sections for $\delta(\tilde{\chi}^{\pm}_1$, $\tilde{\chi}^0_1) = $ 50 GeV, resulting in a lower limit of 290 GeV on the mass of the $\tilde{\chi}^{\pm}_1$, which is the most stringent to date and surpasses the bounds from the LEP experiments. | ||
| Links: e-print arXiv:1910.01185 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
png pdf |
Figure 1:
The ${m_{\mathrm {T}}}$ distribution for SR events with 2016 data (left) and 2017 data (right). In the upper panels of the figures, the solid colors correspond to the expected background processes, the black dots to the observed data, and the dashed lines to the expected signal from simulation. The lower panels of the figures show the ratio between the observed data and the total expected pre-fit background (BG). The shaded band corresponds to the total pre-fit uncertainty on the BG prediction, while the error bars on the black dots represent the statistical uncertainties on the data yields. |
png pdf |
Figure 1-a:
The ${m_{\mathrm {T}}}$ distribution for SR events with 2016 data (left) and 2017 data (right). In the upper panels of the figures, the solid colors correspond to the expected background processes, the black dots to the observed data, and the dashed lines to the expected signal from simulation. The lower panels of the figures show the ratio between the observed data and the total expected pre-fit background (BG). The shaded band corresponds to the total pre-fit uncertainty on the BG prediction, while the error bars on the black dots represent the statistical uncertainties on the data yields. |
png pdf |
Figure 1-b:
The ${m_{\mathrm {T}}}$ distribution for SR events with 2016 data (left) and 2017 data (right). In the upper panels of the figures, the solid colors correspond to the expected background processes, the black dots to the observed data, and the dashed lines to the expected signal from simulation. The lower panels of the figures show the ratio between the observed data and the total expected pre-fit background (BG). The shaded band corresponds to the total pre-fit uncertainty on the BG prediction, while the error bars on the black dots represent the statistical uncertainties on the data yields. |
png pdf |
Figure 2:
(left) The 95% confidence level (CL) upper limits on the SSM1 production cross sections ($\sigma _{95%\,CL}$) as a function of $m(\tilde{\chi}^{\pm}_1)$. The solid blue line corresponds to the theoretical cross section, and the dashed blue line to its uncertainty. The observed limit is shown with the solid black line, while the expected limit is represented with the dashed black line. The green (yellow) band corresponds to the one (two) standard deviation range about the central value of the expected limit. (right) The ratio of the 95% CL upper limit on the direct $\tilde{\tau}$ pair production signal cross section in SSM2 to the theoretical cross section, as a function of $m(\tilde{\tau})$ and $\Delta m(\tilde{\tau}, \tilde{\chi}^0_1)$. |
png pdf |
Figure 2-a:
(left) The 95% confidence level (CL) upper limits on the SSM1 production cross sections ($\sigma _{95%\,CL}$) as a function of $m(\tilde{\chi}^{\pm}_1)$. The solid blue line corresponds to the theoretical cross section, and the dashed blue line to its uncertainty. The observed limit is shown with the solid black line, while the expected limit is represented with the dashed black line. The green (yellow) band corresponds to the one (two) standard deviation range about the central value of the expected limit. (right) The ratio of the 95% CL upper limit on the direct $\tilde{\tau}$ pair production signal cross section in SSM2 to the theoretical cross section, as a function of $m(\tilde{\tau})$ and $\Delta m(\tilde{\tau}, \tilde{\chi}^0_1)$. |
