Compact Muon Solenoid
LHC, CERN
Visit us: CMS Public Website, CMS Physics ;
Contact us: CMS Publications Committee
| CMS-PAS-B2G-16-028 | ||
| Search for third-generation scalar leptoquarks decaying to a top quark and a $\tau$ lepton at $\sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| December 2017 | ||
| Abstract: A search for pair production of heavy scalar leptoquarks (LQs) decaying into a top quark and a $\tau$ lepton is presented. The search considers final states with an electron or a muon, one or two $\tau$ leptons decaying to hadrons, and additional jets. The data collected in proton-proton collisions in 2016 at $\sqrt{s}= $ 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb$^{-1}$ are used. No evidence for pair production of leptoquarks is found. Upper limits on the production cross section are set as a function of LQ mass, assuming a branching fraction of unity for the decay $\mathrm{LQ}\to \mathrm{t} \tau$, excluding masses below 900 GeV at 95% confidence level. These results provide the most stringent exclusion limits on the production of scalar leptoquarks in the top quark and $\tau$ lepton decay channel to date. | ||
|
Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, EPJC 78 (2018) 707. The superseded preliminary plots can be found here. |
||
| Figures | |
png pdf |
Figure 1-a:
Shape comparison between the signal region A and the corresponding control region, as a function of ${p_{\mathrm {T}}^{\mathrm{t}}}$, for simulated ${\mathrm{t} {}\mathrm{\bar{t}}}$ and W+jets events. Events with an opposite-sign $\mu {\tau _{\mathrm {h}}} $ pair are shown on the left, while those with a same-sign $\mu {\tau _{\mathrm {h}}} $ pair are shown on the right. The full selection is applied and the $ {S_{\text {T}}} $ categories are combined. All histograms are normalized to the total number of entries. The gray band in the ratio plot corresponds to the statistical uncertainty in the simulated samples. |
png pdf |
Figure 1-b:
Shape comparison between the signal region A and the corresponding control region, as a function of ${p_{\mathrm {T}}^{\mathrm{t}}}$, for simulated ${\mathrm{t} {}\mathrm{\bar{t}}}$ and W+jets events. Events with an opposite-sign $\mu {\tau _{\mathrm {h}}} $ pair are shown on the left, while those with a same-sign $\mu {\tau _{\mathrm {h}}} $ pair are shown on the right. The full selection is applied and the $ {S_{\text {T}}} $ categories are combined. All histograms are normalized to the total number of entries. The gray band in the ratio plot corresponds to the statistical uncertainty in the simulated samples. |
png pdf |
Figure 2:
Strategy for the background estimation in category B. The $ {{\mathrm{t} {}\mathrm{\bar{t}}} _{\mathrm {f}}} $ background in the signal region is derived from the control region $ {\mathrm {CR}_{\mathrm {B1}}} $. The $ {{\mathrm{t} {}\mathrm{\bar{t}}} _{\mathrm {p+f}}} $ background in the signal region is derived from the control region $ {\mathrm {CR}_{\mathrm {B2}}} $. To obtain an estimate of the $ {{\mathrm{t} {}\mathrm{\bar{t}}} _{\mathrm {f}}} $ background in the control region $ {\mathrm {CR}_{\mathrm {B2}}} $, the control region $ {\mathrm {CR}_{\mathrm {B1}}} $ is used. |
png pdf |
Figure 3-a:
Distributions of $ {p_{\mathrm {T}}^{\mathrm{t}}} $ for events in the electron channel passing the full selection in category A. The events are separated into OS (top), SS (bottom), low $ {S_{\text {T}}} $ (left) and high $ {S_{\text {T}}} $ (right) categories. The hatched areas represent the total uncertainties of the SM background. In the bottom panel, the ratio of data to SM background is shown together with statistical (dark gray) and total (light gray) uncertainties of the total SM background. |
png pdf |
Figure 3-b:
