We present recent results from searches for new physics beyond supersymmetry
performed at the Tevatron accelerator at Fermilab. The CDF and D0 analyses
presented here utilized data of integrated luminosity up to 6 fb-1. We cover
leptonic and bosonic resonances interpreted in the Randall-Sundrum graviton and
new-boson models, rare final states, and the search for vector-like quarks.Comment: Proceedings of the XLVI Rencontres de Moriond, International
  Conference on QCD and High Energy Interactions, La Thuile, Italy, Mar.
  20-127, 2011, 33

Strologas, John

English

arXiv

We present recent results from searches for new physics beyond supersymmetry performed at the Tevatron accelerator at Fermilab. The CDF and D0 analyses presented here utilized data of integrated luminosity up to 6 fb{sup -1}. We cover leptonic and bosonic resonances interpreted in the Randall-Sundrum graviton and new-boson models, rare final states, and the search for vector-like quarks. The search for new phenomena beyond the weak-scale supersymmetry is a vital part of the Fermilab program. Both CDF and D0 experiments at the Tevatron collider actively look for signals not expected by the standard model (SM) or minimal supersymmetric models. The searches can be sorted in three categories: (a) searches for generic resonances that can be interpreted in several new-physics models; (b) searches for exotic combinations of final-state objects or abnormal kinematics (not necessarily predicted by current theories); and (c) model-dependent searches that test a particular theory. We present here latest results from all these categories: searches for new dilepton and diboson resonances (interpreted as gravitons and new gauge bosons), searches for anomalous {gamma} + E{sub T} + X production, and searches for vector-like quarks