png pdf |
Figure 2-b:
(left) The 95% confidence level (CL) upper limits on the SSM1 production cross sections ($\sigma _{95%\,CL}$) as a function of $m(\tilde{\chi}^{\pm}_1)$. The solid blue line corresponds to the theoretical cross section, and the dashed blue line to its uncertainty. The observed limit is shown with the solid black line, while the expected limit is represented with the dashed black line. The green (yellow) band corresponds to the one (two) standard deviation range about the central value of the expected limit. (right) The ratio of the 95% CL upper limit on the direct $\tilde{\tau}$ pair production signal cross section in SSM2 to the theoretical cross section, as a function of $m(\tilde{\tau})$ and $\Delta m(\tilde{\tau}, \tilde{\chi}^0_1)$. |
| Summary |
| In summary, we have presented a search for compressed supersymmetry. It is the first collider search with exactly one soft, hadronically-decaying tau lepton and missing transverse momentum recoiling against an initial-state radiation jet with high transverse momentum. The search utilizes data corresponding to an integrated luminosity of 77.2 fb$^{-1}$ collected in 2016 and 2017 with the CMS detector in proton-proton collisions at $\sqrt{s} = $ 13 TeV. This search targets compressed mass spectra where the mass difference ($\delta m$) between the stau ($\tilde{\tau}$) particle and the lightest neutralino ($\tilde{\chi}^0_1$) is $\leq$ 50 GeV. This is motivated by models considering $\tilde{\tau}$-$\tilde{\chi}^0_1$ CA to maintain consistency in the estimation of the relic DM density between particle physics and cosmology. In the context of the minimal supersymmetric standard model, the search considers electroweak production of $\tilde{\tau}$ via decays of the lightest chargino ($\tilde{\chi}^{\pm}_1$) and the next-to-lightest neutralino ($\tilde{\chi}^0_2$), and direct production of $\tilde{\tau}$. The data do not reveal evidence for new physics. For a mass splitting $\delta m(\tilde{\chi}^{\pm}_1,\tilde{\chi}^0_1) = $ 50 GeV and a branching fraction of 100% for $\tilde{\chi}^{\pm}_1\to \tilde{\tau}\nu_{\tau} \to \tau\tilde{\chi}^0_1\nu_{\tau}$, $\tilde{\chi}^{\pm}_1$ masses up to 290 GeV are excluded at 95% confidence level. This sensitivity exceeds that of all other $\tilde{\tau}$ searches to date in these scenarios. The search presented in this Letter provides the first results from the LHC to surpass the LEP bounds. |
| References | ||||
| 1 | P. Ramond | Dual theory for free fermions | PRD 3 (1971) 2415 | |
| 2 | Y. A. Gol'fand and E. P. Likhtman | Extension of the algebra of Poincare group generators and violation of P invariance | JEPTL 13 (1971) 323 | |
| 3 | S. Ferrara and B. Zumino | Supergauge invariant Yang-Mills theories | NPB 79 (1974) 413 | |
| 4 | J. Wess and B. Zumino | Supergauge transformations in four dimensions | NPB 70 (1974) 39 | |
| 5 | A. H. Chamseddine, R. Arnowitt, and P. Nath | Locally supersymmetric grand unification | PRL 49 (1982) 970 | |
| 6 | R. Barbieri, S. Ferrara, and C. A. Savoy | Gauge models with spontaneously broken local Supersymmetry | PLB 119 (1982) 343 | |
| 7 | L. Hall, J. Lykken, and S. Weinberg | Supergravity as the messenger of supersymmetry breaking | PRD 27 (1983) 2359 | |
| 8 | S. Dimopoulos and G. F. Giudice | Naturalness constraints in supersymmetric theories with nonuniversal soft terms | PLB 357 (1995) 573 | hep-ph/9507282 |