Distributions of $ {p_{\mathrm {T}}^{\mathrm{t}}} $ for events in the electron channel passing the full selection in category A. The events are separated into OS (top), SS (bottom), low $ {S_{\text {T}}} $ (left) and high $ {S_{\text {T}}} $ (right) categories. The hatched areas represent the total uncertainties of the SM background. In the bottom panel, the ratio of data to SM background is shown together with statistical (dark gray) and total (light gray) uncertainties of the total SM background. |
png pdf |
Figure 3-c:
Distributions of $ {p_{\mathrm {T}}^{\mathrm{t}}} $ for events in the electron channel passing the full selection in category A. The events are separated into OS (top), SS (bottom), low $ {S_{\text {T}}} $ (left) and high $ {S_{\text {T}}} $ (right) categories. The hatched areas represent the total uncertainties of the SM background. In the bottom panel, the ratio of data to SM background is shown together with statistical (dark gray) and total (light gray) uncertainties of the total SM background. |
png pdf |
Figure 3-d:
Distributions of $ {p_{\mathrm {T}}^{\mathrm{t}}} $ for events in the electron channel passing the full selection in category A. The events are separated into OS (top), SS (bottom), low $ {S_{\text {T}}} $ (left) and high $ {S_{\text {T}}} $ (right) categories. The hatched areas represent the total uncertainties of the SM background. In the bottom panel, the ratio of data to SM background is shown together with statistical (dark gray) and total (light gray) uncertainties of the total SM background. |
png pdf |
Figure 4-a:
Distributions of $ {p_{\mathrm {T}}^{\mathrm{t}}} $ for events in the muon channel passing the full selection in category A. The events are separated into OS (top), SS (bottom), low $ {S_{\text {T}}} $ (left) and high $ {S_{\text {T}}} $ (right) categories. The hatched areas represent the total uncertainties of the SM background. In the bottom panel, the ratio of data to SM background is shown together with statistical (dark gray) and total (light gray) uncertainties of the total SM background. |
png pdf |
Figure 4-b:
Distributions of $ {p_{\mathrm {T}}^{\mathrm{t}}} $ for events in the muon channel passing the full selection in category A. The events are separated into OS (top), SS (bottom), low $ {S_{\text {T}}} $ (left) and high $ {S_{\text {T}}} $ (right) categories. The hatched areas represent the total uncertainties of the SM background. In the bottom panel, the ratio of data to SM background is shown together with statistical (dark gray) and total (light gray) uncertainties of the total SM background. |
png pdf |
Figure 4-c:
Distributions of $ {p_{\mathrm {T}}^{\mathrm{t}}} $ for events in the muon channel passing the full selection in category A. The events are separated into OS (top), SS (bottom), low $ {S_{\text {T}}} $ (left) and high $ {S_{\text {T}}} $ (right) categories. The hatched areas represent the total uncertainties of the SM background. In the bottom panel, the ratio of data to SM background is shown together with statistical (dark gray) and total (light gray) uncertainties of the total SM background. |
png pdf |
Figure 4-d:
Distributions of $ {p_{\mathrm {T}}^{\mathrm{t}}} $ for events in the muon channel passing the full selection in category A. The events are separated into OS (top), SS (bottom), low $ {S_{\text {T}}} $ (left) and high $ {S_{\text {T}}} $ (right) categories. The hatched areas represent the total uncertainties of the SM background. In the bottom panel, the ratio of data to SM background is shown together with statistical (dark gray) and total (light gray) uncertainties of the total SM background. |
png pdf |
Figure 5-a:
Upper limits at 95% confidence level on the cross section times branching fraction squared (top) and the leptoquark mass as a function of the branching ratio (bottom) on the pair production of scalar leptoquarks decaying to a top quark and a $\tau $ lepton. The results include all search categories in the $\ell $+$ {\tau _{\mathrm {h}}} $+jets channels. In the top plot, the theory curve corresponds to the NLO cross section with uncertainties from PDF and scale variations [34]. |