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NON-SUSY SEARCHES AT THE TEVATRONJohn StrologasDepartment of Physics and Astronomy, University of New Mexico,Albuquerque, New Mexico 87131, USAWe present recent results from searches for new physics beyond supersymmetry performed atthe Tevatron accelerator at Fermilab. The CDF and DØ analyses presented here utilized dataof integrated luminosity up to 6 fb−1. We cover leptonic and bosonic resonances interpretedin the Randall-Sundrum graviton and new-boson models, rare final states, and the search forvector-like quarks.1 IntroductionThe search for new phenomena beyond the weak-scale supersymmetry is a vital part of the Fer-milab program. Both CDF and DØ experiments at the Tevatron collider actively look for signalsnot expected by the standard model (SM) or minimal supersymmetric models. The searchescan be sorted in three categories: a) searches for generic resonances that can be interpreted inseveral new-physics models b) searches for exotic combinations of final-state objects or abnormalkinematics (not necessarily predicted by current theories) and c) model-dependent searches thattest a particular theory. We present here latest results from all these categories: searches fornew dilepton and diboson resonances (interpreted as gravitons and new gauge bosons), searchesfor anomalous γ + ET/ +X production, and searches for vector-like quarks.2 Search for New Resonances2.1 Search for RS-gravitonsThe Randall-Sundrum (RS) model offers an explanation for the hierarchy problem with theintroduction of an extra dimension accessible only to gravity-carrying gravitons. CDF completeda search for the RS-gravitons in the dielectron1 and dimuon2 channels using 5.7 fb−1 of integratedluminosity. Two electrons (muons) are selected, at least one with ET (pT ) above 20 GeV(GeV/c). The leptons are isolated, i.e., the excess energy in a cone ∆R =√∆φ)2 + (∆η)2 = 0.4around each lepton is less than 10% of the energy (momentum) of the electron (muon). Cosmic-ray veto and γ → ee conversion removal are applied; no opposite charge is enforced. Mainbackgrounds come from the Drell-Yan (DY) process, and QCD background associated with onereal lepton and one ”fake” lepton (i.e., jet (track) faking an electron (muon)). Minor backgroundscome from diboson and tt̄ processes. The QCD background is determined with CDF data, withthe application of a probability that a jet (track) fakes an electron (muon) on events with oneidentified lepton. All other backgrounds are estimated with Monte Carlo simulations (MC)absolutely normalized to the next-to-leading order cross sections, the data luminosity, lepton-identification scale factors and trigger efficiencies. The dielectron and dimuon mass spectra areconsistent with expectation. At the same time, the highest-dielectron-mass event ever observedis detected (Mee = 960 GeV/c2). The probability that at least one event is observed with adielectron mass at least that high is 4%. The results are interpreted in the RS-graviton model,combined with a previous diphoton3 graviton search. For the RS-model parameter k/MPl = 0.1,RS-gravitons with mass less than 1111 GeV/c2 are excluded at 95% confidence level (CL). Figure1 shows the dielectron spectrum and Figure 2 shows the cross-section uper limit as a functionof the graviton mass, along with theoretical cross sections for several values of k/MPl.FERMILAB-CONF-11-473Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. )2Dielectron Mass (GeV/c100 200 300 400 500 600 700 800 900 1000N of events-210-110110210310410510 DATADrell-YanQCDDibosontt)-1CDF Run II Preliminary (L=5.7 fbFigure 1: Dielectron mass spectrum from the CDFsearch for RS-gravitons.)2Graviton Mass (GeV/c200 400 600 800 1000 1200)(pb)µµ/ee/γγ→Br(G×σ -310-210 = 0.01PlMk/0.0250.05 0.07 0.1)-1CDF Run II Preliminary (L=5.7 fbRS model, NLO cross sectionObserved 95% CL upper limitExpected limitσ 1±Expected limit σ 2±Expected limit Figure 2: Exclusion plots from the CDF search forRS-gravitons decaying to γγ or ee or µµ.2.2 Search for Z ′New gauge-bosons are predicted by Grand Unifying Theories and would appear as resonancesat hadron colliders. DØ recently searched for a new gauge boson Z ′ → ee using 5.4 fb−1 ofintegrated luminosity 4. Two electrons with pT > 25 GeV/c are selected and no opposite chargeis required. The electrons are isolated: the excess energy in a cone ∆R = 0.4 around the electronis less than 7% of its energy; additional track-based isolation is applied. The backgrounds areidentical to the CDF dielectron search. The QCD background is estimated using a dielectronmass shape from DØ data that fail the electron identification selection and fitting in the Zresonance along with the DY background. The remaining minor SM backgrounds (diboson, tt̄)are estimated using MC absolutely normalized. The dielectron spectrum is consistent with theone expected by the SM. For a Z ′ interacting with SM couplings, Z ′ masses below 1023 GeV/c2are excluded at 95% CL. Figure 3 shows the exclusion limits for several Z ′ models.CDF recently published a Z ′ → µµ search using 4.6 fb−1 of integrated luminosity 5. Thetwo muons are above 30 GeV/c, a cosmic-ray veto is applied and no opposite charge is required.The isolation requirements and the electroweak/QCD background estimations are the same asin the CDF RS-graviton search using dimuons. The mass spectrum is consistent with the SM;the SM-like Z ′ allowed masses are above 1071 GeV/c2 at 95% CL. Figure 4 shows the exclusionlimits for several Z ′ models.2.3 Search for W ′The leptonic decay of the W ′ boson will lead to a lepton and missing transverse energy (ET/ )coming from the undetected neutrino. CDF completed a 5.3 fb−1 search for W ′ decaying toelectron and a neutrino 6. One isolated electron with ET > 25 GeV and ET/ > 25 GeV arerequired. Given that the two objects have to have similar energy, 0.4 < ET /ET/ < 2.5 is required.Events with two electrons are rejected. The main SM background is coming from the SM Wdecaying to the identical