| 9 | WMAP Collaboration | First year wilkinson microwave anisotropy probe (WMAP) observations: determination of cosmological parameters | Astrophys. J. Suppl. 148 (2003) 175 | astro-ph/0302209 |
| 10 | Planck Collaboration | Planck 2015 results. XIII. Cosmological parameters | Astron. Astrophys. 594 (2016) A13 | 1502.01589 |
| 11 | K. Griest and D. Seckel | Three exceptions in the calculation of relic abundances | PRD 43 (1991) 3191 | |
| 12 | R. L. Arnowitt et al. | Detection of SUSY signals in stau neutralino co-annihilation region at the LHC | AIP Conf. Proc. 903 (2007) 229 | hep-ph/0611089 |
| 13 | V. Khotilovich, R. L. Arnowitt, B. Dutta, and T. Kamon | The stau neutralino co-annihilation region at an international linear collider | PLB 618 (2005) 182 | hep-ph/0503165 |
| 14 | M. Carena et al. | Light stau phenomenology and the Higgs $ \gamma\gamma $ rate | JHEP 07 (2012) 175 | 1205.5842 |
| 15 | A. Aboubrahim, P. Nath, and A. B. Spisak | Stau coannihilation, compressed spectrum, and SUSY discovery potential at the LHC | PRD 95 (2017) 115030 | 1704.04669 |
| 16 | G. H. Duan et al. | Vacuum stability in stau-neutralino coannihilation in MSSM | PLB 788 (2019) 475 | 1809.10061 |
| 17 | R. Arnowitt et al. | Determining the dark matter relic density in the minimal supergravity stau-neutralino coannihilation region at the Large Hadron Collider | PRL 100 (2008) 231802 | hep-ph/0802.2968 |
| 18 | B. Dutta et al. | Vector boson fusion processes as a probe of supersymmetric electroweak sectors at the LHC | PRD 87 (2013) 035029 | 1210.0964 |
| 19 | A. G. Delannoy et al. | Probing dark matter at the LHC using vector boson fusion processes | PRL 111 (2013) 061801 | 1304.7779 |
| 20 | A. Fl\'orez et al. | Probing the stau-neutralino coannihilation region at the LHC with a soft tau lepton and an ISR jet | PRD 94 (2016) 073007 | hep-ph/1606.08878 |
| 21 | B. Dutta et al. | Probing compressed bottom squarks with boosted jets and shape analysis | PRD 92 (2015) 095009 | 1507.01001 |
| 22 | B. Dutta et al. | Probing compressed top squarks at the LHC at 14 TeV | PRD 90 (2014) 095022 | 1312.1348 |
| 23 | B. Dutta et al. | Probing compressed sleptons at the LHC using vector boson fusion processes | PRD 91 (2015) 055025 | 1411.6043 |
| 24 | A. Fl\'orez et al. | Searching for new heavy neutral gauge bosons using vector boson fusion processes at the LHC | PLB 767 (2017) 126 | 1609.09765 |
| 25 | A. Fl\'orez et al. | Expanding the reach of heavy neutrino searches at the LHC | PLB 778 (2018) 94 | 1708.03007 |
| 26 | A. Fl\'orez et al. | Probing heavy spin-2 bosons with $ \gamma\gamma $ final states from vector boson fusion processes at the LHC | PRD 99 (2019) 035034 | 1812.06824 |
| 27 | CMS Collaboration | Combined search for electroweak production of charginos and neutralinos in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | JHEP 03 (2018) 160 | CMS-SUS-17-004 1801.03957 |
| 28 | CMS Collaboration | Search for new physics in events with two soft oppositely charged leptons and missing transverse momentum in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | PLB 782 (2018) 440 | CMS-SUS-16-048 1801.01846 |
| 29 | ATLAS Collaboration | Search for the direct production of charginos and neutralinos in final states with tau leptons in $ \sqrt{s} = 13 TeV pp $ collisions with the ATLAS detector | EPJC 78 (2018) 154 | 1708.07875 |