png pdf |
Figure 5-b:
Upper limits at 95% confidence level on the cross section times branching fraction squared (top) and the leptoquark mass as a function of the branching ratio (bottom) on the pair production of scalar leptoquarks decaying to a top quark and a $\tau $ lepton. The results include all search categories in the $\ell $+$ {\tau _{\mathrm {h}}} $+jets channels. In the top plot, the theory curve corresponds to the NLO cross section with uncertainties from PDF and scale variations [34]. |
| Summary |
| References | ||||
| 1 | W. Buchmuller, R. Ruckl, and D. Wyler | Leptoquarks in lepton-quark collisions | PLB 191 (1987) 442, . [Erratum: \DOI10.1016/S0370-2693(99)00014-3] | |
| 2 | J. C. Pati and A. Salam | Lepton number as the fourth ``color" | PRD 10 (1974) 275, . [Erratum: \DOI10.1103/PhysRevD.11.703.2] | |
| 3 | H. Georgi and S. L. Glashow | Unity of all elementary particle forces | PRL 32 (1974) 438 | |
| 4 | H. Fritzsch and P. Minkowski | Unified interactions of leptons and hadrons | Ann. Phys. 93 (1975) 193 | |
| 5 | E. Farhi and L. Susskind | Technicolor | PR 74 (1981) 277 | |
| 6 | K. D. Lane and M. V. Ramana | Walking technicolor signatures at hadron colliders | PRD 44 (1991) 2678 | |
| 7 | B. Schrempp and F. Schrempp | Light leptoquarks | PLB 153 (1985) 101 | |
| 8 | B. Gripaios | Composite leptoquarks at the LHC | JHEP 02 (2010) 045 | 0910.1789 |
| 9 | BaBar Collaboration | Evidence for an excess of $ \bar{B} \to D^{(*)} \tau^-\bar{\nu}_\tau $ decays | PRL 109 (2012) 101802 | 1205.5442 |
| 10 | BaBar Collaboration | Measurement of an excess of $ \bar{B} \to D^{(*)}\tau^- \bar{\nu}_\tau $ decays and implications for charged Higgs bosons | PRD 88 (2013) 072012 | 1303.0571 |
| 11 | Belle Collaboration | Observation of $ B^0 \to D^{*-} \tau^+ \nu_\tau $ decay at Belle | PRL 99 (2007) 191807 | 0706.4429 |
| 12 | Belle Collaboration | Observation of $ B^+ \to \bar{D}^{*0} \tau^+ \nu_\tau $ and Evidence for $ B^+ \to \bar{D}^0 \tau^+ \nu_\tau $ at Belle | PRD 82 (2010) 072005 | 1005.2302 |
| 13 | Belle Collaboration | Measurement of the branching ratio of $ \bar{B} \to D^{(\ast)} \tau^- \bar{\nu}_\tau $ relative to $ \bar{B} \to D^{(\ast)} \ell^- \bar{\nu}_\ell $ decays with hadronic tagging at Belle | PRD 92 (2015) 072014 | 1507.03233 |
| 14 | LHCb Collaboration | Measurement of the ratio of branching fractions $ \mathcal{B}(\bar{B}^0 \to D^{*+}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}^0 \to D^{*+}\mu^{-}\bar{\nu}_{\mu}) $ | PRL 115 (2015) 111803 | 1506.08614 |
| 15 | B. Dumont, K. Nishiwaki, and R. Watanabe | LHC constraints and prospects for $ S_1 $ scalar leptoquark explaining the $ \bar B \to D^{(*)} \tau \bar\nu $ anomaly | PRD94 (2016) 034001 | 1603.05248 |
| 16 | M. Tanaka and R. Watanabe | New physics in the weak interaction of $ \bar B\to D^{(*)}\tau\bar\nu $ | PRD 87 (2013) 034028 | 1212.1878 |
| 17 | Y. Sakaki, M. Tanaka, A. Tayduganov, and R. Watanabe | Testing leptoquark models in $ \bar B \to D^{(*)} \tau \bar\nu $ | PRD 88 (2013) 094012 | 1309.0301 |
| 18 | I. Dor\vsner, S. Fajfer, N. Ko\vsnik, and I. Ni\vsand\vzi\'c | Minimally flavored colored scalar in $ \bar B \to D^{(*)} \tau \bar \nu $ and the mass matrices constraints | JHEP 11 (2013) 084 | 1306.6493 |
| 19 | B. Gripaios, M. Nardecchia, and S. A. Renner | Composite leptoquarks and anomalies in $ B $-meson decays | JHEP 05 (2015) 006 | 1412.1791 |
| 20 | S. Chakdar, T. Li, S. Nandi, and S. K. Rai | Unity of elementary particles and forces for the third family | PLB 718 (2012) 121 | 1206.0409 |
| 21 | S. Chakdar, T. Li, S. Nandi, and S. K. Rai | Top SU(5) Models: Baryon and lepton number violating resonances at the LHC | PRD 87 (2013), no. 9, 096002 | 1302.6942 |