final state, W/Z decaying to taus with at least one leptonic decay andQCD multijets with fake leptons and fake or real ET/ . The electron-neutrino transverse-massspectrum is in good agreement with expectation. Assuming W ′ with SM left-right symmetriccouplings, W ′ with a mass less than 1.12 TeV/c2 are excluded at 95% CL. Figure 5 shows thisexclusion limit.In some models the new gauge boson couples stronger to the third generation. DØ performeda 2.3 fb−1 analysis looking for W ′ decaying to a top and a bottom quark with a final state of twobottom quarks, a lepton, and a neutrino 7. The events selected include one e(µ) with pT above (GeV)Z’M200 300 400 500 600 700 800 900 1000 1100 ee) (fb)→ BR(Z’ × Z’) → p(pσ110210ObservedExpectedσ1±Expected σ2±Expected SSM Z’ = 0.02∈ StSMZ’ = 0.03∈ StSMZ’ = 0.04∈ StSMZ’ = 0.05∈ StSMZ’ = 0.06∈ StSMZ’ -1DØ, 5.4 fb95% CL {Figure 3: Exclusion plot from the DØ search for Z′decaying to two electrons.]2Z’ mass [GeV/c800 850 900 950 1000 1050) [pb]µµ →(Z’) * BR(Z’σ-310-210 95% CL limitIZ’secZ’NZ’ψZ’χZ’ηZ’SMZ’-1CDF Run II Preliminary 4.6 fbFigure 4: Exclusion plot from the CDF search for Z′decaying to two muons.15/20 GeV/c. Events are segregated based on jet multiplicity (2, 3, or 4 jets) counting jetswith ET > 15 GeV (leading jet above 25 GeV) and based on b-tagging (1 or 2 tags). The totalinvariant mass is required to be above 400 GeV/c2. Main SM backgrounds include W+jets andtt̄ production. Minor backgrounds come from QCD multijet and Z+jets. Lower mass limits arepresented for different combinations of left-handed and right-handed couplings and range from863 to 916 GeV/c2 at 95% CL. Figure 6 shows the exclusion limits for a W ′ with SM couplings.2.4 Diboson ResonancesDØ searched for WW and WZ resonances using 4.1 fb−1 (trileptons) or 5.4 fb−1 (lepton(s)+jets)of data8. Three selections were used: either a W decays leptonically or the Z decays leptonicallyor both bosons decay leptonically, leading to 1-lepton+jets, 2-leptons+jets, or 3-lepton finalsignatures respectively. The leptons and jets are required to be above 20 GeV, where the ET/ forthe three channels is required to be ET/ > 20, ET/ < 50, and ET/ > 30 GeV respectively. In thisanalysis boosted W/Z decays to two jets could be reconstructed as one jet. Main backgroundsare W/Z+jets and diboson. The observations are consistent with the SM expectation. Due tohigher backgrounds and under the assumption of lower branching fractions to leptons, the limitsinterpreted in the RS-graviton model or in W ′ are weaker than the respective direct dileptonones (M(W ′) > 690 GeV/c2and M(G) > 754 GeV/c2 at 95% CL).3 Search for Exotic Signatures3.1 Search for exotic production of γ+jetCDF performed a 4.8 fb−1 analysis 9 searching for abnormal generation of photon+jet, requiringthe photon ET to be above 30 GeV and the jet above 15 GeV. The photon and jet were separatedso that ∆φ(photon, jet) > 0.4 rad. Four channels were investigated (>= 1 and >= 2 jets, withand without requiring ET/ > 20 GeV). Main backgrounds are the SM production of γ, γγ,charged-lepton, QCD multijets, cosmic rays and beam halo. Good agreement is observed inseveral kinematic distributions and no hint of new physics is seen.3.2 Search for exotic production of lepton+γ+ET/ +b-quarkCDF also performed a 6 fb−1 search 10 for abnormal production of lepton+γ+ET/ +b-quarkrequiring lepton ET > 20 GeV, ET/ > 20 GeV, photon ET > 12 GeV, and a b-tagged jet with]2 [GeV/cW’m500 600 700 800 900 1000 1100 1200 1300) [pb]ν e→ B(W’ × σ-310-210-110110 Br(NNLO) × σ) σ 1± Br(× σobs. Limit 95 % C.L. exp. Limit 95 % C.L. 68 % exp. Limit 95 % C.L. 95 % exp. Limit 95 % C.L. -1CDF Run II Preliminary, 5.3 fbFigure 5: Exclusion plot from CDF search for W ′decaying to an electron and a neutrino. M(W’) [GeV]600 650 700 750 800 850 900 950 1000 tb) [pb]→ p (pσ00.511.522.533.544.55  -1DØ 2.3 fbObserved limitExpected limit=0)R=1, aLW’ (a tb) [pb]→ p (pσ(a)Figure 6: Exclusion plot from the DØ search for W ′decaying to a top and bottom quarks.ET > 20 GeV. Main backgrounds are tt̄ + γ and W + γ+jets. No new physics is seen, and thisanalysis yields an impressive measurement of SM tt̄ + γ cross section of σ = 0.18± 0.07(stat.)±0.04(sys.)± 0.01(lum.) pb.4 Search for Vector-like QuarksDØ performed a 5.4 fb−1 search for vector-like quarks that would manifest themselves in W/Z +2 jets 11. For the Z+jets channel two electrons or muons above 20 GeV with pT (dilepton) > 100GeV/c, at least two jets above 20 GeV (leading > 100 GeV), ET/ < 50 GeV and 70 < M`` < 110GeV/c2 are required. Main background comes from SM Z+jets. The mass of the vector-likequark must be above 430-551 GeV/c2 (depending on the couplings) at 95% CL. For the W+jetschannel one electron or muon is selected with pT > 50 GeV/c, same jet requirement, ET/ > 50/40GeV and (2MWT c2 +ET/ ) > 80 GeV. The main backgrounds come from SM W+jets, top quarks,QCD multijets, Z+jets, and diboson. The mass of the vector-like quark must be above 403-693GeV/c2 (depending on the couplings) at 95% CL.References1. T. Aaltonen et al. (CDF Collaboration), arXiv:1103.4650 [hep-ex] (2011).2. T. Aaltonen et al. (CDF Collaboration), CDF public note 10479 (2011).3. T. Aaltonen et al. (CDF Collaboration), Phys. Rev. D 83, 011102(R) (2011).4. V. Abazov et al. (D0 Collaboration), Phys. Lett. B 695, 88 (2011).5. T. Aaltonen et al. (CDF Collaboration), Phys. Rev. Lett. 106, 121801 (2011).6. T. Aaltonen et al. (CDF Collaboration), Phys. Rev. D 83, 031102 (2011).7. V. Abazov et al. (D0 Collaboration), Phys. Lett. B 699, 145 (2011).8. V. Abazov et al. (D0 Collaboration), Phys. Rev. Lett. 107, 011801 (2011).9. T. Aaltonen et al. (CDF Collaboration), CDF public note 10355 (2011).10. T. Aaltonen et al. (CDF Collaboration), CDF public note 10270 (2011).11. V. Abazov et al. (D0 Collaboration), Phys. Rev. Lett. 106, 081801 (2011).

Non-SUSY Searches at the Tevatron

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Non-SUSY Searches at the Tevatron

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