| 30 | ATLAS Collaboration | Search for electroweak production of supersymmetric states in scenarios with compressed mass spectra at $ \sqrt{s} = $ 13 TeV with the ATLAS detector | PRD 97 (2017) 052010 | 1712.08119 |
| 31 | CMS Collaboration | Search for supersymmetry in the vector-boson fusion topology in proton-proton collisions at $ \sqrt{s}= $ 8 TeV | JHEP 11 (2015) 189 | CMS-SUS-14-005 1508.07628 |
| 32 | CMS Collaboration | Search for supersymmetry with a compressed mass spectrum in the vector boson fusion topology with 1-lepton and 0-lepton final states in proton-proton collisions at $ \sqrt{s}= $ 13 TeV | JHEP 08 (2019) 150 | CMS-SUS-17-007 1905.13059 |
| 33 | CMS Collaboration | Search for direct pair production of supersymmetric partners to the $ \tau $ lepton in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | Submitted to EPJC | CMS-SUS-18-006 1907.13179 |
| 34 | ALEPH Collaboration | Search for scalar leptons in e+ e- collisions at center-of-mass energies up to 209 GeV | PLB 526 (2002) 206 | hep-ex/0112011 |
| 35 | DELPHI Collaboration | Searches for supersymmetric particles in e+ e- collisions up to 208 GeV and interpretation of the results within the MSSM | EPJC 31 (2003) 421 | hep-ex/0311019 |
| 36 | L3 Collaboration | Search for scalar leptons and scalar quarks at LEP | PLB 580 (2004) 37 | hep-ex/0310007 |
| 37 | OPAL Collaboration | Search for anomalous production of dilepton events with missing transverse momentum in e+ e- collisions at $ \sqrt{s} = $ 183 GeV to 209 GeV | EPJC 32 (2004) 453 | hep-ex/0309014 |
| 38 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
| 39 | CMS Collaboration | The CMS trigger system | JINST 12 (2017) P01020 | CMS-TRG-12-001 1609.02366 |
| 40 | CMS Collaboration | Particle-flow reconstruction and global event description with the CMS detector | JINST 12 (2017) P10003 | CMS-PRF-14-001 1706.04965 |
| 41 | M. Cacciari, G. P. Salam, and G. Soyez | The anti-$ {k_{\mathrm{T}}} $ jet clustering algorithm | JHEP 04 (2008) 063 | 0802.1189 |
| 42 | M. Cacciari, G. P. Salam, and G. Soyez | FastJet user manual | EPJC 72 (2012) 1896 | 1111.6097 |
| 43 | CMS Collaboration | Performance of missing transverse momentum reconstruction in proton-proton collisions at $ \sqrt{s} = $ 13 TeV using the CMS detector | JINST 14 (2019) P07004 | CMS-JME-17-001 1903.06078 |
| 44 | CMS Collaboration | Jet algorithms performance in 13 TeV data | CMS-PAS-JME-16-003 | CMS-PAS-JME-16-003 |
| 45 | 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 |
| 46 | 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 |
| 47 | 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 |
| 48 | 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 |
| 49 | CMS Collaboration | Performance of reconstruction and identification of $ \tau $ leptons decaying to hadrons and $ \nu_\tau $ in pp collisions at $ \sqrt{s}= $ 13 TeV | JINST 13 (2018) P10005 | CMS-TAU-16-003 1809.02816 |
| 50 | CMS Collaboration | Search for dark matter and supersymmetry with a compressed mass spectrum in the vector boson fusion topology in proton-proton collisions at $ \sqrt{s} = $ 8 TeV | PRL \bf 118 (2017) 021802 | CMS-SUS-14-019 1605.09305 |
| 51 | A. Fl\'orez et al. | Anapole dark matter via vector boson fusion processes at the LHC | PRD 100 (2019) 016017 | 1902.01488 |
| 52 | 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 |
| 53 | LHC New Physics Working Group Collaboration | Simplified models for LHC new physics searches | JPG 39 (2012) 105005 | 1105.2838 |
| 54 | T. Sjostrand et al. | An introduction to PYTHIA 8.2 | CPC 191 (2015) 159 | 1410.3012 |
