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| CMS-EXO-19-010 ; CERN-EP-2020-043 | ||
| Search for disappearing tracks in proton-proton collisions at $\sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 10 April 2020 | ||
| Phys. Lett. B 806 (2020) 135502 | ||
| Abstract: A search is presented for long-lived charged particles that decay within the volume of the silicon tracker of the CMS experiment. Such particles can produce events with an isolated track with no associated hits in the muon detectors, little energy deposited in the calorimeters, and missing hits in the outermost layers of the silicon tracker. The search for events with this "disappearing track'' signature is performed in a sample of proton-proton collisions recorded by the CMS experiment at the LHC with a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 101 fb$^{-1}$ recorded in 2017 and 2018. The observation of 48 events is consistent with the estimated background of 47.8$_{-2.3}^{+2.7}$ (stat) $\pm$ 8.1 (syst) events. Upper limits are set on chargino production in the context of an anomaly-mediated supersymmetry breaking model for purely wino and higgsino neutralino scenarios. At 95% confidence level, the first constraint is placed on chargino masses in the higgsino case, excluding below 750 (175) GeV for a lifetime of 3 (0.05) ns. In the wino case, the results of this search are combined with a previous CMS search to produce a result representing the complete LHC data set recorded in 2015-2018, the most stringent constraints to date. At 95% confidence level, chargino masses in the wino case are excluded below 884 (474) GeV for a lifetime of 3 (0.2) ns. | ||
| Links: e-print arXiv:2004.05153 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
The expected and observed 95% CL upper limits on the product of cross section and branching fraction for direct production of charginos as a function of chargino mass for chargino lifetimes of 0.33, 3.34, 33.4, and 333 ns, for a purely wino LSP with the branching fraction for $\tilde{\chi}^{\pm}_1 {\to}\tilde{\chi}^0_1 \pi^{\pm} $ set to 100%. Shown are the full Run 2 results, derived from the results of the search in the 2017 and 2018 data sets combined with those of Ref. [17], obtained in the 2015 and 2016 data sets. The cross section includes both $\tilde{\chi}^{\pm}_1 \tilde{\chi}^0_1 $ and $\tilde{\chi}^{\pm}_1 {\tilde{\chi}^{\mp}_1} $ production in roughly a 2:1 ratio for all chargino masses considered. The dashed line indicates the theoretical prediction for the AMSB model, described in Section 3. |
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Figure 1-a:
The expected and observed 95% CL upper limits on the product of cross section and branching fraction for direct production of charginos as a function of chargino mass for chargino lifetimes of 0.33 ns, for a purely wino LSP with the branching fraction for $\tilde{\chi}^{\pm}_1 {\to}\tilde{\chi}^0_1 \pi^{\pm} $ set to 100%. Shown are the full Run 2 results, derived from the results of the search in the 2017 and 2018 data sets combined with those of Ref. [17], obtained in the 2015 and 2016 data sets. The cross section includes both $\tilde{\chi}^{\pm}_1 \tilde{\chi}^0_1 $ and $\tilde{\chi}^{\pm}_1 {\tilde{\chi}^{\mp}_1} $ production in roughly a 2:1 ratio for all chargino masses considered. The dashed line indicates the theoretical prediction for the AMSB model, described in Section 3. |
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Figure 1-b:
The expected and observed 95% CL upper limits on the product of cross section and branching fraction for direct production of charginos as a function of chargino mass for chargino lifetimes of 3.34 ns, for a purely wino LSP with the branching fraction for $\tilde{\chi}^{\pm}_1 {\to}\tilde{\chi}^0_1 \pi^{\pm} $ set to 100%. Shown are the full Run 2 results, derived from the results of the search in the 2017 and 2018 data sets combined with those of Ref. [17], obtained in the 2015 and 2016 data sets. The cross section includes both $\tilde{\chi}^{\pm}_1 \tilde{\chi}^0_1 $ and $\tilde{\chi}^{\pm}_1 {\tilde{\chi}^{\mp}_1} $ production in roughly a 2:1 ratio for all chargino masses considered. The dashed line indicates the theoretical prediction for the AMSB model, described in Section 3. |