| 22 | CMS Collaboration | Search for Third-Generation Scalar Leptoquarks in the t$ \tau $ Channel in Proton-Proton Collisions at $ \sqrt{s} = $ 8 TeV | JHEP 07 (2015) 042 | CMS-EXO-14-008 1503.09049 |
| 23 | D0 Collaboration | Search for third-generation leptoquarks in $ p \bar{p} $ collisions at $ \sqrt{s} = $ 1.96 TeV | PRL 99 (2007) 061801 | 0705.0812 |
| 24 | CDF Collaboration | Search for third generation vector leptoquarks in $ p \bar{p} $ collisions at $ \sqrt{s} = $ 1.96 TeV | PRD 77 (2008) 091105 | 0706.2832 |
| 25 | ATLAS Collaboration | Search for third generation scalar leptoquarks in pp collisions at $ \sqrt{s} = $ 7 TeV with the ATLAS detector | JHEP 06 (2013) 033 | 1303.0526 |
| 26 | CMS Collaboration | Search for third-generation leptoquarks and scalar bottom quarks in pp collisions at $ \sqrt{s}= $ 7 TeV | JHEP 12 (2012) 055 | CMS-EXO-11-030 1210.5627 |
| 27 | CMS Collaboration | Search for pair production of third-generation scalar leptoquarks and top squarks in proton-proton collisions at $ \sqrt{s} = $ 8 TeV | PLB 739 (2014) 229 | CMS-EXO-12-032 1408.0806 |
| 28 | CMS Collaboration | Searches for third-generation squark production in fully hadronic final states in proton-proton collisions at $ \sqrt{s} = $ 8 TeV | JHEP 06 (2015) 116 | CMS-SUS-14-001 1503.08037 |
| 29 | ATLAS Collaboration | Searches for scalar leptoquarks in pp collisions at $ \sqrt{s} = $ 8 TeV with the ATLAS detector | EPJC 76 (2016) 5 | 1508.04735 |
| 30 | 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 |
| 31 | CMS Collaboration | Search for third-generation scalar leptoquarks and heavy right-handed neutrinos in final states with two tau leptons and two jets in proton-proton collisions at $ \sqrt{s}= $ 13 TeV | JHEP 07 (2017) 121 | CMS-EXO-16-023 1703.03995 |
| 32 | G. R. Farrar and P. Fayet | Phenomenology of the Production, Decay, and Detection of New Hadronic States Associated with Supersymmetry | PL76B (1978) 575--579 | |
| 33 | R. Barbier et al. | R-parity violating supersymmetry | PR 420 (2005) 1--202 | hep-ph/0406039 |
| 34 | M. Kramer, T. Plehn, M. Spira, and P. M. Zerwas | Pair production of scalar leptoquarks at the CERN LHC | PRD 71 (2005) 057503 | hep-ph/0411038 |
| 35 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
| 36 | CMS Collaboration | CMS luminosity measurements for the 2016 data taking period | CMS-PAS-LUM-17-001 | CMS-PAS-LUM-17-001 |
| 37 | T. Sjostrand, S. Mrenna, and P. Z. Skands | A Brief Introduction to PYTHIA 8.1 | Comput.Phys.Commun. 178 (2008) 852--867 | 0710.3820 |
| 38 | P. Nason | A New method for combining NLO QCD with shower Monte Carlo algorithms | JHEP 11 (2004) 040 | hep-ph/0409146 |
| 39 | S. Frixione, P. Nason, and C. Oleari | Matching NLO QCD computations with Parton Shower simulations: the POWHEG method | JHEP 11 (2007) 070 | 0709.2092 |
| 40 | S. Alioli, P. Nason, C. Oleari, and E. Re | A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX | JHEP 06 (2010) 043 | 1002.2581 |
| 41 | S. Frixione, P. Nason, and G. Ridolfi | A positive-weight next-to-leading-order Monte Carlo for heavy flavour hadroproduction | JHEP 09 (2007) 126 | 0707.3088 |
| 42 | S. Alioli, P. Nason, C. Oleari, and E. Re | NLO single-top production matched with shower in POWHEG: s- and t-channel contributions | JHEP 09 (2009) 111 | 0907.4076 |
| 43 | E. Re | Single-top Wt-channel production matched with parton showers using the POWHEG method | EPJC 71 (2011) 1547 | 1009.2450 |
| 44 | 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 |
| 45 | R. Frederix and S. Frixione | Merging meets matching in MC@NLO | JHEP 12 (2012) 061 | 1209.6215 |
| 46 | M. L. Mangano, M. Moretti, F. Piccinini, and M. Treccani | Matching Matrix Elements and Shower Evolution for Top-Quark Production in Hadronic Collisions | JHEP 01 (2007) 013 | hep-ph/0611129 |
| 47 | CMS Collaboration | Event generator tunes obtained from underlying event and multiparton scattering measurements | EPJC76 (2016), no. 3, 155 | CMS-GEN-14-001 1512.00815 |