| 55 | CMS Collaboration | Event generator tunes obtained from underlying event and multiparton scattering measurements | EPJC 76 (2016) 155 | CMS-GEN-14-001 1512.00815 |
| 56 | CMS Collaboration | Extraction and validation of a new set of CMS PYTHIA8 tunes from underlying-event measurements | Submitted to EPJC | CMS-GEN-17-001 1903.12179 |
| 57 | NNPDF Collaboration | Parton distributions for the LHC Run II | JHEP 04 (2015) 040 | 1410.8849 |
| 58 | GEANT4 Collaboration | GEANT4--a simulation toolkit | NIMA 506 (2003) 250 | |
| 59 | CMS Collaboration | The fast simulation of the CMS detector at LHC | J. Phys. Conf. Ser. 331 (2011) 032049 | |
| 60 | J. Debove, B. Fuks, and M. Klasen | Threshold resummation for gaugino pair production at hadron colliders | NPB 842 (2011) 51 | 1005.2909 |
| 61 | B. Fuks, M. Klasen, D. R. Lamprea, and M. Rothering | Gaugino production in proton-proton collisions at a center-of-mass energy of 8 TeV | JHEP 10 (2012) 081 | 1207.2159 |
| 62 | B. Fuks, M. Klasen, D. R. Lamprea, and M. Rothering | Precision predictions for electroweak superpartner production at hadron colliders with $ \sc $ Resummino | EPJC 73 (2013) 2480 | 1304.0790 |
| 63 | J. Fiaschi and M. Klasen | Neutralino-chargino pair production at NLO+NLL with resummation-improved parton density functions for LHC Run II | PRD 98 (2018) 055014 | 1805.11322 |
| 64 | CMS Collaboration | Search for heavy neutrinos or third-generation leptoquarks in final states with two hadronically decaying tau leptons and two jets in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | JHEP 03 (2017) 077 | CMS-EXO-16-016 1612.01190 |
| 65 | CMS Collaboration | Search for heavy neutrinos and third-generation leptoquarks in hadronic states of two $ \tau $ leptons and two jets in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | JHEP 03 (2019) 170 | CMS-EXO-17-016 1811.00806 |
| 66 | CMS Collaboration | Search for heavy resonances decaying to tau lepton pairs in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | JHEP 02 (2017) 048 | CMS-EXO-16-008 1611.06594 |
| 67 | CMS Collaboration | Measurement of the inclusive $ \mathrm{W} $ and $ \mathrm{Z} $ production cross sections in pp collisions at $ \sqrt{s}= $ 7 TeV | JHEP 10 (2011) 132 | CMS-EWK-10-005 1107.4789 |
| 68 | J. Butterworth et al. | PDF4LHC recommendations for LHC Run II | JPG 43 (2016) 023001 | 1510.03865 |
| 69 | P. M. Nadolsky et al. | Implications of CTEQ global analysis for collider observables | PRD 78 (2008) 013004 | 0802.0007 |
| 70 | A. D. Martin, W. J. Stirling, R. S. Thorne, and G. Watt | Update of parton distributions at NNLO | PLB 652 (2007) 292 | 0706.0459 |
| 71 | M. Ubiali | NNPDF1.0 parton set for the LHC | NPPS 186 (2009) 62 | 0809.3716 |
| 72 | CMS Collaboration | CMS luminosity measurements for the 2016 data-taking period | CMS-PAS-LUM-17-001 | CMS-PAS-LUM-17-001 |
| 73 | CMS Collaboration | CMS luminosity measurement for the 2017 data-taking period at $ \sqrt{s} = $ 13 TeV | CMS-PAS-LUM-17-004 | CMS-PAS-LUM-17-004 |
| 74 | G. Cowan, K. Cranmer, E. Gross, and O. Vitells | Asymptotic formulae for likelihood-based tests of new physics | EPJC 71 (2011) 1554 | 1007.1727 |
| 75 | T. Junk | Confidence level computation for combining searches with small statistics | NIMA 434 (1999) 435 | hep-ex/9902006 |
| 76 | A. L. Read | Presentation of search results: the $ CL_s $ technique | JPG 28 (2002) 2693 | |
| 77 | R. J. Barlow and C. Beeston | Fitting using finite Monte Carlo samples | CPC 77 (1993) 219 | |
|
|
Compact Muon Solenoid LHC, CERN |
|
|
|
|
|
|