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Figure 1-c:
The expected and observed 95% CL upper limits on the product of cross section and branching fraction for direct production of charginos as a function of chargino mass for chargino lifetimes of 33.4 ns, for a purely wino LSP with the branching fraction for $\tilde{\chi}^{\pm}_1 {\to}\tilde{\chi}^0_1 \pi^{\pm} $ set to 100%. Shown are the full Run 2 results, derived from the results of the search in the 2017 and 2018 data sets combined with those of Ref. [17], obtained in the 2015 and 2016 data sets. The cross section includes both $\tilde{\chi}^{\pm}_1 \tilde{\chi}^0_1 $ and $\tilde{\chi}^{\pm}_1 {\tilde{\chi}^{\mp}_1} $ production in roughly a 2:1 ratio for all chargino masses considered. The dashed line indicates the theoretical prediction for the AMSB model, described in Section 3. |
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Figure 1-d:
The expected and observed 95% CL upper limits on the product of cross section and branching fraction for direct production of charginos as a function of chargino mass for chargino lifetimes of 333 ns, for a purely wino LSP with the branching fraction for $\tilde{\chi}^{\pm}_1 {\to}\tilde{\chi}^0_1 \pi^{\pm} $ set to 100%. Shown are the full Run 2 results, derived from the results of the search in the 2017 and 2018 data sets combined with those of Ref. [17], obtained in the 2015 and 2016 data sets. The cross section includes both $\tilde{\chi}^{\pm}_1 \tilde{\chi}^0_1 $ and $\tilde{\chi}^{\pm}_1 {\tilde{\chi}^{\mp}_1} $ production in roughly a 2:1 ratio for all chargino masses considered. The dashed line indicates the theoretical prediction for the AMSB model, described in Section 3. |
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Figure 2:
The expected and observed constraints on chargino lifetime and mass for a purely wino LSP in the context of AMSB, where the chargino lifetime is explicitly varied. The chargino branching fraction is set to 100% for $\tilde{\chi}^{\pm}_1 {\to}\tilde{\chi}^0_1 \pi^{\pm} $. Shown are the full Run 2 results, derived from the results of the search in the 2017 and 2018 data sets combined with those of Ref. [17], obtained in the 2015 and 2016 data sets. The region to the left of the curve is excluded at 95% CL. The prediction for the chargino lifetime from Ref. [28] is indicated as the dashed line. |
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Figure 3:
The expected and observed constraints on chargino lifetime and mass for a purely higgsino LSP in the context of AMSB, where the chargino lifetime is explicitly varied. Following Ref. [29], the branching fractions are taken to be 95.5% for $\tilde{\chi}^{\pm}_1 {\to}{\tilde{\chi}_{1,2}^{0}} \pi^{\pm} $, 3% for $\tilde{\chi}^{\pm}_1 {\to}{\tilde{\chi}_{1,2}^{0}} \mathrm{e} \nu $, and 1.5% for $\tilde{\chi}^{\pm}_1 {\to}{\tilde{\chi}_{1,2}^{0}} \mu \nu $ in the range of chargino masses of interest, with equal branching fractions and production cross sections between $\tilde{\chi}^0_1 $ and $\tilde{\chi}^{0}_{2} $. The region to the left of the curve is excluded at 95% CL. The prediction for the chargino lifetime from Ref. [50] is indicated as the dashed line. |
| Tables | |
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Table 1:
Summary of estimated values of $P_{\text {veto}}$. The uncertainties shown represent only the statistical component. |
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Table 2:
Summary of the systematic uncertainties in each background estimate. Each value listed represents the average across all data-taking periods. Some uncertainties are single-sided, as indicated, and those given as a dash are negligible. |
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Table 3:
Summary of the systematic uncertainties in the signal efficiencies. Each value listed is the average across all data-taking periods, all chargino masses and lifetimes considered, and wino and higgsino cases. The values given as a dash are negligible. |