| 48 | P. Skands, S. Carrazza, and J. Rojo | Tuning PYTHIA 8.1: the Monash 2013 Tune | EPJC 74 (2014) 3024 | 1404.5630 |
| 49 | NNPDF Collaboration | Parton distributions for the LHC Run II | JHEP 04 (2015) 040 | 1410.8849 |
| 50 | CMS Collaboration | Particle-flow reconstruction and global event description with the CMS detector | JINST 12 (2017), no. 10, P10003 | CMS-PRF-14-001 1706.04965 |
| 51 | CMS Collaboration | Description and performance of track and primary-vertex reconstruction with the CMS tracker | JINST 9 (2014) P10009 | CMS-TRK-11-001 1405.6569 |
| 52 | M. Cacciari, G. P. Salam, and G. Soyez | The Anti-$ k_t $ jet clustering algorithm | JHEP 04 (2008) 063 | 0802.1189 |
| 53 | M. Cacciari, G. P. Salam, and G. Soyez | FastJet user manual | EPJC 72 (2012) 1896 | 1111.6097 |
| 54 | CMS Collaboration | Performance of CMS muon reconstruction in pp collision events at $ \sqrt{s}= $ 7 TeV | JINST 7 (2012) P10002 | CMS-MUO-10-004 1206.4071 |
| 55 | 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 |
| 56 | M. Cacciari, G. P. Salam, and G. Soyez | The catchment area of jets | JHEP 04 (2008) 005 | 0802.1188 |
| 57 | CMS Collaboration | Determination of jet energy calibration and transverse momentum resolution in CMS | JINST 6 (2011) P11002 | CMS-JME-10-011 1107.4277 |
| 58 | CMS Collaboration | Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV | JINST 12 (2017), no. 02, P02014 | CMS-JME-13-004 1607.03663 |
| 59 | CMS Collaboration | Identification of b-quark jets with the CMS experiment | JINST 8 (2013) P04013 | CMS-BTV-12-001 1211.4462 |
| 60 | CMS Collaboration | Identification of b quark jets at the CMS experiment in the LHC Run 2 | CMS-PAS-BTV-15-001 | CMS-PAS-BTV-15-001 |
| 61 | CMS Collaboration | Performance of tau-lepton reconstruction and identification in CMS | JINST 7 (2012) P01001 | CMS-TAU-11-001 1109.6034 |
| 62 | CMS Collaboration | Performance of reconstruction and identification of tau leptons in their decays to hadrons and tau neutrino in LHC Run-2 | CMS-PAS-TAU-16-002 | CMS-PAS-TAU-16-002 |
| 63 | CMS Collaboration | Performance of the CMS missing transverse momentum reconstruction in pp data at $ \sqrt{s} = $ 8 TeV | JINST 10 (2015), no. 02, P02006 | CMS-JME-13-003 1411.0511 |
| 64 | CMS Collaboration | Measurement of the $ t\bar{t} $ production cross section using events in the e$ \mu $ final state in pp collisions at $ \sqrt{s} = $ 13 TeV | EPJC77 (2017) 172 | CMS-TOP-16-005 1611.04040 |
| 65 | N. Kidonakis | NNLL threshold resummation for top-pair and single-top production | Phys. Part. Nucl. 45 (2014) 714 | 1210.7813 |
| 66 | CMS Collaboration | Observation of the associated production of a single top quark and a W boson in pp collisions at sqrt(s) = 8 TeV | PRL 112 (2014) 231802 | CMS-TOP-12-040 1401.2942 |
| 67 | CMS Collaboration | Cross section measurement of t-channel single top quark production in pp collisions at $ \sqrt{s} = $ 13 TeV | Submitted to: PLB (2016) | CMS-TOP-16-003 1610.00678 |
| 68 | CMS Collaboration | Measurement of inclusive W and Z boson production cross sections in pp collisions at $ \sqrt{s} = $ 8 TeV | PRL 112 (2014) 191802 | CMS-SMP-12-011 1402.0923 |
| 69 | J. M. Campbell, R. K. Ellis, and C. Williams | Vector boson pair production at the LHC | JHEP 07 (2011) 018 | 1105.0020 |
| 70 | T. Gehrmann et al. | $ W^+W^- $ Production at Hadron Colliders in Next-to-Next-to-Leading-Order QCD | PRL 113 (2014) 212001 | 1408.5243 |
| 71 | CMS Collaboration | Measurement of the inelastic proton-proton cross section at $ \sqrt{s}= $ 7 TeV | PLB722 (2013) 5--27 | CMS-FWD-11-001 1210.6718 |
| 72 | J. Butterworth et al. | PDF4LHC recommendations for LHC Run II | JPG43 (2016) 023001 | 1510.03865 |
| 73 | J. Ott | theta - a framework for template-based modeling and inference | http://www.theta-framework.org | |
|
|
Compact Muon Solenoid LHC, CERN |
|
|
|
|
|
|