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Table 4:
Summary of the estimated backgrounds and the observation. The first and second uncertainties shown are the statistical and systematic contributions, respectively. |
| Summary |
|
A search has been presented for long-lived charged particles that decay within the CMS detector and produce a "disappearing track'' signature. In the sample of proton-proton collisions recorded by CMS in 2017 and 2018, corresponding to an integrated luminosity of 101 fb$^{-1}$, 48 events are observed, which is consistent with the expected background of 47.8$_{-2.3}^{+2.7}$ (stat) $\pm$ 8.1 (syst) events. These results are applicable to any beyond-the-standard-model scenario capable of producing this signature and, in combination with the previous CMS search [17], are the first such results on the complete Run 2 data set, corresponding to a total integrated luminosity of 140 fb$^{-1}$. Two interpretations of these results are provided in the context of anomaly-mediated supersymmetry breaking. In the case of a purely higgsino neutralino, charginos are excluded up to a mass of 750 (175) GeV for a mean proper lifetime of 3 (0.05) ns, using the 2017 and 2018 data sets. In the case of a purely wino neutralino, charginos are excluded up to a mass of 884 (474) GeV for a mean proper lifetime of 3 (0.2) ns. These results make use of the upgraded CMS pixel detector to greatly improve sensitivity to shorter particle lifetimes. For chargino lifetimes above approximately 0.1 ns, this search places the most stringent constraints on direct chargino production with a purely wino neutralino obtained with the disappearing track signature. For a purely higgsino neutralino, these constraints are the first obtained with this signature. |
| References | ||||
| 1 | C. H. Chen, M. Drees, and J. F. Gunion | A nonstandard string / SUSY scenario and its phenomenological implications | PRD 55 (1997) 330 | hep-ph/9607421 |
| 2 | M. Ibe, S. Matsumoto, and T. T. Yanagida | Pure gravity mediation with $ m_{3/2} = $ 10 - 100 TeV | PRD 85 (2012) 095011 | 1202.2253 |
| 3 | L. J. Hall, Y. Nomura, and S. Shirai | Spread supersymmetry with wino LSP: gluino and dark matter signals | JHEP 01 (2013) 036 | 1210.2395 |
| 4 | A. Arvanitaki, N. Craig, S. Dimopoulos, and G. Villadoro | Mini-split | JHEP 02 (2013) 126 | 1210.0555 |
| 5 | M. Citron et al. | End of the CMSSM coannihilation strip is nigh | PRD 87 (2013) 036012 | 1212.2886 |
| 6 | M. Garny, J. Heisig, B. Lulf, and S. Vogl | Coannihilation without chemical equilibrium | PRD 96 (2017) 103521 | 1705.09292 |
| 7 | J.-W. Wang et al. | Exploring triplet-quadruplet fermionic dark matter at the LHC and future colliders | PRD 97 (2018) 035021 | 1711.05622 |
| 8 | A. Bharucha, F. Brummer, and N. Desai | Next-to-minimal dark matter at the LHC | JHEP 11 (2018) 195 | 1804.02357 |
| 9 | A. Biswas, D. Borah, and D. Nanda | When freeze-out precedes freeze-in: sub-TeV fermion triplet dark matter with radiative neutrino mass | JCAP 1809 (2018) 014 | 1806.01876 |
| 10 | A. Belyaev et al. | Minimal spin-one isotriplet dark matter | PRD 99 (2019) 115003 | 1808.10464 |
| 11 | D. Borah, D. Nanda, N. Narendra, and N. Sahu | Right-handed neutrino dark matter with radiative neutrino mass in gauged B - L model | NPB 950 (2020) 114841 | 1810.12920 |
| 12 | G. B\'elanger et al. | LHC-friendly minimal freeze-in models | JHEP 02 (2019) 186 | 1811.05478 |
| 13 | A. Filimonova and S. Westhoff | Long live the Higgs portal! | JHEP 02 (2019) 140 | 1812.04628 |
| 14 | G. F. Giudice, M. A. Luty, H. Murayama, and R. Rattazzi | Gaugino mass without singlets | JHEP 12 (1998) 027 | hep-ph/9810442 |
| 15 | L. Randall and R. Sundrum | Out of this world supersymmetry breaking | NPB 557 (1999) 79 | hep-th/9810155 |
| 16 | ATLAS Collaboration | Search for long-lived charginos based on a disappearing-track signature in pp collisions at $ \sqrt{s}= $ 13 TeV with the ATLAS detector | JHEP 06 (2018) 022 | 1712.02118 |
| 17 | CMS Collaboration | Search for disappearing tracks as a signature of new long-lived particles in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | JHEP 08 (2018) 016 | CMS-EXO-16-044 1804.07321 |
| 18 | CMS Collaboration | CMS technical design report for the pixel detector upgrade | CMS-TDR-011, FERMILAB-DESIGN-2012-02 | |
| 19 | CMS Collaboration | Performance verification of the CMS phase-1 upgrade pixel detector | JINST 12 (2017) C12010 | 1710.03842 |
| 20 | CMS Collaboration | The CMS trigger system | JINST 12 (2017) P01020 | CMS-TRG-12-001 1609.02366 |
| 21 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
| 22 | 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 |
| 23 | CMS Collaboration | CMS luminosity measurement for the 2018 data-taking period at $ \sqrt{s} = $ 13 TeV | CMS-PAS-LUM-18-002 | CMS-PAS-LUM-18-002 |
| 24 | T. Sjostrand et al. | An introduction to PYTHIA 8.2 | CPC 191 (2015) 159 | 1410.3012 |
| 25 | NNPDF Collaboration | Parton distributions for the LHC Run II | JHEP 04 (2015) 040 | 1410.8849 |
| 26 | CMS Collaboration | Extraction and validation of a new set of CMS PYTHIA8 tunes from underlying-event measurements | CMS-PAS-GEN-17-001 | CMS-PAS-GEN-17-001 |
| 27 | F. E. Paige, S. D. Protopopescu, H. Baer, and X. Tata | ISAJET 7.69: A Monte Carlo event generator for $ pp $, $ \bar{p}p $, and $ e^+e^- $ reactions | hep-ph/0312045 | |
| 28 | M. Ibe, S. Matsumoto, and R. Sato | Mass splitting between charged and neutral winos at two-loop level | PLB 721 (2013) 252 | 1212.5989 |
| 29 | S. D. Thomas and J. D. Wells | Phenomenology of massive vectorlike doublet leptons | PRL 81 (1998) 34 | hep-ph/9804359 |
| 30 | 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 |
| 31 | B. Fuks, M. Klasen, D. R. Lamprea, and M. Rothering | Precision predictions for electroweak superpartner production at hadron colliders with Resummino | EPJC 73 (2013) 2480 | 1304.0790 |
| 32 | P. M. Nadolsky et al. | Implications of CTEQ global analysis for collider observables | PRD 78 (2008) 013004 | 0802.0007 |
| 33 | A. D. Martin, W. J. Stirling, R. S. Thorne, and G. Watt | Parton distributions for the LHC | EPJC 63 (2009) 189 | 0901.0002 |
| 34 | J. Butterworth et al. | PDF4LHC recommendations for LHC Run II | JPG 43 (2016) 023001 | 1510.03865 |
| 35 | CMS Collaboration | Jet production rates in association with W and Z bosons in pp collisions at $ \sqrt{s}= $ 7 TeV | JHEP 01 (2012) 010 | CMS-EWK-10-012 1110.3226 |
| 36 | CMS Collaboration | Search for top-squark pair production in the single-lepton final state in pp collisions at $ \sqrt{s} = $ 8 TeV | EPJC 73 (2013) 2677 | CMS-SUS-13-011 1308.1586 |
| 37 | GEANT4 Collaboration | GEANT4--a simulation toolkit | NIMA 506 (2003) 250 | |
| 38 | CMS Collaboration | Particle-flow reconstruction and global event description with the CMS detector | JINST 12 (2017) P10003 | CMS-PRF-14-001 1706.04965 |
| 39 | M. Cacciari, G. P. Salam, and G. Soyez | The anti-$ {k_{\mathrm{T}}} $ jet clustering algorithm | JHEP 04 (2008) 063 | 0802.1189 |
| 40 | M. Cacciari, G. P. Salam, and G. Soyez | FastJet user manual | EPJC 72 (2012) 1896 | 1111.6097 |
| 41 | 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 |
| 42 | 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 |
| 43 | CMS Collaboration | Measurements of inclusive W and Z cross sections in pp collisions at $ \sqrt{s}= $ 7 TeV | JHEP 01 (2011) 080 | CMS-EWK-10-002 1012.2466 |
| 44 | Particle Data Group, M. Tanabashi et al. | Review of particle physics | PRD 98 (2018) 030001 | |
| 45 | CMS Collaboration | Muon tracking efficiency using tag and probe method for 2017 dataset | CDS | |
| 46 | CMS Collaboration | Muon Tracking Efficiency for 2018 dataset using Tag and Probe method | CDS | |
| 47 | T. Junk | Confidence level computation for combining searches with small statistics | NIMA 434 (1999) 435 | hep-ex/9902006 |
| 48 | A. L. Read | Presentation of search results: The $ CL_{s} $ technique | JPG 28 (2002) 2693 | |
| 49 | G. Cowan, K. Cranmer, E. Gross, and O. Vitells | Asymptotic formulae for likelihood-based tests of new physics | EPJC 71 (2011) 1554 | 1007.1727 |
| 50 | H. Fukuda, N. Nagata, H. Otono, and S. Shirai | Higgsino dark matter or not: role of disappearing track searches at the LHC and future colliders | PLB 781 (2018) 306 | 1703.09675 |
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